Accession Number : ADP009022

Title :   Velocity Measurements in the End-Gas Region During Homogeneous-Charge Combustion in a Spark Ignition Engine,

Corporate Author : SANDIA NATIONAL LABS LIVERMORE CA COMBUSTION RESEARCH FACILITY

Personal Author(s) : Witze, Peter O.

Report Date : 23 JUL 1992

Pagination or Media Count : 6

Abstract : Premixed-charge combustion in spark ignition engines is governed by the propagation of a reaction zone through the turbulent mixture in the chamber. It has been established that during the early and fully-developed phases of this process the reaction zone is a continuous, highly-wrinkled, thin sheet propagating at a speed characterized by the laminar burning velocity and the turbulent eddies in the preflame gases. However, as combustion of the charge nears completion, the burning rate slows down in an exponential fashion that has led empirical analyses to conclude that in its final stages the flame is a thick zone of burning islands of reactants. Other direct experimental evidence contradicts this thick flame model. Resolution of this controversy will require a better understanding of the turbulence/combustion interactions in the end-gas region. In this study, LDV measurements were obtained for two components of velocity and turbulence intensity in the end-gases between the approaching flame and the cylinder wall. Both ensemble-averaged and instantaneous velocity measurements are presented for the region from 20 mm to 0.25 mm of the endwall, and comparisons between motored and fired operation of the engine are discussed. (Author)

Descriptors :   *SPARK IGNITION ENGINES, *COMBUSTION, *FLAME PROPAGATION, *LASER VELOCIMETERS, GAS DYNAMICS, TURBULENCE, PRESSURE DISTRIBUTION, LAMINAR FLOW, ENTRAINMENT, INTENSITY, QUALITATIVE ANALYSIS, FLOW FIELDS, PHASE STUDIES, BOUNDARY LAYER, THERMAL EXPANSION.

Subject Categories : Reciprocating and Rotating Engines
      Combustion and Ignition
      Optical Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE