Information
-
Patent Grant
-
6616415
-
Patent Number
6,616,415
-
Date Filed
Tuesday, March 26, 200222 years ago
-
Date Issued
Tuesday, September 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Walberg; Teresa
- Fastovsky; L
Agents
- Harness, Dickey & Pierce, P.L.C.
-
CPC
-
US Classifications
Field of Search
US
- 417 26
- 417 441
- 060 277
- 060 676
- 062 228
- 062 210
- 290 52
- 318 803
- 318 433
- 307 106
- 388 934
- 236 10
-
International Classifications
-
Abstract
A fuel gas compression system includes a system which operates on direct current, a system which operates on alternating current and a system which is capable of operating on either direct current or alternating current. In the system that operates on either direct current or alternating current, a jumper is provided which is placed in the circuit when an alternating current is provided. When a direct current is provided, the jumper is removed from the circuit.
Description
FIELD OF THE INVENTION
The present invention relates generally to scroll-type machinery. More particularly, the present invention relates to scroll-type machinery specifically adapted for use in the compression of fuel gas and the control system for the scroll-type machinery.
BACKGROUND AND SUMMARY OF THE INVENTION
Scroll machines are becoming more and more popular for use as compressors in refrigeration systems as well as air conditioning and heat pump applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit with respect to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the scroll members via a suitable drive shaft.
As the popularity of scroll machines increase, the developers of these scroll machines continue to adapt and redesign the scroll machines for compression systems outside the traditional refrigeration systems. Additional applications for scroll machines include helium compression for cryogenic applications, air compressors, fuel gas compressors for distributed power generation and the like. The present invention is directed towards a scroll machine which has been designed specifically for the compression of fuel gas and the control system which operates the compressor in order to supply compressed fuel gas for distributed power generation.
Distributed power generation has emerged in recent years as a means to provide on-site power generation for commercial and industrial customers seeking a degree of independence from the possibility of a power shortage or power loss. While previous distributed power generation equipment was designed primarily to address the need for backup power, today's products are focused on providing continuous reliable power at an attractive price. Specifically, today's distributed power generators are intended to continuously supply clean, quiet and reliable power for both grid parallel and stand alone applications.
One important vehicle for the emerging distributed power generation market is the microturbine power generators. This device, about the size of two refrigerators, contains a jet turbine engine capable of using multiple fuels including pressurized fuel gas. Inlet air is compressed in the centrifugal compressor section, mixed with pressurized fuel gas, and then combusted to drive a turbine and a generator on a common high-speed shaft with the compressor. The high frequency power is then rectified and converted to a useable 50/60-cycle three-phase power through the use of an onboard inverter. Single microturbine generators are currently sized for 30 to 100 kilowatts of power generation but may eventually service a 200 to 300 kilowatt load. Fuel sources for microturbines include pipeline quality natural gas and biogas from landfill and digester plants.
Another technology well suited for distributed power generation is a conventional diesel driven generator converted for use with pressurized fuel gas. In this application termed “dual fuel”, a small percentage of diesel fuel is mixed with pressurized fuel gas to enhance the power generation output of the reciprocating engine. Low emissions are obtained relative to conventional diesel gensets, allowing this equipment to be used for continuous power generation versus the limited use operation allowed previously with emergency power applications. Dual fuel diesel gensets are being developed for power needs up to several megawatts.
An additional potential application option for the fuel gas compressor is a fuel cell using natural gas as the fuel. With this device pressurized natural gas flows through a reformer element which separates out hydrogen from the methane in the natural gas. The hydrogen fuel is then combined with pressurized air (oxygen) to provide the necessary ingredients for the electrochemical reaction that results in DC electric power.
To meet the need of these emerging power generation technologies for pressurized fuel gas, a reliable and efficient gas compression system was required to boost gas pressure at the site to the typical 60-100 psig operating pressure needed by the equipment. Normal variability in gas pressure and energy content, as well as the need for the power generator to operate at part load, required this gas compression system to efficiently supply a variable amount of fuel. This requirement is accomplished by the present invention through a custom variable speed electronic drive that also includes a microcompressor based logic control for use in fault and safety mode detection. Finally, to insure many years of reliable operation, a proven compressor technology, utilized in air conditioning and refrigeration products, was adapted to meet the specific needs of fuel gas compression.
The cyclic compression of fuel gas presents very unique problems with respect to compressor design because of the high temperatures encountered during the compression process. The temperature rise of fuel gas during the compression process can be more than twice the temperature rise encountered during the compression process of a conventional refrigerant. In order to prevent possible damage to the scroll machine from these high temperatures, it is necessary to provide additional cooling for the scroll machine in addition, fuel gas compression systems as well as other compression applications need to be capable of being powered from a variety of electrical sources. These electrical sources can be a direct current source or an alternating current source depending upon the particular application.
The present invention, in one embodiment, comprises a scroll compressor system which is specifically adapted for use in the compression of fuel gas. The scroll compressor of the system includes the conventional low pressure oil sump in the suction pressure zone of the compressor as well as a second high pressure oil sump located in the discharge pressure zone. An internal oil cooler is located within the low pressure oil sump. Oil from the low pressure oil sump is circulated to the bearings and other movable components of the compressor in a manner similar to that of conventional scroll compressors. A portion of the oil used to lubricate these moving components is pumped by a rotating component onto the windings of the electric motor to aid in cooling the motor. The oil in the high pressure oil sump is routed through an external heat exchanger for cooling and then is routed through the internal oil cooler located in the low pressure oil sump. From the internal oil cooler, the oil is injected into the compression pockets to aid in the cooling of the compressor as well as to assist in the sealing and lubrication of the intermeshed scroll wraps. An internal oil separator is provided in the discharge chamber to remove at least a portion of the injected oil from the compressed gas and thus replenish the high pressure oil sump. An oil overflow orifice prevents excessive accumulation of oil in the high pressure oil sump. A second external oil separator is associated with the external heat exchanger in order to remove additional oil from the natural gas to provide as close as possible for an oil free pressurized natural gas supply.
In another embodiment of the present invention, a unique scroll type compressor which is modified from proven air conditioning scroll compressor technology is provided for compressing the fuel gas. The compressor is a hermetic design which means both the motor and the scroll compression mechanism are in the same enclosure. This eliminates shaft seals and the possibility of gas leakage as is possible with open drive type compressors. Due to the high specific heat ratio and high compression temperatures inherent with fuel gas, the compression process is oil flooded to prevent overheating and insure compressor durability. Compressor durability is also enhanced by the lower outlet pressures of this application relative to the higher pressures typical in air conditioning applications. Both UL and CE approval have been obtained for this product.
