充水保压蜗壳
pressure-maintaining spiral case by water filling
大小圆蜗壳
major and small circle casing
垫层蜗壳
Spiral Case with Cushion Layer
cushioned spiral case
非圆断面蜗壳水力设计
hydraulic design of spiral case with non-circular
保压蜗壳
spiral case of pressure preservations