Browse Topic: Antigravity

Items (14)
Find
An Aerodynamic Equation of State—Part I: Introduction and Aerospace Applications - QA Test Tatsiana01-17-01-00014/19/2023
Abstract In subsonic aircraft design, the aerodynamic performance of aircraft is compared meaningfully at a system level by evaluating their range and endurance, but cannot do so at an aerodynamic level when using lift and drag coefficients, CL and CD , as these often result in misleading results for different wing reference areas. This Part I of the article (i) illustrates these shortcomings, (ii) introduces a dimensionless number quantifying the induced drag of aircraft, and (iii) proposes an aerodynamic equation of state for lift, drag, and induced drag and applies it to evaluate the aerodynamics of the canard aircraft, the dual rotors of the hovering Ingenuity Mars helicopter, and the composite lifting system (wing plus cylinders in Magnus effect) of a YOV-10 Bronco. Part II of this article applies this aerodynamic equation of state to the flapping flight of hovering and forward-flying insects. Part III applies the aerodynamic equation of state to some well-trodden cases in fluid mechanics found in fluid-mechanics textbooks.
Burgers, Phillip
Nonlinear IMM-SUKF Algorithm for Maneuvering Target Tracking with Bearings-Only Measurement2019-01-600512/30/2019
Abstract In this paper, we present an efficient filtering algorithm to perform accurate estimation in jump Markov nonlinear systems, which we aim to contribute in solving the problem of model-based body motion estimation using bearings-only measurement, the Interacting Multiple Model (IMM) algorithm is specially designed to track accurately maneuvering targets whose state and/or measurement (assumed to be linear) models change during motion transition. However, when these models are nonlinear, the IMM algorithm must be modified in order to guarantee an accurate track. In this paper we propose to avoid the Extended Kalman Filter (EKF) because of its limitations and substitute it with the Scaled Unscented Kalman Filter (SUKF) which seems to be more efficient especially according to the simulation results obtained with the Interacting Multiple Model Scaled Unscented Kalman Filter (IMM-SUKF).
Sebbagh, Abdennour, Kechida, Sihem
Understanding Base Oils and Lubricants for Electric Drivetrain Applications2019-01-233712/19/2019
ABSTRACT The penetration of hybridization and electrification (HEV and EV) technology into automotive powertrain designs is an evolving trend resulting from global regulations intended to reduce transportation-related emissions of greenhouse gases and other pollutants and to improve vehicle fuel efficiency. In many HEV and EV hardware designs, drivetrain fluids have contact with the integrated electric motor (e-motor), which requires electrical and thermal properties to be considered in addition to traditional fluid properties. This paper discusses new insights gained around electrical and thermal properties of drivetrain fluids, with a specific emphasis on understanding the critical impacts of base oils (BOs). Electrical and thermal properties data as a function of temperature for a range of BOs as well as automatic transmission fluids are shared. We found that BOs and their viscosities play a critical role in cooling performance, while additives play a critical role in electrical conductivity (EC). That being said, we also have observed that additives in BOs can modify cooling performance. We will demonstrate how each component in the additive package affects EC and in some cases cooling performance. The successful utilization of this knowledge is demonstrated on a proof-of-principle basis to show that fluids with appropriate electrical and thermal properties can be designed to meet critical factors for electrification such as cooling capacity and EC, while still maintaining essential performance features for conventional driveline fluids.
Kwak, Yungwan, Cleveland, Christopher, Adhvaryu, Atanu, Fang, Xinggao, Hurley, Susie, Adachi, Tsuneo
Three-dimensional simulations of oil dilution in DI diesel engines under motoring conditions with varying injection timing2019-01-218612/19/2019
ABSTRACT This study presents a simulation method for oil dilution in diesel engines by a post injection to understand the oil dilution mechanism and to improve an empirical model predicting the evolution of oil dilution. To consider the wall film, two-dimensional governing equations are additionally solved along the cylinder wall. Primary critical Weber numbers are used to determine adhesion or a splash of droplets at wall impingements. Motoring engine simulations at different injection timings show that dilution ratios in simulations are in good agreements with those in experiments. Oil dilution is not proportional to injection timings in this motoring conditions.
