| As the problems with energy crisis and environmental pollutionare getting increasingly severe, biodiesel has great potential for using in engines because it is regarded as a renewable oxygenated clean fuel. Meanwhile, based on our country energy resources that petroleum and natural gas are scarcity while coal is relatively sufficient, producing and using F-T diesel is an effective way to deal with the problem with energy crisis.F-T diesel fuel has higher cetane number and lower viscosity which allows a reduction of NOX, HC and CO emissions but it lead to more wears to engine components. On the other hand, biodiesel has high combustion efficiency and can also reduce CO, HC and smoke emissions. However the high viscosity of biodiesels produces negative effects on fuel supply and mixture formation. It is possible to mix these two fuels together to overcome the disadvantages. Therefore, this research examines the effects of different fuel blends combined from these fuels on engine characteristics-including performances, emission, noise and vibrations based on a four cylinder turbocharge diesel engine, widely used in automobiles.For maximising output power and minimizing emissions, the mixed fuels: B10, B30and B100, which means10%,30%and100%biodiesel in the blends respectively by volume, was prepared for experimental study. Experimental results show that:when fuel with mixed fuel, by comparing the speed characteristic under the throttle opening of80%, output torque and power is less than0#diesel. With the increase of F-T diesel ratio, descend range is bigger, and F-T diesel declined by up to ten percents. In terms of fuel consumption rates, B100fuel consumption rate goes up, F-T diesel fuel consumption rate is falling, B30fuel consumption is same with0#diesel oil. In terms of emissions, compared with0#diesel, B10, B30, B100and F-T diesel’s NOX emission concentration, CO emission concentration and carbon smoke emission concentrations are lower than0#diesel oil. And descend range increased with the increase of biodiesel mixed ratio, HC emission concentrations increased except for B100. By comparing the combustion parameters of B10、B30、B100and F-T diesel, it has found that, with the increase of biodiesel proportion, cylinder pressure, pressure rise rate and heat release rate increase gradually.Vibration and noise generated by engine fueled with biodiesel, F-T diesel and0#diesel are different due to differences of3kinds of fuel properties. The influences of vibration and noise made by fuel properties are studied by time-frequency analysis in this paper. The result showed vibration and noise of fueled with FT diesel decreased significantly, vibration of fueled with biodiesel closed to that fueled with0#at low load while increased at high load, the signal in the frequency of fuels is also different. This provides some basic data support for decreasing vibration and noise of diesel engine by improving fuel quality in the future.To gain futher understanding of combustion processes of the fuel belends, this paper research also performed a simulation analysis using FIRE software. The result shows that, compared with F-T diesel, the cylinder high temperature and high NO concentration area of B30is larger, which are consistent with the experimental result.Based on results mentioned above,with an acceptable level of power loss, the combustion of biodiesel and F-T diesel allows clear advantages of fuel economical efficiency, emissions, noise and vibration reduction. It can be taken as a type of alternative clean fuel to solve energy crisis in our country. In addition, choosing the appropriate blend ratio on different engine working conditions can obtain better effect. |
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