Thesis-2005-Stapleton.pdf (30.27 MB)
An investigation of in-cylinder flows in a direct injection compression ignition engine using particle image velocimetry
thesis
posted on 2012-10-19, 11:08 authored by Brian J. StapletonThe Compression Ignition (Cl) engine has been the engine of choice for heavy duty on and
off-highway power generation due to its robustness and high fuel efficiency. Cl engines also
emit lower amounts of carbon dioxide (C02) than other prime-movers. Many governments
are currently promoting the reduction of C02 emissions and hence the efficient and robust Cl
engine is expected to be used increasingly in many on and off-highway sectors. However, Cl
engines emit pollutants such as oxides of nitrogen (NO,), particulate matter (PM) and hydrocarbons
(HC), and hence increasingly strict legislative limits to these are being phased in over
the next I 0 years. To aid the development of engines that meet this legislation, designers
require a better understanding of the combustion and pollution formation processes in the
engine cylinder. In-cylinder air charge motion is known to fundamentally affect the mixing
and combustion of the injected fuel in Cl engines and hence the emissions produced by the
engine. Therefore, characterisation and quantification of the in-cylinder flow is an important
step in the process of achieving the conditions necessary for optimal combustion. This research has investigated, using optical measurement techniques, the in-cylinder air flow
characteristics for three different Cl engine inlet regimes. An optical engine was developed
with directed and helical inlet ports, which were designed to provide similar swirl numbers as
measured on steady-flow swirl test rigs. The aim of the research was to link the steady-flow
test rig results with measurements taken, using Digital Particle Image Velocimetry (DPIV) at
top dead centre (TDC). Testing involved two different piston bowls (deep and shallow bowl
pistons) and three different engine speeds (800 rpm, 1200 rpm and 1600 rpm), to observe
their affects on the charge air motion at TDC. A phenomenological model based on kinetic
energy analysis of the flow was used in the current work for comparison with measured data.
The model used measured data from the steady-flow swirl rig as initial conditions to model
the flowfield of the charge air at TDC and these results were compared with measured data. The measured data compared well with the modelled data for the shallow bowl piston, with a
velocity profile that was between solid body rotation and a pre-determined velocity profile in
the model. Results from the model for deep bowl piston geometry showed less agreement
with the measured data and this was believed to be due to the effect of squish motion on the
charge air motion at TDC. The velocity profile of the different inlet port geometries exhibited
good repeatability across different engine speeds. This result showed how the steady-flow
swirl rigs under-predict the charge air motion for combined inlet ports. Whole field datasets
are valuable for the validation of computational fluid dynamic (CFD) models.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© B.J. StapletonPublication date
2005Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en