Vibrations of water hydraulic systems – an experimental approach

This paper presents an experimental study of the vibrations induced both by cavitating and by non-cavitating flow in a hydraulic installation that comprises the main elements of a water hydraulic system. The cavitation was triggered by progressively closing a butterfly valve. The vibrations were measured on the pump, on the bearings housing, on the pump drive motor, and at nine measurement points located upstream and downstream of the main elements of the installation. The measurements were carried out at different flow rates obtained at different openings of the butterfly valve. The results suggest that the phenomena that take place inside the pump and inside the bearings cause vibrations having frequencies of up to 10 kHz. The results also indicate that the cavitation that occurs at the butterfly valve causes vibrations of high frequency, above 3 kHz, that have a distinct peak at about 18 kHz. These results could be useful in establishing proper maintenance plans for hydraulic installations

Dynamic behaviour of pneumatic actuators in open-loop controlled by proportional valves

The development of proportional and servo-mechanisms hydraulic control technique offered the premises of the development of pneumatic control, too. Despite the disadvantages of the nonlinearities appeared in the pneumatic systems (air compressibility being one of the causes), the new generation of proportional equipment made it possible to have a good quality pneumatic control system in our days. The goal of the paper is to demonstrate, by using numerical simulation technique, that the proportional valves used in pneumatic actuator drives occur at a good system dynamic at a reasonable cost as against to the directional control valve as it usually used in pneumatic actuator drives

FROUDE VERSUS FROUDE IN FISH LADDER DESIGN

Hydrodynamic modelling is based on the similitude theory and the dimensional analysis. The complexity of flows in different geometric environments and fluids, requires the use of the similarity criteria in both the construction of a physical model and a numerical simulation model. That is why expressing a criterion of similarity is important. In modelling of open channel flows, the Froude similarity criterion is used. By definition, as a ratio between the force of the inertia and the weight mass, the Froude number is dependent on the square of the velocity. And yet, there are situations in which the Froude number expression is preferred as linear speed dependence. The paper shows that the way of expressing the Froude number is especially important when we scale and design a fish ladder or fish passage

Pneumatic Actuator Controlled by Proportional Valve. Experimental results

In nowadays the pneumatic controlled systems are widely used in industrial applications where valves must be operated, where there is a fire ignition risk, or in different automation systems where a positioning action is desired. The paper presents the experimental results of a pneumatic actuator controlled by a proportional control valve. The goal of the paper is to compare the experimental results with the numerical simulation results and to improve the mathematical model associated with the experiment

Fish Ladder Geometrical Sizes and Hydraulic Performances. Experimental Approach

The paper presents the hydraulic experimental results from different types of fish ladders heaving pools and baffles with submerged orifice or vertical slot. The goal of the experiments is to develop a database of velocities and power densities for each type of fish ladder with the baffles in different arrangements, for different lengths of the pools. So, based on the fish ladder type, the hydraulic characteristic database and the experimental laboratory model size provided by this study, one can improve the design of a fish ladder. The laboratory experimental model is designed with respect to Froude similarity criterion

Vibrations of water hydraulic systems – an experimental approach

This paper presents an experimental study of the vibrations induced both by cavitating and by non-cavitating flow in a hydraulic installation that comprises the main elements of a water hydraulic system. The cavitation was triggered by progressively closing a butterfly valve. The vibrations were measured on the pump, on the bearings housing, on the pump drive motor, and at nine measurement points located upstream and downstream of the main elements of the installation. The measurements were carried out at different flow rates obtained at different openings of the butterfly valve. The results suggest that the phenomena that take place inside the pump and inside the bearings cause vibrations having frequencies of up to 10 kHz. The results also indicate that the cavitation that occurs at the butterfly valve causes vibrations of high frequency, above 3 kHz, that have a distinct peak at about 18 kHz. These results could be useful in establishing proper maintenance plans for hydraulic installations

Monitoring the State of Small Power Equipment

The paper presents analyses of vibrations measured on power equipment that can be encountered in rural spaces. A centrifugal pump that can be used in a small supply water network or in an irrigation system and a small hydraulic turbine designed for small hydropower plants were tested. Power spectra obtained with the Fast Fourier Transform for the vibrations measured at the pump and at the turbine are presented and discussed and defects that affect the normal operation of the machines are identified. The results highlight the importance of vibration diagnosis in the process of monitoring the operation of the machines, as a proactive maintenance method