Showing papers on "Burn rate (chemistry) published in 2016"

Schlieren and OH* chemiluminescence imaging of combustion in a turbulent boundary layer over a solid fuel

Abstract: Combustion in a turbulent boundary layer over a solid fuel is studied using simultaneous schlieren and OH* chemiluminescence imaging. The flow configuration is representative of a hybrid rocket motor combustor. Six different hydrocarbon fuels, including both classical hybrid rocket fuels and a high regression rate fuel (paraffin wax), are burned in an undiluted oxygen free-stream at pressures ranging from atmospheric to 1524.2 kPa (221.1 psi). A detailed explanation of methods for registering the schlieren and OH* chemiluminescence images to one another is presented, and additionally, details of the routines used to extract flow features of interest (like the boundary layer height and flame location) are provided. At atmospheric pressure, the boundary layer location is consistent between all fuels; however, the flame location varies for each fuel. The flame zone appears to be smoothly distributed over the fuel surface at atmospheric pressure. At elevated pressures and correspondingly increased Dahmkohler number (but at constant Reynolds number), flame morphology is markedly different, exhibiting large rollers in a shear layer above the fuel grain and finer structures in the flame. The chemiluminescence intensity is found to be roughly proportional to the fuel burn rate at both atmospheric and elevated chamber pressures.

Solid propellant combustion in a high-velocity cross-flow of gases (review)

Abstract: Combustion of solid propellants in rocket propulsion systems usually occurs in an intense cross-flow of combustion products (solid rocket motor), gaseous oxidizer (hybrid rocket motor) or air (ramjet and air-breathing engines). This leads to the so-called erosive burning effects, resulting in a change in the burning law under the influence of the gas flow. The main approaches to modeling the erosive burning of solid propellants in a high-velocity cross-flow of gases are considered. Methods for the criterial description of the results of experimental studies of the erosive burning of solid propellants under transonic and supersonic flow conditions are analyzed.

Assessment of the Burning Rate of Liquid Fuels in Confined and Mechanically-Ventilated Compartments using a Well-Stirred Reactor Approach

Abstract: The objective of this work is to provide a ‘support tool’ to assess the burning rate of a pool fire in a well-confined and mechanically-ventilated room using a single-zone model based on conservation equations for mass, energy and oxygen concentration. Such configurations are particularly relevant for nuclear facilities where compartments are generally sealed from one another and connected through a ventilation network. The burning rates are substantially affected by the dynamic interaction between the fuel mass loss rate and the rate of air supplied by mechanical ventilation. The fuel mass loss rate is controlled by (i) the amount of oxygen available in the room (i.e. vitiation oxygen effect) and (ii) the thermal enhancement via radiative feedback from the hot gas to the fuel surface. The steady-state burning rate is determined by the ‘interplay’ and balance between the limiting effect of oxygen vitiation and the enhancing effect of radiative feedback. An extensive sensitivity study over a wide range of fuel areas and mechanical ventilation rates shows that a maximum burning rate may be obtained. For the studied HTP (Hydrogenated Tetra-Propylene) pool fires, the maximum burning rate is up to 1.75 times the burning rate in open air conditions.

Hybrid propulsion in-situ resource utilization test facility results for performance characterization

