Search Results

The vehicle Heating, Ventilation and Air conditioning (HVAC) system is designed to meet both the safety and thermal comfort requirements of the passengers inside the cabin. The thermal comfort requirement, however, is highly subjective and is usually met objectively by carrying out time dependent mapping of parameters like the velocity and temperature at various in-cabin locations. These target parameters are simulated for the vehicle interior for a case of hot soaking and its subsequent cool-down to test the efficacy of the AC system. Typically, AC performance is judged by air temperature at passenger locations, thermal comfort estimation along with time to reach comfortable condition for human. Simulating long transient vehicle cabin for thermal comfort evaluation is computationally expensive and involves complex cabin material modelling.

In automotive FEA analysis, there are many components or assemblies which can be simplified to two-dimensional (2D) plane or axisymmetric analytical problems instead of three-dimensional (3D) simulation models for quick modeling and efficient analysis to meet the timing in the design development process, especially in the advanced design phase and iteration studies. Even though some situations are not perfectly planar or axisymmetric problems, they may still be approximated in 2D planar or axisymmetric models, achieving results accurate enough to meet engineering requirements. In this paper, the authors have presented and summarized several complex 3D analytical situations which can be replaced by simplified plane axisymmetric models or 2D plane strain analytical models.

To ensure reliable Diesel Particulate Filter (DPF) regeneration, even in critical situations such as slow city driving, a fuel vaporizer can be used to introduce additional hydrocarbons directly into the Diesel aftertreatment system. The fuel vaporizer provides significantly shorter reaction times than possible with engine measures alone and also helps minimize the extensive engine measures normally required to achieve the DPF ignition temperatures. As with other components, correctly optimizing complex aftertreatment systems requires not simply characterizing and optimizing an individual component, but also understanding the interaction between components and the behaviour of the system as a whole. The value of a system simulation lies in rapid turnaround times combined with the ability to address three-dimensional phenomena, since they often have a decisive impact on the system performance (e.g., the hydrocarbon distribution and its associated catalytic heat release).

Steady induction port flow has been simulated in a complex configuration, which is modelled on a four-valve engine with a pent-roof chamber. The numerical solution has been obtained using a finite volume method coupled with the standard k - ε turbulence model. It is shown that the 3D flow field is characterised by large vortices with horizontal axes induced by the inlet jets, and by flow interaction between inlet jets from both valves. Special attention has been paid to flow distributions in the valve curtain areas. Velocity and turbulence energy profiles have been obtained in these areas and compared with previous hot-wire measurements and 2D calculations using Reynolds stress models as well as the k - ε model. The findings in this study are expected to enhance our understanding of complex engine induction port flows and to provide better boundary conditions for in-cylinder flow calculations

A novel CFD simulation technique has been developed that unites realistic three-dimensional resolution of diesel particulate filter systems with computational efficiency. Three-dimensional resolution of the thermofluiddynamic behaviour during transient soot loading and regeneration is necessary for the optimization of the function, durability, weight and cost of DPF systems. Computational efficiency is required to allow its use as a standard development tool during all engineering phases and to allow the simulation of driving cycles. The detailed conclusions that can be drawn about soot distribution and thermal characteristics during the regeneration assist in ensuring the DPF function and avoiding DPF failures over the operational lifetime.

The present work addresses the possibility to correctly simulate Partial Homogeneous Charge Compression Ignition (PHCCI) combustion, obtained by the application of EGR up to 60% without using detailed kinetic models. In particular, the laminar and turbulent time characteristic model has been analyzed and improved. The study illustrates the prediction capabilities that can be achieved with such an approach. The paper reports the results obtained from the simulation of a single cylinder research engine and a four-cylinder diesel engine to verify the validity of the proposed method independently of engine geometry and configuration. All numerical results are compared with experimental pressure traces and rates of heat release, as well as with NOx and soot emissions over a wide range of operating conditions. With the modified characteristic time model, realistic simulations of engine combustion up to EGR values of about 60% have been obtained for both engines.

