Dissertations / Theses on the topic 'Rocket engines – Design and construction'

In this thesis, a simple moving boundary technique has been suggested, implemented and verified. The technique may be considered as a generalization of the well-known "ghost" cell approach for boundary condition implementation. According to the proposed idea, the moving body does not appear on the computational grid and is allowed to move over the grid. The impermeable wall boundary condition is enforced by assigning proper gasdynamic values at the grid nodes located inside the moving body close to its boundaries (ghost nodes). The reflection principle taking into account the velocity of the boundaries assigns values at the ghost nodes. The new method does not impose any particular restrictions on the geometry, deformation and law of motion of the moving body.
The developed technique is rather general and can be used with virtually any finite-volume or finite-difference scheme, since the modifications of the schemes themselves are not required. In the present study the proposed technique has been incorporated into a one-dimensional non-adaptive Euler code and a two-dimensional locally adaptive unstructured Euler code.
It is shown that the new approach is conservative with the order of approximation near the moving boundaries. To reduce the conservation error, it is beneficial to use the method in conjunction with local grid adaptation.
The technique is verified for a number of one and two dimensional test cases with analytical solutions. It is applied to the problem of supersonic inlet starting via variable geometry approach. At first, a classical starting technique of changing exit area by a moving wedge is numerically simulated. Then, the feasibility of some novel ideas such as a collapsing frontal body and "tractor-rocket" are explored.

Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2006.
Thesis Advisor(s): Christopher M. Brophy. "December 2006." Includes bibliographical references (p. 97). Also available in print.

Turbo-machinery design is clearly about making many decisions often under uncertainty and with multiple conflicting objectives. In this work, a computational tool has been developed to assist in the preliminary design optimization of supersonic turbines with application on turbopump rocket engines. It was proposed an evolutive approach based on genetic algorithm to automatize the process of selecting values, based on hands-on experience, for decision variables and fulfill simultaneously decisive compromises faced by the designer. At design point, exploring multiple optima solutions, the tool allows to fast estimate in a robust and accurate manner, performance, main dimensions, mass of rotor-wheel and the lower possible flow rate of the turbine. Out of this point, performance maps can be calculated varying rotational speed and pressure ratio. Because, it is involved by many objectives, a Pareto-optimum set is found. The search ends when the relation power-to-weight converges. The power-to-weight ratio characterizes a good option to relate performance and weight among distinct turbopump turbines. The empirical loss models adopted as well as the recommended values in the selection of decision variables were obtained in the Russian literature. To demonstrate the functionalities of tool, the single-stage of the Soviet RD109 rocket turbine was redesigned. The results were validated from those found in the engine';s atlas of construction and also, by a statistical method of calculation defined from an experimental study that estimates the maximum turbine efficiency.

Radial gas turbines engines have established prominence in the field of small turbomachinery because of their simplicity, relatively high performance and installation features. Thus they have been used in a variety of applications such as generator sets, small auxiliary power units (APu), air conditioning of aircraft cabins and hybrid electric vehicles turbines. The current research describes the design, manufacturing, construction and testing a radial type small gas turbine. The aim was to design and build the engine to drive directly a high-speed permanent magnet alternator running at 60000 rpmand developing a maximum of 60 W. This direct coupling arrangement produces a portable, light, compact, reliable and environment friendly power generator. These features make the generator set very attractive to use in many applications including emergency power generation for hospitals, in areas of natural disasters such as floods and earthquakes, in remote areas that cannot be served from the national grid, oil rigs, and in confined places of limited spaces. It is important to recognize that the design of the main components, that is, the inward flow radial UFR turbines, the centrifugal compressor and the combustion chamber involve consideration of aero-dynamics, thermodynamics, fluid mechanics, stress analysis, vibration analysis, selection of bearings, selection of suitable materials and the requirements for manufacturing. These considerations are all inter-linked and a procedure has been followed to reach an optimum design. This research was divided into three phases: phase I dealt with the complete design of the inward radial turbine, the centrifugal compressor, the power transmission shaft, the selection of combustion chamber and the bearing housing including the selection of bearings. Phase 2 dealt with mechanical consideration of the rotating components that is stress, thermal and vibration analyses of the turbine rotor, the impeller and the rotating shaft, respectively. Also it dealt with the selection of a suitable fuel and oil lubrication systems and a suitable starting system. Phase 3 dealt with the manufacturing of the gas turbine components, balancing the rotating components, assembling the engine and finally commissioning and then testing the engine. The current work in this thesis has put the light on a new design methodology on determining the optimum principal dimensions of the rotor and the impeller. This method, also, has defined the optimum number of blades and the axial length of the rotor and the impeller. Mathematical models linking the performance parameters and the design variables for the turbine and the compressor have been developed to assist in carrying out parametric studies to study the influence of the design parameters on the performance and on each other. Also, a new graphical matching procedure has been developed for the gas turbine components. This technique can serve as a valuable tool to determine the operating range and the engine running line. Furthermore, it would decide whether the gas turbine engine operates in a region of satisfactory compressor and turbine efficiencies.

