Patent Application
20180058218
This disclosure relates generally to a cryogenic pump for delivering liquefied natural gas to an internal combustion engine and, more particularly, to a hydraulic drive piston for the cryogenic pump.
Machines such as mining trucks, locomotives, marine vessels and the like have recently begun using alternative fuels, alone or in conjunction with traditional fuels, to power their engines. For example, large displacement engines may use a gaseous fuel, alone or in combination with a traditional fuel such as diesel, to operate. Because of their relatively low densities, gaseous fuels, for example, natural gas or petroleum gas, are carried onboard vehicles in liquid form. These liquids, the most common including liquefied natural gas (LNG) or liquefied petroleum gas (LPG), are cryogenically stored in insulated tanks on the machine at cryogenic temperatures, from where a desired quantity of fuel is pumped, evaporated, and provided to fuel the engine.
Pumps used to deliver the LNG to the engine of the machine may include a piston, that is reciprocally mounted in a cylinder bore. The piston is moved back and forth in the cylinder by hydraulic pressure to actuate a pumping assembly of the pump to draw in and then pressurize the LNG. Power to move the piston may be provided by different means, such as electrical, mechanical or hydraulic power. Pumps that include multiple pistons are also known.
One example of a cryogenic pump can be found in U.S. Pat. No. 7,293,418, which describes a cryogenic, single-element pump for use in a vehicle. The pump discharges into an accumulator that is located within the tank, and uses a single piston pump that is connected to a drive section via a piston rod. The drive section is disposed outside of the tank.
Some pumps are designed to control the motion of the piston at the designed end of stroke with features in the form of structural stops. Physical contact of the piston with the stop arrests the motion of the piston. Other pumps incorporate control systems or other features to control the motion of the piston and thus contact with any physical parts can be reduced or avoided. These types of no-impact designs are often more reliable. Linearly actuated hydraulic pistons, when designed for no-impact operation, will continue to move or stroke as long as there is a hydraulic pressure force acting upon them. To stop a hydraulic piston from stroking, the driving pressure must be reduced or eliminated. One method of reducing the driving pressure is to incorporate a designed leakage or dump at the end of normal stroke operation such as is shown in U.S. Pat. No. 9,228,574. Under certain circumstances that exceed normal operating conditions, such as the presence of over-pressurized hydraulic fluid in the drive cell, the designed end of stoke features for normal operation may not be sufficient to keep the piston from impacting other structures of the pump or impacting at a velocity that causes damage. For a multi-element cryogenic pump that operates at a relatively fast frequency (˜28 Hz) and where the firing event maybe be only a few electronic control module (ECM) clock cycles or even a sub clock cycle, it may take time for the ECM controls to discern that over-speed stroking, over travel or impact is occurring. A corrective action may be taken but may not be possible to effect until after over travel has already occurred. Also, the ECM may sense that the system is running within normal operating parameters but in reality, due to sensor error and offset, the stroke velocity of the elements exceeds specifications.
The disclosed system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
The present disclosure is generally directed to a cryogenic fluid pump. The cryogenic pump includes a drive assembly and a pumping assembly. The drive assembly includes a cylinder. The cylinder includes an annular dump channel that is formed in and extends about an interior wall of the cylinder. A piston is reciprocatable within the cylinder between a first position and a second position and a hydraulic pressure chamber is defined by the cylinder and the piston. The piston includes at least one axial spill passage in communication with the hydraulic pressure chamber and a transverse spill passage in communication with the at least one axial spill passage. The transverse spill passage includes a piston dump port. The piston dump port is sealed to the cylinder in the first position and in the second position unsealed to the cylinder to permit fluid exit from the hydraulic pressure chamber. The second position includes an over travel state and the dump area of the piston dump port when unsealed to the cylinder continues to increase as the piston advances in the over travel state.
In another aspect, a pumping system is disclosed for providing a cryogenic fluid for use as a fuel for an engine including an electronic controller. The cryogenic pump is operably associated with the electronic controller, wherein operation of the cryogenic pump is responsive to pump commands from the electronic controller. The cryogenic pump has a plurality of pumping elements, each of the plurality of pumping elements include a drive assembly and a pumping assembly. The pumping assembly is operably responsive to the drive assembly. The drive assembly includes a cylinder. The cylinder includes an annular dump channel that is formed in and extends about an interior wall of the cylinder. A piston is reciprocatable within the cylinder between a first position and a second position. A hydraulic pressure chamber is defined by the cylinder and the piston. The piston includes at least one axial spill passage in communication with the hydraulic pressure chamber and a transverse spill passage in communication with the at least one axial spill passage. The transverse spill passage includes a piston dump port. The piston dump port is sealed to the cylinder in the first position and in the second position unsealed to the cylinder to permit fluid exit from the hydraulic pressure chamber, wherein the second position includes an over travel state and wherein the dump area of the piston dump port unsealed to the cylinder continues to increase as the piston advances in the over travel state.
