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Journal Article

Experimental and Calculation Analysis of Rotational Vibration for an Engine Front End Accessory Drive System

2011-05-17
2011-01-1534
Experimental methods for measuring static and dynamic characteristics of an engine Frond End Accessory Drive System (FEADS) are presented. The static performance of a FEADS is the static tension of the belt, and the dynamic properties of a FEADS are transverse vibration of belt, and rotational vibration performances that include rotational response of pulleys and tensioner arm, dynamic tension of belt span, slip factor between belt and pulley. A mathematical model and calculation method for rotational vibration analysis of a 8 pulley-belt FEADS is established. In the model, creeping effect of a belt on pulley wrap arc, viscous damping and dry friction of a tensioner are considered. In calculation of dynamic performances of the FEADS, the excitation torques with multi-frequency components from crankshaft torsional vibration are obtained from the measurement.
Technical Paper

In-Cylinder Pressure Modelling with Artificial Neural Networks

2011-04-12
2011-01-1417
More and more stringent emission regulations require advanced control technologies for combustion engines. This goes along with increased monitoring requirements of engine behaviour. In case of emissions behaviour and fuel consumption the actual combustion efficiency is of highest interest. A key parameter of combustion conditions is the in-cylinder pressure during engine cycle. The measurement and detection is difficult and cost intensive. Hence, modelling of in-cylinder conditions is a promising approach for finding optimum control behaviour. However, on-line controller design requires real-time scenarios which are difficult to model and current modelling approaches are either time consuming or inaccurate. This paper presents a new approach of in-cylinder condition prediction. Rather than reconstructing in-cylinder pressure signals from vibration transferred signals through cylinder heads or rods this approach predicts the conditions.
Journal Article

Characterizing the Onset of Manual Transmission Gear Rattle Part I: Experimental Results

2009-05-19
2009-01-2063
The objective of this investigation is to characterize the ability of loose gears to resist rattle in a manual transmission driven by an internal combustion engine. A hemi-anechoic transmission dynamometer test cell with the capability to produce torsional oscillations is utilized to initiate gear rattle in a front wheel drive (FWD) manual transmission, for a matrix of operating loads and selected gear states. A signal processing technique is derived herein to identify onset of gear rattle resulting from a standardized set of measurements. Gear rattle was identified by a distinct change in noise and vibration measures, and correlated to gear oscillations by a computed quantity referred to as percent deviation in normalized gear speed. An angular acceleration rattle threshold is defined based upon loose gear inertia and drag torque. The effects of mean speed, mean and dynamic torque, and gear state on the occurrence of loose gear rattle are reported.
Technical Paper

Transverse Vibration of a Composite Shaft

2009-05-19
2009-01-2066
The advantages of having higher stiffness to weight ratio and strength to weigh ratio that composite materials have resulted in an increased interest in them. In automotive engineering, the weight savings has positive impacts on other attributes like fuel economy and possible noise, vibration and harshness (NVH). The driveline of an automotive system can be a target for possible use of composite materials. The design of the driveshaft of an automotive system is primarily driven by its natural frequency. This paper presents an exact solution for the vibration of a composite driveshaft with intermediate joints. The joint is modeled as a frictionless internal hinge. The Euler-Bernoulli beam theory is used. Lumped masses are placed on each side of the joint to represent the joint mass. Equations of motion are developed using the appropriate boundary conditions and then solved exactly.
Technical Paper

Shearplate – A New Innovative Approach to Reduce Powertrain Noise

2009-05-19
2009-01-2065
This Paper is evaluating the development and effectiveness of using a Shearplate, a new and innovative approach to reduce powertrain noise and vibrations. The results show that the approach is offering monumental improvements in terms of reduced noise and vibrations. Sound quality evaluations also show very clearly that the approach is an effective countermeasure to the targeted problems. With the knowledge gathered during the development and with what is partly presented in this paper we now have an additional tool that car manufacturers can deploy in their efforts to design more fuel efficient and cleaner burning engines without sacrificing NVH performance.
Technical Paper

Vibro-Acoustic Simulation of Diesel Injection Ducts

2009-05-19
2009-01-2057
High pressure pipes of the diesel injection system seem to represent a weak point in terms of vibration and acoustic radiation of the whole injection system. Investigations have highlighted this phenomenon. The injectors induce acoustic waves which propagate in the viscous diesel contained in the injection pipes. A strong coupling can occur sometimes between these acoustic waves and the duct structural modes leading to intensive mechanical vibration and acoustic radiation; and sometimes to a possible failure of the pipe. Numerical simulations offer a good platform to predict such vibration and can be used in order to prevent any structural component failure and to decrease the resulting acoustic radiation. This paper presents a vibro-acoustic study performed with the finite element code ACTRAN to estimate which parameters play a role in this process and to provide some guidelines for avoiding problems.
Technical Paper

Study on Natural Torsional Vibration Characteristics of Dual Mass - Flywheel Radial Spring Type Torsional Vibration Damper

