Gas turbines are extensively used in aviation because of their advantageous volume as weight characteristics. The objective of this project proposed was to look at advanced propulsion systems and the close coupling of the airframe with advanced prime mover cycles. The investigation encompassed a comparative assessment of traditional and novel prime mover options including the design, off-design, degraded performance of the engine and the environmental and economic analysis of the system. The originality of the work lies in the technical and economic optimisation of gas turbine based on current and novel cycles for a novel airframes application in a wide range of climatic conditions. The study has been designed mainly to develop a methodology for evaluating and optimising biofuel combustion technology in addressing the concerns related to over-dependence on crude oil (Jet-A) and the increase in pollution emissions. The main contributions of this work to existing knowledge are as follows: (i) development of a so-called greener-based methodology for assessing the potential of biofuels in reducing the dependency on conventional fuel and the amount of pollution emission generated, (ii) prediction of fuel spray characteristics as one of the major controlling factors regarding emissions, (iii) evaluation of engine performance and emission through the adaptation of a fuel’s properties into the in-house computer tools, (iv) development of optimisation work to obtain a trade-off between engine performance and emissions, and (v) development of CFD work to explore the practical issues related to the engine emission combustion modelling. Several tasks have been proposed. The first task concerns the comparative study of droplet lifetime and spray penetration of biofuels with Jet-A. In this task, the properties of the selected biofuels are implemented into the equations related to the evaporation process. Jatropha Bio-synthetic Paraffinic Kerosine (JSPK), Camelina Bio-synthetic Paraffinic Kerosine (CSPK), Rapeseed Methyl Ester (RME) and Ethanol are used and are evaluated as pure fuel. Additionally, the mixture of 50% JSPK with 50% Jet-A are used to examine the effects ofblend fuel. Results revealed the effects of fuel volatility, density and viscosity on droplet lifetime and spray penetration. It is concluded that low volatile fuel has longer droplet lifetime while highly dense and viscous fuel penetrates longer. Regarding to the blending fuel, an increase in the percentage of JSPK in the blend reduces the droplet lifetime and length of the spray penetration. An assessment of the effect of JSPK and CSPK on engine performance and emissions also has been proposed. The evaluation is conducted for the civil aircraft engine flying at cruise and at constant mass flow condition. At both conditions results revealed relative increases in thrust as the percentage of biofuel in the mixture was increased, whilst a reduction in fuel flow during cruise was noted. The increase in engine thrust at both conditions was observed due to high LHV and heat capacity, while the reduction in fuel flow was found to correspond to the low density of the fuel. Regarding the engine emissions, reduction in NOx and CO was noted as the composition of biofuels in the mixture increased. This reduction is due to factors such as flame temperature, boiling temperature, density and volatility of the fuel. While at constant mass flow condition, increases in CO were noted due to the influence of low flame temperature which leads to the incompletion of oxidation of carbon atoms. Additionally, trade-off between engine thrust, NOx, and CO through the application of multi-objective genetic algorithm for the test case related to the fuel design has been proposed. The aim involves designing an optimal percentage of the biofuel/Jet-A mixture for maximum engine thrust and minimum engine emissions. The Pareto front obtained and the characteristics of the optimal fuel designs are examined. Definitive trades between the thrust and CO emissions and between thrust and NOx emissions are shown while little trade-off between NOx and CO emissions is noted. Furthermore, the practical issues related to the engine emissions combustion modelling have been evaluated. The effect of assumptions considered in HEPHAESTUS on the predicted temperature profile and NOx generation were explored. Finally, the future works regarding this research field are identified and discussed.

