Water turbines are turbomachines utilising water power. The Francis turbine is a type of reaction turbine which converts the pressure energy of the water into kinetic energy in the control device and in the impeller. The water is fed in the control device by means of a spiral housing. The flowing water is accelerated in the control device by the adjustable guide vanes and directed onto the vanes of the impeller. The redirection and further acceleration of the water in the impeller generates an impulse which is transmitted to the impeller.
HM 150.20 is the model of a Francis turbine demonstrating the function of a reaction turbine.
The experimental unit consists of the impeller, the control device with adjustable guide vanes, a band brake for loading the turbine and a housing with a transparent front panel. The transparent cover enables to observe the water flow, the impeller and the guide vanes during operation. The angle of incidence and thus the speed of the impeller are modified by adjusting the guide vanes.
The turbine torque is determined by force measurement on a band brake and is read on spring balances. For measuring the rotational speed, a non-contact speed sensor, e.g. HM 082, is required. A manometer shows the water pressure at the turbine inlet.
The experimental unit is positioned on the working surface of the HM 150 Base Module in a simple and safe manner. The water supply and flow rate measurement are provided via HM 150. Alternatively, the experimental unit can be operated by the laboratory supply.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- design and function of a Francis turbine - determination of torque, power and efficiency - graphical representation of characteristic curves for
torque, power and efficiency
* Model of a reaction turbine1 * Transparent operating area1 * Turbine with adjustable guide vanes1 * Loading by band brake
 function of a Francis turbine  transparent front panel for observing the operating area  loading the turbine by use of the band brake  adjustable guide vanes for setting different angles of incidence  marking on brake drum for non-contact speed measurement  instruments: spring balances for determining the torque, manometer shows pressure at turbine inlet  flow determination by base module HM 150  water supply using the base module HM 150 or via lab supply