Computational Modeling of Transient Processes During Run-In for Tribological Systems

Understanding the frictional behavior of machine elements in mutual rolling or sliding contact is important for many engineering applications. When frictional sliding is initiated, the tribological system passes through several stages with each stage possessing its own unique frictional property. The initial transition process preceding stationary sliding is usually called “run-in”. During the run-in time interval, surface topographies of frictional contacts as well as lubricant distribution and surface tribofilms reorganize and adjust through asperity deformation and wear processes before reaching the steady state. This surface stability formed during run-in leads to an improvement in frictional performance during steady state operation, which increases equipment life and efficiency. Thus, understanding of the frictional transient process and optimizing the time schedule required for the run-in of equipment such as for aircraft engines and naval vessel gas turbines can lead to improved solutions for more desirable operating conditions for the lifetime of the equipment. This thesis investigates the running-in of both lubricated and unlubricated frictional contact in order to gain insight into how friction changes during this time interval. For lubricated friction, it is shown that the surface topography and lubricating fluid goes through a self-organization process during run-in caused by frictional mechanisms that change the surface topography and removes fluid from the area of contact until friction and wear at the interface reaches its equilibrium value. For unlubricated friction, three common tribo-mechanical systems undergoing dry sliding during run-in are investigated: the pin-on-disk, a journal bearing, and a piston-cylinder system. Using computer simulation, a transient frictional response curve is presented for various frictional conditions in order to gain insight into how the frictional value changes during run-in. It is shown that adjustment of the static coefficient of friction can dramatically affect the response behavior with higher coefficient of friction values resulting in higher frictional forces and longer times to reach equilibrium, while smaller values shorten time to equilibrium and reduce frictional forces. These discoveries suggest seeking ways to optimize the materials in order to optimize the transient friction during run-in which are summarized in the conclusion

DESIGN AND ANALYSIS OF THERMO HYDRO DYNAMIC PLAIN JOURNAL BEARING BY USING FSI TOOL

Journal bearings have the longest history of scientific study of any class of fluid film bearings. In a fluid film bearing, the pressure in the oil film satisfies the Reynolds equation which intern is a function of film thickness. Structural distortion of the housing and the development of thermo hydrodynamic pressure in a full journal bearing are strongly coupled thus require a combined solution.Oil film pressure is one of the key operating parameters describing the operating conditions in thermo hydrodynamic journal bearings. Thermo hydrodynamic journal bearings are analyzed by using Computational fluid dynamics (CFD) and fluid structure interaction (FSI) approach in order to find deformation of the bearing.In this thesis journal bearings for different L/D ratios and eccentricity ratios are modeled in 3D modeling software Pro/Engineer. The L/D ratios considered are 0.5, 1.0, 1.5 and eccentricity ratios considered are 0.3, 0.5, 0.7 and 0.9. Journal bearing models are developed for speed of 2000 rpm to study the interaction between the fluid and elastic behavior of the bearing. The speed is the input for CFD analysis and the pressure obtained from the CFD analysis is taken as input for structural analysis.Computational fluid dynamics (CFD) and fluid structure interaction (FSI) is done in Ansys

DESIGN AND ANALYSIS OF THERMO HYDRO DYNAMIC PLAIN JOURNAL BEARING BY USING FSI TOOL

Journal bearings have the longest history of scientific study of any class of fluid film bearings. In a fluid film bearing, the pressure in the oil film satisfies the Reynolds equation which intern is a function of film thickness. Structural distortion of the housing and the development of thermo hydrodynamic pressure in a full journal bearing are strongly coupled thus require a combined solution.Oil film pressure is one of the key operating parameters describing the operating conditions in thermo hydrodynamic journal bearings. Thermo hydrodynamic journal bearings are analyzed by using Computational fluid dynamics (CFD) and fluid structure interaction (FSI) approach in order to find deformation of the bearing.In this thesis journal bearings for different L/D ratios and eccentricity ratios are modeled in 3D modeling software Pro/Engineer. The L/D ratios considered are 0.5, 1.0, 1.5 and eccentricity ratios considered are 0.3, 0.5, 0.7 and 0.9. Journal bearing models are developed for speed of 2000 rpm to study the interaction between the fluid and elastic behavior of the bearing. The speed is the input for CFD analysis and the pressure obtained from the CFD analysis is taken as input for structural analysis.Computational fluid dynamics (CFD) and fluid structure interaction (FSI) is done in Ansys

