Showing papers on "Burn rate (chemistry) published in 1995"

Experimental studies of the plasma-propellant interface for electrothermal-chemical launchers

Abstract: A plasma-propellant interaction experiment "PIPE" has been constructed to investigate the plasma-propellant interface physics, and plasma augmentation to the propellant burn rate of electrothermal-chemical launchers. The experimental facility consists of an electrothermal plasma source that injects plasma to the surface of solid or liquid propellants. The source is powered by a 340 /spl mu/F Maxwell capacitor (17 kJ at 10 kV, up to 100 kA, 400 /spl mu/s pulse duration) via a pulse forming network. Experiments with JA2 granular solid propellant under vacuum operation (20 Torr base pressure) showed incomplete burn of the propellant. However, the overall chamber pressure is a factor of two higher than that without propellant. Preliminary measurements showed that the burn rate with plasma injection has been increased by a factor of three at a pressure of 0.7 kbar compared to conventional ignition. >

Diluents and Lean Mixture Combustion Modeling for SI Engines with a Quasi-Dimensional Model

Abstract: Lean mixture combustion might be an important feature in the next generation of SI engines, while diluents have already played a key role in the reductions of emissions and fuel consumption. Lean burning modeling is even more important for engine modeling tools which are sometimes used for new engine development. The effect of flame strain on flame speed is believed to be significant, especially under lean mixture conditions. Current quasi-dimensional engine models usually do not include flame strain effects and tend to predict burn rate which is too high under lean burn conditions. An attempt was made to model flame strain effects in quasi-dimensional SI engine models. The Ford model GESIM was used as the platform. A new strain rate model was developed with the Lewis number effect included. A 2.5L V6 4-valve engine and 4.6L V8 2-valve modular engine were used to validate the modified turbulent entrainment combustion model in GESIM. Results showed that the current GESIM can differ by as much as 10 crank angle degrees compared with test data. The modified GESIM can predict burn duration to within 1--2 CA of experimental data, which is considered very good for engine models.

The Effects of Ferrocenic and Carborane Derivative Burn Rate Catalysts in AP Composite Propellant Combustion: Mechanism of Ferrocene-Catalysed Combustion.

Abstract: : The combustion of HTPB/AP propellants containing ferrocene-type and carborane-type burn rate catalysts was examined. The ferrocenic catalysts are good burn rate enhancers, but the carborane-type compounds showed little improvement, even at 3% catalyst concentration. An order of relative catalyst effectiveness was established for 1% catalyst concentration at 20 deg C. Examination reveals the enhancing effect of 1% Catocene is approximately equivalent to 0.5% Butacene. Characteristic surface features observed for the carborane- catalysed propellants contrast to those for the ferrocene-catalysed propellants. For ferrocene-catalysed combustion, the experimental evidence is in favour of a mechanism whereby the ferrocenic catalyst acts in the binder to catalyse the heterogeneous reactions between the binder and the AP at the binder/oxidiser interface. The evidence includes the following: (1) Enhanced burn rates of the Butacene propellant over the Catocene propellant, both propellants containing the same amount of iron in the ferrocenic catalysts; (2) Fe particles dispersed in the binder of the quenched propellant surface; (3) undercuttings along the boundaries of surface AP particles; and (4) the convex, protruding (sometimes apparently intact) AP particle surface. There was no evidence of the catalyst promoting surface AP decomposition reactions. p50

Pressure feed for liquid propellant

Abstract: One of the propellants used in a bipropellant rocket engine has a vapor pressure sufficiently high under prevailing condition to generate vapor at a pressure sufficiently high to pressurize both the volatile component and the second rocket propellant and provide substantially the sole means for forcing the two rocket propellants from their storage to the rocket engine. In the preferred arrangement, both the components will be stored within the same pressure vessel, one preferably being contained within an expandable/collapsible bladder.

Electrothermal-Chemical (ETC) Propulsion with High Loading Density Charges.

Abstract: : This report investigates and quantifies the requirements for increasing performance (muzzle kinetic energy) in existing high performance (tank) gun systems utilizing solid propellants. Factors studied include propelling charge mass or loading density, propellant specific energy, grain geometry, and the use of electrothermal-chemical concepts. Results indicate that significant increases in performance require not only increased system energy but, more importantly, propellant combustion control in terms of the mass generation rate to operate near "ideal" gun performance. Specific requirements and approaches (e.g., propellant burn rate modification by plasma radiative heating) to obtain the "ideal" gun performance are discussed. Pertinent experimental results are also included.

