Ruzgâr turbinlerinde kanat modelleri yuksek performans icin buyuk oneme haizdir. Bu calismada, ruzgâr turbini kanat profili yaygin olarak kullanilan NACA 2412 modelinde kiris yapisinin aerodinamik performansa etkisi sayisal olarak incelenmistir. RHINOCEROS programi ile modellenen kanat profilleri ANSYS FLUENT programi ile akis analizleri yapilmistir. Sayisal analizler, 3,24x105 Reynolds sayisinda (Re) ve k-e realizable turbulans modeli kullanilarak gerceklestirilmistir. 0,25 m veter uzunluguna bagli olarak kanat profillerinin aciklik orani 5’tir. Serbest hava akim hizinin 20 m/s oldugu calismada kanat profilleri kaldirma (CL), suruklenme (CD) katsayilari ve aerodinamik performansi (CL / CD) incelenmistir. Duz kanat profili (K0), maksimum kaldirma katsayisina 22,5° hucum acisinda ulasirken, kiris yapisi ile modifiye edilmis kanat (K1) profili 25° hucum acisinda ulasmistir. K1 kanadinin maksimum CL degeri 1,1462 olup K0 kanadinin maksimum degerinden %1 fazladir. Irtifa kaybi sonrasi, K1 kanat profilinin ortalama CL / CD degeri K0 kanadinin ortalama degerinden %5 fazla olarak gerceklesmistir. Kiris yapisi yuksek hucum acilarinda, aerodinamik performansa olumlu yonde etkisi bulunmaktadir.

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Rüzgâr Türbinlerinde Kiriş Yapısının Performansa Etkisinin Sayısal Olarak İncelenmesi

This paper proposes a study in theoretical and experimental terms focused on the vibration beating phenomenon produced in particular circumstances: the addition of vibrations generated by two rotating unbalanced shafts placed inside a lathe headstock, with a flat friction belt transmission between the shafts. The study was done on a simple computer-assisted experimental setup for absolute vibration velocity signal acquisition, signal processing and simulation. The input signal is generated by a horizontal geophone as the sensor, placed on a headstock. By numerical integration (using an original antiderivative calculus and signal correction method) a vibration velocity signal was converted into a vibration displacement signal. In this way, an absolute velocity vibration sensor was transformed into an absolute displacement vibration sensor. An important accomplishment in the evolution of the resultant vibration frequency (or combination frequency as well) of the beating vibration displacement signal was revealed by numerical simulation, which was fully confirmed by experiments. In opposition to some previously reported research results, it was discovered that the combination frequency is slightly variable (tens of millihertz variation over the full frequency range) and it has a periodic pattern. This pattern has negative or positive peaks (depending on the relationship of amplitudes and frequencies of vibrations involved in the beating) placed systematically in the nodes of the beating phenomena. Some other achievements on issues involved in the beating phenomenon description were also accomplished. A study on a simulated signal proves the high theoretical accuracy of the method used for combination frequency measurement, with less than 3 microhertz full frequency range error. Furthermore, a study on the experimental determination of the dynamic amplification factor of the combination vibration (5.824) due to the resonant behaviour of the headstock and lathe on its foundation was performed, based on computer-aided analysis (curve fitting) of the free damped response. These achievements ensure a better approach on vibration beating phenomenon and dynamic balancing conditions and requirements.

An Experimental Approach on Beating in Vibration Due to Rotational Unbalance

Residual stresses are one of the most important factors in the integrity of welded structures. There have been vast majorities of research conducted on the mechanism of vibratory stress relief method (VSR), but the lack of a specific mechanism, explaining the process, was tangible. Therefore, in this article, the mechanism of VSR was explained using a new finite element model by focusing on the welded residual stresses, being widely used in industry. To be more specific, the effect of resonant vibration on residually stressed specimens was investigated numerically and experimentally. To model the welding simulation, a volumetric moving heat flux was defined using Goldak’s model in Abaqus/CAE. In addition, experiments were planned in a way to investigate not only the effects of vibration time, but also the effect of amplitude of the vibration. Residual stresses were measured using Incremental Centre Hole Drilling (ICHD) method. Finally, a mechanical shaker was designed and assembled to induce higher frequencies and larger amplitudes.

