The aircraft engine is paramount for standard flight operations, allowing for fuel-and-air mixtures to be combusted for the means of generating the necessary propulsion for lift. While in flight, engines and other aircraft apparatuses are constantly exposed to various stressors and elements, thus warranting the need for robust assemblies that can guard sensitive components. The nacelle of an aircraft is the housing that serves to protect the engine from such elements while increasing aerodynamics. Alongside guarding the engine, they also house instruments, fuel tanks, weaponry, and other equipment. In this blog, we will discuss the design and components of the nacelle, allowing you to better understand their use and importance.
Depending on the type of nacelle and its location, there are different standard components of such assemblies. For the engine, cowlings feature inlet and fan cowls that are implemented for guarding aircraft engine parts. Additionally, they also serve to mitigate parasitic drag caused by solid objects moving through the atmosphere, deterring both form drag and skin friction drag. To reduce form drag, the nacelle that is placed in the flow of air will need a cross-section that has the smallest dimensions that are feasible. For skin direction drag, on the other hand, mitigation is made possible through the promotion of laminar flow. This is done by having a smooth and evenly transitioned cone shape that ensures that flow separation does not occur.
Thrust reversers are another component that is common to engine nacelles, coming in the form of equipment that allows for the redirection of exhaust gases that are flowing out of the engine. Generally, this air is directed to the sides and forward, allowing for a net flow that produces a large amount of drag. thrust reversers are quite useful for standard aircraft, allowing for a slowing of the aircraft’s forward motion. As such, they are commonly activated during landing procedures to assist in braking.
Lastly, the exhaust system is another standard component of engine nacelle systems. The exhaust system will typically include parts such as the exhaust cone and exhaust nozzle. To protect all of these components, they are placed within a nacelle in an aircraft.
Alongside the engine nacelle, another common implementation of such structures is for horizontal axis wind turbines (HAWT). As such wind turbines feature crankshafts, gearboxes, and other components that are sensitive to environmental stressors, it is important that they are housed and guarded. Beyond these components, such nacelle systems also protect low- and high-speed shafts, generators, brakes, yaw drives, and more.
Due to the role that nacelle systems play in guarding sensitive components and maintaining optimal aerodynamics, such structures follow very specific design practices. Oftentimes, engineers will seek to minimize the size of nacelle systems while ensuring that there is still enough room for all components to be stored with extra spacing for ample ventilation. One of the most challenging aspects of designing the nacelle for an aircraft is the development of the narrow pylon that attaches the engine nacelle to the airframe itself. For the nacelle to optimally serve its role without deterring standard operations, various connecting lines such as power cables, instrumentation leads, pneumatic lines, engine controls, and fuel lines must all fit.
Another important aspect of nacelle system design is acoustic performance. Engines are powerful apparatuses that are consistently combusting fuel mixtures, thus they generate a high amount of noise. With the use of acoustic liners that are implemented along the internal surfaces of the engine nacelle, generated noise can be amply mitigated. In order to efficiently dissipate acoustic energy, the liners are designed with sheets that are perforated with small holes over a honeycomb structure. With such construction, the liners take advantage of the Helmholtz resonance principle.
Due to the various aspects of nacelle system design and the parameters that they present, it is important that materials are carefully chosen. Generally, weight and temperature resistance characteristics are quite important as immense heat is generated by the engine, and aerodynamics depend on low weight. Across all designs, the most common materials include epoxy systems and bis-maleimide (BMI) resins. Additionally, titanium, inconel, and other superalloys are beneficial for the high temperatures that are present near the engine components.
Whether you are in search of parts for nacelle systems or components related to the fuel tank, cowling, nozzle, or other structures, let the experts at ASAP Fasteners help you secure all you need with competitive pricing. ASAP Fasteners is a premier supplier of aerospace specialty fasteners and aerospace hardware parts, presenting customers an inventory of over 2 billion new, used, obsolete, and hard-to-find items. Take the time to explore our current offerings at your leisure, and our representatives are always on standby to assist you throughout the purchasing process however necessary. Begin procuring the parts you need today and see why customers choose to rely on ASAP Fasteners for all their purchasing needs.