CN115290337A - Engine endurance test load calibration method - Google Patents

Abstract

The invention discloses a load calibration method for an engine endurance test, which comprises the following steps: step 1, determining a design load Q ₀ (ii) a Step 2, test operation: starting a test, and operating the working condition to a target rotating speed and a target torque; step 3, determining a data recording address, and recording data according to a preset frequency; step 4, calculating the load Q of each second according to the average rotating speed Nengine and the average effective pressure S of the engine; the load Q of each second is accumulated and summed to obtain the test load Q of the test i hours under full speed and full load _i (ii) a Step 5, designing the load Q of the engine ₀ And test load Q _i Performing comparison, if Q _i ＜Q ₀ If the test load does not reach the target load, the test is continued while the target engine torque T is set ₀ Outputting residual test time t1 as the torque calculated by the residual load time; if Q _i ≥Q ₀ And the test is finished. The invention ensures that the test load is consistent with the target load.

Description

Engine Endurance Test Load Calibration Method

technical field

The invention belongs to the technical field of engine testing, and in particular relates to a load checking method for an engine durability test.

Background technique

The engine steady-state fatigue endurance test is an accelerated test verification method equivalent to the 300,000-kilometer load of the user's vehicle engine. Its purpose is to shorten the test verification time under the condition of meeting the test load verification. The time t for the engine to run at the target speed N and target torque T0 can be obtained by converting the load of the user's vehicle engine to 300,000 kilometers.

In the actual test process, the target speed N can be accurately controlled by the dynamometer, but due to the instability of engine combustion, the actual torque will fluctuate around the target torque. Finally, there is a certain deviation between the actual load and the target load. If the actual load is higher than the target load, the test will be over-assessed; but if the actual load is lower than the target load, the test verification will be insufficient and the purpose of test verification will not be achieved. It may be because of the test and assessment that a qualified product is unqualified, or because the test verification is insufficient, the unqualified product is missed, which seriously affects the design and finalization of the product by the engineer.

Existing patents CN201210353293.2 - method for preparing vehicle engine load spectrum, CN202010630354.X, a multi-dimensional comprehensive stress life test load spectrum design method based on load information matrix, explain the conversion and design method of load spectrum; CN201910441354.2 - A load spectrum acquisition method and system, CN200910092143.9—a load spectrum actual measurement test data reading system and its method describe the load spectrum acquisition and acquisition methods. However, none of them compared and checked the converted target load and the actual load completed in the accelerated test, which cannot fully explain that the actual load of the accelerated test is equivalent to the target load.

Therefore, it is necessary to develop a new load verification method for engine endurance test.

Contents of the invention

The object of the present invention is to provide a method for verifying the load of an engine endurance test, which can ensure that the test load is consistent with the target load during the actual engine endurance test.

A kind of engine durability test load checking method described in the present invention, comprises the following steps:

Step 1. Determine the design load Q ₀ : Before the test starts, calculate the engine design load Q ₀ according to the engine target speed N, the engine target torque T ₀ and the test working condition target time t;

Step 2, test operation: start the test, and run the working condition to the target speed and target torque;

Step 3. Data recording: determine the data recording address, and perform data recording according to the preset frequency;

Step 4, load calculation Q _i : process the recorded data, calculate the load Q per second according to the average engine speed N _engine and the average effective pressure S; accumulate and sum the load Q per second to obtain the full speed and full load Q i Test load Q _i under load for i hour test;

Step 5. Load verification: compare the engine design load Q ₀ with the test load Q _i , if Q _i <Q ₀ , it means that the test load has not reached the target load, then continue the test, and at the same time use the engine target torque T ₀ is the torque calculated as the remaining load time, and the remaining test time t1 is output; if Q _i ≥ Q ₀ , the test ends.

Optionally, in step 4, the recorded data is processed, specifically:

Put the data into the specified path, read the data put into the specified path, and perform data splicing, filter out the data of non-test working conditions, obtain the data containing only the specified working conditions of the test, and sort the filtered data in chronological order put in order.

Optionally, in the step 4, the average effective pressure S is calculated according to the _average torque T of the engine and the displacement L of the engine, specifically:

S = T _average * 12.57/L.

