An online detection and optimization method for the operating status and performance parameters of a vehicle-mounted diesel engine

Abstract

The present application belongs to the field of engine technology, and specifically relates to an online detection and optimization method for the operating state and performance parameters of a vehicle-mounted diesel engine. The method comprises the following steps: Step 1: obtaining the control operating parameters under the actual vehicle operating state and the experimental analysis results of the bench steady-state universal characteristics; Step 2: predicting the engine combustion efficiency, adiabatic efficiency, expansion efficiency, and average temperature during combustion and expansion after the excess air coefficient is increased; Step 3: comparing the calculated engine performance with the experimental analysis results of the bench steady-state universal characteristics; Step 4: adjusting the excess air coefficient λ or entering the next operating condition. The analysis of the quantitative relationship between the engine cylinder combustion and heat-to-work conversion process and performance and the engine control parameters and operating parameters in the present application is based on a large amount of actual engine measured data. The performance prediction and optimization results can ensure high calculation accuracy and achieve rapid prediction and optimization of diesel engine performance under actual vehicle driving conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of engines, and in particular relates to an online detection and optimization method for the operating status and performance parameters of a vehicle-mounted diesel engine. Background Art

[0002] Current diesel engine performance prediction and optimization methods on the market include algorithm optimization, such as CN202311251382.0, which improves the accuracy of diesel engine performance prediction by building a prediction model based on a reinforcement learning machine. In-cylinder explosion pressure control, such as CN202311117073.4, utilizes a correction formula to modify the explosion pressure limit to ensure safe diesel engine operation. A performance balance utility model, such as CN202310448308.1, is established based on real-time diesel engine performance data. This model monitors diesel engine performance status in real time to diagnose and locate engine faults and improve engine reliability. While these methods improve the accuracy of diesel engine performance prediction, they cannot achieve rapid prediction and optimization of diesel engine performance under on-vehicle operating conditions.

[0003] During actual operation, the load and speed of automotive engines fluctuate constantly with vehicle demands. For the same engine, varying control parameters can lead to significant performance variations to achieve the same load and speed. Optimum engine performance requires precise control of various control parameters, such as intake air volume, fuel injection rate, and injection timing. Therefore, current automotive engine control during actual operation relies on interpolation of key control and operating parameters from a calibrated MAP stored in the engine ECU under steady-state test bench conditions.

[0004] However, due to the large and frequent variations in engine operating conditions under actual operating conditions, key engine control parameters derived from interpolation of a calibrated MAP are prone to deviating from their optimal values. This can lead to significantly lower performance under actual operating conditions than what can be achieved on a steady-state test bench under these conditions. Therefore, engine control urgently requires a parameter optimization method that can optimize multiple engine control and operating parameters to achieve the optimal combination of these parameters under actual operating conditions, i.e., varying engine load and speed, thereby achieving optimal engine performance.

[0005] However, there are many engine control and operating parameters and they are coupled with each other, which makes it difficult to apply complex optimization methods to the control of engine control and operating parameters. This is mainly due to factors such as the high operating frequency of engine operating conditions and the low computing power of ECU. This is also the reason why the industry is generally aware of the above problems but still uses the calibrated MAP control method for various key control and operating parameters obtained under steady-state test bench conditions. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention proposes an online detection and optimization method for the operating status and performance parameters of a vehicle-mounted diesel engine. By reading parameters such as the cyclic injection amount, speed, intake pressure, and excess air coefficient in the ECU, and combining the quantitative relationship between the engine performance and the control and operating parameters analyzed under steady-state operating conditions, the online rapid prediction and optimization of the engine performance can be achieved.

[0007] In order to achieve the technical purpose of the present invention, the present invention will adopt the following technical solutions:

[0008] A method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine, the method comprising:

[0009] Step 1: The engine ECU performs real-time detection of the engine's dynamic operating conditions on board the vehicle. Based on the steady-state engine universal characteristic database and at the same speed as the benchmark, if it detects that the engine's dynamic operating performance is lower than its steady-state performance, it compares the control operating parameters that affect the engine's current dynamic performance with those of its steady-state performance.

