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This paper presents research into a novel autoselective electric discharge method for regenerating monolithic wall flow diesel particulate filters using low power over the entire range of temperatures and oxygen concentrations experienced within the exhaust systems of modern diesel engines. The ability to regenerate the filter independently of exhaust gas temperature and composition significantly reduces system complexity compared to other systems. In addition, the system does not require catalyst loading and uses only mass- produced electronic and electrical components, thus reducing the cost of the after-treatment package. Purpose built exhaust gas simulation test rigs were used to evaluate, develop and optimise the autoselective regeneration system. On-engine testing demonstrated the performance of the autoselective regeneration process under real engine conditions.

This paper proposes a method of determining residual gas fraction (RGF) by sampling the CO2 concentration in the exhaust manifold of a single cylinder HSDI diesel engine. During a skip-fire event, the CO2 concentration in the exhaust gas for the last firing cycle and the subsequent motoring cycle were measured using a fast-response emissions analyzer. The ratios of these two values are shown to be indicative of the RGF. To simulate the increase in exhaust pressure found with EGR or aftertreatment systems, the exhaust back pressure was elevated using an exhaust throttle. The intake pressure was held constant over a range of engine speed and load conditions. The results demonstrate that the RGF increases linearly with increasing exhaust back pressures for all engine operating conditions.

It is widely accepted that engine combustion is fundamentally affected by the in-cylinder charge motion. Flow field structures present at the time and location of spark ignition are known to have a controlling effect on early flame development. Therefore, improved understanding of the variation in flow field structures local to the spark plug at the time of ignition is required. This study investigates the spatial and temporal development of flow field structures within the pent roof combustion chamber of a single cylinder, direct injection spark ignition (DISI) optical engine. High speed particle image velocimetry (HSPIV) has been used to quantify the flow field leading up to and following spark ignition. HSPIV data was recorded at a rate of 5 kHz, providing a temporal resolution of 1.8 crank angle degrees (CAD) between measurement fields and a spatial resolution of 512 by 512 pixels.

Time resolved digital particle image velocimetry (TRDPIV) data is presented for the in-cylinder flow field of a motored four stroke multi-valve direct injection spark ignition (DISI) optical internal combustion (IC) engine. It is widely accepted that IC engine performance, in terms of both engine emissions and efficiency, is fundamentally affected by the in-cylinder air motion. Therefore improved knowledge of the fundamental fluid flow processes present during the intake and compression phase of the engine cycle is required. More specifically, increased understanding of the flow field cyclic variation will facilitate accurate control of the mixing and ignition development. This paper highlights the application of a new TRDPIV system to provide both spatial and temporal in-cylinder flow field development over multiple engine cycles for improved understanding of cyclic variation.

There is a great deal of interest in new technologies to assist in reducing the CO2 output of passenger vehicles, as part of the drive to meet the limits agreed by the EU and the European Automobile Manufacturer's Association ACEA, itself a result of the Kyoto Protocol. For the internal combustion engine, the most promising of these include gasoline direct injection, downsizing and fully variable valve trains. While new types of spray-guided gasoline direct injection (GDI) combustion systems are finally set to yield the level of fuel consumption improvement which was originally promised for the so-called ‘first generation’ wall- and air-guided types of GDI, injectors for spray-guided combustion systems are not yet in production to help justify the added complication and cost of the NOx trap necessary with a stratified combustion concept.

Time resolved intake runner flow field data is presented for a motored single cylinder four stroke, direct injection spark ignition (DISI) optical internal combustion (IC) engine with an optically accessible intake runner. Previous studies have shown the fundamental influence in-cylinder air motion has on engine performance, exhibiting a controlling factor on the mixing process and early flame kernel development. An improved understanding of the in-cylinder flow fields during the intake and compression process leading up to ignition is required. However, knowledge of the intake runner flow field during the intake phase of the engine cycle is required to establish the effect of intake runner flow variation on in-cylinder flow field development. This paper presents the use of a new time resolved digital particle image velocimetry system within the intake runner to study runner flows and their variation over many engine cycles.

