Showing papers in "International Journal of Energetic Materials and Chemical Propulsion in 2022"
TL;DR: In this paper , six different methods of analysing the experimental T-burner data are presented in order to calculate the growth rate, decay rate and the response function for a self-excited test.
Abstract: The measurement of response function for a given solid propellant is mostly done using a T-burner to address the issue of combustion instability in solid rocket motors. Once the experiment has been conducted, it becomes important to carefully analyse and reduce the data to the required response function using the measured pressure. Six different methods of analysing the experimental T-burner data are presented in this paper. An experiment conducted at 1 MPa pressure at 390 Hz frequency is utilized for this purpose. Detailed procedure is given to calculate the growth rate, decay rate and the response function for a self-excited test. These methods include Perry's method, Culick's method and exponential method with different combinations which is reported for the first time. Analyzing with different methods revealed that Culick's method is better and more consistent than the other methods. The response function of the given solid propellant calculated using this method for the self-excited tests of T-burner is in good qualitative agreement with the response measured using Laser Doppler Velocimetry technique.
3 citations
TL;DR: In this article , the performance of a small-scale liquid bipropellant rocket engine with an average thrust of 534 N (120 lbf) at the design condition was analyzed.
Abstract: The sea level performance of nitrous oxide and ethanol for use in liquid bipropellant rocket engines was characterized through theoretical and experimental efforts. Theoretical study of the propellant combination's peak performance at sea level was conducted using two rocket engine models. Validation of the theoretical performance predictions was made using an experimentally measured specific impulse of a purpose built, small-scale engine with an average thrust of 534 N (120 lbf) at the design condition. Maximum theoretical specific impulse for sea level operation was predicted by both engine models to be 264 sec for the standard chamber pressure operating condition of 6.9 MPa (1000 psi). Model predictions are found to represent real engine performance well, with an average difference of 3.2% between the experimental measurements and theoretical predictions of specific impulse. An assessment was also made of the exhaust species composition. The presence of NO and CO in the engine exhaust was found under certain engine operating conditions. Operating practices are identified to mitigate the formation of NO and CO in the engine exhaust for the propellant combination.
1 citations
1 citations
TL;DR: In this article , the influence of the catalytic copper additive on the ignition delay time (IDT) was analyzed for green propellant combination consisting of an ionic liquid and highly concentrated hydrogen peroxide.
Abstract: The hypergolic reaction between the recently developed green propellant combination consisting of an ionic liquid and highly concentrated hydrogen peroxide was investigated for various fuel to oxidizer ratios and heights of fall. The influence of the catalytic copper additive on the ignition delay time (IDT) was analyzed. Flame emission/absorption spectroscopy revealed the chemical constituents. All emission spectra were dominated by the sodium D-lines at a wavelength of λ = 589 nm. Further lines of alkali metals such as lithium and potassium were found. The copper additive showed its characteristic lines according to its amount in the fuel. Emission spectra of the ultraviolet regime showed the characteristic OH* molecular lines around a wavelength of λ = 306 nm with its temperature dependent intensity ratios. The catalytic additive copper (I) thio-cyanate (CuSCN) increases the temperature of the OH* molecule in the flame while it decreases the IDT from 31 ms for pure ionic liquid to 15 ms (5% mass percentage).
1 citations
TL;DR: In this article , the authors used Viton as a coating for the aluminum powder for enhancing its reactivity to overcome the two-phase losses and slag formation in the rocket motor.
Abstract: Aluminum powder is used as an additive in composite propellants to increase the specific impulse. However, the use of aluminum increases the two-phase losses and slag formation in the rocket motor. This study uses Viton as a coating for the aluminum powder for enhancing its reactivity to overcome these drawbacks. Viton-coated aluminum powder exhibited an enhanced reactivity over the uncoated powder. This Viton-coated aluminum demonstrated an increase of around 25% in the burn rates compared to uncoated aluminum when used in the composite solid propellant. The end mix viscosity of the propellant mixture remains constant with the prolonged mixing with the use of Viton compared to an increased viscosity observed with polytetrafluoroethylene as an additive.
