No description available.

No description available.

Investigations into lubricating oil degradation and engine wear were carried out during the course of this work. Lubricating oil degradation models were studied and verified. This study has resulted in the development of an integrated, miniaturised, automated oil analysis system for the determination of water content, Total Base Number and Total Insoluble Matter for new and used oils. The study on the engine wear and oil degradation was based on two air- cooled Petter AA1, single cylinder engines running on a 1% sulphur diesel fuel and a minimum military specification oil (OMD 75). The results obtained indicated that the combination of engine operating conditions, diesel fuel and lubricating oil used, resulted in the premature loss of oil consumption control due to severe bore polish which was caused by corrosive wear. Oil analysis methods were developed requiring minimal quantities of oil sample in order not to disturb the engine/lubricating oil system integrity. The oil analysis methods developed were automated into a single integrated instrument for the determination of water content, Total Base Number and Total Insoluble Matter for new and used oils using 1gram (or less) of oil sample and with analysis times in the region of three minutes for doing all three analysis. A detailed study into new and used formulated oil chemistry revealed that the measurement of Total Base Number as determined by the Institute of Petroleum standard test methods (IP 177 and IP 276) provided information that were overestimates of the true levels of basicity of the oil. A new technique, based on the same chemistry as the original (IP) method, was developed for the Total Base Number determination with improved end-point detection for not only new oils, but more importantly for used oils as well. Other oil analysis data obtained during this study revealed the need to modernise the existing Industry test methods with regard to chemistry, equipment and functionality, for example Total Acid Number determination. The data obtained from the analysis of the used oil was studied and the rates of change of each of the measured parameters were calculated, based on the Quasi-Continuous Stirred Tank Reactor model. The data obtained from this model was compared to . two previously proposed models which indicated that the QCSTR model is a better model for representing the degradation of lubricating oils in running engines. This work has shown the need for the trapping of oil from the top-ring zone to understand the nature of the degradation and interaction of this oil with that (bulk) oil in the sump in order to successfully model the degradation characteristics of the oil.

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 .

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.

The results contained within this thesis were taken from a largely experimental project tto compare a conventional turbocharger and the unique Comprex pressure wave supercharger. A large truck Diesel engine, the Leyland 690 was fitted in turn with a Holset H2B turbocharger and a Brown Boveri CX140 supercharger. A series of both steady state and transient investigations was completed with both systems. The turbocharged experimental results were also compared with predicted results from the steady state computer program (EMAT). The introduction gives; a detailed description of the Comprex operation, history, range and applications. The second chapter is devoted to a description of the apparatus and calibration of the instrumentation. The following four chapters give the experimental results in tabular and graphical form, for both systems and for the steady state and transient tests. In Chapter 7 the steady state tests for both systems are compared and the transient tests are compared in Chapter 8. The Comprex supercharger theory is briefly described in Chapter 9 with several ideas of the obtaining the air flow which bypassed the engine under certain conditions. The predicted results for the turbocharged engine are compared with experimental results in Chapter 10. Some of the problems encountered during the experimental testing are discussed in Chapter 11. With the engine operating under steady state conditions, the limiting torque curves for each system were slightly different. At the lower engine speeds (1400 - 8800 revs/min) the engine fitted with the Comprex produced a higher power than with the turbocharger. The specific fuel consumption at higher speeds was marginally better (lower) with the turbocharger but at lower speeds the Comprex produced favourable values. As expected, the boost pressure was higher with the Comprex wnth better air/fuel ratios particularly at the lower engine speeds. Using the Hart ridge smoke meter, the smoke levels with the Comprex were considerably better at the important lower engine speeds. Under transient conditions the Comprex produced considerably better results, especially in the response time to reach steady conditions. This was due to the higher boost pressure ratios at comparable operating conditions. During the very severe changes in load applied to the engine, the Comprex enabled stabilisation within 0.6 seconds compared with 1.5 seconds with the turbocharger. Transient smoke levels, measured by a high response opacimeter were also lower with the Comprex. Despite these very favourable results with the Comprex supercharger, its higher cost and weight, and the added complications associated with the drive and pipework, have so far militated against the wider adoption. However, for certain applications, such as tractors, excavators and shovel loaders with their rapidly changing load and speed cycles, the Comprex has considerable advantages.

