含ACP的无烟改性双基推进剂燃烧特性研究

快燃物ACP作为一种有效含能助剂用来提高推进剂的燃速具有一定的效果。通过DSC和TG-DTG研究了ACP对无烟改性双基推进剂(CMDB)热分解特性的影响,采用靶线法研究了不同含量的ACP对无烟改性双基推进剂燃速和燃速压力指数的影响,用燃烧火焰单幅照相技术和微热电偶测温获得了含ACP无烟改性双基推进剂在稳态燃烧条件下的火焰结构和燃烧波温度分布,分析了该推进剂中主要组分对燃烧性能的影响。结果表明:含ACP推进剂的燃速随ACP含量的增加而增大,推进剂燃烧火焰结构随ACP含量增加而更加明亮。     

高能少烟推进剂应用参数反演研究

通过试验验证、理论计算和参数反演的方法,对高能少烟的复合推进剂和改性双基推进剂性能进行研究。设计了典型内弹道试验发动机进行点火试验,对比冲、燃速和压强指数等推进剂主要性能的试验参数与理论值进行了对比,总结出不能满足要求的推进剂性能指标,再结合参数反演的方法对推进剂主要参数控制提出了改进方向;同时,对同一推进剂在不同装药工艺下对性能的影响进行了试验和分析。目前,还需对高能少烟推进剂的压强指数、低温性能和装药工艺等进行进一步优化和选取,以便研制出符合空空导弹发动机使用要求的高能少烟推进剂。     

超细SC/Fe2O3@AP核壳结构复合粒子的制备及表征

为了提高AP基复合固体推进剂的燃速,采用反相乳状液法制备了超细柠檬酸钠(SC)/氧化铁(Fe2O3)@高氯酸铵(AP)核壳结构复合粒子,同时对比研究了SC/Fe2O3@AP与SC/Fe2O3-AP普通混合物的热分解特性,并将其应用于AP基复合固体推进剂中,探究2种复合粒子对AP基复合固体推进剂燃烧性能的影响。研究结果表明:与SC/Fe2O3-AP相比,SC/Fe2O3@AP的热分解峰温降低,表观活化能降低了约8.6%,热分解反应活性得到提高,并且含SC/Fe2O3@AP的AP基复合固体推进剂较含SC/Fe2O3-AP的AP基复合固体推进剂的热分解峰温提前。此外,含SC/Fe2O3-AP的AP基复合固体推进剂的燃速为45.33mm/s,含SC/Fe2O3@AP的AP基复合固体推进剂的燃速为46.46mm/s,燃速提高了2.5%。     

微量Sr对Al-Mg-Si-Cu基合金的时效析出过程及动力学的影响

采用差热扫描量（differential scanning calorimeter,DSC）分析Sr含量对Al-Mg—Si—Cu基合金时效β＇和Q相激活能的影响。结果表明,加入Sr不改变β″和Q相的析出温度,但能影响它们的激活能。当Sr含量较低（0．033％,质越百分数）时,时效相的激活能较低,比较容易析出,使合金得到更好强化;当Sr含量较高（0.093％）时,时效相的激活能较大,从而较难析出,对合金的强化作用较弱。     

表面改性剂处理纳米SiO_2填充改性聚丙烯研究

利用比表面积法和傅立叶红外光谱仪(FT-IR)研究了表面改性剂KH560对纳米SiO2的影响,结果表明,表面改性剂处理纳米SiO2有较好的分散效果。通过力学性能测试、DSC热分析和SEM照片观测对PP/纳米SiO2复合材料的结构和性能进行了研究。结果表明:纳米SiO2对PP有异相成核作用,当纳米SiO2含量为2%时,复合材料的综合力学性能好。SEM电镜分析得出,经表面改性的纳米SiO2均匀地分散于PP中,从而起到良好的改性作用。     

