JP2015161214A - motor jet engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify and downsize structure of a motor jet engine and furthermore to secure high efficiency and high thrust thereof.SOLUTION: A motor jet engine comprises: a casing having an intake port and an exhaust nozzle; a compressor provided in the casing and compressing the air sucked in from the intake port; a motor connected to the compressor and driving the compressor; a fuel cell which is provided closer to the exhaust nozzle side than the compressor in the casing, generates electric power and supplies the electric power to the motor and heats the compressed air with thermal energy generated by heat generation during the electric power generation; and a combustor which is provided closer to the exhaust nozzle side than the fuel cell in the casing, mixes the compressed air heated by the fuel cell with fuel, combusts the resultant mixture and discharges the exhaust from the exhaust nozzle.

Description

  The present invention relates to a motor jet engine using power generation and exhaust heat by a built-in fuel cell.

  As shown in FIG. 10, the conventional jet engine 100 includes a compressor 101, a combustor 102, and a turbine 103, for example. Furthermore, the conventional jet engine 100 is configured based on the Brayton cycle. The air adiabatically compressed by the compressor 101 is mixed with the fuel injected in the combustor 102 and burned under an equal pressure to generate high-temperature and high-pressure gas. The high-temperature high-pressure gas is adiabatically expanded while driving the turbine 103 and is discharged through the nozzle 104. The compressor 101 and the turbine 103 are connected by a single shaft 105. The conventional jet engine 100 rotates the turbine 103 by transmitting rotational work to the compressor 101 via the shaft 105.

  Here, the parameters indicating the efficiency of the Brayton cycle are thermal efficiency and specific output. In order to obtain a high specific output, it is necessary to increase the temperature ratio. Furthermore, when the temperature ratio is increased, the pressure ratio at which the thermal efficiency is maximized increases. Therefore, the conventional jet engine 100 requires the working fluid to have a high temperature and a high pressure in order to achieve high output and high efficiency. In addition, since the conventional jet engine 100 has a limit in increasing the pressure ratio in the case of single-stage compression, the pressure ratio is increased by using multistage compression to achieve high efficiency.

  Furthermore, as described above, the conventional jet engine 100 needs to flow high-temperature and high-pressure gas in order to achieve high efficiency. This high-temperature and high-pressure gas hits the turbine 103. Therefore, it is necessary to provide the turbine blades constituting the turbine 103 with a material having a property capable of withstanding high temperature and pressure and a cooling structure. However, it is difficult to increase the efficiency of materials that can withstand high temperatures and pressures because they have heat and pressure limits. In addition, the use of heat-resistant / pressure-resistant materials leads to an increase in production cost. Furthermore, providing a cooling structure for the turbine blades requires advanced processing technology, making it difficult to manufacture and process. Further, since the structure becomes complicated, the entire system cannot be enlarged. Furthermore, in terms of maintenance and inspection, the turbine blades need to be carefully inspected, which causes problems such as labor and cost. Further, in the conventional jet engine 100, the pressure decreases when the high-temperature high-pressure gas generated in the combustor 102 adiabatically expands while driving the turbine 103. For this reason, the pressure at the inlet of the exhaust nozzle decreases, and all the work that can be taken out cannot be taken out.

JP 2012-505348 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a motor jet engine that can be simplified in terms of structure such that a turbine is not necessary. It is another object of the present invention to provide a motor jet engine that can ensure high efficiency and high thrust.

  A motor jet engine according to the present invention includes a casing having an intake port and an exhaust nozzle, a compressor provided in the casing and compressing air sucked from the intake port, and coupled to the compressor. A motor for driving the compressor and an exhaust nozzle side of the compressor in the casing are configured to generate electric power to supply the electric power to the motor and to compress the heat by heat energy generated during power generation. A fuel cell that heats the heated air and an exhaust nozzle side of the fuel cell in the casing. The fuel is mixed with the compressed air heated by the fuel cell, burned, and discharged from the exhaust nozzle. Combustor.

  Furthermore, a solid oxide fuel cell (SOFC) may be used as the fuel cell.

