A digital computer model of a diesel engine and load is developed which takes into account in cycle calculations the input temperature and pressure, mass of fuel injected, angle of injection, and cylinder temperature and pressure, and gives as outputs the average torque and speed. A typical heat release curve from a practical engine test is used with ignition delay considered constant in time. Results from the program are validated by comparison with data taken from laboratory engine tests. This model is subsequently linearized to obtain the transfer function matrix relating input manifold pressure, mass of fuel injected, and angle of advance to output torque and speed. The design of a feedback controller is then investigated using pole and zero placement techniques, the system inputs and outputs being demanded and achieved torque and speed .

One of the limiting factors for improved performance of the spark ignited internal combustion engine is the phenomenon of knock. The present investigation makes a survey of the available models for auto-ignition for introduction into an existing phenomenological combustion model. A mathematical model of knock, based on a degenerate branched chain mechanism for the prediction of autoignition delay time, was considered and introduced into the combustion model. Experiments were carried out on a single cylinder variable compression ratio engine to validate the model. The interaction of acoustic waves with unsteady combustion leading to unstable combustion and thus triggering knock is considered. This work examines the relationship between the variation in the power of the frequency component corresponding to the natural frequency of the combustion chamber, and the occurrence of knock. A model based on the relaxation oscillation phenomenon is developed to calculate the oscillating frequency of the flame front. This model was developed on the basis that the gas contents of the combustion chamber in an internal combustion engine can be considered as a 'lumped parameter' spring mass damper system. Analysis of the frequency spectrum of flame ionization data show a favourable comparison with the predictions from the model, thus, opening the possibility of future work on correlating the acoustic instability in the combustion chamber to knock in spark ignition engines.

This thesis details an experimental and computational investigation of the relationship between exhaust system geography, the exhaust port pressure history and the gas exchange process in reciprocating four-stroke engines. The study was conducted in four phases. In the first phase, an extensive experimental programme was undertaken, during which key engine performance indicators together with exhaust and intake system manifold pressure and temperature data were recorded on a Rover 1.4 litre 16-valve K series engine. Measured data from each test were used to validate computational predictions. In the second phase the effect of the phasing of pressure waves at the exhaust port was systematically studied using a modified version of the validated model. The relationships between key engine performance indicators and the pressure at the exhaust port during specific periods of the exhaust event were identified. In the third phase, exhaust system gas dynamics were studied and the effect of exhaust system junctions and components on the transmitted and reflected characteristics of pressure waves were investigated. A method was identified by which the dynamic pressure history at the exhaust port could be broken down into its principal incident and reflected pressure wave components.

This research is focused on the performance evaluation of micro Combined Heat and Power (mCHP) systems based on modern prime mover technologies using both theoretical and experimental analysis. Estimations of the environmental and economic impact associated with their deployment in residential conditions were also carried out. Experimental work was performed on assessing the dynamic and steady-state performance of the 1 kWe Stirling based mCHP system (Whispergen), the 0.75 kWe Proton Exchange Membrane Fuel Cell (PEMFC, PA Hilton Ltd) and the 5.5 kWe Internal Combustion Engine (ICE) based mCHP (Dachs). Results obtained from experiments (such as partial efficiencies, nominal capacities etc.) were fed directly in a theoretical model. Primary energy requirements corresponding to average UK domestic conditions were simulated based on real life technical data. All theoretical work was conducted using EnergyPlus building simulation tool in which the operation of several hydronic heating systems was modelled. Furthermore, attained experimental data and previously published research results were used to validate the theoretical modelling process. Several operating strategies of the Stirling based mCHP unit were simulated in order to determine the regime which offers highest reduction in carbon emissions and household expenditures. In addition, variations in a number of parameters that significantly affect the performance of the system were investigated including energy consumption profiles, occupancy characteristics, dwelling thermal requirements, domestic hot water tank volume, etc). For the optimum performance strategy, several configurations of co-generation systems with nominal capacity in the range from 1 to 3 kWe were simulated. All simulated mCHP scenarios were compared against a conventional heating equipment. Finally, the advantages of a mass installation on a district level, consisting of 60, 120 and 240 dwellings and utilising a mixture of different mCHP units (ICE, Stirling, PEMFC), were estimated.

