Showing papers on "Burn rate (chemistry) published in 2014"

Activated charcoal: as burn rate modifier and its mechanism of action in non-metalized composite solid propellants

Abstract: Modification of composite solid propellant burning rates becomes a requirement based on the necessities of a mission. Literature discusses about various burn rate modifiers which can modify the burning rates effectively. This paper attempts to understand the behavior and mechanism of (dry) activated charcoal (a recently reported burn rate modifier) in composite solid propellant combustion. Extensive experimental studies are performed to achieve this objective. Effects of activated charcoal are studied on the individual components (fuel and oxidizer) of a composite solid propellant. Its behavior when present at various locations in a sandwich propellant and the quenched surface structures these sandwich propellants is also studied. These studies are further extended to composite propellants as well. From these studies, it is concluded that activated charcoal acts on the primary diffusion flame and enhances the binder melt flow over the surface. The unique features observed with activated charcoal (enhancement in burning the rates is observed only at low pressures and burn rate pressure index reduced) are justified with the proposed mechanism and site of its action. Understanding the mechanism of activated charcoal provided an opportunity to tailor a propellant composition, with activated charcoal coated on ammonium perchlorate, which exhibited very high burning rates (17.34 mm/s at 70 bar) and a near plateau burning (n ~0.08) in the pressure range of 20–70 bar. Also, this paper proposes a mechanism, as to what causes a propellant to have a relatively larger binder melt flow and consequently lower n has been answered.

Understanding the Effect of Wall Conditions and Engine Geometry on Thermal Stratification and HCCI Combustion

Abstract: Thermal stratification of the unburned charge in the cylinder has a profound effect on the burn characteristics of a Homogeneous Charge Compression Ignition (HCCI) engine. Experimental data was collected in a single cylinder, gasoline-fueled, HCCI engine in order to determine the effects of combustion chamber geometry and wall conditions on thermal stratification and HCCI combustion. The study includes a wall temperature sweep and variations of piston top surface material, piston top geometry, and compression ratio. The data is processed with a traditional heat release routine, as well as a post-processing tool termed the Thermal Stratification Analysis, which calculates an unburned temperature distribution from heat release. For all of the sweeps, the 50% burned point was kept constant by varying the intake temperature. Keeping the combustion phasing constant ensures the separation of the effects of combustion phasing from the effects of wall conditions alone on HCCI and thermal stratification.The results for the wall temperature sweep show no changes to the burn characteristics once the combustion phasing has been matched with intake temperature. This result suggests that the effects of wall temperature on HCCI are mostly during the gas-exchange portion of the cycle. The ceramic coatings were able to very slightly decrease the thermal width, increase the burn rate, increase the combustion efficiency, and decrease the cumulative heat loss. The combustion efficiency increased with the lower surface area to volume ratio piston and the lower compression ratio. Lastly, the compression ratio comparison showed a noticeable effect on the temperature distribution due to the effect of pressure on ignition delay, and the variation of TDC temperature required to match combustion phasing.Copyright © 2014 by ASME and General Motors

Pool Fires Of Biofuels And Their Blends With Petroleum Diesel

Abstract: The combustion characteristics of pool fires of biofuels, canola methyl ester (CME), soy methyl ester (SME), and their blends with a petroleum fuel (No 2 diesel) were studied The fuels were burned in cups of two sizes (0042 m and 0057 m in diameter and 0038 m height) that simulated convection-dominated small pool fires of liquids Blends of CME and SME with diesel fuel were tested with biofuel concentrations of 25, 50, and 75% by volume The mass burn rate, the fuel surface regression rate, the radiation emission from the flames, the flame temperature field, and the emission indices of CO and NOx were recorded The fuel surface regression rate in both containers was comparable Both the fuel mass burning rate and surface regression rate varied non-monotonically with the volume concentration of biofuel in the blend The radiation fraction of heat release and the temperature profiles were similar for all the flames The CO emission index decreased with the biofuel content in the fuel The NOx emission

Optimal Control of the Heat Release Rate of an Internal Combustion Engine With Pressure Gradient, Maximum Pressure, and Knock Constraints

Abstract: In this paper, we present an analysis of the optimal burn rate in an internal combustion engine ( ICE) considering pressure gradient, maximum pressure, and knocking A zero-dimensional model with heat losses is used for that purpose The working fluids are assumed to behave like ideal gases with temperature dependent gas properties In the first part, it is assumed that the burn rate can be arbitrarily chosen at every time instance in order to maximize the mechanical work This leads to an optimal control problem with constraints In the second part, a Vibe type burn rate is assumed, where the center of combustion, the duration and the form factor can be chosen in order to maximize the mechanical work This Vibe type burn rate is finally compared with the arbitrary combustion as the benchmark in order to evaluate the potential of the more realistic burn shape

