Showing papers in "Combustion Science and Technology in 2012"

Feedback Control of Combustion Instabilities Using a Helmholtz Resonator with an Oscillating Volume

Abstract: A feedback control strategy is developed for mitigating combustion instabilities using a Helmholtz resonator with an oscillating volume. This is based on the fact that the frequency at which the resonator provides maximum damping can be controlled by oscillating its cavity volume. For this, two algorithms are developed. One is a real-time plane-wave decomposition algorithm; the other is a finite impulse response filter, its coefficients being optimized by the least-mean-square method but with a variable step size. The filter uses the decomposed incident wave to determine the optimum actuation signal. The performance of the control strategy, carried out with off-line system identification, is evaluated via a numerical model of an unstable combustion system with a dominant longitudinal mode. It is successfully demonstrated that the control strategy is more robust and capable of stabilizing the combustion system at a faster rate than that of conventional filters with fixed step size.

Experimental Realization of H2/Air Continuous Rotating Detonation in a Cylindrical Combustor

Abstract: Results of experimental studies on a H2/air continuous rotating detonation engine (CRDE) in an annular combustor are presented. A tangentially injected H2/O2 hotshot jet is used to ignite the engine. H2/air continuous rotating detonations are realized at a wide range of total mass flow and equivalence ratio conditions. The detonation propagation modes of all the tests can be divided into four kinds: two-wave, hybrid two/one wave, one-wave, and transient one wave. The mean propagation velocities of the two-wave and one-wave modes are in the range 1365–1476 m/s and 1606–1791 m/s, respectively. The propagation mode and velocity are influenced by both the total mass flow rate and equivalence ratio. Detonation wave propagation processes of the two-wave and one-wave modes are also observed, which further demonstrates the realization of CRDE.

Deflagration-to-Detonation Transition in Hydrogen/Air Mixtures with a Concentration Gradient

Abstract: The hazardous potential of hydrogen/air mixtures has intensively been studied assuming a perfect mixture of fuel and oxidant. However, comprehensive risk assessment studies have shown that an inhomogeneous mixture with a vertical concentration gradient is much more likely to be generated in a real accident scenario. From a safety point of view, an open question is whether established criteria such as the 7λ criterion for the determination of the deflagration-to-detonation transition (DDT) limits can be applied to inhomogeneous mixtures as well. For the experimental investigation of DDT in such mixtures an injection mechanism has been developed that produces vertical fuel concentration gradients inside a horizontal channel with large aspect ratio. The channel is equipped with obstacles to enhance flame acceleration. Photodiodes and pressure transducers measure flame and shock arrival times. Schlieren measurements are conducted to track gas mixing behind the obstacles and to track the formation of the deton...

Comparison of Different Global Combustion Mechanisms Under Hot and Diluted Oxidation Conditions

Abstract: Moderate and intensive low-oxygen dilution (MILD) combustion is a new combustion technology. It features as combustion under a hot and diluted oxidation condition. The objective of this article is to optimize global mechanisms for predicting the major species concentration of CH4 combustion under MILD condition. For this purpose, six different global combustion mechanisms, including the four-step mechanism of Jones and Lindstedt (1988), the two-step mechanism of Westbrook and Dryer (1981), and several modified versions of them, were investigated. Reference calculations were also conducted with detailed chemical kinetic mechanism GRI-Mech 3.0. The interaction between turbulence and chemistry was modeled by eddy dissipation concept (EDC). All of these global mechanisms are validated first by a fictitious plug flow reactor and then by a non-premixed turbulent jet flame of a H2/CH4 fuel mixture (Dally et al., 2002). The results show that modified the Westbrook and Dryer mechanism (WD4), which includes both CO...

Identification of the Flame Describing Function of a Premixed Swirl Flame from LES

Abstract: Thermo-acoustic characterization of gas turbine combustion systems is crucial for a successful development of new gas turbine engines to meet emission and efficiency targets. In this context, it becomes more and more necessary to predict the limit cycle amplitudes of thermo-acoustic induced combustion instabilities in order to figure out if they can be tolerated or if they are above the critical design limit and will cause damage to the engine. For the prediction of limit cycle amplitudes, the nonlinear flame response of the combustion system is needed, which is represented in this work by the flame describing function (FDF). In this article, the identification of the FDF from a large eddy simulation (LES) is validated. The test case used was a premixed atmospheric swirl flame, for which experimental data on the FDF were available. First a steady reacting LES solution was obtained and compared to experimental data. The simulation was then excited by superimposing a mono-frequency harmonic wave on the velo...

