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In this paper we numerically investigated the impact of large droplets on smooth solid surfaces to understand the splashing mechanism involved in ice accretion due to supercooled large droplets. A Navier-Stokes solver was used to describe the flow field, the moment-of-fluid (MOF) method was used to capture the droplet interface evolution, and the adaptive mesh refinement technique was employed to refine the mesh near the region of interest. We investigated the effect of air on splashing mechanism and confirmed that a low pressure can suppress the droplet splashing. The size distribution of splashed secondary droplets was studied and showed good agreement with experimental results. The effect of surface curvature on the splashing phenomenon was highlighted. Finally, the droplet impact on a NACA 23012 airfoil was studied and the water collection efficiency was investigated.

Because of local modifications of the grain structure in the heat-affected zone of the welding as well as a different chemical composition of the weld metal as compared to the base material the various areas of a welding exhibit a different deformation- and strain behaviour. To evaluate the influence of the material behaviour and the process behaviour of the joining procedure on the strain behaviour of the welding the application of laser-optical sensoring offers a new source of information. In particular, results of investigations of weldings made of sheet metals will be presented. As a welding process for tailored blanks, high frequency welding is particular emphasized in this presentation apart from the process of laser beam welding. The investigations also have the purpose to be a basis for the verification of FEM calculations and to develop appropiate material models.

In recent studies, much research is focused on the silicides alloys based in refractory transitions metal, becoming these materials as potential candidate for structural applications in high-temperatures for the fact of them possess excellent balance of properties. This work presents results of microstructural characterization of the Ta5Si3 and Cr5Si3 alloys, these silicides were obtained by arc melting under argon atmosphere. X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were used to obtain information about chemical and crystallographic characteristics of the samples generated before and after the heat-treatment.

Each year the technical defects found during inspection of passenger cars, two-wheeled and commercial vehicles after accidents are analyzed with regard to their accident-causing potential at DEKRA. Since each accident vehicle and usually each accident site is examined by an expert on traffic accidents, details on the causes of the accidents are collected in addition to general statistical data. This paper is a collective analysis describing which vehicle components and subassemblies are considered the causes of the accidents, what influence the vehicles' age had on the accidents and who is responsible for the defects (manufacturer, repair shop or driver).

The mathematical thermal design of the vehicle brakes will lead to success if all influence parameters such as friction (fading effect), car geometry and inertia, brake amplifier, tire, convective heat flow, heat conductance and heat radiation are taken into consideration. In addition to a lot of design criteria, the thermal stability of the vehicle brake is becoming more and more important because of permanently increasing engine powers and weight of the vehicles. This requires both stable friction behavior in the contact zone between brake lining and brake disk and a sufficient transfer of the friction energy by means of convective heat flow. In order to accomplish these two tasks, considerable expense on a brake test bed and innumerable brake trials are necessary. It must be guarantied at the end of the brake design process that the vehicle reaches the required braking distance and the thermal stability of the brake, e.g. after several freeway braking sequences.

Hydro-pneumatic suspension systems have been used increasingly in recent times because of the well known advantages they offer. It is equally well known that the spring force is time- and temperature dependent, resulting in varying ride height and ride comfort of vehicles equipped with hydro-pneumatic suspension systems. In the present study, the temperature- and time dependent characteristics of hydro-pneumatic springs are modelled mathematically. This is done in order to investigate the effect of heat transfer on the spring characteristic so that it can be taken into account during the design of such systems. The mathematical analysis is based on the solving of the energy equation of a gas in a closed container by using the Benedict-Webb-Rubin equations for real gas behaviour. This differs from the traditional method which makes use of the ideal gas approach and polytropic processes to determine the spring characteristic.

In order to meet future emission standards of small two-stroke engines (CARB 2), detailed knowledge of in-cylinder charge motion and mixture distribution is essential to be able to provide new ways of reducing exhaust emissions. The aim is to minimize fuel short circuiting accompanying the scavenging flow, which in turn leads to high HC emissions. Therefore, an experimental investigation was carried out to investigate the in-cylinder flow structure during the gas exchange process inside a small two-stroke engine. An optically accessible cylinder was fitted to a 64 cm3 two-stroke engine and the transient gas motion examined with Particle-Image-Velocimetry (PIV) under a variety of operating conditions and speeds up to 6000 rpm. The flow was investigated in two vertical cross- sectional planes through the cylinder and in a horizontal plane. The flow was observed through endoscopic optics to overcome the limitations associated with the design of an optical aperture in the small engine.

