Jamel Bessrour

The analysis of internal flows in diffuserless centrifugal turbomachinery using CFD must address unsteady problems related to the interaction between the moving domain (impeller) and the stationary domain (volute). Published studies deal with this problem in stationary mode (frozen rotor) or in fully unsteady mode. Unsteady-state calculation is generally more accurate, but it is still very time-consuming, costly and difficult to integrate into an industrial approach. In this study, we show that it is possible to use the quasi-statio nar y technique to determine, at lower cost, representative mean performances of the machine and output pressure fluctuations (aerodynamic source of the high noise level). We adopted this quasi-stationary technique to establish the performance of a radial centrifuga l fan (static pressure, total pressure and efficiency as a function of flow rate), with results very much in line with experimental findings. We have also used it, in an industrial approach, to optimize impeller performance by modifying blade inclination angles.

The objective of this article is to evaluate, through an experimental and numerical study, the effect of the addition of isooctane on the performance and Nox emissions of a spark–ignition engine four different mixtures in addition to gasoline were tested in a spark–ignition engine using the DIN70020 standard at full load. The tests were conducted by adding 10, 20, 30, and 40% isooctane by volume to unleaded commercial gasoline. This practice makes a significant contribution to improving engine performance, increasing fuel efficiency, and reducing pollutant emissions. As a result, the addition of isooctane is establishing itself as a standard in the manufacture of premium fuels, providing not only an improved driving experience but also preserving the health of the engine. Extensive studies have been conducted to explore the potential of isooctane as a fuel in this regard. NOx emissions were reduced by adding a proportion of isooctane to unleaded commercial gasoline for all fuel blends, which could be explained by the high vaporization enthalpy of isooctane. This reduces the maximum temperature reached in the cylinder and thus reduces nitrogen oxide (NOx) emissions. A significant reduction in emissions of approximately 5% is achieved for the I10 blend (10% isooctane + 90% unleaded commercial gasoline) with the maintenance of engine performance (torque and power). This experimental study is confirmed by a numerical simulation using the DIESL-RK software with an average convergence of results that varies from 0.47% to 5.01%.

The main purpose of this research is to study the effect of various blends of an environmental friendly alternative fuel “methyl ester” on the performance of a heavy diesel engine. The biodiesel was obtained from a chemical process: the transesterification of waste oils (frying oils). Tests were conducted on an engine test bench in accordance to DIN 2020 standards. Results obtained demonstrate that the biodiesel gives very interesting ecological advantages but engine performance was reduced slightly comparatively to those obtained with a pure diesel fuel. We have noted about 5% decrease in power and torque and about 2% in Nox emission for every 10% of biodiesel blend added comparatively to pure diesel. However, the use of biodiesel has slightly increased specific fuel consumption (about 6% for every 10% of biodiesel blend added).