Pyrolitic and Oxidative Structures in Hot Oxidant Diluted Oxidant (HODO) MILD Combustion

Abstract: The typical reactive structure stabilized in a diffusion layer in standard conditions can be significantly modified whether injected flows are diluted and/or preheated. The flow high initial enthalpy and the low fuel and/or oxygen concentration can drastically modify the structure of the oxidative and pyrolytic region due to change of the physical and chemical kinetics respect to conventional diffusion flame. Such operative conditions are typical of MILD (Moderate or Intense Low-oxygen Dilution)combustion processes. The effect of inlet conditions on the stabilized reactive structure has been studied by analyzing the behavior of a steady, one-dimensional diffusive layer. The change of the structures of the reactive region induced by a hot oxidant and diluted oxidant flow (HODO) fed towards a fuel jet at environmental temperature was numerically analyzed by means of temperature and heat release profiles, that are key parameters to understand the main features of the reactive region. In addition, the effect ...

An Improved Method of Smoke Point Normalization

Abstract: The most widely used method of normalizing laminar smoke points from different studies has been the threshold sooting index (TSI). TSI has several drawbacks, particularly a nonphysical dependence on fuel molar mass. An improved normalization method, called normalized smoke point (NSP), is introduced here. For each fuel, NSP is a weighted average of the smoke point lengths measured by different studies. NSP eliminates the major TSI drawbacks. NSP values were determined for 112 hydrocarbons by averaging 256 smoke point measurements from 12 past studies. This allows for the most extensive evaluation to date of the effects of fuel type on the smoke points of hydrocarbon diffusion flames. Hydrocarbon sooting propensity generally increases with increasing fuel carbon/hydrogen atom ratio. For n-alkanes, sooting propensity increases with carbon number, however it generally decreases with carbon number for alkenes and 1-alkynes. Sooting propensity generally increases according to alkanes < alkenes < 1-alkynes < ar...

Conditional Moment Closure for Turbulent Premixed Flames

Abstract: The conditional moment closure (CMC) is a well-established method for the modelling of turbulent non-premixed combustion, but its suitability when applied to turbulent premixed combustion is still a topic of research. Recently, the method has been improved and implemented with encouraging results. The method is used as a closure for the mean reaction rate, which includes the averaged species transport equation. Unlike the flamelet-based methods, its transport equations are derived with no explicit assumptions about the effect of turbulent vortices on the flame front structure. Hence, the CMC is expected to capture the finite-rate chemistry effects and thus predicts species with slow chemical time scales more efficiently. Most importantly, the method would apply to all regimes in turbulent premixed combustion. In this chapter, the method is described comprehensively along with its numerical implementation and some selected results.

An Experimental and Kinetic Modeling Study of Pyrolysis and Combustion of Acetone–Butanol–Ethanol (ABE) Mixtures

Abstract: The excellent fuel characteristics of bio-butanol are responsible for the renewed interest in the acetone–butanol–ethanol (ABE) fermentation process and the combustion and pyrolysis behavior of mixtures of acetone, butanol, and ethanol. Therefore, in this work, a detailed mechanism for the pyrolysis and oxidation of ABE is presented containing ∼350 species and more than 10,000 reactions. The mechanism is validated against newly acquired and published pyrolysis data for the ABE-mixture and the respective components. Excellent agreement is obtained between measured and simulated product yields as a function of the conversion. Laminar flame speed computations of alcohols and ABE complement the detailed comparisons of the pyrolysis data and allow for further validation of the combustion behavior of bio-butanol and its mixtures. Supplemental materials are available for this article. Go to the publisher's online edition of Combustion Science and Technology to view the free supplemental file.

Flow Blurring Atomization for Low-Emission Combustion of Liquid Biofuels

Abstract: In this study, clean combustion of straight vegetable oil (VO) is achieved by utilizing a novel flow blurring (FB) fuel injector with superior atomization characteristics. Experiments are conducted in an atmospheric pressure combustor using three different fuels: straight VO, which is fully-refined soybean oil, biodiesel produced from soybean VO, and No. 2 diesel. Combustion performance is assessed by comparing flame images, emissions profiles at the combustor exit plane, and pressure drop in fuel and atomizing air lines. Results show that the FB atomizer can create clean burning spray flames of straight VO without preprocessing and/or preheating. The FB injector produces sprays with smaller diameter fuel droplets to promote combustion in the premixed mode. All fuels resulted in similar CO emissions, while biodiesel flames had the lowest NOX emissions. Pressure drop in the fuel and atomizing air lines was independent of the fuel.

