Nicolae Vasiliu

A procedure to develop elevation-area-capacity curves of reservoirs from depth sounding surveys

This paper proposes a procedure for developing reservoir elevation-area-storage capacity curves and bathymetric charts of a reservoir from depth sounding surveys. The Morii Reservoir, located in Bucharest (Romania), on Dambovita River, was chosen as case study. A single beam bathymeter with GPS was used in 2016 to survey the reservoirs bed. The acquired bathymetric data were denoised with a custom-made program written in Python, that uses the Butterworth filter and a zero-phase noise cancellation function. The decontaminated data were subsequently interpolated in ArcGIS to produce a gridded DEM of the reservoir bed surface and a bathymetric chart with contour lines. The area-capacity-elevation curves were obtained by calculating the 2D area and volume between horizontal planes and the interpolated bed surface. Comparisons with bathymetric survey from 2010 show differences of less than 14% in terms of storage capacity and 8% of the area of the reservoir during these 6 years.

Experimental Researches on the Magneto-Rheological Dampers Response to the Control Parameters

The magneto-rheological (MR) dampers used in automotive suspension improve the energy dissipation capacity for the vertical oscillations of the car body and wheel of the vehicle by increasing the damping force developed by piston motion. The determining of the time constant of the magneto-rheological fluid is essential in order to build a realistic dynamic model of an actuator, needed for implementing a real time control system provided with a comfort feedback. In this paper the authors compare the information collected from the dedicated literature, which currently are relatively restricted, to the results obtained from their own experimental determinations. The final objective of the paper is to help the optimal design a control structure for the assembly of the car magneto-rheological dampers.

Modelling and Simulation of the Dynamic Behaviour Automotive’s Suspension By AMESim

The main objective of this paper consists in the preliminary analyse of the dynamic behaviour of an automobile’s suspension using a model built in AMESim simulation program. For the dynamic study of a car suspension the authors have used a full vehicle model with 15 degrees of freedom, hear including the steering system. A strong nonlinear model was used in order to optimize the performance of the suspension by a long series of numerical simulations. The entirely research has shown that AMESim offers a real aid in the suspension study, because it significantly reduces the working time. Once created a model, and validated by experimental measurements, it can be used to study any type of similar suspension.

Experimental Identification of the Automotive Magnetorheological Shock Absorbers

The effectiveness of the shock absorbers in terms of comfort and automotive manoeuvrability is closely linked to the free and forced vibrations generated by the road irregularities and the driver’s orders (acceleration, braking etc.). The passengers mass, the sprung mass parties (car body), the free parties mass (wheels and a part of the suspension), the stiffness and the damping coefficient of the various elements of the car are involved in this process. In the road vehicles’ suspensions field, the dampers control through the valves is an extremely difficult target due to the unpredictable flow’s variation and the pressure difference generated inside them. This was the main reason for developing and using magneto rheological fluids as dampers fluids. The authors have designed and built a complex test bench in order to compare the behaviour of a classical dampers and a magneto rheological one. A high speed National Instruments data acquisition system was used to obtain information about the correlation between the damping force, stroke, and speed, control current, temperature etc. The results were compared with the similar ones supplied by some top level manufacturers.

Numerical Simulation - a Design Tool for Electro Hydraulic Servo Systems

Electro hydraulic servo systems are complex technical entities that involve both phenomena of fluid mechanics, and phenomena specific to control processes with feedback. Due to the complexity of these interactions, the optimal design goal is achieved by an iterative process, using some dedicated software. To obtain the required performance the use of mathematical modeling and numerical simulation of these systems is always very effective. In any optimal synthesis process of an electro hydraulic control systems, the analysis of the stablity is an important stage. Several methods are used to provide a good stability for such type of systems: the increase of the dead band of the control valves, the use of some additional feedback, the decrease of the flow gain of the control valve around the hydraulic null point etc. Numerical simulation of the dynamic systems allows gathering of necessary information about their behaviour based on a mathematical models that describe those systems. Obtaining of mathematical models as close as posible to the physical phenomena that are to be reproduced or impoved is helpful in making decisions for optimization. The most recent tendences in this field regard novel concepts, such as co-simulation and real time simulation. This chapter presents two different examples of developing a numerical co-simulation environment, based on two software packages: AMESim (LMS IMAGINE SA, 2009) and LabVIEW (National Instruments, 2009). The most important parameters investigated are the following: a. the influence of the variable area gradient of an electrohydraulic flow amplifier on the stability reserves of a electro hydraulic servomecahnism (a. Ion Guta et al., 2010); b. a hybrid solution of modeling / simulation of a hydrostatic transmission with mixed control (b. Ion Guta et al., 2010). By means of AMESim software a model of an electrohydraulic servomechanism was developed, while analysis of data collected as a result of simulations in AMESim was performed by means of virtual instrumentation, using LabVIEW software. The real time use of these two simulation / programming environments can lead to the development of advanced modeling / simulation networks of complex fluid systems controlled by digital hardware, useful for optimal system design.

Performance Identification of a New Type of Speed Governor for Kaplan Turbines

The paper contains a summary of the experimental results of a long-term research program aiming to design, manufacture, setup and full industrial test a new type of electro hydraulic digital speed governor for Kaplan water turbines. Computational methods, control software, design problems, and mainly performance validation are shortly presented. The work represents the second part of a final research report on the modern electro hydraulic speed control of the power units.Copyright