In contrast to other alternative fuels, methanol offers a plethora of advantages; it can be produced from natural gas, coal or any organic biomass matter. Methanol is the cheapest of all alternative fuels and has a reduced likelihood of reacting to form pollutants such as soot, CO, NOx. Furthermore, methanol is a liquid at standard atmospheric conditions and can be stored and transported much more cheaply and safely than gaseous fuel. There are also drawbacks that impinge on its overall utility: Methanol has a lower energy density as compared to conventional fossil liquid fuels (kerosene, diesel oil etc.), it has the propensity to react to form aldehyde emissions and to dissolve in atmospheric moisture. Methanol also has a low vapor pressure that could lead to cold start problems in IC engines, at temperatures below 15°C. The objective of the present work is to perform an experimental investigation and a chemical kinetic comparison of combustion characteristics between methanol and kerosene & diesel fueled swirl stabilized burner. A special emphasis is given to the impact of fuel conversion of existing combustion systems from kerosene (or diesel) to methanol.
The experimental set-up is based on a modified industrial burner with heating power of 50kW. In order to have a better control over the incoming air flow, the original blower is replaced with a larger and more stable industrial blower that allowed precise monitoring of the air flow rate. The combustion chamber consists of a stainless steel tube, 10cm in diameter and 80cm in length. The experiments include measurements of temperature distribution inside the combustor: wall temperature distribution is recorded with the use of thermocouples and a calibrated infra-red camera. The composition of the combustion pollutants is also monitored at the exhaust. A National Instruments cRIO 9074 controller is used in conjunction with a National Instruments LabView interface for data acquisition. The comparison between methanol and kerosene characteristics is carried out for equal heat release and equivalence ratios.
Experimental results show that methanol burns slower than kerosene and therefore requires a longer combustor. It is found that the larger methanol droplet size and its larger volume flux contribute significantly to this extended length requirement for complete methanol combustion. The measured CO emission values for kerosene and methanol were 25 and 110 ppm respectively, and 40 and 10ppm for NOx. These results clearly indicate the reduced NOx emission during methanol combustion; however, the notable presence of CO indicates that methanol needs a longer combustor length to complete the combustion process.
