Diesel engine in-cylinder gas heat transfer control equation analysis and combustion chamber wall temperature prediction method

Abstract

The invention discloses a diesel engine in-cylinder gas heat transfer control equation analysis and combustion chamber wall temperature prediction method, and relates to the field of engines, and the method comprises the following steps: calculating an excess air coefficient, an average temperature during combustion and expansion, an in-cylinder average pressure and a heat transfer coefficient based on control operation parameters obtained by a vehicle-mounted ECU in a vehicle driving process; the control operation parameters comprise the rotating speed, the circulating oil injection quantity, the air inlet pressure and the like; the heat transfer coefficient comprises a combustion chamber side heat transfer coefficient, a cooling side heat transfer coefficient and a comprehensive heat transfer coefficient; respectively calculating the wall surface temperatures of the combustion chamber side and the cooling side based on the obtained parameters; comparing the predicted wall temperature of the combustion chamber of the engine with a wall temperature limit value of the engine, judging whether the wall temperature of the combustion chamber reaches the expectation or not, entering the next working condition if the wall temperature reaches the expectation, and readjusting the flow of the cooling water if the wall temperature does not reach the expectation; and re-optimizing the wall temperature of the combustion chamber according to the steps of calculating the excess air coefficient, the average temperature and the heat transfer coefficient and calculating the wall temperature.

Description

Technical Field

[0001] This invention relates to the technical field of engines, and more specifically, to the analysis of in-cylinder gas heat transfer control equations and the method for predicting combustion chamber wall temperature in diesel engines. Background Technology

[0002] The purpose of diesel engine cooling is to keep the combustion chamber wall material below a certain temperature to maintain its mechanical strength and avoid excessive thermal stress.

[0003] Because the flow rate of a traditional mechanical water pump only changes passively with the speed and cannot be actively adjusted with the load, in order to ensure sufficient cooling at the maximum torque point, the cooling water flow rate setting will generally cause varying degrees of overcooling at other speeds and loads, resulting in unnecessary in-cylinder gas heat loss and additional accessory power loss of the cooling system.

[0004] In today's era of widespread adoption of electronic water pumps, intelligent control of cooling water flow based on engine operating conditions has become possible. However, the calibration of cooling water flow under different speeds and loads in steady-state conditions, the control strategy for cooling water flow, and its impact on engine thermal load are issues that urgently need to be studied and require theoretical guidance. Summary of the Invention

[0005] The purpose of this invention is to propose a cooling water flow control strategy based on engine operating conditions, so as to minimize in-cylinder heat dissipation loss and cooling system accessory loss under the premise that the heat load does not exceed the limit, thereby indirectly improving the thermal efficiency of the engine.

[0006] The technical solution of this invention is: providing an analytical method for the control equation of in-cylinder gas heat transfer in a diesel engine and a method for predicting the combustion chamber wall temperature, the method comprising:

[0007] S1. During vehicle operation, the excess air coefficient, average temperature during combustion and expansion, average cylinder pressure, and heat transfer coefficient are calculated based on the control operating parameters obtained from the vehicle ECU. The control operating parameters include engine speed, fuel injection quantity, and intake pressure. The heat transfer coefficient includes the combustion chamber side heat transfer coefficient, the cooling side heat transfer coefficient, and the overall heat transfer coefficient.

[0008] S2. Calculate the wall temperatures on the combustion chamber side and the cooling side based on the parameters obtained above.

[0009] S3. Compare the predicted engine combustion chamber wall temperature with the engine wall temperature limit to determine whether the combustion chamber wall temperature has reached the expected value. If it has reached the expected value, proceed to the next operating condition. If it has not reached the expected value, readjust the cooling water flow rate and re-optimize the combustion chamber wall temperature according to the above steps S1 for calculating the excess air coefficient, average temperature, and heat transfer coefficient, and S2 for calculating the wall temperature.