  In the motor jet engine of the present invention, the compressor is electrically driven using the electric power generated by the fuel cell, so that it is not necessary to incorporate a turbine for driving the compressor in the casing. That is, the motor jet engine of the present invention can omit the turbine. Therefore, the motor jet engine of the present invention can be expected to reduce the size of the entire rotating system including the axial length. Furthermore, since the motor jet engine of the present invention can omit the turbine, the structure can be simplified and the cost can be reduced.

  Furthermore, the motor jet engine of the present invention generates heat by itself during power generation. Therefore, in the motor jet engine of the present invention, the fuel cell is provided closer to the intake port than the combustor in the casing, and the air compressed by the compressor is heated by the heat energy generated by the heat generated during the power generation of the fuel cell. Thus, the thermal energy generated by the heat generated by the fuel cell can also be extracted and used as a thrust. Furthermore, the motor jet engine of the present invention improves the combustion efficiency of the combustor by preheating the air compressed by the compressor with the heat energy generated during the power generation of the fuel cell before combustion by the combustor. Can be made. Therefore, the motor jet engine of the present invention can ensure high efficiency and high thrust as compared with the conventional jet engine having the same pressure ratio and temperature ratio.

  That is, the motor jet engine of the present invention may have a fuel flow rate smaller than that of the conventional jet engine when the thrust comparable to that of the conventional jet engine is ensured. It can be expected to obtain a larger thrust than the jet engine.

It is the schematic which showed the motor jet engine to which this invention is applied. 1 is a block diagram showing a motor jet engine to which the present invention is applied. It is the figure which showed the energy balance of the motor jet engine to which this invention is applied. It is the graph which showed the relationship between equivalence ratio and cell temperature. It is the graph which showed the relationship between cell temperature and power generation efficiency. It is the graph which showed the relationship between cell temperature and a pressure ratio. It is the graph which showed the relationship between cell temperature and total efficiency. It is the graph which showed the relationship between cell temperature and a dimensionless ratio output. It is the graph which showed the relationship between cell temperature and the Mach number of exhaust gas. It is the block diagram which showed the conventional jet engine.

  Hereinafter, a motor jet engine to which the present invention is applied will be described in detail with reference to the drawings. In addition, this invention is not limited to the following examples, It can change arbitrarily in the range which does not deviate from the summary of this invention.

<1. Description of motor jet engine configuration>
The motor jet engine 1 to which the present invention is applied is, for example, a jet engine mounted on an aircraft on which a person can board, an unmanned aircraft on which a person does not board, an hobby aircraft, or the like. Further, the motor jet engine 1 does not have a turbine, and the compressor is not driven by a turbine directly connected to the compressor like a conventional jet engine, but is driven by external power, so-called a motor jet engine. It is.

  Specifically, as shown in FIG. 1, the motor jet engine 1 includes a casing 2 having an intake port 2a and an exhaust nozzle 2b, a compressor 3 that compresses air sucked from the intake port 2a, and a compressor 3 And a motor 4 that drives the compressor 3, a fuel cell 5 that generates electric power and supplies the electric power to the motor 4, and mixes and burns the compressed air with fuel and discharges it from the exhaust nozzle 2b. Combustor 6.

  As shown in FIG. 1, the casing 2 has substantially the same structure as that of a conventionally known jet engine casing, and is formed in a cylindrical shape having an intake port 2a and an exhaust nozzle 2b. Further, the casing 2 includes a compressor 3, a motor 4, a fuel cell 5 and a combustor 6. Further, in the casing 2, the compressor 3 (motor 4), the fuel cell 5, and the combustor 6 are arranged in this order from the intake port 2 a toward the exhaust nozzle 2 b. Further, the exhaust nozzle 2b of the casing 2 is provided to expand the combustion gas generated by the combustor 6 to increase the air flow velocity and exhaust the combustion gas. In the casing 2, an afterburner that is a reburning device for completely burning the unburned residue of the combustor 6 may be further disposed on the exhaust nozzle 2 b side than the combustor 6.

