Peter Raffai

Computer Simulation of the Behavior of the Piston Ring Pack of Internal Combustion Engines

The continuously tightening regulations limiting the amount of exhaust gas components of internal combustion engines force the manufacturers to further increase the effectivity of their power units. Due to the already relatively highly-developed state of engines result in the need of research and development of even smaller engine parts – e.g. piston rings. The main aim of this project was to develop a tool for the computer simulation of the behavior of the piston ring pack, which could aid the optimization process of the piston ring pack towards lowered friction losses.

Advanced Computational Analysis of Connecting Rod of an Aircraft Engine

Development of internal combustion engine’s components is based on the use of advanced computational models in order to compare and verify the individual design proposals. Connecting rod, which performs a general planar motion, is exposed to the gas pressure forces, inertia, contacts, and hydrodynamic pressure during the engine operation cycle. To incorporate all these aspects, Finite Element Method (FEM) is extended by Finite Difference Method (FDM) simulating a slide bearing of connecting rod’s end. It includes different properties of lubricating oil (pressure and temperature dependent viscosity and density) and elastic deformations, so the pressure distribution in an oil film can be evaluated. The computational process concludes with an estimation of the endurance safety factor of the connecting rod. The four-cylinder inverted aircraft engine is used as an example.

The Influence of Rotor Unbalance on Turbocharger Rotor Dynamics

Shrnutí Članek analyzuje vliv nevyvahy na dynamiku rotoru turbodmychadla. Je zde prezentovan 3D vypočtovy model rotoru turbodmychadla a hydrodynamicky model kluzne ložiska. Sestaveni vysledneho vypočtoveho modelu na urovni virtualniho prototypu je provedeno v prostředi software pro řešeni dynamiky těles. Članek prezentuje vybrane vysledky, na kterych je podrobně rozebran vliv velikosti nevyvahy na dynamiku rotoru turbodmychadla. Abstract This paper describes the influence of an unbalance on turbocharger rotor dynamics. The structural model of the turbocharger rotor and the hydrodynamic model of the journal floating ring bearing are described and assembled in multibody dynamics software. Moreover, the paper presents various results describing rotor dynamics where the influence of an unbalance is discussed.

Selection Of Analytical Computational Model Of Contact Pressure

Abstract This paper presents a comparison of two contact pressure calculation methods between two real rough surfaces: a calculation based on FEM (Finite Element Method) using commercial software tool ANSYS and a calculation based on FDM (Finite Difference Method) using analytical functions implemented in programing tool MATLAB. This comparison, lately, leads to the selection of the most appropriate analytical contact model useful for time-effective and precise contact pressure determination. Surface data for numerical simulations are obtained by optical profilometry. For the case of the modelling process of 3D FEM models of rough surfaces the description of their building is included in this article. Furthermore, this paper discusses all challenges connected with the convergence of such simulations and essential post-processing of FEM simulation results, together with their comparison, along the results obtained by user-written MATLAB functions.

Multi Body Analysis Of A Turbocharger Supported By A Fully Floating Ring Bearing

Abstract This paper describes an advanced tool for turbocharger rotor dynamics analysis and its development. The hydrodynamic model of the journal bearing based on Reynolds equation is presented. The paper also describes assembly of the turbocharger rotor model. At the end the basic results are presented and analyzed.

Role Of Computational Simulations In The Design Of Piston Rings

Abstract The paper presents computational approaches using modern strategies for a dynamic piston ring solution as a fluid structural problem. Computational model outputs can be used to understand design parameter influences on defined results of a primarily integral character. Piston ring dynamics incorporates mixed lubrication conditions, the influence of surface roughness on oil film lubrication, the influence of ring movement on gas dynamics, oil film formulation on a cylinder liner and other significant influences. The solution results are presented for several parameters of SI engine piston rings.

Overview of Computational Models Used for Mixed Lubrication

The ability to describe a mixed lubrication regime correctly has higher and higher importance along with the continued downsizing trend. Therefore, this paper deals with the application of different methods for determining the contact pressure in slide bearings, as well as the description of several strategies of 3D rough surfaces computer modelling. Furthermore, in this paper are shown result example of surface roughness generation and analysis results of slide bearing operated under different lubrication regimes.

A conceptual study of a cranktrain with low friction losses

Shrnutí Tento článek popisuje výpočtový přístup pro ověření koncepční studie klikového mechanismu s nízkými třecími ztrátami a analysu jeho vibrací. Snížení třecích ztrát je dosaženo snížením počtu hlavních ložisek klikového hřídele, přičemž se sleduje torsní kmitání řemenice klikového hřídele a zatížení hlavních ložisek. Výpočtový model zahrnuje modálně redukovaná pružná tělesa, hydrodynamická ložiska a je sestaven i numericky řešen v prostředí Multi-Body System. ABSTRACT This article presents computational approaches for verification of a conceptual study of a low-friction-loss cranktrain design and its vibration analysis. A decrease in friction losses is achieved by reduction of the number of crankshaft main bearings whilst the influence of a crankshaft pulley torsional vibration and main bearing loads are investigated. The computational model is assembled and numerically solved in a Multi-Body System into which are incorporated modally reduced bodies, whilst the hydrodynamic aspect is also taken into account.