[0010] In any of the above technical solutions, step S1 further includes:

[0011] S11. Calculate the excess air coefficient based on engine speed, intake pressure, and fuel injection quantity. :

[0012] ;

[0013] ;

[0014] In the formula: P is the excess air coefficient; n is the rotational speed; P in This refers to the intake pressure. This refers to the recirculation intake volume; This refers to the fuel injection quantity per cycle; AFR is the air-fuel ratio. , The fitting coefficients of the equation are . For constant terms;

[0015] S12. Predict the average gas temperature during combustion and expansion in the engine cylinder using the excess air coefficient, wherein the average temperature during combustion and expansion... Calculated using the following formula:

[0016] ;

[0017] , , The fitting coefficients of the equation are . For constant terms;

[0018] S13. Based on the current operating conditions, including engine speed, intake pressure, injection pressure, injection advance angle, and cyclic injection quantity, predict the average cylinder pressure, where the average cylinder pressure is... Determined by the following formula:

[0019] ;

[0020] In the formula: These are the main injection advance angle, injection pressure, and intake pressure under the current operating conditions; , , , The fitting coefficients of the equation are . For constant terms;

[0021] S14. Predict the combustion chamber wall heat transfer coefficient based on the average gas temperature and cylinder pressure during combustion and expansion. Predict the cooling side heat transfer coefficient based on the cooling water flow rate and temperature. Then calculate the comprehensive heat transfer coefficient based on the combustion side, cooling side heat transfer coefficients, and wall thickness. The combustion side heat transfer coefficient is... for:

[0022] ;

[0023] in The average speed of the piston:

[0024] ;

[0025] Where S is the piston stroke;

[0026] The heat transfer coefficient on the cooling side is :

[0027] ;

[0028] Overall heat transfer coefficient Determined by the following formula:

[0029] ;

[0030] In the formula: , These are the heat transfer coefficients on the combustion side and the cooling side, respectively; Cylinder diameter; Q is the conversion factor; cool T is the cooling water flow rate; c This refers to the cooling water temperature. Where is the wall thickness; K is the thermal conductivity of the cylinder block.

[0031] In any of the above technical solutions, further, in step S2, the combustion chamber sidewall temperature Determined by the following formula:

[0032] .

[0033] In any of the above technical solutions, step S3 further includes:

[0034] The engine combustion chamber sidewall temperature obtained from the steps If the wall temperature exceeds the wall temperature limit, the current cooling water flow rate is increased, and the calculation parameters are returned. The adjusted cooling water flow rate is then used in the following steps: Determined by the following formula:

[0035] ;

[0036] In the formula: The original cooling water flow rate; This refers to the wall temperature limit.

[0037] If the predicted combustion chamber sidewall temperature is at least 3 degrees Celsius below the limit, then adjust the cooling water flow rate according to the following formula and return to step S1 of the calculation parameters. The adjusted cooling water flow rate will then be... Determined by the following formula:

[0038] ;

[0039] ;

[0040] In the formula: This is a proportional parameter; The fitting coefficients of the equation are . For constant terms; This refers to the engine's relative load coefficient. This represents the cooling water flow rate at full load and the current operating speed.

[0041] If the calculated engine combustion chamber wall temperature is less than 3 degrees Celsius below the limit, the cooling water flow rate is considered to meet the requirements and no adjustment is needed, thus allowing direct entry into the next operating condition.

[0042] The beneficial effects of this invention are:

[0043] The technical solution in this invention is based on a large amount of measured data from engines. It establishes an analysis of the quantitative relationship between the combustion chamber wall temperature in the engine cylinder and the engine's control and operating parameters, thereby achieving accurate prediction of the diesel engine combustion chamber wall temperature. Based on the engine's operating conditions, a cooling water flow control strategy is proposed to minimize in-cylinder heat dissipation loss and cooling system accessory losses under the premise that the heat load does not exceed the limit, thereby indirectly improving the engine's thermal efficiency. Attached Figure Description

[0044] The advantages of the above and additional aspects of the present invention will become apparent and readily understood in the description of the embodiments in conjunction with the following drawings, wherein:

[0045] Figure 1 This is a schematic flowchart of a method for analyzing the control equations of in-cylinder gas heat transfer in a diesel engine and predicting the combustion chamber wall temperature according to an embodiment of the present invention.

[0046] Figure 2 This is a graph showing the variation of cyclic intake air volume with intake pressure in a diesel engine in-cylinder gas heat transfer control equation analysis and combustion chamber wall temperature prediction method according to an embodiment of the present invention.

