涡流室柴油机燃油与空气混合过程的三维数值计算和实验验证

通过改进ＫＩＶＡ－Ⅱ程序中的油滴破碎和喷雾碰壁两个子模型,对涡流室柴油机燃油与空气混合过程进行三维数值计算。获得了涡流室中典型截面的油滴运动轨迹和燃料蒸汽质量分数以及温度场的分布图。用激光莫尔偏折技术实测涡流室内的温度场,测试结果表明：三维数值计算与实测数据取得了定性上的一致。     

某柴油机进气道数值模拟及试验研究

采用基于AVL Fire软件的模拟分析方法和基于涡流动量计的试验方法,对某型柴油机进气道的性能进行研究,得到5个工况点下气道的流量系数和涡流比。结果表明:模拟分析可以得到准确的流量系数和平均流量系数、涡流比和平均涡流比。在气道的开发过程中,模拟分析可以替代气道试验。     

涡流室式柴油机非对称主燃烧室的试验研究

本文提出将新鲜空气较多地集中在涡流室柴油机的主燃烧室偏进气门一侧的容积里对燃烧有利的观点,根据此观点设计研制了非对称式主燃烧室,在S195柴油机上进行了试验验证,结果表明,改善了发动机的动力指标,降低了油耗率。     

涡流室式柴油机空气运动的3维数值模拟

通过对标准κ－ε模型作适当修正来模拟气体的湍流运动，建立了涡流室式柴油机的空气运动的３维数值计算模型，开发了大型微机化３维数值模拟程序。首次对吊钟型涡流室式柴油机的流场进行了３维计算，计算结果与ＬＤＶ实验结果具有良好的一致性。画出了涡流室纵截面，横截面和侧截面上的速度矢量图。     

4气门直喷柴油机进气道组合和位置对进气涡流的影响

在稳流气道试验台上,对4气门直喷柴油机采用螺旋进气道和切向进气道的不同组合和不同相互位置时,气道的流动特性进行了试验研究。为了上邻气道的进气气流在缸内干涉的程度及其对缸内涡流运动的影响,提出了流量系数损失率和角动量矩损失率的概念。研究结果表明：柴油机采用切向气道在后的气道组合时,涡流比的变化受后面螺旋气道方位的影响较小,相邻气道的进气气流干涉较小。     

数值模拟方法在柴油机进气道改进中的应用

以实际产品为研究对象 ,将三维数值模拟方法应用于柴油机螺旋进气道的改进设计中。根据模拟计算结果对气道流场结构进行了分析 ,找出了气道结构中不合理的部位 ,对此部位进行修改 ,再进行三维数值模拟。结果表明 :修改后的气道具有更合适的流场结构 ,从而具有更高的流量系数和更合适的涡流比。将原气道和修改后的气道分别进行气道稳流试验台试验 ,试验结果与计算结果吻合良好。     

Control of peak pressures of an HCCI engine under varying swirl and operating parameters

The major advantages of homogeneous charge compression ignition (HCCI) are high efficiency in combination with low NO _x -emissions. However, one of the major challenges with HCCI is the control of higher peak pressures which may damage the engine, limiting the HCCI engine life period. In this paper, an attempt is made to analyze computationally the effect of induction swirl in controlling the peak pressures of an HCCI engine under various operating parameters. A single cylinder 1.6 L reentrant piston bowl diesel engine is chosen. For computational analysis, the ECFM-3Z model of STAR–CD is considered because it is suitable for analyzing the combustion processes in SI and CI engines. As an HCCI engine is a hybrid version of SI and CI engines, the ECFM- 3Z model with necessary modifications is used to analyze the peak pressures inside the combustion chamber. The ECFM-3Z model for HCCI mode of combustion is validated with the existing literature to make sure that the results obtained are accurate. Numerical experiments are performed to study the effect of varying properties like speed of the engine, piston bowl geometry, exhaust gas recirculation (EGR) and equivalence ratio under different swirl ratios in controlling the peak pressures inside the combustion chamber. The results show that the swirl ratio has a considerable impact on controlling the peak pressures of HCCI engine. A reduction in peak pressures are observed with a swirl ratio of 4 because of reduced in cylinder temperatures. The combined effect of four operating parameters, i.e., the speed of the engine, piston bowl geometry, EGR, and equivalence ratio with swirl ratios suggest that lower intake temperatures, reentrant piston bowl, higher engine speeds and higher swirl ratios are favorable in controlling the peak pressures.     

Minimum superficial fluid velocity in a gas–solid swirled fluidized bed

A swirl flow is achieved in a bed of solids by passing air through multiple fluid inlets, which are tangentially located at the base of a flat-based circular column. The minimum superficial velocities needed to achieve swirling of the bed are measured experimentally under varied conditions. An empirical correlation for the minimum swirl velocity has been proposed. The results indicate that a stable swirling regime operation of the bed is possible. There exists an upper limit of static bed depth beyond which stable swirling of entire bed is not possible. The minimum swirl velocities are found to be 1.2–1.3 times the minimum fluidization velocities predicted for conventional fluidized beds.     

Flow development behind a swirl generator in a hot-water standard measuring facility for large volume rates

The flow development behind a swirl generator according to EN 14154 of a gravimetric cold- and hot-water standard measuring facility is shown at different positions by measurements carried out using Stereoscopic Particle Image Velocimetry (SPIV). Hereby, the effects of the swirl generator downstream are shown, and the prevailing flow condition is evaluated by means of characteristic values.SPIV is suited as a fast and accurate measurement procedure for the high-resolution determination – temporally and spatially – of 3C velocity profiles in piping.