关键词: 突扩扩压器；扩张角；流动分离； 数值模拟

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