Patent Application
20110262269
The present invention, in some embodiments, relates to the field of gas-turbines, and more particularly, but not exclusively, to gas-turbines operable in both high-pressure (Brayton cycle) and low-pressure (inverse Brayton cycle) modes. The present invention, in some embodiments, relates to the field of gas-turbines, and more particularly, but not exclusively, to gas-turbines operable in low-pressure mode (inverse Brayton cycle).
Gas-turbines are known for being lightweight, reliable and requiring little maintenance compared to alternative work-producing motors, e.g. an internal combustion engine (ICE). Above all, gas-turbines are known for efficiently converting chemical energy stored in a combustible fuel to mechanical energy when working at an optimum work point. However, in spite of their potential, gas-turbines are currently not well known in applications requiring work-producing motors—for example ground vehicles such as cars and trucks—for several reasons.
One reason is that a given gas-turbine may generate a certain power at high efficiency for a prescribed load, but is less efficient at part load, particularly if turbine speed is maintained. Many applications, vehicular applications in particular, generally have changing power demands, for instance requiring more power for rapid acceleration or climbing hills, and requiring less power when driving in traffic.
A second reason is “turbine lag”: it takes a noticeably long time for a given gas-turbine to speed-up to produce more power, e.g., for acceleration. Thus, if turbine speed is reduced when power demand is low, a sudden increased power demand can be met only after a noticeable time lag.
A third reason is that the lifetime of gas-turbines is severely limited by startup/shutdown events. Unlike an ICE, it is not practical to shut down a gas-turbine when idling.
A fourth reason is that the power requirements for many applications, e.g. ground vehicles, are low compared to the power gas-turbines efficiently produce. Although large gas-turbines are relatively efficient, the efficiency of a gas-turbine decreases with smaller size (less than 300 kW) for various reasons including leakage around the periphery of the turbine which is increasingly significant with smaller turbine size.
Commonly, gas-turbines are operated according to either a high-pressure Brayton cycle or a low-pressure inverse Brayton cycle. A gas-turbine operating according to the inverse Brayton cycle efficiently produces less power than a similar-sized gas-turbine operating according to the Brayton cycle. In
In typical high-pressure (Brayton-cycle) operation,
In typical low-pressure (inverse Brayton-cycle) operation,
In both the Brayton cycle and inverse Brayton cycle, the rotation of shaft 24 by exhaust gases expanding through turbine 22 provides usable mechanical work, e.g. for generation of electric power by generator 32.
Gas-turbines such as 2 or 4 typically include gas-turbine controller 36 that monitors and controls the gas-turbine, including by regulating the amount of fuel supplied to combustor 26 by fuel-supply unit 34.
To increase thermal efficiency, gas-turbines such as 2 or 4 typically include a heat-exchanger 52, such as a recuperator or regenerator. Heat-exchanger 52 includes a cold-stream conduit 54 and a hot-stream conduit 56, both having inlets 58 and 60, respectively, and outlets 62 and 64, respectively. Heat-exchanger 52 increases the thermal efficiency of a gas-turbine by recovering heat from hot exhaust gases passing through hot-stream conduit 56 to preheat air passing through cold-stream conduit 54 prior to entering combustor 26.
In U.S. Pat. Nos. 6,526,757 and 6,606,864 both of McKay are provided multipressure mode gas-turbines, gas-turbines with valving having two configurations. In a first valving configuration the gas-turbine operates in a high-pressure mode according to a Brayton cycle. In a second valving configuration the gas-turbine operates in a low-pressure mode according to an inverse Brayton cycle. The gas-turbine is toggled between the two modes by the synchronized switching of a plurality of valves between the two valving configurations changing the pressure and therefore the mass flow through the gas-turbine while maintaining a constant temperature and shaft speed, allowing two substantially equally efficient power outputs, where the power output during low-pressure mode operation is less than during high-pressure mode operation.
Aspects of the invention relate to valves suitable for use with gas-turbines that, in some embodiments, allow switching between high-pressure and low-pressure operation modes of a gas-turbine. Aspects of the invention relate to gas-turbines that are configured to operate in both high-pressure and low-pressure modes.
Aspects of the invention relate to valves suitable for use with gas-turbines that, in some embodiments, allow switching between high-pressure, low-pressure and intermediate-pressure operation modes of a gas-turbine. Aspects of the invention relate to gas-turbines that are configured to operate in high-pressure, low-pressure and intermediate-pressure modes.
Aspects of the invention relate to valves that allow simple and efficient varying of the pressure and power output of a gas-turbine, that in some embodiments is substantially continuous. Aspects of the invention relate to gas-turbines that are configured to efficiently operate in different pressure modes, allowing different power outputs at substantially similar efficiencies.
