By evaluating combustion duration and flame development, it is possible to evaluate the effects of utilizing a new type of fuel. This allows for optimization of the operational parameters such as the ignition timing, air–fuel ratio, and throttle opening with respect to efficiency, knock, emissions, and performance. In this work, the combustion of a Brazilian hydrous ethanol fuel was evaluated in a commercial flexfuel engine. Investigations were conducted by performing a heat release analysis of the experimental data and providing combustion characteristics. The experimental design comprised of variations in engine speed, load, ignition timing, and air–fuel ratio under lean condition. The results indicated the relationship between the engine parameters and combustion characteristics under a wide range of operational conditions, and identified the relationship between the physical characteristics of the fuels and their combustion in the commercial engine. For high engine speed, lean combustion presented a similar duration to the stoichiometric combustion duration. When comparing the combustion characteristics obtained for the hydrous ethanol with gasoline combustion, the main differences noted were reduced sensitivity to detonation and a shorter duration of combustion, although the temperature at the start of combustion was lower for ethanol. In addition to shorter combustion duration, ethanol presented a lower value for the Wiebe exponent. The results obtained from the combustion duration values and Wiebe function parameters enable the composition of a set of data required for a simplified combustion simulation.

中文翻译：

---

火花点火发动机含水乙醇燃烧的诊断

通过评估燃烧持续时间和火焰发展，可以评估使用新型燃料的效果。这允许在效率、爆震、排放和性能方面优化运行参数，例如点火正时、空燃比和节气门开度。在这项工作中，对巴西含水乙醇燃料在商用灵活燃料发动机中的燃烧进行了评估。通过对实验数据进行放热分析并提供燃烧特性来进行调查。实验设计包括在稀薄条件下发动机转速、负载、点火正时和空燃比的变化。结果表明发动机参数和燃烧特性之间的关系在广泛的运行条件下，并确定了燃料的物理特性与其在商用发动机中的燃烧之间的关系。对于高发动机转速，稀薄燃烧的持续时间与化学计量燃烧持续时间相似。比较含水乙醇与汽油燃烧获得的燃烧特性时，注意到的主要区别是对爆炸的敏感性降低和燃烧持续时间更短，尽管乙醇在燃烧开始时的温度较低。除了较短的燃烧持续时间外，乙醇的 Wiebe 指数值也较低。从燃烧持续时间值和 Wiebe 函数参数获得的结果能够组成简化燃烧模拟所需的一组数据。