Search Results

There is an increasing interest in transient thermal simulations of automotive brake systems. This paper presents a high-fidelity CFD tool for modeling complete braking cycles including both the deceleration and acceleration phases. During braking, this model applies the frictional heat at the interface on the contacting rotor and pad surfaces. Based on the conductive heat fluxes within the surrounding parts, the solver divides the frictional heat into energy fluxes entering the solid volumes of the rotor and the pad. The convective heat transfer between the surfaces of solid parts and the cooling airflow is simulated through conjugate heat transfer, and the discrete ordinates model captures the radiative heat exchange between solid surfaces. It is found that modeling the rotor rotation using the sliding mesh approach provides more realistic results than those obtained with the Multiple Reference Frames method.

Contamination protection of brake rotors has been a challenge for the auto industry for a long time. As contamination of a rotor causes corrosion, and that in turn causes many issues like pulsation and excessive wear of rotors and linings, a rotor splash protection shield became a common part for most vehicles. While the rotor splash shield provides contamination protection for the brake rotor, it makes brake cooling performance worse because it blocks air reaching the brake rotor. Therefore, balancing between contamination protection and enabling brake cooling has become a key critical factor when the splash shield is designed. Although the analysis capability of brake cooling performance has become quite reliable, due to lack of technology to predict contamination patterns, the design of the splash protection shield has relied on engineering judgment and/or vehicle tests. Optimization opportunities were restricted by cost and time associated with vehicle tests.

In the present work, the effect of various nanofluids on convective heat transfer performance in an automotive radiator was analyzed based on measured nanofluid properties. Al2O3, TiC, SiC, MWNT (multi-walled nanotube) and SiO2 nanoparticles ranging between 1 and 100 nm in size were dispersed in distilled water to form nanofluids. An ultrasonic generator was used to provide uniform particle dispersion in the fluid and keep the mixture stable for a long period of time. The impact of various particle types and their volume concentration on fluid properties such as density, thermal conductivity and viscosity were experimentally analyzed. It is observed that the nanofluid properties increased with the increase in particle volume concentration. TiO2 nanofluids were observed to show the highest increase in density (2.6% higher than the base fluid at a 1% vol. concentration) and also the largest enhancement in thermal conductivity (7.5% augmentation at 1% concentration).

As the need for super high speed components (pumps, motors, etc) continue to grow rapidly, so does the need to make measurements at speeds higher than ever before. Bearings are a major component in any rotating system. With continually increasing speeds, bearing failure modes take new unconventional forms that often are not understood. Such measurements are impossible if bearings fail to perform. This paper will address the dynamic modes a bearing passes through and the potential failure modes associated with each. A review of the state of the art of current failure modes will be given, and then a hypothesis on some new failure modes associated with particular speeds will be discussion. The paper will also describe an apparatus that was designed especially to study these phenomena. Range of speed studied is 0- 60,000 rpm. Preliminary measurements indicated that this range breaks into three different zones: low (0-15,000 rpm), moderate (15,000-25,000 rpm) and high (25,000- 60,000 rpm).

This work studies an optimization tool for 2D and 3D a multi-element airfoil which utilizes the power of CFD solver of a Shape Optimizer package to find the most optimal shape of multi-element airfoil as per designer's requirement. The optimization system coupled with Fluent increases the utilization and the importance of CFD solver. This work focuses on combining the high fidelity commercial CFD tools (Fluent) with numerical optimization techniques to morph high lift system. In this work strategy we performed morphing (grid deformation) directly inside the Fluent code without rebuilding geometry and the mesh with an external tool. Direct search method algorithms such as the Simplex, Compass, and Torczon are used; Navier-Stokes equations were solved for turbulent, incompressible flow using k-epsilon model and SIMPLE algorithm using the commercial code ANSYS Fluent.

This paper discusses the uses of shape morphing/optimization in order to improve the lift to drag ratio for a typical 3D multi-element airfoil. A mesh morpher algorithm is used in conjunction with a direct search optimization algorithm in order to optimize the aerodynamics performance of a typical high-lift device. Navier-Stokes equations are solved for turbulent, steady-state, incompressible flow by using k-epsilon model and SIMPLE algorithm using the commercial code ANSYS Fluent. Detailed studies are done on take-off/landing flight conditions; the results show that the optimization is successful in improving the aerodynamic performance.