According to an aspect of some embodiments of the invention, there is provided a gas-turbine configured for operation according to both Brayton-cycle and inverse-Brayton cycle, comprising:
a) a multiport valve including movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port, and a fifth port;
b) a compressor-outlet of a compressor of the gas-turbine in fluid communication with the compressor-outlet inlet port; and
c) a heat-exchanger cold-stream inlet of a heat-exchanger of the gas-turbine in fluid communication with the heat-exchanger cold-stream inlet outlet port;
According to an aspect of some embodiments of the invention there is also provided a multiport valve suitable for use with a gas-turbine and allowing switching the mode of operation of a gas-turbine between a high-pressure mode according to a Brayton cycle and a low-pressure mode according to an inverse Brayton cycle, the valve comprising:
a) a valve body defining a void in the form of a plurality of fluid conduits;
b) at least five ports leading to the void of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port and a fifth port;
c) a first valve member inside the valve body movable between at least two positions, a first position and a second position; and
d) a second valve member inside the valve body movable between at least two positions, a first position and a second position.
where the position of the first valve member and the position of the second valve member (together) define fluid communication between the inlet ports and the outlet ports through the void.
According to an aspect of some embodiments of the invention, there is also provided a gas-turbine, configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising a multiport valve as described herein. In some embodiments, the gas-turbine is also configured to switch to an intermediate pressure mode between the high-pressure operation mode and the low-pressure operation mode.
Aspects of the invention relate to gas-turbines operating in low-pressure mode that have reduced NOx emissions. Thus, according to an aspect of some embodiments of the invention, there is also provided a method of operating a gas-turbine according to an inverse Brayton cycle, comprising:
a) providing a conduit allowing fluid communication between a compressor of the gas-turbine and a cold-stream inlet of a heat-exchanger of the gas-turbine; and
b) during inverse Brayton cycle operation of the gas-turbine, directing fluid from the compressor to the heat-exchanger cold-stream inlet through the conduit so that a portion of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. As a result, inlet air is mixed with a portion of the oxygen-depleted exhaust from the compressor, decreasing oxygen content of the combustible mixture in the combustor, reducing the amount of NOx produced in the combustor and emitted by the gas-turbine.
According to an aspect of some embodiments of the invention, there is also provided a gas-turbine comprising, when operating according to an inverse Brayton cycle,
a) an air inlet configured to direct fluid into a cold-stream conduit of a heat-exchanger through a cold-stream inlet;
b) conduits to direct fluid from the cold-stream conduit to a combustor, from the combustor to a turbine, from the turbine to a hot-stream conduit of the heat-exchanger, from the hot-stream conduit to a compressor, and from the compressor to an exhaust outlet port; and
c) a conduit allowing passage of fluid from the compressor into the cold-stream inlet of the heat-exchanger. In some embodiments, the gas-turbine is configured to operate only according to the inverse Brayton cycle. In some embodiments, the gas-turbine is a multi-power gas-turbine configured to operate according to both the Brayton cycle and the inverse Brayton cycle.
According to an aspect of some embodiments of the invention, there is also provided a motor vehicle (e.g., an automobile, a light truck, a truck, a bus) comprising a gas-turbine substantially as described herein.
As used herein, the term “high-pressure mode” refers to operation of a gas-turbine where compressor inlet pressure is close to atmospheric (˜1× ambient) and compressor outlet (exhaust) pressure is superatmospheric (typically ˜3× ambient pressure).
As used herein, the term “low-pressure mode” refers to operation of a gas-turbine where compressor inlet pressure is subatmospheric (˜0.3× ambient pressure) and compressor outlet (exhaust) pressure is close to atmospheric (˜1× ambient pressure).
As used herein, the term “intermediate pressure mode” refers to operation of a gas-turbine where compressor inlet pressure is subatmospheric (between above 0.3× ambient pressure to ˜1× ambient pressure) and compressor outlet (exhaust) pressure is higher than atmospheric (between above 1× ambient pressure to ˜3× ambient pressure).
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the patent specification, including definitions, will control.
As used herein, the terms “comprising”, “including”, “having” and grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. These terms encompass the terms “consisting of” and “consisting essentially of”.
As used herein, the indefinite articles “a” and “an” mean “at least one” or “one or more” unless the context clearly dictates otherwise.
Some embodiments of the invention are described herein, with reference to the accompanying figures The description, together with the figures, makes apparent how embodiments of the invention may be practiced to a person having ordinary skill in the art. The figures are for the purpose of illustrative discussion of embodiments of the invention and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, objects depicted in the figures are not drawn to scale.
In the Figures:
Some embodiments of the invention relate to multiport valves that allow switching between high-pressure operation (Brayton cycle) and low-pressure operation (inverse Brayton cycle) modes of a gas-turbine.
Some embodiments of the invention relate to multiport valves that allow operation of a gas-turbine in high-pressure, low-pressure and intermediate pressure modes.
Some embodiments of the invention relate to multiport valves that allow operation of a gas-turbine at a variable power output in high-pressure modes and/or low-pressure modes at relatively high efficiency by varying the mass flow through the gas-turbine. Some embodiments of the invention relate to valves that allow simple and efficient varying of the pressure, mass flow and power output of a gas-turbine, that in some embodiments is substantially continuous.
Some embodiments of the invention relate to gas-turbines operating in a low-pressure mode (inverse Brayton mode) having reduced NOx emissions as well as valves useful for such gas-turbines.
