A method for enhancing power of air-cooled diesel engine with heat dissipation and insulation

Abstract

The invention discloses a power enhancement method for an air-cooled diesel engine with coordinated heat dissipation and insulation, which belongs to the field of engine technology. The specific process is as follows: step 1, based on a determined model of an air-cooled diesel engine, constructing and verifying a thermodynamic simulation model of the air-cooled diesel engine; step 2, performing heat insulation treatment near the top dead center of the engine cylinder liner by a user-defined method, and obtaining the power of the air-cooled diesel engine after heat insulation near the top dead center; step 3, performing heat dissipation treatment near the bottom dead center of the air-cooled diesel engine cylinder liner by increasing the outer diameter of the enhanced heat dissipation fin; step 4, determining the enhanced heat exchange amplification coefficient after enhanced heat dissipation near the bottom dead center of the air-cooled diesel engine cylinder liner; step 5, determining the power of the air-cooled diesel engine after enhanced heat dissipation near the bottom dead center of the cylinder liner; step 6, determining the limit of the boost pressure of the air-cooled diesel engine; step 7, determining the optimal heat insulation coating height and the optimal enhanced heat dissipation height; step 8, determining the power level of the diesel engine after the coordinated enhancement of heat dissipation and insulation.

Description

Technical Field

[0001] The invention belongs to the technical field of engines, and in particular relates to a method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation coordination. Background Art

[0002] Air-cooled diesel engines are widely used in heavy vehicles, construction machinery, power generation equipment and other fields due to their rapid cold start, high reliability and easy maintenance. However, air-cooled diesel engines are limited by the limitations of air-cooling cooling, and are restricted when the power is further enhanced. On the one hand, when the power is further enhanced, when the engine is running stably, the combustion chamber components will be subjected to higher combustion temperatures, which will lead to higher temperature difference heat transfer, and the heat released by fuel combustion will be dissipated, which is not conducive to thermal conversion; on the other hand, when the power of air-cooled diesel engines is further enhanced, the combustion chamber components will be subjected to higher heat loads, and failures are prone to occur under high heat loads, which seriously affects the reliability of diesel engine operation. In addition, the thermal insulation of the diesel engine combustion chamber can be used to regulate the direction of the combustion heat flow, which was once believed to improve the efficiency and power of the diesel engine. However, in fact, it is not feasible to make a diesel engine into an insulated engine. On the one hand, when the diesel engine combustion chamber is fully insulated, the temperature of the combustion chamber will increase significantly, causing the intake air to be heated quickly, affecting the intake charge, resulting in insufficient intake air, and affecting subsequent combustion; on the other hand, in order to fully insulate the combustion chamber of the diesel engine, insulating ceramics must be used, but ceramics are very brittle and have extremely poor reliability; in addition, the comprehensive use of insulation technology in the diesel engine has caused problems with the lubrication of the internal components of the diesel engine. Summary of the invention

[0003] The purpose of the present invention is to provide a method for enhancing the power of an air-cooled diesel engine with coordinated insulation and heat dissipation, which adopts a local insulation method to regulate the direction of combustion heat and a local enhanced heat dissipation method to ensure the intake charge, so as to further improve the power of the air-cooled diesel engine when the heat dissipation capacity of the air-cooled diesel engine is limited.

[0004] To achieve the above object, the present invention provides a method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation coordination, comprising the following steps:

[0005] Step 1: Based on the determined model of air-cooled diesel engine, build and verify the thermodynamic simulation model of the air-cooled diesel engine; based on the determined model of air-cooled diesel engine, determine the engine's cylinder diameter, stroke, crank-connecting rod ratio, intake and exhaust timing structure and performance parameters; based on the determined structure and engine parameters, build the engine's thermodynamic simulation model in GT-SUITE, and use the engine's bench test data to calibrate and verify the thermodynamic simulation model;

[0006] Step 2: Insulate the vicinity of the top dead center of the engine cylinder liner by a user-defined method to obtain the power of the air-cooled diesel engine after insulation near the top dead center;

[0007] Step 3, heat dissipation treatment is performed near the bottom dead center of the cylinder liner of the air-cooled diesel engine by increasing the outer diameter d2 of the enhanced heat dissipation fin;

[0008] Step 4, determining the enhanced heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine;

[0009] Step 5, determine the power after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine;

[0010] Step 6, determining the limit of the boost pressure of the air-cooled diesel engine;

[0011] Step 7, determine the optimal heat insulation coating height and the optimal enhanced heat dissipation height;

[0012] Step 8, determine the power level of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation; update the determined optimal heat insulation height and optimal enhanced heat dissipation height of the thermal insulation coating to the parameters of the thermodynamic simulation model, and run the thermodynamic simulation model to determine the power of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation.

[0013] Preferably, in step 1, when building a thermodynamic simulation model of the engine in GT-SUITE, the setting of the heat transfer model is included, specifically: the Woshini heat transfer model is selected as the heat transfer model, and the heat transfer amplification coefficient is set separately for each combustion chamber component, the heat transfer amplification coefficient of the combustion components cylinder head, piston, intake and exhaust valves is set to 1, the amplification coefficient of the cylinder liner is set to user-defined, and the user sets the heat transfer amplification coefficient at each crankshaft angle by himself.

