JP2010064745A - Engine system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine system on which a medium chemically repeating the storage and release of hydrogen is mounted and which can suppress the discharge of CO<SB>2</SB>and is excellent in system efficiency. <P>SOLUTION: The engine system includes a hydrogen supply device which generates hydrogen rich gas from the medium chemically repeating the storage and release of hydrogen and drives an engine using, as one of the fuels, the hydrogen rich gas generated by the hydrogen supply device. The engine system includes a waste heat supply device for supplying the waste heat of the engine to the hydrogen supply device, a generator for generating a power by the power of the engine, a power storage device for charging the electric power generated by the generator, and a motor for converting the electric power discharged from the power storage device into a power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrogen engine system equipped with a medium that chemically repeats storage and release of hydrogen and using a hydrogen rich gas generated from the medium as a fuel.

  In a system that is equipped with a hydrogen supply device that generates hydrogen-rich gas from the medium and that chemically stores and releases hydrogen, and supplies the engine with the hydrogen-rich gas generated by the hydrogen supply device, the hydrogen supply device It is necessary to supply heat for generating the hydrogen-rich gas. By utilizing the waste heat of the engine for this heat, it is not necessary to supply new energy to the hydrogen supply device, so that the system becomes highly efficient. However, since the engine waste heat varies depending on the operating point, a system for managing the engine waste heat supplied to the hydrogen supply device is required.

  As described in, for example, Patent Document 1, a conventional heat and power management system has a configuration of an engine, a reformer, and a fuel cell. Or a system that combines both an engine and a system that manages power using the load-efficiency characteristics of the fuel cell.

JP 2000-303836 A

The system described in Patent Document 1 is a hybrid system that uses an engine that uses a medium as fuel, and a fuel cell that generates power using a fuel gas containing hydrogen reformed by a reformer and an oxidizing gas as a power source. is there. In this hybrid system, since the fuel supplied to the engine serves as a medium, it is difficult to suppress CO ₂ emissions. On the other hand, in the system that supplies the hydrogen-rich gas generated by the hydrogen supply device to the engine, it is possible to suppress CO ₂ emission and to make the system excellent in environmental performance. However, in the system that supplies the hydrogen-rich gas generated by the hydrogen supply system to the engine, the fuel reformed from the medium using the engine waste heat is supplied to the engine, so the engine waste heat and the engine efficiency are managed accordingly. There is a need to. Further, in order to make the whole system highly efficient, a system for managing power such that a motor, a power storage device, and an engine are combined and the engine operating point is operated in a region with high thermal efficiency is required.

An object of the present invention is to provide an engine system that can suppress CO ₂ emission and is excellent in system efficiency in an engine system equipped with a medium that chemically stores and releases hydrogen.

  An engine system comprising a hydrogen supply device that generates a hydrogen-rich gas from a medium that chemically repeats storage and release of hydrogen, and driving the engine using the hydrogen-rich gas generated by the hydrogen supply device as one of fuels, A waste heat supply device that supplies waste heat of the engine to the hydrogen supply device, a generator that generates power using the power of the engine, a power storage device that charges the power generated by the generator, and a discharge from the power storage device And an engine system including a motor that converts the generated electric power into power. In this engine system, power is generated by the power of the engine, the power storage device is charged, discharged from the power storage device according to the user's request, and converted into power by the motor, so that the motor follows the user's request. . Therefore, the engine operation does not need to completely follow the user's request, the heat supply ratio of the engine waste heat supplied to the hydrogen supply device is high, and the engine can be driven in a highly efficient operation region. It is characterized by low consumption rate and high system efficiency.

According to the present invention, it is possible to generate power using hydrogen-rich gas generated from a hydrogen supply device, so that it is possible to suppress CO ₂ emission, provide a low system consumption rate, and provide an engine system with high system efficiency. it can.

The block diagram of the whole system. The relationship between the engine operating state and the amount of hydrogen that can be generated by the hydrogen supply device. Relationship between engine operating conditions and engine thermal efficiency. Relationship between engine operating conditions and engine exhaust gas temperature. Relationship between engine operating conditions and hydrogenation medium consumption rate. The operation | movement flowchart of the whole system. A heat supply control method by a combustor to a hydrogen supply device. The block diagram of a hydrogen supply apparatus. The block diagram of a combustor. The whole system block diagram which supplies a dehydrogenation medium to an engine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of the entire system. A medium that stores hydrogen chemically (hereinafter referred to as a hydrogenation medium) is mounted in the hydrogenation medium tank 1, and the hydrogenation medium is supplied to the hydrogen supply device 3. The medium stored in the dehydrogenation medium tank 2 is fuel after hydrogen is released from the hydrogenation medium by the hydrogen supply device 3 (hereinafter, dehydrogenation medium). The hydrogenation medium is, for example, hydrocarbon fuels such as decalin, cyclohexane, and methylcyclohexane, and their mixed fuels. The dehydrogenation medium is hydrocarbon fuels such as naphthalene, benzene, and toluene, and their mixed fuels. Show. The case where methylcyclohexane is used as the hydrogenation medium will be described below.

