Foil bearings are widely used for oil-free micro turbomachinery. One of the critical technical issues related to reliability of the foil bearings is a coating wear on the top foil and rotor during start/stops. Bearing cooling is also mandatory for certain applications because the foil bearings can generate significant amount of heat depending on operating conditions. Usually axial flow is used through the space between the top foil and bearing sleeve. In this thesis, a hybrid air foil bearing with external pressurization is introduced. The hybrid operation eliminates the coating wear during start-up/shut down, and also reduces drag torque during starts. Furthermore, this hybrid foil bearing does not need cooling system. An experimental test with a loaded bearing under hydrostatic mode demonstrates the high potential of hybrid air foil bearings. The load capacity of the hybrid foil bearing was measured at 20,000 rpm, and compared with that of hydrodynamic foil bearing. The hybrid foil bearing has much higher load capacity than the hydrodynamic foil bearing. The starting torque was also measured and compared with hydrodynamic bearing. A simple analytical model to calculate top foil deflection under hydrostatic pressurization has been developed. Predictions via orbit simulations indicate the hybrid air foil bearings can have a much higher critical speed and onset speed of instability than the hydrodynamic counter part. Major benefits of the hybrid foil bearings also include very low starting torque, reduced wear of the top foil and rotor, and very effective cooling capability by the pressurized air itself. This new concept of hybrid air foil bearings are expected to be widely applied to the oil free turbomachinery industry, especially for heavily loaded and/or high temperature applications.

This thesis work is the study of the effect of an aluminium foil on the losses that produced by a radiator, situated under a window, through the wall behind it. The reason behind this topic is due to the energy problem and the different goals that governments have set up to try to reduce the use of energy. For example, more specifically a Swedish national goal is to decrease the energy use of the built stock with 50% by 2050.   For this purpose, an experimental set-up was built in the University of Gävle, Sweden. The arrangement was composed by a radiator and a window facing a climate chamber. A total of twenty-one temperatures and two heat fluxes in the exterior wall were measured in the set-up. Ten different measurement scenarios with different radiator temperature, 40°C, 50°C and 60°C; two different distance between the radiator and the wall, 5 and 9 centimetres and with and without the aluminium foil, were performed.   With the experimental results, a CFD model was validated. Two different models were done, first a 2D model and afterwards a 3D model. For the turbulence, the chosen model was standard k-ε model. There were 54 cases simulated with the 2D model and the 3D model was used just for validation. The cases had different variables such as radiator temperature, outdoor temperature and wall insulation. With these cases, analysis of the effectiveness of the presence of an aluminium foil behind the radiator is performed to evaluate if there is a significant reduction of the losses.   The results showed with both methods that the aluminium foil reduces the losses of the wall behind the radiator. The savings varied depending on the boundary conditions of the case and it were obtained a maximum of 4% and a minimum of 1,3%.

Air foil bearings offer several advantages over oil-lubricated bearings in high speed micro-turbomachinery. With no contact between the rotor and bearings, the air foil bearings have higher service life and consequently lesser standstills between operations. However, the foil bearings have reliability issues that come from dry rubbing during start-up/shutdown and limited heat dissipation capability. Regardless of lubricating media, the hydrodynamic pressure generated provides only load support but no dissipation of parasitic energy generated by viscous drag and the heat conducted from other parts of the machine through the rotor. The present study is a continuation of the work on hybrid air foil bearings (HAFB) developed by Kim and Park, where they present a new concept of air foil bearing combining hydrodynamic air foil bearing with hydrostatic lift. Their experimental studies show that HAFB has superior performance compared to its hydrodynamic counterpart in load capacity and cooling performance. In this article, the bearing stiffness and damping coefficients of HAFB are calculated using a linear perturbation method developed for HAFB. The study focuses on circular HAFB with a single continuous top foil supported by bump foil. The research also includes a parametric study which outlines the dependence of the stiffness and damping coefficients on various design parameters like supply pressure ( P s ), feed parameter ( Г s ), excitation frequency (v), and bearing number (Λ). Furthermore the present research also includes experimental investigation of HAFB with bump foil as compliant structure. In the first phase of the experimental research a high speed test facility was designed and fabricated. The facility has the capability of running up to 90,000 RPM and has an electric motor drive. This article gives detailed description of this test rig and also includes data acquired during the commissioning phase of the test rig. The test rig was then used to measure the load capacity of HAFB.

