Showing papers on "Burn rate (chemistry) published in 1986"

Engine HC Emissions Modeling: Partial Burn Effects

Abstract: A comparison of predicted and experimental HC emissions at high rates of exhaust gas recirculation (EGR), indicates that partial burning is responsible for significant changes in HC emission trends under otherwise normal, non-misfiring engine operating conditions. Ion-probe experiments show a measurable fraction of engine cycles in which the flame did not completely propagate across the chamber whenever HC emissions were high. A simple semi-empirical model is proposed to predict HC emissions from partial burning based on measured burn rate parameters.

Solid rocket motor propellants with reticulated structures embedded therein to provide variable burn rate characteristics

Abstract: A solid propellant grain which comprises an homogeneous mass of propellant material including an oxidant. A variable burn rate is provided by embedding a reticulated structure in a portion only of the propellant mass. The reticulated structure may be coated with a high thermal conductivity material to provide an increased burning rate. The coat of material is selected to preferably provide improved bonding to the propellant mass.

Solid fuel burn enhancer

Abstract: A solid rocket motor grain construction is disclosed for use in a ramjet to improve performance. The solid fuel burn enhancer adds oxidizer for burn rate control. Two constructions are disclosed. The inlaid approach places cores of solid low-oxidizer fuel within solid unoxidized fuel and the integrated approach provides shells of low oxidizer around the solid unoxidized fuel. The low-oxidizer fuel has a faster burn rate and smaller burn area requirements than the unoxidized fuel. During initial ramjet operation, when the burn area is constrained, the low-oxidizer fuel burns initially with its smaller burn area requirements. Subsequently, the conventional unoxidized fuel burns when larger burn areas are available.

Wood or coal burning heater

Abstract: A high-efficiency clean burning heater for the burning of wood or coal is disclosed The heater has a primary combustion chamber for the burning of solid fuel positioned above a secondary combustion chamber for the burning of combustible gases and pollutants which pass downwardly from the primary combustion chamber Separate air supplies are provided for the two combustion chambers and the supply of air to the primary combustion chamber is governed by a damper plate to control the burn rate

Acceleration effects in solid propellant rocket motors

Abstract: The performance variations due to acceleration loads imposed on spinning solid propellant rocket motors are investigated. The four potentially most significant modes of acceleration-induced phenomena are identified from a study of the literature and modeled. The four modes are a mechanical mode which deals with deformations of the propellant and case: a thermodynamic mode which covers acceleration-induced combustion phenomena; a stress mode which covers the stressed propellant's effect on burn rate; and a gas dynamic mode which deals with changes in gas flow in the chamber and through the nozzle. Simplified models of each mode are developed or taken from the literature and are added to an internal ballistics evaluation computer program. The resulting analysis is the first to include all of the modes. In order to do this an original analysis of the mechanical and stress modes was necessary. However, the analysis shows that the stress mode is not important for the circular perforated grains studied. The other effects are shown to have a significant influence on solid rocket motor performance. The magnitude of the different mode effects are such that one may not be ignored over the others as has been done in the past. The results of the analysis are compared to published rocket motor data. The comparisons indicate an erosive burning effect that is a function of spin rate. A qualitative explanation of the erosive effect is presented.

Demilitarization of high burn rate propellants containing ferrocene or its derivatives

Abstract: An effective method to recover the catalyst material, ferrocene or its deatives, from high burn rate propellants comprises the method which uses compressed gas in the form of a near critical liquid to extract, remove, and recover the specific catalyst material directly from rocket motors or from chunks of cut propellant. The method comprises introducing compressed carbon dioxide into a pressure vessel containing the propellant from which the catalyst material is to be recovered. The carbon dioxide as a near critical liquid (NCL) is circulated within the pressure vessel where extraction of ferrocene or its derivatives directly from the propellant takes place. The NCL with extractibles is transported to a warming and recovery zone where the extractibles are recovered after the carbon dioxide is volatilized and returned for recycling, compressing, and further extracting after being adjusted to a near critical liquid. Analytical data indicates that from 99.8% to 100% of ferrocence or its derivatives is readily recoverable from propellant which is undergoing demilitarization after it is determined to have burning rate, sensitivity, or other measureable changes to be out of system specification. After recovery of the high dollar value catalyst material, the propellant can be safely handled for removal using conventional water jet apparatus to cut and remove the propellant for reclamation of any of the propellant ingredients.