Thesis (Aeronautical and Astronautical Engineer)--Naval Postgraduate School, June 2003.
Thesis advisor(s): I. Michael Ross, Steve Matousek. Includes bibliographical references (p. 149-150). Also available online.

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: The aim of this study was to design and manufacture an experimentally testable free-piston Stirling engine (FPSE), including a linear electric generator; to develop and validate a theoretical simulation model; to identify problem areas pertaining to its manufacture; and finally to assess the work undertaken, to lay out the groundwork for the future development of a 3 kWe FPSE suitable for incorporation in a solar Stirling dish power generator. A redesigned version of the Beale B- 10B demonstrator engine was manufactured to overcome design diffculties and to simplify testing. The design made use of an electric generator designed at the Department of Electrical and Electronic Engineering at Stellenbosch University. Experimental measurements included piston and displacer motions, hot side and cold side temperatures, working space pressure, electric generator output, as well as heat rejection via a water jacket. Experimental measurements were taken prior to and subsequent to the addition of the electric generator. Indicated power was calculated as 0,659 W at a frequency of 10,99 Hz prior to the addition of the electric generator. The addition of the electric generator was unsuccessful since it was not well matched with the engine. The indicated power calculated was between 0,138 W and 0,144 W for different loads on the electric generator, while the electrical output power ranged from 1,23 mWe to 1,79 mWe. The addition of the electric generator produced non-continuous motion caused by magnetic forces instead of engine pressure variations. The major manufacturing diffculty was the attachment of magnets for the electric generator, but this was overcome with the manufacture of a special assembly jig. The theoretical simulation model was a combination of a third-order and dynamic analysis. Working space values were solved by the application of the conservation of mass, momentum and energy equations for a one-dimensional discretised model of the engine, while the motion of the piston and displacer was determined by applying the equations of motion. The majority of experimental measurements were predicted more accurately when higher heat transfer coeficients were used between the working space and wall temperatures. The theoretical simulation model was used to gain insight into the effect of input parameters on engine operation. The displacer rod diameter was shown to have implications on output power and stability, while it was shown that there is a natural tendency to deliver constant output power at a near-constant frequency over a range of piston loads for an FPSE. It was also shown that the design of an FPSE is complex and that the design of all components should be done in parallel. The control of an FPSE was seen to be both a necessity and can be used to exploit the advantages of the uncoupled nature of an FPSE.
AFRIKKANSE OPSOMMING: Die doel van hierdie studie was om 'n eksperimentele toetsbare vrye-werksuier Stirling enjin te vervaardiging, wat 'n lineêre elektriese kragopwekker insluit; om 'n teoretiese simulasie model te ontwikkel en te yk; om vervaardiging probleme te identi seer; en om die ondernemende werk te assesseer om 'n fondasie te lê vir die toekomstige ontwikkeling van 'n 3 kWe vrye-werksuier Stirling enjin wat by 'n Stirling sonskottel ingelyf kan word. 'n Herontwerpte weergawe van die Beale B-10B demonstrasie enjin was vervaardig om ontwerp probleme te bowe te kom en om die toets daarvan te vereenvoudig. Die ontwerp het gebruik gemaak van 'n elektriese kragopwekker wat by die Departement Elektriese en Elektroniese Ingenieurswese aan die Universiteit van Stellenbosch ontwerp is. Eksperimentele metings het die werksuier en verplaser bewegings ingesluit, sowel as die warm kant en koue kant temperature, die werkruimte druk, die elektriese uitset van die kragopwekker, sowel as die hitteuitruiling wat met 'n water verkoelingskringloop gepaard gaan. Eksperimentele metings was geneem voor en na die byvoeging van die elektriese kragopwekker. Kraglewering was bereken op 0,659 W teen 'n frekwensie van 10,99 Hz voordat die elektriese kragopwekker bygevoeg is. Die byvoeging van die elektriese kragopwekker was onsuksesvol omdat die nie gepas was vir die enjin nie. Die kraglewering is bereken op vlakke wat gewissel het tussen 0,138 W en 0,144 W vir die verskillende belastings op die elektriese kragopwekker, terwyl die elektriese uitset gewissel het tussen 1,23 mWe en 1,79 mWe. Die byvoeging van die elektriese kragopwekker het 'n nie-aaneenlopende beweging veroorsaak weens die magnetiese kragte wat dit beinvloed het in plaas van enjindruk variasies. Die belangrikste ontwerpuitdagings was die ontwerp van 'n werksuier en verplaser wat 'n klein toleransie passing kon handhaaf om sodoende 'n seël te verseker terwyl dit aan temperatuur variasies blootgestel was. Die grootste vervaardigingsprobleem was die aanheg van magnete vir die elektriese kragopwekker, maar dit is te bowe gekom deur 'n spesiale voeg te vervaardig. Die teoretiese simulasie model was 'n kombinasie van 'n derde-orde en 'n dinamiese analise. Werkruimte waardes was opgelos deur die toepassing van die behoud van massa, momentum en energie vergelykings vir 'n een-dimensionele gediskretiseerde model van die enjin, terwyl die beweging van die werksuier en verplaser bepaal was deur die toepassing van die bewegingvergelykings. Die meerderheid van die eksperimentele metings was meer akkuraat voorspel wanneer hoër warmteoordrag koë siënte tussen die werkruimte en muurtemperature gebruik was. Die teoretiese simulasie model was gebruik om insig in terme van die e ek van invoer veranderlikes op die enjin gedrag te toon. Daar was getoon dat die verplaserstaaf diameter implikasies het op kragoplewering en stabiliteit, terwyl die natuurlike tendens van 'n vrye-werksuier Stirling enjin gewys was om 'n konstante kraguitvoer te lewer op 'n naby-konstante frekwensie oor 'n reeks werksuier laste. Daar was ook gewys dat die ontwerp van 'n vryewerksuier Stirling enjin kompleks is en dat die ontwerp van alle komponente in parallel gedoen moet word. Die beheer van 'n vrye-werksuier Stirling enjin was gewys om beide noodsaaklik te wees, sowel as gebruik kan word om die unieke voordele van 'n vrye-werksuier Stirling enjin se ongekoppelde natuur te ontgin.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Mavris, Dimitri; Committee Member: Gaeta, Richard; Committee Member: German, Brian; Committee Member: Jones, Scott; Committee Member: Schrage, Daniel; Committee Member: Tai, Jimmy.

The fire department depends on the fire apparatus to support the many roles firefighters fulfill in the community. The instrument panel of the fire apparatus is the primary man-machine interface for controlling the vehicle. The instrument panel contains many gauges and controls for the numerous features of the apparatus. This research reflects the investigation of how the fire apparatus instrument panel is used by the Atlanta Fire Department. Research involves an immersive study observing the Atlanta firefighters. Surveys and a design critique were developed to obtained firefighter feedback. A comparison of similar tasks was completed to Based on the feedback from fire apparatus drivers and captains design concepts were developed. Concepts are desiged to help the driver and the captain of the apparatus.

Thermoacoustic engines convert heat into acoustic pressure waves with no moving parts; this inherently results in high reliability, low maintenance and low manufacturing costs. Significant increases in the performance of these devices have enabled rivalry with more mature energy conversion methods in both efficiency and power output. This optimal production of acoustic power can be ultimately used to achieve cryogenic temperatures in thermoacoustic refrigerators, or can be interfaced with reciprocating electro-acoustic power transducers to generate electricity. This thesis describes the design, fabrication and testing of a Thermoacoustic Power Converter. The system interfaces a thermoacoustic-Stirling heat engine with a pair of linear alternators to produce 100 watts of electricity from a heat input. It operates with helium at 450 psig internal pressure and a hot side temperature of 1200F. Through thermoacoustic phenomena, these conditions sustain a powerful pressure wave at a system specific 100 Hz. This pressure wave is used to drive the two opposed linear alternators in equal and opposite directions to produce a single phase AC electrical output at that same system frequency. The opposing motion of the two alternators enables a vibration-balanced system. The engine has created 110 watts of acoustic power and the complete Thermoacoustic Power Converter system has produced 70 watts of AC electricity. Compensating for some heat leaks, the converter reaches 26.3% heat to acoustic power efficiency and 16.8% heat to electric efficiency when those maximum values are achieved. This conversion of heat to acoustic power is 40% of the Carnot thermodynamic efficiency limit.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Recent years have seen a decline in the rate of space exploration due to the inefficiency of chemical rockets. Therefore alternative fuel efficient propulsion methods are being sought to enable cost effective deep space exploration. The high fuel efficiency of electric thrusters enable a spacecraft to travel further, faster and cheaper than any other propulsion technology available. Thus electric propulsion has become the propulsion of choice for scientists and engineers. A typically electric thruster contains some sort of electrode to ionise the propellant. Although this is feasible for short space missions, it becomes impractical for more ambitious space missions as electrodes erode over time. The alternative is to ionise the propellant using electromagnetic fields, which eliminates lifespan issues associated with electrode based thrusters. In order to examine methods of improving the lifespan and performance of electric thrusters, this thesis aimed to study the method of microwave discharge ionisation for an electric thruster. This includes the design of an RF Ion Thruster with extraction and acceleration grids to generate thrust. A 600 W 2.45 GHz magnetron (obtained from a conventional microwave oven), coupled to circular TM010 resonant cavity, was used to ionise neutral argon gas. The process of electron cyclotron resonance (ECR) was used to ensure the efficient ionisation of a high density plasma. The thrust was achieved with a three-grid system biased at high voltages to accelerate positively charged argon ions to high exhaust velocities. Results yielded the success of the designed electromagnetic based thruster, measuring approximatively 1.78 mN of thrust with a specific impulse of Isp = 3786 seconds. The ECR process produced a high plasma density with a plasma absorption rate of approximately 77% of the total input microwave power. The final results obtained were found to match the predicted results extremely well and resembled results found in literature. This demonstrates the efficiency of the RF ion thruster that was designed in this project and the future use in space exploration activities. However, future research needs to be undertaken on a controlled feedback system that will ensure optimal operating conditions for maximum performance. In addition, the method of grid-less acceleration needs to be studied to achieve maximum thrust and specific impulse.