In another aspect a cryogenic fluid pump is disclosed that includes a plurality of pumping elements in communication with an electronic controller, each of the pumping elements including a drive assembly. The drive assembly includes an electromechanical actuator having a pin associated therewith, the pin arranged in a bore having a fluid supply passage, a spool valve supply outlet, and a drain outlet, wherein the pin is moveable between a deactivation position, in which the hydraulic oil supply passage is fluidly connected with the spool valve supply outlet, and an activation position, in which the spool valve supply outlet is fluidly connected with the drain outlet. The drive assembly also includes a cylinder. The cylinder includes an annular dump channel that is formed in and extends about an interior wall of the cylinder. A piston is reciprocatable within the cylinder between a first position and a second position, and a hydraulic pressure chamber defined by the cylinder and the piston. The piston includes at least one axial spill passage in communication with the hydraulic pressure chamber and a transverse spill passage in communication with the at least one axial spill passage. The transverse spill passage includes a piston dump port. The piston dump port is sealed to the cylinder in the first position and in the second position unsealed to the cylinder to permit fluid exit from the hydraulic pressure chamber, wherein the second position includes an over travel state and wherein the dump area of the piston dump port unsealed to the cylinder continues to increase as the piston advances in the over travel state. The drive assembly is associated with and is configured to selectively activate one end of a pushrod in response to a command by the electronic controller. A pump assembly is associated with an opposite end of the pushrod wherein the pump assembly is activated for pumping a fluid by the drive assembly. The electronic controller is configured to selectively activate the drive assembly such that a flow of fluid from the cryogenic fluid pump results from successive activations thereof at selected dwell times between activations.
This disclosure relates to machines with engines using a gaseous fuel (e.g., methane of other hydrocarbon mixtures commonly known as natural gas or petroleum gas) source such as direct injection gas (DIG) or indirect injection gas engines using diesel or spark ignition. More particularly, the disclosure relates to a hydraulic drive system for a cryogenic liquid natural gas (LNG) pump that supplies pressurized natural gas fuel to an engine. A schematic diagram of a DIG, engine system 100, which in the illustrated embodiment uses liquid diesel fuel as the ignition source, is shown in
The fuel injector 104 is connected to a high-pressure gaseous fuel rail 106 via a high-pressure gaseous fuel supply line 108 and to a high-pressure liquid fuel rail 110 via a liquid fuel supply line 112. In the illustrated embodiment, the gaseous fuel is natural or petroleum gas that is provided through the high-pressure gaseous fuel supply line 108 at a pressure of between about 10-50 MPa, and the liquid fuel is diesel, which is maintained within the high-pressure liquid fuel rail 110 at about 15-100 MPa, but any other pressures or types of fuels may be used depending on the operating conditions of each engine application. The liquid fuel can be any hydrocarbon based fuel; for example DME (Di-methyl Ether), biofuel, MDO (Marine Diesel Oil), or HFO (Heavy Fuel Oil).
Whether the engine system 100 is installed in a mobile or a stationary application, each of which is contemplated, the gaseous fuel may be stored in a liquid state in a tank 114, which can be a cryogenic storage tank that is pressurized at a relatively low pressure, for example, atmospheric, or at a higher pressure. In the illustrated embodiment, the tank 114 is insulated to store liquefied natural gas (LNG) at a temperature of about −160° C. (−256° F.) and a pressure that is between about 100 and 1750 kPa, but other storage conditions may be used. The tank 114 further includes a pressure relief valve 116. In the description that follows, a DIG engine system embodiment is used for illustration, but it should be appreciated that the systems and methods disclosed herein are applicable to any machine, vehicle or application that uses cryogenically stored gas, for example, a locomotive in which the tank 114 may be carried in a tender car.