A Presumed Joint pdf Model for Turbulent Combustion with Varying Equivalence Ratio

Abstract: Modeling of the joint probability density function of the mixture fraction and progress variable with a given covariance value is studied. This modeling is validated using experimental and direct numerical simulation (DNS) data. A very good agreement with experimental data of turbulent stratified flames and DNS data of a lifted hydrogen jet flame is obtained. The effect of using this joint pdf modeling to calculate the mean reaction rate with a flamelet closure in Reynolds averaged Navier–Stokes (RANS) calculation of stratified flames is studied. The covariance effect is observed to be large within the flame brush. The results obtained from RANS calculations using this modeling for stratified jet- and rod-stabilized V-flames are discussed and compared to the measurements as a posteriori validation for the joint probability density function model with the flamelet closure. The agreement between the computed and measured values of flame and turbulence quantities is found to be good.

Spray combustion characteristics of palm biodiesel

Abstract: The potential of palm methyl esters (PME) as an alternative fuel for gas turbines is investigated using a swirl burner. The main air flow is preheated to 623 K, and a swirling spray flame is established at atmospheric pressure. The spray combustion characteristics of PME are compared to diesel and Jet-A1 fuel under the same burner power output of 6 kW. Investigation of the fuel atomizing characteristics using phase Doppler anemometry (PDA) shows that most droplets are distributed within the flame reaction zone region. PME droplets exhibit higher Sautermean diameter (SMD) values than baseline fuels, and thus higher droplet penetration length and longer evaporation timescales. The PME swirl flame presents a different visible flame reaction zone while combusting with low luminosity and produces no soot. NOx emissions per unit mass of fuel and per unit energy are reduced by using PME relative to those of conventional fuels.

Attrition of Limestone During Fluidized Bed Calcium Looping Cycles for CO2 Capture

Abstract: Attrition of a limestone during calcium looping cycles for CO2 capture was studied in a lab-scale fluidized bed apparatus Batch experiments under alternating calcination–carbonation conditions were carried out to investigate the effect of chemical reactions and temperature changes on the attrition propensity of the sorbent particles Attrition processes were characterized by following the modifications of bed sorbent particle size distribution and the elutriation rates of fines throughout conversion over repeated cycles Different bed temperatures and CO2 inlet concentrations during the calcination stage were tested in the experiments Results show that relatively large attrition rates were experienced by the sorbent particles only during the first cycle From the second cycle on the attrition rate progressively declines, also during the calcination stage where the softer CaO is produced It is inferred that the combined chemical-thermal treatment affects the particle structure making it increasingly har

A Detailed Kinetic Study of Pyrolysis and Oxidation of Glycerol (Propane-1,2,3-triol)

Abstract: Glycerol (propane-1,2,3-triol) has been an object of interest in recent years as a byproduct in the production of biodiesel, a parental molecule for syngas production, and a representative compound of the tar components derived from the carbohydrate fraction of biomass. Kinetic models describing the thermal degradation of glycerol toward lighter hydrocarbons and noncondensable gases are considered beneficial to an effective implementation of processes for its valorization. The aim of this work is to analyze and discuss the primary propagation reactions of glycerol, together with the ones of acetol (1-hydroxypropan-2-one) and 3-hydroxypropanal (the primary products of glycerol). This kinetic model is then evaluated in comparison with three independent sets of experimental measurements. The first one refers to pyrolysis experiments at intermediate temperatures, while syngas is obtained from glycerol pyrolysis at higher temperatures in the second one. The model is also tested against experiments on combustio...

Experimental Studies on the Influence of Diesel Engine Operating Parameters on Properties of Emitted Soot Particles

Abstract: Physical and chemical properties of emitted soot particles are influenced by diesel engine operating parameters. In order to find correlations between the in-cylinder processes of combustion and the engine-out properties of soot particles, parameter studies were carried out on a modern light duty production diesel engine (turbo direct injection, TDI) and an optically accessed single cylinder diesel engine (single cylinder). Several techniques have been combined to analyze the combustion process as well as the emitted particles. The size of emitted soot particles of the TDI engine has been determined by a scanning mobility particle sizer (SMPS), and soot samples have been analyzed by a high-resolution transmission electron microscope (HR-TEM) and by thermogravimetry (TG). In addition, the internal combustion in an optically accessed single cylinder engine has been observed by time resolved spectroscopy as well as OH*- and C2-imaging. It turns out that in both cases, increasing injection pressure leads to a...