[0010] Step 2: Determine the excess air coefficient calculation model. Using the corresponding cycle injection amount in the steady-state engine universal characteristic data at the current speed as a reference, increase the excess air coefficient by reducing the cycle injection amount. Predict the engine's combustion efficiency, adiabatic efficiency, expansion efficiency, and average temperature during combustion and expansion after the excess air coefficient is increased.

[0011] Step 3: Based on the combustion efficiency, adiabatic efficiency, and expansion efficiency obtained in Step 2, and in combination with the speed and cycle injection amount, a computational model is established for calculating the high-pressure cycle indicated fuel consumption rate, the high-pressure cycle indicated mean pressure, the pumping loss mean effective pressure, and the friction loss mean effective pressure, thereby obtaining optimized engine performance parameters; wherein: the high-pressure cycle indicated thermal efficiency is determined by the combustion efficiency, adiabatic efficiency, and expansion efficiency, and the high-pressure cycle indicated fuel consumption rate is determined accordingly; the high-pressure cycle indicated mean pressure is determined by the cycle injection amount and the high-pressure cycle indicated thermal efficiency; and the pumping loss mean effective pressure and the friction loss mean effective pressure are determined by the speed and cycle injection amount;

[0012] Step 4: Compare the engine performance parameters optimized in step 3 with the engine steady-state universal characteristic curve performance parameters to determine whether the engine performance parameters optimized in step 3 meet expectations. If so, proceed to the next operating condition. If not, readjust the excess air coefficient and re-optimize the engine performance according to steps 2 and 3.

[0013] Furthermore, step 2 includes:

[0014] Step 2.1: Adjust the excess air coefficient based on the cycle intake volume and the injection volume of the previous cycle;

[0015] Step 2.2: Predict the combustion efficiency in the engine cylinder using the adjusted excess air coefficient, and predict the adjusted combustion characteristic parameters based on the measured correspondence between the cyclic injection amount and the injection advance angle, the injection advance angle to CA50 duration, and the combustion duration at different speeds;

[0016] Step 2.3: Under the same speed, a real-time adiabatic efficiency correction model is established by obtaining the adiabatic efficiency, average in-cylinder temperature, and cylinder wall temperature of the engine's steady-state universal characteristics, as well as the average in-cylinder temperature and cylinder wall temperature of the current dynamic operating condition. This correction is used to correct the adiabatic efficiency under the current operating conditions.

[0017] Step 2.4: Determine the effective expansion ratio (EER) based on the adjusted combustion characteristic parameters, the geometric compression ratio, and the exhaust valve opening timing; determine the polytropic index during the expansion period based on the adjusted excess air coefficient and the average temperature during the combustion and expansion periods at the measured speed; and determine the expansion efficiency based on the effective expansion ratio (EER) and the polytropic index during the expansion period.

[0018] Furthermore, the excess air coefficient λ after adjustment in step 2.1 is determined by the following formula:

[0019]

[0020] Where: λ is the excess air coefficient, -; M air is the circulating air intake volume, mg; M fuel is the cycle injection amount, mg; AFR is the air-fuel ratio.

[0021] Furthermore, the combustion efficiency η in the engine cylinder in step 2.2 is comb Determined by the following formula:

[0022] η comb =f(n,λ)

[0023] Where: η comb is the combustion efficiency in the engine cylinder; n is the current speed, r / min; λ is the excess air coefficient, -;

[0024] The adjusted combustion characteristic parameters include CA50 position and combustion duration. The CA50 position calculation formula is:

[0025] CA50=CA IA-CA50 -IA

[0026] CA IA-CA50 =f(n,M fuel )

[0027] Where: CA50 is the 50% combustion point, °C A ATDC; CA IA-CA50 CA is the duration from the main injection advance angle to CA50; IA is the injection advance angle, °ABTDC;

[0028] The combustion duration is determined by the following formula:

[0029] CA10-90=f(n,M fuel )

[0030] Where: CA10-90 is the combustion duration from burning 10% to 90% of the mixture; n is the current speed, r / min; M fuel is the cycle injection amount, mg.

