This paper presents the experimental results of subsonic and underexpanded sonic jets delivered from a central nozzle surrounded by a co-flow. The role of central nozzle lip thickness on the co-flow jet characteristics has been studied. The jet-mixing enhancement is achieved in the case of jet from the thick-lip nozzle compared to that of thin-lip nozzle. The extent of supersonic zone for the thick-lip is much shorter than the thin-lip jet.

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This paper presents the experimental results of underexpanded jets delivered from a central nozzle surrounded by a co-flow. The co-flow is found to be effective in elongating the supersonic core length of the central jet, at all levels of underexpansion. However, the expansion level of the central jet dictates the elongation caused by the co-flow.

The effect of inner nozzle lip thickness on the co-flow jet characteristics has been studied experimentally. Co-flow nozzles with inner nozzle lip thicknesses of 3 mm and 15 mm have been investigated. The thick-lip nozzle promotes mixing better than the thin-lip nozzle, for all the underexpanded operating conditions. The co-flow nozzle with thin-lip is effective in preserving the shock-cells nature, bringing down the longer shock-cell into shorter one and increasing the number of shock-cells compared to that of the co-flow nozzle with thick-lip.

This paper deals with the power system operation, frequency error and voltage control problems. In actual power system operations the load is changing continuously and randomly. As the ability of the generation to trace the change in load is limited due to physical/technical considerations. They result an imbalance between actual and the scheduled generation quantities. This imbalance leads to a frequency error and voltage problems. In general, as the speed of the machine depends on the frequency, any deviation in the frequency may lead to mal-operation of the system. So load frequency control is the key problem in the power system. For specified power rating of the machine the voltage should maintain constant otherwise the system insulation may get damage. In modern power system multi area inter connected systems are used for more reliability and economic purpose. In the multi area inter connected systems the frequency errors and voltage problems can be effectively decreased by using fuzzy logic controller with either of the 3, 5 or 7 membership functions. Here this fuzzy logic controller action also compared with automatic generation control and PI controllers also. By using fuzzy logic controller the frequency error, settling time, peak overshoot, under overshoots are effectively reduced.