[0014] Preferably, the specific process of the user-defined method in step 2 is as follows:

[0015] S21, determining the height H of the heat insulation area below the top dead center of the cylinder liner;

[0016] S22, calculate the piston displacement curve The specific calculation formula of the piston displacement curve is as follows:

[0017]

[0018] Where, X is the piston displacement; S is the stroke; λ is the crank-connecting rod ratio; Indicates the crankshaft angle;

[0019] S23. Determine the heat transfer amplification coefficient Cymul. When the value of the piston displacement curve is between 0 and the height of the cylinder liner thermal insulation coating, the local heat transfer amplification coefficient is zero, and the heat transfer amplification coefficient of other crankshaft angles is 1. The specific function expression is as follows:

[0020]

[0021] In the formula, is the function of the heat transfer amplification coefficient of the cylinder liner under thermal insulation conditions as a function of the crankshaft angle; H is the height of the thermal insulation coating of the cylinder liner;

[0022] S24, inputting the determined series of heat transfer amplification coefficient along with crankshaft rotation angle into the cylinder liner custom heat transfer amplification coefficient.

[0023] Preferably, the method for determining the outer diameter d2 of the enhanced heat dissipation fin in step 3 is as follows:

[0024] S31, determining the cylinder center distance d3 of the air-cooled diesel engine;

[0025] S32, determine the spacing ε between the original fin outer diameters, the specific expression is as follows:

[0026] ε=d3-d1 Formula 3

[0027] In the formula, d1 represents the outer diameter of the common fin;

[0028] S33. According to the determined ε, determine the outer diameter d2 of the enhanced heat dissipation fins. The specific expression is as follows:

[0029] d2=d1+ε*μ Formula 4

[0030] Where μ is the proportionality coefficient, and its value range is 0.4-0.6.

[0031] Preferably, the specific process of determining the enhanced heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine in step 4 is as follows:

[0032] S41, determining the thermal boundary conditions of the cylinder liner, obtaining the heat transfer coefficient and temperature at each crankshaft angle in the cylinder based on the constructed thermodynamic simulation model, calculating the average heat transfer coefficient and average heat transfer temperature according to the heat transfer coefficient and temperature at each crankshaft angle, and taking the average heat transfer coefficient and average heat transfer temperature as the heat transfer coefficient and heat transfer temperature of the thermal boundary conditions;

[0033] S42, determining the wind field boundary conditions of the cylinder liner, based on the bench test data of the air-cooled diesel engine, obtaining the pressure and temperature of the air chamber inlet and the pressure and temperature of the air chamber outlet of the air-cooled diesel engine, taking the inlet pressure and temperature of the air chamber as the inlet boundary conditions of the air-cooled diesel engine, and taking the outlet pressure and temperature of the air chamber as the outlet boundary conditions;

[0034] S43. Determine the heat dissipation before and after the enhancement of different cylinder liners based on the FLUNENT fluid-solid coupling simulation model, input the determined cylinder liners thermal boundary conditions and wind field boundary conditions into the fluid-solid coupling simulation model, and perform steady-state heat transfer simulations of ordinary fin cylinder liners and enhanced heat dissipation fin cylinder liners respectively under the condition that the boundary conditions remain unchanged, and obtain the heat transfer of cylinder liners with different types of fins under steady-state simulation according to the simulation results;

[0035] S44. Determine the enhanced heat transfer amplification factor κ. The specific calculation formula is as follows:

[0036] κ=Q1 / Q2 Formula 5

[0037] Where Q1 is the heat transfer of the enhanced heat dissipation fin cylinder liner under fluid-solid coupling simulation, and Q2 is the heat transfer of the ordinary fin cylinder liner under fluid-solid coupling simulation.

[0038] Preferably, the specific process of step 5 is: determining the curve of heat transfer amplification coefficient changing with crankshaft angle, inputting the determined curve of heat transfer amplification coefficient changing with crankshaft angle into the thermodynamic simulation model, running the thermodynamic simulation model, and obtaining the power of the air-cooled diesel engine after enhanced heat dissipation. The specific expression is as follows:

[0039]

[0040] In the formula, H q To enhance the height of the heat dissipation fins, S is the stroke, and H is the height of the cylinder liner thermal insulation coating. is the piston displacement curve, The heat transfer amplification coefficient of the cylinder liner changes as a function of the crankshaft angle under heat insulation conditions.

[0041] Preferably, the specific process of determining the limit of the boost pressure of the air-cooled diesel engine in step 6 is:

[0042] S61. Determine the maximum boost pressure for the turbocharger system to match the work. Based on the thermodynamic simulation model constructed in GT-SUITE, set n working conditions for the thermodynamic simulation model. The thermal insulation amplification factor of the cylinder liner in each working condition changes from 0 to 1 with a step size of

[0043] S62, observing the speed and expansion ratio of the turbine of the turbocharger system in the interface when the thermodynamic simulation model is running;

[0044] S63. When the speed and expansion ratio of the turbocharger system in the operating interface do not appear an alarm that exceeds the matching map range, the simulation result of the model boost pressure under this working condition is recorded. Among all the recorded working conditions, the maximum value of the boost pressure simulation result is used as the limit of the boost pressure of the air-cooled diesel engine.

