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A mechanical analysis of polydicyclopentadiene with metal inserts through flexu...
Camboa, André; Ribeiro, Bernardo Sousa; Nunes, J. P.; Alves, Jorge LinoPolydicyclopentadiene (PDCPD) is being used in several products with particular success regarding to weight reduction and surface finish improvement. Despite the enough good mechanical properties presented by this thermosetting polymer, it needs to be adequately reinforced in applications requiring extra structural stability. This work studies the improvement of mechanical properties that may be achieved in PDC...
Thermodynamic analysis of Spark Ignition engines using the Entropy Generation M...
Martins, Jorge; Ribeiro, Bernardo Sousa; Ion, Ion V.The recent improvement on Spark Ignition Engines has been the result of improved engine thermodynamic cycles, made possible by advances in technologies such as Variable Valve Timing (VVT) and Variable Compression Ratio (VCR). To evaluate the potential of these techniques a thermodynamic analysis is made. Numerical models were implemented in Matlab Simulink using the laws of thermodynamics and include heat trans...
In-cylinder swirl analysis of different strategies on over-expanded cyclies
Martins, Jorge; Ribeiro, Bernardo Sousa; Teixeira, S. F. C. F.Innovative series hybrid vehicles have a small Internal Combustion Engine used as a “range extender”. This engine should work at steady conditions whenever is running. Therefore its development is quite different from engines intended to be driven (unsteady working conditions, such as accelerations). For thıs applicatıon the engine development seeks optimisation on a specified speed/load condition. Previous wor...
Thermodynamic optimisation of spark ignition engines under part load conditions
Ribeiro, Bernardo SousaTese de Doutoramento em Engenharia Mecânica - Máquinas Térmicas e de Fluidos ; The rational use of fossil fuels, the minimisation of noxious emissions and the reduction of green house gases emissions are the targets of internal combustion engines research and development activities. Several technological developments have been proposed to reduce the fuel consumption from engines. The integration of variable va...
Direct comparasion of an engine working under Otto, Miller end Diesel cycles : ...
Ribeiro, Bernardo Sousa; Martins, JorgeOne of the ways to improve thermodynamic efficiency of Spark Ignition engines is by the optimisation of valve timing and lift and compression ratio. The throttleless engine and the Miller cycle engine are proven concepts for efficiency improvements of such engines. This paper reports on an engine with variable valve timing (VVT) and variable compression ratio (VCR) in order to fulfill such an enhancement of eff...
Generation of entropy in spark ignition engines
Ribeiro, Bernardo Sousa; Martins, Jorge; Nunes, AntónioRecent engine development has focused mainly on the improvement of engine efficiency and output emissions. The improvements in efficiency are being made by friction reduction, combustion improvement and thermodynamic cycle modification. New technologies such as Variable Valve Timing (VVT) or Variable Compression Ratio (VCR) are important for the latter. To assess the improvement capability of engine modificatio...
Desenvolvimento do conceito de motor sobre-expandido : análise teórica, numéric...
Martins, Jorge; Ribeiro, Bernardo SousaOs motores de combustão interna de ciclo Diesel têm, convencionalmente, maior rendimento que os motores de ignição comandada. Porém, é possível, com recurso a técnicas de variação de abertura de válvulas e de variação de taxa de compressão, aumentar o rendimento de motores de ignição comandada para valores superiores aos dos motores Diesel. Este trabalho relata o potencial de alteração do vulgar ciclo Otto para...
Miller cycle analysis using EGM
Ribeiro, Bernardo Sousa; Martins, JorgeThe Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to asses...
Thermodynamic analysis of an over-expanded engine
Martins, Jorge; Uzuneanu, Krisztina; Ribeiro, Bernardo Sousa; Jasansky, OndrejWhen the exhaust valve of a conventional spark ignition engine opens at the end of the expansion stroke, a large quantity of high pressure exhaust gas is freed to the atmosphere, without using its availability. An engine that could use this lost energy should have a better efficiency. The equations for an over-expanded cycle (Miller cycle) are developed in this paper, together with equations for the Otto cycle,...
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