About What I hope to major in the future by 임천하 https://padlet.com/limchchch/5kjs5bzwd643 30816 박성재 30824 임천하 Department of Aerospace Engineering, Topic: Jet Engines en-us 2019-04-12 01:41:40 UTC 2024-05-31 18:03:55 UTC hello@padlet.com https://imgglb.padletcdn.com/v13/image?t=g_auto&url=https%3A%2F%2Fpadlet.net%2Ficons%2Fpng%2F1f30f.png Jet Engine Operation evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/352695564 A jet engine is a type of reacton gengine discharging a fast-moving jet that generates thrust by jet proplusion. Jet engines move the airplane forward with a great force that is produced by a tremendous thrust and causes the plane to fly in high velocity. There is a principle that all jet engines share to work. 

1. The engine sucks air in at the front with a fan.
2. A compressors raises the pressure of the air. The compressor is made with may blades attatched to a shaft.
3. The blades spin at hihg and compress or squeeze the air.
4. The compressed air is then sprayed with fuel and an electric spark lights the mixture.
5. The burning gases expand and blast out through the nozzle, it passes through another group of blades called the turbine. 
6. The turbine is attated to teh smae shaft as the comprasser. Spinning the turbine causes th e compressor to spin.
7. This proccess is repeated to operate.  

]]> 2019-04-19 01:31:25 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/352695564 This course will deal with the general concepts and characteristics of various kinds of airbreathing engines such as turbo prop, turbo shaft, turbo fan, turbo jet, ram jet and scram jet. It will also examine the micro-engines used in MAV(Micro Aerial Vehicle) and discuss the exhaust gas and noise reduction methods. limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/352696319 2019-04-19 01:40:49 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/352696319 Learning materials for understanding Jet Engine principles. evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/358720857 2019-05-10 01:24:48 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358720857 Turbojet engine limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/358721327 Source: https://en.wikipedia.org/wiki/Jet_engine]]> 2019-05-10 01:26:55 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358721327 Propulsion Performance Graph evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/358722649 1. Specific impulse as a function of speed for different jet types with kerosene fuel.

2. Theoretical maximum H2 fuel in air is much higher than Theoretical maximum HC fuel in air.

3. Efficiency per unit distance (per km or mile) is roughly independent of speed for jet engines.

Soruce:  https://en.wikipedia.org/wiki/Jet_engine 

]]> 2019-05-10 01:33:56 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358722649 Turbofan engine limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/358723143 Source: https://en.wikipedia.org/wiki/Jet_engine]]> 2019-05-10 01:36:38 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358723143 Dependence of propulsion efficiency upon the vehicle speed/exhaust velocity ratio for air-breathing jet and rocket engines. limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/358724931 Source: https://en.wikipedia.org/wiki/Jet_engine]]> 2019-05-10 01:45:10 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358724931 Representative moments for Jet Engine Tests evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/358725027 The video is for visual sources for testing Jet Turbines. This marterial is especiallly focused on Turbines, so you can visuallly learn how jet engine extracts energy from the hot gases leaving the combustor.

]]> 2019-05-10 01:45:43 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358725027 Turbojet Engine vs Turbofan Engine evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/358725299 Turbojet Engine is a simple turbine engine that produces all of its thrust from the exhaust from turbine section. However, since all of it must burn tuel, which means it is inefficent.

The Turbofan Engine, which is more efficient, primarily drives a fan at the front of the engine. Most engines drive the fan directly from the turbine. There are generally at least two sparate shfts to allow the fan to spin slopwer than the inner core of the engine. 

