Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Modal Testing and Shaker Excitation: Setup Considerations and Guidelines

2011-05-17
2011-01-1652
Electrodynamic shakers or exciters are commonly used in experimental modal analysis. The practical aspects regarding the setup of the shakers, stingers and transducers are often the source of test difficulties and avoidable measurement errors. This paper reviews the basics of shakers as beneficial to modal testing, and common problems associated with setup issues and resulting measurement errors. These include shaker alignment, sensor's considerations, stinger selection, amplifiers, reciprocity assumptions and other test related circumstances.
Technical Paper

Acoustic Test Facility Capabilities at Gulfstream Aerospace

2011-05-17
2011-01-1647
Gulfstream Aerospace Corporation (GAC) owns and operates an Acoustic Test Facility (ATF) in Savannah, GA. The ATF consists of a Reverberation Chamber, Hemi-Anechoic Chamber, and a Control Room. Types of testing conducted in the ATF include Transmission Loss, Sound Power, and Vibration testing. In addition to accommodating typical types of acoustic testing, the ATF has some unique capabilities. The ATF can be used to conduct testing at cold temperatures representative of up to 45,000 ft flight altitude, while simultaneously taking Transmission Loss measurements of the chilled test sample. Additionally, the ATF has the capability of conducting Transmission Loss testing of a full mockup of the aircraft sidewall, including a section of fuselage, all the thermal/acoustic materials up to and including the interior decorative panel. A sound source capable of very high amplitudes at high frequencies is required to obtain good measurements from testing multiple wall systems such as this.
Technical Paper

Development of an Experimental Facility to Characterize Performance, Surge, and Acoustics in Turbochargers

2011-05-17
2011-01-1644
A cold turbocharger test facility was designed and developed at The Ohio State University to measure the performance characteristics under steady state operating conditions, investigate unsteady surge, and acquire acoustic data. A specific turbocharger is used for a thermodynamic analysis to determine the capabilities and limitations of the facility, as well as for the design and construction of the screw compressor, flow control, oil, and compression systems. Two different compression system geometries were incorporated. One system allows compressor performance measurements left of the surge line, while the other incorporates a variable-volume plenum. At the full plenum volume and a specific impeller tip speed, the temporal variation of the compressor inlet and outlet and the plenum pressures as well as the turbocharger speed is presented for stable, mild surge, and deep surge operating points.
Technical Paper

Practical Considerations of Driveline Vibration and Acoustic Test Cell with Case Study of McLaren's Driveline Dynamometers

2011-05-17
2011-01-1645
Test Facilities for Vibrations and Acoustics can be very complicated. With the addition of necessary high power motor dynamometers for load application, the complexity of the test cell increases dramatically. The motors and subsequent additional fixtures and shafts necessary to apply loading conditions can produce additional source noises that would interfere with test measurements. In addition, facility interfaces can dramatically influence the test cell setup and reduce the measurement capabilities. This paper addresses common considerations needed in considering a new test cell for driveline vibration, acoustics, efficiency, and durability testing using motored dynamometers. In addition to outlining common design points, a practical application of 2 new dynamometers utilized for vibration, acoustics, efficiency, and durability testing and their subsequent capabilities are outlined.
Technical Paper

Spirit AeroSystems Acoustics Lab: Measurement and Analysis Capabilities

2011-05-17
2011-01-1643
Previously part of a larger OEM, Spirit AeroSystems became a standalone company 5 years ago and is currently a Tier One supplier of aerostructures. Products include fuselage components, wing structures, engine struts and nacelles, and at the request of various OEMs, fully stuffed fuselages and podded engines where all of the wiring, heating, duct work, etc. is installed prior to delivery. While operating as part of the Propulsion Structures and Systems Business Unit, the design, testing and analysis services provided by the acoustics lab potentially impact all programs at all stages of development because of increasing noise regulations and material certification requirements for implementation in high noise environments.
Technical Paper