A new method of continuous measurement of engine oil consumption using sulfur as the tracer has been developed. The modified non-dispersive-infrared (NDIR) analyzer with the SO2 absorbent and a permeable plastic type dryer enable to measure very low concentration of SO2 in the exhaust gas. By the use of this method, the engine oil consumption under the transient engine operating condition has been analyzed. The experimental result show that the measured value of the transient oil consumption is larger than the estimated value by the quasisteady method using the experimental data of steady-state operations. The difference between these value is explained by the simple model developed here. This model also show that the total oil consumption under the transient engine operating condition depends mainly on the amount of oil drawn into the combustion chamber by the high vacuum during engine-brake conditions.

Computational Fluid Dynamics (CFD) tools play an important role in the early stages of vehicle aerothermal development. Arguably, the RANS (Reynolds Averaged Navier-Stokes) approaches are most widely used in industry due to their acceptable accuracy with affordable computational cost and faster turnaround time. In many automotive flows, RANS models cannot very accurately capture the absolute flow features or even the integral force coefficients. In spite of this, the RANS based CFD prediction results can conveniently be used to assess the magnitude and direction of a trend. However, even for such purposes, notable disagreements often exist between the flow features predicted by different RANS turbulence models. Whilst comparisons of different RANS models for various applications are abundant in literature, such evaluations on full-car models are limited, especially the evaluations of the cooling airflow inside the underhood compartment.

The demand for better fuel economy pushed by both consumer and Environmental Protection Agency (EPA), made OEMs to put more effort on other areas beside vehicle external aerodynamics. As one of these areas, under-hood aero-thermal management has taken an important role in the new road vehicle design process, due to the combination of growing engine power demands, utilization of sophisticated under-hood and underbody devices, and emission regulations. The challenge of the under-hood aerothermal management is not only due to the complexity of under-hood compartment, but also as a result of the complex heat transfer phenomena involving conduction, convention and thermal radiation. In this study, 3D CFD simulations were used to investigate the under-hood aerothermal flow features. The full vehicle model with detailed under-hood components used in this study is a Hyundai Veloster. A commercial CDF code Star-CCM+ version 11.04 from CD-adapco was used to run all the simulations.

Diesel engine is being used widely in many industrial fields, as it provides merits in the aspects of higher thermal efficiency and less CO₂ emission. However, NOx regulations for diesel engines are being strengthened and it is impossible to meet the emission standard without aftertreatment systems such as SCR (Selective catalytic reduction), LNC (Lean NOx catalyst), and LNT (Lean NOx trap). Among the NOx reduction aftertreatments, Urea-SCR system is known as the most stable and efficient method to solve the problem of NOx emission. But this device has some issues associated with the ammonia slip phenomenon which is occurred by shortage of evaporation and thermolysis time, and that makes it difficult to achieve uniform distribution of the injected urea.

One of the main causes of the torsional and bending fluctuations of the driveline is the angularity of the driveshaft and its universal joints. Most of the previous studies of the driveline vibrations have considered constant and equal angularities of these joints. However, the exact equality of the angularity is very difficult to maintain for ground vehicles under different ride vibration modes. This paper is concerned with the coupling between the driveline fluctuations and the ride vibrations of the rear drive vehicles. The coupled motions, which are; drive axle suspension deformation and vehicle body pitch angle and their derivatives, have been used to study the driveshaft and output shaft bending and torsional fluctuations. The results have showed that the fluctuations of the driveshaft due to the base angularity of the joints are superimposed by another fluctuation due to the bounce and pitch of the vehicle body.

An experimental and numerical investigation, using the Laser Doppler Anemometry (LDA) technique and a 3D fluid-dynamic code (KIVA 3V), was carried out in a prototype engine under steady-state conditions. The aim of the present activity was the flow field characterization and the effect of the intake geometry on the in-cylinder tumble flow. A new steady flow test rig designed for capturing the tumble motion within a test cylinder, made by a blower and an engine head, was assembled to simulate the intake flow. The engine head was mounted on an aluminum cylinder, having the same bore as the real engine. The cylinder was provided with optical accesses on the periphery and a flat optical window located at the bottom to a depth equal to the stroke of the engine. The cylinder was also equipped with two cylindrical ducts, used as air outflow ports.