Hori, Tsukasa, Yamaji, Kohei, Akamatsu, Fumiteru
Analysis on flow motion and combustion process in pre-chamber and main chamber for low-speed two-stroke dual-fuel engine2019-01-217512/19/2019
ABSTRACT Low-speed two-stroke dual-fuel engines has been paid more attention due to the energy efficiency design index and Tier III emissions limitations issued by International Marine Organization. Although the dual-fuel engines have strong merits on emissions reduction, which can reach the IMO Tier III without aftertreatment, the power output is much lower than that of diesel engines. Therefore, the dual-fuel engine is also needed to improve continuously. However, the mixing and combustion processes in the engine have not been fully understood. In this study, a 3D-CFD model of the dual-fuel engine was established using CONVERGE to explore the mixing and combustion processes. Locally embedding fine grids are considered at scavenging ports, natural gas injection ports, pre-chamber. The model was validated by experimental in-cylinder pressure. Then, the flow motion, mixing of natural gas and air, flow in pre-chamber, torch and combustion in main-chamber were analyzed based on swirl variation, flow velocity distribution, equivalence ratio distribution and torch propagation.
Liu, Long, Wu, Yue, Xiong, Qian, Liu, Teng
CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines2019-01-219212/19/2019
ABSTRACT The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.
Giramondi, Nicola, Mihaescu, Mihai, Erlandsson, Anders Christiansen, Jäger, Anders
Wall Heat Transfer Modeling Based on the Energy Equation For Zero Dimensional Engine Simulation2019-01-231312/19/2019
ABSTRACT It was important for predicting wall heat flux to apply wall heat transfer model by taking into account of the behavior of turbulent kinetic energy and density change in wall boundary layer. Although energy equation base wall heat transfer model satisfied above requirements, local physical amounts such as turbulent kinetic energy in near wall region should be applied. In this study, in order to predict wall heat transfer by zero dimensional analysis, how to express wall heat transfer by using mean physical amounts in engine combustion chamber was considered by experimental and numerical approaches.
Harada, Yuji, Uchida, Kenji, Yamashita, Hiroyuki
Oxidation of Soybean Biodiesel Fuel in Diesel Engine Oils04-12-03-001512/5/2019
Abstract During diesel engine operation, some fuel is entrained in engine oil, particularly as a consequence of strategies to regenerate NOx traps or particle filters. This “fuel dilution” of oil can adversely affect engine oil properties and performance. Compared to diesel fuel, biodiesel is more prone to fuel dilution and more susceptible to oxidation. Oxidation stability experiments were conducted at 160°C using a modified Rapid Small-Scale Oxidation Test (RSSOT) and a Rancimat instrument with 0, 5, 10, and 20 wt% biodiesel in four fully formulated engine oils, two partially formulated engine oils, and two base oils. These experiments showed decreasing oxidation stability with increasing biodiesel content. An exception was noted with the least stable oils (two base oils and one engine oil) in which 5 wt% biodiesel improved the oxidation stability relative to oil without biodiesel. Experiments with biodiesel distillation fractions identified this stability enhancement within the least volatile biodiesel fraction, consistent with natural antioxidants in the biodiesel. Omission of two engine oil additives, antioxidants and zinc dialkyldithiophosphates (ZDDP), led to an unexpected increase in oxidation stability (with and without biodiesel). Time-series oxidation experiments at 160°C with one of the fully formulated engine oils, with and without 20 wt% biodiesel, demonstrated that the biodiesel caused greater oxidation instability and extent of oxidation, greater formation of peroxides and reduction in total base number (TBN), increased ester content, and higher density. Kinematic viscosity increased with aging time and eventually surpassed that of the engine oil aged without biodiesel. With extended aging time, the fully formulated engine oil containing biodiesel “broke,” forming black tar-like materials with high viscosity.
Ball, James C., Anderson, James E., Duckworth, Jacob A., Uy, Dairene, Wallington, Timothy J.