The principles, uses and implementations of the teachings of the invention may be better understood with reference to the accompanying description and Figures. Upon perusal of the description and figures present herein, one skilled in the art is able to implement the teachings of the invention without undue effort or experimentation, including by consulting U.S. Pat. No. 6,526,757, which is included by reference as if fully set forth herein. In the Figures, like reference numerals refer to like parts throughout.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth herein. The invention is capable of other embodiments or of being practiced or carried out in various ways. The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting.
As noted in the introduction, in U.S. Pat. Nos. 6,526,757 and 6,606,864 are disclosed gas-turbines provided with valving that allow the gas-turbines to switch between high-pressure operation with efficient high-power output and low-pressure operation with efficient low-power output. However, a problem with the gas-turbines as described in U.S. Pat. Nos. 6,526,757 and 6,606,864 is that of complexity: the valving system of a simplest embodiment includes six separate on-off valves that must be operated synchronously to toggle between the two modes. Furthermore, in order to achieve additional, intermediate pressure—and thus intermediate power—turbine operation modes, even more complex embodiments which include more than one spool and many separate valves, must be employed.
It has been found that it is possible to simplify the valving system necessary to allow a gas-turbine to switch between high-pressure and low-pressure operation.
Thus, according to an aspect of some embodiments of the invention, there is provided a gas-turbine configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising:
a) a multiport valve including movable valve members and at least five ports of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port, and a fifth port;
b) a compressor outlet of a compressor of the gas-turbine in fluid communication with the compressor-outlet inlet port; and
c) a heat-exchanger cold-stream inlet of a heat-exchanger of the gas-turbine in fluid communication with the heat-exchanger cold-stream inlet outlet port;
wherein during Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the exhaust outlet port and a valve member blocks fluid communication between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port; and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port.
In some embodiments, the fifth port is a compressor-inlet outlet port in fluid communication with an inlet of the compressor of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the ambient inlet port and the compressor-inlet outlet port. In some such embodiments, the gas-turbine further comprises an additional valve functionally associated with the hot-stream outlet of the heat-exchanger, wherein during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger to an inlet of the compressor. In some such embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger to an exhaust outlet of the gas-turbine. An exemplary such embodiment is depicted in
In some embodiments, the fifth port is a heat-exchanger hot-stream outlet inlet port in fluid communication with a hot-stream outlet of the heat-exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, a valve member blocks fluid communication between the heat-exchanger hot-stream outlet inlet port and the exhaust outlet port. In some such embodiments, the gas-turbine further comprises an additional valve functionally associated with a hot-stream outlet of the heat-exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger to an inlet of the compressor. In some embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from ambient to an inlet of the compressor. An exemplary such embodiment is depicted in
In some embodiments, the multiport valve includes six ports, of which three are inlet ports and three are outlet ports.
In some such embodiments where the multiport valve includes six ports, the fifth port is a compressor-inlet outlet port in fluid communication with an inlet of the compressor, and during inverse Brayton-cycle operation of the gas-turbine a valve member blocks fluid communication between the ambient inlet port and the compressor-inlet outlet port; and the multiport valve further includes a sixth port, a heat-exchanger hot-stream outlet inlet port in fluid communication with a hot-stream outlet of the heat-exchanger of the gas-turbine.
In some embodiments including such a six-port valve, the gas-turbine further comprises an additional valve functionally associated with a hot-stream outlet of the heat-exchanger of the gas-turbine, and during inverse Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger of the gas-turbine to an inlet of the compressor of the gas-turbine. In some such embodiments, during Brayton-cycle operation of the gas-turbine, the additional valve allows fluid communication from the hot-stream outlet of the heat-exchanger of the gas-turbine to an exhaust outlet of the gas-turbine through the heat-exchanger hot-stream outlet inlet port. In some such embodiments, the gas-turbine further comprises a component functionally associated with the heat-exchanger hot-stream outlet inlet port, allowing flow of fluid from the hot-stream outlet of the heat-exchanger through the heat-exchanger hot-stream outlet inlet port and blocking flow of fluid from the multiport valve to the hot-stream outlet of the heat-exchanger through the heat-exchanger hot-stream outlet inlet port. In some such embodiments, the component is a undirectional valve that is part of the multiport valve. An exemplary such embodiment is depicted in
In some such embodiments where the multiport valve includes six ports, the multiport valve further comprising a bypass conduit bypassing the valve void, providing fluid communication between the heat-exchanger hot-stream outlet inlet port and the compressor-inlet outlet port, wherein during Brayton-cycle operation of the gas-turbine, a valve member blocks the fluid communication between the heat-exchanger hot-stream outlet inlet port and the compressor-inlet outlet port through the bypass conduit. An exemplary such embodiment is depicted in
According to an aspect of some embodiments of the invention there is also provided a multiport valve suitable for use with a gas-turbine and allowing switching the mode of operation of a gas-turbine between a high-pressure mode according to a Brayton cycle and a low-pressure mode according to an inverse Brayton cycle, the valve comprising:
a) a valve body defining a void in the form of a plurality of fluid conduits;
b) at least five ports leading to the void of which at least two inlet ports and at least two outlet ports: a compressor-outlet inlet port, an ambient inlet port, a heat-exchanger cold-stream inlet outlet port, an exhaust outlet port and a fifth port;
c) a first valve member inside the valve body movable between at least two positions, a first position and a second position; and
d) a second valve member inside the valve body movable between at least two positions, a first position and a second position
where the position of the first valve member and the position of the second valve member (together) define fluid communication between the inlet ports and the outlet ports through the void.
