Heat for non-regenerative supercritical carbon dioxide brayton cycle for liquefied natural gas power engines

Abstract

Systems and methods for burning liquefied natural gas (LNG) in an aircraft turbofan engine are disclosed. Various components utilize a non-recuperated supercritical carbon dioxide (sCO2) Brayton cycle that extracts heat from a heat exchanger (218) through which a main exhaust stream of a gas turbine engine flows. The sCO2 is split into two streams. One stream flows through an sCO2 turbine (226) that rotates a shaft (214) coupled to a gearbox (236) to perform useful work. The other stream is pressure balanced and recombined with the stream from the sCO2 turbine. The recombined stream flows through an evaporator (208) in a fuel injection system that converts the LNG to a gaseous natural gas (GNG) suitable for combustion.

Description

Technical Field

[0001] This disclosure relates generally to aircraft, and more specifically to systems and methods for generating power for liquefied natural gas-powered engines on aircraft. Background Technology

[0002] A growing area of ​​research and development in the aviation industry involves the use of liquefied natural gas (LNG) and other types of cryogenic fuels in aircraft turbofan engines. Using LNG-powered turbofan engines offers several potential advantages, including reduced carbon emissions, significantly lower nitrogen oxide emissions, improved aircraft efficiency, and higher specific energy than jet engine fuels. LNG also lacks many of the additional pollutants found in standard jet engine fuels (e.g., soot, mercury, sulfur dioxide, etc.). However, a drawback of existing and proposed LNG-based turbofan engines is that the combustion chamber requires LNG to be in a gaseous state, or gaseous natural gas (GNG), before combustion. Furthermore, researchers in this field generally believe that the heat generated by existing aircraft sources is insufficient to convert LNG into GNG for combustion, thus hindering the successful operation of turbofan engines. Summary of the Invention

[0003] This disclosure addresses and overcomes the aforementioned disadvantages by employing components as part of a system or method that uses supercritical carbon dioxide (sCO2) as the working fluid, along with heat energy from the main exhaust of a gas turbine engine and an evaporator in a fuel injection system, to create a non-regenerative Brayton cycle to absorb sufficient heat energy from the cycle's sCO2 to successfully convert LNG into GNG—suitable for injection into a combustor to burn GNG.

[0004] In one aspect of this disclosure, a system for a liquefied natural gas (LNG) powered aircraft includes an LNG turbine engine. The engine includes a combustor coupled between a main compressor and a main turbine, a main shaft coupled to the main turbine and the main compressor, and a heat exchanger through which main exhaust gas from the engine flows to heat sCO2.

[0005] The system also includes a fuel injection system coupled to a burner and comprising an evaporator, the evaporator having a first inlet and a first outlet through which LNG flows. The system also includes components for implementing a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle. These components include an sCO2 turbine coupled between a heat exchanger and a second inlet of the evaporator; an sCO2 compressor having an inlet coupled to a second outlet of the evaporator and an outlet coupled to the inlet of the heat exchanger for recirculating sCO2 through the heat exchanger; and an sCO2 shaft coupled to the sCO2 turbine and the sCO2 compressor. Some or all of the sCO2 heated from the heat exchanger flows through the sCO2 turbine to rotate the sCO2 shaft to operate the sCO2 compressor. The sCO2 from the second outlet of the evaporator is compressed by the sCO2 compressor.

[0006] The system also includes a controller configured to control (1) the flow of some or all of the sCO2 to the second inlet of the evaporator to convert LNG into gaseous natural gas (GNG) at the first outlet of the evaporator, and (2) the flow of GNG to the burner for burning GNG to run the engine.

[0007] In various embodiments, the engine includes a turbofan engine. These components may also include a pressure control valve disposed between a second output of the evaporator and the sCO2 turbine. The pressure control valve may be configured to control the circulating mass flow rate of the sCO2. LNG may include methane-based LNG, but in some embodiments, for the purposes of this disclosure, LNG may be considered to include cryogenic fuels such as liquefied hydrogen, or other variations defined below. A heat exchanger may be located in or near the main engine nozzles. The main turbine may include a high-pressure turbine and a low-pressure turbine. The main shaft may include a high-pressure shaft and a low-pressure shaft. The main compressor may include a high-pressure compressor and a low-pressure compressor.

[0008] In various embodiments, the components include a controllable bypass. The controllable bypass may include a splitter disposed between the input of the heat exchanger and the sCO2 turbine for receiving sCO2 heated from the heat exchanger and splitting the sCO2 into first and second sCO2 streams. The first sCO2 stream enters the sCO2 turbine. The controllable bypass may also include a pressure valve configured to receive a second sCO2 stream from the splitter and balance the pressure drop between the first and second sCO2 streams at the output of the sCO2 turbine. The controllable bypass may also include a mixer disposed between the output of the sCO2 turbine, the output of the pressure valve, and a second inlet of the evaporator. The mixer may be configured to recombine the first and second sCO2 streams to heat the second evaporator inlet, thereby evaporating LNG. The engine may also include a gearbox coupled to the sCO2 shaft, the main turbine, and the main shaft. The sCO2 shaft and the gearbox may be configured to generate additional power. The controller may be configured to use the controllable bypass to control how much power is used to generate additional power and how much power is used to heat the LNG.