This work presents the development and implementation of a spray combustion model based on the spray droplet number size distribution moments approach to spray modelling. In this spray model, the droplet size distribution of spray is characterised by the first four moments related to number, radius, surface area and volume of droplets, respectively. The governing equations for both the gas and liquid phases are solved by the finite volume method based on an Eulerian framework. These constructed equations and source terms are derived based on the moment-average quantities which are the key concept for this work. Regarding to the application in diesel spray combustion, the auto-ignition and combustion models are substantially required to be implemented. The model employed in the auto-ignition and combustion analysis here is the PDF-Eddy Break-Up (PDF-EBU) model. This scheme is developed in order to effectively validate both ignition and combustion phases. It is designed to compromise between the chemical reaction rate dealing with the ignition mode, and turbulence reaction rate dominating the combustion mode via a reaction progress variable which represents the reaction level. These average reaction rates are evaluated by a probability density function (PDF) averaging approach. In order to assess the potential of this developed model, the auto-ignition and combustion models are further required to be validated. In auto-ignition process, the predicted results from both the developed PDF-EBU and the Shell ignition models are completely satisfactory in predicting the ignition delay time. However, the ignition kernel location predicted by the Shell model is slightly nearer injector than that by the PDF-EBU model resulting in shorter lift-off length. In combustion mode, the PDF-Chemical Equilibrium (PDF-EQ) combustion model presents slightly stronger reaction rate than the PDF-EBU model results. So the combustion period of the PDF-EQ model is then slightly shorter due to the same amount of liquid fuel. Comparing with the experimental data obtained from the literature, the lift-off lengths of luminous flames are in reasonably good agreement with the simulation results of the PDFEBU ignition model. Furthermore, the power-law scaling of Siebers et al. [1, 2] generally employed for predicting the lifted flame provides corresponding lift-off lengths to the PDFEBU and experimental results as well. In overall, there are insignificant differences in predicting the flame areas and average surface flame temperatures by different ignition and combustion models. However, the PDF-EBU ignition model seemingly yields the predicted results in moderately good agreement with the experimental data. The performance of the developed PDF-EBU combustion model is comparable to that of the more complicated PDFEQ combustion model. The other CFD simulation results in literature employed for comparison are obtained from the detailed kinetic mechanism of n-heptane, which have high reliability and accuracy. Similar to the experiment comparison, the lift-off lengths predicted by a power-law scaling more corresponds to the PDF-EBU ignition model results than to the CFD simulation results. However, the simulation results of flame temperature predicted by any ignition and combustion models are relatively comparable to the complex CFD simulation results.

This thesis initially considers the commercial and practical aspects of the problem. being addressed. Several different modelling methods were then assessed including linear, nonlinear, static and dynamic methods in order to accurately capture a description of the normal operation of a family of industrial gas turbines. Most of the methods that were assessed were found to be unsuitable, in large part due to the nature of the data available. The method that was found to perform best, because it could meet all of the required objectives within a single methodology, was the Self-Organizing Map (SOM). A comprehensive evaluation of the SOM was carried out using data from several commercial gas turbines. Some difficulties in the application of the 80M were encountered. These were largely overcome using empirical studies and a novelty threshold. A computer package was developed using the SOM to detect novelty and provide the user with the tools necessary to proceed from novelty to anomaly detection with the minimum of effort. An alternative method to create SOM-like maps was then developed using existing optimisation techniques rather than the heuristic methods associated with the conventional SOM algorithm.. The resulting maps were found to have several properties that were superior to the conventional SOM. These included being more effective in both novelty detection and in constructing meaningful topology preserving maps of the process.

The VIVACE European Cycle Program (“VIVACE-ECP”) was part of the virtual engine sub-project of VIVACE and was worth 6.63 million Euros. The main outcome of the “VIVACE-ECP” was the development of a cost effective gas turbine simulation environment called PROOSIS. PROOSIS, which is the Greek word for “propulsion”, is an acronym for “PRopulsion Object Oriented SImulation Software”. PROOSIS was developed by facilitating optimal use of multi-partner gas turbine performance simulation research and development resources and expertise. PROOSIS is a single framework which provides shared standards and methodologies for the European Union (EU) gas turbine community, including original equipment manufacturers (OEMs), industrial companies, universities and research centres. The primary objective of this doctoral thesis is to present advanced performance simulation models of gas turbine components and advanced fluid modelling capabilities developed by the author for the PROOSIS standard components library (SCLib). The main aims of this research are to provide a detailed insight into the effects of dissociation on fluid thermodynamic properties and subsequently on gas turbine performance. Detailed descriptions of the development of an advanced fluid model and a robust flow continuity model, which are the foundation of the PROOSIS standard component library, are provided. The effects of dissociation on isolated Burner and Afterburner components as well as overall engine performance are discussed with the aid of several case studies. Additionally, advanced performance simulation models of Burner and Afterburner components are presented. The development of an extended parametric representation of compressor characteristics is also analysed. Several advanced capabilities of PROOSIS (including test analysis, customer deck generation, 3D compressor zooming and distributed computing) are also introduced. The “evolution of PROOSIS” is presented with an in-depth analysis of the collaborative structure and project management of the VIVACE- ECP, as well as the channels of communication, technology transfer and quality control. A clear emphasis is placed on the contribution of the author to each of these tasks and subsequently the “VIVACE-ECP” as a whole. The main outcome of this work is the development of an advanced fluid model which comprises multi-dimensional fluid property tables for several fuels. The advanced fluid model also caters for “levels of dissociation” ranging from “no dissociation” to chemical equilibrium. This advanced fluid model is complimented by a robust flow continuity model, also developed by the author, which calculates the unknown local flow properties at any point in an engine model. These robust, advanced fluid and flow continuity models facilitate improved accuracy thereby providing a solid foundation for several advanced gas turbine performance simulation capabilities.