Relative to the particular embodiment illustrated, during operation, LNG from the tank is pressurized, still in a liquid phase, in a pump 118, which raises the pressure of the LNG while maintaining the LNG in a liquid phase. The pump 118 is configured to selectively increase the flow of the LNG that can vary in response to a command signal provided to the pump 118 from an electronic controller 120. The pump 118 is shown external to the tank 114 in
The pressurized LNG provided by the pump 118 is heated in a heat exchanger 122. The heat exchanger 122 provides heat to the compressed LNG to change the LNG phase to a gaseous/supercritical state which is more suitable for combustion. In one exemplary application, the LNG may enter the heat exchanger 122 at a temperature of about −160° C., a density of about 430 kg/m3, an enthalpy of about 70 kJ/kg, and a viscosity of about 169 μPa s as a liquid, and exit the heat exchanger at a temperature of about 50° C., a density of about 220 kg/m3, an enthalpy of about 760 kJ/kg, and a viscosity of about 28 μPa s. It should be appreciated that the values of such representative state parameters may be different depending on the particular composition of the fuel being used. In general, the fuel is expected to enter the heat exchanger in a cryogenic, liquid state, and exit the heat exchanger in a supercritical gas state, which is used herein to describe a state in which the fuel is gaseous but has a density that is between that of its gaseous and liquid phases.
The heat exchanger 122 may be any known type of heat exchanger or heater for use with LNG. In the illustrated embodiment, the heat exchanger 122 is a jacket water heater that extracts heat from engine coolant. In alternative embodiments, the heat exchanger 122 may be embodied as an active heater, for example, a fuel fired or electrical heater, or may alternatively be a heat exchanger using a different heat source, such as heat recovered from exhaust gases of the engine 102, a different engine belonging to the same system such as what is commonly the case in locomotives, waste heat from an industrial process, and other types of heaters or heat exchangers. In the embodiment shown in
Liquid fuel, or in the illustrated embodiment diesel fuel, is stored in a fuel reservoir 136. From there, fuel is drawn into a fuel pump 138 through a filter 140. The fuel pump 138 may have a variable flow capability to provide fuel to the engine at a variable rate depending on the operating mode of the engine. The rate of fuel provided by the fuel pump 138 can be controlled in response to a command signal from the electronic controller 120. Pressurized fuel from the fuel pump 138 is provided to the high-pressure liquid fuel rail 110. Similarly, the pump 118 has a variable supply capability that is responsive to a signal from the electronic controller 120.
Contaminants may be removed from the natural gas exiting the heat exchanger 122 by a filter 124. As can be appreciated, the natural gas passing through the filter 124 may be present in more than one phase such as gas or liquid. An optional natural gas accumulator 126 may collect filtered gas upstream of a pressure regulator 128 that can selectively control the pressure of gas provided to the high-pressure gaseous fuel rail 106 that is connected to the high-pressure gaseous fuel supply line 108. To operate the pump 118, a hydraulic pump 150 having a variable displacement and selectively providing pressurized hydraulic fluid to the pump 118 via a valve system 152 is used. Operation of the hydraulic pump 150 is controlled by an actuator 154 that responds to commands from the electronic controller 120. The valve system 152 also operates in response to commands from the controller 120. It will be appreciated that while system 100 illustrates one or more embodiment, other configurations are contemplated.
A section view of the tank 114 having the pump 118 at least partially disposed therein is shown in
The pump 118 in the illustrated embodiment includes a pump flange 220 that supports the pump 118 on the mounting flange 216 of the tank 114. A partially sectioned view of the pump 118, removed from the tank 114, is also shown in
In the illustrated embodiment, the pushrods 304, shown in cross section in
The pressurized hydraulic fluid to activate the piston 314 is provided in the space behind the piston, and is also vented, by the selective positioning of a spool valve 322, which is shown in two operating positions in
The spool valve 322 in the illustrated embodiment includes a spool valve element 324 that is reciprocally mounted and operates within a bore 326. The bore 326, which accommodates the spool valve element 324, is fluidly connected to a fluid supply passage 328, which supplies pressurized fluid to move the piston 314. For example, as shown in
The bore 326 is also fluidly connected to a vent passage 330 (partially shown in
In the illustrated embodiment, the spool valve element 324 at an energized condition is disposed in the fill position (
More specifically, during operation, depending on the activation state of the solenoid 336, the position of the pin 338 within the pin guide 346 operates between an activation position and a drain position. In the activation position, a lower seat valve 347 opens as the armature 344 moves upward, which places the spool valve supply outlet 352 in fluid communication with the drain outlet 354, which, as shown in
Operation of the actuator 334 depends on the presence of electrical power, which is selectively provided by the electronic controller 120 (
Turning to
For purposes of the present disclosure, travel of the piston 314 within a specified range, i.e., from 0-100 percent of the designed travel will be considered a normal or specified travel state with 100 percent the end of specified travel. Travel of the piston 314 beyond a specified range, i.e., greater than 100 of the designed travel will be considered an over travel state.