[0009] In another aspect of this disclosure, a method for a liquefied natural gas (LNG) powered gas turbine engine includes absorbing thermal energy by passing the main exhaust gas cycle of the gas turbine engine through a heat exchanger arranged at or near the main exhaust nozzle. The method further includes receiving heated sCO2 from the heat exchanger and passing a portion of the heated sCO2 through an sCO2 turbine. The sCO2 turbine is coupled to an sCO2 shaft. The sCO2 shaft is coupled to an sCO2 compressor. The method further includes bypassing the remaining portion of the heated sCO2 through a different channel, recombining the heated sCO2 portion with the remaining heated sCO2, and passing LNG through a first inlet of an evaporator arranged in a fuel injection system. The method includes delivering the recombined sCO2 to a second inlet of the evaporator. The sCO2 has sufficient thermal energy to evaporate the LNG into gaseous natural gas (GNG) at a first outlet of the evaporator. The method also includes sending sCO2 exiting the evaporator through a second outlet via a sCO2 compressor to generate additional power through the sCO2 shaft, recirculating the sCO2 exiting the sCO2 compressor through a heat exchanger, and injecting a controlled amount of GNG from the evaporator into a combustor located in the engine to burn the GNG. The combustor is coupled between the main compressor and the main turbine, and the main airflow from the engine's main inlet passes through the main turbine to generate energy to operate the main turbine, thereby rotating the engine's main shaft for operation.

[0010] In various embodiments, the amount of thermal energy of the sCO2 and the controlled amount of GNG are regulated by a controller. The method may also include passing the bypassed remainder of the heated sCO2 through a pressure control valve to balance the pressure drop of the remaining heated sCO2 with that of the heated sCO2 exiting the sCO2 turbine. In some embodiments, the method may include controlling the circulating mass flow rate, including passing the sCO2 exiting the evaporator through another pressure control valve before sending the sCO2 through the sCO2 compressor. The method may include engaging a gearbox in an engine located between the main turbine and the main shaft via the sCO2 shaft to generate additional power. A fuel injection system may be positioned at a predetermined distance from the engine airflow. The engine may include a turbofan engine. The main turbine may include multiple turbines. The main compressor may include multiple corresponding compressors. The main shaft may include multiple corresponding shafts.

[0011] In another aspect of the invention, a system for a liquefied natural gas (LNG) powered aircraft includes an LNG turbine engine comprising a combustor coupled between a main compressor and a main turbine, a main shaft coupled between the main turbine and the main compressor, a heat exchanger through which main exhaust gas from the engine flows to heat sCO2, and a gearbox coupled between the main turbine and the main shaft. The system also includes a fuel injection system coupled to the combustor and including an evaporator having a first inlet and a second inlet through which LNG flows, and first and second outlets. The system further includes components for implementing a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle. The components include an sCO2 turbine, an sCO2 compressor, and an sCO2 shaft connected therebetween; an sCO2 splitter connected between a heat exchanger and the sCO2 turbine and configured to split the sCO2 into first and second sCO2 streams, the first sCO2 stream passing through the sCO2 turbine; a first pressure control valve configured to balance the pressure drop between the first and second sCO2 streams at the output of the sCO2 turbine; a mixer configured to recombine the first and second sCO2 streams at the output of the sCO2 turbine back into sCO2; and a second pressure control valve arranged between the sCO2 compressor and the outlet of a second evaporator and configured to control the mass circulation flow rate. After recombination, the sCO2 circulates through the evaporator via a second inlet and a second outlet. The sCO2 has sufficient thermal energy to evaporate the LNG flowing through the first inlet of the evaporator into gaseous natural gas (GNG) at the outlet of the first evaporator. The sCO2 compressor is connected via the second pressure control valve to the outlet of the second evaporator and to the input of the heat exchanger for recirculating the sCO2 leaving the outlet of the second evaporator through the heat exchanger. The sCO2 shaft is configured to rotate to operate (1) an sCO2 compressor, which is configured to compress sCO2 from the second outlet of the evaporator via a second pressure control valve, and (2) a gearbox to generate additional power.

[0012] In various embodiments, the system also includes a controller configured to control (1) the amount of thermal energy sufficient to convert LNG into GNG and (2) the amount of GNG injected into the burner to burn GNG.

[0013] The foregoing summary is not intended to represent every embodiment or aspect of this disclosure. Rather, it provides only examples of some novel concepts and features described herein. The foregoing features and advantages, as well as other features and accompanying advantages, will become apparent from the following detailed description of illustrative examples and representative modes for implementing this disclosure, taken in conjunction with the accompanying drawings and appended claims. Furthermore, this disclosure explicitly includes various combinations and sub-combinations of the elements and features presented above and below. Attached Figure Description

[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the specification, explain the principles of the present disclosure.

[0015] Figure 1 It is a perspective view of an aircraft having an integrated power generation system according to this disclosure.

[0016] Figure 2 This is a block diagram of a gas turbine engine, a fuel injection system, and components for realizing a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle for heating liquefied natural gas (LNG) fuel, according to one aspect of this disclosure.

[0017] Figure 3 It is shown that it is used for Figure 2 The curves of an exemplary phase diagram of a supercritical fluid in a power generation system.

[0018] Figure 4 This is an example flowchart of a method for implementing a non-regenerative Brayton cycle according to an embodiment.

[0019] The accompanying drawings are not necessarily drawn to scale and may present simplified representations of various features of this disclosure, including, for example, specific dimensions, orientations, locations, and shapes. In some cases, certain recognized features in the drawings may be omitted to avoid unduly obscuring the concepts of this disclosure. The details associated with these features may be determined in part by the specific intended application and use case environment. Detailed Implementation

[0020] This disclosure includes many different forms of implementation. Representative examples of this disclosure are shown in the accompanying drawings and are described in detail herein as non-limiting examples of the disclosed principles. Accordingly, elements and limitations described in the abstract, technical field, background, summary, and detailed description sections, but not expressly set forth in the claims, should not be incorporated individually or collectively into the claims by implication, reasoning, or otherwise.