[0031] Furthermore, the adiabatic efficiency under the current operating conditions in step 2.3 is determined by the following formula:

[0032]

[0033] Where: η adi2 、 T w2 are the adiabatic efficiency, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature under the current operating conditions; η adi1 、 T w1 are the adiabatic efficiency of the steady-state universal characteristics, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature at the same speed and cyclic injection rate.

[0034] Furthermore, the expansion efficiency η in step 2.4 expd Determined by the following formula:

[0035]

[0036] Where: η expd is the expansion efficiency; EER is the effective expansion ratio during the combustion process; k is the polynomial index during the expansion period;

[0037] The effective expansion ratio EER is determined by the following formula:

[0038] EER=f(n,CA50,CA10-90)

[0039] Where: n is the current speed, r / min; CA50 is the 50% combustion point position, °C AATDC; CA10-90 is the combustion duration from burning 10% to 90% of the mixture;

[0040] The polytropic index k during expansion is determined by the following formula:

[0041] k=f(λ,Tg)

[0042] Where: λ is the adjusted excess air coefficient at the current rotational speed, -; Tg is the average temperature during combustion and expansion at the measured rotational speed, i.e., the average in-cylinder temperature.

[0043] Further, the indicated fuel consumption rate of the high-pressure cycle, the average indicated pressure of the high-pressure cycle, the mean effective pressure of the pumping loss, and the mean effective pressure of the friction loss in step 3 are determined by the following formulas respectively:

[0044] The indicated fuel consumption rate of the high-pressure cycle ISFC HP and the average indicated pressure of the high-pressure cycle IMEP HP are determined by the following formulas respectively:

[0045]

[0046] Where: IMEP HP is the average indicated pressure of the high-pressure cycle, Pa; m fuel is the adjusted fuel injection quantity per cycle, mg; H CL is the calorific value of the fuel, J / kg; η i_HP is the indicated thermal efficiency of the high-pressure cycle; Vs is the cylinder displacement, m 3 ;

[0047] The mean effective pressure of the pumping loss PMEP and the mean effective pressure of the friction loss FMEP are determined by the following formulas respectively:

[0048] PMEP = f(n, m fuel )

[0049] FMEP = f(n, m fuel )

[0050] Where: n is the current rotational speed, r / min; M fuel is the fuel injection quantity per cycle, mg.

[0051] Further, in step 4, compare the engine performance calculated in step 3 with the experimental analysis results of the engine steady-state universal characteristics. If the performance difference ≥ X1%, return to step 2 to adjust the excess air coefficient λ;

[0052] Or, compare the calculated engine performance with the experimental analysis results of the engine steady-state universal characteristics. If the performance difference < X2%, enter the next working condition;

[0053] The engine performance includes BSFC, BMEP, and engine torque.

[0054] Furthermore, when BSFC is used as the performance judgment indicator, if the BSFC difference is ≥5%, return to step 2 and adjust the excess air coefficient λ. The adjusted excess air coefficient λ ensures that the difference between BMEP or engine torque and the steady-state calibration result is ≤10%, and then enter the next operating condition.

[0055] The beneficial effects of the present invention are:

[0056] The present invention uses the engine ECU to detect the engine in the on-vehicle dynamic working condition in real time, takes the excess air coefficient as the optimization benchmark, increases the excess air coefficient by adjusting the cyclic injection amount, and then realizes online rapid prediction of the engine combustion efficiency, adiabatic efficiency, expansion efficiency, and average temperature during combustion and expansion after the excess air coefficient is increased, thereby realizing online detection of the on-vehicle diesel engine operating state and online rapid prediction of the on-vehicle diesel engine performance; based on a large amount of actual measured data of the engine, an analysis of the quantitative relationship between the combustion and heat-to-work conversion process in the engine cylinder and the performance and the control parameters and operating parameters of the engine is established, realizing online optimization of the on-vehicle diesel engine performance and operating state, solving the limitations of the high operating frequency of the engine operating condition and the small computing power of the ECU, so that the performance prediction and optimization results can ensure high calculation accuracy, and make the performance of the engine under actual use conditions equivalent to the results that can be achieved by the engine on a steady-state test bench under such conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flow chart of the on-line detection and optimization method for the diesel engine vehicle operating status and performance parameters according to an embodiment of the present invention. Figure 1 ;