Foil bearings are widely used for oil-free micro turbomachinery. One of the critical technical issues related to reliability of the foil bearings is a coating wear on the top foil and rotor during start/stops. Bearing cooling is also mandatory for certain applications because the foil bearings can generate significant amount of heat depending on operating conditions. Usually axial flow is used through the space between the top foil and bearing sleeve. In this thesis, a hybrid air foil bearing with external pressurization is introduced. The hybrid operation eliminates the coating wear during start-up/shut down, and also reduces drag torque during starts. Furthermore, this hybrid foil bearing does not need cooling system. An experimental test with a loaded bearing under hydrostatic mode demonstrates the high potential of hybrid air foil bearings. The load capacity of the hybrid foil bearing was measured at 20,000 rpm, and compared with that of hydrodynamic foil bearing. The hybrid foil bearing has much higher load capacity than the hydrodynamic foil bearing. The starting torque was also measured and compared with hydrodynamic bearing. A simple analytical model to calculate top foil deflection under hydrostatic pressurization has been developed. Predictions via orbit simulations indicate the hybrid air foil bearings can have a much higher critical speed and onset speed of instability than the hydrodynamic counter part. Major benefits of the hybrid foil bearings also include very low starting torque, reduced wear of the top foil and rotor, and very effective cooling capability by the pressurized air itself. This new concept of hybrid air foil bearings are expected to be widely applied to the oil free turbomachinery industry, especially for heavily loaded and/or high temperature applications.

A new foil bearing with compression springs is designed, built, analyzed, and tested. This foil gas bearing uses a series of compression springs as a compliant structure instead of corrugated bump foils. A spring model to estimate the stiffness of compression springs was developed and showed a good level of agreement with the experimental results. The spring dynamics model was combined with a non-linear orbit simulation to investigate the non-linear behavior of foil gas bearings. The approach could also predict the structural loss factor given the geometry of the underlying springs. A series of rotor-bearing orbit simulations using the compression spring with stiffness of the free-free case, predicted the critical speed and the onset speed of instability at around 7500 rpm and 14,500 rpm with a WFR ~ 0.5. The low critical speed was due to the relatively soft support. The hydrodynamic rotor instability was predicted under the equivalent viscous damping extracted from the spring dynamics, implying the viscous damping alone within the spring cannot suppress hydrodynamic instability of the foil gas bearings. The load capacity of the compression spring foil gas bearing was measured at 20,000 rpm with and without air cooling, to demonstrate the feasibility of the new foil bearing. The constructed bearing with rather soft springs showed a small load capacity of 96N at 20,000 rpm under no cooling. The developed cooling method using direct air supply holes machined on the bearing sleeve, proved to be very effective in cooling the test bearing. The measured level of structural stiffness and damping evidenced the existence of a necessary level of damping for stable bearing operation. The structural stiffness was highly nonlinear and showed different behavior for static loading and the sinusoidal dynamic loading. The measured equivalent viscous damping coefficients increased with the applied load amplitude. A series of parametric design studies were performed to investigate the effects of various design parameters on the bearing stiffness and overall rotordynamic performance. Rotor-bearing orbit simulations showed there is a range of spring stiffness for high onset speeds of instability. Increasing the pitch of the spring while maintaining the same stiffness increased the structural loss factor slightly, manifesting a smaller number of coils is better in terms of damping. The onset speed of instability increases slightly with the rotor mass due to increased static eccentricity and presumably smaller cross-coupled stiffness. However, increasing the rotor mass in order to render a high eccentricity was not effective in increasing the onset speed of instability because of reduced natural frequency and increased inertia. Instead, orbit simulations confirmed that small rotor mass with external loading is the most effective way to increase the bearing stability.

