化学结构对平台推进剂催化燃烧性能影响的理论分析

利用建立的以准一维气相反应流为基础的推进剂稳态燃烧模型,计算了推进剂配方组成对催化燃烧性能的影响,从化学结构的角度分析了平台燃烧的影响因素。由此解释了平台燃烧全过程的化学本质和推进剂燃速压强指数的化学本质,提出了平台推进剂配方和燃速优化设计的原则,为燃速和燃速压强指数的调节提供了理论依据,其结论与国内外实践结果相一致。     

新型燃烧稳定剂对浇铸RDX-CMDB推进剂燃烧性能的影响

为选择理想的新型燃烧稳定剂,研究了WB、WC、ZrB2、ZrO2、SiC和BN对浇铸RDX-CMDB推进剂燃速和燃速压力指数的影响。结果表明,6种材料都能降低推进剂的燃速,但降低幅度各有差异;ZrB2、ZrO2和SiC对推进剂燃速的降低作用随其粒度的减小而增大;WB和WC在一定含量下可以降低推进剂18～20.5MPa下的燃速压力指数;只有BN使推进剂的燃烧平台效应消失。     

低铝含量NEPE推进剂燃烧性能研究

研究了铝粉含量为8％的NEPE推进剂。采用配浆浇铸法制备推进剂，并用恒压静态燃速仪测试了推进剂的燃烧性能。考察了NG／DEGDN的比例、AP粒度、HMX粒度对燃速及燃速压力指数的影响。发现增大NG／DEGDN的比例、减小AP粒径或增加细粒度AP含量，将提高NEPE推进剂的燃烧速度，压力指数升高；而HMX粒度降低，NEPE推进剂燃速降低，压力指数降低；不同来源的PbCO3对NEPE推进剂燃烧性能影响很大。     

NEPE推进剂燃烧性能研究

NEPE高能固体推进剂因其优良的综合性能具有十分良好的应用前景。通过调整氧化剂含量、种类及含能增塑剂用量,对NEPE推进剂的燃烧速度和燃速压力指数进行了调节,燃速在9．3～11．6mm／s(7.0MPa)范围内可调，燃速压力指数由0．61降为0.54。     

金属氧化物对HNIW单元推进剂燃烧的催化研究

对六硝基六氮杂异伍兹烷 (HNIW)的催化燃烧进行了初步的实验探讨 ,实验结果表明 ,HNIW单元推进剂的燃烧速度是 HMX单元推进剂燃烧速度的 2倍左右 ,HNIW单元推进剂的燃烧速度随着压力的增加而直线增加 ,其燃速压力指数为 0 .846 ,通过加入金属氧化物可使 HNIW单元推进剂的燃烧速度发生变化 ,但对其燃速压力指数影响不大     

铜盐和碳黑对微烟NEPE推进剂燃烧性能的影响

通过测定不同压力下推进剂的燃烧性能及熄火表面元素分析,研究了两种铜盐（AD和BC）和3种碳黑对微烟NEPE推进剂燃烧性能的影响.结果表明,适量AD可改善推进剂的燃烧性能,使推进剂在3～20 MPa压力范围内的压强指数降至0.45以下;AD在12～18 MPa压力范围内比等量BC对微烟NEPE推进剂燃烧性能的催化作用弱,这可能与AD所含铜元素在燃面的富集程度小于BC有关.3种碳黑均能改变微烟NEPE推进剂在3～18 MPa压力范围内的燃速.增加乙炔碳黑含量可使推进剂在3～20 MPa压力范围内的燃速提高,压力指数降低.     