Abstract: Hybrid propulsion presents a promising alternative to conventional systems for in-space propulsion applications using In-Situ Propellant Production (ISPP). A hybrid propulsion test facility has been built at the NASA Jet Propulsion Laboratory (JPL) with the capability of evaluating ISPP oxidizers (gaseous mixtures of O2 and CO2) and modifying fuel type and chamber geometry. This work is the result of a continuing e ort at JPL to characterize the burn characteristics and performance of different propellant combinations and motor configurations in order to re ne and support preliminary designs. Twelve tests using gaseous oxygen and two paraffin based fuels (Black Paraffin and SP1X) from the 2015 campaign are presented. Different reduction techniques are compared in an e ort to determine the uncertainty associated with deriving a regression rate law and evaluating c* efficiency with the collected data.Hybrid motors are mechanically and chemically simple propulsion systems that have the potential forlong-term storability with low gross mass. The oxidizer (such as gaseous O2) can be produced in-situ,signicantly reducing the landed mass. The solid, inert fuel is stored in the combustion chamber in its most dense state, further reducing the total structural mass and volume. Considerable eorts have been focusedon ISPP for Environmental Control and Life Support Systems (ECLSS) and human exploration of Mars.At optimum oxidizer to fuel ratio (O/F), about 70% of the total propellant mass could be produced in-situ.Paran based fuels exhibit a fast regression rate behavior due to the formation of a thin liquid layer on thefuel surface.1 A high burn rate is necessary in order to reach a medium to high thrust range. In order toachieve an O/F ratio close to optimum performance (between 2.1 and 2.7 for the O2/Paran combination),the fuel mass ow needs to be suciently large compared to the oxidizer ow. The slow regression rateof classical hybrid rocket fuels leads to long fuel grain designs or complicated multi-port structures. Singleport, high regression rate fuels have the potential to reduce residual propellant mass and have a grainlength to diameter ratio (L/D) more favorable for packaging. However, hybrid motors remain at a fairly lowTechnology Readiness Level (TRL), and solutions to accurately measure and increase performance are stilllacking, especially for small-scale motors that are constrained to tight packaging.A total of 12 hotres were performed and analyzed in this campaign. All of these tests were conductedat pressures above the critical pressure of paran wax, approximately 6.7 bar (97 psi).2 Three dierentmotor congurations were explored while conserving a single cylindrical port fuel grain. Additionally, sincethrottling is a crucial advantage of hybrid rocket propulsion systems, low oxidizer mass ows (60 - 100 g/s)and uxes (5 - 30 g/cm2/s) were investigated to determine the performance impact in this regime.

Emulation and Calculation of the Burning Surface of 3D Grains of Partially Cut Multi‐Perforated Stick Propellant using the Level Set Method

Abstract: In order to calculate the burnt mass fraction of complex three-dimensional (3D) propellant grains to meet the requirements of interior ballistic modelling; the level set method is introduced to emulate and calculate the burning surface area of partially cut 7-perforated propellant. The surface evolution and simulation of a 3D grain of partially cut 7-perforated propellant are divided into two parts: the grain configuration initialization and the level set calculation of the propellant regression process. Parallel layer burning is assumed so that the burning surface regresses layer by layer in a direction normal to the surface until the grain is burnt completely. As the burnt mass fraction increases, the remaining propellant volume decreases gradually. The level set method easily simulates the slivering process for complex grain geometries. In this way, the burnt mass fraction of partially cut 7-perforated propellant grain can be calculated by the level set method for the entire combustion process. Results show that the level set method is suitable to capture the burning surface for each burning step and its related parameters, such as the burning area, the remaining propellant volume and burnt mass fraction. More importantly, the level set method gives a possible solution to the coupling of grain combustion with the internal fluid simulation by the pressure and velocity. It is impossible for geometry-based methods to integrate the internal fluid parameters in an interior ballistic model. Also, the level set method will benefit substantially the grain design and lead to improved internal ballistic performance.

Negative erosion effect and the emergence of unstable combustion. 2. numerical simulation

Abstract: This paper describes the numerical simulation of combustion with the manifestation of the Vilyunov–Dvoryashin effect that comes down to reduction of the burning rate in the case of blowing of gaseous combustion products past the propellant gasification surface. The cases of endothermic and exothermic reactions of gasification of the solid propellant are considered. The Vilyunov–Dvoryashin effect can terminate combustion even before the erosion coefficient reaches a minimum value of 0.61. Self-oscillating combustion may also occur. The simulation of propellant combustion similar in its properties to the propellant N shows qualitative agreement between the theoretical and experimental results. However, it also reveals the need for more accurate data with regard to performance conditions and experimental results. The existing models of solid-propellant combustion require significant updates as well.

Propellant charge or grain

Abstract: The invention is directed to a propellant charge, to a method of preparing a propellant charge, and to uses of the propellant charge. The propellant charge or grain of the invention comprises two or more energetic materials with different linear burn rate, wherein the two or more energetic materials are distributed within the charge or grain such that two perpendicular cross-sections of said propellant charge or grain have at least two linear burn rate gradients in non-parallel directions, wherein said propellant charge or grain is layered with layers having a layer thickness in the range of 1-10 000 μm, wherein, if the propellant charge or grain has a longitudinal axis, at least one of said perpendicular cross-sections is along said longitudinal axis, and wherein said propellant charge or grain further comprises one or more perforations.