The present paper reports the results of the numerical simulations carried out by means of a modified version of the KIVA-3V code and of the comparison with experimental results obtained by using different optical techniques in a single-cylinder optically accessible diesel engine. The engine is equipped with a commercial four valves cylinder head and a second-generation, Common-Rail injection system. A detailed kinetic model consisting of 283 reactions involving 69 species is applied to simulate the combustion process and the soot and NOx formation. The fuel surrogate model consisting of two constituent components, n-heptane and toluene, approximating the physical and ignition properties of the diesel oil, is considered. The Partially Stirred Reactor (PaSR) assumption is adopted to maintain the computational cost within acceptable limits.

This paper aims to validate chemical kinetic mechanisms of surrogate gasoline three components fuel by calculating one-dimensional laminar burning velocity of iso-octane/air mixture. Next, the application of level-set method on premixed combustion without consideration the effect of turbulence eddies on flame front is also studied in three-dimensional computational fluid dynamic (3D-CFD) simulation. In the 3D CFD simulation, there is an option to calculate laminar burning velocity by using empirical correlations, however it is applicable only for particular initial pressure and temperature in spark ignition engine cases. One-dimensional burning velocities from lean to rich of iso-octane/air mixture are calculated by using CHEMKIN-PRO with detailed chemistry and transport phenomena as a function of different equivalence ratios, different unburnt temperature and pressure ranges.

To develop injection nozzles and to improve the numerical simulation technology of fuel spray, a measuring technology to analyze the process of disintegration into droplets accurately is required. Performances required by a spray droplets measuring device are: “ability to measure in the combustion condition inside the engine cylinder”, “ability to measure the diameter of spray droplets in high-density fields”, “ability to measure the structure of spray droplets in 3D”, and an improved measuring accuracy of non-spherical droplets. These elements are required in order to analyze the spray droplets structure of gasoline direct injection engines. As a promising method to satisfy these requirements, the laser holography method has been already suggested. However, it has some drawbacks, such as a difficulty in measuring spray droplets in high-density fields and over a long analysis period.

This work describes the definition and implementation of a dedicated system (hardware and software) for the quantitative evaluation of the anthropometrics and morphological parameters of the back shape. This was applied to the digital 3D analysis of subjects affected by spinal pathologies. In fact in clinical practice it is needed to have a repeatable and easy method to frequent non invasive screening of the rib system records a 3D model of the back shape standard and automated procedure. Its clinical validation is presented.

Particulate Matter (PM) filters are becoming a standard component of Diesel engines exhaust aftertreatment devices to comply with the forthcoming engine emission regulations. However, cost reduction and durability are still critical issues in particular for the integration of the PM-filter with other components of the after-treatment system (e.g. pre-turbo-catalyst, close-coupled-catalyst, PM-filter, SCR). To respect functional (available temperature and gas composition) and space restraints, very complex shapes may result from the design causing tortuous flow patterns and influencing the flow distribution into the PM-filter. Uneven soot distributions in the filter may cause a non-homogeneous development of filter regeneration, leading to failures, for example due to the occurrence of large temperature gradients during the oxidation of soot deposits.

A new and innovative approach for 3D vision systems is presented. The systems can be used not only for the acquisition of 3D distance images, but also for the acqui­sition of the corresponding 2D gray-scale images. Silicon imagers which are based on so-called photonic mixer devices are the key components. Photonic mixer devices (PMD) represent a new kind of active pixel sensors (APS), fabricated in CMOS technology. With a PMD camera an entire 3D-scene can be monitored. Therefore, PMD technology offers high potential for automotive applications with respect to both active and passive safety. Conti Temic is developing an occupant detection system as a first application of a PMD camera. Further applications, such as traffic environment perception, can benefit from the new opportunities of 3D-vision and are already being considered.

A Lagrangian random vortex-boundary element method has been developed for the simulation of unsteady incompressible flow inside three-dimensional domains with time-dependent boundaries, similar to IC engines. The solution method is entirely grid-free in the fluid domain and eliminates the difficult task of volumetric meshing of the complex engine geometry. Furthermore, due to the Lagrangian evaluation of the convective processes, numerical viscosity is virtually removed; thus permitting the direct simulation of flow at high Reynolds numbers. In this paper, a brief description of the numerical methodology is given, followed by an example of induction flow in an off-centered port-cylinder assembly with a harmonically driven piston and a valve seat situated directly below the port. The predicted flow is shown to resemble the flow visualization results of a laboratory experiment, despite the crude approximation used to represent the geometry.

