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The measurement of the instantaneous flame temperature and soot concentration in the combustion chamber of a running diesel engine can provide useful information relating to the formation of two important exhaust pollutants, NOx and particulates. The two-colour method is based on optical pyrometry and it can provide estimates of the instantaneous flame temperature and soot concentration. The theoretical basis of the method is outlined in a companion paper. This paper deals with the practical problems involved in the construction of a working system, including suitable calibration techniques. The accuracy of the measurements of flame temperature and soot concentration is also discussed using results from a various sources.

Our earlier experimental study has shown that exhaust unburnt hydrocarbon emissions from spark-ignition engines can be reduced effectively by using in-cylinder catalysts on the surface of the piston top-land crevice. In order to improve the understanding of the process and mechanism by means of which unburnt hydrocarbon emissions are reduced, a phenomenological mathematical model was developed for catalytic oxidation processes in the piston-ring-pack crevice. This paper describes in details the modelling of the processes of the gas flow, mass diffusion and reaction kinetics in the crevices. The flow in the crevices is assumed to be isothermal and at the temperature of the piston crown surface. The overall rate of reaction is calculated using expressions for mass diffusion for laminar flows in channels and a first-order Arrhenius-type expression for catalytic reaction kinetics of hydrocarbon oxidation over platinum.

A mathematical model has been developed which describes the evaporation and trajectories of fuel droplets during their flight in the inlet manifold of port-injected gasoline engines. Based on the model, a computer simulation program was developed, and sample results of this program are given in this paper. Extensive results obtained using the simulation program are described in a companion paper. The simulation program can be used as a tool to improve understanding of mixture preparation in port injected engines. Such effects as: engine load and speed, air and fuel temperature, fuel type, fuel injection velocity, injection timing, and spray droplet size can be investigated.

The work was concerned with experimental study of the turbulent flame development process of ethanol fuels in an optically accessed spark ignition research engine. The fuels were evaluated in a single cylinder engine equipped with full-bore overhead optical access and operated at typical stoichiometric part-load conditions. High-speed natural light (or chemiluminescence) imaging and simultaneous in-cylinder pressure data measurement and analysis were used to understand the fundamental influence of both low and high ethanol content on turbulent flame propagation and subsequent mass burning. Causes for the difference in cyclic variations were evaluated in detail, with comparisons made to existing burning velocity correlations where available.

The paper first describes three linked computational models which allow the estimation of: swirl generated during the induction process; the modification of swirl with bowl-in-piston combustion chambers during compression as the piston approaches top dead centre; the interaction of the fuel sprays with swirl including relative crosswind velocities between the air and the fuel sprays and spray impingement velocities. The paper then presents experimental results from a single-cylinder direct injection diesel engine, during which both the fuel spray and swirl parameters were changed systematically. Finally, the predicted spray impingement and crosswind velocities for this engine are correlated with the engine performance obtained experimentally, in particular, with fuel economy and smoke emission.

Tumble and swirl motions in the cylinder of a four-valve SI engine with production type cylinder head were investigated using a cross-correlation digital Particle Image Velocimetry (PIV). Tumble motion was measured on the vertical symmetric plane of the combustion chamber. Swirl motion was measured on a plane parallel to the piston crown with one of intake ports blocked. Large-scale flow behaviours and their cyclic variations were analysed from the measured two-dimensional velocity data. Results show that swirl motion is generated at the end of the intake stroke and persists to the end of the compression stroke. Tumble vortex is produced in the early stage of the compression stroke and distorted in the late stage of the stroke. The cyclic variation of swirl motion is noticeable. The cyclic variation in tumble dominated flow field is much greater.

Due to its potential for simultaneous improvement in fuel consumption and exhaust emissions, controlled autoignition (CAI) combustion has been subject to continuous research in the last several years. At the same time, there has been a lot of interest in the use of alternative fuels in order to reduce reliance on conventional fossil fuels. Therefore, this experimental study has been carried out to investigate the effect of alcohol fuels on the CAI combustion process and on the resulting engine performance. The experimental work was conducted on an optical single cylinder engine with an air-assisted injector. To achieve controlled autoignition, residual gas was trapped in the cylinder by using negative valve overlap and an intake air heater was used to ensure stable CAI combustion in the optical engine. Methanol, ethanol and blended fuels were tested and compared with the results of gasoline.