This dissertation is concerned with the physical processes which determine friction and lubrication in metal rolling in the mixed lubrication regime, with particular attention paid to the conditions encountered when rolling aluminium foil. Two areas of relevance to the analysis of the rolling process are initially investigated. Firstly, the rheological properties of a typical aluminium foil rolling oil at high pressures and shear rates have been measured using a disc machine. The behaviour of the oil was found to be well described by the Eyring viscous model, at the shear rates and pressure likely to be found in metal rolling. Secondly, the deformation of asperities when the bulk material is deforming has been examined. The theory developed here was found to agree reasonably with experiments. The results of these investigations are used in the analysis of lubrication in metal rolling, considering the hydrodynamic buildup of oil pressure in the entry region and the crushing of the asperities both in the entry region and at the beginning of the work zone. The contact between roll and strip is divided into two regions, that under the asperities and that in the intervening valleys. Calculations for conditions appropriate to strip and foil rolling give the proportion of the two types of contact and the film thicknesses in each region. Measurements of film thicknesses with an experimental mill in a regime where roughness is unimportant were not found to agree well with an existing simple theory of lubrication. This was ascribed to uneven lubrication in the experiments. After taking this into account, the experiments in a regime where roughness was important were found to agree reasonably with the theory developed here. The effect of roughness on traction is measured in a disc machine with elastic contacts. Its behaviour is found to be determined by the bulk properties of the lubricant at the pressures and strain rates under the asperities. Theory and experiments presented in this dissertation lead to a greater understanding of the physical processes determining friction in metal rolling in the mixed lubrication regime. Film thicknesses and friction coefficients in metal rolling may now be estimated with more confidence.

Abstract Electrodeposited Copper Foil (ED Foil) is the most essential conductive material to PCB. With the recession of electronic industry and the appearance of Internet Economy Bubble for printed circuit board (PCB) industry, PCB industry slowed down its productivity around 2000 and the ED Foil industry in Taiwan had to face the vicious circle as the supply exceeds the demand. As for America, because of the declination of the industry, it is now almost out of the ED Foil industry which means that the global chief city of the field has changed from the States to Japan. However, with the high production costs and labor expenses, Japan is now suspending the enlargement of productivity, Therefore, the productivity of Taiwan till 2005 already ranked the top one in the world. Unfortunately, we are now facing the biggest competitor, China, who has tried enthusiastically to attract our ED Foil and PCB companies to move to his land, especially it has aimed the ED Foil industry as his top target to enkindle. This research has consulted several diverse documents from inside and outside Taiwan through the analyses of industrial structures, ¡§Diamond System¡¨ and ¡§SWOT Analysis¡¨ to have a clear understanding towards the construction of Taiwan¡¦s ED Foil industry and its ¡§competitive advantages¡¨. Owning these accomplished advantages as the base, we can come out the cooperative strategies for ED Foil industry¡¦s future and its ¡§Anti Competition Policy¡¨ according to the ¡§scenarios¡¨. We deeply hope that with these devices, we can strengthen the industrial¡¦s efficiency in our ED Foil¡¦s industry and at the same time, our status in this field can remain competitive around the world. The research found out that in ED Foil industry¡¦s area, the early players monopolized the market and twisted the market¡¦s efficiency at the same time. Therefore, those early players got the chance to earn a huge sum of money and as a result, some potential competitors joined the market to share the benefits. Besides, because of the rising concept of globalization among the mega electronic companies, more and more module and component companies are willing to be localized to correspond to the change. Simultaneously, the demand of both PCB and ED Foil has started to increase in Asia; therefore, the ED Foil industry in Taiwan is getting more and more prosperous because of the favorable geographical position. Moreover, high performing and large-sized facilities are adapted to produce high quality and low cost merchandizes efficiently to enhance the competitiveness in the industry. Therefore, the chain that connected with the downstream industry has become more completed and moreover, the bunching effect can be elaborate thoroughly. According to the research, we have discovered that there are many uncertainties within the operation of Taiwan¡¦s ED Foil industry such as the slight increase of the demand in Taiwan and the exports are overly centered on Hong Kong and China. Other concern like the percentage of the fixed prime cost is excessively high matters the efficiency of the productivity and as a result, a price war comes out easily because of the supply exceeds the demand. In the meantime, we have come out with the conclusion that the government should actively help the integration of the industry¡¦s future development. And we suggest that the ED Foil industry in Taiwan should take the co-opetition policy as follows: 1. The buying-associations that share the supplementary values of the recycling copper wires and R&D-associations can share the R&D cost in the area of the newly applying development will be erected to largely reduce the prime costs. Furthermore, an information exchange center will be provided for those associations to utilize others¡¦ useful experiences. 2. The business cooperative operations either with the same upstream or downstream companies all necessarily needed to be constructed. Those united cooperation such as Mergers & Acquisitions should be promoted within industries, including investments. These strategies will accelerate the development of the business. 3. New and prosperous markets such as Thailand and Vietnam need to be explored to disperse our export markets to decrease our dependency on China. 4. Complementary relationship and proper division of labors should be built up within cross-Strait without making other vicious competitions.

