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This paper presents a numerical study for predicting the steam ejector performance for different pressure ratios. The considered steam ejector operates at small pressure ratios of back to motive pressures. Both the suction and motive fluids are regarded to be dry steam. Due to low pressure created by the motive steam nozzle flow, entrainment of steam to be mixed with motive steam where both resume flowing toward the ejector exit. Mass ratio of suction to motive flows is an important element to describe the ejector performance.The present study aims to optimize the steam ejector efficiency that runs at different pressure ratio for each suction pressure. The variation of the mass ratio and ejector efficiency with the ejector back pressure at different values of the suction pressure and constant motive pressure, also a variation of the mass ratio and ejector efficiency with the ejector back pressure at different values of the motive pressure and constant suction pressure are investigated. The numerical results are validated with the available experiments from the literature. The results show that the mass ratio is almost constant at low values of back pressure, depending on the suction and back pressures, then the mass ratio decreases sharply with increasing the back pressure. The suction pressure has the positive consequence on the mass ratio. Moreover, the results show that the ejector efficiency increases with increasing the back pressure to gain its upper limit value, subsequently that the efficiency decreases with raising the back pressure. Also, raising the suction pressure will cause an improvement in the ejector efficiency. The value of back pressure at which the maximum efficiency is achieved and its value increases with magnifying the suction pressure.

At the present time, the energy crisis, climate and air pollution represent major global problems in addition to the high prices of fossil fuel and vegetable oils. These problems were increased with the current global conflicts which have led to an increase in global warming and rising global temperatures causing significant climate change in many regions of the world. A carbon dioxide emission is one of the main pollutants that cause an increase in global warming. Waste vegetable oils can be used directly as an alternative fuel in diesel engines because they are environmentally friendly. In this paper, the effect of used waste vegetable oils on the emissions of a diesel engine with different blends compared to pure diesel fuel was studied. One of the important results of this research is that with the increase in the proportion of used waste vegetable oil blend in the fuel; it leads to a decrease in carbon dioxide emissions. Carbon dioxide emissions increase by 5 % and 10.13 % for B20-WPKO and B20-WSFO fuels respectively compared to pure diesel fuel at 60 % of load and carbon dioxide emissions decrease by 12.66 % and 7.6 % for B40-WPKO and B40-WSFO fuels respectively compared to pure diesel fuel at 60% of load. The use of these oils has led to a further decrease in carbon dioxide emissions, and thus a decrease in global warming, furthermore re-processing and reusing these oils is harmful to human health.

Decreasing the emission pollution linked with petrol combustion is gaining a great interest world-wide. Lately, HHO has been inserted to internal combustion engines as a novel clean source of energy. The effect of different HHO addition into intake manifold on the gasoline engine performance and emissions had evaluated experimentally and compared in this research. The purpose of this work is improving the performance and emissions of gasoline engine. The experimenters were performed on an air-cooled single cylinder gasoline engine with and without HHO. With the same engine loads (25%, 50%, 60%, 75% and 80%) and constant engine speed (2000 rpm) at various HHO addition into intake manifold (VR=0.037, 0.045, and 0.052) and without HHO, the engine performance parameters (BSFC and BTE) and exhaust emissions (CO, CO 2 , HC, and NO X ) were measured. The results pointed out that: BSFC decreased, BTE incremented, CO minimized, CO 2 slight increased, HC reduced and NO X diminished with increasing HHO addition at overall operation conditions when compared to gasoline fuel (without HHO).

The diesel engine is an internal combustion engine that converts the chemical energy in the fuel into kinetic energy. Waste vegetable oils can be used as an alternative fuel in conventional diesel engines. When waste vegetable oils are used directly as a fuel in a diesel engine; the injection pressure of diesel engines can be altered to help ensure that the viscosity of the vegetable oils is low enough to allow proper atomization of the fuel. Waste vegetable oils can also be blended with diesel fuel for use under a wide range of conditions. The injection pressure is one of the important variables affecting the performance of the engine. In this paper, the effect of changing the injection pressure from 170 to 200 bars on the performance of diesel engine was studied by using different types of blends of waste vegetable oils with diesel fuel. From the most important results of increasing in the injection pressure is improving the engine performance by increasing the brake thermal efficiency in a range of percentages from 3.8% to 19% compared to the 170 bar injection pressure at different loads and reducing the brake specific fuel consumption in a range of percentages from 3.5% to 13% compared to the 170 bar injection pressure at different loads thus increasing the air-fuel ratio in a range of percentages from 3.5% to 19% compared to the 170 bar injection pressure at different loads. The use of these oils in engines helps to reduce dependence on conventional fuels, which leads to preserving the climate, in addition to the fact that re-processing and reusing these oils is harmful to human health.