Experimental Investigation On Reducing Smoke Emissions Of Turbocharged Diesel Engine With An Electric Supercharger At Accleration Process

Under the pressures of environmental pollution and energy crisis, the energy conservation and emissions reduction technology of diesel engine has been widely discussed. Using the exhaust-gas turbo technology to improve the intake air's density not only can improve the liter power of diesel engine, reduce fuel consumption, but also help exhaust smoke have a sharp decrease in steady state.However, the turbocharger has certain inertia and driven by exhausted gas, it responses slower compared with naturally aspirated diesel engine. Electric supercharger has great potential to improve the responsiveness of the turbocharger, reduce smoke emissions, improve the smoke and other aspects of diesel engine at accelerate process.Based on a small four-cylinder turbocharged diesel engine, the paper had an experimental investigation on reducing smoke emission in accelerated loading condition. First the related components of electric supercharger contrast selection and matching with diesel engine and had been completed, the main test device had been compared to make a selection and an engine test bench had been set up at the same time. Then, had an external characteristic test and a calibration to ensure that after calibration, the external characteristic data is matched with the external characteristic data from the manufacturers.The trend of parameters and combustions at different kinds of working conditions were analyzed from the data of external characteristics. Meanwhile, had the test of the load characteristic at 2000r/min. After that, had a simulation about the acceleration process of the engine in different control modes to select the optimal control model in Simulink. Finally, accelerated loading test on the engine test bench had been completed.The experiment shows that (1)Based on the condition of the external characteristic of the engine, the maximum explosion pressure appears at 3000r/min and 10?15° after top dead center. Further analysis found that there are roughly two peaks and troughs in one working cycle in the curve of the rate of pressure rise. By analyzing the gas exchange process, we found that,except for 1000r/min, the exhaust pressure is greater than the intake pressure under all rotating speed.(2)By analyzing the acceleration conditions and loading conditions under three control mode in Simulink,which is constant dynamometer torque/constant engine speed control M/n, constant dynamometer speed/constant engine torque control n/M and constant torque/constant throttle opening control M/P, the n/M control mode is adopted, which is more close to the actual condition of a real car. (3) Using electric supercharger and changing the ventilation strategy.when the engine accelerate and load from 1400r/min,50N·m to 2500r/min,100N·m in 10 seconds,the maximum smoke emission of the original engine decrease from 0.602 m-1 to 0.420 m-1,which is 30.2%.Without initial air supply, higher the final frequency of the electric supercharger, better emission performance of the engine is. Besides, the smoke emission using linear response curve is lower than that using S type response curve. With certain amount of initial air supply, the ideal amount of air ventilation for the electric supercharger should be small at first and larger then. The electric supercharger is proved to have significant improvement to smoke emission when the acceleration time is relevantly short and the reduction of maximum smoke emission in small load is greater than that in heavy load.