The scope of this project was, as a team of four, to design a ramjet that was capable of free flight, that is without the stability of an attached vehicle after a suitable Mach number is reached. After research and developmental designs were finalised it was planned that the vehicle be built and launched for testing. The ramjet was to be attached on a Zuni rocket provided by the University of Queensland in order to reach the speeds necessary to for the ramjet to function. After the Zuni burn out was the designated time when the ramjet would detach from Zuni to fly solo, itself having a burn time of 1 second. During the entire flight the ramjet was to collect data so that upon impacting the earth the data acquisition memory would be recovered and flight data could be analysed.
In order to manage all aspects of the project effectively it was broken down into subsections and distributed amongst the team. The other members of the team were Michael Martyn, Andy Yip and Logan Smith and their responsibilities included the design and functionality of the:
· Inlet Nozzle, Aerodynamics and Stability - Michael
· Combustion Chamber, Ignition, Exit Nozzle, Outer Cowling - Andy
· Separation System, Recovery System – Logan
The Inlet Nozzle was a key component in the overall design as many variables, such as the fuel flow rate required and size of the outer structure, were determined from its predicted performance and structure. The designer had to create a nozzle that would produce the right type of shockwave with a reasonable pressure recovery at the start of the combustion chamber. And as with any vehicle in flight it was necessary to analyse the aerodynamics of the ramjet and determine the centres of pressure and gravity for stability.
Following from the Inlet Nozzle, the geometry of the combustion chamber had to allow for the fuel injected and the air to mix optimally with recirculation. The purpose of the Ignition system was to provide back up heat should the temperature in the Combustion Chamber not reach the calculated value required for auto ignition. The objective of the exit nozzle was to have a geometry such that the most thrust possible would be produced from combustion. The Outer Cowling had to withstand dynamic loading during launch and flight so it had to be designed accordingly.
The Separation System was a critical element in the flight trajectory of the ramjet as the defining stage of the ramjet was to fly unaided. The mechanism had to be simple and yet reliable enough to deploy at the designated time and also as light as possible as not to hinder the stability of the ramjet by disturbing the centre of gravity. It was not expected that the vehicle would be recovered intact after the flight, however the inclusion of a parachute was a step in minimising the force of impact on the ramjet and hence would help to preserve the state of the data acquisition memory.
The sub-sections that this thesis was to cover were Fuel Injection and Data Acquisition Systems. The fuel injection system had to have the capacity to inject the right amount of fuel at the correct velocity for a high equivalence ratio for combustion. The system also had to be small enough to fit within the volume constraints of the vehicle and have a simple initiation system that would have a low probability of failure. The positioning of the injection nozzles were also to be at a place where fuel access would be easy and where fuel and air mixing would be optimal. The objective of the Data Acquisition System was to gain information during the ramjet’s flight for analysis and to gain a comprehension of the ramjet’s overall performance using the most appropriate instrumentation that would interface well with other components of the vehicle.