Optionally, in the step 4, the calculation method of the load Q per second is:

Optionally, in step 1, the calculation method of the test load Q _i of the test i hour under full speed and full load is:

Wherein, n _b is the engine speed at the bth second, and T _b is the engine torque at the bth second.

Optionally, in the step 4, the calculation method of the engine design load Q0 is _:

Optionally, in the step 5, the calculation method of the remaining test time t1 is as follows:

Optionally, in the early stage of the test, the load calculation and verification are performed every day, and the test time is corrected; in the later stage of the test, the load calculation and verification are performed every hour, and the test time is corrected.

The invention has the following advantages: in the actual engine endurance test process, the problem of the difference between the actual load and the target load caused by the fluctuation of the measured torque near the target torque is solved. By making statistics on the actual test load and correcting the theoretical accelerated test time, it is ensured that the test load is consistent with the target load.

Description of drawings

Figure 1 is a flow chart of load correction during the test;

Figure 2 is a graph of actual torque and target torque in the test;

Figure 3 is a flow chart of automatic load calculation;

Figure 4 is a graph of load correction and time correction.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, in this embodiment, a method for verifying the load of an engine endurance test includes the following steps:

Step 1. Determine the design load Q ₀ : Before the test starts, calculate the engine design load Q ₀ according to the engine target speed N, the engine target torque T ₀ and the test working condition target time t;

Step 2, test operation: start the test, and run the working condition to the target speed and target torque;

Step 3. Data recording: determine the data recording address, and perform data recording according to the preset frequency (1HZ);

Step 4, load calculation Q _i : process the recorded data, calculate the load Q per second according to the average engine speed N _engine and the average effective pressure S; accumulate and sum the load Q per second to obtain the full speed and full load Q i Test load Q _i under load for i hour test;

Step 5. Load verification: compare the engine design load Q ₀ with the test load Q _i , if Q _i <Q ₀ , it means that the test load has not reached the target load, then continue the test, and at the same time use the engine target torque T ₀ is the torque calculated as the remaining load time, and the remaining test time t1 is output; if Q _i ≥ Q ₀ , the test ends.

Referring to Fig. 2, in order to solve the problem of the difference between the actual load and the target load due to the fluctuation of the measured torque near the target torque during the actual engine endurance test. By making statistics on the actual test load and correcting the theoretical accelerated test time, it is ensured that the test load is consistent with the target load.

This method uses the data analysis function of python to compile data processing related programs. During the test, the data recorded in the test process is automatically read and calculated through the program, and the actual load is automatically and quickly calculated, and compared with the target load to judge.

As shown in Figure 3, in this embodiment, in the step 4, the recorded data is processed, specifically:

Put the data into the specified path, read the data put into the specified path, and perform data splicing, filter out the data of non-test working conditions, obtain the data containing only the specified working conditions of the test, and count the length of the data, and at the same time, according to the time Order sorts the filtered data. The data is then fitted for loading verification.

In this embodiment, according to the S-N theory, the average effective pressure acting on the crankshaft of the engine can be taken as S, and the rotational speed of the engine can be taken as the stress frequency N. From this reasoning, it can be concluded that the load acting on the crankshaft can be obtained by the speed and the mean effective pressure S:

For a four-stroke engine, the engine completes a working cycle every 2 revolutions, and the torque output by the engine after completing a working cycle is taken as the average torque. The average torque and speed of the engine are measured by the dynamometer.

Calculate the average effective pressure S according to the average torque T _average of the engine and the displacement L of the engine, specifically:

S = T _average * 12.57/L.

In this embodiment, in the step 4, the calculation method of the load Q per second is:

In the present embodiment, in the step 4, the calculation method of the test load Q _i of the test i hour under full speed and full load is:

Wherein, n _b is the engine speed at the bth second, and T _b is the engine torque at the bth second.

In the present embodiment, in the step ₁ , the calculation method of the engine design load Q is:

Among them, L is the displacement of the engine.

In the present embodiment, in the step 5, the calculation method of the remaining test time t1 is as follows:

The following takes a 2.0L displacement engine as an example:

(1) The target engine speed N is 5500r/min, and the target torque _T0 is 280N·m. After converting the engine load of the user's 300,000-kilometer vehicle, the target time t of the test condition is 300h.