Homogeneous charge compression ignition (HCCI) technology is promising to reduce engine exhaust emissions and fuel consumption. However, it is still confronted with the problem of its narrow operation range that covers only the light and medium loads. Therefore, to expand the operation range of HCCI, mode switching between HCCI combustion and transition SI combustion is necessary, which may bring additional problems to be resolved, including load fluctuation and increasing the complexity of control strategy, etc. In this paper, a continuously adjustable load strategy is proposed for gasoline engines. With the application of the strategy, engine load can be adjusted continuously by the in-cylinder residual gas fraction in the whole operation range. In this research, hybrid combustion is employed to bridge the gaps between HCCI and traditional SI and thus realize smooth transition between different load points.

A novel approach was proposed and investigated to reduce unburned hydrocarbon emissions from spark-ignition engines using in-cylinder catalysts. The unburned hydrocarbons in spark-ignition engines arise primarily from sources near the combustion chamber walls, such as flame quenching at the entrance of crevice volumes and at the combustion chamber wall, and the absorption and desorption of fuel vapour into oil layers on the cylinder wall. The proximity of these sources of unburned hydrocarbons to the wall means that they can be reduced significantly by simply using in-cylinder catalysts on the combustion chamber walls, in particular on the surfaces of the crevice volumes. A platinum-rhodium coating was deposited on the top and side surfaces of the piston crown, and its effects on the engine combustion and emission characteristics were examined in this experimental investigation.

Fast throttle opening in port-injected gasoline engines often results in a lean air-fuel ratio excursion lasting several engine cycles. Even when the engine is equipped with a three-way catalyst this lean excursion can lead to high tailpipe emissions. This paper will describe an in-cylinder method of measuring these air-fuel ratio excursions, using a fast flame ionisation detector. Examples will be given of air-fuel ratio excursions obtained on a four-valve-per-cylinder sequentially-injected gasoline engine equipped with a lambda sensor. The air-fuel ratio excursions together with measurements of the engine air flow are used to estimate me build up of the fuel film on the inlet manifold walls. Whilst air-fuel ratio excursions have been recorded previously by other investigators, their results were obtained from exhaust gas analysis using fast oxygen sensors.

Increasingly stringent regulations on gasoline engine fuel consumption and exhaust emissions require additional technology integration such as Cylinder Deactivation (CDA) and Variable valve actuation (VVA) to improve part load engine efficiency. At part load, CDA is achieved by closing the inlet and exhaust valves and shutting off the fuel supply to a selected number of cylinders. Variable valve actuation (VVA) enables the cylinder gas exchange process to be optimised for different engine speeds by changing valve opening and closing times as well as maximum valve lift. The focus of this study was the investigation of effect of the integration of the above two technologies on the performance of a gasoline engine operating at part load conditions. In this study, a 1.6 Litre in-line 4-cylinder gasoline engine is modelled on engine simulation software and simulated data is analysed to show improvements in fuel consumption, CO2 emissions, pumping losses and effects on CO and NOx emissions.

This work was concerned with study of lubricant introduced directly into the combustion chamber and its effect on pre-ignition and combustion in an optically accessed single-cylinder spark ignition engine. The research engine had been designed to incorporate full bore overhead optical access capable of withstanding peak in-cylinder pressures of up to 150bar. An experiment was designed where a fully formulated synthetic lubricant was deliberately introduced through a specially modified direct fuel injector to target the exhaust area of the bore. Optical imaging was performed via natural light emission, with the events recorded at 6000 frames per second. Two port injected fuels were evaluated including a baseline commercial grade gasoline and low octane gasoline/n-heptane blend. The images revealed the location of deflagration sites consistently initiating from the lubricant itself.

A novel experimental technique was used to investigate the in-cylinder air-fuel ratio excursions of a port-injected spark-ignition engine during load and fuel transients. This involved sampling directly from the engine cylinder using a fast flame ionisation detector (FID) system throughout an engine transient test. All tests were conducted with the coolant at the normal operating temperature of 90°C. The research engine used was a 1.6ltr four-cylinder multi-point fuel injection spark-ignition (SI) engine with four-valves-per-cylinder, with sequential injection and an electronic management system. The engine transient involved a rapid throttle opening within about 15msec. Various load steps were investigated at 2000rev/min along with the effect of altering the type of fuel injector.

Controlled Auto-Ignition (CAI) combustion was realised in a production type 4-stroke 4-cylinder gasoline engine without intake charge heating or increasing compression ratio. The CAI engine operation was achieved using substantially standard components modified only in camshafts to restrict the gas exchange process The engine could be operated with CAI combustion within a range of load (0.5 to 4 bar BMEP) and speed (1000 to 3500 rpm). Significant reductions in both specific fuel consumption and CO emissions were found. The reduction in NOx emission was more than 93% across the whole CAI range. Though unburned hydrocarbons were higher under the CAI engine operation. In order to evaluate the potential of the CAI combustion technology, the European NEDC driving cycle vehicle simulation was carried out for two identical vehicles powered by a SI engine and a CAI/SI hybrid engine, respectively.

