1. THE CONCORDE’S ENGINE NACELLES Rohan Karandikar for Prof. Owenby (ASCI 509)

2. Abstract  The BAE Concorde was powered by four Rolls-Royce Olympus 593 turbojet engines. Like most other turbojet engines, these also had the limitation of Mach 0.5 as the maximum air intake speed. Therefore, as the Concorde accelerated to, and surpassed, the speed of sound, it became necessary to perform certain aerodynamic adjustments to the intakes of the engines, in order to decelerate the intake air speed to avoid damaging the engines, as well as to stabilize the airflow. The methods by which these adjustments occurred are covered in the paper.

3. THE CONCORDE’S ENGINES  Designed by Rolls-Royce and Snecma, the Olympus 593 Mark 610 engines were, and still are, the only commercial airliner engines equipped with afterburners

4. THE CONCORDE’S ENGINES  The intake ramps are the most visible part of the nacelles  Each nacelle also had, along with the variable ramps, secondary air doors, an engine bay vent door, and a spill door

5. Engine surge  At supersonic speeds, the airflow starts to produce shockwaves, which can form either at the ramps or directly in front of the engine’s low pressure compressor  The tremendous static pressure increase across the shockwave can cause a complete breakdown of the compression process  The sudden reversal of airflow through the engine creates a huge pressure wave due to its tremendously high velocities, and this pressure wave then thoroughly wrecks the engine’s low pressure compressor. This is called a surge condition.

6. Take-off and sub-sonic cruise  Take-off required maximum power  After take-off, the Concorde was to follow noise-abatement procedures  At take-off, the secondary air doors were fully shut and the ramps completely retracted. This provided the Concorde’s engines with all the air entering the nacelles  The dump door was opened inwards to allow extra airflow into the engine intakes

7. Sub-sonic to transonic cruise  As the Concorde accelerated in cruise and approached the Mach 1 point, the dump door on the nacelle began to close as a function of the free stream velocity, and it was fully closed around the Mach 0.93 point  The secondary nozzle at the very rear of the nacelle was also fully retracted at low sub-sonic speeds  During sub-sonic and transonic cruise, the engine, intake and nozzle produced thrust in a 13.7 : 3.5 : 1 ratio or 82%, 21% and 6%, respectively

8. Supersonic cruise  The dump door began closing at cruise speeds. It was completely closed by the time the Concorde reached Mach 0.93  It became necessary to deploy the secondary nozzle starting at Mach 0.55, and to have it completely open when the aircraft reached Mach 1.1. This was done by an automated control system  To avoid supersonic air ramming into the engine, the intake ramps would begin to move into position at the Mach 1.3 mark  Past Mach 2, the ramps had closed down to half their available manoeuvring distance  During supersonic cruise the engine, intake and nozzle thrust that was in a 13.7 : 3.5 : 1 ratio at sub-sonic cruise was now at a 1 : 3.675 : 7.875 ratio

9. Emergency engine shutdown  In the case of a sudden engine failure, the powerful engines had the capacity to cause a thrust imbalance beyond the design and structural limits of the Concorde’s airframe  At engine malfunction, the bad engine had to be shut down  The intake ramps were closed and the dump door was opened the other way, i.e. outwards

10. Landing  The aircraft needs to be slowed down significantly to allow flaring just before touchdown  After touchdown, the airspeed needs to be rapidly decreased to bring the aircraft to a halt  Prior to landing, the Concorde’s engine nacelle went back to sub-sonic cruise mode  After landing, the dump door was again opened inwards to allow extra airflow into the engine  The secondary nozzle was fully deployed and now functioned as the aforementioned thrust bucket

11. REFERENCES Concorde Technical Specs: Powerplant. (n.d.). Retrieved June 27, 2010, from Concorde SST: http://www.concordesst.com/powerplant.htmlhttp://www.concordesst.com/powerplant.html Darling, K. (2004). Concorde. Ramsbury, UK: The Crowood Press. Orlebar, C. (1997). The Concorde story. London, UK: Osprey Aerospace. Owen, K. (2002). Concorde: Story of a supersonic pioneer. London, UK: Science Museum. Rettie, I. H., & Lewis, W. G. (1968). Design and development of an air intake for a supersonic transport aircraft. Journal of Aircraft, 5:6, 513-521. Trubshaw, B. (2004). Concorde: The complete inside story. Stroud, UK: Sutton Publishing.