Documents disponibles écrits par cet auteur

Active compressor stability management via a stall margin control mode / Yuan Liu in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 5 (Mai 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 5 (Mai 2010) . - 10 p. Titre : Active compressor stability management via a stall margin control mode Type de document : texte imprimé Auteurs : Yuan Liu, Auteur ; Manuj Dhingra, Auteur ; J. V. R. Prasad, Auteur Année de publication : 2011 Article en page(s) : 10 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Aerospace  engines  Aircraft  control  Compressors  Gas  turbines  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode are described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000005 [...] [article] Active compressor stability management via a stall margin control mode [texte imprimé] / Yuan Liu, Auteur ; Manuj Dhingra, Auteur ; J. V. R. Prasad, Auteur . - 2011 . - 10 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 5 (Mai 2010) . - 10 p. Mots-clés : Aerospace  engines  Aircraft  control  Compressors  Gas  turbines  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode are described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000005 [...]

Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization / Tong-xu Liu in Industrial & engineering chemistry research, Vol. 50 N° 13 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7841–7848 Titre : Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization Type de document : texte imprimé Auteurs : Tong-xu Liu, Auteur ; Yuan Liu, Auteur ; Zhao-ji Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 7841–7848 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Radiation  chemistry  Photochemistry  photographic  Reprographic  processes Résumé : In aqueous photoreaction systems, the existence of gradient light intensity throughout the reaction solution is one of the important restrictions to the efficiency of the overall photoreaction, which highly relies on the optical properties of the catalyst such as light absorption and scattering effects, the particle size of the catalyst, and the degree of agglomeration in its slurry. In this study, both synthesized TiO2 hydrosol and commercial TiO2 powder, Degussa TiO2 P25, were used as catalysts for comparison, in which their particulate and optical properties in aqueous solution/suspension were investigated. The characteristic results showed that the TiO2 hydrosol had smaller crystal sizes and particle sizes, but a lower degree of crystallinity compared to the P25 powder. As TiO2 hydrosol solution had the much lower light extinction coefficient than P25 suspension, the attenuation of light intensity gradient in the reaction solution containing more transparent TiO2 hydrosol was greatly eliminated. However, both types of catalysts demonstrated similar effects of significant light scattering in their solution/suspension. The photocatalytic activities of two catalysts were then evaluated in two sets of experiments for methyl orange (MO) and methylsulfonic acid (MSA) degradations, respectively. The much higher reaction rates of MO and MSA degradations were found in the TiO2 hydrosol solution than in the P25 suspension, because TiO2 hydrosol catalyst with much finer particles and higher transparency allowed the photoreactor system to work at a higher catalyst loading than the conventional TiO2 powdery catalyst. A new kinetic model considering three main factors of (i) the volumetric rate of photon absorption, (ii) effective reaction volume, and (iii) the effective surface area of catalyst in a cylindrical photoreactor was also established. This new model summarizes that the catalyst with a higher surface area, a lower light extinction coefficient, and a lesser light scattering effect would achieve better light utilization within the photoreactor system and is beneficial to achieve a higher efficiency of overall photoreaction. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102584j [article] Comparison of aqueous photoreactions with TiO2 in its hydrosol solution and powdery suspension for light utilization [texte imprimé] / Tong-xu Liu, Auteur ; Yuan Liu, Auteur ; Zhao-ji Zhang, Auteur . - 2011 . - pp. 7841–7848. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7841–7848 Mots-clés : Radiation  chemistry  Photochemistry  photographic  Reprographic  processes Résumé : In aqueous photoreaction systems, the existence of gradient light intensity throughout the reaction solution is one of the important restrictions to the efficiency of the overall photoreaction, which highly relies on the optical properties of the catalyst such as light absorption and scattering effects, the particle size of the catalyst, and the degree of agglomeration in its slurry. In this study, both synthesized TiO2 hydrosol and commercial TiO2 powder, Degussa TiO2 P25, were used as catalysts for comparison, in which their particulate and optical properties in aqueous solution/suspension were investigated. The characteristic results showed that the TiO2 hydrosol had smaller crystal sizes and particle sizes, but a lower degree of crystallinity compared to the P25 powder. As TiO2 hydrosol solution had the much lower light extinction coefficient than P25 suspension, the attenuation of light intensity gradient in the reaction solution containing more transparent TiO2 hydrosol was greatly eliminated. However, both types of catalysts demonstrated similar effects of significant light scattering in their solution/suspension. The photocatalytic activities of two catalysts were then evaluated in two sets of experiments for methyl orange (MO) and methylsulfonic acid (MSA) degradations, respectively. The much higher reaction rates of MO and MSA degradations were found in the TiO2 hydrosol solution than in the P25 suspension, because TiO2 hydrosol catalyst with much finer particles and higher transparency allowed the photoreactor system to work at a higher catalyst loading than the conventional TiO2 powdery catalyst. A new kinetic model considering three main factors of (i) the volumetric rate of photon absorption, (ii) effective reaction volume, and (iii) the effective surface area of catalyst in a cylindrical photoreactor was also established. This new model summarizes that the catalyst with a higher surface area, a lower light extinction coefficient, and a lesser light scattering effect would achieve better light utilization within the photoreactor system and is beneficial to achieve a higher efficiency of overall photoreaction. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102584j

Correlation measure-based stall margin estimation for a single-stage axial compressor / Yuan Liu in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 1 (Janvier 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 1 (Janvier 2012) . - 09 p. Titre : Correlation measure-based stall margin estimation for a single-stage axial compressor Type de document : texte imprimé Auteurs : Yuan Liu, Auteur ; Manuj Dhingra, Auteur ; J. V. R. Prasad, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Aircraft  control  Compressors  Correlation  methods  Gas  turbines  Rotors  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a method for estimating compressor stall margin and the results of applying the estimation technique to an axial compressor rig. Stall margin estimation is accomplished through the use of a compressor stability detection parameter called the “correlation measure.” The correlation measure captures the periodicity of the pressure in the rotor tip region of the compressor. The downcrossing frequency of the correlation measure across some preset threshold is measured while operating the compressor rig at various steady-state points along the design speed characteristic line. These measurements are used to generate a relationship with stall margin as a function of downcrossing frequency. The estimation technique is evaluated by applying it while dynamically ramping the operating point of the compressor up the design speed line towards surge. A brief investigation on the effects of inlet distortions on the correlation measure-based estimation system is also given. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000001 [...] [article] Correlation measure-based stall margin estimation for a single-stage axial compressor [texte imprimé] / Yuan Liu, Auteur ; Manuj Dhingra, Auteur ; J. V. R. Prasad, 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° 1 (Janvier 2012) . - 09 p. Mots-clés : Aircraft  control  Compressors  Correlation  methods  Gas  turbines  Rotors  Stability Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper presents a method for estimating compressor stall margin and the results of applying the estimation technique to an axial compressor rig. Stall margin estimation is accomplished through the use of a compressor stability detection parameter called the “correlation measure.” The correlation measure captures the periodicity of the pressure in the rotor tip region of the compressor. The downcrossing frequency of the correlation measure across some preset threshold is measured while operating the compressor rig at various steady-state points along the design speed characteristic line. These measurements are used to generate a relationship with stall margin as a function of downcrossing frequency. The estimation technique is evaluated by applying it while dynamically ramping the operating point of the compressor up the design speed line towards surge. A brief investigation on the effects of inlet distortions on the correlation measure-based estimation system is also given. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000001 [...]