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Technical Paper

A Generic Testbody for Low-Frequency Aeroacoustic Buffeting

2020-09-30
2020-01-1515
Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises due to structural transmission of aerodynamic wall pressure fluctuations and/or, as indicated in this work, through rear vent excitation. A possible workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from a CFD simulation. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility.
Technical Paper

Advanced CAE Methods for NVH Development of High Speed Electric Axle

2020-09-30
2020-01-1501
The rate in the electrification of vehicles has risen in recent years. With intensified development more and more attention is paid to the noise and vibration in such vehicles especially from the EDU (Electric Drive Unit). In this paper the main NVH simulation process of a high-speed E-axle up to 30,000 rpm for premium class vehicle application is presented. The high speed, high-power density and lightweight design introduces new challenges. Benchmarking of different EDUs and vehicles leads to targets which can be used at the early stage of development as subsystem targets. This paper shows the CAE methodology which can be used to verify the design and guarantee the target achievement. Using CAE both source and structure can be optimized to improve the NVH behavior.
Technical Paper

Numerical Analysis of the Influences of Wear on the Vibrations of Power Units

2020-09-30
2020-01-1506
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.
Technical Paper

Analytical Prediction of Acoustic Emissions From Turbocharger Bearings

2020-09-30
2020-01-1504
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.
Technical Paper

Analytical Rotordynamic Study of a High-Speed Gear Transmission System for Race Applications

2020-09-30
2020-01-1502
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.
Technical Paper

A Diagnostic Technology of Powertrain Parts that Cause Abnormal Noises using Artificial Intelligence

2020-09-30
2020-01-1565
In general, when a problem occurs in a component, various phenomena appear, and abnormal noise is one of them. The service technicians diagnose the noise through the analysis using hearing and equipment. Depending on their experiences, the analysis time and diagnosis accuracy vary widely. The newly developed AI-based diagnostic technology diagnoses parts that cause abnormal noises within seconds when a noise is input to the equipment. To create a learning model for diagnosis, we collected as many abnormal noises as possible from various parts, and selected good and bad data. This process is very important in the development of diagnostic techniques. Artificial intelligence was learned by deep learning with selected good data. This paper is about the technology that can diagnose the abnormal noises generated from the engine, transmission, drivetrain and PE (Power Electric) parts of the eco-friendly vehicle through the diagnosis model composed of various methods of deep learning.
Technical Paper

Experimental Rattle Source Characterization Using Matrix Inversion on a Reception Plate

2020-09-30
2020-01-1541
Minimising rattle noises is becoming increasingly important for hybrid and electrical vehicles as masking from the IC engine is missing and in view of the functional requirements of the office-like interiors of next generation automated vehicles. Rattle shall therefore be considered in the design phase of component systems. One hurdle is the modelling of the excitation mechanisms and its experimental validation. In this work we focus on excitation by loose parts having functional clearances such as gear systems or ball sensors in safety belt retractors. These parts are excited by relatively large low frequency displacements such as road-induced movements of the car body or low order rigid body engine vibrations generating multiple impacts with broad band frequency content. Direct measurement of the impact forces is in many cases not possible.
Technical Paper

Root Cause Analysis and Structural Optimization of E-Drive Transmission

2020-09-30
2020-01-1578
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.
Technical Paper

Multi-Domain NVH Model for the Complete Electro-Mechanical Power Unit

2020-09-30
2020-01-1584
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.
Technical Paper

Determination of energy-saving potentials by reducing the rolling bearing friction in the tractor drive train

2020-09-27
2020-24-0024
Increased efficiency and emission reduction have, in recent years, introduced several changes in the architecture of agricultural tractors transmissions. As one of the leading rolling bearing manufacturers for this industry, Schaeffler has explored energy saving potentials related to rolling bearings friction reduction. Starting point of the activity is the actual status of the design of tractor transmission manufactured by one of the key players in the sector.
Technical Paper

Modelling and Numerical Simulation of the Noise Generated by Automotive Turbocharger Compressor

2020-09-30
2020-01-1512
An effective technology to reduce emission and fuel-consumption is the use of turbochargers. A turbocharger increases the air pressure at the inlet manifold of the engine by using the waste energy from the exhaust gas to drive a turbine wheel that is linked to the compressor through a shaft. Besides the use in combustion engines, fuel cell systems for vehicle applications also need compressed air to achieve high power densities. Thereby, in fuel cell systems the noise emission of turbochargers is no longer masked by the combustion engine. In operation, the main noise sources are generated by the flow in the compressor and the different noise phenomena need to be understood in order to efficiently reduce the emitted noise and increase comfort. A huge potential in order to achieve this goal is a simulation based investigation to study in detail the flow mechanism, the aeroacoustic sources and its sound propagation.
Technical Paper

High-Speed High-Efficiency Engines

1928-01-01
280039
MARKED improvement in high-speed high-efficiency engines will be accomplished during the next few years, according to the author. They will have better balance, longer life and greater efficiency, and will develop more power and be more satisfactory to the motoring public. Details of recent developments in this class of engine are given by the author after remarking that the present trend is toward a large number of small changes in design and construction rather than toward radical departures from former design and methods. Mr. Duesenberg comments upon the main features of design of his 91-cu. in. racing-car engine and its parts, and on the troubles that necessitated design changes. The combustion-chamber is stated to be the most important contributor to high efficiency. If the shape of the combustion-chamber, the area of the valves, and the location of the valves and spark-plugs are not right, all the other refinements of detail are of little value.
Technical Paper