[0021] For the purposes of this specification, unless otherwise stated, the use of the singular includes the plural, and vice versa; the terms “and” and “or” should be both conjunction and disjunction; and words such as “including,” “containing,” “comprising,” and “having” should mean “including, but not limited to.” Furthermore, approximate terms such as “about,” “almost,” “substantially,” “generally,” and “approximately” can be used in the sense of “being in, near, or close to,” or “within 0-5% of,” or “within acceptable manufacturing tolerances,” or logical combinations thereof. As used herein, a component “configured to” or “operable to” perform the specified function is capable of performing the specified function without modification, and not merely potentially capable of performing the specified function after further modification. In other words, when explicitly configured to perform the specified function, the described hardware is selected, created, implemented, used, programmed, and / or designed specifically for performing the specified function. The term “connection” used to describe a connection between two components (e.g., via a cable, channel, hardware connection, etc.) does not necessarily require the connection to be direct, unless otherwise specified in the claims.

[0022] The detailed description and accompanying drawings are intended to support and illustrate this teaching, but the scope of this teaching is defined solely by the claims. While some embodiments for implementing this teaching have been described in detail, various alternative designs and embodiments exist for practicing the teaching as defined in the appended claims. Furthermore, this disclosure explicitly includes combinations and sub-combinations of the elements and features presented above and below.

[0023] Figure 1This is a perspective view of an LNG-powered aircraft 102 with an integrated power generation system according to this disclosure. Aircraft 102 can operate with or without passengers as needed. Aircraft 102 can be a large passenger aircraft, a small aircraft for transporting a limited number of people, or another aircraft for transporting cargo. In other embodiments, aircraft 102 can be a high-speed aircraft. Aircraft 102 is merely one configuration of an aircraft capable of using different types of gas turbine engines, traveling at different speeds, and being equipped with other configurations as needed. For example, aircraft 102 can have different shapes, sizes, aspect ratios, etc., as needed. Therefore, for the purposes of discussion, aircraft 102 is shown only in a specific configuration.

[0024] Aircraft 102 has a fuselage 180 or airframe that can accommodate a cockpit and passenger or cargo sections. The aircraft in this embodiment has two wings 168, four liquefied natural gas (LNG) powered turbofan engines 162 (although other numbers of engines are possible), and an LNG tank 166 for transporting LNG at the necessary cryogenic conditions, which in this embodiment is located at the rear of the aircraft. The LNG engines are optionally or additionally integrated into the tail assembly 170; in other instances, the gas tank is integrated into the wings 168.

[0025] In some instances, engine 162 may include a main inlet nozzle 160, which includes a fan (partially visible) to which the main airflow is directed; a longitudinally guided housing 163 that may house components including a compressor, combustor or burner, turbine, shaft, and main nozzle 164, which may operate to exhaust the main exhaust to generate thrust. In some embodiments, the engine may include a splitter (not shown) whose outer periphery surrounds the main airflow region and is used to generate additional thrust. Aircraft 102 may include a nose cap 182 whose shape contributes to the aerodynamics of the aircraft during flight.

[0026] During operation of aircraft 102, LNG can be sourced from locations such as LNG tank 166 and delivered to engines 162. Adjacent to the engines is a fuel injection system (obscured from view) for injecting gaseous LNG into the combustors of each engine 162, as described below according to aspects of this disclosure. The natural gas is burned in the combustors to ignite air in the main airflow, causing combustion that results in continuous aircraft operation. Various areas of the wings 168 and aircraft 102—including areas adjacent to engines 162 or within the fuselage 180—may include electronic control circuitry for regulating engine operation and thermodynamic cycles to enable the engines to maintain continuous thrust. It should be noted that, in addition to engines in different locations or configurations, engines may also include at least some components responsible for performing functions related to regulating the Brayton cycle. Electronic control systems may also be included in the cockpit, and components within engines 162, as well as the fuel injection system and other components for performing thermodynamic cycles to achieve successful combustion in the engines, may be interconnected in different areas of the aircraft. For the sake of simplicity and to keep the focus on the key aspects of this disclosure, the electronic control system that controls the operation of the engine and the components that generate combustion heat is generally referred to as the controller of the aircraft 102.

[0027] In some embodiments, aircraft 102 includes a system for generating power from a heated surface. Extracting heat from the surface also cools it, allowing the surface to be formed of a material that does not require excessively high temperatures, thereby reducing material costs and weight. Examples of such systems can be found in co-pending U.S. Patent Application Publication No. US2022 / 0260036 A1, published August 18, 2002, and are expressly incorporated herein by reference as if fully set forth herein.

[0028] Apart from Figure 1 In addition to the aircraft 102, the liquefied natural gas (LNG) powered engine can be mounted in a dedicated area of ​​a small aircraft (such as a fighter jet or drone), in which case the engine can be shielded from view and housed within the aircraft itself. In other embodiments, as described above, the LNG engine can be located on the wing and / or tail of the aircraft (e.g., a passenger plane).

[0029] Based in part on information from original equipment manufacturers (OEMs) of aircraft engines, a scientific consensus has established that LNG needs to be converted into its gaseous (GNG) form before it can successfully initiate combustion in the combustor (also known as the combustion chamber) of a gas turbine engine. Therefore, LNG needs to evaporate before it can sustain the operation of a turbofan engine. However, as previously mentioned, existing heat sources from the aircraft are insufficient to generate enough heat to achieve this.