Gas Metal Arc Welding Process Parameter Optimization to Reduce Porosity Defect in a Longitudinal Seam Welding of Pressure Vessels05-13-01-000512/2/2019
Abstract Pressure vessels are critical equipment used in industries for storing liquids or gases at a pressure significantly different from ambient conditions. Porosity is one of the major weld defects in pressure vessels that leads to failure during inspection and as well as during its service. Gas Metal Arc Welding (GMAW) process is widely used in industries to fabricate pressure vessels using carbon steel “IS 2062 E250BR” material for storing compressed air. The main objective of this article is to reduce the porosity defect in the longitudinal seam (LS) welding of the pressure vessels. Detailed analysis is carried out to identify the parameters which are influencing the porosity defect. Central Composite Design (CCD) and Response Surface Methodology (RSM) approaches are used to find the optimum value of the weld parameters which produce weld without porosity or any major defects in the pressure vessel. An experimental setup has been established and welding experiments have been conducted under a controlled environment. Experiments were conducted without any external disturbances ensuring clean weld surface and filler wire without any moisture, rust, oil, and the presence of any organic materials. For all the weld specimens, visual and radiography examinations were carried out to identify the severity of porosity. A porosity index is proposed in this study for conducting statistical analysis. Statistical analysis shows current, travel speed, gas flow rate, and torch angle have a linear relationship and stickout distance has a nonlinear relationship with porosity. In square term, stickout distance has a significant influence on porosity defect. In two-way interaction studies, current and gas flow rate, current and torch angle, and travel speed and torch angle have a significant influence on porosity. Confirmatory tests were carried out to validate the optimum weld parameters obtained in this study.
Kuppusamy, A., Rameshkumar, K., Sumesh, A., Premkumar, S.
Stall Mitigation and Lift Enhancement of NACA 0012 with Triangle-Shaped Surface Protrusion at a Reynolds Number of 105 01-12-02-000711/21/2019
Abstract Transient numerical simulations are conducted over a NACA 0012 airfoil with triangular protrusions at a Reynolds number (Re) of 100000 using the γ-Reθ transition Shear Stress Transport (SST) turbulence model. Protrusions of heights 0.5%c, 1%c, and 2%c are placed at one of the three locations, viz, the leading edge (LE), 5%c on the suction surface, and 5%c on the pressure surface, while the angle of attack (AOA) is varied between 0° and 20°. Results obtained from the time-averaged solution of the unsteady Navier-Stokes equation indicate that the smaller protrusion placed at 5%c on the suction surface improves the post-stall lift coefficient by up to 59%, without altering the pre-stall characteristics. The improvement in time-averaged lift coefficients comes with enhanced flow unsteadiness due to vigorous vortex shedding. For a given protrusion height, the vortex shedding frequency decreases as the AOA is increased, while the amplitude of fluctuations in lift coefficient increases as the protrusion height is increased or as the AOA is increased. Nevertheless, mitigation of static stall phenomena is observed for most configurations investigated, and this finding can be beneficial for the design of Unmanned Aerial Vehicles (UAVs) and Micro Aerial Vehicles (MAVs). The enhancement in the vortex shedding frequencies due to triangular protrusion can be utilized for Vortex-Induced Vibrations (VIVs)-based energy generators.
Bodavula, Aslesha, Yadav, Rajesh, Guven, Ugur
Material Characterization of Extruded Aluminum Axial Tubes as Energy-Absorbing Structural Members05-13-01-000411/21/2019
Abstract The increasing use of aluminum alloy extrusion in automotive vehicle chassis as structural members has necessitated the need to investigate their crushing behaviors. This article experimentally examines in detail, for the first time with respect to strength, ductility, and microstructure, AA6063-T7 (overaged) condition and the standard T6 temper and their capacity to meet crashworthiness requirements. Both tempers were assessed based on their mechanical properties (strength, ductility, true stress/strain behavior to necking, plastic anisotropy, strain rate sensitivity, and post-instability ductility to fracture) and microstructure, which were determined using basic tensile testing methods and metallographic approach. The implications of these properties/microstructures were further assessed experimentally by investigating the crushing behavior and energy absorption capacities of two extruded geometric profiles: a general rectangular profile and a novel cross-shaped profile investigated in a previous study. Typical modes of collapse were observed for rectangular tubes. In the case of the cross-shaped tubes, geometric modifications in the form of horizontal grooves along the sidewalls were introduced to promote controlled, stable, and repeatable folding patterns during the collapse in addition to serving as peak force reducers. It was concluded that the basic tensile test data recorded up to the point of necking failed to describe accurately the performances of both tempers (T6 and T7) of AA6063 alloy. The post-instability data of the alloys served as a better predictor of material behavior in assessing the crashworthiness of tubes under axial compression. Furthermore, novel cross-shaped tubes outperformed conventional rectangular shaped tubes and showed tremendous potential as energy-absorbing members for applications where weight savings is desired by using aluminum alloys over steel alloys.
