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Effect of Mechanism Error on Input Torque of Scroll Compressor  [PDF]
Man Zhao,Shurong Yu,Chao Li,Yang Yu
International Journal of Rotating Machinery , 2013, DOI: 10.1155/2013/438127
Abstract: Based on the fundamental principle of plane four-bar mechanism, the force on the equivalent parallel four-bar mechanism was analyzed for scroll compressor with mini-crank antirotation, and the formula of input torque was proposed. The change of input torque caused by the mechanism size error was analyzed and verified with an example. The calculation results show that the mechanism size error will cause large fluctuation in input torque at the drive rod and connecting rod collinear and the fluctuation extreme value increases with rotational speed. Decreasing of the crankshaft eccentricity errors is helpful for reducing the effects of dimension error on input torque but will increase the friction loss of orbiting and fixed scroll wrap. The influence of size error should be considered in design in order to select suitable machining accuracy and reduce the adverse effect caused by size error. 1. Introduction With the needs of clean and oil-free pollution compressed air in food, medicine, fuel cells, and other industries, the investigation of oil-free scroll compressor research has been one of hot topics in scroll compressors. The mini-crank antirotation mechanism is often used to achieve the orbiting scroll work under the oil-free lubrication conditions. The movement relationship of mini-crank, orbiting scroll, crankshaft, and the bracket body can be represented by planar four-bar mechanism [1], and the ideal working should be planar parallel four-bar mechanism. But in fact, machining error and running wear are inevitable, such as the orbiting scroll deviating from the ideal state, resulting in excessive friction wear or large tangential leaking [2], also causing the movable linkages uneven movement. The research of the size error on the four-bar mechanism critical rod’s uneven movement and the change of input torque can provide some theoretical foundation for machining accuracy and scroll compressor reliable operation. 2. Four-Bar Linkage Mechanism The structure of scroll compressor with mini-crank antirotation is shown in Figure 1. The mini-crank is respectively connected with the orbiting scroll and the bracket body through the bearing. In order to ensure the orbiting scroll's revolving translational motion, the gyration radius of mini-crank and eccentric crankshaft should be in the same size; that is, the plane equivalent four-bar mechanism of scroll compressor, shown in Figure 2, should be the parallel four-bar mechanism. Figure 1: Configuration diagram of scroll compressor. Figure 2: Four-bar mechanism. Figure 2 illustrates the four-bar mechanism in
Studies of Modified Hydrogen Storage Intermetallic Compounds Used as Fuel Cell Anodes  [PDF]
Yun Chen,Diogo M. F. Santos,César A. C. Sequeira,Rui F. M. Lobo
Crystals , 2012, DOI: 10.3390/cryst2010022
Abstract: The possibility of substituting Pt/C with the hydrogen storage alloy MlNi 3.6Co 0.85Al 0.3Mn 0.3 as the anode active material of a proton exchange membrane fuel cell system has been analyzed. The electrochemical properties indicate that a much more electrochemically active anode is obtained by impregnating the active material loaded anode in a Nafion proton conducting polymer. Such performance improvement might result from the increase of three-phase boundary sites or length in the gas diffusion electrode where the electrochemical reaction occurs. The experimental data revealed that the membrane electrode assembly (MEA) shows better results when the anode active material, MlNi 3.6Co 0.85Al 0.3Mn 0.3, is treated with a hot alkaline KBH 4 solution, and then chemically coated with 3 wt.% Pd. The MEA with the aforesaid modification presents an enhanced surface capability for hydrogen adsorption, and has been studied by molecular beam-thermal desorption spectrometry.
Shape Optimization of a Regenerative Blower Used for Building Fuel Cell System  [PDF]
Choon-Man Jang, Jong-Sung Lee
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A023
Abstract: This paper describes the optimal design of a Cathode blower used for a building fuel cell system. The Cathode air blower has a regenerative blower type. Two design variables, extension angle and number of impeller blade are introduced to enhance the blower performance. Pressure and efficiency of the blower are selected as an object function, and the optimal design is performed by a response surface method. Three-dimensional Navier-Stokes equations are introduced to analyze the performance and internal flow of the blower and to find the value of object function for the training data. Throughout the design optimization, it is found that an extension angle is effective to increase blower efficiency in the blower. The pressure rise for the optimal blower is successfully increased up to 3.17% compared with that of reference one at the design flow rate. It is noted that low velocity region disturbs to make strong recirculation flow in the each blade passage, thus increases local pressure loss. Detailed flow field inside a regenerative blower is also analyzed and compared.
