Hydrogen engine performance acquisition method

Abstract

To provide a hydrogen engine performance acquisition method capable of acquiring performance of a hydrogen engine that uses hydrogen fuel.SOLUTION: A hydrogen engine performance acquisition method is used for acquiring engine performance of a hydrogen engine. The hydrogen engine performance acquisition method includes: a step S102 of receiving input of fuel physical properties including an equivalence ratio φ and an atmospheric condition and calculating laminar flow combustion speed SL in the hydrogen engine by performing calculation using a laminar flow combustion speed model corresponding to a case where the equivalence ratio φ is less than 0.5; and a step S107 of acquiring a value indicating engine performance on the basis of the laminar flow combustion speed SL following the step S102.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a hydrogen engine performance acquisition method. [Background technology]

[0002] Patent Document 1 describes a predictive analysis method for predicting engine performance. In this method, the engine combustion cycle is divided into four processes, intake, compression, expansion, and exhaust, and the flow of the engine working gas in each of the intake and exhaust processes is described by CFD calculation. On the other hand, in the compression and expansion processes, at least the working gas in the combustion chamber is simulated by a larger number of gas components than in the intake and exhaust processes, and the state is described by calculation of chemical reaction equations.

[0003] In Patent Document 1, the above method is described in a system that performs a simulation of engine operation by describing the flow of intake air and exhaust gas, which are the working gas of the engine, by one-dimensional or three-dimensional CFD calculations, and describing the combustion in the cylinder by chemical reaction formulas, and combining them. Also, in order to handle the huge amount of calculations required for three-dimensional CFD, it is described that multiple high-speed server computers are connected in parallel and used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-239130 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the method described in the above Patent Document 1 uses a one-dimensional CFD physical model and a three-dimensional model. However, conventional models for hydrocarbon fuels such as the model described in the above Patent Document 1 (e.g., laminar burning velocity model) do not support lean combustion with an equivalence ratio φ of less than 0.5. On the other hand, in a hydrogen engine using hydrogen fuel, lean combustion with an equivalence ratio φ of less than 0.5 is possible, so it is difficult to fully obtain the engine performance of a hydrogen engine with the conventional model.

[0006] Therefore, an object of the present disclosure is to provide a hydrogen engine performance acquisition method capable of acquiring the performance of a hydrogen engine that uses hydrogen fuel. [Means for solving the problem]

[0007] As a result of intensive research by the inventors to solve the above problems, the inventors have developed a laminar burning velocity model that also supports lean combustion with an equivalence ratio φ of less than 0.5. The present disclosure is based on this research.

[0008] In other words, the hydrogen engine performance acquisition method according to the present disclosure is a hydrogen engine performance acquisition method for acquiring the engine performance of a hydrogen engine, and includes a first step of calculating the laminar burning velocity in the hydrogen engine by receiving input of fuel properties including an equivalence ratio and atmospheric conditions, and performing calculations using a laminar burning velocity model corresponding to cases where the equivalence ratio is less than 0.5, and a second step, after the first step, of acquiring a value indicating engine performance based on the laminar burning velocity calculated in the first step.

[0009] In this method, in the first step, the laminar burning velocity in a hydrogen engine using hydrogen fuel is calculated by a calculation using a laminar combustion model corresponding to lean combustion with an equivalence ratio φ of less than 0.5, and in the second step, it becomes possible to obtain a value indicating the engine performance of the hydrogen engine (e.g., heat balance, etc.) based on the calculated laminar burning velocity.

[0010] Furthermore, the hydrogen engine performance acquisition method according to the present disclosure may include a third step between the first and second steps, in which a flame propagation speed in the hydrogen engine is calculated by performing a calculation using a flame propagation model that takes into account the airflow including swirl and tumble and the ignition position based on the laminar burning speed calculated in the first step, and in the second step, a value indicating engine performance may be acquired further based on the flame propagation speed calculated in the third step. In this case, it is possible to acquire a more accurate value indicating engine performance of the hydrogen engine based on the flame propagation speed that reflects the airflow including swirl and tumble and the ignition position.

