Abstract: A method and apparatus for frequency offset estimation exploits the differences in reference symbol timing for different channels to resolve ambiguities in the frequency offset estimation. Based on the initial frequency offset estimates, a hypothesis table is constructed providing hypothesized frequency offsets for each channel for a plurality of possible offset regions. An error metric for each offset region is calculated based on the difference of the hypothesized frequency offsets. The set of hypothesized frequency offsets that minimize the error metric is selected as the final frequency offset estimates.

Abstract: A brush seal for use between a rotating component and a stationary component in a turbomachine is disclosed. The brush seal according to embodiments of this invention includes a set of bristles having a fixed end and a free end, wherein the fixed end is attached to the rotating component with a mechanical clamping element and the free end extends towards the stationary component, and wherein the set of bristles are angled axially at an axial angle with respect to the rotating component. In one embodiment, the fixed end of the set of bristles are wrapped at least partially around a core element and the clamping element partially surrounds the core element and the fixed end of the set of bristles, wherein the clamping element secures the fixed end of the set of bristles within a circumferential groove in the rotating component.

Abstract: A cathode for use in a direct oxidation fuel cell (DOFC) comprises a gas diffusion medium (GDM) including a backing layer and a microporous layer comprising a fluoropolymer and an electrically conductive material, wherein loading of the fluoropolymer in the microporous layer is in the range from about 10 to about 60 wt. %. In use, a concentrated solution of a liquid fuel is supplied to an anode and an oxidant to the cathode of the fuel cell, and the fuel cell may be operated at a low oxidant stoichiometry ?c not greater than about 2.5.

Abstract: A direct methanol fuel cell unit is provided with a fuel cell including an anode, a cathode with a hydrophobic microporous layer, an electrolyte membrane put in-between, and a fuel supply path supplying fuel to the anode. The fuel supply path is provided with an upwind water barrier preventing back-diffusion of water and a gas flow path channeling gas generated at the anode and disposed between the barrier and the anode. A water-rich zone is formed between the water barrier and the cathode microporous layer. Water loss from either side of this zone is eliminated or minimized, thereby permitting direct use of highly concentrated methanol in the fuel flow path with good fuel efficiency and power performance. The cell unit can be applied equally well to both an active circulating air cathode and an air-breathing cathode.

Abstract: A direct oxidation fuel cell (DOFC) system, comprises at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween, adapted for performing selected electrochemical reactions; a source of concentrated liquid fuel in fluid communication with an inlet of the anode; an oxidant supply in fluid communication with an inlet of the cathode; a liquid/gas (L/G) separator in fluid communication with outputs of the anode and cathode for receiving unreacted fuel and liquid and gaseous products of the electrochemical reactions; and a converter for catalytically converting a portion of the unreacted fuel to the liquid and gaseous products.

Abstract: A cathode for use in a direct oxidation fuel cell (DOFC) comprises a gas diffusion medium (GDM) including a backing layer and a microporous layer comprising a fluoropolymer and an electrically conductive material, wherein loading of the fluoropolymer in the microporous layer is in the range from about 10 to about 60 wt. %. In use, a concentrated solution of a liquid fuel is supplied to an anode and an oxidant to the cathode of the fuel cell, and the fuel cell may be operated at a low oxidant stoichiometry not greater than about 2.5.

Abstract: Methods for increasing the durability of direct oxidation fuel cells are disclosed. In one instance, the method for increasing durability of a vapor fed direct oxidation fuel cell includes reducing fluctuations in output power, provided by the vapor fed direct oxidation fuel cell, to a load. The reduction of the fluctuations in output power can include, in one instance, utilizing a mass flow controller or an electro-osmotive pump to supply fuel to the vapor fed direct oxidation fuel cell.

Abstract: A cathode for use in a direct oxidation fuel cell (DOFC) comprises a gas diffusion medium (GDM) including a backing layer and a microporous layer comprising a fluoropolymer and an electrically conductive material, wherein loading of the fluoropolymer in the microporous layer is in the range from about 10 to about 60 wt. %. In use, a concentrated solution of a liquid fuel is supplied to an anode and an oxidant to the cathode of the fuel cell, and the fuel cell may be operated at a low oxidant stoichiometry ?c not greater than about 2.5.

Abstract: A direct oxidation fuel cell system includes a membrane electrode assembly (MEA), a high concentration fuel and an oxidant source. Embodiments include a controller for adjusting the oxidant stoichiometric ratio or air flow to maximize the liquid water phase in the cathode exhaust and minimize the water vapor in the exhaust thereby eliminating the need for a water condenser for condensing water vapor produced and exhausted from the cathode of the MEA.

Abstract: A cathode for use in a direct oxidation fuel cell (DOFC) comprises a gas diffusion medium (GDM) including a backing layer and a microporous layer comprising a fluoropolymer and an electrically conductive material, wherein loading of the fluoropolymer in the microporous layer is in the range from about 10 to about 60 wt. %. In use, a concentrated solution of a liquid fuel is supplied to an anode and an oxidant to the cathode of the fuel cell, and the fuel cell may be operated at a low oxidant stoichiometry ?c not greater than about 2.5.

Abstract: A direct oxidation fuel cell (DOFC) system, comprises at least one fuel cell assembly including a cathode and an anode with an electrolyte positioned therebetween, adapted for performing selected electrochemical reactions; a source of concentrated liquid fuel in fluid communication with an inlet of the anode; an oxidant supply in fluid communication with an inlet of the cathode; a liquid/gas (L/G) separator in fluid communication with outputs of the anode and cathode for receiving unreacted fuel and liquid and gaseous products of the electrochemical reactions; and a converter for catalytically converting a portion of the unreacted fuel to the liquid and gaseous products.

Abstract: A direct oxidation fuel cell system includes a membrane electrode assembly (MEA), a high concentration fuel and an oxidant source. Embodiments include a controller for adjusting the oxidant stoichiometric ratio or air flow to maximize the liquid water phase in the cathode exhaust and minimize the water vapor in the exhaust thereby eliminating the need for a water condenser for condensing water vapor produced and exhausted from the cathode of the MEA.

Abstract: A direct methanol fuel cell unit is provided with a fuel cell including an anode, a cathode with a hydrophobic microporous layer, an electrolyte membrane put in-between, and a fuel supply path supplying fuel to the anode. The fuel supply path is provided with an upwind water barrier preventing back-diffusion of water and a gas flow path channeling gas generated at the anode and disposed between the barrier and the anode. A water-rich zone is formed between the water barrier and the cathode microporous layer. Water loss from either side of this zone is eliminated or minimized, thereby permitting direct use of highly concentrated methanol in the fuel flow path with good fuel efficiency and power performance. The cell unit can be applied equally well to both an active circulating air cathode and an air-breathing cathode.