Search Results

Investigations of the aerodynamic influence of rotating wheels on a simplified vehicle model as well as on a series production car are presented. For this research CFD simulations are used together with wind tunnel measurements like LDV and aerodynamic forces. Several wheel rim geometries are examined in stationary and in rotating condition. A good agreement could be achieved between CFD simulations and wind tunnel measurements. Based on the CFD analysis the major aerodynamic mechanisms at rotating wheels are characterized. The flow topology around the wheels in a wheel arch is revealed. It is shown, that the reduction of drag and lift caused by the wheel rotation on the isolated wheel and the wheel in the wheel arch are based on different effects of the airflow. Though the forces decrease at the front wheel due to the wheel rotation locally, the major change in drag and lift happens directly on the automotive body itself.

When undertaking investigations into the aerodynamic behavior of automobiles using scale models in a wind tunnel, Reynolds number dynamic equivalence is often difficult or impossible to obtain. The boundary layer transition from laminar to turbulent flow thus does not occur at a point on the model which corresponds to the transitional location on the real vehicle. To improve results obtained in such tests, roughness elements can be applied to the scale model to be tested and the transitional position of the boundary layer manipulated to correspond to the position of transition on the actual vehicle of interest. This paper describes such techniques and illustrates their use.

An ice shape database has been created to document ice accretions on a 21-inch chord NACA0012 model and a 72-inch chord NACA 23012 airfoil model resulting from an exposure to a Supercooled Large Drop (SLD) icing cloud with a bimodal drop size distribution. The ice shapes created were documented with photographs, laser scanned surface measurements over a section of the model span, and measurement of the ice mass over the same section of each accretion. The icing conditions used in the test matrix were based upon previously used conditions on the same models but with an alternate approach to evaluation of drop distribution effects. Ice shapes resulting from the bimodal distribution as well as from equivalent monomodal drop size distributions were obtained and compared.

This research focuses on the commercial 6111 aluminum alloy as the subject of investigation. By designing tensile specimens with the same characteristic dimensions but varying fillet radii, the effects of fillet radius on the tensile properties and stress concentration effects of the aluminum alloy were studied through tensile testing and digital image correlation techniques. The results demonstrate that with an increase in fillet radius, the failure strength and stress distribution of the aluminum alloy specimens have both undergone alterations. This phenomenon can be attributed to the reduction of stress concentration at the fillet due to the larger fillet radius. Further verification through digital image correlation reaffirms that samples with a fillet radius of 10mm exhibit notable stress concentration effects at the fillet, while specimens with a fillet radius increased to 40mm display uniform plastic deformation across the parallel section.

A study was conducted to assess the effects of controlling filter face temperatures and two differently sized collection systems on diesel total particulate matter (TPM) and vapor phase hydrocarbon levels from a diesel engine. The results were used to revise sampling protocols so that variability associated with quantitation of polynuclear aromatic hydrocarbons (PAH) is minimized. Particulate soluble organic fraction (SOF) levels (%) were compared 1) for tests where the dilute exhaust filter face temperature was held constant by varying dilution ratio (DR) to account for day to day variations in inlet air temperature to the tunnel and 2) for tests in earlier studies where the DR was held constant and the filter face temperature then varied because of varying tunnel inlet air temperature. Between date variations in %SOF were reduced by about 60% due to holding filter face temperatures constant, compared to holding DR constant.

The investigation was carried out with a driving simulator, where 20 subjects had the task to drive in a passenger car on a synthetic, curved road which was displayed on a screen. The subjects could steer the car on the road with the steering wheel and by using the accelerator and the brake pedal they had free choise of the driving speed. Besides driving, the subjects had to detect visual signals at various defined contrasts to the surrounding field and to confirm detection. The number of right answers and the reaction times were taken as measure of the influence of scattered light on driver's vision through four different windshields, i.e. three clear windshields with haze levels of 0.2, 1.5 and 4.9 % and a green tinted windshield with a haze level of 0.2 %.

One of the goals of the ICES conference is to highlight developments in Life Support Systems. Furthermore this paper addresses the requirement of the necessity of a development rather than its results In the early days of space flight a life support system had to supply the astronaut with breathable air at an acceptable temperature. In the era of Apollo missions nutrition and waste management were added. Until now physical/chemical Life Support Systems (LSS) are the baseline of all existing LSS in space. These apparatuses are able to keep a person in acceptable bodily health even for many months in flight. The issue of mental health of humans on long duration flights has become even more important since the Mir space station allowed such flights. The mental stress is reduced by psychological help from the ground crew. For longer flights, to Moon and Mars, spacecraft based methods are needed. Sources of help well known to all of us are music, pictures, videos and food.