The control system of the present invention allows the powering of the compressors by either a direct current (DC) source or an alternating current (AC) source. The system can be designed to be powered by only a DC source, only an AC source or it can be a “universal” compressor which can be powered by either a DC or an AC source.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:
FIG. 1
is an external elevational view of a fuel gas compression system in accordance with the present invention;
FIG. 2
is an external elevational view of the fuel gas compression system shown in
FIG. 1
in a direction opposite to that shown in
FIG. 1
;
FIG. 3
is a vertical cross-sectional view of the compressor shown in
FIGS. 1 and 2
;
FIG. 4
is a schematic diagram illustrating an electrical architecture for a gas booster control module for the compressor system shown in
FIG. 1
which is supplied with an alternating current;
FIG. 4A
is a schematic illustration of the jumper board assembly in accordance with the present invention;
FIG. 5
is a schematic diagram illustrating an electrical architecture for a gas booster control module for the compressor system shown in
FIG. 1
which is supplied with a direct current;
FIG. 6
is a schematic diagram illustrating an electrical architecture for a gas booster control module for the compressor system shown in
FIG. 1
which can be supplied with either an alternating current or a direct current;
FIG. 7
is a schematic illustration of the jumper system which is utilized in
FIG. 6
to switch between AC and DC supply;
FIG. 8
is a vertical cross-sectional view of a scroll compressor in accordance with another embodiment of the present invention;
FIG. 9
is a detailed cross-sectional view of the oil injection fitting shown in
FIG. 8
;
FIG. 10
is an external elevational view of a fuel gas compression system in accordance with another embodiment of the present invention;
FIG. 11
is a schematic diagram showing the fuel gas compression system shown in
FIG. 10
;
FIG. 12
is a schematic diagram of the electronic architecture of the gas booster control module for operating the fuel gas compression system illustrated in
FIGS. 10 and 11
; and
FIG. 13
is a graph illustrating both output and input parameters as a function of variable flow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in
FIGS. 1 and 2
a scroll machine in accordance with the present invention which is designated generally by the reference numeral
10
. Scroll machine
10
comprises a scroll compressor
12
, a filter
14
, an external oil/gas cooler
16
, an external oil separator
18
and a pressure regulator
20
.
Referring to
FIG. 3
, compressor
12
includes an outer shell
22
within which is disposed a compressor assembly including an orbiting scroll member
24
having an end plate
26
from which a spiral wrap
28
extends, a non-orbiting scroll member
30
having an end plate
32
from which a spiral wrap
34
extends and a two-piece main bearing housing
36
supportingly secured to outer shell
22
. Main bearing housing
36
supports orbiting scroll member
24
and non-orbiting scroll member
30
is axially movably secured to main bearing housing
36
. Wraps
28
and
34
are positioned in meshing engagement such that as orbiting scroll member
24
orbits, wraps
28
and
34
will define moving fluid pockets that decrease in size as they move from the radially outer region of scroll members
24
and
30
toward the center region of the scroll members.
A variable speed driving motor
38
is also provided in the lower portion of shell
22
. Variable speed motor
38
includes a stator
40
supported by shell
22
and a rotor
42
secured to and drivingly connected to a drive shaft
44
. Drive shaft
44
is drivingly connected to orbiting scroll member
24
via an eccentric pin
46
and a drive bushing
48
. Drive shaft
44
is rotatably supported by main bearing housing
36
and a lower bearing housing
50
which is secured to shell
22
. The lower end of drive shaft
44
extends into an oil sump
52
provided in the bottom of shell
22
. A lower counterweight
54
and an upper counterweight
56
are supported on drive shaft
44
. Counterweights
54
and
56
serve to balance the rotation of drive shaft
44
and counterweight
56
acts as an oil pump as described in greater detail below. In order to prevent orbiting scroll member
24
from rotating relative to non-orbiting scroll member
30
, an Oldham coupling
58
is provided. Oldham coupling
58
is supported on main bearing housing
36
and interconnecting with both orbiting scroll member
24
and non-orbiting scroll member
30
.
In order to supply lubricant from oil sump
52
to the bearings and other moving components of compressor
12
, an oil pump is provided in the lower end of drive shaft
44
in the form of a large axial bore
60
which serves to direct oil axially upward through an eccentric axially extending passage
62
. A radial passage
64
is provided to supply lubrication oil to main bearing housing
36
. The oil that is pumped through passage
62
will be discharged from the top of eccentric pin
46
to lubricate the interface between drive bushing
48
and orbiting scroll member
24
. After lubricating these interfaces, the oil accumulates within a chamber
66
defined by main bearing housing
36
. Upper counterweight
56
rotates within chamber
66
and acts as a pump to pump oil through a passage
68
extending through main bearing housing
36
. Passage
68
receives oil from chamber
66
and routes this oil to stator
40
to aid in the cooling of the motor. Upper counterweight
56
also pumps lubricating fluid up through a passage
70
also defined by main bearing housing
36
. Passage
70
receives oil from chamber
66
and directs this oil up towards Oldham coupling
58
, the lower surface of end plate
26
of orbiting scroll member
24
and into the suction port formed by scroll members
24
and
30
.
Outer shell piece
22
includes a lower shell
76
, an upper shell
78
, a lower cover
80
and an upper cap
82
. A partition or muffler plate
84
is also provided extending across the interior of shell
22
and is sealing secured thereto around its periphery at the same point that lower shell
76
is sealingly secured to upper shell
78
. Muffler plate
84
serves to divide the interior of shell
22
into a lower suction chamber
86
and an upper discharge chamber
88
.
In operation, suction gas will be drawn into suction chamber
86
through a suction inlet
90
and into the moving pockets defined by scroll wraps
28
and
34
. As orbiting scroll member
24
orbits with respect to non-orbiting scroll member
30
, the fluid pockets will move inwardly decreasing in size and thereby compressing the fluid. The compressed fluid will be discharged into discharge chamber
88
through a discharge port
92
provided in non-orbiting scroll member
30
and a discharge fitting assembly
94
secured to muffler plate
84
. The compressed fluid then exits discharge chamber
88
through a discharge outlet
96
. In order to maintain axially movable non-orbiting scroll member
30
in axial sealing engagement with orbiting scroll member
24
, a pressure biasing chamber
98
is provided in the upper surface of non-orbiting scroll member
30
. A portion of discharge fitting assembly
94
extends into non-orbiting scroll member
30
to define biasing chamber
98
. Biasing chamber
98
is pressurized by fluid at an intermediate pressure between the pressure in the suction area and the pressure in the discharge area of compressor
12
. One or more passages
100
supply the intermediate pressurized fluid to biasing chamber
98
. Biasing chamber
98
is also pressurized by the oil which is injected into chamber
98
by the lubrication system as detailed below.
With the exception of discharge fitting assembly
94
, compressor
12
as thus far described is similar to and incorporates features described in general detail in Assignee's U.S. Pat. No. 4,877,382; 5,156,539; 5,102,316; 5,320,506; and 5,320,507 the disclosures of which are hereby incorporated herein by reference.
As noted above, compressor
12
is specifically adapted for compressing fuel gas. The compression of fuel gas results in the generation of significantly higher temperatures. In order to prevent these temperatures from being excessive, it is necessary to incorporate various systems for cooling the compressor and the compressed fuel gas. In addition to the cooling for the compressor and the fuel gas, it is also very important that substantially all oil be removed from the compressed gas before it is supplied to the apparatus using the compressed fuel gas.