AFRIKAANSE OPSOMMING: In onlangse jare het ’n afname in die tempo van die verkenning van die ruimte dit te danke aan die ondoeltreffendheid van chemiese vuurpyle. Derhalwe moet alternatiewe brandstof aandrywing metodes ondersoek word, om koste-effektiewe diep ruimte-eksplorasie moontlik te maak. Die hoë brandstof-doeltreffendheid van elektriese ontbranders stel ’n ruimtetuig in staat om verder, vinniger en goedkoper te reis as enige ander aandrywing tegnologie wat tans beskikbaar is. Dus het elektriese aandrywing metodes die aandrywings keuse vir wetenskaplikes en ingenieurs geword. ’n Tipies elektriese vuurpyl/aandrywer bevat ’n vorm van elektrode om die brandstof (argon gas) te ioniseer. Alhoewel hierdie elektrode proses van ionisasie effektief is vir kort ruimte missies, word dit onprakties vir meer ambisieuse ruimte missies as gevolg van verweering van elektrodes met verloop van tyd. ’n Alternatief is om die dryfmiddel/brandstof te ioniseer deur gebruik te maak van elektromagnetiese velde. Die elekromagnetiese velde sal die lewensduur van die vuurpyl vermeerder deur die verweering van elektrodes, wat geassosieer word met tipiese elektrieses vuurpyle, te elimineer. Hierdie tesis se doelwit is om die metode van mikrogolf ontslag ionisasie vir ’n elektriese vuurpyl/aandrywer te bestudeer om ten einde die lewensduur en doeltreffendheid van elektriese vuurpyl/aandrywer te ondersoek. Dit sluit in die ontwerp van ’n radio frekewensie ioon vuurpyl/aandrywer met ’n ontginning en versnelling matriks/rooster om stukrag te genereer. ’n 2,45 GHz magnetron (verkry vanaf ’n konvensionele mikrogolfoond), gekoppel aan ’n TM010 resonante holte, was gebruik om neutrale argon gas te ioniseer. Die proses van elektron siklotron resonansie (ESR) was gebruik om die doeltreffende ionisasie van ’n hoë digtheid plasma te verseker. Die aandrywing/stukrag was behaal met ’n drie-matriks-stelsel, bevoordeel deur hoë spannings om die positief-gelaaide argon ione te versnel. Resultate opgelewer, het die sukses van die ontwerp van ’n elektromagnetiese gebaseerde vuurpyl/aandrywer met ’n benaderde meting van ongeveer 1.78 mN van stukrag/aandrywing met ’n spesifieke impuls van Isp = 3786 sekondes bewys. Die ECR proses het ’n hoë plasma digtheid geproduseer met ’n plasma opname persentasie van ongeveer 77% van die totale inset mikrogolf energie. Die finale uitslae wat verkry was, het bevind dat die voorspelde resultate baie goed inpas met resultate in beskikbare literatuur. Dit dui op die doeltreffendheid van die RF ioon vuurpyl/aandrywer wat ontwerp is in hierdie projek vir die toekomstige gebruik in ruimte eksplorasie-aktiwiteite. Toekomstige navorsing moet op ’n beheerde terugvoer sisteem onderneem word, wat optimale werktoestande verseker vir maksimum prestasie. Daarbenewens moet die metode van matriks-lose versnelling bestudeer word, om maksimum versnelling/stukrag en spesifieke impuls te verseker.

Thesis submitted in fulfilment of the requirements for the degree of Master of Technology in Mechanical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology, 2012
Our planet is continuously being depleted of its natural resources leading to a need to conserve energy and the environment. One of the major energy consumers is the conventional internal combustion engine. Many attempts have been made to make these conventional internal combustion engines more efficient focussing mostly on the combustion side of the engine. The focus of this study is on the modification of the reciprocating and rotating components of the sub-assembly of a conventional internal combustion engine. An in-depth review was carried out on the fundamentals of spark ignition internal combustion engines and savings on fuel consumptions. A prototype single piston internal combustion engine was developed that can adjust its stroke length. Lengthening or shortening the stroke and simultaneously extending or retracting the connecting rod’s travel distance, allows the internal combustion engine to function very efficiently consequently reducing the free space between the piston and cylinder head at TDC position. This allows the internal combustion engine to alter its power capability on demand whilst maintaining relatively high compression efficiency. The method of altering the stroke length is achieved by manipulating gears situated internally and externally of the engine sub-assembly. The control of these eccentric gears lowers or lifts the crankshaft in a radial motion. The eccentrics also control the automatic extension or retraction of the connecting rod’s travel distance. The externally concentric gears control the mechanism that allows the internal combustion engine to change its capacity easily as adapted for automation. This study does not extend into the automation issues of the external mechanism. The prototype engine that was built could not endure vigorous testing and it failed after running for a short while. The primary focus had been on the kinematics of the engine mechanism – and to show whether the idea was feasible. The engine passed the kinematics test but failed possibly due to dynamic loads. Investigating this requires measuring instantaneous temperatures from which peak pressures can be deduced. This was not done because it was outside the scope of the project.