The reliabilities of the gas-path components (compressor, burners and turbines) of a gas turbine (GT) are usually high when compared with those of other GT systems such as fuel supply and control. However, in the event of forced outage, downtimes are normally high, giving a relatively low availability. The purpose of condition monitoring and fault diagnostics is to detect, isolate and assess (i.e. estimate quantitatively the magnitude of) the faults within a system, which in this case is the gas turbine. An effective technique would provide a significant improvement in economic performance, reduce operational and maintenance costs, increase availability and improve the level of safety achieved. However, conventional analytical techniques such as gas-path analysis and its variants are limited in their applications to engine diagnostics due to several reasons that include their inability to:- operate effectively in the presence of noisy measurements; distinguish effectively sensor bias from component faults; preserve the nonlinearity in the gas-turbine parameter relationships; and the requirement for more sensors for achieving accurate diagnostics. The novelty of this research stems from its objective of overcoming most of these limitations and much more. In this thesis, we present the approach adopted in developing a diagnostic framework for the detection of faults in the gas-path of a gas turbine. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess the faults in the gas-path components of the engine. Input to the diagnostic framework are engine measurements such as spool speeds, pressures, temperatures and fuel flow while outputs are either levels of changes in sensor(s) for the case of sensor fault(s) or the level of changes in efficiencies and flow capacities for the case of faulty components. The diagnostic framework has the capacity to assess both multiple component and multiple sensor faults over a range of operating points. In the case of component faults, the diagnostic system provides changes in efficiencies and flow capacities from which interpretations can be sought for the nature of the physical problem. The implication of this is that the diagnostic system covers a wide range of problems - both likely and unlikely-. The technique has been applied to several developed test cases, which are not only thermodynamically similar to operational engines, but also covers a range of engine configurations and operating conditions. The results obtained from the developed approach has been compared against those obtained from linear and nonlinear (recursive linear) gas-path analysis, as well as from the use of fuzzy logic. Analysis of the results demonstrates the promise of ANN applied to engine gas-path fault diagnostic activities. Finally, the limitations of this research and direction for future work are presented.

Rocket engines have low specific impulse (Isp) compared to jet propulsion. Over the last few decades, a number of space launch vehicles that utilise airbreathing propulsion to aid their ascent have been proposed, though none have been flown. High-speed airbreathing engines such as ramjets, scramjets, and others, may significantly improve the performance of launch vehicles, potentially allowing for single-stage-to-orbit vehicles to become possible. Such vehicles should have better reliability and shorter down-time between missions than their multi-stage counterparts. A crucial component in high-speed air-breathing engines is the air intake, which must capture sufficient air-flow, and compress it to the conditions required by the engine. The compression occurs through one or more shockwaves. The performance of the intake is strongly dependent upon the positioning of these shockwaves. Unfortunately, the optimum positioning for these shockwaves in terms of performance is usually an unsafe position for engine operation. Furthermore, these shockwaves will move from their nominal locations during atmospheric disturbances such as gusts. A margin on their nominal position must be employed, to ensure that they do not move to unsafe locations within the intake during these disturbances. Calculation of the necessary size of this margin is not trivial; full CFD models can be used, but take a prohibitively long time to complete for an entire flight envelope and varying weather conditions. Since the performance of the intake is directly tied to the positioning of these shockwaves, it is important to develop a low-order model of shockwave motion during disturbances that can be solved much more rapidly than higher fidelity CFD techniques. This model could then be used to solve for shod;wave motion over a wide range of flight, weather, and design conditions. The work presented here uses the example of the Reaction Engines Ltd. SABRE engine to first demonstrate that shockwave motion during gusts can be significant, and then goes on to develop a low-order model to predict this motion. The accuracy of the model is demonstrated against inviscid CFD for a range of frequencies and lengths of discrete gusts.