[0047] Figure 3According to an embodiment of the present invention, the in-cylinder gas heat transfer control equation analysis and combustion chamber wall temperature prediction method for diesel engines is based on the in-cylinder temperature following an embodiment of the present invention. The graph shows the pattern of change. Detailed Implementation

[0048] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0049] In the following description, many specific details are set forth in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0050] like Figure 1 As shown, this embodiment provides an analytical method for the control equation of in-cylinder gas heat transfer in a diesel engine and a method for predicting the combustion chamber wall temperature. This method includes:

[0051] S1. During vehicle operation, the excess air coefficient, average temperature during combustion and expansion, average cylinder pressure, and heat transfer coefficient are calculated based on the control operating parameters obtained from the on-board ECU. The control operating parameters include engine speed, fuel injection quantity, and intake pressure. The heat transfer coefficient includes the combustion chamber side heat transfer coefficient, the cooling side heat transfer coefficient, and the overall heat transfer coefficient.

[0052] The calculation process for each coefficient includes:

[0053] S11. Calculate the excess air coefficient based on engine speed, intake pressure, and fuel injection quantity. :

[0054] ;

[0055] ;

[0056] In the formula: P is the excess air coefficient; n is the rotational speed; P in This refers to the intake pressure. This refers to the recirculation intake volume; This refers to the fuel injection quantity per cycle; AFR is the air-fuel ratio. , The fitting coefficients of the equation are . This is a constant term.

[0057] The relationship between the excess air coefficient and the average temperature at each speed is shown in Table 1 below:

[0058] Table 1;

[0059] ;

[0060] like Figure 2 As shown, the above-mentioned pattern of change can be approximately fitted to a quadratic equation in one variable.

[0061] S12. Predict the average gas temperature during combustion and expansion in the engine cylinder using the excess air coefficient, wherein the average temperature during combustion and expansion... Calculated using the following formula:

[0062] ;

[0063] Average temperature during combustion and expansion The unit is K. , , The fitting coefficients of the equation, All are constant terms.

[0064] Excess air coefficient at various speeds The relationship with the average temperature is shown in Table 2 below:

[0065] Table 2;

[0066] ;

[0067] like Figure 3 As shown, the above variation pattern can be approximately fitted to a cubic equation in one variable.

[0068] S13. Based on the current operating conditions, including engine speed, intake pressure, injection pressure, injection advance angle, and cyclic injection quantity, predict the average cylinder pressure, where the average cylinder pressure is... Determined by the following formula:

[0069] ;

[0070] In the formula: These are the main injection advance angle, injection pressure, and intake pressure under the current operating conditions; , , , The fitting coefficients of the equation are . This is a constant term.

[0071] Average pressure inside the cylinder The variation patterns of the parameters in the expression are shown in Table 3 below:

[0072] Table 3;

[0073] ;

[0074] S14. Predict the combustion chamber wall heat transfer coefficient based on the average gas temperature and cylinder pressure during combustion and expansion. Predict the cooling side heat transfer coefficient based on the cooling water flow rate and temperature. Then calculate the comprehensive heat transfer coefficient based on the combustion side, cooling side heat transfer coefficients, and wall thickness. The combustion side heat transfer coefficient is... for:

[0075] ;

[0076] in The average speed of the piston:

[0077] ;

[0078] Where S is the piston stroke.

[0079] The heat transfer coefficient on the cooling side is :

[0080] ;

[0081] Overall heat transfer coefficient Determined by the following formula:

[0082] ;

[0083] In the formula: , These are the heat transfer coefficients on the combustion side and the cooling side, respectively; Cylinder diameter; Q is the conversion factor; cool T is the cooling water flow rate; c This refers to the cooling water temperature. Where is the wall thickness; K is the thermal conductivity of the cylinder block.

[0084] S2. Based on the parameters obtained above, calculate the wall temperatures on the combustion chamber side and the cooling side respectively, where the combustion chamber side wall temperature... It is determined by the following formula.