Developments for the calculation of heavily loaded journal bearings

This thesis describes the development of an ElastoHydroDynamic (EHD) bearing calculation. The effect of body forces is shown to be important for highly loaded bearings in reciprocating internal combustion engines. Extension of the program to rotating machinery includes an examination of instability in the shaft bearings of a turbocharger. The development of a parameter to predict cavitation damage in a bearing is promising. Several calculation results using the program are shown. These are engine main bearing and connecting rod big-end bearings and full floating bearings for a turbocharger. The calculations on the big-end bearing if a racing engine show why the designers were having difficulty understanding the correct location for the oil feed hole position. Effects of elastic deformation, thermal deformation and manufacturing/assembly deformation all have a significant effect on the extent of the oil film. A novel calculation for a cavitation damage parameter is demonstrated successfully for a heavily loaded diesel engine bearing. The importance of body forces on the oil film due to high accelerations on certain bearings is shown to be theoretically important but not yet demonstrated. The program was written with the intention to be incorporated into the sponsoring company’s range of engine design software. A part of that development process included carrying out calculations to demonstrate to customers and present papers at conferences. The results of some of these calculations have been included in this thesis. Results of a study on the effect of crankshaft geometry on racing engine viscous friction losses were reported in a paper presented at the IDETC conference in Long Beach, 2005. This study used the first version of the software which only included Rigid Hydro Dynamics (RHD) at the time but was usable. Results of a study on stability of shaft motion in high speed turbocharger bearings were reported in a paper at the 8th International Turbocharger conference in London, 2006. At this time the program was still only capable of RHD calculations but could now solve for multiple oil films simultaneously and sweep through the speed range. The studies on the effects of body forces and the development of a cavitation parameter will be presented in papers in the near future

Contra-rotating marine current turbines : single point tethered floating system - stabilty and performance

The Energy Systems Research Unit within the Department of Mechanical Engineering at the University of Strathclyde has developed a novel contra-rotating tidal turbine (CoRMaT). A series of tank and sea tests have led to the development and deployment of a small stand-alone next generation tidal turbine. Novel aspects of this turbine include its single point compliant mooring system, direct drive open to sea permanent magnet generator, and two contra-rotating sets of rotor blades. The sea testing of the turbine off the west coast of Scotland in the Sound of Islay is described; the resulting stability of a single-point tethered device and power quality from the direct drive generator is reported and evaluated. It is noted that reasonably good moored turbine stability within a real tidal stream can be achieved with careful design; however even quite small instabilities have an effect on the output electrical power quality. Finally, the power take-off and delivery options for a 250kW production prototype are described and assessed

Making the Most of the Energy We Have: Vehicle Efficiency

With global concerns over emissions from non-renewable sources and its dwindling global supplies. Optimization of our energy usage is highly important. Converting energy to various forms is usually an imperfect process with energy being wasted. Vehicle’s convert on-board stored energy to a kinetic form to drive a vehicle. Understanding the sources of energy losses allow us to (a) reduce emissions created by combustion engines, and (b) improve driving range of electrified powertrains. Within this chapter energy losses across the vehicle will be explored for both non-powertrain and powertrain components. Modes of losses and test methods for vehicle components will also be outlined to highlight their significance in vehicle efficiency

Tribology and Industry: From the Origins to 4.0

There is an increasing diffusion of the industry 4. 0 concept today. The fourth industrial revolution, following three other previous industrial revolutions, is considered related to the introduction of modern information and communication technologies in production. Tribological concepts are much older than industry. Tribology has always been connected to industrial problems from the birth of industry. It was strongly connected with the previous industrial revolutions and it is surely related to industry 4.0. In this work, the main aspects of the four industrial revolutions and the main evolutions of tribology are firstly reviewed from a historical point of view. The relationships between tribology and industry are described with particular attention to the aspects that relate the modern tribology 4.0 to industry 4.0. Tribology can have in particular a big impact on the industrial needs to reduce losses and wastes, for instance with the development of new tribological components and materials also in connection with electronic smart systems and taking advantage of the information and communication technologies

Development of a novel magnetic clutch thruster

This thesis describes the comprehensive process of designing, constructing, and testing a fully enclosed magnetic clutch thruster concept model for an autonomous underwater vehicle. Originally conceived as an enhancement to a pre- existing unit developed by Dr. Hinchey, the project faced various limitations in terms of equipment selection and physical sizing. The primary objective was to demonstrate the feasibility of such a design within these constraints. The design phase involved modeling in SolidWorks, followed by fabrication using a combination of 3D printing and machining services aided by Technical Services at MUN. Additionally, testing unit structures were engineered and tailored specifically for this project. Evaluation procedures were carried out in the Engineering Fluids Lab at MUN using self- designed and constructed equipment. Upon completion, the thruster underwent a series of rigorous tests aimed at collecting and analyzing data for comparison. These extensive model tests, conducted with the thruster integrated into our testing structure and measured with a load cell, revealed maximum responses and excellent repeatability. Further verification testing was undertaken to ensure the credibility of our testing apparatus and setup. The collected data was subsequently compared against model-based computational fluid dynamics (CFD) simulations, validating our concept and solid evidence of the results obtained through real-world testing. This thesis comprehensively explores the design, construction, and testing processes involved in developing an innovative thruster concept for autonomous underwater vehicles