1 citations
TL;DR: In this article , the impact of debondings on the performance of a solid rocket motor is assessed through the adoption of advanced computer graphic techniques like the offsetting of the burning surface discretized as a dynamic three-dimensional triangular mesh.
Abstract: In solid rocket motors, propellant debondings are very dangerous since they could cause an increment of the burning surface area and anticipate the exposure of case-insulating thermal protection material. Therefore, when a debonding internal zone is discovered, it is of primary importance to guarantee that the solid rocket motor is still able to accomplish the mission within its operational requirements. From a numerical point of view, debondings cannot be evaluated in an analytical, closed form due to their variety of shapes. The present study is aimed at assessing the impact of debondings through the adoption of advanced computer graphic techniques like the offsetting of the solid rocket motor burning surface discretized as a dynamic three-dimensional triangular mesh. Mesh handling algorithms are discussed in detail. Numerical results are obtained through an in-house simulation software which has been developed based on the aforementioned methods.
1 citations
TL;DR: In this article , the authors studied the combustion behavior of pure and boron-loaded gel fuel under atmospheric conditions, and the results showed a linear variation of viscosity with an increasing shear rate and with increasing BORON content.
Abstract: Droplet combustion of pure and boron-loaded gel fuels is studied to understand the combustion behavior of gel fuel under atmospheric conditions. Here, Jet A-1 is taken as a base fuel, Thixatrol ST as gellant, and boron as energetic particles. Four kinds of gel fuels are taken for this study with varying boron loadings of 0%, 10%, 20%, and 30% (by weight). Before combustion studies, the rheological properties of all gel fuels were determined. The results show a linear variation of viscosity with an increasing shear rate and with increasing boron content. Combustion characteristics of all these fuels were studied and analyzed. The droplet combustion process was captured using a time-resolved high-speed imaging system. The evolution of droplet profile shows that droplet regresses smoothly for pure gel (PG) sample (0% boron), whereas for the GB10 and GB20 cases with 10% and 20% boron, respectively, the droplet regresses with puffing, disruption, and is followed by micro-explosions. For the GB30 case with 30% boron, the phenomena of micro-explosion occur immediately after the ignition of the droplet. Flame standoff distance decreases with the higher boron-loaded gel fuel. Analysis of secondary droplets explains that: (1) puffing induces a smaller diameter, while micro-explosion ejects daughter droplets of larger diameter. (2) Average secondary flame length increases with the increase of boron loading. As a result, the boron component in gel fuel appears to have a good impact on the whole combustion process. Scanning electron microscopy (SEM) image shows numerous micropores (blow holes) on particle surface in case of GB30 sample while no such pores were present on other counterparts. The micrograph also reveals eroded, flaky, and ashy-like structures in the residue of the GB30 case.
1 citations
TL;DR: In this article , the thermal decomposition characteristics of TAGZT mixed with AP, NQ, RDX, HMX, Cl-20, and TKX-50 were studied by thermal analysis and kinetic analysis.
