叶片泵相对性能曲线与比转数的理论关系研究

Theoretical Relations between Relative Characteristics of Impeller Pumps and Specific Speed

摘要:

为了从理论上探讨比转数对叶片泵水力性能的影响，以叶片泵基本方程为基础，推导出在理想流体条件下的相对扬程—流量方程和相对轴功率—流量方程，并对方程与比转数的关系以及方程的应用意义进行了分析和讨论。分析结果表明：叶片泵相对性能曲线方程是高效工况集内关于比转数的泛函数，与穿过额定工况点的等效曲线的斜率有关；相对扬程—流量曲线是关于比转数的二次抛物线；相对轴功率—流量曲线是关于比转数的三次抛物线；当相对流量不等于1时，随着比转数的增大，水泵相对效率降低。比转数越大，穿过额定工况点的等效曲线就越平缓，水泵高效工况区在型谱图中的位置越靠近流量轴，反之，则越靠近扬程轴。

Abstract:

In order to analyze the effects of specific speed ns of impeller pumps on hydraulic performance theoretically, relative head-flow equation and shaft powe-flow equation were deduced under the ideal fluid condition based on the basic equation of impeller pumps. The relations between the equations and ns were analyzed as well as the equations application. The results showed that the equations of relative characteristic curves of impeller pumps were functional set of high efficient operation relevant to ns and the slope of iso-efficiency curve (IeC) passing the nominal operation point (NOP). The characteristic curve describing the relation of relative head to relative capacity (RC) was the quadratic parabola of ns and the curve describing the relation of relative shaft power to RC is the cubic parabola of ns; for the RC unequal 1, pump efficiency is decreasing with increased ns. A high ns causes gentle slope of IeC passing NOP, consequent on the high efficient operation range of impeller pump approaching the capacity axis in the comprehensive characteristic curves charts; conversely, the high efficient operation range approaching the head axis for a low ns.