Automated Identification of NVH- Phenomena in Vehicles

2011-05-17
2011-01-1656
The NVH (Noise Vibration Harshness) behavior of modern vehicles becomes more and more important - especially in terms of new powertrain concepts, like in hybrid electric or full electric vehicles. There are many tools and methods to develop and optimize the NVH behavior of modern vehicles. At the end of the development process, subjective ratings from road tests are very important. For objective analyses, different approaches based on artificial neural networks exist. One example is the AVL-DRIVE™ system, a driveability analysis and benchmarking system which allows, based on a very small set of sensors, an adequate objective rating of the vehicle's driveability. The system automatically detects driving maneuvers and rates the driveability. This article presents a method which is able not only to rate different maneuvers and the behavior of the vehicle but also to detect phenomena and causes in the domain of NVH.
Technical Paper

Advanced Tire Noise Pass by Noise Solution Meets ISO 13325 and the Recently Updated ISO 362 Standards

2011-05-17
2011-01-1654
Pass by noise is a complex test that requires meeting several different standards with regard to the physical track layout, measurement systems, data acquisition, triggering, processing and analysis. Overview of the pertinent standards for Tire and Vehicle pass by testing is provided along with the description of development of an advanced solution to meet our specific needs. Key features of the solution are provided along with the lessons learned from our operation of the system at our facility and several other test tracks.
Technical Paper

Measuring and Comparing Frequency Response Functions of Torque Converter Turbines Submerged in Transmission Fluid

2011-05-17
2011-01-1662
When testing dynamic structures, it is important to note that the dynamic system in question may be submerged into a fluid during operation and to properly test the structure under the same condition in order to understand the true dynamic parameters of the system. In this way, the mass and stiffness coupling to the particular fluid, for the case of this study, automatic transmission fluid, may be taken into account. This is especially important in light structures where the coupling between the fluid mass and the structural mass may be great. A structure was tested with a laser vibrometer using several impact methods in open air to determine which impact method would be most suitable for submerged testing. The structure was then submerged in transmission fluid with an accelerometer attached and subsequently tested and compared to the previous results.
Journal Article

Development of the J2825 On-Highway Motorcycle Sound Test Procedure

2011-05-17
2011-01-1614
In response to a growing need for a practical and technically valid method for measuring exhaust sound pressure levels (SPL) of on-highway motorcycles, the SAE Motorcycle Technical Steering Committee has developed Surface Vehicle Recommended Practice J28251, “Measurement of Exhaust Sound Pressure Levels of Stationary On-Highway Motorcycles,” which includes a new stationary sound test procedure and recommendations for limit values. Key goals of the development process included: minimal equipment requirements, ease of implementation by non-technical personnel, and consistency with the federal EPA requirements; in particular, vehicles compliant with the EPA requirements should not fail when assessed using J2825. Development of the recommended practice involved a comprehensive field study of 25 motorcycles and 76 different exhaust systems, ranging from relatively quiet OEM systems to unbaffled, aftermarket exhaust systems.
Journal Article

Numerical Simulation of the Measurement of the Diffuse Field Absorption Coefficient in Small Reverberation Rooms

2011-05-17
2011-01-1641
The Diffuse Field Absorption Coefficient (DFAC) is a physical quantity very often used in the automotive industry to assess the performance of sound absorbing multilayers. From a theoretical standpoint, such quantity is defined under rather ideal conditions: the multilayer is assumed to be infinite in extent and the exciting acoustic field is assumed to be perfectly diffuse. From a practical standpoint, in the automotive industry the DFAC is generally measured on samples having a relatively small size (of the order of 1m2) and using relatively small cabins (in the order of 6-7 m₃). It is well known that both these factors (the finite size of the sample and the small volume of the cabin) can have an influence on the results of the measurements, generating deviations from the theoretical DFAC.
Journal Article

Design of a Self-Contained Acoustical Testing Facility

2011-05-17
2011-01-1642
This paper presents an overview of the acoustical design of a small volume self-contained acoustical testing facility (SCATF). The design focuses on a small volume (25 m₃) reverberation room for testing the random incidence sound absorption performance of small samples of acoustical materials and automotive parts. This reverberation room also couples to a small volume hemi-anechoic room and serves as the random incidence source room for sound transmission loss testing. These testing approaches respectively target the SAE J2883 (pending) and J1400 test standards.
Technical Paper