Burning Rate Studies: Potassium-Doped Ammonium Perchlorate with Other Burn-Rate Modifiers

Abstract: Iron oxide and copper chromite have been used as burn-rate modifiers of composite solid propellants. In recent times, studies have been reported on potassium-doped ammonium perchlorate and on dry activated charcoal. These have shown an increase in composite solid propellant burning rates. The studies on composite solid propellants using dry activated charcoal have also shown a reduction in the burn-rate pressure index for a composite solid propellant. With this knowledge, experiments are conducted to develop compositions that result in both high burning rates and low burn-rate pressure index of the propellant. In addition to these, the study also reports propellants with dual burn-rate pressure index. The change in the burn-rate pressure index is from 0.2 to 0.65 in one of the propellants. These could be very useful in that the same grain can act as boost and sustain grain depending on the combustion chamber pressure. With the addition of different burn-rate modifiers, the pressure at which the change in ...

Effect of Nano Combustion Modifier on Combustion Properties of DB and CMDB-propellant

Abstract: In order to investigate the effects of several nano combustion modifiers (nm-DPT, nm-CB and nm-Al) on the combustion properties of DB/Al-CMDB/RDX-CMDB propellants, the propellant samples were prepared through a solventless extrusion technique. The burning rates of propellants were measured by the strand burner method. The results showed that the nm-DPT enabled a plateau burning effect to appear for the Al-CMDB propellant in the pressure range of 8~22MPa, and the burning rate at 10MPa to exceed 29mm/s. The additional nm-CB powder increased the burning rates of the propellant, and the propellant burning rate at 10MPa exceeded 35mm/s. The nm-DPT enabled a plateau burning effect to appear for the RDX-CMDB propellant in the pressure range of 8~22MPa and a mesa effect in the pressure range of 12~22MPa, and the burning rate at 10MPa to exceeded 28mm/s. The additional nm-CB increased the burning rate of the propellant, the burning rate at 10MPa exceeded 30mm/s and the pressure exponent in the pressure of 16~22MPa was -0.10.

Development of Strand Burner Test by Using Aluminized AP/HTPB

Abstract: One of the key factors that play an important role in the performance of a solid propellant rocket is dependent on its burning rate. A strand burner is a type of apparatus used to measure the propellant burning rate at elevated pressure. This study investigates the relation between burning rates of aluminized ammonium perchlorate at low pressure. Chamber pressure was varied from 1 atm, 3 atm, 5 atm and 7 atm. This study shows that propellant burning rate is about 50%-62% higher when the burn rate test is conducted at atmospheric condition compared to when it is done in inert gas. The investigation’s results also revealed an increasing propellant burning rate when the chamber pressure is increased. In conclusion, the burning condition and chamber pressure influences the propellant burning rate.

Single burn rate solid fuel heating appliance with managed airflow

Abstract: A single combustion chamber, single burn rate solid fuel combustion heating appliance (e.g., a wood stove) is provided. The heating appliance includes a firebox having a top and a side and a first secondary air manifold. The first secondary air manifold extends longitudinally within the firebox proximate the top and the side of the firebox. The first secondary air manifold has a plurality of air orifices configured to provide secondary air to a burn chamber of the heating appliance.

Characteristics of the Biodiesel Palm Oil Methyl Ester Pool Fire

Abstract: The characteristics of biodiesel pool fires with palm oil methyl ester concentrations of 7% by volume in various pan diameter sizes (0.05 m, 0.10 m and 0.15 m) were studied. Initially, biodiesel was heated on a hot plate to increase the temperature close to the flash point temperature. Later fuel was ignited and stable pool fire formed. Flame temperature along the centerline pool fire from flame base to flame tip were measured. Flame temperature shows that the temperature at flame base is higher than that the flames tip. This is due to the complete burning occurs near flame base and at flame tip incomplete burning exists. Incomplete burning produces yellow flame appearance. Moreover, the mass burn rate varies linearly with pan size. Small diameter pan produces low mass burn rate compared to the large diameter pan. Low and high mass burn rate contributes to the flame height. Flame with higher mass burn rate is longer than that the low mass burn rate. Thus, the characteristic of the biodiesel palm oil methyl ester is successfully studied in the present study.

Propellant Grain with Maximum Combustion Efficiency of Metal

Abstract: This paper reports on the ways of allocating the metal particles in the propellant grain of tube cross-sectional type to provide maximum combustion efficiency of metal. Two-dimensional flow field and the burning rate law govern a transport of the burning metal particles. The analytical correlation for the optimum allocation of metal particles in the case-bounded propellant grain of tube cross-sectional type under the assumption of equilibrium two-phase flow is deduced.

