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首页> 外文会议>EAEC European automotive congress >A CFD STUDY ON THE EFFECTS OF THE VALVE LIFT ON THE INTAKE PROCESS
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A CFD STUDY ON THE EFFECTS OF THE VALVE LIFT ON THE INTAKE PROCESS

机译：CFD研究阀门升降机对进气过程的影响

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The reduction of fuel consumption is a fundamental aspect of the automotive industry. This comes from customers, as well as from legal demands. While diesel engine made enormous progress during the last period and features good fuel economy, the spark ignition engine still suffers from this point of view. Variable valve actuation (VVA) offers many opportunities to improve the spark ignition engine’s performances in areas like fuel economy, emissions and it seems it will become the next industry standard on gasoline engines. This paper presents a variable intake valve lift (ViVL) mechanism, used to enhance fuel economy. Two operational, in-line, 4 cylinders engines prototypes are working on the test benches: one is a side mounted camshaft and overhead valves (OHV) version (i.e. a pushrod engine), still being built in some countries and the other is an overhead camshaft (OHC) version. Experiments that proved also their ability for the unthrottled operation have been conducted on the engine test bench. Our previous experimental studies revealed an improvement of fuel economy at idle operation of about 20% in spite of an increased pumping work. This gain in fuel economy was mainly generated by an increased flow velocity of the fresh mixture into the cylinders, causing an improvement of fuel-air mixing process and, in the end, a better combustion. One idea drawn from these previous studies is that even though minimal pumping losses should be one goal to fulfil, this must not be done with impairing of other aspects such as mixing process, charge kinetic energy prior to spark. Thus, in order to have intimate details about the phenomenon happening during the intake stroke within our prototype ViVL engine, a CFD study on the airflow was launched using the numerical code FLUENT and choosing the k-ω turbulence model. The study was performed to simulate the airflow at an engine speed of 800 rpm, corresponding to the idle operation. Actually, for the case of still having the throttle plate, the purpose was to obtain results about air velocity, turbulence at the valve gap, for different openings of throttle plate and different valve lifts between 1 and 8.5 mm. In order to set the boundary conditions, data were taken from experiments performed in a steady-state flow within the ViVL engine fitted with in-cylinder and intake manifold pressure sensors.
机译：减少燃料消耗是汽车行业的基本方面。这是来自客户，以及法律要求。虽然柴油发动机在上一期间做出了巨大进步并具有良好的燃料经济性，但火花点火引擎仍然存在这一观点。可变阀驱动（VVA）提供了许多机会，可以改善燃料经济性，排放等领域的火花点火发动机的表现，似乎将成为汽油发动机的下一个行业标准。本文介绍了一种可变的进气门升力（VIVL）机构，用于增强燃油经济性。两种操作，在线，4个气缸发动机原型在测试台上工作：一个是侧面安装的凸轮轴和架空阀（OHV）版本（即推杆发动机），仍在一些国家建造，另一个国家仍然是一个开销凸轮轴（OHC）版本。在发动机试验台上进行了证明其对未努力操作能力的实验。我们以前的实验研究表明，尽管泵送工作增加，但仍然提高了怠速运行的燃料经济性约20％。这种燃料经济性的增益主要由新鲜混合物的流速增加，使燃料 - 空气混合过程增加，并且最终燃烧更好的燃烧。从这些前面的研究中汲取的一个想法是，即使最小的泵送损失应该是实现的一个目标，这一定不能损害其他方面，如混合过程，在火花之前充电动能。因此，为了具有关于在我们的原型VIVL发动机内的进气冲程期间发生的现象的亲密的细节，使用数值代码流畅并选择K-ω湍流模型，启动对气流的CFD研究。进行该研究以以800rpm的发动机速度模拟气流，对应于怠速操作。实际上，对于仍然具有节流板的情况，目的是获得关于空气速度，阀间隙处的湍流的结果，用于节流板的不同开口，不同的阀门升降机在1到8.5mm之间。为了设置边界条件，从VIVL发动机内的稳态流动的实验中取出数据，该实验在装有缸内的缸内和进气歧管压力传感器。

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