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Nagode M.,University of Ljubljana | Langler F.,BorgWarner Turbo Systems Engineering GmbH | Hack M.,LMS Deutschland
International Journal of Fatigue | Year: 2011

The damage operator approach is extended to time dependent viscoplasticity and creep. The oxidation is taken into account indirectly. Time efficient viscoplastic approximation based on the nonlinear Maxwell model and the corresponding lifetime prediction is presented. Both thermo-mechanical fatigue tests on the specimens and the thermal shock tests on turbine housings of a turbocharger subject to a complex change of temperature and strain are conducted for identification and verification purposes. The material is casting material Ni-resist D-5S. The research points out that the mean stress correction and the multiaxial criterion affect the predictive lifetimes significantly. For the turbine housing of a turbocharger the Smith-Watson-Topper mean stress correction, tensile-compressive creep and the critical plane mode I approach is the most suitable parameter combination. The lifetime predictions are convenient. The time consuming elastoviscoplastic finite element analyses can thus often be replaced by the elastoplastic FEA with kinematic hardening even at extreme conditions. © 2010 Elsevier Ltd. All rights reserved.

Nagode M.,University of Ljubljana | Langler F.,BorgWarner Turbo Systems Engineering GmbH | Hack M.,LMS Deutschland
Engineering Failure Analysis | Year: 2011

The turbine housing of a turbocharger is exposed to extensive cyclic thermo-mechanical loading. This leads to a major challenge to design the turbine housing in order to ensure its guaranteed lifetime in relation to the high temperature behaviour of the material. The first step is to develop and validate a damage operator based lifetime calculation approach together with a constitutive material model for application on the casting material Ni-resist D-5S. A satisfactory prediction of the number of cycles until crack initiation by considering fatigue and creep damage is demonstrated on specimens subject to characteristic loading conditions and further on the critical positions of turbine housings, respectively. © 2011 Elsevier Ltd.

Agency: Cordis | Branch: H2020 | Program: IA | Phase: GV-03-2016 | Award Amount: 11.69M | Year: 2016

Mild Hybrid cOst effective solution for a fast Market penetratiON. THOMSON (Mild Hybrid cOst effective solutions for a fast Market penetration) project aims to the development of cost effective solutions, based on 48V architectures, answering the need in reducing the environmental impact of the transportation sector through a clever combination of advanced engines technologies, electrification and wider use of alternative/renewable fuels. The project addresses very precise and consistent objectives to support a quick transition towards high efficient, cleaner and affordable electrified powertrains focusing on the 48V architectures, intended as key element to increase fuel economy and reduce environmental impact and to support a quick penetration on the market of the hybrid powertrains. Approaches developed in the THOMSON project will demonstrate how the right combination of advanced engine downsizing/turbocharging technologies, coupled with a 48V motor-generator system, can provide the most cost effective solution for a rapid electrification through conventional vehicles. The project will provide an exhaustive evaluation of this concept through the development of two different 48V architectures (one integrating the e-machine on the front engine belt drive, the other between the engine and the transmission) on two different engine families: on one side a mid-size 1.6 litre Diesel engine and, on the other one, a small downsized Spark Ignited CNG engine equipped with a Direct Injection system. This twin approach will allow to demonstrate how 48V architecture interacts with Diesel technologies (especially with regard to noxious pollutant reduction) and, on the other side, with Spark Ignited CNG ones, emphasizing the CO2 reduction already achieved through the use of a low carbon fuel such as CNG. Moreover, for both engine families, 48V architecture represent an important enabler to introduce electrically driven auxiliaries and sub-systems leading to a global better man

Chasalevris A.,BorgWarner Turbo Systems Engineering GmbH | Chasalevris A.,Alstom
Journal of Tribology | Year: 2015

The three-lobe bearings widely used in rotating machinery follow the design data evaluated using numerical methods for the solution of the Reynolds equation. This paper defines exact and approximate analytical solutions of the Reynolds equation for the case of three-lobe bearings with finite length. Dynamic characteristics are provided analytically with closed-form expressions for laminar regimes of operation, using an approximate analytical solution that proves to be reliable and of low cost of evaluation time. The results for eccentricity ratio, equilibrium locus, stiffness and damping coefficients are presented for a range of Sommerfeld number and different cases of load orientation and compared with theoretical and experimental data from the literature. Copyright © 2015 by ASME.