In some embodiments, the first valve member and the second valve member are configured to cooperatively move between the first positions and the second positions. In some embodiments, the first valve member and the second valve member are configured to move independently between the first positions and the second positions.
In some embodiments, in the first position the first valve member is in contact with a first valve seat and in the second position in contact with a second valve seat. In some embodiments, in the first position the second valve member is in contact with a third valve seat and in the second position in contact with a third valve seat.
As detailed hereinbelow, in some embodiments, in a first or second position a given valve member blocks fluid communication between specific ports. By blocking fluid communication is meant that the fluid communication between the ports is blocked to a sufficient degree to achieve the desired purpose (e.g., operating an associated gas-turbine in a desired mode), although there may be some leakage, for example as described below. As detailed hereinbelow, in some embodiments, in a first or second position a given valve member contacts a specific valve seat. By contacting a valve seat is meant contacting to a sufficient degree to achieve a desired purpose as described immediately herein above, for example, in some embodiments is meant “sealing contact”.
In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the ambient inlet port and the fifth port, a compressor inlet outlet port; and the second valve member in the first position blocks fluid communication (through the void) between the compressor-outlet inlet port and the exhaust outlet port and in the second position blocks fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is valve 100 depicted in
In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the compressor-outlet inlet port and the exhaust outlet port and in the second position blocks fluid communication (through the void) between the fifth port, a heat-exchanger hot-stream outlet inlet port, and the exhaust outlet port; and the second valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in
In some embodiments, the first valve member in the first position blocks fluid communication (through the void) between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the ambient inlet port and the fifth port, a compressor inlet outlet port; and the second valve member in the first position blocks fluid communication (through the void) between a sixth port, a heat-exchanger hot-stream outlet inlet port, and the heat-exchanger cold-stream inlet outlet port and in the second position blocks fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in
In some embodiments, the valve further comprises a bypass conduit providing fluid communication bypassing the valve void between the heat-exchanger hot-stream outlet inlet port and the compressor inlet outlet port, and a third valve member inside the valve body movable between at least two positions, a first position and a second position, wherein in the first position the third valve member blocks fluid communication through the bypass conduit between the heat-exchanger hot-stream outlet inlet port and the compressor inlet outlet port through the bypass conduit and in the second position the third valve member blocks fluid communication through the void between the heat-exchanger hot-stream outlet inlet port and the exhaust outlet port. In some embodiments, in the first position the third valve member is in contact with a fifth valve seat and in the second position the third valve member is in contact with a sixth valve seat. An exemplary such embodiment is depicted in
In some embodiments of the multiport valve at least one of the valve members is movable to at least one intermediate position between a respective first position and respective second position, thereby allowing fluid communication (through the void) between an inlet port and at least two outlet ports. In some such embodiments, at least one valve member is fashioned as an airfoil having an aerodynamic profile (generally predefined aerodynamic profile) configured to direct the flow of fluid as desired through the fluid conduits of the valve body.
In some embodiments, the second valve member is movable to at least one intermediate position, providing fluid communication (through the void) between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port and the exhaust outlet port. Exemplary such embodiments include valve 100, valve 102 and valve 103 depicted in
In some embodiments, the first valve member is movable to an intermediate position, providing fluid communication between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port and the compressor-inlet outlet port. Exemplary such embodiments include valve 100, valve 102 and valve 103 depicted in
In some embodiments comprising a third valve member, the third valve member is movable to an intermediate position, providing fluid communication between the heat-exchanger hot-stream outlet inlet port and the exhaust outlet port and the compressor-inlet outlet port. An exemplary such embodiment is valve 103 depicted in
In some embodiments, at least one valve member is configured to vary a size of a fluid path between an inlet port and an outlet port while the valve member in the first position and/or the second position.
