Engineering topics
Publications and source records attributed to Madavan, N. K..
Report presents computational study of flow in first stage of three alternative versions of proposed transonic turbine. Study demonstrates application of computational fluid dynamics to predict performance and analyze effects of changes in designs of these advanced machines.
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The accurate numerical simulation of unsteady, three-dimensional viscous flow in turbomachines is computationally very intensive, requiring prohibitively large amounts of computer time on current vector supercomputers. In recent years, computer systems based on massively parallel architectures have been developed that offer the promise of meeting the computational power requirements of such large-scale simulations. However, a rethinking of existing algorithms and methodology is required in order to fully harness the computational power of such architectures. In this paper the capabilities of the Connection Machine (CM-2) in predicting unsteady flows in turbomachines are evaluated. The implementation on the CM-2 of an implicit, time-accurate, zonal algorithm for the Navier-Stokes equations in two dimensions is described. Programming issues and modifications made to the original algorithm (developed for vector, pipelined supercomputers) in order to improve performance on the CM-2 are outlined. Algorithm performance is evaluated and compared with a functionally equivalent code for the CRAY-YMP.
Finer grid yields more accurate results. Report describes numerical simulation of flow in axial-turbine stage, showing interactions between rotor- and stator-airfoil rows. Complements earlier three-dimensional, time-accurate Navier-Stokes numerical simulation.
This paper deals with the development and validation of a 3D multipassage Navier-Stokes code for predicting the unsteady effects due to rotor-stator interaction in turbomachines. Prior work in two dimensions has demonstrated the necessity of including multiple rotor and stator passages in order to closely approximate the stator-to-rotor airfoil count ratio and thus accurately predict the unsteady flowfield resulting from rotor-stator interaction. In the present paper, this multipassage capability is extended to three dimensions. Numerical results obtained from a multipassage (three stator and four rotor passage) calculation of an axial turbine stage are presented. The stator-to-rotor airfoil count ratio (3:4) used in the present calculations is a close approximation to that in the actual turbine configuration (22:28). The present multipassage calculation results in a more accurate prediction of the unsteady flowfield than that possible from a single-passage calculation.
Results from a three-dimensional, time-accurate Navier-Stokes simulation of rotor-stator interaction in an axial turbine stage are presented. The present study uses a fine grid in the spanwise direction to better resolve endwall and tip cllearance effects and complements coarse-grid calculations that were reported earlier. A realistic turbine stage with 22 stator vanes and 28 rotor blades is simulated as a single-stator, single-rotor airfoil combination with the stator geometry modified to properly account for blockage effects. This is in contrast to the earlier coarse-grid calculations where the rotor geometry was modified. The improved grid resolution and the unmodified rotor geometry result in a more accurate simulation of the flow field, particularly in the rotor channel where the interaction effects are more severe. The numerical results are compared to experimental data wherever possible and to earlier calculations.