[0011] Here, hydrogen fuel has a shorter quenching distance (i.e., the flame reaches closer to the cylinder inner wall surface) than conventional hydrocarbon fuel. Therefore, it is difficult to accurately obtain the cooling loss in a hydrogen engine using a conventional cooling loss model for calculating the heat transfer coefficient to the cylinder inner wall surface. The present inventor therefore conducted intensive research into this problem and constructed a cooling loss model that takes into account the quenching distance of hydrogen fuel. Based on this research, the present inventor has come up with the following method for obtaining hydrogen engine performance.

[0012] That is, the hydrogen engine performance acquisition method according to the present disclosure may include a fourth step between the first and second steps, in which a heat transfer coefficient in the hydrogen engine is calculated by performing a calculation using a cooling loss model that takes into account the quenching distance of the hydrogen fuel based on the laminar burning speed calculated in the first step, and in the second step, a value indicating engine performance may be acquired further based on the heat transfer coefficient calculated in the fourth step. In this case, the heat transfer coefficient in the hydrogen engine is calculated using a cooling loss model that takes into account the quenching distance of the hydrogen fuel. This makes it possible to acquire a more accurate value indicating engine performance of the hydrogen engine in the second step based on the laminar burning speed and the heat transfer coefficient. Effect of the Invention

[0013] According to the present disclosure, it is possible to provide a hydrogen engine performance acquisition method capable of acquiring the performance of a hydrogen engine that uses hydrogen fuel. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a functional block diagram showing a hydrogen engine performance acquisition device according to this embodiment. [Diagram 2] FIG. 2 is a flowchart showing the hydrogen engine performance acquisition method according to this embodiment. [Diagram 3] FIG. 3 is a graph showing the relationship between the equivalence ratio φ and the laminar burning velocity SL calculated by the conventional laminar burning velocity model. [Figure 4] FIG. 4 is a graph showing the relationship between turbulence intensity u' and turbulent burning velocity ST. [Diagram 5] FIG. 5 is a schematic diagram showing the state of flame propagation inside the cylinder. [Figure 6] FIG. 6 is a graph showing the relationship between the crank angle and the heat release rate. [Figure 7] FIG. 7 is a graph showing the relationship between the crank angle and the heat release rate. [Figure 8] FIG. 8 is another graph showing the relationship between the crank angle and the heat release rate. [Figure 9] FIG. 9 is a schematic diagram showing the quenching distance and the flame contact surface. [Figure 10] FIG. 10 is a graph comparing cooling losses. [Figure 11] FIG. 11 is a graph showing engine performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a hydrogen engine performance acquisition device and a hydrogen engine performance acquisition method according to an embodiment will be described with reference to the drawings.

[0016] Fig. 1 is a functional block diagram showing a hydrogen engine performance acquisition device according to this embodiment. The hydrogen engine performance acquisition device 1 shown in Fig. 1 is for acquiring the performance of a hydrogen engine that uses hydrogen fuel. The hydrogen engine performance acquisition device 1 is physically configured as a computer system including, for example, a main storage device constituted by memories such as a CPU, RAM and ROM, an auxiliary storage device constituted by a hard disk and memory, etc., a communication control device, etc. Furthermore, the hydrogen engine performance acquisition device 1 may further include an input device such as a touch panel or keyboard, or a speaker or display.

[0017] 1 of the hydrogen engine performance acquisition device 1 can be realized by loading specific computer software onto hardware such as a CPU, a main memory device, etc., to operate a communication control device etc. under the control of the CPU, and by reading and writing data in the main memory device and auxiliary memory device. Data required for processing can be stored in the main memory device and auxiliary memory device.

[0018] Functionally, the hydrogen engine performance acquisition device 1 comprises a model storage unit 10, an ignition model calculation unit 11, a laminar burning velocity calculation unit 12, a turbulent burning velocity calculation unit 13, a flame propagation velocity calculation unit 14, a heat release rate calculation unit 15, a heat transfer rate calculation unit 16, and a performance acquisition unit 17. An overview of each unit is provided in Fig. 1. Specific operations of each unit, including the hydrogen engine performance acquisition method according to this embodiment, will be described later.

[0019] The model storage unit 10 stores models used for calculations in each part of the hydrogen engine performance acquisition device 1. The ignition model calculation unit 11 performs calculations using the ignition model. The ignition model provides a small volume (also a specified value) of ignition energy (thermal energy that can be generated by an ignition plug) of a specified value into the combustion chamber. Combustion occurs in the mixture for this volume, and flame propagation starts from here. The laminar burning velocity calculation unit 12 receives input of fuel properties including the equivalence ratio φ and atmospheric conditions, and calculates the laminar burning velocity in the hydrogen engine by performing calculations using a laminar burning velocity model that corresponds to cases where the equivalence ratio is less than 0.5.

