scholarly journals Unsteady wakes-secondary flow interactions in a high-lift low-pressure turbine cascade

2020 ◽  
Vol 33 (3) ◽  
pp. 879-892 ◽  
Author(s):  
Xiao QU ◽  
Yanfeng ZHANG ◽  
Xingen LU ◽  
Junqiang ZHU
Keyword(s):  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Cascade ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Flow Interactions

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2020 ◽  
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 2·105) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1D-CTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probe measurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

Measurements of Secondary Losses in a High-Lift Front-Loaded Turbine Cascade With the Implementation of Non-Axisymmetric Endwall Contouring

2009 ◽  
Author(s):  
D. C. Knezevici ◽  
S. A. Sjolander ◽  
T. J. Praisner ◽  
E. Allen-Bradley ◽  
E. A. Grover
Keyword(s):  
Secondary Flow ◽  
Low Pressure ◽  
Current Work ◽  
Test Facility ◽  
Test Case ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Baseline Test ◽  
Endwall Contouring ◽  
Turbine Airfoils

This paper is the second in a series from the same authors studying the mitigation of endwall losses using the low-speed linear cascade test facility at Carleton University. The previous paper documented the baseline test case for the study. The current work investigates the secondary flow in a cascade of more highly-loaded low-pressure turbine airfoils with and without the implementation of endwall profiling. This study is novel in two regards. First, the contouring is applied to low-pressure turbine airfoils, whereas studies conducted by other researchers have focused their endwall profiling efforts on the high-pressure turbine. Second, while previous researchers have optimized contouring designs for a given airfoil, the current work demonstrates the potential to open the design space by employing high-lift airfoils in conjunction with endwall contouring. Seven-hole pneumatic probe measurements taken within the blade passage and downstream of the trailing edge track the progression of the secondary flow and losses generated. The contouring divides the vorticity associated with the passage vortex into two weaker vortices, and reduces the secondary kinetic energy. Overall the secondary losses are reduced and the loss reduction is discussed with regards to changes in the flow physics. A detailed breakdown of the mixing losses further demonstrates the benefits of endwall contouring.

Effects of Periodic Wakes and Freestream Turbulence on Coherent Structures in Low-Pressure Turbine Boundary Layer

2012 ◽  
Author(s):  
Weihao Zhang ◽  
Zhengping Zou ◽  
Kun Zhou ◽  
Huoxing Liu ◽  
Jian Ye
Keyword(s):  
Boundary Layer ◽  
Coherent Structures ◽  
Low Pressure ◽  
Turbine Cascade ◽  
Freestream Turbulence ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Large Eddy ◽  
Separation Bubbles

The effects of periodic wakes and inlet freestream turbulence intensity (FSTI) on coherent structures in the boundary layer of a high-lift low-pressure turbine cascade are studied in this paper. Large-eddy simulations (LES) are performed on T106D-EIZ profile at Reynolds number (Re) of 60,154 (based on the chord and outflow velocity). Eight cases, considering FSTI of 0, 2.5%, 5% and 10% as well as the wake reduced frequency (fr) of 0.67, 1.34 and 0.335, are conducted and discussed. The results show that the open separation could be compressed by freestream turbulence to a small extent, whereas, it could be replaced by separation bubbles under wake conditions. Stripe structures and turbulence spots appear in shear layer over the separation bubbles. The increments of wake frequency or FSTI can accelerate the transition progress which result in shorter separation bubbles, meanwhile, emphasize the turbulence spots.

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2021 ◽  
pp. 1-12
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 200 000) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1DCTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probemeasurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

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