(2) Before the test, calculate Q ₀ according to the engine target load calculation formula:

(3) The test starts, and starts to record parameters such as engine speed, torque, and throttle position according to the frequency of 1HZ;

(3.1) In the early stage of the test, due to the large difference between the actual load and the target load, it can be considered to carry out load calculation and verification every day (24h), and to correct the test time; in the later stage of the test (10h), the load calculation can be carried out once in 1h , verification, so that it can be guaranteed that the verification difference between the actual load and the target load is only generated within the last hour.

(3.2) The test process may generate multiple data record files, and it is necessary to put multiple data files together for calculation when performing load calculations.

(4) See Figure 4. After the test has been carried out for a period of time, the load calculation is started, and the load calculation is carried out based on the data from a certain test to the test time of 107h. According to the measured torque data, the program automatically counts the load per second:

The calculated actual load for 107 hours is Q _i =26538198317, and the target load is calculated according to the Q ₀ calculation formula to obtain the target load is Q ₁₀₇ =31069269000. It can be seen that the actual load is lower than the target load, so the remaining test time needs to be corrected.

Remaining test time:

Calculated to get t1 = 208.6h, it can be seen that although the test actually runs for 107h, the theoretical remaining 193h. However, due to the difference between the target load and the actual load in the test process, the actual test time after correction is 208.6 hours.

(5) During the subsequent test run, the actual completion time can be corrected according to the method in step (4) to obtain the remaining test time t1.

(6) By using the above test process load correction during the steady-state durability acceleration test of the engine, the actual load can be verified in real time and the test time can be corrected. Through data statistics and relying on real data, it is guaranteed that the test verification is sufficient and there will be no over-examination phenomenon.

The above-mentioned embodiment is a preferred embodiment of the method of the present invention, but the embodiment of the method of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, Combination and simplification should all be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (8)

1. a kind of engine durability test load verification method, it is characterized in that: comprise the following steps: Step 1. Determine the design load Q ₀ : Before the test starts, calculate the engine design load Q ₀ according to the engine target speed N, the engine target torque T ₀ and the test working condition target time t; Step 2, test operation: start the test, and run the working condition to the target speed and target torque; Step 3. Data recording: determine the data recording address, and perform data recording according to the preset frequency; Step 4, load calculation Q _i : process the recorded data, calculate the load Q per second according to the average engine speed N engine and the average effective pressure S; accumulate and sum the load Q per second to obtain the full speed and full load Q i Test load Q _i under load for i hour test; Step 5. Load verification: compare the engine design load Q ₀ with the test load Q _i , if Q _i <Q ₀ , it means that the test load has not reached the target load, then continue the test, and at the same time use the engine target torque T ₀ is the torque calculated as the remaining load time, and the remaining test time t1 is output; if Q _i ≥ Q ₀ , the test ends. 2. The engine endurance test load verification method according to claim 1, characterized in that: in the step 4, the recorded data is processed, specifically: Put the data into the specified path, read the data put into the specified path, and perform data splicing, filter out the data of non-test working conditions, obtain the data containing only the specified working conditions of the test, and sort the filtered data in chronological order put in order. 3. The engine endurance test load verification method according to claim 1 or 2, characterized in that: in the step 4, the average effective pressure S is calculated according to the _average torque T of the engine and the displacement L of the engine, specifically : S = T _average * 12.57/L. 4. The engine endurance test load verification method according to claim 3, characterized in that: in the step 4, the calculation method of the load Q per second is:

5. engine durability test load verification method according to claim 4, is characterized in that: in described step 4, the calculation method of the test load Q of test _i hour under full speed and full load is:

Wherein, n _b is the engine speed at the bth second, and T _b is the engine torque at the bth second. 6. The engine durability test load verification method according to claim ₅ , characterized in that: in the step 1, the calculation method of the engine design load Q is:

7. The engine endurance test load verification method according to claim 6, characterized in that: in the step 5, the calculation method of the remaining test time t1 is as follows:

8. The engine durability test load verification method according to claim 1 or 2 or 4 or 5 or 6 or 7, characterized in that: in the early stage of the test, load calculation and verification are carried out once a day, and the test time is corrected; In the later stage of the test, the load calculation and verification are carried out every hour, and the test time is corrected.

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