水轮-风机组中水轮机工况特性的理论研究与实验

冷却塔水轮机作为工业循环水系统余压利用的一种措施，已获得了比较广泛的应用。它与风机直连形成水轮-风机组，工作在串联有压环境中，属超低比转速水轮机。首先从理论上研究了水轮-风机组中水轮机的工作特性，发现：（1）水轮-风机组中风机转速与水轮机的流量成正比，即水轮-风机组具有自适应特性，表明水轮-风机组的转速随着冷却水量的增减成比例地增减，使风机输出的风量随着增减，这种规律正好符合冷却水量对风量的要求；（2）在系统压力及流量发生变化时，水轮机的单位转速和单位流量保持为常数，即水轮机始终保持工况自相似特性，表明只要设计时使水轮机处于较好的工况，就可以基本保持水轮-风机组工作在较好工况，无须与常规发电水轮组一样进行复杂的工况调节。最后，实验台实验和现场实验结果进一步验证了这些工作特性。因此，水轮-风机组无需调节系统，这可使水轮-风机组的建设成本和运行成本大大降低。这些特性对于余压回收用水轮机的设计和运行具有重要意义。

Theoretical study and experiment on turbine operating characteristics of turbine-fan units

Cooling tower hydraulic turbines, as an important energy saving device in recycling the residual pressure of industrial circulating water system, have been widely used in practice for driving the fan in replacement of motors. Such a turbine-fan unit, with the turbine and fan in series connection, often works at an ultra-low specific speed in a pressured environment, which differs from the conventional power turbines. This paper presents a theoretical study on the working characteristics of a hydraulic turbine in a turbine-fan unit. First, we found that the fan speed is proportional to the turbine flow, namely it is self-adaptive in characteristics ? the speed of the turbine-fan unit is proportional to the flowrate of cooling water, producing the right air flow exactly demanded by cooling water. Second, in the condition of system pressure and flow always changing, the unit speed and unit flow of the turbine are constant, or the turbine always maintains an operating condition of self-similar characteristics. This means that the turbine-fan unit can maintain an optimal working condition if its design condition is well adjusted, different from the power turbine that needs a complicated control on its working conditions. Finally, all these characteristics of working conditions are validated by our experimental results. Thus, such a turbine-fan unit does not need an adjusting system, greatly reducing its construction and operating costs, and the characteristics revealed in this study would be very useful to the design and operation of residual pressure recycling turbines.