E-MA-GMA改善PC/PBT共混体系相容性的研究

采用E—MA—GMA改性剂AX-8900作为相容改性剂,研究其用量对PC/PBT合金的结构及性能的影响。试验发现:当其添加量在3phr时综合性能最佳,而不含MA的AX-8840与其相比容易出现分层、起皮等相容性不良现象,通过DSC、SEM手段也验证了AX-8900在一定添加量时可改善体系的相容性。     

低碳含铌微合金钢的连续冷却相变行为及显微组织

利用Gleeble-1500D型热/力模拟试验机,采用热膨胀法测定了不同铌含量低碳含铌微合金钢在不同冷速下的相变点,研究了奥氏体连续冷却时的相变行为及铌含量和冷却速率对该钢相变组织与硬度的影响。结果表明:随着铌含量和冷速的提高,γ→α相变温度降低,相变组织变得复杂,显微硬度升高;铌含量较低(小于0.024%,质量分数)的钢在冷速较低(3℃·s~(-1))时,显微组织为较粗大的铁素体和少量珠光体,冷速提高后主要是由尖角形、多边形铁素体和贝氏体组成的混合组织;铌含量较高(0.06%)的钢在高冷速(50℃·s~(-1))下出现了针状铁素体组织。     

TG-DSC技术在水泥研究中的应用

采用热重分析(TG)和差示扫描量热分析(DSC)研究了水泥生料转变成的热效应特征和水泥水化产物含量变化规律,重点研究了Al坩埚封装方式(高压密闭、低压密闭和传统加盖扎孔)对TG-DSC方法分析水泥中石膏结晶水含量的影响。发现Al坩埚密闭时石膏脱水的两个热效应峰完全分开,可大大提高热焓法定量分析二水石膏中不同性质结晶水含量的精度。     

LiCl对PA6溶液络合改性研究

采用LiCl对PA6进行溶液络合改性,通过红外光谱(IR)、差示扫描量热法(DSC)研究了LiCl含量对PA6改性程度的影响。研究表明,随着含量的增加,LiCl对PA6络合改性的程度加大,改性PA6的结晶温度及结晶度逐渐下降;当LiCl含量达到7%以后,改性PA6已转变成无定型状态。     

轻烧MA90尖晶石加入量对刚玉-尖晶石浇注料显微结构和性能的影响

通过固定尖晶石总含量(质量分数23.5%),改变轻烧和死烧MA90尖晶石质量比制备了不同轻烧尖晶石含量的刚玉-尖晶石浇注料,在1 600℃下进行了钢包渣侵蚀试验,研究了轻烧尖晶石含量对该浇注料显微结构和抗渣性能的影响。结果表明:随着轻烧尖晶石质量分数从0增加到23.5%,浇注料的线收缩率增大、显气孔率和体积密度基本不变、强度降低;侵蚀后基体中出现裂纹,且轻烧尖晶石含量较高的裂纹较多;随着轻烧尖晶石含量的增加,浇注料的抗渣侵蚀性逐渐降低,抗渣渗透性逐渐增强;当轻烧尖晶石质量分数为17.6%时,其综合性能最好,显气孔率为15.7%,抗折和耐压强度分别为26.9,107.8 MPa,侵蚀指数和渗透指数分别为0.32和0.91。     

Numerical simulation of the unsteady combustion of solid rocket propellants at a harmonic pressure change

This study focuses on a numerical investigation of the unsteady burning rate of solid propellants at a harmonic pressure change in the combustion chamber of a solid propellant rocket engine. The physico-mathematical model includes the equations of heat transfer and decomposition of the oxidizer in the solid phase and two phases, the dual velocity, and the two-temperature reaction flow of gasification products. The boundary conditions on the solid fuel surface implement the conservation of energy fluxes and the mass of components. We numerically calculate the unsteady burning rate of metallized solid propellant and nitroglycerin powder under a harmonic pressure change in the combustion chamber of a solid propellant rocket engine and determine the dependence of the burning rate amplitude on the frequency of pressure oscillations. The amplitude of the burning rate depends nonmonotonously on the oscillation frequency. With increasing frequency, the amplitude first rises and then declines.

