Transient High-Pressure Fuel Injection Processes

Abstract

The transient behavior of the jet emerging from the orifice during the start-up and shut-down portion of a typical high-pressure diesel-engine fuel injection is addressed in the present work. The liquid jet injected into air at high pressure has been simulated during start-up, steady-state, and shut-down. Use has been made of an unsteady axisymmetric code with a finite-volume solver of the Navier-Stokes equations for liquid streams and adjacent gas, a boundary-fitted-gridding scheme, and a level-set method for liquid/gas interface tracking. Full jet calculations and analysis have been made. In addition, to ease the resolution problem and capture the shortest unstable surface wavelengths, a new model has been developed to examine stream-wise segments of the jet during transients. The frame of reference has been transferred from the laboratory frame to an accelerating frame fixed to the liquid. This transformation generates a new term as a generalized body force analogous to gravity in equations of motion. Periodic conditions before and aft of the segment are used in this liquid-segment model. Consistent results follow from the two approaches. The acceleration of the liquid during start-up is about 10^6 m/s^2 at the orifice exit for high Reynolds numbers. When the jet emerges from the orifice, drag forces due to the dense ambient air cause a deceleration. The classical "mushroom" cap for the developing jet is shredded and non-existent at high Reynolds number. Also, the dynamic protrusions from the jet surface created by shear instability are subject to local accelerations that lead to Rayleigh-Taylor (RT) instability. The higher the Weber and the Reynolds numbers, the shorter the unstable surface wavelengths which appear; so, the more challenging is the resolution problem. Effects of the acceleration, surface tension, and liquid viscosity on the interface instability have been investigated.

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Document Details

Document Type
Technical Report
Publication Date
Nov 21, 2012
Accession Number
ADA581153

Entities

People

  • Dorrin Jarrahbashi
  • William A. Sirignano

Organizations

  • University of California, Irvine

Tags

Communities of Interest

  • Energy and Power Technologies
  • Materials and Manufacturing Processes
  • Weapons Technologies

DTIC Thesaurus Topics

  • Boundary Layer
  • Computational Fluid Dynamics
  • Computational Science
  • Computations
  • Convection
  • Dispersion Relations
  • Engineering
  • Equations
  • Equations Of Motion
  • Fluid Dynamics
  • Fuel Injection
  • High Acceleration
  • High Pressure
  • Navier Stokes Equations
  • Reynolds Number
  • Turbulent Mixing
  • Two Dimensional

Fields of Study

  • Physics

Readers

  • Computational Fluid Dynamics (CFD)
  • Explosive Engineering.
  • Fluid Mechanics and Fluid Dynamics.