Combustion Of Ammonium Dinitramide Research Articles

Experimental study on microwave ignition of ADN-based liquid propellant droplets doped with alumina nanoparticles

The objective of this study was to investigate the effects of alumina (Al2O3) nanoparticles on the evaporation, ignition, and combustion of ammonium dinitramide (ADN)-based liquid propellants under microwave irradiation. The alumina nanoparticles were uniformly dispersed in the ADN-based propellant at mass ratios of 25, 50, and 100 ppm, resulting in the formation of nano-fuel. Experimental methods were employed to examine the influence of alumina nanoparticles on the micro-explosion intensity, ignition delay time, combustion duration, critical ignition power, and emission spectra of the nano-fuel droplets. The experimental findings revealed a significant increase in the intensity and frequency of micro-explosion events with the inclusion of alumina nanoparticles. Compared to pure propellant, the nano-fuel with a concentration of 25 ppm exhibited a reduction of 33.5% in ignition delay time and a decrease of 9% in critical ignition power. Furthermore, the emission spectra characteristics of the pure propellant and nano-fuel were analyzed, indicating that alumina nanoparticles notably enhanced the thermal decomposition of ADN and the exothermic reaction of methanol combustion. This study provides an effective approach to improve the evaporation and combustion performance of ADN-based liquid propellants, offering potential possibilities for future applications.

On the mechanism of thermal decomposition of ammonium dinitramide (review)

Despite significant progress in studying thermal decomposition of ammonium dinitramide (ADN), the kinetics of the process at the level of elementary stages has not been adequately understood. The aim of this review is to summarize various published data, which are of interest for studying and simulating the processes of thermal decomposition and combustion of ADN. Considerable attention is paid to physical and chemical properties of ADN, dinitramide and its anion N(NO2) 2 - , which play a key role in ADN decomposition. Various paths of decomposition of ADN, dinitramide, and N(NO2) 2 - are discussed. Results illustrating alternative points of view on the decomposition process are presented.

Condensed Phase Behavior in the Combustion of Ammonium Dinitramide

AbstractThis paper reports on the thermal and combustion behaviors of ammonium dinitramide (ADN). The thermal behavior is measured by a pressure thermogravimetric analysis (TGA) at pressures below 8 MPa. The burning rates of pure ADN and ADN/ammonium nitrate (AN) mixtures are measured in the range 0.2–12 MPa, and the burning temperature profiles are obtained using thermocouples with diameters of 5 and 25 μm. This report mainly focuses on the condensed‐phase behavior in the vicinity of a burning surface. The temperature profiles are complicated because the ADN decomposition and AN dissociation compete during the condensed phase, and the bubbles of the decomposition gas and gas‐phase flame also affect the surface temperature. AN addition helps to understand the effects of AN during the condensed phase, and it was shown that the burning temperature rises to the critical temperature of AN. Based on these experimental results, the pressure dependency of the burning rates is also discussed.

Role of Additives in the Combustion of Ammonium Dinitramide

AbstractThe thermal decomposition behavior and combustion characteristics of mixtures of ammonium dinitramide (ADN) with additives were studied. Micrometer‐sized particles of Al, Fe2O3, TiO2, NiO, Cu(OH)NO3, copper, CuO, and nanometer‐sized particles of aluminum (Alex) and CuO (nano‐CuO) were employed. The thermal decomposition was measured by TG‐DTA and DSC. The copper compounds and NiO lowered the onset temperature of ADN decomposition. The heat value of ADN with Alex was larger than that of pure ADN in closed conditions. The burning rates and temperature of the pure ADN and ADN/additives mixtures were measured. CuO and NiO enhance the burning rate, particularly at pressures lower than 1 MPa, because of the catalyzed decomposition in the condensed phase; the other additives lower the burning rate. This negative effect on the burning rate is explained based on the surface temperature measurements by a physicochemical mechanism, which involves a chemical reaction, a phase change of the ammonium nitrate, and the blown‐off droplets of the condensed phase.

Modeling of ammonium dinitramide (ADN) monopropellant combustion with coupled condensed and gas phase kinetics

A comprehensive multi-phase combustion model has been developed to study the physiochemical processes involved in the combustion of ammonium dinitramide (ADN). The numerical model is based on the conservation equations of mass, species concentration, and energy, and takes into account finite-rate chemical kinetics in both condensed and gas phases. Based on an extensive review of the literature on ADN thermal decomposition, three global decomposition reactions in the condensed phase of ADN are included. A detailed chemical kinetics scheme involving 34 species and 165 reactions is employed in the gas phase. Detailed combustion-wave structures and burning rate characteristics of ADN are described. The optimized gas-phase kinetics mechanism was able to predict the multi-stage flame structure. Good agreements between the predicted and measured profiles of temperature and species mole fractions were obtained at different pressures. Reasonable agreements between calculated and measured values of propellant burning rates and surface temperatures were obtained over a broad range of pressure from 0.7 to 350atm. The burning rate increases with pressure, except in the mid range of ∼60–100atm. The coupled condensed- and gas-phase analysis employed in the current model is able to capture this irregular/unstable combustion behavior in the mid range, where the burning rate decreases with the increase in pressure.

