In this article effect of ambient condition including temperature, pressure and humidity and also variation of fuel composition on engine specific fuel consumption and fuel consumption of vehicle and also nitrogen oxides has been investigated. Simulation has been done by engine cycle simulator GT-Power. Selected working points for simulation in this research are all in part load and in driving cycle are repeated high and consumption fuel is CNG. Selected engine for simulation is EF7.1.7NA. Base simulation model, validated by experimental part load data with sufficient precision. Also for investigating effect of ambient pressure variation, a test has been done on engine that results shows acceptable adjusting with simulation. Also vehicle fuel consumption and NOx emission standard is compared with results of simulation.

In this study evaporation of biodiesel droplet under different operating conditions is investigated. The model is a common droplet vaporization model for multicomponent fuels. In this model, gas phase quasi-steady equations are solved analytically and energy and species transport equations in liquid phase are solved numerically. The sub-models are modified to consider high pressure effects. Peng-Robinson equation of state is used for gas phase and phase equilibrium is determined using fugacity. Effects of pressure on the thermophysical and transport properties of gas phase are considered. Five biodiesels with different composition are studied. These biodiesels have different composition of methyl esters. Biodiesel composition shows little effect on droplet lifetime and maximum difference is about 20%. It is observed that increasing ambient temperature leads to decrease in droplet lifetime and increases temperature gradient inside droplet. Ambient pressure has different effects on droplet vaporization behavior at different ambient temperature. At lower temperature environment, increasing pressure increases the droplet lifetime while at higher temperatures droplet lifetime first increases and then decreases with pressure. Increasing initial velocity of droplet reduces the droplet lifetime. Results show that at high pressures, droplet temperature reach to values near to critical temperature and accuracy of quasi-steady approximation decreases. Radius of vapor influenced sphere increases with temperature and decreases with pressure.

The aim of this study was to investigate the effect of using portulaca oleracea as a source of plant antioxidants for feeding fattening male lambs, on carcass traits, meat quality, and oxidative stability. Twenty-one male lambs with an average weight of 24±1.5 kg and 150±15 days old were fed with one of the experimental rations included a diet without portulaca oleracea as control, a diet containing 7.5%, and a diet containing 15% portulaca oleracea, for 84 days. The muscle (Longissimus dorsi) samplewas used to determine pH, chemical composition, colorimetric properties, and oxidative stability of meat. Meat lipid oxidation was determined after 1, 7, and 30 days of refrigerated storage using thiobarbituric acid (TBARS). The use of portulaca oleracea in diets improved meat color characteristics such as L, chroma, and Hue. The highest ash concentration and the lowest meat moisture were observed in the treatment of 15% portulaca oleracea (P<0.05). Meat pH was the lowest in the first hour after slaughter but did not differ at 24 h. Compared to the control, in both treatment groups feeding the lambs with portulaca significantly reduced the concentration of Malondialdehyde in the meat of the lambs and increased the meat oxidative stability (P<0.05). The results of this experiment showed that feeding portulaca oleracea by improving properties such as color and increasing the meat oxidative stability improves meat quality, which may have lead to an increase in its nutritional value in terms of human health.

Homogeneous charge compression ignition (HCCI) is regarded as the next generation combustion trend in terms of high thermal efficiency and low emissions. It is difficult to control autoignition and combustion because they are controlled primarily by the chemical kinetics of air/fuel mixture. In this study, a homogeneous mixture of natural- gas and air was used in a compression ignition engine to reduce NOx emissions and improve thermal efficiency. In order to control ignition timing and combustion, a small amount of Dimethyl Ether (DME) was mixed with the natural-gas. In this paper, a multi- dimensional computational fluid dynamics (CFD) model coupled with chemical kinetics mechanisms was applied to investigate the effects of various temperatures, pressures, equivalence ratios and fuel compositions on the combustion performance and emission characteristics of an HCCI engine. The mixture could run the engine quietly and smoothly over a wide range of loads. Under the present test conditions, finite amount of DME was necessary in order to achieve ignition of the mixture. In addition, thermal efficiency was higher than that of methane fueled engine, when the DME proportion was optimized. NOx emissions were extremely low, however, the emissions of total unburned hydrocarbon were high.

This article presents the results of engine and laboratory tests with fuel before and after treatment with a heavy particle generator. The results of the research have shown that in the course of conducted research the impact of heavy particle generator on fuel during engine tests leads to an increase in its detonation resistance and a reduction in fuel consumption (up to 15%), as well as significantly improves the environmental performance of the engine. The reduction in concentration of carbon monoxide (CO) from 0.09% to 0.03%, carbon dioxide - by 6% and nitrogen oxides - by 7%. The results of research of hydrocarbon composition of fuels by GC-MS method have shown that the impact of heavy particles generator have a favorable effect on the octane number of gasoline, as well as low-temperature properties of diesel fuel. The change of engine operation parameters after the impact of heavy particles generator is established. The change can occur as a result of complex influence on fuel and engine systems, and as a result of influence on a single factor, which is the root cause of the subsequent change of parameters.

Introduction: One of the quality parameters of combustion is Diesel index (DI) that Indicating the degree and quality of diesel fuel. One of the methods that can be measured this parameter without spending too much time is the ASTM D 611 standard.Material and Methods: In this study to produce biodiesel fuel was used ethanol and by transesterification method from seven kinds of vegetable oils (corn, soybean, rice bran, grape seed, olive, sunflower and rapeseed) method was used. In order to get the diesel index, determination of aniline point and the API degree is required. Therefor Aniline point was evaluated by ASTM D611-04.Results and Discussion: The results showed that the values of index of diesel fuels produced form from Fatty Acid Ethyl Ester Composition are in 38-45 range. While the DI value of diesel fuel is 51.56. Also, the results presented that the low values of density of biodiesel fuels is reduced the degree of API.