This PhD work is motivated by on-board condition monitoring of gas turbine engines (GTEs) and presents a constructive robust fault detection procedure integrating system identification, time delay compensation, eigenstructure assignment, zero assignment and dynamic observer design techniques, to detect faults in a dynamic system corrupted by disturbances at some frequencies. The main results achieved in this PhD study are: (1) Application of nonlinear least squares to Output Error (OE) model identification. Although OE model shows better performance on long-term prediction, the challenge is the dependency within the long-term prediction errors. The dependency is tackled by an iterative calculation of the gradient, and an approximation of the Hessian matrix is adopted to accelerate the convergence. (2) Delay compensation for high-gain observer based time-varying parameter estimation. In the high-gain observer based parameter estimation, it is usually assumed that the estimation delay is zero. This assumption puts some constraints on the observer design and may not be satisfied in some situations. By examining the transfer function matrices associated with the high-gain observer, a novel time delay calculation and compensation approach is proposed. The main contribution is the proof of the fact that the estimation delay is free from the plant parameter variation. Then a nonlinear phase delay filter approximation technique is used to compensate the delay. (3) Zero assignment in dynamic fault detection observer design. It is well known in filter design that zeros have the ability to block the propagation of some input signal through the system at some frequency. In this thesis. this idea is used to assign zeros to the desired places so that the disturbance can be attenuated. In most observer design research, however, the structure is confined to the classic (static) Luenberger structure where the gain is a constant. numerical matrix. As proved in this thesis, zeros of static observers arc invariant. Hence the dynamic observer is proposed, where a dynamic system (dynamic feedback gain) substitutes for the constant numerical gain matrix. As a result, some additional zeros are introduced and can be assigned arbitrarily to the desired places. To the best of our knowledge, although the concept of zeros in multivariable systems has been proposed by Rosenbrock over thirty years, there have been no known results of utilising zero assignment to robust fault detection observer design.

Modern gasoline port fuel injected (PFI) engmes have improved performance and efficiency through the use of variable valve technology. A PFI engine with continuously variable intake valve lift is now a viable option for reduced C02 emissions levels through an improvement in the cycle efficiency. This improvement is due to a reduction in the negative pumping work associated with throttled, four-stroke, engine operation. However, when operating at peak intake valve lifts of the order of 5% of conventional peak lift values, the nature of the air and fuel mixing process is fundamentally altered. The characteristics of the mixture preparation processes are not clearly understood. In order to investigate and evaluate these features, a BMW Valvetronic cylinder head was modified to allow optical access to the intake port, near-valve region and upper cylinder. This was incorporated into a Steady State Flow Rig (SSFR). The operating conditions of the steady-state flow rig were derived from data recorded in a four-cylinder, firing engine study. A sequence of well proven optical and laser diagnostic techniques were applied experimentally to describe the characteristics of the air and fuel mixing processes through the intake port and valve orifice and within the upper regions of the combustion chamber. These included Laser Light Sheet Scattering, Particle Image Velocimetry and Phase Doppler Anemometry. The experimental methods were used to establish the characteristics of the port discharge coefficient, mean and turbulent airflow and the liquid fuel spray over a range of peak intake valve lifts and flow conditions. The characteristics of the port fuel injector were initially investigated in a quiescent spray chamber. The four-hole fuel injector produced two streams of liquid fuel with an approximate cone angle of 14°. The angle between each liquid jet was approximately 20°. The spray was comprised of droplets with a mean diameter of 50Jlm and a mean axial velocity magnitude of20m/s during the main, quasi-steady, spray phase. In the steady-state flow rig measurements, five intake valve flow regimes were identified; high valve lift, the first transition phase, intermediate valve lift, the second transition phase and low valve lift. A simple analysis based upon the predicted droplet Weber number was used to provide supporting evidence to the in-situ airflow and droplet size measurements. At the highest valve lifts, the characteristics of the fuel spray were similar to that observed in the quiescent spray chamber. The fuel droplets were entrained in the free flow air regime. For valve lifts between 9mm and 3mm, the air motion in the cylinder exhibited a conventional, forward tumble, bulk motion pattern. In the intermediate range of valve lifts, between 1.5mm and 3mm, the forward tumble bulk flow motion was less evident and the discharge coefficient indicated some degree of flow separation at the valve orifice. Multiple secondary break-up mechanisms occurred at the intake valve orifice. The bulk in-cylinder air motion was consistent with a pair of counter-rotating vortex-like structures above and below the intake valve exit jet, exhibited by regions of high turbulence intensity. At the low peak valve lifts, the predicted droplet Weber number indicated catastrophic break-up of the fuel through the intake valve orifice. A narrow air and fuel spray flow was observed in the tumble plane. A 50% reduction in the mean droplet diameters was measured at an intake valve lift of OAmm compared to the full lift case. Features of the mixture preparation processes at low valve lifts included oscillating velocity measurements in the air flow that were consistent with jet flapping instabilities near the valve exit. A finely dispersed fuel spray mist was recorded in the cylinder. Both the air motion and fuel spray studies exhibited cross-flow asymmetry throughout the entire valve lift range.

