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In the present study, the effects of inlet isothermal jet geometry on the mixing process with variable density have been investigated numerically. Four density ratios were considered, namely R ρ =7.2, 1.8,1 and 0.66 for He-air, CH4-air, Air-air and CO2-air mixtures respectively. The jets are produced through rectangular and elliptic nozzles with aspect ratio Ar = 2:1. The elliptic and rectangular nozzles have approximately the same exit area as the circular nozzle. A second-order Reynolds stress model (RSM) is used to investigate variable density effects in asymmetric turbulent jets. Comparative studies are presented for the calculations of the variables such as the longitudinal velocity, the longitudinal fluctuating velocity and the turbulent kinetic energy.The results indicate that the asymmetric geometry noticeably enhances mixing in comparison with the axisymmetric case. Typical phenomenon of 3D jets is observed.

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International audienceBiofuels are a promising alternative to petroleum-based fuels. This paper investigates the performance, combustion, and exhaust emissions of a single cylinder diesel engine operated on baseline diesel and biofuel produced by vegetable oil and processing animal fat. The vegetable oil is called PODL20, which is a blend of palm oil and D-Limonen in proportion of 80% and 20%, respectively. The second biofuel is synthesized from the animal fat wastes (WAF) after transesterification process. Both experimental and numerical investigations are achieved in this work. The experiments are conducted at constant engine speed mode (1800 rpm) with applied loads on a wide domain. The CFD code CONVERGE is used to simulate the in-cylinder combustion for all the tested fuels. Comparative measures of brake thermal efficiency, break specific fuel consumption (bsfc), exhaust gas temperature, volumetric efficiency, and pollution (THC, CO2, CO, NO, NOx) are presented and discussed. Also, a step is achieved with in-cylinder CFD simulation of biofuel combustion. The obtained results indicate that the combustion characteristics are slightly changed when comparing neat diesel to biofuels. Some of the results obtained in this work indicate that WAF fuel decreases the total unburned fuel as well as the nitrogen oxides (NOx) emissions. The numerical results are in logic agreement with those obtained experimentally, which promotes more detailed investigations and combustion characteristics optimization in forthcoming works. [DOI: 10.1115/1.4005660

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