  As shown in FIG. 1, the compressor 3 is provided on the intake port 2 a side in the casing 2. Furthermore, the compressor 3 is composed of a compressor used in a conventionally known jet engine such as a centrifugal compression type or an axial flow compression type. Further, the compressor 3 may be configured by providing at least one of a centrifugal compression type compressor and an axial flow compression type compressor, and at least one of both. It may be configured to be provided.

  And the compressor 3 compresses the air suck | inhaled from the inlet 2a. Furthermore, the compressor 3 supplies the compressed air to the fuel cell 5 (cathode 5a) as shown in FIG.

  The motor 4 is an electric motor for driving the compressor 3 as shown in FIG. Further, the motor 4 is provided in the casing 2 and is directly connected to the rotating shaft of the compressor 3 or indirectly through a transmission member such as a gear group. Further, the motor 4 is electrically connected to the fuel cell 5 and is driven by power supplied from the fuel cell 5.

  As shown in FIG. 1, the fuel cell 5 is provided on the exhaust nozzle 2 b side of the compressor 3 in the casing 2 and on the intake port 2 a side of the combustor 6. That is, the fuel cell 5 is provided in a so-called cold section through which low-temperature air flows. Further, the fuel cell 5 is electrically connected to the motor 4. The fuel cell 5 may be any fuel cell as long as it is a conventionally known fuel cell. For example, the fuel cell 5 is a solid oxide fuel cell that is excellent in operation at high temperatures, has a high load, and has a high degree of freedom in fuel selection. Solid Oxide Fuel Cell (SOFC) is preferred.

  As shown in FIG. 2, in the fuel cell 5, air is supplied to the cathode 5 a of the fuel cell 5 and raw fuel is supplied to the reformer 9 by, for example, a blower (or pump) 8 and reformed by the reformer 9. Is supplied to the anode 5b of the fuel cell 5. Then, the fuel cell 5 generates electric power and supplies the electric power to the motor 4. The fuel cell 5 may supply the generated power to the motor 4 via a motor regulator such as a DC / AC inverter. Further, the fuel cell 5 may be configured such that the raw fuel is directly supplied to the anode 5 b without using the blower (or pump) 8 or the reformer 9.

  Furthermore, the fuel cell 5 generates heat itself during power generation. Therefore, the fuel cell 5 heats the air compressed by the compressor 3 and guided to the combustor 6 by the heat energy generated by the heat generated during power generation. That is, the motor jet engine 1 also uses thermal energy generated by heat generation during the power generation of the fuel cell 5 as a thrust.

  As shown in FIG. 1, the combustor 6 is provided on the exhaust nozzle 2 b side of the fuel cell 5 in the casing 2. Further, the combustor 6 has substantially the same structure as a conventionally known jet engine combustor. The combustor 6 mixes the fuel with the compressed air heated by the fuel cell 5 and burns it, and discharges the generated high-temperature exhaust gas from the exhaust nozzle 2 b to the outside of the casing 2.

  In the motor jet engine 1 configured as described above, the electric power generated by the fuel cell 5 is supplied to the motor 4, and the compressor 3 is driven by the motor 4. That is, in the motor jet engine 1, the compressor 3 is electrically driven using the electric power generated by the fuel cell 5.

  Next, in the motor jet engine 1, when the compressor 3 is driven, the air sucked from the intake port 2 a is compressed by the compressor 3, and the air compressed by the compressor 3 is heated by the fuel cell 5. That is, the motor jet engine 1 takes out and uses the thermal energy generated by the heat generated by the fuel cell 5 as a thrust.

  Next, in the motor jet engine 1, fuel is mixed with the compressed air heated by the fuel cell 5 and burned by the combustor 6, and the generated high-temperature exhaust gas is discharged from the exhaust nozzle 2 b to the outside of the casing 2. The engine output is obtained by being discharged. At this time, in the motor jet engine 1, the high-temperature exhaust gas generated by the combustor 6 becomes the highest pressure in the exhaust nozzle 2b, and the expansion ratio that is the ratio between the total inlet pressure and the total outlet pressure can be increased. The exhaust speed can be increased.

