Hero of Alexander - 150BC
invented the Aeolipile, mans first application of jet propulsion making the idea over 2000 years old.
Newton's 1st Law
A body at rest will remain at rest unless acted upon by an outside force.
Newton's 2nd Law
Force is proportional to the product of mass and velocity.
Newton's 3rd Law
For every action there is an equal and opposite reaction.
The Force needed to overcome drag.
Turbojet, Turboprop, and Turbofan engines
These are the three most popular types of engines powering the A/C in the Air Foce inventory.
Intake, Compression, Combustion, and Exhaust
Basic Continuous four cycle process that gas tubine engines use.
Basic Continuous four cylce process of a Gas Turbine Engine is accomplished by
taking in an air mass, compressing it, adding fuel and burning the mixture, and expelling the air/gas mass through a nozzle. A continuous process as long as fuel is available for combustion.
The major sections of all turbine engines
Air Inlet, Compressor, Diffuser, Combustion,Tubine, Exhaust, and Accessory Sections.
This recovers as much total pressure as possible, delivers it to the front of the engine and delivers air to the compressor inlet with a minimum of turbulence and pressure variation.
This increases the pressure of the air received form the air inlet duct and discharges it into the combustion chambers. This supplys air in sufficient quantity to produce the required engine thrust (power).
Main components of the Compressor
Rotor and Stator
Rotating Blades that collect air from the compressor inlet and force it rearward.
Stationary Blades fixed within the engine acting as diffusers that partially convert high vilocity into pressure.
Stage or Compressor Stage
Each consecutive pair of rotor and stator blades.
diffuses (it slows down and evenly spreads out) compressor discharge air into the combustion section.
houses the combustion chambers or burner cans that contain the combustion process.
transforms 60 to 80 percent of the energy from the exhaust gases into mechanical energy to drive the compressor and accessories. Similar construction as a compressor except in reverse.
Engine Speed and Temperature
must be controlled to keep turbine operation within safe limits
its purpose is to direct flow of hot gases leaving the turbine section to prevent turbulence and impart a high exit velocity to the gases in a cone shape.
has various functions but primarily provides space for operation and control of the engine. Mounting point for components such as generators, and fluid pumps.
Types of Gas Turbine Engines
Ramjet, Turbojet, Turboprop, and Turbofan
Simplest design of all jet engines. The faster it moves the better it operates and the more thrust it develops.
Advantages of Ramjet
No moving parts, so incredibly reliable. It can achieve enormous speeds up to mach 6, or approx. 4,200mph.
Disadvantages of Ramjet
Cannot accelerate from rest, cannot takeoff under its own power. If operated at rest exhaust would escape out the front as well as the rear because it doesnt have a compressor or turbine.
A straight gas turbine engine that gets thrust by accelerating a mass of air through the engine.
Advantages of Turbojet
best at high speeds
Disadvantages of Turbojet
They cannot produce exceptionally high thrust at low altitudes and airspeeds. They need long runways for takeoff and their climbout capabilities are poor.
Combines the thrust from a propeller with the thrust produced by the exhaust gases at the exhaust nozzle. Unites the gas turbine engine with the efficient lower speed characteristics of a propellor.
How much of the gas energy does the turboprop tubines take from the gas stream? What are the percentages and where do those percentages go?
The maximum amount possible. 90 percent converts to shaft horsepower driving the propeller reduction gears and accessories. 10 percent produces jet thrust as the gases exit out the exhaust nozzle.
In a turboprop engine the turbine is attached to what?
An additional driveshaft that passes through the core shaft and is connected to a gear box which is connected to a propeller that produces most of the thrust.
Advantages of a Turboprop
high thrust at low altitude. Ideal for lifting heavy loads off short or medium length runways.
Disadvantages of Turboprop
efficiency drops as airspeed and altitude increase. best under 400 knots and altitudes below 31,000 feet.
Similar to a turboprop but instead of a propeller it has an enclosed fan that accelerates the air through the engine and through a fan discharge nozzle or an annular fan discharge duct.
Advantages of a Turbofan
combines the good operating efficiency and high thrust capability of a turboprop with the high speed, high altitude capability of a turbojet.
Disadvantages of a Turbofan
No major disadvantages making it the most nearly ideal powerplant for all large conventional military A/C
Pounds of Thrust under various operating conditions such as takeoff, climb, cruise, or for continuous operation as determined by the manufacture.
Three basic conditions which influence the power output of an engine.
(1) Temp of Atmosphere- High Temp=less power
(2) Pressure of the Atmosphere- Low Pressure=less power
(3)Bleed air extracted from the engine for systems operation
Power supplied by a turboprop engine is measured in?