Effects of Stator/Rotor Leakage Flow and Axisymmetric Contouring on Endwall Adiabatic Effectiveness and Aerodynamic Loss

2011 ◽  
Vol 42 (1) ◽  
pp. 45-64 ◽  
Author(s):  
Terrence W. Simon ◽  
Ryan Erickson
Keyword(s):  
Leakage Flow ◽  
Aerodynamic Loss ◽  
Adiabatic Effectiveness

Numerical Investigation on the Effect of Slot Leakage on a NGV With 2D Contoured Endwall: Adiabatic Effectiveness and Aerodynamic Loss

2017 ◽  
Author(s):  
Pingting Chen ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Numerical Method ◽  
Main Flow ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Experiment Data ◽  
Aerodynamic Loss ◽  
Pressure Loss Coefficient ◽  
Adiabatic Effectiveness ◽  
Total Pressure Loss Coefficient ◽  
Typical Design

Endwall 2D contouring is a typical design to reduce the strength of secondary flows within the passage. Such contouring can lead to significant changes in the passage flow. A leakage slot at the combustor-turbine interface is a typical turbine endwall design. The leakage flow can be used to cool the endwall and vane surface. Moreover, the leakage flow interacts with the main flow and results in the change of aerodynamic loss. A 3D numerical method was used to investigate endwall adiabatic effectiveness and passage total pressure loss coefficient (TPLC) on a NGV with 2D contoured endwall under a series of mass flow ratios (MFRs). The numerical method was validated by comparision with the experiment data. The results indicate that under the condition of this study, When MFR<0.625%, there is ingestion, and when 0.625%<MFR<1.0%, the TPLC is high. When 0.875%<MFR<1.0%, the area averaged adiabatic effectiveness (AAAE) decreases and the TPLC stays high as the MFR increases. When 1.0%<MFR<1.5%, the adiabatic effectiveness is high and the TPLC is low. To accomplish high adiabatic effectiveness, low aerodynamic loss and slight ingestion, the recommended range of MFR is 1.0%<MFR<1.5%.

Computational Study of a Midpassage Gap and Upstream Slot on Vane Endwall Film-Cooling

2006 ◽  
Author(s):  
Satoshi Hada ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Reasonable Agreement ◽  
Computational Study ◽  
Leakage Flow ◽  
Relative Height ◽  
Adiabatic Effectiveness ◽  
Endwall Film Cooling ◽  
Cooling Methods ◽  
Computational Predictions ◽  
Flat Pattern

Currently, turbines are being designed to operate with increasing inlet temperatures to improve the engine’s performance. To reduce NOx combustion, combustors are being designed to provide flat pattern factors. For these reasons, the endwall of the first stage vane is under severe heat transfer conditions. Film-cooling is one of the most effective cooling methods for the endwall of the vane. This paper presents results from a computational study of a film-cooled endwall. The endwall design considers both an upstream slot and a mid-passage slot, whereby the slot considered is both aligned and misaligned with respect to the endwall. Results indicate reasonable agreement between computational predictions and experimental measurements of adiabatic effectiveness levels along the vane endwall. The results of this study show the mid-passage slot has a large effect on the endwall film coverage. In addition, the relative height of the upstream slot to the downstream endwall is important to consider for improving the cooling benefit from the leakage flow between the combustor and turbine.

Analysis of Cooling Effectiveness and Heat Transfer Variations on the End Wall of a Nozzle Guide Vane Caused by Turbine Leakage Flows

2008 ◽  
Author(s):  
Axel Dannhauer
Keyword(s):  
Mass Flow ◽  
Side Wall ◽  
Superposition Method ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Adiabatic Effectiveness ◽  
Nozzle Guide ◽  
End Wall

Extensive thermodynamic measurements were carried out on a vane endwall to investigate the interaction with the upstream rotor leakage flow. The experiments were performed at the low speed cascade wind tunnel (NGG) of the German Aerospace Centre (DLR), Go¨ttingen. The investigated cascade consists of three large nozzle guide vanes. The effect of tip leakage flow was simulated by blow-off air. This was ejected through a leakage gap in the side wall closely upstream of the cascade. To investigate the different, possible constructive solutions of tip clearances, at least two different blowing directions were investigated: tangential and perpendicular to the mainstream at three different mass flow ratios. The influence of inlet turbulence was investigated too, applying an active turbulence grid in the intake. To get a realistic temperature gradient the leakage air was cooled down by a heat exchanger to adjust a distinctive temperature difference to the mainstream. The surface temperatures were detected by an infrared camera. Heat flux measurements assisted the interpretation of the resulting distributions of film-cooling effectiveness. It appeared that even for perpendicular injection a large amount of leakage air is distributed to the front area of the end wall although the secondary flow structure is amplified. The leakage air for mass flow ratios until 1.0% is visible between the 3D-separation lines of the horseshow vortices. With tangential ejection an adiabatic effectiveness of ηaw = 0.2 at the cascade outlet was detectable. For both investigated injection directions it was possible to weaken the three dimensional vortex structures. For a further increase in resolution of the adiabatic effectiveness some examinations applying the so-called superposition method were performed.

