The Investigation On Combustion Process Of 2-Valve Electronic Controlling Diesel Engine For Low Exhaust Emission Regulations

With the increasingly stringent exhaust emission standards of the diesel engine aswell as the development of the diesel engine technology, it is very imperative forChina to design a diesel engine that can satisfy the requirements of Euro-3 emissionstandards. In this thesis, a two-valve diesel engine with ECD-U2 common rail systemfor Euro-3 has been developed based on the prototype of inter-cooler turbochargeddiesel engine D6114. Because the engine smoke deteriorates when increasing thetorque of the electronic-controlled diesel engine, a pre-mixed combustion techniqueusing pilot injection is introduced to reduce the engine smoke at low speed and fullload. The study about the influence of the sulfur in diesel fuel on the particulateemission from the diesel engine without catalyst has also been carried out. The maincontributions of this thesis are summarized as follows:1. An electronic-controlled high-pressure common rail system has beendeveloped with Wuxi Weifu Company. Its working principle andperformance parameters are studied in detail. The major differencesbetween this system and ECD-U2 common rail system made by NIPPONDENSO are analyzed.2. The electronic-controlled system was calibrated on the EFS test rig. Theidentity of injectors and injecting rate are investigated and the difference ofinjectors can be compensated by software proposed in this work.3. By designing a new combustion system and investigating on the controlstrategy of the common rail system, the two-valve diesel engine can meetthe Euro-3 emission regulation with the results of NOX = 4.87g/kW.h,CO=1.097g/kW.h, HC=0.212g/kW.h, PM=0.0857g/kW.h, SOMKE =0.72m-1。4. In the low speed range, improving the torque of the electronic-controlleddiesel engine results in increased smoke. After analyzing the reason ofsmoke from engine and its affecting factors, traditional techniques, such asincreasing the injection pressure and changing the injection time, areemployed to decrease the smoke emission. However, these methods have noobvious effects on smoke reduction. As an alternative way, the pre-mixedcombustion by pilot injection is adopted to reduce the smoke from engine atlow speed and full load. The test results show that the pre-mixedcombustion is a very effective method to decrease the diesel engine smoke.5. In order to understand the principle of the diesel engine smoke emissionreduction by pilot injection, the pre-mixed combustion process is calculatedby FIRE, a commercial software which can be used for the multi-dimensionnumerical simulation of the engine. The combustion processes with andwithout pilot injection are calculated. The results prove that the pre-mixedcombustion has a significant negative effect on the formation of the smokein the engine cylinder.6. At the end of this work, the compositions of particulate from diesel engineare measured using soxhlet extraction and ion chromatography. The solubleorganic fractions (SOF) were separated by extraction and the sulfate wasmeasured by ion chromatography. The result shows that the particulateemission from D6114 electronic-controlled diesel engine cannot beimproved distinctly even if the diesel fuel with sulfur 273ppm instead of800ppm is used.