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This research investigated a novel combustion system for gasoline direct injection spark ignition (DISI) engines. This combustion system burned an unthrottled, stoichiometric, homogenous charge at part load, in comparison to the unthrottled,lean, stratified charge burned by conventional DISI engines. Unthrottled homogeneous operation, enabled by the use of variable valve timing. allowed high fuel efficiencies to be achieved while addressing the particulate emissions, poor combustion stabilities and NOx after-treatment issues associated with stratified charge DISI engines, when compared to the port fuel injection (PFI) engines they are replacing. Experiments were performed to quantifY the bulk in-cylinder air motions, determine their effect on the fuel spray, and examine the resulting air-fuel mixture preparation of various early inlet valve closing (EIVC) and late inlet valve opening (LIVO) strategies that were suitable for controlling engine load under homogeneous engine conditions. A broad matrix of engine conditions has been investigated, with engine speeds ranging from idle (750 rpm) to 5000 rpm, and engine loads ranging from 2.7 bar indicated mean effective pressure (!MEP) to wide open throttle (WOT). Particle Image Velocimetry (PIV) was used to record mean in-cylinder flow fields in the tumble and swirl planes for a range of engine conditions and valve profiles. This included measurements at higher engine speeds (3500rpm) than previously published. Air flows in the difficult-to-access cylinder head were measured with Laser Doppler Anemometry (LDA) and the effect of these air flows on the fuel spray produced by a latest generation multi-stream fuel injector was investigated with Mie imaging. The resulting mixture preparation was then investigated over a crank angle period ranging from the start ofinjection (SOl) to the time of spark with Laser Induced Exciplex Fluorescence (LIE F). Supporting data from a thermodynamic sister engine with identical combustion chamber geometry was recorded at University College London. Unthrottled, homogeneous operation with low lift EIVC valve profiles improved engine fuel consumption by up to 20% compared to throttled operation with conventional, full-lift profiles. This was a consequence of a reduction in the throttling losses and improvements in air-fuel mixing. The intake air momentum was more significant than the fuel spray momentum from the injection system in determining the air-fuel mixing process. This resulted in engine performance being strongly affected by engine speed, intake valve lift and injection timing. The greatest benefits in ISFC occurred when only one of the two inlet valves was operated. This was attributed to an overall increase in the level ofin-cylinder swirl. However, the choice of which inlet valve was opened was critical, with greater gains occurring if the fuel spray from the centrally mounted injector was directed towards the spark plug than when the spray was directed away from the plug. EIVC combustion also exhibited significantly longer burn times than throttled operation. This was due to lower cylinder pressures that reduced the laminar flame speed and lower levels of turbulence around the spark plug at the time of ignition. Flame front measurements on the optical engine showed that during the longer early heat release phase (0-10% mass fraction burned), the flame kernel was transported away from the spark plug and towards the combustion chamber wall beneath the inlet valves. Investigations into the fuel mixture preparation using Laser Induced Exciplex Fluorescence (LIE F) demonstrated that, under high load conditions, a source of particulate emissions from PFI engines was large droplets in the vicinity of the spark plug around the time of ignition. These fuel rich regions were precursors in the generation of soot and were all but eliminated with direct injection fuelling strategies. Late Intake Valve Opening (LIVO) valve strategies generated a sub-atmospheric cylinder pressure of between 0.5 to 0.3bar (absolute). Spray images obtained under these conditions showed greater penetration of the fuel spray and a poorly defined spray cone boundary. Due to the increased momentum and increased shear forces of the inducted air, and the cylinder pressure falling below the saturation vapour pressure of some components of the gasoline fuel at the temperature of the mixture, flash evaporation of those components was seen to occur. The improvement in atomisation and faster burn rate with LIVO compensated to some extent for the increase in irrecoverable pumping work of this operating strategy over conventional EIVC. However, a practical disadvantage of LIVO was poor control of the trapped air mass, arising from the intake air momentum supercharging the engine cylinder at the conditions tested.

