Numerical Investigation of Active Flow Control for Low-Pressure Turbine Blade Separation

2004 ◽  
Author(s):  
Dieter Postl ◽  
Andreas Gross ◽  
Hermann Fasel
Keyword(s):  
Flow Control ◽  
Numerical Investigation ◽  
Turbine Blade ◽  
Active Flow Control ◽  
Low Pressure ◽  
Low Pressure Turbine ◽  
Active Flow

Numerical Simulation of a Low Pressure Turbine Blade Employing Active Flow Control

2006 ◽  
Author(s):  
Marshall C. Galbraith ◽  
Amit Kasliwal ◽  
Kirti Ghia ◽  
Urmila Ghia
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Turbine Blade ◽  
Cfd Simulation ◽  
Control Method ◽  
Active Flow Control ◽  
Low Pressure ◽  
Synthetic Jets ◽  
Low Pressure Turbine ◽  
Active Flow

High altitude aircraft experience a large drop in the Reynolds number (Re) from take off conditions to cruise conditions. It has been shown in previous research performed by Simon and Volino [1] that this reduction in Re number causes the flow inside the turbine cascades to become laminar, and separate more readily on the suction side of the turbine blade. This boundary-layer separation greatly reduces the efficiency of the turbine and aircraft engine as a whole, and therefore is undesirable. To prevent this loss of efficiency, research will be pursued for active and passive means to delay and/or eliminate the flow separation. Lake et al. [2] used passive boundary layer trip, dimples, and V-grooves in an extensive study to reduce separation on the Pak-B turbine blade. Although these passive techniques were able to reduce the separation at fixed Re numbers, an active flow control method is needed for more efficient separation reduction over a range of Re numbers. Currently, researchers are investigating several different active flow control devices, including pulsating synthetic jets, vortex generator jets (VGJ), and moving protuberances. The proposed study intends to further investigate the mechanism of flow control via synthetic jets, which alternate between suction and blowing, on a low pressure turbine blade utilizing a Large Eddy Simulation (LES) Computational Fluid Dynamics (CFD) solver. Optimum values of the associated parameters such as jet angle, blowing ratio, frequency, duty cycle, etc., of the synthetic jets will be determined. However, before investigation of the effectiveness of synthetic jets, the CFD simulation will be validated with experimental data on VGJ. A description of the implementation is presented along with preliminary results.

Numerical Study of Active Flow Control for a Transitional Highly Loaded Low-Pressure Turbine

2006 ◽  
Vol 128 (5) ◽  
pp. 956-967 ◽  
Author(s):  
Donald P. Rizzetta ◽  
Miguel R. Visbal
Keyword(s):  
Flow Control ◽  
Numerical Study ◽  
Active Flow Control ◽  
Low Pressure ◽  
Transitional Flow ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Baseline Case ◽  
Active Flow ◽  
Highly Loaded

Active control was simulated numerically for the subsonic flow through a highly loaded low-pressure turbine. The configuration approximated cascade experiments that were conducted to investigate a reduction in turbine stage blade count, which can decrease both weight and mechanical complexity. At a nominal Reynolds number of 25,000 based upon axial chord and inlet conditions, massive separation occurred on the suction surface of each blade due to uncovered turning. Vortex generating jets were then used to help mitigate separation, thereby reducing wake losses. Computations were performed using both steady blowing and pulsed mass injection to study the effects of active flow control on the transitional flow occurring in the aft-blade and near-wake regions. The numerical method utilized a centered compact finite-difference scheme to represent spatial derivatives, that was used in conjunction with a low-pass Pade-type nondispersive filter operator to maintain stability. An implicit approximately factored time-marching algorithm was employed, and Newton-like subiterations were applied to achieve second-order temporal accuracy. Calculations were carried out on a massively parallel computing platform, using domain decomposition to distribute subzones on individual processors. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are described, and simulations are compared with each other, with available experimental data, and with a previously obtained baseline case for the noncontrolled flow. It was found that active flow control was able to maintain attached flow over an additional distance of 19–21% of the blade chord, relative to the baseline case, which resulted in a reduction of the wake total pressure loss coefficient of 53–56%.

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