Session: 37-03 Radial Compressor Unsteady Flow

Paper Number: 128143

128143 - A Study of Loss Model Parameter Sensitivity in Compressor Unsteady Flow Simulations 

This paper presents results from a comprehensive sensitivity analysis focused on loss models used in a recently developed compressor unsteady mean line flow model for a transonic axial-centrifugal compressor.

The developed unsteady mean line flow model uses the concept of curved stream tubes that are placed along the mean line of the blade cascades. In this approach, the governing momentum equation along the mean line does not have any source terms, and consequently, the aerodynamic force supplied by the blades is decoupled from the mean line equations. It can be determined independently from the auxiliary momentum equation in the direction perpendicular to the mean line. The developed scheme treats flow through the stage elements, namely rotors and stators, in their respective reference frames (rotating or stationary). The transformations of frames are considered in the inter-domain boundary conditions, which also serve as compact loss zones. The work done to the flow is the direct result of the added tangential velocity at rotors, and the pressure ratio of the compressor can be seen as the result of the work addition and loss models. The prediction of the compressor performance at steady state entails the evaluation of the stagnation enthalpy and stagnation pressure as well as the progressive choking of the stages. While prediction of the stagnation enthalpy is reasonably simple as it is mostly a function of the added kinetic energy due to the rotational velocity, accurate prediction of the stagnation pressure and, more so, the choking process requires adequate modeling of different losses. In the realm of the dynamic code, most of the losses need to be accommodated in the interdomain compact numerical interfaces. To that end, physics-based loss models are used so that, with relatively a few fixed parameters, the compressor performance in the entire speed and flow range including the choking process can be adequately modeled. The steady-state performance predicted by the developed model is validated against test data. It is found that with proper setting of the parameters, the model predicts accurately the pressure, efficiency and choking process of the compressor in a wide range of speeds and flow rates, ranging from near stall to deep choke. It is to be noted that while the model does provide the compressor characteristics in the left (positive slope) branch, there is no data to validate this part.

The loss models for each stage element include expansion loss, incidence loss, wall friction, and tip leak head loss. Additional loss models specific for axial stages account for transonic speed loss, while those included for centrifugal stages encompass impeller loss, vaneless diffuser loss, and vaned diffuser loss. Sensitivity studies on selected loss models are conducted to illustrate how changing those loss model parameters impact compressor performance.

The final paper will encompass (1) a description of the developed unsteady mean line flow model, (2) an explanation of loss models for axial and centrifugal compressors, (3) validation of steady-state predictions using test data, and (4) sensitivity studies on the effects of loss models.

Presenting Author: J. v. R. Prasad Georgia Institute of Technology

Presenting Author Biography: Dr. J.V.R. Prasad is a Professor in the School of Aerospace Engineering at the Georgia
Institute of Technology working in the area of Flight Mechanics and Control. He received his
B.Tech degree from the Indian Institute of Technology, Madras, India and his M.S and Ph.D.
degrees from the Georgia Institute of Technology, Atlanta, USA. He is currently a CoPrincipal Investigator and the Associate Director for the US Army, Navy and NASA
sponsored Vertical Lift Rotorcraft Center of Excellence (VLRCOE) program at Georgia Tech.
He has extensive research and design experience in rotorcraft system modeling, control
and simulation, and autonomous air vehicle modeling and control. He has published parts
of four books, over three hundred and fifty research publications including journal and
conference papers, and over eighty research project reports. He has eight invention
disclosures and five patents to his credit. He is a recipient of the Melville Medal award
from the American Society of Mechanical Engineers (ASME) in 2009, the Aero Lion
Technologies Outstanding Journal Paper award from the International Journal of
Unmanned Systems in 2015 and the Unmanned Systems best journal paper (application
category) award in 2019. He served as the Editor-In-Chief of the Journal of the
American Helicopter Society (AHS), Chair of the Handling Qualities and UAV Tech
Committees of the AHS, and as Member and Secretary of the Atmospheric Flight
Mechanics Technical Committee of the American Institute of Aeronautics and
Astronautics (AIAA). He currently serves as a Member of the VFS Technical Council,
Southern Regional Director on the VFS Board of Directors, Member of the Board of
Directors of the Vertical Lift Consortium, Member of the Editorial Board for the
International Journal on Mathematical Modeling and Simulation and the Advisory Board
for the International Journal of Unmanned Systems. He is a Fellow of the AIAA, a
Technical Fellow of the VFS and a Member of the ASME.

Authors:

Zhenhao Jing N/A
Yedidia Neumeier Georgia Institute of Technology
J. v. R. Prasad Georgia Institute of Technology
Darrell James Honeywell International, Inc.