As part of a broader research project of adiabatic engine investigation, the present work concerns the effect of heat barriers in the suppression of heat loss and on the thermal loading conditions in pistons, from both a steady-state and transient point of view. The theoretical work has been concerned primarily with the development of a comprehensive set of computer programs dealing with either the steady-state axisymmetric heat transfer and stress analysis, or the transient heat transfer analysis. In developing the programs, the present work provides a subdomain integral approach to the finite element method, the integration of which can be either weighted or non-weighted. In the latter case, the subdomain integral can often be physically interpreted as, e.g. the energy balance in a control volume or the force equilibrium on a free body, hence it provides much more intuitive and physical insights to the finite element method, with the same accuracy and same applicability to solving various engineering differential equations as the Galerkin method. The subdomain integral approach can be directly applied to the initial value problems, where the subdomain is offset in the time-dimension. By this method the time-marching process can be represented in the form of a system matrix, which enables the direct solution of periodic phenomena without the requirement of incorporating and iterating the guessed initial conditions from cycle to cycle. In this way, the convergence from cycle to cyle is inherently satisfied. More importantly, the present work also provides a one-dimensional linearization model of the axisymmetric heat transfer and thermal stress field, from which may be deduced the equivalent thermal resistance (two-terminal model) or its three components (three-terminal model) of the configuration, as well as the thermal stress sensitivity to the thermal loadings. By incorporating the equivalent thermal resistances into the engine cycle simulation program, the heat flow rate over the full cycle in the engine cycle simulation can be matched with the heat flow rate through the combustion chamber components. The experimental work has concentrated on methods for determining the gas-side boundary conditions from measured piston temperatures. The area-mean wall temperatures (and hence the total heat flow through the piston when the effective gas temperature is known), can be obtained from the measured maximum surface temperatures by applying the present one-dimensional model. Furthermore, a novel differential probe is proposed to measure the heat transfer coefficient and the effective gas temperature simultaneously. By applying these specially developed finite-element programs, matched either with the experimentally determined boundary conditions or with the corresponding engine cycle simulation program, a detailed investigation on various heat barrier configurations, concentrating on a specially designed and manufactured air-gap piston, leads to the following conclusions: 1. The practical range of insulation design lies between 40-65% reduction of heat loss. The air-gap piston design presented in this thesis can give about 50% reduction of heat loss, which is in the desired range of insulation. 2. The effect of insulation on the percentage suppression of heat loss is influenced by the engine rating conditions, and by the gas-side boundary conditions. The higher the rating, or the higher the gas-side heat transfer coefficient, the more significant is the effect of insulation on the suppression of heat loss. 3. In the "ideal transient adiabatic" operation, about 50% of the total recovered heat can be converted into work. However, in real thermal barrier configurations, the wall surface temperature fluctuation is small. Therefore, nearly all real thermal barriers (including the air-gap design) undergo "steady-state" operation, where only about 30% of the total recovered heat can be converted into work. 4. Insulation of the piston is not only tolerable, but actually favourable to piston ring life as the ring groove temperature is well below the permissible range. The maximum radial thermal expansion in a high temperature air-gap piston is well below the cold tolerance limit between the piston and the liner. 5. The fatigue analysis shows that the present air-gap design satisfies the demands of fatigue strength. The cyclic thermal stresses in the air-gap piston do not add significantly to the compressive stresses on the crown. 6. By matching the finite element analysis with the engine cycle simulation program, the reciprocal effect of insulation on the gas-side boundary condition in raising the mean effective gas-temperature is clearly shown. The present matching method can thus be used in the further investigation of the effect of insulation on the performance of the whole compound engine system.

This thesis describes a theoretical and experimental programme designed to produce a self optimizing control system to the Differential Compound Engine (DCE). Optimum control surfaces for the relevant variables are obtained experimentally and theoretically and used as the basis for microprocessor control. The system adopted relies on analogue inputs from appropriate transducers to the microprocessor via analogue-to-digital converters with outputs representing optimum control settings implemented via electrohydraulic actuators. An additional theoretical investigation is concerned with further measures to improve efficiency and output torque of the current DCE system particularly through the incorporation of a continuously variable turbine transmission (CVT) and a main drive line torque converter to improve the system. A final theoretical section of the work deals with attempts to determine the best nozzle angle schedule for transient operation, and the application of such a schedule to the calculation of a complete vehicle transient.

An investigation on the sequential turbocharging of a Kelvin TFSC6 6-cylinder 4- stroke marine diesel engine developing 320 kW at 1200 r/min is reported in this thesis. The sequential turbocharging (ST) system, utilising turbochargers of unequal size, resulted in significant improvement when compared with previously designed systems. The engine test results show that the new sequential turbocharging system improves the engine performance at both high speeds and low speeds except at or near to the 'transfer' speed. The engine low speed performance is obviously improved with the fuel saving of up to 7 g/kwh for the 1st sequence. The engine high speed performance is also improved for the 2nd sequence where both turbochargers are in operation. There is some boost air leakage from the delivery pipe which is used for connecting the peak unit to the intercooler inlet. This restricts the 2nd sequence gains. An optimised sequence transfer control mode is also proposed in this research and validated by both test and simulation results. Two control valves, one at the peak unit turbine inlet and the other at the compressor outlet, are specifically designed for the ST system and both of them worked very well during the engine test programme. Both simulation models - "Filling& Emptying" and "Method of Characteristic" were modified and used for the sequential turbocharging simulation. The modified program of the "Filling& Emptying" model can be used to analyse and compare the effects of different exhaust systems. It can also be applied to simulate and design a pulse converter system for a sequential turbocharged diesel engine. The modification on the "MOC" program makes it possible to simulate the exhaust pressure wave for the ST system with different turbocharger arrangements (concentrated or separated). The consideration of pressure losses in the 'three branch junction' boundary improves the simulation accuracy. In addition, a comprehensive engine test data acquisition and control system has been developed in this study. The advanced system with many new features can be used for engine condition monitoring. diagnosis and other similar applications for engine development and test. The efficiency and reliability of the system have been corroborated by the engine test process. The real time data process, analysis and display in various forms are available using the developed program with 'LabVIEW'. The proposed self-adaptive auto-load setting with optimised parameters is validated as an economic solution for engine load control with an early type of hydraulic dynamometer.

No description available.