Study of biomethanol as sustainable replacement of Autogas at variable ignition timing

Bio-methanol has recently interested researchers looking for a suitable alternative due to its low carbon/hydrogen (C/H) ratio. Adding methanol to Autogas could thereby improve combustion while lowering emissions. In the present investigation, testing is conducted at a compression ratio of 14:1 on various fuel ratios (55/45 to 75/25 with a 5% change) of methanol/Autogas with ignition timing ranging from 28°CA bTDC to 14°CA bTDC. The results indicate improvements due to the addition of 65% methanol. Improved brake thermal efficiency (BTE) by 6.27%, peak pressure (P(max)) by 0.36%, heat release rate (HRR(max)), peak temperature (T(max)) by 0.89%, and rise in exhaust gas temperature (EGT). Simultaneously, combustion duration, HC & CO emissions, and the coefficient of variations in indicated mean effective pressure (CoV(IMEP)) are reduced. With methanol, the volumetric efficiency (η(vol)) improves continuously. Optimal ignition timing is shown to advance with increasing methanol concentration. With ignition retard, the flame development phase (CA10) decreases by 1.7%/2°CA ignition retard, whereas the flame propagation phase (CA10–90) decreases to a minimum and then increases. Due to combustion instability, ignition retard increases the Cyclic variation and CoV(IMEP), while P(max), HRR(max), T(max), and BTE increase to a maximum and then drop. Ignition retard is an effective way of reducing NO(x) emissions, although CO and HC emissions increase significantly. Due to reduced carbon supply, carbon emissions are extremely low even at higher methanol concentrations than Autogas-rich fuel. NOx emissions are also extremely low (62.5 % of the ignition angle at 24°CA), revealing that a higher methanol ratio could be used with minimal risk of power loss.