Heat Transfer Study on Liner Wall of Heat Recirculating Combustor

Abstract

In gas turbine combustors, the internal walls of the liner are always subjected to intense radiation heat, always damaging the combustor liner, resulting in cracking and premature failures of the components. For small diameter combustion, as surface-area-to-volume ratio increases, controlling of wall temperatures again becomes more challenging. The present work employs the concept of liquid film evaporation combustor for small-scale combustion chamber. It uses the wall heat loss for evaporation of liquid fuel, which is very effective way of controlling the high wall temperatures. It acts as cushion to the effect of the radiation heating and recirculates the same heat into the chamber as fuel vapor which otherwise leaves the chamber by cooling air. The previous experiments on such combustor show unstable combustion, highly attributed due to evaporation characteristics of fuel. Understanding of wall heat transfer is therefore very important for successful operation of such combustor. The effect of convective heat transfer coefficient and thermal conductivity on the combustor wall temperatures and the amount of heat that is transferred through the combined effect of radiation, convection and conduction at the surface is investigated in present work. The study is carried out considering both the cases, i.e., without liquid film and with liquid film on outer surface of combustor wall. A computer program in MATLAB using important parameters as input is used to handle the heat transfer computations. The study reveals that the thermal conductivity affects the outer wall temperature, whereas the convective heat transfer coefficient affects both outer and inner wall temperatures. Combustor with liquid film handles higher values of heat flux with relatively lower wall temperatures as compared with the combustor without liquid film.