Automotive electronics power up

People are spending increasing amounts of time in their cars. As a result, automakers are equipping vehicles with more and more power-draining creature comforts as selling points. Cup holders have given way to navigational systems, separate driver and passenger climate controls, and surround sound and compact disk players. But performance and handling improvements under the hood, such as dynamic stability controls, electronic suspensions, and precision-controlled fuel injection, also need power from the 14-V system featured in today's cars. To handle the situation, automotive manufacturers and suppliers are embracing a 42-V standard for system voltage as they design new products. The challenge for designers, however, is that the cost of the new electronics cannot prohibit the economic production of automobiles. This hurdle must be cleared before cars with 42-V systems will become available to consumers. The paper discusses why 42 Volts was chosen, how many batteries will be needed, control systems, start/stop operation, and the influence of silicon devices on cost     

Heat transport in structured packings with co-current downflow of gas and liquid

Improvements in catalyst activity make the heat transport in fixed bed reactors increasingly important. Structured packings operated in two-phase flow are expected to outperform randomly packed beds, but heat transfer data on structured packings is scarce. In this work structured packings such as OCFS (Open Cross Flow Structures), CCFS (Closed Cross Flow Structures), knitted wire, and foam were characterised with respect to the heat transfer performance. A dedicated set-up was designed and built which enabled us to measure the heat transfer rates in two-phase flow at ambient pressure in the absence of reaction. Benchmarking and set-up validation was carried out using glass beads. The structured packings—especially OCFS and CCFS—show heat transfer coefficients that are superior over those of glass beads, at lower energy dissipation.     

Electrical Conductivity of the High-Temperature Proton Conductor BaZr0.9Y0.1O2.95

The impedance of the cubic perovskite BaZr_0.9Y_0.1O_3-δ has been systematically investigated in dry and wet atmospheres at high and low oxygen partial pressures. In the grain interior, conductivity contributions from oxygen ions, electron holes, and protons can be identified. Below 300°C, proton conduction dominates and increases linearly with the frozen-in proton concentration. The proton mobility, with an activation energy of 0.44 ± 0.01 eV is among the highest ever reported for a perovskite-type oxide proton conductor. For dry oxygen atmos-pheres, electron hole conduction dominates with an activation energy of ∼0.9 eV. At temperatures <500°C, the grain-boundary conductivity can be separated and increases upon incorporation of protons. The high electrical conductivity and chemical stability make acceptor-doped barium zirconate a good choice for application as a high-temperature proton conductor.     

Path Integration on a Quantum Computer

We study path integration on a quantum computer that performs quantum summation. We assume that the measure of path integration is Gaussian, with the eigenvalues of its covariance operator of order j^-k with k>1. For the Wiener measure occurring in many applications we have k=2. We want to compute an -approximation to path integrals whose integrands are at least Lipschitz. We prove: Path integration on a quantum computer is tractable. Path integration on a quantum computer can be solved roughly ^-1 times faster than on a classical computer using randomization, and exponentially faster than on a classical computer with a worst case assurance. The number of quantum queries needed to solve path integration is roughly the square root of the number of function values needed on a classical computer using randomization. More precisely, the number of quantum queries is at most 4.46 ^-1. Furthermore, a lower bound is obtained for the minimal number of quantum queries which shows that this bound cannot be significantly improved. The number of qubits is polynomial in ^-1. Furthermore, for the Wiener measure the degree is 2 for Lipschitz functions, and the degree is 1 for smoother integrands. PACS: 03.67.Lx; 31.15Kb; 31.15.-p; 02.70.-c     

Measurement of the current distribution in a direct methanol fuel cell—Confirmation of parallel galvanic and electrolytic operation within one cell

Current production in fuel cells is typically unequally distributed along the cell surface due to inhomogeneous concentration of reactants and temperature. The inhomogeneities in fuel cells can result in reduced output power and accelerated ageing. To quantify the inhomogeneities a measurement system has been developed which allows measuring the local distribution of current and temperature in hydrogen and direct methanol fuel cells. With this system we are able to directly observe the coexistence of galvanic and electrolytic domains in a single channel direct methanol fuel cell (the electrolytic domain is the domain where electrolysis occurs in contrast to the galvanic domain where the fuel cell process takes place). The measurement device also allows for the measurement locally resolved impedance spectra.     

Short-side-chain proton conducting perfluorosulfonic acid ionomers: Why they perform better in PEM fuel cells

Short-side-chain (SSC) perfluorosulfonic acid ionomers of different ion exchange capacity, IEC, (Dow 840 and Dow 1150) are characterized with respect to water sorption, transport (proton conductivity, electroosmotic water drag and water diffusion), microstructure and visco-elastic properties as a function of temperature and degree of hydration. The data are compared to those of Nafion 117 (Nafion 1100), and the implications for the use of such ionomers as separator materials in direct methanol and hydrogen fuel cells are discussed. For this purpose, a scheme is used which allows for the simulation of the water distribution and the resulting solvent (water, methanol) fluxes and potential losses across the membranes under transient and steady state conditions. The lower solvent (water, methanol) transport across Dow 1150 in direct methanol fuel cells is essentially the result of the reduced swelling. The smaller potential losses across Dow 840 compared to Nafion 117 in hydrogen fuel cells is mainly the result of the higher charge carrier concentration. The present comparison demonstrates that combining high IEC with high mechanical stability, e.g. by increasing crystallinity as in the present case, or by increasing molecular weight, cross-linking or introducing interacting particles, results in an increase in proton conductivity and lower electroosmotic drag of water. The improved stability is also anticipated to preserve the morphology of the membrane/electrode interface under conditions at which Nafion 117 starts to show plastic deformation. Hence, this may prove to be a suitable approach to improve membrane performance in both direct methanol and PEM fuel cells.     

Venturi scrubber calculation and optimization

Collection efficiency and pressure loss of a venturi scrubber can usually be determined from the calculation models of Barth and Calvert. However, this only leads to reasonable results if the droplets are uniformly distributed throughout each cross-section of the washing zone. In this work, a two-zone models is developed which allows the calculation of the venturi scrubber at operating conditions with a non-uniform droplet distribution. The scrubber geometry is also taken into account. A venturi scrubber was developed on the basis of this new model. Its energy consumption is significantly lower than the well-Known optimum characteristic of Wicke and Holzer. For ideal operating conditions, a new optimum characteristic is given which should be the aim of future optimizations.