Numerical and experimental study of trenched hole film cooling with forward and backward injection angles

The gas turbine has a wide range of applications. The demand for higher efficiency is increasing, which results in increase in turbine inlet temperature. Current operating temperature of a gas turbine is about 2000K, which may go up in future to about 3000K. This temperature is very high as compared with the melting point of turbine component material. This shows the necessity of sophisticated cooling technique to protect turbine components from such a high temperature. Film cooling is the most commonly method used, because of its good cooling performance. It forms a thin layer of coolant which avoids direct contact of hot gases with metal surface. Major drawbacks of film cooling technique are the aerodynamic losses.;To achieve better cooling in span-wise direction and also in downstream region, different shaped holes with diffused angles are introduced. Also the backward injection scheme is analyzed, but it shows poor performance in far downstream region. To have more uniform cooling and to avoid manufacturing difficulties, a trenched hole configuration is proposed. The work in this thesis is to get advantages of a trenched hole and backward injection to improve cooling performance with minimum losses. The main analysis is done numerically with commercial software, Fluent. The results are compared together with earlier study of forward and backward injection.;Experimental study is also conducted to validate the numerical simulation. A small wind tunnel is constructed which simulates film cooling concept. Thermocouples are used to measure temperature and IR camera is used to capture temperature contour over the test surface. The results are used to validate the numerical analysis with same geometry and boundary conditions applied for experimental analysis. After this validation, further study of trenched hole configuration film cooling at operating conditions are continued using numerical simulation. Results show that the trenched hole configuration shows improved and uniform cooling as compared with the normal flat surface hole configuration.