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开发了一种4气门直喷柴油机用的可变涡流进气道系统。该系统由两个相互独立的进气道组成,一个是螺旋气道,用于产生极高的涡流比;另一个是切向气道,用于产生低涡流比。切向气道装有涡流控制阀,通过改变流量控制涡流比。为了考察进气道系统的性能,在三维计算的同时,进行了稳态流量试验。在试验中发现,叶轮式流量传感器不适合用来评定高涡流气道的特性,而必须使用脉冲涡流仪。为了在连续数值计算中使用,最近开发了一种自动网格生成器,它能有效地生成螺旋气道、切向气道和两者各种组合的计算网格。首先,为了选择能有效产生高涡流的气道形状,进行了螺旋气道几何形状的参数研究。结果表明,产生高涡流比的关键因素是适当控制通过气门应的进气流方向。然后测试和计算两个气道组合起来时的涡流比和流量系数。结果显示,两个气道总的性能可用单个气道的性能来计算。本研究最后一个步骤,在宽广工况范围内考察组合进气道型式和气门布置的影响。结果得出涡流比可在很大范围内变化的实用气道设计。在此基础上研制出涡流比能在宽达3.5～10的大范围内进行控制的变涡流进气系统。
A variable vortex air intake system for 4-valve direct injection diesel engine was developed. The system consists of two separate inlets, one is a spiral airway, which produces a very high turbulence ratio and the other is a tangential airway that produces a low turbulence ratio. The tangential airway is fitted with a vortex control valve to control the vortex ratio by changing the flow rate. In order to investigate the performance of the inlet system, a steady-state flow test was carried out at the same time as the three-dimensional calculation. It has been found in experiments that impeller flow sensors are not suitable for assessing the characteristics of high vortex airways and that pulsed eddies must be used. For use in continuous numerical calculations, an automatic grid generator has recently been developed which efficiently generates a computational grid of spiral airways, tangential airways, and various combinations of both. First, in order to select the airway shape that can effectively generate high vortices, parametric studies of the helical airway geometry were performed. The results show that the key factor in generating a high swirl ratio is the proper control of the direction of intake flow through the valve. Then test and calculate the turbulence ratio and flow coefficient when the two airways are combined. The results show that the overall performance of both airways can be calculated using the performance of a single airway. The final step in this study examines the effects of the combined inlet type and valve arrangement over a wide range of operating conditions. The result is a practical airway design with a wide range of swirl ratios. On the basis of this, a variable vortex air intake system is developed that can control the vortex ratio within a wide range of 3.5 ~ 10.