A method of adjusting an optical single cylinder engine EGR rate

Abstract

The application provides a method for adjusting an optical single-cylinder engine EGR rate, comprising the following steps: S1, determining a target test working condition of the optical single-cylinder engine; S2, determining an initial CO2 flow rate required to be introduced into the optical single-cylinder engine according to test parameters of a four-cylinder engine in the market when the four-cylinder engine performs the target test working condition on a test bench; S3, opening a CO2 cylinder and a pressure reducing valve, and controlling a manual valve switch to introduce pure CO2 into the optical single-cylinder engine, and running the optical single-cylinder engine in a motoring mode; S4, calculating an actual EGR rate of the optical single-cylinder engine according to CO2 concentrations measured by a first CO2 concentration measuring device and a second CO2 concentration measuring device; S5, judging whether the actual EGR rate reaches a target EGR rate; S6, if the actual EGR rate does not reach the target EGR rate, controlling the manual valve switch to correct the CO2 flow rate, and measuring the corrected actual EGR rate again; repeating the steps S5 to S6 until the corrected actual EGR rate reaches the target EGR rate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine test, and particularly relates to a test method for quickly adjusting an EGR rate on an optical single-cylinder engine. BACKGROUND

[0002] The optical single-cylinder engine is based on a single-cylinder engine, and an optical channel is formed on the cylinder or the piston. Under the condition of not damaging the in-cylinder working process, various non-contact, high-resolution and high-accuracy optical methods are used to perform visualization test projects such as in-cylinder airflow movement, spray speed field and flame propagation.

[0003] The exhaust gas recirculation technology (EGR) is to send part of the exhaust gas (mainly CO2) discharged by the engine back to the intake manifold to mix with fresh air and then enter the cylinder for combustion. The main functions of the EGR system are to reduce fuel consumption, improve NOx emission, suppress knocking and reduce exhaust gas temperature. At present, the mixed engine generally adopts the technical route of high compression ratio + EGR, and the EGR can effectively solve the knocking problem under high compression ratio.

[0004] The scheme with the patent application number CN201921070159.5 provides a system for realizing EGR of a diesel single-cylinder engine. Different proportions of various gases are introduced into the combustion chamber to simulate EGR circulating exhaust gas. The composition proportion of the various gases introduced is automatically adjusted through the feedback of the tail gas concentration measuring device during the ignition process, so that the influence of a single variable in the exhaust gas recirculation gas on the combustion system is conveniently studied. However, since there is no cooling jacket outside the combustion chamber of the optical single-cylinder engine as in the traditional engine, the allowed continuous ignition time is very short (usually within 20s), and stable exhaust gas cannot be formed in the combustion chamber during the ignition process. At the same time, the very short continuous ignition time is also not enough to complete the automatic adjustment of the EGR rate. Therefore, the patent is not applicable to the EGR rate adjustment on the optical single-cylinder engine.

[0005] In summary, there is no suitable method for realizing the adjustment of the EGR rate on the optical single-cylinder engine in the current industry. SUMMARY

[0006] The application provides a test method for quickly adjusting an EGR rate on an optical single-cylinder engine.

[0007] The technical scheme of the application is as follows:

[0008] The application provides a method for adjusting an EGR rate of an optical single-cylinder engine, which is applied to a test system for adjusting the EGR rate of the optical single-cylinder engine. The system comprises:

[0009] The CO2 cylinder, the pressure reducing valve, the first one-way valve, the manual valve switch, the flow meter, the pressure sensor, the second one-way valve, the optical single-cylinder machine intake pipeline, the optical single-cylinder machine and the optical single-cylinder machine exhaust pipeline, the first CO2 concentration measuring device arranged in the optical single-cylinder machine intake pipeline and the second CO2 concentration measuring device arranged in the optical single-cylinder machine exhaust pipeline are sequentially connected.

[0010] The method comprises:

[0011] Step S1, determining a target test working condition of the optical single-cylinder machine;

[0012] Step S2, determining an initial CO2 flow rate required to be introduced into the optical single-cylinder machine according to test parameters of the in-market four-cylinder engine when the in-market four-cylinder engine executes the target test working condition on the test bench;

[0013] Step S3, opening the CO2 cylinder and the pressure reducing valve, and controlling the manual valve switch to introduce pure CO2 into the optical single-cylinder machine at the initial CO2 flow rate, and operating the optical single-cylinder machine in a motoring mode;

[0014] Step S4, calculating an actual EGR rate of the optical single-cylinder machine according to CO2 concentrations respectively measured by the first CO2 concentration measuring device and the second CO2 concentration measuring device;

[0015] Step S5, judging whether the actual EGR rate reaches a target EGR rate;

[0016] Step S6, if the actual EGR rate does not reach the target EGR rate, controlling the manual valve switch to gradually correct the CO2 flow rate, and measuring the actual EGR rate after each correction again;

[0017] Steps S5 to S6 are repeated until the corrected actual EGR rate reaches the target EGR rate.

