径流式涡轮排气扩压器流动性能模拟研究

本文研究了径流式涡轮排气扩压器特性对涡轮增压器与中速柴油机匹配性能的影响。在研究过程中，假定排气扩压器的气流为一元准稳定不可压缩气流，试验装置采用压缩气源供气。根据相似理论模拟中速柴油机排气的气流状态进行内壁为直线型面（定为Ａ型）及内壁为曲线型面（定为Ｂ型）这两种型面的扩压器模拟试验。计算和试验结果表明：（１）不论Ａ型或Ｂ型排气扩压器都能改善径流式涡轮的性能，从而提高涡轮效率及涡轮增压器总效率；（２）当扩张角较大时，Ｂ型扩压器因有较高的扩压器效率及压力恢复系数，其性能优于Ａ型扩压器，这将更有利于改善涡轮增压器与中速柴油机的匹配性能。

SIMULATION INVESTIGATION ON FLOW-BEHAVIOR OF EXHAUST GAS DIFFUSER FOR A RADIAL - INWARD-FLOW TURBINE

The purpose of the experimental investigation was to study the effects of characteristics of exhaust gas diffusers connected to radial-inward-flow turbine on performance of turbosupercharger matching with a medium- speed diesel engine. In the process of investigation, it is assumed that gas flow through the exhaust diffusers is of one dimensional quasi-steady incompressible flow. As a result, based on the principle of simulitude, the test setup was designed to supply compressed air flow for simulating the flow conditions of exhaust gas of the medium-speed diesel engine in question, so that the simulation tests of two diffusers, namely, the rectilinear wall diffuser designated A model and the curved wall diffuser dasignated B model, were conducted. The calculation and experimental results show' (1) the two types of diffuser can improve the performance of the radial-inward -flow turbine, whether it is A model diffuser, or B model, resulting in an increase both of turbine efficiency T and of overall efficiency Tc of turbosupercharger and (2) when adopting the large divergence angle, the flow behavior of B model diffuser is superior to that of A model, owing to the hihger diffuser efficiency and pressure recovering coefficient. Therefore, it will be all more in favour of improvement of the performance for turbosupercharger matching with the medium-speed diesel engine.