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Effect of Temperature Stratification on the Auto-Ignition of Lean Ethanol/Air Mixture in HCCI Engine

Yu, Rixin LU ; Joelsson, Tobias LU ; Bai, Xue-Song LU and Johansson, Bengt LU (2008) SAE International Powertrains, Fuels and Lubricants Congress In SAE Technical Paper Series
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Large Eddy Simulation
in
SAE Technical Paper Series
issue
2008-01-1669
publisher
Society of Automotive Engineers
conference name
SAE International Powertrains, Fuels and Lubricants Congress
external identifiers
  • scopus:84877494141
  • other:SAE paper 2008-01-1669
ISSN
0148-7191
DOI
10.4271/2008-01-1669
language
English
LU publication?
yes
id
54e615fb-f1ac-4f78-9b42-cd4eb9a03ce8 (old id 1396289)
date added to LUP
2009-05-13 12:37:21
date last changed
2017-03-19 03:58:33
@article{54e615fb-f1ac-4f78-9b42-cd4eb9a03ce8,
  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.},
  author       = {Yu, Rixin and Joelsson, Tobias and Bai, Xue-Song and Johansson, Bengt},
  issn         = {0148-7191},
  keyword      = {Large Eddy Simulation},
  language     = {eng},
  number       = {2008-01-1669},
  publisher    = {Society of Automotive Engineers},
  series       = {SAE Technical Paper Series},
  title        = {Effect of Temperature Stratification on the Auto-Ignition of Lean Ethanol/Air Mixture in HCCI Engine},
  url          = {http://dx.doi.org/10.4271/2008-01-1669},
  year         = {2008},
}