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Study of Friction Reduction Potential in Light- Duty Diesel Engines by Lightweight Crankshaft Design Coupled with Low Viscosity Oil

General Motors-Salvatore Mafrici
  • Technical Paper
  • 2020-37-0006
To be published on 2020-06-23 by SAE International in United States
Over the last two decades, engine research has been mainly focused on reducing fuel consumption in view of compliance with more stringent homologation cycles and customer expectations. As it is well known, the objective of overall engine efficiency optimization can be achieved only through the improvement of each element of the efficiency chain, of which mechanical constitutes one of the two key pillars (together with thermodynamics). In this framework, the friction reduction for each mechanical subsystem has been one of the most important topics of modern Diesel engine development. The present paper analyzes the crankshaft potential as contributor to the mechanical efficiency improvement, by investigating the synergistic impact of crankshaft design itself and oil viscosity characteristics (including new ultra-low-viscosity formulations already discussed in SAE Paper 2019-24-0056). For this purpose, a combination of theoretical and experimental tools have been used to design an extremely lightweight crankshaft and to evaluate the effects of main and conrod bearings dimensioning, clearances and oil viscosity, considering not only the impact from a friction perspective but also from a structural and…
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Root Cause Analysis and Structural Optimization of E-Drive Transmission

AVL LIST GmbH-Thomas Resch
AVL-AST d.o.o.-Borislav Klarin, Ivan Grozdanovic, Denis Pevec
  • Technical Paper
  • 2020-01-1578
To be published on 2020-06-03 by SAE International in United States
We face a growing demand for so-called eAxles (electric axle drive) in vehicle development. An eAxle is a compact electric drive solution for full electric vehicles (and P4 hybrids) with integrated electric machine and transmission. The transmission can be rather simple using fixed gear with cylindrical gear steps but increasing demands on power and speed range as well as efficiency increase its complexity with planetary stages or switchable gear steps. Such an electro-mechanic system has different behavior than the classical ICE-driven powertrains, for example regarding NVH, where high frequency and tonal noise from gear whining and electro-magnetic excitation is an important comfort issue that needs to be understood and controlled. As knowledge base for such drives is currently low, development needs to be supported by methodologies, which are not only on high predictive level for NVH responses, but also allow a detailed understanding and insight into the causes and reasons of a certain behavior to identify noise effects and to accelerate learning for such systems. In addition, such methods should lead to the possibility to…
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Multi-domain NVH Model for the Complete Electro-mechanical Power Unit

Robert Bosch GmbH-Yashwant kolluru, Rolando Doelling PhD
  • Technical Paper
  • 2020-01-1584
To be published on 2020-06-03 by SAE International in United States
Multi-domain NVH Model for the Complete Electro-mechanical Power Unit Yashwant Kolluru, Rolando Doelling eBike Department Robert Bosch GmbH Kusterdingen, Germany yashwant.kolluru@de.bosch.com rolando.doelling@de.bosch.com Lars Hedrich Institute of Informatics Goethe University Frankfurt Frankfurt, Germany hedrich@em.informatik.uni-frankfurt.de Acoustics and vibrations are amongst the foremost indicators in perceiving the quality of power units. Analyzing these factors is vital to improve the performances of electro-mechanical systems. This paper deals with development of a generic simulation method enabling the multi-domain vibro-acoustic modelling for the drive trains. Excitation's for these systems majorly arise from the electric motor and mechanical gears. The paper initially depicts a flexible gear model for gear whining, which are generated for reasons like gear tooth bending. The forces generated from gear mesh (lumped parameter model) to gear components (multi-body model and nonlinear static model) and the excitations resulting from motor model are coupled for the frequency domain analysis of complete drive train. Additionally, paper discusses the influences of these forces on bearings (dynamic implicit model) and effect of bearing deformations on the harmonics of drive unit. Furthermore, velocities on…
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Analytical Rotordynamic Study of a High-Speed Gear Transmission System for Race Applications