This work aims to numerically investigate the aerodynamic characteristics of a multi-element airfoil NACA 23012. The investigation was conducted through Computational Fluid Dynamics (CFD), using ANSYS FLUENT software. The Navier-Stokes equations were solved for turbulent, incompressible flow using k-epsilon model and SIMPLE algorithm. The study was carried out for both take-off / landing conditions and the results were compared to experimental data of the NACA 23012 from wind tunnel tests. The experimental and computational results for drag and lift coefficients match effectively up to pre-stall attack angles. The pressure coefficients, velocity distribution, and wall Y+ data were presented for different angles of attack (0 deg, 4 deg, and 8 deg). The CFD analysis could help acquire a closer and detailed understanding of airfoil performance, which is usually not easy through normal experimentation.

In this study three dimensional numerical simulations were carried out for steady incompressible flows around complex airfoil shapes. NACA-0012 and NACA-23012 wing with 20 percent-c Clark Y flap were used for this study. This work shows that the CutCell mesh method has the ability to generate high quality mesh which captures the details of the viscous boundary layer.

Increased energy costs make optimal aerodynamic design even more critical today as even small improvements in aerodynamic performance can result in significant savings in fuel costs. Energy conscious industries like transportation (aviation and ground based) are particularly affected. There have been a number of different optimization methods, some of which require geometrically parameterized models. For non-parameterized models (as it is the case often in reality where models and shapes are very complex). Shape optimization and adjoin solvers are some of the latest approaches. In our study we are focusing on generating best practices and investigating different strategies of employing the commercially available shape optimizer tool from ANSYS'CFD solver Fluent. The shape optimizer is based on a polynomial mesh-morphing algorithm. The simple case of a low speed, airfoil/flap combination is used as a case study with the objective being the lift to drag ratio.

The engine valve spring is a very important component in automotive engine systems. The non-metallic inclusions in an engine valve spring will significantly reduce its reliability. In this study, an attempt was made to establish a correlation between fatigue failures and non-metallic inclusions by applying statistical methods. Fatigue tests with BZ and OTEVA-90 materials are performed with two different types of experiments, which are rotating bending fatigue test (Nakamura test) and spring fatigue test. By using RELIASOFT, the data of these two tests are analyzed with the Weibull distribution in order to statistically estimate BZ and OTEVA-90's fatigue lives at 90% low confidence under different stresses. On the other hand, fatigue strength of these materials can be estimated by Murakami and Endo's model with maximum inclusion size predicted from the Gumbel distribution.

With advances in computing power and Computational Fluid Dynamics (CFD) algorithms, the complexity of CutCell based simulation models has significantly increased. In this study three dimensional numerical simulations were created for steady incompressible flow around airfoil shape. The NACA-0012 airfoil was used for this study. Boundary layer thickness, mesh expansion ratio, and mesh density variation parameters were investigated. Drag and lift coefficients were compared to experimental data. Use of the CutCell method results in a good agreement between CFD results and experimental data.

Finite element analysis (FEA) predictions of magnesium beams are compared to load versus displacement test measurements. The beams are made from AM60B die castings, AM30 extrusions and AZ31 sheet. The sheet and die cast beams are built up from two top hat sections joined with toughened epoxy adhesive and structural rivets. LS-DYNA material model MAT_124 predicts the magnesium behavior over a range of strain rates and accommodates different responses in tension and compression. Material test results and FEA experience set the strain to failure limits in the FEA predictions. The boundary conditions in the FEA models closely mimic the loading and constraint conditions in the component testing. Results from quasi-static four-point bend, quasi-static axial compression and high-speed axial compression tests of magnesium beams show the beam's behavior over a range of loadings and test rates. The magnesium beams exhibit significant material cracking and splitting in all the tests.

Magnesium alloy extrusions offer potentially more mass saving compared to magnesium castings. One of the tasks in the United States Automotive Materials Partnership (USAMP) ?Magnesium Front End Research and Development? (MFERD) project is to evaluate magnesium extrusion alloys AM30, AZ31 and AZ61 for automotive body applications. Solid and hollow sections were made by lowcost direct extrusion process. Mechanical properties in tension and compression were tested in extrusion, transverse and 45 degree directions. The tensile properties of the extrusion alloys in the extrusion direction are generally higher than those of conventional die cast alloys. However, significant tension-compression asymmetry and plastic anisotropy need to be understood and captured in the component design.

