<p>This report describes the results of the project "Concept development of jet engine inspection plugs" carried out in the spring of 2008. The work was done at the department of product definition at the company Volvo Aero in Trollhättan. The objective of the work was to develop concepts for a "Volvo-unique" inspection plug. The work is part of Volvo Aero's focus on proprietary (self-developed) technologies. Inspection plugs can be found on virtually all aircraft engines and gas turbines. They are used during inspections with fiber optics done at regular intervals during engine operation. Since the inspection plugs are screwed in and out many times during the life of an engine, it is important that the handling (the assembly and disassembly) is simple. It is also very important that the plugs are properly fixed in position to prevent them from coming off during operation. The focus of the work was to develop proposals on how the assembly and fixing of plugs could be designed to simplify the handling and have adequate and simple function. The procedure during the work was to first study relevant theory and methods that could be used. Then development was carried out according to the first steps of the systematic design methods. These steps include product specifications, concept generation, evaluation and selection of concepts, and development of selected concept. During the implementation, a number of tools and methods, including QFD, FMEA and decision matrices were used. Out of 14 developed concepts, two were chosen for comparison with a leading rival. Both developed concepts turned out to outscore the competitor and the main difference was the cost of production. One of the concepts was considered to have advantages over the other and was consequently chosen for further development. Geometry, manufacturing, materials, sealing and misalignment were the focus areas of the development. CAD models were made of the various design ideas that were identified and one principal inspection plug was recommended for further development.</p>

In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation (MTA) method provides an efficient tool for modeling this large order system with localized nonlinearities in the ball bearings. The gas turbine engine, which is composed of the power turbine and gas generator rotors, is modeled with 38 lumped masses. A nonlinear angular contact bearing model is employed, which has ball and race degrees of freedom and uses a modified Hertzian contact force between the races and balls and for the seal rub. This combines a dry contact force and viscous damping force. A flexible housing with seal rub is also included whose modal description is imported from ANSYS. Prediction of the maximum contact load and the corresponding stress on an elliptical contact area between the races and balls is made during the blade loss simulations. A finite-element based squeeze film damper (SFD), which determines the pressure profile of the oil film and calculates damper forces for any type of whirl orbit is utilized in the simulation. The new approach is shown to provide efficient and accurate predictions of whirl amplitudes, maximum contact load and stress in the bearings, transmissibility, thermal growths, maximum and minimum damper pressures and the amount of unbalanced force for incipient oil film cavitation. It requires about 4 times less computational time than the traditional approaches and has an error of less than 5 %.

This report describes the results of the project "Concept development of jet engine inspection plugs" carried out in the spring of 2008. The work was done at the department of product definition at the company Volvo Aero in Trollhättan. The objective of the work was to develop concepts for a "Volvo-unique" inspection plug. The work is part of Volvo Aero's focus on proprietary (self-developed) technologies. Inspection plugs can be found on virtually all aircraft engines and gas turbines. They are used during inspections with fiber optics done at regular intervals during engine operation. Since the inspection plugs are screwed in and out many times during the life of an engine, it is important that the handling (the assembly and disassembly) is simple. It is also very important that the plugs are properly fixed in position to prevent them from coming off during operation. The focus of the work was to develop proposals on how the assembly and fixing of plugs could be designed to simplify the handling and have adequate and simple function. The procedure during the work was to first study relevant theory and methods that could be used. Then development was carried out according to the first steps of the systematic design methods. These steps include product specifications, concept generation, evaluation and selection of concepts, and development of selected concept. During the implementation, a number of tools and methods, including QFD, FMEA and decision matrices were used. Out of 14 developed concepts, two were chosen for comparison with a leading rival. Both developed concepts turned out to outscore the competitor and the main difference was the cost of production. One of the concepts was considered to have advantages over the other and was consequently chosen for further development. Geometry, manufacturing, materials, sealing and misalignment were the focus areas of the development. CAD models were made of the various design ideas that were identified and one principal inspection plug was recommended for further development.

In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation (MTA) method provides an efficient tool for modeling this large order system with localized nonlinearities in the ball bearings. The gas turbine engine, which is composed of the power turbine and gas generator rotors, is modeled with 38 lumped masses. A nonlinear angular contact bearing model is employed, which has ball and race degrees of freedom and uses a modified Hertzian contact force between the races and balls and for the seal rub. This combines a dry contact force and viscous damping force. A flexible housing with seal rub is also included whose modal description is imported from ANSYS. Prediction of the maximum contact load and the corresponding stress on an elliptical contact area between the races and balls is made during the blade loss simulations. A finite-element based squeeze film damper (SFD), which determines the pressure profile of the oil film and calculates damper forces for any type of whirl orbit is utilized in the simulation. The new approach is shown to provide efficient and accurate predictions of whirl amplitudes, maximum contact load and stress in the bearings, transmissibility, thermal growths, maximum and minimum damper pressures and the amount of unbalanced force for incipient oil film cavitation. It requires about 4 times less computational time than the traditional approaches and has an error of less than 5 %.

