Prediction of Low Temperature Hot Corrosion Rate in Film Cooled Coal Fired Gas Turbines

2003 ◽  
Author(s):  
Vaidyanathan Krishnan ◽  
Sanjeev Bharani ◽  
J. S. Kapat ◽  
Y. H. Sohn ◽  
V. H. Desai
Keyword(s):  
Corrosion Rate ◽  
Hot Corrosion ◽  
Film Cooling ◽  
Gas Turbines ◽  
Power Plants ◽  
Gas Temperature ◽  
Air Temperatures ◽  
Operational Life ◽  
Cooling Hole ◽  
Cooling Air

The concept of coal based gas turbine power plants has drawn considerable interest in recent years. Coal or syngas based power plants like IGCC have shown significant potential for meeting the ever-increasing power demands as well as stricter environmental regulations. The trouble free operational life of such power plants is limited by a major factor namely hot corrosion of the turbine components. Hitherto, the mechanism of hot corrosion has been investigated in a simpler context, which is not directly applicable to gas turbines in the presence of film cooling techniques. The present paper is an attempt to model hot corrosion in the presence of film cooling relevant to gas turbines, using a simple resistance model and the inherent analogy between heat and mass transfer. This paper considers film cooling air temperatures in the range of 450°C to 550°C, and a free stream gas temperature of 1425°C, with 0.5% sulfur in the fuel. For lower cooling air temperatures (less than 500°C), film cooling air suppresses corrosion, whereas for higher cooling air temperature corrosion rate is more in the presence of film cooling. With film cooling, there is a sharp peak in corrosion rate close to the cooling hole (within 10 slot widths). Due to the possibility that the base superalloy may be exposed in this region, designers should consider the high corrosion rate seriously. However, the present model is limited in its prediction because of its simplicity. Further improvement of the model is essential for optimization purposes.

Effect of Film Cooling on Low Temperature Hot Corrosion in a Coal Fired Gas Turbine

2003 ◽  
Author(s):  
Vaidyanathan Krishnan ◽  
J. S. Kapat ◽  
Y. H. Sohn ◽  
V. H. Desai
Keyword(s):  
Low Temperature ◽  
Corrosion Rate ◽  
Hot Corrosion ◽  
Film Cooling ◽  
Gas Turbines ◽  
Primary Source ◽  
Operating Conditions ◽  
Coal Gas ◽  
A Chain ◽  
Lower Corrosion Rate

In recent times, the use of coal gas in gas turbines has gained a lot of interest, as coal is quite abundant as a primary source of energy. However, use of coal gas produces a few detrimental effects that need closer attention. This paper concentrates on one such effect, namely hot corrosion, where trace amounts of sulfur can cause corrosion (or sulfidation) of hot and exposed surfaces, thereby reducing the life of the material. In low temperature hot corrosion, which is the focus of this paper, transport of SO2 from the hot gas stream is the primary process that leads to a chain of events, ultimately causing hot corrosion. The corrosion rate depends on SO2 mass flux to the wall as well as wall surface temperature, both of which are affected in the presence of any film cooling. An analytical model is developed to describe the associated transport phenomena of both heat and mass in the presence of film cooling The model predicts how corrosion rates may be affected under operating conditions. It is found that although use of film cooling typically leads to lower corrosion rate, there are combinations of operating parameters under which corrosion rate can actually increase in the presence of film cooling.

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.

Leading Edge Shielding Concept in Gas Turbines With Can Combustors

2012 ◽  
Vol 135 (2) ◽  
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 by 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 a further increase in turbine temperature without the 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 showerhead 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 analyzes 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 nonrestrictive 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.

