Effects of Shock-Wave on Flow Structure in Tip Region of Transonic Compressor Rotor

Proceedings of the Institution of Mechanical Engineers, Part A:

Baek

Chung

et al. 2008

As the gas turbine becomes smaller and is operated at high altitude, the aerodynamic condition frequently lies at the low Reynolds number. In the present study, three-dimensional computations were performed to understand the effects of the low Reynolds number on the loss characteristics in an axial compressor. The numerical results showed that the performance of the axial compressor like the static pressure rise is reduced by the full-span separation on the suction surface and the boundary layer on the hub, caused by the low Reynolds number. Compared with that at the reference Reynolds number, the total pressure loss at the low Reynolds number was found to be greater from the hub to 85 per cent span and smaller above the 85 per cent span. For a detailed analysis, the total pressure loss was scrutinized through three major loss categories available in the subsonic axial compressor: profile loss, tip leakage loss, and endwall loss.

Section: Numerical Resultsmentioning

confidence: 99%

Effects of the low Reynolds number on the loss characteristics in an axial compressor

Proceedings of the Institution of Mechanical Engineers, Part A:

Baek

Chung

et al. 2008

“…16) This flow solver has been pre-validated by a series of calculations in a transonic axial compressor, a subsonic axial compressor and a subsonic axial turbine, and has also been used to simulate rotating stall in a subsonic rotor. 13,[17][18][19] TFlow uses compressible RANS (Reynolds Averaged Navier-Stokes) equations as the governing equations, discretized in space by the finite volume method. An upwind TVD (Total Variational Diminishing) scheme based on Roe's flux difference splitting method was used to discretize inviscid flux terms and the MUSCL (Monotone Upstream Centered Scheme for Conservation Law) technique was used to discretize viscous flux terms.…”

Section: Methodsmentioning

confidence: 99%

“…However, the internal flow in a transonic compressor is more complex due to the presence of shocks. [8][9][10][11][12][13] This study investigated the effects of low Reynolds numbers on loss characteristics in a transonic compressor using numerical simulations. A comprehensive analysis of the loss mechanism was attempted by applying Denton's loss model 14) to the computational result.…”

Section: Introductionmentioning

confidence: 99%

Effects of Low Reynolds Number on Loss Characteristics in Transonic Axial Compressor

Trans. Japan Soc. Aero. S Sci.

Baek

Park

et al. 2010

Self Cite

A three-dimensional computation was conducted to understand effects of low Reynolds numbers on loss characteristics in a transonic axial compressor, Rotor 67. As a gas turbine becomes smaller and it operates at high altitude, the engine frequently operates under low Reynolds number conditions. This study found that large viscosity significantly affects the location and intensity of the passage shock, which moves toward the leading edge and has decreased intensity at low Reynolds number. This change greatly affects performance as well as internal flows, such as pressure distribution on the blade surface, tip leakage flow and separation. The total pressure ratio and adiabatic efficiency both decreased by about 3% with decreasing Reynolds number. At detailed analysis, the total pressure loss was subdivided into four loss categories such as profile loss, tip leakage loss, endwall loss and shock loss.

“…This flow solver has been validated through a series of calculations in a subsonic axial compressor, a transonic axial compressor and a subsonic axial turbine by Choi et al 15) and Park et al 16,17) since its development in the mid-1990s. TFlow uses the compressible RANS (Reynolds Averaged Navier-Stokes) equation as the governing equation.…”

Section: Discretization Methodsmentioning

confidence: 99%

Effects of Inlet Boundary Layer Thickness on Characteristics of Rotating Stall in Subsonic Axial Compressor

Trans. Japan Soc. Aero. S Sci.

Chung

et al. 2011

Self Cite

A 3D numerical simulation was conducted to study the effect of inlet boundary layer thickness on rotating stall in an axial compressor. The inlet boundary layer thickness had significant effects on the hub-corner-separation at the corner of hub and suction surfaces. The hub-corner-separation grew considerably for a thick inlet boundary layer as the load increased, while it diminished to become indistinguishable from the rotor wake for a thin inlet boundary layer and another corner-separation originated near the casing. This difference in the internal flow near stall also had a large effect on characteristics of the rotating stall, especially the initial asymmetric disturbance and the size of stall cells. While a prestall disturbance arises firstly in the hub-corner-separation for the thick inlet boundary layer, an asymmetric disturbance was initially generated in the tip region because of the corner-separation for the thin inlet boundary layer. This disturbance was transferred to the tip leakage flow and grew to become an attached stall cell, which adheres to the blade passage and rotates at the same speed as the rotor. When this attached stall cell reached a critical size, it started moving along the blade row and became a short-length-scale rotating stall. The size of the stall cell for the thick inlet boundary layer was larger than for the thin inlet boundary layer. Due to the bigger size of the stall cell, the performance of the single rotor for the former case dropped more significantly than for the latter case.