<p>Pitch and heave are limiting motions when driving at high speed on water. The installation ofa T-foil is an effective solution that reduces these motions. Commercial T-foils are available,but today none of them are non-magnetic. This thesis studies the possibility to design anon-magnetic T-foil that can carry the considerable loads that such a constructionexperiences. The T-foil is designed for vessels such as the Visby Class corvette.</p><p>Vortex lattice theory is used to calculate the pressure distribution acting on the construction atdifferent load cases. Required laminate thickness is determined by iteration using a linearfinite element model of the fin.</p><p>The conclusion is that it is possible to manufacture a non-magnetic T-foil of the required size.A critical area in the construction is the T-joint between the vertical strut and the horizontalfoil. Future investigations should include laboratory tests of the T-joint as well as moredetailed hydrodynamic analysis for more accurate input parameters of the T-foil.</p>

As disc-shaped detectors are one of the primary means of measuring the neutron density, a better solution is desirable if the error due to the depression factor is to be made negligible. In this paper, an attempt is made to solve this problem in the oblate spheroidal co-ordinate system which most nearly describes the disc-shaped detector, so that solutions may be obtained that describe depression factors for detectors of varying thicknesses and radii.

Comprehensive modeling of gas foil bearings (GFBs) anchored to reliable test data will enable the widespread usage of GFBs into novel turbomachinery applications, such as light weight business aircraft engines, hybrid fuel cell-turbine power systems, and micro-engines recharging battery packs for clean hybrid electric vehicles. Pressurized air is often needed to cool GFBs and to carry away heat conducted from a hot turbine in oil-free micro turbomachinery. Side end pressurization, however, demonstrates a profound effect on the rotordynamic performance of GFBs. This dissertation presents the first study that devotes considerable attention to the effect of side end pressurization on delaying the onset rotor speed of subsynchronous motions. GFB performance depends largely on the support elastic structure, i.e. a smooth foil on top of bump strips. The top foil on bump strips layers is modeled as a two dimensional (2D), finite element (FE) shell supported on axially distributed linear springs. The structural model is coupled to a unique model of the gas film governed by modified Reynolds equation with the evolution of gas flow circumferential velocity, a function of the side end pressure. Predicted direct stiffness and damping increase as the pressure raises, while the difference in cross-coupled stiffnesses, directly related to rotor-bearing system stability, decreases. Prediction also shows that side end pressurization delays the threshold speed of instability. Dynamic response measurements are conducted on a rigid rotor supported on GFBs. Rotor speed-up tests first demonstrate the beneficial effect of side end pressurization on delaying the onset speed of rotor subsynchronous motions. The test data are in agreement with predictions of threshold speed of instability and whirl frequency ratio, thus validating the model of GFBs with side end pressurization. Rotor speed coastdown tests at a low pressure of 0.35 bar evidence nearly uniform normalized rotor motion amplitudes and phase angles with small and moderately large imbalance masses, thus implying a linear rotor response behavior. A finite element rotordynamic model integrates the linearized GFB force coefficients to predict the synchronous responses of the test rotor. A comparison of predictions to test data demonstrates an excellent agreement and successfully validates the rotordynamic model.