[0030] Therefore, in one aspect of this disclosure, a system and method are disclosed that rely on a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle to generate the heat required for LNG evaporation. In other aspects, these systems and methods can also be used to increase the power of other applications in aircraft, such as aircraft 102. While a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle has been shown by way of embodiment, other techniques for evaporating LNG into GNG and burning it are possible and are considered to fall within the spirit and scope of this disclosure. For example, architectures that can be implemented instead of a non-regenerative sCO2 Brayton cycle include regenerative Brayton cycles, cascaded architectures, recompression architectures, and variations thereof. Furthermore, while the working fluid is sCO2 in the following embodiments, other working fluids are also possible.

[0031] Figure 2 This is a block diagram of a gas turbine engine 202, a fuel injection system 204, and components 206 implementing a non-regenerative supercritical carbon dioxide (sCO2) Brayton cycle for heating liquefied natural gas (LNG) fuel, according to one aspect of this disclosure. The Brayton cycle is a thermodynamic cycle that more typically describes the operation of a gas turbine. The general principle is to extract energy from a flowing air-fuel mixture, for example, to do work, which includes providing the necessary thrust for flight. In this example, Figure 2 Component 206 enables a non-regenerative Brayton cycle using sCO2 as the working fluid. Other fluids involved in the relevant heat exchange during the non-regenerative sCO2 Brayton cycle will be further described below.

[0032] Figure 2 The example diagram illustrates the use of heat from the main engine exhaust to ultimately vaporize LNG into GNG via a non-regenerative sCO2 Brayton cycle. In a gas turbine engine, the main engine exhaust typically exits the engine through a main nozzle 216, which may be the engine's final longitudinal stage. As discussed in more detail below, Figure 2 The schematic diagram has the added advantage of simultaneously improving overall system efficiency by providing the ability to generate additional power to increase engine thrust or for other purposes. A gas turbine engine may include a splitter 244 circumferentially positioned around the main engine inlet for receiving a secondary airflow that can build pressure and exit through a secondary nozzle (NozSec) 254, which can typically generate significant thrust in existing engines. The splitter 244 used in existing gas turbine engines differs from splitter 220, which can operate in various embodiments to split a working fluid (sCO2) flow into two sCO2 flows for controlling heat transfer, as described herein.

[0033] Reference Figure 2A non-regenerative sCO2 Brayton cycle operates to connect the fuel injection system 204 to the LNG-powered gas turbine engine 202. While turbofan engines are discussed herein for illustrative purposes, the principles of this disclosure are equally applicable to other types of proposed or operating LNG-powered engines. The non-regenerative sCO2 Brayton cycle according to an embodiment will now be described. For clarity, a random time point is selected in the cycle at the outlet 207 of the evaporator 208 originating from the fuel injection system 204. After the sCO2 stream (hereinafter sometimes simply “sCO2”) leaves the evaporator 208 at outlet 207, the sCO2 initially travels through the pressure control valve 210. While the specific location of components relative to the engine or aircraft may vary based on specific designs and other criteria, the pressure control valve 210 is one of the components 206 involved in implementing the non-regenerative sCO2 Brayton cycle. Pressure control valve 210 can be used to control the circulating mass flow rate of sCO2 by changing the pressure drop between the outlet 207 of evaporator 208 and sCO2 compressor 212 by a specified amount (e.g., as indicated by controller 250). After the circulating mass flow rate is set, sCO2 is compressed by sCO2 compressor 212, thereby increasing the pressure of sCO2. (In subsequent cycles, compressor 212 can be used to repressurize sCO2 as it circulates through it). After compression, sCO2 is recirculated through heat exchanger 218. Heat exchanger 218 can be arranged longitudinally relative to engine 202, just before or within engine main exhaust nozzle 216 through which the engine main exhaust exits engine 202. Heat exchanger 218 can be any suitable design in which a first fluid (main exhaust) is introduced, and in which a second fluid (sCO2) physically separated from the first fluid by a thermally conductive material absorbs heat from the first fluid. At heat exchanger 218, sCO2 absorbs heat from heat exchanger 218 due to the very high temperature of the main engine exhaust. As described above, in some embodiments, the heat exchanger 218 may be physically positioned in or near the main nozzle 216 such that at least a portion of the flowing hot gas can be captured as the airflow passes through the engine 202 and exits the main nozzle 216.

[0034] It is also worth noting that the arrowed and non-arrowed lines between the various components through which sCO2 passes in the Brayton cycle (e.g., evaporator 208, pressure control valve 210, sCO2 compressor 212, heat exchanger 218, distributor 220, sCO2 turbine 226, pressure control valve 222, mixer 224, and return evaporator 208) can also be referred to as fluid channels. These fluid channels or pipes are manufactured to withstand the high pressure and high temperature of the sCO2 flowing through them.

[0035] The heat from the heat-conducting material in heat exchanger 218 enables sCO2 to maintain a temperature and pressure above its critical point. Figure 3The critical point of a substance is illustrated graphically, where temperatures and pressures above the critical point result in a supercritical fluid. The substance in this example is SO2. Figure 3 The lieutenant general noted that fluids exceeding the prescribed combination of pressure and temperature will eventually reach their critical point. One objective of this embodiment is to maintain the gas at or above its critical point to ensure that the sCO2 Brayton cycle continues and that the sCO2 contains sufficient heat to power the burner to perform combustion, as well as to generate additional power for further thrust and / or other uses.

[0036] In one embodiment, after recirculation through channels in heat exchanger 218, the newly heated sCO2 travels from heat exchanger 218 to a controllable splitter 220, where the sCO2 is split into two sCO2 streams. The main sCO2 stream flows through sCO2 turbine 226 for power extraction. The sCO2 turbine is a discrete component 206 of the engine turbine used to generate power in a non-regenerative Brayton cycle. For example, the main sCO2 stream can cause sCO2 turbine 226 to rotate a shaft (e.g., sCO2 shaft (Sh sCO2) 214) to initiate the conversion of a predetermined amount of thermal energy from the sCO2 into useful work. The secondary sCO2 stream is delivered to another pressure control valve 222. Pressure control valve 222 is configured to allow the secondary sCO2 stream to achieve the same pressure drop as the main sCO2 stream exiting the turbine at output 209. Thereafter, the main and secondary sCO2 streams are balanced in pressure and recombine into a single sCO2 stream via mixer 224.

