The Experts below are selected from a list of 900 Experts worldwide ranked by ideXlab platform
Marilia G. Justino Vaz - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the system behaviour of a variable compression ratio (VCR) connecting rod with eccentrically Piston Pin suspension and hydraulic moment support
Energy Conversion and Management, 2020Co-Authors: Karsten Wittek, Frank Geiger, Marilia G. Justino VazAbstract:Abstract Making the geometrical compression ratio an adjustable parameter is considered the last remaining significant technological step in combustion engine design. Numerous prototype engines with variable compression ratio (VCR) were designed and tested. The implementation of VCR technology increases the averaged energy conversion efficiency in stoichiometric spark ignition (SI) engines ranging from 3 to 8% depending on the driving cycle, the fuel and the degree of turbo charging. The approach of a connecting rod with an adjustable length, a so called VCR connecting rod, is considered a promising solution because it can be implemented in almost every reciprocating engine regardless the type (inline, V or boxer engine) with a minimum of changes on existing engine layout. One design approach for a VCR connecting rod consists on an eccentrically Piston Pin suspension in combination with two hydraulic cylinders keePing the eccentric in a desired angular position. A change in compression ratio (CR) is initiated by means of actuating a hydraulic switch valve on the VCR connecting rod. The gas and mass forces acting on the Piston Pin result into a moment acting on the eccentric. In order to optimize the design of a VCR connecting rod with respect to robustness, weight and manufacturing costs, the dynamic behaviour and any arising phenomena must be known and understood. The aim of this work was to investigate this dynamic behaviour by means of fired engine testing. For this purpose, a VCR connecting rod was instrumented with sensors and the measured data was acquired synchronously to the crank angle. During these tests, operational parameters such as engine speed and load and the oil feed stream conditions were assessed for the two compression ratios stages and during the transitions from one to another compression ratio.
Karsten Wittek - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the system behaviour of a variable compression ratio (VCR) connecting rod with eccentrically Piston Pin suspension and hydraulic moment support
Energy Conversion and Management, 2020Co-Authors: Karsten Wittek, Frank Geiger, Marilia G. Justino VazAbstract:Abstract Making the geometrical compression ratio an adjustable parameter is considered the last remaining significant technological step in combustion engine design. Numerous prototype engines with variable compression ratio (VCR) were designed and tested. The implementation of VCR technology increases the averaged energy conversion efficiency in stoichiometric spark ignition (SI) engines ranging from 3 to 8% depending on the driving cycle, the fuel and the degree of turbo charging. The approach of a connecting rod with an adjustable length, a so called VCR connecting rod, is considered a promising solution because it can be implemented in almost every reciprocating engine regardless the type (inline, V or boxer engine) with a minimum of changes on existing engine layout. One design approach for a VCR connecting rod consists on an eccentrically Piston Pin suspension in combination with two hydraulic cylinders keePing the eccentric in a desired angular position. A change in compression ratio (CR) is initiated by means of actuating a hydraulic switch valve on the VCR connecting rod. The gas and mass forces acting on the Piston Pin result into a moment acting on the eccentric. In order to optimize the design of a VCR connecting rod with respect to robustness, weight and manufacturing costs, the dynamic behaviour and any arising phenomena must be known and understood. The aim of this work was to investigate this dynamic behaviour by means of fired engine testing. For this purpose, a VCR connecting rod was instrumented with sensors and the measured data was acquired synchronously to the crank angle. During these tests, operational parameters such as engine speed and load and the oil feed stream conditions were assessed for the two compression ratios stages and during the transitions from one to another compression ratio.
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Two-stage Variable Compression Ratio with Eccentric Piston Pin
MTZ worldwide, 2009Co-Authors: Stefan Pischinger, Karsten Wittek, Christof TiemannAbstract:By variation of the compression ratio the fuel consumption of high boosted gasoline engines can be reduced. The two-stage VCR system (variable compression ratio) enables a high share of fuel saving potential relative to full variable systems. FEV has evaluated different known and new two-stage VCR systems. Considering a low cost manufacturability and a beneficial integratability into common engine architectures the length-adjustable conrod using an eccentric Piston Pin in the small eye has proved as a favorable concept. The adjustment is performed by a combination of gas and mass forces.
