Ignition envelope and bubbly spray combustion of a cost-effective self-igniting fuel with rocket-grade hydrogen peroxide

Since the beginning of this century, the space industry has been searching for stable non-toxic propellants to replace hydrazine-based fuels. In this paper, we introduce a novel eco-friendly self-igniting fuel, denoted PAHyp 3, which comprises a blend of N,N,N′,N′-tetramethylethylenediamine (TMEDA) and N-methylethanolamine (MMEA) catalyzed with a copper-based catalyst. This promising formulation is coupled with hydrogen peroxide as the oxidizer. To map near-optimal formulations in terms of performance and chemical stability, we varied the proportions of MMEA and TMEDA, each catalyzed with copper nitrate trihydrate concentrations ranging from 0.25% to 3% by weight. Drop tests revealed that a 50:50 mixture of TMEDA and MMEA, catalyzed with 2 wt% copper nitrate trihydrate, exhibited a rapid ignition delay time (IDT) of approximately 14 ms when paired with 94% hydrogen peroxide. This composition was subsequently chosen for evaluation using an impinging jet apparatus capable of capturing simultaneous visible and shadowgraph high-speed imaging, facilitating the detailed study of the ignition process. Screenshots from impinging jet firing tests unveiled that the majority of ignition events, utilizing 94% hydrogen peroxide, occurred downstream less than 20 ms after impingement. Subsequently, foam-like structures engulfed the vaporized and combusted liquid sheet, emitting stable orange/green flames. These promising outcomes indicate that PAHyp 3 presents novel prospects in aerospace propulsion, with the potential to replace hazardous and toxic hydrazine-based propellants. Moreover, a model was proposed to explain how bubble nucleation and growth from hydrogen peroxide decomposition can enhance atomization, leading to a new atomization mode we have termed “catalytic decomposition-assisted atomization”.