| Over the past decades, global warming trend is becoming increasingly serious. To address this situation, many regulations, which target on decreasing green house gases emission, especially carbon dioxide (CO2), have been enacted. Thus, cutting CO2 emission has become one of the central schemes in IC engine research field. Meanwhile, since fossil fuel supply is close to depleted, automotive engines are facing more stringent requirement on lowering fuel consumption. On the other hand, there has been tremendous movement toward the further control of automotive engines' harmful emissions over the past years. Therefore, automotive engines are confronted with great challenges. To overcome these challenges, IC engine engineering field is endeavoring on developing ultra clean and energy saving automotive engines. The only way to decrease CO2 and fuel consumption is improving fuel conversion efficiency. Due to the limitation of knock, conventional gasoline engines generally have low compression ratio, which directly results in low thermal efficiency and low fuel economy. Thus, people pay more attention to Direct Injection diesel engines, which have much better fuel economy than conventional gasoline engines. However, the characteristics of conventional DI diesel engine combustion determine the compromise between fuel conversion efficiency improvement and harmful emission control, as well as the tradeoff between NOx and PM emissions control. To solve this problem, the conventional DI diesel engine combustion must be renovated. As a new kind of combustion, diesel Homogeneous Charge Compression Ignition (HCCI) combustion can decrease NOx and PM emission simultaneously and maintain high fuel conversion efficiency close to DI diesel engine's level. With these two advantages, diesel HCCI combustion is becoming one of the most promising technologies in IC engine field. However, there are a number of obstacles that must be overcome before the potential benefits of diesel HCCI combustion can be fully realized in practice. These obstacles can be concluded into three challenges: premixture preparation, ignition control and combustion rate control. This dissertation focuses on diesel premixture preparation, the kernel of diesel HCCI combustion, also on the effective ignition control and combustion rate control strategies.The research on diesel HCCI combustion in this dissertation is based on Diesel Hot Premixed Combustion (DHPC) concept and the application of Conical Spray, which were initiated by Dalian University of Technology at early 1980s. The dissertation developed a new kind of conical spray, which keeps the advantages of the former two generations conical spray, and acts with flexible penetration in design. The spray and combustion characteristics of the new spray system were studied. In addition, the essential features of the impingement components and structure of combustion chamber were investigated. The dissertation designed different kinds of impingement structure and analyzed spray process by three-dimensional CFD package-AVL FIRE 8.2. Different combustion chamber shapes were designed and analyzed to optimize the combination of impingement spray and combustion chamber. With the combination of optimized combustion chamber and impingement spray system, diesel HCCI combustion was simulated. In the calculation, the effects of combustion chamber shape, start of fuel injection timing, intake temperature and EGR on combustion were analyzed.For the purpose of optimization of spray system and combustion chamber for dieselHCCI combustion, the following research work has been performed:· The combination of cone-shape impingement orientation sleeve and reentrant combustion chamber was adopted and the premixture formation was analyzed.· Early injection premixture preparation diesel HCCI combustion was simulated.· Advantageous impingement along with harmful impingement in premixture preparation were compared and analyzed.The results of research work in the dissertation indicate conclusions as follows:· By means of impin...
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