[0045] Preferably, the specific process of determining the optimal thermal insulation coating height and the optimal enhanced heat dissipation height in step 7 is as follows:

[0046] S71. Based on the constructed thermodynamic simulation model, the cylinder liner insulation height is set in the thermodynamic simulation model to change from the stroke height of the diesel engine to 0, with a step length of 5 mm. The height of the enhanced heat dissipation area under each working condition is the stroke height of the engine minus the height of the insulation area.

[0047] S72. Set the working conditions, run the thermodynamic simulation model, and record the height of the thermal insulation coating, enhanced heat dissipation height, effective power and boost pressure under each working condition.

[0048] S73. Predict the optimal thermal insulation coating height and the optimal enhanced heat dissipation height for power enhancement under boost pressure limitation based on a neural network.

[0049] Preferably, the specific process of predicting the optimal heat insulation coating height and the optimal enhanced heat dissipation height for power enhancement under the boost pressure limitation based on the neural network in S73 is as follows:

[0050] S731. The heat insulation coating height and enhanced heat dissipation height are used as input layers, and the boost pressure and effective power are used as output layers of the neural network. The enhanced heat dissipation height is expressed by subtracting the heat insulation coating height from the stroke height. The neural network uses the perception layer neural network to fit the input layer and the output. The specific expression is as follows:

[0051] Pe=Sn1(H,SH) Formula 7

[0052] Rb=Sn2(H,SH) Formula 8

[0053] Where Pe is the effective power, H is the height of the cylinder liner insulation area, SH is the height of the enhanced heat dissipation area, Sn1 represents the fitting function of the effective power, Sn2 represents the fitting function of the boost pressure, and Rb represents the boost pressure;

[0054] S732, increase the number of perception layer neural networks in sequence, use fitting functions Sn1 and Sn2 to make the determination coefficient between 1.03 and 0.97 to ensure the credibility of the prediction. The calculation formula of the determination coefficient is as follows:

[0055]

[0056]

[0057] Where P1 is the determination coefficient of Sn1, n is the number of working conditions, Pe ri is the i-th indicated power predicted by the fitting function, Pe ti is the ith indicated power counted, Pe - is the average value of the statistical indicated power, P2 is the coefficient of determination of Sn2, the value of n is 20, and Rb ri is the i-th boost pressure predicted by the fitting function, Rb ti is the ith boost pressure, Rb - is the average value of the statistical boost pressure;

[0058] S733. Determine the optimal thermal insulation coating height of the cylinder liner thermal insulation area based on the fitting function. The optimal thermal insulation coating height is the height of the cylinder liner thermal insulation area with maximum diesel engine power under boost pressure limitation. The optimal enhanced heat dissipation height is the engine stroke height minus the optimal thermal insulation coating height.

[0059] Therefore, the present invention adopts the above-mentioned heat insulation and heat dissipation coordinated air-cooled diesel engine power enhancement method, which has the following beneficial effects:

[0060] (1) Use coating for heat insulation near the top dead center to avoid high temperature difference heat transfer, prevent heat dissipation, and facilitate heat-to-work conversion;

[0061] (2) When the piston moves downward to a certain point, the wall area is used to enhance heat transfer and cooling, thereby reducing the heat of the entire combustion system and ensuring the intake air charge.

[0062] (3) Combining the ideas of heat insulation and enhanced heat dissipation, the power of the diesel engine can be further improved under the condition that the cooling capacity of the air-cooled diesel engine is limited.

[0063] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a logic block diagram of a method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to the present invention;

[0065] Figure 2 It is a schematic diagram of a cylinder liner with enhanced heat dissipation of an air-cooled diesel engine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] See also Figure 1-2 , a method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation synergy, comprising the following steps:

[0068] Step 1. Based on the determined model of air-cooled diesel engine, construct and verify the thermodynamic simulation model of the air-cooled diesel engine; based on the determined model of air-cooled diesel engine, determine the structure and performance parameters of the engine's cylinder diameter, stroke, crank-connecting rod ratio, and intake and exhaust timing; based on the determined structure and engine parameters, construct the engine's thermodynamic simulation model in GT-SUITE, and use the engine's bench test data to calibrate and verify the thermodynamic simulation model; when constructing the engine's thermodynamic simulation model in GT-SUITE, include the setting of the heat transfer model, specifically: the heat transfer model selects the Woshini heat transfer model, and selects to set the heat transfer amplification coefficient for each combustion chamber component separately, the heat transfer amplification coefficient of the combustion components cylinder head, piston, intake and exhaust valves is set to 1, the amplification coefficient of the cylinder liner is set to user-defined, and the user sets the heat transfer amplification coefficient at each crankshaft angle by himself;

[0069] Step 2: Insulate the area near the top dead center of the engine cylinder liner using a user-defined method to obtain the power of the air-cooled diesel engine after insulation near the top dead center. After the cylinder liner of the air-cooled diesel engine is insulated, the heat transfer amount in the insulation area can be considered zero, and the heat transfer coefficient at this time can be considered zero. However, the GT-SUITE software does not have the function of directly setting local insulation of the cylinder liner. It can only be achieved through a user-defined method. The specific process of the user-defined method is as follows:

[0070] S21, determining the height H of the heat insulation area below the top dead center of the cylinder liner;

[0071] S22, calculate the piston displacement curve The specific calculation formula of the piston displacement curve is as follows:

[0072]

[0073] Where, X is the piston displacement; S is the stroke; λ is the crank-connecting rod ratio; Indicates the crankshaft angle;

[0074] S23. Determine the heat transfer amplification coefficient Cymul. When the value of the piston displacement curve is from 0 to the height of the cylinder liner thermal insulation coating, that is, when thermally insulated, the local heat transfer amplification coefficient is zero, and the heat transfer amplification coefficient of other crankshaft angles is 1. The specific function expression is as follows:

[0075]

[0076] In the formula, is the function of the heat transfer amplification coefficient of the cylinder liner under thermal insulation conditions and the crankshaft angle; H is the height of the thermal insulation coating of the cylinder liner;

[0077] S24. Input the determined series of heat transfer amplification coefficient along with crankshaft rotation angle into the customized heat transfer amplification coefficient of cylinder liner. With such setting, GT-SUITE can realize the modeling of air-cooled diesel engine with partial insulation of cylinder liner. When the cylinder liner is insulated, the local amplification coefficient is set to zero. In this way, when the software calculates heat transfer, the value of heat transfer coefficient multiplied by temperature difference multiplied by heat transfer amplification coefficient 0 multiplied by heat exchange area multiplied by heat exchange time is 0, which is actually equivalent to the effect of completing the insulation calculation. Other types of engines can also refer to the above method for modeling of partial insulation of cylinder liner. After completing the customization of cylinder liner insulation amplification coefficient, running the simulation model can determine the power of the diesel engine after the diesel engine cylinder liner is insulated near the top dead center.

[0078] Step 3, heat dissipation treatment is performed near the bottom dead center of the cylinder liner of the air-cooled diesel engine by increasing the outer diameter d2 of the enhanced heat dissipation fins; wherein the outer diameter d1 of the ordinary fins remains unchanged, and the size of the outer diameter d2 of the enhanced heat dissipation fins needs to be determined according to the structural parameters of the actual air-cooled diesel engine. The method for determining the outer diameter d2 of the enhanced heat dissipation fins is as follows:

[0079] S31, determining the cylinder center distance d3 of the air-cooled diesel engine;

[0080] S32, determine the spacing ε between the original fin outer diameters, the specific expression is as follows:

[0081] ε=d3-d1 Formula 3

[0082] In the formula, d1 represents the outer diameter of the common fin;

[0083] S33. According to the determined ε, determine the outer diameter d2 of the enhanced heat dissipation fins. The specific expression is as follows:

[0084] d2=d1+ε*μ Formula 4

[0085] Where μ is the proportionality coefficient, and its value range is 0.4-0.6.

[0086] Step 4, determine the enhanced heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center of the air-cooled diesel engine cylinder liner; after the heat dissipation near the bottom dead center of the cylinder liner is enhanced, the circulating heat dissipation changes, and the power of the diesel engine will also change. Therefore, if you want to determine the power of the air-cooled diesel engine after enhanced heat dissipation near the bottom dead center, you need to clarify the heat dissipation after enhanced heat dissipation near the bottom dead center of the air-cooled diesel engine, that is, determine the multiple of heat dissipation increase after enhanced heat exchange near the bottom dead center compared with the original, that is, calculate the heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center. The specific process is as follows:

[0087] S41, determining the thermal boundary conditions of the cylinder liner, obtaining the heat transfer coefficient and temperature at each crankshaft angle in the cylinder based on the constructed thermodynamic simulation model, calculating the average heat transfer coefficient and average heat transfer temperature according to the heat transfer coefficient and temperature at each crankshaft angle, and taking the average heat transfer coefficient and average heat transfer temperature as the heat transfer coefficient and heat transfer temperature of the thermal boundary conditions;

[0088] S42, determining the wind field boundary conditions of the cylinder liner, based on the bench test data of the air-cooled diesel engine, obtaining the pressure and temperature of the air chamber inlet and the pressure and temperature of the air chamber outlet of the air-cooled diesel engine, taking the inlet pressure and temperature of the air chamber as the inlet boundary conditions of the air-cooled diesel engine, and taking the outlet pressure and temperature of the air chamber as the outlet boundary conditions;

[0089] S43. Determine the heat dissipation before and after the enhancement of different cylinder liners based on the FLUNENT fluid-solid coupling simulation model, input the determined cylinder liners thermal boundary conditions and wind field boundary conditions into the fluid-solid coupling simulation model, and perform steady-state heat transfer simulations of ordinary fin cylinder liners and enhanced heat dissipation fin cylinder liners respectively under the condition that the boundary conditions remain unchanged, and obtain the heat transfer of cylinder liners with different types of fins under steady-state simulation according to the simulation results;

[0090] S44. Determine the enhanced heat transfer amplification factor κ. The specific calculation formula is as follows:

[0091] κ=Q1 / Q2 Formula 5

[0092] Where Q1 is the heat transfer of the enhanced heat dissipation fin cylinder liner under fluid-solid coupling simulation, and Q2 is the heat transfer of the ordinary fin cylinder liner under fluid-solid coupling simulation.