[0018] Preferably, a calculation formula of the initial CO2 flow rate required to be introduced into the optical single-cylinder machine is:

[0019] Q co2 = 3.65 * η EGR / (1-η EGR )*k*λ*FB_rate

[0020] Wherein, η EGR is the target EGR rate of the optical single-cylinder machine, FB_rate is a fuel consumption rate of the in-market four-cylinder engine when the in-market four-cylinder engine executes the target test working condition on the test bench, λ is an excess air coefficient of the in-market four-cylinder engine when the in-market four-cylinder engine executes the target test working condition on the test bench, and k is a 1 / 4 intake flow rate conversion coefficient of the optical single-cylinder machine and the in-market four-cylinder engine.

[0021] Preferably, the actual EGR rate = the CO2 concentration measured by the second CO2 concentration measuring device / (the CO2 concentration measured by the first CO2 concentration measuring device + the CO2 concentration of the first CO2 concentration measuring device) * 100%.

[0022] Preferably, the CO2 flow Q co2,corr By the formula:

[0023] Q co2,corr = Q 实测co2 *sqrt(P0 / P s )

[0024] Q 实测co2 is the actual CO2 flow in the flowmeter, P1 is the actual CO2 pressure in the flowmeter measured by the pressure sensor, and P0 is the atmospheric pressure.

[0025] The beneficial effects of the present application are:

[0026] According to the test data of the similar engine model on the market, the CO2 flow of the optical single-cylinder engine is estimated, and then the EGR regulation of the optical single-cylinder engine under specific test conditions is realized, so that the in-cylinder visualization tests such as in-cylinder airflow movement, spray velocity field and flame propagation based on EGR technology can be carried out on the optical single-cylinder engine, which is beneficial to more directly understand the in-cylinder combustion phenomenon and the generation process of pollutants, and the power performance, economic performance and emission performance of the engine can be improved through optimization of the EGR control strategy. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a CO2 flow calculation model diagram;

[0028] Figure 2 is a schematic diagram of using pure CO2 gas instead of exhaust gas circulation (EGR);

[0029] Figure 3 is a work instruction flowchart for regulating the EGR rate on the optical single-cylinder engine;

[0030] Figure 4 is a test device structure diagram for quickly regulating the EGR rate on the optical single-cylinder engine. DETAILED DESCRIPTION

[0031] The present application estimates the CO2 flow demand of the optical single-cylinder engine under the target EGR rate by establishing a model, so as to solve the problem that the EGR rate cannot be regulated due to insufficient ignition time of the optical single-cylinder engine, and can be used for research work of EGR optimization of the combustion system on the optical single-cylinder engine.

[0032] In this embodiment, the CO2 flow calculation model framework schematic diagram of the optical single-cylinder engine under the target EGR rate is shown in Figure 1The specific method is as follows:

[0033] Intake airflow Q of similar four-cylinder engines under the same operating conditions on a conventional test bench 进气，四缸 for:

[0034] Q 进气，四缸 =14.6*λ*FB_rate

[0035] FB_rate — Fuel consumption rate of a similar engine model under the same operating conditions on a standard test bench.

[0036] λ — Excess air coefficient of an engine of similar model under the same operating conditions on a conventional test bench.

[0037] So, the estimated intake flow rate Q of the optical single-cylinder engine. 进气 for:

[0038] Q 进气 =k*Q 进气，四缸 / 4=3.65*k*λ*FB_rate (1)

[0039] k – a conversion factor of 1 / 4 intake airflow between an optical single-cylinder engine and a similar four-cylinder engine.

[0040] EGR rate η EGR The amount of waste gas defined as recirculated is Q. 循环废气 The total intake air volume Q of the cylinder 进气 The amount of recirculated exhaust gas Q 循环废气 The ratio of the sums, i.e., the EGR rate η of the optical single-cylinder engine. EGR satisfy:

[0041] η EGR =Q 循环废气 / (Q 进气 +Q 循环废气 )*100% (2)

[0042] This allows us to obtain the theoretically required circulating exhaust gas volume Q for an optical single-cylinder engine. 循环废气 for:

[0043] Q 循环废气 =η EGR / (1-η EGR )*Q 进气 (3)

[0044] Q 循环废气 —The theoretical required volume of circulating exhaust gas for an optical single-cylinder engine.

