Ageing is an irreversible process during which, the material undergoes a series of slow chemical degradation/oxidation reactions. The aim of this paper is to study the effect of ageing of ammonium perchlorate-copper chromite (AP-CC) pellets on the burn rate. It also focuses on any change in CC properties due to direct contact with an oxidizer (AP). Accelerated ageing with cyclic temperature profile has been used to replicate the natural ageing. The effect of ageing of individual ingredients on the burn rate was studied. The burn rate of AP-CC pellets was found to reduce when AP-CC were aged together. X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) analysis were used to identify the change in properties of copper chromite during ageing. © 2019 The Combustion Institute

Periyapatna A. Ramakrishna

Department of Aerospace Engineering

Kumar Nagendra

CHROMITE

Energy dispersive spectroscopy

Inorganic compounds

Pelletizing

Statistical mechanics

ACCELERATED AGEING

AMMONIUM PERCHLORATES

Chemical degradation

COPPER CHROMITE

CYCLIC TEMPERATURES

EFFECT OF AGEING

Energy dispersive spectroscopies (EDS)

IRREVERSIBLE PROCESS

Copper compounds

Ammonia

Copper

perchlorate

article

combustion

Degradation

energy dispersive X ray spectroscopy

oxidation

priority journal

Temperature

X ray diffraction

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Combustion and Flame

The combustion characteristics of Ammonium Perchlorate (AP) monopropellant have been revisited. The use of silica grease to prevent heat loss from the sides of the pellet and the ignition methodology opened up new area; one of them being the low pressure deflagration limit (LPDL) of AP itself and the other being the burn rate of AP at different pressures. The new burn rate law for pure AP was obtained for conditions close to adiabatic. Using slow depressurization method, wherein the LPDL was independent of ignition transients, the LPDL of pure AP was found to be 14 bar The burn rate of pure AP at 70 bar was found to be 10.66 mm/s, which was much higher than the ones reported in literature. The pressure index for this case was found to be 0.71. This new result completely changes the understanding of AP combustion and called for a new set of parameters to be developed to predict the results obtained with silica grease on the sides. Using the same set of parameters, along with a heat loss model the predictions for the case when there was no silica grease applied was made. These results were in reasonable agreement with the experimental data reported in literature without the silica grease on the sides of the AP pellet. This brings out the critical role of heat loss in AP combustion. © 2019 The Combustion Institute

Combustion of Ammonium Perchlorate monopropellant: Role of heat loss

This paper deals with the low pressure deflagration limit (LPDL), which is the minimum pressure below which burning of a propellant ceases without the assistance of an external energy source. The LPDL of AP monopropellant reported in literature is around 20 bar and it is reported to shift to different higher pressures with the addition of small fraction of impurities or additives. Most of these additives (such as iron oxide and copper chromite) are known to catalyze AP combustion, but yet their reported LPDL is significantly higher than the LPDL of AP itself. In present study, reasons for this behavior have been explored experimentally. Three additives (each of 1% by mass) namely iron oxide (IO), copper chromite (CC) and activated charcoal (AC) were used. The LPDL of AP with these additives was determined using three methods. Two of these methods (method I and method II) include the effect of ignition dynamics on LPDL while in method III (slow depressurization) ignition dynamics does not play a role. In method I, hot nichrome wire was used for ignition, while in method II, nichrome wire ignition in conjunction with an in-situ propellant was used to ignite the pellets. The effect of convective heat loss on LPDL was studied with the use of silica grease whose role through carefully thought out experimentation has been identified as an insulation on sides of pellet. The LPDL of AP with additives was found to be higher for method I compared to method II. Lastly, method III (slow depressurization) was found to result in lowest LPDL for these additives. The LPDL of pure AP, which has been reported as around 20 bar, was revisited and method III along with the use of silica grease has lowered the LPDL of pure AP to 14 bar. © 2019 The Combustion Institute

Experimental studies on low pressure deflagration limit of ammonium perchlorate with additives

This study makes an attempt to demonstrate the feasibility of a technique to embed the catalyst on ammonium perchlorate (AP) surface, in aluminized composite solid propellants. Micron sized iron oxide (IO) and nano sized IO were used in this study and its effect on the viscosity and burn rates of composite solid propellants were recorded. Burn rates of propellants prepared with this catalyst embedded AP were measured using a Crawford bomb and observed to be increasing using this technique due to the proximity of the catalyst with AP. The increase in burn rate obtained with micron sized and nano sized catalyst embedded on AP were 27.4% and 7.3%, respectively over those mechanically mixed in the propellant. The end of mix viscosity of the propellant prepared with nano IO was observed to be highest (4.27 × 103 Poise) when it is mechanically mixed in the propellant. The viscosity of the propellant was observed to improve to 3.79 × 103 Poise with the use of the technique of embedding the nano catalyst on AP as the total number of particles reduced. These explanations were the result of a computational model of randomly packed particles of AP, aluminum and catalyst generated for a propellant with 1% catalyst. © 2017 The Combustion Institute

An effective method to embed catalyst on AP and its effect on the burn rates of aluminized composite solid propellants

Iron oxide and copper chromite are the known burn rate enhancers used in a composite solid propellant. Lot of research has been carried out to understand the mechanism or location of action of the burn rate modifiers so as to better tailor the burning rate of a composite propellant. The literature is still very confusing in affirming the mechanism. Here, a systematic study has been carried out, by undertaking experiments at varying levels of combinations of the individual components (ammonium perchlorate, which is oxidizer and hydroxyl terminated poly butadiene, which is both fuel and binder) of composite solid propellant. Firstly, thermal gravimetric analysis, differential scanning calorimetry and burning rate measurements on the individual components are carried out to study the effect of iron oxide and copper chromite on the components themselves. It has been noticed that though both iron oxide and copper chromite are effective on ammonium perchlorate, iron oxide is slightly more effective than copper chromite. Also, copper chromite enhanced the binder melt flow, while iron oxide reduced it. These are followed-up by experiments on sandwich propellants, which give greater insight and enables better understanding of the behavior of iron oxide and copper chromite in composite propellants, as these are simple two-dimensional analogue of the composite solid propellants. Finally, experiments are carried out on the composite solid propellants to obtain a holistic understanding of the behavior/location of action of iron oxide and copper chromite in them. These studies are used to explain certain unexplained but observed phenomena, at the same time elucidating the location of action of these burn rate modifiers in composite solid propellant combustion. Based on these observations, it has been proposed that both iron oxide and copper chromite are primarily acting on the condensed phase. These studies are further complimented with experiments to analyze the thermal conductivity measurements of various propellant samples. This is pursued to understand the reason for the differences in burn rate pressure index for the composite propellants with iron oxide and with copper chromite. It has been understood from these studies that the thermal conductivity of a composite propellant is a key parameter, which affects the burn rate pressure index. Literature has never addressed it from this perspective. © 2014 The Combustion Institute.

Studies on the role of iron oxide and copper chromite in solid propellant combustion

52nd AIAA/SAE/ASEE Joint Propulsion Conference

Effect of Ageing on Mechanical Properties of Composite Solid Propellants

Effect of ageing on combustion of ammonium perchlorate with copper chromite additive

Journal	Data powered by TypesetCombustion and Flame
Publisher	Data powered by TypesetElsevier Inc.
ISSN	00102180
Open Access	No