https://ijmf.shirazu.ac.ir/article_5998_b1b741f288b44eb28ff9053b516b5b20.pdf

Vibratory Stress Relief of Welded Austenite Stainless Steel Plates: Numerical and Experimental Approach

At a high frequency of vibration; the cam of a vibrator always encounters the issue of jamming or the follower rolling off or losing contact with the cam when the appropriate design is not carried out. This study, therefore, developed the shape of the cam profile of mechanical yam vibrator using cycloid motion in the South. Displacement equations from the base circle to the cam profile were developed to obtain the shape of the cam using cycloid motion. A vibrometer was used to evaluate the developed 5 mm, 10 mm, and 20 mm cam sizes installed in a mechanical yam vibrator. The maximum displacement recorded for 5 mm, 10 mm and 20 mm cam sizes were 4.47 mm, 8.71 mm, and 14.54 mm respectively for low (1 – 5 Hz) frequency; 4.58 mm, 8.84 mm and 16.34 mm respectively for medium (60 – 100 Hz) frequency; and 4.66 mm, 9.09 mm and 17.30 mm respectively for high (150 – 200 Hz) frequency. This study shows that a cycloid cam would operate smoothly at low, medium, and high frequencies of vibration and function properly for frequency and displacement of vibration up to 200 Hz and 20 mm respectively without jamming and failing. A cycloid cam is therefore recommended for low, medium, and high frequencies motion of vibration.

Development of the shape of the cam profile of mechanical yam vibrator using cycloid motion

Aerodynamic characteristic of wind turbine with the leading edge slat and Microtab

A vibration exciter is a machine which produces mechanical vibratory motion to which the test object is subjected. This article presents design, construction, performance and testing of mechanical vibrations exciter, which have unbalanced mass to generate uniaxial vibrations. The exciter is designed to produce a given range of harmonic or time dependent excitation force and displacement through a given range of frequencies. The mechanical vibration exciter produces vibrations due to centrifugal force of rotating eccentric mass. The vibrations produced lie in the low frequency range. The construction of working device and its important parts are described here. The most important part of exciter is unbalanced mass attached with rotating disc of motor. Exciter has unbalanced mass at one end of disc, base frame, top plate as platform, springs and motor. This exciter is used for testing of welded parts, consolidation of concrete, concrete filling in mould. The obtained experimental results are in line with theoretical results.

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Design and testing of unbalanced mass mechanical vibration exciter

Aerodynamic effects of leading edge (LE) slats and slotted trailing edge (TE) flaps on NACA-2412 airfoil in prospect of optimization

The performance of the central solar receiver should be properly examined for an effective design of a solar power or solar heating system. The performance of solar receiver is affected by three parameters. These are the amount of solar radiations, the state of the heating medium and the temperature of the surrounding air. Also, while evaluating the performance of a solar receiver, the ambient weather conditions should be taken into account. As a result, when a large amount of direct light strikes a solar receiver, the power generated increases as well. In contrast, as the amount of direct light falling on the solar receiver diminishes, so does the amount of electricity generated. As a result, it is generally understood that on sunny days, the performance of the central solar receiver will be higher, while on overcast days, the performance will be reduced. The solar receiver collects heat from diffused or reflecting light (when the sun is obscured by clouds) and absorbs reflective light from glossy or light-colored surfaces. The experimental results reveal that solar radiation collection performance is dependent on climatic circumstances; thus, when installing a solar receiver, it should be suitable for the specific region depending on weather conditions.

Shrikant Nimbalkar

Papers

Design and testing of unbalanced mass mechanical vibration exciter

Aerodynamic effects of leading edge (LE) slats and slotted trailing edge (TE) flaps on NACA-2412 airfoil in prospect of optimization

An experimental study of solar receiver under cloudy weather conditions