Congratulations Mahesh Negi For securing AIR 22 with our Live batch in GATE Aerospace 2021.
His success story is captured in the Interview , link is given below.
https://youtu.be/K_yXpYXbu2g?si=cxy0fsyu6S2ODuSb
Different Types of Aero Engine, their positions on aircraft body and so advantages.
Viru Sir|GATE AEROSPACE Previous years questions based Discussion|September 06, 2024
The location of engines in aircraft varies based on the type and design of the aircraft. Understanding where engines are situated is crucial for aerodynamics, safety, and maintenance considerations.
Common Engine Locations
Underwing Mounting: This is the most prevalent configuration in commercial aviation. Engines are mounted in pods beneath the wings, which helps to:
Provide wing-bending relief, counteracting the lift forces that bend the wings upwards.
Facilitate easier access for maintenance.
Reduce the risk of engine fires affecting the wing structure, as any fire can be more easily managed when the engine is separate from the wing.
Fuselage Mounting: Some aircraft, particularly regional jets and turboprops, have engines mounted on the fuselage, often at the rear. This setup can enhance aerodynamic efficiency and reduce noise in the passenger cabin. Examples include:
The Embraer ERJ family.
The COMAC ARJ21 regional jet.
Tail Mounting: In certain designs, such as the Cessna 337 Skymaster, engines are mounted at the rear of the fuselage, allowing for a push-pull configuration. This design can improve performance and stability during flight.
Pylon Attachment: In underwing configurations, engines are not directly bolted to the wing but are attached to pylons. This design allows for:
Safety in the event of an engine failure or fire.
The ability to absorb significant forces during flight and landing.
Engine Types and Their Locations
The type of engine also influences its location:
Turbofan Engines: Most commonly found in large commercial aircraft, these engines are typically mounted under the wings. They are designed for high efficiency at cruising altitudes and are favored for their thrust-to-weight ratios and fuel efficiency.
Turboprop Engines: Often mounted on the wings or fuselage, turboprop engines are used in smaller regional aircraft. They provide excellent performance for short-haul flights and can operate efficiently at lower altitudes.
Reciprocating Engines: These engines can be found in smaller general aviation aircraft, often mounted at the front of the fuselage. They are used primarily in light aircraft and provide a different power-to-weight ratio compared to turbine engines.
Factors to Consider in Engine Design Selection
Aircraft Type and Mission: The intended use of the aircraft (commercial, military, cargo, etc.) greatly influences engine design. For example, commercial airliners typically benefit from wing-mounted turbofan engines for efficiency and maintenance ease, while military aircraft may require rear-mounted engines for aerodynamic advantages and reduced radar cross-section.
Aerodynamic Efficiency: The location of engines affects the aircraft's aerodynamics. Wing-mounted engines can reduce wing bending moments and improve fuel efficiency by allowing for a more streamlined wing design. Conversely, rear-mounted engines can lead to cleaner wing designs and improved lift characteristics.
Maintenance and Accessibility: Engine placement impacts maintenance procedures. Wing-mounted engines are generally easier to access for routine maintenance, while rear-mounted engines may complicate access but offer other operational benefits, such as reduced cabin noise.
Weight Distribution and Center of Gravity: The placement of engines affects the aircraft's center of gravity (CG). Engines mounted closer to the CG (like rear-mounted engines) can lead to better control during an engine failure, while wing-mounted engines may require more robust design features to manage yaw during such events.
Noise and Vibration: Passenger comfort is a significant consideration. Rear-mounted engines typically produce less cabin noise, enhancing the passenger experience. In contrast, wing-mounted engines can lead to higher noise levels in the cabin.
Foreign Object Damage (FOD) Risk: The risk of FOD is higher for wing-mounted engines, which are closer to the ground and more susceptible to debris ingestion. Rear-mounted engines are less vulnerable, which can be a critical factor in certain operational environments.
Regulatory and Certification Requirements: Compliance with aviation regulations and safety standards is essential. Engine design must meet specific performance and safety criteria, which can vary based on the aircraft's intended operation.
Advantages and Disadvantages of Engine Locations
Wing-Mounted Engines
Advantages:
Reduced wing bending moments, allowing for lighter wing structures.
Easier maintenance access.
Gravity-fed fuel supply in case of pump failure.
Cleaner air intake away from the aircraft structure.