[0037] Still referencing Figure 2 Component 206 therefore includes a controllable bypass feature (“controllable bypass”), characterized by a controllable splitter 220, an sCO2 turbine 226, a pressure control valve 222, a mixer 224, an sCO2 shaft 214, and the interconnections between each of these components. One or more of these components can be controlled by a controller 250, which can be broadly interpreted as one or more processors—similar or different, or other hardware components—placed close together or separate from each other. The controller, including one or more of these elements, controls how much heated sCO2 is used for additional power generation to provide additional thrust (or, in other instances, to provide an additional power source for the aircraft for different purposes), and how much power in the form of thermal energy is determined to be sufficient to heat the LNG. The relative amounts of sCO2 in the primary and secondary sCO2 streams can be set by the controller 250 according to the kinetic energy required for LNG combustion; for example, the surplus can be used to provide additional power to generate thrust for the aircraft engine 202 or for other purposes. The controller bypass or other components 206 may include sensors to feed back information to the controller, such as pressure, temperature, and other variables related to the cycle. Figure 2Sensors have been omitted to avoid further obscuring the operating principle of this disclosure.

[0038] As an example of the aforementioned controllable bypass, controller 250 can determine that the heated sCO2 from heat exchanger 218 may contain more heat energy than is sufficient to convert LNG into GNG for combustion. In this case, the controller can regulate the controllable splitter 220 by specifying how much heated sCO2 should be sent to the sCO2 turbine as part of the main sCO2 stream, and how much heated sCO2 should bypass the sCO2 turbine as part of the secondary sCO2 stream. The main sCO2 stream runs the sCO2 turbine, which in turn rotates the sCO2 shaft 214 to generate additional power. Because running the sCO2 turbine 226 requires work, the main sCO2 stream will lose a certain amount of heat energy. The sCO2 turbine 226 is used to generate the aforementioned additional power (undergoing unavoidable thermodynamic losses). After the secondary sCO2 stream flows through pressure control valve 222 to balance the pressure drop between the primary and secondary sCO2 streams at the output 209 of the sCO2 turbine 226, as described above, the primary and secondary sCO2 streams are recombined into a single sCO2 stream by mixer 224.

[0039] Therefore, the two streams are recombined to provide a predetermined amount of heat to the evaporator 208 to convert LNG into GNG. It should be noted that the controller 250 can also be coupled to and control other components in the controller bypass, such as the pressure control valve 222, mixer 224, sCO2 turbine 226, etc. In short, a controllable bypass can be used to prevent excessive waste of heat energy, for example, in the case where heated sCO2 from the heat exchanger is directly circulated to the evaporator 208 in the fuel injection system 204. In this case, it may be undesirable for the LNG to receive excessive heat energy, as sCO2 directly drawn from the heat exchanger could increase the evaporation rate to an excessive or unacceptable amount. In one embodiment, the controllable bypass addresses and corrects this problem by controlling the amount of heat energy sent to the inlet 245 of the evaporator 208.

[0040] While the specific hardware implementation of controller 250 depends on design choices, a particular instance includes one or more processors coupled to a current driver. The one or more processors may include any electronic and / or optical circuitry capable of performing the functions described herein. For example, the processor may perform any of the functions described herein with respect to controller 250. The processor may include one or more central processing units (CPUs), microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable logic devices (PLDs), control circuitry, etc. Some examples of processors include Intel® Core™ processors, Advanced Reduced Instruction Set Computing (RISC) machines (such as ARM® processors), etc. Controller 250 may be coupled to any component 206 implementing a non-regenerative sCO2 cycle and controlled bypass, including gas turbine engine 202, fuel injection system 204, and other electronic control units, via hardware or network connections used in the aircraft. Figure 2 In the text, the lines representing the aforementioned electrical / optical interconnections with various components and elements are greatly omitted to unduly obscure them. Figure 2 The operating principle explained in the text.

[0041] It should be emphasized that the controller 250 as defined herein may include a single controller, or multiple identical or different controllers located in different areas within a system or aircraft. For example, the controller 250 as defined herein may include two or more independent controllers, each for performing one or more individual functions. If more than one controller is implemented (i.e., the controller is divided into two or more controllers), some or all of the control / processing elements may be wirelessly or via hardware connections, cables, wires, or other conductive traces connected together or networked together. These connections may potentially include intervening components such as hardware, combinational logic, transistor arrays, passive devices (such as resistors, capacitors, inductors, transformers, diodes), etc. Therefore, controller 250 is considered to embody each of these variations and in Figure 2 The code is simplified using boxes to allow focus on the physical components that execute the loop and their interactions.

[0042] As described above, the sCO2 turbine 226 is connected to the sCO2 compressor via the sCO2 shaft 214. The sCO2 shaft 214 can also be connected to the gearbox 236 in the high-pressure shaft (ShH) 241 of the engine 202. Through this connection, the sCO2 shaft 214 can provide additional power generation capacity to the high-pressure shaft 241 in the engine 202, thereby increasing the aircraft's total thrust. In other configurations, the power generated by the main sCO2 flow through the sCO2 turbine can be used to rotate the shaft to generate additional power for other purposes within the aircraft.