Method for determining the aging of an oxidation catalyst in an exhaust gas aftertreatment system of an internal combustion engine, method for detecting ash in a particle filter of an exhaust gas aftertreatment system, control device, and internal combustion engine

Abstract: The invention relates to a method for determining the aging of an oxidation catalyst (7) in an exhaust gas aftertreatment system (3) of an internal combustion engine (1), having the following steps: ascertaining a soot burn rate (31) of a particle filter (7) of the exhaust gas aftertreatment system (3); adapting a function comprising at least one adaptation parameter (39) to the soot burn rate (31) dependent on at least one variable, a value of the adaptation parameter (39) depending on an aging of the oxidation catalyst (7); and determining the aging of the oxidation catalyst (7) using the adaptation parameter (39) value ascertained by adapting the function.

Laser-Controlled Combustion of Solid Propellant

Abstract: This paper describes experimental work on laser-controlled combustion of solid propellants. Combustion of AP/HTPB, including ignition, combustion, extinction and re-ignition could be controlled by CO2 laser irradiation at the back pressure of 0.1, 0.3 and 0.5 MPa in nitrogen. Burning rate of propellant increased linearly with the increasing of laser power density. Vieilles law was used here to check pressure effect to burning rate, pressure exponent under different power density (except 0.5 MW/m2) are very close to 0.17.

3D Flow Simulation of Dual Thrust Solid Rocket Motors during Starting Transient

Abstract: Numerical studies have been carried out to examine the pre-ignition chamber dynamics of dual-thrust solid rocket motors. Using a three-dimensional unsteady, second-orderimplicit, shear-stress transport k–ω turbulence model, detailed parametric studies have been carried out to examine conclusively aerodynamic choking and the existence of a fluid throat at the transition region during the startup transient of dual-thrust motors. In the numerical study, a fully implicit finite volume scheme of the compressible, pressure based Navier– Stokes equations is employed. It is confirmed that, at the subsonic inflow conditions, there is a possibility of the occurrence of internal flow choking in dual-thrust motors with large length-to-diameter ratio (L/d > 44) due to the formation of a fluid throat at the beginning of the transition region induced by area blockage caused by boundarylayer-displacement thickness. The internal flow choking results in the formation of shock waves inside the dualthrust motor. The shock waves and the new turbulence level altered the location of the reattachment point and also enhanced the heat flux to the propellant surface, which obviously will lead to undesirable startup transient due to erosive/transient burn rate enhancement. More numerical results of inert simulators of dual-thrust motors with horizontal and flip-horizontal positions are presented with tangible explanations in this paper for establishing the internal flow choking in dual-thrust solid rocket motors with narrow upstream port.

Combustion Study of Composite Solid Propellants Containing Metal Phthalocyanines

Abstract: Transition metal Phthalocyanines have been used as burn rate modifiers for AP-HTPB composite solid propellants. An effort has been made to investigate the effect of Cu-Co-and Fe Phthalocyanines on the burn rate of composite propellants, as also on the combustion characteristics of such propellants. The burn rate has been determined in Crawford Strand Burner at 56 kg/cm 2 pressure as also in low pressure burner setup at vacuum of 0.5 kg/cm 2 . Thermal analysis was performed using Thermo Gravimetric Analyzer (TGA), Differential Scanning Calorimeter (DSC) and heat of reaction has been measured by conventional Bomb Calorimeter. Scanning Electron Microscope (SEM) and Elemental Analyzer have been used for material characterization and possible composition of composite solid propellants. Metal Phthalocyanines have been found to influence the decomposition and to enhance the burn rate of the composite solid propellants.

Burn rate modifier

Abstract: The invention relates generally to burn rate modifiers and propellants comprising a burn rate modifier. The Invention also relates to methods of producing a propellant comprising a burn rate modifier as well as an ammunition cartridge comprising the propellant. The bum rate modifier comprises a compound of formula 1 and the propellant comprises a compound of formula 1 and an energetic material.

