Showing papers on "Burn rate (chemistry) published in 2017"

The consideration of the turbulence influence on the gas explosion expansion in non-closed areas

Abstract: In the gas explosions simulation practice in non-closed areas there is a common opinion of burning rate increase at turbulization of initial gas mixture stream. The article shows that in conditions of turbulization there is no increase of the burn rate, but of the flame front area. A wording change of pressure rise reason does not lead to a change of the calculation results, but gives the opportunity to look at the problem differently and interpret a physical process correctly. In order to prove it there are results of the vibrational combustion modeling in terms of gas explosion in the cylinder with an opening on the side. The results show that along with the pressure fluctuation there is burning area size fluctuation that occur synchronous and with the same amplitude. The modeling basis is the system of differential equations, that describe the adopted in gas dynamics fundamental conservation laws, the equation of state, written in the so-called Euler’s form. The system is supplemented with flame spread conditions. The system solution is based on the Russian method of the numerical approximation of this system-the large-particle method.

Smokeless GAP-RDX Composite Rocket Propellants Containing Diaminodinitroethylene (FOX-7)

Abstract: Composite rocket propellants prepared from nitramine fillers (RDX or HMX), glycidyl azide polymer (GAP) binder and energetic plasticizers are potential substitutes for smokeless double-base propellants in some rocket motors. In this work, we report GAP-RDX propellants, wherein the nitramine filler has been partly or wholly replaced by 1,1-diamino-2,2-dinitroethylene (FOX-7). These smokeless propellants, containing 60% energetic solids and 15% N-butyl-2-nitratoethylnitramine (BuNENA) energetic plasticizer, exhibited markedly reduced shock sensitivity with increasing content of FOX-7. Conversely, addition of FOX-7 reduced the thermochemical performance of the propellants, and samples without nitramine underwent unsteady combustion at lower pressures (no burn rate catalyst was added). The mechanical characteristics were quite modest for all propellant samples, and binder-filler interactions improved slightly with increasing content of FOX-7. Overall, FOX-7 remains an attractive, but less than ideal, substitute for nitramines in smokeless GAP propellants.

High‐Fidelity Microstructural Characterization and Performance Modeling of Aluminized Composite Propellant

Abstract: Image processing and stereological techniques were used to characterize the heterogeneity of composite propellant and inform a predictive burn rate model. Composite propellant samples made up of ammonium perchlorate (AP), hydroxyl-terminated polybutadiene (HTPB), and aluminum (Al) were faced with an ion mill and imaged with a scanning electron microscope (SEM) and x-ray tomography (micro-CT). Properties of both the bulk and individual components of the composite propellant were determined from a variety of image processing tools. An algebraic model, based on the improved Beckstead-Derr-Price model developed by Cohen and Strand, was used to predict the steady-state burning of the aluminized composite propellant. In the presented model the presence of aluminum particles within the propellant was introduced. The thermal effects of aluminum particles are accounted for at the solid-gas propellant surface interface and aluminum combustion is considered in the gas phase using a single global reaction. Properties derived from image processing were used directly as model inputs, leading to a sample-specific predictive combustion model.

Experimental Study of the Combustion of Kerosene and Binary Surrogate in the Model Combustion Chamber

Abstract: The purpose of this paper is to conduct experimental research of hazardous substance emissions at the simulated combustion chamber output. The experiment was carried in a simulated combustion chamber. The combustion chamber included a burner device; a liquid fuel feed system; and a flame tube with two rows of mixing holes and one row of cooling holes. The combustion chamber operation mode was = 0.435, = 423 K, and the atmospheric pressure. The liquid fuel burn rate was 0.77 g/s. The pressure ratio in the combustion chamber remained constant at = 3%. Two types of fuel were used: aviation kerosene of Russia’s TS-1 brand and the fuel surrogate was n-decane mixture (C10H22) with benzene additions (C6H6). The benzene additions were 5% through 30% (n-decane/benzene: 95/5, 90/10, 85/15, 80/20, 75/25, and 70/30).

