Turboprop motorlar için akçaağaç tohumu yaprağından esinlenmeli biyomimetik pervane tasarımı
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Dosyalar
Tarih
2024
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Turboprop motorlar düşük hızlarda yüksek itki ve düşük yakıt tüketimi sağladıklarından günümüz havacılık endüstrisinde İHA'lardan yolcu uçaklarına kadar birçok uygulamada en çok tercih edilen tahrik sistemlerinin arasında yer almaktadır. Turboprop motorların itki verimleri, büyük ölçüde tahrik sisteminin en önemli parçalarından biri olan pervanelerin aerodinamik performansına bağlıdır. Bu yüzden, turboprop motor pervanelerinin aerodinamik performansının optimize edilmesi önemli bir araştırma konusu olarak karşımıza çıkmaktadır. Basitçe, bir pervane geometrisi, eksen boyunca farklı hücum açılarında dizilmiş belirli kesit şekline sahip 2 boyutlu geometrilerin birleşiminden oluşan, burulmuş 3 boyutlu model olarak tarif edilebilir. Bu nedenle, pervane tasarımının ilk aşamasının, aerodinamik performans açısından kesit geometrisinin optimize edilmesi olduğunu söylemek mümkündür. Genellikle uygulamada düşük hızlarda makul kaldırma-sürükleme oranı sağladığı bilinen NACA 44 serisi (örn. NACA 4412 ve 4415) kesit geometrileri kullanılmaktadır. Ancak, literatürde, turboprop motorlar için en uygun pervane kesit geometrisinin araştırıldığı kapsamlı bir çalışma bulunmamaktadır. Bu çalışmanın temel amacı, turboprop motorlar için HAD ve FSI analizleri ile alternatif bir pervane kesit geometrisi önermektir. Bu doğrultuda, kesit geometrisine ilişkin tasarım parametrelerinin pozitif hücum açısı (5°) ve düşük uçuş hızı (30 m/s) gibi kritik koşullar altında aerodinamik yükler üzerindeki etkileri HAD analizleri ile detaylı olarak incelenmiştir. NACA dört-dijit serisinde kesit geometrisi, maksimum kamburluk (𝑚), maksimum kamburluk noktası (𝑝) ve kalınlık oranı (𝑡) olmak üzere üç temel tasarım parametresine sahiptir. Bu çalışmada, aynı veter uzunluğu (140 mm) farklı 𝑚, 𝑝 ve 𝑡 değerlerine sahip 120 farklı kesit geometrisi üzerindeki 2- boyutlu sıkıştırılamaz türbülanslı akış durumu sürekli akış koşulu altında HAD ile analiz edilerek aerodinamik yükler tahmin edilmiştir. Türbülans modeli olarak Spalart-Allmaras kullanılmış, referans kesit geometrisi (NACA 4412) üzerinden detaylı ağ bağımsızlık çalışması ve NASA tarafından sunulan deneysel ve sayısal sonuçlar ile doğrulama çalışması yapılmıştır. HAD sonuçları kullanılarak, pervane kesit geometrisi tasarım parametreleri ile aerodinamik yükler arasında cevap yüzey yöntemi ile matematiksel modeller oluşturulmuştur. Daha sonra bu modeller yardımıyla kaldırma kuvvetini maksimum, sürükleme kuvvetini minimum yapacak olası pervane kesit geometrileri çok amaçlı optimizasyon işlemi ile tahmin edilmiştir. Yapılan optimizasyon çalışması neticesinde 𝑚 = 7.8926, 𝑝 = 3.1536 ve 𝑡 = 6.9928 değerine sahip kesit geometrisin NACA 4412'e göre yaklaşık %40,95 daha iyi kaldırma-sürükleme oranı sağladığı belirlenmiştir. Pervane tasarımının ikinci aşamasında ise, optimize edilen kesit geometrisi kullanılıp doğadan toplanan akçaağaç tohumlarının kanat yapıları detaylı olarak incelenerek kanat planformunun tasarım parametreleri ve seviyeleri belirlendi ve optimizasyon yöntemleri ve HAD analizleri sonucunda nihai turboprop pervanesinin 3B katı modeli oluşturulurdu. Son aşamada ise, aerodinamik ve yapısal açıdan en uygun geometriyi elde edebilmek için belirlenen akçaağaç tohum yaprağından esinlenmeli biyomimetik pervane geometrileri, 2000 𝑑/𝑑𝑘 ve 70 𝑚/𝑠 yüksek hız koşulları altında çift yönlü FSI analizleri ile pervane üzerinde oluşabilecek yapısal yükler öngörülmüştür. FSI analizleri sonucunda maksimum gerilme değerinin pervane malzemesi olarak seçilen alüminyum alaşımın akma sınırının altında kaldığı, maksimum deformasyonun milimetre düzeylerinde gerçekleştiği ve pervanenin dinamik yükler altında ömür hesaplaması tespit edilerek, tasarlanan pervane geometrisinin uygulanabilir olduğu sonucuna varılmıştır.
