ISSN 2343–7707 ; ISSN-L 1453-7303

HIDRAULICA Magazine No. 4 / 2016

Hidraulica no.4/2016

Experimental and Numerical Investigation of the Flow Past a Thin Circular Airfoil with Mid-Chord Slot
Authors: Andrei DRAGOMIRESCU, Carmen-Anca SAFTA, Marius STOIA-DJESKA

Results of an experimental and numerical study of the flow past thin, circular arc cambered airfoils with a narrow slot at mid-chord are presented in this paper. The purpose of the study was to investigate the aerodynamic characteristics of this type of airfoils from the point of view of using them in the aerodynamic structure of a small wind turbine. The experimental study was carried out in a closed (return-flow) wind tunnel. Drag forces were measured at different Reynolds numbers for airfoils having slots of different widths, placed at a constant angle of attack of 90°. The numerical study was extended to similar airfoils intended to (read more)

Study of Surface Roughness for Steel Parts Cut with Abrasive Water Jets
Authors: Sandor RAVAI-NAGY, Nicolae MEDAN

Today, abrasive water jet technology is used into a full scale production process such us contour cutting, drilling, milling, turning, threading. The purpose of this paper is to determine the surface roughness for two type of steel (S235JR and S355JO) cutting with abrasive water jet (AWJ) cutting machine – Bystronic ByJet Pro L, varying the traverse speed and (read more)

About Wind Turbine Power Estimation and Measurement
Authors: Mircea BĂRGLĂZAN, Teodor MILOŞ

Power of wind turbine offers various values if there are calculated with different formulas. The reason consists from different models considered and the influence of various factors. The article tries to compare and conclude about the relevance of these factors and influences on the true values. Also there are given characteristic curves measured on (read more)

Aspects Regarding the Special Hydraulic Distributors Operation
Author: Fănel Dorel ȘCHEAUA

At the beginnings of fluid use as an energy carrier medium inside mechanical systems called hydrostatic drives were not many differences between static or mobile drives because the majority of circuit specific components (pumps, motors) were the same. Lately they were developed highly efficient systems adapted for each application type. This has led to the development of a comprehensive array of different devices, specific to each application. Such devices used within the hydrostatic systems are hydraulic distributors necessary to adjust and direct the working fluid through the working circuit different branches. In this paper are described the hydraulic distributors of special construction which have the adjustment and control element of … (read more)

Combined Energy Systems for Obtaining Energy from Renewable Sources Used in Isolated Areas
Authors: Corneliu CRISTESCU, Catalin DUMITRESCU, Genoveva VRÂNCEANU,

The paper presents some aspects of obtaining energy from renewable sources, especially for remote areas, where we meet, usually, individual users or very limited groups of consumers. In the second part there are presented some solutions for combined systems that use renewable energies, which is a secure path to increase efficiency of their use and supply, throughout the day and even … (read more)

Aspect about Design of Experiment (DOE) to Study the Impact Forces Produced by Water Jets Used in Sewage Cleaning
Author: Nicolae MEDAN

The purpose of this paper is to present the steps necessary to make a design of experiment with application to study the impact forces produced by water jets used to cleaning the sewage system. The functioning of the cleaning sewer is dependent on certain process parameters, which can vary, causing variations of the impact forces. The research method used is that of the full factorial design of experiment. In the first part of the experimental research the Taguchi method shall be used to determine … (read more)

Pressure Setting and Control System with PWM Direction Control Valve
Authors: Mihai AVRAM, Victor CONSTANTIN, Despina DUMINICĂ, Constantin BUCŞAN

The paper presents a system that sets and controls pressure in a given volume. The system features an original solution of PWM direction control valve. Intelligent control algorithms are implemented and comparatively tested in order to (read more)

Role of Engine Design in Combustion Process
Author: Sanjay SINGH

Structural design of engines plays an important role in combustion based noise in engines. In this work the attenuation of engines has (read more)

Approaches of the Best Maintenance Strategies Applied to Hydraulic Drive Systems
Authors: Alexandru-Daniel MARINESCU, Teodor Costinel POPESCU,
Alina-Iolanda POPESCU, Carmen-Anca SAFTA

As a consequence of global competition priority measures are necessary for a total elimination of losses and failures of hydraulic drive systems. This is the reason why the maintenance activity must be continuously improved. So, the maintenance activity must be understood more than a periodic revision to remove the damages that may occur. Many companies are not underestimating the maintenance activity and large amounts of funds are invested in maintenance management. The research activity is encouraged to develop new design methods in the reliability of hydraulic systems and in preventive and predictive maintenance. The paper extends a careful review of all maintenance strategies capable of (read more)

An Introduction to Combustion Engines
Authors: Sunny NARAYAN, Aman GUPTA

A numerical model for the skirt is studied to consider the effects of the connecting rod inertia on the piston skirt–liner system lubrication. The piston motion, the oil film lubrication model and the friction losses of the system have been studied and compared. The results on a dual cylinder diesel engine show that inertia of connecting rod also affects system lubrication as well as (read more)

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