  Here, FIG. 3A shows the energy balance of a conventional jet engine in which a compressor and a turbine for driving the compressor are connected by a single shaft. In FIG. 3B, a compressor and a turbine for driving the compressor are connected by at least one shaft, and a fuel cell such as a solid oxide fuel cell (SOFC) is incorporated. It shows the energy balance of a jet engine with a built-in fuel cell. In FIG. 3C, the present invention in which the turbine for driving the compressor is not incorporated in the casing 2 and the fuel cell 5 such as a solid oxide fuel cell (SOFC) is incorporated is applied. The energy balance of the motor jet engine 1 is shown.

  As shown in FIG. 3 (A), the conventional jet engine has energy 20 that can be extracted when all the fuels shown in FIG. 3 (A) have reacted. And the conventional jet engine has the energy 21 as shown to (b) in FIG. 3 (A), when a fuel is mixed with the air compressed with the compressor with the combustor. Specifically, the total energy 21 from which work is extracted is the sum of the energy 20 that can be extracted when all the fuel has reacted and the energy 21a that the air compressed by the compressor has.

  When the conventional jet engine is burned by the combustor, it has energy 22 as shown in (c) of FIG. Specifically, the total energy 21 of the energy 20 that can be taken out when all of the fuel has reacted and the energy 21 a that the air compressed by the compressor has becomes the thermal energy 22.

  As shown in (d) of FIG. 3 (A), a part 23a of this thermal energy 22 is released to the outside of the casing as heat transfer loss and heat of exhaust gas, and the other 23b is taken out as work. . Then, as shown in FIG. 3A, (e), the work 23b to be taken out is used by a part 24a for driving the compressor via the turbine (= the air compressed by the compressor is The energy 21a) and the other 24b are extracted to the outside. Here, for example, it is the thrust of the engine.

  As shown in FIG. 3B, the conventional jet engine with a built-in fuel cell has energy 30 that can be taken out when all the fuels shown in FIG. And the conventional fuel cell built-in type jet engine has the energy 31 as shown to (b) in FIG.3 (B), when a fuel is mixed with the air compressed with the compressor by the combustor. Specifically, the energy 31 is the total energy of the energy 30 that can be extracted when all of the fuel has reacted and the energy 31a that the air compressed by the compressor has.

  When the conventional fuel cell built-in jet engine is combusted by the combustor and generated by the fuel cell, it has energy 32 as shown in (c) of FIG. Specifically, it has thermal energy 32a obtained from energy 31 and electrical energy 32b obtained from power generation of the fuel cell.

  As shown in (d) of FIG. 3B, the heat energy 32a is partly released to the outside of the casing as heat transfer loss and exhaust gas heat, and the other 33b is taken out as work. . Then, as shown in FIG. 3B, (e), the work 33b to be taken out is used by a part 34a for driving the compressor via the turbine (= the air compressed by the compressor is The energy 31a) and the other 34b are extracted to the outside. Here, for example, it is the thrust of the engine.

  As shown in FIG. 3 (C), the motor jet engine 1 to which the present invention is applied has energy 40 that can be taken out when all the fuels shown in FIG. 3 (C) have reacted. When the motor jet engine 1 to which the present invention is applied is mixed with the air compressed by the compressor 3 by the combustor 6, the motor jet engine 1 generates energy 41 as shown in FIG. Have. Specifically, the energy 41 is the total energy of the energy 40 that can be taken out when all the fuel has reacted and the energy 41a that the air compressed by the compressor has.

  When the motor jet engine 1 to which the present invention is applied is combusted by the combustor 6 and generated by the fuel cell 5, the motor jet engine 1 has energy 42 as shown in (c) of FIG. Specifically, it has thermal energy 42 a obtained from the energy 41 and electric energy 42 b obtained from the power generation of the fuel cell 5.