[0058] Figure 2 This is a flow chart of the performance prediction method for diesel engine vehicle operating status and performance parameters of the present invention. Figure 2 . DETAILED DESCRIPTION

[0059] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0060] The terms "up", "down", "left", "right", "front", and "back" in this application are based on the positional relationships shown in the accompanying drawings. The corresponding positional relationships may vary depending on the drawings, and should not be construed as limiting the scope of protection.

[0061] In this application, the terms "installed," "connected," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, integral connection, mechanical connection, electrical connection, or mutual communication. They can also be directly connected or indirectly connected through an intermediate medium. They can also refer to internal communication between two components or interaction between two components. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0062] This invention describes a method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine. This method rapidly predicts and optimizes engine performance online by reading parameters such as the cyclic injection rate, speed, intake pressure, and excess air coefficient from the ECU, and combining them with quantitative equations analyzing the relationship between engine performance and control and operating parameters under steady-state operating conditions. The method analyzes the quantitative relationship between the in-cylinder combustion and heat-to-power conversion process and performance, and the engine's control and operating parameters based on extensive real-world engine data. The performance prediction and optimization results achieve high computational accuracy, enabling rapid prediction and optimization of diesel engine performance while the vehicle is in motion.

[0063] Refer to the instruction manual Figure 1-2 The online detection and optimization method of the operating status and performance parameters of a vehicle-mounted diesel engine includes the following steps:

[0064] Step 1: The engine ECU performs real-time detection of the engine's dynamic operating conditions on board the vehicle. Based on the steady-state engine universal characteristic database and taking the same speed as the benchmark, when it detects that the engine's dynamic operating performance is lower than the engine's steady-state performance, it compares the differences between the control operating parameters that affect the engine's current dynamic performance and the control operating parameters that affect the engine's steady-state performance.

[0065] Specifically, the steady-state engine universal characteristics database includes benchmarks for the performance of various electronically controlled accessories, quantitative relationship equations or charts between performance and control operating parameters, and optimization directions for performance and control operating parameters.

[0066] Step 2: Determine the excess air coefficient calculation model. At the current speed, use the corresponding cyclic injection amount in the steady-state engine universal characteristic data as a reference, increase the excess air coefficient by reducing the cyclic injection amount, and predict the engine combustion efficiency, adiabatic efficiency, expansion efficiency and average temperature during combustion and expansion after the excess air coefficient is increased.

[0067] Step 2.1: Adjust the excess air coefficient λ based on the cycle intake amount and the injection amount of the previous cycle (or the target injection amount). The adjusted excess air coefficient λ is determined by the following formula:

[0068]

[0069] Where: λ is the excess air coefficient, -; M air is the circulating air intake volume, mg; M fuel is the cycle injection amount, mg; AFR is the air-fuel ratio.

[0070] Specifically, the cycle injection amount M in formula (1) fuel It should be reduced to the average of the sum of the current cycle injection amount and the steady-state bench cycle injection amount.

[0071] In formula (1), the cycle intake volume M is calculated based on the current speed and the intake pressure measured or given by the ECU: air , circulating air intake volume M air Determined by the following formula:

[0072] M air =f(n,Pin) (2)

[0073] Where: M air is the circulating air intake volume, mg; n is the current speed, r / min; Pin is the intake pressure, bar.