One system which is incorporated for the cooling of compressor
12
is the circulation of cooled lubricating oil. Upper shell
78
and muffler plate
84
define a sump
110
which is located within discharge chamber
88
. The oil being supplied to the suction port formed by scroll members
24
and
30
through passage
70
continuously adds to the volume of oil within sump
110
. An oil overflow fitting
112
extends through muffler plate
84
. Fitting
112
has an oil over flow orifice which keeps the level of oil in sump
110
at the desired level. Oil in sump
110
is routed through an outlet fitting
114
(
FIG. 1
) extending through upper shell
78
and into oil/gas cooler
16
by a connecting tube
116
. The cooled oil exits oil/gas cooler
16
through a connecting tube
118
and enters lower shell
76
through an inlet fitting
120
Oil entering fitting
120
is routed through a heat exchanger in the form of a cooling coil
122
which is submerged within oil sump
52
. The oil circulates through cooling coil
122
cooling the oil in oil sump
52
and is returned to inlet fitting
120
Oil entering inlet fitting
120
from coil
122
is directed to biasing chamber
98
through a connecting tube
124
. The oil enters biasing chamber
98
where it enters the compression chambers formed by wraps
28
and
34
through passages
100
to cool compressor
12
as well as assisting in the sealing and lubricating of wraps
28
and
34
. The oil injected into the compression chambers is carried by the compressed gas and exits the compression chambers with the fuel gas through discharge port
92
and discharge fitting assembly
94
.
Discharge fitting assembly
94
includes a lower seal fitting
126
and an upper oil separator
128
which are secured together sandwiching muffler plate
84
by a bolt
130
. Lower seal fitting
126
sealingly engages and is located below muffler plate
84
and it includes an annular extension
132
which extends into non-orbiting scroll member
30
to close and define biasing chamber
98
. A pair of seals
134
isolate biasing chamber
98
from both suction chamber
86
and discharge chamber
88
. Lower seal fitting
126
defines a plurality of discharge passages
136
which receive compressed fuel gas from discharge port
92
and direct the flow of the compressed fuel gas towards oil separator
128
Oil separator
128
is disposed above muffler plate
84
. Compressed fuel gas exiting discharge passages
136
contacts a lower contoured surface
138
of oil separator
128
and is redirected prior to entering discharge chamber
88
. The contact between the compressed fuel gas and surface
138
causes the oil within the gas to separate and return to sump
110
. During the assembly of compressor
12
, lower seal fitting
126
and upper oil separator
128
are attached to muffler plate
84
by bolt
130
. Bolt
130
is not tightened until the rest of the components of compressor
12
are assembled and secured in place. Once this has been accomplished, bolt
130
is tightened. Access to bolt
130
is provided by a fitting
140
extending through cap
82
. Once bolt
130
is tightened, fitting
146
is sealed to isolate discharge chamber
88
.
Compressed fuel gas exits discharge chamber
88
through discharge outlet
96
. Discharge outlet
96
includes a discharge fitting
142
and an upstanding pipe
144
. Discharge fitting
142
extends through upper shell
78
and upstanding pipe
144
extends toward cap
82
such that the compressed fuel gas adjacent cap
82
is directed out of discharge chamber
88
. By accessing the compressed fuel gas located adjacent cap
82
, the gas with the least amount of oil contained in the gas is selectively removed. Compressed fuel gas exiting discharge chamber
88
through discharge outlet
96
is routed to oil/gas cooler
16
through a connecting pipe
146
. Oil/gas cooler
16
can be a liquid cooled cooler using Glycol or other liquids known in the art as the cooling medium or oil/gas cooler
16
can be a gas cooled cooler using air or other gases known in the art as the cooling medium if desired. The cooled compressed fuel gas exits oil/gas cooler
16
through a connecting pipe
148
and is routed to oil separator
18
. Oil separator
18
removes substantially all of the remaining oil from the compressed gas. This removed oil is directed back into compressor
12
by a connecting tube
150
which connects oil separator
18
with connecting tube
118
. The oil free compressed and cooled fuel gas leaves oil separator
18
through an outlet
152
to which the apparatus using the fuel gas is connected. An accumulator may be located between outlet
152
and the apparatus using the fuel gas if desired. A bypass fitting
154
is connected to connecting pipe
146
for routing the fuel gas to pressure regulator
20
by a connecting pipe
156
. Pressure regulator
20
controls the outlet pressure of fuel gas at outlet
152
by controlling the pressure input to oil/gas cooler
16
through connecting pipe
146
. Pressure regulator
20
is connected to filter
14
and filter
14
includes an inlet
158
to which is connected to the uncompressed source of fuel gas.
Thus, low pressure gas is piped to inlet
158
of filter
14
where it is supplied to suction inlet
90
and thus suction chamber
86
along with gas rerouted to suction inlet
90
and suction chamber
86
through pressure regulator
20
. The gas in suction chamber
86
enters the moving pockets defined by wraps
28
and
34
where it is compressed and discharged through discharge port
92
. During the compression of the gas, oil is mixed with the gas by being supplied to the compression chambers from biasing chamber
98
through passages
100
. The compressed gas exiting discharge port
92
impinges upon upper oil separator
128
where a portion of the oil is removed from the gas prior to the gas entering discharge chamber
88
. The gas exits discharge chamber
88
through discharge outlet
96
and is routed through oil/gas cooler
16
and then into oil separator
18
. The remaining oil is separated from the gas by oil separator
18
prior to it being delivered to the appropriate apparatus through outlet
152
. The pressure of the gas at outlet
152
is controlled by pressure regulator
20
which is connected to connecting pipe
156
, connecting pipe
146
and to suction chamber
86
.
In addition to the temperature problems associated with the compression of the fuel gas, there are problems associated with various components of or contaminants within the fuel gas such as hydrogen sulfide (H
2
5). All polyester based materials degrade and are thus not acceptable for use in any fuel gas application. One area which is of a particular concern is the individual components of motor stator
40
.
Motor stator
40
includes a plurality of windings
200
which are typically manufactured from copper. For the compression of fuel gas, windings
200
are manufactured from aluminum in order to avoid the degradation of windings
200
from the fuel gas. In addition to the change of the material of the coil windings itself, the following table lists the other components of stator
40
which require revision in order to improve their performance when compressing fuel gas.
|
Current
Natural Gas
|
Item
Material
Material
|
|
Varnish
PD George 923
Guardian GRC-59
|
PD George 423
|
Schenectady 800P
|
Tie Cord
Dacron
Nomex
|
Cotton
|
Nylon treated w/
|
acrylic
|
Phase Insulation
Mylar
Nomex
|
Nomex-Kapton-
|
Nomax
|
Slot Liner
Mylar
Nomex
|
Nomex-Kapton-
|
Nomax
|
Soda Straw
Mylar
Teflon
|
Lead Wire
Dacron and Mylar
Hypalon
|
Insulation
(DMD)
|
Lead Wire Tubing
Mylar
Teflon
|
Terminal Block
Valox 310
Vitem 1000-7100
|
Fibcrite 400S-464B
|
Ultrason E2010G4
|
|
The above modification for the materials reduces and/or eliminates degradation of these components when they are utilized for compressing fuel gas.
Referring now to
FIG. 4
, a compression system
300
is illustrated. Compression system
300
includes scroll machine
10
and control system
302
. Control system
302
is provided with an alternating current (AC) from a customer supplied voltage. The customer supplied voltage is connected to a three pole fused disconnect
304
. From disconnect
304
, power is supplied to an inverter
306
and to an AC-DC power supply
308
. Inverter
306
receives the customer supplied AC voltage typically in the range of 380-480 VAC at either 50 or 60 Hz and converts this voltage to 205-366 VAC at 45-80 Hz which is required for powering scroll machine
10
.
