Doctor of Philosophy / Department of Mechanical Engineering / Steven J. Eckels / Byron W. Jones / Poor air quality in commercial aircraft cabins can be caused by volatile organophosphorus (OP) compounds emitted from the jet engine bleed air system during smoke/fume incidents. Tri-cresyl phosphate (TCP), a common anti-wear additive in turbine engine oils, is an important component in today’s global aircraft operations. However, exposure to TCP increases risks of certain adverse health effects. This research analyzed used aircraft cabin air filters for jet engine oil contaminants and designed a jet engine bleed air simulator (BAS) to replicate smoke/fume incidents caused by pyrolysis of jet engine oil. Field emission scanning electron microscopy (FESEM) with X-ray energy dispersive spectroscopy (EDS) and neutron activation analysis (NAA) were used for elemental analysis of filters, and gas chromatography interfaced with mass spectrometry (GC/MS) was used to analyze used filters to determine TCP isomers. The filter analysis study involved 110 used and 74 incident filters. Clean air filter samples exposed to different bleed air conditions simulating cabin air contamination incidents were also analyzed by FESEM/EDS, NAA, and GC/MS. Experiments were conducted on a BAS at various bleed air conditions typical of an operating jet engine so that the effects of temperature and pressure variations on jet engine oil aerosol formation could be determined. The GC/MS analysis of both used and incident filters characterized tri-m-cresyl phosphate (TmCP) and tri-p-cresyl phosphate (TpCP) by a base peak of an m/z = 368, with corresponding retention times of 21.9 and 23.4 minutes. The hydrocarbons in jet oil were characterized in the filters by a base peak pattern of an m/z = 85, 113. Using retention times and hydrocarbon thermal conductivity peak (TCP) pattern obtained from jet engine oil standards, five out of 110 used filters tested had oil markers. Meanwhile 22 out of 74 incident filters tested positive for oil fingerprints. Probit analysis of jet engine oil aerosols obtained from BAS tests by optical particle counter (OPC) revealed lognormal distributions with the mean (range) of geometric mass mean diameter (GMMD) = 0.41 (0.39, 0.45) [mu]m and geometric standard deviation (GSD), [sigma][subscript]g = 1.92 (1.87, 1.98). FESEM/EDS and NAA techniques found a wide range of elements on filters, and further investigations of used filters are recommended using these techniques. The protocols for air and filter sampling and GC/MS analysis used in this study will increase the options available for detecting jet engine oil on cabin air filters. Such criteria could support policy development for compliance with cabin air quality standards during incidents.

Environmental issues such as climate change are leading to important sustainability challenges in the aerospace industry. Composites are light materials that are extensively used to replace metals and reduce the aircraft weight, the goal being to decrease the fuel consumption in flight and limit the emission of greenhouse gases. However, these high performance materials are associated with a complex supply chain including energy-consuming processes. Most of the decommissioned composite products are currently landfilled and nothing proves that the weight reduction allowed by these materials compensates those negative aspects. The purpose of this master thesis is to determine if the introduction of composites in aero-engines can be sustainable and how it can be achieved. To do so, three polymer-matrix composite components from GKN Aerospace have been studied and compared with their metallic baseline from environmental, social and economic perspectives. Several options for materials selection, manufacturing processes and recycling possibilities have been investigated in the same way. The assessment on GKN Aerospace’s components showed that the weight savings provided by composites have a strong and positive influence on their sustainability. Component B shows the best results: with 16% of weight savings with composites versus the titanium baseline, it appears clearly that the composite version is the most sustainable one. Component A2 composite version also provides interesting weight savings (14%) but has an aluminum baseline, which makes the composite component more sustainable in some aspects but not all of them, especially economically speaking. Finally, for component A1, the composite version, which does not provide weight savings, is more economically feasible, but quite tight with the titanium baseline on environmental and social aspects. Therefore, it appears that composite components are more likely to be sustainable if they provide significant weight reduction and if the baseline is titanium. A few strategies would merit attention to make future composite components more sustainable. On the one hand, using thermoplastic composites have potential to reduce the environmental, social and economic impact. In fact, these materials can be fully recycled and reused, present less risks to handle and can be produced for a lower cost. Nevertheless, the knowledge on these materials is more limited than on thermoset composite and the implementation of such a solution will take time. On the second hand, introducing composite recycling processes in the products lifecycle can increase a lot the sustainability of composite components. The manufacturing scrap and the decommissioned products can both be recycled in order to reduce the environmental impact and generate benefits by re-using or selling the recycled material.

