ABSTRACT
The parametric analysis of a tugboat propeller blade was carried out with solidworks computer aided simulation software. The aim is to achieve vibration and noise mitigation as well as performance improvement of the propulsion system by varying the number of propeller blade to ascertain minimum allowable pressure on the propulsion system. To determine the magnitude of stiffness assumed in the dynamic part of the propulsion system, modeling the propulsion system as an elastic spring and perform vibration analysis-static and dynamic analysis on the propulsion system, and to analyze the fluid dynamics on the structure which may in turn have impact on the propulsion system. For this study, Concept design and vibration analysis were adopted with external militating factor like the mass of the tug (5000 tons), the viscosity of the water, the power of the propeller engine,2nd order vertical moment, of the propeller engine and experimental modal parameters (natural frequency, propeller blade radius, number of propeller blade, length of shaft). In consideration, the research finding shows that the pressure build-up (2.14 × 108) around the propeller with six blades is high compared to that of with three blades which is (1.27 × 108) The performance of the propulsion system improves, but the pressure on the propeller resulting to increased pressure build-up on the blade may result in possible failing. Thus for a tugboat of mass 5000 tons the research finding shows that an RPM of 49.7785rad/sec for the propeller blade is feasible. The research however recommends that in operation, if the propeller RPM is higher than the number of propeller blade, it ensures that the torque required to spin the propeller is reduced. The length and diameter obtained be considered in other to increase the stiffness.
CHAPTER ONE
INTRODUCTION
1.1 Background of study
It is believed that in operation, mechanical structures are subjected to dynamic forces which cause vibrations and if not well managed or mitigated against the structure, failure may take place. Because vibration can be total vibration of the entire structure or local which is vibration of selective structural components or a mix of both, it has to be considered in a comprehensive way. Proper levels of vibration need to be maintained to limit an increased rate of fatigue failure in structural members and the malfunction of machinery and equipment.
Personnel task performance is a key component of operational safety, and a critical component of task performance is habitability, which includes noise and whole-body vibration. Designing for performance and habitability goals allows for improvement of productivity, morale, safety, and comfort, and it reduces potential risk of fatigue and human error.
Noise and vibration performance goals are best achieved if noise and vibration analysis are carried out and mitigation are considered in early design stages. The cost of correcting a potential noise and/or vibration issue can be up to ten (10) times as expensive after construction than if incorporated into the design from preliminary design stage (ABS, 2018).
The word Propulsion originated from the Latin words pro, which means before or forward, and pellere, which means to drive. Propulsion systems comprise of all the components used in generating power, transmitting these power to the propeller via a shaft and reduction gear, which in turn converts this power to thrust used in moving a vessel forward. Ship propulsion is not only restricted to just moving vessel forward against forces such as air drag, friction, towing resistance etc., but is also responsible for stopping, maneuvering of the vessel and keeping it in a static position against water current when required. A tug boat is a small but very powerful vessel used in towing (pulling) or tugging bigger vessels that cannot move by themselves or are not self- propelled like some barges. Tug boats can also be used as fire fighters, ice breakers etc. the strength of a tug boat and its ability to maneuver effectively depends solely on the propulsion system installed (Nitonye et al., 2017). There are different types of propulsion system for marine operation. Diesel electric propulsion system is one of the propulsion that has configuration that is fitted with the bow and aft thrusters, and is often mounted with one up to eight azimuth thrusters. The bow and aft thrusters are electrically driven. Although the impacts of these ships on the whole maritime industry is most times been neglected, but their value is mostly felt in maneuvering during bad weather conditions and during vessel breakdown etc. Most important factor of the propulsion system is the interaction between the propeller and the nozzle with the hull. It is also believed that this research work will be significant in terms of designing tugboats with low fuel consumption and operating cost.
1.2 Statement of the Research Problem
The importance of tugboat cannot be over emphasized in a region like the Niger Delta with vast coastal lines. The effectiveness of a tugboat is characterized by its ability to tow and maneuver easily, which is a major concern in the marine industry. Excessive vibration and noise has done so many damages to the propulsion system by causing crew discomfort and inefficient performance of the tugboat. This has also led to causing potential damage to the system, increased rate of fatigue in structure members and also malfunctioning of materials /equipment. However, the aftermath effect of increased negative pressure on the propeller blade of the propulsion system have caused tugging effort being futile, leading to time wastage, accrued cost and possible loss of life (Geertsma et al., 2017).
There is so much demand for more efficient propulsion system in a tugboat due to increased maritime operations with the view of improving crew comfort and performance by imposing limitation and restriction to vibration and noise limit. Appropriate vibration levels can enhance operational safety by improving task performance, habitability, proper functioning of sensitive equipment, such as sensors and modern monitoring technologies as well as whole-body structural integrity at sea.It is worth therefore to investigate performance characteristics of the propulsion system that will ensure optimal performance improvement of the propulsion against possible issues that may prompt failure.
1.3 Justification of the Study
This project involves Optimum Performance Analysis of a Tugboat Propulsion System using solidworks engineering CAD software to aid the analysis. The tugboat propulsion is a model to be able to tug a ship of minimum mass of 5000 tons. The vibration of propulsion system might occur due to the low magnitude of skew angle. These optimum parameters will be determined for propeller with 3, 4, 5 and 6 blades.
1.4 Aim and Objectives of the Study
Aim
The aim of this project is to evaluate the performance of propulsion system of a tugboat through the analysis of the mechanical structures with a view to getting the desired tugboat dimensions. To achieve the aim, the study is guided with the following specific objectives to:
(1) Carry out design analysis of effective power, tug resistance and power of a tugboat propulsion system
(2) Carry out simulation and parametric analysis of various blades of propeller.
(3) Examine the vibration effect of propulsion where different numbers of blades are used.
(4) Estimate properties of a tugboat that will enhance effectiveness of propulsion.
1.5 Significance of the Study
The findings of this study would help in predicting possible issues/factors associated with vibration of a propulsion system.
It will also serve as a reference for further research(es) for propulsion system performance improvement in tugboat.
Finally, it is expected to contribute to the body of knowledge in the area of the dynamic part of propeller performance improvement.
1.6 Scope of the Work
This work is limited to the design and optimum performance analysis of a tugboat propulsion system capable of transporting a ship of a maximum load of about 5000 tons (4.53 ×106kg) to any suitable direction, mitigating possible failure due to vibration. The forcing function Modal analysis and Finite Element Analysis is performed using Excel Sheet and the solidworks modeling and simulation tool of analysis defined on the structural model of the mass, the damping and the stiffness of the propeller shaft with the aim to acquire information on the local vibration response which depends on the type of structural elements to which the analysis is oriented.
This material content is developed to serve as a GUIDE for students to conduct academic research
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