[0043] After the primary and secondary sCO2 streams recombine at mixer 224, the resulting sCO2 is conveyed through a channel to inlet 245 of evaporator 208 in fuel injection system 204. Evaporator 208 includes two channels for conveying fluids. LNG 228 flows through the first channel of evaporator 208 via inlet 229. sCO2 flows through the second channel of evaporator 208 via inlet 245. Evaporator 208 then uses the heat from the sCO2 to heat the LNG 228 entering evaporator 208.

[0044] Controller 250 can regulate the flow rate of LNG 228. According to the aforementioned controllable bypass, sCO2 is configured to include sufficient thermal energy to convert LNG 228 into a gaseous form, or GNG 230, after absorbing the thermal energy. Therefore, GNG 230 exits the heat exchanger at outlet 243. Next, GNG 230 is injected into the combustor 238 of the gas turbine engine 202 through appropriately positioned channels or pipes. The injection rate of GNG 230 can be carefully adjusted by controller 250 as needed. Sufficient heat has been added to the fuel injection system 204 through the non-regenerative sCO2 cycle to enable the controllable injection of GNG 230 into the gas turbine engine 202, while the potential remaining useful work of the sCO2 shaft 214 can add more thrust as needed. In some implementations, the controllable flow of GNG 230 can be generated by the interaction of controller 250, which can adjust various inlets and outlets in the combustor so that the periodic amount of GNG 230 flowing to the combustor is appropriate, taking into account engine specifications, required thrust and other factors.

[0045] The LNG-powered gas turbine engine 202 can also operate as a conventional turbofan engine. Airflow enters the engine through inlet 248, propelled by fan 246, which generates suction at inlet 248 to collect a large volume of air. At splitter 244, the airflow is separated into a main flow and a bypass flow, the bypass flow surrounding the main flow circumferentially or peripherally. In one embodiment, the main flow enters the low-pressure compressor (CmpL) 242 and then the high-pressure compressor (CmpH) 240, which includes compressor blades (rotors) and fixed airfoil blades (stator). As the airflow moves through the low-pressure compressor 242 and the high-pressure compressor 240, the continuously decreasing rotor blades contribute additional energy and pressure to the airflow. Compressors 240 and 242 have the net effect of increasing the total pressure and energy of the airflow and converting the rotational energy present in the airflow into a more linear direction parallel to the longitudinal axis of engine 202. The compressed gas in the airflow is then heated in combustor 238 (also called combustion chamber), where GNG 230 is ignited and burned. Following this process, the high-pressure, high-temperature airflow enters high-pressure turbine (TrbH) 234 and then low-pressure turbine (TrbB) 232. The turbine may include a series of airfoil blades that rotate upon encountering the heated main airflow, thereby rotating the high-speed shaft 241 or low-speed shaft (ShL) 252, which are respectively connected to turbines 234 and 232. Because in this embodiment, the low-pressure shaft 252 and high-pressure shaft 241 are also connected to the low-pressure compressor 240 (for ShL 252) and the high-pressure compressor 240 and fan 246 (for ShR 252), respectively, the physical operation of the compressor and fan is maintained to achieve continuous engine operation.

[0046] Subsequently, in one embodiment, at least a portion of the main exhaust gas generated by the heated and compressed main airflow is conveyed through the passages of heat exchanger 218 to again transfer heat to the components of the non-regenerative sCO2 Brayton cycle, as described above. After passing through heat exchanger 218, the main exhaust gas can expand into the environment through the main nozzle (NozPrim) 216. The bypass flow can also significantly increase the thrust of the aircraft (in some cases, most of the thrust) as it exits the secondary nozzle (NozSec) 254, in a typical embodiment where the secondary nozzle 254 surrounds the main nozzle 216. It is also noteworthy that, according to one aspect of the invention, the high-pressure compressor 240 and high-pressure turbine 234 are also connected to the gearbox 236 via a high-pressure shaft 241 for additional power generation.

[0047] Advantageously, the systems and methods described above address the long-standing problem of maintaining LNG engine operation in a continuous and logical manner without introducing a large number of unnecessary components and interconnections into an already complex system to generate thrust to power the aircraft. However, the above implementation offers additional advantages. Besides successfully achieving combustion and providing additional power generation, using the aforementioned sCO2 Brayton cycle to heat the LNG allows the fuel injection system 204 to be physically positioned at a predetermined distance from the engine airflow prior to fuel injection. This relative positioning reduces system complexity because the GNG 230 can flow directly to the combustor 238 through at least one dedicated channel. This benefit can be seen, for example, by comparing the above implementation with theoretical suggestions considering the use of gas leaving the compressor as a heat source for the LNG 228. The latter approach could lead to some unnatural integration between the fuel injection system 204 and the gas turbine engine 202, requiring additional hardware even if it appears feasible, which could introduce additional interconnections and points of failure, potentially compromising the performance or integrity of the gas turbine engine 202.

[0048] In various embodiments, LNG 228 may consist primarily of methane, with smaller proportions of other components such as propane, butane, and possibly trace amounts of nitrogen. For the purposes of this disclosure and the appended claims, the terms "liquefied natural gas" or "LNG" also apply to cryogenic fuels that require vaporization before combustion. For example, in other embodiments, the principles of this disclosure are equally applicable to hydrogen, and for the purposes of this disclosure, LNG 228 may be interpreted as constituting liquefied hydrogen. Other variations and types of natural gas and cryogenic gases are also possible, referred to as LNG within the scope and spirit of this disclosure, and as GNG after vaporization.

[0049] Figure 4 This is an example flowchart of a method for implementing a non-regenerative Brayton cycle according to an embodiment. Figure 4 The steps in the process can be performed by various components 206, engine 202 or elements therein, fuel injection system 204 including evaporator 208, and controller 250. In implementation Figure 4 During the steps, Figure 2 Air or gas passages between any of the components described may also be involved. Feedback from the non-regenerative sCO2 Brayton cycle can be obtained from various sensors distributed throughout the system or connected to or near various components.

