简介:摘要:随着人们对使用燃气发动机作为遵守船舶市场日益严格的环境法规的手段的期望不断提高,这使得人们对以液化天然气为燃料的发动机产生了兴趣,因为液化天然气可以显著减少氮氧化物、硫氧化物、颗粒物和二氧化碳,尤其二氧化碳和甲烷综合温室气体明显低于燃烧液态柴油的发动机。但随着燃料的改变,燃气发动机燃烧室部件同样面临着新挑战-润滑。天然气的主要成分是CH4, 完全以气体形式进入汽缸,其燃烧产物也无润滑成分,使得气阀密封面与阀座密封面之间处于干摩擦状态,磨损速度快。研究结果表明,目前主流的船用柴油发动机排气阀使用的高温镍基合金Nimonic 80A材料,在燃气发动机使用工况下无法有效抵抗因干摩擦所造成的磨损。排气阀密封面堆焊具有共晶层状结构和硬质金属间化合物(Laves)相的钴基合金,可以有效的提高排气阀密封面的耐磨损性和耐腐蚀性,特别适用于存在润滑问题的燃气发动机。
简介:摘要:利用热电偶测量缸体在砂型内保温的温度曲线,采用盲孔法测量缸体在砂型保温后的残余应力。结果表明,缸体在砂型内冷却至 300℃以下开箱,残余应力值< 60MPa。该工艺方法操作简单、节能、环保,是绿色铸造的发展方向之一。
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