氢和氨作为清洁能源受到广泛关注，为深入探究氢-氨混燃的燃烧特性和影响因素，本文借助Chemkin仿真平台建立相关反应模型，以氢-氨混合气体为燃料，空气作为助燃剂，采用Otomo等人提出的一种氨氧化机理对其燃烧过程进行模拟计算，并模拟研究了混合气体的点火延迟时间、层流燃烧速度、绝热燃烧温度、NO排放等燃烧特性随当量比、初始压力以及燃料中H2比例的具体变化规律，对不同工况下的层流火焰结构、H和OH自由基的产率(rate of production，ROP)、NO生成的敏感度进行了化学动力学分析。结果表明:纯氨气体的点火延迟时间长、层流燃烧速度慢，掺氢后燃烧特性均有所改善，且提高了火焰的绝热燃烧温度，但掺氢比例越大，NO排放越多。NO摩尔分数随当量比变化的趋势先增后减，在当量比为0。8左右达到峰值。综合考虑氢-氨混燃的一系列燃烧特性以及掺氢、加压的成本和收益情况，推荐H2占比15%、当量比φ=1。1、压力P=0。2 MPa为氢-氨混合燃烧的最优条件。
Simulation of enhanced mixed combustion characteristics of hydrogen and am-monia
Hydrogen and ammonia have been widely concerned as clean energy sources,and the mixed combustion of the two can promote the application of hydrogen and ammonia in practical combustion.In this paper,a relevant reaction model is established with the help of Chemkin simulation platform,and the combustion process is simulated by Otomo mechanism with hydrogen-ammonia gas mixture as fuel and air as accelerant.The ignition delay time,laminar flow com-bustion speed,adiabatic combustion temperature,NO emission and other combustion characteristics of the mixed gas were simulated varying the equivalent ratio,initial pressure and hydrogen ratio in the fuel.Chemical kinetic analysis was carried out on the laminar flow flame structure,ROP yield of H and OH radicals and sensitivity of NO generation under different working conditions.The influencing factors and essential reasons of the combustion characteristics of hydrogen-ammonia mixed combustion were deeply investigated.The results show that pure ammonia gas has long ignition delay time,slow laminar flow combustion rate,improved combustion characteristics after hydrogen mixing,and increased the adiabatic combustion temperature of the flame,but the higher the proportion of hydrogen mixing,the more NO emission.Considering a series of combustion characteristics of hydrogen-ammonia mixed combustion and the costs and benefits of hydrogen mixing and pressurization,this paper recommends 15%hydrogen,equivalent ratio φ=1.1,and pressure P=0.2 MPa as the optimal conditions for hydrogen-ammonia mixed combustion.
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