  As shown in (d) of FIG. 3 (C), a part 43a of this thermal energy 42a is released to the outside of the casing 2 as heat transfer loss and exhaust gas heat, and the other 43b works outside. As taken out. Here, for example, it is the thrust of the engine. And as shown to (e) in FIG.3 (C), the electrical energy 42b obtained from the electric power generation of the fuel cell 5 is used for a part 44a driving the compressor 3 (= compressor). Energy 41a) of compressed air.

  That is, a conventional jet engine and a conventional jet engine with a built-in fuel cell (hereinafter, also referred to as a conventional jet engine) have a turbine for driving a compressor, and thus are extracted from thermal energy 22 and 32a. Part of the work 23b, 33b will be used to drive the compressor through the turbine. In contrast, in the motor jet engine 1 to which the present invention is applied, since the compressor 3 is electrically driven using the power generated by the fuel cell 5, all the work 43b extracted from the thermal energy 42a is used. Can be taken out. That is, the motor jet engine 1 to which the present invention is applied does not require a turbine because the compressor 3 is driven by the electric energy generated by the power generation of the fuel cell. In addition, the motor jet engine 1 to which the present invention is applied can take out thermal energy obtained by the heat generation of the fuel cell as work for propulsion by the nozzle without losing it by the turbine. Therefore, the motor jet engine 1 to which the present invention is applied is more efficient than a conventional jet engine or the like.

  Furthermore, in order for the conventional jet engine etc. to increase the work taken out outside, it is necessary to increase the thermal energy 22, 32 obtained from the total energy 21, 31. Furthermore, in order to increase the thermal energy 22, 32, it is necessary to compress the air greatly by the compressor 3 to increase the temperature and pressure. On the other hand, in the motor jet engine 1 to which the present invention is applied, the compressor 3 is electrically driven using the electric power generated by the fuel cell 5, so that the conventional jet engine or the like is driven by the compressor 3. It is not necessary to compress the air greatly to increase the temperature and pressure. Therefore, the motor jet engine 1 to which the present invention is applied does not need to use a heat-resistant / pressure-resistant material as much as that of a conventional jet engine, and does not require a cooling structure like the conventional jet engine. The structure can be simplified and the cost can be reduced, for example, the thickness can be reduced.

<2. Explanation of effects of motor jet engine>
As described above, the motor jet engine 1 to which the present invention is applied is compressed like the conventional jet engine by the compressor 3 being electrically driven using the power generated by the fuel cell 5. A turbine for driving the machine 3 need not be incorporated in the casing 2. That is, the motor jet engine 1 to which the present invention is applied can omit the turbine. Therefore, the motor jet engine 1 to which the present invention is applied can shorten the entire rotation system and can be miniaturized as compared with a conventional jet engine or the like. Furthermore, since the motor jet engine 1 to which the present invention is applied can omit the turbine, the structure can be simplified and the cost can be reduced as compared with a conventional jet engine or the like.

  Further, the motor jet engine 1 to which the present invention is applied generates heat by itself during power generation. Therefore, in the motor jet engine 1 to which the present invention is applied, the fuel cell 5 is provided on the intake port 2a side with respect to the combustor 6 in the casing 2, and the compressor 3 is heated by the heat energy generated by the heat generated when the fuel cell 5 generates power. By heating the compressed air, the heat energy generated by the heat generated by the fuel cell 5 can be taken out and used as a thrust. Furthermore, in the motor jet engine to which the present invention is applied, the air compressed by the compressor 3 is preheated by the heat energy generated by the heat generated when the fuel cell 5 generates power before being combusted by the combustor 6. The combustion efficiency by 6 can be improved. Therefore, even if the motor jet engine 1 to which the present invention is applied is downsized, high efficiency and high thrust can be ensured. As an example, the motor jet engine 1 to which the present invention is applied can have an efficiency equivalent to that of a large gas turbine engine with a thermal efficiency of 40% to 60%.

  Further, in the motor jet engine 1 to which the present invention is applied, since the compressor 3 is electrically driven using the electric power generated by the fuel cell 5, all the work 43b obtained from the thermal energy 42a is taken out to the outside. be able to. Therefore, the motor jet engine 1 to which the present invention is applied can extract work to the outside with higher efficiency than a conventional jet engine or the like.

