A bibliography /with abstracts/ on gas-lubricated bearings Interim report

Gas lubricated bearings - annotated bibliograph

Effect of manufacturing method of a centrifugal fan hub on its heat dissipation characteristics.

As the process temperature of a fan system increases, the amount of heat that gets transmitted to the bearings and/or motor increases. If this is not accounted for, it can lead to catastrophic failure. The main heat conduction path is through the shaft, and certain mechanisms must be considered when looking for new solutions. These include; how heat is transmitted through the shaft or increasing the thermal resistance of the shaft, and dissipating heat as it is conducted through the shaft. These aspects must always be considered in addition to the impact of the manufacturing complexity. In the present study, an existing heat dissipation arrangement is reviewed and replaced by a new design which reduces the time taken to machine the part, and ultimately the overall cost of the product. Computation Fluid Dynamics (CFD) based techniques have been used to numerically simulate the designs under operating conditions, and the resulting heat transfer through the shaft compared with respect to the heat dissipation properties. The results demonstrate that although the new design is less effective at dissipating heat, it provides a substantial cost reduction compared to the existing design, while substantially reducing the impact of the design on various aspects of production

Aeronautical Engineering: A special bibliography, supplement 60

This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975

Effect of Manufacturing Method of a Centrifugal Fan Hub on its Heat Dissipation Characteristics

As the process temperature of a fan system increases, the amount of heat that gets transmitted to the bearings and/or motor increases. If this is not accounted for, it can lead to catastrophic failure. The main heat conduction path is through the shaft, and certain mechanisms must be considered when looking for new solutions. These include; how heat is transmitted through the shaft or increasing the thermal resistance of the shaft, and dissipating heat as it is conducted through the shaft. These aspects must always be considered in addition to the impact of the manufacturing complexity. In the present study, an existing heat dissipation arrangement is reviewed and replaced by a new design which reduces the time taken to machine the part, and ultimately the overall cost of the product. Computation Fluid Dynamics (CFD) based techniques have been used to numerically simulate the designs under operating conditions, and the resulting heat transfer through the shaft compared with respect to the heat dissipation properties. The results demonstrate that although the new design is less effective at dissipating heat, it provides a substantial cost reduction compared to the existing design, while substantially reducing the impact of the design on various aspects of production

A case study of the design related aspects of the introduction of a new turbocharger

The design related aspects of the introduction of a new turbocharger - the Napier NA355. Napier Turbochargers Ltd. manufacture a range of turbochargers suitable for most medium and slow speed diesel engines above about 1000 hp. This work describes the many and varied aspects associated with the design of a new turbocharger during the early 1980's. The company was producing two similarly sized products designated the SA105 and the NA350, intended for engines developing about 3000 hp. A replacement for these two turbochargers was required. The demands of the engines in the marketplace were determined together with the extractable performance of the major competitor's products. The performance levels of the two Napier models was examined, and was found wanting, particularly with respect to the compressor efficiency. Also the mechanical limitations of the two models were less than desirable. A number of technical proposals were considered, with the aim of deciding how best the needed improvements could be introduced. The SA 105 offered more items that could be utilised in a new turbocharger, although both compressor and turbine required improvement. It was necessary to avoid lengthy and expensive development wherever possible, therefore only proven technology was employed. The major casings and rotor forgings were to be retained, if possible, due to the lcngthy, expensive, and often troublesome procurement cycles. Only those components that had a lack of performance or had a mechanical limitation would definitely be replaced. A new backswept compressor and an improved turbine stage were designed. A new rotor assembly incorporating the new impeller, together with many detail improvements, was also designed. The work describes the analytical techniques that were used to carry out these designs. The turbocharger was rig tested, as an open cycle gas turbine, to simulate service duty and environment. The first turbocharger was built and tested with encouraging results. A satisfactory number of turbochargers have been manufactured and are now in service. Although some problems occurred that necessitated modifications the basic concept was clearly satisfactory. The NA355 can be considered as a particularly successful turbocharger

