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Title: An investigation of in-cylinder flows in a direct injection compression ignition engine using particle image velocimetry
Author: Stapleton, Brian J.
ISNI:       0000 0004 2695 0848
Awarding Body: Loughborough University
Current Institution: Loughborough University
Date of Award: 2005
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The 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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Mechanical Engineering not elsewhere classified