Hydrodynamic Design Structural Analysis and Optimization of Marine Propeller Blade

Abstract

There are many problems to be addressed in the design of marine propeller blade. Among these, the foremost is the efficiency of the propeller. The design of ship propeller involves a number of competing variables including the rake, pitch distribution and blade surface area. The propeller design also aims at achieving high propulsive efficiency at low levels of noise and vibration with reduced cavitation. All of these factors affect vessels top speed, fuel efficiency, and handling. A thorough understanding of propeller dynamics is necessary to design an efficient and reliable propeller blade. Numerical models are commonly used for the dynamic characterization of propeller blades, due to the difficulties of performing full-scale measurements. In contrast, the current research focuses on the hydrodynamic design of a Wageningen B-series four bladed propeller used for marine applications. The analyses presented in this thesis have been divided into three main phases.

In the first phase, the hydrodynamic design of Wageningen B-series four bladed marine propeller is carried out, to determine the suitability and applicability of propeller blade for underwater conditions is done by
1) Open water characteristics determination,
2) Cavitation inception point determination for metallic propeller blade.
The prevailing conditions applied for evaluating these hydrodynamic characteristics are taken from reference and validated with standard series data.

In the second phase of the research, Strength determination of both metallic and composite propeller (E-glass epoxy material) are determined in terms of its stress and free vibration characteristics. Numerical analyses are carried out using suitable numerical methods for the deflection calculations and to determine the stress distribution in the blade foot and the blades at operational load conditions. A modal vibrational analysis for prediction of vibration response was also conducted for the blade, because the composite blades tend to deform more than that of metallic one and the deformation can be used in the analysis of hydrodynamic performance. Experiments are performed to compare the results with that obtained from the numerical analysis.

In the last phase Structural optimization of composite propeller was done both for non-hybrid and hybrid composites, (comprises a series of combination of Glass fiber reinforced plastic and Carbon reinforced plastic GFRP & CFRP), using the mid-surface as reference and meshed with shell elements to find out the optimum ply stacking sequence for Interlaminar shear stresses and deflection minimization and operational efficiency improvement of composite propeller blade compared to metallic one. The obtained final stacking sequence of the composite propeller was evaluated by varying the number of layers in steps the Interlaminar shear stresses are calculated, and the results are compared with the metallic propeller. The following basic data are used for analysis and the main points performed during the works are given below.

1. The open water characteristics are predicted computationally on the basis of a validated small sized propeller where the delivered power (PD), the advanced coefficient (Vga), and the propeller revolution (N) are known.

2. The cavitation inception point for the metallic propeller is determined which can be used for structural analysis.

3. The Aluminum propeller blade is replaced with E-glass epoxy material blade and structural analyses for both the materials are carried out.

4. An optimum stacking sequence for composite material blade varied with non-hybrid and hybrid materials are determined.

5. Finally, a comparison has been made with metallic and composite materials in terms of their strength behavior.