In some embodiments, the second valve member is configured to vary a size of a fluid path between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port when in the first position. An exemplary such embodiment is depicted in
In some embodiments, the first valve member is configured to vary a size of a fluid path between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port when in the second position. An exemplary such embodiment is depicted in
In some embodiments, the multiport valve further comprises an additional valve member movable inside the valve body and, the additional valve member configured to vary a size of a fluid path between the compressor-outlet inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in
In some embodiments, the multiport valve further comprises an additional valve member movable inside the valve body and configured to vary a size of a fluid path between the ambient inlet port and the heat-exchanger cold-stream inlet outlet port. An exemplary such embodiment is depicted in
In some embodiments, the valve further comprises a permeable section between a first region and a second region of the void in the valve body, providing fluid communication between the first region and the second region. Such a permeable section may be implemented in any suitable way including a conduit, slits, pores and the like. The utility of such a permeable section is described hereinbelow. In some such embodiments, the first region is in proximity of the exhaust outlet port and in some such embodiments between the second valve member and the exhaust outlet port. In some such embodiments, the second region is in proximity of the heat-exchanger cold-steam inlet outlet port and in some such embodiments between the second valve member and heat-exchanger cold-stream inlet outlet port. In some such embodiments, the permeable section is unidirectional, allowing passage of fluid from the first region to the second region, and blocking passage of fluid from the second region to the first region. Such a unidirectional permeable section may be implemented in any suitable way including with the help of a unidirectional valve, a check valve (a unidirectional valve that functions automatically without an external control, e.g. variants of a swing check valve or reed valve) or a pump. In some embodiments, the permeable section is part of the second valve member.
According to an aspect of some embodiments of the invention, there is also provided a gas-turbine, configured to switch between a high-pressure operation mode according to a Brayton cycle and a low-pressure operation mode according to an inverse Brayton cycle, comprising a multiport valve as described herein. In some embodiments, the gas-turbine is also configured to switch to an intermediate pressure mode between the high-pressure operation mode and the low-pressure operation mode.
Embodiment of 5-Port Valve Suitable for Use with a Gas-Turbine
First movable valve member 171 is movable between the first and second positions by rotating around a first valve member axis 174. Second movable valve member 181 is movable between the first and second positions by rotating around a second valve member axis 184.
When valve members 171 and 181 are in the respective first position depicted in
In some embodiments, valve members 171 and 181 are configured for cooperative movement, that is to say both valve members move together between the first position (
In some embodiments valve members 171 and 181 are configured for positioning in at least one intermediate position, between the first positions and the second positions, allowing fluid from a given inlet port to flow to two outlet ports. Specifically, a portion of the fluid entering valve 100 from ambient inlet port 151 is directed to compressor-inlet outlet port 161, and another portion is directed to heat-exchanger cold-stream inlet outlet port 162. Similarly, a portion of the fluid entering through compressor-outlet inlet port 152 is directed to heat-exchanger cold-stream inlet outlet port 162 and another portion is directed to exhaust outlet port 163. The utility of some such intermediate positions is described hereinbelow.
Gas-Turbine with 5-Port Valve 100
Valve 100 is configured to switch gas-turbine 10 between a high-pressure operation mode (Brayton cycle) depicted in
In
In
It is important to note that generally the flow directions through the various conduits including fluid conduits 120 of valve 100 are the same in both high-pressure operation mode and low-pressure operation mode, and do not change when switching gas-turbine 10 from one mode to the other.
In
Further Embodiments of Gas-Turbine with 5-Port Valve 100
In some embodiments, a gas-turbine comprises an embodiment of a valve similar to valve 100 of
Valve 100 is configured to switch gas-turbine 11 between a high-pressure operation mode in configuration “1” depicted in
In configuration “1” (
In configuration “2” (
Embodiment of 6-Port Valve Suitable for Use with Gas-Turbine
In some embodiments described above, exhaust exits gas-turbine 10 through two different outlets. In some embodiments described below the exhaust exits a gas-turbine through a single exhaust outlet.
Valve 102 further includes a first valve member 171 and a second valve member 181. First valve member 171 is movable inside valve body 110 having at least two positions: a first position, depicted in
Valve 102 also includes a check valve 130 operable as a unidirectional valve and configured in valve body 110 to allow fluid flowing from heat-exchanger hot-stream outlet inlet port 153 to any of the outlet ports 161, 162 or 163 of valve 102, and to block fluid flowing from any of the outlet ports of valve 102 out through heat-exchanger hot-stream outlet inlet port 153.
As discussed with reference to valve 100, in some embodiments, valve members 171 and 181 of valve 102 are configured for cooperative movement, that is to say both valve members move together between the first position (
As discussed with reference to valve 100, in some embodiments valve members 171 and 181 of valve 102 are configured for positioning in at least one intermediate position, between the first positions and the second positions, thereby allowing fluid from a given inlet port to flow to two outlet ports. The utility of some such intermediate positions is described hereinbelow.
Valve 102 is configured to switch gas-turbine 12 between a high-pressure operation mode depicted in
In
In
Additional Embodiment of 6-Port Valve Suitable for Use with Gas-Turbine
Valve 103 further includes three valve members, 171, 181 and 191.
First valve member 171 is movable inside valve body 110 having at least two positions: a first position as depicted in
Second valve member 181 is movable inside valve body 110 having at least two positions: a first position, depicted in
Third valve member 191 is movable inside valve body 110 having at least two positions: a first position, depicted in
Analogously to the discussed above with reference to valves 100 and 102, in some embodiments, two or three valve members 171, 181 and 191 are configured for cooperative movement. Analogously to the discussed above with reference to valves 100 and 102, in some embodiments, one or more valve members 171, 181 and 191 are independently operable.