  The hydrogen supply device 3 performs the following reaction.

C ₇ H ₁₄ (methylcyclohexane) ⇒C ₇ H ₈ (toluene) + 3H ₂ (hydrogen) −205 kJ
... Formula (1)
According to the above formula (1), the generated toluene and hydrogen are separated into toluene and hydrogen by the separator 12, hydrogen is supplied to the engine 5, and the toluene is recovered in the dehydrogenation medium tank 2. Since hydrogen supplied to the engine 5 may be mixed with toluene or methylcyclohexane, it is hereinafter referred to as hydrogen-rich gas. In order to generate 1 mol of hydrogen from methylcyclohexane from the formula (1), a calorific value of about 68 kJ / mol is required. Therefore, the gas of the engine 5 is supplied to the hydrogen supply device 3. In order to keep the reaction temperature within a predetermined range (250 to 400 ° C.), the exhaust gas flow rate of the exhaust gas from the engine 5 is adjusted by the exhaust gas flow rate adjusting device 13 to the hydrogen supply device 3. The engine 5 is connected to the generator 6, and the electric power generated by the generator 6 is charged into the power storage device 7. The power storage device 7 also includes a power conversion device. Electric power is discharged from the power storage device 7 to the motor 8 to transmit power to the tire 10. Further, when the tire 10 is decelerated, regenerative energy is generated by the generator 9 and the power storage device 7 is charged. When the amount of heat necessary for the reaction formula (1) is insufficient for the hydrogen supply device 3, the amount of heat is supplied from the combustor 4 or the power storage device 7 via the heater 11. The power supply to the heater 11 may be performed only by power conversion without discharging the power in the power storage device 7 and discharged to the motor. Although the hydrogen rich gas is supplied to the combustor 4, a dehydrogenation medium may be supplied as necessary. With the configuration of FIG. 1, the stored fuel uses a hydrogenation medium that is a liquid fuel, and when generating power, the hydrogen supply device 3 generates a hydrogen rich gas and supplies it to the engine 5 to generate power. It becomes composition. The liquid fuel is stored with high safety, convenience, and energy density, and the entire system is configured to generate power without discharging CO ₂ .

  FIG. 2 shows the relationship between the amount of hydrogen that can be generated by the engine 5 and the hydrogen supply device 3.

When the engine speed and the engine torque that are the operating states of the engine 5 are determined in S201, the exhaust gas temperature T_ex, the exhaust gas flow rate F_ex, and the engine exhaust gas specific heat Cp_ex of the engine 5 are determined in S202. Assuming that the minimum temperature of reaction formula 1 is T_re and the heat recovery efficiency is η_re, in S203, the heat quantity Q ₁ that can be supplied to the hydrogen supply device 3 is determined as follows.

Q ₁ = F_ex · Cp_ex · (T_ex−T_re) · η_re Equation (2)
By determining Q _{1, the} amount of heat necessary to generate 1 mol of hydrogen is 68 kJ from equation (1), and therefore the hydrogen amount F ₂ that can be generated by the hydrogen supply device 3 is determined in S204. On the other hand, when the operating state of the engine 5 is determined by S201, determines the thermal efficiency of the engine, the amount of hydrogen F ₁ is determined necessary to the engine 5 at S205. In the configuration of FIG. 1, in order to improve fuel efficiency, it is necessary to reduce the medium consumption rate. For that purpose, it is necessary to consider the following values.

・ F ₁ −F ₂・ Pe / (F ₁・ L _H2 )
However, Pe is an output of the engine 5. L _H2 is the lower heating value of hydrogen.

