E-01：Miniaturization and High-Power Output of Small Hydropower Generation Using a Contra-Rotating Rotor

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＜E-01＞：Mechanical Engineering, Environmental Science, Energy Engineering

Miniaturization and High-Power Output of Small Hydropower Generation Using a Contra-Rotating Rotor
― Effective Utilization of Energy Losses through a Pressure-Reducing Valve Equipped with an Inline Small Hydroturbine ―

Toru Shigemitsu	Professor
Energy System, Mechanical Science, Division of Science and Technology, Graduate School of Technology, Industrial and Social Sciences

Keywords	Turbomachinery, Contra-Rotating Impellers, Computational Fluid Dynamics, Inline Turbine, Miniaturization, High Power Output
Laboratory URL	http://pub2.db.tokushima-u.ac.jp/ERD/person/140130/profile-ja.html

Research Overview

● Establishing high-performance design methods for contra-rotating rotors remains a bottleneck
Owing to their high-power density and torque cancellation effect, contra-rotating rotors have been commercialized in applications such as electronic device cooling fans and drones, where compactness and lightweight design are required. However, because the two-stage rotors rotate in opposite directions (Fig. 1), the internal flow becomes highly complex.
As a result, high-performance design methodologies based on high-accuracy numerical flow analysis capable of quantitatively capturing velocity and pressure distributions have not yet been fully established, preventing the technology from achieving its full potential.

● High-accuracy numerical flow analysis and high-performance design methodology
Contra-rotating rotors have been applied to inline small hydroturbines and axial-flow fans, and their internal flow characteristics have been clarified through high-accuracy computational fluid dynamics (CFD) analysis.
Based on these findings, a high-performance design methodology for contra-rotating rotors has been established, enabling the development of an inline, high-power, small axial-flow hydroturbine with a turbine diameter of less than 100 mm (Fig. 2).
Currently, new contra-rotating rotor configurations combining mixed-flow and axial-flow hybrid rotors with centrifugal rotors (Fig. 3) are being proposed and investigated to achieve higher pressure and efficiency.

Expected Applications and Product / Commercialization Concept

● Effective utilization of energy losses using a pressure-reducing valve with an inline small hydroturbine The contra-rotating rotor turbine (100 mm diameter) can generate the maximum output of 1 kW under conditions of a pressure of 1 kg/cm² and a flow rate of 5–20 L/s, achieving a power output 2–10 times higher than that of conventional configurations.
This performance enables significant miniaturization of inline turbines, allowing them to replace conventional valves in pipelines with diameters of 100 mm or less.
Furthermore, by utilizing centrifugal effects, the system can be adapted to inch-sized piping, expanding its applicability to municipal water supply systems, small-scale waterworks, and agricultural irrigation pipelines.