Critical Ignition Criteria for Monomethylhydrazine and Red Fuming Nitric Acid

Abstract

Understanding the parameters governing ignition is crucial for safe rocket engine design, and while hypergolic propellants have been used for several decades, there is still a lack of data on the early condensed-phase reactions for many systems. The ignition and combustion of monomethylhydrazine (MMH) and red fuming nitric acid (RFNA) have been investigated in an unlike doublet impinging jet apparatus. Variation of the jet diameter and total propellant mass flow rate at constant oxidizer-to-fuel and jet momentum ratio allowed for investigation of critical ignition thresholds. Ignition probability was determined for each condition and classified as good ignition, a transition region, or failed ignition. Conditions resulting in reactive stream separation are compared with literature data obtained with hydrazine/nitrogen tetroxide. Two critical MMH/RFNA ignition thresholds were identified: a residence time of 0.2-0.4 ms and a nondimensional sheet growth rate of 2.75-5.5 s −1 . Two power law correlations were identified allowing for prediction of an MMH/RFNA sheet growth rate given a residence time or Reynolds number. Thermal ignition theory was adapted to simulate the experiment, and selection of model parameters resulted in a trend that supports the experimental data and provides insight into the condensed-phase reaction rates. The results from this work are intended to provide an experimental data set for validation of MMH/RFNA combustion models and to guide the selection of injection conditions for impinging jet systems.

[Bis(imidazolyl)–BH2]+[Bis(triazolyl)–BH2]− Ionic Liquids with High Density and Energy Capacity

“…The new ionic liquids (1a-1e)w ere synthesized as shown in Scheme 1. To simplify the separation of the final products, the IL precursors were converted to [bis(imidazolyl)-BH 2 ] 2 SO 4 13 C, and 11 BNMR spectroscopy,I Rs pectroscopy,a nd HRMS) support the expected structures. The physicochemical properties of these ionic liquids, includingt he thermalp roperties (T g ), densities (1), viscosities (h), heats of formation (DH f ), heats of combustion (DH c ), ignitiond elay times (IDs), specific impulse (I sp ), and density specific impulse (1I sp ), were measured or calculated( see Ta ble 2l ater).…”

“…Hypergolic bipropellants are commonly composed of a fuel and an oxidizer that can ignite spontaneously upon mixing without external ignition devices. Nowadays, the choice of fuel mainly focuses on hydrazine and its derivatives, such as monomethyl hydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH) . Hydrazine‐based fuels are acutely toxic and highly volatile so costly safety precautions and handling procedures are necessary.…”

“…Nowadays, the choice of fuel mainly focuses on hydrazine and itsd erivatives, such as monomethyl hydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH). [1][2][3][4] Hydrazine-based fuels are acutely toxic and highly volatile so costly safety precautions and handling procedures are necessary.T herefore, the developmento fa dvanced rocket fuels as alternative green fuels has received increasingi nterest from the materials and space sciences.…”

First Example of 1,2,5‐Oxadiazole‐Based Hypergolic Ionic Liquids: A New Class of Potential Energetic Fuels

“…[15][16][17] Currently, hydrazine and its analogues (mainly, 1,1-dimethylhydrazine, UDMH) are usually used as bipropellant fuels, whereas white fuming nitric acid (WFNA), dinitrogen tetraoxide (N 2 O 4 ), and hydrogen peroxide (H 2 O 2 ) are applied as oxidizers. [18][19][20] However, hydrazine-derived fuels are extremely toxic and volatile substances capable of causing serious health damage and safety hazard. On the contrary, energetic ILs are usually devoid of such disadvantages due to extremely low vapor pressure, high bulk density, inflammability, resistance to mechanical stimuli and low toxicity.…”

Ignition Delays of Mixtures of the Non‐Hypergolic Energetic Ionic Liquid Hydroxyethylhydrazinium Nitrate Blended with Unsymmetrical Dimethylhydrazine

“…Ignition delay is defined as the time elapsed between the first contact between the fuel-oxidizer pair and subsequent ignition. As a general rule of thumb, the ignition delay should be less than ten milliseconds to avoid excessive accumulation of propellants in the engine, leading to avoid dangerous pressure spikes, known as 'hard starts' [6].…”