Experimental Investigation And Numerical Simunation Of Low NOx Emission In Gas Combution

Supported by the Important Natural Science Foundation of Tianjin (Research and Development of Low NOx Emission of Gas Burners with High Efficiency ), experimental investigation and numerical simulation of low NOx emission in gas combustion are accomplished in this paper, which provides guidance for the development of low NOx emission of gas burners.In this paper a perfect and flexible experimental system of low NOx combustion is established firstly. The influences of the temperature of combustion, the air excess coefficient , a certain amount of vapor added in advance, the temperature of preheated air, adding microwave into gas before combustion, gas recycling combustion and the mode of combustion (diffused and premixed) on NOx emission are analyzed respectively. The combustion of Liquid Petroleum Gas is simulated with PHOENICS 3.5.The NOx concentration increases with the temperature of outlet of the combustion chamber. It is firstly found that the NOx concentration increases rapidly when is less than 0.75, which complements the staged combustion and the rich-lean combustion that are well considered currently as low NOx combustion. It does not mean that the combustion must be the low NOx combustion when <1. There is a limited least value of air excess coefficient. The combustion is not the low NOx combustion when is less than the limited least value. There is a perfect in the first stage combustion which is determined by the properties of fuel. It is firstly found that the amount of NOx emission can reduce by more than 70% and the amount of CH, CO emission also can reduce greatly when a certain amount of vapor is added into the air and/or gas system before combustion. The NOx concentration of the outlet of the combustion chamber increases with the temperature of preheated air. It is firstly found that the NOx concentration decreases greatly when adding microwave into gas before combustion. The lower NOx combustion generates when the special designed gas reburning burner is used in the experiment. The temperature distribution and the distribution of NOx concentration are achieved by PHOENICS 3.5, which can describe the practical situation.