Papers by Keyword: Surge

Abstract: The aim of this study is to investigate the main contributing factors to the degradation of the intrinsic body diode in SiC MOSFETs, caused by the expansion of stacking faults (SFs) from the substrate into the epitaxial layer, and how it affects their performance. Additionally, a comparison between DC forward current stress and surge current pulse stress is shown.

Abstract: A p-n junction diode with mesa structure by silicon carbide (SiC) has been developed to utilize the avalanche breakdown in an excessed reverse bias condition to clamp the surge voltage in switch-mode power supplies. Static voltage-current correlation by pulsed reverse voltage has been measured. The increase of the breakdown voltage was measured to be 32 volts with increased current density up to 3900 A/cm². The operational performance in suppressing the surge voltage in a step-down DC/DC converter has been evaluated. A superior performance in suppressing the surge voltage by the SiC p-n junction diode has been confirmed. It was also found that a resonant oscillation induced during clamping period limits the performance. By a circuit analysis with an equivalent circuit model, it was found that a parasitic wiring inductance between the diode and switching element induces the resonance. It was also found that a promising way to mitigate the disturbing effect is to minimize the inductance.

Abstract: Silicon Carbide JBS diodes are capable, in forward bias, of carrying surge current of magnitude significantly higher than their rated current, for short periods. In this work, we examine the mechanisms of device failure due to excess surge current by analyzing variation of failure current with device current and voltage ratings, as well as duration of current surge. Physical failure analysis is carried out to correlate to electrical failure signature. We also quantify the impact, on surge current capability, of the resistance of the anode ohmic contact to the p-shielding region.

Abstract: The surge of a sintered exhauster is regarded as a safety hazard during production. The occasional machine shutdown may be caused by the exhauster surge. Severe surge my cause the damages of the exhauster, injuries to personnel, and potentially casualties. In this paper, a curve that describes the character of a sintered exhauster is presented based on the site testing and analysis. The aim of this work is to avoid exhauster surge and to guarantee safe production. The working conditions for technicians and efficiency of operations for the exhauster will be insured through the use of the characteristic curve presented in the paper.

Abstract: Surge is a type of instability, that dramatically affects the operation and life of the turbocharger. There were analyzed the options for the control of surge of which were control designed for surge avoidance (method of minimizing the flow through the control valve). This algorithm is based on the logic of closure control valve at a constant speed regardless of the error. Besides of control were designed surge and control curves. To verify the solution was modeled and implemented nonlinear parametric model with downstream with control valve (Fink model) in Matlab. The simulation models are needed for physical systems, and develop good management strategy. Derivation of the compressor characteristic is presented. Dynamic model also includes two characteristics of valves describing mass flow.

Abstract: Currently shipping costs are increasing sharply due to the rising oil prices. In order to reduce shipping costs, most low-speed two-stroke diesel engines run at low speeds to reduce fuel oil consumption, and this measure might result turbocharger surge. For modern marine diesel engines, the exhaust gas turbochargers are becoming more and more important; their working conditions have a direct impact on the performance of diesel engines, consequently affecting the operation of the ship. Surge will fail a turbocharger to achieve the supercharging ratio, damage the turbocharger components and even lead to a damage accident of the whole turbocharger. Therefore, a good understanding of the reasons for marine diesel engine turbocharger surge will help to prevent and eliminate turbocharger surge in operation. This paper is to make an analysis on the special surge mechanism occurred to the turbocharger on MV "Crystal Star", and propose some appropriate supervisory and preventive measures against the problem.

Abstract: The surge wave induced by the landslide on reservoir bank is extremely disaster .The prediction of surge height is a difficult problem because the velocity of landslide is hard to obtain. The discontinuous deformation analysis (DDA) is able to simulate landslide movement with real time and acceleration. The whole movement process of Muzhuping landslide in the Qing river reservoir is simulated by DDA method, including startup, accelerating, deceleration and stop, and velocity along time is obtained. Last, empirical formula for computing surge height is discussed.

Abstract: In order to avoid surge of turbocharger for marine diesel engine, extending service life of turbocharger, we find out some causes and preventive measures of surge of turbocharger for diesel engine due to our accumulation and research in practice. According to the practical test of our company, the causes of surge is accurate and the preventive measures are somewhat productive

Abstract: Instability of landslides will lead to high-speed of rock and soil into the water, sparking a huge surge, causing significant harm to residents and infrastructure of coastal areas. With regard to the surge by landslide, the climbing height and the dynamic pressure are dominant characteristic parameters of concern, which influence the scope and extent of damage. The paper selected five important factors which influence characteristic parameters, that are time into water, sliding volume, angle into water, climbing angle, and water depth, based on simulation and MATLAB, established the BP neural network model of the characteristic parameters. Through training the network at various hidden node, the optimal training network has been gained, characteristic parameters at four groups of sample data have been predicted and verified respectively, and the best forecasting network can be selected as the predicting network.

Abstract: Every compressor has a stall line. In the vicinity of the stall line, the flow field is inherently unsteady due to the interactions between adjacent rows of blades, formation of small stall cells, flow separation and the viscous effects including shock-boundary layer interactions. These factors may aggravate to a state of local breakdown of flow or a total breakdown of flow or with a disastrous flow reversal. This paper starts with an overview on the previous researches about compressor stall and surge. Subsequently, it describes the effects of these instabilities in overall engine performance and design with/ without any control. The main objectives of this paper are to review the phenomenon of instability and methodology to suppress the rotating stall and surge by enlarging the stable operating range of compressor with the application of various control systems. This paper surveys research developments in this field and also tries to find an improved solution to increase the engine performance by applying various surge control strategies. Finally, the paper focuses on some recommendations towards a better design of compressor especially for aircraft power plant.