This paper investigates an approach to modelling real-world drive cycles for the prediction of fuel economy and emission levels. It demonstrates that a steady-state engine performance data based modelling approach can be used for real-world drive cycle simulation. It identifies and demonstrates that a steady-state performance data-based approach is the only current viable approach for real-world tailpipe-out CO level predictions. It also identifies quantitatively the difference between the modal emission measurements and constant volume sampling (CVS) bag values for emission modelling validation. A systematic validation and sensitivity analysis of the modelling approach is also described.

As part of an ongoing programme of Exhaust Gas Recirculation (EGR) wear investigations, this paper reports a study into the effect of Exhaust Gas Recirculation, and a variety of interacting factors, on the wear rate of the top piston ring and the liner top ring reversal point on a 1.0 litre/cylinder medium duty four cylinder diesel engine. Thin Layer Activation (TLA - also known as Surface Layer Activation in the US) has been used to provide individual wear rates for these components when engine operating conditions have been varied. The effects of oil condition, EGR level, fuel sulphur content and engine coolant temperature have been investigated at one engine speed at full load. The effects of engine load and uncooled EGR have also been assessed. The effects of these parameters on engine wear are presented and discussed. When EGR was applied a significant increase in wear was observed at EGR levels of between 10% and 15%.

Particle Image Velocimetry (PIV) has been used to investigate flame propagation and unburned gas velocity fields within an optically accessed cylindrical combustion chamber. The flame propagation process and the flame structure of the quiescent and swirling flow inside the chamber is presented. An ionisation probe technique and also a nonintrusive laser refraction technique were used to determine the local flame speed in conjunction with the PIV measurement. The laminar burning velocity of quiescent propane-air mixtures initially at atmospheric condition for different equivalence ratios ranging from 0.7 - 1.4 were measured. These were determined directly from the difference between the local flame propagation speed and the unburned gas velocity immediately ahead of the flame front. Close agreement with other measurements and predicted results was found.

Particle Image Velocimetry (PIV) here has been used to measure the instantaneous velocity field within a realistic geometry motored single cylinder engine. Through-the-piston-crown illumination of a vertical plane bisecting the inlet and exhaust valves in a four valve pent roof combustion chamber and the use of a corrective optical system has for the first time allowed the velocity field in a vertical plane within a cylindrical bore to be quantified with PIV. Techniques are described which permit accurate and repeatable camera focusing, laser to engine synchronisation and seeding density control. Large scale motion observed at 180° ATDC has been interpreted as barrel swirl. Limitations of the current technique are discussed with respect to general in-cylinder applications.

This paper describes the development of an interactive model to simulate a direct injection diesel engine under both steady and transient conditions, based on the application of concurrent process computing methods. Initially the engine is modelled operating under steady conditions and induction, injection, air entrainment, fuel air mixing, combustion, emission and the mechanical friction processes are considered. The fuel pump, governor, engine crankshaft and external load dynamics are incorporated in the model to study the transient behaviour of a 2.5 litre D. I. engine and its associated load. Employing a two zone combustion model enables detailed performance and exhaust emissions predictions to be produced with economic use of computing time. The model written in FORTRAN is implemented in parallel on a transputer based concurrent computer by using the transputer operating system language OCCAM as a harness. Model predictions compare favourably with experimental results.

The concept of using low power microwave energy to efficiently assist the regeneration of ceramic monolith diesel particulate traps is explained. A prototype Microwave Assisted Regeneration (M.A.R.) system is presented and is demonstrated to work reasonably well on both bench and engine tests. The system, which is inexpensive, reliable and controllable, requires 1 kW of overall electrical power for a short period prior to trap regeneration. The M.A.R. technique presented merits further consideration as an alternative to other proposed vehicle trap regeneration systems.

A generalized model describing oxidation in a porous substance is developed and applied to the thermal regeneration of both monolithic and fibrous diesel particulate traps. With typical engine and trap data the regeneration process is analysed using the model. A parametric study demonstrates how the exhaust gas oxygen concentration, flow rate and initial trap particulate loading affect the regeneration time and peak trap temperatures. The model is shown to be in reasonable agreement with published experimental results.