When F ₁ -F ₂ is 0 or less, only the exhaust gas heat of the engine can cover the amount of heat necessary for the hydrogen supply device 3. That is, when F ₁ -F ₂ is 0 or less, the consumption rate of the hydrogenation medium depends only on Pe / (F ₁ · L _H2 ). On the other hand, when F ₁ -F ₂ is larger than 0, it is necessary to supply heat quantity other than the exhaust gas from the combustor 4 or the heater 11 of FIG. 1 to the hydrogen supply device 3, and as F ₁ -F ₂ increases, The amount of heat supplied from the combustor 4 or the heater 11 increases. When this amount of heat is large, the consumption rate of the medium increases and the fuel consumption deteriorates. Therefore, it is desirable that F ₁ -F ₂ is 0 or less, or when F ₁ -F ₂ is greater than 0, the consumption rate of the hydrogenation medium is F ₁ -F ₂ , Pe / (F _1. Both L _H2 ). That is, when F ₁ -F ₂ is 0 or less, Pe / (F ₁ · L _H2 ) is increased, and when F ₁ -F ₂ is greater than 0, Pe / (F ₁ · L _H2 ) is increased, By reducing F ₁ -F ₂ , the consumption rate of the hydrogenation medium can be reduced.

The relationship between the operating conditions of the engine 5 and the engine thermal efficiency is shown in FIG. Generally, in the case of a spark ignition engine, the engine thermal efficiency is high in a region where the engine torque is high. When the engine thermal efficiency is high, Pe / (F ₁ · L _H2 ) is high, so that the medium consumption rate is low. On the other hand, FIG. 4 shows the relationship between the operating conditions of the engine 5 and the engine exhaust gas temperature at a predetermined position of the exhaust pipe. The higher the engine output, the higher the exhaust temperature of the engine 5. As the exhaust temperature of the engine 5 increases, Q ₁ increases from the equation (2), and F ₂ increases. Therefore, F ₁ −F ₂ becomes small, and the consumption rate of the medium becomes small. When the engine having the characteristics shown in FIGS. 3 and 4 is used in the engine 5 having the configuration shown in FIG. 1, the region where the consumption rate of the hydrogenation medium is small is as shown in FIG. Thus, when the operating point of the engine 5 is determined, the consumption rate of the hydrogenation medium is determined. Thus, in this system, since the heat supply rate from the engine 5 to the hydrogen supply device 3 affects the consumption rate map of the hydrogenation medium, the thermal efficiency of the engine does not necessarily match the consumption rate of the hydrogenation medium.

  FIG. 6 shows an operation flowchart of the entire system. Based on the vehicle speed and accelerator opening in S601 and S602, the power requested by the user is determined in S603. Thereafter, the motor is controlled in S604 by the power output from the power storage device in S605. In S606, the remaining amount of the power storage device is measured, and the requested engine output is determined in S607 so that the remaining amount is within a predetermined range. Further, the required engine output may be determined based on the required power in S603. Based on the required engine output and the hydrogenation medium consumption rate map in S608, the engine speed and engine torque are set so that the hydrogenation medium consumption rate is minimized on the engine output line in S609 as shown in FIG. The generator 6 and the engine 5 are controlled in S610 and S611 so that the engine speed and the engine torque are determined. Then, heat supply control to the hydrogen supply device 3 is performed in S612.

  A heat supply control method by the combustor 4 to the hydrogen supply device 3 is shown in FIG. In S701 of the engine 5, the heating amount of the combustor 4 is determined in S703 from the current operating point and the insufficient heat amount map of the hydrogen supply device 3 in S702, and the supply amount of the hydrogen rich gas to the combustor 4 in S704. And a hydrogen rich gas is supplied to the combustor 4. It is determined whether the hydrogen rich gas supply amount is within the predetermined range in S706 from the hydrogen rich gas limit supply map in S705 and the current engine operating region in S701. The hydrogen rich gas limit supply map in S705 is determined by the oxygen concentration in the engine exhaust gas. The oxygen concentration in the engine exhaust gas is determined by the ratio of fuel and air supplied to the engine. That is, when the engine operating range is determined, the limit supply amount of the hydrogen rich gas is determined. If this limit is exceeded, it is necessary to reduce the supply amount of the hydrogen rich gas in S707. Thereafter, in S709, it is examined in S710 whether the catalyst temperature detected by the catalyst temperature measuring device or the estimating device is within the predetermined range. If the catalyst temperature is out of the predetermined range, the process proceeds to S703 so that the catalyst temperature is within the predetermined range. Thus, the heating amount of the combustor 4 is controlled. In the heat supply control method, heat may be supplied using the heater 11 instead of the combustor 4.

