Abstract: Diffuser is one key component of the gas turbine combustor following the compressor. Its primary function is to slow down the air flow delivered by the compressor in order to promote efficient combustion and avoid large total pressure losses. An experimental and computational study of cold flow in the dump diffusers was presented. The main aims were to evaluate the influence of pre-diffuser wall angle and pre-diffuser length on the performance of dump diffusers，and to identify the pressure loss mechanisms. PIV experiments were conducted in a simplified test model to help choose?of?congruent?turbulence model.? It was observed that apparent flow separation occurred on pre-diffuser wall when pre-diffuser wall angle amplified to certain degree .The pre-diffuser exit flow was distorted，indicating that the uniform exit conditions typically assumed in the diffuser design were violated. Skew distribution of the pre-diffuser outlet flow can result in strong transverse mixing for liquid，the total pressure loss of pre-diffuser increases significantly. The formula of ?the?total pressure?loss coefficient and the pressure recovery coefficient was?developed. The optimal pre-diffuser length and pre-diffuser wall angle can be?conveniently obtained?by?this?equation，the?calculation?error?was less than?5%.

Key words: Dump diffuser；Pre-diffuser wall angle；Flow?separation；Numerical simulation

摘要： 研究了突扩扩压器中前置扩压器各参数与总压损失和静压恢复间的关系。采用实验与FLUENT计算结合的方法，通过水槽PIV实验得出扩压器内的流场信息，对照不同的湍流模型，得出最佳的计算方案。根据此计算方案计算不同的扩张角下前置扩压器性能的变化，得出各参数之间的规律。结果表明雷诺应力模型能够较好地预测扩压器内部流场；前置扩压器扩张角存在一个最佳值，大于最佳值前置扩压器会出现流动分离；结合理论分析和计算数据总结出计算前置扩压器总压损失系数和静压恢复系数的公式，利用此公式还可求出最佳的前置扩张角和前置扩压器长度，计算误差在5%左右。

关键词: 突扩扩压器；扩张角；流动分离； 数值模拟