Turbocharger turbine rotor tip leakage loss and mass flow model valid up to extreme off-design conditions with high blade to jet speed ratio

A numerical investigation of the flow and heat transfer characteristics of tip leakage in a typical film cooled industrial gas turbine rotor is presented in this paper. The computations were performed on a rotating domain of a single blade with a clearance gap of 1.28% chord in an engine environment. This standard blade featured two coolant and two dust holes, in a cavity-type tip with a central rib. The computations were performed using CFX 5.6, which was validated for similar flow situations by Krishnababu et al., [18]. These predictions were further verified by comparing the flow and heat transfer characteristics computed in the absence of coolant ejection with computations previously performed in the company (SIEMENS) using standard in-house codes. Turbulence was modelled using the SST k-ω turbulence model. The comparison of calculations performed with and without coolant ejection has shown that the coolant flow partially blocks the tip gap, resulting in a reduction of the amount of mainstream leakage flow. The calculations identified that the main detrimental heat transfer issues were caused by impingement of the hot leakage flow onto the tip. Hence three different modifications (referred as Cases 1 to 3) were made to the standard blade tip in an attempt to reduce the tip gap exit mass flow and the associated impingement heat transfer. The improvements and limitations of the modified geometries, in terms of tip gap exit mass flow, total area of the tip affected by the hot flow and the total heat flux to the tip, are discussed. The main feature of the Case 1 geometry is the removal of the rib and this modification was found to effectively reduce both the total area affected by the hot leakage flow and total heat flux to the tip while maintaining the same leakage mass flow as the standard blade. Case 2 featured a rearrangement of the dust holes in the tip which, in terms of aero-thermal-dynamics, proved to be marginally inferior to Case 1. Case 3, which essentially created a suction-side squealer geometry, was found to be inferior even to the standard cavity tip blade. It was also found that the hot spots which occur in the leading edge region of the standard tip and all modifications contributed significantly to the area affected by the hot tip leakage flow and the total heat flux.

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The Tip Leakage Flow of an Unshrouded High Pressure Turbine Blade With Tip Cooling

Journal of Turbomachinery ◽

10.1115/1.4001174 ◽

2011 ◽

Vol 133 (4) ◽

Cited By ~ 19

Author(s):

Chao Zhou ◽

Howard Hodson

Keyword(s):

Mass Flow ◽

Suction Side ◽

Aerodynamic Performance ◽

Flow Ratio ◽

Tip Leakage Flow ◽

Momentum Exchange ◽

Leakage Loss ◽

Tip Leakage ◽

Lower Loss ◽

Mass Flow Ratio

Experimental, analytical, and numerical methods have been employed to study the aerodynamic performance of four different cooled tips with coolant mass ratios between 0% and 1.2% at three tip gaps of 1%, 1.6%, and 2.2% of the chord. The four cooled tips are two flat tips with different coolant holes, a cooled suction side squealer tip and a cooled cavity tip. Each tip has ten coolant holes with the same diameter. The uncooled cavity tip produces the smallest loss among all uncooled tips. On the cooled flat tip, the coolant is injected normally into the tip gap and mixes directly with flow inside the tip gap. The momentum exchange between the coolant and the flow that enters the tip gap creates significant blockage. As the coolant mass flow ratio increases, the tip leakage loss of the cooled flat tip first decreases and then increases. For the cooled cavity tip, the blockage effect of the coolant is not as big as that on the cooled flat tip. This is because after the coolant exits the coolant holes, it mixes with flow in the cavity first and then mixes with tip flow in the tip gap. The tip leakage loss of the cooled cavity tip increases as the coolant mass flow ratio increase. As a result, at a tip gap of 1.6% of the chord, the cooled cavity tip gives the lowest loss. At the smallest tip gap of 1% of the chord, the cooled flat tip produces less loss than the cooled cavity tip when the coolant mass flow ratios larger than 0.23%. This is because with the same coolant mass flow ratio, a proportionally larger blockage is created at the smallest tip gap. At the largest tip gap of 2.2% of the chord, the cavity tip achieves the best aerodynamic performance. This is because the effect of the coolant is reduced and the benefits of the cavity tip geometry dominate. At a coolant mass flow ratio of 0.55%, the cooled flat tips produce a lower loss than the cavity tip at tip gaps less than 1.3% of the chord. The cooled cavity tip produces the least loss for tip gaps larger than 1.3% of the chord. The cooled suction side squealer has the worst aerodynamic performance for all tip gaps studied.

