Computational Analysis of a Double-Nozzle Crossflow Hydroturbine

Abstract

The crossflow turbines commonly used in small hydropower systems have a single nozzle. We are unaware of any studies of double-nozzle crossflow turbines which could have twice the power output of the single-nozzle design by doubling the flow through the same runner, with a high maximum efficiency. We present a computational analysis of a double-nozzle crossflow turbine, to determine the turbine efficiency and fundamental flow patterns. This work was based on a single-nozzle crossflow turbine with a maximum efficiency of 88%, one of the highest reported in the open literature through extensive experimental measurements. Previous numerical studies on this turbine have shown that the water flow in the runner was confined to less than half the runner periphery, implying that the other half could be used to double the runner power output by employing a second nozzle. We show that adding a second, identical nozzle without making any other changes to the design achieves a doubling of the power output. The dual-nozzle turbine, therefore, has the same efficiency as the original turbine. We also investigate the use of a slider to control the flow at part-load and show that part-load efficiency of the double-nozzle is very similar to that of the original turbine. This demonstrates the feasibility of using two nozzles for crossflow turbines.

History of Utilization of the Computational Fluid Dynamics Method for Study Pico Hydro Type Cross-Flow

“…Furthermore, [20] using the CFD method investigated flow pattern and turbine performance when CFT run under the part-load condition which resulting in more efficient water discharge control of CFT. And, Adhikari and Wood (2018) [21] investigated CFT with a double nozzle to attain more efficiency. At the end of 2018, a summary of prior studies been made into a review paper related to the effort of several studies to attain the high efficiency of CFT [29].…”

“…Another CFT's nozzle improvement has found the 90% of efficiency CFT by using numerical simulations validated by experimental testing [11][20]. Currently, their study was trying to improve CFT efficiency by doubling its nozzle [21].…”

Consideraciones de diseño de una turbina Michell-Banki

“…La turbina Michell-Banki funciona bajo el principio de transformación de la energía potencial (cabeza de altura), en energía cinética justo antes de que el fluido ingrese al rodete el cual opera a presión atmosférica [9].…”

“…Además, Adhikari y Woods [52] diseñaron y evaluaron mediante simulación numérica el efecto de un inyector adicional en una turbina Michell-Banki. Dado que en los trabajos previos lograron identificar que el flujo a través del rodete está confinado a menos de la mitad de este; concluyeron que la porción restante del rodete se podría aprovechar con la instalación de un nuevo inyector, direccionado en sentido contrario al convencional, tal como se observa en la figura 14.…”

Application of Computational Fluid Dynamics Method for Cross-flow Turbine in Pico Scale

“…Furthermore, another study of CFT nozzle enhancement has discovered a 90% efficiency utilizing numerical simulations validated by experimental results [11][20]. Their research was currently focused on increasing CFT efficiency by doubling the nozzle size [21].…”