Thermochemical properties of dinitramidic acid salts

Enthalpies of formation and solution of hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium salts of nitric and dinitramidic (HN(NO2)2, DN) acids were determined by combustion and solution calorimetry methods. Enthalpies of formation of respective cations in infinitely dilute aqueous solution were calculated using the enthalpy of formation of the nitrate ion. The enthalpy of formation of the DN acid anion was determined based on the enthalpy of formation and solution of the acid salts. The weight-average enthalpy of formation of the DN acid anion equal to 8.40±0.13 kcal mol−1 was obtained. The enthalpy of solution of ammonium dinitramide (ADN) was measured (8.71±0.01 kcal mol−1). From these data, the enthalpy of formation of ADN was calculated (−32.14±0.14 kcal mol−1). The energy of combustion of ADN was measured by the calorimetry method, and the enthalpy of formation of ADN was calculated for a sample with purity above 99.9% (−32.20±0.19 kcal mol−1). The weight-average enthalpy of formation of ADN equal to −32.16±0.11 kcal mol−1 is recommended for use. Enthalpies of formation of sodium, potassium, and cesium salts of DN acid were determined.

Combustion of Ammonium Dinitramide, Part I: Burning Behavior

The paper presents a detailed analysis of the ammonium dinitramide (ADN) combustion behavior depending on organic and inorganic additives, material of the surrounding shell, and the sample cross-section size. In spite of the fact that ADN is an oxidizer, combustible surroundings have been found to exert practically no effect on the burning rate of ADN pressed strands. In contrast, minor amounts of organic and inorganic admixtures were shown to have a strong effect on ADN burning behavior, extending considerably the pressure limit of sustained combustion to the vacuum area. Within the pressure range of 1-10 MPa, a decrease in the strand cross-section size leads to a decrease in the ADN burning rate, accompanied by a notable burning-rate data scatter. The main reason for the observed combustion behavior is assumed to be a dominant role of exothermic condensed-phase decomposition reactions in burning of ADN. A descriptive mechanism has been proposed to explain the influence of small amounts of different substances added to ADN on its combustion behavior and the low-pressure limit of self-sustained burning.

Combustion of Ammonium Dinitramide, Part 2: Combustion Mechanism

Temperature profiles in the ammonium dinitramide (ADN) combustion wave were measured in the 0.04-10 MPa pressure interval using thin tungsten-rhenium thermocouples. The data obtained suggest that the ADN decomposition reaction in the condensed zone plays a dominant role in burning at low pressures. The heat feedback from the gas to the surface appeared to be negligibly small. It has been concluded that the reaction of AN dissociation to form NH 3 and HNO 3 controls the ADN burning surface temperature. The three-zone flame structure of the ADN combustion wave has been found, and the main chemical reactions occurring in the zones have been proposed. At low pressures (below 1 MPa), the burning of ADN can be satisfactorily described by a condensed-phase combustion model with the rate-controlling reaction being the ADN decomposition in the melt. A gas-phase model with the rate-controlling reaction being HNO 3 decomposition in the first flame can be used at high pressures (above 10 MPa). In the middle pressure interval, ADN shows combustion instability caused by deficiency of heat produced in the condensed material. In this area the fast but energy-limited heat-release process in the condensed phase has to adapt itself to the slow but energy-rich heat-release process in the gas phase.

Thermal Decomposition and Combustion of Ammonium Dinitramide (Review)

