铝/煤油纳米流体燃料液滴点火和燃烧特性研究

Ignition and Combustion Characteristics of Aluminum/Kerosene Nanofluid Fuel Droplets

关键词:  纳米流体燃料  点火延迟  微爆炸  蒸发速率  燃烧机理

Key words:  Nanofluid fuel  Ignition delay  Micro-explosion  Evaporation rate  Combustion mechanism

摘要:

为了明确铝纳米颗粒（Al NPs）对煤油点火和燃烧过程的影响，通过“挂滴法”，以纯煤油和5wt%蓖麻油酸/煤油液滴作为对照，研究并分析了在常压（0.1MPa）和高温（650，700，750，800℃）下，5wt%铝/煤油纳米流体燃料液滴的点火和燃烧特性。深入讨论了Al NPs对煤油液滴燃烧机理的影响。结果表明：Al NPs能够降低煤油液滴的点火延迟，其最高降幅达24.4%。铝/煤油纳米流体燃料液滴自点火至第一次微爆炸发生的时长受液滴燃烧前消耗量和燃烧速率的影响，且从点火到第一次剧烈微爆炸发生的时长和总燃烧时长具有较好的线性正相关性。Al NPs良好的导热性可使煤油液滴燃烧时的蒸发速率提升近3倍。铝/煤油纳米流体燃料液滴直径相较于点火时刻减少至50%时，Al NPs会在液滴表面形成致密的核-壳结构，表面活性剂也会形成相应的包覆层，从而阻碍了煤油的蒸发，但微爆炸在一定程度上破坏了液滴的核-壳结构。

Abstract:

To understand the effects of Al NPs on ignition and combustion process of kerosene， setting pure kerosene and 5wt% ricinoleic acid/kerosene droplets as control， the ignition and combustion characteristics of 5wt% aluminum/kerosene nanofluid fuel droplets at atmospheric pressure （0.1MPa） and high temperature （650， 700， 750， 800℃） were studied and analyzed by a droplet suspension method. The effects of Al NPs on the combustion mechanism of kerosene droplets were discussed in detail. The results show that Al NPs can reduce the ignition delay time of kerosene droplets， and the maximum reduction is 24.4%. Aluminum/kerosene nanofluid fuel droplets’ time history from ignition to the first micro-explosion is affected by the consumption before burning and the burning rate of the droplet. The time history from ignition to the micro-explosion and the total combustion duration has a good linear positive correlation. The good thermal conductivity of Al NPs can make the evaporation rate of kerosene droplet increase by nearly three times. When the droplet diameter of the Al/kerosene nanofluid fuel decreases to 50% compared with that of the ignition time， Al NPs form a compact core-shell structure on the surface of the droplet， and the surfactant also forms a corresponding coating layer， which prevent the evaporation of kerosene， but the micro-explosion can destroy the core-shell structure of the droplet to a certain extent.