[0020] The turbulent burning velocity calculation unit 13 calculates the turbulent burning velocity in the hydrogen engine by performing a calculation using a turbulent burning velocity model based on the laminar burning velocity and turbulence intensity calculated by the laminar burning velocity calculation unit 12. The flame propagation velocity calculation unit 14 calculates the flame propagation velocity in the hydrogen engine by performing a calculation using a flame propagation model that takes into account the airflow including swirl and tumble and the ignition position based on the turbulent burning velocity calculated by the turbulent burning velocity calculation unit 13 (i.e., the laminar burning velocity calculated by the laminar burning velocity calculation unit 12).

[0021] A heat release rate calculation unit 15 calculates the true heat release rate based on the flame propagation speed calculated by the flame propagation speed calculation unit 14. A heat transfer rate calculation unit 16 calculates the heat transfer rate in the hydrogen engine by performing calculations using a cooling loss model that takes into account the quenching distance of the hydrogen fuel based on the laminar burning speed calculated by the laminar burning speed calculation unit 12. A performance acquisition unit 17 acquires values ​​indicating the performance of the hydrogen engine, such as the apparent heat release rate, indicated work, and heat balance, based on the above calculated values.

[0022] Next, specific operations of the hydrogen engine performance acquisition device 1 will be illustrated, and an example of a hydrogen engine performance acquisition method according to this embodiment will be described. FIG. 2 is a flowchart showing the hydrogen engine performance acquisition method according to this embodiment. The hydrogen engine performance acquisition method shown in FIG. 2 is for acquiring the performance of a hydrogen engine that uses hydrogen fuel. As shown in FIG. 2, in this method, first, the ignition model calculation unit 11 performs calculations using an ignition model (step S101). The ignition model provides a small volume (also an indicated value) of ignition energy (thermal energy that can be generated at an ignition plug) of a specified value in the combustion chamber. Combustion occurs in the mixture in this volume, and flame propagation starts from here.

[0023] Next, the laminar burning velocity calculation unit 12 calculates the laminar burning velocity (step S102, first step). Here, FIG. 3 shows the equivalence ratio φ and the laminar burning velocity S calculated by the conventional laminar burning velocity model. L As shown in FIG. 3, in the conventional laminar burning velocity model for hydrocarbon fuels, the laminar burning velocity S L has not been obtained for the region where the equivalence ratio φ is less than 0.5 (i.e., the region where the excess air ratio λ is greater than 2.0), and the laminar burning velocity S L It is difficult to obtain

[0024] Therefore, the inventors have conducted extensive research and developed a laminar burning velocity model that corresponds to the region where the equivalence ratio φ is less than 0.5 (i.e., the excess air ratio λ is greater than 2.0) and is sensitive to pressure, temperature, equivalence ratio, and dilution ratio. In this case, the inventors have derived the model by integrating literature, research data, and elementary reaction analysis data from a wide range of fundamental combustion research fields that are not based on engine combustion. This laminar burning velocity model is based on the laminar burning velocity S L[m / s] is expressed by the following formula (1) using the fuel properties and atmospheric conditions including equivalence ratio φ, pressure (or cylinder internal pressure) P [bar], temperature (or cylinder internal temperature) T [K], and dilution ratio (exhaust dilution ratio: ratio of dilution of the mixture by exhaust gas or combustion products, etc.). α is a function of equivalence ratio φ, and is α=0.35·ln(φ / 1.7). 4 It is expressed as +1.5.

[0025] S L =240·(φ-1) 3 ·exp{-0.035·ln(P / 18) 2 +0.29}·(T / 300) α ·[{(1+3.84·P 0.18 D) exp(-3.84 P 0.18 ·D)} / (1+25·D 8 )]·(1-1.5D 1.6 )…(1)

[0026] The laminar burning velocity model constructed in this manner can be stored in the model storage unit 10. Therefore, in step S102, the laminar burning velocity calculation unit 12 receives input of fuel properties including the equivalence ratio φ and atmospheric conditions (i.e., the above-mentioned equivalence ratio φ, pressure P, temperature T, and dilution ratio D), and performs calculations using the laminar burning velocity model of the above-mentioned formula (1) corresponding to the case where the equivalence ratio φ stored in the model storage unit 10 is less than 0.5, thereby calculating the laminar burning velocity S in the hydrogen engine. L Calculate.

