Simulation of Air/Mist Cooling Among Shock Waves and Passing Wakes Interactions in a Transonic Gas Turbine Stage

2021 ◽  
Author(s):  
Ting Wang ◽  
Ramy Abdelmaksoud
Keyword(s):  
Shock Waves ◽  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Water Droplets ◽  
Discrete Phase Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Enhancement ◽  
Mist Cooling

Abstract This paper presents a 2-D numerical investigation of the effect of interactions of moving wakes and shock waves on mist cooling performance over airfoils in the first stator-rotor stage of a transonic gas turbine. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. Breakup and coalescence sub-models are used to simulate the interaction between the droplets themselves. A linear sliding mesh technique is used to study the transient stator-rotor interaction. The results show that the passing unsteady wakes caused by the blade rotation press the mist on the blade suction side flowing near the blade surface, providing more enhanced film cooling effectiveness. The weak oblique shock waves do not exert a significant effect on the air/mist cooling effectiveness. Injecting a 10% mist ratio noticeably improved the cooling enhancement by reducing the wall temperature values up to 200 K in some locations. Injecting the tiny water droplets does not cause a noticeable pressure loss compared to the air-only cooling case. Injecting mist doesn’t alter the effect of shocks.

scholarly journals Computational Analysis of Surface Curvature Effect on Mist Film-Cooling Performance

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Leading Edge ◽  
Operating Conditions ◽  
Curved Surfaces ◽  
Curvature Effect ◽  
Water Droplets ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Air Film

Air-film cooling has been widely employed to cool gas turbine hot components, such as combustor liners, combustor transition pieces, turbine vanes, and blades. Studies with flat surfaces show that significant enhancement of air-film cooling can be achieved by injecting water droplets with diameters of 5–10 μm into the coolant airflow. The mist/air-film cooling on curved surfaces needs to be studied further. Numerical simulation is adopted to investigate the curvature effect on mist/air-film cooling, specifically the film cooling near the leading edge and on the curved surfaces. Water droplets are injected as dispersed phase into the coolant air and thus exchange mass, momentum, and energy with the airflow. Simulations are conducted for both 2D and 3D settings at low laboratory and high operating conditions. With a nominal blowing ratio of 1.33, air-only adiabatic film-cooling effectiveness on the curved surface is lower than on a flat surface. The concave (pressure) surface has a better cooling effectiveness than the convex (suction) surface, and the leading-edge film cooling has the lowest performance due to the main flow impinging against the coolant injection. By adding 2% (weight) mist, film-cooling effectiveness can be enhanced approximately 40% at the leading edge, 60% on the concave surface, and 30% on the convex surface. The leading edge film cooling can be significantly affected by changing of the incident angle due to startup or part-load operation. The film cooling coverage could switch from the suction side to the pressure side and leave the surface of the other part unprotected by the cooling film. Under real gas turbine operating conditions at high temperature, pressure, and velocity, mist-cooling enhancement could reach up to 20% and provide a wall cooling of approximately 180 K.

scholarly journals Computational Analysis of Surface Curvature Effect on Mist Film Cooling Performance

2007 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Convex Surface ◽  
Leading Edge ◽  
Operating Conditions ◽  
Curvature Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Enhancement ◽  
Air Film

Air film cooling has been widely employed to cool gas turbine hot components such as combustor liners, combustor transition pieces, turbine vanes and blades. Enhancing air film cooling by injecting mist with tiny water droplets with diameters of 5–10μm has been studied in the past on flat surfaces. This paper focuses on computationally investigating the curvature effect on mist/air film cooling enhancement, specifically for film cooling near the leading edge and on the curved surfaces. Numerical simulations are conducted for both 2-D and 3-D settings at low and high operating conditions. The results show, with a nominal blowing ratio of 1.33, air-only adiabatic film cooling effectiveness on the curved surface is less than on a flat surface. The concave (pressure) surface has a better cooling effectiveness than the convex (suction) surface, and the leading edge film cooling has the lowest performance due to main flow impinging against the coolant injection. By adding 2% (weight) mist, film cooling effectiveness can be enhanced approximately 40% at the leading edge, 60% on the concave surface, and 30% on the convex surface. The leading edge film cooling can be significantly affected by changing of the incident angle due to startup or part-load operation. The film cooling coverage could switch from the suction side to the pressure side and leave the surface of the other part unprotected by the cooling film. Under real gas turbine operating conditions at high temperature, pressure, and velocity, mist cooling enhancement could achieve 20% and provides a wall cooling of approximately 180K.

