Investigation On Cycle Fuel Injection Accuracy Of Electronic Control Fuel Injection System

The diesel engine is highly sensitive to the quantity and quality of cycle fuel feeding for fuel system, which directly affects the power and economic performance of the diesel engine. The mixture forming and combustion process of diesel engine is short. Fuel injection system must provide accurate the amount of fuel oil, that can meet the demands of the operation of diesel engine. The electronic control fuel injection system is the core of the diesel engine, and its precise electronic control technology lay the precondition for the circulation of oil supply.Firstly, from the theoretical aspect, the influence of cycle fuel supply on the combustion performance of diesel engine was analyzed. Through the analysis such as combustion process and fuel injection characteristic, presented the requirements of the electronic control fuel injection system. Through the analysis of details and theoretical goal of electronically controlled fuel injection system instead of traditional fuel injection system, studied correlative factors which affected the accuracy of the cycle fuel supply.This paper developed a set of control system, as well as built the electronic fuel injection system test platform. The control system was designed based on classical PID algorithm and incremental PID algorithm which can effectively control oil temperature and pressure in the common rail system. On the control interface, users can independently set parameters(such as pulse width and frequency of the driving signal and so on). The test shows that the common rail pressure adjustment range is 0~150MPa, the maximum error is about ±3Mpa; the pump speed can be set in the range of 0~3800rpm, the maximum speed error is about ±2rpm; the injection pulse width range is 0~20ms.Based on the experimental platform, this paper carried out the relevant factors of the experimental study. The factors which affected the injection and return quantity, including rail pressure, pulse width, speed, pump head pressure, tubing length, orifice number, oil temperature and tubing diameter, were studied by experimental optimization. Through the analysis of variance, under 99% confidence level, injection pulse width, common rail pressure and their interaction on fuel injection quantity were highly remarkable; under 95% confidence level, orifice number had a significant influence; under the 90% confidence level, tubing length had a certain effect on the fuel injection quantity. The remaining factors had a little effect, and the fuel injection pulse width was significantly more than the pressure of the injection. Under the 99% confidence level, the influence of rail pressure and pulse width on the oil return was highly significant. Under the 90% confidence level, the interaction between rail pressure and pulse width were significantly correlated with the amount of oil return.Rail pressure, pulse width, tubing length and orifice number were the key factors of cycle fuel injection accuracy. Using quadratic general rotary unitized design, established a math model between the fuel injection quantity and key factors. The result showed that the regression equation was significant under the confidence of 99%.This investigation has great reference value for the development of high pressure common rail fuel injection test device and the matching of diesel engine with high pressure injection system test. And it also provides important reference for perfecting the design of test-bed and improving the accuracy and stability of the test parameters.