Showing papers by "S.V. Prabhu published in 2012"

Performance Study of Modified Savonius Water Turbine with Two Deflector Plates

Abstract: Savonius rotor is a vertical axis rotor with simple in design and easy to fabricate at lower cost. The rotation of the rotor is due to the drag difference between the advancing blade and returning blade. Net driving force can be increased by reducing the reverse force on the returning blade or increasing the positive force on the advancing blade. Former can be realized by providing a flow obstacle to the returning blade and latter can be realized by concentrating the flow towards the advancing blade. The objective of the present work is to identify the optimal position of the deflector plate (on advancing blade side) placed upstream to the flow which would result in increase in power generated by the rotor. Tests are conducted to identify the optimum position of the deflector plate on the advancing blade side in the presence of a deflector plate on the returning blade side at its optimum position. Results suggest that two deflector plates placed at their optimal positions upstream to the flow increase the coefficient of power to 0.35. This is significantly higher than the coefficient of power of 0.14 observed for the rotor without deflector plates.

Study on the Interaction between Two Hydrokinetic Savonius Turbines

Abstract: Savonius turbine is simple in design and easy to fabricate at a lower cost. The drag is the basic driving force for Savonius turbine. Savonius turbines are mainly used for the small-scale electricity generation in remote areas. In real life, multiple Savonius turbines are to be arranged to form a farm to scale up the electricity generation. So, it is important to study the interaction among them to avoid the power loss due to negative interaction between turbines. The purpose of this investigation is to examine closely the effect of interaction between two Savonius turbines arranged in line. Experimental investigations are carried out to study the mutual interaction between turbines with water as the working medium at a Reynolds number of 1.2×105 based on the diameter of the turbine. Influence of separation gap between the two Savonius turbines is studied by varying the separation gap ratio (𝑋/𝑅) from 3 to 8. As the separation gap ratio increases from 3 to 8, becomes lesser the mutual interaction between the turbines. Results conclude that two turbines placed at a separation gap ratio of 8 performed independently without affecting the performance of each other.

Measurement of Flame Emissivity of Hydrocarbon Pool Fires

Abstract: Flame emissivity is an important parameter in the study of pool fires. A series of pool fire experiments are carried out with four different fuels namely diesel, gasoline, hexane and kerosene for pool diameters of 0.10 m, 0.13 m and 0.20 m. Flame emissivity at a height of 0.25 times the pool diameter from the base is measured by observing the flame with reference to a black body using infrared camera. Influence of pool diameter (0.3 m, 0.34 m, 0.5 m, 0.7 m and 1.0 m) on flame emissivity at a height of 0.25 times the pool diameter is studied with diesel as the fuel. Variation of flame emissivity with the height of the flame along the center of diesel pool fire is investigated for diameters of 0.3 m, 0.5 m, 0.7 m and 1.0 m. It is observed that the flame emissivity is less at the tip of the flame in comparison with that at the base of the pool fire. The measurement of flame emissivity by observing flame with reference to a black body using infrared camera is corroborated with the measurements conducted with reference to an electrically heated black body for diesel pool fires with diameters 0.3 m, 0.5 m and 0.7 m. Flame emissivity is also inferred from the mass burning rate measurements for diesel oil pool fires of 0.3 m, 0.5 m, 0.7 m and 1.0 m diameters. Flame emissivities are independent of the measurement method. Temperature and surface emissive power distributions of the diesel pool fires for diameters 0.3 m, 0.5 m, 0.7 m and 1.0 m are computed using infrared thermography.

Frequency detection in vortex flowmeter for low Reynolds number using piezoelectric sensor and installation effects

Abstract: Piezoelectric sensors are one of the most widely used sensors for vortex flowmeter application due to their low cost. Various researchers have employed piezoelectric sensor for this application. However, the location of the sensor and the performance of vortex flowmeter under disturbed conditions are seldom reported. In the present study, experimental investigations are conducted with water as the working medium in a circular pipe of diameter 52.5 mm. The optimum position of the piezoelectric sensor behind the trapezoidal bluff body is found out be 0.85 times the width of the bluff body. A new algorithm based on empirical mode decomposition and autocorrelation decay rate is suggested to identify the vortex shedding frequency under low Reynolds numbers flow condition. The performance of the flowmeter is also evaluated under different disturbed flow conditions to quantify the sensitivity of the flowmeter. The disturbances studied are single 90° bend, gate valve, globe valve, and two 90° out of plane bends. The overall uncertainty in the Strouhal number is within ±1.71%.

Review on Savonius Rotor for Harnessing Wind Energy

Abstract: Wind machines convert kinetic energy of the wind into usable form of mechanical energy or electrical energy. The Savonius rotor is a vertical axis wind machine which is simple in design. High starting torque characteristics make it suitable for standalone power generation as well as water pumping applications. This paper reviews the literature on the performance characteristics of the Savonius rotor. Multi-bladed rotor, multistage rotor, shape of the blade, use of deflecting plate, guide vanes and nozzle augmentation are several ways to enhance the performance characteristics. This review would help an engineer in building an improved Savonius rotor for a given application.