Biogas is deemed as one of the most promising renewable fuels emerging in the past several decades. At present, biogas is mainly applied to cooking for substituting fossil fuels. However, biogas is rarely reported to be used for space heating. In this paper, we designed a biogas-fired partially premixed burner for gas-fired wall-mounted boilers, which has the heat input of 25 kW and can be used for space heating and water heater tank heating. The reference gas was assumed as 60% of methane (CH₄) and 40% of CO₂, and the burner port area was designed as 4744.5 mm² according to the calculation. Then, experiments were conducted to study the performance of this burner. Jet diameters were modified in order to investigate their effects on heat input, primary air ratio and flame stability of the burner. The results indicate that the burner shows superior performance when the jet diameter is 2.0 mm. Meanwhile, the primary air ratio (⁠|${\alpha}^{\prime }$|⁠) satisfies the design requirement. Moreover, a gas-fired wall-mounted boiler with this burner was examined to investigate the influence of different biogas composition on exhaust emissions and thermal efficiency. The results show that the concentration of CO in the flue gas meets the national standard when CH₄ varied from 40% to 60% in the biogas. However, the thermal efficiency of the biogas-fired wall-mounted boiler reduces greatly with the increase of CH₄ percentage.

中文翻译：

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用于沼气壁挂炉的部分预混合燃烧器的设计

在过去的几十年中，沼气被认为是最有前途的可再生燃料之一。目前，沼气主要用于替代化石燃料的烹饪。然而，很少有沼气被用于空间加热。在本文中，我们为燃气壁挂式锅炉设计了一种沼气部分预混燃烧器，其热量输入为25 kW，可用于空间加热和热水器水箱加热。假定基准气体为60％的甲烷（CH ₄）和40％的CO ₂，燃烧器端口面积设计为4744.5 mm ²根据计算。然后，进行实验以研究该燃烧器的性能。修改了喷嘴直径，以研究其对燃烧器的热量输入，一次空气比和火焰稳定性的影响。结果表明，当喷嘴直径为2.0 mm时，燃烧器表现出优异的性能。同时，一次空气比（⁠| $ {\ alpha} ^ {\ prime} $ |⁠满足设计要求。此外，还研究了带有这种燃烧器的燃气壁挂炉，以研究不同沼气成分对废气排放和热效率的影响。结果表明，CH ₄时烟气中CO的浓度符合国家标准。沼气的比例从40％到60％不等。但是，随着CH ₄百分比的增加，沼气壁挂式锅炉的热效率大大降低。