Model-based calibration of the reaction-based diesel combustion dynamics

Abstract: A control-oriented reaction-based combustion model is implemented and used to simulate the combustion process in a diesel engine. The model integrates a homogeneous thermodynamic system with a two-step chemical reaction mechanism that consists of six species. The accuracy of the model is evaluated by comparing with experimental data from a GM 6.6L, 8 cylinder Duramax engine. The model is calibrated for different key points over the entire engine map as well as various injection timings and exhaust gas recirculation (EGR) ratio using an automated calibration algorithm. The reaction-based model is shown to provide accurate predictions of incylinder pressure, temperature, mass-fraction-burned and heat release rate. As an alternative to Wiebe-based method, this approach could lead to a better model with less calibration effort. The improvement is due to the fact that the burn rate is online calculated based upon the dominated fuel chemical components and combustion chamber properties, such as temperature, oxygen and burned gas concentration, etc.

Studies on the Internal Ballistics of Composite Solid Rocket Propellants Incorporating Nano-Structured Catalysts

Abstract: This paper deals with the analysis of burn rate using various catalysts of Iron Oxide and determining which gives the higher burn rate with low pressure variation. The Ammonium Perchlorate (AP) was obtained and ground into fine powder with the particle size ranging from 63 to 125 μm. The propellant strands were prepared with proportions by mixing AP with the binder (Hydroxyl Terminated Polybutadiene), the catalyst (Iron Oxide), curing agent (Isophorone diisocyanate) and the plasticizer (Dioctyladipate). The prepared propellant mixture was cured at around 63 deg C to get various propellant strands. The first strand was prepared with the absence of a catalyst to set an initial base of comparison with other Iron Oxide catalysts, namely, Flower Shaped, Micro and Nano, based on the size of the particles. The combustion process was carried out in a strand burner, which was in turn connected to a data acquisition system. The obtained output was analysed in the form of graphs. The burn rate was achieved by calculating the slope of the graph i.e . by calculating the difference between the highest and the lowest peak of the graph and dividing the total time by the answer. The experiment was repeated with the different catalyst types, as mentioned above, at different pressures. It was observed that the Nano shaped Iron Oxide exhibits better burning characteristics when compared to the rest with the pressure index of 0.792. In this paper, the various experiments carried out along with their procedures are explained in detail. The results obtained and the techniques used are also elaborately described in this paper.

Solid Propellant Burn Rate Measurement in a Micro Closed Bomb

Abstract: In the present work experimental data from seven perforated (7PF) JA2 propellant combustion in a micro closed bomb is presented and the linear burning rate of the JA2 propellant is determined. The burn rate measurement is based on a sophisticated lumped parameter model which accounts among other things for arbitrary cross sectional propellant geometries with the help of the ICT-Cellular-Combustion-Algorithm (ICCA), pressure dependent thermophysical parameters and heat loss. The model is used to construct a vivacity based objective function which depends on the parameters of the empirical law for the linear burning velocity. With the Nelder-Mead downhill simplex optimization algorithm the objective function is minimized and the burn rate parameters determined. The comparison of the results to published data show that with the new burn rate measurement method the linear burning rate can be determined with great accuracy even when only a few propellant grains with a total propellant mass of less than 8 g per shot are used.

Combustion and Decomposition of Monomethylhydrazinium Nitrate

Abstract: Monomethylhydrazinium nitrate was synthesized by mixing the hypergolic bipropellant monomethylhydrazine and nitric acid under nonignition condition. The burn rate of this nitrate-based monopropellant is studied by using a high-pressure strand burner with optical access, coupled with a high-speed camera for capturing and analyzing the combustion characteristics. In addition, pyrolysis of this energetic material was investigated by a confined rapid pyrolysis setup with heating rates on the order of 2000 K/s, coupled to a rapid-scan Fourier transform infrared spectroscope. The decomposition mechanism of monomethylhydrazinium nitrate is discussed.

Study on Combustion Characteristics and Propelling Projectile Motion Process of Bulk-Loaded Liquid Propellant

Abstract: Data are presented showing that the problem of gas–liquid interaction instability is an important subject in the combustion and the propellant projectile motion process of a bulk-loaded liquid propellant gun (BLPG). The instabilities themselves arise from the sources, including fluid motion, to form a combustion gas cavity called Taylor cavity, fluid turbulence and breakup caused by liquid motion relative to the combustion chamber walls, and liquid surface breakup arising from a velocity mismatch on the gas–liquid interface. Typically, small disturbances that arise early in the BLPG combustion interior ballistic cycle can become amplified in the absence of burn rate limiting characteristics. Herein, significant attention has been given to developing and emphasizing the need for better combustion repeatability in the BLPG. Based on this goal, the concept of using different geometries of the combustion chamber is introduced and the concept of using a stepped-wall structure on the combustion chamber ...

