Studies of condensed-phase hypergolic reactions in a counter-flow stagnation reactor

The ignition process between hypergols involves a complex interrelation between physical and chemical phenomena which is poorly understood. Prior experimental research on hypergolic propellants in drop-ondrop experiments has been plagued by variabilities usually caused by droplet sizes of the reactants as well as the impact and the mixing between the propellants. To control the mixing of the hypergolic reactants in a well-defined fluid flow, this study uses micro-reactors made from silicon and glass. The flow field was characterized by measuring the velocity field and comparing with modeling calculations. Experiments were performed with tetramethylethylenediamine (TMEDA) as the fuel, along with nitric acid as the oxidizer. Steady reactions were observed (via high-speed photography under a microscope) between the reactants accompanied with an increasing temperature rise at the outlets, with increasing flow rates (strain rates). This observation can be attributed to the change in diffusion rates of the reactants across the interface as the velocity at the interface increases. This paper presents an analysis of the effect of diffusion based mixing on the interfacial reactions between hypergolic propellants using micro-reactors.