[0050] from Figure 4Starting at logic block 402, the main exhaust gas from the gas turbine engine, or a portion thereof, circulates through a heat exchanger located at or near the main exhaust nozzle to absorb heat energy, maintain the supercritical state of the sCO2, and ultimately use it for LNG evaporation. At logic block 404, heated sCO2 is received from the heat exchanger at a flow splitter. Then, at logic block 406, and according to control bypass features, the splitter allows a portion of the heated sCO2 to pass through the sCO2 turbine. The sCO2 turbine is connected to the sCO2 shaft. The sCO2 shaft is in turn connected to the sCO2 compressor. At logic block 408, the remaining portion of heated sCO2 that does not pass through the sCO2 turbine bypasses it through a different airflow path. At logic block 410, this remaining portion of heated sCO2 flows through a pressure control valve. In one embodiment, the controller can control the pressure control valve to balance the pressure of the remaining portion of heated sCO2 with the pressure of the portion of sCO2 leaving the sCO2 turbine.

[0051] Next, in logic block 412, according to the controller's regulation, a portion of the heated sCO2 is combined with the remainder of the heated sCO2 via a mixer. Additionally, at logic block 414, referring to fuel injection system 204, LNG is delivered from the storage tank through the first inlet of the evaporator in the fuel injection system. Simultaneously, at logic block 416 and referring back to the sCO2 Brayton cycle, the recombined sCO2 from the mixer is delivered to the second inlet of the evaporator. As the sCO2 passes through the evaporator, its thermal energy is sufficient to evaporate the LNG into GNG at the first outlet of the evaporator. Next, at logic block 418, the sCO2 exiting the second outlet of the evaporator is sent through the sCO2 compressor to generate additional power through the sCO2 shaft. In one embodiment, for example at logic block 420, the mass flow rate of the Brayton cycle can be controlled by allowing the sCO2 exiting the evaporator to pass through another pressure control valve to achieve a controlled pressure drop before sending the sCO2 through the sCO2 compressor. In this example, the other pressure control valve would be arranged between the second outlet of the evaporator and the input of the sCO2 compressor. The heated portion of the sCO2, through the flow of the turbine and the compression of the sCO2 compressor, causes the sCO2 shaft to rotate. At logic block 422, the sCO2 shaft engages with the gearbox in the engine located between the main turbine and the main shaft to generate the aforementioned additional power.

[0052] After the sCO2 passes through the sCO2 compressor and engages the sCO2 shaft, at logic block 424, the sCO2 exiting the sCO2 compressor is recirculated through a heat exchanger and reheated by the main exhaust, thus maintaining a continuous sCO2 Brayton cycle. The controller can be connected to one or more components 206 ( Figure 2 (and other components in the engine 202 and fuel injection system 204) to regulate this flow. Figure 4At logic block 426, the reference fuel injection system is returned. A controlled amount of GNG from the evaporator can be injected into the combustor located in the engine to burn GNG. As shown in the example above, the combustor is connected between the main compressor and the main turbine. The main airflow from the engine's main inlet generates energy through the main turbine to operate the main turbine, thereby rotating the engine's main shaft.

[0053] For the purposes of the above embodiments, engine 202 may include at least one main turbine, at least one main compressor, and at least one main shaft. That is, the main turbine can be interpreted as including one or more main turbines. The main compressor can be interpreted as including one or more main compressors. The main shaft can similarly be interpreted as including one or more main shafts. The sCO2 shaft can be connected via gearbox 236 (… Figure 2 It can be connected to any main turbine, so the gearbox 236 can be connected to the main shaft associated with that particular main turbine (if there is more than one).

[0054] The detailed description and accompanying drawings support and illustrate this teaching, but the scope of this teaching is defined solely by the claims. While some best modes and other embodiments for carrying out this teaching have been described in detail, various alternative designs and embodiments exist to practice the teaching as defined in the appended claims. Furthermore, this disclosure explicitly includes combinations and sub-combinations of the elements and features presented above and below.

[0055] This patent claims the benefit of U.S. Patent Application No. 18 / 392489, filed December 21, 2023. The entire contents of U.S. Patent Application No. 18 / 392489 are incorporated herein by reference. Priority of U.S. Patent Application No. 18 / 392489 is hereby claimed.

Claims

1. A system for a liquefied natural gas (LNG) powered aircraft, comprising: An LNG turbine engine includes a combustor connected between a main compressor and a main turbine, a main shaft connected to the main turbine and the main compressor, and a heat exchanger, wherein the main exhaust from the engine flows through the heat exchanger to heat supercritical carbon dioxide (sCO2). A fuel injection system coupled to the burner and including an evaporator, the evaporator including a first inlet through which LNG flows and including a first outlet; Components for implementing a non-regenerative (sCO2) Brayton cycle, the components including an sCO2 turbine, an sCO2 compressor, and an sCO2 shaft, the sCO2 turbine being connected between the heat exchanger and a second inlet of the evaporator, the sCO2 compressor having an input end connected to a second outlet of the evaporator and an output end connected to an input end of the heat exchanger for recirculating sCO2 through the heat exchanger, the sCO2 shaft being connected to the sCO2 turbine and the sCO2 compressor, wherein some or all of the sCO2 heated from the heat exchanger flows through the sCO2 turbine for rotating the sCO2 shaft to operate the sCO2 compressor, and wherein the sCO2 from the second outlet of the evaporator is compressed by the sCO2 compressor; and A controller configured to control (1) part or all of the flow of sCO2 to the second inlet of the evaporator to convert the LNG into gaseous natural gas (GNG) at the first outlet of the evaporator, and (2) the flow of the GNG to the burner for burning the GNG to operate the engine.

