جستجوی مقالات مرتبط با کلیدواژه "سوخت جایگزین" در نشریات گروه "مکانیک"

In recent decades, rising greenhouse gas emissions have become a major challenge and concern. Environmental pollution is one of the greatest human challenges of the 21st century. Improving the performance of internal combustion engines and reducing the amount of pollutant emissions has always been a concern for researchers. The use of alternative fuels and the control and adjustment of the lambda coefficient are known as the most effective ways to increase fuel efficiency, reduce pollution and improve engine mobility. Therefore, in this study, the relationship between air-to-fuel equilibrium ratio or lambda coefficient with engine performance and exhaust emissions of a diesel engine using diesel-ethanol fuel blends as an alternative fuel at 1700, 1800 and 1900 rpm engine speeds has been investigated. The results showed that increasing the percentage of ethanol in the diesel-ethanol fuel blend increased the lambda coefficient. This increase reduced engine power and torque. The highest power reduction was achieved at 1900 rpm at the rate of 1.18 kW and the maximum torque reduction at 1800 rpm at the rate of 5.94 N.m. As the lambda coefficient increased, the exhaust oxygen output increased by 42.89% at 1700 rpm. The increase in lambda also reduced the emissions of unburned hydrocarbons and carbon monoxide. Thus, the highest reduction of these pollutants was 23.8% at 1800 rpm and 38.75% at 1900 rpm, respectively. Also, increasing the lambda coefficient slightly increased the nitrogen oxides. Finally, due to the use of diesel-ethanol fuel blends and as a result of increasing the lambda coefficient, a significant reduction in the amount of emissions of exhaust gases was achieved.

Utilization of natural gas as a clean fuel in internal combustion engines, has potential to reduce pollutants compared to other fuels. New mixture preparation technologies and optimal combustion management has led to a reduction in the pollutants of natural gas engines and efficiency increase. Study of the research works on natural gas engines shows that use of lean combustion strategies has important role in reducing pollutants and improving efficiency. In this study, lean combustion of natural gas with pre-chambered spark plug is reviewed. Experimental study showed that in many engine operating conditions, the combustion stability range was increased and emissions were reduced. Pre-chambered plug ignites the mixture with more speed and turbulence and has more energy to maintain combustion stability. In the experimental study, performance tests were performed on stoichiometric and lean mixture at different loads. For numerical simulation quasi-dimensional model of Gt-power software and 3D simulation of Fire software are used. For validation of analytical and simulation modeling, results of empirical combustion pressure are used

Concerning the adverse environmental impacts of fossil fuel consumption, many investigations have been performed on choosing more environmentally friendly fuel alternatives and sustainable resources. In this regard, hydrogen is considered to be one of the promising alternative fuels as its combustion features are the most similar to fossil fuels and it also falls into the category of renewable and clean fuels. This article studies the simulation of hydrogen-diesel combustion in heavy duty engine at full load and speed of 1600 rpm. All engine features including speed, spray angle, spray duration and input power are held fixed in the simulation. Variable parameter is the ratio of mass or hydrogen energy to diesel. Depending on input power of diesel, hydrogen is changed from 0% (pure diesel) to 70% (i.e. 70% is supplied from the input power of hydrogen and the remaining 30% from diesel fuel). The results of simulation show that hydrogen substitution with diesel at the best state leads to reduction of pollutants such as nitric oxides, carbon dioxide, unburned hydrocarbon, soot and carbon monoxide to 8%, 14%, 54%, 14% and 70%, respectively. This substitution however causes the reduction of indicated efficiency to 2.8%. Hydrogen substitution with diesel can also postpone the combustion, and resulting to increase PRR and HRR; however, this pressure enhancement does not lead to knocking.

In recent years, natural gas and gasoline blended fuels have been considered as alternative fuels in spark ignition (SI) engines. In order to utilize their potential benefits, a precise identification of those alternative fuels is attractive and inevitable studies to predict their performance in SI engines. In this study, the laminar flame speed of natural gas and gasoline blended fuels in the constant volume chamber at different equivalence ratios of 0.8 to 1.2, via the Schlieren optical method was measured and the un-stretched laminar flame speed by following the theory of the weekly stretched flame was obtained. Direct injectors, were installed at the top of the chamber and were used to inject liquid and gaseous fuels. To ensure that the liquid fuel would evaporate completely, the chamber wall was heated with four band heaters and liquid injection was done in the vacuumed chamber. The result showed that adding the natural gas to the gasoline would increase its flame speed at low equivalence ratio, from 0.8 to 0.95. Adding the natural gas to the gasoline in high equivalence ratio caused the flame instability that originated from cracking and the cellularity of the flame surface occurred at higher equivalence ratio.