[0093] Step 5, determine the power of the air-cooled diesel engine after enhanced heat dissipation near the bottom dead center of the cylinder liner; the specific process is: determine the curve of heat transfer amplification coefficient changing with the crankshaft angle, input the determined curve of heat transfer amplification coefficient changing with the crankshaft angle into the thermodynamic simulation model, run the thermodynamic simulation model, and obtain the power of the air-cooled diesel engine after enhanced heat dissipation. The specific expression is as follows:

[0094]

[0095] In the formula, H q To enhance the height of the heat dissipation fins, S is the stroke, and H is the height of the cylinder liner thermal insulation coating. is the piston displacement curve, The heat transfer amplification coefficient of the cylinder liner changes as a function of the crankshaft angle under heat insulation conditions.

[0096] Step 6: Determine the limit of the boost pressure of the air-cooled diesel engine. After the diesel engine cylinder liner is insulated, the energy flowing toward the exhaust gas increases, so the energy available to the exhaust gas turbocharger system increases, which increases the low turbine speed of the exhaust gas turbocharger system and increases the boost ratio provided. However, the matching point of the turbocharger system also shifts. Therefore, the limiting condition for wall insulation is that after the wall insulation is applied, the matching point of the turbocharger system cannot deviate from the map of the turbocharger system. The specific process is as follows:

[0097] S61. Determine the maximum boost pressure for the turbocharger system to match the work. Based on the thermodynamic simulation model constructed in GT-SUITE, set n working conditions for the thermodynamic simulation model. The thermal insulation amplification factor of the cylinder liner in each working condition changes from 0 to 1 with a step size of

[0098] S62, observing the speed and expansion ratio of the turbine of the turbocharger system in the interface when the thermodynamic simulation model is running;

[0099] S63. When the speed and expansion ratio of the turbocharger system in the operating interface do not appear an alarm that exceeds the matching map range, the simulation result of the model boost pressure under this working condition is recorded. Among all the recorded working conditions, the maximum value of the boost pressure simulation result is used as the limit of the boost pressure of the air-cooled diesel engine.

[0100] Step 7: Determine the optimal thermal insulation coating height and the optimal enhanced heat dissipation height; the specific process is as follows:

[0101] S71. Based on the constructed thermodynamic simulation model, the cylinder liner insulation height is set in the thermodynamic simulation model to change from the stroke height of the diesel engine to 0, with a step length of 5 mm. The height of the enhanced heat dissipation area under each working condition is the stroke height of the engine minus the height of the insulation area.

[0102] S72. Set the working conditions, run the thermodynamic simulation model, and record the height of the thermal insulation coating, enhanced heat dissipation height, effective power and boost pressure under each working condition.

[0103] S73. Based on the neural network, the optimal heat insulation coating height and the optimal enhanced heat dissipation height for power enhancement under the boost pressure limitation are predicted. The specific process is as follows:

[0104] S731. The heat insulation coating height and enhanced heat dissipation height are used as input layers, and the boost pressure and effective power are used as output layers of the neural network. The enhanced heat dissipation height is expressed by subtracting the heat insulation coating height from the stroke height. The neural network uses the perception layer neural network to fit the input layer and the output. The specific expression is as follows:

[0105] Pe=Sn1(H,SH) Formula 7

[0106] Rb=Sn2(H,SH) Formula 8

[0107] Where Pe is the effective power, H is the height of the cylinder liner insulation area, SH is the height of the enhanced heat dissipation area, Sn1 represents the fitting function of the effective power, Sn2 represents the fitting function of the boost pressure, and Rb represents the boost pressure;

[0108] S732, increase the number of perception layer neural networks in sequence, use fitting functions Sn1 and Sn2 to make the determination coefficient between 1.03 and 0.97 to ensure the credibility of the prediction. The calculation formula of the determination coefficient is as follows:

[0109]

[0110]

[0111] Where P1 is the determination coefficient of Sn1, n is the number of working conditions, Pe ri is the i-th indicated power predicted by the fitting function, Pe ti is the ith indicated power counted, Pe - is the average value of the statistical indicated power, P2 is the coefficient of determination of Sn2, the value of n is 20, and Rb ri is the i-th boost pressure predicted by the fitting function, Rb ti is the ith boost pressure, Rb - is the average value of the statistical boost pressure;

[0112] S733. Determine the optimal thermal insulation coating height of the cylinder liner thermal insulation area based on the fitting function. The optimal thermal insulation coating height is the height of the cylinder liner thermal insulation area with maximum diesel engine power under boost pressure limitation. The optimal enhanced heat dissipation height is the engine stroke height minus the optimal thermal insulation coating height.

[0113] Step 8, determine the power level of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation; update the determined optimal heat insulation height and optimal enhanced heat dissipation height of the thermal insulation coating to the parameters of the thermodynamic simulation model, and run the thermodynamic simulation model to determine the power of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation.