Since turboprop engines provide high thrust and low fuel consumption at low speeds, they are among the most preferred propulsion systems in many applications in today's aviation industry, from UAVs to passenger aircraft. The thrust efficiency of turboprop engines largely depends on the aerodynamic performance of the propellers, which are one of the most important parts of the propulsion system. Therefore, optimizing the aerodynamic performance of turboprop engine propellers emerges as an important research topic. Simply, a propeller geometry can be described as a twisted 3D model consisting of a combination of 2D geometries with a specific cross-sectional shape arranged at different angles of attack along the axis. Therefore, it is possible to say that the first stage of propeller design is to optimize the cross-section geometry in terms of aerodynamic performance. NACA 44 series (e.g., NACA 4412 and 4415) section geometries, which are known to provide reasonable lift-to-drag ratio at low speeds, are generally used in practice. However, there is no comprehensive study in the literature investigating the most suitable propeller cross-section geometry for turboprop engines. The main purpose of this study is to propose an alternative propeller cross-section geometry for turboprop engines with CFD and FSI analyses. In this direction, the effects of design parameters related to the cross-section geometry on aerodynamic loads under critical conditions such as positive angle of attack (5°) and low flight speed (30 m/s) were examined in detail with CFD analyses. In the NACA four-digit series, the section geometry has three basic design parameters: maximum hump (𝑚), maximum hump point (𝑝) and thickness ratio (𝑡). In this study, aerodynamic loads were estimated by analysing the 2-dimensional incompressible turbulent flow situation on 120 different cross-sectional geometries with the same chord length (140 mm) and different 𝑚, 𝑝 and 𝑡 values with CFD under steady flow condition. Spalart-Allmaras was used as the turbulence model, and a detailed network independence study was carried out on the reference section geometry (NACA 4412) and a validation study was carried out with experimental and numerical results provided by NASA. Using CFD results, mathematical models were created between the propeller cross-section geometry design parameters and aerodynamic loads using the response surface method. Then, with the help of these models, possible propeller cross-section geometries that would maximize the lift force and minimize the drag force were estimated through a multi-objective optimization process. As a result of the optimization study, it was determined that the section geometry with 𝑚 = 7.8926, 𝑝 = 3.1536 and 𝑡 = 6.9928 provides approximately 40.95% better lift-drag ratio compared to NACA 4412. In the second stage of the propeller design, the design parameters and levels of the wing planform were determined by using the optimized cross-section geometry and examining the wing structures of maple seeds collected from nature in detail, and because of optimization methods and CFD analysis, a 3D solid model of the final turboprop propeller was created. In the last stage, in order to obtain the most suitable geometry in terms of aerodynamics and structure, biomimetic propeller geometries inspired by the maple seed leaf were determined, and the structural loads that may occur on the propeller were predicted with bi-directional FSI analyses under high-speed conditions of 2000 𝑑/𝑑𝑘 and 70 𝑚/𝑠. As a result of FSI analyses, it was concluded that the maximum stress value was below the yield limit of the aluminium alloy selected as the propeller material, the maximum deformation occurred at millimeter levels, and the life calculation of the propeller under dynamic loads was determined and the designed propeller geometry was applicable.