Simulation of Mist Film Cooling on Rotating Gas Turbine Blades

2009 ◽  
Author(s):  
T. S. Dhanasekaran ◽  
Ting Wang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Single Pair ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Cooling Enhancement ◽  
Mist Cooling

Film cooling technique has been successfully applied to gas turbine blades to prevent it from the hot flue gas. However, a continuous demand of increasing the turbine inlet temperature to raise the efficiency of the turbine requires continuous improvement in film cooling effectiveness. The concept of injecting mist (tiny water droplets) into the cooling fluid has been proven under laboratory conditions to significantly augment adiabatic cooling effectiveness 50–800% in convective heat transfer and impingement cooling. The similar concept of ejecting mist into air film cooling has not been proven in the laboratory, but computational simulation has been performed on stationary turbine blades. As a continuation of previous research, this paper extends the mist film cooling scheme to the rotating turbine blade. For the convenience of understanding the effect of rotation, the simulation is first conducted with a single pair of cooling hole located near the leading edge at either side of the blade. Then a row of multiple-hole film cooling jets are simulated at stationary and rotational condition. Operating condition under both the laboratory (baseline) and elevated gas turbine conditions are simulated and compared. The effects of various parameters including mist concentration, water droplet diameter, droplet wall boundary condition, blowing ratio, and rotational speed are investigated. The results showed the effect of rotation on droplets at lab condition is minimal. The CFD model employed the Discrete Phase Model (DPM) including both wall film and droplet reflect conditions. The results showed that the droplet-wall interaction is stronger on the pressure side than on the suction side resulting in a higher mist cooling enhancement on the pressure side. The average mist cooling enhancement of about 15% and 35% are achieved on the laboratory and elevated conditions, respectively. This translates into a significant blade surface temperature reduction of 100–125 K with 10% mist injection at elevated condition.

Experimental Investigations of SYCEE Film Cooling Performance on a Plate and a Tested Vane of an F-Class Gas Turbine

2014 ◽  
Author(s):  
Chang Han ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Round Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive ◽  
Cooling Technology ◽  
Compound Angle

Film cooling is widely used in modern gas turbines for the protection of the hot components against hot gases from the combustion process. Film cooling directly influences the thermal efficiency of the gas turbine, as the cooling gas is extracted from the compressor and mixed with the mainstream in the hot component. Huge efforts by industry as well as research organizations have been undertaken to improve the film cooling effectiveness. It can been concluded that there are two key points for the improvement of film cooling effectiveness, constraining the blow-off of cooling ejection and extending the lateral coverage of cooling gas. The paper presents a new cooling technology, which reaches high film-cooling effectiveness as a result of a well-designed cooling hole, named SYCEE film cooling technology (SFCT). Plate film cooling experiments of SYCEE tested by pressure sensitive paint (PSP) are carried out in this work, and traditional shape-hole are included as well for baselines. It is resulted that SFCT has a better film cooling performance than shape-hole in the same conditions, and the gap of the averaged film cooling effectiveness between them continuously enlarges as the blowing ratio increases. Furthermore, an application of SFCT on the first stage vane of an F-class gas turbine is studied as well. A two-dimension cascade has been employed to measure the cooling performance of SFCT using pressure sensitive paint (PSP) as well, and the tested vanes separately with round-hole and shape-hole are considered again for baselines. The different kinds of film holes separately locate on the pressure and suction side, while the showerhead in different cases are kept the same, arranged with round-holes. The cooling air is ejected at inclination angle 45° with compound-angle 90° in the showerhead and inclination angle 35°∼45° without compound-angle on the pressure side and suction side. The detailed local cooling effectiveness distributions as well as the span-averaged effectiveness over the vane surface are presented. As expected, the film cooling performance of round-hole is the worst due to the lift-off of the cooling ejection. SFCT has better film cooling performance than shape-hole on the pressure side, but the advantage decreases along the mainstream direction. However, the span-averaged film cooling effectiveness of SYCEE is similar with that of the shape-hole on the suction side. This may be due to enhanced impact of mainstream flow derived from the pressure gradient in the turbine passage, and consequently weakening the effect of film hole on the suction side.

