LEE- Isı Akışkan Lisansüstü Programı

Bu topluluk için Kalıcı Uri

http://hdl.handle.net/11527/20279

Gözat

Yazar "Arslan, Mehmet Emin" ile LEE- Isı Akışkan Lisansüstü Programı'a göz atma
  • Öge
    Aerodynamic performance enhancement of a 27-inch APC propeller through geometric modifications
    (Graduate School, 2025-06-12) Arslan, Mehmet Emin ; Çadırcı, Sertaç ; 503221109 ; Heat and Fluid
    Propellers are undergoing a significant resurgence in aviation, vital for Unmanned Aerial Vehicles (UAVs), general aviation, and emerging Electric Vertical Take-Off and Landing (eVTOL) aircraft. The design of a propeller—encompassing its dimensions, material, and particularly its blade geometry—is paramount for vehicle efficiency, stability, endurance, and mission success. Inefficient propellers lead to increased energy consumption and environmental impact. This thesis focuses on enhancing the propulsive efficiency of propellers through systematic, computationally-driven geometric modifications. The primary research objective was to develop and apply a methodology for improving propeller propulsive efficiency by parametrically altering key blade geometric parameters. Specifically, this study investigated the effects of static pitch, blade twist distribution, and airfoil thickness distribution using Computational Fluid Dynamics (CFD) simulations, with all analyses conducted at a fixed rotational speed of 3000 RPM across a range of advance ratios. The methodology commenced with selecting the APC 27x13E propeller as the baseline, chosen for the availability of its geometric data and published performance metrics. The blade geometry was reconstructed into a 3D CAD model using a workflow involving a Julia script and OpenVSP. An initial CFD setup using the k-ω SST turbulence model on a half-domain showed that very fine meshes (around 15.7 million cells) were needed for high accuracy but were computationally prohibitive for extensive parametric studies. Consequently, a turbulence model evaluation was performed using a full-domain model. The Realizable k-ε model with standard wall functions, applied to a mesh of approximately 2.45 million cells, was selected as the final CFD setup. This configuration predicted thrust and torque with error of approximately 6% and 5.5% respectively, when compared to vendor data, offering a suitable balance between accuracy and computational efficiency for the subsequent comparative analyses. Geometric manipulation strategies involved three campaigns. First, static pitch variants (7, 10, 13, 16, and 19-inch pitch for the 27-inch diameter propeller) were generated by adjusting local blade angles according to blade angle equation for static pitch propellers. The 13-inch baseline was found to offer a good overall performance profile across a wider range of advance ratios and was selected for further modifications. Second, four twist angle distribution variants were created (mild/aggressive root untwist with tip overtwist, and mild/aggressive root overtwist with tip untwist), keeping the blade angle at the 75% span station identical to the baseline. Third, four airfoil thickness distribution variants were developed (mild/aggressive uniform thickness changes, and mild/aggressive tapered thickness changes), anchoring the thickness at the 75% span station to the baseline value. Aerodynamic results indicated distinct impacts from each modification type. For static pitch, higher pitch propellers generally yielded better efficiency at higher advance ratios. The twist angle modifications showed the most promising results for efficiency enhancement. Specifically, the B1 variant (mild root overtwist, mild tip untwist) achieved a peak efficiency of approximately η = 0.70 at J ≈ 0.5, a modest gain of about 1.8% over the baseline's peak. However, this variant demonstrated a more substantial relative improvement at higher advance ratios; for instance, at J ≈ 0.6, its efficiency was approximately η = 0.62, a significant gain of over 23% compared to the baseline's η = 0.50 at that condition. In contrast, modifications to the airfoil thickness distribution were generally detrimental, reducing aerodynamic efficiency at moderate to high advance ratios compared to the baseline, suggesting the baseline's thickness profile was already well-optimized. This thesis successfully demonstrated a systematic CFD-driven approach for evaluating and improving propeller aerodynamic performance. The findings highlight that carefully considered twist distribution modifications can yield significant relative efficiency gains, particularly in specific segments of the operational envelope, which is valuable for UAV designers. Limitations include the steady-state MRF approach and the assumption of rigid blades. Future work could involve multi-parameter optimisation, the application of CFD-based adjoint methods for finer refinement of promising designs like the B1 twist variant, aero-acoustic analysis, and experimental validation.