Documents disponibles écrits par cet auteur

Effects of charge preheating methods on the combustion phasing limitations of an HCCI engine with negative valve overlap / Laura Manofsky Olesky in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 11 (Novembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 11 (Novembre 2012) . - 12 p. Titre : Effects of charge preheating methods on the combustion phasing limitations of an HCCI engine with negative valve overlap Type de document : texte imprimé Auteurs : Laura Manofsky Olesky, Auteur ; Jiri Vavra, Auteur ; Dennis Assanis, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : gas turbines Langues : Anglais (eng) Mots-clés : homogeneous  charge  compression  ignition  (HCCI);  fuel  consumption;  spark-ignited  (SI)  combustion Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Homogeneous charge compression ignition (HCCI) has the potential to reduce both fuel consumption and NOx emissions compared to normal spark-ignited (SI) combustion. For a relatively low compression ratio engine, high unburned temperatures are needed to initiate HCCI combustion, which is achieved with large amounts of internal residual or by heating the intake charge. The amount of residual in the combustion chamber is controlled by a recompression valve strategy, which relies on negative valve overlap (NVO) to trap residual gases in the cylinder. A single-cylinder research engine with fully-flexible valve actuation is used to explore the limits of HCCI combustion phasing at a load of ~3 bar gross indicated mean effective pressure (IMEPg). This is done by performing two individual sweeps of (a) internal residual fraction (via NVO) and (b) intake air temperature to control combustion phasing. It is found that increasing both of these variables advances the phasing of HCCI combustion, which leads to increased NOx emissions and a higher ringing intensity. On the other hand, a reduction in these variables leads to greater emissions of CO and HC, as well as a decrease in combustion stability. A direct comparison of the two sweeps suggests that the points with elevated intake temperatures are more prone to ringing as combustion is advanced and less prone to instability and misfire as combustion is retarded. This behavior can be explained by compositional differences (air versus residual gas dilution) which lead to variations in burn rate and peak temperature. As a final study, two additional NVO sweeps are performed while holding intake temperature constant at 30 °C and 90 °C. Again, it is seen that for higher intake temperatures, combustion is more susceptible to ringing at advanced timings and more resistant to instability/misfire at retarded timings. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000011 [...] [article] Effects of charge preheating methods on the combustion phasing limitations of an HCCI engine with negative valve overlap [texte imprimé] / Laura Manofsky Olesky, Auteur ; Jiri Vavra, Auteur ; Dennis Assanis, Auteur . - 2012 . - 12 p. gas turbines Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 11 (Novembre 2012) . - 12 p. Mots-clés : homogeneous  charge  compression  ignition  (HCCI);  fuel  consumption;  spark-ignited  (SI)  combustion Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Homogeneous charge compression ignition (HCCI) has the potential to reduce both fuel consumption and NOx emissions compared to normal spark-ignited (SI) combustion. For a relatively low compression ratio engine, high unburned temperatures are needed to initiate HCCI combustion, which is achieved with large amounts of internal residual or by heating the intake charge. The amount of residual in the combustion chamber is controlled by a recompression valve strategy, which relies on negative valve overlap (NVO) to trap residual gases in the cylinder. A single-cylinder research engine with fully-flexible valve actuation is used to explore the limits of HCCI combustion phasing at a load of ~3 bar gross indicated mean effective pressure (IMEPg). This is done by performing two individual sweeps of (a) internal residual fraction (via NVO) and (b) intake air temperature to control combustion phasing. It is found that increasing both of these variables advances the phasing of HCCI combustion, which leads to increased NOx emissions and a higher ringing intensity. On the other hand, a reduction in these variables leads to greater emissions of CO and HC, as well as a decrease in combustion stability. A direct comparison of the two sweeps suggests that the points with elevated intake temperatures are more prone to ringing as combustion is advanced and less prone to instability and misfire as combustion is retarded. This behavior can be explained by compositional differences (air versus residual gas dilution) which lead to variations in burn rate and peak temperature. As a final study, two additional NVO sweeps are performed while holding intake temperature constant at 30 °C and 90 °C. Again, it is seen that for higher intake temperatures, combustion is more susceptible to ringing at advanced timings and more resistant to instability/misfire at retarded timings. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000011 [...]