The powerhouse layout is a critical aspect of the design of a mixed-flow (Francis) hydropower station, as it directly affects operational efficiency, construction cost, safety, and maintenance.A rational, compact, and functionally well-defined equipment room layout ensures stable operation of the units and facilitates future maintenance and expansion.
1. Introduction
Francis turbines are widely used in medium-head hydropower stations due to their high efficiency, stable operation, and wide operating range. As the core structure housing the turbine-generator units and auxiliary systems, the powerhouse must be carefully arranged to meet hydraulic, mechanical, electrical, and structural requirements. A well-designed layout ensures smooth energy conversion from water to electricity and supports long-term reliable operation.
2. Design Principles of Powerhouse Layout
The layout of a Francis hydropower station powerhouse generally follows the following principles:
Hydraulic rationality: The water flow passage, including the spiral case, draft tube, and tailrace, should be short, smooth, and symmetrical to reduce hydraulic losses.
Structural safety: The powerhouse structure must safely bear loads from equipment, water pressure, vibration, and seismic forces.
Operational convenience: Adequate space should be reserved for equipment installation, operation, inspection, and maintenance.
Economic efficiency: The layout should minimize excavation volume and concrete usage while ensuring performance and safety.
Adaptability: The design should consider future expansion or equipment replacement where possible.
3. Functional Zoning of the Powerhouse
A typical Francis turbine powerhouse is divided vertically into several functional levels:
Generator floor: Located at the upper level, this floor houses the generator, main shaft, thrust bearing, and overhead crane. It provides sufficient headroom for lifting and maintenance operations.
Turbine floor: Positioned below the generator floor, it contains the turbine runner, guide vanes, and spiral case. This level is closely connected to the water passage system.
Draft tube level: Located at the lowest part of the powerhouse, it allows water to exit the turbine efficiently and flow into the tailrace channel.
Auxiliary equipment rooms: These include rooms for cooling water systems, oil systems, compressed air systems, drainage and dewatering equipment, as well as control and protection systems.
4. Typical Powerhouse Layout Forms
Depending on topography, geological conditions, and head range, Francis hydropower stations may adopt different layout forms:
Surface powerhouse: Built above ground, suitable for low- to medium-head stations in open terrain. It features convenient construction and operation.
Underground powerhouse: Excavated within rock mass, commonly used in high-head stations or mountainous areas. This layout improves structural stability and reduces environmental impact.
Semi-underground powerhouse: A combination of surface and underground arrangements, balancing construction difficulty and operational needs.
5. Equipment Arrangement
Within the powerhouse, turbine-generator units are usually arranged in a single-row configuration, with the machine axis perpendicular to the river flow. The spacing between units must satisfy requirements for vibration control, maintenance access, and crane operation. Electrical equipment such as transformers and switchgear may be arranged in adjacent halls or separate caverns to enhance safety and reliability.
Post time: Jan-28-2026
