operating principle of the burner

　　I. operating principle of the burner26vBoiler Burner

　　The liquid (gas) fuel is burned in the radiant chamber (furnace) of the burner, producing high-temperature flue gas and using it as a heat carrier, which flows to the convection chamber and is discharged from the chimney.The crude oil to be heated first enters the convection chamber furnace tube of the burner, and the crude oil temperature is generally 29.The furnace tube receives heat mainly by convection from the flue gas (9) flowing through the convection chamber. This heat is transferred from the outer surface of the furnace tube to the surface of the furnace tube by heat transfer, and at the same time, it is transferred to the crude oil flowing in the tube by convection.Crude oil enters the radiating chamber by the convection chamber furnace tube. In the radiating chamber, the flame ejected by the burner mainly radiates part of the heat to the outer surface of the furnace tube and the other part to the furnace wall laying the furnace tube. The furnace wall radiates the heat to the outer surface of the furnace tube on the side of the back fire surface.The radiant heat of these two parts ACTS together to make the outer surface of the furnace tube warm up and form a temperature difference with the inner surface of the tube wall. The heat flows to the inner wall of the tube in a conductive way, and the crude oil flowing in the tube continuously gets heat from the inner wall in a convective way, thus realizing the technological requirements of heating crude oil.26vBoiler Burner

　　The heating capacity of the burner depends on the intensity of the flame (furnace temperature), surface area of the furnace tube and the total heat transfer coefficient.The stronger the flame, the higher the furnace temperature, the greater the temperature difference between the furnace and the oil flow, the greater the heat transfer;The larger the area of the furnace tube in contact with the flame and flue gas, the more heat is transferred.The better the thermal conductivity of the furnace tube, the more reasonable the furnace structure and the more heat transfer.The strength of the flame can be adjusted by controlling the nozzle.However, for a furnace of a certain structure, the temperature of the furnace will not rise after reaching a certain value under normal operating conditions.The total heat transfer coefficient on the surface of the furnace tube is certain for a furnace, so the heating capacity of each furnace has a certain range.In practical use, poor flame combustion and coking of furnace tube will affect the heating capacity of the burner, so it is necessary to control the burner to make it completely burn, and to prevent the local furnace tube temperature is too high and coking.26vBoiler Burner

　　Operating parameters of the burner26vBoiler Burner

　　Furnace temperature (retaining wall temperature)26vBoiler Burner

　　Furnace temperature generally refers to the temperature of the flue gas leaving the radiation chamber, that is, the temperature of the flue gas not entering the convection chamber or the temperature in front of the retaining wall of the radiation chamber.The heat generated by fuel combustion in the furnace (radiant chamber) is transmitted to the furnace tube by radiation and convection.The quantity of heat transfer is related to the temperature of furnace and tube wall.The heat of crude oil from the combustion engine is mainly radiative heat transfer.Radiant heat transfer is proportional to the fourth square of the absolute temperature of the flame. Therefore, in the high temperature area, the effect of radiant heating surface is better than that of convection heating surface. The same amount of heat is absorbed.The furnace temperature selected during the design determines the heat absorption ratio between radiant heating surface and convection heating surface of the burner.Furnace chamber temperature is high, radiative room transfers quantity of heat big, so furnace chamber temperature can reflect furnace outlet temperature more sensitively.However, from the perspective of operation, the furnace temperature is too high and the heat intensity of the furnace tube in the radiation chamber is too large, which may lead to local overheating of the radiation tube and coking, and the flue gas temperature entering the convection chamber is also too high. The furnace tube in the convection chamber is also easy to be burned, making the smoke exhaust temperature too high and reducing the thermal efficiency of the combustion engine.Therefore, the furnace temperature is an index to ensure the long-term safe operation of the combustion engine.The maximum furnace temperature in the oil burner shall not exceed.26vBoiler Burner

　　Exhaust temperature26vBoiler Burner

　　Smoke temperature is the temperature at which smoke leaves the last set of convection heating surfaces in the burner and enters the chimney.Exhaust smoke temperature should not be too high, otherwise heat loss.The smoke exhaust temperature should be controlled during operation, and the smoke exhaust temperature should be reduced under the condition that the combustion machine is in full negative pressure combustion.The regulation of exhaust smoke temperature is generally used to control the air intake, that is, to adjust the excess air coefficient.Reducing the exhaust temperature can reduce the exhaust heat loss of the combustion engine, improve the thermal efficiency, thus saving fuel consumption and reducing the operating cost of the combustion engine.However, the exhaust smoke temperature is too low, which reduces the temperature difference between the flue gas at the end of the convection heating surface and the heat transfer substance, increases the metal consumption of the heating surface, and increases the investment cost of the combustion machine.Therefore, the selection of smoke extraction temperature should be compared economically.26vBoiler Burner

　　The influence of low temperature corrosion should also be considered when choosing the most reasonable exhaust temperature.Since the sulfur in the fuel forms + after combustion, it forms sulfuric acid vapor in the flue gas and water vapor. When the temperature of the heated surface is lower than the dew point temperature of sulfuric acid vapor, the sulfuric acid vapor condenses and corrodes the wall metal.If the temperature of the heated surface wall is lower than the dew point of the steam in the flue gas, the steam will condense on the pipe wall, aggravating corrosion, and easy to cause blocking ash.Measures to reduce dew point, corrosion and ash accumulation are: purification of fuel oil.At present, it has been used abroad, but whether it can be widely used is still worth studying.26vBoiler Burner