  Next, the configuration of the hydrogen supply device 3 shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 8, the structure of the hydrogen supply device 3 is a catalyst made of Pt / alumina catalyst on pure aluminum (thermal conductivity: 250 W / mK) high thermal conductive substrate 22 provided with flow passage protrusions 21. Layer 24 is formed. A hydrogen separation membrane 20 that selectively permeates only hydrogen is laminated on the catalyst layer 24, and a structure in which the hydrogen flow path 18 is laminated via the spacer 19 is a basic structure and is installed in the engine exhaust pipe.

  The hydrogenation medium supplied to the hydrogen supply device 3 passes through the fuel flow path 23, proceeds with the dehydrogenation reaction while contacting the catalyst layer 24 formed on the surface of the high thermal conductive substrate 22, and generates hydrogen. The produced hydrogen passes through the hydrogen separation membrane 20 and is discharged from the hydrogen supply device 3 through the hydrogen channel 18 via the spacer 19. Further, the hydrogen that has not permeated the hydrogen separation membrane 20 and the dehydrogenation medium are discharged out of the hydrogen supply device 3 through the fuel flow path 23. The hydrogen discharged here and the dehydrogenation medium merge with the hydrogen discharged from the hydrogen flow path 18, mixed, and supplied to the separation device 12 of FIG. 1. The hydrogen discharged from the hydrogen flow path 18 may be supplied between the separation device 12 and the engine 5 without being mixed with the hydrogen discharged from the fuel flow path 23 and the dehydrogenation medium. In FIG. 8, the hydrogen separation membrane 20 is provided in order to efficiently perform the dehydrogenation reaction from the hydrogenation medium at a low temperature. However, a configuration without the hydrogen separation membrane 20 is also possible. Further, the basic structure shown in FIG.

  FIG. 9 shows a configuration diagram of the combustor 4. In the configuration in which the exhaust gas from the engine 5 is supplied to the hydrogen supply device 3, the hydrogen supply device 3 exhibits a temperature distribution in the flow direction of the exhaust gas. Depending on the operating conditions of the engine 5, the catalyst temperature is such that hydrogen can be generated in the exhaust gas upstream part of the hydrogen supply device 3, but the catalyst temperature decreases in the exhaust gas downstream part of the hydrogen supply device 3 and hydrogen generation is impossible. An area where the catalyst temperature range is reached appears. At this time, as shown in FIG. 9, the hydrogen supply device 3 is installed on the upstream side and the downstream side of the exhaust gas of the combustor 4, and the hydrogen rich gas generated in the upstream portion of the exhaust gas of the hydrogen supply device 3 is used for the hydrogen supply device 3. , And supplied into the exhaust pipe on the downstream side. By doing so, it becomes possible to compensate for the heat shortage in the hydrogen supply device 3 installed in the exhaust gas downstream portion with the heat supplied to the hydrogen supply device 3 installed in the exhaust gas upstream portion.

  After the exhaust gas and the hydrogen rich gas are mixed by the mixing device 16, the oxygen and the hydrogen rich gas in the exhaust gas are burned by the ignition device 15. Instead of the ignition device 15, a catalyst may be used for combustion. The mixing device 16 mixes the exhaust gas and the hydrogen-rich gas in a blade-like structure that imparts a swirl to the flow, or a structure that mixes by providing protrusions and throttles. With this system, oxygen in the exhaust gas has a higher temperature than oxygen in the outside air, so the amount of hydrogen-rich gas required to improve to a predetermined combustion gas temperature is small, and the thermal efficiency of the combustor 4 is increased. In addition, compared with the case of using oxygen from the outside air, the number of newly required auxiliary equipment such as a pump is reduced, so that the system is low-cost and simple.

  In order to burn hydrogen-rich gas using oxygen in the exhaust gas, it is necessary to perform lean combustion in the engine 5. The oxygen concentration in the air when the lean burn is performed is detected using the oxygen concentration detectors 17 and 25. From the oxygen concentration detected by the oxygen concentration detector 17, monitoring is performed so as not to supply the combustor 4 with an amount of hydrogen-rich gas over which oxygen is completely combusted. Alternatively, when the oxygen concentration detection device 25 is used, the supply of the hydrogen rich gas to the combustor 4 is controlled so that the oxygen concentration does not become a predetermined value or less.

  FIG. 10 shows the configuration of a system for supplying the dehydrogenation medium to the engine 5.

