A Numerical Investigation of Air/Mist Cooling in a Conjugate, 3-D Gas Turbine Vane With Internal Passage and External Film Cooling

2019 ◽  
Author(s):  
Ramy Abdelmaksoud ◽  
Ting Wang
Keyword(s):  
Numerical Investigation ◽  
Size Distribution ◽  
Gas Turbine ◽  
Wall Temperature ◽  
Film Cooling ◽  
Droplet Size Distribution ◽  
Cooling Enhancement ◽  
Mist Cooling ◽  
Film Cooling Holes ◽  
Uniform Droplet

Abstract This paper describes a numerical investigation to study the effect of injecting mist (tiny water droplets, micrometers in size) into the cooling airstream to cool down gas turbine vanes. In this study, the conjugate heat transfer method is employed which consists of the simulation of the air/mist fluid flow inside and outside the vanes as well as the heat conduction through the vane body. The complete 3-D vane with internal cooling passages and external film cooling holes on the surface is simulated in a rotational periodic sector. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. The effects of different parameters such as the mist/air ratio (10–20%) and the mist droplets size (20–50μm) on mist cooling enhancement are investigated. The results show that by using a mist/air ratio of 10%, 15%, and 20% with 20 μm droplets size, on the pressure side, a maximum wall temperature reduction of 250 K, 340 K, and 450 K respectively can be achieved. On the suction side, the corresponding maximum wall temperature reductions are 160 K, 260 K, and 360 K, respectively. Using larger droplets of 50μm did not achieve better cooling enhancement because the droplets were rushed far away from the surface by the acceleration through the film cooling holes. Using the uniform droplet size distribution provides noticeably better cooling enhancement in the first 40% of the vane’s height (from the shroud) than the non-uniform droplet size distribution (Rosin-Rammler Distribution) does.

A Numerical Investigation of Air/Mist Cooling Through a Conjugate, Rotating 3-D Gas Turbine Blade With Internal, External, and Tip Cooling

2019 ◽  
Author(s):  
Ramy Abdelmaksoud ◽  
Ting Wang
Keyword(s):  
Numerical Investigation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Outer Surface ◽  
Film Cooling ◽  
Internal Cooling ◽  
Blade Tip ◽  
Mist Cooling ◽  
Film Cooling Holes ◽  
Cooling Air

Abstract This paper describes a numerical investigation to study the effect of injecting mist (tiny water droplets) into the cooling air used to cool down rotating gas turbine blades. In this study, the conjugate heat transfer method is employed which consists of the simulation of the air/mist fluid flow inside and outside the blades as well as the heat conduction through the blade body. The complete 3-D blade with internal cooling passages and external film cooling holes on the surface and blade tip is simulated in a rotating, periodic sector of the blade. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. The rotation effect of the turbine blade is included in the CFD simulation by using the moving reference frame method. The effects of different parameters such as the mist/air ratio (10–20%) and the mist droplets size (20–40μm) on mist cooling enhancement are investigated. The results show that the mist cooling enhancements are about 10% to 25% on the outer surface of the blade and reach 50% in some locations inside the blade on the internal cooling passages walls. Most of the liquid droplets completely evaporate inside the internal cooling passages; only a limited amount of mist is able to escape from the film cooling holes to enhance the blade outer surface and blade tip cooling. The effect of 10% mist on enhanced cooling is also converted to an equivalent of a 30% reduction in cooling air flow.

A Numerical Investigation of Air/Mist Cooling through a Conjugate, Rotating 3-D Gas Turbine Blade with Internal, External, and Tip Cooling

2020 ◽  
pp. 1-30
Author(s):  
Ramy Abdelmaksoud ◽  
Ting Wang
Keyword(s):  
Numerical Investigation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Outer Surface ◽  
Film Cooling ◽  
Internal Cooling ◽  
Blade Tip ◽  
Mist Cooling ◽  
Film Cooling Holes ◽  
Cooling Air

Abstract This paper describes a numerical investigation to study the effect of injecting mist into the cooling air used to cool down rotating gas turbine blades. The conjugate heat transfer method is employed which consists of the simulation of the air/mist fluid flow inside and outside the blades as well as the heat conduction through the blade body. The complete 3-D blade with internal cooling passages and external film cooling holes on the surface and blade tip is simulated in a rotating, periodic sector of the blade. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. The rotation effect of the turbine blade is included in the simulation by using the moving reference frame method. The effects of different parameters such as the mist/air ratio (10-20%) and the mist droplets size (20-40 µm) on mist cooling enhancement are investigated. The results show that the mist cooling enhancements are about 10% to 25% on the outer surface of the blade and reach 50% in some locations inside the blade on the internal cooling passages walls. Most of the liquid droplets completely evaporate inside the internal cooling passages; only a limited amount of mist is able to escape from the film cooling holes to enhance the blade outer surface and blade tip cooling. The effect of 10% mist on enhanced cooling is also converted to an equivalent of a 30% reduction in cooling air flow.