Multistage Mechanism of Thermal Decomposition of Hydrogen Azide

Abstract: A kinetic mechanism for combustion of hydrogen azide (HN3) comprising 61 reactions and 14 flame species (H2, H, N, NH, NH2, NNH, NH3, HN3, N3, N2H2, N2H3, N2H4, N2, and Ar) was developed and tested The CHEMKIN software was used to calculate the flame speed at a pressure of 50 torr in mixtures of HN3 with various diluents (N2 and Ar), as well as the self-ignition parameters of HN3 (temperature and pressure) at a fixed ignition delay The modeling results of the flame structure of HN3/N2 mixtures show that at a 25–100% concentration of HN3 in the mixture, the maximum temperature in the flame front is 25–940 K higher than the adiabatic temperature of the combustible mixture Analysis of the mechanism shows that burning velocity of a HN3/N2 mixture at a pressure of 50 torr is described by the Zel’dovich-Frank-Kamenetskii theory under the assumption that the burn rate controlling reaction is HN3 + M = N2 + NH + M (M = HN3) provided that its rate constant is determined at a superadiabatic flame temperature The developed mechanism can be used to describe the combustion and thermal decomposition of systems containing HN3

Visualization and Measurement of the Burning Surface of Wire-Embedded Energetic Materials, Part 1: JA2 and Pentolite

Abstract: : To increase the burning rates of minimum-smoke propellant formulations that are less sensitive than current standards, the Army is investigating gains that are achievable by embedding propellant with thermally conductive wires. The mechanisms that lead to increased burning rates in wired propellant are not fully understood; therefore, grain design optimization is a significant technical challenge. As part of an effort to gain insight into the mechanisms underlying the phenomenon, and thereby accelerate development of the technology, an experimental technique was developed that enables the burning surface of a wire-embedded strand to be visualized throughout the course of a burn rate measurement. Revealing details of the process that are hidden to standard burn rate measurement techniques, the U.S. Army Research Laboratory is developing a state-of-the-art computational fluid dynamics model for simulating the performance of rocket motors with wire-embedded propellant grains.

Controlling an internal combustion engine operated on gaseous fuel

Abstract: A method for controlling an internal combustion engine operating on at least partly gaseous fuel is disclosed. The method may include providing a desired burn rate profile corresponding to a desired operation of the internal combustion engine. The method may further include selecting first operating parameters such that an operation of the internal combustion engine with a first gas composition produces a first burn rate profile that corresponds to the desired burn rate profile. The method may also include operating the internal combustion engine with the first operating parameters using a second gas composition. The method may include determining that the second burn rate profile differs from the desired burn rate profile. In addition, the method may include adjusting an operating parameter from among the first operating parameters of the internal combustion engine to approach the desired burn rate profile.

Influence of Initial Propellant Temperature on Solid Rocket Internal Ballistics

Abstract: The influence of initial propellant temperature on solid propellant rocket motor performance is examined in the present study, with the focus primarily on predicted steady and nonsteady burning rate behavior. The present evaluation includes an examination of quasi-steady burning of a conventional composite propellant under pressure, core flow (erosive burning), and normal acceleration (say, due to motor spinning). The most direct and well-known influence of initial propellant temperature is on the pressure-dependent burning rate. The pressure-dependent burning rate, as the base burning rate, in turn influences the degree of augmentation seen under core flow and normal acceleration; in general, the lower the base rate, the higher the augmentation. The explicit presence of initial propellant temperature in various model equations for the flow- and acceleration-dependent burning components, and the corresponding effect of the initial temperature on the propellant’s burning surface temperature, can produce an...

Burning Behavior of Solid Propellants at High Pressure

Abstract: In this article, the method of the constant volume burner was used to measure the solid propellant burning rate under high pressure. The burning rate formula and the heat loss rate equation of the constant volume burner method were derived, and the effects of four factors (pressure increasing rate, burning time, ignition, and burning rate) on the heat loss of the constant volume burner during operation were carried out. Furthermore, the testing reproducibility on burning rate was analyzed. It was shown that sample size precision, moles per unit mass of propellant, and heat loss were the main factors for the accuracy of the constant volume burner method. The shorter the burning time, the faster the pressure increasing rate and the burning rate; the less the heat loss, the appropriate ignition way was to reduce heat loss ignition. Moreover, for both various burning rates of propellants, the parallel error of the test results obtained by the method was low, and the reproducibility was high. The burning rates...

