Aerodynamic Design and Analysis of a High Pressure Ratio Aspirated Compressor Stage

Abstract

The pressure ratio of axial compressor stages can be significantly increased by controlling the development of blade and endwall boundary layers in regions of adverse pressure gradient by means of boundary layer suction. This concept is validated and demonstrated through the design and analysis of a unique aspirated compressor stage which achieves a total pressure ratio of 3.5 at a tip speed of 1500 ft/s. The aspirated stage was designed using an axisymmetric through-flow code coupled with a quasi three-dimensional cascade plane code with inverse design capability. Validation of the completed design was carried out with three-dimensional Navier-Stokes calculations. Spanwise slots were used on the rotor and stator suction surfaces to bleed the boundary layer with a total suction requirement of 4% of the inlet mass flow. Additional bleed of 3% was also required on the hub and shroud near shock impingement locations. A three-dimensional viscous evaluation of the design showed good agreement with the quasi three-dimensional design intent, except in the endwall regions. The three-dimensional viscous analysis predicted a mass averaged total pressure ratio of 3.7 at an isentropic efficiency of 93% for the rotor, and a mass averaged total pressure ratio of 3.4 at an isentropic efficiency of 86% for the stage.

Experimental Investigation of an Aspirated Fan Stage

“…Because of the large number of variables in the study, the inlet rotor face Mach number (M) is set to 0.65, and the flow coefficient is set to 0.475 and 0.89, two values representing the two designs proposed by Merchant in reference [14]. shows the maximum pressure ratio that can be achieved by a conventional design for # = .89 at the hub streamline is 1.55, and the maximum efficiency of 92% is achieved for a stage pressure ratio of 1.4.…”

“…1. Merchant [14]. The analysis shows a constant radial total pressure distribution for the rotor except for a small bump at the hub.…”

“…The primary objective of this research is to experimentally examine a fully aspirated compressor, by construction and testing of the low speed design offered by Merchant [14]. The experiment focuses on the effect of suction on the main flow through the compressor, therefore less emphasis will be placed on the means for handling the aspirated flow to optimize overall system performance.…”

“…This section presents the variation of stator Mach number, absolute flow angle, and stator diffusion factor for the hub and tip section of the stator at 100% and 79% design mass flow. From Merchant [14], the hub section of the stator is the most sensitive to flow disturbances. The result of this parameter analysis is that at lower mass flows the stator tip section boundary layer is more likely to separate than the hub section because of the increase in diffusion factor and incidence.…”

Surrogate Modeling for Optimization of a Centrifugal Compressor Impeller

“…Wu et al [10] used the total pressure ratio, mass flow and efficiency as an objective function and showed that pressure ratio and rotor loading can be improved further through optimizing swirl distribution using adaptive simulated annealing (ASA) algorithm. Merchant et al [11] demonstrated the possibility of substantially increasing the pressure ratio of a compressor stage at a given tip speed and increased the pressure ratio by controlling the development of blade and end-wall boundary layer in region of adverse pressure gradient by means of boundary layer suction.…”