Parasitic drag analysis of a high inertia flywheel rotating in an enclosure

There are currently millions of people throughout the world who live in isolated, rural communities without electricity. An ongoing effort has been initiated to provide reliable power to such communities. These efforts are being made to utilize renewable energy sources such as wind and solar power to solve this problem. Renewable energy sources can be both intermittent and unpredictable. Thus, an effective energy storage system is sought to store excess energy when available to disperse during times of scarcity.;The use of a high-inertia flywheel was proposed as a means of energy storage due to its simplicity, low cost, and reliability. A previously proposed design integrated a flywheel with a windmill and grid system to effectively distribute consistent power for a village of approximately 200 residents. The flywheel was designed to store enough energy for the residents for up to two days without input. The proposed design consists of a cylindrical flywheel with a diameter of 5.9 meters, a thickness of almost 0.9 meters, and a mass of 152 tons. A rotating disk with these proportions creates a large amount of parasitic drag at its maximum angular velocity. The amount of drag created causes major losses to the overall power output of the wind energy storage system.;Parasitic drag is predominantly caused by the skin friction an object moving through a viscous fluid experiences. This skin friction is strongly influenced by the viscosity of the surrounding fluid. Viscosity is a function of pressure and temperature and can be greatly reduced as the atmospheric pressure surrounding the concerned object is lowered. A drag analysis was completed to assess the benefits of reducing the air pressure within the chamber created between the flywheel and its enclosing walls. It was found that placing the flywheel within a housing alone reduces the frictional losses by approximately 15 percent; this reduction is governed by proper spacing based on boundary layer interactions. As the chamber pressure is reduced, the friction moment of the flywheel can be diminished even further. It was found that at one-twentieth of an atmosphere, the parasitic drag was reduced by an additional 80 percent. Several design methods are considered in order to reduce the pressure around the flywheel to a target of 1/20 of an atmosphere. With the help of a reduced pressure chamber tightly fit around the flywheel, the overall viscous torque of the flywheel can be reduced by over ninety percent when compared to the same flywheel operating in free space at atmospheric conditions. Using CFD methods (FLUENT) as a simulated design tool, the optimum gap spacing for the housing was analyzed; a variety of casing geometries were considered in an attempt to determine optimal clearance. A central low pressure drag reduction system can be created by enclosing the rotating flywheel, leaving an optimal spacing of 0.0826 meters in the axial direction and 0.0826 meters in the radial direction (optimization based on comparison between specific geometries modeled using FLUENT) using a vacuum pump to evacuate the region between the spinning flywheel and stationary housing down to a target of 1/20 of an atmosphere

Study of process intensification for post-combustion carbon capture based on chemical absorption through modelling and simulation

