Method for estimating engine thermodynamic loss angle and electronic device

Abstract

This invention discloses a method and electronic device for estimating the thermal loss angle of an engine. The method includes the following steps: Step 1: Obtaining cylinder pressure curves; Step 2: Obtaining the crankshaft rotation angle coordinates and thermal loss angle of the maximum pressure point for each cylinder pressure curve; Step 3: Calculating the zero heat transfer phase difference vector for each cylinder pressure curve; Step 4: Constructing the rotation angle difference vector for each cylinder pressure curve; Step 5: Establishing the thermal loss angle θ. i and the angle difference vector Ω i Step 6: Calculate the estimated thermal loss angle based on the functional relationship f between the thermal loss angle and the rotation angle difference vector. This invention provides a convenient method for top dead center correction during engine production lines, inspection, and maintenance.

Description

Technical Field

[0001] This invention relates to the field of piston engines, and more particularly to a method and electronic device for estimating the thermal loss angle of an engine. Background Technology

[0002] The thermal loss angle of an engine is the angular difference between the point of maximum cylinder pressure and the point of minimum combustion chamber volume. Existing methods for determining the thermal loss angle include thermodynamic analysis, piston position measurement, and empirical formulas. In practical applications, the thermal loss angle is mainly used to locate the top dead center (TDC), and is generally calculated by a combustion analyzer using empirical formulas. The piston position measurement method does not require a combustion analyzer, providing a method for determining TDC during production line or maintenance. Thermodynamic analysis methods determine the thermal loss angle based on the thermodynamic characteristics of the cylinder pressure curve. Both combustion analyzers and piston position measurement methods require complex instrument systems to estimate TDC, and the thermodynamic analysis method has limited versatility and accuracy. Developing a thermal loss angle estimation method based on the cylinder pressure curve and adaptable to minor variations in engine structure is crucial for supporting newly developed cycle-based engine combustion process control technologies and is one of the most important problems urgently needing to be solved in this field. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide an easy method for estimating the thermal loss angle of an individual engine, avoiding the limitations of traditional methods that require professional technicians to estimate the thermal loss angle using instruments and equipment such as combustion analyzers and complex algorithms.

[0004] To achieve the above objectives, the present invention provides a method for estimating the thermal loss angle of an engine, comprising the following steps:

[0005] Step 1: Obtain cylinder pressure curves; the number of cylinder pressure curves... ;

[0006] Step 2: Obtain the crankshaft angle coordinates and thermal loss angle of the maximum pressure point for each cylinder pressure curve;

[0007] Step 3: Calculate the zero heat transfer phase difference vector for each of the cylinder pressure curves;

[0008] No. i The zero heat transfer phase difference of the cylinder pressure curve is determined by the first... i The zero heat transfer phase difference is calculated from the cylinder pressure curve and cylinder volume curve. The calculation formula is:

[0009] (1)

[0010] In formula (1), the The crankshaft rotation angle coordinates; The value at the top dead center is 0, as described before the top dead center. The value is negative, after the top dead center. The value is positive. A For the symmetrical crankshaft rotation angle range [ -A,A The radius of the interval; is the heat capacity ratio of the gas inside the cylinder; d is the differential operator; It is the pressure inside the cylinder, in Pa; It is the instantaneous volume of the cylinder. ; It is the first i The cylinder pressure curves in the symmetrical interval [ -A,A The zero heat transfer phase difference is calculated from equation (1);

[0011] For each of the cylinder pressure curves, take m Symmetrical intervals of different sizes -A j ,A j ], j =1… m The zero heat transfer phase difference for each interval is calculated using formula (1). , m The zero heat transfer phase difference constitutes the zero heat transfer phase difference vector. for:

[0012] (2)

[0013] In formula (2), the subscript i Indicates the first i Individual cylinder pressure curve;

[0014] Step 4: Construct the rotation angle difference vector for each cylinder pressure curve; obtain the first... i The cylinder pressure curves of the aforementioned m Symmetrical intervals of different sizes [ -A j ,A j ], j =1… m The aforementioned angle difference vector ; Rotational difference vector The calculation formula is:

[0015] (3)

[0016] In formula (3), These are the angular coordinates of the maximum pressure point on the cylinder pressure curve; subscript i Indicates the firsti Individual cylinder pressure curves; the superscript mp indicates the maximum pressure;

[0017] Step 5: Establish the aforementioned heat loss angle and the angle difference vector The functional relationship between them;

[0018] Step 6: For the angle of thermal loss to be measured The cylinder pressure curve is used to calculate the angle difference vector. The functional relationship between the thermal loss angle and the rotation angle difference vector The thermal loss angle to be estimated is calculated using the following formula:

[0019] (4)

[0020] In formula (4) The heat loss angle to be estimated is... The angle difference vector Mapped to thermal loss angle The correspondence, The heat loss angle to be estimated The corresponding cylinder pressure curve's angle difference vector is expressed as: , t It is a subscript.

[0021] The method for estimating the engine thermal loss angle as described above, wherein, optionally, the step 1... n The cylinder pressure curves are taken from the set of operating conditions used to collect the cylinder pressure curves; the variables in the set of operating conditions are four factors: engine speed, intake pressure, coolant temperature, and intake air temperature; n The value is greater than or equal to 2.

[0022] In the method for estimating the engine thermal loss angle as described above, optionally, the cylinder pressure curve in step 2 is set as a smoothed cylinder pressure curve.

[0023] The method for estimating the engine thermal loss angle as described above, wherein, optionally,

[0024] In step 2,

[0025] No. i The crankshaft angle coordinates at the maximum pressure point of the cylinder pressure curve are marked as follows: , i The value of is 1, ..., n ;

[0026] The thermal loss angle is the difference between the crankshaft angle coordinates at the maximum pressure point and the crankshaft angle coordinates corresponding to the minimum cylinder volume.i The thermal loss angle of the cylinder pressure curve is denoted as... ;

[0027] Step 5 includes,

[0028] Establish the rotation angle difference vector Mapped to thermal loss angle A correspondence f, the result of the correspondence calculation With the aforementioned heat loss angle The difference between them satisfies the following constraints:

[0029] (5)

[0030] In formula (5) E For tolerance, Let x be the error function, and let x be the independent variable of the function.

[0031] The method for estimating the engine thermal loss angle as described above, wherein, optionally, the location of the maximum pressure point is determined by curve fitting in step 2.

[0032] The method for estimating the engine thermal loss angle as described above, wherein, optionally, the symmetric interval in step 3 [ -A j ,A j ], j =1… m middle, m Take 3, and A j+1 =2 A j .

[0033] In the method for estimating the engine thermal loss angle as described above, optionally, the functional relationship in step 5 is a neural network model; the neural network includes an input layer, a hidden layer, and an output layer; the hidden layer has... l The hidden layer has one node, the output layer has one node, the activation function of the hidden layer is the sigmoid function, the activation function of the output layer is a linear function, and the neural network model is represented by equation (6):

[0034] (6)

[0035] In equation (6), It is the angle of heat loss; The input vector; The weights of the input layer are matrix, It is the input vector Length; yes The vector represents the weights of the output layer. It is the bias vector of the hidden layer. It is the output layer bias vector.

[0036] The present invention also proposes an electronic device for predicting the thermal loss angle of an engine, applying any of the thermal loss angle calculation methods described above. In one aspect, an electronic device is provided, comprising a processor and a memory, wherein the memory stores at least one instruction, which is loaded and executed by the processor to implement the above-described method for estimating the thermal loss angle of an engine.

[0037] On the one hand, a computer-readable storage medium is provided, wherein at least one instruction is stored therein, the at least one instruction being loaded and executed by a processor to implement the above-described method for estimating the thermal loss angle of an engine.

[0038] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0039] In this embodiment of the invention, the rotation angle difference vector is obtained based on zero heat transfer phase difference; the magnitude of the rotation angle difference vector is approximately independent of the rotation angle positioning error of the cylinder pressure curve. The engine thermal loss angle model established based on the rotation angle difference vector does not require specialized instruments for correction, providing a convenient method for top dead center correction during engine production lines, inspections, and maintenance.

[0040] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the process for determining the thermodynamic loss angle based on zero heat transfer phase difference provided in an embodiment of the present invention;

[0042] Figure 2 This is a cylinder pressure curve provided in an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the maximum pressure point angle, thermal loss angle, zero heat transfer phase difference, and angle difference provided in the embodiments of the present invention;

[0044] Figure 4 This is a coordinate diagram of zero heat transfer phase difference and maximum pressure point provided in an embodiment of the present invention;

[0045] Figure 5 This is a comparison diagram between the neural network-predicted thermal loss angle and the actual thermal loss angle provided by this invention. Detailed Implementation

[0046] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0047] Example 1

[0048] This embodiment proposes a method for estimating the thermal loss angle of an engine, which includes the following steps:

[0049] Step 1: Obtain n The number of cylinder pressure curves; On the same type or the same engine, obtain cylinder pressure curves under multiple operating conditions; operating parameters include intake pressure, engine speed, etc.; multiple cylinder pressure curves can be obtained under each operating condition. n It is the total number of cylinder pressure curves obtained under all operating conditions.

[0050] Step 2: Obtain the crankshaft angle coordinates and thermal loss angle of the maximum pressure point for each cylinder pressure curve; specifically, the first... i The crankshaft angle coordinates at the maximum pressure point of the cylinder pressure curve are marked as follows: , i The value of is 1, ..., n The thermal loss angle is the difference between the crankshaft angle coordinates at the maximum pressure point and the crankshaft angle coordinates corresponding to the minimum cylinder volume. i The thermal loss angle of the cylinder pressure curve is denoted as... That is, through this step, the maximum pressure point and the corresponding crankshaft angle of all cylinder pressure curves are obtained.

[0051] Step 3: Calculate the zero heat transfer phase difference vector for each of the cylinder pressure curves; specifically, the zero heat transfer phase difference of the i-th cylinder pressure curve is calculated by the vector of the first cylinder pressure curve. i The zero heat transfer phase difference is calculated from the cylinder pressure curve and cylinder volume curve. The calculation formula is:

[0052] (1)

[0053] In formula (1), the The crankshaft rotation angle coordinates; The value at the top dead center is 0, as described before the top dead center. The value is negative, after the top dead center. The value is positive. A For the symmetrical crankshaft rotation angle range [ -A,A The radius of the interval; is the heat capacity ratio of the gas inside the cylinder; d is the differential operator; It is the pressure inside the cylinder, in Pa; It is the instantaneous volume of the cylinder. ; The i-th cylinder pressure curve is in the symmetrical interval [ -A,A The zero heat transfer phase difference is calculated by equation (1). Zero heat transfer phase difference is a new concept introduced in this invention; its definition is shown in equation (1), used to describe the engine cylinder pressure curve in the angular interval [ -A,A The shape change characteristics of the cylinder pressure curve; in ideal adiabatic conditions, when the volume curve is symmetrical about the origin of the coordinate axis, the pressure curve is also symmetrical about the origin of the angular coordinate axis. At this time, the zero heat transfer phase difference calculated by formula (1) is zero. For non-ideal adiabatic conditions, the cylinder pressure curve is not symmetrical about the origin of the angular coordinate axis. At this time, the zero heat transfer phase difference calculated by formula (1) is not equal to zero; the zero heat transfer phase difference reflects the symmetry of the cylinder pressure curve.