NOx Formation in H2-CH4 Blended Flame Under MILD Conditions

Abstract: In this article, NO production mechanisms for CH4-H2 combustion under MILD (moderate or intense low-oxygen dilution) conditions are studied using CDF and also zero-dimensional well stirred reactor (WSR) analysis. A H2/CH4 jet into a heated and diluted coflow is modeled in CFD analysis. The RANS equations with modified k − ϵ equations are solved in an axisymmetric 2D computational domain. The GRI2.11 full mechanism is considered to represent the chemical reactions. The effects of oxidizer oxygen concentration, fuel hydrogen content, and fuel jet Reynolds number are studied on NO formation reactions. Results show that the measurements are predicted with an acceptable accuracy. The NNH and N2O routes are the most important pathways in NO formation under MILD conditions. An increase in oxidizer O2concentration or decrease in fuel hydrogen content addressesthe decrease in importance of the mentioned NO formation routes.

Burning Behavior of Vertical Matchstick Arrays

Abstract: Vertical arrays of horizontally protruding wood matchsticks, 0.25 cm in diameter and 1.91 cm long, arranged from one to five matches across were used to investigate the influence of the spacing of discrete fuel elements on rates of upward flame spread. Vertical spacing's between the matchsticks in the array (0.0, 0.6, 0.8, 1.0, 1.2, and 1.4 cm) were used to reveal the influence of separation distance on rates of upward flame spread, defined as progression of the ignition front, time to burnout, and mass-loss rates. Advancement of the ignition front was found to vary linearly with time for the 0.0 cm spacing, while reaching nearly a t1.7 advancement with time for the furthest-spaced arrays. Rates of upward flame spread were found to increase dramatically for spacings between 0 cm and 0.8 cm and experienced only a slight increase thereafter. Based on these observations, the influence of convective heating was hypothesized to dominate this spread mechanism, and predictions of ignition times were developed us...

Effect of High-Amplitude Forcing on Turbulent Combustion Intensity and Vortex Core Precession in a Strongly Swirling Lifted Propane/Air Flame

Abstract: The present work reports stereoscopic particle image velocimetry (PIV) measurements in a strongly swirling nonreacting jet and partially premixed lifted flame. The spatial distributions of the average velocity and components of turbulent kinetic energy were calculated from the measured ensembles of the instantaneous velocity fields. A pronounced bubble-type vortex breakdown was observed for the studied flows. Based on proper orthogonal decomposition (POD) of the PIV data and on estimates of velocity fluctuation spectra by a laser Doppler velocimetry (LDV) probe, it was concluded that the combustion did not fundamentally affect the type of coherent structures in the strongly swirling flow: a pair of secondary helical vortices was induced by a precessing vortex core in both cases. Because a strongly swirling jet flow is usually insensitive to weak forcing, strong perturbations were superimposed on the flow bulk velocity to force the formation of ring-like vortices in the flow and to investigate the possible...

Shock Tube Study of the Influence of NOx on the Ignition Delay Times of Natural Gas at High Pressure

Abstract: The ignition delay times of diluted reference gas/O2/NO2/Ar mixtures (Φ = 0.25, 0.5, and 1.0, dilution 1:2 and 1:5, [NO2] = 20–250 ppm) were determined in a high-pressure shock tube. The temperature range was 1000 K ≤ T ≤ 1700 K at pressures of about 16 bar. The addition of NO2 leads to a significant reduction of the ignition delay times. This reduction increases with decreasing equivalence ratio. The effect of NO2 is well predicted by the NOx chemistry of different published reaction mechanisms. The differences in the predictions of the ignition delay times using a common hydrocarbon reaction mechanism and NOx subsystems of four published reaction mechanisms are negligible. Supplemental materials are available for this article. Go to the publisher's online edition of Combustion Science and Technology to view the free supplemental file.

Gasification of Waste Biomass Chars by Carbon Dioxide via Thermogravimetry—Effect of Catalysts

Abstract: The effect of catalyst addition on thermal conversion characteristics and kinetics of waste biomass chars was investigated. The experiments were performed in a thermogravimetric analysis system, at non-isothermal heating conditions, under a carbon dioxide atmosphere. Reaction rates were determined by a power law model. The bulk of char gasification process occurred between 800 °C and 950 °C. Addition of alkali salts improved char conversion and increased the reactivity of the samples by lowering the reaction temperature. Peak values were reduced by 4 to 138 °C. The catalytic activity was enhanced when 10% Na2CO3, 10% CaCO3, and 10% Li2CO3 were used during the gasification of municipal solid wastes, sewage sludge, and waste paper, respectively. Alkali carbonates and especially binary mixtures of them increased the reactivity of the fuels by significantly reducing the activation energy. Activation energies ranged from 180 to 370 kJ/mol without catalysts, whereas from 82 to 353 kJ/mol with catalyst addition.