[0027] Here, in hydrogen combustion, the Lewis number Le, which is related to the turbulence of the flame, is significantly different from that of hydrocarbon fuels, so it is effective to reflect the characteristics of hydrogen by constructing and implementing a model corresponding to this characteristic, instead of the conventional turbulent burning velocity model for hydrocarbons. Therefore, in the next step, as shown in Figure 2, the turbulent burning velocity calculation unit 13 calculates the turbulent burning velocity (step S103). Here, Figure 4 shows the relationship between the turbulence intensity u' and the turbulent burning velocity S T In Fig. 4, the horizontal axis is the turbulence intensity u' [m / s] / laminar burning velocity S L [m / s], and the vertical axis is the turbulent burning velocity ST [m / s] / Laminar burning velocity S L [m / s]. Figure 4 (a) shows the case where the turbulence intensity u' is 15 [m / s]. Figure 4 (b) shows the relationship between the turbulence intensity u' and the turbulent burning velocity S T 1 is a graph showing a prediction formula that fits data showing the relationship between

[0028] As shown in Fig. 4, the turbulence intensity u´ and the turbulent burning velocity S T The relationship between the laminar burning velocity S L By taking the ratio of the turbulent burning velocity S T This is a turbulent burning velocity model that calculates the equivalence ratio φ. However, m in the following equation (2) is a function of the equivalence ratio φ, and is expressed as m = 1-[1 / {1+exp(-5.5·(φ-1.0))}]. This reflects in the model the characteristic that the Lewis number Le of hydrogen tends to differ from that of hydrocarbons with respect to the equivalence ratio φ.

[0029] S T / S L ={1+1.9·(u´ / S L ) m} / {1+0.02·(u´ / S L )}…(2)

[0030] The turbulent burning velocity model represented by the above formula (2) can be stored in the model storage unit 10. Therefore, in step S103, the turbulent burning velocity calculation unit 13 calculates the laminar burning velocity S L Based on (e.g. laminar burning velocity S L , equivalence ratio φ, and turbulence intensity u' are input, and calculation is performed using the turbulent burning velocity model of the above formula (2) stored in the model storage unit 10, to obtain the turbulent burning velocity S T Calculate.

[0031] In the next step, the flame propagation speed calculation unit 14 calculates the flame propagation speed (step S104, third step). Here, FIG. 5 is a schematic diagram showing the state of flame propagation in a cylinder. (a), (b), and (c) of FIG. 5 are diagrams showing the state of flame propagation in the cylinder W0 in the case of center injection / side ignition, (b) of FIG. 5 is a diagram showing the state of flame propagation in the cylinder W0 in the case of side injection / center ignition, and (c) of FIG. 5 is a diagram showing the state of flame propagation in the cylinder W0 in the case of center injection / center ignition. (d) and (e) of FIG. 5 show swirl F1 and tumble F2 in the cylinder W0 at bottom dead center (BDC) and top dead center (TDC), respectively.

[0032] In the example shown in FIG. 5(a) (swirl-based, first case), the flame generated at the ignition position Fp propagates in the circumferential direction D1 along the swirl F1, so the flame propagation speed S b is the turbulent burning velocity S T and the speed of the swirl F1 S r In other words, the flame propagation speed in this case is S b can be calculated by the model expressed by the following formula (3). In addition, since the flame propagation distance is πD / 2 with respect to the bore D, it is π times longer than the tumble base center ignition, and the combustion period is also π times longer.

[0033] S b =S T +S r …(3)

[0034] In the example (second case) shown in FIG. 5(b), the flame generated at the ignition position Fp propagates while being swirled by the swirl F1, but propagates along a direction D2 from the center toward the bore end like a tumble base. That is, the flame propagation speed S b can be calculated by the model expressed by the following formula (4). In addition, the flame propagation distance depends on the flame propagation speed and the speed of the swirl F1, but as an example, it is 1.1 times longer than the tumble base center ignition, and the combustion period is also 1.1 times longer.