[0045] In optical single-cylinder engines, pure CO2 is directly used instead of the CO2 in the recirculated exhaust gas when it is introduced into the combustion chamber (see...). Figure 2 Furthermore, theoretically, the amount of waste gas recirculated (Q) in a similar four-cylinder engine is...循环废气 The amount of CO2 introduced into the optical single cylinder is equal to the amount of pure CO2 gas actually introduced into the optical single cylinder, i.e. the amount of pure CO2 gas actually introduced into the optical single cylinder n co2 Satisfies:

[0046] n co2 = (Q co2 + Q 进气 ) * C 进气 = Q 循环废气 * C 循环废气 (4)

[0047] C 循环废气 The optical single cylinder theoretically requires a cycle exhaust CO2 concentration equal to the exhaust CO2 concentration C 排气 ;

[0048] Q CO2 The optical single cylinder requires the introduction of CO2 flow;

[0049] C 进气 The CO2 concentration in the intake pipeline after the optical single cylinder introduces CO2,

[0050] Since the formula for calculating the EGR rate using the concentration method is defined as:

[0051] η EGR = C 进气 / C 排气 * 100% (5)

[0052] Bringing formulas (1), (2), (3), and (5) into (4), the initial CO2 flow Q introduced into the optical single cylinder can be obtained co2 :

[0053] Q co2 = 3.65 * η EGR / (1-η EGR )*k*λ*FB_rate (6)

[0054] Wherein, initially k is defaulted to 1 for calculation, and subsequently can be adjusted according to the accumulation of measured data to further improve the accuracy of CO2 flow estimation.

[0055] At the same time, since the flowmeter 5 selected is a orifice differential pressure flowmeter, there is a large difference between the actual CO2 pressure in the pipeline and atmospheric pressure, therefore, according to the formula (7) in the equipment instruction manual, the measured values of the flowmeter 5 and the pressure sensor 6 are real-time corrected through the virtual channel of the bench data acquisition system, and the actual CO2 flow after the correction of the manual valve switch 4:

[0056] Q co2,corr = Q 实测co2 *sqrt(P0 / Ps (7)

[0057] P0 — Atmospheric pressure

[0058] P s —The actual CO2 pressure inside the flow meter 5 is measured by the pressure sensor (6).

[0059] like Figure 4 This invention specifically includes a test device for rapidly adjusting the EGR rate on an optical single-cylinder engine, comprising a CO2 cylinder 1, a pressure reducing valve 2, a first one-way valve 3, a manual valve switch 4, a flow meter 5, a pressure sensor 6, a second one-way valve 7, an optical single-cylinder engine intake pipe 8, a first CO2 concentration measuring device 9 and a second CO2 concentration measuring device 11, an optical single-cylinder engine 10, and an optical single-cylinder engine exhaust pipe 12. The CO2 cylinder 1 is used for storing and releasing CO2 gas. The pressure reducing valve 2 is used to reduce the pressure of the released CO2 gas to a safe range to avoid damage to the equipment. One-way valves 3 and 7 are used to prevent reverse flow of gas from damaging the equipment. The manual valve switch 4 is used to adjust the CO2 gas flow rate. The flow meter 5 is used to measure the CO2 gas flow rate. The data collected by the pressure sensor 6 is used to correct the CO2 gas flow rate using the manual valve switch 4. The first CO2 concentration measuring device 9 and the second CO2 concentration measuring device 11 are used to measure the CO2 concentration in the intake and exhaust pipes and calculate the actual EGR rate accordingly.

[0060] Adjusting the EGR rate on an optical single-cylinder engine, such as Figure 3 As shown, the initial CO2 flow rate needs to be estimated based on the performance of a similar four-cylinder engine under the same operating conditions on a conventional test bench. The calculation method is shown in formula (6). Then, as... Figure 4 As shown, open CO2 cylinder 1, then reverse-drive the optical single-cylinder engine 10 to create a stable gas flow within the combustion system. Adjust the CO2 flow rate to the calculated value Q using manual valve switch 4. co2 Then, the optical single-cylinder engine 10 is ignited for combustion. The CO2 concentration is measured using the first CO2 concentration measuring device 9 and the second CO2 concentration measuring device 11, and the actual EGR rate of the optical single-cylinder engine 10 is calculated. If the actual EGR rate is inconsistent with the target EGR rate, the CO2 flow rate is finely adjusted by adjusting the manual valve switch 4, and the above steps are repeated until the actual EGR rate reaches the target EGR rate.