  That is, the motor jet engine 1 to which the present invention is applied can be made smaller than the conventional jet engine or the like when the same thrust force as that of the conventional jet engine or the like is secured. In the case of the size, it is possible to obtain a larger thrust than a conventional jet engine or the like.

  Furthermore, in the motor jet engine 1 to which the present invention is applied, the compressor 3 is electrically driven using the power generated by the fuel cell 5, so that the air is increased by the compressor 3 as much as the conventional jet engine. There is no need to compress and increase the temperature and pressure. As an example, the motor jet engine 1 to which the present invention is applied can be operated at a maximum temperature of 1000 ° C. or less. Therefore, the motor jet engine 1 to which the present invention is applied does not need to use a heat-resistant / pressure-resistant material as much as that of a conventional jet engine, and does not require a cooling structure like the conventional jet engine. The structure can be simplified and the cost can be reduced, for example, the thickness can be reduced.

<3. Explanation of motor jet engine performance evaluation>
Next, performance evaluation was performed focusing on the overall efficiency and specific output of the motor jet engine 1 to which the present invention is applied.

3-1. Description of Performance Calculation Method Here, the fuel component is assumed to be an aircraft fuel, and n-decane (C ₁₀ H ₂₂ ) used as the main component of the kerosene surrogate fuel. An attempt has been made to increase the amount of hydrogen generated by steam reforming for a fuel having a large carbon number such as n-decane. Here, the simplest dry reforming without using steam is assumed. The general reaction formula as the reforming reaction is represented by the following formula.

  Furthermore, power generation is performed by the following reaction in the cell.

  The overall reaction formula is expressed by the following formula.

Accordingly, the equivalence ratio φ is defined as fuel: oxygen = φ: 15.5 in terms of molar ratio. The generated power is used to drive the compressor. The SOFC exhaust gas contains unreacted H ₂ and CO and the fuel that has been added. Normally, fuel is added to this and then re-combusted in the afterburner section at the latter stage, but this calculation is simplified. Therefore, the calculation was performed under the assumption that all of the cells react inside the battery. In addition, the cell outlet temperature was regarded as the operating temperature of the cell for evaluation.

  Table 1 shows the calculation conditions. The initial pressure and the nozzle outlet pressure were both 1 atm, and the initial temperature was 298K. Mechanical efficiency was ignored for simplicity of calculation. For other efficiencies, the calculation was performed under a condition that considered the efficiency (With loss case) and a condition where the efficiency was all 1 (Ideal case). The compressor heat insulation efficiency and nozzle efficiency were 0.85 and 0.90, respectively. Subscripts 1 to 4 to be used hereinafter represent a cell outlet and a nozzle outlet before and after compression, respectively.

  First, the change amount ΔG of Gibbs free energy before and after the reaction is calculated. The amount of change in Gibbs free energy that occurs under constant temperature is given by the following equation.

The calculation was performed by polynomial calculation using the thermodynamic coefficient used in the chemical equilibrium calculation program “NASA CEA”. TΔS cannot be taken out as electric power in SOFC and becomes exhaust heat, but this heat is finally utilized as thrust by expansion at the nozzle. In an actual cell, a voltage drop (polarization) due to internal resistance occurs, and the actual electromotive force is lower than the theoretical electromotive force. If the power loss rate α at the electrode is defined by the ratio of the lost power to the theoretical output, the SOFC output W _cell is expressed as follows using the Gibbs free energy change ΔG _cell and α before and after the reaction in the _cell . It is expressed by a formula.

Further, when power transmission efficiency η _trans between the battery and the motor is used in consideration of a loss due to resistance or the like, the compressor power W _c has the following relationship.

  Furthermore, the following formula is established by the energy balance.

Here, H ₁ is the amount of change in enthalpy that occurs when it is assumed that the fuel has all reacted under the initial temperature. Using this H ₁ and the output of the cell, the power generation efficiency η _e is expressed by the following equation.

