Basic Research On Combustion Characteristics Of Biomass Gas/Oxygen-enriched Air Laminar Premixed Flame

Excessive consumption of energy is causing coal,petroleum and other non-renewable energy sources to be depleted,affecting economic development and threatening human life.It is a major problem that human beings are facing.The emergence of renewable energy and clean alternative energy is the main way to fundamentally solve the energy problem.In recent years,with people’s continuous research on energy,biomass energy has entered people’s vision,the traditional biomass energy utilization method is mainly direct combustion,but this method makes its energy utilization low,and needs energy conversion technology to make biomass energy better utilized,so biomass gasification technology has become the main way to use biomass energy effectively.biomass gasification gas is mainly composed of H₂,CO,CH₄,CO2,N₂and a small amount of other high hydrocarbon gas.its composition is complex,the calorific value is low,the combustion temperature cannot meet the industrial requirements well,and direct utilization will produce a large number of pollutants.Oxygen-enriched air combustion technology is a low-consumption,high-efficiency and clean combustion method.The application of oxygen-enriched air combustion technology to the study of combustion characteristics of biomass gas is helpful to improve its combustion efficiency.Oxygen-enriched air combustion technology can reduce the content of nitrogen in the oxide,reduce the content of inert gas in the mixed gas,and accelerate the combustion speed,thereby increasing the flame temperature of the combustion and improving the combustion efficiency.Based on the constant volume combustion system,the combustion characteristics of biomass mixture of seven different components under different Oxygen-enriched air coefficient were studied.and using the CHEMKIN software to simulate the experimental working conditions.The main findings are as follows:（1）The self-built constant volume combustion system test bench was used to experimentally study the combustion flame radius,laminar flame combustion speed,flame elongation,Markstein length and combustion pressure of biomass gas under different operating conditions.The results show that:1.The flame radius changes linearly with time.As the oxygen enrichment coefficient increases and the hydrogen content increases,the flame propagation rate will increase.This is because the size of the oxygen-enriched coefficient directly affects the level of energy released by the combustion reaction of the premixed gas.The faster the energy release rate,the higher the flame propagation speed;the increase in H₂content will increase the proportion of combustible components in the biomass gas,the probability of collision between combustible components and O₂molecules increases,at the same time the calorific value of the mixed gas is increased,and the combustion reaction rate of the biomass mixed gas is accelerated.2.Increasing the oxygen enrichment coefficient will gradually reduce the influence of flame elongation on flame propagation speed;as the methane concentration increases,the flame instability increases.3.The increase of oxygen-rich coefficient and the increase of CH₄content will increase the pressure generated by combustion.This is because the increase of the oxygen-enriched coefficient and the increase of the content of CH₄make the premixed gas burn faster,the energy release increases,and the pressure level increases.（2）The combustion of biomass mixture was numerically calculated by CHEMKIN software.The effects of oxygen enrichment coefficient and fuel composition on the combustion characteristics of biomass gas were studied from the reaction mechanism.The results show that:1.The consumption of hydrogen in fuel components without methane is higher than that of oxygen and carbon monoxide.The elementary reaction R84:OH+H₂<=>H+H₂O is dominant.Its consumption also decreases;the increase of the oxygen-enriched coefficient will significantly accelerate the consumption rate of H2 and promote the combustion reaction.2.The increase of methane content will make the consumption of carbon monoxide slow.This trend becomes more and more obvious with the increase of methane concentration and the increase of oxygen enrichment coefficient;and the increase of CH₄concentration will increase the consumption of O₂.3.The increase of CH₄content and the increase of oxygen-rich coefficient will increase the amount of nitrogen oxides.This paper analyzes the combustion characteristics of biomass mixtures under different Oxygen-enriched air coefficient and different components through experimental and simulation calculations,and analyzes the size of the oxygen-enriched coefficient and the content of methane and hydrogen in the fuel components on the combustion rate,combustion pressure,and flame Effects of stability,nitrogen oxide emissions,etc.Studying the combustion characteristics of biomass gas under oxygen-rich conditions is of great significance in alleviating the pressure of energy consumption,improving the combustion efficiency of biomass gas,and increasing the industrial application range of biomass gas.