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Next: Conclusions Up: UNSTEADY TWO- AND THREE-DIMENSIONAL Previous: Two-Dimensional Results

Three-Dimensional Results

A single-stage turbine configuration has been used to validate the STAGE-3 code. Both time-averaged and unsteady data are available in an experimental database generated by Dring, et al. [8] of United Technologies Research Center. The single-stage turbine is a large-scale, low-speed test rig of similar dimensions to the 2.5 stage compressor test rig. The experimental turbine configuration is composed of 28 stator airfoils and 22 rotor airfoils which operate at low subsonic Mach numbers. At design conditions, the flow coefficient is tex2html_wrap_inline198 , and inlet Mach number is tex2html_wrap_inline180 and the inlet Reynolds number is Re = 100,000 per inch.

It would be prohibitively expensive to compute the three-dimensional flow field through the entire 50 airfoil turbine system. It was therefore necessary to reduce the computational expense of the simulation in a manner similar to that used with the GGG turbine. The number of rotor blades was reduced from 28 to 22, such that the ratio of stators to rotors was 1:1. The rotor airfoils were then increased in size by a factor of 28/22 in order to maintain the same blockage. The flowfield was assumed to be periodic in the circumferential direction and a 1 stator, 1 rotor calculation was then performed. This procedure reduced the simulation to a 2 airfoil computation and required 6 grids. The computational grid on the hub and airfoil surfaces is shown in Figure 9. Time-averaged pressures at the midspan are presented in Figure 10. The numerical results are compared with the experimental data for both the stator and rotor midspan stations. The pressures are normalized and plotted relative to their axial positions. The time-averaged pressures are in good agreement with the experimental data for the stator. Both the suction and pressure surfaces on the stator are well predicted. The pressure surface on the rotor is also well predicted. There are slight differences between the computed results and experimental data on the rotor suction surface. The trailing edge spikes are grid dependent, and reduce in size when the grid is refined. In general, both the shapes and levels of pressure are well predicted in the turbine.

These results do provide a partial validation of the codes STAGE-2 and STAGE-3. A three-dimensional multistage compressor computation is currently being carried out to validate the multistage capability of STAGE-3.


next up previous
Next: Conclusions Up: UNSTEADY TWO- AND THREE-DIMENSIONAL Previous: Two-Dimensional Results

Karen L. Gundy-Burlet
Wed Apr 9 13:50:35 PDT 1997