Effects Of Methanol/biodiesel/F-T Diesel Blended Fuels On Diesel Engines Performance

Faced with the limited energy and the stringent emissions regulations, thesolutions are to optimize the design of engines structure and develop newtechnologies for energy conservation and emissions reduction. In addition, it isreasonable and feasible to search ideal alternatives to traditional fossil fuels.This article chose two coal-based fuels including F-T diesel and methanol as thebasic fuels, and mixed them with biodiesel to confect intomethanol/biodiesel/F-T diesel multi-fuels (MBFT fuels for short) to realize thecomplementary advantages of three fuels.Due to the miscible between alcohols and hydrocarbon, we carried out aseries of experiments, and determined to select n-decanol as the cosolvent ofMBFT blended fuels, and then confected into M0, M5, M10and M15blendedfuels. Then the effect of those MBFT fuels on the engines performance wasevaluated through the experiments on the test bench. And this research focusedon the effect of methanol proportion and engine loads on the performance ofengine using MBFT fuels.1) Methanol proportion in the MBFT blended fuels would directly affectthe physical and chemical properties of the blended fuels. It is concluded thatincreasing methanol content would cause the increase of the density and oxygencontent of the blended fuels while it would reduce the heat value, surface tensionand cetane number.2) The properties of fuels is important enough to determine the combustionperformance, so the MBFT fuels with different methanol content would make adifference on the combustion characteristics. The results indicate that the addition of methanol would prolong the ignition delay period significantly tocause a larger and later heat release peak value. The above heat releasephenomenon led to a higher pressure rise ratio with methanol content increasing,which would increase the in-cylinder pressure. On the other hand, the moderatemethanol content could decrease the pressure oscillation. The increase of engineloads would shorten the ignition delay and rapid combustion period, increaseand advance the peak values of heat release and pressure rise ratio, as a result,the pressure increase with an acute oscillation.3) The changes of fuels’component and combustion process would have aneffect on the engine power, economy and emissions. The results show that theengine power and efficiency would increase slightly with a small proportion ofmethanol, but it would lead to the reduction of power and efficiency whenmethanol content was increased further. Methanol could decrease NOx and sootemissions significantly. Although methanol could cause more incompleteoxidation products, the increase of engine loads could effectively decrease theseemissions.4) The vibration of diesel engines draws the users’attention nowadays. Thisarticle studied the vibration characteristics of MBFT fuels to decrease thevibration with the methods of fuels design. Firstly, the acquisition signals werehandled with the wavelet analysis to reduce the noise signal and retain theeffective signal. And then, the signal analysis on time-domain indicates that theaverage vibration energy of diesel engines increased with methanol contentincrease, but the mechanical shock was weakened.The above experiment results indicate that MBFT blended fuels are flexible,which means that methanol content in the blended fuels affects the physical andchemical properties to change the combustion process and emissionperformance. As a result, the suitable MBFT blended fuels could be designedaccording to the different needs.