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Tek pervaneli yük gemilerine uygulanan ''asimetrik kıç formları ile merkezden kaçık şaft düzenine ait sevk'' karekteristiklerinin deneysel incelenmesi

Başlık çevirisi mevcut değil.

  1. Tez No: 39424
  2. Yazar: Y.ZAFER KANIPEK
  3. Danışmanlar: PROF.DR. MACİT SÜKAN
  4. Tez Türü: Doktora
  5. Konular: Gemi Mühendisliği, Marine Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1993
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 173

Özet

ÖZET Bu çalışmada tek pervaneli yük gemilerinin sevk verimini arttırmak için geliştirilmiş olan Grim Tekeri. Nozuilar, Dümen f inleri, Girdap f lapları kısa olarak tanımlanmış» esas olarak Asimetrik kıç formları ve Merkezden Kaçık Şaftlı kıç formlarının sevk karakteristikleri değişik modeller Üzerinde incelenmiştir. Asimetrik kıç formları ve Merkezden kaçık şaftlı kıç formları ile ilgili günümüze kadar yapılan çalışmalar çok kısa olarak anlatılmış, geliştirilen metodlar verilmiştir. Asimetrik kıç formu ile ilgili İ.T.U. Ata NUTKU Gemi Model Deney Laboratuvarında 1987 yılında başlatılan çalışmalar anlatılmıştır. Son aşamada ise aynı boyutlara sahip sadece giriş ve çıkış prizmatik katsayıları farklı üç adet SERÎ 60 formlu modelin sevk karakteristikleri, simetrik kıç formlu, asimetrik kıç formlu ve merkezden kaçık şaftlı kıç formlu olarak direnç, sevk ve iz dağılımı deneyleri ile belirlenmiştir. ilk olarak simetrik formlu modeller ile deneylere başlanılmıştır. Deneyler sakin su şartlarında gerçekleştirilmiştir. Direnç ve sevk deneyleri kontinental metodla, iz deneyleri iz tarakları ile yapılmıştır. Bu deneylerden sonra laboratuvarımızda deneylerde kullandığımız pervanenin dönüş yönünü esas alarak geliştirdiğimiz Asimetrik Kıç Formları ve Merkezden Kaçık Şaftlı Kıç Formları üretilmiş, ve bunların sevk karakteristikleri de.simetrik formdaki gibi yapılmıştır. Tüm bu formların Denizcilik, Rota-dengesi ve Manevra deneyleri konumuz dışında tutulmuş» bunlar için ayrı bir çalışma yapılması düşünülmüştür. Bu çalışmanın sonunda asimetrik kıç formu ve merkezden kaçık şaftlı kıç formunda sevk veriminin modelin çıkış prizmatik katsayısı ile nasıl değiştiği belirlenmiştir. vıı

Özet (Çeviri)

EXPERIMENTAL INVESTIGATION INTO THE CHARACTERISTICS OF THE APPLICATION OF ASYMMETRIC STERN DESIGN WITH OFF-CENTER SHAFT MECHANISM IN SINGLE PROPELLER BULK CARRIERS SUMMARY Extensive research has been carried out in order to increase fuel saving in sea transportation, which yieidea in designs of ships with bulbous bows. Since then the attention of researchers have focused on stern designs m order to improve propulsive efficiency. Both in the model scale or ships > the researchers have tried new designs of the“Grim Wheel”which can be.described as a free- turning wheel with water flow just behind the propeller. Vortex flaps, rudder fins. asymmetric stern and off-center shafts are other devices that attracted the researchers interestover the years. The Grim Wheel increases the propulsive efficiency by 5& to 15?.; depending upon the type of the ship and the load of the propeller. Thus the lost energy is utilized for extra propulsion for the ship. Grim wheel turns in the same direction with the propeller and the speed can be as much as 40% that. of propeller's depending upon the number of blades, hence the lost energy is again UT_iIi2:ed as an extra propulsion for the -ahip. An increase in the propulsive efficiency by placing hydrodynamic fins before the propeller in stern was.found by K.G. Spark during- the experimentations in Berlin model towing tank. F\ ns increase the area of flow regionally on the ship side and also, remove the spoil whirepoois.. In order to piace the fins, it is necessary to view the flow in the item, which requires experimentation in the towing tanks. F6.-search on the asymmetric stern designs started in 1950* s after the Venedician Gondol* s stern patterns. The first asymmetric stern ship was built with no apparent success in 1350 by France. vxnBetween“ 1965 and 1968 four different high block ship models had been fitted with asymmetric stern and tested at the Hamburg Ship Model Basin CHSVA5. All the experiments showed savings of between 5 and 8 percent. In spite of these succesful results, shippowners and shipbuilders at that time still regarded the risk involved as too high. Fuel at less than thirty dollars per ton was a factor not to be upset and Nönnecke's concept remained âh unfulfilled hope, at least for a further decade. Meanwhile the situation changed, and constantly rising fuel oil prices led to a reconsideration of the idea. In 1980 a new test series was started at HSVA, sponsored by the West German Federal Ministry for Research and Technology. For the project of a container vessel, two asymmetric sterns wore manufactured and compared with a symmetric parent form. All three afterbodies were designed as close as possible in displacement and were tested with two different propellers at two different drafts, which means twelve different test configurations in total. Another project, also sponsored by BMFT, belongs to a very extensive research program called ”Schiff der Zukunft“. In total, nine model versions were tested, seven with symmetric and two with asymmetric sterns. The first asymmetric design was not fully satisfactory where as the second proved to be the best within the entire series. The oil-crisis had resulted in an increase in the asymmetric ship stern research and on May, 1982, the 502 TEU container vessel ”Thea-S", first succesful ship with asymmetric stern according to Nönnecke's concept, was Lounched. Very high propulsive efficiency and low fuel consumption were obtained with this ship. These results, made the asymmetric ship sterns a standart in the shipyard Heinrich Brand, at Oldenburg. West Germany. Prior to keel laying, also in this case extensive model experiments had been carried out. Two alternative sterns, a symmetric one and an asymmetric one, were tested with the same forebody. The asymmetric stern turned out to be superior to its symmetric counterpart by approximately 8 'per cent at design draft, and 6 per cent at ballast draft, followed by J.W. Piskorz-Nalecki *s research at the SSPA model towing tanks in Göteborg. During 1984-1988 a model of Bulk-Carrier type ships was tested in the Gdansk model towing tank. With success proving superiorty of the design, the 26300 DWT Bulk Carrier ship was ordered to be built in the Pendik Shipyards. IXThe asymmetric stern design provides lower fuel consumption than that of bulbous designs for all sea-conditions considered, and %8 power saving is also noticable.. This power-saving is the direct result of the effect of the direction of propeller rotation on the propulsive efficiency. A.change in the direction of the propeller rotation either increases or decreases the propulsive efficiency. Since the propeller is placed on one side, its performance differs for the portside and starboard-side. Therefore, the center of pressure is shifted to one side where the propeller blades move downward, resulting in an asymmetric pressure distribution. The clockwise rotation of propeller creates a critical pressure distribution above the propeller shaft on the port-side. As a result, the angles of run became larger on starboard-side where the propeller blades move downwards. But Nönnecke hoped that this would not have an adverse effect as the asymmetry also generated a prerotation of the propeller in flow opposite to the direction of propeller rotation. He expected an additional increase of propulsion resulting from a reduction of the rotational loses in the propeller slipstream.. Later on studies were carried out by J.W. Piskorz Nalecki in SSPA model towing tank, in Goteburg. In these studies, the post cut-off above the propeller axis was shifted to one side. The post cut-offs were less deformed by this method. The change in water-lines above the propeller axis is the opposite of the propeller rotation direction. Thus in this region of the stern, the prerotation of the water flow can be obtained, yielding an increase in the propulsive efficiency. Since September 1987, the asymmetric stern design experiments were started in Technical University. of İSTANBUL, Ata NUTKU Model Towing Tank, and a 8% power saving stern design was obtained at the end. In these experiments, three different series 60 Models was used with the same Length, Breadth, Draft and Block Coefficient values which are shown below. Lenght over water line : L^ = 124.020 m. Length between perpendicular : W== 121.920 m.Breadth- moulded Design draft Block coefficient Midsection coefficient Water line coefficient Prismatic coefficient Run prismatic coefficient A Run prismatic coefficient B Run prismatic coefficient C Form factor Scale factor : B = 17.416 m. During the experiments, only the run lengths and the run prismatic coefficients of the models were changed in order to determine the best Tun angle. Experiments were carried out in Model Towing Tank of the Technical University of Istanbul which has the dimension of 160 x 6 x 3,4 m. with steady water conditions to test the resistance, propulsive efficiency and wake distribution with different speed intervals. The propeller has the following characteristics and its parameters are given below. B-4.55 Diameter = D = 0.116 m. Blade area ratio = Ae/Ao= 0.550 Number of blades = Z =4 Pitch/diameter ratio= P/D = 0.629 Nominal rate of revs= n = 720/min After an increase in the propulsive efficiency was found with the asymmetric stern design, Ata NUTKU Model Testing Tank, Technical University of Istanbul, Laboratories focused on the off-centre stern desian. X!Th.LS second stage of the study is based on the useful physical properties of the propeller rotation direction as well as the similar properties of the asymmetric stern. The propeller shaft on the main axis is shifted off-center and a new design is obtained in which 11% of the propeller diameter is shifted to the port side. Although the ship's stern was a symmetric one, an asymmetric flow was obtained in the off-side. Inilitially, the three models were modified according to this off-center propeller design and the propulsion and wake line experiments showed an increased resistance. However, it is found that this type of stern design is highly effective in increasing the propulsive efficency depending upon the run angle. This increase in the propulsive efficiency is found to reach values of 3 to obtained in asymmetric stern experiments. Since off-center shaft designs are much easier and economical to implement than asymmetric design in shipyard practice, although is does not increase the resultant power-saving as much, it may be a preferred stern design in the future due to its simplicity and success when compared to asymmetric sterns. XI I

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