A comprehensive review of thermal decomposition and combustion of ammonium dinitramide (ADN) has been conducted. The basic thermal properties, chemical pathways, and reaction products in both the condensed and gas phases are analyzed over a broad range of ambient conditions. Detailed combustion-wave structures and burning-rate characteristics are discussed. Prominent features of ADN combustion are identified and compared with other types of energetic materials. In particular, the influence of various condensed- and gas-phase processes in dictating the pressure and temperature sensitivities of the burning rate is examined. In the condensed phase, decomposition proceeds through the mechanisms ADN → NH4NO3 + N2O and ADN → NH3 + HNO3 + N2O, the former mechanism being the basic one. In the gas phase, the mechanisms ADN → NH3 + HDN and ADN → NH3 + HNO3 + N2O are prevalent. The gas-phase combustion-wave structure in the range of 5–20 atm consists of a near-surface primary flame followed by a dark-zone temperature plateau at 600–1000°C and a secondary flame followed by another dark-zone temperature plateau at 1000–1400°C. At higher pressures (60 atm and above), a final flame is observed at about 1800°C without the existence of any dark-zone temperature plateau. ADN combustion is stable in the range of 5–20 atm and the pressure sensitivity of the burning rate has the form r b = 20.72p 0.604 [mm/sec] (p = 0.5–2.0 MPa). The burning characteristics are controlled by exothermic decomposition in the condensed phase. Above 100 atm, the burning rate is well correlated with pressure as r b = 8.50p 0.608 [mm/sec] (p = 10–36 MPa). Combustion is stable, and intensive heat feedback from the gas phase dictates the burning rate. The pressure dependence of the burning rate, however, becomes irregular in the range of 20–100 atm. This phenomenon may be attributed to the competing influence of the condensed-phase and gas-phase exothermic reactions in determining the propellant surface conditions and the associated burning rate.

Modeling the chemical reactions of ammonium dinitramide (ADN) in a flame

Ammonium dinitramide (ADN) is a new energetic material that can be used as an oxidizer in solid rocket propellants. In the last few years, a number of papers devoted to the study of ADN combustion mechanism have been published. Molecular beam mass-spectrometry and thermocouple measurements are here used to study ADN flame structure at pressures of 0.3 and 0.6 MPa. Measurements include species concentrations and temperature profiles. A general mechanism for describing the chemical reactions in an ADN flame (172 reactions and 31 species) is developed based on these experimental studies and literature data. The scheme includes a sub-mechanism (98 reactions and 22 species) for propellants combustion suggested by Yetter and Dryer. The latter is further supplemented by a set of 74 reactions, including 63 steps suggested by Lin and Park and the ADN dissociation reactions suggested by the authors of this paper. The correlation between the experimental and calculation results is satisfactory.

Combustion of ammonium dinitramide

The burning rate of ammonium dinitramide (ADN) has been studied as a function of pressure and different additives, the temperatures in the combustion front, and the composition of combustion products. Some kinetic characteristics of decomposition have been also obtained. A combustion model has been used that accounts for decomposition and evaporation, and calculated parameters of combustion are compared with experimental data. The mechanism of ADN combustion is similar to that of many other onium salts. Its peculiarities are conditioned by a rather high decomposition rate in the liquid state, low reactivity of decomposition products, and formation of ammonium nitrate as an intermediate product at low pressures.

Molecular-Beam Mass-Spectrometry to Ammonium Dinitramide Combustion Chemistry Studies

The methods for the study of flame structure and kinetics of the thermal decomposition of solid propellant by probing mass spectrometry are described. The developed methods were applied to the study of ammonium dinitramide (ADN) combustion chemistry. The study has shown that along with ADN decomposition, sublimation takes place to give gaseous ADN followed by dissociation to yielding ammonia and dinitraminic acid (HD). Gaseous ADN has been observed in ADN decomposition products. The structure of ADN combustion zones at 1-6 atm was studied using a molecular-beam mass-spectrometry as well as a microthermocouple technique. Three combustion zones have been observed. Gaseous ADN has been discovered in the first cool flame zone at 3 atm. Gaseous ADN dissociation on NH3 and HD followed by HD decomposition in the near-surface zone are key reactions resulting in a temperature rise of about 150 K. The second high-temperature zone is found within 6-8 mm from the ADN burning surface at 6 atm. The main reaction in this zone is ammonia oxidation by nitric acid and the combustion temperature is 1400 K. The third zone was observed at 40 atm, the measured final temperature was —2000 K. The obtained data form the basis for the development of a chemical mechanism of reactions in both the ADN flame and combustion model.

Thermal Decomposition of Ammonium Dinitramide at Moderate and High Temperatures

Temperature-controlled gas cell and thin film laser pyrolysis techniques have been used to investigate the condensed phase thermal decomposition of ammonium dinitramide (ADN). Gas cell experiments have been performed at heating rates of 10-2−10-1 °C s-1 and in a temperature region 20−250 °C. Pulsed CO2 laser heating of thin ADN films has allowed heating rates of 107 °C s-1 and temperatures of about 630 °C to be reached. The thermal decomposition products have been monitored by FTIR spectroscopy. Both experimental techniques show that the primary decomposition products are N2O and NO2. Nitric oxide is produced at a later stage in the reaction. No evidence has been found for participation of dinitramidic acid in the reaction mechanism. The fact that the same initial products are observed over a wide range of temperatures and heating rates shows that this mechanism can be used to model the initial stages of combustion of ADN.