Study On The Control Characteristics Of Quality Adjustment Load In The Unthrottled Gasoline Engine

The thermal efficiency and fuel economy of gasoline engines are lower than that of diesel engines,the pumping loss caused by the existence of the throttle is the main reason that restricts the improvement of gasoline engines’fuel economy.The quality-adjusted load control method was adopted to calibrate the fuel injection at each operating point,which can cancel the throttle of the gasoline engine to achieve unthrottled load control,that is beneficial to reduce the pumping loss of the gasoline engine.At the same time,adopts the quality-adjusted load control method is beneficial to further tap the fuel-saving potential of gasoline engines.Based on GT-POWER and CONVERGE to HONDA single-cylinder four-stroke gasoline engine,this paper carried out the model construction of one-dimensional performance simulation and three-dimensional combustion numerical simulation respectively.Based on the bench test data,the relevant boundary conditions were set,and the model simulation data and test data were combined and use the test data to verify the accuracy of the model.Using one-dimensional performance simulation model of GT-POWER to calibrate the fuel injection of the unthrottled gasoline engine.The fuel injection MAP of the unthrottled gasoline engine under the typical operating point of the original engine is obtained,and the main performances of the original engine and the unthrottled gasoline engine are compared and analyzed.Compared with the original engine with throttle of the same power,under 30%throttle opening load condition of maximum torque speed3000r/min,the effective fuel consumption rate of the unthrottled gasoline engine is reduced by 20.1%,and the indicated thermal efficiency is increased by 24.9%.The NO_xand HC emissions increase to varying degrees based on operating conditions.Using Isight to optimize the fuel-air ratio and advance angle of ignition of the unthrottled gasoline engine with multiple objectives.The optimal Latin hypercube experimental design method is used to sample the optimized interval at a single working condition point,and the optimized Kriging model is established based on the GT-POWER simulation data.Using genetic algorithm NSGA-II to perform multi-objective optimization on the built Kriging model,and the best fuel-air ratio and advance angle of ignition under each operating condition are obtained.Using CONVERGE to numerically simulate the original engine and the unthrottled gasoline engine at 3000r/min,with an average effective pressure of 9.58 bar,and analyze the flow field and combustion conditions in the cylinder of the unthrottled gasoline engine.The comparative analysis found that the structure and distribution evolution process of in-cylinder swirl and tumble flow of the unthrottled gasoline engine are similar to those of the original engine,but due to the absence of throttle pumping loss,the airflow movement intensity in the cylinder during the intake phase and most compression phase generally higher than the original engine,the average turbulent kinetic energy of the circulation in the cylinder also increases.The unthrottled gasoline engine under medium and small load conditions can burn a leaner mixture,but it will slow down the flame propagation speed and prolong the combustion duration.