Valve 103 is configured to switch gas-turbine 13 between a high-pressure operation mode depicted in
In
In
In general terms, in some embodiments a gas-turbine such as 13 is switched between a high-pressure operation mode and a low-pressure operation mode as is described above, using a six-port valve, having three inlet ports designated “X” (ambient inlet port 151), “Y” (compressor-outlet inlet port 152) and “Z” (heat-exchanger hot-stream outlet inlet port 153), and three outlet ports designated “x” (compressor-inlet outlet port 161), “y” (heat-exchanger cold-stream inlet outlet port 162) and “z” (exhaust outlet port 163). In a first configuration, the valve provides fluid communication exclusively between inlet port “X” and outlet port “x”, between inlet port “Y” and outlet port “y” and between inlet port “Z” and outlet port “z”. In a second configuration, the valve provides fluid communication exclusively between inlet port “X” and outlet port “y”, between inlet port “Y” and outlet port “z” and between inlet port “Z” and outlet port “x”. Providing flow communication exclusively between the specified pairs of inlet and outlet ports means that only fluid communication which is explicitly described between the specified ports is provided, and there is no fluid communication between the ports which is not explicitly described.
Aspects of the invention relate to multiport valves suitable for use with gas-turbines that allow switching between high-pressure, low-pressure and at least one intermediate-pressure operation modes of a gas-turbine. According to such embodiments, a valve is configured and operable to be in at least one intermediate configuration, in addition to the high-pressure (Brayton cycle) configuration “1” and low-pressure (inverse Brayton cycle) configuration “2” discussed above, for example in
In some embodiments, a mixing region 126 within fluid conduits 120 is configured to function as jet pump ejector. In some embodiments, such configuration includes fashioning at least one of valve members 171, 181 as an airfoil having a pre-defined aerodynamic profile. When mixing region 126 is configured as a jet pump ejector, the pressure of fluid flowing from compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port 162 drops, producing a suction zone (for example, through the Bernoulli effect). The suction zone sucks fluid from ambient inlet port 151 into valve 103 and to heat-exchanger cold-stream inlet outlet port 162.
Compressed fluid coming from compressor 20 flows into compressor-outlet inlet port 152 at high-pressure and is directed to both heat-exchanger cold-stream inlet outlet port 162 and to exhaust outlet port 163, the exact ratio dependent, inter alia, on the position of valve member 181.
Thus, in some embodiments when one or more of valve members 171, 181 and 191 are positioned in an intermediate position, for example as depicted in
In some embodiments an intermediate pressure operation mode of a gas-turbine such as 13 is obtained by positioning only one valve member 171, 181 or 191 in a respective intermediate position while the other two valve members are positioned in either a first or second position. In some embodiments, an intermediate pressure operation mode of gas-turbine 13 is obtained by positioning two valve members in a respective intermediate position, while the remaining valve member is positioned in either a first or a second position.
In some embodiments, a gas-turbine such as gas-turbine 13 comprising a valve with three valve members as described herein such as valve 103, is switched to an intermediate pressure operation mode by positioning a first valve member 171 and a second valve member 181 in an intermediate position, substantially as is described above, and positioning a third valve member 191 in a first position or in a second position.
Analogously, in some embodiments, a gas-turbine such as gas-turbine 10 of
In some embodiments, the position of at least one valve member is not continuously variable. That is to say, one or a series of intermediate pressure operation modes of gas-turbine 13 is obtained by maintaining at least one valve member in a fixed position while varying the position of the remaining valve members. In some embodiments, valve members 171, 181 and 191 are moveable between two endpoints, and may be maintained at a specific intermediate position between the endpoints. In such embodiments, valve 103 has at least three configurations, and gas-turbine 13 comprising valve 103 may be efficiently operated in at least three different pressure operation modes.
Returning to
In some embodiments, a valving system is provided that allows high-pressure operation mode and/or low-pressure operation mode of a gas-turbine (including, inter alia, a combustor and a heat-exchanger) at a continuously varying power output at relative high efficiency. Such a valving system operates by reducing the mass flow of fluid to the combustor through the heat-exchanger. Such mass flow reduction is similar to the achieved by inlet throttling, for example with the use of variable inlet guide vanes.
In the art, variable inlet guide vanes are often used with large gas-turbines. Such guide vanes are unsuitable for use with small turbines due to high expense and technical complexity at small sized. Further, as there is a need for matching between the whirl caused by the guide vanes and the compressor blades, the guide vanes can be varied only by about 15% which allows a change of about 20% in power output at reasonable efficiencies.
It is understood that valve 104 allows a gas-turbine to operate in a high-pressure operation mode in a continuity of configurations as described above, since valve member 181 is continuously in contact with valve seat 182, in the described continuity of positions, substantially blocking flow of fluid from compressor-outlet inlet port 152 to exhaust outlet port 163. Further, when valve 104 is in a high-pressure mode configuration as described above, valve member 171 is maintained in contact with valve seat 172, substantially blocking flow from ambient inlet port 151 to heat-exchanger cold-stream inlet outlet port 162.