[0114] Example

[0115] Take an existing six-cylinder air-cooled diesel engine with a cylinder diameter of 100mm, a stroke of 100mm, a connecting rod length of 220mm, and a rated power of 213.1386kW as an example:

[0116] According to step 1, determine the cylinder diameter of the air-cooled diesel engine to be 100mm, the stroke to be 100mm, the crank-connecting rod ratio to be 0.2272, the engine intake timing to be 322-634CAD (crank angle degree), the exhaust timing to be 96-408CAD, the range of the cycle crankshaft angle to be (0-720)CAD and other engine parameters, and build a thermodynamic simulation model of the engine in GT-SUITE. The heat transfer model is set as follows: the heat transfer model selects the Woschni heat transfer model, and sets the heat transfer amplification coefficient for each combustion chamber component separately. The heat transfer amplification coefficient of the combustion components cylinder head, piston, intake and exhaust valves is set to 1, and the amplification coefficient of the cylinder liner is set to user-defined. Users can define the heat transfer amplification coefficient at each crankshaft angle.

[0117] According to step 2, the engine cylinder liner is insulated near the top dead center, and the insulation height is initially set to 20 mm. The piston displacement curve is determined according to formula 1, and the insulation amplification factor of the cylinder liner at each crankshaft angle is determined according to formula 2. The determined insulation amplification factor is input into the thermodynamic simulation model to determine the engine power is 217.94 kW;

[0118] According to step 3, the cylinder diameter of the original engine is 100 mm, the outer diameter of the ordinary fin is 128 mm, the cylinder center distance is 148 mm, the outer diameter spacing of the original fin calculated according to formula 3 is 20 mm, the outer diameter of the enhanced heat dissipation fin determined according to formula 4 is 138 mm, the proportional coefficient μ is 0.5, and the schematic diagram of the cylinder liner of the disclosed air-cooled diesel engine with enhanced heat dissipation is shown in the attached figure. Figure 2 As shown;

[0119] According to step 4, the average heat transfer coefficient of the thermal boundary conditions is determined to be 1240.19 W / (m 2 *K), the average heat transfer temperature is 832.56K; the boundary conditions of the wind field are that the pressure of the wind pressure chamber is 1.2kpa (gauge pressure), the temperature is 25℃, and the heat transfer amplification factor is finally determined to be 1.2;

[0120] According to step 5, the determined cylinder liner heat transfer amplification coefficient is input into the simulation model, where the height of the enhanced heat dissipation fin is 20 mm, and the power of the air-cooled diesel engine after enhanced heat dissipation near the bottom dead center is determined to be 215.29 kW;

[0121] According to step 6, 21 working conditions are constructed for the thermodynamic simulation model. The cylinder liner heat transfer amplification coefficient of the working condition varies from 0 to 1, and the step length is 0.05, as shown in Table 1. Then the simulation model is run, and the simulation model operation interface is observed. When the speed and expansion ratio of the turbocharger system in the operation interface do not have an alarm that exceeds the matching map range, the simulation result of the model boost pressure under this working condition is recorded. Among all the recorded working conditions, the maximum value of the boost pressure simulation result is used as the limit of the boost pressure of the air-cooled diesel engine, and the boost pressure limit is determined to be 3.8 bar.

[0122] Table 1 Cylinder liner insulation amplification factor under working conditions

[0123] Working condition number 1 2 3 4 …… 20 21 Cylinder liner insulation magnification factor 0.05 0.1 0.15 0.2 …… 0.95 1

[0124] According to step 7, 21 working conditions are set for the constructed air-cooled diesel engine thermodynamic simulation model. The insulation height changes from the stroke height to 0 with a step length of 5 mm. The height of the enhanced heat dissipation is the stroke height minus the insulation height. The detailed settings of the 21 working conditions are shown in Table 2:

[0125] Table 2 Height of the cylinder liner insulation area and height setting for enhanced heat dissipation

[0126] Working condition number 1 2 3 4 …… 20 21 Insulation area height mm 100 95 90 85 …… 5 0 Enhanced heat dissipation height mm 0 5 10 15 …… 95 100

[0127] After setting the working conditions, run the simulation model and record the effective power and boost ratio under each working condition. Some data are shown in Table 3:

[0128] Table 3 Pressure ratio and effective power under various working conditions

[0129] Working condition number 1 2 3 4 …… 20 21 Effective power kW 228.80 229.05 229.14 229.13 …… 207.88 206.86 Pressure ratio 3.92 3.87 3.84 3.82 …… 3.47 3.46

[0130] Construct a BP neural network, take the height of the insulation area and the height of the enhanced heat dissipation as input values, and the boost ratio and effective power as the output results. Adjust the number of hidden layers of the neural grid so that its determination coefficient is between 0.97 and 1.03, set the learning rate to 0.01, and the maximum number of training times is 1000. Train the neural network with all the data, and predict the data based on the trained neural network. Some of the predicted data are shown in Table 4:

[0131] Table 4 Partial predicted boost ratio and predicted effective power

[0132]

[0133] The determination coefficients P1 and P2 are 1.0001 and 1.0004 respectively, which meet the determination coefficient requirements, indicating that the constructed neural network has high prediction accuracy. Finally, based on the constructed neural network, under the limit of boost pressure of 3.8 bar, the optimal thermal insulation coating height for power enhancement and the optimal enhanced heat dissipation height are determined. The optimal thermal insulation area height is determined to be 80 mm, and the optimal enhanced heat dissipation height is 20 mm.