The microstructure and silicon particle morphology of Al-Si cladding alloys are known to influence brazing properties and the quality of brazed joints. This paper reviews published literature on Al-Si system, melting mechanisms, grain size, solid state silicon particle growth and the influence on brazed joint formation. Common filler metals used for brazing sheet were thermally treated to modify Si morphology. The resultant microstructures were examined and Differential Scanning Calorimetry used to establish thermodynamic properties. The impact of silicon concentration and particle morphology on the melting kinetics is discussed.

Modern engine developments result in very different gas pressure-temperature histories to those in RON/MON determination tests and strain the usefulness of those knock scales and their applicability in SI engine knock and HCCI autoignition onset models. In practice, autoignition times are complex functions of fuel chemistry and burning velocity (which affects pressure-temperature history), residual gas concentration and content of species such as NO. As a result, autoignition expressions prove inadequate for engine conditions straying far from those under which they were derived. The currently reported study was designed to separate some of these effects. Experimental pressure crank-angle histories were derived for an engine operated in skip-fire mode to eliminate residuals. The unburned temperature history was derived for each cycle and was used with a number of autoignition/knock models.

It is widely accepted that engine combustion is fundamentally affected by the in-cylinder charge motion. Flow field structures present at the time and location of spark ignition are known to have a controlling effect on early flame development. Therefore, improved understanding of the variation in flow field structures local to the spark plug at the time of ignition is required. This study investigates the spatial and temporal development of flow field structures within the pent roof combustion chamber of a single cylinder, direct injection spark ignition (DISI) optical engine. High speed particle image velocimetry (HSPIV) has been used to quantify the flow field leading up to and following spark ignition. HSPIV data was recorded at a rate of 5 kHz, providing a temporal resolution of 1.8 crank angle degrees (CAD) between measurement fields and a spatial resolution of 512 by 512 pixels.

A new technique of translating linear to rotary motion, using the Stiller- Smith mechanism, can be applied to the design of internal combustion engines and compressors. This new mechanism produces purely sinusoidal motion of the pistons relative to crank angle, which is a different motion from that produced by a conventional slider-crank mechanism, Influence of this sinusoidal motion on thermodynamic performance of engines and compressors was investigated theoretically and experimentally. Data are presented from a numerical analysis of compression and of spark-ignited combustion. Also, pressure-time curves for a standard and a modified (long connecting rod) spark ignition engine are compared. All data confirm that there is little thermodynamic difference between the Stiller-Smith and slider-crank devices.

The roll stability of heavy-duty trucks and truck combinations is discussed both on the level of the fundamental mechanics of vehicle response and from the viewpoint of the quantitative influence of size and weight variables. The presentation on fundamentals begins with the case of a rigidly-suspended vehicle and builds up to the case of a tractor-semitrailer with distinctive suspension stiffnesses and spring lash properties at the various axle positions. Size and weight considerations cover variations in axle load, gross weight, and overall width as well as incidental issues involving the height and possible lateral offset of the payload center of gravity. Size and weight influences on roll stability are interpreted in terms of the likely implications for rollover accident involvement.

Drivers searched for known symbols on a simulation of a dimly lit (5 1x) instrument panel. The symbols, from 2 mm to 25 mm diameter, were in groups of nine. They were randomly selected from 24 used to identify controls and displays on European Ford vehicles. The probability of recognition was related to size for eight symbols. This gives a rational basis for the size used in vehicles. No reliable difference was found between the performance of black symbols on white backgrounds and white on black. Substantial differences exist between the effectiveness of different symbols. Recommendations for improvements were based on confusions between symbols.

Flame spread over a melting thermally thick composite polymer is investigated in a channel flow above a condensed fuel. The condensed fuel consists of an isotropic (melted layer of) liquid near the heated surface and an anisotropic (not-yet-melted) solid surrounding it. The influence of the solid anisotropy is evaluated by changing the solid conductivity (ksx or ksy) in one particular direction (x in horizontal flame spread direction or y in vertical direction, see schematics in Figure 1) while keeping the other properties fixed. Note that the liquid conductivity kl has no isotropic behavior. Numerically, it is found that the flame spread rate decreases with either increasing ksx or ksy. The decrease with respect to ksy is less than for a comparable case described by the de Ris formula for an isotropic pure solid. The flame spread rate is more accurately determined by an analytical formula derived for spread across a melting solid fuel.