scholarly journals On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

2017 ◽  
Author(s):  
Hongmei Jiang ◽  
Li He ◽  
Qiang Zhang ◽  
Lipo Wang
Keyword(s):  
High Speed ◽  
Flow Distribution ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Scaling Method ◽  
Low Speed ◽  
Aerodynamic Loss ◽  
Tip Leakage ◽  
Speed Condition

Modern High Pressure Turbine (HPT) blades operate at high speed conditions. The Over-Tip-Leakage (OTL) flow, which plays a major role in the overall loss generation for HPT, can be high-subsonic or even transonic. In practice from the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low speed experiments. It has been assumed a redesigned low speed blade profile with a matched blade loading should be sufficient to scale the high speed OTL flow down to the low speed condition. In this paper, the validity of this conventional scaling approach is computationally examined. The CFD methodology was firstly validated by experimental data conducted in both high and low speed conditions. Detailed analyses on the OTL flows at high and low speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22.2%, and the total pressure loss at the low speed condition is 10.7% higher than the high speed case. An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high speed to low speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally. The limitations of this proposed method are also addressed in this paper.

High Pressure Turbine Rotor Stage Endwall Cooling and Passage Thermal Fields as Affected by Leakage Flow and Combustor Liner Coolant Streams

2013 ◽  
Author(s):  
Arya Ayaskanta ◽  
Terrence W. Simon ◽  
Ryan Erickson ◽  
Hee Koo Moon ◽  
Luzeng Zhang
Keyword(s):  
High Pressure ◽  
Turbine Rotor ◽  
Leakage Flow ◽  
High Pressure Turbine ◽  
Flow Temperature ◽  
Thermal Fields ◽  
Adiabatic Effectiveness ◽  
Combustor Liner ◽  
Endwall Cooling ◽  
Insight Into

The effects of an engine-representative combustor exit temperature profile and different disc cavity leakage flow rates on endwall adiabatic effectiveness distributions and passage temperature fields in a high pressure turbine rotor stage of a gas turbine are experimentally documented. The measurements are made on a stationary linear blade row cascade with an axisymmetrically-contoured endwall of modern engine geometry and with engine-representative approach flow thermal and fluid mechanics characteristics. The measurements give insight into mixing of coolant emerging as leakage flow and combustor liner coolant mix with hot core gases ahead of the airfoil row. Reported results are thermal fields in the passage, adiabatic wall temperatures and adiabatic effectiveness values in using an engine-representative approach flow temperature profile and with approach flow temperature profiles with 1) no coolant in the approach flow (flat profile) and 2) coolant only within 10% of the span (approach flow profile with a thin thermal boundary layer).The results give insight into mixing between the leakage flow and the mainstream passage flow and its effects on endwall cooling. The results demonstrate that for the conditions studied; much of the endwall cooling is contributed by the coolant in the approach flow. This is an important result that has previously not been well documented.

Aerodynamic Loss for a Turbine Blade With Endwall Leakage Features and Contouring

2013 ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane ◽  
Tom Praisner
Keyword(s):  
Turbine Blade ◽  
Aerodynamic Performance ◽  
Secondary Flows ◽  
Leakage Flow ◽  
Aerodynamic Loss ◽  
Endwall Contouring

Secondary flows near the endwall of a turbine blade contribute to a loss in aerodynamic performance in the engine. Further reductions in performance occur when the secondary flows interact with leakage flow from necessary clearance features, such as the clearance gap between the blade rotor and an upstream stator or gaps between adjacent blade platforms. Non-axisymmetric endwall contouring has been shown to reduce the strength of secondary flows near the endwall, but relatively little research has been done to test the sensitivity of the contouring to the endwall leakage features. This paper describes aerodynamic measurements taken downstream of a cascade with representative leakage features. In general, upstream leakage flow with swirl relative to the blade increased aerodynamic loss, relative to leakage that was matched to the blade wheelspeed. Non-axisymmetric contouring for an endwall without a platform gap reduced underturning of the flow but had no effect on overall loss, relative to a flat endwall without a gap. A contoured endwall with a platform gap had 12% higher mixed-out loss than a contoured endwall without a gap.

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