Investigation of vortex ring-like structures in internal combustion engines, taking into account thermal and confinement effects

这一建议涉及对先前开发的用于分析多相涡环结构的模型的非平凡推广，以考虑热、漩涡和限制效应。热效应包括载流子相中温度梯度的存在，以及液滴的加热和蒸发。限制效果将考虑外壳中墙壁的作用，这在内燃机过程建模的情况下尤其重要。将使用三种建模方法：直接数值模拟、完全拉格朗日方法(奥西普佐夫-拉格朗日方法)和渐近/分析模型。迄今为止，所有这些用于模拟涡环结构的方法的发展主要集中在可以忽略上述热效应和限制效应的情况下。在本项目中，上述三种方法都将被推广，以考虑热和限制效应。这种概括并不是微不足道的，特别是在完全拉格朗日和渐近/解析方法的情况下，就我们所知，没有人试图这样做。建模将专门针对可燃气体和汽油内燃机，但预计将开发的方法可以推广到更广泛的应用领域。该项目的建模工作将通过对上述发动机中涡环状结构的实验研究来补充。气体和液体燃料喷雾(LPG/CNG和汽油发动机)的直接喷射和连续相的运动将在封闭的静态观察室中使用基于激光的测量技术进行研究。将获得描述喷射速度分布和液滴浓度的新数据，以支持建模方法。实验研究将考虑供暖和限制。最初阶段的工作将集中在可燃气体内燃机，这将使我们能够限制我们的分析只针对单相流，使用域名系统和渐近/分析方法。在这一阶段考虑的主要新影响将是围护结构中温度梯度的存在、漩涡和内墙的存在。在下一阶段，将对上述模型进行推广，以考虑外壳内液体喷雾的影响。这种模拟多相流的新方法将结合EPSRC项目EP/F069855/1的工作成果开发的射流和液滴破碎模型。在适当的情况下，将全拉格朗日模型和解析/渐近模型得到的预测与基于瞬变涡环状结构的DNS模拟得到的预测进行比较。我们还将研究将完整的拉格朗日模型和解析/渐近模型整合到研究CFD程序KIVA 3和商业CFD程序Vectis和FLUENT中的可行性。数值和分析模型的预测将与在可燃气体和类似汽油发动机的条件下获得的内部实验结果进行验证。研究结果对优化这些发动机的工艺的适用性进行了研究。这将是一个外部访问研究人员参与的合作项目，他们的专长主要集中在开发数值和分析/渐近涡环模型以及全拉格朗日方法。该项目将确保物理和数学模型的质量达到一个新的水平，如先前资助的EPSRC项目EP/E047912/1和目前正在进行的项目EP/K005758/1中所开发的那样。本项目的工作与目前正在进行的EPSRC项目EP/K005758/1之间预期的时间重叠将确保在这一方向上的研究的连续性。

This proposal is concerned with the non-trivial generalisation of previously-developed models for the analysis of multi-phase vortex ring-like structures to take into account thermal, swirl and confinement effects. Thermal effects include the presence of thermal gradients in the carrier phase, and heating and evaporation of droplets. Confinement effects will take into account the contribution of walls in the enclosure, which are particularly important in the case of modelling processes in internal combustion engines. Three modelling approaches will be used: Direct Numerical Simulation (DNS), the full Lagrangian approach (the Osiptsov-Lagrangian method) and asymptotic/analytical models. Development of all these approaches for modelling vortex ring-like structures has so far been mainly focused on cases when the contribution of the above-mentioned thermal and confinement effects can be ignored. In the present project, all three above-mentioned approaches will be generalised to take thermal and confinement effects into account. This generalisation is not trivial, especially in the case of the full Lagrangian and asymptotic/analytical approach, and nobody, to the best of our knowledge, has attempted to do this. Modelling will be specifically focused on combustible gas and gasoline internal combustion engines, but it is expected that the methods to be developed could be generalised to a much wider range of applications. Modelling work on the project will be complemented by experimental studies of vortex ring-like structures in the above-mentioned engines. The direct injection of gas and liquid fuel sprays (LPG/CNG and gasoline engines) and the motions of the continuous phase will be studied in a closed, quiescent observation chamber using laser-based measurement techniques. New data to describe the injection velocity profile and droplet concentration will be acquired to support the modelling approaches. The experimental study will take into account heating and confinement. The initial stage of the work will be focused on combustible gas internal combustion engines, which will allow us to restrict our analysis to a one-phase flow, using the DNS and asymptotic/analytical approach. The main new effect taken into account at this stage will be the presence of temperature gradients in the enclosure, swirl and the presence of interior walls. At the next stage the above model will be generalised to take into account the effects of liquid sprays in the enclosure. This new approach to the modelling of multiphase flows will incorporate the jet and droplet break-up models developed as a result of work on the previous EPSRC project EP/F069855/1. Where appropriate, predictions resulting from the full Lagrangian and analytical/asymptotic models will be compared with predictions based on DNS simulations of transient vortex ring-like structures. We will also investigate the feasibility of incorporating of the full Lagrangian and analytic/asymptotic models into the research CFD code KIVA 3 and commercial CFD codes VECTIS and FLUENT. Predictions from numerical and analytical models will be validated against in-house experimental results obtained in combustible gas and gasoline engine-like conditions. The applicability of the results to the optimisation of processes in these engines will be investigated. This will be a collaborative project involving external visiting researchers whose expertise is mainly focused on the development of the numerical and analytical/asymptotic vortex ring models and the full Lagrangian method. This project will ensure a qualitatively new level of physical and mathematical models, as developed in the previously-funded EPSRC project EP/E047912/1, and the currently active project EP/K005758/1. The anticipated overlap in time between the work on this project and currently active EPSRC project EP/K005758/1 will ensure the continuity of research in this direction.