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Impact of Gas Turbine Outflow on Diffuser Performance: A Numerical Study

Volume 5: Turbo Expo 2004, Parts A and B ◽

10.1115/gt2004-53043 ◽

2004 ◽

Cited By ~ 1

Author(s):

David Kluß ◽

Alexander Wiedermann ◽

Werner Volgmann

Keyword(s):

Numerical Study ◽

Turbine Rotor ◽

Industrial Applications ◽

Specific Work ◽

Turbine Stage ◽

Leakage Loss ◽

Tip Leakage ◽

First Order ◽

Multi Stage ◽

Diffuser Flow

A systematic numerical study will be described considering a coupled arrangement of turbine and diffuser flow fields. For this purpose a multi-stage solver commonly used for industrial applications has been applied. The interaction with the turbine stage was investigated assuming two annular axis-symmetric diffuser configurations. One of these has been designed according to the performance charts by Sovran and Klomp [1] at optimum performance and the other close to stall conditions. In addition to a classical mixing plane approach, a frozen rotor solution has been considered as a first-order approach to the unsteady flow to study the effect of rotor wakes on the diffuser flow field. The predicted diffuser performance was strongly influenced by the rotor wakes, and their effect could only be obtained by an approximate frozen-rotor calculation. The results for the computed specific work and pressure recovery for both configurations showed an optimum distance of a/cR = 0.431 between rotor exit and diffuser inlet. Increase of radial rotor clearance gap has a beneficial effect on the diffuser characteristic for the built near the stall point. However, the larger tip leakage loss of the turbine rotor cannot be compensated by improved diffuser performance.

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The Tip Leakage Flow of an Unshrouded High Pressure Turbine Blade With Tip Cooling

Volume 7: Turbomachinery, Parts A and B ◽

10.1115/gt2009-59637 ◽

2009 ◽

Cited By ~ 7

Author(s):

Chao Zhou ◽

Howard Hodson

Keyword(s):

Mass Flow ◽

Suction Side ◽

Aerodynamic Performance ◽

Flow Ratio ◽

Tip Leakage Flow ◽

Momentum Exchange ◽

Leakage Loss ◽

Tip Leakage ◽

Lower Loss ◽

Mass Flow Ratio

Experimental, analytical and numerical methods have been employed to study the aerodynamic performance of four different cooled tips with coolant mass ratios between zero and 1.2% at three tip gaps of 1%, 1.6% and 2.2% of the chord. The four cooled tips are two flat tips with different coolant holes, a cooled suction side squealer tip and a cooled cavity tip. Each tip has ten coolant holes with the same diameter. The uncooled cavity tip produces the smallest loss among all uncooled tips. On the cooled flat tip, the coolant is injected normally into the tip gap and mixes directly with flow inside the tip gap. The momentum exchange between the coolant and the flow that enters the tip gap creates significant blockage. As the coolant mass flow ratio increases, the tip leakage loss of the cooled flat tip first decreases and then increases. For the cooled cavity tip, the blockage effect of the coolant is not as big as that on the cooled flat tip. This is because after the coolant exits the coolant holes, it mixes with flow in the cavity first, and then mixes with tip flow in the tip gap. The tip leakage loss of the cooled cavity tip increases as the coolant mass flow ratio increase. As a result, at a tip gap of 1.6% of the chord, the cooled cavity tip gives the lowest loss. At the smallest tip gap of 1% of the chord, the cooled flat tip produces less loss than the cooled cavity tip when the coolant mass flow ratios larger than 0.23%. This is because with the same coolant mass flow ratio, a proportionally larger blockage is created at the smallest tip gap. At the largest tip gap of 2.2% of the chord, the cavity tip achieves the best aerodynamic performance. This is because, the effect of the coolant is reduced and the benefits of the cavity tip geometry dominate. At a coolant mass flow ratio of 0.55%, the cooled flat tips produce a lower loss than the cavity tip at tip gaps less than 1.3% of the chord. The cooled cavity tip produces the least loss for tip gaps larger than 1.3% of the chord. The cooled suction side squealer has the worst aerodynamic performance for all tip gaps studied.