Stirling engines are an external combustion heat engine that converts thermal energy into mechanical work that a closed cycle is run by cyclic compression and expansion of a work fluid (commonly air or Helium) in which, the working fluid interacts with a heat source and a heat sink and produces network. The engine is based on the Stirling cycle which is a subset of the Carnot cycle. The Stirling cycle has recently been receiving renewed interest due to some of its key inherent advantages. In particular, the ability to operate with any form of heat source (including external combustion, flue gases, alternative (biomass, solar, geothermal) energy) provides Stirling engines a great flexibility and potential benefits since it is convinced as engines running with external heat sources. However, several aspects of traditional Stirling engine configurations (namely, the Alpha, Beta, and Gamma), specifically complexity of design, high cost, and relatively low power to size and power to volume ratios, limited their widespread applications to date. This study focuses on an innovative Stirling engine configuration that features a rotary displacer (as opposed to common reciprocating displacers), and aims to utilize analytical and numerical analysis to gain insights on its operation parameters. The results are expected to provide useful design guidelines towards optimization. The present study starts with an overview of the Stirling cycle and Stirling engines including both traditional and innovative rotary displacer configurations, and their major advantages and disadvantages. The first approach considers an ideal analytical model and implements the well-known Schmidt analysis assumptions for the rotary displacer Stirling engine to define the effects of major design and operation parameters on the performance. The analytical model resulted in identifying major variables that could affect the engine performance (such as the dead volume spaces, temperature ratios and the leading phase angle). It was shown that the dead volume could have a drastic effect over the engine performance and the optimum phase angle of the engine is 90o. The second approach considers a non-ideal analytical model and aims to identify and account the main sources of energy losses in the cycle to better represent the engine performance. The study showed that the ideal efficiency and the non-ideal efficiency could have 15% difference that could have as an enormous effect on the engine performance.

Thesis (MScEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The main components of a micro gas turbine engine are a centrifugal or mixed-flow compressor, a combustion chamber and a single stage axial-flow or radial-flow turbine. The goal of this thesis is to formulate a design methodology for small axial-flow turbines. This goal is pursued by developing five design-related capabilities and applying them to develop a turbine for an existing micro gas turbine engine. Firstly, a reverse engineering procedure for producing digital three-dimensional models of existing turbines is developed. Secondly, a procedure for generating candidate turbine designs from performance requirement information is presented. The third capability is to use independent analysis procedures to analyse the performance of a turbine design. The fourth capability is to perform structural analysis to investigate the behavior of a turbine design under static and dynamic loading. Lastly, a manufacturing process for prototypes of a feasible turbine design is developed. The reverse engineering procedure employs point cloud data from a coordinate measuring machine and a CT-scanner to generate a three-dimensional model of the turbine in an existing micro gas turbine engine. The design generation capability is used to design three new turbines to match the performance of the turbine in the existing micro gas turbine engine. Independent empirical and numerical turbine performance analysis procedures are developed. They are applied to the four turbine designs and, for the new turbine designs, the predicted efficiency values differ by less than 5% between the two procedures. A finite element analysis is used to show that the stresses in the roots of the turbine rotor blades are sufficiently low and that the dominant excitation frequencies do not approach any of the blade natural frequencies. Finally prototypes of the three new turbine designs are manufactured through an investment casting process. Patterns made of an organic wax-like material and a polystyrene material are used, with the former yielding superior results.
AFRIKAANSE OPSOMMING: Mikro-gasturbiene-enjins bestaan uit 'n sentrifugaal- of ‘n gemende-vloeikompressor, 'n verbrandingsruim en 'n enkel-stadium-aksiaalvloei- of ‘n radiaalvloei-turbine. Die doel van hierdie tesis is om 'n ontwerpsmetodologie vir klein aksiaalvloei-turbines saam te stel. Hierdie doel word deur die ontwikkeling en toepassing van vyf ontwerpsverwante vermoëns nagestreef. Eerstens word 'n tru-waartse-ingenieursproses ontwikkel om drie-dimensionele rekenaarmodelle van die bestaande turbines te skep. Tweedens word 'n metode om kandidaatturbineontwerpe vanaf werkverrigtingsvereistes te verkry, voorgestel. Die derde ontwerpsvermoë is om die werksverrigting van 'n turbineontwerp met onafhanklike analises te evalueer. Die vierde ontwerpsvermoë is om die struktuur van 'n turbinelem te analiseer sodat die effek van statiese en dinamiese belastings ondersoek kan word. Laastens word 'n vervaardigingsproses vir prototipes van geskikte turbineontwerpe ontwikkel. Die tru-waartse-ingenieursproses maak gebruik van 'n koördinaat-meet-masjien en 'n CT-skandeerder om puntewolkdata vanaf die turbine in 'n bestaande mikro-gasturbiene-enjin te verkry. Die data word dan gebruik om 'n drie-dimensionele model van die turbine te skep. Die ontwerpskeppingsvermoë word dan gebruik om drie kandidaatturbineontwerpe vir die bestaande mikro-gasturbiene-enjin te skep. Onafhanklike empiriese en numeriese prosedures om die werkverrigting van 'n turbineontwerp te analiseer word ontwikkel. Beide prosedures word op die vier turbineontwerpe toegepas. Daar word gevind dat die voorspelde benuttingsgraadwaardes van die nuwe ontwerpe met minder as 5% verskil vir die twee prosedures. 'n Eindige-element-analise word dan gebruik om te wys dat die spannings in die wortels van die turbinelemme laag genoeg is, asook dat die dominante opwekkingsfrekwensies nie die lem se natuurlike frekwensies nader nie. Laastens word prototipes van die drie nuwe turbineontwerpe deur 'n beleggingsgietproses vervaardig. In die vervaardigingproses word die effektiwiteit van twee materiale vir die gietpatrone getoets, naamlik 'n organiese wasagtige materiaal en 'n polistireen-materiaal. Daar word bevind dat die gebruik van die wasagtige gietpatrone tot beter resultate lei.

