Propulsion System
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Dept of Mech. Engg.
III Sem Auto
Chapter 8 Jet Propulsion System Introduction: Jet propulsion systems are systems in which the work output of the gas turbine plant is used to produce high velocity jet of hot gases and this jet is used to propel the vehicles in which the systems are mounted. Jet propulsion may be defined as the propulsion of the jet aircrafts or other missiles by reaction of jet coming out with high velocity Jet Propulsion Systems: 1. Screw Propeller
In this system, the total power developed by the turbine is used to drive the compressor and propeller. The above fig shows the power plant for the screw propeller. By controlling the supply of fuel in the combustion chamber, the power supplied to the propeller can be controlled. The rate of increase of efficiency of the screw propeller is higher at lower speeds 2. Turbojet The fig below shows a turbojet unit. Here the turbine of the unit produces power by partial expansion just sufficient to drive the compressor. The exhaust gases from the
Compiled by NSY
Page 1 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
turbine which are at higher pressure than the atmospheric pressure are expanded in a nozzle and a very high velocity jet is produced which provides a forward motion to
the aircraft by the jet reaction. At higher speeds the turbojet gives higher propulsion efficiency. The turbojets are most suited to the aircrafts traveling above 800 km/h 3. Ramjet
Compiled by NSY
Page 2 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
It is an air breathing engine which operates on the principles of turbojet. Its basic operating cycle is similar to that of a turbojet engine. Ramjet consists of a diffuser, fuel injector, flame holding device, combustion chamber and exit nozzle. The air taken in is compressed by the diffuser. Fuel is injected and mixed with the air in the diffuser. The fuel air mixture burns in the region of low velocity created by the flame holder. These gases pass through the combustion chamber increasing its temperature and volume. Velocity is increased and gases go out of this portion and allow fresh charge to come in the combustion chamber. The gases are expanded in the nozzle and produce thrust. Ramjet produces very high thrust with high efficiency at super sonic speeds. This characteristic makes it useful on high speed aircrafts and missiles. Ramjets are used where boosting up can be provided by rockets or turbojet engines. Guided missiles and high supersonic speed aircrafts are its applications. Rocket Propulsion:
Compiled by NSY
Page 3 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
Similar to the jet propulsion, the thrust required for rocket propulsion is provided by the high velocity jet of gases passing through the nozzle, but the main difference is that in case of jet propulsion the oxygen required for combustion is taken from the atmosphere and fuel is stored where as for rocket engine the fuel and oxidiser both are contained in a propelling body and as such, it can function in vacuum. The fig shows a simple type, single stage liquid propellant rocket. It consists of a fuel tank FT, an oxidiser tank O, two pumps P1 and P2, a steam turbine ST and a combustion chamber CC. The fuel tank contains alcohol and the oxidiser tank contains liquid oxygen. The fuel and the oxidiser are supplied by the pumps to the combustion chamber, where the fuel is ignited by electrical means. The pumps are driven with the help of steam turbines. Steam is produced by mixing concentrated hydrogen peroxide and potassium permanganate. The products of combustion are discharged from the combustion chamber through the nozzle N, so that the rocket moves in the opposite direction. In some modified form rockets may be used as missiles. Uses of Rockets 1. Long range artillery 2. Lethal weapons 3. Signaling and fire work display 4. Jet assisted take off 5. For satellites 6.
For space ships
Compiled by NSY
Page 4 of 4
TE-1- Chapter 8
III Sem Auto
Chapter 8 Jet Propulsion System Introduction: Jet propulsion systems are systems in which the work output of the gas turbine plant is used to produce high velocity jet of hot gases and this jet is used to propel the vehicles in which the systems are mounted. Jet propulsion may be defined as the propulsion of the jet aircrafts or other missiles by reaction of jet coming out with high velocity Jet Propulsion Systems: 1. Screw Propeller
In this system, the total power developed by the turbine is used to drive the compressor and propeller. The above fig shows the power plant for the screw propeller. By controlling the supply of fuel in the combustion chamber, the power supplied to the propeller can be controlled. The rate of increase of efficiency of the screw propeller is higher at lower speeds 2. Turbojet The fig below shows a turbojet unit. Here the turbine of the unit produces power by partial expansion just sufficient to drive the compressor. The exhaust gases from the
Compiled by NSY
Page 1 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
turbine which are at higher pressure than the atmospheric pressure are expanded in a nozzle and a very high velocity jet is produced which provides a forward motion to
the aircraft by the jet reaction. At higher speeds the turbojet gives higher propulsion efficiency. The turbojets are most suited to the aircrafts traveling above 800 km/h 3. Ramjet
Compiled by NSY
Page 2 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
It is an air breathing engine which operates on the principles of turbojet. Its basic operating cycle is similar to that of a turbojet engine. Ramjet consists of a diffuser, fuel injector, flame holding device, combustion chamber and exit nozzle. The air taken in is compressed by the diffuser. Fuel is injected and mixed with the air in the diffuser. The fuel air mixture burns in the region of low velocity created by the flame holder. These gases pass through the combustion chamber increasing its temperature and volume. Velocity is increased and gases go out of this portion and allow fresh charge to come in the combustion chamber. The gases are expanded in the nozzle and produce thrust. Ramjet produces very high thrust with high efficiency at super sonic speeds. This characteristic makes it useful on high speed aircrafts and missiles. Ramjets are used where boosting up can be provided by rockets or turbojet engines. Guided missiles and high supersonic speed aircrafts are its applications. Rocket Propulsion:
Compiled by NSY
Page 3 of 4
TE-1- Chapter 8
Dept of Mech. Engg.
III Sem Auto
Similar to the jet propulsion, the thrust required for rocket propulsion is provided by the high velocity jet of gases passing through the nozzle, but the main difference is that in case of jet propulsion the oxygen required for combustion is taken from the atmosphere and fuel is stored where as for rocket engine the fuel and oxidiser both are contained in a propelling body and as such, it can function in vacuum. The fig shows a simple type, single stage liquid propellant rocket. It consists of a fuel tank FT, an oxidiser tank O, two pumps P1 and P2, a steam turbine ST and a combustion chamber CC. The fuel tank contains alcohol and the oxidiser tank contains liquid oxygen. The fuel and the oxidiser are supplied by the pumps to the combustion chamber, where the fuel is ignited by electrical means. The pumps are driven with the help of steam turbines. Steam is produced by mixing concentrated hydrogen peroxide and potassium permanganate. The products of combustion are discharged from the combustion chamber through the nozzle N, so that the rocket moves in the opposite direction. In some modified form rockets may be used as missiles. Uses of Rockets 1. Long range artillery 2. Lethal weapons 3. Signaling and fire work display 4. Jet assisted take off 5. For satellites 6.
For space ships
Compiled by NSY
Page 4 of 4
TE-1- Chapter 8
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