Water startup time is defined as the time, with an instantaneous gate opening, to accelerate the fluid column from zero to rated discharge. The ratio of mechanical to water startup time is the primary parameter in determining the stability of the generating system that the governor must be able to control. Water startup time is a theoretically calculated value, with a high degree of uncertainty. For a spiral case, it is little more than a guess. The reason is the flow is continually exiting from the inner radius, through the distributor's wicket gates. Therefore, by convention, the water startup time for a spiral case is calculated by the basic method and then 50% of that value is assumed. This paper uses a new technique of treating stream lines as terms of an infinite series to calculate water startup time in a spiral case. The results show the industry standard of a 50% value is quite conservative and therefore our present hydropower designs are more stable than assumed.
展开▼