Ali, Muhammad, Ohioma, Eboreime, Kraft, Frank, Jenson, Sean
An Optimization Framework for Fixture Layout Design for Nonrigid Parts: An Automotive Perspective05-13-01-000111/19/2019
Abstract The inspection process of non-rigid parts during manufacturing and assembly is inherently challenging. This is exacerbated by the need for accurate real-time part data in the digital age. Although many ad hoc techniques exist, there are no rigorous methods to evaluate the quality of a fixture layout before final parts and gauges are available. This typically happens so late in the manufacturing process that errors found can scarcely be remedied. Additionally, the modifications to the gauge are usually costly and can result in significant delays, when performed this late in the process. This article proposes an optimization-driven mathematical approach tailored toward non-rigid parts to identify the best locator layout, early in the part design phase. A metric is proposed using robotic grasping theory to quantify the quality of the locating scheme and serves as the objective of optimization. The proposed method is implemented using a tolerancing software that performs finite element analysis (FEA) on the parts to predict its state given the force and torque inputs, including the effect of gravity. An evolutionary algorithm is used that optimizes the performance of the fixture layout. We demonstrate a significant improvement in gauge repeatability when compared with an arbitrary layout scheme on two design problems. The first problem is a representative design problem using a sheet metal part, while the second one is an actual automotive production part. General recommendations regarding fixture layout design for non-rigid parts are made, as well as directions for future work are provided.
Slon, Christopher, Pandey, Vijitashwa
Nondestructive Measurement of Residual Strain in Connecting Rods Using Neutrons05-12-03-001810/15/2019
Abstract Increasing the strength of materials is effective in reducing weight and boosting structural part performance, but there are cases where the residual strain generated during the process of manufacturing of high-strength materials results in a decline of durability. It is therefore important to understand how the residual strain in a manufactured component changes due to processing conditions. In the case of a connecting rod, because the strain load on the connecting rod rib sections is high, it is necessary to clearly understand the distribution of strain in the ribs. However, because residual strain is generally measured by using X-ray diffractometers or strain gauges, measurements are limited to the surface layer of the parts. Neutron beams, however, have a higher penetration depth than X-rays, allowing for strain measurement in the bulk material. The research discussed within this article consists of nondestructive residual strain measurements in the interior of connecting rods using the Second Generation Neutron Residual Stress Mapping Facility (NRSF2) at Oak Ridge National Laboratory (ORNL), measuring the Fe (211) diffraction peak position of the ferrite phase. The interior strain distribution of the connecting rod, which was prepared under different manufacturing processes, was revealed. By the visualization of interior strains, clear understandings of differences in various processing conditions were obtained. In addition, it is known that the peak width, which is also obtained during measurement, is suggestive of the size of crystallites in the structure; however, the peak width can additionally be caused by microstresses and material dislocations.
Ikeda, Tomohiro, Jeffery, Bunn R., Fancher, Christopher M., Motani, Ryuta, Matsuda, Hideki, Okayama, Tatsuya
Comparison of Regulated and Unregulated Emissions and Fuel Economy of SI Engines with Three Fuels: RON95, M15, and E1004-12-03-001310/4/2019
Abstract This article focuses on a comparative research of the emissions discharged from four vehicles equipped with SI engines, which comply with different emission control systems (Euro 6, Euro 5, and Euro 3). The vehicles used for this work were installed with two different fuel injection technologies (direct injection and port fuel injection) and were operated with three different types of fuels (RON 95, M15, and E10). The tests were performed at the Joint Research Center (JRC) in Ispra using a state-of-the-art emissions test facility according to the European emissions legislation. The test bench included a chassis dynamometer and two different driving cycles were used: NEDC and US06. The main conclusions observed by this article are: (1) Emissions levels from vehicles fueled with M15 are similar to or lower than from those fueled with RON95. (2) Using M15 has the potential to decrease carbon dioxide emissions and to save fuel on an energetic basis. (3) PM emissions are lower for gasoline/alcoholic fuels. (4) No statistically significant effects on carbonyl emissions were found with M15.
Goldwine, Gideon, Sher, Eran, Sher, Diana
Items per page:
1 – 14 of 14