Effects Of The Components On The Combustion Characteristics Of The Alternative Fuel Gas

With the fast development of the global economy and rapid deplection of conventional fossil fuel, developing clean and efficient alternative energy sources has become a practical demand. For the low heat value gas has extensive sources or abundant reserves, or can be renewable, it receives more and more attention. However, because of its low heat value, high dilution gas of N2or CO2, the utilization of alternative fuel often brings problems of combustion stability and pollutant emission which need to be specially studied.1. The comparative lean blowout experiments between the combustion stability device A (multi-swirl-dome model combustor) and B (single-swirl-dome model combustor) have been carried out at atmospheric pressure. The experimental results showed that the changes of the swirler structrues and the components of the fuel gas would strongly influence the combustion characteristics. When the inlet flowrate and the experimental apparatus remained fixed, the excess air coefficients at lean blow out would vary with the fuel composition variation. The device A had a superior lean blowout(LBO) performance when the combustor reference velocity was within the range from3.5m/s to5.6m/s and the inlet flowrate remained the same.2. An experimental setup has been built to experimentally investigate the impact of the components on the combustion characteristics of the alternative fuel gas, such as its flammable limits and pollutant emission etc. With the help of the fast mixer, the gas mixture which contained different proportions of CO, CH4, CO2, N2with different heat values could be easily achieved and its flammability limits and NO emission have been measured. The results showed that CO2as diluent had a bigger excess air coefficient and better LBO performance compared with N2as diluent in the range of experimental data. This was later confirmed by the flame emission spectrum. However, the NO emission would be higher when CO2as diluent.3. Various divergent segments with different geometrical structures (the divergence angles and heights) have been designed to further explore the impact of the structures with various gas mixture on the combustion characteristics of the low heat value gas. It was found that the smaller the swirl number was, the better the LBO performance would be. A small divergence angle would contribute to both the stability of the flame and the low heat value of the fuel which was coincident with the simulation results with the110-degree and125-degree divergence angles. However, a small divergence angle would lead to the phenomena that the unburned reactants further reacted downstream and thus the flame became longer. This also sacrificed the mixing effectiveness and the NO emission. In addition, when the divergence angle was too large, the flame would shake violently.