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.

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.

Simulation of Mist Film Cooling on Rotating Gas Turbine Blades

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
T. S. Dhanasekaran ◽  
Ting Wang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Pressure Side ◽  
Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Laboratory Conditions ◽  
Cooling Enhancement ◽  
Mist Cooling

Film cooling techniques have been successfully applied to gas turbine blades to protect them 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 by up to 50%–800% in convective heat transfer and impingement cooling. The similar concept of injecting mist into air film cooling has not been proven in the laboratory, but computational simulations have 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 holes located near the leading edge at either side of the blade. Then, a row of multiple-hole film cooling jets is put in place under both stationary and rotating conditions. Both the laboratory (baseline) and elevated gas turbine conditions are simulated and compared. Elevated conditions refer to a high temperature and pressure closer to actual gas turbine working conditions. 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 that the effect of rotation on droplets under laboratory conditions is minimal. The computational fluid dynamics (CFD) model employed is 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 rates of mist cooling enhancement of about 15% and 35% were achieved under laboratory and elevated conditions, respectively. This translates to a significant blade surface temperature reduction of 100–125 K with 10% mist injection at elevated conditions.

Numerical Study on Flow and Heat Transfer of a Cooled First Stage Vane of a Gas Turbine

2016 ◽  
Author(s):  
Lv Ye ◽  
Zhao Liu ◽  
Xiangyu Wang ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Film Cooling ◽  
Numerical Study ◽  
Coolant Flow ◽  
The Other ◽  
Edge Region ◽  
Flow Rates ◽  
Flow And Heat Transfer ◽  
Film Cooling Holes

This paper presents a numerical simulation of composite cooling on a first stage vane of a gas turbine, in which gas by fixed composition mixture is adopted. To investigate the flow and heat transfer characteristics, two internal chambers which contain multiple arrays of impingement holes are arranged in the vane, several arrays of pin-fins are arranged in the trailing edge region, and a few arrays of film cooling holes are arranged on the vane surfaces to form the cooling film. The coolant enters through the shroud inlet, and then divided into two parts. One part is transferred into the chamber in the leading edge region, and then after impinging on the target surfaces, it proceeds further to go through the film cooling holes distributed on the vane surface, while the other part enters into the second chamber immediately and then exits to the mainstream in two ways to effectively cool the other sections of the vane. In this study, five different coolant flow rates and six different inlet pressure ratios were investigated. All the cases were performed with the same domain grids and same boundary conditions. It can be concluded that for the internal surfaces, the heat transfer coefficient changes gradually with the coolant flow rate and the inlet total pressure ratio, while for the external surfaces, the average cooling effectiveness increases with the increase of coolant mass flow rates while decreases with the increase of the inlet stagnation pressure ratios within the study range.

A Method for Correlating the Influence of External Crossflow on the Discharge Coefficients of Film Cooling Holes

2000 ◽  
Vol 123 (2) ◽  
pp. 258-265 ◽  
Author(s):  
D. A. Rowbury ◽  
M. L. G. Oldfield ◽  
G. D. Lock
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Discharge Coefficient ◽  
Guide Vane ◽  
Discharge Coefficients ◽  
Nozzle Guide Vane ◽  
Aero Engine ◽  
Nozzle Guide ◽  
Film Cooling Holes ◽  
Asme Paper

An empirical means of predicting the discharge coefficients of film cooling holes in an operating engine has been developed. The method quantifies the influence of the major dimensionless parameters, namely hole geometry, pressure ratio across the hole, coolant Reynolds number, and the freestream Mach number. The method utilizes discharge coefficient data measured on both a first-stage high-pressure nozzle guide vane from a modern aero-engine and a scale (1.4 times) replica of the vane. The vane has over 300 film cooling holes, arranged in 14 rows. Data was collected for both vanes in the absence of external flow. These noncrossflow experiments were conducted in a pressurized vessel in order to cover the wide range of pressure ratios and coolant Reynolds numbers found in the engine. Regrettably, the proprietary nature of the data collected on the engine vane prevents its publication, although its input to the derived correlation is discussed. Experiments were also conducted using the replica vanes in an annular blowdown cascade which models the external flow patterns found in the engine. The coolant system used a heavy foreign gas (SF6 /Ar mixture) at ambient temperatures which allowed the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. These experiments matched the mainstream Reynolds and Mach numbers and the coolant Mach number to engine values, but the coolant Reynolds number was not engine representative (Rowbury, D. A., Oldfield, M. L. G., and Lock, G. D., 1997, “Engine-Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade,” ASME Paper No. 97-GT-99, International Gas Turbine and Aero-Engine Congress & Exhibition, Orlando, Florida, June 1997; Rowbury, D. A., Oldfield, M. L. G., Lock, G. D., and Dancer, S. N., 1998, “Scaling of Film Cooling Discharge Coefficient Measurements to Engine Conditions,” ASME Paper No. 98-GT-79, International Gas Turbine and Aero-Engine Congress & Exhibition, Stockholm, Sweden, June 1998). A correlation for discharge coefficients in the absence of external crossflow has been derived from this data and other published data. An additive loss coefficient method is subsequently applied to the cascade data in order to assess the effect of the external crossflow. The correlation is used successfully to reconstruct the experimental data. It is further validated by successfully predicting data published by other researchers. The work presented is of considerable value to gas turbine design engineers as it provides an improved means of predicting the discharge coefficients of engine film cooling holes.

