Effects of Endwall Motion on the Aero-Thermal Performance of a Winglet Tip in a HP Turbine

2011 ◽  
Author(s):  
Chao Zhou ◽  
Howard Hodson ◽  
Ian Tibbott ◽  
Mark Stokes
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Mass Flow ◽  
Thermal Performance ◽  
Film Cooling ◽  
Suction Side ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Tip Leakage ◽  
Mass Flow Ratio

In a gas turbine, the casing endwall moves relative to the blades. In this paper, numerical methods are first validated using experimental results for a stationary endwall. They are then used to study the effects of endwall motion on the aero-thermal performance of both winglet tips with and without tip film cooling at a tip gap of 1.9%C. The endwall motion imposes a tangential force on the flow. A scraping vortex is formed and the flow pattern within the tip gap, changes significantly. The tip leakage mass flow rate that exits the tip gap from the suction side edge reduces by about 42% with endwall motion. Overall, the endwall motion reduces the tip leakage loss by 15%. The flow field downstream of the cascade also changes with endwall motion. With endwall motion, the changed flow pattern within the tip gap significantly changes the distribution of the Nusselt number on the winglet tip. For the winglet tip without tip film cooling, the Nusselt number and the heat load decrease with endwall motion. This is mainly due to the reduction in the tip leakage mass flow ratio, which reduces the leakage velocity over the tip. On the winglet tip with tip film cooling, the cooling effectiveness increases by 9% with endwall motion. Combined with the reduced Nusselt number, the heat flux on the winglet tip with tip film cooling reduces by 31% with endwall motion. The cooling effectiveness on the near tip region of the pressure side remains almost unchanged, but the heat flux rate in this area reduces. This is because the reduced tip leakage mass flow ratio reduces the Nusselt number. With the moving endwall, the thermal performance of the suction side surface of the blade is affected by the scraping vortex. The effects of endwall motion should be considered during the design of the blade tip.

Effects of Endwall Motion on the Aero-Thermal Performance of a Winglet Tip in a HP Turbine

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Chao Zhou ◽  
Howard Hodson ◽  
Ian Tibbott ◽  
Mark Stokes
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Mass Flow ◽  
Thermal Performance ◽  
Film Cooling ◽  
Suction Side ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Tip Leakage ◽  
Mass Flow Ratio

In a gas turbine, the casing endwall moves relative to the blades. In this paper, numerical methods are first validated using experimental results for a stationary endwall. They are then used to study the effects of endwall motion on the aero-thermal performance of both winglet tips with and without tip film cooling at a tip gap of 1.9% C. The endwall motion imposes a tangential force on the flow. A scraping vortex is formed and the flow pattern within the tip gap changes significantly. The tip leakage mass flow rate that exits the tip gap from the suction side edge reduces by about 42% with endwall motion. Overall, the endwall motion reduces the tip leakage loss by 15%. The flow field downstream of the cascade also changes with endwall motion. With endwall motion, the changed flow pattern within the tip gap significantly changes the distribution of the Nusselt number on the winglet tip. For the winglet tip without tip film cooling, the Nusselt number and the heat load decrease with endwall motion. This is mainly due to the reduction in the tip leakage mass flow ratio, which reduces the leakage velocity over the tip. On the winglet tip with tip film cooling, the cooling effectiveness increases by 9% with endwall motion. Combined with the reduced Nusselt number, the heat flux on the winglet tip with tip film cooling reduces by 31% with endwall motion. The cooling effectiveness on the near tip region of the pressure side remains almost unchanged, however, the heat flux rate in this area reduces. This is because the reduced tip leakage mass flow ratio reduces the Nusselt number. With the moving endwall, the thermal performance of the suction side surface of the blade is affected by the scraping vortex. The effects of endwall motion should be considered during the design of the blade tip.

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

2011 ◽  
Vol 133 (4) ◽  
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.

Numerical Investigation of the Effect of Inlet Flow Angle on Film Cooling Performance for the Blade Tip With Suction Surface Squealer Rim

2019 ◽  
Author(s):  
Zhiqiang Yu ◽  
Jianjun Liu ◽  
Chen Li ◽  
Baitao An
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Incidence Angle ◽  
Leading Edge ◽  
Flow Ratio ◽  
Suction Surface ◽  
Cooling Performance ◽  
Tip Leakage ◽  
Pressure Surface ◽  
Mass Flow Ratio

