Aqueous ethanol laminar burning velocity measurements using constant volume bomb methods
Aqueous ethanol laminar burning velocity measurements using constant volume bomb methods
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DOI：
10.1016/j.fuel.2017.10.113
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发表时间：
2018-02-15
期刊：
影响因子：
7.4
通讯作者：
Olm, Carsten
中科院分区：
文献类型：
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作者：
Hinton, N.;Stone, R.;Olm, Carsten
乙醇作为火花点火发动机的可再生燃料很有吸引力，并且还可以用作汽油的增量剂（按体积计最多约 20%）或作为主要成分（按体积计超过 70%）。想要了解水/乙醇/空气混合物的层流燃烧速度有三个原因。第一个原因是，需要很大一部分燃料热值来从生物乙醇中去除最后10%左右体积的水，并且在某些应用中，可能不需要去除所有的水。第二个原因是为模型验证提供扩展数据。第三个原因是，在涡轮增压发动机中，可以通过加水来扩展无爆震工作范围，从而提高输出和效率。使用体积比高达 40% 的水，使用两种不同的技术在定容燃烧容器中进行层流燃烧速度测量：a) 恒压期间火焰锋的成像，b) 分析压力上升数据。当压力升高时，绝热核心被等熵压缩，因此如果使用燃烧模型，单个实验会生成一系列测量结果，其中包括与火花点火发动机燃烧相关的高温（高达 600 K）和高压（高达 12 bar）下的数据。此处显示的两种方法的数据与已发表的乙醇数据一致且一致，并且与乙醇/水/空气混合物的动力学机制的预测也存在令人满意的比较。恒定体积燃烧容器还生成有关马克斯坦长度和细胞开始时的压力的数据，两者都会因水的存在而增加。层流燃烧速度对火花点火发动机中的早期火焰增长有直接影响，除非针对缓慢燃烧的混合物调整点火正时，否则效率将显着损失。发动机数据显示，即使乙醇中含有 40% 体积的水，如果点火正时提前，燃烧性能仍然可以接受。
Ethanol is attractive as a renewable fuel for spark ignition engines, and can also be used as an extender in gasoline (up to about 20% by volume) or as a major component (say above 70% by volume). There are three reasons for wanting to know the laminar burning velocity of water/ethanol/air mixtures. The first reason is that a significant fraction of the fuel calorific value is required to remove the last 10 per cent or so by volume of water from bio-ethanol, and in some applications it might not be necessary to remove all the water. The second reason is to provide extended data for model validation. The third reason is that in turbocharged engines the knock-free operating range can be extended through water addition so as to improve both output and efficiency.Laminar burning velocity measurements with up to 40% water by volume have been made with a constant volume combustion vessel using two distinct techniques: a) imaging of the flame front during the constant pressure period and b) analyzing the pressure rise data. When the pressure rises the adiabatic core is compressed isentropically, so if a combustion model is used, a single experiment generates a sequence of measurements that include data at high temperatures (up to 600 K) and high pressures (up to 12 bar) that are relevant to spark ignition engine combustion. Data from the two methods is shown here to be consistent and in-line with published data for ethanol, and satisfactory comparisons have also been found with predictions from kinetic mechanisms for the ethanol/water/air mixtures. The constant volume combustion vessel also generates data on the Markstein length and the pressure at the onset of cellularity, with both being increased by the presence of water.The laminar burning velocity has a direct influence on the early flame growth in a spark ignition engine, and unless the ignition timing is adjusted for slow burning mixtures there will be a significant loss of efficiency. Engine data show that even with 40% water by volume in the ethanol, combustion performance is still acceptable if the ignition timing is advanced.