Loughborough Univ-Stephanos Theodossiades, Mahdi Mohammadpour
Loughborough Univ.-Brett Friskney
  • Technical Paper
  • 2020-01-1502
To be published on 2020-06-03 by SAE International in United States
In motorsport power transmission systems, high-speed operation can be associated with significant rotordynamic effects. Changes in the natural frequencies of lateral (bending) vibrational modes as a function of spin speed are brought about by gyroscopic action linked to flexible shafts and mounted gear components. In the investigation of high-speed systems, it is important that these effects are included in the analysis in order to accurately predict the critical speeds encountered due to the action of the gear mesh and other sources of excitation. The rotordynamic behaviour of the system can interact with crucial physical parameters of the transmission, such as the stiffnesses of the gear mesh and rolling element-to-raceway contact in the bearings. In addition, the presence of the gear mesh acts to couple the lateral and torsional vibration modes of a dual-shaft transmission through which a torque flows. The relative interactions and effects of bearing and gear components can be captured in the form of modal analysis with parametric studies of key stiffness elements, such as mean value as a linear representation of stiffness.…
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Numerical Analysis of the Influences of Wear on the Vibrations of Power Units

Robert Bosch GmbH-Yashwant kolluru
  • Technical Paper
  • 2020-01-1506
To be published on 2020-06-03 by SAE International in United States
Numerical Analysis of the Influences of Wear on the Vibrations of Power Units Yashwant Kolluru, Rolando Doelling eBike Department Robert Bosch GmbH Kusterdingen, Germany yashwant.kolluru@de.bosch.com rolando.doelling@de.bosch.com Lars Hedrich Institute of Informatics Goethe University Frankfurt Frankfurt, Germany hedrich@em.informatik.uni-frankfurt.de The prime factor, which influences vibrations of electro-mechanical drives, is wear at the components. This paper discusses the numerical methods developed for abrasion, vibration calculations and the coupling between wear and NVH models of drive unit. Wear is a complex process and understanding it is essential for vibro-acoustics. The paper initially depicts finite element static model used for wear calculations. The special subroutines developed, aids in coupling the wear equations, various contact and friction formulations to the numerical model. The vibration domain model initially, focuses on calculations of mechanical excitation's at the gear shafts, which are generated via a nonlinear dynamic model. Furthermore, the bearings are studied for the influences on its stiffness and eventually its impact on harmonics of the drive trains. Later, free and forced vibrations of the complete drive train are simulated via steady-state dynamic…
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Analytical Prediction of Acoustic Emissions From Turbocharger Bearings

Loughborough Univ-Nader Dolatabadi, Homer Rahnejat
Loughborough Univ.-Ramin Rahmani
  • Technical Paper
  • 2020-01-1504
To be published on 2020-06-03 by SAE International in United States
Turbochargers are progressively used in modern automotive engines to enhance engine performance and reduce energy loss and adverse emissions. Use of turbochargers along with other modern technologies has enabled development of significantly downsized internal combustion engines. However, turbochargers are major sources of acoustic emissions in modern automobiles. Their acoustics has a distinctive signature, originating from fluid-structure interactions. The bearing systems of turbochargers also constitute an important noise source. In this case, the acoustic emissions can mainly be attributed to hydrodynamic pressure fluctuations of the lubricant film. The developed analytical model determines the lubricant pressure distribution in the floating journal bearings used mainly in the modern turbocharges. This allows for an estimation of acoustic emissions. The use of such an analytical approach is computationally efficient when compared with full numerical analysis approaches, whilst also providing reliable predictions. The results from the developed analytical model are used to determine the power loss as well as sound pressure levels generated in the turbocharger bearings due to oil flow which can be correlated with the acoustic emissions of turbochargers.
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Rolling Element Bearings - Advanced Modeling for Multibody Simulations

