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Effects of Negative Valve Overlap on the Autoignition Process of Lean Ethanol/Air Mixture in HCCI-Engines

Joelsson, Tobias LU ; Yu, Rixin LU ; Sjöholm, Johan LU ; Tunestål, Per LU and Bai, Xue-Song LU (2010) In SAE Technical Paper Series
Abstract
This paper presents a computational study of the effects of

fuel and thermal stratifications on homogenous charge

compression ignition (HCCI) combustion process in a

personal car sized internal combustion engine. Stratified

HCCI conditions are generated using a negative valve overlap

(NVO) technique. The aims of this study are to improve the

understanding of the flow dynamics, the heat and mass

transfer process and the onset of auto-ignition in stratified

charges under different internal EGR rate and NVO

conditions. The fuel is ethanol supplied through port-fuel

injection; the fuel/air mixture is assumed to be homogenous

before discharging to... (More)
This paper presents a computational study of the effects of

fuel and thermal stratifications on homogenous charge

compression ignition (HCCI) combustion process in a

personal car sized internal combustion engine. Stratified

HCCI conditions are generated using a negative valve overlap

(NVO) technique. The aims of this study are to improve the

understanding of the flow dynamics, the heat and mass

transfer process and the onset of auto-ignition in stratified

charges under different internal EGR rate and NVO

conditions. The fuel is ethanol supplied through port-fuel

injection; the fuel/air mixture is assumed to be homogenous

before discharging to the cylinder. Large eddy simulation

(LES) is used to resolve in detailed level the flow structures,

and the mixing and heat transfer between the residual gas and

fresh fuel/air mixtures in the intake and compression strokes.

Multi-Zone model based on a detailed chemical kinetic

mechanism is then used to simulate the onset of auto-ignition

in the combustion stroke near TDC, based on the mixtures

predicted in LES. It is found that for low and moderate EGR

rates (low and moderate NVO) the onset of ignition is more

sensitive to the temperature of the mixture than to the fuel

concentration. For the high EGR rate and large NVO case,

there is a preferred mixture and temperature at which the first

ignition occurs. Under similar operating conditions the

moderate NVO and EGR rate case is found to have the

earliest ignition, whereas the longest combustion duration is

found in the lowest EGR rate and the lowest NVO case. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
LES, HCCI, combustion modeling, internal combustion engines
in
SAE Technical Paper Series
publisher
Society of Automotive Engineers
ISSN
0148-7191
project
Competence Centre for Combustion Processes
language
English
LU publication?
yes
id
388c8c94-d6e3-439a-99a5-a97e2251efae (old id 1887303)
alternative location
http://papers.sae.org/2010-01-2235
date added to LUP
2011-04-04 14:56:10
date last changed
2018-05-29 11:49:52
@article{388c8c94-d6e3-439a-99a5-a97e2251efae,
  abstract     = {This paper presents a computational study of the effects of<br/><br>
fuel and thermal stratifications on homogenous charge<br/><br>
compression ignition (HCCI) combustion process in a<br/><br>
personal car sized internal combustion engine. Stratified<br/><br>
HCCI conditions are generated using a negative valve overlap<br/><br>
(NVO) technique. The aims of this study are to improve the<br/><br>
understanding of the flow dynamics, the heat and mass<br/><br>
transfer process and the onset of auto-ignition in stratified<br/><br>
charges under different internal EGR rate and NVO<br/><br>
conditions. The fuel is ethanol supplied through port-fuel<br/><br>
injection; the fuel/air mixture is assumed to be homogenous<br/><br>
before discharging to the cylinder. Large eddy simulation<br/><br>
(LES) is used to resolve in detailed level the flow structures,<br/><br>
and the mixing and heat transfer between the residual gas and<br/><br>
fresh fuel/air mixtures in the intake and compression strokes.<br/><br>
Multi-Zone model based on a detailed chemical kinetic<br/><br>
mechanism is then used to simulate the onset of auto-ignition<br/><br>
in the combustion stroke near TDC, based on the mixtures<br/><br>
predicted in LES. It is found that for low and moderate EGR<br/><br>
rates (low and moderate NVO) the onset of ignition is more<br/><br>
sensitive to the temperature of the mixture than to the fuel<br/><br>
concentration. For the high EGR rate and large NVO case,<br/><br>
there is a preferred mixture and temperature at which the first<br/><br>
ignition occurs. Under similar operating conditions the<br/><br>
moderate NVO and EGR rate case is found to have the<br/><br>
earliest ignition, whereas the longest combustion duration is<br/><br>
found in the lowest EGR rate and the lowest NVO case.},
  author       = {Joelsson, Tobias and Yu, Rixin and Sjöholm, Johan and Tunestål, Per and Bai, Xue-Song},
  issn         = {0148-7191},
  keyword      = {LES,HCCI,combustion modeling,internal combustion engines},
  language     = {eng},
  publisher    = {Society of Automotive Engineers},
  series       = {SAE Technical Paper Series},
  title        = {Effects of Negative Valve Overlap on the Autoignition Process of Lean Ethanol/Air Mixture in HCCI-Engines},
  year         = {2010},
}