Frank Geiger - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the system behaviour of a variable compression ratio (VCR) connecting rod with eccentrically Piston Pin suspension and hydraulic moment support
Energy Conversion and Management, 2020Co-Authors: Karsten Wittek, Frank Geiger, Marilia G. Justino VazAbstract:Abstract Making the geometrical compression ratio an adjustable parameter is considered the last remaining significant technological step in combustion engine design. Numerous prototype engines with variable compression ratio (VCR) were designed and tested. The implementation of VCR technology increases the averaged energy conversion efficiency in stoichiometric spark ignition (SI) engines ranging from 3 to 8% depending on the driving cycle, the fuel and the degree of turbo charging. The approach of a connecting rod with an adjustable length, a so called VCR connecting rod, is considered a promising solution because it can be implemented in almost every reciprocating engine regardless the type (inline, V or boxer engine) with a minimum of changes on existing engine layout. One design approach for a VCR connecting rod consists on an eccentrically Piston Pin suspension in combination with two hydraulic cylinders keePing the eccentric in a desired angular position. A change in compression ratio (CR) is initiated by means of actuating a hydraulic switch valve on the VCR connecting rod. The gas and mass forces acting on the Piston Pin result into a moment acting on the eccentric. In order to optimize the design of a VCR connecting rod with respect to robustness, weight and manufacturing costs, the dynamic behaviour and any arising phenomena must be known and understood. The aim of this work was to investigate this dynamic behaviour by means of fired engine testing. For this purpose, a VCR connecting rod was instrumented with sensors and the measured data was acquired synchronously to the crank angle. During these tests, operational parameters such as engine speed and load and the oil feed stream conditions were assessed for the two compression ratios stages and during the transitions from one to another compression ratio.
Dini Daniele - One of the best experts on this subject based on the ideXlab platform.
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Experimental Measurement of Roughness Data and Evaluation of Greenwood/Tripp Parameters for the Elastohydrodynamic Analysis of a Conrod Small-End/Piston Pin Coupling
'SAE International', 2020Co-Authors: Ferretti Andrea, Giacopini Matteo, Dini Daniele, Fantoni StefanoAbstract:For the investigation of the tribological behavior of lubricated contacts, the choice and the calibration of the adopted asperity contact model is fundamental, in order to properly mimic the mixed lubrication conditions. The Greenwood/Tripp model is extensively adopted by the commercial software commonly employed to simulate lubricated contacts. This model, based on a statistic evaluation of the number of asperities in contact and on the Hertzian contact theory, has the advantage of introducing a simple relationship between oil film thickness and asperity contact pressure, considerably reducing the simulation time. However, in order to calibrate the model, some non-standard roughness parameters are required, that are not available from commercial roughness measuring equipment. Standard values, based on some limited experiences, are typically used, and a limited literature can be found focusing on how to evaluate them, thus reducing the predictivity of the model. In this contribution, the roughness profile of the surfaces of the conrod small-end and the Piston Pin of a high performance motorbike engine are measured, adopting an optical measurement equipment. An algorithm is developed in order to properly evaluate the Greenwood/Tripp non-standard roughness parameters and set an elastohydrodynamic analysis of the lubricated coupling. A complementarity form of the Reynolds equation capable of handling the cavitation problem is coupled with both Greenwood/Tripp theory and with an alternative complementarity formulation of the asperity contact problem. The results obtained adopting the two different models are critically discussed, comparing them with empirical evidences provided by small-end/Piston Pin coupling failures, occurred in a severe running condition test at an early stage of the design process of the engine
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Investigation of the Influence of Different Asperity Contact Models on the Elastohydrodynamic Analysis of a Conrod Small-End/Piston Pin Coupling
