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首页> 外文期刊>Applied thermal engineering: Design, processes, equipment, economics >Effects of application of variable valve timing on the exhaust gas temperature improvement in a low-loaded diesel engine
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Effects of application of variable valve timing on the exhaust gas temperature improvement in a low-loaded diesel engine

机译：可变气门正时在低负载柴油发动机排气温度改善中的应用

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摘要

Engine manufacturers generally use aftertreatment systems to meet the strict emission criteria on automotive diesel engines. However, those systems operate inefficiently particularly at low-loaded cases of diesel engines since exhaust gas temperatures at aftertreatment inlet remain below 250 degrees C. For those cases, variable valve timing (VVT) method can be applied to elevate exhaust temperatures and improve aftertreatment emission conversion efficiency. Therefore, in this study, intake valve closing (IVC) timing is advanced and retarded sufficiently from the base condition on a low-loaded diesel engine to increase aftertreatment inlet exhaust temperature above 250 degrees C. A specially designed computer program, Lotus Engine Simulation (LES), is utilized to model the diesel engine. Experimental data of a similar study is used for the validation of the simulation. Engine loading (taken as brake mean effective pressure (BMEP)) is kept constant at 2.5 bar by adjusting the fuel injection rate. The results show that there is a considerable exhaust temperature rise (up to 65 degrees C) at aftertreatment inlet with the method and it is adequate for effective aftertreatment performance (Texhaust > 250 degrees C). It is also seen that the increase on exhaust temperature is due to the sudden reduction on volumetric efficiency (from 94% to 65%). Therefore, there is lower air induction into the cylinders and hence lower pumping losses which result in fuel-efficiency in the system. However, air flow reduction also causes a sharp decrease on the exhaust flow rate which affects the heat capacity of exhaust gases negatively in the system. (C) 2017 Elsevier Ltd. All rights reserved.
机译：发动机制造商通常使用后处理系统来满足汽车柴油发动机的严格排放标准。然而，这些系统效率低下，特别是在柴油发动机的低负载情况下，由于后处理入口处的废气温度保持在250摄氏度以下。对于那些情况，可变气门正时（VVT）方法可以应用于提升排气温度并改善后处理排放转换效率。因此，在本研究中，进气门关闭（IVC）定时推进并延迟，从基于低负载的柴油发动机上的基础条件充分延迟，以提高250摄氏度高于250℃的后处理入口排气温度。莲花发动机仿真（ LES）用于模拟柴油发动机。类似研究的实验数据用于验证模拟。发动机负载（作为制动平均有效压力（BMEP））通过调节燃料喷射率，在2.5巴保持恒定。结果表明，随着该方法，在后处理入口处有相当大的排气升温（最多65℃），适用于有效的后处理性能（Texhaust> 250℃）。还可以看出，排气温度的增加是由于体积效率的突然降低（从94％到65％）。因此，在汽缸中较低的空气感应，因此降低泵送损耗，从而导致系统中的燃料效率。然而，空气流量减少也导致排气流量的急剧下降，这在系统中影响废气的热量。 （c）2017 Elsevier Ltd.保留所有权利。

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