The gas turbine which has found numerous applications in Air, Land and Sea applications, as a propulsion system, electricity generator and prime mover, is subject to deterioration of its individual components. In the past, various methodologies have been developed to quantify this deterioration with varying degrees of success. No single method addresses all issues pertaining to gas turbine diagnostics and thus, room for improvement exists. The first part of this research investigates the feasibility of non-linear W eighted Least Squares as a gas turbine component deterioration quantification tool. Two new weighting schemes have been developed to address measurement noise. Four cases have been run to demonstrate the non-linear weighted least squares method, in conjunction with the new weighting schemes. Results demonstrate that the non-linear weighted least squares method effectively addresses measurement noise and quantifies gas path component faults with improved accuracy over its linear counterpart and over methods that do not address measurement noise. Since Gas turbine diagnostics is based on analysis of engine performance at given ambient and power setting conditions; accurate and reliable engine performance modelling and simulation models are essential for meaningful gas turbine diagnostics. The second part of this research therefore sought to develop a multi-fuel and multi-caloric simulation method with the view of improving simulation accuracy. The method developed is based on non-linear interpolation of fuel tables. Fuel tables for Jet-A, UK Natural gas, Kerosene and Diesel were produced. Six case studies were carried out and the results demonstrate that the method has significantly improved accuracy over linear interpolation based methods and methods that assume thermal perfection.

An experimental study of the particle-to-metal interaction during high temperatures and velocity impact conditions is presented. A novel continuous erosion testing facility have been used to study the effect of particle and metal target temperatures as well as impact particle velocity on the erosion/deposition behaviour of the stainless steel 321, Nimonic 75, and aluminium target materials. The study was carried out to provide database information on the behaviour of those metals under simulated gas turbine conditions. The erosive particles used were quartz sand with diameters ranging from 20-30 μm. The erosion characteristics of stainless steel 321 were recorded at target surface temperature of 285°C, 415°C, 570°C and 715°C. The tests were carried out at two different impingement angles of 30° and 60° and at particle impact velocities of up to 300m/s. The effects of particle temperatures of 550°C, 750°C and 950°C on erosion/deposition rates were examined. The Nimonic 75 target temperatures were slightly modified to give a similar surface to melting point ratio as the stainless steel. The Nimonic 75 was tested at 545°C, 685°C, 825°C and 965°C surface temperatures and at the same particle velocities and temperature used for the stainless steel tests. The Nimonic targets were only tested at one impact angle of 30°. The aluminium targets were only tested at an impact angle of 60° and particle impact velocity of 100 m/s. The surface temperature was modified to give a ratio up to 0.8 of the melting point temperature, where the particle temperature was set to be 350°C, 550°C and 750°C. It was found that particle and target temperatures, impact velocity and angle have a significant effect on the erosion/deposition characteristics. There is a threshold target and particle temperature for which deposition begins, and it depends on impact velocity and angle. The Nimonic 75 targets exhibit a better resistance to particle deposition over the stainless steel 321 at high impact velocity and temperatures. Simple models of the erosion/deposition were established to describe the conditions of particle deposition on the stainless steel and Nimonic targets. The aluminium targets show an increase in the erosion rate as target temperature reaches certain level, which then drops as target temperature continues to increase beyond this point.

One of the greatest challenges that the world is facing is that of providing everyone access to safe and clean energy supplies. Since the liberalization of the electricity market in the UK during the 1990s many combined cycle gas turbine (CCGT) power plants have been developed as these plants are more energy efficient and friendlier to the environment. The core component in a combined cycle plant is the gas turbine. In this project the MEA’s Pulrose Power Station CCGT plant is under investigation. This plant cronsists of two aeroderivative LM2500+ gas turbines of General Electric for producing a total of 84MW power in a combined cycle configuration. Cont/d.