Internal combustion engine system
The system recovers waste heat from exhaust gases by vaporizing liquefied gas fuel to drive a turbine for electricity generation, ensuring efficient fuel supply to the internal combustion engine, thus maintaining engine efficiency and simplifying the system design.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KK TOYOTA CHUO KENKYUSHO
- Filing Date
- 2024-11-20
- Publication Date
- 2026-06-01
AI Technical Summary
Existing systems that recover waste heat from exhaust gas using liquefied ammonia face a decrease in supply efficiency due to ammonia becoming too hot in the gaseous state when the waste heat is significantly greater than its latent heat, leading to reduced gas density and efficiency in internal combustion engines.
A system that vaporizes liquefied gas fuel using exhaust heat, drives a turbine to generate electricity, and supplies the remaining fuel to the internal combustion engine, utilizing the waste heat for both fuel vaporization and electricity generation, with a control unit managing power generation load based on supply pressure.
This approach recovers waste heat without reducing supply efficiency to the internal combustion engine, allowing for a smaller and simpler system design by integrating fuel vaporization and electricity generation, and maintaining optimal fuel temperature and density.
Smart Images
Figure 2026089573000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an internal combustion engine system.
Background Art
[0002] Patent Document 1 discloses a system that vaporizes liquefied ammonia, which is a fuel, by using the waste heat of exhaust gas.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Here, in the configuration of Patent Document 1, when the amount of waste heat of exhaust gas is sufficiently larger than the latent heat of liquefied ammonia, if an attempt is made to sufficiently recover the waste heat, the ammonia will become too hot in the gaseous state. When the temperature of the fuel is high, the gas density decreases, and the supply efficiency to the internal combustion engine decreases.
[0005] In consideration of the above facts, an object of the present disclosure is to recover the waste heat of exhaust gas without reducing the supply efficiency to the internal combustion engine.
Means for Solving the Problems
[0006] A first aspect includes a tank that stores liquefied gas fuel, a heat exchanger that vaporizes the gas fuel from the tank by heat exchange with exhaust gas, a turbine driven by the gas fuel vaporized in the heat exchanger, a generator that generates electricity by the driving force of the turbine, and an internal combustion engine to which the gas fuel after driving the turbine is supplied and that discharges the exhaust gas.
[0007] In the first embodiment, gaseous fuel from a tank is vaporized by heat exchange with exhaust gas, and this fuel is used to drive a turbine. A generator generates electricity using the driving force of the turbine. The fuel remaining after driving the turbine is then supplied to an internal combustion engine. In this way, in the first embodiment, the waste heat from the exhaust gas is utilized for fuel vaporization and electricity generation by driving the turbine.
[0008] Therefore, even when the amount of waste heat from the exhaust gas is significantly greater than the latent heat of the fuel, compared to a configuration that uses the waste heat from the exhaust gas only for fuel vaporization, the temperature of the vaporized fuel supplied to the internal combustion engine does not become too high, and sufficient waste heat can be recovered. As a result, waste heat from the exhaust gas can be recovered without reducing the supply efficiency to the internal combustion engine.
[0009] The second embodiment includes a control unit that controls the power generation load of the generator in accordance with the supply pressure required for the gas fuel supplied to the internal combustion engine, as in the first embodiment.
[0010] According to the second embodiment, the control unit controls the power generation load of the generator in accordance with the required supply pressure of the gas fuel supplied to the internal combustion engine, so there is no need to provide an adjustment mechanism for adjusting the supply pressure between the turbine and the injector. Therefore, the system can be made smaller and simpler.
[0011] The third embodiment is a configuration in which, in the first embodiment, a portion of the gas fuel after driving the turbine is returned to the heat exchanger, and a circulation path is provided through which the gas fuel can flow in from the tank.
