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Chapter 12
Thrust Gas Turbines
© Springer Science+Business Media Dordrecht 2015
E. Dick, Fundamentals of Turbomachines, Fluid Mechanics and Its Applications 109,
DOI 10.1007/978-94-017-9627-9_12
Abstract Due to the high power compared to weight and volume, gas turbines are
very suitable components of aircraft propulsion systems. Almost all modern aircraft
propulsion is gas turbine based. Only with low power (< 300 kW), as for very light
aircraft, are reciprocating engines used. Aircraft propulsion systems exist in a wide
variety of types. The basic principle is always that the propulsive force (thrust) is
reaction onto the acceleration of an air flow. In this chapter, we discuss the different
systems and we analyse the performance of the core part, which is a gas turbine, and
the performance of double-flow engines with mixed and unmixed jets, which are
the most commonly used types. The chapter is concluded by a discussion of some
technological aspects.
12.1 Thrust Generation
There are three basic propulsion systems: propeller, reactor and rocket. The first
two systems are applied in conventional aircraft.
12.1.1 Screw or Propeller
A propeller is a rotor with blades, similar to aircraft wings, but twisted. The blades
provide acceleration to a part of the air around the aircraft. A force is generated as
reaction to this acceleration. With an aeroplane, the propeller generates the propulsive force, called thrust, while lift force is produced by the wings. Helicopter rotors
generate both thrust and lift force. Helicopters therefore are sometimes called rotary
wing aircraft, to distinguish them from fixed wing aircraft. The acceleration of the
surrounding air is generated by forces exerted onto the blades by the relative air
flow. Thrust may thus also be considered as a result of the blade forces. Figure 12.1
represents a blade section and the forces on this section.
As an absolute coordinate system, we take a frame bound to the aircraft (moving
relative to the surrounding air) and as a relative system, a frame rotating with the
propeller. The inflow velocity in the absolute frame is v 0 , the flight velocity. Flow
accelerates due to propeller action. Within the plane of the propeller , the velocity in
Chapter 12
Thrust Gas Turbines
© Springer Science+Business Media Dordrecht 2015
E. Dick, Fundamentals of Turbomachines, Fluid Mechanics and Its Applications 109,
DOI 10.1007/978-94-017-9627-9_12
Abstract Due to the high power compared to weight and volume, gas turbines are
very suitable components of aircraft propulsion systems. Almost all modern aircraft
propulsion is gas turbine based. Only with low power (< 300 kW), as for very light
aircraft, are reciprocating engines used. Aircraft propulsion systems exist in a wide
variety of types. The basic principle is always that the propulsive force (thrust) is
reaction onto the acceleration of an air flow. In this chapter, we discuss the different
systems and we analyse the performance of the core part, which is a gas turbine, and
the performance of double-flow engines with mixed and unmixed jets, which are
the most commonly used types. The chapter is concluded by a discussion of some
technological aspects.
12.1 Thrust Generation
There are three basic propulsion systems: propeller, reactor and rocket. The first
two systems are applied in conventional aircraft.
12.1.1 Screw or Propeller
A propeller is a rotor with blades, similar to aircraft wings, but twisted. The blades
provide acceleration to a part of the air around the aircraft. A force is generated as
reaction to this acceleration. With an aeroplane, the propeller generates the propulsive force, called thrust, while lift force is produced by the wings. Helicopter rotors
generate both thrust and lift force. Helicopters therefore are sometimes called rotary
wing aircraft, to distinguish them from fixed wing aircraft. The acceleration of the
surrounding air is generated by forces exerted onto the blades by the relative air
flow. Thrust may thus also be considered as a result of the blade forces. Figure 12.1
represents a blade section and the forces on this section.
As an absolute coordinate system, we take a frame bound to the aircraft (moving
relative to the surrounding air) and as a relative system, a frame rotating with the
propeller. The inflow velocity in the absolute frame is v 0 , the flight velocity. Flow
accelerates due to propeller action. Within the plane of the propeller , the velocity in