Computational Study of Mist Assisted Film Cooling on a Flat Plate

2019 ◽  
Author(s):  
Mallikarjuna Rao Pabbi Setty ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Computational Study ◽  
Operating Conditions ◽  
Main Stream ◽  
Air Cooling ◽  
Water Droplets ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Air

Abstract Previous investigation [1, 2] proposed that an introduction of water droplets into the film cooling air significantly improves the effectiveness of gas turbine blade. In order to allow comparison with experimental data, all the previous studies were confined to laboratory conditions. However, under typical gas turbine operating conditions temperature difference between the main stream flow (1561 K) and the coolant air (644 K) is approximately 917 K. The aim of this study is to numerically investigate the performance of mist assisted film cooling under the typical operating conditions of the gas turbine. Results showed the value of mist assisted film cooling effectiveness are greater than pure air cooling. Trajectories of droplets show that the water droplets vaporize faster. Typical percentage enhancement of the mist assisted film cooling effectiveness is 16% when the cooling air contains 6% mist with droplet diameter of one micron.

Measurement of Film Cooling Effectiveness for the First-Stage Vane and Endwall of a Gas Turbine With Fan-Shaped Holes

2017 ◽  
Author(s):  
Jin Young Jeong ◽  
Jae Su Kwak ◽  
Jung Shin Park ◽  
Kidon Lee
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Sulfur Hexafluoride ◽  
Surface Film ◽  
Density Ratio ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Density Ratios

The adiabatic film cooling effectiveness for the first-stage vane and endwall of a gas turbine were investigated in a low speed cascade using the pressure sensitive paint (PSP) technique. The cascade consisted of four linear vanes. The tested Reynolds number based on the vane chord and vane exit velocity was 7.15 × 105. The overall blowing ratio of the coolant was controlled between 1 to 2, and two density ratios, 1.5 and 2.0, were tested. In order to test the different density ratios, two different coolants were used, one carbon dioxide and the other a mixture of nitrogen and sulfur hexafluoride. All cases showed clear traces of coolant on the vane surfaces and the endwall. The film cooling effectiveness near the film cooling holes was very high and gradually decreased downstream. The coolant trace showed an almost two-dimensional distribution on the pressure side. However, the coolant on the suction side shifted mid-span due to the passage vortex. Generally, the film cooling effectiveness on the vane and the endwall increased as the blowing ratio increased. The film cooling effectiveness on the vane was strongly affected by the shower head injection. Depending on the blowing ratio, the effect of density ratio on the vane surface film cooling effectiveness was varied. On the endwall, the film cooling effectiveness was higher for higher density ratio cases.

scholarly journals Film Cooling Effectiveness in the Showerhead Region of a Gas Turbine Vane: Part II — Stagnation Region and Near-Suction Side

1999 ◽  
Author(s):  
Virginia C. Witteveld ◽  
Marc D. Polanka ◽  
David G. Bogard
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Line Position ◽  
Stagnation Region ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Turbine Vane

An experimental study was conducted to determine the effects of film cooling on a gas turbine vane at two mainstream turbulence intensities of Tu = 0.5% and Tu = 22%. The low speed turbine vane test facility was designed to match the Reynolds number of operating engine conditions. The nine-time scale model airfoil simulates a gas turbine first-stage stator vane. The leading edge film cooling hole showerhead array included six rows of film cooling holes configured with one stagnation row, two pressure side rows, and three suction side rows. This paper presents film cooling effectiveness measurements in the stagnation region and near-suction side. Cooled air injection was used to conduct the tests at a density ratio of DR = 1.8 and blowing conditions over a range of M = 0.5 to M = 2.9. Infrared imaging techniques were used to measure the surface temperature distribution. The results provide a detailed evaluation of the effects of blowing ratio, mainstream turbulence, and stagnation line position on the measured effectiveness in the showerhead. The effect of increasing blowing ratio generally resulted in increased spanwise averaged effectiveness levels. The effect of mainstream turbulence varies with blowing ratio within the showerhead region. At low blowing ratio, high turbulence produced greater effectiveness, whereas at high blowing ratio, low turbulence produced greater effectiveness. The effect of stagnation line position also varied with blowing ratio. Overall, the dominating effect occurred when the blowing ratio was sufficiently strong to cause a spanwise merging of adjacent cooling jets resulting in very good spanwise uniformity and high adiabatic effectiveness.