Abstract: Original Manuscript Submitted: 3/23/2022; Final Draft Received: 6/27/2022 The bis-(triam inoguanidinium)-5,5'-azotetrazolate (TAGZT) is a very attractive high-nitrogen compound. Its nitrogen content is up to 82.3 wt.% and its enthalpy of formation is as high as +2955 kJ/kg (+1106 kJ/mol). In particular, its detonation velocity reaches 9441 m/s. Therefore, TAGZT has attracted the attention of many scholars in recent years. Herein, the TAGZT was superfine, and the thermal decomposition characteristics of superfine TAGZT mixed with AP, NQ, RDX, HMX, Cl-20, and TKX-50 were studied by thermal analysis and kinetic analysis. The results indicated that after superfine TAGZT was compounded with AP and RDX, the differential scanning calorimetry (DSC) curves were a simple combination of the two DSC decomposition curves, and the thermal decomposition peaks and activation energies were significantly lower compared with those of the pure substances, and the two promoted each other's decomposition; after superfine TAGZT was compounded with HMX and CL-20, only one peak appeared in the DSC curves. The heat and products released from the decomposition of superfine TAGZT will intensify the decomposition of HMX and CL-20, and the two promote each other's decomposition; after superfine TAGZT is compounded with NQ, the activation energy is significantly higher compared with the pure substance, and the two inhibit each other's decomposition. After compounding with TKX-50, there are two exothermic peaks on the DSC curve, and the presence of TKX-50 makes the decomposition of superfine TAGZT more stable. The presence of TKX-50 decreased the thermal decomposition peak and activation energy of superfine TAGZT, while the presence of superfine TAGZT increased the activation energy of TKX-50.
TL;DR: In this article , the effect of piezoelectricity on the sensitivity to ignition by laser radiation of 10 × 10 cm was investigated, and it was shown that both the application of an electric field and the activation of the piezolectric properties of PVDF sensitize the composite as measured by a decrease in a mean time to ignition.
Abstract: In this study, the effect of piezoelectricity on the sensitivity to ignition by laser radiation of 10% wt nanoaluminum/poly(vinylidene fluoride-trifluoroethylene) [nAl/P(VDF-TrFE)] composite films was investigated. Nanoaluminum particles were dispersed in P(VDF-TrFE) copolymer solution and cast into ~ 45 μm thick films. Ignition samples across which an electric field of 25 kV/mm could be applied were created by sputter coating gold electrodes on opposing sides of the film. Electrodes were coated on one side with a layer of carbon paint to absorb laser radiation. Samples were tested under four conditions: unmodified, unpoled with an applied electric field, poled without an electric field, and poled with an electric field. Results from this study indicate that both the application of an electric field and the activation of the piezoelectric properties of PVDF sensitize the composite as measured by a decrease in a mean time to ignition, with piezoelectricity activation sensitizing the composite to a greater degree than only an applied electric field.
TL;DR: In a lecture at the California Institute of Technology, on 29 December 1959, Richard P. Feynman drew the attention to the bottom scale of nanosized metal (nMe) particles as discussed by the authors .
Abstract: In a lecture at the California Institute of Technology, on 29 December 1959, Richard P. Feynman drew the attention to the “bottom scale”. That year, studies of nanosized metal (nMe) particles had started for the initiation of nuclear reactions in USA and for material science in the then-USSR. Nanosized energetic ingredients were first prepared at the Semenov Institute of Chemical Physics, Moscow, when Gen et al. produced nMe particles by vaporization and consequent condensation of metal vapors in argon. In rocket propulsion, because of its high combustion enthalpy and easy availability, Al is widely used to improve performance mainly of composite AP/HTPB formulations, the workhorse of space launcher solid motors.
TL;DR: In this article , the authors used the laser Doppler velocimetry technique to measure the velocity of the particles which are emerging out from the propellant burning surface in the gas phase zone under steady-state to determine the mean burning rate of aluminized solid propellant and double base propellant in the pressure range of 1-5 MPa.
Abstract: The main focus of this study is to utilize the laser Doppler velocimetry technique to measure the velocity of the particles which are emerging out from the propellant burning surface in the gas phase zone under steady-state to determine the mean burning rate of aluminized solid propellant and double base propellant in the pressure range of 1-5 MPa. The steady-state experiments are conducted under the high mean chamber pressure with the incorporation of a servomechanism feedback system to maintain the relative distance between the laser probe volume and the propellant regression surface. It is clear from the literature that only limited work has been reported on the LDV of solid propellants and hardly there is any work reported on characterizing aluminized solid propellants at high mean chamber pressure using the LDV technique, which has high spatial and temporal resolution features. A high-pressure window bomb with multiple optical access and coupled with a feedback actuation system serves the purpose of visualizing the propellant burning with the help of a camera and allowing the laser beam to align over the propellant surface. The actuation system is operated under two modes, viz., open loop and closed loop mechanism. The combustion photography is performed up-to-the mean chamber pressure of 5 MPa to compare the data with that of the LDV. It can be concluded that the LDV of solid propellant has shown promising results for the aluminized propellant and double base propellant burning rate estimation under steady-state combustion for high mean chamber pressure.