The Research on Transient Burning Rate of Solid Propellant by Digital Image Processing

Abstract: In order to obtain the burn rate of the solid propellant that is the important parameter of transient burning, the new method named digital image processing is presented. In the article , the principle of digital image processing is analysed; The burning face of the sample in the each time is located according the image and the coordinates of the burning face is obtained. In experiment the transient burn rate is measured by digital image processing and the accuracy is acceptable.

Limits of Stable Combustion in an Engine of Ultra-Small Spacecrafts

Abstract: Using the analytical and numerical methods, an analysis of low-frequency stability of combustion in a micro-thruster rocket of solid propellant under the condition of a loss of heat from the combustion zone is conducted. The problem of stability of the engine is solved by applying the phenomenological T0*-theory. In a micro-thruster rocket, the domain of stable combustion becomes much narrower, due to occurrence of strong 0-instability, i.e. the exponential grow of perturbations with time. Nevertheless, there is a range of parameters, characterizing the laws of propellant combustion for which the sustained combustion may be possible.

Electrode ignition and control of electrically operated propellants

Abstract: Electrical ignition of electrically operated propellant in a gas generation system provides an ignition condition at an ignition surface between a pair of electrodes that satisfies three criteria of a current density J that exhibits a decreasing gradient along an axis normal to an ignition surface, is substantially constant across the ignition surface and exceeds an ignition threshold at the ignition surface. These criteria may be satisfied by one or more of an angled electrode configuration, a segmented electrode configuration or an additive to the electrically operated propellant that modifies its conductivity. These configurations improve burn rate control and consumption of the available propellant and are scalable to greater propellant mass to support larger gas generation systems.

Correlation of parameters in the burning rate law and its influence on intraballistic characteristics of a rocket motor

Abstract: Experimental data demonstrating the correlation of parameters in the power-law dependence of the burning rate of composite solid propellants on pressure are reported. The reasons for changes in the burning rate due to changes in propellant mixing conditions are discussed. The deviation of the pressure in the combustor of a solid-propellant rocket motor is analyzed with due allowance for the correlation of parameters in the burning rate law. It is shown that the relative deviation of the burning rate depends on pressure at which propellant combustion occurs. Moreover, for each propellant, there exists a pressure level at which the burning rate deviation is theoretically equal to zero, regardless of the differences in propellant compositions and properties.

Integrated model of a composite propellant rocket

Abstract: The combustion of composite solid propellants was investigated and an available numerical model was improved for taking into account the change of pressure, when the process occurs in a confined environment, as inside a rocket. The pressure increase upon ignition is correctly described by the improved model for both sandwich and dispersed particles propellants. In the latter case, self-induced fluctuations in the pressure and in all other computed variables occur, as consequence of the periodic rise and depletion of oxidizer particles from the binder matrix. The comparison with the results of the constant pressure model shows a different fluctuating profile of gas velocity, with a possible second order effect induced by the pressure fluctuations.

Comparison of Predictive Gasoline Combustion Models Using GT-Power

Abstract: With rising fuel prices and stringent emission regulations, OEMs are constantly working on improving the performance, fuel efficiency and reducing emissions of the internal combustion engines Gas exchange simulation tools plays a very important role in the development of new concepts Simulation tools helps to reduce the lead time significantly in developing new concepts The engine performance is dependent on the combustion efficiency which is analysed through burn rate But measuring burn rate during the combustion is a difficult task One of the major tool developers Gamma Technologies have developed a predictive combustion model which predicts the burn rate using the cylinder pressure Calibration of the models is important for obtaining reliable results Volvo Car Corporation (VCC) use FKFS combustion model for the development of the gasoline engines Using a different combustion system requires recalibration of the combustion model to develop new concepts The aim of the thesis is to calibrate and validate the two predictive combustion models, SI Turb and FKFS in GT-Power and comparison of the models in order to assist future development of Gasoline engines at VCC Predicting capabilities of the two calibrated combustion models is evaluated by its ability to predict the main operating parameters such as IMEP, Peak pressure, CA at 50% burn fraction and Ignition delay Calibration of the model is done against the test data obtained from a single cylinder test rig and the data was validated for different errors before using it for calibration The predicting capabilities for FKFS combustion model is good for the complete engine map, whereas SITurb combustion model predicts well only for the calibrated range

Control of predefined diesel combustion processes by a burn-rate model

Abstract: The interaction between air-path and injection system is of great importance for the future engine control concepts. Currently, some of these interactions like reduction of the injection quantity at the smoke limit are considered. However, a physically-based consideration of the real effects of the intake air states like temperature, pressure, and composition under transient engine operating conditions should be more developed.