Experiment And Numerical Simulation Studies On A Gasoline Girect Injection Engine Burning Gasoline And Butanol Blended Fuels

In order to meet the increasing demand for petroleum,it is necessary to find new fuels that can be used in internal combustion engines.Butanol has higher calorific value than methanol and ethanol,and less corrosiveness convenient transportation and can be used as engine fuel alone or mixed with diesel oil and gasoline,which makes butanol to be a new engine fuel to replace part of petroleum in the future.So it is of great significance to study the combustion of butanol in engines.In this paper,n-butanol fuel is studied by combining experimental and numerical simulation methods.Experiments were carried out on a four-cylinder turbocharged gasoline direct injection(GDI)engine.Four different proportions of n-butanol/gasoline blends were used in the tests.The volume fractions of n-butanol in the mixing fuels were 0,15%,30% and 50% respectively,which were expressed by Bu00,Bu15,Bu30 and Bu50,respectively.The engine speed was maintained at 2000r/min under low,medium and high load conditions.By changing the spark timing,the effects of different spark timing on the combustion process,fuel economy,emissions and knock of the engine using different gasoline/n-butanol blended fuels are studied.The test results show that the peaks pressure and temperature of gas in the cylinder increase and the combustion duration shortens with spark timing advanced.At low load conditions,the brake thermal efficiency(BTE)of Bu30 and Bu50 increases while firstly increases and then decreases for Bu00 and Bu15 with retarding spark timing.However,the BTE decreases with spark timing delayed under medium and high load.Meanwhile,the CO emissions don't change too much,but the NOx and HC emissions decrease when spark timing is retarded.And the knock tendency of the engine decreases with retarding spark timing.On the other hand,increasing the proportion of n-butanol in the blended fuels decreases the NOx emissions but increases the HC and CO emissions.Additionally,the brake thermal efficiency of the engine can be improved,bu tknock tendency of engine also increases with n-butanol content increased in the blended fuels.Converge,a three-dimensional CFD software,was used to simulate the combustion process of the engine under medium load conditions.The thermal efficiency of Bu30 fuel combustion in the GDI engine was simulated and studied.The simulation results show that when the GDI engine compression ratio is increased from11 to 13,the indicated thermal efficiency of GDI engine increases by 4.5%,and the emission of NOx increases by 11.3%,and the knock tendency increases sharply.In order to reduce the knock tendency,the scheme of intake valve delayed closure is adopted.The results show that the indicated thermal efficiency of GDI engine decreases by 1.7%,while the emission of NOx decreases by 27%,and the knock tendency of engine decreases significantly.These studies above provide a reference for improving fuel economy of gasoline engine.