防空穴多级节流器

当节流阀前后压力比过大时,将发生空穴现象,为防止出现空穴,本文提出一种多级节流器的结构,并对其工作原理及设计方法作了详细分析。按该方法设计的节流器曾用于某钢厂真空精炼炉电极的电液伺服控制系统上的乳化液防冻装置中,并取得了良好的效果,每年为国家增产数百万元。

Cavitation Preventing Multi-stage Throttle

If the pressure ratio of upstream to downstream of a throttle valve in hydraulic especially in emulsion medium system is too large, the cavitation will occur. This problem is expected to be resolved through designing a new kind of throttle valve. The principle of operation and design procedure for that is discussed.Summary. In order to prevent the occurence of cavitation, the pressure ratio of upstream to downstream of a throttle valve has to be less than 3-3.5, but frequently it is over 3.5 in some hydraulic system. A multi-stage throttle is therefore introduced, of which the pressure ratio at every stage is provided to be less than 3.5 (see Fig.1). To ensure the velocity distribution of flow to return normal as the flow passing out one orifice but prior to entering into the next, the distance from one to next must satisfywhere D is the channel diameter of throttle, d the orifice diameter and a the expansion angle of flow from orifice.Let the pressure ratio of upstream to downstream of an orifice be k, then p0 = kp1, p1 = kp2,......pn-1=kpn, hence P0=k*pn or n = lg(p0/pn)/lgk.Therefore the number of stages n of a multi-stage throttle can be determined. The design procedure is given in detailed steps and a multi-stage throttle used in a freeze-proof device of electrode servo control system for vacuum refining furnace in steelmaking is instanced. This throttle has run normally without noise and shocking, and an annual gainings has increased by several millions Yuans(RMB) for the plant. Fig.1 A schematic drawing of three-stage throttle