[0012] According to the third embodiment, since a portion of the fuel after driving the turbine can be returned to the heat exchanger, the turbine can be driven regardless of the amount of fuel consumed by the internal combustion engine. Therefore, the amount of waste heat recovered from the exhaust gas is not affected by the load on the internal combustion engine. [Effects of the Invention]
[0013] According to this disclosure, waste heat from exhaust gases can be recovered without reducing the supply efficiency to the internal combustion engine. [Brief explanation of the drawing]
[0014] [Figure 1] This is a schematic diagram showing the internal combustion engine system according to this embodiment. [Figure 2] This is a temperature-entropy diagram of the fuel in the internal combustion engine system according to this embodiment. [Figure 3] Figure 2 shows an example where the state of the fuel supplied to the internal combustion engine is below the saturated vapor line in the temperature-entropy diagram. [Figure 4] This schematic diagram shows a modified example of the internal combustion engine system according to this embodiment, which is further equipped with a supply mechanism for supplying auxiliary fuel. [Figure 5] This is a schematic diagram showing a modified example of the internal combustion engine system according to this embodiment, which has a Rankine cycle in which fuel is used as the working fluid to drive a turbine. [Modes for carrying out the invention]
[0015] An example of an embodiment according to the present invention will be described below with reference to the drawings. However, this disclosure is not limited to the following embodiments. When an embodiment is described in this disclosure with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings.
[0016] In the following drawings, similar parts are denoted by the same reference numerals. However, the sizes of the components in each drawing are conceptual, and the relative sizes of the components are not limited thereto. Furthermore, unless otherwise specified in the specification, the number of each component in this disclosure is not limited to one, but may be multiple.
[0017] <Internal Combustion Engine System> First, the internal combustion engine system 10 according to this embodiment will be described. Figure 1 is a schematic diagram showing the internal combustion engine system 10 according to this embodiment.
[0018] The internal combustion engine system 10 shown in FIG. 1 is a system that burns fuel in an internal combustion engine and obtains mechanical work using the combustion gas generated thereby. As shown in FIG. 1, the internal combustion engine system 10 includes a fuel tank 12, a supply pump 14, a heat exchanger 16, a turbine 18, a generator 20, an injector 24, an internal combustion engine 30, a throttle 33, and an exhaust gas purification device 38.
[0019] <The fuel tank 12 and the supply pump 14> The fuel tank 12 is a storage unit that stores liquefied gas fuel 13, which is liquefied gas fuel (hereinafter referred to as fuel 13). As the fuel 13, liquefied natural gas (LNG), liquefied petroleum gas (LPG), dimethyl ether (DME), ammonia, and the like can be used.
[0020] The supply pump 14 is a pump that supplies the fuel 13 stored in the fuel tank 12 to the heat exchanger 16. In the present embodiment, the supply pump 14 pressurizes the fuel 13 stored in the fuel tank 12 and pumps the fuel 13 to the heat exchanger 16.
[0021] Note that as the internal combustion engine system 10, at least a part of the fuel may be liquefied gas fuel, and a configuration in which diesel fuel such as light oil is supplied to the internal combustion engine 30 in addition to the liquefied gas fuel may be adopted.
[0022] <The heat exchanger 16> The heat exchanger 16 vaporizes the fuel 13 from the fuel tank 12 by heat exchange with the exhaust gas. In the heat exchanger 16, the heat of the exhaust gas is transferred to the fuel 13 to generate superheated steam. The superheated steam is supplied to the turbine 18.
[0023] In this embodiment, as shown in Figure 1, the heat exchanger 16 is located downstream of the exhaust gas purification device 38 in the exhaust pipe 34. Here, the exhaust gas sent to the heat exchanger 16 has unburned components (e.g., hydrocarbons) oxidized by the exhaust gas purification device 38, causing its temperature to rise. Therefore, by locating the heat exchanger 16 downstream of the exhaust gas purification device 38 in the exhaust pipe 34, the amount of waste heat recovered increases.
[0024] <Turbine 18 and Generator 20> The turbine 18 is a mechanical element driven by the fuel 13 vaporized in the heat exchanger 16. The generator 20 is a device that generates electricity using the driving force of the turbine 18. The electricity generated by the generator 20 can be used to operate auxiliary equipment in the internal combustion engine system 10 or to store electricity in the battery. The fuel 13, whose enthalpy has decreased after passing through the turbine 18, is supplied to the intake manifold 32 of the internal combustion engine 30.
