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Catalytic converter is recognized as an essential after burn-treatment device and used in a wide range, especially with new generation of emission standards. The prediction of its performance and efficiency and the endeavor for the optimization are critical issues to reduce the cost and emissions. Most of the works done on the simulation of catalytic converters are limited to special cases and don't cover detailed aspects required for description of catalytic converter behavior. In this paper, a generalized mathematical model is introduced for catalytic converter performance, including detailed description of chemical and physical phenomena, in two individual one and two-dimensional structures. Some numerical methods, including finite difference and finite element, have been developed to simulate the behavior of three-way monolithic catalysts.

A complete transient, three dimensional simulation of the flow-field around a generic pickup truck geometry is carried out. A 1/12-scale replica of an actual pickup truck, with simplified features such as a smooth underbody, is considered in the study. The purpose of the study is twofold. First, it seeks to improve our understanding of the complex flow field around a pickup truck, which is predominantly a bluff body with a prominent wake. To this end a detail description of the time-averaged pressure distribution on the vehicle body as well as time-averaged velocities in the wake of the truck is provided. Secondly, the study seeks to judge the accuracy with which modern CFD techniques can predict complex, practical, bluff-body wake flows. This is accomplished by making a close comparison of the time-averaged wake velocity profiles predicted by CFD with analogous measurements made in a wind tunnel experiment using particle image velocimetry.

A hybrid calibration model combining dimensional and empirical modeling has been used to model transient smoke and demonstrate transient smoke reduction strategies during the turbocharger lag period of an electronically controlled heavy-duty diesel engine. This new hybrid approach termed the Non-Parametric Reduced Dimensionality approach (NPRD) uses GT-Power to transform the engine operating parameter model input space to a more fundamental, lower dimensional and less correlated model input space. A non-parametric nearest neighbor approach is then applied over this transformed model input space to make new predictions. The NPRD approach was used to predict transient FTP emissions of cumulative particulate matter (PM) within 7% of measured value, based solely on steady state training data.

The transient solution of a two-dimensional problem with thermoelastic instability (TEI) has been investigated using a “reduced order model”. Thermoelastic instability results from the interaction of frictional heat generation, elastic contact pressure and thermoelastic distortion of two bodies in contact and sliding relative to each other. In practice this class of problem is encountered with the automotive brakes and clutches. The goal has been to construct a mathematical model with a few degrees of freedom that will approximate the real system. The method was found to work well when compared with results from FE computer simulation but involves a dramatically reduced computational time.

Both the power spectrum analysis and the sound intensity analysis are based upon the Fourier analysis and are widely used for sound analysis. And as wellknown, they can perform poorly in the case of unsteady or tarnsient sound. For such unsteady signals, the time-frequency distribution functions can provide much clearer interpretation. We have been working to apply the Wigner-Ville Distribution (WVD) to the transient sound analysis and the transient sound intensity analysis. In this paper, basic theories and a practical way of calculation are explained. In addition, an analysis example is introduced. The WVD can be used as a powerful tool to analyze rapidly changing signals or to detect abnormal impact noises buried in machinery sounds.

The effect of tire speed and temperature on rolling loss is described by two new tire characteristics: The speed factor indicates the relative change of rolling loss at a rapid speed change, and the temperature factor indicates the relative change of rolling loss at a tire temperature change. The two factors are derived from a general relation between rolling loss, tire temperature, and speed; this relation is valid for steady-state as well as transient conditions.

Gasoline direct injection (GDI) technology is already in use in four wheeler applications owing to the additional benefits in terms of better combustion and fuel economy. The air-assisted in-cylinder injection is the emerging technology for gasoline engines which works with low pressure injection systems unlike gasoline direct injection (GDI) system. GDI systems use high pressure fuel injection, which provides better combustion and reduced fuel consumption. It envisages small droplet size and low penetration rate which will reduce wall wetting and hydrocarbon emissions. This study is concerned with a CFD analysis of an air-assisted injection system to evaluate mixture spray characteristics. For the analysis, the air injector fitted onto a constant volume chamber (CVC) maintained at uniform pressure is considered. The analysis is carried out for various CVC pressures, mixture injection durations and fuel quantities so as to understand the effect on mixture spray characteristics.

