GAS JET STUDIES FOR THE CHARACTERIZATION OF ADVANCED INJECTION SCHEDULES AND BOWL DESIGN IN DIESEL ENGINES

Open Access
Author:
Borz, Meghan Justine
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 13, 2016
Committee Members:
  • Jacqueline Antonia O'Connor, Thesis Advisor
  • Daniel Connell Haworth, Committee Member
  • Mary I Frecker, Committee Member
Keywords:
  • gas jet
  • compression ignition
  • schlieren
  • jet-tip penetration
  • multiple injections
  • pilot injection
  • post injection
  • split injection
  • laser induced fluorescence
  • jet-jet interaction
  • piston geometry
Abstract:
In-cylinder strategies such as advanced fuel injection schedules and optimal piston bowl designs are often utilized in diesel combustion for to improve efficiency and/or reduce emissions. The large design space for injection schedules makes choosing the optimal schedule for an engine particularly challenging. Additionally, experimental in-engine studies of advanced injection schedules are time-consuming and costly. Gas jet experiments can provide a good approximation for the behavior of diesel jets and more tests can be conducted in a shorter period of time without incurring the costs of an engine research facility. The goal of this work is to gain a further understanding of some of the fundamental fluid mechanics of multiple injections, jet-jet interactions, and jets impinging on surfaces. Gas jet experiments are conducted using z-schlieren and acetone tracer planar laser-induced fluorescence (PLIF). Three studies are conducted focusing on free jets, multiple jet interactions, jet-jet interaction, and bowl geometry effects. The first study is a comparison of penetration results for helium gas jets with penetration results for vaporizing and non-vaporizing sprays, which shows that by non-dimensionalizing the results of gas jet experiments, the penetration curve follows a similar trend to the non-dimensionalized penetration curve for vaporizing and non-vaporizing liquid sprays. The second study explores the fluid mechanic interactions between multiple injections and the effects of injection duration and dwell. The schlieren results of the multiple-injection studies showed that before the end of injection (EOI) the non-dimensional jet-tip penetration was not significantly different for the first and second injection, however, the average dispersion half angle during the quasi-steady portion of injection was higher for the first injection than for the second injection. There are two multiple-injection cases where the average dispersion half angle of the second injection is higher than that of the first injection by a statistically significant amount. These differences in jet dispersion angle are indicative of differences in mixing and entrainment during the first and second injections. Future studies with acetone-PLIF will allow the concentration to be quantified and differences in the jet composition for the first and second injections in multiple-injection schemes to be compared. The last study focuses on the effects of piston bowl geometry and the angle between interacting jets. The effects of the geometry on fluid recirculation and mixing are studied using schlieren and PLIF with jets of acetone vapor and air and two different piston bowl designs. The results showed that a deeper bowl and wider angle between the jets allows for improved mixing and air utilization.