Three-dimensional (3D) whole body scanners provide an opportunity for collecting large quantities of precise point data on human forms. However, product designers will likely always need some access to traditional point-to-point dimensional measurements. These measurements can also be obtained from the 3D whole body scanner if appropriate software is developed. This project describes a validation test for a collection of software tools designed to extract traditional dimensions from 3D whole body scans. To validate the software we scanned 123 male and female subjects on a Cyberware WB4 whole body scanner. Subjects were also measured for point-to-point dimensions using traditional instruments. We compared the mean absolute differences between traditional and software measurements to interobserver error data collected in a large traditional anthropometric survey (ANSUR), and to various criteria specific to garment applications.

Composites reinforced with 3D woven fiber preforms are known to display improved through thickness performance when tested using methods such as the ASTM D6415 curved beam protocol. The presence of reinforcing fiber in the through-thickness direction eliminates delamination as a mode of failure and allows the composite to continue to carry increasing loads well beyond first crack initiation. We propose that this characteristic of 3D woven composites may be exploited for applications such as automotive crash structures, which are required to dissipate large amounts of energy during an impact event. The rate dependent nature of these materials, however, is not well understood. An empirical study was conducted to provide an initial understanding of the dynamic behavior of 3D composites.

The quality of mixture formation in gasoline direct injection (GDI) engines has a significant influence on combustion, emissions and mileage. A new measurement technique was set up at an optically accessible high pressure / high temperature spray chamber to investigate the spatial mass distribution of vapor and liquid phase in order to optimize the stratified engine operation mode. Therefore a laser light sheet is traversed through the spray, the exciplex fluorescence is detected and the tomography results are quantified by the global information of the injected mass, which allows detailed spray investigations with λ-charts. For spray homogeneity analysis a new method based on histogram calculation is presented allowing grid independent comparison of different injector types.

CFD techniques are more and more utilized in the development of new solutions for performance improvement of internal combustion engines. Three dimensional models, in general, are able to provide detailed and sound information on engine phenomena, but often they are time consuming and hard to be implemented. On the other hand, one-dimensional models can reproduce the entire engine cycle with acceptable computational times; however they need semi-empirical correlations in order to model the flow field details and the burning speed within each cylinder. In this paper, an example of hierarchical structure of 3-D and 1-D models has been proposed. The main performances of a small turbocharged spark-ignition engine have been calculated. Variable-speed and full load operating points have been analyzed. The 3-D model provided the details of the in-cylinder flow field and turbulent indices.

Self-calibration of sensors has become highly essential in the era of self-driving cars. Reducing the sensors’ errors increases the reliability of the decisions made by the autonomous systems. Various methods are currently under investigation but the traditional methods still prevail which maintain a strong dependency on human experts and expensive equipment that consume significant amounts of labor and time. Recently, various calibration techniques proposed for extrinsic calibration for Autonomous Vehicles (AVs) mostly rely on the camera 2D images and depth map to calibrate the 3D LiDAR points. While most methods work with the whole frame, some methods use the objects in the frame to perform the calibration. To the best of our knowledge, majority of these self-calibration methods rely on using actual or falsified ground truth values.

Hydrodynamic radial journal bearings under unsteady load, which are common for automotive applications, are exposed to cavitation, e.g. flow, suction, shock and exit cavitation. The fluid mechanic description of the flow in journal bearings takes advantage of the small bearing clearance, which allows the reduction of the Navier-Stokes equations and leads to the Reynolds equation. The Reynolds equation is two-dimensional, the radial pressure gradient and the radial velocity component are neglected. However, the equation includes the surface velocities, oil density and viscosity and describes the relation between hydrodynamic pressure and local clearance. With the introduction of a cavitation index or a mass flow coefficient a powerful method to carry out numerical studies can be created, which allows the calculation of flow properties and the prediction of regions where the lubrication film disintegrates.