Experimental Investigation of Louver Cooling Scheme on Gas Turbine Vane Suction Side

2011 ◽  
Author(s):  
T. Elnady ◽  
O. Hassan ◽  
I. Hassan ◽  
L. Kadem ◽  
T. Lucas
Keyword(s):  
Experimental Investigation ◽  
Gas Turbine ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Thermochromic Liquid Crystal ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes

An experimental investigation has been performed to measure the film cooling performance of louver scheme over a scaled vane of high-pressure gas turbine using a two-dimensional cascade. Two rows of axially oriented louver scheme are used to cool the suction side and their performance is compared with two similar rows of standard cylindrical holes. The effect of hole location on the cooling performance is investigated for each row individually, then the row interaction is investigated for both rows at four different blowing ratios ranging from 1 to 2 with a 0.9 density ratio. The exit Reynolds number based on the true chord is 1.5E5 and exit Mach number is 0.23. The temperature distribution on the vane is mapped using a transient Thermochromic Liquid Crystal (TLC) technique to obtain the local distributions of the heat transfer coefficient and film cooling effectiveness. The louver scheme shows a superior cooling effectiveness than that of the cylindrical holes at all blowing ratios in terms of protection and lateral coverage. The row location highly affects the cooling performance for both the louver and cylindrical scheme.

A Numerical Investigation of Stator-Rotor Interaction Effects on Flow Field and Film Cooling Effectiveness in a 3D Transonic Turbine Stage With Highly Twisted Rotors

2013 ◽  
Author(s):  
Huazhao Xu ◽  
Jianhua Wang ◽  
Ting Wang
Keyword(s):  
Shock Waves ◽  
Film Cooling ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Suction Side ◽  
Turbine Stage ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Air

To reduce aerodynamic losses and optimize turbine blade cooling designs, a comprehensive understanding of rotor-stator interaction effects on the blade aerodynamics and film cooling performance is essential. This paper focuses on the numerical analysis of the interactions between shock waves and unsteady wakes and their effects on cooling effectiveness of a highly twisted rotor within a transonic turbine stage. The parameters of the turbine stage are from the Pratt & Whitney Energy Efficient Engine (E3) program. The Realizable k-ε turbulence model was selected as the suitable turbulence model by our previous study. The investigation is conducted first by analyzing mean static pressure and the Root Mean Square (RMS) of the static pressure, followed by a detailed study of the flow field in the rotor passage at blowing ratios (Br) of 0.5, 1.0 and 1.5. Effects of the complicated interactions among shock waves, trailing edge wake shedding, and blockage of moving rotors are separated and identified individually through shock strength, vortices, and entropy production. The results show that: 1) For the stator, the shock waves emanating from the trailing edge of the neighboring stator impinging on the later part of the stator’s suction side, creating static pressure fluctuations as large as 20%. 2) For the rotor, the variation of static pressure is synchronized with the rotor passing frequency, but out of phase between the suction and pressure sides. 3) A high entropy region generated by the wake flow from the upstream trailing edge in the rotor passage intensifies and moves towards the rotor hub during the rotor passing periods. 4) Most of the cooling air injected from the rotor leading edge bends towards the suction side, and the cooling air injected from the pressure side turns towards the rotor hub. 5) An increase in the blowing ratio from Br = 0.5 to Br = 1.5 does not affect the pressure fluctuations, but does significantly increase film cooling effectiveness on the rotor pressure side. 6) The mean static pressure on the suction side of the twist blade is lower than a straight blade, indicating the benefit of producing larger torque by using twist rotors.

The Effects of Obstructions on Film Cooling Effectiveness on the Suction Side of a Gas Turbine Vane

2006 ◽  
Author(s):  
Patricia Demling ◽  
David G. Bogard
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Temperature Profiles ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

The effects of obstructions on film cooling performance on a scaled-up 1st stage turbine vane will be discussed. Experimental results show that obstructions located upstream or inside of a film cooling hole will degrade adiabatic effectiveness up to 80% of the levels found with no obstructions. Downstream obstructions had little effect on performance. The location where the upstream obstructions ceased to degrade adiabatic effectiveness was determined and temperature profiles were constructed to determine how the upstream obstructions were affecting the mainstream and coolant flow.

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