Burn rate (chemistry)

About: Burn rate (chemistry) is a research topic. Over the lifetime, 847 publications have been published within this topic receiving 8908 citations. The topic is also known as: Burning rate.

Development of the Multifactorial Computational Models of the Solid Propellants Combustion by Means of Data Science Methods – Phase II

Abstract: In this paper, we present the results of usage of data science methods, in particular artificial neural networks, for the creation of new multifactor computational models for prediction of burn rate of the solid propellants (SP). The analytical system PolyAnalyst and analytical platform Loginom were used for the model creation. The particular model developed was for burn rate prediction of double base propellants with thermite additives, both nano and micro by means of training the ANN using experimental data published in scientific literature. The basis (script) of a creation of Data Wharehouse of SP combustion was developed. The Data Wharehouse can be supplemented by new data in automated mode and serve as a basis for creating new generalized combustion models of SP and thus the beginning of work in a new direction of combustion science, which the authors propose to call �Propellant Combustion Genome� (by analogy with a very famous Materials Genome Initiative (MGI)). Propellant Combustion Genome opens possibilities for accelerating the advanced propellants development.

Burning Rate Characterization of Ammonium Perchlorate Pellets Containing Micro- and Nano-Catalytic Additives

Abstract: Ammonium perchlorate (AP) is a common oxidizer in composite propellants, and its combustion behavior can be tailored by micro- and nano-metal oxide catalysts. Ammonium perchlorate pellets were manufactured with micro- and nano-titanium oxide and iron oxide at several mass loadings (0–3%) to isolate their effects on AP. The samples were burned from 3.45 to 34.5 MPa (500–5000 psi) in a constant-volume strand bomb. Microscopy characterization was completed for both additives and representative pellets. The incorporation of 1% micro- yielded the highest burning rate within the investigated pressure range. All micro-additive formulations increased the burning rate at pressures ranging from roughly 13.45 to 17.24 MPa (1950–2500 psi) and from 4.50 to 8.60 MPa (650–1250 psi) for micro- and micro-, respectively, and these effects were dependent on catalyst mass loading. The burning rates were increased at pressures greater than 11.27 (1620 psi) and 8.27 MPa (1200 psi) for nano- and nano-, respectively. Both nano-additives yielded burning rates that were independent of mass loading within the range of evaluated concentrations (0.25–1%). In all cases, the presence of the catalytic additives removed the negative slope generally observed in the burning rate curve of plain AP. Higher low-pressure deflagration limits were observed for nano-additive formulations, potentially due to radiative heat losses.

Combustion performance of DNTF-CMDB propellant

Abstract: The factors affecting burning rate and pressure exponent of DNTF-CMDB propellant were studied,including the content of DNTF,the different catalyst systems,the contains of carbon black and the granularity of DNTFThe results show that when the content of DNTF is 30%,the pressure exponent of propellant can be decreased to 037 by the composite catalyst system of energetic lead salt,aromatic cuprum salt and carbon black in 8～14MPaWhen the content of DNTF is 50%,the pressure exponent of propellant can not be suppressed by the composite catalyst system of common Pb-Cu-CB(including energetic lead salt and aromatic lead salt and aromatic cuprum salt)The burningrate and pressure exponent of propellant will increase with the increasing content of carbon blackThe burningrate of propellant can be affected by the granularity of DNTF obviouslyThe larger granularity of DNTF is,the higher burningrate is(5319mm/s,16MPa),and pressure exponent increases

Heat Transfer Induced Irregular Burning

Abstract: In the analysis of a ballistic evaluation motor (BEM) for extruded double base motors, an irregular burning phenomenon was encountered. The irregular burning manifested as a drop in pressure. This was not combustion instability as acoustic instability is associated with high frequency pressure oscillations 2 , usually a mean pressure rise and steep fronted shock waves. L* instability is also eliminated as a possibility as the pressure is much higher than the pressure associated with this phenomena (>5MPa), and the pressure did not oscillate at the frequencies associated with L*-instability 3 . The reason for this phenomenon lies in the unique design of the motor. An internal/external burning cylindrical grain, inhibited on one end, was used. The external grain initially vented onto the cold steel wall, resulting in a significant heat loss. Experimental measurements of the steel wall temperature indicated that the heat losses to the wall were in the order of 14-15kJ or 4-6% of the heat released by combustion. This heat loss is also only experienced by the external burning surface of the propellant, thus amplifying the heat loss effect for the outside wall of the propellant. Inserting a silica-phenolic sleeve eliminated the irregular burning. This indicated that the heat transfer at the external wall surface is the most likely source of the irregular burning. This was also confirmed by the increase in severity of the irregular burning for cold firings, where the total heat loss was increased due to the lower temperature of the motor wall and more energy was absorbed by the casing to heat the surface. The burn rate was measured from the pressure/time curve because pressure was the only practical parameter that could be measured. It is not, however, the mechanism that drives the burn rate but is directly related to it. The propellant decomposes at the surface when the surface temperature reaches the ignition temperature. This mass flux from the surface moves into the flame zone and then combusts releasing heat. This heat is then absorbed by the surface, speeding up the decomposition (usually, some form of the Arrhenius equation applies to the surface decomposition), increasing the mass flux and finally increasing the heat released by the combustion. The increased mass addition and flame temperature resulted in the increase in pressure. In most cases the propellant is an internally burning grain that is axis symmetric. In the case of this BEM motor it is also burning from the outside. This has a significant effect on the heat transfer within the motor. In an internally burning axis symmetric motor the radiative heat transfer away from the surface is the same as the incoming energy from the surface directly opposing it. Thus, both surfaces transfer energy to each other. This may not be significant in terms of conductive as most of the conductive heat transfer to the surface comes from the combustion nearest the surface, but can be significant in terms of radiation. Basic propellant combustion theory states that radiation can account for up to 25-30% of the heat transfer to the surface. The energy radiated from the propellant surface should be the same as the energy radiated from the opposing surface. In the case of the motor burning inwards the opposing surface (in this case a steel wall) is not another source of radiant heat but will only be a heat sink. This, combined with the cooling of the combustion gasses, causes the propellant surface not to heat up at the same rate as the propellant surface in the internally burning grain. Thus, its burn rate is lower, resulting in a drop in pressure. This phenomenon warranted a more fundamental approach in the burn rate calculation and heat transfer modeling to confirm the above assertions. To accomplish this, a complete heat transfer calculation was performed. In parallel a CFD simulation with radiation and conduction effects was performed. The results of the two approaches showed remarkable similarity and both pointed to the heat losses as the origin of the irregular burning.

An Analytical Investigation of the Caseless Rocket Motor

Abstract: : An analysis of a caseless and nozzleless solid-propellant rocket motor employing the external burning concept was made. Performance was calculated for a wide range of supersonic flight conditions. The results of the analysis show that acceptable values of specific impulse and thrust are possible for propellants having sufficiently high burn rates in a base burning configuration. The effect of boattailing with combustion along the boattail was investigated and found to degrade the performance. An analysis of a thin planar airfoil with external burning occurring on part of its surface was also made. The specific lift, that is the ratio of the lifting force to propellant flow rate. was found to be an order of magnitude lower than the corresponding specific lift for a conventional airfoil propelled by a turbine engine. (Author)