Effect of a Ceramic Matrix Composite Surface on Film Cooling

2021 ◽  
Author(s):  
Peter H. Wilkins ◽  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
San Quach ◽  
Tyler Vincent ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Matrix Composite ◽  
Film Cooling ◽  
Gas Turbines ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix ◽  
Composite Surface ◽  
Minimal Impact ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

Abstract Ceramic matrix composite (CMC) parts create the opportunity for increased turbine entry temperatures within gas turbines. To achieve the highest temperatures possible, film cooling will play an important role in allowing turbine entry temperatures to exceed acceptable surface temperatures for CMC components, just as it does for the current generation of gas turbine components. Film cooling over a CMC surface introduces new challenges including roughness features downstream of the cooling holes and changes to the hole exit due to uneven surface topography. To better understand these impacts, this study presents flowfield and adiabatic effectiveness CFD for a 7-7-7 shaped film cooling hole at two CMC weave orientations. The CMC surface selected is a 5 Harness Satin weave pattern that is examined at two different orientations. To understand the ability of steady RANS to predict flow and convective heat transfer over a CMC surface, the weave surface is initially simulated without film and compared to previous experimental results. The simulation of the weave orientation of 0°, with fewer features projecting into the flow, matches fairly well to the experiment, and demonstrates a minimal impact on film cooling leading to only slightly lower adiabatic effectiveness compared to a smooth surface. However, the simulation of the 90° orientation with a large number of protruding features does not match the experimentally observed surface heat transfer. The additional protruding surface produces degraded film cooling performance at low blowing ratios but is less sensitive to blowing ratio, leading to improved relative performance at higher blowing ratios, particularly in regions far downstream of the hole.

scholarly journals FEATURES OF ORGANIZATION OF FILM COOLING OF HIGH TEMPERATURE GAS TURBINES BLADES

2017 ◽  
Vol 39 (4) ◽  
pp. 11-20
Author(s):  
A. A. Khalatov ◽  
A. S. Kovalenko ◽  
S. B. Reznik
Keyword(s):  
High Temperature ◽  
Film Cooling ◽  
Gas Turbines ◽  
Small Dimension ◽  
Cooling Efficiency ◽  
Local Distribution ◽  
Cooling Air ◽  
High Temperature Gas

The features of the release of the cooling air in the interscapular channel high temperature gas turbines at the film cooling are considered. Possibilities of its local distribution on contour of an entrance edge of the perforated blades are investigated. The presented calculations show that the substantial increase in the cooling efficiency can be attained due to channels of small dimension in the blade wall.  

scholarly journals Investigation of Flow through a Labyrinth Seal

2021 ◽  
Vol 13 (2) ◽  
pp. 51-58
Author(s):  
Marius ENACHE ◽  
Razvan CARLANESCU ◽  
Andreea MANGRA ◽  
Florin FLOREAN ◽  
Radu KUNCSER
Keyword(s):  
Gas Turbines ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Cfd Modeling ◽  
Gas Temperature ◽  
Continuous Increase ◽  
Seal Design ◽  
Air Temperatures ◽  
Flow Through ◽  
Gas Leaks

Growing performance requirements for gas turbines have led to a continuous increase in gas temperature and pressure ratios. Together with the resulting increase in cooling flows, this requires more and more minimization and control of internal gas leaks. To meet future performance goals, the application of a new seal design and an improved understanding of leakage flow characteristics are of particular importance. The air mass flow through a labyrinth seal designed for a low-pressure turbine has been determined both through analytical calculus and CFD modeling. Different radial clearances and different air temperatures have been considered. In the next stage, the results will be validated through experiments.

Effects of a Reacting Cross-Stream on Turbine Film Cooling

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Wesly S. Anderson ◽  
Marc D. Polanka ◽  
Joseph Zelina ◽  
Dave S. Evans ◽  
Scott D. Stouffer ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Thermal Protection ◽  
Critical Role ◽  
Cylindrical Hole ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Secondary Combustion ◽  
Cooling Hole ◽  
Reactor Operating

