Experimental Study On Work Mode Switch Of GDI Engine

According to International Energy Agency data, only 1.1 trillion barrels of crude oil could be economically exploited. And they could be exploited only more than 30 years. Moreover, since carbon dioxide (CO2) concentrations increased dramatically from burning fuels, it could cause higher temperatures. Therefore, the earth today would face two major challenges. The first is to find reliable and affordable energy sources. And the other is to use energy with low-carbon, efficiently and environmental friendly.Automobiles consume more than half of China's oil. While the automobile production increases, more crude oil will be needed. China urgently needs to develop high efficiency, low power, low emission engine. Gasoline direct injection engine is a good choice which has high efficiency and the potential for ultra-low emissions. At the same time, gasoline direct injection engine is one of the important technologies of internal combustion engine.There are three work modes in gasoline direct injection engine. When the load is small, engine will work at stratified combustion mode. When the throttle opens wider, and the smaller throttle will loss. And the air-fuel ratio is between 24 and 44. It is high heat efficiency. At the part load, engine will work at homogeneous lean mixture combustion mode. When the part of throttle opens up, the air-fuel ratio is between 15 and 24. It is even higher heat efficiency. At the big and full load, engine will work at homogeneous or power mixture. At this time engine must be ensured power output. In this research paper, it shows the engine in the homogeneous lean mixture switch to a homogeneous mixture, and from homogeneous mixture to homogeneous lean mixture.In this paper, following work had been done:1. Analyzed the electronic control system components of gasoline direct injection engine was, and summarized the characteristics of sensors and actuators.2. Designed the engine control hardware system which used microcontroller named MC9S12XDP512 as control chip. Specific designed temperature acquisition circuit, pressure acquisition circuit, speed acquisition circuit, camshaft position signal acquisition circuit and the electronic throttle position acquisition circuit; also designed the drive circuit of each actuator.3. Designed the fuel injector driver boost circuit, and achieved PEAK-HOLD current drive the injector.4. PortedμC/OS-Ⅱreal-time operating system to MC9S12XDP512 microcontroller, layered design of control software; and task management used for fuel injection calculation, ignition computation, analog capture, electronic throttle control, high pressure pump solenoid valve control and operating mode management, facilitate change the control functions.5. Building a test bench to research work conversion from stoichiometric homogeneous mixture (lambda=1.0) to lean homogeneous mixture (lambda=1.4) when brake mean effective pressure (BMEP) is 0.15MPa (42.9Nm) at speed of 2500 r/min. Adjust the fuel injection pulse width and throttle opening to realize lean burn (lambda=1.4) of torque being 40N.m at speed of 2500 r/min, and adjust injection timing to find the best injection timing which is 350 crank angle degree, and then adjust the ignition advance angle to fine the best ignition advance angle which is 13 crank angle degree. At last, when the fuel injection pulse width is 8.3ms, and the throttle opening is 11°, and the injection advance angle is 350°(CA) and the ignition advance angle is 13°(CA) obtain lean burn of torque being 42.5N.m at speed of 2500 r/min. Using the same method find the fuel injection pulse width, the best injection timing, the best ignition advance angle and throttle opening to realize lean burnλ=1.0 toλ=1.3, torque being around 42.5Nm at speed 2500 r/min. After the above parameters obtained using two methods to study the work mode conversion, one is fixed injection timing and ignition timing; adjust the fuel injection pulse width and the throttle opening to achieve mode conversion, test results show that this method can't complete the work mode conversion well. The other method is using best injection timing and ignition timing ofλ=1.0 toλ=1.4, and then adjust the fuel injection pulse width and throttle opening to complete the work mode switch. In this paper, many methods were used to adjust the fuel injection pulse width and throttle opening. The first one is reducing the fuel injection pulse width first, and then increases the throttle opening. The second one is increasing the throttle opening first, and then reduces the fuel injection pulse width. The third one is reducing the fuel injection pulse width first, and then increases the throttle opening, and reduces the fuel injection pulse width again. The forth one is reducing the fuel injection pulse width first, and then increases the throttle opening and reduces the fuel injection pulse width at the same time. The last one is increasing the throttle opening and reducing the fuel injection pulse width at the same time. Finally, the work mode conversion was completed by the optimal parameters linear interpolation, reducing the fuel injection pulse width and increasing the throttle opening at the same time complete.