[0074] Step 2.2: Predict the combustion efficiency in the engine cylinder using the adjusted excess air coefficient, and predict the adjusted combustion characteristic parameters based on the measured correspondence between the cyclic injection amount and the injection advance angle, the injection advance angle to CA50 duration, and the combustion duration at different speeds.

[0075] Specifically, the combustion efficiency η in the engine cylinder comb Determined by the following formula:

[0076] η comb =f(n,λ) (3)

[0077] Where: η comb is the combustion efficiency in the engine cylinder; n is the current speed, r / min; λ is the excess air coefficient, -.

[0078] Specifically, the adjusted combustion characteristic parameters include CA50 position and combustion duration (CA10-90).

[0079] The duration from the main injection advance angle to CA50 is determined by the following formula:

[0080] CA IA-CA50 =f(n,M fuel ) (4)

[0081] The CA50 position calculation formula is obtained through equations (4) and (5):

[0082] CA50=CA IA-CA50-IA (5)

[0083] Where: CA50 is the 50% combustion point, °C A ATDC; CA IA-CA50 CA is the duration from the main injection advance angle to CA50; IA is the injection advance angle (a control parameter read directly from the ECU), °A BTDC.

[0084] The combustion duration (CA10-90) is determined by the following formula:

[0085] CA10-90=f(n,M fuel ) (6)

[0086] Where: CA10-90 is the combustion duration from burning 10% to 90% of the mixture; n is the current speed, r / min; M fuel is the cycle injection amount, mg.

[0087] Step 2.3: At the same speed, a real-time adiabatic efficiency correction model is established by obtaining the adiabatic efficiency, average in-cylinder temperature, and cylinder wall temperature of the engine's steady-state universal characteristics, as well as the average in-cylinder temperature and cylinder wall temperature of the current dynamic operating condition, to correct the adiabatic efficiency under the current operating conditions.

[0088] The adiabatic efficiency under current operating conditions is determined by the following formula:

[0089]

[0090] Where: η adi2 、 T w2 are the adiabatic efficiency, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature under the current operating conditions; η adi1 、 T w1 are the adiabatic efficiency of the steady-state universal characteristics, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature at the same speed and cyclic injection rate.

[0091] It should be noted that the cylinder wall temperature T w1 and T w2 It is a constant term, and the default value is usually 500K.

[0092] Specifically, in formula (7), η is obtained from the engine bench steady-state universal characteristic data according to the speed and cycle injection amount. adi1 、 Determined by the following formula:

[0093] η adi1 =f(n,M fuel ) (8)

[0094]

[0095] Combined with formula (1), the average temperature in the cylinder during combustion and expansion under the current operating conditions in formula (7) is Determined by the following formula:

[0096]

[0097] Where: n is the current speed, r / min; λ is the excess air coefficient, -.

[0098] Step 2.4: Determine the effective expansion ratio (EER) based on the adjusted combustion characteristic parameters, the geometric compression ratio, and the exhaust valve opening timing; determine the polytropic index during the expansion period based on the adjusted excess air coefficient and the average temperature during the combustion and expansion periods at the measured speed; and determine the expansion efficiency based on the effective expansion ratio (EER) and the polytropic index during the expansion period.

[0099] Expansion efficiency η expd Determined by the following formula:

[0100]

[0101] Where: η expd is the expansion efficiency; EER is the effective expansion ratio during the combustion process phase; k is the polynomial index during the expansion period.

[0102] In formula (11), the effective expansion ratio EER is determined by the following formula:

[0103] EER=f(n,CA50,CA10-90) (12)

[0104] Where: n is the current speed, r / min; CA50 is the 50% combustion point position, °CA ATDC; CA10-90 is the combustion duration from burning 10% to 90% of the mixture.

[0105] In formula (11), the polynomial index k during expansion is determined by the following formula:

[0106] k=f(λ,Tg) (13)

[0107] Where: λ is the adjusted excess air coefficient at the current speed, -; Tg is the average temperature during combustion and expansion at the measured speed, that is, Average temperature in the cylinder.