Calculation of pressure in a solid-propellant rocket motor with the use of a real dependence of the solid propellant burning rate on pressure

Abstract: Five variants of calculating the burning rate of a solid propellant as a function of the pressure in a solid-propellant rocket motor are considered. Two variants of analytical expressions are proposed for approximating real dependences. In all variants, the pressure in the rocket motor can be presented by simple analytical expressions as a function of solid propellant parameters, charging conditions, and structural factors of the charge and motor.

Investigation on parameters influence for intrinsic instability analysis of solid propellant (AP+HTPB+TDI) using computational image-processing technique

Abstract: The effect of the different mixture in a high volumetric concentration of oxidizer – (AP), with least percentage of binder – (HTPB+TDI), for improving the propellant burn rate was investigated. The combustion experiment is performed using a window bomb set-up and the high-speed camera is utilized to capture the flame images. An image processing approach is used to measure the burn rate and intrinsic instability of flame by discrete wavelet transform method. Region growing algorithm technique is used for image segmentation. The morphological operation is implemented with Euclidean distance measurement for the identification of flame height in configuring with dependent parameters (burning rate, diffusion flame height). The qualitative analysis (signal characterization) and quantitative analysis (mean, kurtosis, skewness, standard deviation, and frequency) were used to study the intrinsic instability characteristics of the flame diffusion. A result obtained from the analysis proves that the instability in fuel combustion occurs at higher mix and pressure level.

Solid Propellant Rocket Motors

Abstract: Solid rocket motors and various solid propellant grain configurations are described. Burning rate and grain design effects on thrust-time tailoring are discussed as well as the sensitivity of the solid propellant to temperature. Analysis of the transient behavior and equilibration of the combustion chamber pressure, the stability of the combustion chamber pressure, and the effects of erosive burning is presented. Solid rocket performance characteristics, dual thrust solid rockets, rocket motor casings, and transient operation are discussed. Rocket motor nozzle heat transfer and ablative and film cooling techniques are described. Methods for optimally sizing a rocket motor are presented. Hybrid rocket motors are introduced and their characteristics and operation are covered.

Study on Dynamic Burning Rate Equation of Propellant

Abstract: Aiming at the difficulty that the actual burning law of propellant in the gun bore couldn't be described exactly by static burning rate equation in the closed-bomb, propellant dynamic burning rate equation and its acquisition method were established in the paper, which are based on static burning rate equation and considering burning gas flow and loading density influence factors in bore. A numerical code for interior ballistic two-phase flow was successfully developed. And corresponding firing tests were also carried out. The comparison of simulations with interior ballistic code and firing test results show that the propellant dynamic burning rate equation makes the maximum errors of muzzle velocity and pressure in breech decreased from 2.97 % to 0.75 % and from 6.68 % to 0.38 %, respectively. This method not only improves simulation precision of gun muzzle velocity and pressure significantly, but also provides a means to improve the design accuracy for interior ballistic performance.

Development of the Multifactorial Computational Models of the Solid Propellants Combustion by Means of Data Science Methods – Phase II

Abstract: In this paper, we present the results of usage of data science methods, in particular artificial neural networks, for the creation of new multifactor computational models for prediction of burn rate of the solid propellants (SP). The analytical system PolyAnalyst and analytical platform Loginom were used for the model creation. The particular model developed was for burn rate prediction of double base propellants with thermite additives, both nano and micro by means of training the ANN using experimental data published in scientific literature. The basis (script) of a creation of Data Wharehouse of SP combustion was developed. The Data Wharehouse can be supplemented by new data in automated mode and serve as a basis for creating new generalized combustion models of SP and thus the beginning of work in a new direction of combustion science, which the authors propose to call �Propellant Combustion Genome� (by analogy with a very famous Materials Genome Initiative (MGI)). Propellant Combustion Genome opens possibilities for accelerating the advanced propellants development.