Ghent University - Soete-Dieter Fauconnier
Siemens DI Software NV-Pavel Jiranek
  • Technical Paper
  • 2020-01-0508
To be published on 2020-04-14 by SAE International in United States
The electrification of vehicles, together with the ever-increasing need for more lightweight and durable designs, is putting the NVH performances of the transmission in the spotlight since the generated noises are not masked by the internal combustion engine. To correctly estimate the performances of the transmission while still in the design-phase, predictive models for the main components of the gearbox are of paramount importance. This paper focuses on the modeling of rolling element bearings, a key component that is responsible of transmitting the vibrations from the gear pairs to the surrounding structure while introducing additional excitation frequencies. The modeling techniques use the relative displacement of the rings to compute the corresponding reaction forces by calculating the equilibrium of each rolling element. To do so, the interaction between the rolling elements and the raceways can be modeled employing two different contact models depending on the level of accuracy required. The contact models are, respectively, a Hertz-Based approach that allows for fast computations, and an EHL (Elasto-Hydrodynamic Lubricated) contact model which accounts for the effects of lubrication.…
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Bearing Fault Diagnosis of the gearbox using blind source separation

Nanjing University of Science & Technology-Hong Zhong, Jingxing Liu, Liangmo Wang, Yang Ding, Yahui Qian
  • Technical Paper
  • 2020-01-0436
To be published on 2020-04-14 by SAE International in United States
Gearbox fault diagnosis is one of the core research areas in the field of rotating machinery condition monitoring. The signal processing-based bearing fault diagnosis in the gearbox is considered as challenging as the vibration signals collected from acceleration transducers are, in general, a mixture of signals originating from an unknown number of sources, i.e. an underdetermined blind source separation (UBSS) problem. In this study, an effective UBSS-based algorithm solution, that combines empirical mode decomposition (EMD) and kernel independent component analysis (KICA) method, is proposed to address the technical challenge. Firstly, the nonlinear mixture signals are decomposed into a set of intrinsic mode function components (IMFs) by the EMD method, which can be combined with the original observed signals to reconstruct new observed signals. Thus, the original problem can be effectively transformed into an over-determined BSS problem. Then, the whitening process is carried out to convert the over-determined BSS into determined BSS, which can be solved by the KICA method. Finally, the ant lion optimization (ALO) is adopted to further enhance the performance of the EMD-KICA…
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Test Bench for Static Transmission Error Evaluation in Gears

Politecnico di Torino-Carlo Rosso
Politecnico di Torino / GeDy TrAss-Tommaso Maggi, Claudio Marcellini, Fabio Bruzzone
  • Technical Paper
  • 2020-01-1324
To be published on 2020-04-14 by SAE International in United States
In this paper a test bench for measuring the Static Transmission Error of two mating gears is presented and a comparison with the results obtained with the code GeDy TrAss and a commercial Finite Element software are shown. Static Transmission Error is considered as the main source of overloads and Noise, Vibration and Harshness issues in mechanical transmissions. It is defined as the difference between the theoretical angular position of a gear under load in quasi-static conditions and the real one. This parameter strictly depends on the applied torque and the tooth macro and micro-geometry. The test bench illustrated in this work is designed to evaluate the actual Static Transmission Error of two gears under load in quasi-static conditions. In particular this testbed can be divided in two macro elements: the first one is the mechanism composed by weights and pulleys that generates a driving and a breaking torque up to 500 Nm. The second element is composed by two structures called “support”: one fixed to the floor and the other movable in order to…
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Vibration and Dynamic Analysis of Right-angle Geared Drives Considering the Influence of Gear-Shaft-Bearing Assembly Design

Marshall University-Xia Hua
  • Technical Paper
  • 2020-01-0415
To be published on 2020-04-14 by SAE International in United States
Dynamics of hypoid or spiral bevel gears like most high-speed precision gears employed in the powertrains of automobiles, commercial trucks, and off highway vehicles are significantly influenced by the design of the shafts and bearings. The finite element modeling approach is one of the useful methodologies applied to perform gear dynamic analysis. One of the major advantages of the finite element modeling approach is that it is able to account for the gear-shaft-bearing assembly design more accurately than other modeling approaches, for example, the lumped parameter modeling approach. In this paper, the finite element formulation, which can generally represent more complete characteristics of the gear-shaft-bearing assembly design, is employed to investigate how the key design changes of gear-shaft-bearing assembly influence the dynamics of spiral bevel gears. Accordingly, the underlying physics controlling these effects is also uncovered.