Experimental Investigation on Additively Manufactured Transpiration and Film Cooling Structures

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Zheng Min ◽  
Gan Huang ◽  
Sarwesh Narayan Parbat ◽  
Li Yang ◽  
Minking K. Chyu
Keyword(s):  
Blood Vessel ◽  
Film Cooling ◽  
Area Ratio ◽  
Wire Mesh ◽  
Transpiration Cooling ◽  
High Porosity ◽  
Fluid Interface ◽  
Interface Area ◽  
Cooling Effectiveness ◽  
Promising Alternative

The last 50 years has witnessed significant improvement in film cooling technologies while transpiration cooling is still not implemented in turbine airfoil cooling. Although transpiration cooling could provide higher cooling efficiency with less coolant consumption compared to film cooling, the fine pore structure and high porosity in transpiration cooling metal media always raised difficulties in conventional manufacturing. Recently, the rapid development of additive manufacturing (AM) has provided a new perspective to address such challenge. With the capability of the innovative powder bed selective laser metal sintering (SLMS) AM technology, the complex geometries of transpiration cooling part could be precisely fabricated and endued with improved mechanical strength. This study utilized the SLMS AM technology to fabricate the transpiration cooling and film cooling structures with Inconel 718 superalloy. Five different types of porous media including two perforated plates with different hole pitches, metal sphere packing, metal wire mesh, and blood vessel shaped passages for transpiration cooling were fabricated by EOS M290 system. One laidback fan-shaped film cooling coupon was also fabricated with the same printing process as the control group. Heat transfer tests under three different coolant mass flow rates and four different mainstream temperatures were conducted to evaluate the cooling performance of the printed coupons. The effects of geometry parameters including porosity, surface outlet area ratio, and internal solid–fluid interface area ratio were investigated as well. The results showed that the transpiration cooling structures generally had higher cooling effectiveness than film cooling structure. The overall average cooling effectiveness of blood vessel-shaped transpiration cooling reached 0.35, 0.5, and 0.57, respectively, with low (1.2%), medium (2.4%), and high (3.6%) coolant injection ratios. The morphological parameters analysis showed the major factor that affected the cooling effectiveness most was the internal solid–fluid interface area ratio for transpiration cooling. This study showed that additive manufactured transpiration cooling could be a promising alternative method for turbine blade cooling and worthwhile for further investigations.

Experimental Investigation on Additively Manufactured Transpiration and Film Cooling Structures

2018 ◽  
Author(s):  
Zheng Min ◽  
Gan Huang ◽  
Sarwesh Narayan Parbat ◽  
Li Yang ◽  
Minking K. Chyu
Keyword(s):  
Additive Manufacturing ◽  
Blood Vessel ◽  
Film Cooling ◽  
Area Ratio ◽  
Manufacturing Technology ◽  
Transpiration Cooling ◽  
Fluid Interface ◽  
Interface Area ◽  
Cooling Effectiveness ◽  
Additive Manufacturing Technology

The last 50 years has witnessed significant improvement in film cooling technologies while transpiration cooling is still not implemented in turbine airfoil cooling. Although transpiration cooling could provide higher cooling efficiency with less coolant consumption compared to film cooling, the fine pore structure and high porosity in transpiration cooling metal media always raised difficulties in conventional manufacturing. Recently, the rapid development of additive manufacturing has provided a new perspective to address such challenge. With the capability of the innovative powder bed selective laser metal sintering (SLMS) additive manufacturing technology, the complex geometries of transpiration cooling part could be precisely fabricated and endued with improved mechanical strength. Present study utilized the SLMS additive manufacturing technology to fabricate the transpiration cooling and film cooling structures with Inconel 718 supperalloy. Five different types of porous media including two perforated plates with different hole pitches, metal sphere packing, metal wire mesh and blood vessel shaped passages for transpiration cooling were fabricated by EOS M290 System. One laidback fan-shaped film cooling coupon was also fabricated with the same printing process as the control group. Heat transfer tests under 3 different coolant mass flow rates and 4 different mainstream temperatures were conducted to evaluate the cooling performance of the printed coupons. The effects of geometry parameters including porosity, surface outlet area ratio and internal solid-fluid interface area ratio were investigated as well. The results showed that the transpiration cooling structures generally had higher cooling effectiveness than film cooling structure. The overall average cooling effectiveness of blood vessel shaped transpiration cooling reached 0.35, 0.5 and 0.57 respectively with low (1.2%), medium (2.4%) and high (3.6%) coolant injection ratios. The morphological parameters analysis showed the major factor that affected the cooling effectiveness most was the internal solid-fluid interface area ratio for transpiration cooling. This study showed that additive manufactured transpiration cooling could be a promising alternative method for turbine blade cooling and worthwhile for further investigations.

