Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors

Abstract

The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. A wall-bounded shear layer formed by the relative motion between the overtip leakage flow and the shroud wall is found to have a major influence on the development of the tip clearance flow field. This shear layer, which has not been recognized by earlier investigators, impacts the stable operating range of the rotor. Simulation accuracy is dependent on the ability of the numerical code to resolve this layer. While numerical simulations of these flows are quite sophisticated, they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip-clearance flow details (e.g., trajectory and radial extent) with corresponding data obtained from a numerical simulation. Laser-Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor is simulated using a Navier–Stokes turbomachinery solver that incorporates an advanced k–ε turbulence model derived for flows that are not in local equilibrium. A simple method is presented for determining when the wall-bounded shear layer is an important component of the tip clearance flow field. [S0889-504X(00)02504-6]

A Computational Validation Study of Parallel TURBO for Rotor 35

“…Since this is a single-stage facility, a rotor-only configuration was used to accurately get experimental measurements for R35 alone [14]. In this rotor-only configuration the R35, with a design speed of 17,194 rpm and aspect ratio of 1.19, was run at 80% design speed due to rotor/stator matching requirements for a follow-up stage investigation [14]. Data capture for the 80% design speed at peak efficiency occurred at a tip speed of 363 m/s and a total pressure ratio of 1.44.…”

“…Grid cells in this region maintain a size ratio of 1.0 across the tip into the gap and cluster as they approach the shroud. A configuration such as this treats the tip region simply as an inviscid region where no changes take place in mass, momentum, or energy and the boundaries are periodic [14]. Construction of the twelve and four blade passage grids was a relatively simple process.…”

Self-Recirculating Casing Treatment Concept for Enhanced Compressor Performance

“…The ability of the APNASA code to predict the stalling mass flow rate for an isolated transonic rotor (R35) has been demonstrated by Van Zante, et al (1999), see Figure 1. Van Zante, et al concluded that accurate prediction of the stable operating range requires careful attention to grid resolution near the casing.…”

Blade Row Interaction Effects on the Performance of a Moderately Loaded NASA Transonic Compressor Stage

“…The rotor had 9 cells and the stator had 8 cells across the clearance gap at the casing. The cells were packed at the casing in both blade rows to capture the wall bounded shear layer so that the rotor tip clearance flow is accurately simulated [17]. The rotor had 51 nodes and the stator 79 nodes in the circumferential direction.…”