COMBUSTION CHARACTERISTICS OF A CAN COMBUSTOR WITH DIFFERENT FUEL INJECTOR CONFIGURATIONS
Flow and combustion characteristics of reverse airflow CAN combustor are investigated for different fuel injector configurations. In existing combustor, a simple conical shaped fuel injector is used. In order to promote the burning rate of fuel, fuel flow pattern is altered by modifying the fuel injector geometry. The philosophy of reverse fuel injection is devised. The existing conical shaped injector is replaced by cylindrical shaped reverse fuel injector. The fuel comes out in axially opposite direction towards the wall of hemispherical head. This fuel flow pattern allows fuel to radially spread in the primary region.
ANSYS-FLUENT is used to perform numerical investigations on CAN combustor for different fuel injector arrangements. Reynolds Averaged Navier Stokes (RANS) based k-ε model is used to evaluate turbulence parameters. The radiative heat transfer is included in the simulations by incorporating Discrete Ordinates (DO) model. Interaction between turbulence and chemistry is modelled using Probability Density Function (PDF) approach. Methane is used as fuel. Results obtained in terms of axial velocity and temperature are plotted along radial position at different axial locations in the combustor. Experimental measurements of temperature at combustor exit are reported along with comparison of temperature fields obtained from the two fuel injector models. Combustor performance is evaluated based on calculations of combustion efficiency and pattern factor.
Higher average exit temperature in CAN combustor is achieved due to reverse fuel injection in the primary region. This increase in temperature at exit is attributed to increased turbulence kinetic energy in the primary region due to improved mixing between fuel and air in this region. The reverse fuel injector shows higher combustion efficiency and improved pattern factor in reverse air flow combustor. Thermographic image of outer casing wall of combustor demonstrates that outer wall temperature increases due to reverse fuel injection compared to existing conical fuel injection. This increase in outer wall temperature shows that the radiative heat transfer is increased in near liner wall region due to radial expansion of hot flame.