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JET ENGINE PROPULSION Chapter 9 Thrust Augmentation System A method of extracting more power from Internal Combustion Engines.

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Presentation on theme: "JET ENGINE PROPULSION Chapter 9 Thrust Augmentation System A method of extracting more power from Internal Combustion Engines."— Presentation transcript:

1 JET ENGINE PROPULSION Chapter 9 Thrust Augmentation System A method of extracting more power from Internal Combustion Engines

2 Thrust Augmentation Piston engines:- Supercharging or turbo chargingForced air aspiration Higher Octane fuelsMore power per bang Gas turbines engines:- Rocket boosters RATO – Rocket Assisted Take-OffSingle use only Other methods Water injection Afterburning Water injection + more fuelMethanol – Argosy and Brittannia Booster enginesHS121 Trident and early V/STOL a/c Mainly military but also Concorde Argosy and Brittannia Hercules

3 Thrust Augmentation C130 Hercules JATO Take-Off

4 Older style engines lacked power at high ambient temperature and therefore required some way of boosting power to be able to take-off. Modern engines do not require this as they are designed to cope with high ambient temperatures. Also water weighs more than fuel and the extra weight needs more power to overcome it. But by injecting water into the airflow it cools the airflow and increases pressure and therefore density. Thrust Augmentation Water Methanol Injection The limiting factor in achieving maximum thrust is the maximum burner temperature. Once this is reached no more power is available. This reduces the burner temperature so more fuel (can be methanol mixed with the water) can be added to regain maximum burner temperature and so achieve more power. Using water injection continuously would damage the engine as it changes the combustion characteristics of the engine. A small amount of water is carried to be used just for take-off and initial climb.

5 Thrust Augmentation Dart Engine Series Water Methanol Injection How is it injected? Water Methanol Tank and Pump Water Methanol Control Unit Torque Pressure (ENGINE POWER) Prop Shaft Torque (ENGINE POWER) In the Dart engine, more power means coarser propeller pitch = more thrust. Use limited because of combustion characteristics

6 Thrust Augmentation Take a closer look here Water Injection Water cools the burner which drops the burner temperature. This will allow RPM to increase and therefore the airflow so producing more power. Rolls-Royce Spey Series Primary Fuel flow Increased Primary Fuel flow Water flow This allows the maximum temperature control system to add more fuel to regain maximum burner temperature

7 Thrust Augmentation Engine Rear End Reheat System (Afterburner) Spray Tubes Vapour Gutters Heat Shields Variable Nozzle

8 Thrust Augmentation

9 Engine Gas Stream without Reheat Variable Nozzle ‘Closed’

10 Thrust Augmentation Reheat Starts with Vapour Gutters Spraying Fuel

11 Thrust Augmentation And Variable Nozzle ‘Opens’ This is to prevent higher jet pipe pressure to ensure that reheat has no effect on jet engine Then Spray Tubes add more fuel to combustion process

12 Thrust Augmentation Typical Reheat System Rolls-Royce Phantom Spey and Jaguar Adour series

13 Thrust Augmentation Just a little bit!! MacDonald Douglas F4 Phantom – Reheat Lit Visible ‘Shock’ waves appear in exhaust plume! FA18 Hornet on Carrier Take-off – Reheat Lit Does the Afterburner get hot? Use of the afterburner is restricted to take-off and combat only (except Concorde of course) due to the extremely high fuel consumption rate

14 Thrust Augmentation Typhoon


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