Abstract Numerical investigations have been performed to study the effect of incidence angle on the aerodynamic and film cooling performance for the suction surface squealer tip with different film-hole arrangements at τ = 1.5% and BR = 1.0. Meanwhile, the full squealer tip as baseline is also investigated. Three incidence angles at design condition (0 deg) and off-design conditions (± 7 deg) are investigated. The suction surface, pressure surface, and the camber line have seven holes each, with an extra hole right at the leading edge. The Mach number at the cascade inlet and outlet are 0.24 and 0.52, respectively. The results show that the incidence angle has a significant effect on the tip leakage flow characteristics and coolant flow direction. The film cooling effectiveness distribution is altered, especially for the film holes near the leading edge. When the incidence angle changes from +7 deg to 0 and −7 deg, the ‘re-attachment line’ moves downstream and the total tip leakage mass flow ratio decreases, but the suction surface tip leakage mass flow ratio near leading edge increases. In general, the total tip leakage mass flow ratio for suction surface squealer tip is 1% greater than that for full squealer tip at the same incidence angle. The total pressure loss coefficient of suction surface squealer tip is larger than that for full squealer tip. The full squealer tip with film holes near suction surface and the suction surface squealer tip with film hole along camber line show high film cooling performance, and the area averaged film cooling effectiveness at positive incidence angle +7 deg is higher than that at 0 and −7 deg. The coolant discharged from film holes near pressure surface only cools narrow region near pressure surface.

Film Cooling Effectiveness Enhancement Using Multi-Longitudinal Vortex Generated by Alternating Elliptical Film Holes

2021 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Major Axis ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Longitudinal Vortices ◽  
Pressure Loss Coefficient ◽  
Total Pressure Loss Coefficient ◽  
Mass Flow Ratio

Abstract This paper proposed an alternating elliptical film hole for gas turbine blade to restrain kidney vortex and enhance film cooling effectiveness, based on the multi-longitudinal vortexes generated in alternating elliptical tube. The detailed flow structures in film hole delivering tube and out of the film hole, adiabatic film cooling effectiveness distributions as well as the total pressure loss coefficient were investigated. The delivering tube of alternating elliptical film hole consists of two straight sections and a transition section. In the straight sections, the cross section of the film hole is elliptical, and in the transition section, along flow direction, the major axis gradually shortened into the minor axis, and the minor axis gradually expanded to the major axis. But, the cross-section area of the film hole kept constant. Numerical simulations were performed by using 3D steady flow solver of Reynolds-averaged Navier-Stokes equations (RANS) with the SST k-ω turbulence model. To reveal the mechanism of kidney vortex suppression and film cooling effectiveness enhancement, the simulation results were compared with the cylindrical film hole set as the baseline at different mass flow ratios (MFR). Besides, the aerodynamic characteristics of these two kinds of film holes were also investigated. The results showed that obvious jet effect could be found in the cylindrical film hole, and the coolant mainly flowed along the upper wind wall, then interacted with the main flow, forming a strong kidney vortex after flowing out, which made the coolant to lift away from the wall surface and reduced the cooling effectiveness. The alternating elliptical film hole had a good inhibition impact on the jet effect in the hole due to the longitudinal vortices, which made the film adhere to the wall surface better after the coolant flowed out. The longitudinal vortices generated by alternating elliptical film hole have the opposite rotation direction to the vorticity of the kidney vortices, thus the kidney vortices were restrained to a certain extent. The height of kidney vortices is lower, and the size of kidney vortices is also smaller. As a result, the film cooling effectiveness of alternating elliptical film hole is distinctly higher than that of the cylindrical film hole, and the enhancement effect is more significant at higher mass flow ratio. In addition, the total pressure loss coefficient of alternating elliptical film hole is only slightly higher than the cylindrical film hole at the mass flow ratio of 1%, 2% and 3%, and is even lower at the mass flow ratio of 4%, thus inducing an excellent comprehensive performance.

Experimental Study on the Effects of Slot Jet on Film Cooling Performance in the Cascade Endwall With Purge Flow

2019 ◽  
Author(s):  
Yao Yunjia ◽  
Zhu Peiyuan ◽  
Tao Zhi ◽  
Song Liming ◽  
Li Jun
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Ejection Angle ◽  
Purge Flow ◽  
Endwall Film Cooling ◽  
Mass Flow Ratio

Abstract Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE‘s E3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15Cx to 0.45Cx, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90°, the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR) = 1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR = 1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.