[0035] Sb =S T …(4)

[0036] In the example (tumble base) shown in FIG. 5(c), the flame generated at the ignition position Fp propagates without delay along a direction D3 from the center toward the bore end. That is, the flame propagation speed S b can be calculated by a model expressed by the following formula (5) (similar to formula (4) above).

[0037] S b =S T …(5)

[0038] The flame propagation speed model represented by the above formulas (3) to (5) can be stored in the model storage unit 10. Therefore, in step S104, the flame propagation speed calculation unit 14 calculates the turbulent burning speed S T (i.e., based on the laminar burning velocity calculated by the laminar burning velocity calculation unit 12) (for example, the turbulent burning velocity S T and the speed S of the swirl F1 r The flame propagation speed S in a hydrogen engine is calculated by using a flame propagation model that takes into account the airflow including swirl F1 and tumble F2 and the ignition position Fp. b Calculate.

[0039] In the next step, the heat release rate calculation unit 15 calculates the flame propagation speed S calculated by the flame propagation speed calculation unit 14. b In step S105, the true heat release rate is calculated based on the flame propagation speed S calculated in step S104, for example. b The burned volume is assumed to increase spherically from the ignition point Fp in response to the heat release rate, and the true heat release rate is calculated based on the increase in heat volume. A general model can be used to calculate the heat release rate.

[0040] 6 and 7 are graphs showing the relationship between the crank angle and the heat release rate. In (a) of Fig. 6, a heat release rate G11 calculated based on the values ​​calculated by the models of this embodiment shown in the above formulas (1) to (3) in the first case shown in (a) of Fig. 5, and a heat release rate G12 calculated based on the values ​​calculated by the models of this embodiment shown in the above formulas (1) to (3) in the second case shown in (b) of Fig. 5 are shown.

[0041] Also, Fig. 6(b) shows the heat release rate G01, which is an experimental fact in the first case, and the heat release rate G02, which is an experimental fact in the second case. Fig. 7(a) and (b) show a comparison between the heat release rate G02 and the heat release rate G12 in the second case, and a comparison between the heat release rate G01 and the heat release rate G11 in the first case, respectively.

[0042] 6 and 7, it is understood that the use of each model of this embodiment shown in the above formulas (1) to (4) makes it possible to calculate a heat release rate that is consistent with experimental facts both qualitatively and quantitatively. That is, swirl-based hydrogen combustion, which could not be expressed in a conventional 1D model simulation because of the difference in combustion form, can be expressed by using each model of this embodiment shown in the above formulas (1) to (4).

[0043] Fig. 8 is another graph showing the relationship between the crank angle and the heat release rate. In Fig. 8(a), when the air excess ratio λ is 1.0 (stoichiometric), a graph G30 shows the heat release rate calculated using the conventional model, and a graph G31 shows the heat release rate calculated using each model of this embodiment shown in the above formulas (1) to (5). In Fig. 8(b), when the air excess ratio λ is 3.0 (ultra-lean burn), a graph G40 shows the heat release rate calculated using the conventional model, and a graph G41 shows the heat release rate calculated using each model of this embodiment shown in the above formulas (1) to (5).

[0044] As shown in Fig. 8, at stoichiometric (stoichiometric mixture ratio), the heat release rate can be calculated using both the conventional model and the model of this embodiment. However, there is a difference in shape between graph G30 and graph G31, and the conventional model has a problem in reproducing the actual phenomenon. Also, at high λ (ultra-lean burn), it can be seen that while the conventional model does not generate heat (i.e., there is no combustion), the model of this embodiment makes it possible to calculate the heat release rate.

[0045] Next, the heat transfer coefficient calculation unit 16 calculates the heat transfer coefficient in the hydrogen engine (step S106, fourth step). Here, the quenching distance of hydrogen fuel is shorter than that of conventional hydrocarbon fuel (i.e., the flame reaches closer to the cylinder inner wall surface). Therefore, it is difficult to accurately obtain the cooling loss in the hydrogen engine using a conventional cooling loss model for calculating the heat transfer coefficient to the cylinder inner wall surface. The conventional cooling loss model (Woschini model) is expressed by the following formula (6).