Analogously to valve 100 as depicted in
It is understood that valve 105 allows a gas-turbine to operate in a low-pressure operation mode in a continuity of configurations as described above, since valve member 171 is continuously in contact with valve seat 173 in the described continuity of positions, substantially blocking flow of fluid from ambient inlet port 151 to compressor-inlet outlet port 161. Further, when valve 105 is in such a low-pressure mode configuration as described above, valve member 181 is maintained in contact with valve seat 183, substantially blocking flow from compressor-outlet inlet port 152 to heat-exchanger cold-stream inlet outlet port 162.
Analogously to valve 100 as depicted in
In some embodiments, a valve includes two separate valve members that allow both switching of an associated gas-turbine between a high-pressure and a low-pressure operation mode, and varying continuously the size of the path to the heat-exchanger. Referring to
In valve 106 depicted in
A similar variation in the size of the fluid path is implementable in a multiport valve analogous to the depicted in
In valve 107 depicted in
In valve 108 depicted in
Returning to
In the embodiments described above, the valve members are substantially plates configured to rotatably move between the different positions around a single axis close to or at an edge of the valve member. Generally, the teachings herein may be implemented using any suitable type of valve member. For example, in some embodiments valve members used include suitably-configured butterfly valves (especially tricentric butterfly valves), ball valves or rotary valves.
Gas-turbines using valves as described herein may be of any desired power capacity. That said, in some embodiments, a gas-turbine is configured for producing up to about 100 kW. In some embodiments, a gas-turbine is configured for producing from about 14 kW to about 40 kW of power. In some embodiments, a gas-turbine is configured for producing from about 7 kW to about 36 kW of power. Such low powers are useful, for example, for powering a small motor vehicle, such as a light truck or an automobile.
Aspects of the invention relate to gas-turbines operating in a low-pressure operation mode according to an inverse Brayton cycle that have reduced NOx emissions. Due to poor mixing and vaporization at low power operation which create local high temperature zones, gas-turbine NOx emissions are higher under partial load. In some embodiments of the invention, inlet air is mixed with a portion of exhaust and is directed into the combustor, thereby decreasing the oxygen content of the combustible mixture in the combustor, and as a result, reducing the amount of NOx emissions.
Thus, according to an aspect of some embodiments of the invention, there is provided a method of operating a gas-turbine according to an inverse Brayton cycle, comprising: a) providing a conduit allowing fluid communication between a compressor of the gas-turbine and a cold-stream inlet of a heat-exchanger of the gas-turbine; and b) during inverse Brayton cycle operation of the gas-turbine, directing fluid from the compressor to the heat-exchanger cold-stream inlet through the conduit so that a portion of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. In some embodiments, between about 30% and about 70% (in some embodiments, between about 40% and about 60%, in some embodiments between about 45% and about 55%) by mass of the fluid entering the heat-exchanger cold-stream inlet is from the compressor. In one specific preferred embodiment, approximately 50% by mass of the fluid entering the heat-exchanger cold-stream inlet is from the compressor.
In some embodiments, the method further comprises: adjusting a size of the conduit so as to control an amount of fluid entering the cold-stream inlet from the compressor.
According to an aspect of some embodiments of the invention there is also provided a gas-turbine comprising, when operating according to an inverse Brayton cycle, a) an air inlet configured to direct fluid into a cold-stream conduit of a heat-exchanger through a cold-stream inlet; b) conduits to direct fluid from the cold-stream conduit to a combustor, from the combustor to a turbine, from the turbine to a hot-stream conduit of the heat-exchanger, from the hot-stream conduit to a compressor, and from the compressor to an exhaust outlet; and c) a conduit allowing passage of fluid from the compressor into the cold-stream inlet of the heat-exchanger.
In some embodiments, the gas-turbine is configured to operate only according to an inverse Brayton cycle.
In some embodiments the gas-turbine is configured to optionally operate according to a Brayton cycle, for example as described herein. In some such embodiments, the gas-turbine is configured so that during operation according to a Brayton cycle, the conduit is substantially blocked preventing passage of fluid between the compressor and the cold-stream inlet.
In some embodiments, the conduit allowing passage of fluid from the compressor into the cold-stream inlet is of fixed size.
In some embodiments, the size of the conduit allowing passage of fluid from the compressor into the cold-stream inlet is adjustable, for example allowing varying an amount of fluid passing from the compressor into the cold-stream inlet.
In some embodiments, the conduit allowing passage of fluid from the compressor into the cold-stream inlet is configured so that during operation according to an inverse Brayton cycle between about 30% and about 70% (in some embodiments, between about 40% and about 60%, in some embodiments 45% and about 55%) by mass of the fluid entering the heat-exchanger cold-stream inlet is from the compressor.
In some embodiments, the conduit allowing passage of fluid from the compressor into the cold-stream inlet of the heat-exchanger is passive, that is to say, occurs due to the pressure differential between the two regions without investment of any additional work. In some embodiments, the conduit is active, that is to say, comprises a component such as a pump that performs work to direct fluid from the compressor to the cold-stream inlet of the heat-exchanger.
