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This paper summarizes the results of a validation and calibration study for two modern Computational Fluid Dynamics programs that are capable of modeling multistage axial compressors in a multi-blade row environment. The validation test case is a modern 4-stage high pressure ratio axial compressor designed and tested by Honeywell Aerospace in the late 90’s. The two CFD programs employ two different techniques for simulating the steady three-dimensional viscous flow field in a multistage/multiblade row turbo-machine. The first code, APNASA, was developed by NASA Glenn Research Center “GRC” and applies the approach by Adamczyk [1] for solving the average-passage equations which is a time and passage-averaged version of the Reynolds Averaged Navier Stokes (RANS) equations. The second CFD code is commercially marketed by ANSYS-CFX and applies a much simpler approach, known as the mixing-plane model, for combining the relative and the stationary frames of reference in a single steady 3D viscous simulation. Results from the two CFD programs are compared against the tested compressor’s overall performance data and against measured flow profiles at the leading edge of the fourth stator. The paper also presents a turbulence modeling sensitivity study aimed at documenting the sensitivity of the prediction of the flow field of such compressors to use of different turbulence closures such as the standard K-ε model, the Wilcox K-ω model and the Shear-Stress-Transport K-ω/SST turbulence model. The paper also presents results that demonstrate the CFD prediction sensitivity to modeling the compressor’s hub leakages from the inner-banded stator cavities. Comparison to the test data, using the K-ε turbulence closure, show that APNASA provides better accuracy in predicting the absolute levels of the performance characteristics. The presented results also show that better predictions by CFX can be obtained using the K-ω and the SST turbulence models. Modeling of the hub leakage flow was found to have significant and more than expected impact on the compressor predicted overall performance. The authors recommend further validation and evaluation for the modeling of the hub leakage flow to ensure realistic predictions for turbo-machinery performance.

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This paper summarizes the results of evaluating and validating three 3D viscous “RANS” Reynolds-Averaged Navier-Stokes codes for a Honeywell modern design of axial-centrifugal compressor test case with high quality test data. The compressor consists of a single stage axial followed by a single stage centrifugal designs. The axial stage consists of a transonic axial rotor and stator. The centrifugal stage consists of a centrifugal impeller, a vane-island radial diffuser, a 90-degrees bend and tandem deswirl vanes. The compressor was designed and rig tested by Honeywell in the early ‘00s. Detailed measurements of total pressure and total temperature were made at the compressor inlet, exit, and between the stages, including an X-Y survey at the axial stage exit, with sufficient resolution to provide a good estimate of the performance of each stage of this compressor. The validation and calibration was performed by running simulations for the entire compressor as tested in the rig. The RANS CFD programs used in this study are the NASA Glenn Research Center’s average-passage program APNASA, the Numeca’s Fine Turbo program and the ANSYS/CFX. The APNASA program employs only the standard K-ε turbulence model while the Numeca’s Fine Turbo and ANSYS/CFX employ various turbulence closures that are based on the standard two-equation K-ε turbulence model and the Wilcox K-ω model. The paper presents a comparison between the three CFD codes’ predictions and the measured test data for the overall compressor performance and the performance of the different compressor stages. These results shed some light on the ability of these codes to predict the overall compressor performance and the performance of the individual components. Sensitivity of the two codes predictability for mesh resolution and turbulence modeling variations are also presented.

The major problem confronting developers of coal burning boilers, fluidized beds, and gas and steam turbines, is the serious erosion of the systems’ components by the suspension of fly ash or other solid particles in the flow. A permanent loss of performance is associated with surface erosion, which is caused by particle surface impacts. To improve the resistance of hot erosion and corrosion, new alloys and coatings are investigated. The objective of this research work is to investigate the basic erosion process and fluid mechanics associated with material degradation in coated and uncoated INCO 718. This nickel-based superalloy is frequently used for manufacturing of jet engine and rocket components. Chemical vapor deposition (CVD) technique is used to apply a ceramic coating (TiC) to the INCO 718 superalloy. The erosive wear of the samples is investigated experimentally by exposing them to chromite particle laden flow at velocities from 180 to 305 m/s and temperatures from ambient to 538°C in a specially designed erosion wind tunnel. In addition, the eroded surface is examined by scanning electron microscopy (SEM). The obtained results show the effect of the impingement angle, temperature and velocity on the erosion rate. The cumulative effects of the impacting particles mass on the weight loss and the erosion rate of the coating are also investigated. This study demonstrates that the tested CVD titanium carbide is a perfect high temperature erosion resistant coating for INCO 718.