[0054] For each of the cylinder pressure curves, take m Symmetrical intervals of different sizes [ -A j ,A j ], j =1… m The zero heat transfer phase difference for each interval is calculated using the zero heat transfer phase difference calculation formula (1). , m The zero heat transfer phase difference constitutes the zero heat transfer phase difference vector. for:

[0055] (2)

[0056] In equation (2), the subscript i Indicates the first i Individual cylinder pressure curve;

[0057] Step 4: Construct the rotation angle difference vector for each cylinder pressure curve; obtain the first... i The cylinder pressure curves of the aforementioned m Symmetrical intervals of different sizes [ -A j ,A j ], j =(1… m The angle difference vector on ) ; Rotational difference vector The calculation formula is:

[0058] (3)

[0059] In formula (3), These are the angular coordinates of the maximum pressure point on the cylinder pressure curve; subscript i Indicates the first i Individual cylinder pressure curves; the superscript mp indicates the maximum pressure;

[0060] Step 5: Establish the aforementioned heat loss angle and the angle difference vector The functional relationship between them;

[0061] Establish the rotation angle difference vector Mapped to thermal loss angle A correspondence f Correspondence calculation results With the aforementioned heat loss angle The difference between them satisfies the following constraints:

[0062] (5)

[0063] In formula (5) E For tolerance, Let be the error function. x Let be the independent variable of the function; specifically, The error function can be the mean square error function: ( N (The number of samples used to establish the functional relationship).

[0064] Step 6: For the angle of thermal loss to be measured The cylinder pressure curve is used to calculate the angle difference vector. The functional relationship between the thermal loss angle and the rotation angle difference vector The thermal loss angle to be estimated is calculated using the following formula:

[0065] (4)

[0066] In formula (4) The heat loss angle to be estimated is... The angle difference vector Mapped to thermal loss angle The correspondence, The heat loss angle to be estimated The corresponding cylinder pressure curve's angle difference vector is expressed as: , t It is a subscript.

[0067] Through the above steps, this embodiment obtains the angular difference vector based on zero heat transfer phase difference. Research has determined that the magnitude of the angular difference vector is approximately independent of the angular positioning error of the cylinder pressure curve. Furthermore, an engine thermal loss angle model is established based on the angular difference vector, eliminating the need for specialized instruments for correction and providing a convenient method for top dead center correction during engine production lines, inspection, and maintenance.

[0068] As a preferred implementation, the step 1 described above... n The cylinder pressure curves are taken from the set of operating conditions used to collect the cylinder pressure curves; the variables in the set of operating conditions are four factors: engine speed, intake pressure, coolant temperature, and intake air temperature; n The value is greater than or equal to 2. Specifically, n It should be a positive integer.

[0069] For ease of calculation, the cylinder pressure curve in step 2 is set as a smoothed cylinder pressure curve. In practice, data acquisition is usually discrete, and the curve plotted based on the acquired data is not continuous and smooth. Therefore, smoothing facilitates the determination of the maximum pressure point of the cylinder pressure curve. More specifically, step 2 uses curve fitting to determine the location of the maximum pressure point.

[0070] In specific implementation, the symmetrical interval in step 3 [ -A j , A j ], j =1… m middle, m Take 3, and A j+1 =2 A j .

[0071] In specific implementation, the functional relationship in step 5 is a neural network model; the neural network includes an input layer, a hidden layer, and an output layer; the hidden layer has l The hidden layer has one node, the output layer has one node, the activation function of the hidden layer is the sigmoid function, the activation function of the output layer is a linear function, and the neural network model is represented by equation (6):

[0072] (6)

[0073] In equation (6), It is the angle of heat loss; The input vector; The weights of the input layer are matrix, It is the input vector Length; yes The vector represents the weights of the output layer. It is the bias vector of the hidden layer. It is the output layer bias vector.

[0074] Example 2

[0075] This invention provides a method for estimating the thermal loss angle of an engine, which can be implemented by an electronic device. Figure 1 The diagram illustrates the steps involved in determining the thermal loss angle using this method, which includes the following steps:

[0076] S101: Obtain n Individual cylinder pressure curve;

[0077] Number of cylinder pressure curves In this embodiment, 16 cylinder pressure curves were obtained, namely... n =16.

[0078] Using engine speed and intake pressure as variables, a set of operating conditions is constructed; the engine speed is 1500, 3000, 4500, and 6000 rpm; the intake pressure is 0.6, 0.8, 1.0, and 1.2 atmospheres; with two factors, engine speed and atmospheric pressure, each with four levels, there are 4×4=16 operating conditions in the set of operating conditions, as shown in Table 1.