[0108] Step 3: Based on the combustion efficiency, adiabatic efficiency and expansion efficiency obtained in step 2, and in combination with the speed and cycle injection amount, a calculation model is established to calculate the high-pressure cycle indicated fuel consumption rate, the high-pressure cycle average indicated pressure, the pumping loss mean effective pressure and the friction loss mean effective pressure, thereby obtaining the optimized engine performance parameters; wherein: the high-pressure cycle indicated thermal efficiency is determined by the combustion efficiency, adiabatic efficiency and expansion efficiency, and the high-pressure cycle indicated fuel consumption rate is determined accordingly, the high-pressure cycle average indicated pressure is determined by the cycle injection amount and the high-pressure cycle indicated thermal efficiency, and the pumping loss mean effective pressure and the friction loss mean effective pressure are determined by the speed and the cycle injection amount.

[0109] Step 3.1: Determine the high-pressure cycle indicated thermal efficiency based on the adjusted combustion efficiency, adiabatic efficiency, and expansion efficiency, and determine the high-pressure cycle indicated fuel consumption rate based on the high-pressure cycle indicated thermal efficiency.

[0110] High pressure cycle indicated thermal efficiency η i_HP Determined by the following formula:

[0111] η i_HP =η comb *η adi *η expd (14)

[0112] High pressure cycle indicated fuel consumption (ISFC) HP Determined by the following formula:

[0113]

[0114] Where: ISFC HP is the indicated fuel consumption rate of the high-pressure cycle, g / (kW·h); 3600 is 3600s, i.e. 1h, used to convert fuel consumption into hourly specific fuel consumption; H CL is the calorific value of fuel, J / kg; η i_HP Indicates thermal efficiency for high pressure cycles.

[0115] Step 3.2: Determine the high-pressure cycle indicated average pressure (IMEP) based on the cycle injection amount and the high-pressure cycle indicated thermal efficiency. HP Determined by the following formula:

[0116]

[0117] Where: IMEP HP is the average indicated pressure of high pressure cycle, Pa; m fuel is the adjusted cycle injection amount, mg; H CL is the calorific value of fuel, J / kg; η i_HP is the indicated thermal efficiency of the high-pressure cycle; Vs is the cylinder displacement, m3 。

[0118] Step 3.3: Determine the mean effective pressure of pumping loss and the mean effective pressure of friction loss according to the rotational speed and the cyclic fuel injection quantity. The mean effective pressure of pumping loss PMEP and the mean effective pressure of friction loss FMEP are determined respectively by the following formulas:

[0119] PMEP = f(n, m fuel ) (17)

[0120] FMEP = f(n, m fuel ) (18)

[0121] Where: n is the current rotational speed, r / min; M fuel is the cyclic fuel injection quantity, mg.

[0122] Step 3.4: The indexes of the optimized engine performance parameters include the brake specific fuel consumption, the mean effective pressure and the engine torque. The brake specific fuel consumption, the mean effective pressure and the engine torque are determined respectively by the following formulas:

[0123]

[0124] Where: BSFC is the brake specific fuel consumption, g / kWh; BMEP is the mean effective pressure, bar; T b [ is the engine torque, N·m.

[0125] Step 4: Compare the optimized engine performance parameters in Step 3 with the performance parameters of the engine steady-state universal characteristic curve to determine whether the optimized engine performance parameters in Step 3 meet the expectations. If they meet the expectations, proceed to the next working condition; if they do not meet the expectations, readjust the excess air coefficient and optimize the engine performance again according to Steps 2 and 3.

[0126] Specifically, compare the engine performance calculated in Step 3 with the experimental analysis results of the engine bench steady-state universal characteristic. If the performance difference ≥ X1%, return to Step 2 and adjust the excess air coefficient λ;

[0127] Or, compare the calculated engine performance with the experimental analysis results of the engine bench steady-state universal characteristic. If the performance difference < X2%, proceed to the next working condition.

