遠心ポンプ始動時の過渡特性

(急始動時の過渡特性と内部流れ場の関係)

抄録

Fuel supply pumps for liquid fuel rockets and emergency core cooling system pumps for light water reactors are known to start up in extremely short periods of time. It is therefore necessary to know the transient characteristics of the pump in order to estimate the time variation of the flow and pressure in the pump piping system, the shaft torque acting on the impeller and the shaft thrust during transient operation when the pump speed and flow rate change rapidly, such as sudden start-up and shut-down of the pump or sudden opening and closing of the flow control valve.

These transient characteristics are very different between steady state and transient operation of the pump. Even when the pump is in transient operation, if the change is gradual, the operating point of the pump will follow the curve of the steady state characteristics. In other words, a steady-state relationship is established at every instant, even in a transient condition. This is called the quasi-steady-change assumption. However, if the variation of the operating point exceeds a certain limit, the pump cannot respond quickly along the steady-state characteristic and this quasi-steady-change assumption is no longer valid.

In previous studies, the dynamic characteristics of flow rate, total head, and shaft torque during the start-up operation of centrifugal pumps have been clarified from experimental and numerical results, but in the numerical analysis, the experimental results were used for the time variation of speed and flow rate.

This paper describes a method to explicitly calculate flow rate changes based on the relationship between the total head of the pump and the resistance and inertance of the pump piping system in the numerical analysis, and to independently calculate pump transient characteristics other than pump speed changes. The results of the relationship between the pump start-up transient characteristics and the internal flow field of the pump are also presented.