Energy management of fuel cell/battery/ultracapacitor in electrical hybrid vehicle

This paper describes an energy management algorithm for an electrical hybrid vehicle. The proposed hybrid vehicle presents a fuel cell as the main energy source and the storage system, composed of a battery and a supercapacitor as the secondary energy source. The main source must produce the necessary energy to the electrical vehicle. The secondary energy source produces the lacking power in acceleration and absorbs excess power in braking operation. The addition of a supercapacitor and battery in fuel cell-based vehicles has a great potential because it allows a significant reduction of the hydrogen consumption and an improvement of the vehicle efficiency. Other the energy sources, the electrical vehicle composed of a traction motor drive, Inverter and power conditioning. The last is composed of three DC/DC converters: the first converter interfaces the fuel cell and the DC link. For the second and the third converter, two buck boost are used in order to interface respectively the ultracapacitor and the battery with the DC link. The energy management algorithm determines the currents of the converters in order to regulate accurately the power provided from the three electrical sources. This algorithm is simulated with MATLAB_Simulink and implemented experimentally with a real-time system controller based on dSPACE. In this paper, the proposed algorithm is evaluated for the New European Driving Cycle (NEDC). The experimental results validate the effectiveness of the proposed energy management algorithm.     

Design and analysis of a high frequency DC–DC converters for fuel cell and super-capacitor used in electrical vehicle

This work focuses on the application of the high frequency DC–DC converters used in electric vehicles. Two converters are necessary. The first converter is interposed between the fuel cell and the DC–AC inverter. It is unidirectional. The second one is used as interface between the ultra-capacitor and the DC–AC inverter. It allows the bidirectional of the power transfer. Each converter is composed of two full bridges, LC resonant filter and two planar transformers. The use of high frequency transformer allows to minimize the size and weight of the converter, produce a higher voltage in secondary side from input voltage (fuel cell or super-capacitor) and isolate the full bridges. The control strategy of the converters is the phase shift. The converters have been designed, realised and controlled by an FPGA board. To demonstrate the converters feasibility, two converters are implemented and tested. The switching frequency of two converters is 20 kHz. The first converter has a 24-V input and 200 V/1.2 kW output. But, the second converter has a 12.5-V input and 100 V/400 W output.     

Design and control of a direct drive wind turbine equipped with multilevel converters

This paper concentrates on the design and control of a three-level grid side converter (GSC) for direct drive high power wind turbines. The three-level, neutral point clamped (NPC) topology was investigated. The proposed control scheme, based on vector current control, offers very satisfying performances regarding to structure stability and grid connection requirements (GCR). In order to have an accurate evaluation of grid voltage source, two grid synchronization methods are developed and their performances are compared. The GSC performances are evaluated under both normal and grid fault conditions. Simulation results show that stability is maintained during voltage dips and that the proposed direct drive wind turbine satisfies completely GCR.     

Sintering of tricalcium phosphate–fluorapatite composites with zirconia

Zirconia (ZrO₂) addition effects on densification and microstructure of tricalcium phosphate–26.52 wt% fluorapatite composites were investigated, using X-ray diffraction, scanning electron microscopy and by analysis using ³¹P nuclear magnetic resonance. The tricalcium phosphate–26.52 wt% fluorapatite–zirconia composites densification increases versus temperature. At 1300 °C, the composites apparent porosity reaches 9% with 5 wt% zirconia. XRD analysis of the composites reveals the presence of tricalcium phosphate, fluorapatite and zirconia without any other structures. Above 1300 °C, the densification was hindered by grain growth and the formation of both intragranular porosity and new compounds. The ³¹P MAS-NMR analysis of composites sintered at various temperatures or with different percentages of zirconia reveals the presence of tetrahedral P sites. At 1400 °C, XRD analysis of the tricalcium phosphate–26.52 wt% fluorapatite–20 wt% zirconia composites shows the presence of calcium zirconate and tetracalcium phosphate. This result indicated that partial decomposition of tricalcium phosphate during sintering process of composites when 20 wt% or less ZrO₂ was added. Thus, zirconia reacts with tricalcium phosphate forming calcium zirconate and tetracalcium phosphate.     

Determination of porosity from shrinkage curves during sintering of granular materials

This paper investigates the implementation of an analytical model to determine the porosity of a granular material during reactive and nonreactive sintering. A graphical interpretation of this model is proposed to calculate the porosity by comparing the experimental shrinkage curve with the ideal one. For the nonreactive sintering, some examples have been taken from the literature to illustrate the application of this method for two granular materials (alumina and zircon). In the case of reactive sintering, we have used our experiments to study the sintering behavior of magnesium hydroxide. The shrinkage curve was determined by dilatometer and the porosity was measured by helium pycnometer. The comparison revealed that the porosity calculated from the model is fully consistent with the porosity measurements in the both cases.     