Performance Bounds for Expander-based Compressed Sensing in the presence of Poisson Noise  [PDF]
Sina Jafarpour,Rebecca Willett,Maxim Raginsky,Robert Calderbank
Mathematics , 2009,
Abstract: This paper provides performance bounds for compressed sensing in the presence of Poisson noise using expander graphs. The Poisson noise model is appropriate for a variety of applications, including low-light imaging and digital streaming, where the signal-independent and/or bounded noise models used in the compressed sensing literature are no longer applicable. In this paper, we develop a novel sensing paradigm based on expander graphs and propose a MAP algorithm for recovering sparse or compressible signals from Poisson observations. The geometry of the expander graphs and the positivity of the corresponding sensing matrices play a crucial role in establishing the bounds on the signal reconstruction error of the proposed algorithm. The geometry of the expander graphs makes them provably superior to random dense sensing matrices, such as Gaussian or partial Fourier ensembles, for the Poisson noise model. We support our results with experimental demonstrations.
Radiation Effects on Materials Used in Geological Repositories for Spent Nuclear Fuel  [PDF]
Mats Jonsson
ISRN Materials Science , 2012, DOI: 10.5402/2012/639520
Abstract: Safe long-term storage of radioactive waste from nuclear power plants is one of the main concerns for the nuclear industry as well as for governments in countries relying on electricity produced by nuclear power. A repository for spent nuclear fuel must be safe for extremely long time periods (at least 100 000 years). In order to ascertain the long-term safety of a repository, extensive safety analysis must be performed. One of the critical issues in a safety analysis is the long-term integrity of the barrier materials used in the repository. Ionizing radiation from the spent nuclear constitutes one of the many parameters that need to be accounted for. In this paper, the effects of ionizing radiation on the integrity of different materials used in a granitic deep geological repository for spent nuclear fuel designed according to the Swedish KBS-3 model are discussed. The discussion is primarily focused on radiation-induced processes at the interface between groundwater and solid materials. The materials that are discussed are the spent nuclear fuel (based on UO2), the copper-covered iron canister, and bentonite clay. The latter two constitute the engineered barriers of the repository. 1. Introduction The handling of radioactive waste in general and spent nuclear fuel in particular is one of the main concerns in connection to nuclear power. For the used nuclear fuel there, are essentially two options: reprocessing to produce new fuel from fissile material present in the used fuel or final disposal. Both options have their advantages and disadvantages, and the choice is to a large extent a political issue where nonproliferation is a key component. Reprocessing reduces the volumes of high-level radioactive waste, but it does not solve the waste issue completely. Repositories for radioactive waste must be employed, regardless of which nuclear fuel cycle is being used. One of the most developed repository concepts is the KBS-3 model for long-term storage of spent nuclear fuel in granitic bedrock. The concept has been developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) [1] and has also been adopted by Finland [2]. An application for building a repository according to the KBS-3 model is currently being processed in Sweden [3] where a once-through fuel cycle is used. The KBS-3 model is described schematically in Figure 1. Figure 1: Schematic view of the KBS-3 concept. Reproduced with permission from the Swedish Nuclear Fuel and Waste Management Company (SKB). After cooling for a period of at least 30 years, the fuel elements are placed in
Buckling of scroll waves  [PDF]
Hans Dierckx,Henri Verschelde,Ozgur Selsil,Vadim Biktashev
Physics , 2012, DOI: 10.1103/PhysRevLett.109.174102
Abstract: A scroll wave in a sufficiently thin layer of an excitable medium with negative filament tension can be stable nevertheless due to filament rigidity. Above a certain critical thickness of the medium, such scroll wave will have a tendency to deform into a buckled, precessing state. Experimentally this will be seen as meandering of the spiral wave on the surface, the amplitude of which grows with the thickness of the layer, until a break-up to scroll wave turbulence happens. We present a simplified theory for this phenomenon and illustrate it with numerical examples.
Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application  [PDF]
Yulia Glavatskaya,Pierre Podevin,Vincent Lemort,Osoko Shonda,Georges Descombes
Energies , 2012, DOI: 10.3390/en5061751
Abstract: Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in fuel consumption. One solution is to integrate a heat recovery system based on a steam Rankine cycle. The key component in such a system is the expander, which has a strong impact on the system’s performance. A survey of different expander technologies leads us to select the reciprocating expander as the most promising one for an automotive application. This paper therefore proposes a steady-state semi-empirical model of the expander device developed under the Engineering Equation Solver (EES) environment. The ambient and mechanical losses as well as internal leakage were taken into account by the model. By exploiting the expander manufacturer’s data, all the parameters of the expander model were identified. The model computes the mass flow rate, the power output delivered and the exhaust enthalpy of the steam. The maximum deviation between predictions and measurement data is 4.7%. A performance study of the expander is carried out and shows that the isentropic efficiency is quite high and increases with the expander rotary speed. The mechanical efficiency depends on mechanical losses which are quite high, approximately 90%. The volumetric efficiency was also evaluated.
Performance bounds for expander-based compressed sensing in Poisson noise  [PDF]
Maxim Raginsky,Sina Jafarpour,Zachary Harmany,Roummel Marcia,Rebecca Willett,Robert Calderbank
Mathematics , 2010, DOI: 10.1109/TSP.2011.2157913
Abstract: This paper provides performance bounds for compressed sensing in the presence of Poisson noise using expander graphs. The Poisson noise model is appropriate for a variety of applications, including low-light imaging and digital streaming, where the signal-independent and/or bounded noise models used in the compressed sensing literature are no longer applicable. In this paper, we develop a novel sensing paradigm based on expander graphs and propose a MAP algorithm for recovering sparse or compressible signals from Poisson observations. The geometry of the expander graphs and the positivity of the corresponding sensing matrices play a crucial role in establishing the bounds on the signal reconstruction error of the proposed algorithm. We support our results with experimental demonstrations of reconstructing average packet arrival rates and instantaneous packet counts at a router in a communication network, where the arrivals of packets in each flow follow a Poisson process.
Evaluation of chosen quality parameters of used frying rape oil as fuel biocomponent
M. Szmigielski,B. Maniak,W. Piekarski
International Agrophysics , 2008,
Abstract: In this paper higher fatty acids composition, peroxide and acidic value and density of raw commercial rape oil and of oil fraction formed after each of five cycles of oil heating conducted in two ways - with and without potato chips frying, were compared. After each heating, which duration corresponded to time necessary for potato chips frying, oil was left to cool down (to room temperature) and stored in conditions similar to ones found in small gastronomy. Goal of undertaken research was usability assessment of used frying rape oil as a substrate for biofuel production. Utilization of used frying rape oil as fuel seems to be grounded by favourable ratio of saturated and unsaturated fatty acids in oil fraction, which properties stabilize as a result of surface contact with potato chips, as well as by ecological (utilization of waste), energetic (replacement of conventional crude oil based fuels) and economical (utilization of cheap wastes) reasons.
A Pt3Sn/C Electrocatalyst Used as the Cathode and Anode in a Single Direct Ethanol Fuel Cell  [cached]
L. S. Parreira,D. C. Rascio,J. C. M. Silva,R. F. B. De Souza
International Journal of Chemistry , 2012, DOI: 10.5539/ijc.v4n2p38
Abstract: This paper presents a study involving the use of Pt3Sn/C electrocatalysts as cathodes and anodes in a single direct ethanol fuel cell. First, we studied the oxygen reduction reaction (ORR) using commercial Pt/C from ETEK and Pt3Sn/C as electrocatalysts with an alloy degree of 92 %. The electrocatalytic activity of the material for oxygen reduction was assessed using the rotating disk electrode technique (RDE). When Pt3Sn was tested for ORR in the presence of ethanol, the results showed greater tolerance to the cross-over effect than Pt/C in the electrochemical cell. The experiments in a single direct ethanol fuel cell showed that without oxygen pressurization of the cell, the maximum power density is higher using Pt3Sn/C as both cathode and anode than using Pt3Sn as an anode and Pt/C as a cathode. When using Pt3Sn/C as both the cathode and anode in a direct ethanol fuel cell, cell performance enhances.
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