Gaz türbinlerinde kullanılan bal peteği sızdırmazlık elemanı geometrisi ve çalışma şartlarının kaçak debiye etkisinin had analizi ile incelenmesi
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Dosyalar
Tarih
2018
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Yayıncı
Kırıkkale Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Gaz türbinleri gibi tüm turbomakinalarda dönen rotor ile sabit stator arasındaki açıklıklardan istenmeyen akışkan kaçaklarını engellemek ve/veya kontrol etmek için çeşitli sızdırmazlık elemanları (keçeler) kullanılır. Bu keçelerden birisi olan bal peteği keçe, gaz türbinlerinde sıklıkla kullanılan labirent keçe dişlerinin karşısına yerleştirilen bal peteği şeklindeki parçadır. Bu tezde, bal peteği boyutunun, açıklığın ve rotor hızının kaçak debiye etkisi HAD (Hesaplamalı Akışkanlar Dinamiği) analizleri ile incelenmiştir. HAD analizleri için 3-boyutlu periyodik geometri oluşturulmuştur. Sınır şartı periyodikliğini ve geometrik periyodikliği sağlamak için bal peteği bölgesi 1 adet tam, 2 adet yarım petek olacak şekilde ele alınmıştır. HAD modeli, literatürde sonuçları bulunan test çalışmaları ile doğrulanmıştır. İlk aşamada, karşılaştırma amaçlı olarak bal peteği bulunmayan durum yani düz stator analizi yapılmıştır. Ardından; 1/32" (0,793 mm), 1/16" (1,59 mm) ve 1/8" (3,175 mm) boyutundaki bal petekleri için analizler yapılmıştır. İkinci aşamada rotor hızının etkisi incelenmiştir. Rotor hızı analizlerinde; düz stator, 1/32", 1/16" ve 1/8" petek boyutlarında sırasıyla vt=0 m/s, vt=100 m/s ve vt=200 m/s rotor yüzey hızları kullanılmıştır. Üçüncü aşamada dişler ile bal peteği arasındaki açıklığın kaçak debiye etkisi incelenmiştir. Açıklık analizleri bal peteği bulunan durumlarda (1/32", 1/16", 1/8") 0,127 mm, 0,254 mm ve 0,508 mm açıklıklar için yapılmış, düz stator ile karşılaştırılmıştır. Yapılan HAD analizleri sonucunda, 1/32" bal peteği kaçak debinin azalmasına, 1/16" ve 1/8" bal peteği kaçak debinin artmasına neden olmuştur. Bal peteği boyutunun diş ucu kalınlığına göre açıklığı artırma etkisinden dolayı böyle bir farklılık gözlenmiştir. Uygulanacak bal peteği boyutu, diş uç kalınlığına göre belirlenmelidir ki bal peteği uygulaması kaçak debiyi azaltacak etki oluşturabilsin.
Various seals are used to prevent and/or control unwanted fluid leaks from openings between rotor and stator in all rotating turbomachines such as gas turbines. The honeycomb seal, one of these seals, is a honeycomb piece opposing the labyrinth seal teeth that are often used in gas turbines. In this thesis; the effects of honeycomb size, clearance and rotor speed on leakage were investigated by using CFD (Computational Fluid Dynamics) analyses. Three-dimensional periodic geometry was formed for CFD analyses. In order to ensure periodicity in terms of boundary conditions and geometry, the honeycomb zone is considered with 1 full and 2 half honeycombs. The CFD model has been verified with test data available in the literature. First of all, for comparison purposes, a case with a flat stator without honeycomb was analyzed. Then; analyses were made for honeycomb sizes of 1/32" (0.793 mm), 1/16" (1.59 mm) and 1/8" (3.175 mm). In the second step, the effect of rotor speed was investigated. In rotor speed analyses, rotor surface velocities of vt = 0 m/s, vt = 100 m/s and vt = 200 m/s were considered for flat stator, honeycomb sizes of 1/32", 1/16" and 1/8". In the third step, the effect of clearance between the teeth and the honeycomb on leakage was investigated. Clearance analyses were performed for 0.127 mm, 0.254 mm and 0.508 mm clearances in honeycomb cases (1/32", 1/16", 1/8") and were compared with flat stator. As a result of the CFD analyses, 1/32'' honeycomb caused decrease in leakage while 1/16'' and 1/8'' honeycomb caused increase in leakage. Such a difference was observed due to the effect of increasing the clearance according to the tooth thickness and the honeycomb size. The honeycomb size should be determined according to the teeth thickness so that the honeycomb application could reduce the leakage.
Various seals are used to prevent and/or control unwanted fluid leaks from openings between rotor and stator in all rotating turbomachines such as gas turbines. The honeycomb seal, one of these seals, is a honeycomb piece opposing the labyrinth seal teeth that are often used in gas turbines. In this thesis; the effects of honeycomb size, clearance and rotor speed on leakage were investigated by using CFD (Computational Fluid Dynamics) analyses. Three-dimensional periodic geometry was formed for CFD analyses. In order to ensure periodicity in terms of boundary conditions and geometry, the honeycomb zone is considered with 1 full and 2 half honeycombs. The CFD model has been verified with test data available in the literature. First of all, for comparison purposes, a case with a flat stator without honeycomb was analyzed. Then; analyses were made for honeycomb sizes of 1/32" (0.793 mm), 1/16" (1.59 mm) and 1/8" (3.175 mm). In the second step, the effect of rotor speed was investigated. In rotor speed analyses, rotor surface velocities of vt = 0 m/s, vt = 100 m/s and vt = 200 m/s were considered for flat stator, honeycomb sizes of 1/32", 1/16" and 1/8". In the third step, the effect of clearance between the teeth and the honeycomb on leakage was investigated. Clearance analyses were performed for 0.127 mm, 0.254 mm and 0.508 mm clearances in honeycomb cases (1/32", 1/16", 1/8") and were compared with flat stator. As a result of the CFD analyses, 1/32'' honeycomb caused decrease in leakage while 1/16'' and 1/8'' honeycomb caused increase in leakage. Such a difference was observed due to the effect of increasing the clearance according to the tooth thickness and the honeycomb size. The honeycomb size should be determined according to the teeth thickness so that the honeycomb application could reduce the leakage.
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