Dave Janney Page 5/2/2007
Description of components
Supersonic convergent / divergent (intake) – allows the correct amount of air to enter the compressor. Designed similar to a venturi tube. The throat is designed not to let air in at speeds above mach 1 even when the aircraft is travelling at speeds well above mach 1. If this type of intake was not used and air was allowed to enter the intake at speeds above mach1 the compressor becomes overloaded and cannot cope with the excess air, which makes the compressor vibrate, resulting in the compressor blades shattering.
Axial flow (compressor) – draws in air through the intake and increases its pressure. The axial flow compressor contains rotors, which are dynamic, and draw the air through and stators, which are static, and act as diffusers. The rotors and stators narrow towards the rear of the compressor to give an almost constant velocity but a large increase in air pressure.
Advantages – low frontal area
No limit to number of stages used
Disadvantages – pressure ratio only 1.25:1
High cost
High weight
Complicated design
Turbo annular (combustion chamber)- mixes the fuel/air mixture and allows combustion to take place. Similar in design to the multi-can and the annular combustion chambers. It has common air-cooling and two multi flame tubes. It is similar to the other two because it has many flame tubes but is also embodied in a common air-cooling.
Turbine – connected to and drives the compressor. As the hot gasses pass through the turbine it makes the nozzle guide vanes, which are hollow for cooling, spin turning the turbine. As the turbine and the compressor is linked this in turn spins the compressor. The turbine wheel is forged. Because the turbine and the compressor are linked the turbine must exactly match the characteristics of the compressor otherwise the vibration caused would make the compressor and the turbine blades shatter.
Exhaust – the exhaust ensures deceleration of the hot gasses without turbulence. It consists of 3 different components:
Exhaust unit – ensures smooth air flow out of the turbine without any turbulence
Dave Janney Page 5/2/2007
Jet pipe – used to propel the hot gasses from the exhaust unit to the propelling nozzle as smoothly as possible.
Propelling nozzle (convergent/divergent) – gives final boots to the gasses. The convergent/divergent propelling nozzle can expand and contract this eliminates the engine from “chocking” this is done when the pilot selects reheat the nozzle opens to allow the gasses out quicker when a smaller thrust is required the nozzle contracts.
I have chosen the supersonic convergent/divergent intake because I wanted to design a super sonic aircraft engine and this type of intake will allow the aircraft to fly at supersonic speeds.
I have chosen the axial flow compressor because it is not limited to how many stages can be incorporated and has a very low frontal area.
I have chosen the turbo annular combustion chamber because it incorporates the best features of the multi-can and annular combustion chambers so I feel this would be the most efficient combustion chamber.
I have chosen the convergent/divergent propelling nozzle because this is the only type of propelling nozzle available to supersonic aircraft.
Fuel tanks
I have decided to place a fuel tank inside each of the wings which will be constructed as an integral tanks with baffle plates within each wing tank area. I will also have an integral fuel tank inside the fuselage which will be positioned just to the aft of the cockpit, this is because it is close to the centre of gravity so the effects of a full fuel load wont be overpowering. No protective treatments will be required on these fuel tanks.
The fuel of my choice would be AVTUR because this is relatively safe to handle it also works out cheaper than AVTAG due to the current U.K taxation laws.
Bibliography
Handouts
Class notes
Dave Janney Page 5/2/2007