[0128] For example: When taking BSFC as the performance judgment index, if the BSFC difference ≥ 5%, return to Step 2 and adjust the excess air coefficient λ, and ensure that the adjusted excess air coefficient λ makes the difference between BMEP or the engine torque and the steady-state calibration result ≤ 10%, then proceed to the next working condition.

[0129] The readjustment of the excess air coefficient in step 4 is to determine the adjustment strategy of the next excess air coefficient based on the result of the previous step and the gap with the target, and is guided by the optimization algorithm through multiple parameters and multiple constraints.

[0130] The above is only an embodiment of the present invention, and common sense such as the specific structure and characteristics of the scheme are not described in detail here. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claim involved.

Claims

1. A method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine, characterized in that: The method comprises: Step 1: The engine ECU performs real-time detection of the engine's dynamic operating conditions on board the vehicle. Based on the steady-state engine universal characteristic database and at the same speed as the benchmark, if it detects that the engine's dynamic operating performance is lower than its steady-state performance, it compares the control operating parameters that affect the engine's current dynamic performance with those of its steady-state performance. Step 2: Determine the excess air coefficient calculation model. Using the corresponding cycle injection amount in the steady-state engine universal characteristic data at the current speed as a reference, increase the excess air coefficient by reducing the cycle injection amount. Predict the engine's combustion efficiency, adiabatic efficiency, expansion efficiency, and average temperature during combustion and expansion after the excess air coefficient is increased. Step 3: Based on the combustion efficiency, adiabatic efficiency, and expansion efficiency obtained in Step 2, and in combination with the speed and cycle injection amount, a computational model is established for calculating the high-pressure cycle indicated fuel consumption rate, the high-pressure cycle indicated mean pressure, the pumping loss mean effective pressure, and the friction loss mean effective pressure, thereby obtaining optimized engine performance parameters; wherein: the high-pressure cycle indicated thermal efficiency is determined by the combustion efficiency, adiabatic efficiency, and expansion efficiency, and the high-pressure cycle indicated fuel consumption rate is determined accordingly; the high-pressure cycle indicated mean pressure is determined by the cycle injection amount and the high-pressure cycle indicated thermal efficiency; and the pumping loss mean effective pressure and the friction loss mean effective pressure are determined by the speed and cycle injection amount; Step 4: Compare the engine performance parameters optimized in step 3 with the engine steady-state universal characteristic curve performance parameters to determine whether the engine performance parameters optimized in step 3 meet expectations. If so, proceed to the next operating condition. If not, readjust the excess air coefficient and re-optimize the engine performance according to steps 2 and 3.

2. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 1, characterized in that: Step 2 includes: Step 2.1: Adjust the excess air coefficient based on the cycle intake volume and the injection volume of the previous cycle; Step 2.2: Predict the combustion efficiency in the engine cylinder using the adjusted excess air coefficient, and predict the adjusted combustion characteristic parameters based on the measured correspondence between the cyclic injection amount and the injection advance angle, the injection advance angle to CA50 duration, and the combustion duration at different speeds; Step 2.3: Under the same speed, a real-time adiabatic efficiency correction model is established by obtaining the adiabatic efficiency, average in-cylinder temperature, and cylinder wall temperature of the engine's steady-state universal characteristics, as well as the average in-cylinder temperature and cylinder wall temperature of the current dynamic operating condition. This correction is used to correct the adiabatic efficiency under the current operating conditions. Step 2.4: Determine the effective expansion ratio (EER) based on the adjusted combustion characteristic parameters, the geometric compression ratio, and the exhaust valve opening timing; determine the polytropic index during the expansion period based on the adjusted excess air coefficient and the average temperature during the combustion and expansion periods at the measured speed; and determine the expansion efficiency based on the effective expansion ratio (EER) and the polytropic index during the expansion period.

3. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 2, characterized in that: The excess air coefficient λ after adjustment in step 2.1 is determined by the following formula: Where: λ is the excess air coefficient, -; M air is the circulating air intake volume, mg; M fuel is the cycle injection amount, mg; AFR is the air-fuel ratio.

4. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 3, characterized in that: The combustion efficiency η in the engine cylinder in step 2.2 comb Determined by the following formula: or comb =f(n,λ) Where: η comb is the combustion efficiency in the engine cylinder; n is the current speed, r / min; λ is the excess air coefficient, -; The adjusted combustion characteristic parameters include CA50 position and combustion duration. The CA50 position calculation formula is: CA50=CA IA-CA50 -IA CA IA-CA50 =f(n,M fuel ) Where: CA50 is the 50% combustion point position, °CA ATDC; CA IA-CA50 The duration from the main injection advance angle to CA50, CA; IA is the injection advance angle, °CA BTDC; n is the current speed, r / min; M fuel is the cycle injection amount, mg; The combustion duration is determined by the following formula: CA10-90=f(n,M fuel ) Where: CA10-90 is the combustion duration from burning 10% to 90% of the mixture; n is the current speed, r / min; M fuel is the cycle injection amount, mg.

5. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 4, characterized in that: The adiabatic efficiency under the current operating conditions in step 2.3 is determined by the following formula: Where: η adi2 、 T w2 are the adiabatic efficiency, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature under the current operating conditions; η adi1 、 T w1 They are the adiabatic efficiency of the steady-state universal characteristics, the average in-cylinder temperature during combustion and expansion, and the cylinder wall temperature at the same speed and cyclic injection amount.

6. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 5, characterized in that: Expansion efficiency η in step 2.4 expd Determined by the following formula: Where: η expd is the expansion efficiency; EER is the effective expansion ratio during the combustion process; k is the polynomial index during the expansion period; The effective expansion ratio EER is determined by the following formula: EER = f(n, CA50, CA10 - 90) Where: n is the current rotational speed, r / min; CA50 is the position of the 50% combustion point, °CA ATDC; CA10 - 90 is the combustion duration of the mixture from burning 10% to 90%. The polytropic index k during expansion is determined by the following formula: k = f(λ, Tg) Where: λ is the adjusted excess air coefficient at the current speed, -; Tg is the average temperature during combustion and expansion at the measured speed, that is, Average temperature in the cylinder.

7. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 6, characterized in that: In step 3, the indicated fuel consumption rate of the high - pressure cycle, the mean indicated pressure of the high - pressure cycle, the mean effective pressure of the pumping loss, and the mean effective pressure of the friction loss are determined by the following formulas respectively: High pressure cycle indicated fuel consumption (ISFC) HP , High pressure cycle average indicated pressure IMEP HP Determined by the following formula: Where: IMEP HP is the average indicated pressure of high pressure cycle, Pa; m fuel is the adjusted cycle injection amount, mg; H CL is the calorific value of fuel, J / kg; ηi _HP is the indicated thermal efficiency of the high-pressure cycle; Vs is the cylinder displacement, m 3 ; The mean effective pressure of the pumping loss PMEP and the mean effective pressure of the friction loss FMEP are determined by the following formulas respectively: PMEP=f(n,m fuel ) FMEP=f(n,m fuel ) Where: n is the current speed, r / min; M fuel is the cycle injection amount, mg.

8. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 7, characterized in that: In step 4, compare the engine performance calculated in step 3 with the experimental analysis results of the bench steady - state universal characteristics. If the performance difference ≥ X1%, return to step 2 and adjust the excess air coefficient λ; Or, compare the calculated engine performance with the experimental analysis results of the bench steady - state universal characteristics. If the performance difference < X2%, enter the next working condition; The said engine performance includes BSFC, BMEP, and engine torque.

9. The method for online detection and optimization of the operating status and performance parameters of a vehicle-mounted diesel engine according to claim 8, characterized in that: When using BSFC as the performance judgment index, if the BSFC difference ≥ 5%, return to step 2 and adjust the excess air coefficient λ, and the adjusted excess air coefficient λ ensures that the difference between BMEP or engine torque and the steady - state calibration result ≤ 10%, then enter the next working condition.

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