Magnesium alloys are the lightest structural metal and recently attention has been focused on using them for structural automotive components. Fatigue and durability studies are essential in the design of these load-bearing components. In 2006, a large multinational research effort, Magnesium Front End Research & Development (MFERD), was launched involving researchers from Canada, China and the US. The MFERD project is intended to investigate the applicability of Mg alloys as lightweight materials for automotive body structures. The participating institutions in fatigue and durability studies were the University of Waterloo and Ryerson University from Canada, Institute of Metal Research (IMR) from China, and Mississippi State University, Westmorland, General Motors Corporation, Ford Motor Company and Chrysler Group LLC from the United States.

Fully Flexible Valve Actuation (FFVA) systems provide maximum flexibility to adjust lift profiles of engine intake and exhaust valves. A research grade electro-hydraulic servo valve based FFVA system was designed to be used with an engine in a test cell to precisely follow desired lift profiles. Repetitive control was chosen as the control strategy. Crank angle instead of time is used to trigger execution to ensure repeatability. A single control is used for different engine speeds even though the period for one revolution changes with engine speeds. The paper also discusses lift profile extension, instantaneous lift profile switching capability and built-in safety features.

Over the last five years, the automotive industry has experienced a trend towards niche performance vehicles equipped with high-output powertrains. These high performance vehicles also demand higher output braking systems. One method used to provide enhanced pedal feel and fade performance is to equip vehicles with higher apparent friction linings. The challenge then becomes how to design and manufacture these brake systems without high-frequency disc brake squeal and without paying a significant mass penalty. One alternative is to design disc brake rotors with increased damping. There are several options for increasing rotor damping. The classical approach is to increase the rotor's cast iron carbon content, thus increasing the internal material damping of the rotor. However, this methodology provides only a small increase in rotor damping. Alternatively, the rotor damping can be increased by introducing friction, sometimes referred to as Coulomb damping.

A methodology involving Design for Six Sigma (DFSS) and Multi-body dynamic simulation is employed to tune a body-on-frame vehicle, for improved ride (shake) performance. The design space is limited to four sets of symmetric body mounts for a vehicle. The stiffness and damping characteristics of the mounts are the control factors in the virtual experiment. Variation of these design parameters from the nominal settings, as well as axle size, tire and wheel combinations, tire pressure, shock damping, and vehicle speed constitute the noise factors. This approach proves to be an excellent predictor of the vehicle behavior, by which much insight as to influence of each parameter on vehicle performance is gained. Ultimately, specific recommendations for the control factor settings are provided. Subsequent hardware builds show excellent agreement with the analytical model and suggested tuning.

Since 1997, General Motors Body Manufacturing Engineering - Die Engineering Services (BME-DES) has been working jointly with our software vendor to develop and implement a parallel version of stamping simulation software for mass production analysis applications. The evolution of this technology and the insight gained through the implementation of DMP/MPP technology as well as performance benchmarks are discussed in this publication.

A spectroscopic diagnostic system was designed to study the effects of different engine parameters on the chemiluminescence characteristic of HCCI combustion. The engine parameters studied in this work were intake temperature, fuel delivery method, fueling rate (load), air-fuel ratio, and the effect of partial fuel reforming due to intake charge preheating. At each data point, a set of time-resolved spectra were obtained along with the cylinder pressure and exhaust emissions data. It was determined that different engine parameters affect the ignition timing of HCCI combustion without altering the reaction pathways of the fuel after the combustion has started. The chemiluminescence spectra of HCCI combustion appear as several distinct peaks corresponding to emission from CHO, HCHO, CH, and OH superimposed on top of a CO-O continuum. A strong correlation was found between the chemiluminescence light intensity and the rate of heat release.

Architecture exploration could benefit from some early results of a safety analysis process. Typically, classical system safety analysis techniques such as Fault tree analysis (FTA) are performed after the design is completed. We propose an approach for an early safety assessment to improve the design and also shorten the design cycle time. A quick assessment to determine the safety figure of merit of the intended architecture expressed as a parametric expression can be used to determine the overall acceptability of the architecture. The result from a quick assessment of the system safety could be used as a means to explore system trade-offs in reliability and redundancy at the highest design levels.