Study On Control Strategy Of High-pressure Common Rail Vehicular Diesel Engine Of SUV On Traction

Using diesel fuel has been a trend of modern automobile engine, but there are some inherent disadvantages in diesel engine. As general energy crisis become more and more serious and increasingly rigorous emission legislation, it is necessary for diesel to be developed with lower pollution, lower fuel consumption and high power per weigh. As a high flexible fuel injection system,the high pressure common rail (CR) injection system has become a trend of the diesel engines technology for its remarkable advantages. The diesel using ECU can detect its working parameters at any moment and provides optimal injection timings, fuel injection quantity and injection pressure through calculation of running program. Thus, it improves fuel combustion in diesel cylinder and keeps the good performance of power, economic and exhaust of diesel. But no matter how good the injection system also need outstanding control strategy to control can give full play to their performance, so as to achieve the purpose of optimizing engine.This paper from the system and operating principle, the basic control theory and control strategies, research and analysis the high pressure common rail injection system deeply. From the perspective of a vehicle using the method based on the traction control to the control of oil circulation. When the vehicle operating conditions determines, the resistance is determined. Vehicle traction and resistance is the same, traction comes entirely from the output torque of the engine. So the oil supply is determined by the instruction torque from the power and energy translation model. When the vehicle works on the high speed or high load situation, There may be too much heat load, torque exceeding limit, supercharger overload and engine speed over speed limit such phenomena which will cause serious damage to the engine. So in this situation, the oil supply could not be determined only by the vehicle traction and it is necessary to limit the oil supply to protect the engine.Electronic Control system based on control methods is introduced and the different control methods to the different parameters are also determined. On the basis of the electronic control theory, the stable control strategy of injection quantity, injection timing and rail pressure have been designed after designing of system's control project. The injection quantity and the injection timing are controlled on the basis of the MAP, and the rail pressure is mainly controlled by using PID of closed loop. From the actual situations, engine operation conditions are classified to starting, idle, part load, full load and restricting speed conditions by whether there is traction in the conditions or not. Of the conditions there is not traction in the starting and idle condition, the oil supply of the starting is determined by the engine speed and cooling water temperature and the oil supply of the idle only by cooling water temperature. The oil supply of the full load and part load is determined by the traction needed in the conditions then rail pressure and injection timing are determined to control the engine.Construction of the high pressure common rail diesel engine test system is established and experiments on the GW 2.5TC engine of the Great Wall internal combustion engine manufacturing company matching BOSCH high pressure common rail injection system and INCA calibration software produced by ETAS company were done. Mainly, the instruction torque MAP determined by accelerator pedal and engine speed, the oil supply MAP determined by engine speed and instruction torque, injection timing MAP and rail pressure MAP are calibrated.Improving injection pressure can increase injection energy, accelerates the diffusing of the fuel mist in the air in the combustion chamber and makes the mixture of the air and oil more quickly and uniform. Because of the good formation of the mixed gas, the combustion process is improved, and it is useful to improve the thermal efficiency and reduce PM emissions. However, the increased formation of the mixed gas in ignition delay period promotes the pre-combustion and the peak heat release rate increases, which increase NOx emissions and noise. With the increase of the injection advance angel, more combustible gas mixed in the ignition delay period and more mixed gas participate the fast combustion, causing increased rate pressure, high-temperature combustion and accelerating combustion of the latter part of the injected fuel, so as to enhance the power of the diesel engine, reduce fuel consumption and emissions of HC and CO. However, the high combustion temperature increases the hot load to the engine and causes more NOx emission and more noise.Therefore, we must consider all integrated control parameters on the engine output torque, fuel consumption and emission characteristics. In order to achieve the demand of the engine at low speed with high torque output, the oil supply is increased and the rail pressure is enhanced to improve the effect of oil and gas atomization. Also, adjust the injection timing to control the engine emissions. On the high speed conditions, in the assurance of power under the basic premise, optimizing injection timing and rail-pressure control ensures that the emission of the engine comply with the requirements of emissions regulations and the oil consumption decreases slightly. Experiments proof that, after the optimization of the injection parameters, the low speed torque of the full load increases with smoke in the allowable range, and on the high speed conditions with the same good power, the oil consumption and the emission of HC and CO are improved smoothly.