Measurements of the Unsteady Flow Field Within the Stator Row of a Transonic Axial-Flow Fan: I — Measurement and Analysis Technique

Abstract

This two-part paper presents detailed laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective of this study was to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part I of this paper describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the “rotor-wake-generated” and “unresolved” unsteadiness, respectively. The term “rotor-wake-generated” unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term “unresolved” unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc. A procedure for calculating auto and cross correlations of the rotor-wake-generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

A method for the determination of turbulence intensity by means of a fast response pressure probe and its application in a LP turbine

“…Furthermore, the fluctuating component p'(t) is commonly referred as "unresolved unsteadiness" (see for example Suder et al [20]) since it may contain deterministic (large scale structures) and stochastic unsteadiness. An extension of the procedure proposed by Camp and Shin [12] is to filter out the deterministic unsteadiness due to large coherent structures at frequencies non-correated to the rotational speed of the rotor.…”

Three-dimensional flow field downstream of an embedded stator in a multistage axial flow compressor: Part 1: Steady and unsteady flow fields

“…C ps static pressure rise coef cient equation [equation (7)] C pt total pressure rise coef cient equation [equation (7)] N shaft rotational speed (r/min) p static pressure P time-averaged value of quantity P P ijk , P' UR instantaneous quantity P and unresolved component of P (P j ) RAP , (P k ) BP , (P jk ) BAP revolution aperiodic, blade periodic and blade aperiodic components of quantity P [equations (4) to (6)] P o total pressure P r total pressure ratioˆP oloc /P o1 PS, SS pressure and suction sides respectively R radius in percentage span, tip radius T static temperature T o total temperature T or total temperature riseˆT oloc ¡ T o1 T r total temperature ratioˆT oloc /T o1 U t rotor 2 blade tip speed V absolute total velocity (m/s) V eff1 effective cooling velocity at lm orientation 1 V tot total velocity V z in , V z (inlet) average inlet axial velocity a absolute ow angle measured from the axial direction z total pressure loss [equation (9)] Z isen isentropic ef ciency [equation (8)] r uid (air) density o vorticity [equation (11)] O rotation rate Subscripts BAP, BP blade aperiodic and periodic [equations (6) and (5) respectively] ENS ensemble average loc local value o total or stagnation value r, y, z radial, tangential and axial components respectively RAP, RP revolution aperiodic and periodic [equation (4)] respectively sec secondary value [equation (10)] totper, totun total periodic and total unresolved unsteadiness respectively UR unresolved 1 inlet (upstream of the inlet guide vane)…”

“…Based on the terminology of Suder et al [8], an instantaneous quantity (velocity, angle, pressure and temperature) P ijk can be decomposed as follows:…”

Flow Mechanism for Stall Margin Improvement via Axial Slot Casing Treatment on a Transonic Axial Compressor

“…A complete description of the aerodynamic design of the Rotor 67 is given in Refs. (Strazisar et al 1989, Cunnan et al 1978, Urasek et al 1979, Hathaway 1986, Suder et al 1987. …”