[0134] According to step 8, it is determined that the power of the diesel engine after the heat insulation and heat dissipation synergistic enhancement is 228 kW, which is 15 kW higher than the original power, an increase of 7%.

[0135] Therefore, the present invention adopts the above-mentioned method for enhancing the power of an air-cooled diesel engine with coordinated insulation and heat dissipation. By using a coating for heat insulation near the top dead center and enhancing heat transfer and cooling in the wall area when the piston descends to a certain moment, the work is not affected, the heat of the entire combustion system is reduced, high temperature difference heat transfer is avoided, and the power of the air-cooled diesel engine is improved; the problems of high heat dissipation loss, low thermal efficiency and power of the diesel engine, and poor economic performance of the existing air-cooled diesel engine are solved.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation, characterized in that: The following steps are involved: Step 1: Based on the determined model of air-cooled diesel engine, build and verify the thermodynamic simulation model of the air-cooled diesel engine; based on the determined model of air-cooled diesel engine, determine the engine's cylinder diameter, stroke, crank-connecting rod ratio, intake and exhaust timing structure and performance parameters; based on the determined structure and engine parameters, build the engine's thermodynamic simulation model in GT-SUITE, and use the engine's bench test data to calibrate and verify the thermodynamic simulation model; Step 2: Insulate the vicinity of the top dead center of the engine cylinder liner by a user-defined method to obtain the power of the air-cooled diesel engine after insulation near the top dead center; Step 3, heat dissipation treatment is performed near the bottom dead center of the cylinder liner of the air-cooled diesel engine by increasing the outer diameter d2 of the enhanced heat dissipation fin; Step 4, determining the enhanced heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine; Step 5, determine the power after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine; Step 6, determining the limit of the boost pressure of the air-cooled diesel engine; Step 7, determine the optimal thermal insulation coating height and the optimal enhanced heat dissipation height; Step 8, determine the power level of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation; update the determined optimal heat insulation height and optimal enhanced heat dissipation height of the thermal insulation coating to the parameters of the thermodynamic simulation model, and run the thermodynamic simulation model to determine the power of the diesel engine after the synergistic enhancement of heat insulation and heat dissipation.

2. The method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1, characterized in that: In step 1, when building the thermodynamic simulation model of the engine in GT-SUITE, the setting of the heat transfer model is included, specifically: the Woshini heat transfer model is selected as the heat transfer model, and the heat transfer amplification coefficient is set separately for each combustion chamber component. The heat transfer amplification coefficient of the combustion components cylinder head, piston, intake and exhaust valve is set to 1, and the amplification coefficient of the cylinder liner is set to user-defined. The user sets the heat transfer amplification coefficient at each crankshaft angle by himself.

3. The method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The specific process of the user-defined method in step 2 is as follows: S21, determining the height H of the heat insulation area below the top dead center of the cylinder liner; S22, calculate the piston displacement curve The specific calculation formula of the piston displacement curve is as follows: Where, X is the piston displacement; S is the stroke; λ is the crank-connecting rod ratio; Indicates the crankshaft angle; S23. Determine the heat transfer amplification coefficient Cymul. When the value of the piston displacement curve is between 0 and the height of the cylinder liner thermal insulation coating, the local heat transfer amplification coefficient is zero, and the heat transfer amplification coefficient of other crankshaft angles is 1. The specific function expression is as follows: In the formula, is the function of the heat transfer amplification coefficient of the cylinder liner under thermal insulation conditions as a function of the crankshaft angle; H is the height of the thermal insulation coating of the cylinder liner; S24, inputting the determined series of heat transfer amplification coefficient along with crankshaft rotation angle into the cylinder liner custom heat transfer amplification coefficient.

4. The method for enhancing the power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The method for determining the outer diameter d2 of the enhanced heat dissipation fin in step 3 is as follows: S31, determining the cylinder center distance d3 of the air-cooled diesel engine; S32, determine the spacing ε between the original fin outer diameters, the specific expression is as follows: ε=d3-d1 Formula 3 In the formula, d1 represents the outer diameter of the common fin; S33. According to the determined ε, determine the outer diameter d2 of the enhanced heat dissipation fins. The specific expression is as follows: d2=d1+ε*μ Formula 4 Where μ is the proportionality coefficient, and its value range is 0.4-0.

6.