[0085] ;

[0086] S3. Compare the predicted engine combustion chamber wall temperature with the engine wall temperature limit to determine whether the combustion chamber wall temperature has reached the expected value. If it has reached the expected value, proceed to the next operating condition. If it has not reached the expected value, readjust the cooling water flow rate and re-optimize the combustion chamber wall temperature according to the above steps S2 (calculating the excess air coefficient, average temperature, and heat transfer coefficient) and S3 (calculating the wall temperature).

[0087] Specifically, the engine combustion chamber sidewall temperature obtained from the calculation steps If the wall temperature exceeds the wall temperature limit, the current cooling water flow rate is increased, and the calculation parameters are returned. The adjusted cooling water flow rate is then used in the following steps: Determined by the following formula:

[0088] ;

[0089] In the formula: The original cooling water flow rate; This refers to the wall temperature limit, specifically the combustion chamber side wall temperature limit. It is the highest value of the combustion chamber sidewall temperature predicted using the same method under the full Map operating conditions (including all speeds and load conditions) of the engine, and it is the upper limit of the combustion chamber sidewall temperature that the engine has proven to withstand.

[0090] If the predicted combustion chamber sidewall temperature is at least 3 degrees Celsius below the limit, then adjust the cooling water flow rate according to the following formula and return to step S2 of the calculation parameters. The adjusted cooling water flow rate will then be... Determined by the following formula:

[0091] ;

[0092] ;

[0093] In the formula: This is a proportional parameter; The fitting coefficients of the equation are . For constant terms; This refers to the engine's relative load coefficient. This represents the cooling water flow rate at full load and the current operating speed.

[0094] If the calculated engine combustion chamber wall temperature is less than 3 degrees Celsius below the limit, the cooling water flow rate is considered to meet the requirements and no adjustment is needed, thus allowing direct entry into the next operating condition.

[0095] The method of this invention establishes an analytical quantitative relationship between the combustion chamber wall temperature in the engine cylinder and the engine's control and operating parameters, enabling accurate prediction of the diesel engine's combustion chamber wall temperature. Based on the engine's operating conditions, a cooling water flow control strategy is proposed to minimize in-cylinder heat dissipation loss and cooling system accessory losses under the premise that the heat load does not exceed the limit, thereby indirectly improving the engine's thermal efficiency.

[0096] In summary, this invention proposes an analytical method for the control equation of in-cylinder gas heat transfer in diesel engines and a method for predicting combustion chamber wall temperature, including:

[0097] S1. During vehicle operation, the excess air coefficient, average temperature during combustion and expansion, average cylinder pressure, and heat transfer coefficient are calculated based on the control operating parameters obtained from the on-board ECU. The control operating parameters include engine speed, fuel injection quantity, and intake pressure. The heat transfer coefficient includes the combustion chamber side heat transfer coefficient, the cooling side heat transfer coefficient, and the overall heat transfer coefficient.

[0098] S2. Calculate the wall temperatures on the combustion chamber side and the cooling side based on the parameters obtained above.

[0099] S3. Compare the predicted engine combustion chamber wall temperature with the engine wall temperature limit to determine whether the combustion chamber wall temperature has reached the expected value. If it has reached the expected value, proceed to the next operating condition. If it has not reached the expected value, readjust the cooling water flow rate and re-optimize the combustion chamber wall temperature according to the above steps S1 for calculating the excess air coefficient, average temperature, and heat transfer coefficient, and S2 for calculating the wall temperature.

[0100] The steps in this invention can be adjusted, combined, or deleted according to actual needs.

[0101] The units in the device of the present invention can be merged, divided, or reduced according to actual needs.

[0102] In this invention, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0103] The shapes of the components in the accompanying drawings are schematic and may differ from their actual shapes. The drawings are only used to illustrate the principles of the present invention and are not intended to limit the present invention.

[0104] Although the invention has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and not intended to limit the application of the invention. The scope of protection of the invention is defined by the appended claims and may include various modifications, alterations, and equivalents made to the invention without departing from the scope and spirit of the invention.

