CN111206998A

CN111206998A - Method for controlling transient process of engine based on supercharging pressure deviation

Info

Publication number: CN111206998A
Application number: CN201911419713.0A
Authority: CN
Inventors: 黄永杰; 钟桂健
Original assignee: Guangxi Yuchai Machinery Co Ltd
Current assignee: Guangxi Yuchai Machinery Co Ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2020-05-29

Abstract

The invention provides a method for controlling an engine transient process based on boost pressure deviation, which comprises the following steps: when the engine needs to accelerate, the accelerator is stepped on, the ECU reads the current supercharging pressure value according to the supercharging pressure sensor, and compares the current supercharging pressure value with the required supercharging pressure in a steady state, and the supercharging pressure deviation amount is calculated; calibrating different transient factors according to the deviation value; the ECU uses the transient factor to correct the EGR valve, the throttle opening, the oil injection timing and the oil injection pressure; judging whether the exhaust smoke intensity and NOx emission meet the requirements in the transient process, and writing a transient factor corresponding to the deviation into the ECU; the method for controlling the transient process of the engine based on the boost pressure deviation can generate different transient factors according to the boost pressure deviation to obtain different EGR opening degrees in the transient process, thereby achieving the aim of transiently controlling EGR to ensure that the oxygen content and NOx reach optimum compromise.

Description

Method for controlling transient process of engine based on supercharging pressure deviation

Technical Field

The invention belongs to the technical field of emission control of internal combustion engines, and particularly relates to a method for controlling an engine transient process based on supercharging pressure deviation.

Background

With the stricter emission regulations, people pay more and more attention to the emission of a diesel engine under the condition of transient working conditions, a high EGR rate is applied to a supercharged turbo heavy diesel engine, most of the running time of the engine is in the transient working conditions at present, and certain delay exists from the change of exhaust gas energy to the rotation of a turbine, the work of a gas compressor and the establishment of new supercharging pressure due to the compressibility of gas, the inertia of a supercharger impeller rotor, the volume inertia and the pressure loss of an air inlet pipe and an air outlet pipe and a intercooler under the transient working conditions of the supercharged diesel engine, so that the basic stable state can be reached after the intake air flow is stabilized by fuel oil for a while, namely, the intake air is seriously lagged behind the oil injection, and. And because the speed of the establishment of the intake pressure under the transient state is less than the speed of the exhaust pressure formed from the fuel injection combustion to the conversion of the fuel gas energy, the exhaust pressure is greater than the intake pressure in the transient state process, so that the pressure difference at two ends of the EGR valve is always greater than the steady-state value, if the opening degree of the EGR valve adopted in the optimization of the steady-state performance is directly applied to the transient working condition (open-loop control EGR), the increase of the pressure difference at two ends of the EGR valve enables the fuel gas flow to be obviously increased, and the intake flow has. Therefore, the EGR rate eventually overshoots. If closed-loop exhaust gas control EGR is adopted, because transient working condition instantaneous exhaust gas delay causes that an actual value of exhaust gas is smaller than a required value of exhaust gas, a positive deviation is formed, a large PI value is generated, the EGR opening degree is increased, the EGR rate is also overshot, meanwhile, the increase of the EGR exhaust gas quantity also shunts the exhaust flow flowing to an exhaust turbine end, the instantaneous intake mass flow is reduced, the delay phenomenon of a turbocharger is aggravated, the transient air-fuel ratio is too rich, the combustion of an engine is insufficient, and the emission of hydrocarbons (THC) and PM exceeds the standard. Compared with the steady-state working condition, the problems of sharp increase of noise, deterioration of emission and fuel economy and the like exist under the transient working condition. In order to eliminate the phenomenon, the EGR opening degree must be controlled in a transient state, and the oxygen content in the acceleration process is ensured to optimize the performance emission of the transient engine, so the method for controlling the transient process of the engine based on the supercharging pressure deviation is provided.

Chinese invention patent CN 108506105A;

chinese invention patent CN 103362661A;

chinese invention patent CN 101608579A;

chinese invention patent CN 101892914A.

Disclosure of Invention

The invention aims to provide a method for controlling the transient process of an engine based on supercharging pressure deviation, and aims to solve the problems caused by EGR rate overshoot, such as sharp increase of noise, deterioration of emission and fuel economy and the like under the transient working condition in the prior art.

In order to achieve the technical purpose and achieve the technical effect, the invention is realized by the following technical scheme:

the invention provides a method for controlling an engine transient process based on a boost pressure deviation, which comprises the following steps:

step 1: when the engine needs to accelerate, the accelerator is stepped on, the ECU reads the current supercharging pressure value according to the supercharging pressure sensor, and compares the current supercharging pressure value with the required supercharging pressure in a steady state, and the supercharging pressure deviation amount is calculated;

step 2: calibrating different transient factors according to the magnitude of the supercharging pressure deviation;

and step 3: the ECU uses the transient factor to correct the EGR valve, the throttle opening, the oil injection timing and the oil injection pressure;

and 4, step 4: judging whether the exhaust smoke intensity and NOx emission in the transient process meet requirements, if not, entering a step 2, and if so, entering a step 5;

and 5: and writing the transient factor corresponding to the supercharging pressure deviation amount into the ECU, and ending.