This paper describes the transient spray characteristics of a high pressure, single fluid injector, intended for use in a direct-injection spark-ignited (DISI) engine. The injector was a single hole, pintle type injector and was electronically controlled. A variety of measurement diagnostics, including full-field imaging and line-of-sight diffraction based particle sizing were employed for spray characterization. Transient patternator measurements were also performed to obtain temporally resolved average mass flux distributions. Particle size and obscuration measurements were performed at three locations in the spray and at three injection pressures: 3.45 MPa (500 psi), 4.83 Mpa (700 psi), and 6.21 MPa (900 psi). Results of the spray imaging experiments indicated that the spray shapes varied with time after the start of injection and contained a leading mass, or slug along the center line of the spray.

The transient cone angle of pressure swirl sprays from injectors intended for use in gasoline direct injection engines was measured from 2D Mie scattering images. A variety of injectors with varying nominal cone angle and flow rate were investigated. The general cone angle behavior was found to correlate well qualitatively with the measured fuel line pressure and was affected by the different injector specifications. Experimentally measured modulations in cone angle and injection pressure were forced on a comprehensive spray simulation to understand the sensitivity of pulsating injector boundary conditions on general spray structure. Ignoring the nozzle fluctuations led to a computed spray shape that inadequately replicated the experimental images; hence, demonstrating the importance of quantifying the injector boundary conditions when characterizing a spray using high-fidelity simulation tools.

The solid state power controller (SSPC) is one of the most important power electronic components of the aircraft electrical power distribution (EPS) systems. This paper presents an architecture of the DC SSPC and provides the mitigation techniques for transient voltage overshoot during its turn-off. The high source side inductance carries breaking current (9xnominal current) just before turnoff and induces large voltage transient across the semiconductor devices. Therefore, the stored inductive energy needs to be dissipated in order to prevent semiconductor switches from over-voltage/thermal breakdown. Three different transient voltage suppression (TVS) devices to reduce voltage stress across switches are included in the paper for detail study. The comprehensive comparison of the TVS devices is presented. In addition, the thermal impact of the TVS devices on the semiconductor switches is also analyzed.

The results of a head injury model development program are presented. They include a description of the model's features and its capabilities for simulating direct and indirect impact forces. The model's validity is discussed in terms of level of confidence and verification. Skull bone response and brain response are presented for a variety of dynamic simulations. The scope and limitations imposed by the assumption of linearity are discussed. The results demonstrate that while some minor changes appear indicated, the model predictions yield useful insight into the mechanical causes of skull and brain injury.

With the fuel economy and emission requirements more demanding than ever and passenger-car engine control systems more sophisticated than ever, there exists a need for a methodical procedure to optimize the fuel economy subject to emission limits of the entire engine-vehicle-aftertreatment system over the federal fuel economy and emission tests. The optimal feedback control functions should account for: 1) transient system interactions; 2) cold start engine-catalytic converter warm-up dynamics; 3) exhaust aftertreatment; 4) driveability; and 5) any repeatable unknown phenomena which affect end-of-test fuel consumption or emissions. This paper presents an experimental Transient System Optimization (TSO) procedure which meets these requirements.

With the increase of motor speed and the deterioration of operating environment, it is more difficult to predict the transient temperature field (TTF). Meanwhile, it is difficult to obtain the temperature test dataset of key nodes under various complete road conditions, so the cost of bench test or real vehicle test is high. Therefore, it is of great significance to establish a high fidelity, lightweight temperature prediction model which can be applied to real vehicle thermal management for ensuring the safe and stable operation of motor. In this paper, a physical model simulating electromagnetic-heat-flow multi-physical coupling of permanent magnet synchronous motor (PMSM) in electric drive gearbox (EDG) is established, and the correctness of the model is verified by the actual EDG bench test.