5. The method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The specific process of determining the enhanced heat transfer amplification coefficient after enhanced heat dissipation near the bottom dead center of the cylinder liner of the air-cooled diesel engine in step 4 is as follows: S41, determining the thermal boundary conditions of the cylinder liner, obtaining the heat transfer coefficient and temperature at each crankshaft angle in the cylinder based on the constructed thermodynamic simulation model, calculating the average heat transfer coefficient and average heat transfer temperature according to the heat transfer coefficient and temperature at each crankshaft angle, and taking the average heat transfer coefficient and average heat transfer temperature as the heat transfer coefficient and heat transfer temperature of the thermal boundary conditions; S42, determining the wind field boundary conditions of the cylinder liner, based on the bench test data of the air-cooled diesel engine, obtaining the pressure and temperature of the air chamber inlet and the pressure and temperature of the air chamber outlet of the air-cooled diesel engine, taking the inlet pressure and temperature of the air chamber as the inlet boundary conditions of the air-cooled diesel engine, and taking the outlet pressure and temperature of the air chamber as the outlet boundary conditions; S43. Determine the heat dissipation before and after the enhancement of different cylinder liners based on the FLUNENT fluid-solid coupling simulation model, input the determined cylinder liners thermal boundary conditions and wind field boundary conditions into the fluid-solid coupling simulation model, and perform steady-state heat transfer simulations of ordinary fin cylinder liners and enhanced heat dissipation fin cylinder liners respectively under the condition that the boundary conditions remain unchanged, and obtain the heat transfer of cylinder liners with different types of fins under steady-state simulation according to the simulation results; S44. Determine the enhanced heat transfer amplification factor κ. The specific calculation formula is as follows: κ=Q1 / Q2 Formula 5 Where Q1 is the heat transfer of the enhanced heat dissipation fin cylinder liner under fluid-solid coupling simulation, and Q2 is the heat transfer of the ordinary fin cylinder liner under fluid-solid coupling simulation.

6. The method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The specific process of step 5 is: determine the curve of heat transfer amplification coefficient changing with crankshaft angle, input the determined curve of heat transfer amplification coefficient changing with crankshaft angle into the thermodynamic simulation model, run the thermodynamic simulation model, and obtain the power of the air-cooled diesel engine after enhanced heat dissipation. The specific expression is as follows: In the formula, H q To enhance the height of the heat dissipation fins, S is the stroke, and H is the height of the cylinder liner thermal insulation coating. is the piston displacement curve, The heat transfer amplification coefficient of the cylinder liner changes as a function of the crankshaft angle under heat insulation conditions.

7. The method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The specific process of determining the limit of the boost pressure of the air-cooled diesel engine in step 6 is: S61. Determine the maximum boost pressure for the turbocharger system to match the work. Based on the thermodynamic simulation model constructed in GT-SUITE, set n working conditions for the thermodynamic simulation model. The thermal insulation amplification factor of the cylinder liner in each working condition changes from 0 to 1 with a step size of S62, observing the speed and expansion ratio of the turbine of the turbocharger system in the interface when the thermodynamic simulation model is running; S63. When the speed and expansion ratio of the turbocharger system in the operating interface do not appear an alarm that exceeds the matching map range, the simulation result of the model boost pressure under this working condition is recorded. Among all the recorded working conditions, the maximum value of the boost pressure simulation result is used as the limit of the boost pressure of the air-cooled diesel engine.

8. The method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 1 is characterized in that: The specific process of determining the optimal thermal insulation coating height and the optimal enhanced heat dissipation height in step 7 is as follows: S71. Based on the constructed thermodynamic simulation model, the cylinder liner insulation height is set in the thermodynamic simulation model to change from the stroke height of the diesel engine to 0, with a step length of 5 mm. The height of the enhanced heat dissipation area under each working condition is the stroke height of the engine minus the height of the insulation area. S72. Set the working conditions, run the thermodynamic simulation model, and record the height of the thermal insulation coating, enhanced heat dissipation height, effective power and boost pressure under each working condition. S73. Predict the optimal thermal insulation coating height and the optimal enhanced heat dissipation height for power enhancement under boost pressure limitation based on a neural network.

9. The method for enhancing power of an air-cooled diesel engine with heat insulation and heat dissipation coordination according to claim 8, characterized in that: The specific process of the optimal heat-insulating coating height and the optimal enhanced heat dissipation height for power enhancement under the limitation of boost pressure based on the neural network in S73 is as follows: S731. The heat insulation coating height and enhanced heat dissipation height are used as input layers, and the boost pressure and effective power are used as output layers of the neural network. The enhanced heat dissipation height is expressed by subtracting the heat insulation coating height from the stroke height. The neural network uses the perception layer neural network to fit the input layer and the output. The specific expression is as follows: Pe=Sn1(H,SH) Formula 7 Rb=Sn2(H,SH) Formula 8 Where Pe is the effective power, H is the height of the cylinder liner insulation area, SH is the height of the enhanced heat dissipation area, Sn1 represents the fitting function of the effective power, Sn2 represents the fitting function of the boost pressure, and Rb represents the boost pressure; S732, increase the number of perception layer neural networks in sequence, use fitting functions Sn1 and Sn2 to make the determination coefficient between 1.03 and 0.97 to ensure the credibility of the prediction. The calculation formula of the determination coefficient is as follows: Where P1 is the determination coefficient of Sn1, n is the number of working conditions, Pe ri is the i-th indicated power predicted by the fitting function, Pe ti is the ith indicated power counted, Pe - is the average value of the statistical indicated power, P2 is the coefficient of determination of Sn2, the value of n is 20, and Rb ri is the i-th boost pressure predicted by the fitting function, Rb ti is the ith boost pressure, Rb - is the average value of the statistical boost pressure; S733. Determine the optimal thermal insulation coating height of the cylinder liner thermal insulation area based on the fitting function. The optimal thermal insulation coating height is the height of the cylinder liner thermal insulation area with maximum diesel engine power under boost pressure limitation. The optimal enhanced heat dissipation height is the engine stroke height minus the optimal thermal insulation coating height.

Images