含相稳定硝酸铵CMDB推进剂的机械感度和燃烧性能

通过测试撞击感度、摩擦感度和燃速,研究了含相稳定硝酸铵(PSAN)的改性双基(CMDB)推进剂的燃烧性能和机械感度。结果表明,PSAN可改善CMDB推进剂的机械感度;用PSAN作氧化剂,其推进剂的燃速低于RDX作氧化剂的燃速,压强指数高于后者的压强指数;1～5MPa压力范围内随PSAN在配方中含量的增加,推进剂的燃速降低,压强指数升高。     

3-硝基邻苯二甲酸锆的制备及其对双基系推进剂的催化作用

以3-硝基邻苯二甲酸和硝酸氧锆为原料,制备了3-硝基邻苯二甲酸锆,采用元素分析、X射线荧光衍射、FT-IR和TG-DTG对其结构进行了表征.研究了3-硝基邻苯二甲酸锆对双基和RDX-CMDB推进剂燃烧性能的影响.结果表明,3-硝基邻苯二甲酸锆对双基系推进剂燃烧具有良好的催化作用,在低压段能明显提高推进剂的燃速,在中高压段能明显降低燃速压力指数;与铜盐复合后,可显著提高低压段燃速和降低中高压段燃速压力指数.     

高氯酸铵(AP)粒度对端羟基聚丁二烯(HTPB)推进剂燃烧特性的影响

本文研究了含铝粉的HTPB推进剂中AP粒度对推进剂燃烧速度和燃速压力指数的影响。结果表明:AP粒度越小,推进剂燃烧速度就越高、燃速压力指数亦随之增加,并给出了相应的经验公式。本文应用Summerfield粒状扩散火焰模型对AP粒度与HTPB推进剂燃烧特性的关系进行了讨论。     

高氯酸铵(AP)粒度对端羟基聚丁二烯(HTPB)推进剂燃烧特性的影响

本文研究了含铝粉的 HTPB 推进剂中 AP 粒度对推进剂燃烧速度和燃速压力指数的影响。结果表明:AP 粒度越小,推进剂燃烧速度就越高、燃速压力指数亦随之增加,并给出了相应的经验公式。本文应用 Summerfield 粒状扩散火焰模型对 AP 粒度与 HTPB 推进剂燃烧特性的关系进行了讨论。     

Solid Propellant Burning Rate From Strand Burner Pressure Measurement

Strand burner pressure–time data are analyzed to determine if the propellant burning rate can be extracted. This approach is based on strand burner pressure–time history that is related to the temperature change due to exothermic reaction heating of chamber gases and gas addition to the chamber by propellant combustion products. In support of this method, chemical equilibrium calculations were made to project product composition, internal energy, and other needed properties. A mathematical model was formulated and solved numerically and the calculated burning rates were compared with the experimental wire‐break time results provided simultaneously and with the propellant manufacturer's results, when available. The comparisons reveal that the approach has merit and that more accurate pressure determination coupled with additional thermochemical information and strand burner gas temperature measurements has the potential to make this approach a viable technique and one that can be applied in conjunction with other burning rate measurements. The proposed method is similar to a well‐developed technique which is commonly applied to ballistic powders but with adjustments for the differences in geometry, pressure, and time of event.     

Numerical simulation of the two-dimensional flow in high pressure catalytic combustor for gas turbine

The objective of this paper is modeling the mechanism of high pressure and high temperature catalytic oxidation of natural gas, or methane. The model is two-dimensional steady-state, and includes axial and radial convection and diffusion of mass, momentum and energy, as well as homogeneous (gas phase) and heterogeneous (gas surface) single step irreversible chemical reactions within a catalyst channel. Experimental investigations were also made of natural gas, or methane combustion in the presence of Mn-substituted hexaaluminate catalysts. Axial profiles of catalyst wall temperature, and gas temperature and gas composition for a range of gas turbine combustor operating conditions have been obtained for comparison with and development of a computer model of catalytic combustion. Numerical calculation results for atmospheric pressure agree well with experimental data. The calculations have been extended for high pressure (10 atm) operating conditions of gas turbine.     