AC-DC power supply
308
receives the customer supplied AC voltage typically in the range of 380-480 VAC at either 50 or 60 Hz and converts this voltage to 24 volts direct current (VDC). The
24
VDC is supplied from power supply
308
to a heat exchanger fan
310
, a power on light
312
, an electrical circulation fan
314
and a programmable logic control (PLC)
316
. PLC
316
also receives input from various sources including, but not limited to, a low pressure sensor, a high pressure sensor, a high temperature sensor, a customer start signal, an inverter fault signal and a reset fault/purge signal. Based on these signals, PLC
316
outputs signals to various devices including, but not limited to, a valve coil, a run light, a fault light, a customer fault signal, a start inverter signal and a reset inverter signal.
The electronic controls for control system
302
provide compressor motor control, digital logic control, low voltage DC power control and filtering, if required. These controls work together to enable compression system
300
to respond to run commands from the customer, fuel demand levels and protective sensor feedback.
As stated above, three pole fused disconnect
304
is supplied with 380/480 VAC with the frequency being at either 50 or 60 Hz. Three pole fused disconnect
304
includes a supply disconnect handle that is easily accessible. Three pole fused disconnect
304
also functions as an overcurrent protection device.
Control system
302
“communicates” with the customer's equipment through at least two discrete signals. A run signal provided to PLC
316
and a fault signal provided by PLC
316
. The run signal is provided from the customer's equipment by closing the contacts of a relay typically provided by the customer or by other means known in the art. When the relay contacts are closed, the customer start or run signal is provided to PLC
316
. Assuming that there are no faults indicated, PLC
316
will operate compression system
300
. If PLC
316
detects a fault from one or more sensors, the customer fault signal is provided by PLC
316
to indicate that there is a fault condition present. The fault signal is typically supplied by closing the relay contacts of a relay which is a part of control system
302
. When the relay contacts are closed, compression system
300
is indicating that a fault is present with PLC
316
sending the customer fault signal. As indicated above, fault conditions include, but are not limited to, low inlet pressure, high discharge pressure, high oil temperature and variable speed drive fault (inverter fault).
Compression system
300
is able to maintain a constant delivery pressure of fuel gas for a given flow range. The delivery pressure is monitored by a pressure transducer
320
(
FIG. 1
) which feeds back the delivery pressure to the variable speed drive for driving motor
38
. The variable speed drive is programmed with a pressure set point and will speed up or slow down driving motor
38
based upon the pressure feedback. The variable speed drive can vary the speed by varying the frequency between 45 Hz and 80 Hz. For fuel gas demands less than the demands met by driving motor
38
operating at 45 Hz, pressure regulator or bypass valve
20
becomes active diverting the excess flow of compressed fuel gas back to the inlet of compressor
12
.
Referring now to
FIG. 4A
, a jumper board system
330
is illustrated. Jumper board system
330
is utilized to program the pressure set point for compression system
300
. Jumper board assembly
330
comprises a jumper board
332
and a plurality of Jumpers
334
. By arranging the plurality of jumper
334
on jumper board
332
, the pressure set point can be programmed between a low pressure set point and a high pressure jet point using a distinct step. In the preferred embodiment, the low pressure set point is 70 PSIG, the high pressure set point is 100 PSIG and the step is 2 PSIG. The pressure set point is programmed by placing jumper
334
between position J
5
-J
2
in the lower row (ZP
18
) and position J
5
-J
2
in the middle row (ZP
20
). The programmable range for jumper board system
330
is illustrated in the chart below where “0” designates no jumper
334
and “1” designates the presence of jumper
334
.
|
PRESSURE SET POINT CHART
|
J2
J3
J4
J5
PRESSURE
SET POINT
|
|
0
0
0
0
70
PSIG
|
0
0
0
1
72
PSIG
|
0
0
1
1
74
PSIG
|
0
0
1
1
76
PSIG
|
0
1
0
0
78
PSIG
|
0
1
0
1
80
PSIG
|
0
1
1
0
82
PSIG
|
0
1
1
1
84
PSIG
|
1
0
0
0
86
PSIG
|
1
0
0
1
88
PSIG
|
1
0
1
0
90
PSIG
|
1
0
1
1
92
PSIG
|
1
1
0
0
94
PSIG
|
1
1
0
1
96
PSIG
|
1
1
1
0
98
PSIG
|
1
1
1
1
100
PSIG
|
|
In
FIG. 4A
, the pressure set point is programmed to 78 PSIG. Jumper board system
330
simplifies the programming for the pressure set point due to its accessibility to the user of the system and/or the service technician.
The advantages to compression system
300
include safety, efficiency and flexibility Compression system
300
is a safe system due to its ability to respond to condition that may be hazardous to people or to the equipment itself. The efficiency advantage are due to the variable speed control of compressor
12
which uses the minimum amount of power for a given fuel demand level. The flexibility of compression system
300
is dependent on programmable logic control
316
which allows customization to meet varying customer requirements.
Referring now to
FIG. 5
, a compression system
400
is illustrated. Compression system
400
includes scroll machine
10
and control system
402
. Control system
402
is provided with a direct current (DC) from a customer supplied voltage. The customer supplied voltage is corrected to a three pole fused circuit breaker
404
. From circuit breaker
404
, power is supplied to an inverter
406
and to DC-DC power supply
408
. Inverter
406
receives the customer supplied DC voltage typically in the range of 600-800 VDC and converts this voltage to 205-366 VAC at 45-80 Hz which is required for powering scroll machine
10
.
DC-DC power supply
408
receives the customer supplied DC voltage typically in the range of 600-800 VDC and converts this voltage to 24 volts direct current (VDC). The 24 VDC is supplied from power supply
408
to heat exchanger fan
310
, power on light
312
, electrical circulation fan
314
and programmable logic control (PLC)
316
. PLC
316
also receives input from various sources including, but not limited to, a low pressure sensor, a high pressure sensor, a high temperature sensor, a customer start signal an inverter fault signal and a resent fault/purge signal. Based on these signals, PLC
316
outputs signals to various devices including, but not limited to, a valve coil, a run light, a fault light, a customer fault signal, a start inverter signal and a reset inverter signal.
The electronic controls for control system
402
provide compressor motor control, digital logic control, low voltage DC power control and filtering if required. These controls work together to enable compression system
400
to respond to run commands from the customer, fuel demand levels and protective sensor feedback.
As stated above, circuit breaker
404
is supplied with 600-800 VDC. Circuit breaker
404
includes a supply disconnect handle that is easily accessible. Circuit breaker
404
also functions as an overcurrent protection device.
Control system
402
“communicates” with the customer's equipment through at least two discrete signals. A run signal provided to PLC
316
and a fault signal provided by PLC
316
. The run signal is provided from the customer's equipment by closing the contacts of a relay typically provided by the customer or by other means known in the art. When the relay contacts are closed, the customer start or run signal is provided to PLC
316
. Assuming that there are no faults indicated PLC
316
will operate compression system
400
. If PLC
316
detects a fault from one or more sensors, the customer fault signal is provided by PLC
316
to indicate that there is a fault condition present. The fault signal is typically supplied by closing the relay contacts of a relay which is a part of control system
402
. When the relay contacts are closed, compression system
400
is indicating that a fault is present with PLC
316
sending the customer fault signal. As indicated above, fault conditions include, but are not limited to, low inlet pressure, high discharge pressure, high oil temperature and variable speed drive fault (inverter fault).