[0061] Below, taking the adjustment of the EGR rate of a certain type of optical single-cylinder engine as an example, it is necessary to adjust the EGR rate to 8% under the operating conditions of 2000r / min 8bar:

[0062] First, the performance data of the same working condition of the approximate model four-cylinder engine on the conventional test bench is queried, and the initial CO2 flow rate is estimated to be about 15.8 L / min (the CO2 density is calculated according to 1.977 g / L) according to formula (6).

[0063] RPM BMEP FB_rate Lambda r / min bar kg / h \ 2000 8 6.00 0.99

[0064] Then open the CO2 cylinder 1 and dump the optical single-cylinder engine 10, adjust the corrected flow rate display value to 15.8 L / min through the manual valve switch 4, ignite and burn, and then measure the CO2 concentration in the inlet and outlet pipelines of the optical single-cylinder engine through the first CO2 concentration measuring device 9 and the second CO2 concentration measuring device 11 to calculate the actual EGR rate. If the actual EGR rate is inconsistent with the target EGR rate, continue to fine-tune the CO2 flow rate through the manual valve switch 4 and repeat the above steps until the actual EGR rate after ignition reaches the target EGR rate.

Claims

1. A method for adjusting the EGR rate of an optical single-cylinder engine, applied to a test system for adjusting the EGR rate of an optical single-cylinder engine, characterized in that, The system includes: A CO2 cylinder, a pressure reducing valve, a first check valve, a manual valve switch, a flow meter, a pressure sensor, a second check valve, an optical single-cylinder engine intake pipe, an optical single-cylinder engine and an optical single-cylinder engine exhaust pipe are connected in sequence. A first CO2 concentration measuring device is arranged in the optical single-cylinder engine intake pipe, and a second CO2 concentration measuring device is arranged in the optical single-cylinder engine exhaust pipe. The method includes: Step S1: Determine the target test conditions for the optical single-cylinder engine; Step S2: Based on the test parameters of the four-cylinder engine that has entered the market and is performing the target test conditions on the test bench, determine the initial CO2 flow rate that needs to be introduced into the optical single-cylinder engine. Step S3: Open the CO2 cylinder and pressure reducing valve, and control the manual valve switch to introduce pure CO2 into the optical single-cylinder engine according to the initial CO2 flow rate, and reverse the optical single-cylinder engine to run. Step S4: Calculate the actual EGR rate of the optical single-cylinder engine based on the CO2 concentrations measured by the first CO2 concentration measuring device and the second CO2 concentration measuring device respectively. Step S5: Determine whether the actual EGR rate has reached the target EGR rate; Step S6: If the actual EGR rate does not reach the target EGR rate, control the manual valve to gradually correct the CO2 flow rate, and measure the actual EGR rate after each correction. Repeat steps S5 to S6 until the corrected actual EGR rate reaches the target EGR rate.

2. The method for adjusting the EGR rate of an optical single-cylinder engine according to claim 1, characterized in that, The formula for calculating the initial CO2 flow rate required in an optical single-cylinder engine is as follows: Q co2 =3.65*n EGR / (1-th EGR )*k*λ*FB_rate Where, η EGR denoted as the target EGR rate of the optical single-cylinder engine, FB_rate as the fuel consumption rate of the four-cylinder engine under target test conditions on the bench, λ as the excess air coefficient of the four-cylinder engine under target test conditions on the bench, and k as the 1 / 4 intake flow conversion factor between the optical single-cylinder engine and the four-cylinder engine.

3. The method for adjusting the EGR rate of an optical single-cylinder engine according to claim 1, characterized in that, Actual EGR rate = CO2 concentration measured by the second CO2 concentration measuring device / (CO2 concentration measured by the first CO2 concentration measuring device + CO2 concentration of the first CO2 concentration measuring device) * 100%.

4. The method for adjusting the EGR rate of an optical single-cylinder engine according to claim 1, characterized in that, The actual CO2 flow rate Q after manual valve switching correction co2,corr Through the formula: Q co2,corr = Q 实测co2 *sqrt(P0 / P s ) Calculate Q 实测co2 P1 is the actual CO2 flow rate inside the flow meter, P2 is the actual CO2 pressure inside the flow meter measured by the pressure sensor, and P0 is the atmospheric pressure.

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