[0025] <Injector 24, internal combustion engine 30, throttle 33, and exhaust gas purification device 38> The internal combustion engine 30 is a prime mover in which the combustion of fuel takes place inside the engine, and the thermal energy of the combustion gases is converted into mechanical energy. As an example of the internal combustion engine 30, an engine mounted on a vehicle (for example, a four-cylinder engine) can be used.
[0026] An intake manifold 32 is attached to the internal combustion engine 30, to which vaporized fuel 13 is supplied. An injector 24 is provided in the intake manifold 32 to supply fuel 13 to the internal combustion engine 30. A throttle 33 is provided on the internal combustion engine 30 to adjust the amount of intake air drawn into the engine. In the internal combustion engine system 10, the throttle 33 adjusts the amount of air drawn into the internal combustion engine 30, and the injector 24 injects fuel according to that amount of air to adjust the load on the internal combustion engine 30.
[0027] Furthermore, the internal combustion engine 30 is fitted with an exhaust pipe 34 that discharges the combustion gases (i.e., exhaust gases) remaining after the fuel has been burned inside. An exhaust gas purification device 38 is fitted to the exhaust pipe 34.
[0028] The exhaust gas purification device 38 has the function of converting nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC) contained in the exhaust gas into harmless carbon dioxide, water, nitrogen, oxygen, etc.
[0029] In this embodiment, the fuel 13 that has driven the turbine 18 is supplied to the internal combustion engine 30 by the injector 24. The amount of fuel supplied to the internal combustion engine 30 is controlled by the opening time of the injector 24.
[0030] Fuel 13 is burned in the internal combustion engine 30, and exhaust gas is discharged from the internal combustion engine 30 to the exhaust pipe 34. The exhaust gas is purified by the exhaust gas purification device 38 through the exhaust pipe 34 and then discharged to the outside of the internal combustion engine system 10 (for example, into the atmosphere).
[0031] <Relationship between temperature and entropy during the phase change of fuel 13> Here, we will explain the relationship between temperature and entropy in the state change of fuel 13 in the internal combustion engine system 10. Figure 2 shows the temperature-entropy diagram (TS diagram) of fuel 13.
[0032] As shown in Figure 2, fuel 13 is adiabatically compressed from state A by the supply pump 14 to state B. From state B, it undergoes an isobaric change by receiving heat from the heat exchanger 16, passing through point B1 on the saturated liquid line and point B2 on the saturated vapor line to become a gaseous state C. After this, it undergoes adiabatic expansion in the turbine 18 to become state D. The fuel 13 in state D is supplied to the internal combustion engine 30 by the injector 24.
[0033] In Figure 2, state D is above the saturated vapor line, and the fuel 13 is in a gaseous state. The amount of fuel supplied to the internal combustion engine 30 can be controlled by the opening time of the injector 24.
[0034] Note that the states A, B, C, and D in Figure 2 correspond to the states at points A, B, C, and D in Figure 1.
[0035] <Control of the supply pressure of fuel 13 supplied to the internal combustion engine 30> The internal combustion engine system 10 includes a control unit 50 that controls the power generation load of the generator 20 in accordance with the required supply pressure of the gas fuel supplied to the internal combustion engine 30. The control unit 50 controls the power generation load of the generator 20 based on the supply pressure detected by a sensor provided in the intake pipe 32 or the injector 24, for example.
[0036] This controls the gaseous fuel supplied to the internal combustion engine 30 to the required supply pressure. In response to this supply pressure, the injector 24 can adjust the amount of fuel 13 supplied to the internal combustion engine 30 by changing the valve opening time.
[0037] <Effects and Effects of Internal Combustion Engine System 10> In the internal combustion engine system 10, fuel 13 from the fuel tank 12 is vaporized by heat exchange with exhaust gas, and this fuel 13 drives the turbine 18. The generator 20 generates electricity using the driving force of the turbine 18. The fuel 13 that has driven the turbine 18 is then supplied to the internal combustion engine 30. In this way, the internal combustion engine system 10 utilizes the waste heat from the exhaust gas for vaporizing the fuel 13 and for generating electricity by driving the turbine 18.
