The role of thermal analysis in detecting impurity levels during aluminum recycling

Recycling of aluminum scrap has gained interest owing to its economic and ecological benefits. Unfortunately, during the collection of scrap from a mixer of junk from various sectors it is difficult to ensure that the recycled alloy has the same chemical composition as that of already existing commercial alloys. Consequently, some of the alloying elements become trace/tramp elements in the recycled alloy. Therefore, in order to obtain high performance recycled alloys, controlling the impurity levels of the aluminum melt is of vital importance. Normally, computer aided cooling curve analysis (CA-CCA) is used to find the relationship between cooling curve parameters, melt treatments, alloy composition, and properties. In the present study, the first differential thermal analysis (DTA) approach has been used to detect and quantify impurity elements in scrap-like liquid aluminum alloys.     

Comprehensive drive train efficiency analysis of hybrid electric and fuel cell vehicles based on motor-controller efficiency modeling

From the point of view of overall hybrid electric vehicle (HEV) and fuel cell vehicle (FCV) drive train efficiency, the research focus is mainly on the efficiency analysis of the power train components, which prove to be an integral part of modern HEV and FCV drive trains. The critical portion of any HEV electrical system consists of a power electronic converter (inverter) and a suitable traction motor. Thus, the efficiency analysis of the inverter/motor is of prime importance for the calculation of the overall efficiency of the drive trains. This paper aims at modeling the efficiencies of the traction motor/controller through efficiency maps. Efficiency maps are a convenient way to represent motor drive systems of large and complex systems, like that of a HEV. The paper uses the advanced vehicle simulator (ADVISOR) software for the simulations of a large-sized car, similar to a Chevy Lumina, over the urban dynamometer-driving schedule and highway fuel economy test drive cycles. Furthermore, the paper investigates the traction motor efficiency maps and consequent overall drive train efficiencies of commercially available Honda Insight and Toyota Prius HEVs. In all the case studies, the aim is to analyze the overall drive train efficiency over the city and highway drive cycles based on the inverter/motor efficiency maps.     

Constant power loads and negative impedance instability in automotive systems: definition, modeling, stability, and control of power electronic converters and motor drives

Power electronic converters and electric motor drives are being put into use at an increasingly rapid rate in advanced automobiles. However, the new advanced automotive electrical systems employ multivoltage level hybrid ac and dc as well as electromechanical systems that have unique characteristics, dynamics, and stability problems that are not well understood due to the nonlinearity and time dependency of converters and because of their constant power characteristics. The purpose of this paper is to present an assessment of the negative impedance instability concept of the constant power loads (CPLs) in automotive power systems. The main focus of this paper is to analyze and propose design criteria of controllers for automotive converters/systems operating with CPLs. The proposed method is to devise a new comprehensive approach to the applications of power electronic converters and motor drives in advanced automotive systems. Sliding-mode and feedback linearization techniques along with large-signal phase plane analysis are presented as methods to analyze, control, and stabilize automotive converters/systems with CPLs.     

Comparative assessment of hybrid electric and fuel cell vehicles based on comprehensive well-to-wheels efficiency analysis

One of the major issues surrounding the research and development work involving hybrid electric and fuel cell vehicles (HEVs and FCVs) is their overall efficiency of converting the input fuel into actual work at the wheels of the vehicle. The main idea behind efficiency comparisons between HEVs and FCVs is the analysis of their respective well-to-tank (WTT) and tank-to-wheels (TTW) efficiencies, the product of which reveals the well-to-wheels (WTW) efficiency, which is one of the deciding factors for technology acceptance. This paper primarily aims at presenting critical comparative issues with regards to the overall efficiencies of the most popularly proposed HEV and FCV topologies. Finally, the overall efficiency analysis performed in this paper will lay down the foundation for a concrete conclusive comparison between advanced vehicular topologies of the future.     

Explicit Rate–Time Solutions for Modeling Matrix–Fracture Flow of Single Phase Gas in Dual-Porosity Media

One of the widely used methods for modeling matrix–fracture fluid exchange in naturally fractured reservoirs is dual porosity approach. In this type of modeling, matrix blocks are regarded as sources/sinks in the fracture network medium. The rate of fluid transfer from matrix blocks into fracture medium may be modeled using shape factor concept (Warren and Root, SPEJ 3:245–255, 1963); or the rate–time solution is directly derived for the specific matrix geometry (de Swaan, SPEJ 16:117–122, 1976). Numerous works have been conducted to study matrix–fracture fluid exchange for slightly compressible fluids (e.g. oil). However, little attention has been taken to systems containing gas (compressible fluid). The objective of this work is to develop explicit rate–time solutions for matrix–fracture fluid transfer in systems containing single phase gas. For this purpose, the governing equation describing flow of gas from matrix block into fracture system is linearized using pseudopressure and pseudotime functions. Then, the governing equation is solved under specific boundary conditions to obtain an implicit relation between rate and time. Since rate calculations using such an implicit relation need iterations, which may be computationally inconvenient, an explicit rate–time relation is developed with the aid of material balance equation and several specific assumptions. Also, expressions are derived for average pseudopressure in matrix block. Furthermore, simplified solutions (originated from the complex general solutions) are introduced applicable in infinite and finite acting flow periods in matrix. Based on the derived solutions, expressions are developed for shape factor. An important observation is that the shape factor for gas systems is the same as that of oil bearing matrix blocks. Subsequently, a multiplier is introduced which relates rate to matrix pressure instead of matrix pseudopressure. Finally, the introduced equations are verified using a numerical simulator.     

Analytical and Experimental Study to Predict the Residual Resistance Factor on Polymer Flooding Process in Fractured Medium

The major objectives of this study are to analytically and experimentally determine the residual resistance factor in the fractured medium based on the polymer solution properties and operational conditions. The parameters considered in this study are the polymer concentration, power law constitutive equation parameter, and salt concentration, sulfonation content of polymer, temperature, and molecular weight of the water soluble polymers which are used in polymer flooding for enhanced oil recovery. The results indicated that residual resistance factor in fractured medium is dependent on the coil overlap parameter and power law equation parameter of polymer. The coil overlap parameter is a dimensionless number consists of intrinsic viscosity and polymer concentration. Since intrinsic viscosity is a function of polymer diameter in medium conditions, to predict the residual resistance factor in fracture medium, an experimental correlation is generated for determination of the molecular diameter of polymer based on polymer molecular weight, temperature, salt concentration, and sulfonation content.     

Effects of drivetrain hybridization on fuel economy and dynamic performance of parallel hybrid electric vehicles

Hybrid electric vehicles have proved to be the most practical solution in reaching very high fuel economy as well as very low emissions. However, there is no standard solution for the optimal size or ratio of the internal combustion engine and the electric system. The optimum choice includes complex tradeoffs between the heat engine and electric propulsion system on one hand and cost, fuel economy, and performance on the other. Each component, as well as the overall system, have to be optimized to give optimal performance and durability at a low price. In this paper, we look at the effects of hybridization on fuel economy and dynamic performances of vehicles. Different hybridization levels from mild to full hybrid electric traction systems are examined. We also present the optimum level of hybridization for typical passenger cars. This study shows that low hybridization levels provide an acceptable fuel economy benefit at a low price, while the optimal level of hybridization ranges between 0.3 and 0.5, depending on the total vehicle power.