SURFACE HEATER FABRICATION USING MICRO-LITHOGRAPHY FOR TRANSPIRATION COOLING HEAT TRANSFER COEFFICIENT MEASUREMENTS

2021 ◽  
pp. 1-23
Author(s):  
Zheng Min ◽  
Sarwesh Narayan Parbat ◽  
Qing-Ming Wang ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Target Surface ◽  
Transpiration Cooling ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Cooling

Abstract Transpiration cooling is able to provide more uniform coolant coverage than film cooling to effectively protect the component surface from contacting the hot gas. Due to numerous coolant ejection outlets within a small area at the target surface, the experimental thermo-fluid investigation on transpiration cooing becomes a significant challenge. Two classic methods to investigate film cooling, the steady-state foil heater method and the transient thermography technique, both fail for transpiration cooling because the foil heater would block numerous coolant outlets, and the semi-infinite solid conduction model no longer holds for porous plates. In this study, a micro-lithography method to fabricate a silver coil pattern on top of the additively manufactured polymer porous media as the surface heater was proposed. The circuit was deliberately designed to cover the solid surface in a combination of series connection and parallel connection to ensure the power in each unit cell area at the target surface was identical. With uniform heat flux generation, the steady-state tests were conducted to obtain distributions of a pair of parameters, adiabatic cooling effectiveness, and heat transfer coefficient (HTC). The results showed that the adiabatic cooling effectiveness could reach 0.65 with a blowing ratio lower than 0.5. Meanwhile, the heat transfer coefficient ratio (hf/h0) of transpiration cooling was close to 1 with a small blowing ratio at 0.125. A higher HTC ratio was observed for smaller pitch-to-diameter cases due to more turbulence intensity generated at the target surface.

Effect of Pore Blockage on Transpiration Cooling With Additive Manufacturable Perforate Holes

2018 ◽  
Author(s):  
Li Yang ◽  
Zheng Min ◽  
Sarwesh Narayan Parbat ◽  
Minking K. Chyu
Keyword(s):  
Porous Media ◽  
Additive Manufacturing ◽  
Film Cooling ◽  
Transpiration Cooling ◽  
Dust Deposition ◽  
Cooling Effectiveness ◽  
Long Term Stability ◽  
External Cooling ◽  
Pore Blockage ◽  
Turbine Airfoils

Transpiration Cooling is an effective cooling technology to protect hot section components such as gas turbine airfoils, rocket heads and space craft. This external cooling method has much higher efficiency than film cooling with holes when consuming the same amount of coolant, due to the uniformity of coolant distribution. However, pore blockage, which frequently occur during the operation of transpiration cooled components, prevented its application in turbine components which require long term stability. Dust deposition was one the main reasons causing blockage of pores for transpiration cooling. A lot of effort was devoted into dust deposition and erosion while optimization for the components themselves were generally difficult as the blockage caused by dusts was unpredictable for traditional sintered porous media. Additive manufacturing, with capability to precisely construct structures in small scales, is a considerable tool to enhance the controllability of porous media, and furthermore, to find a good solution to minimize the blockage disadvantage. Present study selected a cooling configurations containing perforate straight holes with an additive manufacturable diameter of 0.4 mm. Computational Fluid Dynamics (CFD) methods were utilized to model the pore blockage and its effect on heat transfer. A scripting code in addition to the ANSYS CFX solver was utilized to simulate the random blockage conditions of the holes. Two hundred numerical cases with four different blockage probabilities were calculated and statistically evaluated to quantify the disadvantage of pore blockage on the cooling effectiveness. Results obtained from the numerical analysis indicated that the overall blockage ratio was a dominating parameter for the cooling effectiveness. Upstream regions of the cooled surface were more sensitive to local blockage compared to downstream regions. Randomness of the cooling effectiveness increased with the increase of blockage probability. Present study provided a quantitative understanding of the random blockage disadvantage on the specific transpiration cooling configuration, and could benefit further optimization effort to reduce the blockage disadvantage of transpiration cooling using additive manufacturing.

