Florentina Bunea

Water Quality in Hydroelectric Sites

The most widely form of renewable energy is the hydropower, which produces electrical power using the gravitational force of falling or flowing water. Comparing to fossil fuel powered energy plants, hydropower plants are considered „green” energy source, because they do not produce direct waste and have almost no output level of greenhouse gas carbon dioxide. Hydropower is the most important source of renewable electricity generation – 86.3 %, and essential to operate the others sources of renewable energy that are random generation.

Aeration solution of water used by hydraulic turbines to respect the environmental policies

Preserving the quality of the water is a major concern from ecological, economical and sustainable development point of view, but also a condition when using water for renewable energy production. The European Water Policy defines a common regulation for sustainable and integrated management of water corps and requires that all impact factors to be considered. The environmental friendly concept represents a necessity for worldwide hydropower development. The dissolved oxygen in water courses represents an essential parameter which allows the preservation and development of aquatic habitat. The objective of the work is identification and study of a new solution which will contribute to improvement of the dissolved oxygen quantity in water used as renewable energy resource, so necessary to the aquatic life. The proposed solution takes in consideration the optimum between aeration parameters and energy consumption, in order to be implemented in hydraulic turbines.

On the vortex parameter estimation using wide band signals in active acoustic system

This paper proposes a new method for detection of the vortex presence in fluid flow based on an active acoustic system. The experiment that validates the theory was done on a reduced scale facility using ultrasonic transceivers. The main objective was to highlight the effect of a cavitation vortex on an applied wide band signal. In order to accomplish that, the Recurrence Plot Analysis (RPA) was investigated which emhasizes similar states of a dynamic process. The Tests were done from no vortex cavitation flow to vortex cavitation flow and backward.

Aeration process influence over the operation of a small hydro turbine - generator unit

The environmental friendly concept is a worldwide necessity for the future of the hydropower development as a renewable energy source. For this purpose, aeration devices and techniques are tested and implemented in order to assess the preservation of the aquatic life. The present paper investigates the influence of the aeration process over the operation parameters of a full scale machine (hydro turbine - generator unit) that delivers the energy into the national power grid. The vibrations are measured in different locations along the turbine - generator assembly: radial axial bearing, radial bearing, turbine housing and draft tube. The main components are identified in the vibrations amplitude spectra. The vibration magnitudes in the case of no air injection are compared to the ones in the cases when different air flow rates are injected. Even though the investigation reveals issues regarding misalignment of the shaft and bearing looses in housing, there werent identified any negative effects during operation of the hydro-generator unit due to air injection.

Cavitation characterization using wide band signals in an acoustic active sensing system

The paper presents a different approach based on an active acoustic system for the characterization of a vortex generating cavitation phenomenon. In the present work, the experiment was carried out in a reduced scale facility. The flow rate of the hydraulic system was varied and, when the flow became stable, the acoustic active system was started. The system is based on two ultrasonic transceivers which are placed in a “V” configuration. The main objective is to highlight the vortex presence influence on the acoustic sensing system using wide band signals. The Recurrence Plot Analysis (RPA) is used in order to highlight the vortex spectral signature, information which is not available when analyzing directly the acquired signal. The tests were done step by step, from no vortex flow to vortex flow.

Flow velocity profiling using acoustic time of flight flow metering based on wide band signals and adaptive beam-forming techniques

In this paper, we present a novel approach to non-intrusive flow velocity profiling technique using multi-element sensor array and wide-band signals processing methods. Conventional techniques for the measurements of the flow velocity profiles are usually based on intrusive instruments (current meters, acoustic Doppler profilers, Pitot tubes, etc.) that take punctual velocity readings. Although very efficient, these choices are limited in terms of practical cases of applications especially when non-intrusive measurements techniques are required and/or a spatial accuracy of the velocity profiling is required This is due to factors related to hydraulic machinery down time, the often long time duration needed to explore the entire section area, the frequent cumbersome number of devices that needs to be handled simultaneously, or the impossibility to perform intrusive tests. In the case of non-intrusive flow profiling methods based on acoustic techniques, previous methods concentrated on using a large number of acoustic transducers placed around the measured section. Although feasible, this approach presents several major drawbacks such as a complicated signal timing, transmission, acquisition and recording system, resulting in a relative high cost of operation. In addition, because of the geometrical constraints, a desired number of sensors may not be installed. Recent results in acoustic flow metering based on wide band signals and adaptive beamforming proved that it is possible to achieve flow velocity profiles using less acoustic transducers. In a normal acoustic time of flight path the transducers are both emitters and receivers, sequentially changing their roles. In the new configuration, proposed in this paper, two new receivers are added on each side. Since the beam angles of each acoustic transducer are wide enough the newly added transducers can receive the transmitted signals and additional time of flight estimation can be done. Thus, several flow velocities are possible to be computed. Analytically defined emitted wide band signals makes possible the identification of signals coming from each transducer. Using the adaptive beam-forming algorithm the receiving transducers can record different signals from the receiver, equivalent to different propagation paths. Therefore, different measurements of time of flight are possible, leading to additional flow velocity measurements. Results carried out in an experiment facility belonging to ICPE-CA, Bucharest - Romania allowed to the validation of the flow velocities computed using this new technique, in symmetric, asymmetric and uneven flow conditions. The acoustic derived values were referenced with those provided from a Pitot tube probe installed in the test channel and the results obtained by the method proposed in this paper are relatively close to this reference.