Convective Heat Transfer in a Pneumatic Hybrid Engine

Pascal Brejaud (1) , Pascal Higelin (1) , Alain Charlet (1) , Guillaume Colin (2) , Yann Chamaillard (1)

1 F2ME
2 PRISME - Laboratoire Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique

Several previous studies have proven that pneumatic hybridization of an internal combustion engine is a technically viable and cost-efficient alternative to electric hybridization. Because the heat transfer process remains a first order factor while the engine operates in a motored or pneumatic mode without combustion, an accurate instantaneous heat transfer model is required in order to predict the in-cylinder pressure. This study shows that the original Woschni model is not suitable for describing the shape of the measured instantaneous heat flux versus crank angle while the engine operates in a motored pneumatic mode, because of the extinction of tumble motion near Top Dead Center (TDC). A modified form of the Woschni model is therefore proposed here that better describes the instantaneous heat flux during compression and expansion strokes, applicable to pneumatic and motored with fuel cut-off modes. First, the new constant parameter model is identified from experimental measurements performed in various motored mode conditions. Next, the pneumatic supercharged mode without combustion (ignition not performed) is investigated with the new model using the same identification values as for the motored mode. This study shows that the modified model remains fully applicable to the supercharged mode, despite of a certainly modified in-cylinder aerodynamic structure created by the opening of the charging valve under a high pressure ratio

Domaines: Physique [physics]

Pascal Brejaud, Pascal Higelin, Alain Charlet, Guillaume Colin, Yann Chamaillard. Convective Heat Transfer in a Pneumatic Hybrid Engine. Oil & Gas Science and Technology - Revue d'IFP Energies nouvelles, 2011, 66 (6), pp.1035-1051. ⟨10.2516/ogst/2011121⟩. ⟨hal-00683095⟩