Disadvantages:
Increased susceptibility to FOD.
More complex landing gear design due to engine weight.
Potentially more cabin noise and reduced pitch stability.
Rear-Mounted Engines
Advantages:
Cleaner wing design, allowing for more aerodynamic efficiency.
Better control during engine failure due to proximity to CG.
Reduced cabin noise and vibration.
Less risk of FOD.
Disadvantages:
More complex maintenance access.
Potential for deep stall characteristics with T-tail designs.
Difference between geostationary and geosynchronous orbit with example
Viru Sir|GATE AEROSPACE Previous years questions based Discussion|September 03, 2024
A geosynchronous orbit is an Earth-centered orbit with a period equal to Earth's rotation period of approximately 24 hours. This means a satellite in geosynchronous orbit will appear to trace out a path in the sky over the course of a day.
A special case of geosynchronous orbit is the geostationary orbit. A geostationary orbit is a circular geosynchronous orbit in Earth's equatorial plane with an inclination of 0°. This means a satellite in geostationary orbit will appear stationary relative to an observer on Earth's surface, always at the same point in the sky.
Some key differences:
Geostationary orbits are always above the equator, while geosynchronous orbits can have any inclination
Geostationary satellites appear stationary in the sky, while geosynchronous satellites trace out a path, usually a figure-8
Geostationary orbits have a circular shape, while geosynchronous orbits can be elliptical
Examples
Communications satellites like those used for DirecTV and Dish Network are typically placed in geostationary orbits so their antennas can remain fixed
Weather satellites like those operated by NOAA are often placed in geosynchronous orbits to monitor large portions of Earth
Navigation satellites like those in GPS are not geosynchronous, but some augmentation satellites for GPS are in inclined geosynchronous orbits
In summary, while all geostationary orbits are geosynchronous, not all geosynchronous orbits are geostationary. Geostationary is a specific type of geosynchronous orbit that is circular, equatorial, and appears stationary from Earth's surface.
Combustion chamber important sections asked in GATE Aerospace
Vikash kumar Srivastav (Viru Sir IITian) , 7 times GATE AE qualified, Founder and CEO @ Concept library|GATE AEROSPACE Previous years questions based Discussion|September 02, 2024
The combustion chamber of a jet engine is a critical component where fuel is mixed with compressed air, ignited, and burned to produce high-temperature, high-pressure gases that drive the turbine and generate thrust. The combustion chamber can be divided into three main sections based on airflow: the primary, secondary, and tertiary airflows. Each section plays a distinct role in the combustion process.
Airflow Sections in the Combustion Chamber
Primary Airflow
Percentage: Approximately 20% of the total air entering the combustion chamber.
Role: This airflow is directed towards the core of the combustion chamber where the fuel is injected. The primary airflow is crucial for initiating and sustaining combustion. It mixes with the fuel and creates a recirculation zone that stabilizes the flame, allowing for efficient burning. The air-to-fuel (AF) ratio in this zone is typically around 15:1 for optimal combustion.
Secondary Airflow
Percentage: About 60% of the total air entering the combustion chamber.
Role: This portion of the airflow enters the combustion chamber primarily for cooling purposes. It flows between the combustion chamber liner and its casing, helping to protect the chamber materials from the extreme temperatures generated during combustion. The secondary air also assists in mixing with the combustion gases to ensure complete combustion and reduce emissions.
Tertiary Airflow
Percentage: Roughly 20% of the total air entering the combustion chamber.
Role: The tertiary airflow further enhances the cooling of the combustion chamber and helps in the dilution of exhaust gases before they exit the chamber. This airflow is crucial for maintaining the temperature within safe limits and improving overall engine efficiency. It also contributes to reducing harmful emissions by ensuring that combustion is complete and that the exhaust gases are adequately mixed with cooler air.
Summary of Roles
Primary Airflow: Initiates and sustains combustion, forming a stable flame and allowing for efficient fuel burning.
Secondary Airflow: Provides cooling to the combustion chamber structure and assists in mixing for complete combustion.
Tertiary Airflow: Further cools the exhaust gases and dilutes them to minimize emissions.
The effective management of these airflow sections is essential for the performance, efficiency, and environmental impact of jet engines. By optimizing the combustion process through careful control of these airflows, modern jet engines achieve high levels of efficiency while minimizing harmful emissions.
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