Film Cooling Performance of Converging-Slot Holes With Different Exit-Entry Area Ratios

2009 ◽  
Author(s):  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jiang-tao Bai ◽  
Du-chun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Thermal Protection ◽  
Area Ratio ◽  
Cooling Effectiveness ◽  
Momentum Ratio ◽  
Film Cooling Effectiveness ◽  
Distribution Features

Film cooling performances of two kinds of converging slot-hole (console) with different exit-entry area ratios have been measured using a new transient liquid crystal measurement technique which can process the nonuniform initial wall temperature. Four momentum ratios are tested. The film cooling effectiveness distribution features are similar for the two consoles under all the momentum ratios. Consoles with smaller exit-entry area ratio produce higher cooling effectiveness. And the laterally averaged cooling effectiveness results show that the best momentum ratio for both consoles’ film cooling effectiveness distribution is around 2. For both consoles, the heat transfer in the midspan region is stronger than that in the hole centerline region in the upstream, but gradually becomes weaker as flowing downstream. With the momentum ratio increasing, the normalized heat transfer coefficient h/ho of both consoles increases. In the upstream, heat transfer coefficient of console with small exit-entry area ratio is higher. But in the downstream, the jets’ turbulence and the couple vortices play notable elevating effect on the heat transfer coefficient for large exit-entry area ratio case, especially under small momentum ratios. Consoles with smaller exit-entry area ratio provide better thermal protection because of higher cooling effectiveness. And the distributions of heat flux ratio are similar with those of cooling effectiveness because the influence of η on q/q0 is larger. For the consoles, smaller exit-entry area ratios produce lower discharge coefficients when the pressure variation caused by the hole shaped is regarded as flow resistant.

Study of Film Cooling Effectiveness on a Double-Walled Effusion-Cooled Turbine Blade in a High-Speed Flow Using Pressure Sensitive Paint

2019 ◽  
Author(s):  
Gladys C. Ngetich ◽  
Peter T. Ireland ◽  
Eduardo Romero
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
High Speed ◽  
High Porosity ◽  
Pressure Sensitive Paint ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive ◽  
Double Wall

Abstract A detailed analysis of film cooling performance on a double-walled effusion-cooled blade is essential for both the coolant consumption optimization and assessment of the film to offer the desired levels of the turbine blade protection. Yet there are hardly any film effectiveness studies on double-wall full-coverage film cooled turbine blades. This paper presents a detailed film cooling effectiveness study over the full surface of a double-walled effusion-cooled high-pressure turbine rotor blade using Pressure Sensitive Paint (PSP). PSP permitted a non-intrusive and conduction-errors-free means of obtaining clean and distinct local distribution of film effectiveness on the blade surface making it possible to extract valuable film cooling effectiveness performance data on the whole blade surface. Three large-scale circular pedestal double-wall blade designs with varying pedestal height, pedestal diameter and cooling hole diameter were tested in a high-speed stationary single-blade linear cascade running at engine-representative Mach and Reynolds numbers. All the blades were tested within a range of representative modern engine coolant mass flow, ṁc to mainstream, ṁg ratios; 1.6% < ṁc/ṁ∞ < 5.5%. High porosity blade exhibited a better flow distribution and was found to consistently perform the best.

Enhanced Film Cooling Effectiveness With New Shaped Holes

2010 ◽  
Author(s):  
Jong S. Liu ◽  
Malak F. Malak ◽  
Luis A. Tapia ◽  
Daniel C. Crites ◽  
Dhinagaran Ramachandran ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Area Ratio ◽  
Heat Fluxes ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Ansys Cfx ◽  
Cooling Hole

Gas Turbine Engines operate at temperatures higher than current material temperature limits. This necessitates cooling the metal through internal or external means and/ or protecting the metal with coatings that have higher material limits. Film cooling is one of the major technologies allowing today’s gas turbines to operate at extremely high turbine inlet temperatures, consequently higher power density, and extend the cooled components life. Film cooling is a technique where a coolant is blown over the surface exposed to hot gas and a film of low temperature gas is maintained that protects the metal surface from the hot gas. The application of effective film-cooling techniques provides the first and best line of defense for hot gas path surfaces against the onslaught of extreme heat fluxes, serving to directly reduce the incident convective heat flux on the surface. The effectiveness of film cooling methods depends on the blowing ratio, shape of the cooling holes, and geometrical parameters such as the area ratio and diffusion angle. Film cooling is performed almost exclusively through the use of discrete holes. The holes can be of round or other shaped. A detailed study of the literature shows that the fan shaped has higher effectiveness when compared to other shapes. In this study a number of cooling hole shapes are evaluated numerically using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX-11.0 with the objective of improving cooling effectiveness under a favorable pressure gradient main flow. In order to delineate the effects of shape from that of diffusion, a constant area ratio is assumed first. In the next set of analyses the effect of hole exit diffusion is considered. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole with forward and lateral angles of 10/10/10 degree respectively. Hole shapes that show improvement over the fan shaped hole are identified and optimized.

Film Cooling Performance of Sharp Edged Diffuser Holes With Lateral Inclination

2011 ◽  
Vol 134 (4) ◽  
Author(s):  
Christian Heneka ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer ◽  
Andreas Heselhaus ◽  
Michael E. Crawford
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Area Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Wide Range ◽  
Contour Plots ◽  
Compound Angle

An experimental study on film cooling performance of laterally inclined diffuser shaped cooling holes is presented. The measurements have been conducted on a flat plate with coolant ejected from a plenum. The film cooling effectiveness downstream of a row of four laidback fanshaped holes with sharp edged diffusers has been determined by means of infrared (IR) thermography. A variety of geometric parameters has been tested, including the inclination angle, the compound angle, the area ratio, and the pitch to diameter ratio. All tests have been performed over a wide range of engine typical blowing ratios (M=0.5–3.0). The hot gas Reynolds number and the coolant to hot gas density ratio have been kept constant close to engine realistic conditions. The results, presented in terms of contour plots of related adiabatic film cooling effectiveness as well as laterally averaged related values, clearly show the influences of the cooling hole geometry. Increasing the area ratio and the compound angle, in general, leads to higher values of the effectiveness, whereas steeper injection causes a reduction of the effectiveness.

Film Cooling Performance of Converging-Slot Holes With Different Exit-Entry Area Ratios

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Jiang-tao Bai ◽  
Du-chun Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Area Ratio ◽  
Cooling Effectiveness ◽  
Momentum Ratio ◽  
Film Cooling Effectiveness ◽  
Distribution Features ◽  
The Heat Transfer Coefficient

Film cooling performances of two kinds of converging-slot-hole (console) with different exit-entry area ratios have been measured using a new transient liquid crystal measurement technique, which can process the nonuniform initial wall temperature. Four momentum ratios are tested. The film cooling effectiveness distribution features are similar for the two consoles under all the momentum ratios. Consoles with smaller exit-entry area ratio produce higher cooling effectiveness. And the laterally averaged cooling effectiveness results show that the best momentum ratio for both consoles’ film cooling effectiveness distribution is around 2. For both consoles, the heat transfer in the midspan region is stronger than that in the hole centerline region in the upstream but gradually becomes weaker as flowing downstream. With the momentum ratio increasing, the normalized heat transfer coefficient h∕h0 of both consoles increases. In the upstream, the heat transfer coefficient of console with small exit-entry area ratio is higher. But in the downstream, the jets’ turbulence and the couple vortices play notable elevating effect on the heat transfer coefficient for large exit-entry area ratio case, especially under small momentum ratios. Consoles with smaller exit-entry area ratio provide better thermal protection because of higher cooling effectiveness. And the distributions of heat flux ratio are similar with those of cooling effectiveness because the influence of η on q∕q0 is larger. For the consoles, smaller exit-entry area ratios produce lower discharge coefficients when the pressure variation caused by the hole shape is regarded as flow resistance.

scholarly journals Experiments of Transpiration Cooling Inspired Panel Cooling on a Turbine Blade Yielding Film Effectiveness Levels over 95%

2021 ◽  
Vol 6 (2) ◽  
pp. 16
Author(s):  
Augustin Wambersie ◽  
Holt Wong ◽  
Peter Ireland ◽  
Ignacio Mayo
Keyword(s):  
Turbine Blade ◽  
Mass Flow ◽  
Film Cooling ◽  
Positive Interactions ◽  
Transpiration Cooling ◽  
Surface Porosity ◽  
Cooling Effectiveness ◽  
Flow Rates ◽  
Film Cooling Effectiveness ◽  
Mass Flow Rates

Panels were tested at different locations around the turbine blade, on both suction and pressure surfaces. Three different surface porosities were also tested. Results demonstrated that the approach can be very successful with high levels of film cooling effectiveness, exceeding 95%, achieved using low coolant mass flow rates. Increasing the surface porosity also proved to be an important parameter in the panel’s performance. Additionally, staggering the film holes lead to significant positive interactions between individual films, resulting in much improved panel performance.

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