初始温度对CH4/RP-3航空煤油混合燃料层流燃烧特性的影响

采用定容燃烧实验装置对初始压力为0.1MPa、当量比为0.7~1.5、甲烷体积分数为0、0.4和0.8，以及3种初始温度工况下，CH4/RP-3航空煤油混合燃料层流燃烧特性进行实验研究。获得混合燃料火焰发展图片、层流燃烧速度和马克斯坦长度等,并分析初始温度对CH4/RP-3航空煤油混合燃料层流燃烧速度及燃烧稳定性的影响。结果表明,当火焰拉伸率趋于0时,非线性拟合方法NLM2(nonlinear fitting method 2)能够准确预测拉伸火焰传播速度随火焰拉伸率变化规律,外推可获得较为准确的无拉伸火焰传播速率。初始温度对稀混合燃料火焰传播速度的影响较大,而对化学当量比和浓混合燃料火焰传播速度的影响较小。3种甲烷体积分数混合燃料的层流燃烧速度均随初始温度增加而增加。当初始温度为420K时,马克斯坦长度随当量比减小最快,而当初始温度为480K时,马克斯坦长度减小最慢。在稀混合气和化学当量比工况,随着初始温度增加,混合燃料马克斯坦长度减小,混合燃料燃烧稳定性变差,而在浓混合气工况,各初始温度马克斯坦长度趋于一致,此时,初始温度增加对燃烧稳定性影响较小。 

Effects of initial temperature on the laminar combustion characteristics of CH4/RP-3 mixed fuel

The laminar combustion characteristics of CH4/RP-3 mixed fuel were studied in a constant volume chamber at initial pressures of 0.1MPa, equivalence ratios of 0.7-1.5, methane volume fraction of 0, 0.4, 0.8 and three initial temperatures. The flame propagation photos, laminar burning velocity and Markstein length were obtained, and the effects of initial temperature on laminar burning velocity and combustion stability of CH4/RP-3 mixed fuel were analyzed. The results showed that when the flame stretch was close to 0, the nonlinear fitting method NLM2 can well predict the change of stretched flame speed with varying stretch rate, and extrapolation can obtain more accurate unstretched flame speed. The initial temperature had a great influence on the flame propagation velocity of lean mixed fuels, but little effect for chemical equivalent ratio or concentrated mixtures. The laminar burning velocities of CH4/RP-3 mixed fuel with three methane volume fractions increased with the growing initial temperature. When the initial temperature was 420K, Markstein length reduced fastest with the increase of equivalence ratio, and when the initial temperature was 480K, Markstein length reduced slowest with the increase of equivalence ratio. Under lean and stoichiometric mixture conditions, with the increase of initial temperature, Markstein length decreased and combustion stability became worse. Under rich mixture condition, Markstein length with different initial temperatures tended to the same, and the effects of initial temperature on combustion stability was small.