Experimental investigation on combustion characteristic of PE in solid fuel ramjet

Abstract: The combustion characteristics of polyethylene( PE) in the solid fuel ramjet( SFRJ) were investigated by using a direct tube test facility.The impact of air mass flow rate and stepheight ratio on regression rate and performance were considered.Under different experimental conditions,rules for the variation of combustor pressure,after burning chamber pressure and after burning chamber temperature along with time,and the mean regression rate and the local regression rate of PE were obtained. The results show that a pressure difference exists between the chamber and the after burning chamber when the SFRJ works,and the pressure difference is about 0.01 ~ 0.02 MPa; the temperature in the after burning chamber reduces as the air mass flow rate increases; increase of the stepheight ratio helps to raise the temperature in the after burning chamber; the mean regression rate of the fuel increases as the stepheight ratio and the air mass flow rate increase,and the mean regression rate of the fuel is in a linear function relationship with the stepheight ratio and in a power function relationship with the air mass flow rate.

Simulation of the propellant combustion by plasma ignition in a closed bomb

Abstract: The principle of electrothermal chemical gun is changing high-power electrical energy into the ablation plasma. Under the effect of plasma, the combustion performance of propellant is enhanced. Generally, the experimental research of propellant combustion is carried out in a closed bomb. The propellant combustion performance can be judged by analyzing the pressure-time curve. In this paper, discharge model of plasma generator was established based on the discharge characteristics. Then the combustion model of propellant under the condition of Plasma ignition in a closed bomb is formed by the discharge model of plasma generator coupled with the geometry combustion model of propellant. The relationship between propellant burning rate enhancement and the input power is discussed. The computer program of combustion model under the condition of plasma ignition was compiled, and the calculate results consistent well with the experimental results. Simulation results show that the plasma can significantly enhance the propellant burning rate during the discharge process, and the temperature of propellant gas in the closed bomb is also increased significantly.

A One-Dimensional Global-Scaling Erosive Burning Model Informed by Blowing Wall Turbulence

Abstract: A derivation of turbulent flow parameters, combined with data from erosive burning test motors and blowing wall tests results in erosive burning model candidates useful in one-dimensional internal ballistics analysis capable of scaling across wide ranges of motor size. The real-time burn rate data comes from three test campaigns of subscale segmented solid rocket motors tested at two facilities. The flow theory admits the important effect of the blowing wall on the turbulent friction coefficient by using blowing wall data to determine the blowing wall friction coefficient. The erosive burning behavior of full-scale motors is now predicted more closely than with other recent models.

Gas generant with enhanced burn rate and higher gas yield

Abstract: The present invention relates to a gas generator with an enhanced burning rate and an increased amount of combustion gas, which is a key component of an inflator for expanding airback for alleviating the impact of a car crash. In the present invention, as a main oxidizer, copper diamine dinitrate, as a sub oxidizer, basic copper nitrate, as a main fuel, guanidine nitrate, as a burning rate enhancer, 5-aminotetrazole, as a catalyst, a metal oxide and a combustible catalyst, and other additives are used to provide a gas generator with a burning rate of 20 mm/sec or faster and an amount of combustion gas of 33 moles/kg or greater, and a combustion temperature of 2300K or less. The inner pressure of an inflator manufactured by using the gas generator is decreased to 100 bar so the weight of the inflator is remarkably decreased to 250 g from 440g or 330g, the weights of existing inflators. [Reference numerals] (AA) Example; (BB) Pressure of an existing tank A; (CC) Inner pressure; (DD) Tank pressure; (EE) Inner pressure of the present invention; (FF) Composition; (GG) Existing invention A; (HH) Present invention

Experimental study on the temperature compensation effect of plasma in a 300 ml closed bomb

Abstract: The interior ballistic performance of conventional gun is influenced by ambient temperature greatly. In the case of low ambient temperature, the chamber pressure and muzzle velocity are relatively low; and in the case of high ambient temperature, chamber pressure and velocity are higher. The reason is that the propellant combustion performance is affected by ambient temperature. The burning rate is low at low ambient temperatures, and high at high ambient temperature. The interaction of plasma and propellant can change the combustion performance of propellant, reducing or eliminating the temperature sensitivity of propellant, and this is the temperature compensation effect of plasma. In this paper, plasma ignition experiment has been carried on in a 300 ml closed bomb, and the temperatures of propellant were at −40°C, 20°C, and 50°C. Experimental results show that by regulating the electrical energy of discharge, maximum pressure, propellant burning end time and pressure-time curves are roughly the same as the propellant temperatures is −40°C and 20°C. Compared with the high temperature, the maximum pressure increase by 21 Mpa and burning end time shortened by 4.2 ms, which means that the temperature compensation effect of plasma is very significant.