The pressure ratio π _c is expressed by the following equation using the temperature ratio θ _c before and after compression and the arithmetic average value κ _c of the specific heat ratio before and after compression.

Here, since the enthalpy H ₂ after compression changes depending on the temperature after compression, that is, the pressure ratio, the temperature and pressure ratio after compression were obtained by repeated calculation so as to satisfy the above equation (8). The work W _noz made by the gas at the nozzle is expressed by the following equation based on the enthalpy drop before and after the nozzle.

The overall efficiency η _O which is an important parameter for evaluating the performance of this engine is evaluated by the following equation.

  As with thermal efficiency, one of the important parameters that determines the performance of a jet engine is the dimensionless output, which is expressed by the following equation.

Outlet pressure P ₃ of the SOFC, using the pressure loss rate ζ of pressure P ₂ cells after compression is expressed by the following.

The temperature ratio θ _n before and after the nozzle is expressed by the following equation using the pressure ratio π _n before and after the nozzle, the nozzle efficiency η _n and the arithmetic average value κ _n of the specific heat ratio before and after the nozzle.

Accordingly, the nozzle outlet temperature T ₄ is expressed by the following equation from the relationship of T ₄ = T ₃ / θ _n .

The exhaust velocity v and the Mach number M at the nozzle outlet are given by the following equations, where m is the exhaust gas mass, κ _{e is} the specific heat ratio, and R is the gas constant.

3-2. Explanation of calculation results and consideration 3-2-1. Explanation of Effect of Fuel Equivalent Ratio on Cell Outlet Temperature By changing the equivalent ratio, the equivalent ratio that becomes the operating temperature of SOFC from 900 ° C. to around 1000 ° C. was estimated by calculation. FIG. 4 shows the cell temperature of SOFC at each equivalent ratio. The solid line is the efficiency 1, that is, the temperature under the condition (Ideal case) that does not consider the drop in electromotive force and pressure loss due to power loss and polarization, and the broken line is the temperature when the efficiency is considered (With loss case). In the ideal case, the outlet temperature of the cell was about 900 K at φ = 0.22 and about 1000 K at φ = 0.27. In the case of With loss, φ = 0.25 was approximately 900K, and φ = 0.29 was approximately 1000K. Further, it is understood that the fuel equivalence ratio may be about 0.2 to 0.4 considering the actual operation of SOFC.

3-2-2. Explanation of the effect of cell outlet temperature on power generation efficiency The effect of cell outlet temperature on power generation efficiency, pressure ratio and theoretical efficiency was evaluated. FIG. 5 shows the calculation result of the power generation efficiency due to the difference in cell temperature. In the ideal case, a very high power generation efficiency of approximately 64% at 1000K is obtained. Moreover, the power generation efficiency increases as the cell outlet temperature is lower. This is because the TΔS content that cannot be used as work by Gibbs free energy is smaller as the temperature is lower. In the With loss case, the power generation efficiency was naturally reduced, and at 1000K, it was about 38%. Although the power generation efficiency decreases due to the loss of the electric drive system, the heat generated by the resistance or the like can be recovered as work by the nozzle, and the overall efficiency of the entire system can be kept high as will be described later.

3-2-3. Explanation of Effect of Cell Outlet Temperature on Pressure Ratio FIG. 6 shows the calculation result of the pressure ratio due to the difference in cell outlet temperature. When the cell temperature was around 600K, it was about 7 for the Ideal case and about 3 for the With loss case. Also, the higher the cell outlet temperature, the higher the pressure ratio. This is because the cell outlet temperature is high, that is, the cell output is high, so that the compression work is large and the pressure ratio is increased. Moreover, the influence by each loss became remarkable, so that the cell exit temperature was high. In the ideal case, the pressure ratio is about 30 at 900K. This is approximately half the pressure ratio of recent large turbofan engines, but it is not necessary to drive the turbine, so that a very high nozzle pressure ratio can be secured as will be described later. In addition, the pressure resistance can be lowered because the pressure ratio is low, and the number of compressor stages is reduced, which is superior to current engines in terms of reliability and materials. In supersonic flight, ram-compressed and high-enthalpy air flows in, but high output and high efficiency can be realized even if the maximum / minimum temperature ratio and pressure ratio are small.