[0046] h=f convective =C H -0.2 P 0.8 ·U 0.8 T 0.53 …(6)

[0047] where h is the heat transfer coefficient or heat transfer rate [W / (m 2 ·k)], C is a constant, H is the stroke amount [m], P is the pressure or cylinder pressure [bar], U is the representative flow velocity [m / s], and T is the temperature or cylinder temperature [k]. Also, U=C1W·Sp+Uc, Uc=0.66·S T ·{(Tb / Tu)-1}. C1W is a constant (adjustment constant), Sp is the average piston speed (average piston movement speed), S T is the turbulent burning velocity calculated by the turbulent burning velocity model in the above equation (2), (Tb / Tu) is the ratio of the burnt gas temperature Tb to the unburnt gas temperature Tu (ratio of burn to unburn), χ is the flame front survival rate, R B is the bore radius, R f is the mean radius of the flame front, δ L is the flame zone thickness.

[0048] In contrast, for hydrogen fuel, the main factor in the increase in heat loss compared to hydrocarbon fuel is the shorter quenching distance, and a new cooling loss model is developed that takes into account the quenching distance at the flame contact surface. As shown in Figure 9(a), for hydrogen fuel, the quenching distance δ f is short, and the increment in heat transfer coefficient h is approximately k / δ f (k is the thermal conductivity [W / (m k)]). As shown in Fig. 9(b), the edge of the flame front defined by the burning speed forms a contact point with the cylinder wall W1, and the flame front heat receiving area (flame contact ratio, the ratio of the flame contact area to the cylinder wall area) Ca is calculated by multiplying the number of contact points by the flame zone thickness δ L and the area of ​​Linda's wall S cyl That is, Ca=2π{(R f ) 2 -(R f -δ f ) 2} / S cyl In addition, R f is the flame propagation radius.

[0049] Flame zone thickness δ L The general formula is δ L =(α / S L )·{(T f -T ig ) / (T ig -T ub )}, and the quenching distance δ f The general formula is P e =(ρ u ·S L C p δ f ) T f is the flame temperature, T ig is the flame tip temperature, T ub is the unburned temperature, P e is the Peclet number, ρ u is the density, C p is the low pressure specific heat.

[0050] Therefore, the new cooling loss model for hydrogen fuel is different from the conventional cooling loss model represented by the above equation (6) in that the quenching distance δ fAdding terms including the flame surface heat receiving area Ca = f(R f , δ f ,S cyl , π) to adjust the contribution of the additional term, and it is expressed as the following equation (7).

[0051] h = (1-Ca) f convective (C,H,P,U,T)+Ca·f quench (C,δ f ,k)=(1-Ca)·(C·H -0.2 P 0.8 ·U 0.8 T 0.53 )+Ca·{C·(3 / 2)·(k / δ f )}…(7)

[0052] The cooling loss model expressed by the above formula (7) can be stored in the model storage unit 10. Therefore, in step S106, the laminar burning velocity S L Based on (e.g. laminar burning velocity S L and quenching distance δ f (including other values) and the quenching distance δ of hydrogen fuel f The heat transfer coefficient h in a hydrogen engine is calculated by performing calculations using a cooling loss model that takes into account the above.

[0053] FIG. 10 is a graph comparing cooling losses. Graph A0 shows the wall cooling loss [kW] when the heat transfer coefficient h in the conventional cooling loss model expressed by the above formula (6) is used, and graph A1 shows the wall cooling loss [kW] when the heat transfer coefficient h in the new cooling loss model expressed by the above formula (7) is used. As shown in FIG. 10, the quenching distance δ f The difference B arises due to whether or not the above is taken into consideration.

[0054] In the next step, the performance acquisition unit 17 acquires the laminar burning velocity S L , flame propagation speed S b, heat transfer coefficient h, etc.) to obtain various values ​​indicating engine performance (step S107, second step). FIG. 11 is a graph showing engine performance. FIG. 11(a) shows actual measurement results, and FIG. 11(b) shows calculation results using the models shown in the above formulas (1) to (5) and (7). Here, cooling loss, indicated thermal efficiency, exhaust loss, and heat balance taking these into consideration are obtained as values ​​indicating engine performance.

[0055] 11, it is understood that the method according to this embodiment can estimate and calculate the actual cooling loss qualitatively and quantitatively (whereas in the conventional model of the above formula (6), there is a deviation from the actual cooling loss by the difference B). In addition, a comparison of the indicated thermal efficiency and exhaust loss confirms that each of the combustion models of the above formulas (1) to (5) can also accurately calculate the actual phenomenon.

