Effect of Water-Jumper Slope on Performance of Breastshot Wheel
Common problem in the operation of breastshot water wheel in Indonesia is discontinuity operation of the wheel due to very low stream velocity in the channel during dry season. In order to minimize the problem, it is important to study the method of maintaining the continuity operation of the wheel during dry season. Thus, the installation of water-jumper at upstream of the wheel is proposed in the present work. The laboratory models of the water channel and breastshot water wheel were fabricated. The water jumper is attached at the upstream whose slope angle can be adjusted. The present work investigates the effect of water-jumper slope on the performance of the breastshot wheel. The slope angles are set at 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40°and the upstream velocities are 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6 m/s. The result reveals that the use of water-jumper can increase the gross head and hydraulic power of very low stream, and hence the torque and the output power of the breastshot wheel are enhanced. The highest efficiency is achieved at the slope angle of 10º for stream velocity of 1.3 m/s. The water-jumper gives significant effect at stream velocity lower than 1.3 m/s. The hydraulic power is influenced by both discharge and gross head where they increase at increasing slope angle of the water-jumper. However, higher momentum losses occurs at the wheel for stream velocity higher than 1.3 m/s, thus output power and efficiency of the breastshot decreases even though hydraulic power increases. The water-jumper can keep continuous operation of the breastshot wheel in the irrigation channel during dry season.