High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost ...High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost meanwhile it still meets special requirements for pulsed electric fields (PEFs) in food process. The pulse generator utilizes a complex programmable logic device (CPLD) to generate trigger signals. Pulse-frequency, pulse-width and pulse-number are controlled via RS232 bus by a computer. The high voltage pulse generator well suits to the application for fluid food non-thermal effect in pulsed electric fields, for it can increase and decrease by the step length 1.展开更多
In this research, the deformation of water droplets in sunflower oil-interface under pulsatile electric field was studied experimentally. Three types of coalescence were observed:(i) complete coalescence,(ii) incomple...In this research, the deformation of water droplets in sunflower oil-interface under pulsatile electric field was studied experimentally. Three types of coalescence were observed:(i) complete coalescence,(ii) incomplete coalescence and(iii) no-coalescence. The first type is desirable because of leaving no secondary droplets. The second type that produced secondary droplets which caused by necking process, due to extreme elongation of droplets(mostly small droplets), was undesirable; because the small droplets were more difficult to coalesce and remove. The no-coalescence was caused by very fast coalescence and extensive pushing of droplet into the continuous phase. In this work the process was operated with the utilization of a batch cylindrical separator with high voltage system. The lower part of the cylinder was filled with the aqueous phase and its top part was filled with sunflower oil to form an interface between the two phases. The effects of electric field strength,frequency, and waveform types were investigated. It was found that, the ramp-ac waveform was the best waveform, avoiding the production of secondary droplets and in this case the frequency also played an important role.展开更多
文摘High precise, high voltage pulse generator made up of high-power IGBT and pulse transformers controlled by a computer are described. A simple main circuit topology employed in this pulse generator can reduce the cost meanwhile it still meets special requirements for pulsed electric fields (PEFs) in food process. The pulse generator utilizes a complex programmable logic device (CPLD) to generate trigger signals. Pulse-frequency, pulse-width and pulse-number are controlled via RS232 bus by a computer. The high voltage pulse generator well suits to the application for fluid food non-thermal effect in pulsed electric fields, for it can increase and decrease by the step length 1.
基金financially supported by Babol Noshirvani University of Technology, Iran
文摘In this research, the deformation of water droplets in sunflower oil-interface under pulsatile electric field was studied experimentally. Three types of coalescence were observed:(i) complete coalescence,(ii) incomplete coalescence and(iii) no-coalescence. The first type is desirable because of leaving no secondary droplets. The second type that produced secondary droplets which caused by necking process, due to extreme elongation of droplets(mostly small droplets), was undesirable; because the small droplets were more difficult to coalesce and remove. The no-coalescence was caused by very fast coalescence and extensive pushing of droplet into the continuous phase. In this work the process was operated with the utilization of a batch cylindrical separator with high voltage system. The lower part of the cylinder was filled with the aqueous phase and its top part was filled with sunflower oil to form an interface between the two phases. The effects of electric field strength,frequency, and waveform types were investigated. It was found that, the ramp-ac waveform was the best waveform, avoiding the production of secondary droplets and in this case the frequency also played an important role.
