Geometry and Flow Conditions

The blade count of the four-stage turbine-combustor requires a full-annulus simulation for a dimensionally accurate computation. To reduce the compu­tational effort, it was assumed that there were an equal number of airfoils in each turbine row. As a result, all airfoils except for the inlet guide vane airfoils were rescaled by factors equal to the number of airfoils per row i divided by the number of airfoils per row one. An investigation of the influence of air­foil count on the turbine fbw showed that the unsteady effects were amplified when a simplified airfoil count 1:1 was used [Cizmas, 1999]. Consequently, the results obtained using the simplified airfoil count represent an upper limit for the unsteady effects.

The inlet temperature in the turbine-combustor exceeds 1800 K and the inlet Mach number is 0.155. The inlet fbw angle is 0 degrees and the inlet Reynolds number is 194,000 per inch, based on the axial chord of the first – stage stator. The values of the species concentrations at inlet in the turbine – burner are: yco2 = 0.0775, ун2о = 0.068, yco = 5.98 ■ 10-06, ун2 =

2.53 ■ 10-07, yO2 = 0.1131, yN2 = 0.7288 and yAr = 0.0125. The rotational speed of the test turbine-burner is 3600 RPM.

The unsteady effects of in situ reheat will be investigated by comparing the turbine without combustion against three cases of fuel injection in the turbine – combustor. Pure methane will be injected at the trailing edge of the first vane in all the cases of in situ reheat presented herein. The injection velocity and pressure, methane temperature and injection slot dimension are presented in Table 1.

Table 1. Parameters of fuel injection