The Application of Superchargers to Automotive Vehicles

1928-01-01
280040
MOST passenger automobiles are overpowered and probably 80 per cent of such vehicles operate at less than 35 m.p.h. for 90 per cent of the time, according to the author. At 30 m.p.h. an average 3000 to 3500-lb. passenger-car requires from 12 to 15 hp., but the engine carried is capable of developing from 50 to 55 hp. The result is that the car is operated for the greater part of the time at one-third to one-quarter throttle opening. Full power is needed only for accelerating and hill-climbing; during the remainder of the time the excess weight of the engine and other parts must be carried at a loss of efficiency. The author maintains that smaller engines can be used advantageously when equipped with superchargers, the supercharger being used only when excess power is required.
Technical Paper

The Packard X 24-Cylinder 1500-Hp. Water-Cooled Aircraft Engine

1928-01-01
280064
AFTER outlining the history of development of the Packard X engine, the author states the legitimate position in aviation deserved by the water-cooled aviation-engine of this type and predicts large increases in the size, speed and carrying capacity of airplanes within the near future. Passing then to a discussion of the important features of the X-type engine, various illustrations of its parts are commented upon. The cylinders are built-up from steel forgings, with all welds arranged so as to be subjected to no excessive alternating stresses. The novel features of this cylinder design lie in the fact that the valve seats are entirely surrounded by water and that water space is provided above the combustion-chamber and below the top plate of the cylinder. The cylinder-head is extremely rigid, resisting deflection and assuring the maximum integrity of valve seats. The valve ports are machined integrally with the cylinder-head and are not welded thereto as in the Liberty engine.
Technical Paper

How the Ford Company Gets Low Production Costs

1928-01-01
280063
ECONOMIC factors applying to mass production are dealt with in an endeavor to show how, by following certain laws of manufacturing management based on economic laws, the Ford Motor Co. has attained its very low production costs. Some of these laws, which were put into concrete form as recently as 1926 by L. P. Alford, are quoted, and examples of methods are given to show how they operate.
Technical Paper

Simultaneous Inspection and Correction of Gears in Production

1928-01-01
280062
BY means of the gear-correcting process described, spur and helical gears are corrected to give a high degree of uniformity in spacing and profile so that the gears become practically interchangeable. They acquire a “crown face” which enables them to run with unusual quietness under practical conditions. This is essentially an inspection-correction process, as it automatically finds and eliminates the errors. The lap is the important item in the process. It is of chilled cast-iron, gray cast-iron, or type metal, and is made by casting in a mold around a steel chill cut to approximate the gear to be corrected but has a face-width several times that of the gear. The lap, when completed, looks like a wide-faced internal gear.
Technical Paper

Ground Gears and Transmission Design

1928-01-01
280061
GROUND teeth for transmission gears are advocated because they can be made to the same degree of accuracy as the other fine working-parts of a motor-car. The designing engineer is held responsible for conditions unfavorable to the adoption of gear grinding by the production department. Mr. Orcutt believes that cluster gears should be avoided because it is impossible to finish them accurately. Fundamental principles of rigid shafts and correct bearing arrangements are laid down, and the degree of accuracy is specified for the fitting parts. Transmission-case design still needs development and study to avoid resonance. Designs are recommended that will provide ample center distance to avoid pinions with a small number of teeth. The unmodified involute is recommended as the most satisfactory form of tooth. Spigot bearings receive special consideration. Two designs of transmission are submitted, in one of which the spigot bearing is eliminated.
Technical Paper

Pistons and Oil-Trapping Rings for Maintaining an Oil Seal

1928-01-01
280054
PROVISION is made, in the piston and rings described by the author, for an adequate flow of heat from all parts of the piston-head to the cylinder-wall by means of adequate cross-section of aluminum alloy in the head and a tongue-and-groove type of piston-ring structure which provides a greater amount of surface than is usual for heat transfer. A labyrinth oil-seal is provided which aids heat transference and prevents leakage past the piston-rings, and the heat transfer is said to be such that the heat does not destroy the oil seal between the piston and the ring. Charts are included that show the effects in reduced temperatures, oil consumption and gas leakage with the construction described. Attention is given also to a skirt construction most suitable to use with the piston-head and rings described.
Technical Paper

Aircraft Propellers

1929-01-01
290059
NEARLY all the aircraft propellers used by both the Army and the Navy are of the detachable-blade type. The Navy has found it necessary to make its own designs and to furnish the propeller manufacturers with finished detail drawings. The author lists the sources from which data can be obtained and shows a chart from which can be found a diameter and setting of a pair of detachable blades that will give reasonably good performance for nearly any horsepower, revolutions per minute and airspeed commonly used with the direct-drive type of propeller. Discrepancies between model tests and wind-tunnel tests are cited, and the author then considers the subject theoretically. Substitute propellers are next considered, and also the strength of propellers.
Technical Paper

Gearing of Aircraft Propellers

1929-01-01
290062
FOLLOWING a brief outline of the development of aircraft propellers and a statement of the most important fundamentals of propeller design, the authors discuss the problem of propellers for use on geared-down engines, this being the installation of reduction gearing between the crankshaft of the engine and the propeller hub when the increase of airplane-performance characteristics more than offsets the added complication of the installation. The advantages and the disadvantages of using reduction gearing are considered. Concerning the installation of reduction gears, the authors state that the decision whether to use gears or not must result from a compromise between the gains and the losses involved and the amount of net gain depends largely upon the particular engine and airplane combination and its designed performance.
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