Effect of temperature stratification on the auto-ignition of lean ethanol/air mixture in HCCI engine

R. Yu*, T. Joelsson, X. S. Bai, Bengt Johansson

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review

8 Scopus citations

Abstract

It has been known from multi-zone simulations that HCCI combustion can be significantly affected by temperature stratification of the in-cylinder gas. With the same combustion timing (i.e. crank angles at 50% heat release, denoted as CA50), large temperature stratification tends to prolong the combustion duration and lower down the in-cylinder pressure-rise-rate. With low pressure-rise-rate HCCI engines can be operated at high load, therefore it is of practical importance to look into more details about how temperature stratification affects the auto-ignition process. It has been realized that multi-zone simulations can not account for the effects of spatial structures of the stratified temperature field, i.e. how the size of the hot and cold spots in the temperature field could affect the auto-ignition process. This question is investigated in the present work by large eddy simulation (LES) method which is capable of resolving the in-cylinder turbulence field in space and time. The initial temperature field for LES is presumed as the superimposition of a mean temperature and a sine-function fluctuating temperature. The engine runs on ethanol with a relative air/fuel ratio of 3.3. The LES results show that the initial shape of hot/cold spots is quickly modified by turbulence. A particular hot/cold spot size on the order of large eddy integral scale is found at which the combustion duration tends to be shorter. This reveals the fact that not only the magnitude of the temperature stratification but also the spatial structure of the stratification could affect the auto-ignition process.

Original languageEnglish (US)
DOIs
StatePublished - Dec 1 2008
Event2008 SAE International Powertrains, Fuels and Lubricants Congress - Shanghai, China
Duration: Jun 23 2008Jun 25 2008

Other

Other2008 SAE International Powertrains, Fuels and Lubricants Congress
CountryChina
CityShanghai
Period06/23/0806/25/08

ASJC Scopus subject areas

  • Automotive Engineering
  • Safety, Risk, Reliability and Quality
  • Pollution
  • Industrial and Manufacturing Engineering

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