Claims

1. An analytical method for controlling in-cylinder gas heat transfer in diesel engines and a method for predicting combustion chamber wall temperature, characterized in that, The method includes: S1. During vehicle operation, the excess air coefficient, average temperature during combustion and expansion, average cylinder pressure, and heat transfer coefficient are calculated based on the control operating parameters obtained from the vehicle ECU. The control operating parameters include engine speed, fuel injection quantity, and intake pressure. The heat transfer coefficient includes the combustion chamber side heat transfer coefficient, the cooling side heat transfer coefficient, and the overall heat transfer coefficient. S2. Calculate the wall temperatures on the combustion chamber side and the cooling side based on the parameters obtained above. S3. Compare the predicted engine combustion chamber wall temperature with the engine wall temperature limit to determine whether the combustion chamber wall temperature has reached the expected value. If it has reached the expected value, proceed to the next operating condition. If it has not reached the expected value, readjust the cooling water flow rate and re-optimize the combustion chamber wall temperature according to the above steps S1 for calculating the excess air coefficient, average temperature, and heat transfer coefficient, and S2 for calculating the wall temperature.

2. The method for analyzing the in-cylinder gas heat transfer control equation and predicting the combustion chamber wall temperature of a diesel engine as described in claim 1, characterized in that, Step S1 includes: S11. Calculate the excess air coefficient based on engine speed, intake pressure, and fuel injection quantity. : ； ； In the formula: P is the excess air coefficient; n is the rotational speed; P in This refers to the intake pressure. This refers to the recirculation intake volume; This refers to the fuel injection quantity per cycle; AFR is the air-fuel ratio. , The fitting coefficients of the equation are . For constant terms; S12. Predict the average gas temperature during combustion and expansion in the engine cylinder using the excess air coefficient, wherein the average temperature during combustion and expansion... Calculated using the following formula: ； , , The fitting coefficients of the equation, All are constant terms; S13. Based on the current operating conditions, including engine speed, intake pressure, injection pressure, injection advance angle, and cyclic injection quantity, predict the average cylinder pressure, where the average cylinder pressure is... Determined by the following formula: ； In the formula: These are the main injection advance angle, injection pressure, and intake pressure under the current operating conditions; , , , The fitting coefficients of the equation are . For constant terms; S14. Predict the combustion chamber wall heat transfer coefficient based on the average gas temperature and cylinder pressure during combustion and expansion. Predict the cooling side heat transfer coefficient based on the cooling water flow rate and temperature. Then calculate the comprehensive heat transfer coefficient based on the combustion side, cooling side heat transfer coefficients, and wall thickness. The combustion side heat transfer coefficient is... for: ； in The average speed of the piston: ； Where S is the piston stroke; The heat transfer coefficient on the cooling side is : ； Overall heat transfer coefficient Determined by the following formula: ； In the formula: , These are the heat transfer coefficients on the combustion side and the cooling side, respectively; Cylinder diameter; Q is the conversion factor; cool T is the cooling water flow rate; c This refers to the cooling water temperature. Where is the wall thickness; K is the thermal conductivity of the cylinder block.

3. The method for analyzing the in-cylinder gas heat transfer control equation and predicting the combustion chamber wall temperature of a diesel engine as described in claim 2, characterized in that, In step S2, the combustion chamber sidewall temperature Determined by the following formula: 。 4. The method for analyzing the in-cylinder gas heat transfer control equation and predicting the combustion chamber wall temperature of a diesel engine as described in claim 1, characterized in that, Step S3 specifically includes: The engine combustion chamber sidewall temperature obtained from the steps If the wall temperature exceeds the wall temperature limit, the current cooling water flow rate is increased, and the calculation parameters are returned. The adjusted cooling water flow rate is then used in the following steps: Determined by the following formula: ； In the formula: The original cooling water flow rate; This refers to the wall temperature limit. If the predicted combustion chamber sidewall temperature is at least 3 degrees Celsius below the limit, then adjust the cooling water flow rate according to the following formula and return to step S1 of the calculation parameters. The adjusted cooling water flow rate will then be... Determined by the following formula: ； ； In the formula: This is a proportional parameter; The fitting coefficients of the equation are . For constant terms; This refers to the engine's relative load coefficient. This represents the cooling water flow rate at full load and the current operating speed. If the calculated engine combustion chamber wall temperature is less than 3 degrees Celsius below the limit, the cooling water flow rate is considered to meet the requirements and no adjustment is needed, thus allowing direct entry into the next operating condition.

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