2009-05-19
2009-01-2062
The working principle of dual mass flywheel - radial spring (DMF-RS) type torsional vibration damper was analyzed, and the design method of natural torsional vibration characteristics control of DMF-RS type torsional damper for automotive powertrains was studied herein. Based on the multi-freedom lumped mass - torsional vibration spring analysis model of powertrain, the natural torsional vibration characteristics of the system with DMF-RS type torsional damper were analyzed, and compared with the clutch type torsional vibration damper, the effectiveness of DMF-RS type torsional damper on the torsional vibration control was verified.
Technical Paper

Board Recognition of Different Fuels Feeding SI Engines with the Use of Dimensional and Nondimensional Vibration Signal Parameters-Part 1

2009-05-19
2009-01-2056
The availability of gaseous fuels such as natural gas and propane butane mixtures has led to worldwide popularity of internal combustion engines running dual fuel or alternatively gas powered. These gaseous fuels are known as fuels more resistant to knocking than conventional liquid fuels and as less ones pollutant. Their better mixing with air is also well recognized. There are some works published on the use of gaseous fuels, but the problem of the combustion noise, as a very important source of information regarding the combusted fuel, is not receiving much attention. Combustion noise occurs in two forms, direct and indirect. It is transmitted throughout the engine block as a vibration at a different spectrum of frequencies. In this study an attempt is made to relate the combustion noise to the operating parameters for LPG, CNG and Hydrogen enriched CNG powered engine as compared to petrol fueled engine.
Technical Paper

Modeling, Validation and Analysis of the Fuel Supply and Injection System for NVH Improvement

2009-05-19
2009-01-2055
In the powertrain development of an automobile, the accurate prediction and understanding of the fuel supply and injection system behavior is necessary to achieve the targeted vehicle performance. With stronger demand from the customers for quieter vehicles, complementary functional objectives have to be met such as packaging, component or material change, or the modification of the fuel supply system layout. Understand the possible sources of noise and vibration from the fuel supply and delivery system requires having an analytical model of a complete fuel system, from the fuel pump assembly to the injectors. One has to note that adequate level of component details is required for the modeling and validation. In this study, the lumped-parameter model approach of the fluid dynamics on the fuel supply and delivery system has been developed and validated with the test results.
Technical Paper

Modeling, Design and Validation of an Exhaust Muffler for a Commercial Telehandler

2009-05-19
2009-01-2047
This paper describes the design, development and validation of a muffler for reducing exhaust noise from a commercial tele-handler. It also describes the procedure for modeling and optimizing the exhaust muffler along with experimental measurement for correlating the sound transmission loss (STL). The design and tuning of the tele-handler muffler was based on several factors including overall performance, cost, weight, available space, and ease of manufacturing. The analysis for predicting the STL was conducted using the commercial software LMS Virtual Lab (LMS-VL), while the experimental validation was carried out in the laboratory using the two load setup. First, in order to gain confidence in the applicability of LMS-VL, the STL of some simple expansion mufflers with and without extended inlet/outlet and perforations was considered. The STL of these mufflers were predicted using the traditional plane wave transfer matrix approach.
Journal Article

Design of a Multi-Chamber Silencer for Turbocharger Noise

2009-05-19
2009-01-2048
A multi-chamber silencer is designed by a computational approach to suppress the turbocharger whoosh noise downstream of a compressor in an engine intake system. Due to the significant levels and the broadband nature of the source spanning over 1.5 – 3.5 kHz, three Helmholtz resonators are implemented in series. Each resonator consists of a chamber and a number of slots, which can be modeled as a cavity and neck, respectively. Their target resonance frequencies are tuned using Boundary Element Method to achieve an effective noise reduction over the entire frequency range of interest. The predicted transmission loss of the silencer is then compared with the experimental results from a prototype in an impedance tube setup. In view of the presence of rapid grazing flow, these silencers may be susceptible to whistle-noise generation. Hence, the prototype is also examined on a flow bench at varying flow rates to assess such flow-acoustic coupling.
Technical Paper

A New Method to Convert Crankshaft Position Sensor (CPS) Signals into Angular Acceleration for Engine Combustion Evaluation

2009-05-19
2009-01-2052
With ever-increasing oil and gasoline prices, automotive manufacturers are striving to improve fuel economy. There are many factors that affect vehicle fuel consumption, such as engine size, vehicle weight, driving habits, and more. For a particular vehicle, engine combustion quality is one of the most important factors that affect fuel economy. Engine combustion quality also directly affects engine emissions, vehicle drivability, and vehicle NVH. Automotive manufacturers have been using different technologies to control engine combustion quality, such as using low cost pressure transducers to measure and control engine combustion in real time. In this paper, the authors have proposed a method that could directly use the Crank Position Sensor (CPS) signal to measure engine combustion quality.
Journal Article

The Acoustic Impedance of a Wide Side Branch Orifice: Experimental Determination Using Three-Port Methodology

