Documents disponibles écrits par cet auteur

Effects of branching on the pressure-volume-temperature behaviors of PP/CO2 solutions / Y. G. Li in Industrial & engineering chemistry research, Vol. 48 N° 14 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6633–6640 Titre : Effects of branching on the pressure-volume-temperature behaviors of PP/CO2 solutions Type de document : texte imprimé Auteurs : Y. G. Li, Auteur ; C. B. Park, Auteur Année de publication : 2009 Article en page(s) : pp. 6633–6640 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Polymer/gas  solutions  Pressure-volume-temperature  properties  Linear  polypropylene  Branched  polypropylene Résumé : The pressure−volume−temperature (PVT) properties of polymer/gas solutions are characterized by determining their volume dilation at a known temperature and pressure. This paper presents the results of an experiment that measured the volume swelling of linear and branched polypropylene (PP) with CO2 using a new PVT measurement apparatus. The swellings and specific volumes for linear and branched PP/CO2 are compared. The swelling mechanism that occurred due to CO2 dissolution, and the effects of the branched structure on volume swelling are investigated and discussed. Due to its entangled branch structure, the branched PP underwent a lesser degree of volume swelling than did the linear PP. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8015279 [article] Effects of branching on the pressure-volume-temperature behaviors of PP/CO2 solutions [texte imprimé] / Y. G. Li, Auteur ; C. B. Park, Auteur . - 2009 . - pp. 6633–6640. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6633–6640 Mots-clés : Polymer/gas  solutions  Pressure-volume-temperature  properties  Linear  polypropylene  Branched  polypropylene Résumé : The pressure−volume−temperature (PVT) properties of polymer/gas solutions are characterized by determining their volume dilation at a known temperature and pressure. This paper presents the results of an experiment that measured the volume swelling of linear and branched polypropylene (PP) with CO2 using a new PVT measurement apparatus. The swellings and specific volumes for linear and branched PP/CO2 are compared. The swelling mechanism that occurred due to CO2 dissolution, and the effects of the branched structure on volume swelling are investigated and discussed. Due to its entangled branch structure, the branched PP underwent a lesser degree of volume swelling than did the linear PP. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8015279

Gas turbine performance and health status estimation using adaptive gas path analysis / Y. G. Li in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 4 (Avril 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 4 (Avril 2010) . - 09 p. Titre : Gas turbine performance and health status estimation using adaptive gas path analysis Type de document : texte imprimé Auteurs : Y. G. Li, Auteur Année de publication : 2010 Article en page(s) : 09 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Aerospace  engines  Aerospace  testing  Compressors  Condition  monitoring  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In gas turbine operations, engine performance and health status are very important information for engine operators. Such engine performance is normally represented by engine airflow rate, compressor pressure ratios, compressor isentropic efficiencies, turbine entry temperature, turbine isentropic efficiencies, etc., while the engine health status is represented by compressor and turbine efficiency indices and flow capacity indices. However, these crucial performance and health information cannot be directly measured and therefore are not easily available. In this research, a novel Adaptive Gas Path Analysis (Adaptive GPA) approach has been developed to estimate actual engine performance and gas path component health status by using gas path measurements, such as gas path pressures, temperatures, shaft rotational speeds, fuel flow rate, etc. Two steps are included in the Adaptive GPA approach, the first step is the estimation of degraded engine performance status by a novel application of a performance adaptation method, and the second step is the estimation of engine health status at component level by using a new diagnostic method introduced in this paper, based on the information obtained in the first step. The developed Adaptive GPA approach has been tested in four test cases where the performance and degradation of a model gas turbine engine similar to Rolls-Royce aero engine Avon-300 have been analyzed. The case studies have shown that the developed novel linear and nonlinear Adaptive GPA approaches can accurately and quickly estimate the degraded engine performance and predict the degradation of major engine gas path components with the existence of measurement noise. The test cases have also shown that the calculation time required by the approach is short enough for its potential online applications. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000004 [...] [article] Gas turbine performance and health status estimation using adaptive gas path analysis [texte imprimé] / Y. G. Li, Auteur . - 2010 . - 09 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 4 (Avril 2010) . - 09 p. Mots-clés : Aerospace  engines  Aerospace  testing  Compressors  Condition  monitoring  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : In gas turbine operations, engine performance and health status are very important information for engine operators. Such engine performance is normally represented by engine airflow rate, compressor pressure ratios, compressor isentropic efficiencies, turbine entry temperature, turbine isentropic efficiencies, etc., while the engine health status is represented by compressor and turbine efficiency indices and flow capacity indices. However, these crucial performance and health information cannot be directly measured and therefore are not easily available. In this research, a novel Adaptive Gas Path Analysis (Adaptive GPA) approach has been developed to estimate actual engine performance and gas path component health status by using gas path measurements, such as gas path pressures, temperatures, shaft rotational speeds, fuel flow rate, etc. Two steps are included in the Adaptive GPA approach, the first step is the estimation of degraded engine performance status by a novel application of a performance adaptation method, and the second step is the estimation of engine health status at component level by using a new diagnostic method introduced in this paper, based on the information obtained in the first step. The developed Adaptive GPA approach has been tested in four test cases where the performance and degradation of a model gas turbine engine similar to Rolls-Royce aero engine Avon-300 have been analyzed. The case studies have shown that the developed novel linear and nonlinear Adaptive GPA approaches can accurately and quickly estimate the degraded engine performance and predict the degradation of major engine gas path components with the existence of measurement noise. The test cases have also shown that the calculation time required by the approach is short enough for its potential online applications. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000004 [...]

Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method / Y. G. Li in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 3 (Mars 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 10 p. Titre : Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method Type de document : texte imprimé Auteurs : Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Engines  Gas  turbine  power  stations  Genetic  algorithms  Least  squares  approximations  Regression  analysis  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At off-design conditions, engine performance model prediction accuracy depends largely on its component characteristic maps. With the absence of actual characteristic maps, performance adaptation needs to be done for good imitations of actual engine performance. A nonlinear multiple point genetic algorithm based performance adaptation developed earlier by the authors using a set of nonlinear scaling factor functions has been proven capable of making accurate performance predictions over a wide range of operating conditions. However, the success depends on searching the right range of scaling factor coefficients heuristically, in order to obtain the optimum scaling factor functions. Such search ranges may be difficult to obtain and in many off-design adaption cases, it may be very time consuming due to the nature of the trial and error process. In this paper, an improvement on the present adaptation method is presented using a least square method where the search range can be selected deterministically. In the new method, off-design adaptation is applied to individual off-design point first to obtain individual off-design point scaling factors. Then plots of the scaling factors against the off-design conditions are generated. Using the least square method, the relationship between each scaling factor and the off-design operating condition is generated. The regression coefficients are then used to determine the search range of the scaling factor coefficients before multiple off-design points performance adaptation is finally applied. The developed adaptation approach has been applied to a model single-spool turboshaft engine and demonstrated a simpler and faster way of obtaining the optimal scaling factor coefficients compared with the original off-design adaptation method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...] [article] Improved multiple point nonlinear genetic algorithm based performance adaptation using least square method [texte imprimé] / Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 3 (Mars 2012) . - 10 p. Mots-clés : Engines  Gas  turbine  power  stations  Genetic  algorithms  Least  squares  approximations  Regression  analysis  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : At off-design conditions, engine performance model prediction accuracy depends largely on its component characteristic maps. With the absence of actual characteristic maps, performance adaptation needs to be done for good imitations of actual engine performance. A nonlinear multiple point genetic algorithm based performance adaptation developed earlier by the authors using a set of nonlinear scaling factor functions has been proven capable of making accurate performance predictions over a wide range of operating conditions. However, the success depends on searching the right range of scaling factor coefficients heuristically, in order to obtain the optimum scaling factor functions. Such search ranges may be difficult to obtain and in many off-design adaption cases, it may be very time consuming due to the nature of the trial and error process. In this paper, an improvement on the present adaptation method is presented using a least square method where the search range can be selected deterministically. In the new method, off-design adaptation is applied to individual off-design point first to obtain individual off-design point scaling factors. Then plots of the scaling factors against the off-design conditions are generated. Using the least square method, the relationship between each scaling factor and the off-design operating condition is generated. The regression coefficients are then used to determine the search range of the scaling factor coefficients before multiple off-design points performance adaptation is finally applied. The developed adaptation approach has been applied to a model single-spool turboshaft engine and demonstrated a simpler and faster way of obtaining the optimal scaling factor coefficients compared with the original off-design adaptation method. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000003 [...]

Nonlinear multiple points gas turbine off-design performance adaptation using a genetic algorithm / Y. G. Li in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 133 N° 7 (Juillet 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 7 (Juillet 2011) Titre : Nonlinear multiple points gas turbine off-design performance adaptation using a genetic algorithm Type de document : texte imprimé Auteurs : Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur Année de publication : 2011 Note générale : Turbines à gaz Langues : Anglais (eng) Mots-clés : Gas  turbines  Genetic  algorithms  Shafts  Thermodynamics Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Accurate gas turbine performance models are crucial in many gas turbine performance analysis and gas path diagnostic applications. With current thermodynamic performance modeling techniques, the accuracy of gas turbine performance models at off-design conditions is determined by engine component characteristic maps obtained in rig tests and these maps may not be available to gas turbine users or may not be accurate for individual engines. In this paper, a nonlinear multiple point performance adaptation approach using a genetic algorithm is introduced with the aim to improve the performance prediction accuracy of gas turbine engines at different off-design conditions by calibrating the engine performance models against available test data. Such calibration is carried out with introduced nonlinear map scaling factor functions by “modifying” initially implemented component characteristic maps in the gas turbine thermodynamic performance models. A genetic algorithm is used to search for an optimal set of nonlinear scaling factor functions for the maps via an objective function that measures the difference between the simulated and actual gas path measurements. The developed off-design performance adaptation approach has been applied to a model single spool turbo-shaft aero gas turbine engine and has demonstrated a significant improvement in the performance model accuracy at off-design operating conditions. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...] [article] Nonlinear multiple points gas turbine off-design performance adaptation using a genetic algorithm [texte imprimé] / Y. G. Li, Auteur ; M. F. Abdul Ghafir, Auteur ; L. Wang, Auteur . - 2011. Turbines à gaz Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 133 N° 7 (Juillet 2011) Mots-clés : Gas  turbines  Genetic  algorithms  Shafts  Thermodynamics Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Accurate gas turbine performance models are crucial in many gas turbine performance analysis and gas path diagnostic applications. With current thermodynamic performance modeling techniques, the accuracy of gas turbine performance models at off-design conditions is determined by engine component characteristic maps obtained in rig tests and these maps may not be available to gas turbine users or may not be accurate for individual engines. In this paper, a nonlinear multiple point performance adaptation approach using a genetic algorithm is introduced with the aim to improve the performance prediction accuracy of gas turbine engines at different off-design conditions by calibrating the engine performance models against available test data. Such calibration is carried out with introduced nonlinear map scaling factor functions by “modifying” initially implemented component characteristic maps in the gas turbine thermodynamic performance models. A genetic algorithm is used to search for an optimal set of nonlinear scaling factor functions for the maps via an objective function that measures the difference between the simulated and actual gas path measurements. The developed off-design performance adaptation approach has been applied to a model single spool turbo-shaft aero gas turbine engine and has demonstrated a significant improvement in the performance model accuracy at off-design operating conditions. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013300 [...]