Research On Combustion Noise Of Turbocharged Direct Injection Gasoline Engine

To reduce the energy consumption and simultaneously meet the stringentemission regulations is a great challenge for automotive industry in China. Thegasoline engine can improve the fuel economy effectively owing to theadaptation of the turbocharged direct injection (TGDI), which has become thepopular technology widely used in the most of automobile companies. Comparedto the gasoline engine with port fuel injection, the combustion noise of theTGDI engine is an important negative factor affecting the NVH performancedue to the combustion pressure rise in a large level. Therefore it is necessary tostudy and evaluate the combustion noise of the TGDI engine.The separation method of the combustion noise is investigated in this paper. Inorder to make a reasonable estimation on the combustion noise, this paper studies theseparation theory of the combustion noise including the direct combustion noise,indirect combustion noise and flow noise on the basis of fully understanding of thecurrent situation of the combustion noise research at home and abroad. By controllingthe spark ignition advance angle and the intake air temperature, the direct andindirect combustion noises can be abstracted from the engine total noise. Thisresearch builds up the calculation method of transmission function for the directand indirect combustion noises through the analysis of the force excitation andtransmission path of the direct and indirect combustion noise. The measurementand evaluation on a three-cylinder engine is carried out by the methodmentioned and the transmission function of the direct and indirect combustionnoises are obtained, and then the contribution of the combustion noisecomponents and spectrum is evaluated as well.In order to achieve the prediction and optimization of the NVH performance atengine early design stage, the whole engine model has been built up to make the NVHsimulation analysis to obtain the engine structure vibration response and thetransmission function of the indirect combustion noise. The simulation result showsthat a higher precision is achieved at mid-low frequency but lower precision athigh frequency compared to the measurement data. The remarkable difference of the indirect transmission function is found between the simulation result and themeasurement data due to the lower precision in structure radiated noise of simulation.The combustion noise at1750r/min full load condition is predicted by using thetransmission function already obtained, and the relationship between engine torque,fuel consumption、 exhaust emission、 and combustion noise are analyzedsimultaneously through tuning the spark ignition advance angle. These parametersare presented a normalization processing and the best balance point is found betweenthese parameters according to the target requirement. Finally the simultaneousevaluation for engine combustion noise and other engine performance has beenimplemented during engine thermodynamics development process.