Over the last decades, it has been progressively acknowledged that reducing the specific fuel consumption and the emission of pollutants as well as improving the thrust-to-weight ratio involves extensive research on advanced sealing technologies. Amongst these, brush seals are particularly well considered for their excellent leakage performance, their low friction properties, and their ability to cope with inevitable rotor excursions during flights. This thesis presents the experimental work that has been carried on in order to characterize carbon brush seals performance in function of the bristle pack geometry and the operating conditions. The analyzed parameters are the bristle free length, the density, and the inter-platedistance. The work, performed by the ULB in collaboration with French engine manufacturer Safran Aircraft Engines, provides first, a description of the test installation that reproduces accurately the severe working conditions encountered in a bearing chamber. A total of eight samples were submitted to extensive testing, and allowed to perform a qualitative analysis of the main performance indicators of a brush seal: the leakage flow, and the seal torque. Complex phenomena acting on the bristle pack were put in evidence under the effect of differential pressure androtation speed, and oil, which fundamentally deteriorate the leakage performance of a brush seal. Subsequently, performance models were developed through empirical correlations, based on the experimental data. They predict the leakage flow and the seal torque as a function of the geometrical parameters and operating conditions. In addition, hysteresis issues were also addressed, and an IR camera helped investigating the heat generation properties of a brush seal.Brush seal samples were submitted to endurance testing, in order to highlight wear mechanisms, and study the performance degradation with the operating time. Oil plays a major part in extending brush seals operating life, despite the leakage performance degradation. Finally, the correlations developed throughout the PhD thesis were used to develop an optimization process in function of the operating conditions of a modern aero-engine. Ultimately, large savings in air consumption were put in evidence when replacing labyrinth seals by brush seals. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

The purpose of this thesis is design of a crank mechanism for diesel aircraft engine. Next then appropriately balance crank mechanism, strength tests and calculation of crankshaft torsional vibration. Developing of drawings documentation of crankshaft.

This thesis is focused to design piston rods for aircraft petrol six-cylinder engine with 102 kW output power and project their form. Other part deals with analysis of balancing of arranging and fort control one of piston rod.

The aim of this work is to propose a cranktrain of a petrol six-cylinder aircraft engine with the specified parameters. Build dynamic model involved an air reducer and carry out the life-stress analysis important key parts of the crankshaft.

This thesis focuses on obtaining better estimates of remaining life for on-condition (OC) parts in aircraft engines. Aircraft engine components are commonly classified into three categories, life-limited parts (LLP), OC-parts and consumables. Engine maintenance typi-cally accounts for 10% to 20% of aircraft-related operating cost. Current methods to esti-mate remaining life for OC parts have been found insufficient and this thesis aims to devel-op a method that obtains better life estimates of OC part. Improved life estimates are es-sential to facilitate more reliable maintenance plans and lower maintenance costs. In the thesis, OC parts that need a better life estimates are identified and suitable prognosis methodologies for estimating the remaining life are presented. Three papers are appended to the thesis. The first paper lays out the main principles of air-craft engine maintenance and identifies the potential for improving maintenance planning by improving the remaining life estimation for the OC parts. The paper concludes that re-search is needed to find better estimates so that the right amount of maintenance is per-formed at each maintenance occasion. The second paper describes the aircraft and its engine from a system of system perspective. The aim of the paper is to show that no system is stronger than its weakest part and that there is a potential to increase the availability and readiness of the complete system, the aircraft engine, by introducing better life estimates for OC parts. Furthermore, a review of all engine parts, no matter if they are life-limited or on-condition, which needs to be incor-porated in a replacement model for maintenance optimization, is given. The paper con-cludes that the reliability of the complete aircraft engine would be increased if better life estimates are presented also for the OC parts. The third paper includes an evolved analysis of the subject and the analysis moves deeper in to a subsystem/module of the engine, the low pressure turbine. The specific subsys-tem/module is further analyzed to show the potential of increased reliability for the subsys-tem/module and the complete system, the aircraft engine, if better life estimates for the OC parts are obtained. Methods on how to estimate remaining life is discussed in this paper. It is stated that life estimates can be based on visual inspections, available testing methods (e.g. non destructive testing ) or new techniques that may be need to be developed based on remaining useful life estimations. To estimate the remaining life for the OC parts well es-tablished prognostic techniques such as physic-based, data-driven, symbolic, hybrid, or context awareness approaches that combine contextual/situation information awareness will be considered.

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