An Experimental Investigation of Full-Coverage Film Cooling Characteristics of a Turbine Guide Vane

2018 ◽  
Author(s):  
Jin Wu ◽  
Li Zhang ◽  
Li-jian Cheng ◽  
Ru Jiang ◽  
Zhong-yi Fu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mass Flow ◽  
Film Cooling ◽  
Leading Edge ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Pressure Surface ◽  
Film Cooling Holes ◽  
Mass Flow Ratio

This paper researches on the effects of Reynolds number and mass flow ratio on the film cooling characteristics at high turbulence intensity (Tu = 15%). The experiment adopted an actual three-dimensional twisted vane and presents the film cooling characteristics on full-coverage film surface in a two-passage, linear cascade. The cooling effectiveness and heat transfer coefficient of the vane’s whole surface were obtained by using transient liquid crystal measurement technique. The transient liquid crystal is SPN/R35C1W, whose bandwidth is 2°C. There are fifteen rows of film cooling holes which have different diameter, injection angle and yaw angle. The secondary flow was supplied by two cavities. The front cavity supplied the secondary flow to thirteen rows of film cooling holes that were arranged in the suction surface, the leading edge and the front half of the pressure surface. The rear cavity supplied the secondary flow to the rear half of pressure surface which included two rows of film cooling holes. The investigated parameters are Reynolds number of 1 × 105, 1.3 × 105 and 1.6 × 105 and the mass flow ratio of MFR = 5.5%∼12.5% (6 cases). The data recorded in the experiment was analyzed with MATLAB. Results show that the combined effects of mass flow ratio and channel vortex are the maintain reasons that influence the distribution of cooling effectiveness in the contour. Increasing the mass flow ratio can improve the film cooling effectiveness on leading edge and pressure surface, while that presents complex rule on suction surface. Increasing the Reynolds number can improve the heat transfer coefficient at the same mass flow ratio. When increasing the mass flow ratio, the heat transfer coefficient increases on leading edge and pressure surface at Re = 1.6 × 105. However, the decreases at film hole outlet region on the suction side, and not obviously changes at the film hole downstream region.

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

2009 ◽  
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.

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

2013 ◽  
Vol 135 (3) ◽  
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.

scholarly journals Leading Edge Film Cooling Effects on Turbine Blade Heat Transfer

1995 ◽  
Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Film Cooling ◽  
Three Dimensional ◽  
Stagnation Temperature ◽  
Flow Ratio ◽  
Adiabatic Effectiveness ◽  
Mass Flow Ratio

An existing three-dimensional Navier-Stokes code (Arnone et al., 1991), modified to include film cooling considerations (Garg and Gaugler, 1994), has been used to study the effect of spanwise pitch of shower-head holes and coolant to mainstream mass flow ratio on the adiabatic effectiveness and heat transfer coefficient on a film-cooled turbine vane. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. It is found that with the coolant to mainstream mass flow ratio fixed, reducing P, the spanwise pitch for shower-head holes, from 7.5 d to 3.0 d, where d is the hole diameter, increases the average effectiveness considerably over the blade surface. However, when P/d = 7.5, increasing the coolant mass flow increases the effectiveness on the pressure surface but reduces it on the suction surface due to coolant jet lift-off. For P/d = 4.5 or 3.0, such an anomaly does not occur within the range of coolant to mainstream mass flow ratios analyzed. In all cases, adiabatic effectiveness and heat transfer coefficient are highly three-dimensional.

Experimental Study on Comparison of Cooling Effectiveness Between Steam and Air for a Gas Turbine Nozzle Guide Vane

2012 ◽  
Author(s):  
Wei Wang ◽  
Jianmin Gao ◽  
Xiaojun Shi ◽  
Liang Xu ◽  
Zhao Wang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Guide Vane ◽  
Flow Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Cooling Method ◽  
Nozzle Guide ◽  
Mass Flow Ratio

An experimental investigation of the cooling performance for a gas turbine vane with internal passages is conducted on a linear turbine cascade consisting of three nozzle guide vanes with a chord length of 126mm and a blade height of 83 mm. Measurements of temperature and static pressure distribution are implemented on the center guide vane, which is internally cooled by air or steam flowing radially through five smooth channels. The main objective of this investigation is to receive more information on the temperature of vane surface, and to compare the cooling effectiveness between air and superheated steam. The experiments are performed for a variety of exit Mach numbers, exit Reynolds number, coolant-to-mainstream mass flow ratio, and coolant-to-mainstream temperatures ratio. The experimental results show, that at coolant-to-mainstream mass flow ratio 0.08 and coolant-to-mainstream temperatures ratio 0.61, the average surface temperature of steam cooled vane decreases about 25% and the corresponding average cooling effectiveness is 52%, while for the air cooled vane, it is 18% and 42%, respectively. Therefore the coolant steam has much better cooling performance than air. Furthermore, the cooling effectiveness at the middle chord region of vane is much higher than that at the leading and trailing region, as is expected. Consequently, this leads to great temperature gradient and thermal stresses at the leading and trailing region, where the internal convective cooling method has insufficient cooling ability. Therefore, besides convective cooling method, more complicated cooling configuration may be necessitated.

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