Evaluation of an Entropy‐Based Combustion Model using Stochastic Reactors

The entropy transport concept (ETC) presented in this paper is a novel approach to describe reaction systems such that the dynamic behavior of a chemical system can be reproduced with a minimum in independent parameters. It is shown that, for adiabatic conditions, the mixture fraction and the reaction entropy are sufficient to describe combustion processes without significant loss of information. Entropy is used as a measure of the reaction progress in this context. In order to evaluate the applicability of the ETC for combustion modeling in turbulent systems, the entropy transport concept was implemented into a stochastic reactor model. For several test cases, the results of this ETC‐based reactor were compared with a reactor that directly integrates the species transport equations.     

Effects of NTO Oxidizer Temperature and Pressure on Hypergolic Ignition Delay and Life Time of UDMH Organic Gel Droplet

Organic gel propellants are promising candidates for a variety of rocket motor and scramjet applications, since they are intrinsically safe and provide high performance. It is well known that organic gel fuel droplets exhibit distinct combustion characteristics compared with conventional liquid fuel droplets, and furthermore an understanding of the ignition delay and lifetime of these droplets is critical to the improvement of combustor design. In this work, investigations of the combustion of unsymmetrical dimethylhydrazine (UDMH) organic gel droplets in different nitrogen tetroxide (NTO) oxidizing atmospheres were conducted using two sets of experimental apparatus. The combustion characteristics under different conditions of temperature and pressure were compared and analyzed based on the flame shapes observed during experimentation. From these trials, an unsteady combustion model was developed and used for the numerical simulation of spray‐sized UDMH organic gel droplet combustion in an NTO atmosphere. The hypergolic ignition and burning characteristics of the organic gel droplets under conditions simulating either engine startup or steady state combustion were compared, and changes in ignition delay and droplet lifetime with ambient temperature and pressure were analyzed. The experimental and numerical results show that the UDMH organic gel droplets exhibit periodic swell‐burst behavior following the formation of an elastic film at the droplet surface. Each droplet burst results in fuel vapor ejection and flame distortion, the intensity of which declines with increasing ambient pressure. However, the swell‐burst period is extended with increasing ambient pressure, which results in potential flameout. Under conditions of low temperature and pressure similar to those at engine startup, the ignition delay and lifetime of spray‐sized gel droplets decrease with increasing temperature or pressure, although there is a sharp increase in droplet lifetime when the ambient pressure reaches a critical value associated with flameout. The ignition delay was found to be a rate‐limited phenomenon linked to the droplet heating rate. The proportion of ignition delay and droplet lifetime due to droplet heating‐up decreased with increasing temperature or decreasing pressure. Conversely, at high temperatures and pressures simulating the engine’s steady state operating conditions, the droplets were observed to flameout after several swell‐burst periods and both ignition delay and lifetime decreased monotonically with increasing temperature or pressure. The ignition delay time was determined to be rate‐limited by gas phase chemical reactions and contributed very little to the overall droplet lifetime compared with the engine startup condition.     

多基发射药燃烧性能的调节与优化

介绍了近来提出的多基发射药燃烧模型，利用其计算方法计算了多基发射药的化学组成对燃烧性能的影响；从化学结构和化学反应的层次分析了硝胺发射药燃速－压力曲线转折和某一压力范围内压力指数大于１的原因；从化学组成的角度出发提出了多基发射药燃烧性能优化设计的一些基本原则。     

Onset Temperatures in Hot Wire Ignition of AN‐Based Emulsions

Hot wire ignition experiments were carried out recently at the Canadian Explosives Research Laboratory on a few emulsion formulations. The data indicate that there is a pressure‐dependent onset temperature beyond which the wire temperature increases at an accelerated rate. In order to explain this observation and to detect this temperature more consistently, particularly at low pressures, the data are reanalysed by comparing the experimental wire temperature with that predicted from theory for the heating of an inert material. For this purpose, an analytical theory from the literature is reviewed and the numerical solution developed in this report is described. The latter can deal with more general solutions with variable thermal properties and chemical reactions in the condensed medium surrounding the wire.     