TL;DR: In this article , the authors used laser Doppler velocimetry (LDV) to determine the acoustic admittance of an aluminized composite solid propellant at low mean chamber pressure.
Abstract: The present study involves the use of laser Doppler velocimetry (LDV) to determine the acoustic admittance of an aluminized composite solid propellant at low mean chamber pressure. The aim of this study is to measure the fluctuating velocity component perpendicular to the burning surface of the particles in the gaseous phase above the burning surface of the aluminized composite solid propellant for the imposed acoustic pressure oscillations. To check the accuracy and precision of the mini-LDV used in this study the acoustic mode shape was generated for the imposed acoustic oscillations with amplitudes of 215 and 6 Pa. The results obtained are very satisfying; they show that the predicted acoustic velocity mode shape matches with the generated mode shape using the LDV. The response function of a solid propellant indicates the inclination of the propellant to cause acoustic combustion instability. Both velocity fluctuations and imposed pressure fluctuations are measured experimentally and used to determine the acoustic admittance of the solid propellant and hence deducing the pressure coupled response function from acoustic admittance. The probe volume of the laser is maintained at a constant distance of 800-900 μm from the burning surface by a servomechanism using a linear actuator. The incorporation of the linear actuator dramatically increases the number of particles passing through the laser probe volume. The linear actuator is controlled using a microcontroller and the servomechanism is operated under an open loop system. A high-pressure window bomb is designed and fabricated. Low-frequency ranges (140-280 Hz) of the longitudinal acoustic modes are investigated in this paper. Tests were conducted at a mean chamber pressure of 0.5 MPa. To generate the acoustic pressure oscillations a rotary valve is designed and fabricated. The rotary valve generates a standing wave of the characterizing frequency depending upon the length of the chamber. Tests are conducted for two aluminized composite solid propellants. The results obtained are in good agreement with the literature for the pressure coupled response function at these mean chamber pressures.
TL;DR: In this article , a multidimensional numerical study was conducted to explore the ignition and combustion of aluminum powder dispersed by a trinitrotoluene (TNT) charge, where an annular shell of Al powder with a volume fraction of 50% surrounding a TNT charge were simulated in an enclosed domain.
Abstract: A multidimensional numerical study was conducted to explore the ignition and combustion of aluminum powder dispersed by a trinitrotoluene (TNT) charge. The simulations used a high-order numerical method for a compressible reactive gas that is coupled to a Eulerian kinetic-theory-based granular multiphase model. The model is valid up to the packing limit and accounts for effects including compaction waves and particle collisions. Scenarios where an annular shell of Al powder with a volume fraction of 50% surrounding a TNT charge were simulated in an enclosed domain. Monodisperse Al particle diameters of 3, 6, 10, and 30 μm were considered. The simulations fully coupled particle dispersal, ignition, and combustion. The results show the formation of particle "fingers" and other finite Stokes number effects as the particles are radially dispersed by the expanding TNT detonation products. The 3-, 6-, and 10-μm-diameter Al particles ignite when they interact with the afterburning TNT fireball, which is the only location that exceeds the Al ignition temperature. Particle inertia initially separates the Al particles from the TNT fireball, which prohibits ignition. The inner edge of the Al dust cloud comes into contact with the fireball during the reshock phase of the blast due to finite Stokes number effects. The 30-μm-diameter Al particles did not ignite because they were launched too far from the TNT fireball. The energy released from the turbulent Al dust flame produced quasistatic overpressures over 3 bar, which is a dramatic increase of the 0.8 bar produced by a bare TNT charge. The results also show that the energy release rate for the Al particles is much more intense and shorter in duration for the 3-μm-diameter particles than for the 6- or 10-μm-diameter particles.