A Study of Interaction of Clouds of Inert Particles with Detonation in Gases

Abstract: Interaction of a cloud of inert particles with a detonation in gaseous mixture is simulated and studied. The structure of both two- and three-dimensional detonations are modeled using a simplified chemical model with Arrhenius kinetics. Particle clouds are characterized based on the initial solid phase volume fraction ( ) of the particle cloud and the initial cloud length (L 0). The results show that the minimum average detonation speed decreases with increase in at fixed L 0, and with an increase in L 0 at fixed . The detonation propagation through inert particle clouds is observed to fall into three regimes based on and L 0. In the first regime, the detonation speed is suppressed, but the reaction zone and leading shock remain coupled, and the triple points are nearly unaffected. In the second regime, the detonation is temporarily quenched but restored as the particle cloud moves away from the detonation front. In the third regime, the detonation is quenched permanently or at least does not get restored...

Experimental Study of the Combustion Regimes Occurring in a Laboratory Combustor

Abstract: This article examines the combustion regimes occurring in a small-scale laboratory cylindrical combustor, in which the burner and the exhaust port are mounted at the top end of the combustion chamber Flue-gas composition data and hydroxyl radical chemiluminescence (OH*) imaging are presented as a function of the air inlet preheat temperature and excess air coefficient, which in the present configuration implies also changes in the air inlet velocity For three of these combustor operating conditions, detailed in-combustor measurements of temperature and of O2, CO2, CO, unburned hydrocarbons, and NOx concentrations are also reported The flue-gas data reveal that, for a given air inlet preheat temperature, the air inlet velocity has an important impact on the NOx emissions, which decrease as the air inlet velocity increases Furthermore, as the air inlet temperature increases, the burner is able to operate with higher excess air coefficients For a given air inlet temperature, the combustion regime in the

Influence of Residence and Scalar Mixing Time Scales in Non-Premixed Combustion in Supersonic Turbulent Flows

Abstract: In high Mach number turbulent reactive flows, spontaneous ignition appears as a key ingredient for the stabilization of combustion. In our previous analyses devoted to such conditions, chemical kinetics as well as associated finite rate chemistry effects have already received considerable attention. However, the representation of flow time scales, such as residence and mixing time scales, still requires further work. The present modeling study is devoted to this peculiar point. Hence, a transport equation for the quantity of residence time is considered to evaluate the mean residence time associated with both oxidizer and fuel injection streams, while a modeled transport equation for the mean scalar dissipation rate (SDR) is considered to estimate the scalar mixing time scale. This allows us to improve the description of turbulent mixing, including the large-scale engulfment processes through the consideration of the residence time scale, as well as the small-scale molecular mixing processes, the intensit...

Experimental Investigations on Lifted Spray Flames for a Range of Coflow Conditions

Abstract: In the present work, the effect of coflow conditions and fuel injection pressure on flame lift-off height, flame stabilization, and flame fluctuations in liquid spray flames has been experimentally investigated for three different coflow cases: (1) cold flow, (2) cold flow with nitrogen dilution, and (3) preheated and diluted coflow. It has been observed that the flame lift-off height is proportional to the coflow velocity and inversely proportional to the injection pressure. The dependence of flame lift-off height on the fuel mass flow rate has been investigated using fuel injectors of identical spray cone angles, mean droplet diameter, and different fuel mass flow rates. It has been observed that the flame lift-off height decreases with an increase in the fuel flow rate. Mean droplet diameter (SMD) has a dominating effect on flame lift-off height and flame stability. An increase in the SMD increases the fluctuations in the stabilization point of the lifted flame and vice versa. For N2 dilution cas, (21%...

Gas Compression Moderates Flame Acceleration in Deflagration-to-Detonation Transition

Abstract: The effect of gas compression at the developed stages of flame acceleration in smooth-wall and obstructed channels is studied. We demonstrate analytically that gas compression moderates the acceler ...

