Effect of rocket pre-detonator operating conditions and mixing methods on detonation reliability

This thesis presents an examination of various rocket pre-detonator operating parameters to determine the effect of each on detonation reliability and to develop an operating envelope for a variety of applications. Pre-detonators are used to initiate detonations with rotating detonation rocket engines, which have the potential to outperform conventional liquid rocket engines in specific impulse due to an increase in pressure during combustion. A pre-detonator could also be used as an effective ignition system for other aerospace applications such as liquid rockets or scramjets. The pre-detonator must successfully generate a detonation at different operating conditions for good reliability, and it must be compact for aerospace applications. For a pre-detonator, the variable parameters are initial pressure, equivalence ratio, and ignition delay. For this study, a notional pre-detonator was built based on existing designs to function using gaseous hydrogen and oxygen. In order to define the baseline operating map for the pre-detonator, the operating parameters were varied to find the edges of the working envelope. Near the edges of operability, an uncertainty study was conducted. This led to a robust multi-dimensional map of the combined operating parameters that lead to reliable detonations. Different geometric mixing features were studied to determine their influence on detonation reliability at the different operating conditions. It was found that, while the mixing devices did not affect the detonation reliability of the pre-detonator, injection timing scheme and equivalence ratio had a significant impact as mixing of the combustion gases was found to be a significant factor in detonation success rate. The most successful condition for detonation was found to use 10 bar or higher feed pressure, and equivalence ratio near 0.5, and a zero ms ignition delay. The pre-detonator was generally insensitive to ignition delays of less than 500 ms and fill fractions greater than 30%. Detonations were achieved at lower feed pressures, but reliability failed after departing from equivalence ratio of 0.5. By pulsing the fuel or oxidizer valve, it was shown that the reliable equivalence ratios were increased from a range of 0.45 to 0.55 to a range of 0.15 to 0.675. These results will inform the design of future pre-detonators to supply reliable detonations for any high-energy ignition need.