POWER PLANTS LAB
ASSIGNMENT 1
Submitted To: Dr. Fahad Noor
Submitted By: Mohammad Shahid Munir
(2017-ME-307)
DEPARTMENT OF MECHANICAL, MECHATRONICS
& MANUFACTURING ENGINEERING
UET (NEW CAMPUS)
Gas Turbines in Air Crafts
A gas turbine, also called a combustion turbine, is a type of continuous and internal combustion
engine. The main elements common to all gas turbine engines are:



Upstream rotating gas compressor
Combustor
Downstream turbine on the same shaft as the compressor.
Working:
The basic operation of the gas turbine is a Brayton cycle with air as the working fluid: atmospheric air
flows through the compressor that brings it to higher pressure; energy is then added by spraying fuel
into the air and igniting it so that the combustion generates a high-temperature flow; this hightemperature pressurized gas enters a turbine, producing a shaft work output in the process, used to
drive the compressor; the unused energy comes out in the exhaust gases that can be repurposed for
external work
Types of Gas Turbines:

Jet engines

Turboprop engines

Aero-derivative gas turbines

Amateur gas turbines

Auxiliary power units

Industrial gas turbines
Gas Turbines in Air Craft:
Air-breathing jet engines are gas turbines optimized to produce thrust from the exhaust gases,
or from ducted fans connected to the gas turbines.[38] Jet engines that produce thrust from the
direct impulse of exhaust gases are often called turbojets, whereas those that generate thrust
with the addition of a ducted fan are often called turbofans or (rarely) fan-jets.
Gas turbines are also used in many liquid fuel rockets, where gas turbines are used to power
a turbo-pump to permit the use of lightweight, low-pressure tanks, reducing the empty weight
of the rocket.
Characteristics:
1. One distinguishing characteristic of a gas turbine that is especially relevant to high-speed
aircraft is that the heat from the fuel lost to inefficiency in gas turbines for the most part
travels out as the exhaust and, indeed, produces positive thrust. This is in contrast to other
power plants such as piston engines, Rankine and Sterling cycles, and electric drives. These
power plants must explicitly reject waste heat, and their necessary cooling systems can add
considerably to complexity, weight, and drag. Such penalties can be substantial. For example,
the committee estimates that the drag increase (or net thrust decrease) to reject 10 percent of
the propulsion power as heat may be on the order of 5 percent.
2. A second relevant characteristic is that at constant throttle settings, a modern turbofan
engine’s thrust varies with speed and altitude in a way that matches the variation in thrust
required by a commercial subsonic airliner. Specifically, current subsonic airliners require
about three to five times more thrust to take off than they do to cruise, and the power
produced by a high bypass ratio turbofan engine at constant throttle setting varies in much the
same way. Thus, turbofan engines are well suited to current airliners. This is illustrated
in Figure for a single-aisle, 150-180 passenger aircraft fueled for a 1,000 nautical mile (nm)
mission.
Graph 1 Trend with time of the thermodynamic efficiency of commercial aircraft turbofan motors at
cruise.
Graph 1 Trend with time of commercial aircraft turbofan propulsive efficiency at cruise.