scholarly journals A Study on the Effect of Angle in Diffused Hole Film Cooling Effectiveness at Different Blowing Ratios

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Nishant Gandhi ◽  
Suresh Sivan
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Turbine Inlet ◽  
Grid Independence

AbstractHigher the turbine inlet temperature of a gas turbine, higher will be the efficiency, however the increase in the turbine inlet temperature is limited to the materials and the cooling strategies employed. This article presents a study on the effect of blowing ratio on film cooling effectiveness for a cylindrical hole and a diffused hole at different angles. The analysis was done for blowing ratios of 0.5, 1.0, 1.5 and 2.0 while the angle in the diffused hole was varied as 5°, 10° and 15°. A grid independence study was performed and the simulation was validated. The results of cylindrical and different angles of diffused holes were compared. For a cylindrical hole as well as diffused hole, a blowing ratio of 1.0 was found to have an optimal effectiveness. The diffused hole was found to improve the near hole and downstream effectiveness at higher blowing ratios.

Numerical Evaluation of Influence of Internal Ribs on Heat Transfer in Flat Plate Film Cooling

2013 ◽  
Author(s):  
Yukiko Agata ◽  
Toshihiko Takahashi ◽  
Eiji Sakai ◽  
Koichi Nishino
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Inlet

To augment the thermal efficiency of combined power generation plants, the turbine inlet temperature of an industrial gas turbine has been increased. Cooling technology plays a vital role in the durability of gas turbine blades in situations in which the turbine inlet temperature exceeds the allowable temperature of the blade material. Cooling air is also directly associated with the reduction in thermal efficiency because bleed air from the compressor is used for turbine cooling. Thus, improvement in cooling performance has a marked impact on the further augmentation of thermal efficiency by increasing turbine inlet temperature. To evaluate film cooling performance on the basis of heat flux reduction, it is necessary to accurately estimate both heat transfer coefficient and adiabatic film cooling effectiveness. Most studies of film cooling, however, have focused on improving adiabatic film cooling effectiveness. In contrast, there are few studies focusing on heat transfer coefficient. One of the reasons for this is that adiabatic film cooling effectiveness is a performance parameter unique to film cooling. To preliminarily estimate the heat flux through a blade, heat transfer coefficient without film cooling can still be used as substitute. Moreover, the accurate CFD prediction of heat transfer coefficient with film cooling is difficult, compared with the evaluation of adiabatic film cooling effectiveness. Therefore, in this study, we addressed the CFD prediction of heat transfer coefficient with film cooling on a flat plate, and discussed its feasibility. Recent gas turbine blades operated at a turbine inlet temperature of over 1300 degree Celsius employ internal convection cooling with ribbed passages and external film cooling. These cooling technologies have been studied extensively, particularly regarding their individual effects. On the other hand, there are few investigations on the interaction between internal convection cooling and the film cooling. Although most of such film-cooling studies employed stagnant plenums to bleed cooling air, some researchers including the present authors have shown the marked impact of the conditions for supplying coolant air on film cooling performance. In this study, we focus particularly on the influence of internal rib orientation on external film cooling performance along the blade outer surface. CFD analysis is used to resolve the flow fields of the flat plate film cooling and to clarify the influence of rib orientation on heat-transfer.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

Improvement of Film Cooling Effectiveness in the Gas Turbine Endwall by Use of Optimization Framework

2019 ◽  
Author(s):  
Daisuke Hata ◽  
Kazuto Kakio ◽  
Yutaka Kawata ◽  
Masahiro Miyabe
Keyword(s):  
Pressure Gradient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

Abstract Recently, the number of gas turbine combined cycle plants is rapidly increasing in substitution of nuclear power plants. The turbine inlet temperature (TIT) is constantly being increased in order to achieve higher effectiveness. Therefore, the improvement of the cooling technology for high temperature gas turbine blades is one of the most important issue to be solved. In a gas turbine, the main flow impinging at the leading edge of the turbine blade generates a so called horseshoe vortex by the interaction of its boundary layer and generated pressure gradient at the leading edge. The pressure surface leg of this horseshoe vortex crosses the passage and reaches the blade suction surface, driven by the pressure gradient existing between two consecutive blades. In addition, this pressure gradient generates a cross-flow along the endwall. This all results into a very complex flow field in proximity of the endwall. For this reason, burnouts tend to occur at a specific position in the vicinity of the leading edge. In this research, a methodology to cool the endwall of the turbine blade by means of film cooling jets from the blade surface and the endwall is proposed. The cooling performance is investigated using the transient thermography method. CFD analysis is also conducted to investigate the phenomena occurring at the endwall and calculate the film cooling effectiveness.

Simulation Film Cooling in the Leading Edge Region of a Turbine Blade (Trench Effect on Film Effectiveness from Cylinder in Crossflow)

2014 ◽  
Vol 554 ◽  
pp. 317-321
Author(s):  
Mohamad Rasidi Bin Pairan ◽  
Norzelawati Binti Asmuin ◽  
Hamidon bin Salleh
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Leading Edge ◽  
Edge Region ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hot Gas ◽  
Cooling Technique

Film cooling is one of the cooling techniques applied to the turbine blade. Gas turbine used film cooling technique to protect turbine blade from directly expose to the hot gas to avoid the blade from defect. The focus of this investigation is to investigate the effect of embedded three difference depth of trench at coolant holes geometry. Comparisons are made at four difference blowing ratios which are 1.0, 1.25 and 1.5. Three configuration leading edge with depth Case A (0.0125D), Case B (0.0350D) and Case C (0.713D) were compared to leading edge without trench. Result shows that as blowing ratio increased from 1.0 to 1.25, the film cooling effectiveness is increase for leading edge without trench and also for all cases. However when the blowing ratio is increase to 1.5, film cooling effectiveness is decrease for all cases. Overall the Case B with blowing ratio 1.25 has the best film cooling effectiveness with significant improvement compared to leading edge without trench and with trench Case A and Case C.

scholarly journals Cooling Process of Gas Turbine Blade: A Comparison Study

2020 ◽  
Vol 13 (3) ◽  
pp. 215-222
Author(s):  
Akram Luaibi Ballaoot ◽  
Naseer Hamza
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Power Output ◽  
Film Cooling ◽  
Aviation Industry ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Gas Turbine Blade ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

The gas turbine engines are occupied an important sector in the energy production and aviation industry and this important increase day after day for their features. One of the most important parameters that limit the gas turbine engine power output is the turbine inlet temperature. The higher is the turbine inlet temperature, the higher is the power output or thrust but this increases of risks of blade thermal failure due to metallurgical limits. Thus the need for a good and efficient process of blade cooling can lead to the best compromise between a powerful engine and safe operation. There are two major methods: film or external cooling and internal cooling inside the blade itself. . In the past number of years there has been considerable progress in turbine cooling research and this paper is limited to review a few selected publications to reflect recent development in turbine blade film cooling. The maximum drop in the surface temperature of the gas turbine blade and associated thermal stress – due to incorporating cooling systems- were 735 ˚C, 1217 N/mm2 respectively.

Experimental Investigation on the Flat-Plate Film Cooling Enhancement Using the Vortex Generator Downstream for the Cylindrical Hole and Fan-Shaped Hole Configurations

2019 ◽  
Author(s):  
Chao Zhang ◽  
Jie Wang ◽  
Xin Luo ◽  
Liming Song ◽  
Jun Li ◽  
...  
Keyword(s):  
Film Cooling ◽  
Vortex Generator ◽  
Cylindrical Hole ◽  
Combined Model ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Shaped Hole ◽  
Hole Model

Abstract In our experiments, the film cooling performance of the configurations combined the different hole with the vortex generator was investigated experimentally, measured by the infrared camera. Four different configurations were studied at the blowing ratio varying at M = 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. In all cases, the Reynold number of the mainstream based on the hole diameter remained at Re = 8000, and the density ratio kept at DR = 1.7. Experimental results show that for the two models combining the cylindrical hole and fan-shaped hole with the vortex generator respectively, the film cooling performance becomes better when the blowing ratio increases from M = 0.5 to M = 2.0, and then decreases when the blowing ratio increases from M = 2.0 to M = 3.0. The model combining the fan-shaped hole with the vortex generator performs the best among the four models at each blowing ratio. Its film attachment holds the most extensive lateral distribution and its overall film cooling effectiveness could keep at a high level at a wide range of blowing ratios from M = 1.0 to M = 3.0. The combined model of the fan-shaped hole could improve the area-averaged film effectiveness at most 25.5% than that of the single hole model at M = 2.0. Moreover, the combined model of the cylindrical hole could improve the area-averaged film cooling effectiveness at most 431% than that of the single cylindrical hole model at M = 3.0.

Experimental Flow Field Investigations of Nozzle Film Cooling Scheme on a Flat Plate Using Stereo PIV

2013 ◽  
Author(s):  
Yingjie Zheng ◽  
Ibrahim Hassan
Keyword(s):  
Flow Field ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Field Investigations ◽  
Nozzle Hole

This paper presents experimental flow field investigations of a film cooling scheme, referred to as nozzle scheme, on a flat plate using stereo PIV. The nozzle scheme has a cylindrical hole and internal obstacles to change the velocity distribution near the hole exit and hence the jet-mainstream interaction. Counter-rotating vortex pair (CRVP) is known to be one of the detrimental effects that affect the film cooling effectiveness. Previous CFD simulations demonstrated nozzle hole’s capability of reducing CRVP strength and enhancing film cooling effectiveness in comparison with a normal cylindrical hole. The present study examines the nozzle hole flow filed experimentally at blowing ratio ranged from 0.5 to 2.0 and compares with cylindrical hole. The experiments were conducted in a low-speed wind tunnel with a mainstream Reynolds number of 115,000 and the density ratio was 1.0 during all the investigations. The experimental results show that nozzle hole reduces streamwise vorticity of CRVP by an average of 55% at low blowing ratio, and 34%–40% at high blowing ratios. The velocity field and vorticity field of nozzle jet are compared with cylindrical jet. The result reveals that the nozzle jet forms a round bulk in contrast to the kidney shape jet core in cylindrical hole case. In addition, it is found that CRVP strength may not be a primary contributor to the jet lift-off.

Comparative Thermodynamic Analysis of Gas Turbine Systems with Turbine Blade Film Cooling

2012 ◽  
Vol 505 ◽  
pp. 539-543
Author(s):  
Kyoung Hoon Kim ◽  
Kyoung Jin Kim ◽  
Chul Ho Han
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Thermodynamic Analysis ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Blade Cooling ◽  
Turbine Inlet

Since the gas turbine systems require active cooling to maintain high operating temperature while avoiding a reduction in the system operating life, turbine blade cooling is very important and essential but it may cause the performance losses in gas turbine. This paper deals with the comparative thermodynamic analysis of gas turbine system with and without regeneration by using the recently developed blade-cooling model when the turbine blades are cooled by the method of film cooling. Special attention is paid to investigating the effects of system parameters such as pressure ratio and turbine inlet temperature on the thermodynamic performance of the systems. In both systems the thermal efficiency increases with turbine inlet temperature, but its effect is less sensitive in simpler system

Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade

1997 ◽  
Author(s):  
Hui Du ◽  
Je-Chin Han ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Gas Turbine ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Nusselt Numbers ◽  
Unsteady Wake ◽  
Cooled Blade

Unsteady wake effects on detailed heat transfer coefficient and film cooling effectiveness distributions from a gas turbine blade with film cooling are obtained using a transient liquid crystal technique. Tests were performed on a five-blade linear cascade at a axial chord Reynolds number of 5.3 × 105 at cascade exit. Upstream unsteady wakes are simulated using a spoke-wheel type wake generator. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. Air and CO2 were used as coolants to simulate different coolant-to-mainstream density ratio effect. Coolant blowing ratio for air injection is varied from 0.8 to 1.2 and is varied from 0.4 to 1.2 for CO2. Results show that Nusselt numbers for a film-cooled blade are much higher compared to a blade without film injection. Particularly, film injection causes earlier boundary layer transition on the suction surface. Unsteady wakes slightly enhance Nusselt numbers but significantly reduce film cooling effectiveness on a film-cooled blade compared with a film-cooled blade without wakes. Nusselt numbers increase slightly but film cooling effectiveness increases significantly with an increase in blowing ratio for CO2 injection. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher effectiveness at lower blowing ratios (M = 0.8).

Numerical Study of Mist Film Cooling in Combustor at Operating Conditions

2009 ◽  
Author(s):  
Srinivasa Rao Para ◽  
Xianchang Li ◽  
Ganesh Subbuswamy
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Numerical Study ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Cooling Effectiveness ◽  
Wall Functions ◽  
Film Cooling Effectiveness ◽  
Combustor Liner

To improve the gas turbine thermal performance, apart from using a high compression ratio, the turbine inlet temperature must be increased. Therefore, the gas temperature inside the combustion chamber needs to be maintained at a very high level. Hence, cooling of the combustor liner becomes critical. Among all the cooling techniques, film cooling has been successfully applied to cool the combustor liner. In film cooling, coolant air is introduced through discrete holes and forms a thin film between the hot gases and the inner surface of the liner, so that the inner wall can be protected from overheating. The film will be destroyed in the downstream flow because of mixing of hot and cold gases. The present work focuses on numerical study of film cooling under operating conditions, i.e., high temperature and pressure. The effect of coolant injection angles and blowing ratios on film cooling effectiveness is studied. A promising technology, cooling with mist injection, is studied under operating conditions. The effect of droplet size and mist concentration is also analyzed. The results of this study indicate that the film cooling effectiveness can increase ∼11% at gas turbine operating conditions with mist injection of 2% coolant air when droplets of 10μm and a blowing ratio of 1.0 are applied. The cooling performance can be further improved by higher mist concentration. The commercial CFD software, Fluent 6.3.26, is used in this study and the standard k-ε model with enhanced wall functions is adopted as the turbulence model.

Sign in / Sign up

Export Citation Format

Share Document