Effect of quarl angle of liner air-casing on annulus flow of gas turbine combustor

The interaction between the diffuser and combustor external flows plays a key role in controlling the pressure loss and air flow distribution around the flame tube. Flow through casing-liner annulus is crucial as it feeds air to the primary, secondary and dilution holes as well as influences the level and distribution of liner wall temperature. It is important that the annulus flow has sufficient static pressure to achieve adequate penetration of the jets. Moreover, the correct proportion of air enters the combustor liner through the dome and the various ports to maintain stable operation and uniform temperature profile at the exit of the combustor. A desired condition for the annulus flow is to obtain a uniform flow in the annulus passage as early as possible so that proper flow through various liner holes can be ensured allowing a reduction in combustor length. For aircraft applications, the weight can be further reduced by a shorter diffuser length. In the present computational study, an attempt has been made to analyze the modifications in diffuser geometry and its effects in dome region aerodynamics and annulus flow characteristics. A significant length reduction is possible by defining alternative diffuser geometry. A comparison has been made amongst the three models in terms of flow uniformity, static pressure recovery and total pressure loss coefficients (performance parameters) for different dump-gaps. It is observed that the flow uniformity in the annulus and performance parameters are improved if a small modification is made in diffuser geometry. The aim of this study is to optimize diffuser geometries for a given combustor length, depth and dome shape.