Experiments were conducted on two direct injection diesel engines: a standard production 2.5 litre engine, and a single cylinder research engine fitted with a high-pressure electronically controlled unit injector. The influence of some operating parameters (such as load, speed, injection timing and swirl-ratio) on the total mass and composition of particulate emissions sampled in a mini-dilution tunnel was investigated. A data acquisition system was used to record and analyse the cylinder pressure, fuel line pressure and fuel injection needle-lift diagrams. Analysis of the HC and NOx emissions as well as the Bosch smoke number was helpful in the understanding of how the fuel and air mixing process, the flame type and the combustion chamber temperature and pressure affect the amount and composition of diesel particulate emissions. A good correlation between the Bosch smoke number and the exhaust carbon concentration was also found.

General considerations about the use of convex mirrors indicate that they may be very useful to enlarge the field of view. There seems to be no need to use smaller values for the radius of the mirror than 1000 mm. A reaction time experiment is described in which plane mirrors of equal size at different positions on the fender are used. There are indications that the position of about 20° out of the line of sight straight ahead might be optimal. Whether this also holds for convex mirrors is not investigated. An experiment is described in which a driver must decide whether he can overtake a car in front of him, while a car behind him is approaching. This is done with several speeds of the car behind and with different curvatures of the side mirrors. Especially if the radius of curvature is not less than 1200 mm, no serious effects on driver behavior is observed. The instrumented car used in the studies is briefly described.

Nowadays, there is a permanent need to develop alternative fuel production and combustion technologies. The general objective indicated in Directive 2009/28/EC for biofuels in Poland is application in transport 10% of renewable energy by 2020 and 20% by 2030. In Poland, it can be achieved by adding bio-components to liquid fuels. Flexible fuel vehicles are not as popular in Europe as in Brazil, so further ethanol processing is justified. The researched synthetic gasoline was obtained from bioethanol at the Ekobenz Company Ltd. in Poland. In 2008, Sasol launched its 100% synthetic jet fuel produced by CTL (Coal to Liquids). A variety of engine concepts was tested and evaluated in terms of the key criteria for use as a range extender developed by AVL Company. The Wankel engine has been selected for the vehicle prototype as the most compact and of excellent NVH behaviour. The use of this engine in light helicopters is also considered.

A modified equation for the heat transfer coefficient has been established, because the original equation proposed by the author in 1967 provides at low load and motored operation to low results. The reason for this descrepancy seems to be a steady state soot layer, the thickness of which increases with increasing load, where as it does not exist in a motored engine. All equations for the heat transfer coefficient known either to, do not represent the real heat transfer coefficient accuring at the soot layer surface, but include the thermal conductivity resistance of the soot layer. The real heat transfer coefficient is more than two times higher than assumed up to now. These results also show the adiabatic engine in a totally new light.

The technological requirements and the development program required in producing a spacecraft have significant effects on the manufacturing operations of an aerospace corporation, particularly when there is no prospect of follow-on production. The spacecraft’s internal and external environment considerations, weight controls, reliability, traceability, and limited production are reviewed with respect to their influence on manufacturing costs, schedules, operations, skill levels, and training requirements. The importance of visibility into, and control of, day-to-day operations is highlighted. Some salient management problems that result from the spasmodic nature of the development program are discussed.

A base diesel fuel with 37% 1-3 ring aromatics and 12.9% PAH was passed through a dearomatising process that removed the two and three ring aromatics and reduced the single ring aromatics to 14%. These two fuels plus a combination of 60% of the original fuel with 40% of the low aromatic fuel were tested on a Perkins Phaser TCIC diesel engine of US 1991 emissions standards over the EC 13 mode cycle. The fuels and particulate SOF were analysed for all the n-alkanes and all of the PAH of significant concentration. The high speed maximum power particulate SOF were analysed in detail for all three fuels and mass emissions of 15 n-alkanes and 15 PAH determined and 15 other non-fuel PAH searched for. Most of the results showed that the composition of the SOF in terms of n-alkane and PAH was predominantly unburnt fuel compounds, the fuel with negligible PAH had very low PAH emissions compared with the parent fuel with a high PAH content.