Injection Spray Dynamics

Background

The fuel-injection process in modern engines is a critical step to attaining high thermal efficiency and emissions control. Accurate control of the injection performance parameters (timing, delivery, instantaneous flow rate, pressure, spray configuration, etc.) offers one of the most effective means of influencing mixture preparation and combustion kinetics to achieve both clean-burning and high thermodynamic efficiency. Modern fuel-injection equipment provides better control of timing and delivery at much higher injection pressures, resulting in improved diesel engine performance and fuel economy. Unfortunately, direct evaluation of the actual fuel-injection spray is still difficult, and fine-tuning of the injection system is a trial-and-error procedure. Researchers need a new, more powerful means to study and evaluate the characteristics of sprays from fuel injectors so that they can further improve the mixing and combustion processes.

Role of High-Performance Computing

Modeling of sprays is an evolving technology based on the fundamentals of fluid dynamics and multiphase flow. Breakup of a spray, transport of the spray material, and interaction of the spray particles with the boundary and other spray particles can be described with the basic equations of fluid mechanics, but they are significantly complicated by the effects of multiple free surfaces and particle-to-particle interactions. For combustion, the inclusion of chemical reactions inside the droplets and at their surfaces further complicates the physical picture. Nonetheless, mathematical and computational models of the droplet breakup processes and transport are being developed. These computational models are often three-dimensional and time-dependent, requiring large computational resources to facilitate the analysis.

Fuel injector performance and efficiency can be assessed with state-of-the-art computational fluid dynamics methods, such as fluid interface tracking.