Documents disponibles écrits par cet auteur

Calibration of a computational model to predict mist/steam impinging jets cooling with an application to gas turbine blades / Ting Wang in Journal of heat transfer, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 12 (Décembre 2010) . - pp. [122201-1/11] Titre : Calibration of a computational model to predict mist/steam impinging jets cooling with an application to gas turbine blades Type de document : texte imprimé Auteurs : Ting Wang, Auteur ; T. S. Dhanasekaran, Auteur Année de publication : 2010 Article en page(s) : pp. [122201-1/11] Note générale : Physique Langues : Anglais (eng) Mots-clés : Impinging  jets  Mist  cooling  Heat  transfer  enhancement  Two-phase  flow  Gas  turbine  blade  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : In heavy-frame advanced turbine systems, steam is used as a coolant for turbine blade cooling. The concept of injecting mist into the impinging jets of steam was experimentally proved as an effective way of significantly enhancing the cooling effectiveness in the laboratory under low pressure and temperature conditions. However, whether or not mist/steam cooling is applicable under actual gas turbine operating conditions is still subject to further verification. Recognizing the difficulties of conducting experiments in an actual high-pressure, high-temperature working gas turbine, a simulation using a computational fluid dynamic (CFD) model calibrated with laboratory data would be an opted approach. To this end, the present study conducts a CFD model calibration against the database of two experimental cases including a slot impinging jet and three rows of staggered impinging jets. The calibrated CFD model was then used to predict the mist cooling enhancement at the elevated gas turbine working condition. Using the experimental results, the CFD model has been tuned by employing different turbulence models, computational cells, and wall y+ values. In addition, the effects of different forces (e.g., drag, thermophoretic, Brownian, and Saffman's lift force) are also studied. None of the models is a good predictor for all the flow regions from near the stagnation region to far-field downstream of the jets. Overall speaking, both standard k-epsilon and Reynolds stress model (RSM) turbulence models perform better than other models. The RSM model has produced the closest results to the experimental data due to its capability of modeling the nonisotropic turbulence shear stresses in the 3D impinging jet fields. The simulated results show that the calibrated CFD model can predict the heat transfer coefficient of steam-only case within 2–5% deviations from the experimental results for all the cases. When mist is employed, the prediction of wall temperatures is within 5% for a slot jet and within 10% for three-row jets. The predicted results with 1.5% mist at the gas turbine working condition show the mist cooling enhancement of 20%, whereas in the laboratory condition, the enhancement is predicted as 80%. Increasing mist ratio to 5% increased the cooling enhancement to about 100% at the gas turbine working condition. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Calibration of a computational model to predict mist/steam impinging jets cooling with an application to gas turbine blades [texte imprimé] / Ting Wang, Auteur ; T. S. Dhanasekaran, Auteur . - 2010 . - pp. [122201-1/11]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 12 (Décembre 2010) . - pp. [122201-1/11] Mots-clés : Impinging  jets  Mist  cooling  Heat  transfer  enhancement  Two-phase  flow  Gas  turbine  blade  cooling Index. décimale : 536 Chaleur. Thermodynamique Résumé : In heavy-frame advanced turbine systems, steam is used as a coolant for turbine blade cooling. The concept of injecting mist into the impinging jets of steam was experimentally proved as an effective way of significantly enhancing the cooling effectiveness in the laboratory under low pressure and temperature conditions. However, whether or not mist/steam cooling is applicable under actual gas turbine operating conditions is still subject to further verification. Recognizing the difficulties of conducting experiments in an actual high-pressure, high-temperature working gas turbine, a simulation using a computational fluid dynamic (CFD) model calibrated with laboratory data would be an opted approach. To this end, the present study conducts a CFD model calibration against the database of two experimental cases including a slot impinging jet and three rows of staggered impinging jets. The calibrated CFD model was then used to predict the mist cooling enhancement at the elevated gas turbine working condition. Using the experimental results, the CFD model has been tuned by employing different turbulence models, computational cells, and wall y+ values. In addition, the effects of different forces (e.g., drag, thermophoretic, Brownian, and Saffman's lift force) are also studied. None of the models is a good predictor for all the flow regions from near the stagnation region to far-field downstream of the jets. Overall speaking, both standard k-epsilon and Reynolds stress model (RSM) turbulence models perform better than other models. The RSM model has produced the closest results to the experimental data due to its capability of modeling the nonisotropic turbulence shear stresses in the 3D impinging jet fields. The simulated results show that the calibrated CFD model can predict the heat transfer coefficient of steam-only case within 2–5% deviations from the experimental results for all the cases. When mist is employed, the prediction of wall temperatures is within 5% for a slot jet and within 10% for three-row jets. The predicted results with 1.5% mist at the gas turbine working condition show the mist cooling enhancement of 20%, whereas in the laboratory condition, the enhancement is predicted as 80%. Increasing mist ratio to 5% increased the cooling enhancement to about 100% at the gas turbine working condition. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Influence of crystallization of nano TiO2 prepared by adsorption phase synthesis on photodegradation of gaseous toluene / Ting Wang in Industrial & engineering chemistry research, Vol. 48 N° 13 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6224–6228 Titre : Influence of crystallization of nano TiO2 prepared by adsorption phase synthesis on photodegradation of gaseous toluene Type de document : texte imprimé Auteurs : Ting Wang, Auteur ; Xin Jiang, Auteur ; Yanxiang Wu, Auteur Année de publication : 2009 Article en page(s) : pp. 6224–6228 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : TiO2/SiO2  Gaseous  toluene  Catalytic  activity  Photocatalytic  activity Résumé : TiO2/SiO2 was prepared by adsorption phase synthesis, and its photocatalysis on degradation of gaseous toluene was studied. The concentration of water added in preparation and temperature in calcination were changed to regulate formation of anatase TiO2. Ti contents in samples and grain size of anantase TiO2 were measured, and the catalytic activity in photodegrading gaseous toluene was characterized. The photocatalytic activity increased sharply when the calcination temperature increased to 500 °C or the volume of water added in preparation reached 1.5 mL. XRD analysis indicated that the crystal phase transformation of TiO2 from anatase to rutile was restrained and TiO2 remained in the form of anatase even after being sintered at 900 °C. The high constant photocatalytic activity from 500 to 900 °C was attributed to the stability of anatase TiO2 in crystal size and phase transformation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801974y [article] Influence of crystallization of nano TiO2 prepared by adsorption phase synthesis on photodegradation of gaseous toluene [texte imprimé] / Ting Wang, Auteur ; Xin Jiang, Auteur ; Yanxiang Wu, Auteur . - 2009 . - pp. 6224–6228. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6224–6228 Mots-clés : TiO2/SiO2  Gaseous  toluene  Catalytic  activity  Photocatalytic  activity Résumé : TiO2/SiO2 was prepared by adsorption phase synthesis, and its photocatalysis on degradation of gaseous toluene was studied. The concentration of water added in preparation and temperature in calcination were changed to regulate formation of anatase TiO2. Ti contents in samples and grain size of anantase TiO2 were measured, and the catalytic activity in photodegrading gaseous toluene was characterized. The photocatalytic activity increased sharply when the calcination temperature increased to 500 °C or the volume of water added in preparation reached 1.5 mL. XRD analysis indicated that the crystal phase transformation of TiO2 from anatase to rutile was restrained and TiO2 remained in the form of anatase even after being sintered at 900 °C. The high constant photocatalytic activity from 500 to 900 °C was attributed to the stability of anatase TiO2 in crystal size and phase transformation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801974y

Investigation of cooling effectiveness of gas turbine inlet fogging location relative to the silencer / Jobaidur R. Khan in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 2 (Février 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 2 (Février 2012) . - 09 p. Titre : Investigation of cooling effectiveness of gas turbine inlet fogging location relative to the silencer Type de document : texte imprimé Auteurs : Jobaidur R. Khan, Auteur ; Ting Wang, Auteur ; Mustapha Chaker, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Compressors  Computational  fluid  dynamics  Cooling  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The output and efficiency of gas turbines are reduced significantly during the summer, especially in areas where the daytime temperature reaches as high as 50°C. Gas turbine inlet fogging and overspray has been considered a simple and cost-effective method to increase the power output. One of the most important issues related to inlet fogging is to determine the most effective location of the fogging device by determining (a) how many water droplets actually evaporate effectively to cool down the inlet air instead of colliding on the wall or coalescing and draining out (i.e., fogging efficiency), and (b) quantifying the amount of nonevaporated droplets that may reach the compressor bellmouth to ascertain the erosion risk for compressor airfoils if wet compression is to be avoided. When the silencer is installed, there is an additional consideration for placing the fogging device upstream or downstream of the silencer baffles. Placing arbitrarily the device upstream of the silencer can cause the silencer to intercept water droplets on the silencer baffles and lose cooling effectiveness. This paper employs computational fluid dynamics (CFD) to investigate the water droplet transport and cooling effectiveness with different spray locations such as before and after the silencer baffles. Analysis on the droplet history (trajectory and size) is employed to interpret the mechanism of droplet dynamics under influence of acceleration, diffusion, and body forces when the flow passes through the baffles and duct bent. The results show that, for the configuration of the investigated duct, installing the fogging system upstream of the silencer is about 3 percentage points better in evaporation effectiveness than placing it downstream of the silencer, irrespective of whether the silencer consists of a single row of baffles or two rows of staggered baffles. The evaporation effectiveness of the staggered silencer is about 0.8 percentage points higher than the single silencer. The pressure drop of the staggered silencer is 6.5% higher than the single silencer. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000002 [...] [article] Investigation of cooling effectiveness of gas turbine inlet fogging location relative to the silencer [texte imprimé] / Jobaidur R. Khan, Auteur ; Ting Wang, Auteur ; Mustapha Chaker, Auteur . - 2012 . - 09 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 2 (Février 2012) . - 09 p. Mots-clés : Compressors  Computational  fluid  dynamics  Cooling  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The output and efficiency of gas turbines are reduced significantly during the summer, especially in areas where the daytime temperature reaches as high as 50°C. Gas turbine inlet fogging and overspray has been considered a simple and cost-effective method to increase the power output. One of the most important issues related to inlet fogging is to determine the most effective location of the fogging device by determining (a) how many water droplets actually evaporate effectively to cool down the inlet air instead of colliding on the wall or coalescing and draining out (i.e., fogging efficiency), and (b) quantifying the amount of nonevaporated droplets that may reach the compressor bellmouth to ascertain the erosion risk for compressor airfoils if wet compression is to be avoided. When the silencer is installed, there is an additional consideration for placing the fogging device upstream or downstream of the silencer baffles. Placing arbitrarily the device upstream of the silencer can cause the silencer to intercept water droplets on the silencer baffles and lose cooling effectiveness. This paper employs computational fluid dynamics (CFD) to investigate the water droplet transport and cooling effectiveness with different spray locations such as before and after the silencer baffles. Analysis on the droplet history (trajectory and size) is employed to interpret the mechanism of droplet dynamics under influence of acceleration, diffusion, and body forces when the flow passes through the baffles and duct bent. The results show that, for the configuration of the investigated duct, installing the fogging system upstream of the silencer is about 3 percentage points better in evaporation effectiveness than placing it downstream of the silencer, irrespective of whether the silencer consists of a single row of baffles or two rows of staggered baffles. The evaporation effectiveness of the staggered silencer is about 0.8 percentage points higher than the single silencer. The pressure drop of the staggered silencer is 6.5% higher than the single silencer. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000002 [...]

Simulation of mist film cooling on rotating gas turbine blades / T. S. Dhanasekaran in Journal of heat transfer, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 11 p. Titre : Simulation of mist film cooling on rotating gas turbine blades Type de document : texte imprimé Auteurs : T. S. Dhanasekaran, Auteur ; Ting Wang, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : Heat transfer Langues : Anglais (eng) Mots-clés : Blades  Computational  fluid  dynamics  Convection  Cooling  Drops  Flow  simulation  Flue  gases  Gas  turbines  Jets  Liquid  films  Rotational  flow  Thin  films  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : 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. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...] [article] Simulation of mist film cooling on rotating gas turbine blades [texte imprimé] / T. S. Dhanasekaran, Auteur ; Ting Wang, Auteur . - 2012 . - 11 p. Heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 1 (Janvier 2012) . - 11 p. Mots-clés : Blades  Computational  fluid  dynamics  Convection  Cooling  Drops  Flow  simulation  Flue  gases  Gas  turbines  Jets  Liquid  films  Rotational  flow  Thin  films  Two-phase  flow Index. décimale : 536 Chaleur. Thermodynamique Résumé : 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. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000001 [...]

Three-dimensional modeling for wet compression in a single stage compressor including liquid particle erosion analysis / Jobaidur R. Khan in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 1 (Janvier 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 1 (Janvier 2011) . - 13 p. Titre : Three-dimensional modeling for wet compression in a single stage compressor including liquid particle erosion analysis Type de document : texte imprimé Auteurs : Jobaidur R. Khan, Auteur ; Ting Wang, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Acceleration  Compressible  flow  Compressors  Computational  fluid  dynamics  Cooling  Drops  Gas  turbines  Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas turbine inlet fog/overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a 3D computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code FLUENT. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. Eulerian–Lagrangian method is used to calculate the continuous phase and track the discrete (droplet) phase. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on the droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under the influence of local turbulence, acceleration, diffusion, and body forces. A liquid-droplet erosion model is included. The sensitivity of the turbulence models on the results is conducted by employing six different turbulence models and four different time constants. The result shows that the local thermal equilibrium is not always achieved due to short residence time and high value of latent heat of water. Local pressure gradients in both the rotor and stator flow passages drive up the droplet slip velocity during compression. The erosion model predicts that the most eroded area occurs in the leading edge and one spot of the trailing edge of the rotor suction side. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Three-dimensional modeling for wet compression in a single stage compressor including liquid particle erosion analysis [texte imprimé] / Jobaidur R. Khan, Auteur ; Ting Wang, Auteur . - 2012 . - 13 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 1 (Janvier 2011) . - 13 p. Mots-clés : Acceleration  Compressible  flow  Compressors  Computational  fluid  dynamics  Cooling  Drops  Gas  turbines  Turbulence Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Gas turbine inlet fog/overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a 3D computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code FLUENT. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. Eulerian–Lagrangian method is used to calculate the continuous phase and track the discrete (droplet) phase. Models to simulate droplet breakup and coalescence are incorporated to take into consideration the effect of local acceleration and deceleration on water droplet dynamics. Analysis on the droplet history (trajectory and size) with stochastic tracking is employed to interpret the mechanism of droplet dynamics under the influence of local turbulence, acceleration, diffusion, and body forces. A liquid-droplet erosion model is included. The sensitivity of the turbulence models on the results is conducted by employing six different turbulence models and four different time constants. The result shows that the local thermal equilibrium is not always achieved due to short residence time and high value of latent heat of water. Local pressure gradients in both the rotor and stator flow passages drive up the droplet slip velocity during compression. The erosion model predicts that the most eroded area occurs in the leading edge and one spot of the trailing edge of the rotor suction side. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]