Langler F.,BorgWarner Turbo Systems Engineering GmbH | Naumenko K.,Otto Von Guericke University of Magdeburg | Altenbach H.,Otto Von Guericke University of Magdeburg | Ievdokymov M.,Otto Von Guericke University of Magdeburg
Journal of Strain Analysis for Engineering Design | Year: 2014

High-temperature components, for example turbochargers, are often subject to complex thermal and mechanical loading paths. Non-uniform temperature distribution and constraints by neighboring components result in complex timely varying stress and strain states during operation. The aim of this paper is to analyze inelastic behavior of a casting material Ni-resist D-5S in a wide stress, strain rate and temperature ranges. The material model including a constitutive equation for the inelastic strain rate tensor and a non-linear kinematic hardening rule is discussed. To calibrate the model, experimental databases from creep and low cycle fatigue tests are generated. They include creep curves for temperatures within the range 600-800 °C and stress levels from 10 to 150 MPa. The low cycle fatigue data collect a family of hysteresis loops for the strain rate of 10-3 1/s, the strain amplitude from 0.4% to 2% and temperature levels within the range 200-800 °C. For the verification of the model, simulations of the material behavior under uniaxial thermomechanical fatigue loading conditions are performed. The results for the stress response are compared with experimental data. © IMechE 2014.

Gugau M.,BorgWarner Turbo Systems Engineering GmbH | Roclawski H.,University of Kaiserslautern
Journal of Engineering for Gas Turbines and Power | Year: 2014

With emission legislation becoming more stringent within the next years, almost all future internal combustion gasoline engines need to reduce specific fuel consumption, most of them by using turbochargers. Additionally, car manufactures attach high importance to a good drivability, which usually is being quantified as a target torque already available at low engine speeds - reached in transient response operation as fast as possible. These engine requirements result in a challenging turbocharger compressor and turbine design task, since for both not one single operating point needs to be aerodynamically optimized but the components have to provide for the optimum overall compromise for maximum thermodynamic performance. The component design targets are closely related and actually controlled by the matching procedure that fits turbine and compressor to the engine. Inaccuracies in matching a turbine to the engine full load are largely due to the pulsating engine flow characteristic and arise from the necessity of arbitrary turbine map extrapolation toward low turbine blade speed ratios and the deficient estimation of turbine efficiency for low engine speed operating points. This paper addresses the above described standard problems, presenting a methodology that covers almost all aspects of thermodynamic turbine design based on a comparison of radial and mixed-flow turbines. Wheel geometry definition with respect to contrary design objectives is done using computational fluid dynamics (CFD), finite element analysis (FEA), and optimization software. Parametrical turbine models, composed of wheel, volute, and standard piping allow for fast map calculation similar to steady hot gas tests but covering the complete range of engine pulsating mass flow. These extended turbine maps are then used for a particular assessment of turbine power output under unsteady flow admission resulting in an improved steady-state matching quality. Additionally, the effect of various design parameters like either volute sizing or the choice of compressor to turbine diameter ratio on turbine blade speed ratio operating range as well as well as turbine inertia effect is analyzed. Finally, this method enables the designer to comparatively evaluate the ability of a turbine design to accelerate the turbocharger speed for transient engine response while still offering a map characteristic that keeps fuel consumption low at all engine speeds. © 2014 by ASME.

Ryu K.,Hanyang University | Ashton Z.,BorgWarner Turbo Systems Engineering GmbH
Proceedings of the ASME Turbo Expo | Year: 2015

Oil-free turbochargers require gas bearings in compact units of enhanced rotordynamic stability, mechanical efficiency, and improved reliability with reduced maintenance costs compared with oil-lubricated bearings. Implementation of gas bearings into automotive turbochargers requires careful thermal management with accurate measurements verifying model predictions. Foil bearings are customarily used in oil-free microturbomachinery because of their distinct advantages including tolerance to shaft misalignment and centrifugal/ thermal growth, and large damping and load capacity compared with rigid surface gas bearings. Flexure pivot tilting pad bearings are widely used in high performance turbomachinery since they offer little or no cross-coupled stiffnesses with enhanced rotordynamic stability. The paper details the rotordynamic performance and temperature characteristics of two prototype oil-free turbochargers; one supported on foil journal and thrust bearings and the other one is supported on flexure pivot tilting pad journal bearings and foil thrust bearings of identical sizes (OD and ID) with the same aerodynamic components. The tests of the oil-free turbochargers, each consisting of a hollow rotor (~0.4 kg and ~23 mm in outer diameter at the bearing locations), are performed for various imbalances in NVH (i.e, cold air driven rotordynamics rig) and gas stand test facilities up to 130 krpm. No forced cooling air flow streams are supplied to the test bearings and rotor. The measurements demonstrate the stable performance of the rotor-gas bearing systems in an ambient NVH test cell with cold forced air into the turbine inlet. Posttest inspection of the test flexure pivot tilting pad bearings after the hot gas stand tests evidences seizure of the hottest bearing, thereby revealing a notable reduction in bearing clearance as the rotor temperature increases. The compliant flexure pivot tilting pad bearings offer a sound solution for stable rotor support only at an ambient temperature condition while demonstrating less tolerance for shaft growth, centrifugal and thermal, beyond its clearance. The current measurements give confidence in the present gas foil bearing technology for ready application into automotive turbochargers for passenger car and commercial vehicle applications with increased reliability. Copyright © 2015 by ASME.

