Slower burning materials such as propellants develop much lower pressures compared to detonating explosives, but over a longer time period, that may well lead to an effectively-static load on a structure. Basic tests show that the burning rate of these materials increases with increasing temperature and containment pressure. Although there is some guidance on burning rates they use a form of equation developed by British Gas to deal with petrochemical events and this fits the data from trials for a small number of materials in some circumstances: is not generally applicable to other materials, nor materials which are packed for transport, nor materials where small changes in confining pressure lead to large changes in burning rate. Neither of these approaches allow for ’feedback’ to the burning rate equation from confinement pressure and temperature.
This PhD project will develop a more accurate methodology of evaluating the effects on structures from burning type events. The successful applicant will join an internationally recognised experimental research team working in the Centre for Defence Chemistry (https://www.cranfield.ac.uk/centres/centre-for-defence-chemistry
) at Cranfield University and the company DJ Goode & Associates Ltd (DGA: https://www.djgoode.co.uk/
). DGA have worked on the design of many explosives storage and processing buildings. They have questioned the existing design methods and become aware that there is an industry-wide lack of knowledge regarding burning events in terms of their structural effect on buildings. This PhD will support the development of the new burning rate algorithms at DGA by developing, designing and carrying out experiments on the burning of propellants in confined areas and feeding the data in the DGA algorithms.
The research for this PhD will be carried out at Cranfield Defence and Security (CDS) facilities in Shrivenham-UK and at Cranfield Ordnance Testing and Evaluation Centre (https://www.cranfield.ac.uk/centres/centre-for-defence-chemistry/cranfield-ordnance-test-and-evaluation-centre
) in Salisbury plain.
The aim of the project will be realised through the completion of the following objectives:
1. Carry out a literature review to cover conventional burning models for energetic materials (some of which will contain their own oxygen and some will need atmospheric oxygen) and review of available burning rate test data, including the effects of containers, packing, air gaps, non-linear burn rates, confinement, etc
2. Design and develop experiments to measure the burn-rate, temperature and pressure of a propellant using suitable instrumentation
3. Carry out initial experiments on mechanite, and then another propellant to see if the composition affects the parameter
4. Preparation of a new burning equation to give mass vs. time, taking into account temperature, pressure and charge shape
5. Feeding into DGA software which calculates the resulting gas volume flow rate and heat generation rates