[0038] In this case, if the waste heat from the exhaust gas is used solely for vaporizing the fuel 13, and the amount of waste heat from the exhaust gas is significantly greater than the latent heat of the fuel 13, then attempting to recover sufficient waste heat will cause the temperature of the fuel 13 to become too high while it is in a gaseous state. When the fuel temperature is high, the gas density decreases, and the supply efficiency to the internal combustion engine 30 decreases.
[0039] In contrast, the internal combustion engine system 10 utilizes the waste heat from the exhaust gas for vaporizing the fuel 13 and for generating electricity by driving the turbine 18. Therefore, even when the amount of waste heat from the exhaust gas is significantly greater than the latent heat of the fuel 13, the temperature of the vaporized fuel 13 supplied to the internal combustion engine 30 does not become too high, and sufficient waste heat can be recovered. As a result, waste heat from the exhaust gas can be recovered without reducing the supply efficiency to the internal combustion engine.
[0040] Furthermore, in the internal combustion engine system 10, the fuel 13 is used as a working fluid to recover waste heat and drive the turbine 18, and then consumed as fuel for the internal combustion engine 30. This eliminates the need for a separate working fluid passage in addition to the fuel 13 passage. As a result, the system can be miniaturized and simplified.
[0041] Furthermore, in the internal combustion engine system 10, the control unit 50 controls the power generation load of the generator 20 according to the required supply pressure of the gas fuel supplied to the internal combustion engine 30. Therefore, there is no need to provide an adjustment mechanism for adjusting the supply pressure between the turbine 18 and the injector 24. As a result, the system can be made smaller and simpler.
[0042] <Modified example of the state when fuel 13 is supplied to the internal combustion engine 30> The state of the fuel 13 when supplied to the internal combustion engine 30 (state D) may be below the saturated vapor line, as shown in Figure 3. In this case, the fuel 13 is in a gas-liquid mixture state. Even in this case, the amount of fuel can be controlled by the opening time of the injector 24, but flow rate control is difficult due to changes in the gas-liquid ratio.
[0043] In this case, the internal combustion engine system 10 may also be equipped with a separate supply mechanism 70 for supplying auxiliary fuel, as shown in Figure 4. The supply mechanism 70 includes an auxiliary tank 72, an intake pipe 74, and an injector 76.
[0044] The auxiliary tank 72 is a storage section for auxiliary fuel 73. The auxiliary fuel 73 may be a gaseous fuel such as hydrogen or methane, or a liquid fuel such as LPG or gasoline. Furthermore, the auxiliary fuel 73 may be fuel 13 taken from the fuel tank 12, or a gaseous fuel obtained by vaporizing fuel 13 by some means. Additionally, the auxiliary fuel 73 may be, for example, a mixed substance containing hydrogen produced by reforming ammonia with a catalyst.
[0045] Auxiliary fuel 73 is supplied to the internal combustion engine 30 from the auxiliary tank 72 through the intake manifold 74 by an injector 76. The amount of auxiliary fuel 73 supplied to the internal combustion engine 30 is controlled by the opening time of the injector 76. By adjusting the amount of auxiliary fuel 73 supplied in this way, it becomes easier to control the amount of fuel supplied to the internal combustion engine 30 (the amount including fuel 13 and auxiliary fuel 73).
[0046] <Modified example without supply pump 14> The internal combustion engine system 10 may be configured without a supply pump 14. In this case, the pressure of the fuel 13 taken from the fuel tank 12 is determined by the vapor pressure within the fuel 13, and this vapor pressure can drive the turbine 18.
[0047] <Modified form with Rankine cycle> This modified version, as shown in Figure 5, has a Rankine cycle 60 that drives a turbine 18 using fuel 13 as the working fluid. In the example shown in Figure 1, all of the fuel 13 supplied from the fuel tank 12 is supplied to the internal combustion engine 30 after passing through the turbine 18, whereas in this modified version, only a portion of the fuel 13 that has passed through the turbine 18 is supplied to the internal combustion engine 30.
[0048] This modified example includes a circulation path 62, flow control valves 64 and 66, and a condenser 68. The circulation path 62 is located between the fuel tank 12 and the injector 24 and circulates fuel 13 between the fuel tank 12 and the injector 24. Fuel 13 can flow in from the fuel tank 12.