Modeling DME Addition Effects to Fuel on PAH and Soot in Laminar Coflow Ethylene/Air Diffusion Flames Using Two PAH Mechanisms

Abstract: Effects of dimethyl ether (DME) addition to fuel on polycyclic aromatic hydrocarbons (PAH) and soot formation in laminar coflow ethylene/air diffusion flames were revisited numerically. Calculations were conducted using two gas-phase reaction mechanisms with PAH formation and growth: one is the C2 chemistry of the Appel, Bockhorn, and Frenklach (ABF) mechanism with PAH growth up to A4 (pyrene); the other is also a C2 chemistrymechanism newly developed at the German Space Center (DLR) with PAH growth up to A5 (corannulene). Soot was modeled based on the assumptions that soot inception is due to the collision of two pyrene molecules, and soot surface growth and oxidation follow a hydrogen abstraction carbon addition (HACA) sequence. The DLR mechanism predicted much higher concentrations of pyrene than the ABF mechanism. A much smaller value of α in the surface growth model associated with the DLR mechanism must be used to predict the correct peak soot volume fraction. Both reaction mechanisms are capable of...

On Weak Effect of Particle Size on Its Burn Time for Micron-Sized Aluminum Powders

Abstract: This article aims to verify and validate recent experiments with single Al particles demonstrating a weak effect of particle size on its burn time. Individual particles were fed through two laser beams: a low-power laser to in-situ measure particle size using light scattering, and a CO2 laser for ignition. The sensitivity and dynamic ranges of photo-detectors were selected to capture emission from particles in the size range of 1–10 µm. The data processing method was modified. Measured color temperatures for individual particles were supported by spectroscopic measurements from multiple burning particles. The results confirmed that the burn time, t, as a function of the particle diameter, D, can be approximately described as t ∼ D n with n < 1, which is a much weaker function than that expected based on classic droplet combustion models. Experimental data further confirmed that Al particles finer than 10 µm burn in room temperature air, achieving high combustion temperatures and producing significant mole...

Spectral Analysis in the UV-Visible Range for Revealing the Molecular Form of Combustion-Generated Carbonaceous Species

Abstract: A method of UV-visible spectra analysis was developed for investigating the relationship between the optical properties and the complex composition/structure of carbonaceous species formed in a sooting premixed ethylene flame. The UV-visible spectra were measured on carbonaceous species, caught on quartz plates inserted along the flame and recovered by solvent treatment. The contribution and the structure of components in a very wide molecular weight range, from 200 to 1E11 u, were evaluated by size exclusion chromatography coupled with on-line UV-visible spectroscopy of the dichloromethane-soluble and dry soot fractions. The optical band gap and the UV peak position of each MW-segregated fraction were evaluated by means of a spectral deconvolution procedure, to get details on the carbon network structure in terms of sp2 and sp3 sites and size and stacking of the aromatic units. The species included in the 1E8-1E11 u range underwent graphitization/growth reactions during the formation process of carbonace...

Scale-Up Effects of Nanoparticle Production on the Burning Rate of Composite Propellant

Abstract: The use of catalytic nanoparticle additives in composite solid propellant as burning rate modifiers has received much research attention in recent years, and as the widespread application of nanoparticles becomes more practical, scale-up processing and testing will be required. This article investigates the potential benefits of various additive processing methods and their effects on the burning rate of propellant consisting of ammonium perchlorate and hydroxyl terminated polybutadiene. Titania was investigated herein, but many of the results should apply to any metal oxide catalyst. Depending on how the additive was processed, it was seen to be both an effective and ineffective burning rate modifier. The ideal processing method was determined, leading to a better understanding of how the additive interacts with the propellant. The physical properties of the additive agglomerations were found to be a link between the additive processing and its effectiveness. Specifically, sintering of the additive agglo...

Study on the Burning Characteristics of AP/Al/HTPB Composite Solid Propellant Containing Nano-Sized Ferric Oxide Powder

Abstract: This study mainly explores the burning characteristics of AP/Al/HTPB composite solid propellant containing nano-sized ferric oxide (Fe2O3) powder. First, the appropriate dispersed technique is applied to prepare the propellant samples containing the ferric oxide (micro-sized and/or nano-sized) powder, and then the scanning electron microscope (SEM) is used to observe the dispersed effect of ferric oxide powder in the propellant samples. Afterward, the reaction characteristics of the propellant samples are measured using differential scanning calorimeter (DSC), and the difference between their properties is analyzed. Finally, the propellant samples are processed to be used for various experiments, and the window bomb (WB), burning rate meter (BRM), and quenched particle collection bomb (QPCB) are used to study the burning characteristics. The burning phenomena are also analyzed by means of the combustion observation technique. Furthermore, the pull-testing machine is conducted to evaluate the mechanical pr...