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2015 | Buch

Turbocharging Concepts Kapitel lesen Erstes Kapitel lesen

Rotordynamics of Automotive Turbochargers

verfasst von: Hung Nguyen-Schäfer

Verlag: Springer International Publishing

Buchreihe : Springer Tracts in Mechanical Engineering

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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SUCHEN

Über dieses Buch

Rotordynamics of automotive turbochargers is dealt with in this book encompassing the widely working field of small turbomachines under real operating conditions at the very high rotor speeds up to 300000 rpm.

The broadly interdisciplinary field of turbocharger rotordynamics involves

1) Thermodynamics and Turbo-Matching of Turbochargers

2) Dynamics of Turbomachinery

3) Stability Analysis of Linear Rotordynamics with the Eigenvalue Theory

4) Stability Analysis of Nonlinear Rotordynamics with the Bifurcation Theory

5) Bearing Dynamics of the Oil Film using the Two-Phase Reynolds Equation

6) Computation of Nonlinear Responses of a Turbocharger Rotor

7) Aero and Vibroacoustics of Turbochargers

8) Shop and Trim Balancing at Two Planes of the Rotor

9) Tribology of the Bearing Surface Roughness

10) Design of Turbocharger Platforms using the Similarity Laws

The rotor response of an automotive turbocharger at high rotor speeds is studied analytically, computationally, and experimentally. Due to the nonlinear characteristics of the oil-film bearings, some nonlinear responses of the rotor besides the harmonic response 1X, such as oil whirl, oil whip, and modulated frequencies occur in Waterfall diagram. Additionally, the influences of the surface roughness and oil characteristics on the rotor behavior, friction, and wear are discussed.

This book is written by an industrial R&D expert with many years of experience in the automotive and turbocharger industries. The all-in-one book of turbochargers is intended for scientific and engineering researchers, practitioners working in the rotordynamics field of automotive turbochargers, and graduate students in applied physics and mechanical engineering.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Turbocharging Concepts
Abstract
The average CO2 emission for new passenger vehicles in the European Union countries (EU) is limited to 120 g/km from 2012 (65 % produced vehicles) to 2015 (100 %). This emission limit is reduced to the target of 95 g/km from 2020 (95 % produced vehicles) and 2021 (100 %). Therefore, turbocharging concepts with downsized engines are one necessary measure to reduce the CO2 emission and to maintain the same engine power at once.
Hung Nguyen-Schäfer
Chapter 2. Thermodynamics of Turbochargers
Abstract
Some essential thermodynamic characteristics of gases are needed to know in the turbocharging. They are usually applied to thermodynamics of turbochargers where the charge air and exhaust gas are assumed to be compressible perfect gases. In this chapter, we take a close look on thermodynamics of turbochargers.
Hung Nguyen-Schäfer
Chapter 3. Vibrations of Turbochargers
Abstract
Exhaust gas turbochargers used in the automobiles, such as passenger vehicles, commercial vehicles and off-road engines, have some discrepancies to the heavy turbomachines applied to the power plants and chemical industries. The automotive turbochargers are much smaller and operate at high rotor speeds in various operating conditions, such as variable rotor speeds, pressures, temperatures, and mass flow rates. Contrary to the automotive turbochargers, industrial turbomachines are larger, heavier, and mostly operate at stationary conditions. They operate mostly between 3000 and 20,000 rpm since the compressor and turbine wheels are very large compared to the turbochargers. Due to their much smaller wheels, the automotive turbochargers could operate at very high rotor speeds from 100,000 to 400,000 rpm.
Hung Nguyen-Schäfer
Chapter 4. Stability Analysis of Rotordynamic Behaviors
Abstract
Two important aspects in rotordynamics of the automotive turbochargers are resonance and instability of the rotor. Both have a common negative effect that causes damage of the turbochargers during operation. However, there is a big difference between the resonance and instability if we take a close look on them in the following section.
Hung Nguyen-Schäfer
Chapter 5. Linear Rotordynamics of Turbochargers
Abstract
We have thoroughly discussed the rotordynamic stability in Chap. 4. In the following section, it deals with the resonance in linear rotordynamics that is also a harmful effect causing damage of the turbochargers.
Hung Nguyen-Schäfer
Chapter 6. Bearing Dynamics of Turbochargers
Abstract
In the following section, the bearing system is dealt with for the automotive turbochargers operating at very high rotor speeds. To support the rotor during operation, the bearing system including the thrust and radial bearings is necessary for turbochargers. On the one hand, the impulse forces of fluids and pressures acting on the compressor and turbine wheels generate the thrust load on the rotor that depends on various operating conditions.
Hung Nguyen-Schäfer
Chapter 7. Nonlinear Rotordynamics of Turbochargers
Abstract
Some uncertain boundary conditions play a key role for the stability and functionality of the rotor, as shown in Fig. 7.1. Unfortunately, it is very difficult or impossible to take all of them into account in the rotordynamic computation where only the rotor containing the compressor, turbine wheels, rotor shaft, radial bearings, and seal rings is considered. The boundary conditions are generally assumed ideal in the computation, such as sufficient supply oil, good parallelism of the thrust bearing, all wedges of the thrust bearing having the same slope, good quality of the radial bearing in terms of the bearing non-coaxiality, surface roundness, and characteristics of surface roughness. Note that the nonlinear rotordynamic responses of the rotor strongly depend on the initial and boundary conditions. For this reason, a little change of these conditions could bring the rotor response from a stable to an unstable state and vice versa. Therefore, the rotordynamic computation cannot exactly predict the instability and malfunctions of the rotor, or prevent it from damage at inappropriate boundary conditions, like oil insufficiency, contaminated oil with hard particles, foamy oil, or oil coking in the bearing during operation. Nevertheless, the computational results help us better understand the rotor response. Further improvements could be done for the rotor stability and reduction of the bearing friction. Additionally, experimental measurements also provide us with the real rotor response at such uncertain boundary conditions that could not be considered in the computation.
Hung Nguyen-Schäfer
Chapter 8. Rotor Balancing in Turbochargers
Abstract
In the following section, we focus only on the rotor balancing in turbochargers and not on industrial turbomachines that can be found in [1, 4, 6, 10].
Hung Nguyen-Schäfer
Chapter 9. Applied Tribology in the Oil-Film Bearings
Abstract
Tribology is derived from the Greek word tribos, which means rubbing. It deals with the tribological phenomena, such as lubrication, friction, and wears in the moving parts. Thus, tribology becomes more and more important in automotive turbochargers in terms of synthetic lubricating oils, friction reduction, adhesion and abrasion friction, and wear reduction in the oil-film bearings including journal and thrust bearings.
Hung Nguyen-Schäfer
Chapter 10. Design of Turbocharger Platforms
Abstract
After learning how to deal with rotordynamics, bearing systems, balancing of turbochargers, and tribology in the bearings, we will learn how to design a platform of automotive turbochargers so that most current and future customer requirements should be covered in the platform. Therefore, we do not need to design a specific turbocharger for each customer requirement. Instead, we just take a suitable CHRA (Center Housing and Rotating Assembly) and insert it into the required housings of compressor and turbine for the customer applications. Additionally, we cut short the development time, time to market, and save money as well.
Hung Nguyen-Schäfer
Backmatter
Metadaten
Titel
Rotordynamics of Automotive Turbochargers
verfasst von
Hung Nguyen-Schäfer
Copyright-Jahr
2015
Electronic ISBN
978-3-319-17644-4
Print ISBN
978-3-319-17643-7
DOI
https://doi.org/10.1007/978-3-319-17644-4

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