Controlled Auto-Ignition (CAI) combustion has been achieved in a production type 4-stroke multi-cylinder gasoline engine. The engine was based on a Ford 1.7L Zetec-SE 16V engine with a compression ratio of 10.3, using substantially standard components modified only in design dimensions to control the gas exchange process in order to significantly increase the trapped residuals. The engine was also equipped with Variable Cam Timing (VCT) on both the intake and exhaust camshafts. It was found that the largely increased trapped residuals alone were sufficient to achieve CAI in this engine and with VCT, a range of loads between 0.5 and 4 bar BMEP and engine speeds between 1000 and 3500 rpm were mapped for CAI fuel consumption and exhaust emissions. The measured CAI results were compared with those of Spark Ignition (SI) combustion in the same engine but with standard camshafts at the same speeds and loads.

Induction tuning is now used on a wide range of spark ignition and diesel engines. It has also been the subject of research and publications over many years. The literature on induction tuning is reviewed here, and contradictions are identified and clarified. The use of resonator volume systems are also discussed and the various ways of modelling these systems are compared. In order to reconcile the differing theories, and to attempt to clarify the means by which induction tuning occurs, experiments have been undertaken with a single cylinder diesel engine. This was chosen as a single cylinder engine represents the simplest system, and a diesel engine does not have fuel in the induction system (which would otherwise modify the thermodynamic properties. The experimental measurements include the instantaneous air mass flow rate entering the induction system, and the pressure at the inlet port.

This is a first of a series of papers describing how the replacement of some of the inlet air with EGR modifies the diesel combustion process and thereby affects the exhaust emissions. This paper deals with only the reduction of oxygen in the inlet charge to the engine (dilution effect). The oxygen in the inlet charge to a direct injection diesel engine was progressively replaced by inert gases, whilst the engine speed, fuelling rate, injection timing, total mass and the specific heat capacity of the inlet charge were kept constant. The use of inert gases for oxygen replacement, rather than carbon dioxide (CO2) or water vapour normally found in EGR, ensured that the effects on combustion of dissociation of these species were excluded. In addition, the effects of oxygen replacement on ignition delay were isolated and quantified.

A number of tests were conducted on a 2.5 litre, high-speed, direct-injection diesel engine running at various loads and speeds. The aim of the tests was to gain understanding which would lead to more effective use of exhaust gas recirculation (EGR) for controlling exhaust NOx whilst minimising the penalties of increased smoke emission and fuel consumption. In addition to exhaust emission measurements, in-cylinder sampling of combustion gases was carried out using a fast-acting, snatch-sampling valve. The results showed that the effectiveness of EGR was enhanced considerably by cooling the EGR. In addition to more effective NOx control, this measure also improved volumetric efficiency which assisted in the control of smoke emission and fuel consumption. This second of two papers on the use of EGR in diesel engines deals with the effects of EGR on soot emission and on the engine fuel economy.

In order to minimize short-circuiting of the intake charge in the poppet-valved 2-stroke engine, measures are taken to generate reversed tumble in the cylinder. In this study, five different types of intake ports and three types of pent-roof geometries were designed and analysed of their ability to generate and maintain reversed tumble flows by means of CFD simulation for their intake processes on a steady flow rig. Their flow characteristics were then assessed and compared to that of the vertical top-entry ports. Results show that the side-entry port designs can achieve comparatively high tumble intensity. The addition of flow deflectors inside the side-entry ports does not have much effect on the reversed tumble ratio. The top-entry ports have the highest flow coefficient among all the intake ports examined as well as producing strong reversed tumble. It is also found that the pent-roof at a wider angle helps to strengthen the tumble intensity due to increased air flow rate.

The influence of swirl on combustion in diesel and spark ignition engines is reviewed briefly, and this leads to a resumé of the swirl measuring techniques. The numerous ways of analysing swirl data are summarised and the relations between the different swirl parameters are presented. Experimental results are presented from a diesel engine in which the flow has been measured by a hot wire anemometer, a paddle wheel and a swirl torquemeter. The performance of the different measurement techniques is compared. Further results are presented (from a spark ignition engine) which illustrate the influence of the inlet port, manifold and entry conditions on the swirl measurements. Integration techniques are reviewed for producing a single swirl parameter to characterise the combined performance of the inlet port, valve and camshaft. Finally, the difficulty in standardising measurements of barrel swirl are discussed.