Rotating fluidised Beds offer the potential for high intensity combustion, large turndown and extended range of fluidising velocity due to the imposition of an artificial gravitational field. Low thermal capacity should also allow rapid response to load changes. This thesis describes investigations of the validity of these potential virtues. Experiments, at atmospheric pressure, were conducted in flow visualisation rigs and a combustor designed to accommodate a distributor 200mm diameter and 80mm axial length. Ancillary experiments were conducted in a 6" diameter conventional fluidised bed. The investigations encompassed assessment of; fluidisation and elutriation, coal feed requirements, start-up and steady-state combustion using premixed propane and air, transition from propane to coal combustion and mechanical design. Assessments were made of an elutriation model and some effects of particle size on the combustion of premixed fuel gas and air. The findings were: a) more reliable start-up and control methods must be developed. Combustion of premixed propane and air led to severe mechanical and operating problems. Manual control of coal combustion was inadequate. b) Design criteria must encompass pressure loss, mechanical strength and high temperature resistance. The flow characteristics of ancillaries and the distributor must be matcheo. c) Fluidisation of a range of particle sizes was investigated. New correlations for minimum fluidisation and fully supported velocities are proposed. Some effects on elutriation of particle size and the distance between the bed surface and exhaust port have been identified. A conic distributor did not aid initial bed distribution. Furthermore, airflow instability was encountered with this distributor shape. Future use of conic distributors is not recommended. Axial solids mixing was found to be poor. A coal feeder was developed which produced uniform fuel distribution throughout the bed. The report concludes that small scale inhibits development of mechanical design and exploration of performance. future research requires larger combustors and automatic control.

The aim of this research was to assess the effect of oxygenated hydrocarbons on the knocking characteristics of an engine when blended with low-leaded gasoline. Alcohols, ethers, esters and ketones were tested individually and in various combinations up to an oxygen content of 4% wt/wt in a blend with Series F-7 gasoline of 90, 92, 94 and 96 RON. Tests were carried out at wide open throttle, constant speed and standard timing setting. Engine speed was varied using a dynamometer and knock was detected by two piezoelectric transducers, one on the cylinder head monitoring all four cylinders and one monitoring the cylinder most prone to knock. The engine speeds associated with trace and light knock of a continuous nature were noted. Curves were produced for each oxygenate blend of base RON used against engine speed for the two knock conditions which were compared with those produced using pure Series F-7 fuels. From this a suggested RON of the blend was derived. RON increase was less when using a higher RON base fuel in the blend. Most individual oxygenates showed similar effects in similar concentrations when their oxygen content was comparable. Blends containing more than one oxygenate showed some variation with methanol/MTBE/3 methylbutan-2-one and methanol/MTBE/4 methyl pentan-2-one knocking less than expected and methanol/MTBE/TBA also showing good knock resistance. Further tests to optimise initial findings suggested a blend of methanol and MTBE to be superior although partial replacement of MTBE by 4 methyl pentan-2-one resulted in a fuel of comparable performance. Exhaust emissions were tested for a number of oxygenated blends in 2-star gasoline. 2-star and 4-star fuels were also tested for reference. All oxygenate blends reduced carbon monoxide emissions as expected and hydrocarbon emissions were also reduced. The largest reduction in carbon monoxide occurred using a 14.5 % (1 : 1 : 1) methanol/MTBE/4 methyl pentan-2-one blend. Hydrocarbon emissions were most markedly reduced by a blend containing 25.5 % 4 methyl pentan-2-one. Power output was tested for the blends and indicated a maximum increase of about 5 % at low engine speeds. The most advantageous blends were methanol/4 methyl pentan-2-one (6 : 5) 11% in 2-star and methanol/MTBE/4 methyl pentan-2-one (6 : 3 : 2) 11% in 2-star. In conclusion methanol/MTBE (6 : 5) and (5 : 5), and various combinations of methanol/MTBE/4 methyl pentan-2-one, notably (6 : 3 : 2) gave good results in all tests conducted. CFR testing of these blends showed them to increase both RON and MON substantially.

Spark ignition engines are a significant source of air pollution. Emissions are most severe in the period after the engine has been started from cold. This is because fuel enrichment is needed to ensure reliable combustion in the cold cylinder. The problem is compounded by the exhaust treatment catalyst not reaching operating temperature until some minutes after starting. As the majority of car usage is for short journeys, engines spend much of their time in this high emission operating regime. One route to reducing emissions is to improve mixture preparation. This is Particularly effective after a cold start as less enrichment is required to ensure combustion. The aim of this project has been to evaluate a Vortex'Amplifier as a route to improving mixture preparation. The vortex amplifier is a no moving parts fluidic control device. It regulates a large volume supply flow by imparting swirl to it with a small volume control flow. The control flow vortex creates a region of highly turbulent flow at the device outlet which possesses the potential to atomise a fuel spray. The VA has been tested experimentally. The sprays produced by the vortex amplifier were measured by a laser diffraction technique. Numerical analysis has also been undertaken to determine the motion of droplets within the vortex chamber and the potential of the flow to disrupt a fuel spray. The vortex amplifier has been found to be a highly effective atomiser. It produces sprays with a Sauter mean diameter approximately half the size of the best current technology. However the spray impacts on the walls of any pipework downstream of the VA due to the high tangential velocities in the flow exiting the VA. This problem currently precludes engine us'e, but suggestions for improving the situation are contained in the recommendations for future work.