The Development of a Global Brake Insulator Damping Measurement Procedure

2011-05-17
2011-01-1574
The development and validation of a brake pad insulator damping measurement procedure by the SAE Brake NVH Standards Committee was presented at the 2010 SAE Brake Colloquium (Paper 2010-01-1685). In Europe, in 2010, the EKB Working Group identified the need to develop a similar procedure, and started some activities which lead to the release of a standard similar but different than the SAE J3001. The SAE and EKB working groups agreed that having a global standard was of paramount importance, so the 2 groups decided to meet in November of 2010 to flush out the details of the J3001 global procedure. The details of the new test procedure, test setup and recommendation for proper test practices are described in this paper. This description provides an excellent foundation for evaluating the insulator damping properties over a range of temperatures and frequencies.
Technical Paper

The Experimental Consideration of Booming Noise Subjected to Vehicle Speed

2011-05-17
2011-01-1596
This paper shows some discussions regarding an experimental consideration of booming noise level when a vehicle drives over a small protruding object on a road. Booming noise level is subjected to vehicle speed and is not proportional to the speed. Generally, it is known as the maximal noise level is being created with vehicle speed of around 40 km/h, however, the obvious cause of the phenomena have not been completely determined so far. In this paper, at first, it shows an experimental data that was being observed in detail with variable vehicle speed. Based on our detailed observation of the experimental data, reversed-phase two inputs by existence of a protruding object, was confirmed. By considering correlation between time difference of two inputs and vehicle speed, it is demonstrated that those two inputs around 40km/h induce a tire resonance which leads to a booming noise in a cabin. We define it as ‘harsh booming noise’ here.
Technical Paper

Front Loading NVH Test on the Highly Dynamic Powertrain Test Bed

2011-05-17
2011-01-1512
Advanced powertrain test, which is simulating real road load condition, was performed on the dynamic test bed. This cutting edge system can reproduce real road resistance based upon the vehicle dynamic model and wheel slip model. This wheel slip function is simulating the real behavior of the powertrain wheel as close as possible at each wheel independently. Additionally, low inertia of dynamometer motor themselves is another advantage for this purpose. This test bed is capable of testing all kinds of 2WD and 4WD powertrain configuration regardless of transmission type. Also, vehicle configuration can be mounted and tested on this test bed with small addition of supporting system alternatively. For the application, a four wheel drive powertrain was mounted on the test bed and driveline noise and vibration behavior such as transfer rattling noise and tip in/out shock were reproduced on this test bed.
Journal Article

Comparison of fuel economy and exhaust emission tests of 4WD vehicles using single-axis chassis dynamometer and dual-axis chassis dynamometer

2011-08-30
2011-01-2058
The demands of application of dual-axis chassis dynamometers (4WD-CHDY) have increased recently due to the improvement of performance of 4WD-CHDY and an increase in the number of 4WD vehicles which are difficult to convert to 2WD. However, there are few evaluations of any differences between fuel economy and exhaust emission levels in the case of 2WD-CHDY with conversion from 4WD to 2WD (2WD-mode) and 4WD-CHDY without conversion to 2WD (4WD-mode). Fuel economy and exhaust emission tests of 4WD vehicle equipped with a typical 4WD mechanism were performed to investigate any differences between the case of the 2WD-mode and the 4WD-mode. In these tests, we measured ‘work at wheel’ (wheel-work) using wheel torque meters. A comparison of the 2WD-mode and the 4WD-mode reveals a difference of fuel economy (2WD-mode is 1.5% better than that of 4WD-mode) and wheel-work (2WD-mode is 3.9% less than that of 4WD-mode). However, there are almost no differences of exhaust emission levels.
Journal Article

Novel Nondestructive Imaging Analysis for Catalyst Washcoat Loading and DPF Soot Distribution Using Terahertz Wave Computed Tomography

