Gasoline engine knocking judging and occurrence time predicting method considering influence of external exhaust gas recirculation (EGR)

Abstract

The invention provides a gasoline engine knocking judging and occurrence time predicting method considering the influence of external exhaust gas recirculation (EGR). The in-cylinder pressure Pi of the cylinder pressure sensor test on the basis of the crankshaft angle and the in-cylinder pressure PIVC and the temperature TIVC of an air inlet vale at the closing moment and a variable index gamma are user as the input to obtain the temperature Ti of the unburned mixed fuel gas on the basis of the crankshaft angle in a engine cycle starting from the air inlet valve closing moment; the crankshaft angle theta KO is calculated when the provided knocking integral value is 1, the theta K0 is compared with the 95% accumulation heat release rate crankshaft angle theta 95% HR; if theta KO is larger than theta 95% HR, no knocking occurs under the working condition; otherwise, if the theta KO is not larger than the theta 95% HR, knocking occurs under the working condition, and the knocking occurs at theta KO. By the method, an effective approach for gasoline engine knocking prediction and performance development after EGR is used.

Description

technical field [0001] The invention relates to the technical field of internal combustion engines, in particular to a gasoline engine knock determination method including the influence of external exhaust gas recirculation and a prediction method of occurrence time. Background technique [0002] Gasoline engine knocking is generally considered to be abnormal combustion caused by the mixture gas at the end of the cylinder reaching its auto-ignition temperature before the flame front reaches it. Knocking is a chronic problem of gasoline engines, which always restricts the improvement of the thermal efficiency of gasoline engines. Traditional knock suppression methods include retarding the ignition advance angle, enriching the mixture and increasing the octane number of the fuel, etc. However, these methods can no longer meet the development requirements of modern high boost and high compression ratio gasoline engines. External cooling exhaust gas recirculation (EGR, Exhuaus...

AI Technical Summary

Problems solved by technology

In engine design and development, once external EGR is used to suppress knocking, it is necessary to have a method and process that can conveniently and accurately predict whether knocking occurs and when it occurs, but the existing methods for predicting the timing of knocking (Douaud -Eyzat method) does not consider the impact of external cooling EGR on knocking, and cannot know whether knocking occurs and the important information of the timing of knocking, so that it is impossible to accurately determine the geometric compression ratio, ignition angle, and water jacket cooling capacity in the development process of gasoline engines Important design parameters, such as gasoline engine fuel economy and power performance are limited

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