[0079]

[0080] S102: Obtain the crankshaft angle coordinates and thermal loss angle of the maximum pressure point for each cylinder pressure curve. Figure 2 The figure shows the cylinder pressure curves for operating conditions numbered 3, 6, 12, and 15.

[0081] No. i The crankshaft angle coordinates at the maximum cylinder pressure point of the cylinder pressure curve are marked as follows: , i The value of is 1, ..., 16.

[0082] The thermal loss angle is the difference between the crankshaft angle coordinates at the maximum pressure point and the crankshaft angle coordinates corresponding to the minimum cylinder volume. The thermal loss angle of the i-th cylinder pressure curve is denoted as... , i The values ​​are 1, ..., 16. A schematic diagram of the thermal loss angle and the crankshaft rotation angle at the maximum pressure point is shown below. Figure 3 As shown.

[0083] S103: Calculate the zero heat transfer phase difference vector for each cylinder pressure curve;

[0084] The zero heat transfer phase difference of the i-th cylinder pressure curve is calculated from the i-th cylinder pressure curve and the cylinder volume curve. In this embodiment, for each cylinder pressure curve, the turning angle interval of the zero heat transfer phase difference is calculated using equation (1) as [ -A,A Zero heat transfer phase difference of crankshaft rotation angles [-40,40], [-80,80], [-80,80] degrees. , , The value of i is 1, ..., 16; the calculated value is... , , like Figure 4 As shown.

[0085] Depend on , , The zero heat transfer phase difference vector for the i-th operating condition is obtained as follows: .

[0086] S104: Construct the rotation angle difference vector for each cylinder pressure curve; obtain the rotation angle difference vector on the three symmetrical intervals [-40,40], [-80,80], and [-80,80] of different sizes for the i-th cylinder pressure curve. The formula for calculating the angle difference vector is:

[0087] (7)

[0088] In the formula, the value of i is 1, ..., 16.

[0089] S105: Establish the functional relationship between the thermal loss angle and the angle difference vector; In this embodiment, a neural network model is used to establish the functional relationship between the thermal loss angle and the angle difference vector. The neural network includes an input layer, a hidden layer, and an output layer; the input layer has 3 nodes, the hidden layer has 1 node, and the output layer has 1 node. The activation function of the hidden layer is the sigmoid function; the activation function of the output layer is a linear function; The neural network model is represented by equation (6):

[0090] (6)

[0091] In equation (6), It is the angle of heat loss; The input vector has a length of 2; The weights of the input layer are matrix; yes The vector represents the weights of the output layer. It is the bias vector of the hidden layer. It is the output layer bias vector.

[0092] The training process randomly selects the working conditions from Table 1, and the resulting weights are: , , , The comparison between the thermal loss angle predicted by the trained neural network model and the actual thermal loss angle is as follows: Figure 5 As shown, the maximum error between the thermal loss angle predicted by the neural network and the actual thermal loss angle is less than 0.05 degrees of crankshaft rotation angle.

[0093] Specific implementation demonstrates that the thermodynamic loss angle estimation method based on zero heat transfer phase difference provided in this embodiment offers a new physical basis for the analysis of in-cylinder thermodynamic processes in engines. It also provides fundamental support for data-driven intelligent analysis of in-cylinder processes in engines.

[0094] Example 3

[0095] This embodiment proposes an electronic device for predicting the thermal loss angle of an engine, applying the thermal loss angle calculation method disclosed in Embodiment 1 or Embodiment 2.