Thesis (MScEng)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: This thesis is concerned with unsteady, one-dimensional flow, which closely mimics those found in the manifolds of internal combustion engines. The physical equations describing problems of this nature are presented and some of the important concepts introduced. These equations and concepts were verified by comparison to published results. The Method of Characteristics (MaC) for unsteady one-dimensional flow with friction and heat transfer was used to analyse the gas flow through the inlet and exhaust systems of an engine. The theoretical derivation of unsteady gas dynamic boundary conditions is presented and the integration with the unsteady pipe flow explained. A simulation flow model was developed to analyse the flow by using the Mae. Thisflow model was then incorporated into an engine simulation program, ESA,to simulate internal combustion engines and to predict the performance of a specific engine. A cam-profile model and an in-cylinder thermodynamic model are used to complete the ESAsoftware. Experimental work was done on a modified Nissan Z24/NA20 engine to evaluate the simulation model. The manifolds of the Nissan Z24/NA20 were modified to isolate one of the cylinders for a proper single cylinder model. More experimental work was done on a Volkswagen 1.6£ 8-valve and a 1.6£ 20-valve engine to obtain performance data on two inlet manifolds developed using the ESAsoftware. Performance data and pressure traces in the inlet manifold of the Nissan Z24/NA20 were recorded for comparison with the ESA software. Good correspondence was found between tested and modelled data and the differences varied between ±5% on engine performance data and pressure wave frequency predictions, and ± 10% on pressure pulse amplitudes.
AFRIKAANSE OPSOMMING: Hierdie tesis handeloor bestendige, eendimensionele vloei, wat die gasvloei in spruitstukke van binnebrandenjins naboots. Die nodige vergelykings wat hierdie tipe probleme beskryf asook van die belangrikste konsepte, word bespreek. Hierdie vergelykings en konsepte is met behulp van gepubliseerde data geverifieer. Die Metode van Karakteristieke (MVK) vir bestendige, eendimensionle vloei met wrywing en warmte oordrag, is gebruik om die gasvloei deur inlaat en uitlaat sisteme van 'n enjin te analiseer. Die teoretiese afleiding van bestendige gasdinamiese randvoorwaardes asook hul integrasie met die bestendige pypvloei, word verduidelik. 'n Simulasie vloeimodel is ontwikkelom die vloei met behulp van die metode van karakteristieke te analiseer. Hierdie vloeimodel is deel van 'n omvattende enjinsimulasie program, ESA. Dit word gebruik om binnebrandenjins te simuleer en enjinwerkverrigting te voorspel. 'n Nokprofielmodel en 'n termodinamiese ontbrandingsmodel word gebruik om die enjinsimulasie program af te rond. Eksperimentele toetse op 'n gemodifiseerde Nissan Z24/NA20 enjin is gebruik om die simulasie model te evalueer. Die spruitstukke van die Nissan Z24/NA20 is aangepas om een van die silinders te isoleer om so 'n geskikte enkelsilindermodel te skep. Verdere eksperimentele toetse is gedoen op Volkswagen 1.6£8- klep en 1.6£ 20-klep enjins. Werkverrigtingsdata is verkry op twee nuwe inlaatspruitstukke wat met behulp van die ESAsagteware ontwerp is. Werkverrigtingsdata en drukverdelingsdata in die inlaatspruitstuk van die Nissan Z24/NA20is aangeteken om te vergelyk met die resultate van die ESAsagteware. Goeie ooreenstemming is verkry tussen toets- en gemoduleerde data. Die verskille varieer tussen ±5% op enjin werkverrigtingsdata en drukpulsfrekwensie voorspellings, en ± 10%op drukpuls-amplitudes.