Compression system
400
is able to maintain a constant delivery pressure of fuel gas for a given flow range. The delivery pressure is monitored by pressure transducer
320
(
FIG. 1
) which feeds back the delivery pressure to the variable speed drive per driving motor
38
. The variable speed drive is programmed with a pressure set point and will speed up or slow down driving motor
38
based upon the pressure feedback. The variable speed drive can vary the speed by varying the frequency between 45 Hz and 80 Hz. For fuel gas demands less than the demands met by driving motor
38
operating at 45 Hz, pressure regulator or bypass valve
20
becomes active diverting the excess flow of compressed fuel gas back to the inlet of compressor
12
. Compression system
400
also incorporates jumper board system
330
for programming the pressure set point as detailed above for compression system
300
.
The advantages to compression system
400
include safety, efficiency and flexibility. Compression system
400
is a safe system due to its ability to respond to conditions that may be hazardous to people or to the equipment itself. The efficiency advantages are due to the variable speed control of compressor
12
which uses the minimum amount of power for a given fuel demand level. The flexibility of compression system
400
is dependent on its programmable logic control
316
which allows customization to meet varying customer requirements.
Compression system
400
provides additional advantages to applications which require the system to start off battery power. Since the battery voltage is DC, it is desirable to start and run compression system
400
using the DC voltage. If the DC supply voltage is used, it leads to a smaller DC to AC conversion output module since it is unnecessary to supply compression system
400
with AC through that module.
Referring now to
FIG. 6
, a compression system
500
is illustrated. Compression system
500
includes compressor or scroll machine
10
and control system
502
. Control system
502
is provided with either an alternating current (AC) or a direct current (DC) from a customer supplied voltage. The customer supplied voltage is connected to a four pole fused disconnect
504
. From fused disconnect
504
, power is supplied to an input board
506
. Input board
506
receives the customer supplied AC or DC voltage typically in the range of 400-480 VAC at either 50 or 60 Hz for AC or 500-800 VDC for DC and outputs a 500—800 VDC to an inverter board
508
. A jumper card
510
is utilized with input board
506
for switching between an AC or a DC signal being supplied to input board
506
. Details of jumper card
510
are discussed below in reference to FIG.
7
.
Inverter board
508
receives the 500-800 VDC voltage from input board
506
and it supplies power to scroll machine
10
and a fan controller board
512
. Inverter board
508
includes a DSP (digital signal processor) based motor controller
514
, a DC-DC power supply
516
and a microprocessor based programmable logic control system
518
. Motor controller
514
receives the 500-800 VDC voltage from input board
506
and converts this voltage to 137-366 VAC at 30-80 Hz which is required to power scroll machine
10
. In addition, motor controller
514
is capable of varying the capacity for scroll machine
10
in response to a signal received from microprocessor based programmable logic control system
518
as discussed below. DC-DC power supply
516
also receives the 500-800 VDC voltage from input board
506
and converts this voltage to 300 VDC which is supplied to fan controller board
512
. Fan controller board
512
converts the power to 230 VAC and supplied this power to heat exchanger fan
310
based on input it receives from microprocessor based programmable logic control system
518
.
MBP logic control system
518
receives power from input board
506
and it also receives input from various sources including, but not limited to, various safety switches, the customer's interface, a master/slave signal, an analog in signal and a pressure transducer signal. Based on these input signals, MBP logic control system
518
outputs voltage to power scroll machine
10
, power to fan controller board
512
and output signals to various devices. These output signals include, but are not limited to a LED interface board, the customer interface, an hour meter and the box cooling fans.
The electronic controls for control system
502
provide for compressor motor control, digital logic control, low voltage DC power control and filtering, if required. These controls work together to enable control system
502
and thus compression system
500
to respond to run commands from the customer, fuel demand levels and protective sensor set back.
As stated above, four pole fused disconnect
504
is supplied with either 400-480 VAC with the frequency being 50-60 Hz or 500-800 VDC. Four pole fused disconnect
504
includes a supply disconnect handle that is easily accessible. Four pole fused disconnect
504
also functions as an overcurrent protection device. The power from four pole fused disconnect
504
is transmitted to input board
506
. A further detailed description for control system
502
is presented below in reference to FIG.
13
.
Referring now to
FIG. 7
, the input scheme for input board
506
is illustrated. Jumper card
510
illustrated in
FIG. 7
, is utilized when the input power to four pole fused disconnect
504
is AC power. Each of the three phase circuits plus ground include at least one metal-oxide-varistor (MOV)
520
and a plurality of capacitors
522
which are located between each phase of the power supply and ground. Jumper card
510
completes the connection to ground for all of the circuits that lead to ground to provide transient or surge protection for the supplied AC voltage. Input board
506
also includes a diode module
524
and an EMC filtering device
526
which converts the supplied AC power into DC power. When DC power is supplied to four pole fused disconnect
504
, jumper
510
is removed to take MOV's
520
and capacitors
522
out of the circuit.
Control system
502
communicates with the customer's equipment through at least two discrete signals. A run signal provided to logic control system
518
and a fault signal provided by logic control system
518
are two of these signals. The run signal is provided from the customer's equipment by closing the contacts of a relay typically provided by the customer or by other means known in the art. When conditions indicate a need, the relay contacts are closed and the customer's start or run signal is provided to logic control system
518
. Assuming that there are no faults indicated, logic control system
516
will operate compression system
500
. If logic control system
518
detects a fault from one or more sensors, the customer fault signal is provided by logic control system
518
to indicate that there is a problem with the system. The fault signal is typically supplied by closing the relay contacts of a relay which is a part of compression system
500
. When the relay contacts are closed, compression system
500
is indicating a fault is present with logic control system
518
sending the customer fault signal.
Compression system
500
is able to maintain a constant delivery pressure of fuel gas for a given flow range. The delivery pressure is monitored by a pressure transducer which feeds back the delivery to motor controller
514
of logic control system
518
which controls the speed for driving motor
38
. The variable speed is programmed with a pressure set point and it will speed up or slow down driving motor
38
based upon the pressure feed back. The variable speed drive can vary the speed by varying the frequency between 45 Hz and 80 Hz. For fuel gas demands less than the demands met by driving motor
38
operating at 45 Hz, pressure regulator or bypass valve
20
becomes active diverting the excess flow of compression fuel gas back to the inlet of compressor
12
. Compression system
500
also incorporates jumper board system
330
for programming the pressure set point as detailed above for compression system
300
.
The advantages to compression system
500
include safety, efficiency, flexibility and the ability to supply either AC or DC power to the system. Compression system
500
is a safe system due to its ability to respond to conditions that may be hazardous to people or to the equipment itself. The efficiency advantages are due to the variable speed control of compressor
12
which uses the minimum amount of power for a given fuel demand level. The flexibility of compression system
500
is dependent on programmable logic control system
518
which allows customization to meet varying customer requirements as well as the ability to supply either AC or DC power.
