The design of an aircraft engine fan blade based on operational safety regulations in civil aviation

Abstract

Since the invention of airplanes, maintaining safe and reliable flights have been one of the prioritized factors to be ensured. The requirement of an aircraft being relatively lightweight to minimize fuel consumption and take advantage of the lift forces brought a series of challenges during both the design and manufacturing stages. Considering the fact that the civil aviation industry has a general purpose of having a profitable business plan, economic criteria such as initial investment of purchasing an aircraft, fuel consumption, cost of regular and unexpected maintenance periods, and employing and training qualified staff to carry out the maintenance actions are important factors hence research and development efforts in this area are mainly geared towards finding a sustainable, safe and affordable middle ground. As civil aviation as an industry is relatively a new and unfounded concept compared to land route and naval transportation, the majority of the shortcomings of the methods used became known during the trial-and-error approach. Early implementations of both the design and operation methods showed that maintaining the integrity of the aircraft is a challenging task. Apart from engineering an efficient and performant aircraft, ensuring that the harsh operation conditions do not compromise the safety and reliability targets initially set. One of the most important aspects of maintaining the aircraft's safety and structural integrity is preventing external objects from contact in contact with the airplane's exterior. While the types of potentially harmful foreign objects may differ with operational conditions and location, the majority of the objects are globally problematic such as debris, dust, and most importantly birds. In order to have a better understanding of the nature of bird strike events, bird strike statistics from the previous years are examined and the most likely scenarios that may cover the widest scope are determined. Considering the fact that the probability of a bird strike event happening at cruise altitude where the relative velocity of the bird and the airplane is at maximum, is very low even though it is the most harmful scenario; data from the take-off and climb stages of the flight are examined more closely. The computer-aided engineering software ABAQUS is used to perform the simulations. The reference bird model is designed based on the previous bird strike event history and literature review on the subject. In order to validate that the impact model is set up correctly and the impact damage is accurate, a reference aluminum plate with 4 different thickness values was struck with the reference bird model. The primary focus of this study, which is optimizing the design of the fan blades based on how much the impact damage a blade can withhold without being rendered inoperative, was targeted toward optimizing the leading-edge design of the blade at the %80 of height from the fan hub which is where most of the bird strike impacts affect. Within the scope of this study, in which the methods of reducing damage to the fan blades are investigated, 2 different bird models were designed and collided with 7 different fan blade models at 2 different sections. Although the wing models have similar design philosophies in general, the angles of the profiles in the region where the height measured from the wing base is 80% have been changed so that they have different angles of attack during the collision. In this way, although a design similar to the engine blades of turbofan engines currently used in civil aviation is preserved, it is aimed to examine the general damages that occur on the fan blade surface when the profile angle increases or decreases.