  When the catalyst temperature of the hydrogen supply device 3 is low and the power storage rate of the power storage device 7 is low as when the engine 5 is started, the hydrogen supply device 3 generates a hydrogen rich gas amount necessary for the engine 5. It is difficult to generate necessary power by the motor 8. In that case, the dehydrogenation medium is supplied from the dehydrogenation medium tank 2 to the engine 5. At this time, either the hydrogen-rich gas and the dehydrogenation medium or only the dehydrogenation medium may be supplied to the engine 5. Alternatively, when the dehydrogenation medium is insufficient, the hydrogenation medium may be supplied to the engine 5. When methylcyclohexane is used as the hydrogenation medium, the dehydrogenation medium is toluene, and the octane number is equal to or higher than that of gasoline. Therefore, the engine 5 can be operated.

  Further, with such a configuration, the engine 5 can be operated at a higher output than when the output of the engine 5 is supplied with only hydrogen-rich gas. Further, there is a feature that the dehydrogenation medium can be supplied to the engine 5 when the storage amount of the hydrogenation medium tank 1 is exhausted.

  Further, the dehydrogenation medium may be supplied to the combustor 4 without being supplied to the engine, and heat may be supplied to the hydrogen supply device 3.

DESCRIPTION OF SYMBOLS 1 Hydrogenation medium tank 2 Dehydrogenation medium tank 3 Hydrogen supply apparatus 4 Combustor 5 Engine 6, 9 Generator 7 Electric power storage apparatus 8 Motor 10 Tire 11 Heater 12 Separation apparatus 13 Exhaust gas flow rate adjustment apparatus 14 Hydrogen rich gas supply apparatus 15 Ignition Device 16 Mixing device 17, 25 Oxygen concentration detection device 18 Hydrogen flow path 19 Spacer 20 Hydrogen separation membrane 21 Flow path protrusion 22 High thermal conductive substrate 23 Fuel flow path 24 Catalyst layer

Claims (9)

A hydrogen supply device that generates a hydrogen-rich gas and a dehydrogenation medium by a dehydrogenation reaction of a hydrogenation medium that chemically stores hydrogen;
A separation device for separating the hydrogen-rich gas produced by the hydrogen supply device and the dehydrogenation medium;
An engine that drives the hydrogen-rich gas separated by the separator as one of fuels;
A waste heat supply device for supplying waste heat of the engine to the hydrogen supply device;
A generator for generating electric power from the engine;
A power storage device for charging the power generated by the generator;
An engine system comprising: a motor that converts electric power discharged from the power storage device into power.   The engine system according to claim 1, further comprising a catalyst temperature estimation device that estimates or detects a catalyst temperature of the hydrogen supply device, wherein the catalyst temperature of the hydrogen supply device is equal to or lower than a predetermined temperature, and a storage amount of the power storage device An engine system characterized by supplying the hydrogenation medium or the dehydrogenation medium to the engine when is below a predetermined level.   The engine system according to claim 1, wherein electric power output from the power storage device to a motor is controlled with respect to required power requested by a user, and based on a remaining amount of the power storage device or the required power. Control for determining the engine output and controlling the engine speed and the engine torque so that the consumption rate of the hydrogenation medium supplied to the hydrogen supply device is minimized with respect to the engine output determined based on the required power. An engine system comprising the device.   The engine system according to claim 1, further comprising a catalyst temperature estimation device that estimates or detects a catalyst temperature of the hydrogen supply device, wherein the waste heat amount adjustment device adjusts the waste heat amount based on the catalyst temperature. Engine system.   5. The engine system according to claim 4, wherein the waste heat supply device includes a waste heat amount adjusting device that adjusts an amount of waste heat from the engine. The engine system according to claim 1, comprising at least one of a combustion device that burns the hydrogen-rich gas generated by the dehydrogenation medium or the hydrogen supply device, and a heater.
An engine system that supplies heat of the combustion device or heater to the hydrogen supply device.   The engine system according to claim 6, wherein the hydrogen supply device is mounted on an exhaust pipe of the engine, and the combustion device includes a hydrogen rich gas supply device that supplies a hydrogen rich gas into the exhaust gas, and a combination of the exhaust gas and the hydrogen rich gas. An engine system comprising an ignition device for igniting a mixed gas.   8. The engine system according to claim 7, wherein an oxygen concentration detection device that detects an oxygen concentration of exhaust gas between the combustion device and the engine, and an oxygen concentration that detects an oxygen concentration contained in the exhaust gas downstream of the combustion device. An engine system comprising at least one of detection devices.   9. The engine system according to claim 8, wherein a supply amount of the hydrogen rich gas or the dehydrogenation medium supplied to the combustion device is controlled based on a value of the oxygen concentration detection device.

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