2. The system according to claim 1, wherein the engine comprises a turbofan engine.

3. The system of claim 1, wherein the component further comprises a pressure control valve disposed between a second output of the evaporator and the sCO2 turbine, the pressure control valve being configured to control the circulating mass flow rate of the sCO2.

4. The system of claim 1, wherein the LNG comprises liquefied hydrogen.

5. The system of claim 1, wherein the heat exchanger is located in or near the main engine nozzle.

6. The system of claim 1, wherein the main turbine comprises a high-pressure turbine and a low-pressure turbine.

7. The system according to claim 1, wherein the spindle comprises a high-pressure spindle and a low-pressure spindle.

8. The system according to claim 1, wherein the main compressor comprises a high-pressure compressor and a low-pressure compressor.

9. The system of claim 1, wherein the component includes a controllable bypass, the controllable bypass comprising: A splitter is disposed between the heat exchanger and the input end of the sCO2 turbine for receiving sCO2 heated from the heat exchanger and splitting the sCO2 into first and second sCO2 streams, the first sCO2 stream entering the sCO2 turbine. A pressure valve is configured to receive the second sCO2 flow from the splitter and to balance the pressure drop between the first sCO2 flow and the second sCO2 flow at the output of the sCO2 turbine. and A mixer, arranged between the output of the sCO2 turbine, the output of the pressure valve, and the second inlet of the evaporator, is configured to recombine the first and second sCO2 streams to heat the second inlet of the evaporator, thereby evaporating the LNG.

10. The system according to claim 9, wherein The engine also includes a gearbox connected to the sCO2 shaft, the main turbine, and the main shaft, the sCO2 shaft and the gearbox being configured to generate additional power.

11. The system of claim 10, wherein the controller is configured to use the controllable bypass to control a first amount of energy for generating the additional power and a second amount of energy for heating the LNG.

12. A method for using a liquefied natural gas (LNG) powered gas turbine engine, comprising: The main exhaust of the gas turbine engine is circulated through a heat exchanger located at or near the main exhaust nozzle, thereby absorbing heat energy. Heated supercritical carbon dioxide (sCO2) is received from the heat exchanger; A portion of the heated sCO2 is passed through an sCO2 turbine, which is connected to an sCO2 shaft, which is connected to an sCO2 compressor. The remaining portion of the heated CO2 is bypassed through different channels; A portion of the heated sCO2 is recombined with the remaining portion of the heated sCO2; The LNG is passed through the first inlet of the evaporator arranged in the fuel injection system; The recombined sCO2 is fed to the second inlet of the evaporator, the sCO2 having sufficient thermal energy to evaporate the LNG into gaseous natural gas (GNG) at the first outlet of the evaporator; The sCO2 exiting the second outlet of the evaporator is sent through the sCO2 compressor to generate additional power through the sCO2 shaft; The sCO2 flowing out of the sCO2 compressor is recirculated through the heat exchanger; and A controlled amount of GNG is injected from the evaporator into a combustor located in the engine to burn the GNG. The combustor is connected between the main compressor and the main turbine. The main airflow from the main inlet of the engine generates energy through the main turbine to operate the main turbine, thereby rotating the main shaft of the engine.

13. The method of claim 12, wherein the amount of thermal energy of the sCO2 and the controlled amount of the GNG are regulated by a controller.

14. The method of claim 12, further comprising passing the remaining portion of the heated sCO2 bypassed through a pressure control valve to balance the pressure drop of the remaining portion of the heated sCO2 with the portion of the heated sCO2 exiting the sCO2 turbine.

15. The method of claim 14, further comprising controlling the circulating mass flow rate, including passing the sCO2 exiting the evaporator through another pressure control valve before sending the sCO2 through the sCO2 compressor.

16. The method of claim 12, further comprising engaging a gearbox in the engine located between the main turbine and the main shaft via the sCO2 shaft to generate the additional power.

17. The method of claim 12, wherein the fuel injection system is located at a predetermined distance from the main airflow.

18. The method according to claim 12, wherein: The main turbine includes multiple turbines; The main compressor includes multiple corresponding compressors; and The spindle includes multiple corresponding axes.

19. A system for a liquefied natural gas (LNG) powered aircraft, comprising: An LNG turbine engine includes a combustor connected between a main compressor and a main turbine, a main shaft connected to the main turbine and the main compressor, and a heat exchanger, wherein the main exhaust from the engine flows through the heat exchanger to heat supercritical carbon dioxide (sCO2). A fuel injection system coupled to the burner and including an evaporator, the evaporator including a first inlet and a second inlet through which LNG flows, and the evaporator also including first and second outlets; The first fluid passage between the heat exchanger and the evaporator is used to deliver heated sCO2 to the second inlet of the evaporator, such that the heated sCO2 flowing through the heat exchanger causes the LNG to be converted into GNG when gaseous natural gas (GNG) flows through the first outlet of the evaporator; The second fluid passage, located between the second outlet of the evaporator and the sCO2 compressor, is used to repressurize the sCO2; and A third fluid channel, located between the compressor's output and the heat exchanger, is used to recirculate the sCO2 through the heat exchanger. The GNG is configured to flow controllably through a conduit to the burner for combustion, thereby enabling the engine to operate continuously to power the aircraft.

20. The system of claim 19 further includes a controller configured to control (1) an amount of thermal energy of the sCO2 sufficient to convert the LNG into the GNG, and (2) an amount of the GNG injected into the burner for burning the GNG.

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