2011-08-30
2011-01-2064
This paper describes a three-dimensional (3D) visualization framework using terahertz (THz) waves for quantitative analysis of the distribution of catalyst washcoat loading and diesel particulate filter (DPF) soot deposits. THz waves, which are electromagnetic waves located between infrared and microwave in the electromagnetic spectrum, have good directivity and moderate resolution. Accordingly, a computed tomography (CT) technique has been developed to image the interior of an object using the spectral information of THz waves. This THz wave CT technique can be used to analyze the interior of various target objects, and has good penetrability of ceramic substances used as catalysts in automobiles. Against this background, a method using THz CT for nondestructive analysis of catalyst washcoat loading and the density distribution of soot was developed, and this framework was evaluated.
Technical Paper

Simultaneous Measurements of Temperatures of Flame and Wall Surface in a Combustion Chamber of Diesel Engine

2011-08-30
2011-01-2047
In order to investigate the combustion phenomena in a combustion chamber of the diesel engine at transient operations, the simultaneous measurements of temperatures of flame and wall surface in a combustion chamber were conducted. The new technique for simultaneous measurements of flame temperature and wall surface was developed. Laser-Induced phosphorescence was used for the measurement of wall surface temperature which was coupled with the flame temperature measurement by a two-color pyrometry. The NOx and soot emissions were also measured simultaneously in transient operations. The relation between the temporal changes of emissions and temperatures of flame and surface wall are discussed. The results show that the temporal change of NOx emission during transient operation is similar to that of the average gas temperature in a chamber. On the other hand, the temporal change of soot emission is similar to neither that of flame temperature nor that of average gas temperature.
Journal Article

Direct Sampling, TEM Analysis and Optical Measurement of Soot Particles at Different Axial Locations in a Transient Spray Flame

2011-08-30
2011-01-2051
In order for better understanding of soot formation and oxidation processes in diesel spray flame, the morphology, microstructure and sizes of soot particles directly sampled in a transient spray flame were analyzed via high-resolution transmission electron microscopy (HRTEM). The soot distribution in the spray flame was simultaneously observed by high-speed shadowgraphy. The transient spray combustion was achieved in a constant volume combustion chamber under a high pressure and high temperature condition (940 K, 2.5 MPa). The soot samples were taken at different axial locations in the spray flame, 40 - 90 mm from the injector nozzle, using an intrusive soot sampler. Pressure histories, heat release rates and laser shadowgraphs of spray combustion were compared between the cases with and without the soot sampler in order to check the intrusion effect of soot sampler on combustion.
Technical Paper

Development of In-cylinder Mixture and Flame Propagation Distribution Measurement Device with Spark Plug Type Sensor

2011-08-30
2011-01-2045
A new method to measure in-cylinder flame propagation and mixture distribution has been developed. The distribution is derived from analyzing the temporal history of flame spectra of CH* and C2*, which are detected by a spark plug type sensor with multi-optical fibers. The validity of this method was confirmed by verifying that the measurement results corresponded with the results of high speed flame visualization and laser induced fluorescence (LIF) measurement. This method was also applied to analysis of cyclic combustion fluctuation on start-up in a direct injection spark ignition (DISI) engine, and its applicability was confirmed.
Technical Paper

Laser-Induced Phosphorescence Measurements of Combustion Chamber Surface Temperature on a Single-Cylinder Diesel Engine

2011-08-30
2011-01-2049
Non-intrusive, crank-angle resolved measurements of piston temperature have been performed in a single-cylinder direct-injection (DI) Diesel engine operating under highly-dilute low-temperature combustion (LTC) conditions. The laser-induced phosphorescence (LIP) technique exploits the temperature-dependent characteristics of rare-earth or transition metal doped ceramic phosphors. This paper describes the calibration procedure and subsequent application of the technique to measure piston surface temperature in a single-cylinder, optically-accessible Diesel engine for various parametric variations including fueling rate and injector nozzle characteristics. In addition, measurements of the nozzle tip temperature of a Diesel injector are also reported. Furthermore, a fiber-optic solution has been developed which enables piston surface temperature measurements to be performed in standard metal (i.e. non-optical) single-cylinder and multi-cylinder engines.
X