Design Rich Oil Cracker And Research On Combustion Emission Performance

Currently, with the widely usage of gas turbine, controlling the emission of pollutants has become a worldwide research topic by many scholars of the whole world. The RQL low emission combustion technology can avoid the range of fuel stoichiometric ratio burning effectively, so that the emissions of nitrogen oxide can be reduced to a very low level.However, because of the existence of oil rich, combustion chamber wall surface cooling is extremely difficult, and it is so hard for the quenching section to ensure mixing problem rapidly and effectively, so that it can hinder the practical application of the RQL low emission combustion organization scheme. In order to solve this problem, Oil rich self-cracking combustion organization scheme based on RQL principle was proposed to reduce the pollutant emission of a certain type of industrial gas turbine in this paper.Because of the limitation of the prototype gas turbine combustion chamber structure,under the premise of meeting the situ replacement, the structural design of the oil rich combustion part was made in this paper. In order to study the influence of oil rich combustion and pyrolysis process to combustion performance accurately, in this paper, with the method of numerical simulation, firstly, the simplified combustion reaction mechanism model and EDC model were coupled to study the process of oil rich combustion and pyrolysis products. Then,according to the known conditions, the equivalence ratio range of the cracker and fuel residence time were determined with CHEMKIN software, and the overall structure and assembly design of the cracker were completed. Finally, the optimized structure of the cracker was installed in the head of the prototype combustion chamber, the combustion performance of the combustion chamber was studied to achieve the purpose of reducing the emission of the prototype combustion chamber. The main research contents of this paper are as follows:(1) The oil rich combustion process and pyrolysis products were investigated. The simplified Patel n-heptane chemical reaction mechanism including NOx formation model was constructed, and were coupled with the EDC model of the fluent to get the main pyrolysis products and pollutant formation conditions of oil rich combustion process.(2) A kind of oil rich self-cracking burner was designed and completed. According to the known conditions,the combustion equivalence ratio ranges of the cracker and fuel residence time were determined, and the first stage and the second stage nozzle were designed, the integral structure scheme of the cracker was obtained finally.(3)The air ratio of the first stage and the second stage air path of the cracker were optimized. The combustion temperature field distribution of the cracker under different air distribution conditions was analyzed, three kinds of optimal air ratio conditions were determined initially, and the combustion and pyrolysis products were analyzed, the result showed that the cracker has good combustion characteristics when the first stage air flow rate is 0.06kg/s and the second stage air flow rate is 0.25kg/s.(4) The pyrolysis device designed was installed in the head of the prototype combustion chamber, and the study of the combustion and emission characteristics were made. The NOx emission of the combustion chamber was 290.5ppmvd, when the cracker was directly installed to the head of the combustion chamber, which can effectively reduce the emission of the pollutant NOx in the prototype combustion chamber.(5) The structural scheme of air distribution in combustion chamber were designed and optimized. Three kinds of connected and mixed structure of the combustion chamber and the pyrolysis apparatus were designed. The calculation results showed that the lobed hybrid structure of the center sealing can make the combustion chamber temperature field distribution reasonable and the emissions is lower. And the optimization of its distribution was carried out, after optimizing NOx emission was only 93.2ppmvd and CO emissions was only 31.2ppmvd, the pollutant emission of the prototype combustion chamber was reduced remarkably.