Magnetogasdynamic Control of Burning Rate of Condensed System

Abstract: Presents the results of modelling combustion products of solid propellant flow. The product of combustion is the ionized gas occurring in a channel with current conducting walls, when a part of the channel is in the external homogeneous magnetic field, oriented in such a way that the ponderomotive force, occuring in the flow region, is opposite to the flow. This results in gas deceleration and increase of static pressure. For the condenensed systems, whose mass burning rate is in direct proportion to the environment pressure, the static pressure increase causes increase of mass burning rate. The basic parameters have been determined by numerical simulation. The nature of their influence on the process of combustion in a cylindrical channel has also been determined. The study revealed that a ten-fold increase of burning rate is possible at moderate values of the parameter of magnetogasdynamic interaction.

Prediction of Burn Rate of Magnesium-Sodium Nitrate Propellant

Abstract: A method to predict burning rate of Mg-NaNO3, propellant as a function of concentration and particle size of the ingredients with consideration of metal particle agglomeration during combustion has been developed Experimental results indicate that compositions containing NaNO3, of finer particle size (50μ) give higher burning rate at high fuel content than at the stoichiometric ratio, whereas compositions containing NaNO3, of coarser particle size (250 μ) show higher burning rate at higher oxidizer content maximum at the stoichiometric ratio Based on the experimental observations, an attempt has been made to predict the burning rate of the propellant Predicted values have been correlated with the experimental data The method describes fairly well the observed effects of the concentration and particle size of the ingredients on the burning rate

Hybrid fuel formulation and technology development

Abstract: The objective was to develop an improved hybrid fuel with higher regression rate, a regression rate expression exponent close to 0.5, lower cost, and higher density. The approach was to formulate candidate fuels based on promising concepts, perform thermomechanical analyses to select the most promising candidates, develop laboratory processes to fabricate fuel grains as needed, fabricate fuel grains and test in a small lab-scale motor, select the best candidate, and then scale up and validate performance in a 2500 lbf scale, 11-inch diameter motor. The characteristics of a high performance fuel have been verified in 11-inch motor testing. The advanced fuel exhibits a 15% increase in density over an all hydrocarbon formulation accompanied by a 50% increase in regression rate, which when multiplied by the increase in density yields a 70% increase in fuel mass flow rate; has a significantly lower oxidizer-to-fuel (O/F) ratio requirement at 1.5; has a significantly decreased axial regression rate variation making for more uniform propellant flow throughout motor operation; is very clean burning; extinguishes cleanly and quickly; and burns with a high combustion efficiency.

Combustion Mechanisms of Very High Burn Rate (VHBR) Propellant. Phase II.

Abstract: : In this Phase II Small Business Initiated Research (SBIR) program, the various combustion mechanisms of very high burn rate (VHBR) propellant formulations were studied. Toward this end, various diagnostic and specialized instrumentation techniques were developed and evaluated. These techniques included miniature strain gage instrumentation and cine x-ray experimentation. The program resulted in hypotheses regarding combustion mechanisms at work in VHBR propellant formulations.

Summary of Experimental Efforts to Determine Plasma-Augmented Burn Rates for Solid Propellants.

Abstract: : This report summarizes results of plasma propellant combustion studies performed on M5 and JA2 solid propellants. Both static (fixed pressure) and dynamic (variable pressure) closed chamber firings are analyzed to provide insight into the p1asma propellant combustion process. Results indicate that the plasma may influence propellant combustion (as measured by propellant burn rate) early in the combustion cycle, but appears to have little or no impact once ful1 propellant burning begins.

New Energetic Epoxy Binders

Abstract: A new class of epoxy resins having N-N bonds in the backbone has been synthesized with a view to explore their properties as energetic binders. The N-epoxidation of bis-dicarbonylhydrazones of adipic, azelaic and sebacic dihydrazides results in the formation of viscous resins having epoxide end groups. The resins have been characterized by the elemental and end group analyses, IR and NMR spectra. Relevant properties for their use as binders in solid propellants, such as thermal stability, heat of combustion, burn rate and performance parameters of AP-based propellant systems, have been evaluated. A significant increase in the burn rate of AP-based propellants noticed, is perhaps related to the exothermicity of the binder decomposition and the reactivity of N-N bonds with perchloric acid formed during the combustion of AP.

Possible mechanism of nonsteady-state erosion combustion of composite solid propellants

Abstract: It has been demonstrated that in the combustion of composite solid propellants the instantaneous mass burning rate can depend on variations in the velocity of cross-flow of gases even if in the steady-state regime the combustion is insentitive to cross-flow velocity. A method has been proposed for studying the nonsteady-state erosion combustion in experiments with composite systems.