The object of this study was to investigate the laminar burning characteristics of a large number of hydrocarbon fuels and mixtures in an idealised combustion vessel environment and relate them to their molecular structure and consequent thermochemical and chemical kinetics properties. The observed laminar behaviour was compared to that under idealised turbulent conditions in the Leeds University Mkll combustion vessel and LUP0E-2D research engine.

At the moment the main impetus to move towards alternative fuels produced from renewable resources is legislation and market forces, which push the automotive industry to limit pollutant emissions. One way of reducing these hannful emissions is to replace the conventional fossil fuel totally with syngas or partially with alcohols and/or their ethers. The bending of alcohols to gasoline has been attempted since the mid of 1970's and recently it is in practice in some countries. Interestingly, alcohols are more competitive among the other alternatives such as syngas because they are compatible with existing fuelling distribution infrastructure and are easily stored in a vehicle. However, this blending may change the burning rate which consequently changes the level of cyclic variations. Cycle-to-cycle variability is the main cause of reduction in power output and efficiency and deterioration in the vehicle driveabiIity. Therefore, the main objective of this study was to investigate the impact of employing renewable fuels in spark ignition engine on the cycle-to-cycle variations. The employed fuels involved synthetic gas mixture of 2H2+CO, blends of Ethyl Tert Butyl Ether (ETBE) with primary reference fuel (PRF), and a commercial gasoline fuel (EOS) containing 5 % by volume of ethanol. In the first stage of this work, Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) techniques were employed to characterise the in-cylinder turbulent flow at different engine speed during motoring cycles. In the main stage of the current study, PlY and LDV was also employed to monitor the in-cylinder flow during firing experiments simultaneously with natural light video photography for recording the flame propagation and pressure recordings methods. Results verified that, there was a slight increase in the cyclic variability of the indicated mean effective pressure with increasing the percentage of ETBE in the mixture. The cyclic variability has decreased when using E05 in comparison with PRF or its blends with ETBE. On the other hand, it was possible to run the engine at an equivalence ratio of 0.3 with 2H2+CO due to the extended flammability limit of hydrogen containing mixtures. Spatial and temporal analysis of flow field parameters for individual cycles was adopted in the current study. The analysis showed that there is a high degree of connection between early flame kernel development, RMS turbulent velocity and global burning rate of a cycle, such that a cycle that start fast will remain fast throughout the cycle in most cases.

Internal combustion engines are perhaps the most ubiquitous power source in the modern world. Their heavy use in the vehicle industry and the current impetus to improve efficiency whilst reducing emissions means that OEMs are driving research to provide cleaner and 'greener' engines. Though significant effort is being channelled into teasing out improvements in thermodynamic Efficiency by such methods as pressure boosting and power management. the nature of an engine means many moving parts contribute to parasitic frictional loss. Of these interfaces. the reciprocating contacts between cylinder. piston rings and skirt are arguably subject to the most demanding tribological conditions within an engine. required to seal against the high temperature' combustion gases whilst supporting the large side loading inherent to the system. Given that the piston of an engine may perform this action hundreds of millions of times in its lifespan. the lubrication strategy and component design is of key importance in minimising wear frictional losses. Though the use of numerical simulation tools for improving design has seen significant growth as computational capabilities improve and provide cost advantages to full scale testing. robust validation methods are required to guide the development of the underlying models. The aim of this project was to assess the suitability of an ultrasonic method to monitor the condition of lubrication at the aforementioned contacts by measuring film thickness. Though various techniques involving optical and electrical principles have been employed in the past they generally require the cylinder of the engine to be penetrated and implementation. for the most part. is limited to the test cell. The results of investigations at the piston ring contact have shown that the ultrasonic technique can be used to measure lubricant film thickness and have shown the influence of cylinder pressure and reciprocating speed. Measurements correlate well with work by other authors using the alternative methods mentioned. giving confidence in the robustness of the method. Film measurements at the skirt have been also been successful. not only in quantifying the minimum films present. but also in detailing the profile of the film over its surface and enabling some of the secondary motions of the piston to be deduced. It has been shown that the ultrasonic technique offers the ability and freedom to measure film thickness within an operational engine whilst having the distinct advantage of limiting the degree structural modification required. It shows promise as a research tool and with further development. offers the potential to be incorporated into a lubricant monitoring and control System to help reduce friction losses and emissions.

