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Reacting Boundary Layers in Homogeneous Charge Compression Ignition (HCCI) Engine

Författare

Summary, in English

An experimental and computational study of the nearwall

combustion in a Homogeneous Charge

Compression Ignition (HCCI) engine has been conducted

by applying laser based diagnostic techniques in

combination with numerical modeling. Our major intent

was to characterize the combustion in the velocity- and

thermal boundary layers. The progress of the combustion

was studied by using fuel tracer LIF, the result of which

was compared with LDA measurements of the velocity

boundary layer along with numerical simulations of the

reacting boundary layer.

Time resolved images of the PLIF signal were taken and

ensemble averaged images were calculated. In the fuel

tracer LIF experiments, acetone was seeded into the fuel

as a tracer. It is clear from the experiments that a proper

set of backgrounds and laser profiles are necessary to

resolve the near-wall concentration profiles, even at a

qualitative level. Partial resolution of the velocity

boundary layer was enabled by using a slightly inclined

LDA probe operated in back-scatter mode. During these

conditions, it was possible to acquire velocity data within

0.2 mm from the wall. A one-dimensional model of the

flow field was devised to make the connection between

the thermal and the velocity boundary layer.

The investigations suggest that wall interaction is not the

responsible mechanism for the rather high emissions of

unburned hydrocarbons from HCCI engines. It is

believed that the delayed oxidation, indicated by the fuel

tracer LIF experiments and numerical simulations, is due

to the thermal boundary layer. From the data at hand, it

is concluded that the thermal boundary layer is on the

order of 1 mm thick. In this boundary layer the reactions

are delayed but not quenched.

Publiceringsår

2001

Språk

Engelska

Sidor

1086-1098

Publikation/Tidskrift/Serie

SAE Transactions

Dokumenttyp

Konferensbidrag

Förlag

SAE

Ämne

  • Energy Engineering

Conference name

SAE World Congress, 2001

Conference date

2001-03-05 - 2001-03-08

Conference place

Detroit, MI, United States

Status

Published