The alloy Mo-3Si-1B (wt%) may have the fracture toughness and oxidation resistance required for use as jet turbine engine blades. Mo-3Si-1B (wt%) forms a three-phase mixture of and #945;-Moss, A15 (Mo3Si) and T2 (Mo5SiB2). It has been observed that at high-temperatures, the A15 and T2 intermetallics form a oxidation resistant borosilicate glass coating. To achieve the proper combination of mechanical and thermal properties, the material must have a molybdenum matrix with a fine dispersion of intermetallics to produce a continuous protective layer. In this project, reactive sintering of molybdenum, Si3N4 and BN powders was used to create a semi-continuous molybdenum matrix with a fine dispersion of the A15 and T2 intermetallics. Sintering of the materials was further enhanced by the use of submicron-sized reactants. X-ray diffraction analysis was used verify the desired phases were formed. It was determined that formation of the A15 intermetallic phases begins as low as 1200?nd formation of T2 begins at 1300? The reactions are complete by 1400? Samples with bulk densities as high as 95% of theoretical were produced. Scanning electron microscopy images reveal a microstructure with dispersed intermetallics in a semi-continuous molybdenum matrix with grain sizes on the order of 1-4 and #956;m. It was found that by varying parameters such as mixing method and heating rates, it is possible to engineer the final microstructure, changing the level of dispersion of the intermetallics and continuity of the matrix.

Orientador: Marco Lúcio Bittencourt
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-24T09:08:40Z (GMT). No. of bitstreams: 1 LimaeSilva_RafaelAugustode_M.pdf: 10555723 bytes, checksum: 1d037ebafbabc24e214c06ad76c5f54a (MD5) Previous issue date: 2013
Resumo: O trabalho descreve o projeto mecânico convencional de uma biela automotiva de motor de combustão interna e apresenta uma metodologia alternativa baseada em métodos de otimização estrutural com o objetivo de reduzir a massa do componente. Para tal, é feita a descrição de todos os parâmetros de projeto assim como a definição de critérios de projeto. Em virtude da criticidade da aplicação selecionada, motor de ciclo Diesel utilizado em caminhões de trabalho pesado com picos de pressão de combustão de até 240 bar, a biela foi projetada sem bucha utilizando-se extensivamente os métodos numéricos. O Método dos Elementos Finitos foi aplicado para cálculo de tensões, deslocamentos, pressões de contato, flambagem, fadiga e para a síntese modal de componentes utilizados na análise dinâmica de multicorpos com mancais elasto-hidrodinâmicos. Dois modelos de fadiga dos materiais foram estudados: o modelo americano baseado no diagrama de Goodman e tensões principais e o modelo alemão baseado no diagrama de Haigh e efeito do gradiente de tensões multiaxiais; dos quais concluiu-se que o modelo americano é suficiente para o projeto da biela ao passo que o modelo alemão traz oportunidades adicionais de redução de massa. A otimização topológica, otimização de forma e análise de sensibilidade permitiram a obtenção de uma biela 210g (3\%) mais leve e com melhor desempenho dos mancais hidrodinâmicos. Finalmente, concluiu-se que o Método da Otimização Topológica apresenta oportunidades interessantes aos projetistas na fase de conceituação de produtos como alternativa aos desenhos convencionais, no entanto, demanda esforço adicional para o atendimento de todos os critérios de projeto do componente
Abstract: The present work consists of the conventional mechanical design description of an internal combustion engine connecting rod and also the proposal of an alternative methodology based on optimization methods with the objective of reducing the component mass. Therefore, it is performed a detailed view of all design parameters as well as the definition of design criteria. Because of the critical application selected, Diesel engine of heavy duty truck with combustion pressure reaching up to 240bar, the connecting rod was designed without bushing and with extensive use of numerical methods. The Finite Element Method was applied to assess stresses, displacements, contact pressures, buckling, fatigue and to perform the Component Modal Synthesis for multi-body dynamics simulation with elasto-hydrodynamic bearings. Two fatigue models were studied: the American model based on Goodman's diagram and principal stresses and the German model based on Haigh's diagram and multiaxial stress gradient effect; from which it was concluded that the American model is enough to design the connecting rod, while the German model presents additional weight reduction opportunities. The topology optimization, shape optimization and sensitivity analysis enabled a 210g (3\%) lighter connecting rod with improved bearings performance. Finally, it was concluded that the Topology Optimization Method presents good opportunities for the design engineers in the conceptual phases of product development with alternatives to the conventional designs. However, additional effort is necessary to fit the concept into all design criteria
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

This thesis focuses on the development of reduced pressure testing capabilities at Zucrow Laboratories. A two-stage ejector on loan from NASA Marshall is used in series with a supersonic diffuser to allow for the testing of up to100 lb_f rocket engines at equivalent altitudes of up to 100,000 ft. The objective of this research is to implement a one-dimensional (1-D) model which accurately predicts the performance of the two-stage ejector in real time, informing the maximum thrust and simulated altitude capabilities within the altitude chamber located in room 134A of ZL3 during experimental testing.

碩士
臺灣大學
工程科學及海洋工程學研究所
96
This work investigate a novel design of underwater gliders with fore and aft buoyancy engines. The advantages of using a glider for ocean observations are that gliders have low energy cost for long endurance. A buoyancy engine is a device which changes buoyancy of an underwater vehicle by attracting and expelling water. Underwater gliders equipped with buoyancy engines can be driven by net buoyancy forces. The buoyancy engines’ arrangement considered in this study contains two tanks located at the fore and end aft part of the hull. Buoyancy engines considered here are those of piston-type. Forces equations which model buoyancy, gravity, and hydrodynamic forces in gliding are derived. Performances of different sizes of buoyancy engines are compared. Energy for driving a glider with fore and aft buoyancy engines could be estimated by total volume change of buoyancy engines and the cost for holding piston position during transferring. The net buoyancy and position of the center of gravity can be tuned at mean time using the fore and aft buoyancy engines. Operational constrains for gliders using fore and aft buoyancy engines are specified. Following these constrains, energy cost for glider motion will be lower than conventional glider design using single buoyancy and a weight shifting device. This study describes a design methodology for specifying volume capacity of buoyancy engines. Glide angles and glide speeds for optimal energy cost are also specified base on the minimal energy cost. Gliders with rectangular wings of various shape and wing location are then examined in terms of the energy cost for gliding controlled by buoyancy engines.

A Computational Fluid Dynamics (CFD) simulation of the Bishop Rotary Valve (BRV) engine is developed. The simulation used an existing commercial CFD code, CFX 4.3, with a number of new routines written to allow it to simulate the conditions and motions involved in an internal combustion engine. The code is extensively validated using results from other researchers, and several new validations are performed to directly validate the code for simulating internal combustion engine flows. Firstly, tumble vortex breakdown during the compression stroke of a square piston model engine is modelled. The results of the simulation are validated against published high quality experimental data. Both two- and three-dimensional models are tested, using the k-e and Reynolds stress turbulence models. The Reynolds stress turbulence model simulations successfully predicted the tumble break down process during the compression stroke. A simple three-dimensional Large Eddy Simulation model is also presented. The numerical simulation is then applied to the BRV engine. An in-cylinder flow field not previously described is discovered, created by the unique combustion chamber shape of the BRV engine. The flow field is not adequately described by the traditional descriptions of engine flows, being squish, swirl and tumble. The new flow structure is named 'dual cross tumble', and is characterised by two counter-rotating vortices in the cross tumble plane on either side of the inlet air jet. Analysis of the dual tumble structure indicates that it is most beneficial in high bore to stroke ratio engines. This flow structure has been predicted or visualised by a small number of previous researchers, however no published research has recognised its significance or potential benefits. The validated code is then used to predict the effect of modifying the valve cross sectional area, the effect of the inlet manifold wave, the effect of heat transfer from the inlet manifold walls, the effect of bore to stroke ratio, and the effect of engine speed. This work presents a numerical simulation of a new rotary valve engine technology. This opens up a whole new area of engine aerodynamics research as no detailed examination of the flows in a rotary valve engine have been presented previously. In the process, it discovers a new compression stroke turbulence generation mechanism, 'dual cross tumble', which offers the potential of performance levels not possible using poppet valve engines.

A new material system was developed for fabricating the combustion engine of an unmanned aerial vehicle. The material system consisted of a mixture of nanoscale and microscale particles of silicon nitride. Magnesia and yttria were used as sintering additives. The powders were mixed with a paraffin binder system. The binder-powder was analyzed for its properties and molding attributes. The study involved several steps of the development and processing. These steps include torque rheometery analysis, mixing scale-up, property measurements of binder-powder, injection molding, binder removal, sintering, scanning electron microscopy analysis and mechanical properties measurements. Simulations of the injection molding process were conducted to assess the feasibility of manufacturing a ceramic engine and to determine its optimal process parameters. The model building required for the simulation was based on flow and solidification behavior data compiled for the binder-powder mixture. The simulations were performed using the Moldfow software package. A design of experiments approach was set up in order to gain an understanding of critical process parameters as well as identifying a feasible process window. Quality criteria were then analyzed in order to determine the optimal production parameters. The study resulted in the successful development of design parameters that will enable fabrication of silicon nitride engine components by powder injection molding.
Graduation date: 2012