The dual-mode double-gap resonator with asymmetrrical strip line on the suspended ceramic substrate
A new dual-mode double-gap resonator on the basis of asymmetrical suspended stripline for miniature klystron type microwave tubes with field emitter arrays (FEA) cathodes was investigated. The resonator has a smaller size and mass when a doublegap capacitive segment of each quasi-lumped resonator consists of two assimmetrical strip conductors on opposite sides of the substrate and both inductive segments are grounded. This resonance circuit has two oscillation modes (anti-phase and in-phase). On the basis of the 3-D modeling found that such oscillatory systems can achieve the excitation of these modes with multiplicity of frequencies to = 2 with a good efficiency of interaction of electrons with microwave fields.
Research of electrodynamic characteristics of a double-gap Klystron resonator with quasi-fractal microstrip elements
Electrodynamic characteristics of a double-gap klystron resonator with the inductive quasi- fractal microstrip elements on the suspended ceramic substrate have been investigated. The developed resonator can find application in micro vacuum klystron devices in one - and multi-frequency mode of operation.
Evaluation of CuAl2O4 as an Oxygen Carrier in Chemical-Looping Combustion
The chemical-looping combustion (CLC) process is a novel solution for efficient combustion with intrinsic separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor where the fuel, or gasification products of the fuel, reacts with the solid oxygen carrier. In this work, copper(II) aluminate (CuAl2O4) was assessed as a potential oxygen carrier using methane as fuel. The carrier particles were produced by freeze–granulation and calcined at 1050 °C for a duration of 6 h. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900–950 °C during 45 alternating redox cycles. The oxygen carrier exhibited reproducible and stable reactivity behavior in this temperature range. Neither agglomeration nor defluidization was noticed in any of the cycles carried out at 900–925 °C. However, after reactivity tests at 950 °C, soft agglomeration and particle fragmentation were observed. Systematic phase analysis of the Cu–Al–O system during the redox cycle was carried out as a function of duration of reduction and oxygen concentration during the oxidation period. It was found that the CuAl2O4 is reduced to copper(I) aluminate (CuAlO2; delafossite), Cu2O, and elemental Cu. The CuAlO2 phase is characterized by slow kinetics for oxidation into CuO and CuAl2O4. Despite this kinetic limitation, complete conversion of methane with reproducible reactivity of the oxygen carrier is achieved. Thus, CuAl2O4 could be a potential oxygen carrier for chemical-looping combustion.