3-2-4. FIG. 7 shows the relationship between the cell outlet temperature and the overall efficiency. In the ideal case, the cell outlet temperature was 1000K, and the overall efficiency was very high at approximately 87%. It can also be seen that the efficiency is high over a wide temperature range. This is because the lower the cell outlet temperature, the higher the power generation efficiency of the fuel cell, while the Brayton cycle efficiency increases on the higher temperature side. In the With loss case, the overall efficiency was low by about 30% in the temperature range performed this time, but a high efficiency of about 45% can be secured at a cell outlet temperature of 1000K. This is an efficiency equivalent to the power generation end efficiency of a large-scale gas turbine power generation, but has a feature that the temperature of the system is about 1000K.

3-2-5. Explanation of Effect of Cell Exit Temperature on Dimensionless Specific Output FIG. 8 shows the relationship between the cell exit temperature and the dimensionless specific output. In the ideal case, the cell exit temperature was about 650K, and the dimensionless output was about 2.3 at 1,1000K. In the With loss case, the lower the cell outlet temperature, the smaller the difference between the dimensionless output and the case where the loss is ignored, and the higher the temperature, the more significant the difference. When the cell outlet temperature was 1000K, the dimensionless specific power was about 1.2. This is almost the same as a working machine having a pressure ratio of about 40.

3-2-6. FIG. 9 shows the relationship between the cell outlet temperature and the exhaust gas Mach number.

3-3. Conclusion About the motor jet engine 1 to which this invention is applied, performance estimation was performed by calculation using n-decane as fuel. As a result, the following knowledge was obtained.

  (1) The power generation efficiency is higher as the cell outlet temperature is lower, and is approximately 64% at 1000 K when the loss is ignored, and decreases as the temperature increases. On the other hand, the pressure ratio was higher as the cell outlet temperature was higher, and was about 30 at 900K when the loss was ignored. With the above features, overall efficiency is very high in a wide temperature range where SOFC is operated, and high overall efficiency can be obtained even at low temperature and low pressure ratio, and 85% in a wide temperature range where operation is expected. Exceed. In addition, it was found that low-temperature and low-pressure can be achieved without sacrificing efficiency compared with the current engine under conditions that take loss into account.

  (2) When the loss is ignored, the cell outlet temperature is about 600K, the exhaust gas Mach number exceeds 2, and supersonic injection is possible. Even under the condition considering the loss, the cell outlet temperature is about 600K and the Mach number exceeds 1. Since the specific power equivalent to the specific power estimated from the pressure ratio and temperature ratio of the current supersonic flight engine can be secured, the number of compressor stages can be reduced without using the turbine of the compression power source, and at supersonic speed. High thrust operation including operation is possible.

DESCRIPTION OF SYMBOLS 1 Motor jet engine, 2 Casing, 2a Inlet, 2b Exhaust nozzle, 3 Compressor, 4 Motor, 5 Fuel cell, 5a Cathode, 5b Anode, 6 Combustor, 8 Blower, 9 Reformer, 100 Jet engine, 101 Compressor , 102 Combustor, 103 Turbine, 104 nozzles, 105 axes

Claims (2)

A casing having an inlet and an exhaust nozzle;
A compressor provided in the casing and compressing air sucked from the air inlet;
A motor connected to the compressor and driving the compressor;
A fuel cell that is provided on the exhaust nozzle side of the compressor in the casing, generates electric power and supplies the electric power to the motor, and heats the compressed air by heat energy generated during power generation; ,
A combustor that is provided on the exhaust nozzle side of the fuel cell in the casing and that mixes and burns fuel in the compressed air heated by the fuel cell and discharges the fuel from the exhaust nozzle. Motor jet engine.   The motor jet engine according to claim 1, wherein the fuel cell is a solid oxide fuel cell (SOFC).