Environmental compensation closed-loop control method and system for natural gas engine

Abstract

The invention discloses an environmental compensation closed-loop control method and system for a natural gas engine. The control method includes the steps that by comparing the environmental parameters of a gas inlet of the engine with the preset standard environment parameters, when the engine is in the nonstandard environment, an electric control unit obtains the feedforward correction coefficients of the boosting gas inflow and the air-fuel ratio according to the temperature in a cylinder, meanwhile the feedback correction coefficient of the mixed gas inflow is obtained according to the temperature in the cylinder, and finally the equivalent power output is obtained, so that the engine can work normally under any environment. The control system is characterized in that an atmospheric environment sensor is additionally arranged on the gas inlet, an intra-cylinder temperature sensor is arranged in the air cylinder, boosting air inflow feedforward and feedback control, air-fuel ratio feedforward control and mixed gas inflow feedback control can be achieved, and finally under any environment, the engine adopting the environmental compensation closed-loop control method and system can achieve the purposes that the inflow of mixed air entering the air cylinder can be controlled and corrected quickly and precisely, and equivalent power output is reached.

Description

technical field [0001] The invention relates to the technical field of natural gas engines, in particular to a closed-loop control method and control system for environmental compensation of natural gas engines. Background technique [0002] Due to the yearly shortage of oil resources in the world and the increasingly serious pollution caused by urban vehicles, natural gas engines, as a green power that burns new fuels and clean energy, have achieved unprecedented rapid development. [0003] At present, natural gas engines adopt electronic control technology to separately control the amount of fresh air and natural gas injection, and form a mixed gas through the mixing device, which is distributed to the cylinder through the intake manifold to burn and perform work. Among them, the fresh air is pressurized by the supercharger, and the supercharged intake air volume is obtained after the intake manifold temperature and atmospheric humidity are corrected; the natural gas is in...

AI Technical Summary

Problems solved by technology

[0004] However, the current control system can only control and correct the mixed intake air volume in a laboratory environment or a calibrated controllable environment to achieve the engine calibration performance. As the engine working environment becomes worse (relative to the controllable calibration environment), The ambient temperature is high or low, the altitude is high or low, the ambient humidity is high or low, etc., the adjustment and correction of the existing control system can no longer meet the requirements of the normal operation of the engine, for example, in the case of high ambient temperature , the amount of mixed intake air entering the cylinder will be reduced due to the reduction of air density, which will eventually lead to a reduction in engine output power

Further problems and deficiencies include: under normal circumstances, the length of exhaust gas transmission in the engine exhaust pipe under different operating conditions is different, which will cause changes in the feedback signal of the oxygen sensor. When the throttle opening changes greatly , the air-fuel ratio will fluctuate instantaneously due to the large deviation between the feed-forward value and the actual intake air volume, which makes it difficult for the control system to accurately adjust the mixed intake air volume. In severe cases, it will lead to unstable engine speed or power output, or even flameout

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