Since turboprop engines provide high thrust and low fuel consumption at low speeds, they are among the most preferred propulsion systems in many applications in today's aviation industry, from UAVs to passenger aircraft. The thrust efficiency of turboprop engines largely depends on the aerodynamic performance of the propellers, which are one of the most important parts of the propulsion system. Therefore, optimizing the aerodynamic performance of turboprop engine propellers emerges as an important research topic. Simply, a propeller geometry can be described as a twisted 3D model consisting of a combination of 2D geometries with a specific cross-sectional shape arranged at different angles of attack along the axis. Therefore, it is possible to say that the first stage of propeller design is to optimize the cross-section geometry in terms of aerodynamic performance. NACA 44 series (e.g., NACA 4412 and 4415) section geometries, which are known to provide reasonable lift-to-drag ratio at low speeds, are generally used in practice. However, there is no comprehensive study in the literature investigating the most suitable propeller cross-section geometry for turboprop engines. The main purpose of this study is to propose an alternative propeller cross-section geometry for turboprop engines with CFD and FSI analyses. In this direction, the effects of design parameters related to the cross-section geometry on aerodynamic loads under critical conditions such as positive angle of attack (5°) and low flight speed (30 m/s) were examined in detail with CFD analyses. In the NACA four-digit series, the section geometry has three basic design parameters: maximum hump (𝑚), maximum hump point (𝑝) and thickness ratio (𝑡). In this study, aerodynamic loads were estimated by analysing the 2-dimensional incompressible turbulent flow situation on 120 different cross-sectional geometries with the same chord length (140 mm) and different 𝑚, 𝑝 and 𝑡 values with CFD under steady flow condition. Spalart-Allmaras was used as the turbulence model, and a detailed network independence study was carried out on the reference section geometry (NACA 4412) and a validation study was carried out with experimental and numerical results provided by NASA. Using CFD results, mathematical models were created between the propeller cross-section geometry design parameters and aerodynamic loads using the response surface method. Then, with the help of these models, possible propeller cross-section geometries that would maximize the lift force and minimize the drag force were estimated through a multi-objective optimization process. As a result of the optimization study, it was determined that the section geometry with 𝑚 = 7.8926, 𝑝 = 3.1536 and 𝑡 = 6.9928 provides approximately 40.95% better lift-drag ratio compared to NACA 4412. In the second stage of the propeller design, the design parameters and levels of the wing planform were determined by using the optimized cross-section geometry and examining the wing structures of maple seeds collected from nature in detail, and because of optimization methods and CFD analysis, a 3D solid model of the final turboprop propeller was created. In the last stage, in order to obtain the most suitable geometry in terms of aerodynamics and structure, biomimetic propeller geometries inspired by the maple seed leaf were determined, and the structural loads that may occur on the propeller were predicted with bi-directional FSI analyses under high-speed conditions of 2000 𝑑/𝑑𝑘 and 70 𝑚/𝑠. As a result of FSI analyses, it was concluded that the maximum stress value was below the yield limit of the aluminium alloy selected as the propeller material, the maximum deformation occurred at millimeter levels, and the life calculation of the propeller under dynamic loads was determined and the designed propeller geometry was applicable.
Açıklama
Anahtar Kelimeler
Turboprop motor, HAD, Akışkan yapı etkileşimi, Biyomimetik, Cevap yüzey yöntemi, Turboprop engine, CFD, Fluid solid interaction, Biomimetic, Response surface method