Specifically, piston 314 reciprocates in cylinder 316 and, in part, defines a hydraulic pressure chamber 410, defined at least in part by the top 412 of the piston, that is provided with fluid from activation passage 318. Piston 314 includes at least one axial spill passage 414, which extends axially through the piston in communication with the hydraulic pressure chamber 410. Two axial spill passages 414 are shown. Each axial spill passage 414 may extend through the piston 314 less than the axial length of the piston. In one embodiment, the axial spill passage 414 may extend through the piston 314 about a fourth of the axial length of the piston. The at least one axial spill passage 414 is in communication with a transverse spill passage 416 that extends transversely to the axis of the piston 314 and opens to a relief pressure area, for example, on the outside of the piston. The transverse spill passage 416 has a piston dump port 418, which forms the opening of the passage to the outside of the piston 314. The transverse spill passage 416 can have any cross-sectional shape to supply sufficient flow of fluid to the piston dump port 418. The piston dump port 418, in the illustrated embodiments, may have a non-round cross-section to meter the flow area therethrough such that flow of fluid is dumped at a higher rate that can be accomplished with a circular port opening. Some examples of piston dump ports 418 are shown in detail in
The cylinder 316 includes an annular dump channel 420. The annular dump channel 420 may be a groove formed in the inward facing inside wall of the cylinder 316. The annular dump channel 420 is in communication with the transverse spill passage 416 through the piston dump port 418 when the piston 314 is at its expected fully-extended travel position illustrated at pumping element example 400B and not in communication with the transverse spill passage when at an intermediate travel position or its fully-retracted position as shown at pumping element example 400A. When the piston dump port 418 and annular dump channel 420 are in fluid communication with the cylinder dump port 422, a passage is provided for fluid to exit the fluid chamber 410. The cross sectional shape of the piston dump port 418 in combination with the annular dump channel 420 permits a relief or dumping of hydraulic pressure from the hydraulic pressure chamber 410.
Embodiment 418a has a triangular configuration such that the cross sectional area of the passage available for fluid to flow through is small at the beginning of fluid exit at 550 with a relatively small or first dump port area shown at 554. The port area increases in a quadratic fashion as the piston dump port 418a includes the port area shown at 556. In contrast to a circular port area, where the port area increases initially at a fast rate and then increases at a decreasing rate (less than linear) describing a sigmoid curve, the area of the piston dump port 418a increases at a greater than linear rate. In particular, the port dump area 554, 556 continues to increase as the piston progresses in an over travel state.
Embodiment 418b and 418c is a U-shape such that flow through is a small amount at the beginning of fluid exit at 550 with a semicircular dump port area shown at 554. The port area increases as the piston dump port 418a includes the rectangular areas shown at 556. Embodiment 418c has a lesser total throughput at maximum port area of combined port areas 554 and 556. The rectangular area 556 provides a linear rate of fluid exit. The port dump area 554, 556 continues to increase as the piston progresses in an over travel state.
Embodiment 418d is initially the same as 418c including a U-shape such that flow through is a small amount at the beginning of fluid exit at 550 with a semicircular dump port area shown at 554. The port area increases as the piston dump port 418d includes the rectangular areas shown at 556. The rectangular area 556 provides a linear rate of fluid exit. The area shown at 556 includes a flared portion at the upper end 552 thereof which permits a large expansion of fluid flow at the fully open and maximum dump port area which represents an increased rate of flow beyond the linear rate of portion 556. The port dump area 554, 556 continues to increase as the piston progresses in an over travel state.
Embodiment 418e is initially the same as 418d including a semicircular shape such that flow through is a small amount at the beginning of fluid exit at 550 with a semicircular dump port area shown at 554. The port area increases as the piston dump port 418d includes the triangular area shown at 556. The triangular area 556 provides more than a linear rate of fluid exit. The port dump area 554, 556 continues to increase as the piston progresses in an over travel state.
The present disclosure is applicable to any type of application that involves a hydraulic dump to prevent piston over travel. The present disclosure presents several embodiments of dump port configurations that function to protect a cryogenic pump from over travel states. In particular, the embodiments presented herein provide an increase of dump area vs. piston travel in an over travel state.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
