| Summary: | This paper presents the results of a numerical investigation of the gap influence on the turbine efficiency. The rotor-stator interaction in a (1/2)-stage turbine is simulated by
solving the quasi-three-dimensional unsteady Euler/Navier-Stokes equations using a
parallelized numerical algorithm. The reduced turnaround time and cost/MFLOP of
the parallel code was crucial to complete the numerous run cases presented in this
paper. The inter-row gap effect is evaluated for 4 gaps, 3 radial positions and 3 angular
velocities. As expected, the results presented in this paper show that the efficiency
increases and losses decrease while the gap size increases. The maximum efficiency
location, however, corresponds to values of the gap size which may be too large for
practical use (approximately inch). Fortunately, a local maximum efficiency and
minimum losses location has been found at approximately 0.5 inches gap size. The
efficiency variation near the local optimum is large, in some configurations being as high
as 1.4 points for a gap size variation of only 0.076 inches. Data produced by the
numerical simulations can be used to develop a design rule based on the inter-row gap
size.
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