The high speed 2-stroke cycle engine designed for high power-to-weight ratio is relatively inefficient at part throttle. It would be advantageous to incorporate a simple method of allowing extra air to enter the cylinder prior to the fresh mixture, thus stratifying the charge and increasing the proportion of the air-fuel mixture retained in the cylinder at part loads while not deleteriously affecting the maximum power at full throttle. A series of tests, on an engine fitted with a reed valve connecting the atmosphere to the passageway leading to intake ports, were carried out with varying amounts of extra air, the results showed that power, speed, thermal efficiency, and fuel trapping efficiency gave increases at nearly all settings, but with a large excess of extra air, the air-fuel ratio through the carburetor had to be decreased to maintain stable operation. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

No description available.

No description available.

Pressure data measurements have been made in a single-cylinder, spark-ignition engine over 100 consecutive cycles. The engine was operated on natural gas at a wide range of engine speed and equivalence ratios. The effects of spark electrode geometry, combustion chamber geometry, spark gap and throttling have also been examined. From these pressure measurements standard deviations in burning times in mass-fraction-burned values were determined. Because of the existing evidence that the origin of cyclic variations is in the early combustion period, the standard deviations of cyclic variation in time required for a small (almost zero) mass-fraction-burned is estimated by extrapolation. These extrapolated values of standard deviation are compared with the implication of a hypothesis that cyclic variations in combustion in spark-ignition engines originate in the small-scale structure of turbulence (after ignition). The nature of turbulence structure during combustion is deduced from existing knowledge of mixture motion within the combustion chamber of the engine. This research determines the turbulent parameters, such as turbulence intensity, turbulent length scales and laminar burning velocity. The standard deviation in burning times in the early stages of combustion is estimated, within experimental uncertainty, by the parameter ⋋/4uℓ where ⋋ is the Taylor microscale and uℓ is the laminar burning velocity of the unburned mixture. This parameter is the consequence of the Tennekes model of small-scale structure of turbulence and Chomiak's explanation of the high flame propagation rate in regions of concentrated vorticity and the assumption that theignition behaves as though it were from a point source. The general conclusion reached is that the standard deviation in the burning time for small mass-fraction-burned is associated with the early stages of burning-predictable from the knowledge of the Taylor microscale and the laminar burning velocity. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The study of the reciprocating internal combustion engine is of prime importance to the student engineer. In our present civilization, the number of units and the total rated power of internal combustion engines in use is far greater than that of all other prime movers combined. Many basic engineering problems are present in the study of the operation of internal combustion engines. A number of mechanical and electrical devices have been developed to aid the engineer in his studies of engine performance. The purpose of this project is to provide the Mechanical Engineering Department of the North Dakota State University with an addition to its laboratory facilities which will enable the student to do additional experimental work in the internal combustion engines field. / North Dakota State University (NDSU)

Typewritten / Includes bibliographical references / 1 v. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Faculty of Engineering, University of Adelaide, 1956

