Investigation of Discharge Coefficients for Single Element Lean Direct Injection Modules

Lean direct injection (LDI) combustion has a high potential as a low pollution combustion method for gas turbines. The present research aims to further investigate the discharge coefficient of an LDI module, axial swirler and convergent outlet under non-reaction and reaction conditions by theoretical, numerical and experimental methods. The functional relationship between the discharge coefficient of the LDI module, axial swirler and convergent outlet was established, and the effect of swirl angle (30^◦, 32^◦, 34^◦, 36^◦, 38^◦, 40^◦) and vane number (11, 12, 13, 14, 15, 16) on discharge coefficient was studied, and finally the differences in effective flow area of LDI combustor under different inlet conditions were analyzed. The results indicate that the flow separation on the suction side increases as the swirl angle increases, which leads to a decrease of the discharge coefficient of the axial swirler, however the discharge coefficient of the convergent outlet remains unchanged first and then decreases. As the vane number increases, the flow separation on the suction side decreases and the flow friction loss increases, so that the discharge coefficient of the axial swirler and convergent outlet will first increase with the increase of vane number and then decrease with further increases. The effective flow area of combustor changes as the conditions change, but it is approximately equal under high power conditions and normal temperature and pressure conditions.