'SAE International', 2018Co-Authors: Ferretti Andrea, Giacopini Matteo, Mastrandrea Luca, Dini DanieleAbstract:Bearings represent one of the main responsible of friction losses in internal combustion engines and their lubrication performance has a crucial influence on the operating condition of the engine. In particular, the conrod small-end bearing is one of the most critical engine parts from a tribological point of view since limited contact surfaces have to sustain high inertial and combustion forces. In this contribution an analysis is performed of the tribological behaviour of the lubricated contact between the Piston Pin and the conrod small-end of a high performance motorbike engine. An algorithm is employed based on a complementarity formulation of the cavitation problem. A comparison between two different approaches to simulate the asperity contact problem is performed, the former based on the standard Greenwood-Tripp theory and the latter based on a complementarity formulation of the asperity contact problem. A model validation is performed by comparing the results with those obtained adopting the commercial software AVL Excite Power Unit. Similar results are obtained from both the approaches, if a proper calibration of the model input data is performed. However, a remarkable sensitivity is highlighted of the results obtained using the Greenwood/Tripp model to the adjustment parameters. The realistic (engineering) difficulty in defining and identifying the roughness data and their purely statistical nature returns results that may be afflicted by a dose of uncertainty. Considering that results of such simulations usually offer guidelines for a correct design of the coupling, further investigations are suggested to identify a relationship between simply available roughness data and model input, starting from a direct experimental measurements of real roughness profiles
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Investigation of the Influence of Different Asperity Contact Models on the Elastohydrodynamic Analysis of a Conrod Small-End/Piston Pin Coupling
'SAE International', 2018Co-Authors: Ferretti Andrea, Giacopini Matteo, Mastrandrea Luca, Dini DanieleAbstract:Bearings represent one of the main responsible of friction losses in internal combustion engines and their lubrication performance has a crucial influence on the operating condition of the engine. In particular, the conrod small-end bearing is one of the most critical engine parts from a tribological point of view since limited contact surfaces have to sustain high inertial and combustion forces. In this contribution an analysis is performed of the tribological behaviour of the lubricated contact between the Piston Pin and the conrod small-end of a high performance motorbike engine. An algorithm is employed based on a complementarity formulation of the cavitation problem. A comparison between two different approaches to simulate the asperity contact problem is performed, the former based on the standard Greenwood-Tripp theory and the latter based on a complementarity formulation of the asperity contact problem. A model validation is performed by comparing the results with those obtained adopting the commercial software AVL Excite Power Unit. Similar results are obtained from both the approaches, if a proper calibration of the model input data is performed. However, a remarkable sensitivity is highlighted of the results obtained using the Greenwood/Tripp model to the adjustment parameters. The realistic (engineering) difficulty in defining and identifying the roughness data and their purely statistical nature returns results that may be afflicted by a dose of uncertainty. Considering that results of such simulations usually offer guidelines for a correct design of the coupling, further investigations are suggested to identify a relationship between simply available roughness data and model input, starting from a direct experimental measurements of real roughness profiles.Bearings represent one of the main responsible of friction losses in internal combustion engines and their lubrication performance has a crucial influence on the operating condition of the engine. In particular, the conrod small-end bearing is one of the most critical engine parts from a tribological point of view since limited contact surfaces have to sustain high inertial and combustion forces. In this contribution an analysis is performed of the tribological behaviour of the lubricated contact between the Piston Pin and the conrod small-end of a high performance motorbike engine. An algorithm is employed based on a complementarity formulation of the cavitation problem. A comparison between two different approaches to simulate the asperity contact problem is performed, the former based on the standard Greenwood-Tripp theory and the latter based on a complementarity formulation of the asperity contact problem. A model validation is performed by comparing the results with those obtained adopting the commercial software AVL Excite Power Unit. Similar results are obtained from both the approaches, if a proper calibration of the model input data is performed. However, a remarkable sensitivity is highlighted of the results obtained using the Greenwood/Tripp model to the adjustment parameters. The realistic (engineering) difficulty in defining and identifying the roughness data and their purely statistical nature returns results that may be afflicted by a dose of uncertainty. Considering that results of such simulations usually offer guidelines for a correct design of the coupling, further investigations are suggested to identify a relationship between simply available roughness data and model input, starting from a direct experimental measurements of real roughness profiles.Bearings represent one of the main causes of friction losses in internal combustion engines, and their lubrication performance has a crucial influence on the operating condition of the engine. In particular, the conrod small-end bearing is one of the most critical engine parts from a tribological point of view since limited contact surfaces have to support high inertial and combustion forces. In this contribution an analysis is performed of the tribological behavior of the lubricated contact between the Piston Pin and the conrod small-end of a high performance motorbike engine. A mass-conserving algorithm is employed to solve the Reynolds equation based on a complementarity formulation of the cavitation problem. The analysis of the asperity contact problem is addressed in detail. A comparison between two different approaches is presented, the former based on the standard Greenwood/Tripp theory and the latter based on a complementarity formulation of the asperity contact problem. Differently from the Greenwood/Tripp method, the complementarity formulation needs only one parameter related to the roughness of the mating surfaces to be set and allows a solution to be obtained without the need of an iterative procedure thus avoiding convergence issues. Similar results are obtained comparing both the approaches used to solve the asperity contact problem. However, such an agreement is only reached after an appropriate calibration of the model input data is performed; a remarkable sensitivity of the results obtained using the Greenwood/Tripp model to the adjustment parameters is found and highlighted. Finally, a full model validation is performed by comparing the results obtained adopting the proposed algorithm, using the implementation of the Greenwood/Tripp asperity contact model, with those obtained adopting the commercial software AVL Excite Power Unit
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Elastohydrodynamic analysis of the conrod small-end of a high performance motorbike engine via a mass conserving cavitation algorithm
'ASME International', 2015Co-Authors: Mastrandrea, Luca Nicolo', Giacopini Matteo, Dini Daniele, Bertocchi EnricoAbstract:In this contribution a complementarity formulation for the solution of EHL problem in presence of cavitation is employed in order to investigate the tribological behavior of the conrod small-end of a high performance motorbike engine. The influence of different physical and geometrical parameters is discussed. In particular, the clearance between the conrod small-end and the Piston Pin, the lubricant physical properties, the surface roughness and the stiffness of the Piston Pin are investigated, thus providing preliminary guidelines for the correct design of the coupling. Due to the negligible influence of the transversal forces acting on the conrod small-end and of the relative sliding speed between the mating surfaces, a two symmetrical model of the assembly is prepared and results are compared with those obtained adopting a simply symmetrical model
Vitor Luiz Reis - One of the best experts on this subject based on the ideXlab platform.
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Slider-crank mechanism modelling with clearance at Piston-Pin revolute joint
2017Co-Authors: Vitor Luiz ReisAbstract:Resumo: Este trabalho apresenta o desenvolvimento de um modelo dinâmico para o mecanismo biela-manivela com folga na junta de revolução Pino-pistão. As equações do movimento para este sistema são obtidas através do método de Lagrange e os efeitos relacionados ao contato, atrito e lubrificação que atuam nos elementos com folga são alvo de estudo. O modelo da força de contato utilizado baseia-se na formulação de Hertz, considerando a inclusão do efeito dissipativo associado ao impacto entre o Pino e o pistão. A força de atrito adotada baseia-se no atrito de Coulomb, porém adaptada à abordagem da dinâmica multicorpos. Tais modelos são validados com os resultados encontrados na literatura recente. A pesquisa apresenta contribuição na avaliação do efeito introduzido pela lubrificação hidrodinâmica na junta com folga. Dois modelos de lubrificação hidrodinâmica são avaliados: o primeiro apresenta uma solução direta e de baixo custo computacional; o segundo modelo obtém uma solução numérica que leva em consideração o efeito da aceleração imposta ao fluido lubrificante pelo movimento do mecanismo. A resposta dinâmica é obtida sob a variação paramétrica do tamanho da folga e a velocidade de rotação da manivela. Ao final, agrega-se ao sistema um modelo simplificado de geração da curva de pressão para um motor de combustão interna típico. Observou-se que a inclusão do modelo de lubrificação proposto não garante a sustentação do Pino-pistão em regime de lubrificação hidrodinâmica durante as simulações efetuadas. Desta maneira, faz-se necessário o desenvolvimento de um modelo de lubrificação hidrodinâmica e elastohidrodinâmica capaz de determinar o comportamento no contato Pino-pistão de maneira mais realista.Abstract: This work presents the development of a dynamic model for the slider-crank