Experimental investigation of piston heat transfer under conventional diesel and reactivity-controlled compression ignition combustion regimes

Abstract

The piston of a heavy-duty single-cylinder research engine was instrumented with 11 fast-response surface thermocouples, and a commercial wireless telemetry system was used to transmit the signals from the moving piston. The raw thermocouple data were processed using an inverse heat conduction method that included Tikhonov regularization to recover transient heat flux. By applying symmetry, the data were compiled to provide time-resolved spatial maps of the piston heat flux and surface temperature. A detailed comparison was made between conventional diesel combustion and reactivity-controlled compression ignition combustion operations at matched conditions of load, speed, boost pressure, and combustion phasing. The integrated piston heat transfer was found to be 24% lower, and the mean surface temperature was 25 °C lower for reactivity-controlled compression ignition operation as compared to conventional diesel combustion, in spite of the higher peak heat release rate. Lower integrated piston heat transfer for reactivity-controlled compression ignition was found over all the operating conditions tested. The results showed that increasing speed decreased the integrated heat transfer for conventional diesel combustion and reactivity-controlled compression ignition. The effect of the start of injection timing was found to strongly influence conventional diesel combustion heat flux, but had a negligible effect on reactivity-controlled compression ignition heat flux, even in the limit of near top dead center high-reactivity fuel injection timings. These results suggest that the role of the high-reactivity fuel injection does not significantly affect the thermal environment even though it is important for controlling the ignition timing and heat release rate shape. The integrated heat transfer and the dynamic surface heat flux were found to be insensitive to changes in boost pressure for both conventional diesel combustion and reactivity-controlled compression ignition. However, for reactivity-controlled compression ignition, the mean surface temperature increased with changes in boost suggesting that equivalence ratio affects steady-state heat transfer.

Experimental Investigation of Piston Heat Transfer in a Light Duty Engine Under Conventional Diesel, Homogeneous Charge Compression Ignition, and Reactivity Controlled Compression Ignition Combustion Regimes

“…The signal conversion process induces a degree of filtering but the advertised bandwidth of the system is 10kHz [17]. Similar systems have been used by other researchers [12,13].…”

“…The heat transfer for CDC has been studied on both piston surfaces and on stationary locations such as on the engine head and cylinder liners [10,11]. More recently, measurements have been made on the piston surface with engines operating under RCCI and CDC combustion [12]. Measurements made on the piston surface are harder to make than those on fixed locations.…”

Failure Analysis of the Pin Bore of the Combined Piston for the Aero Engine

“…The third type of boundary condition is usually adopted in the analysis of the piston, which requires the temperature T and heat transfer coefficient α of the peripheral medium to be given. The G. Eichelberg formula is usually selected to calculate it [21]. The experiment can be conducted after calculating the heat transfer coefficient and temperature field [22].…”

Influence de la variation de la température de combustion dans un moteur Diesel sur les émissions de polluants (NOx et suies)

“…Les pressions initiales et les valeurs sont obtenues à partir des températures de pression mesurées à l'entrée et dans les cylindres. Les températures limites peuvent être ajustées à partir de valeurs proposées par la littérature spécialisée et les développeurs (ou constructeurs) de logiciels (Lian et al, 2009 ;Hendricks et al, 2014).…”

“…La réduction des émissions de polluants constitue une problématique pour les spécialistes du moteur Diesel. Dans ce type de moteur DI, d'importantes recherches ont été entamées afin de comprendre les processus physiques qui régissent le fonctionnement d'un moteur et de réduire les émissions de polluants comme les oxydes d'azote (NOx), hydrocarbures imbrûlés (HC) et les particules de suie (Gissinger, 2002 ;Hendricks et al, 2014). L'ascension de ces polluants dans les gaz d'échappement, dépend des conditions dans lesquelles se produit la phase de combustion qui dépend de la qualité du mélange air-carburant.…”