Destabilisation of a compressed vortex by a round jet

Destabilisation of a compressed vortex by a round jet This paper presents data and analysis related to the compression and the breakdown of a tumbling motion after radial disruption in a simple geometry of the compression chamber of a model engine with large optical access. The disruption is a round jet injection perpendicular to the vorticity tube. Two configurations of injection are selected. They correspond respectively to a straight jet that competes with the tumble and an inclined jet that adds angular momentum to the large-scale rotating motion. The ratio between the angular momentum brought by the spray and the initial angular momentum of the tumble is of the order of 30% and is representative of the direct-injection engine situation at moderate rotation rate. The injection is performed at bottom dead centre (BDC) in a well-defined and well-known tumbling motion. The data are obtained in the symmetry plane of a square chamber by using particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF). A calibration is made in order to take account of acetone fluorescence yield during compression. The analysis of the injection phase at BDC shows that the mean topology of the flow after both injections differs significantly and that the vorticity tube is significantly distorted only in the vicinity of the injection plane. Strong transverse mean flows are detected by analysing the divergence of the mean velocity field. Although a mean rotation is still observed after injection during the compression phase, the authors show that no strong vortex core is evident. An important consequence of this finding, confirmed by the evolution of the global in-plane mean and fluctuating kinetic energy in the symmetry plane is that no vortex breakdown occurs during the compression after the injection event. Therefore, the global fluctuating kinetic energy at the end of the compression is much lower after an injection. During the first half of the compression, an inhomogeneous distribution of the jet fluid in the chamber is detected by the PLIF measurements. The transport of the jet fluid clearly results from both in-plane and out-of-plane motions triggered by the injection jet. This spatial repartition depends strongly on the injection strategy and can be very difficult to control accurately from cycle to cycle. The mixture is more homogeneous at top dead centre (TDC) with a low value of the spatial variance of the mean concentration field. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Destabilisation of a compressed vortex by a round jet

Loading next page...
 
/lp/springer_journal/destabilisation-of-a-compressed-vortex-by-a-round-jet-wCrFy0lRmD
Publisher
Springer-Verlag
Copyright
Copyright © 2004 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-004-0869-0
Publisher site
See Article on Publisher Site

Abstract

This paper presents data and analysis related to the compression and the breakdown of a tumbling motion after radial disruption in a simple geometry of the compression chamber of a model engine with large optical access. The disruption is a round jet injection perpendicular to the vorticity tube. Two configurations of injection are selected. They correspond respectively to a straight jet that competes with the tumble and an inclined jet that adds angular momentum to the large-scale rotating motion. The ratio between the angular momentum brought by the spray and the initial angular momentum of the tumble is of the order of 30% and is representative of the direct-injection engine situation at moderate rotation rate. The injection is performed at bottom dead centre (BDC) in a well-defined and well-known tumbling motion. The data are obtained in the symmetry plane of a square chamber by using particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF). A calibration is made in order to take account of acetone fluorescence yield during compression. The analysis of the injection phase at BDC shows that the mean topology of the flow after both injections differs significantly and that the vorticity tube is significantly distorted only in the vicinity of the injection plane. Strong transverse mean flows are detected by analysing the divergence of the mean velocity field. Although a mean rotation is still observed after injection during the compression phase, the authors show that no strong vortex core is evident. An important consequence of this finding, confirmed by the evolution of the global in-plane mean and fluctuating kinetic energy in the symmetry plane is that no vortex breakdown occurs during the compression after the injection event. Therefore, the global fluctuating kinetic energy at the end of the compression is much lower after an injection. During the first half of the compression, an inhomogeneous distribution of the jet fluid in the chamber is detected by the PLIF measurements. The transport of the jet fluid clearly results from both in-plane and out-of-plane motions triggered by the injection jet. This spatial repartition depends strongly on the injection strategy and can be very difficult to control accurately from cycle to cycle. The mixture is more homogeneous at top dead centre (TDC) with a low value of the spatial variance of the mean concentration field.

Journal

Experiments in FluidsSpringer Journals

Published: Oct 23, 2004

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off