Aerodynamics of Compressor Casing Treatment: Part I—Experiment and Time-Accurate Numerical Simulation

Abstract

This paper presents both experimental and unsteady RANS investigations of a slot-type casing treatment at a transonic axial flow compressor rotor. Experimental results show that at 60% and 98% of rotor design wheel speeds, approximately 100% and 200% extra extensions of the rotor operation ranges are achieved, respectively. On the other hand, there are about 3.6% and 2.0% drops of efficiencies at 60% and 98% speeds respectively if comparisons are made at the same peak-efficiency mass flow rates of the solid casing case. If comparing the respective peak efficiencies for the solid casing case with those for the treated casing case, there are still about 3.4% and 0.7% drops at 60% and 98% speeds, respectively. As for the unsteady RANS study, an in-house unsteady RANS code has been used to study the casing treatment flow at several operating points, i.e., the peak efficiency and the near stall with regard to the solid casing case at 60% speed and 98% speed, respectively. It is shown that the interactions between the blade passage flow and the casing treatment flow exhibit different manner at two rotating speeds. The flow condition in which the rotor operates, i.e., either the subsonic condition at the 60% speed or the transonic condition with passage shock presented at the 98% speed, is one of the determinate factors that are responsible for the manner the casing treatment works. The loss production due to casing treatment is also particularly discussed.

A Novel Approach to Evaluate the Benefits of Casing Treatment in Axial Compressors

“…The numerical curves shapes are in fairly good agreement with the measurements. However, numerical characteristics are shifted due to a larger mass flow rate at chocked conditions than the measured value (as predicted by Lin et al [22] and Ning and Xu [27]). Simulations overestimate total pressure as well as efficiency magnitudes.…”

“…In order to understand the CT effects on axial compressors features, three axial compressors are numerically investigated with and without CT: NASA Rotor 37 [24,25], CREATE [26], and CBUAA [22,27]. They differ by the geometry of the smooth casing (cylindrical versus noncylindrical), the flow regime (subsonic versus transonic), and the CT geometry incorporated (circumferential grooves or slot-type CT).…”

“…In the experiment, the stator is placed far downstream of test rotor; thus the isolated rotor environment can be established. Experimental and numerical studies of the test case can be found in Lin et al [22] and Ning and Xu [27]. The slot-type CT is illustrated in Figure 4 [22,27].…”

“…Experimental and numerical studies of the test case can be found in Lin et al [22] and Ning and Xu [27]. The slot-type CT is illustrated in Figure 4 [22,27]. The total slot number is 153 (9 times the blade number).…”

“…Results of the CBUAA. Rotor characteristics of both SW and CT configurations obtained at 98% speed by the experiment [22] and predicted by unsteady simulations are compared in Figure 9. The numerical curves shapes are in fairly good agreement with the measurements.…”