Modeling and Measurement of Erosive Burning of Stick Propellants

Abstract: : Interior ballistic performance of unslotted single-perforated stick propellants in a large-caliber gun could be influenced significantly by the erosive burning effect. To analyze erosive burning phenomena, a comprehensive model, with special emphasis on the interaction of turbulence and combustion, has been formulated. Experimentally, a test rig using a center-perforated cylindrical propellant grain with large web thickness (approx. 1.0 cm) was designed, constructed, and tested. The location of the instantaneous propellant burning surface was determined by the use of real time X-ray radiography. Based upon X-ray images, the instantaneous burning rate of NOSOL-363 stick propellant was found to be much higher (up to 3.2 times) than the strand burning rate under strong cross-flow conditions. Keywords: Erosive burning, Stick propellant, Theoretical modeling, Experimental measurements, k-epsilon turbulent closure, Two-variable joint probability density function, Real-time x-ray radiography.

A Solid Propellant Charge Design with Negative Effective Pressure Exponent Using Forced Cone Burning

Abstract: : A novel method of making a solid propellant rocket motor or gas generator charge with a negative effective burning rate pressure exponent (negative drb/dP) is presented. The negative exponent characteristic can be obtained independently of burning rate and other bulk propellant properties (specific impulse, flame temperature, signature, mechanical properties, etc) which can be chosen as required. The charge is constructed with a core, (or several cores), of propellant with an intrinsically negative pressure exponent with the bulk of the charge made up of any propellant with a lower burning rate than the core propellant over the pressure range of interest. The core propellant burning rate range can be adjusted to give the desired value by a method of burning rate acceleration. Suitable core materials and burning rate acceleration methods are reported, and the use of such a charge in a rocket motor or gas generator with a variable area nozzle to give controllable thrust is discussed.

High-energy gas fracturing in cased and perforated wellbores

Abstract: A propellant-based technology, High-Energy Gas Fracturing (HEGF), has been applied to fracturing through perforations in cased boreholes. HEGF is a tailored-pulse fracturing technique originally developed by Sandia National Laboratories for application in uncased, liquid-free gas wells in Appalachian Devonian shales. Because most oil and gas wells are liquid filled as well as cased and perforated, the potential impact of present research is significantly broader. A number of commercial tailored-pulse fracturing services, using a variety of explosives or propellants, are currently available. Present research provides valuable insight into phenomena that occur in those stimulations. The use of propellants that deflagrate or burn rather than detonate, as do high-order explosives, permits controlled buildup of pressure in the wellbore. The key to successful stimulation in cased and perforated wellbores is to control the pressure buildup of the combustion gases to maximize fracturing without destroying the casing. Eight experiments using cased and perforated wellbore were conducted in a tunnel complex at the Department of Energy's Nevada Test Site, which provides a realistic in situ stress environment (4 to 10 MPa (600 to 1500 psi)) and provides access for mineback to directly observe fracturing obtained. Primary variables in the experiments include propellant burn rate andmore » amount of propellant used, presence or absence of liquid in the wellbore, in situ stress orientation, and perforation diameter, density, and phasing. In general, the presence of liquid in the borehole results in a much faster pressure risetime and a lower peak pressure for the same propellant charge. Fracture surfaces proceed outward along lines of perforations as determined by phasing, then gradually turn toward the hydraulic fracture direction. 8 refs., 23 figs., 3 tabs.« less