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The design of Front Wheel Drive transmission side covers is primarily driven by packaging concerns, and secondarily by structural durability requirements. While the side cover design is a very important element in the NVH performance of a transaxle, there has historically been little consideration of this concern at the design stage. The typical approach to NVH considerations on a side cover is to start with the initial prototype hardware and add any stiffening features in order to reduce the cover vibration or radiated sound. A preferred approach would be to factor the NVH considerations into the initial design. Through consideration of the packaging constraints and a goal of maximizing the fundamental natural frequency of the side cover, it is possible to select from various alternative geometries the one which best meets these objectives.

This paper presents new analysis methods for brake judder data. First, a distinction is made between Thickness Variation, TV, judder (shudder or roughness) caused by the geometry variation of the brake rotor, and thermal judder caused by thermal caused changes to the friction couple. Spectrograms of vibration signals are used to distinguish between the two types of judder. Instrumentation of vehicles in order to get significant data is also provided. A linear model is used to describe the mechanism of judder generation. Different case studies are provided. Special tools of analysis like spectrograms, power time and spectral densities, and zero crossing frequency estimates are applied to real data.

Spark knock pressure oscillations can be detected by a cylinder pressure transducer or by an accelerometer mounted on the engine block. Accelerometer-based detection is lower cost but is affected by extraneous mechanical vibrations and the frequency response of the engine block and accelerometer. The knock oscillation frequency changes during the expansion stroke because the chamber geometry is changing due to the piston motion and the burned gases are cooling. Spectrogram analysis shows the time-dependent frequency content of the pressure and acceleration signals, revealing characteristic signatures of knock and mechanical vibrations. Illustrative spectrograms are presented which yield physical insight into accelerometer-based knock detection.

Rattle noise produced in the vehicle interior due to broadband excitation by road irregularities is a major concern with respect to driving comfort, and therefore has become one of the most important topics of acoustic development in recent years. A quantification i.e. measurement of this rattle noise is of fundamental importance for systematic development work and production control. Common noise level measurements (dB, dBA, etc. ) do not represent the rattle character in the vehicle interior as revealed during initial investigations. To overcome this problem and to substitute the subjective assessment with a combination of measurable parameters, the psychoacoustic software AVL-EAR was applied to create an Interior Rattle Quality Index. Based on more than 40 different vehicles that have been subjectively assessed by approximately 70 test persons, the index was generated by means of multiple pair comparisons and statistics on measurement data.

Engine knock and whine are two highly undesirable parameters which many times are exhibited as amplitude modulated signals. Overall quality, cost and timing targets demanded that engine assemblies exhibiting knock and/or whine be screened out before they reach final inspection in their respective motorcycle frames. This required production line QC systems which could quickly and reliably test steady state and time-varying parameters in a production environment. This paper describes a computer networked based system that utilized a real-time 1/3 octave analyzer. The described system was part of a successful program to control and improve the sound quality of Harley-Davidson engines.

Powertrain noise is often dominated by the radiation from individual panels or covers. A structural side cover for a front wheel drive transmission represents a complex noise and vibration design problem. Amongst the NVH concerns are the radiation of structural borne sound and the sound transmission loss characteristics. This paper addresses the use of acoustic boundary elements and structural finite elements to predict the radiation of noise from a structural side cover. A comparison is made to experimental measurements, and discussion provided for practical application of these modeling methods to total side cover design.

A portable in-vehicle NVH data acquisition and analysis system is required to support the product development timing necessary to be competitive in today's automotive market. The components of such a system should include rugged hardware and software to support NVH data acquisition and analysis for frequently performed tests. The system should be easy for the vehicle development engineers to operate while producing results with a high confidence level. Once the data has been measured and analyzed, the system should support automated reporting and databasing of the results. The availability of such a system would make it easy for the vehicle development engineers to perform standardized tests with standardized analysis and reporting. Such a system has been successfully developed at Ford Motor Company.