TL;DR: In this paper , the authors investigated the use of amine boranes to improve the ignition delay and predicted performance of tetramethylethylenediamine (TMEDA)-based hypergolic fuels.
Abstract: Historically, most liquid rocket systems utilizing hypergolic propellants have used hydrazine-based fuels. While offering good performance and short ignition delays, these fuels require special handling precautions which provide motivation to develop safer alternatives. While tetramethylethylenediamine (TMEDA) offers comparable levels of performance, its longer ignition delays (compared to the hydrazine-based fuels) make it less attractive as a replacement fuel. This work investigates the use of amine boranes to improve the ignition delays and predicted performance of TMEDA-based hypergolic fuels. Saturated solutions of ammonia borane (AB), ethylenediamine bisborane (EDBB), and tetramethylethylenediamine bisborane (TMEDABB) in TMEDA reduced the average ignition delays by 43-51%. Mixtures of triethylamine borane (TEB) with TMEDA resulted in the shortest ignition delays observed in this study. Unfortunately, the formation of TMEDABB through a trans-borylation reaction between TMEDA and TEB suggests TEB is unsuitable for use with TMEDA. Gelling the fuel mixtures with higher loadings of these amine-boranes had mixed results, with higher weight fractions of AB or EDBB increasing the ignition delay. The shortest ignition delays measured for the gelled fuels were similar to those measured for the saturated solutions and could be considered if gelled propellants are desired. However, given their short ignition delays, comparable theoretical performance, and simplicity compared to these gelled fuels, the saturated TMEDA liquid solutions appear to be the most promising, while still being much safer alternatives to the conventional hydrazine-based fuels.
TL;DR: In this article , a facile correlation between the resulting volume in the ballistic mortar test and the heat of detonation, density, and volume of the detonation gases is presented.
Abstract: A facile correlation between the resulting volume in the ballistic mortar test and the heat of detonation, density, and volume of detonation gases is presented. This correlation can be used as an alternative to the Ballistic Mortar to determine the strength of an energetic material, which describes the energy it can release.
TL;DR: In this article , a Gas Generator (GG) based pyro cartridge has been used for stage separation of launch vehicle systems, where pyro cartridges generate high levels of shock waves, which leads to failure of many critical components like avionics and electronic packages in the vicinity of the pyro shock source.
Abstract: Pyro Actuated Devices are widely used for carrying out separation of structural components as well as to deploy or release appendages. These Pyro Cartridges, upon initiation of the explosive charge generates high pressure gas which in turn initiates the mechanism. Pyro initiated separation bolts or Pyro Bolts are generally used for stage separation of launch vehicle systems. These pyro cartridges generate high levels of shock waves, which leads to failure of many critical components like avionics and electronic packages in the vicinity of the pyro shock source. Anecdotal evidence suggests that the shock can only be reduced, if the pyro initiation is replaced by non-pyro initiation methods like electrical initiation of unlocking mechanism, pneumatic initiation or initiation by gas generator. The electrical / electro-mechanical and pneumatic initiation comes with a penalty of bulky sub structures. In this paper, studies have been carried out for reduction of shock by implementing Gas Generator (GG) based cartridge in place of Pyro Cartridges. The GG cartridge generates the required minimum pressure for initiating the release mechanism of the separation bolt. Separation bolt ejection test has been carried out with pyro cartridge as well as with gas generator based cartridge and the shock generated has been monitored. It is found that there is an order reduction of shock with the use of gas generator cartridge as compared to that of a pyro cartridge. This paper describes the development work carried out for design, realization and testing of GG cartridge and its prospective application for a low shock stage separation mechanism.
