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首页> 外文会议>EAEC European automotive congress >THE INFLUENCE OF THE INTERNAL EXHAUST GAS RECIRCULATION ON THE COMBUSTION CHARACTERISTICS IN A GASOLINE HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE
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THE INFLUENCE OF THE INTERNAL EXHAUST GAS RECIRCULATION ON THE COMBUSTION CHARACTERISTICS IN A GASOLINE HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE

机译：内部废气再循环对汽油均匀电荷压缩点火发动机燃烧特性的影响

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The homogeneous charge compression ignition (HCCI) engines combines the homogeneous charge from the gasoline engines with the compression ignition from the diesel engines. Unlike the conventional engines, there is not a direct mechanism to initiate the combustion like the spark from the gasoline engines or the fuel injection from the diesel engines. For this reason different strategies where developed for changing the mixture temperature or the mixture chemical properties. The usages of the variable compression ratio, variable valve timing or exhaust gas recirculation are common methods used to modify the auto ignition delay. The internal exhaust gas recirculation (EGR) is used to control the temperature of the mixture which has a big influence on the start of the combustion in the HCCI engines. The EGR is also a method used to reduce the nitrous oxide (NOx) emissions and has different effects on the combustion and on the emissions behavior of the engine. This paper presents the influence of the internal EGR on the combustion characteristics in a gasoline HCCI engine. The tests were made on a gasoline HCCI single cylinder engine. The burned gases are trapped inside the cylinder by closing the exhaust valve before the piston reaches the top dead center. The amount of trapped gases is controlled varying the exhaust valve timings using cam phasers. The results are showing the effects of the internal EGR on the mixture formation and on the combustion. At the beginning, the trapped burned gases due to their higher temperature are heating the fresh mixture of air and fuel. This effect is used to control the auto ignition timing. During compression and combustion, the residual gases have to be heated with the rest of the charge from the cylinder. The residual gases have a higher heating capacity than the fresh mixture. This is lowering the temperatures at the end of compression and during the combustion when very high internal EGR rates are used. The burned gases replace a quantity of air, so the oxygen (O2) concentration is lower. This is also lowering the temperature during the combustion. The combustion analysis was made using the pressure traces obtained using different internal EGR rates. The mean temperature and the heat release rate were calculated and compared. The use of the internal EGR has a big influence on the temperature traces. When the internal EGR rate is higher, the temperatures during the beginning of the compression stroke are higher and the combustion is starting earlier. After the ignition, the maximum temperatures obtained are higher if the internal EGR rate is increasing, until a point when the internal EGR rate is too high, the mixture is too diluted and the maximum temperatures are decreasing. The NOx emissions depend on the temperature evolution during the combustion, so the very high internal EGR rates can be used to lower the NOx emissions.
机译：均质充量压缩点火（HCCI）发动机将来自与来自柴油发动机的压缩点火的汽油发动机的均质充量。不同于传统的发动机，还没有一个直接的机制来启动像从汽油发动机的火花或从柴油发动机的喷油燃烧。出于这个原因不同的策略，其中用于改变所述混合物的温度或将混合物化学性质的发展。可变压缩比，可变气门正时或排气再循环的用途是用于修改自动点火延迟常用方法。内部排气再循环（EGR）是用来控制这对在HCCI发动机中的燃烧开始有很大的影响该混合物的温度。该EGR也是用于减少氮氧化物（NOx）的排放量的方法，并具有对燃烧和对发动机的排放行为不同的影响。本文介绍了内部EGR对汽油HCCI发动机燃烧特性的影响。测试在汽油HCCI单缸发动机制造。燃烧后的气体通过在活塞到达上止点之前关闭所述排气门收集在气缸内。截留的气体的量被控制改变使用凸轮相位器的排气阀定时。其结果示出在混合物上形成与在燃烧内部EGR的影响。在开始时，由于它们的较高温度下截留燃烧后气体被加热的空气和燃料的新鲜混合。这种效应被用来控制自动点火正时。在压缩和燃烧，剩余气体具有与从汽缸的电荷的其余部分被加热。残余气体具有比新鲜混合物更高的加热能力。这是在压缩结束，并且当使用非常高的内部EGR率的燃烧过程中降低温度。燃烧后的气体代替空气的量，所以氧气（O2）浓度较低。这是在燃烧过程中也降低温度。燃烧分析使用利用不同的内部EGR率获得的压力迹线制成。平均温度和热释放率进行了计算和比较。使用内部EGR对温度的痕迹有很大的影响。当内部EGR率越高，压缩冲程开始时的温度较高并且燃烧较早开始。点火后，所获得的最大温度较高，如果内部EGR率在不断增加，直到一个点，当内部EGR率太高，将混合物太稀释，将最高温度降低。的NOx排放的燃烧过程中依赖于温度的变化，所以非常高的内部EGR率可用于降低NOx排放。

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