Thesis (MScEng.)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The last two decades have seen many changes within the automotive industry. Many advances have been made in the design, research and development of the internal combustion engine and technological progress made in the integrated-circuit and computer industry has resulted in the availability of reliable low-cost electronic components. These components have, over time, been incorporated into the very hearts of engines, thereby allowing for the accurate control of engine functions and processes to an extent that was previously impossible. Parallel to these developments is the growing concern for the environment and the realisation that resources are being consumed at ever-increasing rates. This has placed vehicle manufacturers under continual pressure to optimise their engines, not only for fuel efficiency, but also to reduce harmful emissions while continuing to deliver better performance and drivability characteristics. At the same time, engine testing equipment and facilities have had to keep abreast with these advances and this has required the development of more sophisticated testing facilities. One such facility is the dynamic engine test-bed. Among other features, this facility has the ability to subject test-bed mounted engines to loads similar to what would be experienced in a vehicle on the road. This approach allows for the optimisation of engine components and performance under more realistic conditions, yielding results far superior to those obtainable using more conventional steady-state testing and development procedures. This document discusses the development of such a dynamic engine test-bed at the Centre for Automotive Engineering at the University of Stellenbosch. The project was initiated by conducting a literature survey to establish the current state of technology in the field. The dynamic test-bed was developed around an existing direct-current electric motor and industrial speed controller configured in a regenerative manner. This setup enabled the unit to both absorb and deliver power, essential for the simulation of vehicle dynamics. Great care was taken to ensure that signals obtained from the test-bed were accurate and useful for further computer manipulation. Anti-aliasing filters were designed and manufactured to guarantee that signals could not be misinterpreted due to sampling effects. A computer-implemented vehicle model was developed to simulate, in real-time, vehicle response to torque developed by the engine on the test stand. The model included a manual transmission, clutch and a rigid drive-shaft. Driver input (accelerator, brake, clutch and gear selection) was by means of a set of pedals and hand-held gear selector switches. Various vehicle speed control strategies were investigated and recommendations made regarding their possible future implementation. System evaluation was accomplished by the simulated acceleration of a large truck. The simulations indicated that repeatable results could be obtained from the system. The system was also found to be adequately sensitive to reflect the effect of subtle changes made to engine parameters on vehicle acceleration. It was concluded that the dynamic engine test-bed did indeed offer the capability to conduct research and testing not previously available in South Africa. Finally, recommendations were made for the future improvement and expansion of the system's performance and capabilities. / AFRIKAANSE OPSOMMING: Die laaste twee dekades het baie veranderinge in die outomobiel industrie megebring. Groot vooruitgang is gemaak in die ontwerp, navorsing en ontwikkeling van die binnebrand enjin, terwyl tegnologiese vooruitgang in die geïntegreerde-stroombaan en rekenaar industrië betroubare elektroniese komponente teen lae koste beskikbaar gemaak het. Hierdie komponente is mettertyd in enjins geïnkorporeer en het die akkurate beheer van enjin funksies en prosesse moontlik gemaak. Saam met hierdie ontwikkeling, is daar toenemende kommer oor die omgewing en 'n bewuswording dat hulpbronne verbruik word teen 'n groeinde tempo. Hierdie feite plaas voertuig vervaardigers onder volgehoude druk om enjins te optimeer vir brandstof doeltreffendheid, maar ook om skadelike emissies te bekamp terwyl beter werksverrigting en bestuurbaarheid vereis word. Enjin toetstoerusting en fasiliteite moes terselfdetyd met hierdie vooruitgang byhou en het die ontwikkeling van meer gesofistikeerde toetsfasiliteite vereis. Een sodanige fasiliteit is die dinamiese enjin toetsbank. Een van die kenmerke van hierdie fasiliteit is dat dit toetsbank-gemonteerde enjins kan onderwerp aan 'n las soortgelyk as wat ondervind sou word in 'n voertuig op die pad. Hierdie benadering stel ingenieurs in staat om enjin komponente en werksverrigting te optimeer onder meer realistiese kondisies en lewer resultate van 'n baie hoër gehalte as wat verkry kan word deur gebruik te maak van meer konvensionele gestadigde-toestand toets- en ontwikkelings-prosedures. Hierdie dokument bespreek die ontwikkeling van so 'n dinamiese enjin toetsbank by die Sentrum vir Automobielingenieurswese aan die Universiteit van Stellenbosch. Die projek is geïnisieer deur 'n literatuurstudie te doen om die huidige stand van tegnologie in die gebied vas te stel. Die dinamiese enjintoetsbank is ontwikkel rondom 'n bestaande gelykstroom-motor en industriële spoed beheerder wat in 'n regeneratiewe konfigurasie opgestel is. Hierdie opstelling het die absorpsie en lewering van drywing moontlik gemaak, 'n vereiste vir die simulasie van voertuig dinamika. Baie tyd is gespandeer om te verseker dat seine afkomstig van die toetsbank akkuraat en bruikbaar was vir verdere rekenaar manipulasie. Anti-aliaseringsfilters is ontwerp en vervaardig om te verseker dat seine nie verkeerd geïnterpreteer kon word as gevolg van diskritiserings effekte nie. 'n Rekenaar ge-implementeerde voertuigmodel is ontwikkel om 'n voertuig se reaksie op draairnoment ontwikkel deur die enjin op die toetsbank intyds te simuleer. Die model het 'n handrat transmissie, koppelaar en starre dryf-as ingesluit. Bestuurder intree (vernellingspedaal, rem, koppelaar en rat seleksie) is bewerkstellig deur middel van 'n stel pedale en 'n hand geoperateurde rat skakelaar. Verskeie voertuig spoed-beheerders is ondersoek en aanbevelings is gemaak aangaande die toekomstige implementering daarvan. Die sisteem is geëvalueer deur die versnellingsimulasie van 'n groot vragmotor. Die simulasies het daarop gedui dat herhaalbare resultate van die sisteem verkry kon word. Daar is ook bevind dat die sisteem sensitief genoeg was om subtiele veranderinge aan enjinparameters in die resultate te weerspieël. Die gevolgtrekking is gemaak dat die dinamiese enjin toetsbank inderdaad die vermoëns gebied het om ontwikkeling en toetswerk te doen wat nie voorheen in Suid-Afrika moontlik was nie. Voorstelle is laastens gemaak aangaande die toekomstige verbetering en uitbreiding van die sisteem se vermoëns.