The fans surrounded by a cowl which guides the air to and from the fan. Part of the air enters the turbine section of the engine, and the rest is bypassed around the engine. ]]> 2019-05-10 01:47:17 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358725299 Propulsive efficiency comparison for various gas turbine engine configurations limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/358725404 Source: https://en.wikipedia.org/wiki/Jet_engine]]> 2019-05-10 01:48:00 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358725404 Components of jet engines limchchch https://padlet.com/limchchch/5kjs5bzwd643/wish/358726052  Cold section:
  • Air intake (inlet) — For subsonic aircraft, the inlet is a duct which is required to ensure smooth airflow into the engine despite air approaching the inlet from directions other than straight ahead. This occurs on the ground from cross winds and in flight with aircraft pitch and yaw motions. The duct length is minimised to reduce drag and weight] Air enters the compressor at about half the speed of sound so at flight speeds lower than this the flow will accelerate along the inlet and at higher flight speeds it will slow down. Thus the internal profile of the inlet has to accommodate both accelerating and diffusing flow without undue losses. For supersonic aircraft, the inlet has features such as cones and ramps to produce the most efficient series of shockwaves which form when supersonic flow slows down. The air slows down from the flight speed to subsonic velocity through the shockwaves, then to about half the speed of sound at the compressor through the subsonic part of the inlet. The particular system of shockwaves is chosen, with regard to many constraints such as cost and operational needs, to minimize losses which in turn maximizes the pressure recovery at the compressor.
  • Compressor or fan — The compressor is made up of stages. Each stage consists of rotating blades and stationary stators or vanes. As the air moves through the compressor, its pressure and temperature increase. The power to drive the compressor comes from the turbine (see below), as shaft torque and speed.
  • Bypass ducts deliver the flow from the fan with minimum losses to the bypass propelling nozzle. Alternatively the fan flow may be mixed with the turbine exhaust before entering a single propelling nozzle. In another arrangement an afterburner may be installed between the mixer and nozzle.
  • Shaft — The shaft connects the turbine to the compressor, and runs most of the length of the engine. There may be as many as three concentric shafts, rotating at independent speeds, with as many sets of turbines and compressors. Cooling air for the turbines may flow through the shaft from the compressor.
  • Diffuser section: - The diffuser slows down the compressor delivery air to reduce flow losses in the combustor. Slower air is also required to help stabilize the combustion flame and the higher static pressure improves the combustion efficiency.
  •  Hot section:
    • Combustor or combustion chamber — Fuel is burned continuously after initially being ignited during the engine start.
    • Turbine — The turbine is a series of bladed discs that act like a windmill, extracting energy from the hot gases leaving the combustor. Some of this energy is used to drive the compressor. Turboprop, turboshaft and turbofan engines have additional turbine stages to drive a propeller, bypass fan or helicopter rotor. In a free turbine the turbine driving the compressor rotates independently of that which powers the propellor or helicopter rotor. Cooling air, bled from the compressor, may be used to cool the turbine blades, vanes and discs to allow higher turbine entry gas temperatures for the same turbine material temperatures.**A blade with internal cooling as applied in the high-pressure turbine
    • Afterburner or reheat (British) — (mainly military) Produces extra thrust by burning fuel in the jetpipe. This reheating of the turbine exhaust gas raises the propelling nozzle entry temperature and exhaust velocity. The nozzle area is increased to accommodate the higher specific volume of the exhaust gas. This maintains the same airflow through the engine to ensure no change in its operating characteristics.
    • Exhaust or nozzle — Turbine exhaust gases pass through the propelling nozzle to produce a high velocity jet. The nozzle is usually convergent with a fixed flow area.
    • Supersonic nozzle — For high nozzle pressure ratios (Nozzle Entry Pressure/Ambient Pressure) a convergent-divergent (de Laval) nozzle is used. The expansion to atmospheric pressure and supersonic gas velocity continues downstream of the throat and produces more thrust. 
Source: https://en.wikipedia.org/wiki/Jet_engine

]]> 2019-05-10 01:51:36 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358726052 History of Jet engine evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/358727013 From this video, I could find informations about the history of invention and developments of the Jet engines.]]> 2019-05-10 01:56:25 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/358727013 Review of the Project evan031303 https://padlet.com/limchchch/5kjs5bzwd643/wish/363136997 Sungjae: 
From the project, I could understand concepts and principles of Jet Engine. To summarize, a Jet Engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. This Jet engine is broadly being utilized in various parts as a key technology of Aerospace Engineering. 
  
By searching for data about Jet Engines, I could learn components of jet engines, operation, and differences between Turbojet Engine and Turbofan Engine. According to NASA, developments of Jet Engine was so revolutionary that it had a great influence on aerospace engineering. As Jet engine made improvements on the world, I hope to contribute to the development of Aerospace Engineering. 

Cheonha:
 Before I do this project, I just thought the jet engine as 'fast, strong, and ,first of all cool thing'. I could realize thay the jet engine is more complex and segmentalized engine, which is very different from my thought. Thanks to this project, I could learn about the kinds of jet engine(Turbojet engine, and turbofan engine) and that these two kinds are quite different in the way they produce own propulsion. In addition, I specially focused on the 'nozzle' , which was unfamilliar part of engine to me. Searching many data, I could learn nozzle is designed to control the flow of fliud and also used in rocket, while the fan is not. Like the past when Jet engine was a revolution, and future, I think revolutionary time will be coming soon. And I wish I am in the center of that future by designing new kinds of engine. ]]> 2019-05-24 01:28:54 UTC https://padlet.com/limchchch/5kjs5bzwd643/wish/363136997