Preferably, in step 1, the ECU performs filtering processing on the read boost pressure value and then compares the processed boost pressure value with the steady-state required boost pressure to obtain a boost pressure deviation amount.

Preferably, when the transient factor in step 3 is 1, the correction amount is maximum, the EGR valve is fully closed, and the throttle valve is fully opened; when the transient factor is 0, no correction is performed, and the EGR valve and the throttle valve are output according to the required MAP path.

The invention has the advantages that:

the method for controlling the transient process of the engine based on the supercharging pressure deviation can generate different transient factors according to the supercharging pressure deviation to obtain different EGR opening degrees in the transient process, namely, different EGR opening degrees can be controlled and output according to the transient acceleration severity, so that the aim of transiently controlling EGR to ensure that the oxygen content and NOx reach the optimum compromise is achieved.

Drawings

FIG. 1 is a block flow diagram of a method of controlling an engine transient based on a boost pressure deviation according to the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a method for controlling an engine transient process based on a boost pressure deviation, which comprises the following steps as shown in figure 1:

step 1: when the engine needs to accelerate, the accelerator is stepped on, the ECU reads the current supercharging pressure value according to the supercharging pressure sensor, and compares the current supercharging pressure value with the required supercharging pressure in a steady state, and the supercharging pressure deviation is calculated according to the formula (1);

ΔP＝(T_w-T₀)/T_w(1)

where Δ P is a supercharging pressure deviation amount, T_wFor the desired boost pressure at steady state, T₀Is the current boost pressure value, T_wTo set a constant, T₀Is a detection value; setting steady state demand boost pressure T during rapid acceleration_w1627hPa, and the actual current boost pressure T₀1126hPa, the boost pressure deviation amount Δ P is (1627-1126)/1627 is 30.8%;

step 2: according to the magnitude of the boost pressure deviation amount delta P, calibrating different transient factors delta, as shown in Table 1: if delta P is more than or equal to 0 and less than 15 percent, the engine is in a slight acceleration state, and the value of the transient factor delta is 0; if delta P is more than or equal to 15% and less than 40%, the engine is in a rapid acceleration state, and the value range of the transient factor delta is 0-1; if delta P is more than or equal to 40 percent, the engine is in a rapid acceleration state, and the value of the transient factor delta is 1;

TABLE 1 supercharging pressure deviation and transient factor value-taking table

In step 1, the charging pressure deviation amount Δ P ═ 30.8% (1627-; thus, the transient factor δ may take the value of 0.7;

and step 3: the ECU uses the transient factor delta to correct an EGR valve, the opening of a throttle valve, the injection timing and the injection pressure; the final required values of the EGR valve and the throttle valve are equal to basic MAP value (1-delta), namely the opening degree of the EGR valve and the closing degree of the throttle valve become smaller by 70 percent; when a driver needs to accelerate rapidly, the boost pressure deviation amount delta P reaches more than 40%, at the moment, the calibrated transient factor is 1, the final required value of the EGR valve and the throttle valve is equal to the basic MAP value 0 and is equal to 0, the correction amount is maximum, namely the EGR valve is fully closed, and the throttle valve is fully opened; when the engine is in a steady state or slightly accelerated state, the boost pressure deviation amount delta P is smaller than 15%, the transient factor is marked as 0, the final required values of the EGR valve and the throttle valve are the basic MAP value, the correction amount is the minimum, and the EGR valve and the throttle valve output according to the required MAP path; (Note: Final demand value 0, fully closed for EGR valve, fully open for throttle);

in the aspect of utilizing the transient factor delta generated by the supercharging pressure deviation delta P to correct the fuel injection timing and the fuel injection rail pressure, the correction principle formula is as follows: the final values of the fuel injection timing and the rail pressure are the basic MAP value and the transient factor delta of the corrected MAP, the atomization quality can be improved by increasing the fuel injection pressure and adjusting the fuel supply advance angle, the compression end point temperature is improved, the combustion process is improved, and the performance emission in the transient process is optimized;

and 5: the transient factor δ corresponding to the supercharging pressure deviation amount Δ P is written into the ECU, and the process is terminated.

In one embodiment, the ECU compares the read boost pressure value with the steady-state required boost pressure after filtering in step 1 to obtain a boost pressure deviation amount.

In one embodiment, when the transient factor is 1, the correction amount is maximum, the EGR valve is fully closed, and the throttle valve is fully opened; when the transient factor is 0, no correction is performed, and the EGR valve and the throttle valve are output according to the required MAP path.

Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention.

Claims

1. A method for controlling an engine transient process based on a boost pressure deviation, comprising the steps of:

2. The method of controlling engine transients based on boost pressure deviation of claim 1, wherein: and (3) in the step 1, the ECU compares the read supercharging pressure value after filtering with the steady-state required supercharging pressure to obtain the supercharging pressure deviation.

3. The method of controlling engine transients based on boost pressure deviation of claim 1, wherein: when the transient factor is 1 in the step 3, the correction amount is maximum, the EGR valve is fully closed, and the throttle valve is fully opened; when the transient factor is 0, no correction is performed, and the EGR valve and the throttle valve are output according to the required MAP path.