In-bed char combustion of Australian coals in PFBC. 2. Char combustion without secondary fragmentation

Char combustion parameters that significantly affect the in-bed combustion of char in PFBC were determined experimentally using a batch-fed PFBC. The ratio of carbon to oxygen consumed on the surface of a burning char particle was determined and it was concluded that CO was the only product of char combustion in PFBC.

Model simulations revealed that, for PFBC, mass transfer controlled the combustion of large char particles ≥2 mm, whereas the combustion of small char particles below 0.9–2 mm was controlled by both mass transfer and chemical kinetics.

System pressure influenced the char combustion via the interaction between chemical kinetics and the mass transfer of oxygen to the char. Char particle temperature varied markedly with oxygen partial pressure in the particulate phase, indicating a distribution of char particle combustion rates in PFBC. In modelling char combustion in PFBC, the temperature of char particles in the bed should be calculated at different locations based on a heat balance around the burning char particle taking into account the local bed oxygen concentration.     

Optimization of the combustion of blends of domestic fuel oil and cottonseed oil in a non-modified domestic boiler

This study characterizes combustion of blends of DFO (domestic fuel-oil) and refined cottonseed oil produced in Burkina Faso at different percentages in a non-modified DFO burner by determining its overall performance (consumption and thermal capacity) and gas emissions (CO, CO₂, O₂, NO, NO_x, SO₂). The physical and chemical characteristics of the different blends confer on each blend the status of a special fuel requiring specific adjustment of the burner. The influence of combustion parameters such as equivalence ratio and fuel pressure is studied. Results show that emissions of CO, NO_x and CO₂ are similar for all fuel blends at the operating point corresponding to 0.86 equivalence ratio and 20 bars fuel pressure. Whatever the fuel pressure is, SO₂ emission is increasing with DFO percentage in blends.Experimental emission results obtained with suitable adjustments for a blend containing 30% cottonseed oil and 70% DFO are compared to the calculated results obtained using a combustion equation based on a global chemical mechanism. The results show that there is a satisfactory match between the calculation and experimental results.     

Chemical modelling and measurements of the catalytic combustion of CH4/air mixtures on platinum and palladium catalysts

This work reports experimental measurements and a modelling study carried out on palladium and platinum based catalytic monoliths used as methane combustors for heating purposes. It concentrates on the effects of operating conditions on combustion, heat transfer efficiency and pollutant formation. The development of a detailed homogeneous/heterogeneous chemical kinetics model for methane–air combustion over palladium using literature data was undertaken to model the behaviour of one of the experimental catalytic heaters. In addition, a published detailed chemical mechanism for methane combustion over platinum was used in the platinum catalyst model. The fuel–air equivalence ratios ranged from 0.3 to 0.6 and the space velocities used were between 24 000 and 72 000 h⁻¹. Although the model assumed perfectly stirred reactor (PSR) conditions and was applied to localised regions of the monoliths where little radial gradients of temperature and concentrations were measured, it predicted the surface temperature, methane slippage, CO and NO_x at the downstream face of the monolith with reasonable accuracy in some cases, but also highlighted the shortcomings of the PSR assumption in other cases.     

Reduced Kinetic Mechanism of n‐Heptane Oxidation in Modeling Polycyclic Aromatic Hydrocarbon Formation in Diesel Combustion

A reduced chemical mechanism was developed for the chemical kinetics of n‐heptane oxidation in modeling polycyclic aromatic hydrocarbon formation in diesel combustion. The complete kinetic mechanism, which comprises five hundred and seventy‐two reactions and one hundred and eight species, was reduced to a minor mechanism that includes only seventy‐six reactions and forty‐eight species by using net reaction rate analysis and sensitivity analysis, yet the model based on this reduced mechanism predicted the temperature profile and concentrations of C₇H₁₆, O₂, H₂O, CO₂, benzene, naphthalene, phenanthrene, biphenyl, and pyrene that are essentially indistinguishable from those of the complete mechanism under the range of reaction conditions of interest.