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Aerothermal Investigation of Tip Leakage Flow in a Film Cooled Industrial Turbine Rotor

Journal of Turbomachinery ◽

10.1115/1.3144164 ◽

2010 ◽

Vol 132 (2) ◽

Cited By ~ 4

Author(s):

S. K. Krishnababu ◽

H. P. Hodson ◽

G. D. Booth ◽

G. D. Lock ◽

W. N. Dawes

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Mass Flow ◽

Turbine Rotor ◽

Total Heat ◽

Leakage Flow ◽

Total Heat Flux ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Flow And Heat Transfer

A numerical investigation of the flow and heat transfer characteristics of tip leakage in a typical film cooled industrial gas turbine rotor is presented in this paper. The computations were performed on a rotating domain of a single blade with a clearance gap of 1.28% chord in an engine environment. This standard blade featured two coolant and two dust holes, in a cavity-type tip with a central rib. The computations were performed using CFX 5.6, which was validated for similar flow situations by Krishnababu et al. (2007, “Aero-Thermal Investigation of Tip Leakage Flow in Axial Flow Turbines: Part I—Effect of Tip Geometry,” ASME Paper No. 2007-GT-27954). These predictions were further verified by comparing the flow and heat transfer characteristics computed in the absence of coolant ejection with computations previously performed in the company (SIEMENS) using standard in-house codes. Turbulence was modeled using the shear-stress transport (SST) k-ω turbulence model. The comparison of calculations performed with and without coolant ejection has shown that the coolant flow partially blocks the tip gap, resulting in a reduction in the amount of mainstream leakage flow. The calculations identified that the main detrimental heat transfer issues were caused by impingement of the hot leakage flow onto the tip. Hence three different modifications (referred as Cases 1–3) were made to the standard blade tip in an attempt to reduce the tip gap exit mass flow and the associated impingement heat transfer. The improvements and limitations of the modified geometries, in terms of tip gap exit mass flow, total area of the tip affected by the hot flow and the total heat flux to the tip, are discussed. The main feature of the Case 1 geometry is the removal of the rib, and this modification was found to effectively reduce both the total area affected by the hot leakage flow and total heat flux to the tip, while maintaining the same leakage mass flow as the standard blade. Case 2 featured a rearrangement of the dust holes in the tip, which, in terms of aerothermal dynamics, proved to be marginally inferior to Case 1. Case 3, which essentially created a suction-side squealer geometry, was found to be inferior even to the standard cavity-tip blade. It was also found that the hot spots, which occur in the leading edge region of the standard tip, and all modifications contributed significantly to the area affected by the hot tip leakage flow and the total heat flux.

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Modelling of Humidity Dynamics for Open-Cathode Proton Exchange Membrane Fuel Cell

World Electric Vehicle Journal ◽

10.3390/wevj12030106 ◽

2021 ◽

Vol 12 (3) ◽

pp. 106

Author(s):

Fengxiang Chen ◽

Liming Zhang ◽

Jieran Jiao

Keyword(s):

Fuel Cell ◽

Mass Flow ◽

Proton Exchange Membrane ◽

Flow Model ◽

Transport Theory ◽

Gas Diffusion ◽

Proton Exchange ◽

Operating Conditions ◽

Output Performance ◽

Exchange Membrane

The durability and output performance of a fuel cell is highly influenced by the internal humidity, while in most developed models of open-cathode proton exchange membrane fuel cells (OC-PEMFC) the internal water content is viewed as a fixed value. Based on mass and energy conservation law, mass transport theory and electrochemistry principles, the model of humidity dynamics for OC-PEMFC is established in Simulink® environment, including the electrochemical model, mass flow model and thermal model. In the mass flow model, the water retention property and oxygen transfer characteristics of the gas diffusion layer is modelled. The simulation indicates that the internal humidity of OC-PEMFC varies with stack temperature and operating conditions, which has a significant influence on stack efficiency and output performance. In order to maintain a good internal humidity state during operation, this model can be used to determine the optimal stack temperature and for the design of a proper control strategy.

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The Aerothermal Performance of a Cooled Winglet Tip in a High Pressure Turbine Cascade

Journal of Turbomachinery ◽

10.1115/1.4006611 ◽

2013 ◽

Vol 135 (3) ◽

Cited By ~ 10

Author(s):

Chao Zhou ◽

Howard Hodson ◽

Ian Tibbott ◽

Mark Stokes

Keyword(s):

