Pavel Novotný

Experimental Validation Of The Gearbox NVH Parameters

Abstract The noise, vibration and harshness (NVH) plays an important role in the transmission area of automotive industry. To understand all the impacts on the gearbox’s global dynamic behavior it is necessary to gain information from a simplified model, create methods and get an appropriate and well correlated results with the experiment. The method itself can be afterwards reused for more complex transmission, which could be supported by other measurements. This paper deals with creation of a gearbox’s simplified model, including essential mechanisms as gear mesh stiffness, backlash, bearing stiffness and modal properties of the main components. Except for the presented model, more models with different difficulty levels are used. Numerical results are compared with data from experiment with good correlation.

Crankshaft development of a two-stroke compression-ignition engine with contra-running pistons

SHRNUTI Tento članek se zabyva navrhem, porovnanim různych variant a vyběrem vhodneho řešeni klikovych hřidelů pro dvoudoby vznětovy přeplňovany letecky motor s protiběžnymi pisty a souproudym vyplachovanim. Navrh variant klikovych hřidelů je proveden na zakladě analyzy vyvaženi celeho hnaciho ustroji a zahrnuje v sobě různe kombinace požadavků na pevnost, hmotnost a pravě i vyvaženi. Všechny varianty jsou s využitim postupů MKP a MBS podrobeny dynamickym simulacim pro cele spektrum provoznich otaček a vhodne řešeni je zvoleno na zakladě kriteria minimalizace torsniho kmitani, unavove životnosti časti motoru a zatiženi hlavnich ložisek. ABSTRACT The paper is focused on designing and comparing different options, and then selecting the most suitable crankshaft design for a two -stroke CI engine with contra -running pistons and through -flow scavenging. The crankshaft variants are based on analysis performed with the powertrain balance and include various combinations of requirements for strength, weight and balance. Applying FEM and MBS procedures, all variants undergo dynamic simulations across the whole spectrum of operation speeds. A suitable design is selected with reference to the criteria of minimizing torsional vibrations, fatigue life of individual engine parts, and the main bearing load.

Innovative Model of Radial Fluid Bearing for Simulations of Turbocharger Rotordynamics

The paper describes the principles of an innovative computational model of slide bearing for effective and fast simulations of turbocharger rotordynamics. Theoretical background based on a numerical solution of the Reynolds equation is introduced. The developed simulation tool uses multibody software extended by user-written subroutines and specialized programs developed by authors. The capabilities of the innovative computational models and sample results are demonstrated on a middle size turbocharger rotor supported by fully floating ring bearings.

Dynamic Simulation of Progressive Crank Train

This paper presents computational approaches for verification of conceptual study of low-friction-losses crank train design and its vibration analysis. The decrease of friction losses is realized by reduction of crankshaft main bearings number while the influence of a crankshaft pulley torsional vibration and main bearings load are investigated. The computational model is assembled as well as numerically solved in a Multi-Body System whereas the modally reduced bodies are incorporated into it and hydrodynamic problem is also taken into account.

Improvements in Computational Modelling of Slide Bearings

Shrnutí Zaměrem tohoto članku je představit inovace v oblasti vypočtoveho modelovani kluznych ložisek pohonnych jednotek. Tyto inovace spočivaji, mimo jine, v rozšiřeni modelu o podminky smišeneho mazani. Vstupni data pro detailni vypočty jednotlivych kluznych ložisek jsou poskytovana vypočtovym modelem pohonne jednotky vyšši urovně, tzv. virtualnim motorem. Vysledky těchto vypočtů slouži jako teměř nezbytne informace pro spravny navrh parametrů různych typů kluznych ložisek. Prezentovane metody jsou založeny na novych programovych nastrojich, vyvinutych autory během vyzkumu, a take na komerčně dostupnych aplikacich typu ANSYS nebo ADAMS. Vypočtove modely pohonnych jednotek vyšši urovně zahrnuji pružna tělesa na zakladě redukovanych MKP modelů. Nově vyvinute vysoce specializovane programove nastroje jsou sestaveny v programovacich jazycich Fortran a Matlab. Abstract The intent of this paper is to present new improvements in the modelling of a powertrain slide bearing incorporating mixed lubrication conditions. The Virtual Engine as a model of the powertrain provides input data for detailed calculations of individual slide bearings. The results of these calculations serve as essential information for the correct parameter design of various types of slide bearings. The presented methods are based on new software tools developed by the authors during the research and also on commercial tools such as ANSYS or ADAMS. The computational models of the target powertrains incorporate flexible bodies (based on conversed FE models). The newly developed and highly specialized software tools are written in Fortran and Matlab.

Validation of Analytical Calculation of Contact Pressure

This paper discusses the selection of the most appropriate analytical approach for computational modelling of contact pressure using commercial software tool ANSYS. All the analytical relations, characterizing each computational model useful for detailed determination of the contact pressure between two rough surfaces, are presented here. Furthermore, the process of creation of the FEM model of rough surface along with the description and analysis of all the challenges associated with it are described in this paper. In the conclusion are listed results of simulations together with identification of the chosen analytical approach for fast and also accurate calculations.

Contact Area Evaluation Experiment Verified by Computational Model in MBS

This article focuses on the experimental contact area evaluation. Test rig is designed in order to investigate the piston/cylinder liner contact. The conducted experiment is based on the principle of electrical contact resistivity between two tested machinery parts. The measured results are compared with different contact model theories. The computational simulation uses precomputed database of contact pressure and contact area depending on separation distance of surfaces. This simulation is solved by Multibody System (MBS) enhanced by the user-written FORTRAN subroutine. The results of experiment and simulations are discussed.

Numerical Solution of Micro-Lubrication in Internal Combustion Engine Journal Bearing

This article describes a complex and generally applicable computational model for solving the frictional losses of directionally oriented and non-oriented sliding surfaces working under mixed lubrication regime. In the primary phase of this paper are described ways to get characteristics data describing rough surfaces together with the formula for determination of surface pattern directional dependence. Furthermore, formulae describing used contact model are listed and also the structure of the whole powertrain dynamics solution is briefly explained. In the closing section of this paper are shown and discussed results of several types of slide bearing analysis.

Multibody Based Tool for Simulation of the Turbocharger Rotor Dynamics

The turbocharger is a unique example of the rotating machinery. Not only for its very high speed, but also because of its compact design and difficult operating conditions (i.e. high temperature, harsh vibrations, etc.). Moreover, measuring of most parameters characterizing the rotor dynamics is a very difficult task. Thus, it is advantageous to replace the real turbocharger by computational model and determine the turbocharger rotor dynamics using simulation tool. The development of such tool will be presented in this paper.

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.