| As the global fossil consumption and environment problems are becoming more and more serious, the energy-saving and emission reduction has become a big challenge for the industrialization process. In China, the extensive economy development model in the last 40 years has huge impact on the energy and environment, so the energy-saving and emission reduction is a formidable task. As there are many difficulties in the utilization of medium and low calorific fuels, in China most of those fuels are used through the heat recovery steam generators or industrial furnaces, which leads to great waste of energy. As the development of gas turbine techniques, the investigation of gas turbine combustor using the medium and low calorific fuels draw more and more attentions. This paper mainly investigated the medium and low calorific fuel combustor. The structure has been improved and valued data and results have been obtained, which is valuable in the design of gas turbine combustor of medium and low calorific fuels.Firstly, this thesis reviewed the progress of the medium and low calorific fuels utilization methods and theories, summarized the developments of stability analysis of medium and low calorific fuel combustion. By analyzing the abroad and Chinese developments and features of gas turbine combustors of medium and low calorific fuels, we thought that the combustion of pure medium and low calorific gas, improvements of combustion stability and exergy efficiency should be the future trending topics. In this paper, we started the research from the second law of thermodynamics and it was the very first that the combustion of medium and low calorific fuel combustor was analyzed using exergy analysis, CO, CO2, N2 and H2 was used to simulate the medium and low calorific fuels and the influence of the inlet temperature of air and fuels, outlet temperature of flue gas,the component on exergy efficiency was discussed. It was found that the combustor exergy efficiency increased with the inlet temperature of fuels and outlet temperature of flue gas, the maximum value of exergy efficiency accompanied with the change of the inlet temperature of air, the combustor exergy efficiency increased with the CO volume fraction, while the exergy efficiency reached a maximum with N2 changing.Then we constructed a cone-shape burner which was processed for the first time in China and united it with a rectangular flame tube, then some numerical simulations and experiments had been carried on. The feasibility analysis of the modeling experiments was carried out and a low calorific fuel (800-1200kcal/m3) combustion experimental platform was constructed. A instrument for fast mixing of CH4, CO, H2, N2 and CO2 was designed. A series cone-shape origin model combustor experiments were carried out and lots of dates were collected. We also compared the CFD and experimental results of the cone-shape origin model combustor with that of the combustor with the multi-swirler combustor. It was found that the mixture of the inlet air and fuel was blocked by the low velocity of them, the overlarge angle of the swirler was a negative factor for the formation of velocity/pressure gradient, the gas orifices on the main gas pipes were so close to the head of the swirler that made the recirculation zone unstable, the cone-shape swirler did not match the rectangular flame tube, the rectangle shape flame tube blocked the aggrandizement of the recirculation zone, the primary holes suppressed the formation of the recirculation zone and reduced the stability of combustion, the ignitor was too far from the recirculation zone that made the ignition was very difficult. In this case, some improvements of the cone-shape origin model combustor should be proposed: minishing the angle of the swirler, adding a jet in the head of the cone-shape burner, moving the gas orifices to the downstream and decreasing the area of the gas orifices, decreasing the area of the inlet air, altering the combustor to single-cylinder combustor and increasing length of the flame tube suitably, dismissing the primary holes, keeping the dilution holes, and fixing the ignitor along the downstream.At last, we redesigned the cone-shape modified model combustor. The size and shape of the flame tube, the size and angle of the swirler were confirmed, the inlet gas was divided into the different location of the swirler, the ignitor was fixed in the exit of the swirler, and CFD simulation was carried out. The CFD simulation showed that the flow structure was steady and the recirculation zone shape was far better than the origin model combustor. Then we conducted a lot of experiments and summarized a empirical formula of the LBO excess air coefficient which the fuel was CH4, and drew a graph of stable combustion. The results of the experiments showed that the lean blowout limits of the cone-shape modified model combustor were far better than the origin model combustor when the fuel was CH4, the lean blowout limits which fuel was CO were far better than the case with CH4 as fuel. Especially, we conducted a lot of experiments that only using CO and N2 for the first time and collected lots of significative data. The cone-shape modified model combustor is promising to be applied to the gas turbine combustor of medium and low calorific fuels. |
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