Analysis of Influencing Factors on NOxemission in Gas-Fired Heating and Hot Water Combi-Boilers Based on Orthogonal Method

In order to determine the sensitivity of influencing factors on NO(x)emission in gas-fired heating and hot water combi-boilers, the orthogonal method was adopted in this paper. Five predominant factors affecting the formation of NO(x)and four levels were selected to be analyzed, including the diameter of flue restrictor, power of fan, ejection distance of nozzle, aperture of nozzle and relative humidity of air. The test plan was designed by employing L-16(4(5)) orthogonal array, and 16 groups of experiments were conducted. The test results were analyzed with range analysis and variance analysis. The results indicated that the power of fan has the greatest influence on the formation of NO(x)of the gas-fired combi-boilers, followed by the diameter of flue restrictor and the relative humidity of air, while the ejection distance of nozzle and aperture of nozzle have little effect on the formation of NOx. In addition, with the selected optimal combination of five factors, a minimum NO(x)volume fraction is obtained, which confirms the superiority of the orthogonal test. The research finding has a certain guiding significance for the reduction of NO(x)formation of gas-fired heating and hot water combi-boiler.