Lean burn in spark-ignition engines offers a significant efficiency advantage compared with stoichiometric operation. The lean operation is restricted by increasing cyclic fluctuation in torque. In order to make use of the efficiency advantage and meet the mandatory emission standards the lean operation limit has to be further extended. This requires particular control of the mixing of fuel and air. To study the effect of mixture formation on cyclic variability and to provide quantitative information on the mixing of air and fuel planar laser-induced fluorescence (PLIF) was developed and applied to an operating SI engine. The method is based on imaging the fluorescence of a fluorescent marker (3-pentanone) mixed with the fuel (iso-octane). 3-pentanone was found to have similar vaporisation characteristics to those of iso-octane as well as low absorption and suitable spectral properties. The technique was applied to an one-cylinder SI engine with a cylinder head configuration based on the Honda VTEC-E lean burn system. The mixture formation process during the inlet and compression stroke could be described by measuring the average fuel concentration in four planes, between 0.7 and 15.2 mm below the spark plug, in a section of the cylinder orthogonal to the cylinder axis. The results showed that for 4-valve pent-roof cylinder head systems with swirl inlet flows, fuel impinging on the cylinder wall opposite to the inlet valves has a major influence on the mixture formation process. In order to quantify the cyclic variability in the mixture formation process and its contribution to cyclic variability in combustion the fuel concentration in a plane near the spark plug was measured on a large number of cycles. It could be shown, that the fuel concentration in a small region close to the spark plug has a dominating effect on the subsequent pressure development for lean mixtures. Variations in the mixture concentration in the vicinity of the spark plug contribute significantly to cyclic variations in combustion. In order to address the issue of no uniformity in residual gas concentration prior to ignition a laser induced fluorescence method was developed to measure nitric oxide (NO) concentrations in the unburned charge in the same one-cylinder research engine. Measurements of average and instantaneous NO concentrations revealed, that the residual gas is not homogeneously mixed with the air and that significant cyclic variations in the local residual gas concentration exist.

A comprehensive suite of FE based structural optimization computer programs has been developed to minimise vibration and radiated noise of internal combustion engines. Finite element based vibration and noise prediction techniques, dynamic substructuring capabilities and design optimization methods are the key elements of the program suite. The entire engine noise generation process, starting from the combustion pressure and ending with the radiated noise, is within the scope of the programs. Engine structural member sizes, material properties, structural damping and the gasket stiffness and damping between engine components may be used as design variables. Limited shape optimization capabilities are also developed, including removal and addition of structural parts, and geometric modifications without FE mesh regeneration. The design optimization problem, which may involve complex design modifications, is finally transformed into a simple numerical optimization problem with a few design variables. The programs are so structured that any established numerical optimization method may be used to solve the final numerical optimization problem, although straight forward iterative optimization algorithms are shown to be inefficient for this application. The numerical optimization can be carried out either as an integrated part of the whole procedure or as another separate process. Extensive studies have been carried out on the various factors influencing engine noise optimization, including the characteristics of the radiated sound power as a function of structural design variables, the effects of damping, excitation and FE modelling. A comprehensive analysis starting from crank train loads and ending with radiated sound power level has been shown to be the basis of a practical optimization scheme. Sound power level has been identified as a suitable candidate to be used explicitly as the objective function of the optimization. Excitation models which fail to include correctly phased loads at main bearings and cylinders are shown to be inadequate for this application, although the conclusion may not apply at high frequencies (say, above 1 KHz) because the phase relationship at high frequencies might not be correctly predicted. Because engine FE models inevitably have large numbers of degrees of freedom, the sound power evaluation process is computationally very intensive. Therefore, each element of the procedure has been considered carefully to minimise the total computational burden without sacrificing important physical characteristics. The programs have been tested on a few realistic engine FE models, although this thesis will only include the results based on models of a four cylinder in-line diesel engine with up to 6000 degrees of freedom. The tests suggest that the noise optimization scheme is not only theoretically sound but also computationally viable, although further work is required in the related specialisations to fully realise its potential.

Internal combustion (IC) engines have been the predominant technology for sourcing or generating power for over 100 years. The fundamental function of engines has not changed since there first introduction. By combusting fuel within the chamber causes a pressure build from the expanding gasses pushing the piston assembly through the cylinder, this linear action is then translated to rotation through the crankshaft to generate work. During combustion the gasses will try to move past the piston and into the crankcase, to deter this from occurring piston rings are introduced. Thus rings are designed to be in tight contact to the cylinder wall, and is subject to friction and wear as it travels up and down the cylinder wall. When a new ring pack is introduced, a running-in process is required. This involves running the engine at a variation of speeds for set times, typically defined by the manufacturer. While this procedure is executed the compression ring will undergo a series of thermodynamic morphological stages, the material will change shape due to the heat from the combustion process and suffer material loss due to the friction wear between cylinder wall and ring face. This thesis examines the impact of the running-in method on the compression ring and its performance. The work presented shows a novel numerical method that offers the first simulated solution to compression ring rotation around the piston crown and its impact on the engine performance. This has been achieved by adopting simultaneously two modelling packages to compute dynamics and contact mechanics for a more accurate multiphysics result. Using this model a coating refinement has been developed, offering a new chamfer change to the present ISO standard ensuring a longer coating operational life.