The aim of this thesis is to design and evaluate a non-destructive evaluation (NDE) system for the inspection of single crystal turbine blades. Turbine blades are the components within jet-engines that convert the hot, high-pressure gas exiting the combustion stage into mechanical power. During operation, these components are highly stressed and are surrounded by extremely high gas temperatures. As such, there is the potential for defects to initiate in-service. One way to ensure the structural integrity of these engine components is by periodically inspecting them for defects. The ability of the inspection to be performed in situ is highly advantageous, as this eliminates the cost and time delay associated with removing the turbine blades from the engine prior to inspection. A 20 ultrasonic phased array system was chosen for this project, as these systems can perform rapid volumetric inspections whilst being portable enough to be used in situ. Modem turbine blades are manufactured from single crystal nickel-based superalloys for the excellent mechanical properties these materials exhibit at elevated temperatures. However, these materials are elastically anisotropic. The propagation of ultrasonic waves through anisotropic materials is far more complex than the isotropic case. This causes significant difficulties when inspecting anisotropic single crystal components with ultrasonic arrays. Therefore, analytical models are developed to predict the propagation of ultrasonic waves in anisotropic materials. These models are used to correct an ultrasonic imaging algorithm to account for the anisotropic behaviour. To implement the corrected algorithm effectively, the orientation of the crystal in the component under inspection must be known. Therefore, crystallographic orientation methods using 20 ultrasonic arrays are developed and evaluated. The corrected algorithms and crystallographic orientation methods are used to develop an in situ 20 ultrasonic array inspection for a specific high-pressure single crystal turbine blade. The inspection is designed to detect and size cracking in the root section of the turbine blade. The developed inspection system is fully evaluated in a quantitative manner for its defect detection sensitivity and sizing capability.

Increasing environmental constraints have led to a corresponding increase in engine complexity. As a result there is more of a requirement to fully understand and manage the task of hardware selection and engine optimization. Traditionally undertaking these tasks in either experimental or simulation environments would be highly time and cost inefficient and iterative. A technique is developed whereby data is merged from a variety of sources thus reducing the aforementioned problems whilst still retaining high system knowledge. Technologies relating to engine downsizing are focused on since it has been identified as one of the more promising methods in meeting future CO2 constraints. Engine downsizing is a smaller highly boosted engine performing the same role of a larger engine with reduced heat and frictional losses. In order to address these issues this research develops a range of techniques that enable technologies such as high boost, variable valve actuation (WA) , variable compression ratio (VCR) and exhaust gas recirculation (EGR) to be evaluated as part of the overall powertrain optimization process. A novel experimental data merging process proved to be the most successful method and showed improved accuracy over simulation studies, particularly with reference to NOx and BSFC. As part of the experimental work in capturing high boost data a novel charge air handling unit is employed. This emulates the effects of boosting hardware as opposed to having to develop prototype hardware itself. The advantage is it can operate outside the production envelope and is thus capable of emulating a variety of current and future boosting strategies. Within this research the charge air handling unit reaches 2 bar boost irrespective of engine speed, although there is capacity to go up to 3 bar with a reduced compression ratio engine and uprated gaskets. Further development of the technique at full load will give the automotive engineer an invaluable tool to make informed powertrain selection choices early in the development cycle, thus reducing cost and potential problems at later stages.