     

Measurement of flow rate characteristics of pneumatic components based on the dynamic regularity of polytropic exponents

To improve the measurement precision of flow rate characteristics of pneumatic components, a new measurement method is proposed, which is based on the dynamic regularity of instantaneous polytropic exponents during discharge. The dynamic regularity of polytropic exponents is obtained by the stop method, and it can be concluded as two change stages based on pressure time constant. According to piecewise polynomial fitting curves of instantaneous polytropic exponents, a new algorithm for the identification of flow rate characteristics is proposed. This method can accurately measure some components with a large sonic conductance and a small critical pressure ratio. Four pneumatic components are measured to compare the identification precision of those different methods. The results of comparison show that the new polytropic exponent method and its new algorithm have the higher precision than other alternative methods for the ISO6358 method. The identification errors of sonic conductance of the new method are less than 3%, and the identification errors of critical pressure ratio of the new algorithm are less than 15%.     

Pneumatic hydrogen pellet injection system for the ISX tokamak

We describe the design and operation of the solid hydrogen pellet injection system used in plasma refueling experiments on the ISX tokamak. The gun-type injector operates on the principle of gas dynamic acceleration of cold pellets confined laterally in a tube. The device is cooled by flowing liquid helium refrigerant, and pellets are formed in situ. Room temperature helium gas at moderate pressure is used as the propellant. The prototype device injected single hydrogen pellets into the tokamak discharge at a nominal 330 m/s. The tokamak plasma fuel content was observed to increase by (0.5-1.2) x10(19) particles subsequent to pellet injection. A simple modification to the existing design has extended the performance to 1000 m/s. At higher propellant operating pressures (28 bars), the muzzle velocity is 20% less than predicted by an idealized constant area expansion process.     

Measurement of solid propellant burning rates by analysis of ultrasonic full waveforms

The measurement of solid propellant burning rates using ultrasound requires the simultaneous acquisition and analysis of ultrasonic signals and pressure data simultaneously in a wide range of pressure values during the process of propellant burning. Recently, this method has been proposed as an effective approach based on an analysis of full waveforms of ultrasonic signals together with a laboratory prototype system in which the proposed approach has been implemented. However, this prototype system had limitations in terms of data processing speed and signal processing procedures. To overcome such limitations, in the present study, we develop a dedicated, high speed system that can acquire ultrasonic full waveforms and pressure data up to 2,000 times per second. Our system can also estimate the burning rate as a function of pressure using a special software based on ultrasonic full waveform analysis. This paper describes the approach adopted in this high speed system, along with the burning rate measurement results obtained from three propellants with different burning characteristics. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Sung-Jin Song received a B.S. degree in Mechanical Engineering from Seoul National University, Seoul, Korea in 1981, a M.S. degree in Mechanical Engineering from Korea Advanced Institute of Science and Technology in 1983, and a Ph.D in Engineering Mechanics from Iowa State University, Ames, Iowa, USA in 1991. He has worked at Daewoo Heavy Industries, Ltd., Inchoen, Korea for 5 years from 1983, where he has been certified as ASNT Level III in RT, UT, MT and PT. He has worked at Chosun University, Gwangju, Korea as Assistant Professor for 5 years from 1993. Since 1998 he has been at Sungkyunkwan University, Suwon, Korea and is currently Professor of Mechanical Engineering.     

A steady-state combustion modelling of composite solid propellants

By depicting the transfer of heat and combustion reaction to take place within thin gas layers close to the propellant surface burning in a steady-state fashion, a mathematical equation has been deduced to describe the burning rate of solid propellant as a function of initial grain temperature and chamber pressure. It has been also assumed that chemical reaction could take place in premixing-diffusing zone but were carried out mainly in the reaction-flame zone. All these phenomena taken place in each zone of combustion have been assumed to be steady-state. In the present investigation, the equation, γ=k·(1/R(T _i +C))ⁿ. exp (-E _a/R(T _i +C)(P/z) is being presented and it is compared with experimental data. The proposed model has been tested and evaluated vis-a-vis strand burner data for three different propellants based on CTPB, and it has been found that the deviation of the computed burning rates from the measured rates ranged up to 2%.     