Mass Flow ◽

Heat Load ◽

Blade Surface ◽

Flow Ratio ◽

Turbine Cascade ◽

Tip Leakage Flow ◽

High Pressure Turbine ◽

Cooling Effectiveness ◽

Tip Leakage ◽

Coolant Injection

The aerothermal performance of a winglet tip with cooling holes on the tip and on the blade surface near the tip is reported in this paper. The investigation was based on a high pressure turbine cascade. Experimental and numerical methods were used. The effects of the coolant mass flow rate are also studied. Because the coolant injection partially blocks the tip leakage flow, more passage flow is turned by the blade. As a result, the coolant injection on the winglet tip reduces the deviation of the flow downstream of the cascade due to the tip leakage flow. However, the tip leakage loss increases slightly with the coolant mass flow ratio. Both the computational fluid dynamics tools and experiments using the Amonia–Diazo technique were used to determine the cooling effectiveness. On the blade pressure side surface, low cooling effectiveness appears around the holes due to the lack of the coolant from the cooling hole or the lift-off of the coolant from the blade surface when the coolant mass flow is high. The cooling effectiveness on the winglet tip is a combined effect of the coolant ejected from all the holes. On the top of the winglet tip, the average cooling effectiveness increases and the heat load decreases with increasing coolant mass flow. Due to its large area, the cooled winglet tip has a higher heat load than an uncooled flat tip at engine representative coolant mass flow ratio. Nevertheless, the heat flux rate per unit area of the winglet is much lower than that of an uncooled flat tip. The cycle analysis is carried out and the effects of relative tip-to-casing endwall motion are address.

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Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

Volume 2A: Turbomachinery ◽

10.1115/gt2017-64705 ◽

2017 ◽

Cited By ~ 1

Author(s):

Brian M. T. Tang ◽

Marko Bacic ◽

Peter T. Ireland

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Total Pressure ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Turbine Efficiency ◽

Coolant Injection ◽

Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

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Numerical Simulation of Tip Clearance Control in Axial Turbine Rotor: Part 2—Passive Control of Five Different Tip Platforms

Volume 6: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2008-50085 ◽

2008 ◽

Author(s):

Wei Li ◽

Wei-Yang Qiao ◽

Kai-Fu Xu ◽

Hua-Ling Luo

Keyword(s):

Flow Control ◽

Passive Control ◽

Suction Side ◽

Turbine Rotor ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Clearance Flow ◽

Tip Leakage ◽

Clearance Flow

The tip leakage flow has significant effects on turbine in loss production, aerodynamic efficiency, etc. Then it’s important to minimize these effects for a better performance by adopting corresponding flow control. The active turbine tip clearance flow control with injection from the tip platform is given in Part-1 of this paper. This paper is Part-2 of the two-part papers focusing on the effect of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip (Partial SS Squealer), a double squealer tip (Double Side Squealer), a pressure side tip shelf with inclined squealer tip on a double squealer tip (Improved PS Squealer), a tip platform extension edge in pressure side (PS Extension) and in suction side (SS Extension) respectively. Combined with the turbine rotor and the numerical method mentioned in Part 1, the effects of passive turbine tip clearance flow controls on the tip clearance flow were sequentially simulated. The detailed tip clearance flow fields with different squealer rims were described with the streamline and the velocity vector in various planes parallel to the tip platform or normal to the tip leakage vortex core. Accordingly, the mechanisms of five passive controls were put in evidence; the effects of the passive controls on the turbine efficiency and the tip clearance flow field were highlighted. The results show that the secondary flow loss near the outer casing including the tip leakage flow and the casing boundary layer can be reduced in all the five passive control methods. Comparing the active control with the passive control, the effect brought by the active injection control on the tip leakage flow is evident. The turbine rotor efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine rotor efficiency, and it increased by 0.215%.

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Development of a Scaled Rotor Blade for Tank Tests of Floating Wind Turbine Systems

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2018-77156 ◽

2018 ◽

Cited By ~ 1

Author(s):

Paul Schünemann ◽

Timo Zwisele ◽

Frank Adam ◽

Uwe Ritschel

Keyword(s):

Wind Turbine ◽

Rotor Blade ◽

Turbine Rotor ◽

Full Scale ◽

Power Coefficient ◽

Speed Ratio ◽

Model Scale ◽

Floating Wind Turbine ◽

Hydrodynamic Effects ◽

Wind Turbine Rotor

Floating wind turbine systems will play an important role for a sustainable energy supply in the future. The dynamic behavior of such systems is governed by strong couplings of aerodynamic, structural mechanic and hydrodynamic effects. To examine these effects scaled tank tests are an inevitable part of the design process of floating wind turbine systems. Normally Froude scaling is used in tank tests. However, using Froude scaling also for the wind turbine rotor will lead to wrong aerodynamic loads compared to the full-scale turbine. Therefore the paper provides a detailed description of designing a modified scaled rotor blade mitigating this problem. Thereby a focus is set on preserving the tip speed ratio of the full scale turbine, keeping the thrust force behavior of the full scale rotor also in model scale and additionally maintaining the power coefficient between full scale and model scale. This is achieved by completely redesigning the original blade using a different airfoil. All steps of this redesign process are explained using the example of the generic DOWEC 6MW wind turbine. Calculations of aerodynamic coefficients are done with the software tools XFoil and AirfoilPrep and the resulting thrust and power coefficients are obtained by running several simulations with the software AeroDyn.

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