[0056] As described above, in the hydrogen engine performance acquisition method according to this embodiment, in step S102, the laminar combustion velocity S in a hydrogen engine using hydrogen fuel is calculated by using the laminar combustion model (the above formula (1)) corresponding to lean combustion in which the equivalence ratio φ is less than 0.5. L In this way, in step S107, the calculated laminar burning velocity S L Based on (e.g., laminar burning velocity S L The turbulent burning velocity S calculated based on T , turbulent burning velocity S T Based on the flame propagation speed Sb calculated based on the above, and the cooling loss (heat transfer coefficient h), it is possible to obtain values ​​indicating the engine performance of the hydrogen engine (e.g., heat balance, etc.).

[0057] In addition, in the hydrogen engine performance acquisition method according to the present embodiment, between steps S102 and S107, the laminar burning velocity S L Turbulent burning velocity S TBased on this, a flame propagation model (the above formulas (3) to (5)) is performed that takes into account the airflow including the swirl F1 and the tumble F2 and the ignition position Fp, and the flame propagation speed S in a hydrogen engine is calculated. b Then, in step S107, the flame propagation speed S calculated in step S104 is calculated. b To this end, a flame propagation speed S reflecting the airflow including the swirl F1 and the tumble F2 and the ignition position Fp is used. b Based on this, it is possible to obtain more accurate values ​​indicative of the engine performance of the hydrogen engine.

[0058] Furthermore, in the hydrogen engine performance acquisition method according to the present embodiment, between step S102 and step S107, the laminar burning velocity S L Based on this, the quenching distance δ of hydrogen fuel f The method includes a step S106 of calculating the heat transfer coefficient h in the hydrogen engine by performing a calculation using a cooling loss model (the above formula (7)) that takes into account the above. Then, in step S107, a value indicating engine performance is obtained based on the heat transfer coefficient h calculated in step S105. As a result, in step S107, the laminar burning velocity S L , turbulent burning velocity S T Based on the heat transfer coefficient h and the heat transfer rate k, it is possible to obtain more accurate values ​​indicating the engine performance of a hydrogen engine.

[0059] The above embodiment describes one aspect of the hydrogen engine performance acquisition method according to the present invention. Therefore, the hydrogen engine performance acquisition method according to the present invention may be any modification of the hydrogen engine performance acquisition method according to the above embodiment.

[0060] For example, in the hydrogen engine performance acquisition method according to the above embodiment, in step S102, the laminar burning velocity S LAlso, in steps S103, S104, and S106, calculations were performed using the new models represented by the above formulas (2) to (5), and (7). However, in at least one of steps S103, S104, and S106, calculations may be performed using the conventional model.

[0061] Furthermore, in each of the models shown in the above formulas (1) to (5) and (7), the specific values ​​of the coefficients, multipliers, etc. may be changed as appropriate. [Explanation of symbols]

[0062] φ…Equivalence ratio, S L …Laminar burning velocity, S b …Flame propagation speed, h…Heat transfer coefficient, F1…Swirl, F2…Tumble, Fp…Ignition position, δ f ...extinction distance.

Claims

1. A hydrogen engine performance acquisition method for acquiring engine performance of a hydrogen engine, comprising: a first step of calculating a laminar burning velocity in the hydrogen engine by receiving inputs of fuel properties including an equivalence ratio and atmospheric conditions and performing a calculation using a laminar burning velocity model corresponding to a case where the equivalence ratio is less than 0.5; a second step of obtaining a value indicating the engine performance based on the laminar burning velocity calculated in the first step, after the first step; A hydrogen engine performance acquisition method comprising:

2. and a third step between the first step and the second step, of calculating a flame propagation speed in the hydrogen engine by performing a calculation using a flame propagation model that takes into account an ignition position and an airflow including swirl and tumble based on the laminar burning speed calculated in the first step, In the second step, a value indicating the engine performance is obtained further based on the flame propagation speed calculated in the third step. The hydrogen engine performance acquisition method according to claim 1 .

3. and a fourth step between the first step and the second step, of calculating a heat transfer coefficient in the hydrogen engine by performing a calculation using a cooling loss model that takes into account a quenching distance of hydrogen fuel based on the laminar burning speed calculated in the first step, In the second step, a value indicating the engine performance is obtained further based on the heat transfer coefficient calculated in the fourth step. The hydrogen engine performance acquisition method according to claim 1 or 2.

Images