Referring now to
FIGS. 8 and 9
, a horizontal scroll compressor
700
in accordance with another embodiment of the present invention is illustrated. Scroll compressor
700
comprises a generally cylindrical hermetic shell
712
having welded at one end thereof a cap
714
. Cap
714
is provided with a discharge fitting
716
which may have the usual discharge valve therein. Other major elements affixed to the shell include a base cap
718
, an inlet fitting
720
and a transversely extending partition
722
which is welded about its periphery at the same point that cap
714
is welded to cylindrical shell
712
. A discharge chamber
724
is defined by cap
714
and partition
722
.
A main bearing housing
726
and a lower bearing housing
728
having a plurality of radially outwardly extending legs are each secured to cylindrical shell
712
. A motor
730
which includes a rotor
732
is supported within cylindrical shell
712
between main bearing housing
726
and second bearing housing
728
. A crank shaft
734
having an eccentric crank pin
736
at one end thereof is rotatably journaled in bearing housing
726
and second bearing housing
728
.
Crank shaft
734
has, at a second end, a relatively large diameter concentric bore
742
which communicates with a radially outwardly smaller diameter bore
744
extending therefrom to the first end of crankshaft
734
.
Crank shaft
734
is rotatably driven by electric motor
730
including rotor
732
and stator windings
748
passing therethrough. Rotor
732
is press fitted on crank shaft
734
and includes first and second counterweights
752
and
754
respectively.
A first surface of main bearing housing
726
is provided with a flat thrust bearing surface
756
against which is disposed an orbiting scroll
758
having the usual spiral vane or wrap
760
on a first surface thereof. Projecting from a second surface of orbiting scroll
758
is a cylindrical hub
762
having a journal bearing
764
therein in which is rotatably disposed a drive bushing
766
having an inner bore in which crank pin
736
is drivingly disposed. Crank pin
736
has a flat on one surface which drivingly engages a flat surface (not shown) formed in a portion of the bore in drive bushing
766
to provide a radially compliant driving arrangement, such as shown in assignee's U.S. Pat. No. 4,877,382, the disclosure of which is hereby incorporated herein by reference.
An Oldham coupling
768
is disposed between orbiting scroll
758
and bearing housing
726
. Oldham coupling
768
is keyed to orbiting scroll
758
and a non-orbiting scroll
770
to prevent rotational movement of orbiting scroll member
758
. Oldham coupling
768
is preferably of the type disclosed in assignee's U.S. Pat. No. 5,320,506, the disclosure of which is hereby incorporated herein by reference. A floating seal
772
is supported by the non-orbiting scroll
770
and engages a seat portion
774
mounted to partition
722
for sealingly dividing an intake chamber
776
and discharge chamber
724
.
Non-orbiting scroll member
770
is provided having a wrap
778
positioned in meshing engagement with wrap
760
of orbiting scroll
758
. Non-orbiting scroll
770
has a centrally disposed discharge passage
780
defined by a base plate portion
782
. Non-orbiting scroll
770
also includes an annular hub portion which surrounds discharge passage
780
. A dynamic discharge valve or read valve can be provided in discharge passage
780
if desired.
An oil injection fitting
784
, as best shown in
FIG. 9
, is provided through bottom cap
718
which is connected to shell
712
. Oil injection fitting
784
is threadedly connected to a fitting
788
which is welded within an opening
790
provided in bottom cap
718
. Fitting
788
includes an internally threaded portion which is threadedly engaged by an externally threaded portion provided at one end of oil injection fitting
784
. A nipple portion
792
extends from the externally threaded portion of oil injection fitting
784
. Nipple portion
792
extends with an opening provided in a snap ring
794
which is disposed in lower bearing housing
728
. Snap ring
794
holds a disk member
796
in contact with the lower end of crankshaft
734
. Disk member
796
includes a hole
798
which receives, with a clearance, the end of nipple portion
792
therein. Oil injection fitting
784
includes an internal oil passage
800
extending longitudinally therethrough which serves as a restriction on the oil flow. Oil injection fitting
784
includes a main body portion
802
which is provided with a tool engaging portion (such as a hex shaped portion which facilitates the insertion and removal of the fitting
784
by a standard wrench). Oil injection fitting
784
further includes a second nipple portion
806
extending from main body
802
in a direction opposite to first nipple portion
792
. Second nipple portion
806
is adapted to be engaged with a hose or tube
808
which supplies oil to fitting
784
.
Oil is delivered to fitting
784
and into concentric bore
742
, in crankshaft
734
through oil passage
800
extending through fitting
784
. Concentric bore
742
extends to bore
744
which in turn extends through crankshaft
734
to provide lubricating oil to the various bearings, the scroll members and other components of compression
700
which require lubrication.
Referring now to
FIGS. 10 and 11
, scroll compressor
700
is illustrated as part of a fuel gas compression system
820
. Fuel gas compression system
820
is a complete stand-alone system capable of boosting fuel gas pressure from as little as 0.25 psig to up to 100 psig in a single stage of compression. To illustrate the operation of fuel gas compression system
820
, fuel gas flow will be followed from inlet to outlet connections.
Fuel gas enters fuel gas compression system
820
through an inlet connection
822
and flows through an inlet filter
824
, a low pressure switch
826
and a check valve
828
to compressor
700
. For safety purposes, low-pressure switch
826
prevents fuel gas from being extracted from adjacent appliances, and check valve
828
prevents the pressurization of the supply line due to reverse gas flow on compressor shutdown. Upon entering compressor
700
, the fuel gas enters the scroll compression elements and is compressed to the desired pressure. Oil from the lubrication process also enters the scrolls and serves to provide cooling to the gas compression process. High-pressure gas and oil then leave compressor
700
and flow through a first and a second stage oil separator
830
,
832
where the oil in the gas is reduced to less than 5 ppm. High-pressure gas next passes through a gas heat exchanger
834
to an outlet connection
836
where a pressure transducer
838
provides a feedback signal to the electronic variable speed drive for compressor
700
. To accommodate minimal fuel demand requirements, a bypass valve
842
is included to divert high-pressure gas back to the inlet side of compressor
700
.
Power generation applications supported by fuel gas compression system
820
require fuel to be delivered as needed at the design outlet pressure. During the start up mode, the fuel demand may be zero, while during normal full load operation, the fuel demand may be variable due to power generator size, inlet pressure and temperature, and gas heating value. For generator part load operation, fuel requirements may be 50% or less of full load. To meet the need of these variability requirements, fuel gas compression system
820
includes both bypass valve
842
and the electronic variable speed drive for compressor
700
. For the zero fuel requirements needed during generator start up, bypass valve
842
controls fuel flow. For normal flow operation, the electronic variable speed drive for compressor
700
controls compressor motor speed from 1800 to 4800 RPM. Pressure transducer
838
at the gas exit of the system provides the necessary feedback signal to the electronic variable speed drive for compressor
700
to hold fuel pressure at the programmed pressure set point. System overload and safety shutdown features are also included in the onboard electronic package designed specifically for this application as detailed below. Fuel gas compression system
820
also incorporates jumper board system
330
for programming the pressure set point as detailed above for compression system
300
.