This paper outlines the development process of a vibration isolation system for the timing chain guides of an internal combustion engine. It was determined through testing that the timing chain guides are a significant path by which the chain/sprocket impacts are transmitted to other powertrain components. These components radiate the energy as chain mesh order narrow band sound as well as wide band energy. It was found that isolation of the chain guides produced a significant reduction in radiated sound levels, reduced mesh frequency amplitudes, and improved sound quality. The development process utilized indirect force measurement techniques for simulation of the chain loading and FEA prediction of the resulting chain guide forces and displacements. The design of the isolation system involved material selection based on dynamic properties, frequency and temperature ranges, the operating environment, FEA geometry optimization, and durability testing.

A survey is made of compression brake noise levels in heavy duty diesel trucks, using test procedures based on the ISO and EPA driveby acceleration noise tests. The data shows that compression brake noise levels are very high if worn out or open stack exhaust systems are used. Compression brake noise is also audible with OEM exhaust systems and, in at least one case, potentially objectionable. Two methods for reducing brake noise are investigated: improved mufflers and the use of an exhaust brake with the compression brake. Both techniques demonstrate a potential for reducing compression brake noise.

In this paper, a procedure for the measurement of noise produced by compression brakes on heavy duty trucks is proposed and evaluated. The test procedure is an adaptation of the ISO exterior vehicle noise regulation, ISO 362, to measure compression brake noise. The test consists of two parts, a driveby test and a stationary brake test, which are both developed to accentuate compression brake noise. The proposed test is demonstrated to provide results that are indicative of on-road compression brake noise. The sensitivity of the test results to variations in several test parameters is also examined.

A comprehensive methodology for predicting the transient thermal response of spark-ignition engines subject to time-varying boundary conditions is presented. The approach is based on coupling a cycle-resolved quasi-dimensional simulation of in-cylinder thermodynamic events with a resistor-capacitor (R-C) thermal network of the various component and fluid interactions throughout the engine and exhaust system. The dynamic time step of the thermal solution is limited by either the frequency of the prescribed time-dependent boundary conditions or by the minimum thermal time constant of the R-C network. To demonstrate the need for fully-coupled, transient thermodynamic and heat transfer solutions, model behavior is first explored for step-change and staircase variations of engine operating conditions.

Design and optimization of evaporators and condensers requires a reliable simulation of the change of states at the air and refrigerant side. Heat transfer and pressure drop in two phase flow systems with HFC-134a/oil mixtures are strongly dependent on local parameters. To take into account oil effects, it is necessary to modify the correlations for heat transfer and pressure drop which are proposed in the literature for pure refrigerants. At the air side of evaporators the local heat transfer coefficient and heat transfer rate are dependent on whether the local surface temperature is below the dew point of the humid air or not. If partial vapor condensation occurs, mass transport will affect the sensible heat transfer coefficient and fin efficiency.

A computer simulation of the turbocharged direct- injection diesel engine was developed to enhance the capabilities of the Vehicle Engine Cooling System Simulation (VECSS) developed at Michigan Technological University. The engine model was extensively validated against Detroit Diesel Corporation's (DDC) Series 60 engine data. In addition to the new engine model a charge-air-cooler model was developed and incorporated into the VECSS. A Freightliner truck with a Detroit Diesel's Series 60 engine, Behr McCord radiator, AlliedSignal/Garrett Automotive charge air cooler, Kysor DST variable speed fan clutch and other cooling system components was used for the study. The data were collected using the Detroit Diesel Electronic Controls (DDEC)-Electronic Control Module (ECM) and Hewlett Packard data acquisition system. The enhanced model's results were compared to the steady state TTD (top tank differential) data.

