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The emission of NOx from aero-gas turbine combustors, which in the present generation of designs consists mainly of thermal NOx ' is of great concern due to its potential damage to the stratospheric ozone layer. Soot production in gas turbine combustors is also undesirable since it is both the major source of exhaust smoke and, more importantly, the principal agent in thermal radiation to the combustor liner. Furthermore thermal radiation from the soot redistributes energy in the combustor, modifying the temperature field. This consequently affects the production of other pollutants, notably that of thermal NOx > since the production rate is especially sensitive to temperature. Mathematical models for predicting gas turbine combustor emissions can be divided, in general terms, into two main groups, Methods based on zonal (or modular) approach and on CFD modelling. CFD modelling allows the use of computation intensive multi-dimensional Navier-Stokes codes but cannot account for detailed chemistry which is responsible for emissions. On the other hand, although the modular approaches make significant assumptions about the mean flowfield and mixing, they employ detailed chemical kinetics. The work reported in this thesis seeks to develop a model for emission predictions in the gas turbine combustor which combines the advantage of both the modular approach and CFD modelling. The strategy was based on a pdf calculation using the Monte-Carlo simulation technique because the chemical source term is in closed form for the approach and the solution procedure requires a CFD based calculation. Averaging of the particle properties was on an extended zonal or planar basis in order to reduce computational effort. The predictions are evaluated against available experimental results and other predictions employing more conventional approaches. Since the pdf method allows the modelling of slow chemistry and simultaneous influence of multiple scalars, the thermal NO x production rate was implemented considering the effect of NO concentration itself. Predicted exit NOx concentration was higher than the measured exit level. It has been thought that this discrepancy is mainly due to neglecting radioactive heat loss for temperature calculations. The modelling of soot formation and oxidation has proved more problematic since the assumption that soot is simply perturbation to the gaseous field, analogous to the NO concentration, and temperature may be accurately described by single adiabatic flamelet are no longer valid at elevated pressure and temperature conditions. Soot bum-out is under-predicted. The computed mean soot oxidation is less than 10% of the maximum production levels, even when OH is considered to be oxidising species in addition to O2 •• Although high soot formation rate was predicted as a result of neglecting radioactive loss and using single perturbed flamelet calculation, the main uncertainties come from instantaneous soot oxidation rate and the particle size effect which influence the particle surface area.

Current wind turbine performance codes are not yet able to predict the rotor aerodynamic behaviour with sufficient certainty. This has led to both the over-design of blades and to operational restrictions in certain wind conditions. Essentially the problem is one of aerodynamic stall. Steady 3-dimensional stall can occur near the blade root in high wind conditions and may produce more power than predicted. Dynamic stall can also be expected due to the effects of yawed operation, turbulence, tower shadow and the earth's boundary layer. The main aim of this work is to provide a coherent set of measured aerodynamic data accounting for both axial/non-axial flow and stall in high winds. These measurements are designed to highlight the effects of both steady and dynamic stall on the rotor aerodynamic performance. In addition, the data will enable current performance prediction codes to be developed and validated. A completely new turbine has been designed and built at Cranfield to make aerodynamic measurements using pressure transducers. The design has been dominated by the requirements of accommodating the transducer signal processing equipment and allowing variation of many of the rotor parameters. Three commercial glass fibre blades were installed and performance curves measured on a conventional field site at a height of 11.5m for three rotor speed settings. These measurements show the turbine to give adequate power performance. A mobile trailer has been used to tow the turbine at a height of 4m along the Cranfield runways. Mobile testing facilitates an accelerated test schedule and allows aerodynamic data to be acquired under controlled wind conditions. A fully instrumented blade, fitted with forty transducers, has been tested under these circumstances and produced a large database of pressure measurements covering operation in winds up to 25 iq/s and yaw angles between -4511 and +55°. Analysis of the data has shown it to be of good quality and allowed some of the effects of yaw and stall to be identified. The use of the data base for performance prediction code validation has also been established.

Model updating is an important issue in engineering. In fact a well-correlated model provides for accurate evaluation of the structure loads and responses. The main objectives of the study were to exploit available optimisation programs to create an error localisation and updating procedure of nite element models that minimises the "error" between experimental and analytical modal data, addressing in particular the updating of large scale nite element models with severe requirements on the mode shapes correlation. A new methodology and procedure that allows the semi-automatic adjustment of a large nite element dynamic model of a structure to better represent the dynamic characteristics of an actual structure was developed. The key aspect of the procedure is a "two steps" optimisation process to achieve a complete correlation of the modal data. Eigenfrequency deviations and mode shapes cross-othogonality (CO) and/or modal assurance criterion (MAC) are used in the objective functions for the estimation problem of the updating parameters, that are the variables for tuning the analytical model. Theoretical aspects and practical implementation conceming CO and MAC, and their derivatives, have been fully developed and the advantages of using these mode correlation indices in the objective function have been largely commented. The selection of the updating parameters is a complex issue and can be still considered a partially open point. In the new procedure the suggested automated selection of the updating parameters by means of a preliminary calculation of the element modal strain energy and eigenvalue sensitivities is adequate for the reduction of the frequency deviations but could not be to improve the correlation indices of the mode shapes. The new procedure was successfully applied four times: to a cantilever beam model, the Garteur model, the Spacehab dynamic model and the Mini-Pressurised Logistics Module model. The last application was a real life application on a large scale structural mathematical model and in this case the procedure was mainly used for error localisation purposes. The developed procedure is robust, effective and efficient, thus the original objectives of the study were largely met.