Experimental investigation on heat transfer of n-pentane spray impingement on piston surface

Abstract

Fuel spray impingement on piston surfaces is a concern because it can cause particulate exhaust emissions from gasoline direct injection (GDI) engine. Transient heat transfer plays an important role that directly influences liquid film evaporation and its lifetime. In this paper, the effects of injection temperature, injection pressure, piston temperature and impact distance on n-pentane spray impingement heat transfer were fully examined. Results showed that increasing the piston temperature could increase the rate of heat transfer with a larger surface temperature reduction and a higher heat flux, which led to a shorter liquid film lifetime on the piston surface. Increasing the fuel injection temperature helped to improve atomization of the fuel spray, reduce the penetration distance and mitigate impact, which in turn led to reduced surface cooling and less liquid film on the piston surface. A decrease in impact distance and an increase in injection pressure both caused an increase in surface temperature reduction and heat flux but a decrease in the liquid film residence time. The dimensionless heat flux in terms of Biot and Fourier numbers presented a high similarity during the rapid cooling stage. A dimensionless correlation was formed to quantify this fast time-varying heat transfer behaviour.

Investigation of fuel volatility on the heat transfer dynamics on piston surface due to the pulsed spray impingement

“…3) experienced the most obvious temperature change due to the most intense impingement during the transient heat transfer process compared with other measurement points (The typical 8 transient temperature curves were shown in Fig. 5 of the previous work [28]). Therefore, the temperature and heat flux from this measurement point were selected as the salient value in the following subsections to illustrate the effects of injection temperature (Tinj), injection pressure (Pinj), piston temperature (Tpis)…”

“…The spray chamber is made of a full-length optical cylinder liner with an inner diameter of 89 mm, and is open to the atmosphere at the top and the exhaust air is drawn out through extraction system at the bottom. More details about the whole system can be found in our previous study [28].…”

“…Fig. 3 Geometry model of the two-layer system for solution of the Inverse Heat Conduction problem (IHCP) with the PRTs [28] Before the experiment, careful calibration of the eight PRTs yields correlations between the temperature and voltage acquired by the NI-DAQ system. In the experimental system, there is a pulse signal controlled by a manual switch that is used to synchronize the: the fuel injection event, the high speed camera and the temperature data acquisition.…”

“…More details of temperature measurement and heat flux calculation can be found in our previous study [28,29].…”

Experimental investigation of heat transfer for diesel spray impingement on a high temperature wall

“…4 b,c that q s and h both reach the peak rapidly and then decrease rapidly and finally stabilize. During the process of spray-wall impingement, the quick increase of q s and h can be explained by the phenomenon of spray-wall impingement leading to a strong convection on the high temperature surface with a high local heat transfer coefficient 34 . However, the fuel will adhere to the wall and form a liquid film after the fuel injection is finished.…”