Search

This paper presents thermodynamic analysis of piston friction in spark-ignition internal combustion engines. The general effect of piston friction on engine performance was examined during cold starting and normal working conditions. Considerations were made using temperature-dependent specific heat model in order to make the analysis more realistic. A parametric study was performed covering wide range of dependent variables such as engine speed, taking into consideration piston friction combined with the variation of the specific heat with temperature, and heat loss from the cylinder. The results are presented for skirt friction only, and then for total piston friction (skirt and rings). The effect of oil viscosity is investigated over a wide range of engine speeds and oil temperatures. In general, it is found that oils with higher viscosities result in lower efficiency values. Using high viscosity oil can reduce the efficiency by more than 50% at cold oil temperatures. The efficiency maps for SAE 10, SAE 30, and SAE 50 are reported. The results of this model can be practically utilized to obtain optimized efficiency results either by selecting the optimum operating speed for a given oil type (viscosity) and temperature or by selecting the optimum oil type for a given operating speed and temperature. The effect of different piston ring configurations on the efficiency is also presented. Finally, the oil film thickness on the engine performance is studied in this paper. [DOI: 10.1115/1.2795777]

The article investigates the effect of suction and blowing on heat transfer and fluid flow over a backward-facing step (BFS). The reattachment length at the primary recirculation bubble suction is increased by increasing blowing rate and decreased by increasing the suction bleed rate.

Heat transfer enhancement in combined convection around a rotating horizontal cylinder using nanofluids is presented. The transport equations are solved numerically using a second order finite volume scheme.

Byline: A. Al-Ghandoor, I. Al-Hinti, B. Akash, E. Abu-Nada This study presents an analysis of the energy and exergy utilisation of the Jordanian urban residential sector by considering the flows of energy and exergy through the main end uses and applications in Jordanian households. To achieve this purpose, a survey covering 200 households was conducted and energy consumption data were gathered. Exergy analysis of Jordanian urban residential sector utilisation indicates a less efficient picture than that obtained by the energy analysis. Energy and exergy efficiencies were found to be equal to 66.6% and 15.4%, respectively.