2009-05-19
2009-01-2043
The acoustic impedance of a circular, confined, side branch orifice subjected to grazing flow is studied. Two geometries are tested. In both geometries, the side branch dimension is of the same order as that of the main duct. The system is viewed as an acoustic three-port, whose passive properties are described by a system matrix. The impedance is studied with the acoustic field incident at different ports, which is shown to influence the results significantly. When excited from the leading edge or from the side branch, an interaction of the hydrodynamic and acoustic fields is triggered, while excitation from the trailing edge does not trigger such an interaction. For both the resistance and the reactance (here expressed as an end correction) the results vary in the three possible excitation cases. In the quasi-stationary limit the resistance is given by a loss coefficient times the Mach number, and the end correction collapses to a single value.
Technical Paper

An Investigation and Validation of Tailpipe Noise Contribution to Vehicle Cabin via Transfer Path Analysis Concept

2009-05-19
2009-01-2044
To facilitate the design and validation of exhaust system, quantification of tailpipe noise contribution to vehicle cabin is usually necessary. In this paper, transfer path analysis (TPA) concept has been applied to investigate the contributions from tailpipe and other noise sources as well as the interaction between tailpipe noise and its transmission path to vehicle cabin. An artificial acoustic source has been designed for transfer function measurement and an all-wheel-drive dynamometer located in anechoic chamber is used as a testing platform to collect operational data. A validation methodology has also been proposed and implemented by comparing the measured and predicted interior noise response with a big auxiliary muffler (BAM).
Technical Paper

Experimental Determination of Sound Transmission in Turbo-Compressors

2009-05-19
2009-01-2045
In this paper experimental procedures to determine the sound transmission through automotive turbo-charger compressors are described. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed.
Technical Paper

Predicting Shell Vibration and Implosion Issues in Automotive Muffler Design

2009-05-19
2009-01-2038
The muffler shell of an automotive exhaust system can cause significant NVH (noise/vibration/harshness) issues like shell vibration and radiated noise, buzzing, rattling, and implosion problems. Due to the complex relationship between the dynamic behavior of the muffler shell and many parameters like engine operating temperature, curvature of the shell, material density, shell thickness and baffle spacing, the NVH engineers have experienced difficulties identifying the root cause of problems and solutions to them. By considering all design parameters, a theoretical study on shell vibration has been conducted to investigate applicability of an analytical technique to predict and solve the NVH issues of an automotive muffler. We have identified the most promising shell vibration theories by comparing the solutions with the results from modal test and finite element analysis.
Technical Paper

Load Effect on Source Impedance Measurement Accuracy

2009-05-19
2009-01-2041
The source in an intake/exhaust system is commonly modeled as a source strength and impedance combination. Both the strength and impedance are normally measured and measurement accuracy depends on selecting an appropriate acoustic load combination. An incident wave decomposition method is proposed which is based on acoustic wave decomposition concepts instead of an electric circuit analogy providing a more straightforward approach to investigating the effect of acoustic load selection. Based on studying wave reflections in the system, the uncertainty for determining source impedance is estimated.
Technical Paper

Idle Combustion Smoothness

2009-05-19
2009-01-2032
Smooth Vehicle Idle operation requires Engine Combustion events that are extremely repeatable from cylinder to cylinder and from engine cycle to engine cycle. This paper will explore the analysis of engine idle combustion focusing in on the typical metrics, examining their strengths and weaknesses, and proposing new metrics which can help to gain a deeper understanding of what is Idle Combustion Smoothness.
Journal Article

Vibration Analysis of Powertrain Mounting System with a Combination of Active and Passive Isolators with Spectrally-varying Properties

2009-05-19
2009-01-2034
Most of the prior work on active mounting systems has been conducted in the context of a single degree-of-freedom even though the vehicle powertrain is a six degree-of-freedom isolation system. We seek to overcome this deficiency by proposing a new six degree-of-freedom analytical model of the powertrain system with a combination of active and passive mounts. All stiffness and damping elements contain spectrally-varying properties and we examine powertrain motions when excited by an oscillating torque. Two methods are developed that describe the mount elements via a transfer function (in Laplace domain). New analytical formulations are verified by comparing the frequency responses with numerical results obtained by the direct inversion method (based on Voigt type mount model). Eigensolutions of a spectrally varying mounting system are also predicted by new models.
Technical Paper

Transmission Loss Measurement with and without an Anechoic Termination

2009-05-19
2009-01-2035
The definition method and the two load/source method of a transmission loss test of an automotive tuning device are discussed in this paper. For the definition method, the accuracy penalty due to the imperfect anechoic termination quality is studied based on an empirical acoustic model of glass-wool and the best practice of constructing an anechoic termination is attempted. The conclusion is verified with numerical simulations. For the two load/source method, the difference in the two source/load impedances compounded with the error of measured acoustic pressures, as related to transmission loss accuracy, is discussed and demonstrated.
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