[0049] A flow control valve 64 is provided between the fuel tank 12 and the circulation path 62. The flow control valve 64 adjusts the flow rate of fuel 13 flowing from the fuel tank 12 into the circulation path 62.
[0050] A flow control valve 66 is provided between the circulation path 62 and the injector 24. The flow control valve 66 adjusts the flow rate of fuel 13 flowing from the circulation path 62 to the injector 24.
[0051] The circulation path 62 includes a supply pump 14, a heat exchanger 16, a turbine 18, and a condenser 68. Fuel 13 supplied from the fuel tank 12 to the circulation path 62 passes through the supply pump 14, the heat exchanger 16, and the turbine 18 in that order. A flow control valve 66 supplies a portion to the injector 24 (internal combustion engine 30), and the remainder is sent to the condenser 68. The fuel 13 sent to the condenser 68 is converted back into liquid in the condenser 68. Therefore, the circulation path 62 returns a portion of the fuel 13 that has driven the turbine 18 to the heat exchanger 16. Fuel 13 is supplied to the circulation path 62 from the fuel tank 12 in the required amount by a flow control valve 64.
[0052] In this modified configuration, a portion of the fuel 13 after driving the turbine 18 can be returned to the heat exchanger 16. This allows the turbine 18 to be driven regardless of the amount of fuel 13 consumed by the internal combustion engine 30. As a result, the amount of waste heat recovered from the exhaust gas is not affected by the load on the internal combustion engine 30.
[0053] The present invention is not limited to the embodiments described above, and various modifications, changes, and improvements are possible without departing from the spirit of the invention. For example, the modified forms shown above may be combined in any way.
[0054] Furthermore, the following additional information is disclosed. (Note 1) A tank for storing liquefied gaseous fuel, A heat exchanger that vaporizes gaseous fuel from the aforementioned tank by heat exchange with exhaust gas, A turbine driven by gaseous fuel vaporized in the heat exchanger, A generator that generates electricity using the driving force of the turbine, An internal combustion engine is supplied with gaseous fuel after the turbine has been driven, and discharges the exhaust gas. An internal combustion engine system equipped with the following features. (Note 2) A control unit that controls the power generation load of the generator according to the supply pressure required for the gaseous fuel supplied to the internal combustion engine. An internal combustion engine system as described in Appendix 1, comprising: (Note 3) A portion of the gas fuel after driving the turbine is returned to the heat exchanger, and a circulation path is provided through which the gas fuel can flow in from the tank. An internal combustion engine system as described in Appendix 1 or Appendix 2, comprising: [Explanation of Symbols]
[0055] 10 Internal Combustion Engine Systems 12 fuel tanks 13. Liquefied gas fuel 14. Supply pump 16 Heat exchanger 18 Turbines 20 Generators 24 Injectors 30 Internal Combustion Engines 32 Intake pipe 33 Throttle 34 Exhaust pipe 38 Exhaust purifying device 50 Control Unit 60 Ranking Cycles 62 Circulation path 64 Flow control valve 66 Flow control valve 68 Condenser 70 Supply mechanism 72 Auxiliary tanks 73 Auxiliary fuel 74 Intake pipe 76 Injectors
Claims
1. A tank for storing liquefied gaseous fuel, A heat exchanger that vaporizes gaseous fuel from the aforementioned tank by heat exchange with exhaust gas, A turbine driven by gaseous fuel vaporized in the heat exchanger, A generator that generates electricity using the driving force of the turbine, An internal combustion engine is supplied with gaseous fuel after the turbine has been driven, and discharges the exhaust gas. An internal combustion engine system equipped with the following features.
2. A control unit that controls the power generation load of the generator according to the supply pressure required for the gaseous fuel supplied to the internal combustion engine. The internal combustion engine system according to claim 1, comprising:
3. A portion of the gas fuel after driving the turbine is returned to the heat exchanger, and a circulation path is provided through which the gas fuel can flow in from the tank. The internal combustion engine system according to claim 1, comprising: