Performance optimization method and device for methanol-diesel dual-fuel in-cylinder direct injection engine and computer storage medium

Abstract

The invention discloses a methanol-diesel dual-fuel in-cylinder direct injection engine performance optimization method, which comprises the following steps of: setting a geometric model of fuel combustion in an engine cylinder comprising a diesel nozzle and a methanol nozzle, performing grid division, and setting a sub-model required by simulation calculation; initializing a population, wherein each particle in the population is composed of a mass flow value of a diesel curve control point and a mass flow value of a methanol curve control point; generating a diesel curve and a methanol curve based on the starting point, the control point and the ending point; calculating engine power and total emission of population particles by simulation software based on a diesel curve and a methanol curve; performing weighted summation to serve as an optimization target of population particles; and iteratively updating the speed and the position of the population particles to the maximum iterative calculation step number, and obtaining an optimal diesel curve and an optimal methanol curve based on the optimal particles. According to the method, the fuel injection curves of the diesel oil and the methanol are optimized respectively, and the overall performance of the dual-fuel in-cylinder direct injection engine is improved.

Description

Technical Field

[0001] The present invention relates to a method for optimizing engine performance, in particular to a method, device and computer storage medium for optimizing the performance of a methanol-diesel dual-fuel direct injection engine in the cylinder. Background Art

[0002] Traditional fossil fuels, such as gasoline and diesel, are non-renewable resources. The oil reserves on the earth are limited. With the continuous development of the global economy and the increasing energy consumption, oil resources are gradually becoming scarce. With the pollution of the global environment, finding alternative energy sources for engines has become a hot topic of current research. Many scholars have studied the combustion process and the influence of the mixing ratio on power and emissions by mixing different alternative fuels, such as methane, biodiesel, ammonia-hydrogen fuel, etc., with diesel or gasoline. Since the mixing of several fuels enables the adjustment of fuel parameters to be carried out simultaneously, the best performance of each fuel cannot be well exerted. The dual nozzle can better adjust the control parameters of the engine by injecting different fuels at different nozzles, and then fully mix the fuels, which can effectively improve the combustion process. In addition, the fuel injection curve has a great influence on the power and emissions of the engine.

[0003] The prior art often finds the rules between them according to experience or through partial experiments, and finally obtains a suitable injection method. Since the influence of the fuel injection curve on the engine is very complex, it is impossible to obtain the fuel injection curve with the best performance through traditional experience or experiments. Summary of the Invention

[0004] Aiming at the defects of the above prior art, the present invention provides a method for optimizing the performance of a methanol-diesel dual-fuel direct injection engine in the cylinder, which solves the problem that it is difficult to obtain different fuel injection curves for the simultaneous combustion of dual fuels. The present invention also provides a device for optimizing the performance of a methanol-diesel dual-fuel direct injection engine in the cylinder and a computer storage medium.

[0005] The technical solution of the present invention is as follows: A method for optimizing the performance of a methanol-diesel dual-fuel direct injection engine in the cylinder includes the following steps:

[0006] Step 1: Set the geometric model of fuel combustion in the engine cylinder and perform grid division, and set the sub-models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle;

[0007] Step 2: Initialize the population. Each particle in the population is composed of the mass flow rate value of the diesel curve control point and the mass flow rate value of the methanol curve control point;

[0008] Step 3: Generate a diesel curve based on the starting point, each diesel curve control point, and the ending point, and generate a methanol curve based on the starting point, each methanol curve control point, and the ending point;

[0009] Step 4: Calculate the engine power and total emissions of the population particles by a simulation software based on the diesel curve and the methanol curve;

[0010] Step 5: Use the weighted sum of the engine power and the total emissions as the optimization objective of the population particles;

[0011] Step 6: Iteratively update the velocity and position of the population particles until the maximum number of iterative calculation steps is reached, output the optimal particle corresponding to the minimum value of the optimization objective, and obtain the optimal diesel curve and the optimal methanol curve based on the optimal particle.

[0012] Further, the calculation basis of the simulation software when calculating the engine power and total emissions of the population particles by the simulation software includes:

[0013] Conservation of matter:

[0014]

[0015] where k represents any substance K, ρ is the density, u is the flow velocity, y is the mass fraction of the substance, D is the mass diffusion coefficient of the substance, Φ is the convection term, ρ kc is the chemical reaction effect of substance k, ρ ks is the evaporation effect of substance k;

[0016] For the substance k generated by any reaction i:

[0017] ω ki =(v” ki -v′ ki )q i

[0018] where q is the rate of reaction i;

[0019] Calculation of soot amount:

[0020]

[0021] where M is the mass, the subscript s is for soot, K is the soot generation rate, and the subscript pre represents the precursor of soot;

[0022] The velocity U mean at the fuel re-nozzle outlet:

[0023]

[0024] where m is the mass and D is the nozzle radius;

[0025] The spray cone angle θ of the nozzle:

[0026]

[0027] where A is a coefficient related to the nozzle length and diameter, f is a function related to temperature, the subscript g represents gas, and the subscript l represents liquid.

[0028] Further, when the weighted sum of the engine power and the total emissions is used as the optimization objective of the population particles, the following formula is adopted for particle i:

[0029] Obj i = 1 / P i * 0.7 + T i * 0.3

[0030] where Obj i is the optimization objective, P i is the engine power, and T i is the total emissions.

[0031] Further, the following formulas are adopted when updating the velocity and position of the population particles:

[0032] v i,j (s + 1) = wv i,j (s) + τ1σ1[PB i,j - x i,j (s)] + τ2σ2[GB g,j - x i,j (s)];

[0033] x i,j (s + 1) = x i,j (s) + v i,j (s + 1),

[0034] where v i,j represents the velocity of the particle, w represents the weight coefficient, τ1 and τ2 represent the acceleration coefficients, σ1 and σ2 represent random numbers between 0 and 1, PB i,j represents the position where the individual optimization objective Obj is the smallest, GB g,j represents the position where the optimization objective Obj of the entire population is the smallest, and x i,j represents the position of the particle.

[0035] The present invention also provides a device for optimizing the performance of a methanol - diesel dual - fuel in - cylinder direct injection engine, including:

[0036] A model - building module, configured to set the geometric model of fuel combustion in the engine cylinder and perform mesh division, and set the sub - models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle;

[0037] An initialization module for initializing a population, where each particle in the population consists of the mass flow rate values of the diesel curve control points and the mass flow rate values of the methanol curve control points;

[0038] A curve generation module for generating a diesel curve based on a starting point, each diesel curve control point, and an ending point, and generating a methanol curve based on the starting point, each methanol curve control point, and the ending point;

[0039] A simulation calculation module for calculating the engine power and total emissions of the population particles by simulation software based on the diesel curve and the methanol curve;

[0040] An objective calculation module for using the weighted sum of the engine power and the total emissions as the optimization objective of the population particles;

[0041] An iterative output module for iteratively updating the velocities and positions of the population particles to the maximum number of iterative calculation steps, outputting the optimal particle corresponding to the minimum value of the optimization objective, and obtaining an optimal diesel curve and an optimal methanol curve based on the optimal particle.

[0042] The present invention also provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned performance optimization method for a methanol-diesel dual-fuel in-cylinder direct injection engine is implemented.

[0043] The advantages of the technical solution provided by the present invention are as follows:

[0044] Currently, in the existing technology, several fuels are mixed and burned in the engine, so that the fuel injection curves can only be modified simultaneously, which cannot fully exert the best performance of each fuel. In the present invention, the geometric model of fuel combustion in the engine cylinder is set to include a diesel nozzle and a methanol nozzle, and an optimization algorithm is used to design and optimize the fuel injection curves of each fuel respectively. This method can fully mix the fuels, effectively improve the combustion process, and thus improve the overall output performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 FIG. is a schematic flow chart of the performance optimization method for a methanol-diesel dual-fuel in-cylinder direct injection engine according to an embodiment of the present invention.

[0046] Figure 2 FIG. is a schematic diagram of the geometric model of fuel combustion in the engine cylinder according to an embodiment of the present invention.

[0047] Figure 3 FIG. is a schematic diagram of the nozzle setting of the geometric model of fuel combustion in the engine cylinder according to an embodiment of the present invention.

[0048] Figure 4Schematic diagram of the geometric model mesh division of fuel combustion in the engine cylinder according to an embodiment of the present invention.

[0049] Figure 5 It is a diesel curve, that is, the corresponding control point position diagram. Specific implementation manners

[0050] The following further describes the present invention in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading this description, various equivalent modifications of this description by those skilled in the art all fall within the scope defined by the appended claims of this application.

[0051] The methanol-diesel dual-fuel in-cylinder direct injection engine performance optimization device in the embodiment includes the following modules: a model establishment module, an initialization module, a curve generation module, a simulation calculation module, a target calculation module, and an iterative output module.

[0052] The functions of each module are as follows:

[0053] The model establishment module is used to set the geometric model of fuel combustion in the engine cylinder and perform mesh division, and set the sub-models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle.

[0054] The initialization module is used to initialize the population. Each particle in the population consists of the mass flow rate value of the diesel curve control point and the mass flow rate value of the methanol curve control point.

[0055] The curve generation module is used to generate a diesel curve based on the starting point, each diesel curve control point, and the ending point, and generate a methanol curve based on the starting point, each methanol curve control point, and the ending point.

[0056] The simulation calculation module is used to calculate the engine power and total emissions of the population particles by simulation software based on the diesel curve and the methanol curve.

[0057] The target calculation module is used to use the weighted sum of the engine power and the total emissions as the optimization target of the population particles.

[0058] The iterative output module is used to iteratively update the velocity and position of the population particles to the maximum number of iterative calculation steps, output the optimal particle corresponding to the minimum value of the optimization target, and obtain the optimal diesel curve and the optimal methanol curve based on the optimal particle.

[0059] Please combine Figure 1 As shown, the processing content of each module of the methanol-diesel dual-fuel in-cylinder direct injection engine performance optimization device is further described below through a specific methanol-diesel dual-fuel in-cylinder direct injection engine performance optimization method.

[0060] The optimization method specifically includes the following steps:

[0061] Step 1: Set up the geometric model of fuel combustion in the engine cylinder and perform mesh division, and set up the sub-models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle.

[0062] First, construct the geometric model of fuel combustion in the engine cylinder according to the parameters of the engine. The geometric model is as Figure 2 shown, which includes: cylinder head, cylinder wall, piston, nozzle, throttle valve, etc. The position of the nozzle is set as Figure 3 shown. The nozzle includes a diesel nozzle 1 and a methanol nozzle 2.

[0063] Secondly, according to the combustion condition of the engine, initially divide the mesh of the geometric model, and densify the mesh in the piston clearance to ensure the generation of soot, and densify the mesh near the fuel injector to ensure fuel combustion.

[0064] Finally, set up other sub-models required for simulation, including the geometric model of the fuel injector to simulate the shape of the fuel at the nozzle outlet, the turbulence model in the cylinder, the models of fuel jet breakup, droplet evaporation and droplet collision, the model of fuel jet collision with the cylinder wall, the heat dissipation model of the cylinder wall, the fuel combustion mechanism, the turbulence-combustion coupling model, the soot generation model, and the nitrogen oxide generation model.

[0065] Step 2: Initialize the population Z = {z1, z2, z3,..., z n}, and each particle z i in the population is composed of the mass flow rate values of the diesel curve control points and the mass flow rate values of the methanol curve control points, that is, z i is {x i1 , x i2 , x i3 , x i4 , x i5 , x i6 , x i7 , x i8}, where x i1 , x i2 , x i3 , x i4 represent the mass flow rate values of the diesel curve control points, and x i5 , x i6 , x i7 , x i8 represent the mass flow rate values of the methanol curve control points. Initialize the optimization algorithm parameters, including the maximum number of iterations S, the weight coefficient w, and the acceleration coefficients t1 and t2.

[0066] Step 3: Use the CAD method to draw the fuel injection spline curve, generate the diesel curve based on the starting point, each diesel curve control point, and the ending point, and generate the methanol curve based on the starting point, each methanol curve control point, and the ending point. The schematic of the diesel curve is as shown in Figure 5 shown, and the lateral positions of the control points of the methanol curve and the diesel curve are the same.

[0067] Step 4: Based on the diesel curve and the methanol curve, and the geometric model and sub-model of the fuel combustion in the engine cylinder set in Step 1, use the simulation software ANSYS-FORTE to calculate the engine power P i and the total emissions T i , where 1 ≤ i ≤ n.

[0068] Conservation of matter:

[0069]

[0070] where k represents any substance K, ρ is the density, u is the flow velocity, y is the mass fraction of the substance, D is the mass diffusion coefficient of the substance, Φ is the convection term, ρ kc is the chemical reaction influence of substance k, and σ ks is the evaporation influence of substance k.

[0071] For the substance k produced by any reaction i:

[0072] ω ki =(v” ki -v′ ki )q i

[0073] where q i is the rate of reaction i. Summing over all reactions gives the change in substance k. ω ki represents the change in the amount of substance k, v” ki represents the exponent of substance k in the product of the reaction, and v′ ki represents the exponent of substance k in the reactant of the reaction.

[0074] When calculating soot, the amount of soot is estimated based on the number of soot precursors using an empirical formula as follows:

[0075]

[0076] where M is the mass, the subscript s is for soot, the subscript sf is for soot generation amount, and the subscript so is for soot oxidation amount. The soot generation amount predicted from the precursors is:

[0077]

[0078] Among them, K is the soot generation rate, and the subscript pre represents the soot precursor.

[0079] According to the injection time and injection curve, and referring to the nozzle geometry, the velocity U of the fuel at the nozzle outlet can be calculated by the following formula mean :

[0080]

[0081] Among them, the left side of the equal sign is the average flow velocity at the outlet, m is the mass, and D is the nozzle radius;

[0082] The spray cone angle θ of the fuel jet can be obtained by calculating the following formula:

[0083]

[0084] Among them, A is a coefficient related to the nozzle length and diameter, f is a function related to the temperature, the subscript g is for gas, and the subscript l is for liquid.

[0085] Step 5: Use the weighted sum of the engine power and total emissions as the optimization objective of the population particles; for the i-th particle, the optimization objective Obj i is minimized, and the formula is defined as:

[0086] Obj i = 1 / P i * 0.7 + T i * 0.3

[0087] Step 6: Iteratively update the velocity and position of the population particles until the maximum number of iterative calculation steps, output the optimal particle corresponding to the minimum value of the optimization objective, and obtain the optimal diesel curve and optimal methanol curve based on the optimal particle.

[0088] Specifically, it includes:

[0089] Step 601: Store the position and Obj value with the minimum Obj of each current particle in PBEST, and store the position and Obj value of the individual with the minimum Obj in all PBEST in GBEST.

[0090] Step 602: Update the velocity and position of the particles using the following:

[0091] v i,j (s + 1) = wv i,j (s) + τ1σ1[PB i,j - x i,j (s)] + τ2σ2[GB g,j - x i,j (s)];

[0092] x i,j (s + 1) = xi,j (s) + v i,j (s + 1),

[0093] where v i,j represents the velocity of the particle, w represents the weight coefficient, τ1 and τ2 represent the acceleration coefficients, σ1 and σ2 represent random numbers between 0 and 1, PB i,j represents the position where the individual optimization objective Obj is the smallest, GB g,j represents the position where the overall population optimization objective Obj is the smallest, x i,j represents the position of the particle.

[0094] Step 603: Calculate the Obj of the new particle, compare its Obj with the Obj of the best position it has experienced. If it is smaller, then take it as the current best position.

[0095] Step 604: Compare all PBEST and GBEST and update GBEST.

[0096] Step 605: Determine whether s > S holds. If it holds, end the calculation; otherwise, let s = s + 1 and return to Step 602 to continue the iterative calculation. Here, s is the current iteration step number, and S is the maximum iteration step number.

[0097] It should be noted that the specific method of the above embodiment can form a computer program product. Therefore, the computer program product implemented in this application can be stored on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.). In addition, this application can be implemented in a way that combines hardware, software, or a combination of hardware and software, or constitutes a computer device including at least one processor and a memory. The memory stores the computer program for implementing the above process steps, and the processor is used to execute the computer program on the memory to form the method steps of the above embodiment.

Claims

1. A method for optimizing the performance of a methanol-diesel dual-fuel in-cylinder direct injection engine, characterized in that, It includes the following steps: Step 1: Set up the geometric model of fuel combustion in the engine cylinder and perform mesh division, and set up the sub-models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle; Step 2: Initialize the population. Each particle in the population consists of the mass flow rate values of the diesel curve control points and the mass flow rate values of the methanol curve control points; Step 3: Generate a diesel curve based on the starting point, each diesel curve control point, and the ending point, and generate a methanol curve based on the starting point, each methanol curve control point, and the ending point; Step 4: Calculate the engine power and total emissions of the population particles by simulation software based on the diesel curve and the methanol curve; Step 5: Use the weighted sum of the engine power and total emissions as the optimization objective of the population particles; Step 6: Iteratively update the velocity and position of the population particles until the maximum number of iterative calculation steps, output the optimal particle corresponding to the minimum value of the optimization objective, and obtain the optimal diesel curve and the optimal methanol curve based on the optimal particle.

2. The method for optimizing the performance of a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, wherein When calculating the engine power and total emissions of the population particles by simulation software, the calculation basis of the simulation software includes: Mass conservation: where k represents any substance K, ρ is the density, u is the flow velocity, y is the mass fraction of the substance, D is the mass diffusion coefficient of the substance, Φ is the convection term, ρ kc is the chemical reaction effect of substance k, ρ ks is the evaporation effect of substance k; For any substance k generated by reaction i: ω ki = (v” ki - v′ ki )q i where q i is the rate of reaction i, ω ki represents the change in the amount of substance k, v” ki represents the exponent of substance k in the product of the reaction, v′ ki represents the exponent of substance k in the reactant of the reaction; Soot amount calculation: Where M is the mass, the subscript s is for soot, K is the soot generation rate, and the subscript pre represents the precursor of soot; Velocity U at the outlet of the fuel re-nozzle mean : Where m is the mass and D is the nozzle radius; The spray cone angle θ of the nozzle: Where A is a coefficient related to the nozzle length and diameter, f is a function related to the temperature, the subscript g is for gas, and the subscript l is for liquid.

3. The method for optimizing the performance of a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, wherein When using the weighted sum of the engine power and total emissions as the optimization objective of the population particles, the following formula is used for particle i: Obj i = 1 / P i * 0.7 + T i * 0.3 Among them, Obj i is the optimization objective, P i is the engine power, T i is the total emissions.

4. The method for optimizing the performance of a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, wherein When updating the velocity and position of the population particles, the following formula is used: v i,j (s + 1) = wv i,j (s) + τ1σ1[PB i,j -x i,j (s)] + τ2σ2[GB g,j -x i,j (s)]; x i,j (s + 1) = x i,j (s) + v i,j (s + 1), where v i,j represents the velocity of the particle, w represents the weight coefficient, 1 and τ2 represent the acceleration coefficients, σ1 and σ2 represent random numbers between 0 and 1, PB i,j represents the position where the individual optimization objective Obj is the minimum, GB g,j represents the position where the overall population optimization objective Obj is the minimum, x i,j represents the position of the particle.

5. A performance optimization device for a methanol-diesel dual-fuel in-cylinder direct injection engine, characterized in that, It includes: A model establishment module, which is used to set up the geometric model of fuel combustion in the engine cylinder and perform mesh division, and set up the sub-models required for simulation calculation. The geometric model of fuel combustion in the engine cylinder includes a diesel nozzle and a methanol nozzle; An initialization module, which is used to initialize the population. Each particle in the population consists of the mass flow rate values of the diesel curve control points and the mass flow rate values of the methanol curve control points; A curve generation module, which is used to generate a diesel curve based on the starting point, each diesel curve control point, and the ending point, and generate a methanol curve based on the starting point, each methanol curve control point, and the ending point; A simulation calculation module, which is used to calculate the engine power and total emissions of the population particles by simulation software based on the diesel curve and the methanol curve; An objective calculation module, which is used to use the weighted sum of the engine power and total emissions as the optimization objective of the population particles; An iterative output module, which is used to iteratively update the velocity and position of the population particles until the maximum number of iterative calculation steps, output the optimal particle corresponding to the minimum value of the optimization objective, and obtain the optimal diesel curve and the optimal methanol curve based on the optimal particle.

6. The performance optimization device for a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, wherein When calculating the engine power and total emissions of the population particles by simulation software, the calculation basis of the simulation software includes: Mass conservation: where k represents any substance K, ρ is the density, u is the flow velocity, y is the mass fraction of the substance, D is the mass diffusion coefficient of the substance, Φ is the convection term, ρ kc is the influence of the chemical reaction of substance k, ρ ks is the influence of the evaporation of substance k; For any substance k generated by reaction i: ω ki = (v” ki - v′ ki )q i where q i is the rate of reaction i, ω ki represents the change in the amount of substance k, v” ki represents the exponent of substance k in the product of the reaction, v′ ki represents the exponent of substance k in the reactant of the reaction; Soot amount calculation: Among them, M is the mass, the subscript s represents soot, K is the soot generation rate, and the subscript pre represents the precursor of soot; Velocity U at the outlet of the fuel re-nozzle mean : Among them, m is the mass and D is the nozzle radius; The spray cone angle θ of the nozzle: Among them, A is a coefficient related to the nozzle length and diameter, f is a function related to the temperature, the subscript g represents gas, and the subscript l represents liquid.

7. The performance optimization device for a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, characterized in that, When the weighted sum of the engine power and total emissions is used as the optimization objective of the population particles, the following formula is adopted for particle i: Obj i = 1 / P i * 0.7 + T i * 0.3 Among them, Ob ji is the optimization objective, P i is the engine power, T i is the total emission.

8. The performance optimization device for a methanol-diesel dual-fuel in-cylinder direct injection engine according to claim 1, characterized in that, The following formula is adopted when updating the velocity and position of the population particles: v i,j (s + 1) = wv i,j (s) + τ1σ1[PB i,j -x i,j (s)] + τ2σ2[GB g,j -x i,j (s)]; x i,j (s + 1) = x i,j (s) + v i,j (s + 1), where v i,j represents the velocity of the particle, w represents the weight coefficient, 1 and τ2 represent the acceleration coefficients, σ1 and σ2 represent random numbers between 0 and 1, PB i,j represents the position where the individual optimization objective Obj is the smallest, GB g,j represents the position where the overall population optimization objective Obj is the smallest, x i,j represents the position of the particle.

9. A computer storage medium, on which a computer program is stored, characterized in that, When the computer program is executed by a processor, it implements the methanol-diesel dual-fuel in-cylinder direct injection engine performance optimization method according to any one of claims 1 to 4.

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