Numerical study of gas-solid reactive flow in a cylinder

A theoretical model is described for the numerical simulation of unsteady gas-solid reactive flow in packed beds of granular propellants in a tubular geometry. The approach couples continuity, momentum and energy equations in each phase along with porosity and granular stresses. Propellant bed combustion process is neglected, but the mass flow rate due to the combustion is derived using a pressure-based burning rate correlation. As the burning of solid propellant begins, pressure, temperature, density and other gas parameters begin to change rapidly. To catch these changes, a CFD approach with explicit McCormack method is used to solve the coupled system of equations. A moving mesh is used to consider the moving boundary. Pressure history, moving boundary velocity and other parameters of the mixture are obtained and compared with other numerical data.     

内能源转管武器导气装置结构参数对射速的影响

内能源转管武器驱动力来自自身导气装置的火药燃气压力,为了得到导气装置的结构参数,对武器的气室压力和射速的影响,采用基于matlab软件的数值算法,对某6管内能源转管武器导气装置进行动力学计算,得到了导气装置结构参数对武器的气室压力和射速的影响关系。所得结论,对内能源转管武器的设计和改进有一定的借鉴意义。     

Response of radiation driven transient burning of AP and HMX using flame modeling

The radiation driven response function (R _q ) for AP and HMX propellant was obtained and compared with experimental results by using a simple αβγ flame model rather than with detailed chemistry. For an AP propellant, the profile of heat release was assumed by the experimental data. The calculatedR _q shows a frequency shift of the peak amplitude to the higher frequency and a decrease in the maximum amplitude as radiation increases. In addition, it was found the increase in the total flux could enhance the mean burning rate[`(r)]_b\bar r_b while the phase differences between the radiation and resulting conduction could consequently reduce the fluctuation amplitude Δy _b . Fortunately, this is the qualitative duplication of the behavior recently observed in the experiments of RDX propellants. For HMX, the response functionR _q has been calculated and showed a quite good agreement with the experimental data. Even though the fairly good agreement ofR _q with experimental ones, the unsteady behavior of HMX was not reproduced as the radiation input increased. This is due to lack of the material properties of HMX or the physical understanding of HMX burning at high pressure.     

Elastohydrodynamic Lubrication in Extended Parameter Ranges—Part IV: Effect of Material Properties©

The present study extends the full numerical EHL solution to wide parameter ranges that cover practical and severe operating conditions commonly found in heavy-duty components. This article is the fourth part of the present study, and is focused on the effect of material properties on the film thickness, following three previous papers that investigated the effects of speed, load, and contact geometry, respectively. In this article, the pressure-viscosity coefficient is varied in a range from zero to 72.8 GPa^?1 and the elastic modulus from 80 to 400 GPa, sufficiently wide to cover different materials and lubricants commonly used in industries. More than 500 cases have been analyzed, and results show that in the extended parameter ranges the relationships between the material properties and the film thickness still primarily follow the simple power rules proposed by the conventional EHL theory. However, the exponents in the power-law functions no longer appear to be constants. They are indeed functions of speed and load. For the relationship between the pressure-viscosity coefficient and the central film thickness, the exponent appears to be quite close to 0.53 proposed by the Hamrock-Dowson formula if the speed and the load are moderate. When the speed is low and/or the load is heavy, this exponent may be considerably greater. The same trend is observed for the relationship between the elastic modulus and the film thickness. At moderate loads and speeds, the exponent is close to ?0.073, which is used in the Hamrock and Dowson formula. When the speed is decreased and/or the load increased, the exponent may become positive. It is found, in addition, that the exponents in these relationships are only weakly affected by contact ellipticity.