KINETIC STUDY OF SELECTED COMBUSTION PROCESS

MSc. Ahmed Mohamed Ali Maraden

Doctoral thesis

Abstract:

In this research, modified cast double base propellant has been prepared. RDX, BCHMX, and AP energetic fillers have been used to increase the energy density of the prepared solid propellant. DNDA 57 and BuNENA energetic plasticizers have been used for gelatinizing the NC during the mixing operation. The effect of energetic filler content on thermal and ballistic properties of the prepared solid propellant has been investigated. Differential thermal analysis and differential scanning calorimeter have been used to study the thermal behavior of the modified cast double base propellants. Integral and differential isoconversional methods beside Kissinger and Ozawa methods have been used for calculating the activation energy of the NC decomposition reaction. It was found that the activation energy increased with increasing the content of the energetic filler. The sensitivity of MCDB propellants to impact was determined on Kast fall hammer. Applying the probit analysis method, the sensitivity curve of each studied sample was obtained and only 50% probability of initiation is reported. The inclusion of nitramines in DB matrix makes the system more sensitive to impact and the sensitivity to impact increases with increasing the nitramine content. Using the modified VST assembly, experiments were carried out at a temperature of 90 °C for a period of 40 hours. The pressures of the gases that were produced from the decomposition of the samples were continuously measured during the whole reaction. The addition of cyclic nitramines such as RDX and BCHMX in the DB matrix improvs not only the energy output but also the thermal stability of the propellants. Practical investigation of the impact of initial grain temperature on ballistic properties of extruded double base propellant has been carried out. Burning rate of three double base propellant compositions was measured in subscale rocket motor. The propellant burning rate was measured as a function of pressure and initial temperature. Results obtained from subscale rocket motors are confirmed by comparing with burning rate measurements using closed vessel evaluation. Measurements of burning rate were performed at different initial grain temperatures. Temperature variation was from ? 60 °C to + 60 °C for subscale rocket motor and form -20 °C to + 60 °C for the closed vessel. Results revealed that the ignitability, the burning rate and operating pressure increase with increasing the initial grain temperature while the time needed for ignition process and action time were shortened. Validation for the modified SV-2 burning rate measurements for strand burning technique has been introduced. The burning rate of four commercial extruded double base propellants at 20 °C has been measured using three different methods, subscale motors, closed vessel and strand burning. More than 60 shots for subscale motors are compared with about 8 shots of SV-2 closed vessel and about 56 shots for strand burning. Results showed that the burning rates measured from the three methods are comparable and close to each other in spite of the differences in the three measuring techniques. Subscale motors are time and money consuming but their results are considered the most reliable and accurate. Tests in small motors are normally performed only after the neighborhood of the final propellant formulation is reached.

Language used: English

Date on which the thesis was submitted / produced: 21. 9. 2018

Accessible from:: 31. 12. 2999

Thesis defence

University of Pardubice

Faculty of Chemical Technology

Doctoral programme / field:
Chemistry and Technology of Materials / Engineering of Energetic Materials