Design Optimization of Can Type Combustor

Abstract

The combustor in a gas turbine is to add energy to the system to power the turbines, and produce high velocity gas to exhaust through the nozzle in aircraft applications. Combustion chambers must be designed to ensure stable combustion of the fuel injected and optimum fuel utilization within the limited space available and over a large range of air/fuel ratios. In a gas turbine engine, the combustor is fed by high pressure air by the compression system. A combustor must contain and maintain stable combustion despite very high air flow rates. To do so combustors are carefully designed to first mix and ignite the air and fuel, and then mix in more air to complete the combustion process. The design of Can-type combustion chamber, modified can-type combustion chamber geometry and numerical investigations is carried out. The k-ω model used for analysis and also the mean temperature, reaction rate, and velocity fields are almost insensitive to the grid size. Numerical investigation on Can-type combustion chamber and a modified can-type combustion chamber geometry is gives less NOx emission as the temperature at the exit of combustion chamber is less. For methane as fuel and with initial atmospheric conditions, the theoretical flame temperature produced by the flame with a fast combustion reaction is 1950 K. The predicted maximum flame temperature is 1850 K of the combustion products compares well with the theoretical adiabatic flame temperature. Temperature profiles shows increment at reaction zone due to burning of air-methane mixture and decrement in temperature downstream of dilution holes because more and more air will enter in combustion chamber to dilute the combustion mixture along center line. Specie namely NOx is increasing and achieving peak point at reaction zone because they are products of combustion along center line. Due to increase in equivalence ratio, temperature and mass fraction of NOx increases because more fuel is utilized. There in not much variation in temperature and NOx emission by shifting the axial location of dilution holes. In modified can-type combustion chamber geometry Temperature profiles shows increment at reaction zone along the axis due to burning of air-methane mixture and decrement in temperature downstream the walls. In modified can-type combustion chamber clearly shows that temperature and pressure profiles decrease and contribute to cool the chamber walls but the exit velocity profile contributes for some losses. The streamline wall cooling is provided by installing the vanes in the combustion chamber at different position which enables the proper wall cooling for the design considered.