Reverse Osmosis (R/O) is reported by Huff' to offer a high volume engine coolant recycling process with very significant purification capabilities. The higher productivity per investment dollar, in spite of the initial capital cost of the equipment, may present the best opportunity for a practicable commercial recycling method capable of producing coolant that compares favorably with new (virgin) coolant. A system described by Huff has, since its introduction in 1990, been re-invented and re-engineered to optimize both the quality and cost effectiveness of the process. This paper describes many of the technical obstacles in the evolution that had to be overcome, and reports the state-of-the-art in commercial reverse osmosis coolant recycling technology. Process improvements that affected coolant quality and productivity are recorded.

Precision cooling has a number of advantages over the conventional cooling of combustion engines. It is primarily used to prevent component failures and is generally intended to create an even distribution of temperature within the cylinder head and block. This leads to lower thermal stresses and higher component durability. Precision cooling in the form of forced convection and nucleate boiling can be used to greater effect than that of traditional precision cooling concentrating on forced convection only. This paper describes the analytical and experimental precision cooling strategy that has been used to investigate nucleate and transition boiling. Analytical details of the models are described and preliminary experimental data is provided for comparison. The major finding indicates that the diameter of the internal cooling passage is one of the significant factors that influences the critical heat flux.

In this paper, design of a generator is summarized which starts with the analysis of an existing generator, for which experimental measurements existed. First a system model of this existing design is analyzed and analysis results are validated by using these measurements. Then a sensitivity analysis is performed to study the critical features of the existing design. Based on the sensitivity analysis, areas for improvement are identified and modifications are suggested for these areas. One of the suggested modifications is the design of a new fan. For this purpose, a three-dimensional analysis is conducted. Again, starting with the original design of the fan, an optimized design is obtained after several iterations. The end product of the described design procedure is built and tested. Comparison of test results with the original design shows significant improvement in terms of performance and efficiency.

In this paper an analytical and numerical study was conducted on the influence of a Non-uniform fluid inlet flow distribution on a phase-change heat exchanger. The analytical results show that the heat transfer will deteriorate as compared to the case where the inlet velocity distribution is uniform, and the degree of deterioration will decrease when the number of heat transfer units is increased. The numerical results indicated that there is more heat transfer deterioration when the fluid of the small heat capacity fluid is Non-uniformly distributed than when the fluid of the large heat capacity is Non-uniformly distributed with the same heat capacity rate ratio. A new concept of heat exchanger design is studied where the rearrangement of heat transfer area compensates for the effect of fluid flow maldistribution. This concept has the potential to enhance the heat transfer performance of automotive heat exchangers.

This paper describes the use of computational fluid dynamics (CFD) as a tool to investigate fluid flow and heat transfer characteristics in louvered fin heat exchangers that are widely used in automotive industry. CFD supplies you with information from inside the heat exchanger like spatial distributions of temperature and velocity fields between the fins. The right interpretation of this information can reduce the number of prototypes and thus save time and money in the development process. Variations of grid density, differencing schemes and boundary conditions have been performed in 2D to ensure the reliability of the numerical results. With the recommendations of the 2-D study 3-D calculations have been made. The numerical results show good agreement with experimental data. The experimental values for overall pressure drop and heat transfer have been obtained using a test facility for heat exchangers at Behr.

The paper describes a predictive tool for the determination of air and coolant temperatures and heat exchange resulting from the operation of heat exchangers, e.g., radiator or air-conditioner condenser in the underhood of automotive engines. The paper describes a detailed computational model where both the fluid streams are numerically solved and the phase change of the refrigerant is taken into account in a condenser simulation. An actual underhood simulation with interactions with a radiator is presented. A numerical simulation for a condenser is also presented. Reasonable agreement is shown with the test data.

The traditional approach for vehicle thermal development relies heavily on experimentation and experience. A virtual vehicle would be very beneficial in providing upfront engineering support which should lead to time and cost savings. To realize a useful model, the authors have based their approach on experimental data and correlations for each significant vehicle component. The vehicle has been divided into five linked modules representing powertrain cooling and cab climate. The paper describes the approach taken for each module and shows that good agreement can be found between model predictions and actual measurements.