Design And Modeling of Axial Micro Gas Turbine

Micro turbines are becoming widely used for combined power generation and heat applications. Their size varies from small scale units like models crafts to heavy supply like power supply to hundreds of households. Micro turbines have many advantages over piston generators such as low emissions less moving parts, accepts commercial fuels. Gas turbine cycle and operation of micro turbine was studied and reported. Brief description on CAD software and CATIA studied and reported. Different parts (Inlet. Storage, Nozzle, Rotor , coupling ,outlet ,clip ,housing) of turbine are designed with the help of CATIA (Computer Aided Three Dimensional Interactive Analysis) software. Then they were assembled to a single unit and coupled to a generator to produce power. The turbine is of Axial input and axial output type. Finally rapid prototyping machine features and parts were discussed and presented

Development of a Pediatric cardiac assist Maglev pump for use with a universal driver system.

Heart failure (HF) remains the leading cause of death, affecting 26 million adults worldwide and 6.5 million adults in the United States. Pediatric HF patients have been a historically underserved population with few options for mechanical circulatory support (MCS) therapy, a leading treatment as an alternative to heart transplantation. To address this clinical need, the Inspired Universal MagLev System is being developed; a low cost, universal magnetically levitated extracorporeal MCS system with interchangeable single-use pumps that will ultimately provide adult and pediatric patients ventricular and respiratory assist therapies. The Inspired Pediatric VAD is the first single-use pump application for this MCS system and is specifically designed for pediatric circulatory support. This dissertation describes the development efforts to design and evaluate iterative impeller and pump housings for the Inspired Pediatric VAD. Requirements for the Inspired Pediatric VAD design include the need to generate the appropriate hemodynamic parameters (pressures and flows) for pediatric patients, and miniaturization of the pump and impeller to accommodate the pediatric population. Traditional pump theory and design methods were applied to aid in the unique design of the VAD impeller and pump housing, resulting in multiple design iterations. Two impeller and pump designs (V1, V2) were virtually constructed using computer-aided design (CAD) software. Three-dimensional flow and pressure features were analyzed using computational fluid dynamics (CFD) analysis. Simulated pump designs (V1, V2) were operated at 15% higher rotational speeds (~5000 rpm) than initially estimated (4255 rpm) to achieve the desired operational point (3.5 L/min flow at 150 mmHg). V2 design outperformed V1 by generating up to 30% higher pressures at all simulated rotational speeds and with 5% lower priming volume. Simulated hydrodynamic performance (flow, pressure and hydraulic efficiency) of VAD V2 compared favorably to current commercially available MCS devices. A prototype of the Inspired Pediatric VAD V2 was fabricated, the magnitude and range of hydraulic torque and forces of the impeller were quantified, and the hydrodynamic performance benchmarked. A static mock flow loop model containing a heated blood analogue solution was created to test the pump over a range of rotational speeds (500 - 6000 RPM), flow rates (0 - 3.5 L/min), and pressures (0 to ~420 mmHg). The device was initially powered by a shaft driven DC motor, which was used to calculate the fluid torque acting on the impeller. Additional CFD simulations of VAD V2 were compared against the empirical bench-top data at select rotational speed and flow rate conditions. Empirically, the pediatric VAD produced flows as high as 4.3 L/min against a pressure of 127 mmHg at 6000 RPM. Based on the performance of the first two VAD design iterations, a final design iteration, VAD V3, was achieved. Hydrodynamic performance of VAD V3 was numerically assessed using CFD simulations. The results indicated no change in flow and pressure head performance compared to the previous device design (V2). Shear stress and flow residence time volumetric distributions were generated over a range of pump rotational speeds and flow rates. At the lowest pump operating point (3000 RPM, 0.50 L/min, 75 mmHg), 79% of the pump volume was in the shear stress range of 0 – 10 Pa with \u3c 1% of the volume in the critical range of 150 – 1000 Pa associated with potential for increased risk of clinically-significant blood damage. At higher speed and flow (5000 RPM, 3.50 L/min, 176 mmHg), 65% of the volume resided in the 0 – 10 Pa range compared to 2.3% at 150 – 1000 Pa. The initial results from the computational characterization of the Inspired Pediatric VAD V3 were encouraging, and based on the overall research performed to date, future work will include pre-clinical testing of VAD V3 in static and dynamic mock flow loop and acute large animal model studies to further assess device function, hydrodynamic performance, hemodynamic response, and hemocompatibility