Effects of injector recess on heat flux in a combustion chamber with cooling channels

An experimental study has been carried out to study the effects of recess length in swirl coaxial injectors on heat transfer in a combustion chamber with cooling channels. Liquid oxygen and kerosene (Jet A-1) were burned in a range of mixture ratios (2.12–3.07) and chamber pressures (57.3–82.3 bar) in small liquid rocket thrust chambers. Each thrust chamber had nineteen liquid–liquid swirl coaxial injectors. While changing the recess length of the injectors and operating conditions, temperatures of the cooling water passing through the cooling channels were collected and analyzed to calculate the heat flux in the combustion chamber. As expected, operating conditions such as oxidizer-to-fuel mixture ratio and chamber pressure had a large influence on the heat flux in the combustion chamber. The recess length of the injectors also significantly affected the heat flux in the combustion chamber, which showed that the longer recess length gradually increased the heat flux. It is thought that the variation of flame structure with respect to the recess length in swirl coaxial injectors was the main reason. Since heat flux is a very important factor in designing cooling channels, the effects of recess length on heat flux in a combustion chamber must be carefully considered.