Film cooling plays a critical role in providing effective thermal protection to components in modern gas turbine engines. A significant effort has been undertaken over the last 40 years to improve the distribution of coolant and to ensure that the airfoil is protected by this coolant from the hot gases in the freestream. This film, under conditions with high fuel-air ratios, may actually be detrimental to the underlying metal. The presence of unburned fuel from an upstream combustor may interact with this oxygen rich film coolant jet resulting in secondary combustion. The completion of the reactions can increase the gas temperature locally resulting in higher heat transfer to the airfoil directly along the path line of the film coolant jet. This secondary combustion could damage the turbine blade, resulting in costly repair, reduction in turbine life, or even engine failure. However, knowledge of film cooling in a reactive flow is very limited. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred reactor operating at high temperatures over a flat plate. Surface temperatures, heat flux, and heat transfer coefficients are calculated for a variety of reactor fuel-to-air ratios, cooling hole geometries, and blowing ratios. Emphasis is placed on the difference between a normal cylindrical hole, an inclined cylindrical hole, and a fan-shaped cooling hole. When both air and nitrogen are injected through the cooling holes, the changes in surface temperature can be directly correlated with the presence of the reaction. Photographs of the localized burning are presented to verify the extent and locations of the reaction.

scholarly journals Entrance Effects on Diffused Film-Cooling Holes

1998 ◽  
Author(s):  
A. Kohli ◽  
K. A. Thole
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Computational Study ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Supply Channel ◽  
Cooling Hole ◽  
Film Cooling Holes

Film-cooling is a widely used method of prolonging blade life in high performance gas turbines and is implemented by injecting cold air through discrete holes on the blade surface. Most experimental research on film-cooling has been performed using round holes supplied by a stagnant plenum. This can be quite different from the actual turbine blade conditions in that a crossflow may be present whereby the internal channel Reynolds number could be as high as 90,000. This computational study uses a film-cooling hole that is inclined at 35° with respect to the mainstream and is diffused at the hole exit by 15°. An engine representative jet-to-mainstream density ratio of two was simulated. The test matrix consisted of fourteen different cases that were simulated for the two different blowing ratios in which the following effects were investigated: a) the effect of the orientation of the coolant supply channel relative to the cooling hole, b) the effect of the channel Reynolds number, and c) the effect of the metering length of the cooling hole. Results showed that the orientation of the coolant supply had a large effect whereby the worst orientation, in terms of a reduced adiabatic effectiveness, was predicted when the channel supplying the cooling hole was perpendicular to the mainstream. For this particular orientation, higher laterally averaged effectiveness occurred at lower channel Reynolds numbers and with the hole having a short metering length.

Implementation of Hole-Pair in Ramp to Improve Film Cooling Effectiveness on a Plain Surface

2020 ◽  
Author(s):  
Sadam Hussain ◽  
Xin Yan
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Hole Pair ◽  
Cooling Effect ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Plain Surface

Abstract Film cooling is one of the most critical technologies in modern gas turbine engine to protect the high temperature components from erosion. It allows gas turbines to operate above the thermal limits of blade materials by providing the protective cooling film layer on outer surfaces of blade against hot gases. To get a higher film cooling effect on plain surface, current study proposes a novel strategy with the implementation of hole-pair into ramp. To gain the film cooling effectiveness on the plain surface, RANS equations combined with k-ω turbulence model were solved with the commercial CFD solver ANSYS CFX11.0. In the numerical simulations, the density ratio (DR) is fixed at 1.6, and the film cooling effect on plain surface with different configurations (i.e. with only cooling hole, with only ramp, and with hole-pair in ramp) were numerically investigated at three blowing ratios M = 0.25, 0.5, and 0.75. The results show that the configuration with Hole-Pair in Ramp (HPR) upstream the cooling hole has a positive effect on film cooling enhancement on plain surface, especially along the spanwise direction. Compared with the baseline configuration, i.e. plain surface with cylindrical hole, the laterally-averaged film cooling effectiveness on plain surface with HPR is increased by 18%, while the laterally-averaged film cooling effectiveness on plain surface with only ramp is increased by 8% at M = 0.5. As the blowing ratio M increases from 0.25 to 0.75, the laterally-averaged film cooling effectiveness on plain surface with HPR is kept on increasing. At higher blowing ratio M = 0.75, film cooling effectiveness on plain surface with HPR is about 19% higher than the configuration with only ramp.

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