Compressor
700
used with fuel gas compression system
820
is a positive displacement scroll type hermetic design as detailed above. In a scroll type compressor
700
, two identical involute scroll elements
760
,
778
fit together to form a number of “pockets” which continually change in size and location as the gas is compressed. Scroll
778
of non-orbiting scroll member
770
remains stationary while scroll
760
of orbiting scroll member
758
orbits about it. This orbiting scroll movement draws gas into two outer chambers and them moves it through successively smaller volume chambers until it reaches a maximum pressure at the involute center. At this point, the gas is released through discharge passage
780
in non-orbiting scroll member
770
.
During each orbit of orbiting scroll member
758
multiple gas pockets are compressed simultaneously so that compression is virtually continuous. Gas entering the scrolls requires approximately three orbits, or crankshaft rotations, to reach the discharge pressure. This extended duration compression process results in a smooth, efficient and quiet delivery of high-pressure gas to the end product. The scroll compression process is optimal at the design pressure ratio (based on the design volume ration) but works well with minor efficiency loss at higher-pressure ratios. For the fuel gas compression application, a design pressure ratio of 3 works efficiently over the required operating pressure ratios of 3 to 7.
Fuel gas compression requires additional compressor and system design considerations not present in conventional air conditioning applications. With the high specific heat ratio of natural gas compression of 1.35 versus 1.15 for typical refrigerants, discharge gas temperatures can approach 500° F. at higher-pressure ratios. To control discharge temperatures below a 300° F. oil degradation level, an oil flooded compressor design was developed as shown in FIG.
11
.
Both oil and gas flow processes are illustrated for this unique horizontal scroll design which includes a high-pressure oil sump (first on primary oil separator
830
versus the conventional low pressure oil sump used with vertical style scroll compressors. From the high-pressure sump or primary oil separator
830
, oil is routed through an oil cooler
848
and then back to compressor
700
. Second oil separator
832
receives gas mixed with oil from first oil separator
830
and it directs the gas to gas heat exchanger
834
and then to outlet connection
836
. Outlet connection
836
communicates with a pressurized gas mechanism which can be a microturbine power generator, a diesel driven generator conversion, a fuel cell or any other type of compressed gas user. Oil from second oil separator
832
is joined with oil from oil cooler
848
and this oil is injected directly into compressor
700
to lubricate the bearing components. As oil flows from the bearing system, it provides cooling to the interrial motor and collects in the lower area of compressor shell
712
. When the oil level reaches the inlet of scroll members
758
and
770
, oil along with gas enters the scroll compression process where it provides cooling to the compressed gas. Due to the mixing of the oil and gas during compression, gas temperatures are typically well below 200° F. for all operating pressure ratios.
As high pressure gas leaves compressor discharge fitting
716
, it goes through two states of oil separation to minimize yearly oil loss to a small percentage of the available oil sump. Then, before leaving compression system
820
, the gas is cooled by gas heat exchanger
834
to below 150° F. to meet the maximum gas temperature requirement typical of generator fuel control valves. Oil separated in the first and second stage oil separators
830
and
832
is returned to compressor
700
through an oil supply line. The quantity of oil flow to compressor
700
is controlled through the use of an orifice
852
sized to insure adequate bearing lubrication and gas cooling but not allow excessive oil flooding and viscous drag. Overall, high volumetric and energy efficiencies are obtained with this design approach while potentially damaging high gas temperatures are avoided.
The application spectrum of the fuel gas compressor system
820
requires an electronic control package to satisfy multiple. needs including variable fuel flow, delivery pressure control, system fault sensing and run signal response, and the ability to receive power from either AC or DC power sources. In addition, satisfying regulatory agency requirements in both the U.S. and Europe requires the selection of potentially different electrical components. In prior art designs, these varying needs were met with a number of different build options requiring a variety of special parts. With the present invention, all of the required functions were consolidated into a single integrated electronic module with minimal change required to meet specific model needs. The electronic architecture of gas booster control module
502
is shown in
FIG. 12
, FIG.
6
and FIG.
7
. Two key elements shown in this diagram are input board
506
and inverter board
508
. Included in input board
506
are EMC (Electro Magnetic Compatibility) filtering capability,
864
transient protection
866
and three-phase rectification
868
of the supply voltage.
Referring to
FIGS. 12 and 7
, the EMC filtering
864
is accomplished by device
526
which uses capacitors to reduce the amount of conducted noise put back on the mains, or other AC supply source. Transient protection
866
is accomplished through metal oxide varistors
520
that allow the compressor control module to withstand power surges up to 6 kV. Three-phase rectification
868
is accomplished with three-phase diode module
524
. If the power source is AC power, diode module
524
rectifies the three-phase voltage into a DC voltage. If the power source is DC, diode module
524
simply allows it to pass through.
Another versatile feature included in the input board design is the dual AC or DC capability of the input power supply. Jumper card
510
is removed for DC power and left in place for AC power input. Jumper card
510
keeps filtering capacitors
522
and transient overvoltage protection present in the circuit. When jumper card
510
is removed, those components do not function. The filtering and transient protection is not necessary in a DC power application because the power generator supplying the DC power provides this protection.
The heart of the compressor control module is inverter board
508
. Key features include DSP (digital signal processor) based motor control
514
, DC to DC power supply
516
and microprocessor based logic control
518
for monitoring input fault signals, a customer run signal and a pressure transducer feedback control signal.
Motor controller
514
function is realized by using the DC voltage supplied by input board
506
to create a sinusoidal AC voltage delivered to the motor. The DSP controls an insulated gate bipolar transistor module that switches the DC voltage in a PWM (pulse width modulation) control scheme. The resulting waveform looks like a sinusoidal AC voltage to the compressor induction motor. Using this technique allows the DSP to vary the frequency and voltage to the compressor motor, thereby controlling its speed.
DC to DC power supply utilizes 300 VDC on the board, and through a switch mode power supply circuit, provides 24, 18 and 5 VDC for device power and logic signals.
Microprocessor logic control
518
controls the LED's on the customer interface board and communicates compressor faults when abnormal operation occurs. Some examples of system induced fault modes are bypass valve failure causing high pressure, low oil level causing high temperature, and undersized inlet piping causing inlet pressure to fall below USDOT regulated levels. In addition, microprocessor logic control
518
reads the pressure transducer signal that is run through a proportional/integral loop. The resulting error is used to calculate a speed command send to DSP motor control
514
.
A customer Interface board consists of LED's which indicate low inlet pressure, high outlet pressure, high oil temperature, high motor current, motor controller fault and fan controller fault.
Oil and gas cooling is accomplished through air cooled heat exchangers
834
and
848
that utilize a fractional horsepower, single phase AC fan motor. The fan controller board converts 300 VDC to 230 VAC to power this fan motor. The fan motor controller uses the same PWM technique explained earlier for the inverter board. The fan motor controller is designed to operate at a specific temperature. Jumper board system
330
,
FIG. 4A
, is utilized to program this specific temperature. The specific temperature is programmed by placing jumper
334
between position J
1
in the upper row (ZP
17
) and position J
1
in the middle row (ZP
20
). While the use of only one jumper
334
for programming the specific temperature allows the selection between two temperature settings, additional jumper locations can be incorporated if additional temperature settings are required. In the preferred embodiment, absence of jumper
334
programs the system for biogas and the addition of jumper
334
programs the system for natural gas. In
FIG. 4A
, the system is programmed for natural gas and will thus control the heat exchanger fans to maintain the specified temperature for the compressed fuel gas. The temperature setting capability for jumper board system
330
can be utilized in any of the embodiments detailed above.
