Research On The Control And Performance Of Marine Natural Gas Engine

The increasingly stringent emission regulations have prompted major Marine engine manufacturers to develop Marine natural gas engine technology.Domestic research on Marine natural gas engine mainly focuses on the design,development and optimization of software and hardware,but the research on engine performance is still in the preliminary exploration stage.Therefore,the design and development of Marine natural gas engine control system and the experimental study of the influence of main control parameters on engine performance are of great academic and engineering value for improving engine performance and economy and reducing emissions.Based on the YuChai YC6K400LN-C30 natural gas engine,a multi-point gas injection system was installed on the original aircraft,and the Marine natural gas engine controller was redesigned and developed.The hardware design,basic software design,control strategy development and the coordination test of the software and hardware were completed.On this basis,the open-loop calibration experiments of single point and multi-point injection system were carried out.The MAP required by the control strategy was obtained according to the experimental results,and the steady-state performance of the engine under selected working conditions was studied experimentally.The experimental results show that the steady-state fluctuation of rotating speed is no more than 0.89%,and the steady-state fluctuation of excess air coefficient is no more than 1%,which meets the requirements of engine performance experimental research.When the engine is in low load and middle-low speed conditions,the economy is poor and the emission is high.Therefore,on the basis of open-loop calibration experiment and steady-state performance verification,this paper selects three operating points with low load and middle-low speed,using the control variable method to study the effects of ignition timing,injection timing and excess air coefficient on engine burn characteristics,economy and emission performance,and then provide a theoretical basis for optimal Marine natural gas engine control.At selected operating point,the results of single point injection system engine tests show that: with the ignition timing moving forward,the maximum combustion pressure increases,and the timing of combustion moves forward.The duration of combustion varies little,and specific gas consumption increases first and then decreases;CH4 and CO emissions showed a trend of gradual decrease,while NOx emissions gradually increased.With the increase of the excess air coefficient,the maximum combustion pressure in the cylinder decreases,the timing of combustion moves back,and the combustion duration is significantly extended.The specific gas consumption first decreases and then increases..CH4 and CO emissions show a trend of decreasing first and then increasing.Under the selected operating conditions,the performance test results of the multi-point injection system of the engine show that: with the change of ignition timing and excess air coefficient,the change trend of combustion characteristics,economy and emission performance is basically the same as that of the single-point injection system.As the injection timing increase,the maximum combustion pressure and the timing of combustion forward,the combustion duration present the change trend of decrease after extended first,the specific gas consumption reduced after increased first.CH4 and CO have a similar trend of change.As the injection timing moves back,its emissions gradually decrease,while NOx emissions are the opposite.