[0096] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for estimating the thermal loss angle of an engine, characterized in that... Includes the following steps: Step 1: Obtain cylinder pressure curves; the number of cylinder pressure curves... ; Step 2: Obtain the crankshaft angle coordinates and thermal loss angle of the maximum pressure point for each cylinder pressure curve; Step 3: Calculate the zero heat transfer phase difference vector for each of the cylinder pressure curves; The zero heat transfer phase difference of the i-th cylinder pressure curve is determined by the first... i The zero heat transfer phase difference is calculated from the cylinder pressure curve and cylinder volume curve. The calculation formula is: （1） In equation (1), The crankshaft rotation angle coordinates; The value is 0 at the top dead center of compression, and before the top dead center... The value is negative, after the top dead center. The value is positive. A For the symmetrical crankshaft rotation angle range [ -A,A The radius of the interval; is the heat capacity ratio of the gas inside the cylinder; d is the differential operator; It is the pressure inside the cylinder, in Pa; It is the instantaneous volume of the cylinder. ; It is the first i The cylinder pressure curves in the symmetrical interval [ -A,A The zero heat transfer phase difference is calculated from equation (1); For each of the cylinder pressure curves, take m Symmetrical intervals of different sizes [ -A j ,A j ], j =1… m ; The zero heat transfer phase difference for each interval is calculated using formula (1). , m The zero heat transfer phase difference constitutes the zero heat transfer phase difference vector. for: （2） In formula (2), the subscript i Indicates the first i Individual cylinder pressure curve; Step 4: Construct the rotation angle difference vector for each cylinder pressure curve; obtain the first... i The cylinder pressure curves of the aforementioned m Symmetrical intervals of different sizes [ -A j ,A j ], j =1… m The aforementioned angle difference vector ; Rotational difference vector The calculation formula is: （3） In formula (3), These are the angular coordinates of the maximum pressure point on the cylinder pressure curve; subscript i Indicates the first i Individual cylinder pressure curves; the superscript mp indicates the maximum pressure; Step 5: Establish the aforementioned heat loss angle and the angle difference vector The functional relationship between them; Step 6: For the angle of thermal loss to be measured The cylinder pressure curve is used to calculate the angle difference vector. The functional relationship between the thermal loss angle and the rotation angle difference vector The thermal loss angle to be estimated is calculated using the following formula: （4） In formula (4) The heat loss angle to be estimated is... The angle difference vector Mapped to thermal loss angle The correspondence, The heat loss angle to be estimated The corresponding cylinder pressure curve's angle difference vector is expressed as: , t This is a subscript.

2. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, The step 1 mentioned above n The cylinder pressure curves are taken from the set of operating conditions used to collect the cylinder pressure curves; the variables in the set of operating conditions are four factors: engine speed, intake pressure, coolant temperature, and intake air temperature; n The value is greater than or equal to 2.

3. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, The cylinder pressure curve in step 2 is set to a smoothed cylinder pressure curve.

4. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, In step 2, the first i The crankshaft angle coordinates at the maximum pressure point of the cylinder pressure curve are marked as follows: i The value of is 1, ..., n ; The thermal loss angle is the difference between the crankshaft angle coordinates at the maximum pressure point and the crankshaft angle coordinates corresponding to the minimum cylinder volume. i The thermal loss angle of the cylinder pressure curve is denoted as... ; Step 5 includes, Establish the rotation angle difference vector Mapped to thermal loss angle A correspondence f, the result of the correspondence calculation With the aforementioned heat loss angle The difference between them satisfies the following constraints: （5） In formula (5) E For tolerance, Let x be the error function, and let x be the independent variable of the function.

5. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, In step 2, the location of the maximum pressure point is determined using curve fitting.

6. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, The symmetric interval in step 3 [ -A j ,A j ], j =1… m middle, m Take 3, and A j+1 =2 A j .

7. The method for estimating the engine thermal loss angle as described in claim 1, characterized in that, The functional relationship in step 5 is a neural network model; the neural network includes an input layer, a hidden layer, and an output layer; the hidden layer has... l The hidden layer has one node, the output layer has one node, the activation function of the hidden layer is the sigmoid function, the activation function of the output layer is a linear function, and the neural network model is represented by equation (6): (6) In equation (6), It is the angle of heat loss; The input vector; The weights of the input layer are matrix, It is the input vector Length; yes The vector represents the weights of the output layer. It is the bias vector of the hidden layer. It is the output layer bias vector.

8. An electronic device for predicting the thermal loss angle of an engine, using the thermal loss angle calculation method as described in any one of claims 1-6.

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