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The performances of position controllers for a throttle valve used with internal combustion engines of heavy goods vehicles is investigated using different control techniques. The throttle valve is modelled including the hard stops and static friction (stick-slip friction), which are nonlinear components. This includes a new simple approach to the modelling of static friction. This nonlinear model was validated in the time domain using experimental results, parameterised by experimental data using a Matlab based parameter estimation tool. The resulting state space model was linearised for the purpose of designing various linear model based controllers. This linearised model was validated using experimental data in the frequency domain. The correct design of each model based controller is first confirmed by simulation using the linear throttle valve model, the specified step response being expected. Then the robustness is assessed in the frequency domain using the Matlab® Control System Design Toolbox and in the time domain by simulation using Monte Carlo based plant parameter mismatching between the simulated real plant and its model used for the control system design. Once satisfactory performance of a specific controller is predicted by simulation using the linear model, this is replaced by the nonlinear model to ascertain any deterioration in performance. Controllers exhibiting satisfactory performance in simulation with the nonlinear plant model are then investigated experimentally. The set of controllers investigated in this work includes types that are not currently employed commercially, as well as traditional ones, consisting of the IPD, PID, DPI controllers and the linear state feedback controller with and without an integrated observer. The other controllers are the sliding mode iii controller, observer based robust controller (OBRC) and the polynomial controller. The traditional controllers are designed using partial pole placement with the derived linear plant model. The other controllers have structures permitting full pole placement, of which robust pole placement is an important option. In the pole placement design, the locations of the closed loop poles are determined using the settling time formula. Despite the use of robust pole placement, the static friction caused a limit cycle, which led to the use of an anti-friction measure known as dither. The 14 different controllers were investigated for their ability to control the throttle valve position with nonlinear friction, parameter variations and external disturbances. This information was gathered, together with qualitative information regarding ease of design and practicability to form a performance comparison table. The original contributions emanating from the research programme are as follows:  The successful application of new control techniques for throttle valves subject to significant static friction  The first time investigation of partial and robust pole placement for throttle valve servo systems.  A simplified static friction model which can be used for other applications.

The theoretical part of this research work summarised all the known potential lubricant degradation effects during engine operation and in particular with regard to the use of the current generation of biofuels. A qualitative risk assessment was conducted which outlined biodiesel as potentially the most critical fuel. A ‘black box’ model was used to outline the challenge of oil condition monitoring based on summative sensor measurement methods. The theoretical considerations were supported by a statistical analysis which investigated how the presence of multiple contaminants in the oil affects the most common sensor data of permittivity, conductivity and viscosity. ‘Design of Experiments’ (DoE) models were developed for the permittivity, conductivity and viscosity data and expressing mathematically the relationship between the contaminants having a significant influence on each of the sensor data. The findings of the multivariate analysis identified that the effects on permittivity and viscosity provided reliable information about oil condition changes. The concept of an oil condition algorithm in this research was aimed at addressing accuracy and efficiency in predicting the outcome. The core aspect of the algorithm was the use of characteristic maps based on bi-linear regression to predict the fuel, soot and oxidation levels in the oil using permittivity and viscosity as the input data. Based on the predictions using three contaminant components a method to assess the overall condition status is derived. The derived condition status provided the input for an oil drain forecast method which monitors the status within the predefined maximum mileage. Another achievement from this research was the vehicle simulation for different driving profiles and the corresponding simulation of oil degradations. The selected profiles were for a ‘Taxi’, ‘Normal’ driving and ‘Long Distance’ driving. The resulting simulation of fuel, soot and oxidation levels in the oil showed a high correlation compared with the use of real oil analysis based on engineering judgement. The quantitative assessment of the simulated contaminant levels compared with the predicted levels obtained from each characteristic map showed excellent prediction performance. The derived overall condition rating and mileage forecast prediction also showed very good results. The results from this research have shown that this new oil condition algorithm concept using bi-linear characteristic maps has enabled the compromise between predictive accuracy and an efficient and transparent algorithm structure. Validation of the results confirms that the algorithm has the potential to minimise and prevent oil condition related engine failures regardless of the actual fuel used.

Simulation tools are intensively used in the design stage of diesel engines due to their contributions to significant savings in cost and time for the engine development. Since most of DI diesel engines are turbocharged, it is of vital importance to hold a good understanding of turbine and compressor characteristic to predict the engine performance accurately. However, this data is often not available from turbocharger manufacturers, particularly for turbines. On available turbine maps the operating range of the turbine is constrained due to limitations of conventional turbocharger test benches. Operations with a wider range of turbocharger pressure ratios can be achieved by employing complex turbocharger test benches, which will also lead to higher costs including hardware and labour. An alternative solution is to develop numerical models for the turbocharger based on thermodynamics. In this thesis numerical models has been developed for predicting the performance of both the centrifugal compressors and turbines and they have been also validated using test cases, particularly for variable geometry turbines. Following detailed parametric studies, the turbocharger model has been validated against experimental data of a turbocharger with a variable geometry turbine. Results showed that the model was capable of predicting the characteristics maps of the turbocharger accurately, requiring a minimal amount of turbocharger geometric properties, experimental data and calibration parameters. Thus, by combing with the engine performance simulation software there is a highly potential for the numerical model developed in this work to become a useful tool for predicting engine performance and turbo matching calculations or diagnostic applications.

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