Koutsovasilis P.,BorgWarner Turbo Systems Engineering GmbH | Beitelschmidt M.,TU Dresden
Mathematical and Computer Modelling of Dynamical Systems | Year: 2010

The finite element (FE) approach constitutes an essential methodology when modelling the elastic properties of structures in various research disciplines such as structural mechanics, engine dynamics and so on. Because of increased accuracy requirements, the FE method results in discretized models, which are described by higher order ordinary differential equations, or, in FE terms, by a large number of degrees of freedom (DoF). In this regard, the application of an additional methodology, referred to as the model order reduction (MOR) or DoF condensation, is rather compulsory. Herein, a reduced dimension set of ordinary differential equations is generated, i.e. the initially large number of DoF is condensed, while aiming to keep the dynamics of the original model as intact as possible. In the commercially available FE software tools, the static and the component mode syntheses (CMS) are the only available integrated condensation methods. The latter represents the state of the art generating well-correlated reduced order models (ROMs), which can be further utilized for FE or multi-body systems simulations. Taking into consideration the information loss of the CMS, which is introduced by its part-static nature, the improved CMS (ICMS) method is proposed. Here the algorithmic scheme of the standard CMS is adopted, which is qualitatively improved by adequately considering the advantageous characteristics of another MOR approach, the so-called improved reduction system method. The ICMS results in better correlated reduced order models in comparison to all the aforementioned methods, while preserving the required structural properties of the original FE model. © 2010 Taylor & Francis.

Koutsovasilis P.,BorgWarner Turbo Systems Engineering GmbH
Multibody System Dynamics | Year: 2013

This survey focuses on the two known model order reduction schemes being widely integrated in various commercial finite element packages, namely, the static and dynamic condensation methods. The advantages as well as the corresponding drawbacks have been extensively analyzed in several papers throughout the last decades. Based on combining the beneficial properties of the aforementioned methods, several alternative reduction methodologies are outlined in this paper, i.e., the generalized improved reduction system method, the generalized component mode synthesis and the improved component mode synthesis with its generalized version, which incorporate in a more efficient way the system's inertia terms. Therefore, the associated error regarding higher frequency ranges of interest is better controlled. Basis of these methodologies is the so-called master and slave degrees of freedom partitioning, the right selection of which highly influences the reduced order model's dynamics. The methods are tested and verified on a rather small three-dimensional bar structure and on the lever part of a turbocharger's variable turbine geometry. Several reduced order models are generated by varying both the number of Craig-Bampton modes and the selection of the required master degrees of freedom. A comparison is conducted based on the modal criterion of the corresponding eigenvectors and the associated computation time required. © 2012 Springer Science+Business Media B.V.

Ryu K.,Hanyang University | Ashton Z.,BorgWarner Turbo Systems Engineering GmbH
Proceedings of the ASME Turbo Expo | Year: 2016

Oil-free bearings for automotive turbochargers (TCs) offer unique advantages eliminating oil-related catastrophic TC failures (oil coking, severe bearing wear/seizure, and significant oil leakage, for example) while increasing overall system reliability and reducing maintenance costs. The main objective of the current investigation is to advance the technology of the gas foil bearings (GFBs) for automotive TCs by demonstrating their reliability, durability, and static/dynamic force characteristics desirable in extreme speed and temperature conditions. The paper compares drag friction and on-engine performances of an oil-free TC supported on GFBs against an oil-lubricated commercial production TC with identical compressor and turbine wheels. Extensive coastdown and fast acceleration TC rotor speed tests are conducted in a cold-Air driven high-speed test cell. Rotor speed coastdown tests demonstrate that the differences in the identified rotational viscous drag coefficients and drag torques between the oil-free and production TCs are quite similar. In addition, rotor acceleration tests show that the acceleration torque of the oilfree TC rotor, when airborne, is larger than the production TC rotor due to the large mass and moment of inertia of the oil-free TC rotor even though air has lower viscosity than the TC lubricant oil. Separate experiments of the oil-free TC installed on a diesel engine demonstrate the reliable dynamic forced performance and superior rotor dynamic stability of the oil-free TC over the oil-lubricated TC. The post on-engine test inspection of the oil-free TC test hardware reveals no evidence of significant surface wear between the rotor and bearings, as well as no dimensional changes in the rotor outer surfaces and bearing top foil inner surfaces. The present experimental characterization and verified robustness of the oil-free TC system continue to extend the GFB knowledge database. © Copyright 2016 by ASME.

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