In the embodiment depicted in
Depending on the positions of valve members 171 and 181, gas-turbine 19 may be set in configurations analagous to the configurations depicted in for gas-turbine 10 in
Some such embodiments are superficially similar to reversed circulation methods implemented in internal combustion engines, where a significant amount of power is invested in recompressing exhaust into a high-pressure combustion chamber, reducing thermal efficiency but reducing NOx emissions. In contrast, in some embodiments of the invention advantage is taken of the fact that in a gas-turbine operating according to an inverse Brayton cycle the pressure in heat-exchanger cold-stream inlet is lower than at the compressor outlet, so that little if any power is used to bring the exhaust into the heat-exchanger cold-stream inlet. Additionally, in some embodiments, the thermal efficiency of the gas-turbine is increased by the mixing incoming ambient air with the hot exhaust.
Valve member 181 includes a unidirectional valve 186 (e.g., a reed valve) allowing fluid passage from region 121 to region 122 and to block fluid passage from region 121 to 122. Specifically, valve member 181 comprises conduit 185 providing fluid communication from a face 188 to a face 189 of valve member 181. Unidirectional valve 186 is disposed inside conduit 185. When the pressure in region 122 is greater than the pressure in region 121, valve 186 is closed, sealing conduit 185. When the pressure in region 121 is greater than the pressure in region 122, valve 186 opens allowing fluid (e.g., exhaust gas from compressor-outlet inlet port 152) to pass from region 121 to region 122.
Generally, the size of holes 185 determines the amount of exhaust gas mixed and therefore the oxygen content of the gas entering a combustor 26. In some embodiments, the amount of exhaust gas mixed can be controlled, for example, by changing the number or size of holes. It is understood that embodiments of permeable section 140 are not limited to the examples described above and permeable section 140 can comprise holes, slits, pores and the like, allowing passage of fluid from region 121 to region 122 of fluid conduits 120 valve 109.
The reduction of NOx emissions in a gas-turbine operating in low-pressure (inverse Brayton mode) is described with reference to embodiments depicted in
In some embodiments any of the valves of the invention described herein, e.g. valve 100, can be utilized to reduce NOx emission by permitting a portion of the oxygen-depleted exhaust gas to mix with incoming ambient air in low-pressure operation mode of a gas-turbine, by positioning valve member 181 close to, but not in contact with, valve seat 183, when operating the gas-turbine in low-pressure operation mode. Thus, when valve member 181 allows for fluid passage between compressor-outlet inlet port 152 and heat-exchanger cold-stream inlet outlet port 162 in low-pressure operation mode, exhaust gas is forced into the flow of incoming ambient air, where the amount of such exhaust passage is controlled by the exact positioning of valve member 181 with respect to valve seat 183.
In some embodiments, a gas-turbine configured for multipressure operation, e.g., such as described in U.S. Pat. Nos. 6,526,757 and 6,606,864, includes an additional valve (or an existing valve is modified) that allows passage of exhaust from the compressor outlet to mix with air entering the combustor during low-pressure (inverse Brayton) operation, thereby reducing NOx emissions.
In some embodiments, a gas-turbine configured for multipressure operation, e.g., such as described hereinabove, includes an additional valve (not associated with the valve that allows switching between high and low-pressure operation) defining a conduit that allows passage of exhaust from the compressor outlet to mix with air entering the combustor during low-pressure (inverse Brayton) operation, thereby reducing NOx emissions. In some embodiments, such an extra valve has two configurations: closed (blocking passage of exhaust) and open (allowing passage of exhaust) defining a fixed conduit size. In some embodiments, the valve is adjustable, allowing the size of the conduit to be adjusted to allow varying the amount of exhaust passing to mix with the air entering the combustor.
In some embodiments, a gas-turbine configured for low-pressure (inverse Brayton cycle) operation, e.g. such as known in the art, includes a valve defining a conduit that allows passage of exhaust from the compressor outlet to mix with air entering the combustor, thereby reducing NOx emissions. In some embodiments, such a valve has two configurations: closed (blocking passage of exhaust) and open (allowing passage of exhaust). In some embodiments, the valve is adjustable, allowing variation of the amount of exhaust passing to mix with the air entering the combustor.
In the above, oxygen-depleted exhaust is mixed with ambient air prior to entering the heat-exchanger of the gas-turbine. In some embodiments, the exhaust is mixed with the air after exiting the heat-exchanger cold-stream outlet and prior to entering the combustor. However, such embodiments are usually considered less advantageous as lowering combustor inlet temperature reduces thermal efficiency of the gas-turbine.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.
Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.
Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.
The present application gains priority from U.S. Provisional Patent Application No. 61/116,394 filed 20 Nov. 2008 which is included by reference as if fully set forth herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2009/055154 | 11/18/2009 | WO | 00 | 6/22/2011 |
| Number | Date | Country | |
|---|---|---|---|
| 61116394 | Nov 2008 | US |