There have been a lot of questions on impact of greenhouse gas on changes in climate conditions regarding expected future dangers if mitigation measures are not put in place. Carbon dioxide emission from power sector is a major contributor of greenhouse gases. As a result, the sector is key target for deploying carbon abatement technologies such as carbon capture. Post-combustion capture (PCC) based on chemical absorption technology is one of the major capture approaches and the most matured of them. However, it is beset by some challenges such as high capital and operating costs due to required large sizes of packed columns and high solvent re-circulating rate. Through process intensification (PI) technology, the columns could be downsized by an order of magnitude without compromising their processing capacity. However, there have been limited studies on the techno-economics of PI-based technologies.In this study, steady state models for standalone intensified absorber and stripper based on rotating packed bed (RPB) technology were developed and validated with experimental data from Newcastle University UK and Tsing Hua University Taiwan respectively. The models were developed in Aspen Plus® and dynamically linked with visual Fortran subroutines. Therefore, this is same as newly developed RPB models (i.e. absorber and stripper). To obtain more insights into the design and operation of standalone intensified absorber, standalone intensified stripper and close loop intensified PCC process, process analysis was carried out. Process analysis in standalone intensified absorber indicates that: (a) CO₂ capture level increases with increase in rotating speed. (b) Higher lean MEA inlet temperature leads to higher CO₂ capture level. (c) Increase in lean MEA concentration results in increase in CO₂ capture level. (d) Temperature bulge is not present in intensified absorber. (e) With fixed RPB equipment size and fixed Lean MEA flow rate, CO₂ capture level decreases with increase in flue gas flow rate. (f) At higher flue gas temperature (from 30°C to 80°C), the CO₂ capture level of the intensified absorber can be maintained. For standalone intensified stripper, the impact of rotor speed on the regeneration efficiency and energy were studied, the impact of reboiler temperature on the rate of CO₂ stripping was established and the impact of rich-MEA flow rate on regeneration energy and efficiency was determined.From comparative assessment of conventional packed bed and RPB, it was found that a volume reduction factor of 12 and 10 times is possible for the absorber and stripper respectively.The two validated models, together with model for heat exchanger were then linked together to form a closed loop intensified PCC process. Steady state model of the closed loop intensified PCC process was then used to perform process analysis on (i) the impact of liquid to gas (L/G) ratio on regeneration energy and CO₂ capture level, (ii) the impact of lean-MEA loading on regeneration energy and capture level (iii) capital and operating cost estimation for intensified PCC process were done, which shows a reduction in an investment cost compared to conventional PCC process.The findings in this study showed that capital and operating costs can be reduced owing to its smaller size compared to conventional PCC process. Also cooling cost for flue gas and inter-cooling in the absorber can be saved since the RPB absorber can be operated at slightly elevated temperature of up to 80°C without compromising the absorber performance and also since higher lean-MEA temperature and/or higher flue gas temperature shows little or no effect on the performance of the RPB. The newly proposed intensified PCC process PFD in the recommendation section of this thesis if successfully implemented can reduce operating and capital costs of PCC process. Finally, these insights can be useful for the design and operation of intensified PCC process

DEVELOPMENT OF A NOVEL HIGH TEMPERATURE FAN HUB DESIGN

As the process temperature of a fan system increases, the amount of heat that gets transmitted to the bearings and/or motor increases. If this is not accounted for, it can lead to catastrophic failure. The main heat conduction path is through the shaft, and certain mechanisms must be considered when looking for new solutions. These include; how heat is transmitted through the shaft or increasing the thermal resistance of the shaft, and dissipating heat as it is conducted through the shaft. These aspects must always be considered in addition to the impact of the manufacturing complexity. In the present study, an existing heat dissipation arrangement is reviewed and replaced by a new hub which reduces the time taken to machine the part, and ultimately the overall cost of the product. Techniques are employed to determine in detail the manufacturability of the existing design and determining what should be done to reduce the overall cost to manufacture. Finite Element Analysis (FEA) based techniques have been adopted to simulate the stresses the model experiences under the operating loads. Computation Fluid Dynamics (CFD) based techniques have been used to numerically simulate the designs under operating conditions, and the resulting heat transfer through the shaft compared with respect to the heat dissipation properties are analysed. Currently, a special hub is utilised for high temperature applications such as within industrial ovens and furnaces in order to dissipate heat. The hub connects the impeller to the motor shaft, the impeller would be subjected to the high temperatures whilst the motor would remain below 70°C. According to Fourier’s law heat transfer will take place through the shaft. The material the shaft is manufactured from and its geometric properties both affect the shafts overall temperature. Should the temperature become too high at the point along the shaft where the motor bearings sit, permeant damage will occur and result in bearing failure. The current hub utilised is designed to reduce the heat within the shaft through the use of fins. The is current hub design is quite labour intensive to produce leading to potentially unnecessary costs. Subsequently a new hub has been created that can be easily machined, thus reducing the overall manufacturing time leading to cost savings. The results demonstrate that although the new hub is less effective at dissipating heat, it provides a substantial cost reduction compared to the existing design, while substantially reducing the impact of the design on various aspects of production

Detection, Diagnosis and Prognosis: Contribution to the energy challenge: Proceedings of the Meeting of the Mechanical Failures Prevention Group

The contribution of failure detection, diagnosis and prognosis to the energy challenge is discussed. Areas of special emphasis included energy management, techniques for failure detection in energy related systems, improved prognostic techniques for energy related systems and opportunities for detection, diagnosis and prognosis in the energy field