20-Mw Pulsed Amplifying Klystron Operating in Positive Feedback Mode
The results of investigation of the regenerative oscillation amplification mode and the selfoscillation synchronization mode for the power pulsed amplifying positive-feedback klystron are reported. In Ref. there was described the autogenerator on the KUY-12 pulsed amplifying klystron, used for feeding the accelerating sections of the electron linac. To enhance the self-oscillation frequency stability, a high-quality resonator is introduced into the feedback circuit. This however results in noticeable increase in the oscillation growth time with respect to anode pulse. The investigation results of the KUY-12 operating either in the oscillation regeneration mode or in the self-oscillation frequency synchronization mode are presented.
Synchronization of pulsed oscillators
It is shown that driven pulsed oscillators behave in a manner very similar to driven CW oscillators. Simple criteria are given which allow one to decide easily from the frequency spectrum if the oscillators are locked or not.
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.