The results of a program of experimental and analytical research in casing treatments over axial compressor rotor blade tips are presented. Circumferential groove, axial-skewed slot, and blade angle slot treatments were tested at low speeds. With the circumferential groove treatment the stalling flow was reduced 5.8 percent at negligible efficiency sacrifice. The axial-skewed slot treatment improved the stalling flow by 15.3 percent; 1.8 points in peak efficiency were sacrificed. The blade angle slot treatment improved the stalling flow by 15.0 percent; 1.4 points in peak efficiency were sacrificed. These values are consistent with previous experience at transonic speeds. The favorable stalling flow situations correlated well with observations of higher-than-normal surface pressures on the rotor blade pressure surfaces in the tip region, and with increased maximum diffusions on the suction surfaces. Annulus wall pressure gradients, especially in the 50 to 75 percent chord region, are also increased and blade surface pressure loadings are shifted toward the trailing edge for treated configurations. Rotor blade wakes may be somewhat thinner in the presence of good treatments, particularly under operating conditions close to the baseline stall. Annulus wall boundary layer profiles are only slightly influenced by casing treatment.Copyright © 1975 by ASME

A study of casing treatment stall margin improvement phenomena. [for axial compressor rotor blade tips]

Supercritical wing design based on airfoil optimization and 2.75D transformation

Casing grooves to improve aerodynamic performance of a HP turbine blade

Numerical analysis of the circumferential grooves casing treatment in a counter-rotating axial flow compressor

The JENSA gas-jet target was designed for experiments with radioactive beams provided by the rare isotope re-accelerator ReA3 at the National Superconducting Cyclotron Laboratory. The gas jet will be the main target for the Separator for Capture Reactions SECAR at the Facility for Rare Isotope Beams on the campus of Michigan State University, USA. In this work, we describe the advantages of a gas-jet target, detail the current recirculating gas system, and report recent measurements of helium jet thicknesses of up to about 1 0 19 atoms/cm 2 . Finally a comparison with other supersonic gas-jet targets is presented.

Status of the JENSA gas-jet target for experiments with rare isotope beams

Numerical investigations were conducted to predict the performance of a transonic axial compressor rotor with circumferential groove casing treatment. The Notre Dame Transonic Axial Compressor (ND-TAC) was simulated at Tsinghua University with an in-house computational fluid dynamics (CFD) code (NSAWET) for this work. Experimental data from the ND-TAC were used to define the geometry, boundary conditions, and data sampling method for the numerical simulation. These efforts, combined with several unique simulation approaches, such as nonmatched grid boundary technology to treat the periodic boundaries and interfaces between groove grids and the passage grid, resulted in good agreement between the numerical and experimental results for overall compressor performance and radial profiles of exit total pressure. Efforts were made to study blade level flow mechanisms to determine how the casing treatment impacts the compressor's stall margin and performance. The flow structures in the passage, the tip gap, and the grooves as well as their mutual interactions were plotted and analyzed. The flow and momentum transport across the tip gap in the smooth wall and the casing treatment configurations were quantitatively compared.

A Computational Fluid Dynamics Study of Circumferential Groove Casing Treatment in a Transonic Axial Compressor

The stall margin and pressure ratio of an axial compressor can both be increased with the use of circumferential groove casing treatments over the rotor. Performance and stall point measurements we...

Axial Compressor Stall, Circumferential Groove Casing Treatment, and the Tip-Clearance Momentum Flux

Very Large Eddy Simulation of a Transonic Axial Compressor Stage

In order to optimize the performance of gas-jet targets for future nuclear reaction measurements, a detailed understanding of the dependence of the gas-jet properties on experiment design parameters is required. Common methods of gas-jet characterization rely on measuring the effective thickness using nuclear elastic scattering and energy loss techniques; however, these tests are time intensive and limit the range of design modifications which can be explored to improve the properties of the jet as a nuclear reaction target. Thus, a more rapid jet-characterization method is desired. We performed the first steps towards characterizing the gas-jet density distribution of the HIPPO gas-jet target at the University of Notre Dame's Nuclear Science Laboratory by reproducing results from 20 Ne( α , α ) 20 Ne elastic scattering measurements with computational fluid dynamics (CFD) simulations performed with the state-of-the-art CFD software ANSYS Fluent . We find a strong sensitivity to experimental design parameters of the gas-jet target, such as the jet nozzle geometry and ambient pressure of the target chamber. We argue that improved predictive power will require moving to three-dimensional simulations and additional benchmarking with experimental data.

/pdf/exploratory-investigation-of-the-hippo-gas-jet-target-fluid-1otm76c2bn.pdf

Exploratory investigation of the HIPPO gas-jet target fluid dynamic properties

A new finite volume solver for all Mach number flows suitable for the solution on unstructured meshes with the collocated arrangement of variables is presented. The solver is based on the primitive variable equations. The newly proposed method utilizes the fractional step method that resembles the projection methods used in incompressible flow simulations. The proposed solver is suitable for the computations ranging from incompressible to supersonic flows. A notable characteristic of the newly proposed method is that the new formulation of the compressible pressure equation contains the pressure Laplacian term pre-multiplied by the time step size. Unlike the incompressible projection methods, the new pressure equation is derived from the discrete form of the continuity equation, resulting in the equation that has the potential (elliptic) and the hyperbolic (convective) parts of the pressure field separated. Central flux formulation is used for the approximation of numeric fluxes, resulting in small numerical dissipation thus making it suitable for the high fidelity computations including direct and large eddy simulations. A set of validation problems is presented in this work demonstrating the main characteristics of the newly proposed solver.

Ke Shi

Papers

A Computational Fluid Dynamics Study of Circumferential Groove Casing Treatment in a Transonic Axial Compressor

Axial Compressor Stall, Circumferential Groove Casing Treatment, and the Tip-Clearance Momentum Flux

Very Large Eddy Simulation of a Transonic Axial Compressor Stage

Exploratory investigation of the HIPPO gas-jet target fluid dynamic properties

A Primitive Variable Central Flux Scheme for All Mach Number Flows