A Three-Dimensional Unsteady CFD Model of Compressor Stability

Abstract

A three-dimensional unsteady CFD code called CSTALL has been developed and used to investigate compressor stability. The code solved the Euler equations through the entire annulus and all blade rows. Blade row turning, losses, and deviation were modeled using body force terms which required input data at stations between blade rows. The input data was calculated using a separate Navier-Stokes turbomachinery analysis code run at one operating point near stall, and was scaled to other operating points using overall characteristic maps. No information about the stalled characteristic was used. CSTALL was run in a 2-D throughflow mode for very fast calculations of operating maps and estimation of stall points. Calculated pressure ratio characteristics for NASA stage 35 agreed well with experimental data, and results with inlet radial distortion showed the expected loss of range. CSTALL was also run in a 3-D mode to investigate inlet circumferential distortion. Calculated operating maps for stage 35 with 120 degree distortion screens showed a loss in range and pressure rise. Unsteady calculations showed rotating stall with two part-span stall cells. The paper describes the body force formulation in detail, examines the computed results, and concludes with observations about the code.

Experimental Study of the Effect of Radially Distorted Inflow on a Contrarotating Fan Stage

“…Spakovszky et al [7] attempted to stabilize rotating stall and studied stall inception pattern in a single-stage transonic compressor with radial inlet distortion using active feedback control. Chima [8] has computationally studied the performance of NASA stage 35 using a 3D unsteady code and found that the performance agreed well with the experimental results with radial distortion and shows reduction in the stable flow range of the compressor. Yang and Gu [9] have conducted experimental and computational investigations to evaluate the effects of radially distorted incident flow on the performance of an axial flow fan with three kinds of forwarded-skewed blades.…”

“…Many of the recent experimental and numerical studies have focused on studying the effect of different inlet total pressure distortion on the overall performance of a compressor/fan [7,8] to achieve improvement in the performance and distortion insensitive rotors. Spakovszky et al [7] attempted to stabilize rotating stall and studied stall inception pattern in a single-stage transonic compressor with radial inlet distortion using active feedback control.…”

Flow Simulation of N3X Hybrid Wing Body Configuration

“…In Gong's model, components of the body force for the flow loss F p are modeled by increases as the mass flow rate (MFR) increases for a fixed rotor speed. However, Chima 10 showed that entropy production across a blade zone decreases as MFR increases from a near-surge to a near-choking condition, and entropy production is directly connected to F p as…”

“…9 A direct coupling of the inlet and full-annulus fan blades in the computational domain would give a more realistic simulation of the inlet-fan interaction, but the computational cost would be prohibitively large, especially for shape-design applications, in which more than tens of flow simulations are usually required. The body force approach [9][10][11][12] has been drawing attention as an alternative to simulating the coupling with full-annulus fan blades. This approach uses body force terms to model flow turning and loss due to rotor/stator blade rows.…”

Numerical Simulation of Surge in Axial Compressor

“…The flow range for the application of the time lag equations is shown in Figure 2. A throttle is imposed at the outlet according to [19] …”