Leading Edge Shielding Concept in Gas Turbines With Can Combustors

2012 ◽  
Author(s):  
Ioanna Aslanidou ◽  
Budimir Rosic ◽  
Vasudevan Kanjirakkad ◽  
Sumiu Uchida
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Gas Turbines ◽  
Leading Edge ◽  
High Heat ◽  
Gas Temperature ◽  
Cooling Strategies ◽  
Film Cooling Holes ◽  
Cooling Air ◽  
Heat Loads

The remarkable developments in gas turbine materials and cooling technologies have allowed a steady increase in combustor outlet temperature and hence in gas turbine efficiency over the last half century. However, the efficiency benefits of higher gas temperature, even at the current levels, are significantly offset by the increased losses associated with the required cooling. Additionally, the advancements in gas turbine cooling technology have introduced considerable complexities into turbine design and manufacture. Therefore, a reduction in coolant requirements for the current gas temperature levels is one possible way for gas turbine designers to achieve even higher efficiency levels. The leading edges of the first turbine vane row are exposed to high heat loads. The high coolant requirements and geometry constraints limit the possible arrangement of the multiple rows of film cooling holes in the so called showerhead region. In the past, investigators have tested many different showerhead configurations, varying the number of rows, inclination angle and shape of the cooling holes. However the current leading edge cooling strategies using showerheads have not been shown to allow further increase in turbine temperature without excessive use of coolant air. Therefore new cooling strategies for the first vane have to be explored. In gas turbines with multiple combustor chambers around the annulus, the transition duct walls can be used to shield, i.e. to protect the first vane leading edges from the high heat loads. In this way the stagnation region at the leading edge and the shower-head of film cooling holes can be completely removed, resulting in a significant reduction in the total amount of cooling air that is otherwise required. By eliminating the showerhead the shielding concept significantly simplifies the design and lowers the manufacturing costs. This paper numerically analyses the potential of the leading edge shielding concept for cooling air reduction. The vane shape was modified to allow for the implementation of the concept and non-restrictive relative movement between the combustor and the vane. It has been demonstrated that the coolant flow that was originally used for cooling the combustor wall trailing edge and a fraction of the coolant air used for the vane showerhead cooling can be used to effectively cool both the suction and the pressure surfaces of the vane.

scholarly journals Simulation of Mist Film Cooling at Gas Turbine Operating Conditions

2006 ◽  
Author(s):  
Ting Wang ◽  
Xianchang Li
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Water Mist ◽  
Operating Conditions ◽  
Round Hole ◽  
Adiabatic Wall ◽  
Cooling Enhancement ◽  
Temperature And Pressure ◽  
Uniform Droplets ◽  
Air Film

Air film cooling has been successfully used to cool gas turbine hot sections for the last half century. A promising technology is proposed to enhance air film cooling with water mist injection. Numerical simulations have shown that injecting a small amount of water droplets into the cooling air improves film-cooling performance significantly. However, previous studies were conducted at conditions of low Reynolds number, temperature, and pressure to allow comparisons with experimental data. As a continuous effort to develop a realistic mist film cooling scheme, this paper focuses on simulating mist film cooling under typical gas turbine operating conditions of high temperature and pressure. The mainstream flow is at 15 atm with a temperature of 1561K. Both 2-D and 3-D cases are considered with different hole geometries on a flat surface, including a 2-D slot, a simple round hole, a compound-angle hole, and fan-shaped holes. The results show that 10%–20% mist (based on the coolant mass flow rate) achieves 5%–10% cooling enhancement and provides an additional 30–68K adiabatic wall temperature reduction. Uniform droplets of 5 to 20 μm are used. The droplet trajectories indicate the droplets tend to move away from the wall, which results in a lower cooling enhancement than under low pressure and temperature conditions. The commercial software Fluent (v. 6.2.16) is adopted in this study, and the standard k-ε model with enhanced wall treatment is adopted as the turbulence model.

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