摘要
Abstract
The effects of hydrogen-blended combustion on flame stability,heat load,thermal efficiency,and pollutant emissions were experimentally investigated in household atmospheric gas water heaters.The burner structure was modified to explore suitable approaches for hydrogen-blended combustion in such appliances.Hydrogen blending ratios ranging from 10％to 30％were used in the tests,which were conducted under both the rated heat load and 70％rated heat load re-spectively.The test results show that under both heat load conditions,increasing the hydrogen blending ratio leads to a decrease in flame height and an increase in thermal efficiency.However,the measured converted heat load,gas Wobbe index,and flue gas temperature all decrease with higher hydrogen content.Under the rated heat load condition,when the excess air ratio is 1.0,the volume fraction of CO in the flue gas decreases significantly with the increase in hydrogen blending ra-tio.In contrast,under the 70％rated heat load condi-tion,the volume fraction of CO in the flue gas shows no obvious change with the increase in hydrogen blending ratio.Under both load conditions,when the excess air ratio is 1.0,the volume fraction of NOx in the flue gas increases with higher hydrogen blending ratio,accom-panied by an elevated risk of flashback.When a 30％hydrogen blending ratio was applied,the original burner was replaced with a manufactured gas burner for testing under both heat load conditions.The results show that uneven mixing of gas and air leads to yellow flames.Following burner modification,when the excess air ratio is 1.0,the volume fraction of CO in the flue gas increases sharply,while the volume fraction of NOx decreases.Subsequently,for hydrogen blending ratios between 10％and 30％,the burner was further im-proved by covering the fire holes with a metal heat-conducting mesh.Tests under both heat load con-ditions demonstrate no abnormal combustion phenom-ena such as flashback,flame lifting,flame lift,or yel-low flame.Under the same heat load,the measured converted heat load and thermal efficiency are basi-cally consistent with those before the modification.The metal heat-conducting mesh inhibits the formation of thermal NOx,reduces NOx emissions,and mitigates the risk of flashback.Under the 70％rated heat load and an excess air ratio is 1.0,the volume fraction of CO in the flue gas remained at a low level.Based on these findings,the recommended improvement method is to cover the fire holes of the original gas water heater burner with a metal heat-conducting mesh.关键词
掺氢天然气/燃气热水器/火焰稳定性/热效率/污染物排放Key words
hydrogen-blended natural gas/gas water heater/flame stability/thermal efficiency/pollutant emissions分类
建筑与水利