This thesis describes validated improvements in the modelling of micron-sized particle deposition within gas turbine engine secondary air systems. The initial aim of the research was to employ appropriate models of instantaneous turbulent flow behaviour to RANS CFD simulations, allowing the trajectory of solid particulates in the flow to be accurately predicted. Following critical assessment of turbophoretic models, the continuous random walk (CRW) model was chosen to predict instantaneous fluid fluctuating velocities. Particle flow, characterised by non-dimensional deposition velocity and particle relaxation time, was observed to match published experimental vertical pipe flow data. This was possible due to redefining the integration time step in terms of Kolmagorov and Lagrangian time scales, reducing the disparity between simulations and experimental data by an order of magnitude. As no high temperature validation data for the CRW model were available, an experimental rig was developed to conduct horizontal pipe flow experiments under engine realistic conditions. Both the experimental rig, and a new particulate concentration measurement technique, based on post test aqueous solution electrical conductivity, were qualified at ambient conditions. These new experimental data compare well to published data at non-dimensional particle relaxation times below 7. Above, a tail off in the deposition rate is observed, potentially caused by a bounce or shear removal mechanism at higher particle kinetic energy. At elevated temperatures and isothermal conditions, similar behaviour is observed to the ambient data. Under engine representative thermophoretic conditions, a negative gas to wall temperature gradient is seen to increase deposition by up to 4.8 times, the reverse decreasing deposition by a factor of up to 560 relative to the isothermal data. Numerical simulations using the CRW model under-predict isothermal deposition, though capturing relative thermophoretic effects well. By applying an anisotropic Lagrangian time scale, and cross trajectory effects of the external gravitational force, good agreement was observed, the first inclusion of the effect within the CRW model. A dynamic mesh morphing method was then developed, enabling the effect of large scale particle deposition to be included in simulations, without continual remeshing of the fluid domain. Simulation of an impingement jet array showed deposition of characteristic mounds up to 30% of the hole diameter in height. Simulation of a passage with film-cooling hole off-takes generated hole blockage of up to 40%. These cases confirmed that the use of the CRW generated deposition locations in line with scant available experimental data, but widespread airline fleet experience. Changing rates of deposition were observed with the evolution of the deposits in both cases, highlighting the importance of capturing changing passage geometry through dynamic mesh morphing. The level of deposition observed, was however, greater than expected in a real engine environment and identifies a need to further refine bounce-stick and erosion modelling to complement the improved prediction of impact location identified in this thesis.

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In this diploma thesis is elaborated design of diagnostic system for small jet engines. The aim is to describe the types of possible failures of jet engines, to determine important parameters characterizing the immediate state of engine and define methods for measurement of selected parameters. The first part is devoted to a description of selected types of small turbojet engines, followed by a summary of the most widely used diagnostic methods for assessing the health condition of the engine during operation. The next chapter contains calculation of the engine thermal cycle with characteristics of construction components. Then there is analysis of small jet engine failures with a description of their causes and possibilities of identification by diagnostic system. Thesis continues with a description of measurement methods and selection of the required sensors. Next chapter is focused on the proposed diagnostic system for condition monitoring of the engine. The last part is devoted to an excursion in laboratory for jet engine testing at the Technical University in Košice.

