Research On The Control Methods Of Fuel Injection Quantity In High Pressure Common Rail System Of Diesel Engine

As for conventional energy sources of intensified and environment problems arebecoming apparent increasingly, all the people of the world are making our effort in energysaving and emission reduction. The internal combustion engine industry which is a biggreenhouse gas emitter is also in ahead steadily, towards low pollution, low fuelconsumption and high power output. In twentieth century a key technology of internalcombustion engine of the high pressure common rail fuel injection system (hereinafterreferred to as common rail system), with its remarkable superiority become the focus ofhot research point. Its main characteristic is the fuel injection time, pressure, quantity andrate can be controlled flexibly; It can realize a cycle of many injections; And it also canprovide stability of inject fuel pressure and improve fuel spraying and burning effect.Internal combustion engine with the common rail system can be closed to be the ideal fuelinjection law. Compare to the conventional injection system, it would be lower fuelconsumption and less waste emission and better power of engine.Firstly, this paper investigate the high pressure common rail system which is used formarine diesel engine and then analyze it physical structure seriously. High pressurecommon rail diesel engine is established the mathematical model of the system withMATLAB/Simulink. In order to improve the precision of the model compute, on thecomplexities of the high pressure common rail system made the following simplified: oilpumps supply stable oil; high pressure pumps don’t consider to tank return pipe parts; thehigh-pressure tube from high pressure pump to pipe and from common rail pipe to eachinjector oil filled simplify the model. Modeling for high pressure pump, tube, injectorboundary problem would be consider, various modules got the fuel continuous equation.With the Newton’s second law we get the force equation and motion equation. And then therelated parameters are setted for simulation, such as diesel engine speed, oil injection pulsewidth, oil pump parameters and common rail pressure. The simulation result tell us that themain physical parameters affecting the high pressure common rail system injectionquantity and rail pressure stability is the injector structure and common rail pipe pressurevolume respectively. And at the same time the diesel engine the accuracy of model must beensured that, lay the foundation for the next step of control injection quantity.According to the mathematical model simulation results of high pressure common raildiesel engine system, the whole of the high pressure common rail system control was analyzed and put forward different start and after start control strategy. Compensationmodule of injection quantity and rail pressure was added at Matlab/Simulink, and then PIDand fuzzy PID control models were written. Simulation shows that less fuzzy PID controlthan the traditional PID control injection quantity error, but is not allowed within the scopeof the error. So the genetic algorithm of fuzzy PID control parameters was used for furtheroptimization, the optimized model simulated in Simulink, a better control effect wasappeared.RTW of Matlab can convert control model code to C code that can import toECU(electronic control unit)of the common rail system and to try the hardware in the loopexperiment at the fuel pump test bench of high pressure common rail system. Theexperimental result shows that: at steady state rail pressure smoothly, practical fuelpressure follow the gender is good, small overshoot, injection quantity error maintain inthe range of allowable.