TL;DR: Extruded double base (EDB) charges are used mainly due to their efflux having minimum smoke, attractive oxygen balance, and low corrosivity as discussed by the authors , and the propellant class also has desirable burn-rate characteristics since it exhibits plateau burning and has a low temperature sensitivity to burning rate (πk).
Abstract: Extruded double-base (EDB) charges are used mainly due to their efflux having minimum smoke, attractive oxygen balance, and low corrosivity. The propellant class also has desirable burn-rate characteristics since it exhibits plateau burning and has a low temperature sensitivity to burning rate (πk). External ballistic modeling results are presented that illustrate the performance advantages that EDB propellants can provide, compared to more energetic propellants that are also not minimum smoke. For rocket motors, the plateau behavior is generally achieved by the inclusion of lead salts as ballistic modifiers, although these have had increasingly restricted availability, and lead-free alternatives are not yet generally in use. The manufacturing processes, both traditional batch and continuous, are described, including that used for medium- and large-caliber solventless gun propellants. The inhibition methods for rocket propellant charges are discussed. Strengths and weaknesses are considered together with potential developments in processing and materials (e.g., synthetic/nano cellulose). Various current and recent applications for such charges are reviewed, as well as insensitive munitions (IM) aspects. Consideration is also given to the maturity and potential further implementation of other minimum-smoke propellants to predict the future opportunities for solventless EDB propellants in the next five years. This includes an assessment of some historical issues that have arisen when propellant and motor technology advances have been attempted. This paper focuses on topics that are either new or have not been included in previous reviews; it includes more than 65 references.
TL;DR: In this paper , a study on the effect of fluoropolymer F-42L on the relative explosive force of a pyrotechnic composition based on a thermite reaction between nanopowdered aluminum as the fuel and molybdenum oxide as the basic oxidizer is presented.
Abstract: We briefly overview the common and most studied nanothermite composites of different formulations. The paper primarily deals with systems whose main representatives are nanothermite composites for pyroautomatic delay and special devices and initiator primers. The problem of the development of gas-free (low-gas), fast-burning pyrotechnic compositions based on nanothermites is considered herein. The experimental part discusses an understudied issue of explosive transformation mechanisms, including the identification of governing chemical reactions. A study on the effect of fluoropolymer F-42L on the relative explosive force of a pyrotechnic composition based on a thermite reaction between nanopowdered aluminum as the fuel and molybdenum oxide as the basic oxidizer is also reported. The fluoropolymer was shown to reduce the explosive force of the nanocomposite, in which case the governing chemical reaction of explosive transformation was found to be the reaction of Al with the fluoropolymer.
TL;DR: In this paper , the thermochemical stability and thermal decomposition behavior of double base (DB) propellants with and without hexogen (RDX) were studied by a vacuum stability test (VST), methyl violet test, and high-pressure differential scanning calorimeter (DSC).
Abstract: The thermochemical stability and thermal decomposition behavior of double base (DB) propellants with and without hexogen (RDX) were studied by a vacuum stability test (VST), methyl violet test, and high-pressure differential scanning calorimeter (DSC). The thermal decomposition kinetic parameters of the double base components and RDX in these double base propellants were obtained by the Kissinger equation, and the "isokinetic temperature" values were calculated. The results show that various components have certain effects on the thermal stability and thermal decomposition kinetics of DB propellant. The results obtained by the different methods were likely to vary with action mechanisms of the different systems or thermal decomposition stages. There is "kinetic compensation effect" in the decomposition kinetic parameters of double base components and RDX in these formulations, indicating that the interaction between the double base component or RDX and other components cannot change the decomposition of the double base component or RDX, which belongs to the same reaction process or rate-control step. The "isokinetic point temperature" (Tik) values of the double base components decomposition in all formulations are all within the temperature range of 167.3-176.3°C, and the lowest limit temperature of Tik (167.3°C) is higher than the test temperature of VST (90°C) and methyl violet test (120°C), which provides a basis for the evaluation of the stability at lower temperature (< 167.3°C) only by using single kinetic parameter (i.e., apparent activation energy Ea).