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NOx和CO2的减排要求是促进未来内燃机发展的主要因素。NOx排放可通过使用Miller循环冷却燃烧过程来有效地降低。但是高度Miller循环(进气门提前关闭)需要高增压压力。对此,有效的措施之一就是采用二级增压系统,可使增压压力达到10bar。采用二级增压还可提高发动机效率以及降低CO2排放。发动机效率的提高是采用高效二级增压系统以及通过Miller循环使发动机压缩和膨胀冲程之间实现更佳的比例划分的结果。因此,Miller循环与二级增压系统相结合能使NOx和CO2排放都得到有效降低。为查明进气门关闭(IVC)提前与二级增压系统相结合所蕴含的潜力,采用一维模拟软件进行了研究。为寻求各种负荷下的最佳IVC,还利用可变的IVC系统进行了研究。在Wartsila20型柴油机上进行了二级增压系统样机、极端提前的Miller定时以及短的扫气期的试验。将这些试验结果与模拟结果以及与前期试验(一级增压,压比最高达6.2bar,中度Miller定时)的结果进行了对比。本文还介绍了样机的结构以及目前的发动机为适应增压度的提高以及为增设辅助设施而需要作出的修改。模拟结果以及作出的假定通过试验得到验证。以下几点是在Wartsila20型机上通过二级增压技术结合IVC提前技术所得到的结果:①极端提前的Miller定时使NOx排放减少达50%;②燃油消耗率的改进潜力得到证实;③由于高空/燃比使高负荷区热负荷得到改善,但由于进气流量受到限制,使部分负荷性能较差;④负荷承受能力及烟排放性能变差,但可采取可变的进气门关闭(VIC)系统加以解决。
NOx and CO2 emission reduction requirements is to promote the development of the main engine of the future. NOx emissions can be effectively reduced by using the Miller cycle to cool the combustion process. However, a high Miller cycle (intake valve closed early) requires high boost pressure. In this regard, one of the effective measures is to use a two-stage booster system, the supercharger pressure can reach 10bar. Secondary boosting also increases engine efficiency and reduces CO2 emissions. Increased engine efficiency is the result of a highly efficient secondary boosting system and a better scaling of engine compression and expansion strokes through Miller cycles. As a result, the combination of the Miller cycle and the secondary booster system effectively reduces NOx and CO2 emissions. One-dimensional simulation software was used to investigate the potential of early intake valve closing (IVC) integration with a two-stage booster system. In order to find the best IVC under various loads, a variable IVC system was also used for the study. A secondary booster system prototype, an extremely advanced Miller timing, and a short scavenging period were tested on the Wartsila20 diesel engine. The results of these tests are compared with the results of the simulation and from the results of the previous experiments (first stage pressurization, pressure ratio up to 6.2 bar, medium Miller time). This article also describes the prototype structure and the current engine to adapt to increase the degree of pressurization and to add additional facilities needed to make changes. The simulation results and the assumptions made are validated experimentally. The following are the results of the two-stage booster combined with IVC advancement on the Wartsila 20: ① Extremely advanced Miller timing reduces NOx emissions by up to 50%; ② Improved potential for fuel consumption is demonstrated; ③ As a result of altitude / Fuel ratio to improve the heat load in high load zone, but due to the intake air flow rate is limited, so that part of the load performance is poor; ④ load bearing capacity and smoke emission performance worse, but can take a variable intake valve closing (VIC) System to be solved.