Research On Gasoline Engine Knock Characteristic Extraction And Intensity Evaluation Base On CEEMD-HT

Nowadays,the small strengthening technology(Downsizing)represented by gasoline direct injection pressure and turbocharging is an important technical way to improve the thermal efficiency of the gasoline engine,but with the enhancement of the small strengthening technology,the occurrence probability of engine knock increased significantly,a heavy knock will lead to reduced engine power,increased fuel consumption,emissions deterioration,and making noise,even can lead to engine component damage,so the engine knock restricts the development of small gasoline engine strengthen technology severely.But on the other hand,the light knock nearly constant volume combustion,in favor of engine thermal efficiency and improved fuel economy,is the ideal working condition.Therefore the research of extract the knock characteristics(include light knock)is great significance to the development of gasoline engine.Using the vibration signal of the cylinder block to detect the knock is a widely used solution on a gasoline engine.However,compared to methods based on cylinder pressure,the accuracy of the result acquired from vibration signal cannot be guaranteed because of its low signal-to-noise ratio.In this paper,the research is focused on the data processing method of the knock signal.In order to ensure the accuracy of the research,in this paper,both cylinder pressure signal and vibration signal were used to analysis.The Complementary Ensemble Empirical Mode Decomposition,(CEEMD)algorithm is used to extract the knock characteristic.The result show that the CEEMD algorithm can effectively extract the knock shock characteristics(include light knock)from both cylinder pressure signal and cylinder block vibration signal.And the CEEMD method can effectively remove the shock signal excited by the non-knock vibration;prevent define the normal combustion condition as knock conditions.Furthermore,to the multi-cylinder engines,the CEEMD algorithm can detect knock characteristics of each cylinder from vibration signals by using only one vibration acceleration signal.Base on the knock characteristics extracted by CEEMD algorithm,the Hilbert transform has been used to analysis the time frequency rule.The Hilbert transform result shows that the knock shock area has the phenomenon of instantaneous frequency concentration in both cylinder pressure signal and cylinder block vibration signal.In order to evaluate the intensity of knock,a new knock intensity evaluate method was brought up in this paper.In this method,the knock intensity evaluation parameter is defined as the ratio of the knock characteristic energy of the knock window and reference window,which is decomposed by the CEEMD algorithm.The results show that the heavy knock,light knock and normal combustion can be distinguished effectively by using this method.