A Methodology for Modeling the Cat-Heating Transient Phase in a Turbocharged Direct Injection Spark Ignition Engine

Abstract: This paper presents the modeling of the transient phase of catalyst heating on a high-performance turbocharged spark ignition engine with the aim to accurately predict the exhaust thermal energy available at the catalyst inlet and to provide a "virtual test rig" to assess different design and calibration options.The entire transient phase, starting from the engine cranking until the catalyst warm-up is completed, was taken into account in the simulation, and the model was validated using a wide data-set of experimental tests.The first step of the modeling activity was the combustion analysis during the transient phase: the burn rate was evaluated on the basis of experimental in-cylinder pressure data, considering both cycle-to-cycle and cylinder-to-cylinder variations.Then, as far as the exhaust temperatures are concerned, a detailed model of the thermocouples was implemented to replicate the physical behavior of the sensors during the warm-up and to compare the simulated temperatures with the measured ones.Finally, a complete analysis of the energy balance during the transient was carried out: the thermal power available to the catalyst inlet was obtained from a complete analysis of power losses (i.e. friction and pumping losses, in-cylinder heat transfer, engine block and engine coolant heating, exhaust manifold heat transfer, etc.).In conclusion, the proposed methodology allows to reliably simulate in details the Cat-Heating transient, showing a valuable potential in driving the main design and calibration choices during the engine development process.

Analysis of the combustion, burn rate, and grain structure of ammonium nitrate and badge based propellant

Abstract: A rocket solid propellant is a compacted grain of a mixture of a fuel, an oxidant, and a binder. During the combustion process it produces a flux of hot gases intended to produce work through a rocket propulsion system. Two important and most desirable characteristics of a solid propellant are grain high stability and non-toxic trace. Ammonium nitrate oxidant releases low production of toxic traces, such as nitrogen oxides and chlorinated compounds. As a binder, BADGE presents easy handling and good resistance to shock and humidity when cured in a grain. Grains of ammonium nitrate and BADGE with aluminum and iron oxide III, as catalysts, were built and tested. Three different formulations were tested with fixed 8% in mass of aluminum or iron oxide, and varying ammonium nitrate from 60% up to 75%. The measurements of burn rate were conducted in standard ambient temperature and pressure. Gravimetric comparison of ashes and calculation of burning products via numerical simulation methods were carried out. The results presented a significant relationship between the burn rate and the ammonium nitrate concentration. The use of aluminum and iron oxide modified this relationship due to changes in oxygen consumption dynamics, leading to a change in flame temperature. It was also shown that a presence of aluminum elevates the production of CO, while iron oxide III maintained approximated values of non-catalyzed process. The soot formation was present in all formulations.

Methodology and system for reforming liquid fuel

Abstract: An on the fly fuel reformer device to produce variations in the autoignition and burning rate properties of a fuel by appropriate processing of some or all of a single fuel supply in its liquid form. The system includes a non-thermal plasma generator and/or a UV radiation source in contact with a fuel line so as to contact a multi-phase fuel in the line and dynamically modify the fuel to exhibit desired autoignition characteristics and burn rate such that the engine can operate with increased efficiency and lower emissions.

Burn Rate Modification with Carborane Polymers

Abstract: : In the past, propellants containing boron clusters like n-hexyl carborane demonstrated an improved burn rate, decreased pressure exponent, and maintained a high energy output. However, the technology was hampered by expensive and hazardous synthesis as well as migration issues of the n-hexyl carborane plasticizer. A new, affordable synthesis procedure of decaborate salts was established at the University of Missouri-Columbia, which provides material for alkylation and subsequent synthesis to carboranylmethyl acrylate. In this paper, the investigation of the integration of covalently-bonded boron achieved through copolymerization in various binder polymers is presented. Since pure carboranylmethyl acrylate polymer is a solid crystalline material at room temperature, it was co-polymerized to produce a material suitable for formulations. The co-polymerization investigated was a combination of carboranylmethyl acrylate, butyl acrylate, and 2-hydroxyethyl acrylate. The boron-rich carborane was intended to serve as the high energy fuel portion of the polymer, the butyl acrylate provided a glass transition temperature below room temperature and low viscosity, and the hydroxylethyl acrylate contributed a cross-linkable moiety. The resulting polymer was used in a cast-cure formulation containing aluminum and ammonium perchlorate in order to test the effect of the carborane additive on the formulation burn rate when compared to a hydroxyl-terminated polybutadiene baseline. Strand burn rate testing demonstrated a distinctive increase in the burn rate for the carborane containing formulation. Synthesis and characterization of the carborane-based polymer are discussed along with the designed formulation. Further test data including sensitivity and thermal characterization are presented.