The noise emitted by the heating, ventilation and air conditioning system (HVAC) has a great influence on the car acoustical comfort and quality perception. To improve its sound quality, physical properties which determine the subjective perception have to be identified. The HVAC-noise of twelve cars in different arrangements of fan speed and direction of air flow was recorded for later objective and subjective analysis. All cars were of the same model, but with three different types of HVAC-systems, and had just been manufactured. Objective analysis with sound quality software and subjective evaluations was carried out. Using multiple linear regressions on the subjective data, relations between subjective results and psychoacoustic metrics were determined and models to predict subjective response to HVAC sounds are proposed. It is shown that the annoyance caused by the HVAC-noise can be satisfactorily described by Zwicker's stationary loudness model.

Die cracking is one of the most important life-limiting tool failure mechanisms in high pressure die casting (HPDC). Cracking is caused by thermal shock from sudden heating and then cooling of the die surface. Injection of molten aluminium, transfers heat to the die which results in compressive stresses on the die surface. After the casting has been extracted, the die is sprayed with releasing agent which generates tensile stresses on the surface of the die. These stress fluctuations result in heat check cracking or gross cracking forming on the surface of the die. Casting simulation software was used to simulate the casting process; metal filling the die cavity, solidification and thermal stresses in the die. For this paper a comparison was made between a simulation analysis and a cracked die slide. When the die cracks due to thermal fatigue, aluminium penetrates into the cracks which results in visual defects being formed in the casting and will further reduce the die-life.

The aim of the study is to evaluate the possible vanadium emissions from different commercially available vanadium-based SCR monoliths. The vanadium sublimation was studied at laboratory scale using a monolith sample (16 mm diameter × 19 mm long). Vanadia vapors were disposed on an alumina bed placed downstream the catalyst sample, in the hot zone of a furnace. Experiments were carried out with a space velocity of 42 000 h−1. The reactive gas flow was composed of 5%O2, 5%H2O, 500ppm NO and 500ppm NH3. Catalyst samples and alumina bed were exposed to this reactive gas flow during 10 hours at 500°C, 600°C, 650°C, 675°C, 700°C and 750°C, successively. After each test, alumina samples were mineralized from HNO3, HF and HCl mixture. The digests were then diluted with high purity water prior, to ICP-MS analysis. The results revealed that, for full body type catalysts, sublimation of vanadium increases in a significant way from an exposure to the reactive gas flow at 675°C.

Steady state mapping is fundamental to optimizing IC engine operation. Engine variables are set, a predefined settling time elapses, and then engine data are logged. This is an accurate but time consuming approach to engine testing. In contrast the sweep method seeks to speed up data capture by continuously moving the engine through its operating envelope without dwelling. This is facilitated by the enhanced capability of modern test rig control systems. The purpose of this work is to compare the accuracy and repeatability of the sweep approach under experimental conditions, with that of steady state testing. Limiting factors for the accuracy of the sweep approach fall into two categories. Firstly on the instrumentation side - transducers have a characteristic settling time. Secondly on the engine side - thermal and mechanical inertias will mean that instantaneous measurements of engine parameters differ from the steady state values.

Plasma switches ( Cs and Cs-Ba tacitrons PS ) with thick grid have grid with thickness more than mesh aperture size. These grids have some advantages as compared with small-scale /1.2/ ones, for instance, much more electrical strength. This paper contains the “thick-grid” investigation results; the grid controle efficiency, the plasma parameteres, probe researches of these parameteres at conductive state and their variety during the process of quenching. The results showed the “thick-grid” PS plasma differed from the “thin - grid” PS signyficantly at the stationary state as well as by quenching dynamic features.

The mechanism of automobile brake hot spots is unclear, which is a problem in the brake industry. Complex coupling between friction, heat, contact, and structure is the main difficulty in revealing the mechanism of brake hot spots. This paper proposes a new way to study the mechanism of hot spots by analyzing the deformation behavior of brake discs under asymmetric mechanical loading. The actual brake is simplified into a brake disc and friction lining system, and a transient dynamic finite element model under asymmetric mechanical loads is established to analyze the deformation characteristics of the brake disc. The normal deformation of the brake disc under asymmetric mechanical loads consists of two parts: low-frequency bending deformation and high-frequency waviness deformation, which are caused by the squeezing effect of the asymmetric brake pressure on the brake disc and the constraint modal vibration of the brake disc.

Form the viewpoint of low air pollution and energy saving in the internal combustion engines, experiments have been carried out to examine the characteristics of flame propagation near the lean limit mixtures in a closed bomb by using the microgravity techinique. The true flame characteristics is examined by realizing the spherical flame propagation in a closed bomb under microgravity. Furthermore, the effect of hydrogen added in lean limit mixtures and improvement of the reflectivity of the internal surface wall of the combustion bomb are studied to enhance the flame propagation speed of lean limit mixtures.