Low-frequency noise in proton damaged LDD MOSFET's

One of the concerns in the design of a guide camera for a satellite astronomy mission was an increase in the low-frequency noise in the output amplifier of the charge-coupled device (CCD) image sensor due to the radiation environment of the satellite. We investigated this potential problem by measuring the noise in several MOSFET's which had been subjected to varying amounts of high-energy proton radiation. These MOSFET's were typical of those used in the output stage of a CCD. They were lightly-doped drain (LDD) n-type buried-channel devices with aspect ratios between 4 and 6. We found a significant increase in the low-frequency noise of our devices after radiation. The frequency and temperature dependence of the noise indicates that it is generation-recombination noise due to the introduction of bulk trapping states. Fortunately, at the operating temperature of the CCD in the guide camera (-50°C), the noise increase is very small in the frequency range of interest. However, at room temperature, the noise increase is large     

Understanding and enhancing the direct contact membrane distillation performance by modified heat transfer correlation

The sensitivity of direct contact membrane distillation to feed temperatures and feed flow rate is investigated experimentally. At very low flow rates, the process becomes heat transfer limited where the thermal energy of the aqueous feed solution is lost by the conduction resistance minimizing the distillate production. At high flow rates, the film heat transfer coefficient for both liquid solutions increases, creating a larger temperature difference across the membrane boundaries. Hence, the mass fluxes increase linearly with the water flow rate. These findings are also assessed by simulating the heat and mass transfer equations that describe the membrane distillation (MD) thermo-physical operation. It is found that the underlying physics of the MD module must faithfully capture and explain the true process behaviour. Hence, a modified correlation for the Nusselt number is developed and tested.     

Dispersing Properties of Copolymers Able to Act as Binders

Macromolecules, containing both charged groups (COO⁻ and SO₃⁻), in order to ensure powder dispersion, and neutral groups (vinyl alcohol and ethyl hydroxyl acrylate), in order to obtain enough strength in the green parts, were synthesized to be used in the dry pressing process. The evaluation and the comparison of the capacity of these synthesized copolymers with disperse alumina particles in aqueous media are considered in this paper. Both COO⁻ and SO₃⁻ ionized groups are responsible for strong adsorption onto alumina surface and can promote sufficient electrostatic repulsive forces to achieve a good state of dispersion. The role of the copolymers in the stabilization of alumina suspensions was found to be greatly affected by the nature and by the fraction of groups in the macromolecular chains. A low concentration of copolymers (0.5 wt% on alumina basis) containing 35% of carboxylic groups and 65% of vinyl alcohol groups (PV35) or containing 55% of carboxylic groups and 45% of hydroxy ethyl acrylate groups (EH2A55) leads to stable alumina suspensions with a low viscosity similar to that obtained with a classical ammonium polymethacrylate (between 10 and 20 mPa·s for 27 vol% alumina suspensions). Copolymers containing sulfonate groups are less efficient.     

GPR signal de-noising by discrete wavelet transform

Ground penetrating radar (GPR) is a non-destructive investigation tool used for several applications related to civil infrastructures; including buried objects detection and structural condition evaluation. Although GPR can be effectively used to survey structures, signal analysis can be sometimes challenging. The GPR signals can be easily corrupted by noise because the GPR receiver has usually an ultra-wide bandwidth (UWB). The noise collected by the system can easily mask relatively weak reflections resulting from the inhomogeneities within the surveyed structure; especially when they are at a relatively deep location. This paper presents the use of discrete wavelet transform (DWT) to de-noise the GPR signals. Various mother wavelets were used in this study to de-noise experimental GPR signals collected from flexible pavements. The performance of wavelet de-noising was evaluated by computing the signal-to-noise ratio (SNR) and the normalized root-mean-square error (NRMSE) after de-noising. The study found that wavelet de-noising approach outperforms traditional frequency filters such as the elliptic filter. At the same level of decomposition, the Daubechies order 6 and Symlet order 6 outperform the Haar and Biorthogonal mother wavelets when de-noising GPR signals by soft thresholding.     

Numerical Study of Pulsed Turbulent Plane Wall Jet by Low-Reynolds-Number k–ε Model

The present study reports on the numerical characterization of the influence of an initial perturbation in the development of turbulent plane two-dimensional wall jets. At the nozzle exit, the pulsation is imposed by a vertical component velocity: u = u ₀[1 + Asin(ω t)]. In the configuration investigated, the jet may be either isothermal or submitted to various wall thermal boundary conditions: uniform temperature in mixed-convection regime or uniform heat flux in forced-convection regime. Numerical modeling of the pulsed wall jet is performed using a low-Reynolds number k–ε model. A finite-difference method, sing a staggered grid, is employed to solve the coupled governing equations associated to the inlet and boundary conditions. The effects of the parameters characterizing the pulsation, such as the amplitude and the frequency, on the dynamic, turbulent, and thermal characteristics of the turbulent wall jets are investigated in detail.