Demands for designing prime reliant, energy-efficient, and high performance thermal barrier coatings (TBCs) in gas turbines have led to a growing interest toward comprehensive microstructural characterization. Over the last decade, Synchrotron X-ray Diffraction (XRD) has established itself as a high-resolution strain measurement method for the thermally grown oxide (TGO) layer of thermal barrier coatings (TBCs). In this work, we present in-situ X-ray strain measurements of the TGO layer on cycled TBC specimens under thermo-mechanical loading using powerful high energy X-rays (~80.7- 86 keV) at Sector I-ID of the Advanced Photon Source at the Argonne National Laboratory. The evolution of TGO stresses was examined over one complete thermal cycle on TBC samples at various stages of the life fraction under various mechanical loads. Synchrotron X-Ray Diffraction under thermo-mechanical loading has shown the existence of strain qualitatively within the diffraction patterns. Quantitative results obtained through Pseudo-Voigt peak fitting over selected peaks show the evolution of strain over a thermal cycle. In initial experiments, it was shown that mechanical loading at 32 MPa resulted in a tensile strain (£22 = 0.00053±0.00039 for 7 minutes) along the [024] atomic plane of a-AbO3 that was brief before going into strain relief in the compressive region but higher in magnitude than the 64 MPa (£22 = 0.00039±0.00024 for 14 minutes). Follow-on experiments indicate the presence of tensile strains within the bond coat region of the TBC system. After initial assessment of the effect of mechanical loading, our findings indicate that the effect of mechanical load during the cycle, often neglected in TBC studies, is of significance to the strain evolution within each cycle. This determination of critical conditions for strain evolution ( e.g. the first cycle) will serve to improve overall accuracy in life prediction of these coatings and contribute to developing methods of improving fatigue behavior.

No description available.

No description available.

This work will be focused on issue of a jet engine. The thesis will be divided into search retrieval part and computational part. In the search retrieval part it will focus on different configurations of jet engines as well as areas of their use. The main part of the thesis will however focus on a calculations where a turbine, compressor and an exhaust nozzle will be designed in order to give a thrust of approximately 1kN. Next step will be determination of an engine charcteristic that will give us a preview on how the engine performance will look like in off-design modes.

A recent development in the design of control system for a jet engine is to use a suitable, fast and accurate model running on board. Development of linear models is particularly important as most engine control designs are based on linear control theory. Engine control performance can be significantly improved by increasing the accuracy of the developed model. Current state-of-the-art is to use piecewise linear models at selected equilibrium conditions for the development of set point controllers, followed by scheduling of resulting controller gains as a function of one or more of the system states. However, arriving at an effective gain scheduler that can accommodate fast transients covering a wide range of operating points can become quite complex and involved, thus resulting in a sacrifice on controller performance for its simplicity. This thesis presents a methodology for developing a control oriented analytical linear model of a jet engine at both equilibrium and off-equilibrium conditions. This scheme requires a nonlinear engine model to run onboard in real time. The off-equilibrium analytical linear model provides improved accuracy and flexibility over the commonly used piecewise linear models developed using numerical perturbations. Linear coefficients are obtained by evaluating, at current conditions, analytical expressions which result from differentiation of simplified nonlinear expressions. Residualization of the fast dynamics states are utilized since the fast dynamics are typically outside of the primary control bandwidth. Analytical expressions based on the physics of the aerothermodynamic processes of a gas turbine engine facilitate a systematic approach to the analysis and synthesis of model based controllers. In addition, the use of analytical expressions reduces the computational effort, enabling linearization in real time at both equilibrium and off-equilibrium conditions for a more accurate capture of system dynamics during aggressive transient maneuvers. The methodology is formulated and applied to a separate flow twin-spool turbofan engine model in the Numerical Propulsion System Simulation (NPSS) platform. The fidelity of linear model is examined by validating against a detailed nonlinear engine model using time domain response, the normalized additive uncertainty and the nu-gap metric. The effects of each simplifying assumptions, which are crucial to the linear model development, on the fidelity of the linear model are analyzed in detail. A case study is performed to investigate the case when the current state (including both slow and fast states) of the system is not readily available from the nonlinear simulation model. Also, a simple model based control is used to illustrate benefits of using the proposed modeling approach.