Quantifying Heat Transfer Effects of a High-speed, Multi-Stage, Axial Research Compressor

A common assumption often made of dynamic compressors is that they are considered adiabatic, due to the fast-moving flow passing through the turbomachine and the small amount of any heat transfer relative to the large amount of work transferred to/from the flow. This research investigation combined the use of experimental measurements and computational simulations to take a deeper look into the implications that arise from applying this adiabatic assumption or neglecting heat transfer within a high-speed, multi-stage, axial compressor. Preliminary testing of the Purdue 3-Stage (P3S) Axial Compressor Research Facility indicated the presence of heat transfer through stagnation temperature rises across stationary blade rows and higher than expected temperatures on the outside of the aluminum compressor casing, particularly in the front stages. Further experiments performed on the PAX200 compressor in the P3S facility involved a combination of surface temperatures, heat fluxes, and flow stagnation temperatures within the shrouded stator cavities and flowpath. These measurements confirmed that heat transfer was present throughout the stationary components (stators and casing) of the compressor and showed that they could noticeably affect the thermal flow properties within the compressor. The influence of the heat transfer through these components was further explored through computational simulations, which showed the importance of incorporating conjugate heat transfer into the model and applying the correct thermal boundary conditions on the outside of the casing. Additionally, the effects on the spanwise temperature of the flow through increased spanwise mixing, convection, and different geometric and material properties of the casing were also explored. Overall, this investigation seeks to establish a correct thermal boundary condition and approach for validation of computational model. It also aims to reconcile the differences between computational models and experimental data by quantifying the impact that heat transfer has on isentropic efficiency for diabatic compressors

Characterization of Aerodynamic Forcing Functions for Embedded Rotor Resonant Response in a Multistage Compressor

There are two main objectives associated with this research: The first portion examines the flow field within the embedded stage of the Purdue 3-Stage Axial Compressor and the aerodynamics responsible for exciting a forced response condition on an embedded rotor. The second portion focuses on the upgrades made to the facility to accommodate a new compressor design, as well as the basic performance characteristics that were acquired for the baseline model. With the first phase of this research endeavor, the first chord-wise bending vibratory mode was examined with a standard stator 1 (S1) blade-count configuration (44 vanes). Next, a reduced S1 blade-count configuration (38 vanes) was implemented to observe how a reduced vane count might impact the forced response at the first torsion vibratory mode. To capture these aerodynamic considerations, stagnation pressure and thermal anemometry probes were used throughout the embedded stage to provide a detailed picture of the influence associated with rotor and stator wakes. These data were also used to observe the potential field effects from the downstream blade-rows. The overall purpose of this campaign was to provide accurate and reliable dataset that could be used to further enhance and validate the computational aeromechanics tools used by the GUIde V consortium, the sponsors for this research. The second phase of this involves the redesign of the Purdue 3-Stage Axial Compressor Facility to accommodate a new compressor, designed by Rolls-Royce, that requires higher mass flow rates, pressure ratios, speeds, and temperatures. Along with many of the mechanical upgrades associated with an adaptation of the driveline and throttle system, health-monitoring upgrades were made to improve the safety and integrity of the compressor system, particularly with respect to temperature and vibrations. Instrumentation improvements include new pressure transducers to observe higher pressures and mass flow rates and the implementation of a tip clearance measurement system. Finally, structural improvements include reinforcement of the struts to account for higher thrust and modification of the rear bearing plate to accommodate an increase in bleed flow under the shroud of the rear stator. In addition to these facility upgrades, an inlet pressure study was performed and aeromechanical considerations were observed. All this work culminated in the acquisition of a steady performance map that was produced for the baseline configuration of the new compressor design, which will be compared to for future design iterations