| The Kalugin's shaftless hot air stove has many advantages such as larger checker chamber area, symmetrical structure and heavy strength, higher thermal efficiency, higher blast temperature, lower operation and maintain cost, long service life compared with the internal combustion stoves and external combustion stoves. Compared with the other top-fire hot air stoves, it uses the ceramic burner with jet-vortex system of gas and air supply, so the gas and air Jet-vortex gas flows in pre-combustion chamber and there is no pulsing burning in these stoves at all. The ceramic burner is the core part of the top fire hot air stove, but because of the lack of systemic and comprehensive study about the Kalugin's ceramic burner, it is very significant to research the flow field structure and the combustion characteristic in order to optimize the burner's structure and increase thermal efficiency.In this paper, physical and mathematical model of the flow, mix and combustion of the air and coal gas in the Kalugin's hot-air stove burner which the geometric similar ratio is one tenth to the prototype were developed. The turbulence flow was treated with the RSM model. Based on the species transport model, the model is solved by FLUENT software. Given the velocity boundary conditions, the flow fields and component mixing characteristics of the burner, the flow characteristic on different cross-sections of combustion chamber and the distributions of gas flow in Jet-vortex with singly-blowing were studied. Meanwhile, gas flow in the outlet of combustion chamber with checker was obtained.In addition, based on the results of cold state, the PDF combustion model and P1 radiation model were obtained to simulate the combustion process of gas and air in the ceramic burner. The velocity distribution, temperature distribution and component distribution of gas were obtained as well as the blast temperature and combustion efficiency of outlet.The computed results under cold state showed that air and gas flew and mixed intensively in the annular ceramic burner with the structure of multilayer and multi-nozzles. It brought backflow in the center of the combustion chamber and little swirl in some place because of the swirl flow, so that the length of flame would be shorted effectively. Flow rate had no effect on different flow cross-sections of the combustion chamber and flow uniformity of outlet. The uniformity of flow rate was 90% on the jets of the pre-combustion chamber and the air jets had better velocity uniformity than the gas jets. Consequently, it could improve the homogeneous characters of the burner by optimizing the structure of gas jets. The flow on the outlet of combustion chamber didn't distribute uniformly. The edge velocity was high, but the center velocity was low. As a result, the high velocity is 2.5 times higher than the low one. The average uniformity of velocity was 68.74%; concentration uniformity of fuel was 71.76%, and the concentration uniformity of oxygen was 74.91%. Therefore, it was necessary to optimize the structure of burner to improve the flow uniformity.The computed results under hot state showed that the process of gas and air combustion was diffusion combustion. With the structure of upper gas tube and lower air tube, the air enveloped the gas flow in the pre-combustion chamber. The development of the center flame was impeded by the swirl flame burn and backflow, so, the length of reduced flame had no effect to the bricks on the checker chamber. The combustion was started below the air jets, and the hemisphere roof of the pre-combustion chamber was filled with gas. The combustion efficiency was 95.44%; the average velocity of gas on the outlet of combustion chamber was 6.7135m/s and the average temperature was 1534.7K.At last, this paper summarized the subject and suggestions were offered for the design and improvement of the Kalugin's shaftless hot air stove burner. |
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