A fiber optical heterodyne interferometry system was developed to obtain high temporal resolution temperature histories of unburned and burned gases non-intrusively. The effective optical path length of the test beam changes with the gas density and corresponding changes of the refractive index. Therefore, the temperature history of the gas can be determined from the pressure and phase shift of the interference signal. The resolution of the temperature measurement is approximately 0.5 K, and is dependent upon both the sampling clock speed of the A/D converter and the length of the test section. A polarization-preserving fiber is used to deliver the test beam to and from the test section, to improve the feasibility of the system as a sensor probe. This optical heterodyne interferometry system may also be used for other applications that require gas density and pressure measurements with a fast response time, or a transient temperature record.

A heterodyne interferometry system with a fiber-optic sensor was developed to measure the temperature history of unburned gas in an engine cylinder. A polarization-preserving fiber and metal mirror were used as the fiber-optic sensor to deliver the test beam to and from the measurement region. This fiber-optic sensor can be assembled in the engine cylinder or the cylinder head without a lot of improvements of an actual engine. The feasibility of our system was sufficient to be applied to temperature history measurement of an unburned gas compressed by flame propagation in an engine cylinder. The resolution of the temperature measurement is approximately 0.7 K, and is dependent on both the sampling clock speed of the A/D converter and the length of the measurement region.

Various applications of diesel engine transient testing are reviewed and described with particular emphasis on the US Federal Heavy Duty Truck exhaust emissions test procedure. The requirements of such systems are discussed and some results illustrated.

In this paper, a transient thermal analysis model for Diesel fuel systems is presented. The purpose of this work is to determine the fuel temperature at various locations along the system, especially inside the tank and at the returned fuel inlet to the tank. Due to the fact that the fuel level is continuously changing during any driving condition, the fuel mass inside the tank is also continuously changing. Consequently, the fuel temperature will change even under steady driving or idle conditions, therefore, this problem should be analyzed using transient thermal analysis models. Effective thermal management requires controlling the surface temperature of the fuel tank, fuel lines and the fuel temperature at the fuel return line as well as inside the tank [1, 2]. Based on the thermal analysis results, it is possible to determine the major source of heat input at several locations of the fuel system.

This paper describes a method for calculating the temperature of a semi-infinite heat sink plate of a given thickness, subjected to transient heating by a D2Pak power IC. Accurate prediction of the heat sink temperature over time then allows for more accurate calculation of the IC junction temperature. A set of curves have been developed for the time variation of heat sink plate temperature. This has been achieved by the use of finite element methods, and modeling a large range of configurations. The system variables were put into dimensionless form, and the model results plotted. The resulting plot indicates an effective thermal resistance of a given heat sink plate at a given point in time. A curve fit has also performed on the results. The results of the finite element model have been compared with laboratory data.

A secondary concentrator is an optical device that accepts solar energy from a primary concentrator and further intensifies and directs the solar flux. The refractive secondary is one such device; fabricated from an optically clear solid material that can efficiently transmit the solar energy by way of refraction and total internal reflection. When combined with a large state-of-the-art rigid or inflatable primary concentrator, the refractive secondary enables solar concentration ratios of 10,000 to 1. In support of potential space solar thermal power and propulsion applications, the NASA Glenn Research Center is developing a single-crystal refractive secondary concentrator for use at temperatures exceeding 2000K. Candidate optically clear single-crystal materials like sapphire and zirconia are being evaluated for this application.

Accuracy of heat flux models is critical to clutch design in case of excessive temperatures due to large amounts of friction heat generated in the narrow space. Pressure distribution on the clutch friction interface is an important factor affecting heat flux distribution, thus affecting temperature distribution. In this paper, an experiment is conducted to obtain the pressure distribution for one typical dry clutch equipped with a set of diaphragm spring. Considering that the frictional interface is in contact, this study makes use of pressure sensitive film and acquires data based on image processing techniques. Then a polynomial mathematical model with dimensionless parameters is developed to fit the pressure distribution on the friction disc. After that, the proposed pressure model is applied to a thermal model based on finite element method. In addition, two conventional thermal models (i.e., uniform heat flux model and uniform pressure model), are implemented for comparison.