mechanism with clearance on the Piston-Pin revolute joint. The equations of motion for this system are obtained by Lagrange's method and the effects related to contact, friction and lubrication at the elements that operate in the clearance are the targets of study. The contact force model used in this work is based on Hertz formulation, considering the inclusion of the dissipative effect associated with the impact between the Pin and the Piston. The frictional force adopted is based on the Coulomb friction but adapted to the multibody dynamics approach. Such models are validated with the results found in recent literature. The research presents contribution in evaluating the effect introduced by hydrodynamic lubrication in the revolute joint clearance. Two models of hydrodynamic lubrication are investigated: the first model presents a direct solution of low computational cost, the second model results in a numerical solution that consider the effect of the acceleration of the lubricant fluid imposed on the movement of the mechanism. The dynamic response is studied for different sets of parameters of clearance and rotational speed of the crank. Moreover, a simplified model of the generation of the pressure curve for a typical internal combustion engine was included in the system. It was observed that the present lubrication model does not guarantee the support of the Pin-Piston system for hydrodynamic lubrication in the present simulations. Therefore, it is necessary to develop a more realistic model of hydrodynamic lubrication and elastohydrodynamic lubrication that is capable of reproducing the behavior of the Piston-Pin contact
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dynamic analysis of a lubricated planar slider crank mechanism considering friction and hertz contact effects
Mechanism and Machine Theory, 2014Co-Authors: Vitor Luiz Reis, Gregory Bregion Daniel, Katia Lucchesi CavalcaAbstract:Abstract This paper presents the development of a dynamic model for the slider–crank mechanism with clearance on the Piston–Pin revolute joint. The equations of motion for this system are obtained by Lagrange's method and the effects related to contact, friction and lubrication at the elements that operate in the clearance are the targets of study. The contact force model used in this work is based on Hertz formulation, considering the inclusion of the dissipative effect associated with the impact between the Pin and the Piston. The frictional force adopted is based on the Coulomb friction but adapted to the multibody dynamics approach. Such models are verified with the results found in recent literature. The research presents contribution in evaluating the effect introduced by hydrodynamic lubrication in the revolute joint clearance. Two models of hydrodynamic lubrication are investigated: the first model presents a direct solution of low computational cost, the second model results in a numerical solution that consider the effect of the acceleration of the lubricant fluid imposed on the movement of the mechanism. It was observed that the second lubrication model does not guarantee the support of the Piston–Pin system for hydrodynamic lubrication in the simulated interval of time. Therefore, it is necessary to develop a more realistic model of hydrodynamic and elastohydrodynamic lubrication that is capable of reproducing the behavior of the Piston–Pin contact.
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Dynamic analysis of a lubricated planar slider–crank mechanism considering friction and Hertz contact effects
Mechanism and Machine Theory, 2014Co-Authors: Vitor Luiz Reis, Gregory Bregion Daniel, Katia Lucchesi CavalcaAbstract:Abstract This paper presents the development of a dynamic model for the slider–crank mechanism with clearance on the Piston–Pin revolute joint. The equations of motion for this system are obtained by Lagrange's method and the effects related to contact, friction and lubrication at the elements that operate in the clearance are the targets of study. The contact force model used in this work is based on Hertz formulation, considering the inclusion of the dissipative effect associated with the impact between the Pin and the Piston. The frictional force adopted is based on the Coulomb friction but adapted to the multibody dynamics approach. Such models are verified with the results found in recent literature. The research presents contribution in evaluating the effect introduced by hydrodynamic lubrication in the revolute joint clearance. Two models of hydrodynamic lubrication are investigated: the first model presents a direct solution of low computational cost, the second model results in a numerical solution that consider the effect of the acceleration of the lubricant fluid imposed on the movement of the mechanism. It was observed that the second lubrication model does not guarantee the support of the Piston–Pin system for hydrodynamic lubrication in the simulated interval of time. Therefore, it is necessary to develop a more realistic model of hydrodynamic and elastohydrodynamic lubrication that is capable of reproducing the behavior of the Piston–Pin contact.