Several additional capabilities of control module
502
are a broad operating temperature range and the ability to couple together multiple fuel gas compressors in a multi-pack arrangement. The customer electronic design allows the use of components capable of broader ambient temperature operation than with standard components. To accommodate both high and low ambient applications, all electronic components have been selected to operate from −40° F. to 120° F.
When multiple compressors are needed to supply one or more power generation device, the units are operated in a master/slave arrangement where only one unit (master) operates using its pressure transducer feedback signal to maintain outlet pressure. The other units (slaves) operate at the same frequency as the master using an analog signal broadcast by the master to all slaves. Conversion from master to slave duty is accomplished, in this design with a simple jumper wire as is well known in the art.
The performance of a fuel gas booster compressor is similar to that of an air compressor with output being measured in gas volume flow scfm (standard ft
3
/min) or equivalent, and input being measured in electrical power kw (kilowatts). Specific capacity, characterized by output divided by input, is then defined by scfm/kw. For specific fuels such as natural gas, the output parameter can be stated in mass flow by multiplying the scfm of the compressor by the density of the fuel. However, for the purpose of product comparison, it is best to use scfm as the baseline output parameter. By definition, scfm is the gas flow at standard conditions, usually 14.7 psia and 60° F. for natural gas products. With a variable speed or variable flow machine, it is helpful to characterize operating performance in a single chart that indicates product performance over the entire range of flow. One method of characterizing both output and input parameters as a function of variable flow is shown in FIG.
13
.
Two sets of data are shown here to demonstrate performance as a function of both minimum and maximum inlet pressures. Delivery pressure in this chart is set at a typical level of 85 psig although actual use pressures may vary from 60 to 100 psig. Starting with the specific capacity curve at 15 psia, note that specific capacity increases linearly from zero as the compressor bypass valve closes from full bypass to zero bypass at the minimum operating speed of 30 Hz. In this range, the power generator is in a start up mode where the fuel demand starts at zero and increases gradually. As this is a transient situation, the low specific capacity in this region has minimal effect on overall operating performance of the fuel delivery system. When more flow is required than can be supplied at the minimum operating speed (30 Hz), the electronic variable speed drive takes control and peak performance follows.
Specific capacity is highest in the low frequency range and decreases with increasing frequency due to relatively high power from both viscous drag forces in the compressor, and higher flow losses in both the inlet and outlet components. As a function of inlet pressure, specific capacity is highest at high inlet pressure due to the higher theoretical efficiency obtained at lower operating pressure ratios (3.3 versus 6.6) for the compressor. Theoretical performance, as measured by isentropic efficiency, is nearly-constant with inlet pressure: 49% at 15 psia and 47% at 30 psia. This efficiency is comparable to refrigeration scroll compressors and other gas compressors, but well below the 70% attainable with high efficiency air conditioning scroll compressors. The difference in efficiency is due to the relatively high mechanical losses (as a percent of overall power) of the low-pressure gas compressor, the significant heating of the gas entering the scrolls above the 60° F. inlet condition, and the pressure losses of the system that are not included in typical compressor performance data. Without the inclusion of system pressure losses, the isentropic efficiency at the two respective inlet pressures becomes 53% and 58%. Overall, the efficiency of the fuel gas booster system is very good relative to other gas compression technologies, particularly when efficiency over a broad gas flow range is taken into account. Specifically, for compressor systems using outlet gas bypassing (or inlet throttling) as the primary means of flow control, efficiency is very low relative to the nearly uniform efficiency obtained with a variable speed drive.
In addition to long life and efficient operation, low sound and vibration is a desirable attribute for a fuel gas compression product. Due to the scroll compression technology used with this design, compressor noise is very low relative to adjacent power generation equipment. Typically the sound level of the fuel gas booster is 6 or more dBA less than the generator or 25% of the sound power. Measured sound levels are 75 dBA sound pressure level at one meter, or 83 dBA sound power level. Vibration level is also very important in gas appliance due to the correlation of high vibration with potential gas leakage. With scroll compressor technology, nearly perfect dynamic balance is achieved and low vibration levels of less than 0.003 inch are obtained. The net result is a product that runs quietly with no noticeable vibration relative to the adjacent power generator.
The present invention described above was developed and tested primarily for pipeline quality natural gas compression. For this application, as detailed above, chemical resistance of the compressor to hydrogen sulfide and other non-methane components required a special aluminum wound hermetic motor in place of the normal copper wound motor. Also, a polyalphaolefin lubricant which chemical pacifiers was selected to provide extra protection against corrosion of metallic surfaces. These modifications provided a basic level of protection for pipeline applicants but also served to prepare the product for other non-pipeline applications.
While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.
Claims
- 1. A compressor system comprising:a compressor; an electric motor drivingly connected to said compressor; a source of electrical power; a control system disposed between said source of electrical power and said electric motor, said control system operable to provide transfer power from said source of electrical power to said electric motor, said control system including a jumper movable between a first position when said source of electrical power is an alternating current power source and a second position when said source of electrical power is a direct current power source, said jumper controlling the power input to said control system from said source of electrical power.
- 2. The compressor system according to claim 1 wherein said control system includes an inverter board in communication with said electric motor, said inverter board operable to supply alternating current to said electric motor.
- 3. The compressor system according to claim 1 wherein said electric motor is a variable speed motor, said control system including a motor controller for varying the speed of said motor.
- 4. The compressor system according to claim 1 wherein said control system includes a programmable logic control system, said programmable logic control system being in communication with a sensor which monitors an operating characteristic of said compressor.
- 5. The compressor system according to claim 4 wherein said sensor is a pressure sensor and said operating characteristic is discharge pressure of said compressor system.
- 6. The compressor system according to claim 4 wherein said programmable logic control includes a jumper board system for programming a pressure set point for comparison with said discharge pressure.
- 7. The compressor system according to claim 1 further comprising a heat exchanger fan, said control system including a fan controller board for operating said heat exchanger fan when a specified discharge temperature is reached.
- 8. The compressor system according to claim 7 wherein said control system includes a jumper board system for programming said specified discharge temperature.
- 9. The compressor system according to claim 1 wherein said control system includes a DC-DC power supply, said DC-DC power supply being in communication with said fan controller board.
- 10. The compressor system according to claim 1 wherein said control system includes a programmable logic control system, said programmable logic control system providing an output signal indicating the status of said compressor.
- 11. The compressor system according to claim 1 wherein said compressor is a scroll compressor.
- 12. A fuel gas compression system comprising:a compressor for compressing fuel gas from a suction pressure to a discharge pressure selected from one of a plurality of preset discharge pressures; a variable speed electric motor drivingly connected to said compressor; a control system in communication with said electric motor and said compressor, said control system maintaining one of said plurality of discharge pressures by varying the speed of said variable speed electric motor; and a jumper board system for selecting said one of said plurality of discharge pressures.
- 13. The fuel gas compression system according to claim 12 wherein said control system includes a temperature sensor for monitoring a temperature of said fuel gas at said discharge pressure.
- 14. The fuel gas compression system according to claim 13 wherein said jumper board system is operable to program a specified temperature for said fuel gas at said discharge pressure.
US Referenced Citations (13)