In order to study the degree of accuracy with which the analytical methods used in crankshaft design would predict the actual operating stresses in the crankshaft of an internal combustion engine, electrical resistance strain gauges were applied to the accessible parts of the crankshaft of a single-cylinder gasoline engine to sense the actual operating strains. From the recorded strains the operating stresses were determined and were compared to the analytically determined stresses. Oscilloscope and camera were used as the indicating and recording instruments while simplified formulas were used in the calculations. Stresses at various engine speeds and engine loads were determined by both methods and were plotted in curves against engine speeds and crank angles. In the graphical comparisons, the stresses determined by using electrical resistance strain gages agreed well with the stresses obtained analytically. / Master of Science

Orientador: Airton Nabarrete / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T19:07:22Z (GMT). No. of bitstreams: 1 Selim_AndreBaroni_M.pdf: 8247651 bytes, checksum: 306a914d67d3207fb1d8f193b3bf7bd2 (MD5) Previous issue date: 2010 / Resumo: Este trabalho visa estudar a influência do balanceador de massas e das forças de inércia dos componentes internos móveis do motor na dinâmica do motor de combustão interna apoiado sobre amortecedores de vibrações. Para o estudo da influência do balanceador de massas, diversas análises experimentais foram realizadas com um motor em dinamômetro. Chegam-se nas conclusões através da comparação dos deslocamentos medidos do motor com e sem balanceador de massas. Para que a influência das forças de inércia dos componentes internos móveis do motor fosse estudada, um modelo matemático foi criado. Neste modelo consideram-se as forças vindas dos componentes internos móveis atuando em um corpo rígido, neste caso o bloco do motor, apoiado sobre quatro amortecedores de vibrações com seis graus de liberdade. Variam-se dados construtivos como massas e geometria dos componentes internos móveis do motor observando a sua influência sobre o comportamento dinâmico do motor de combustão interna. A validação deste modelo matemático ocorre por meio da comparação de seus resultados com os resultados reais observados nas análises experimentais / Abstract: This work aims at studying the influence of mass balancer and inertia forces coming from engine internal components on internal combustion engine dynamics supported by vibration dampers. For mass balancer study several experimental analyses were performed with a dynamometer. The conclusions are obtained by comparison between measured engine displacements with and without mass balancer. To study the influence of inertia forces from engine internal components, a mathematical model was developed. In this model the inertia forces act on a rigid body, the engine crankcase, supported by four vibration dampers and with six degrees of freedom. Some modifications are made on engine internal components such as mass and geometry observing what is their influence on internal combustion engine dynamics. The mathematical model is validated by comparison against experimental analyses / Mestrado / Dinâmica / Mestre em Engenharia Automobilistica