HTPB/镁铝合金含量对含硼富燃推进剂压强指数影响

通过推进剂的燃速、热重(TG-DTG)分析和高压差示扫描(DSC)分析手段研究了端羟基聚丁二烯(HTPB)/镁铝合金(MA)含量变化对含硼推进剂压强指数的影响。采用燃速u与压强P的关系u=apn,求出该推进剂的压强指数n(压强范围0.5 MPa~1.5 MPa)。燃速测试实验结果表明,当HTPB/MA含量为27.3%/3%时,压强指数为0.280,而当HTPB/MA含量为20.3%/10%时,压强指数升高到0.420。通过推进剂的TG-DTG和DSC热分析可知,含硼推进剂中HTPB含量较低、MA含量较高时,推进剂失重较快,且推进剂的热分解受到压强的影响显著增强,特别是氧化剂高氯酸铵(AP)的低温分解受压强影响非常显著,因而燃速较高,压强指数也高。     

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%。     

富燃推进剂凝相燃烧产物收集实验研究

近年来,国内外研究了多种收集富燃推进剂一次燃烧产物的装置,为相应分析工作奠定了基础。富燃推进剂一次燃烧产物的组成和凝相粒度的分布对火箭发动机的性能、二次燃烧效率等研究都有重要意义。设计了试验发动机,采用大型真空箱无损收集富燃推进剂一次燃烧产物;进行了真空箱的真空度、试验发动机验证试验,收集了富燃推进剂一次燃烧产物;建立了整套装置非稳态内流场数值仿真模型,获得了流场内各参数分布。     

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。     

一种研究柴油甲醇双燃料的定容燃烧弹试验装置

设计并研制了一种定容燃烧弹试验装置,用于对柴油在甲醇/空气预混均质混合气中燃烧特性的基础研究。介绍了该试验装置的各子系统的原理、结构及特点。定容燃烧弹试验结果表明:甲醇抑制了柴油的着火燃烧,随着甲醇/空气混合气浓度的增大,燃烧火焰变暗,碳烟生成受到抑制。与空气热氛围相比,甲醇/空气混合气氛围延长了柴油的滞燃期,加长了火焰的浮起长度。火焰稳定后,甲醇氛围中火焰的浮起长度随时间的变化比在纯空气氛围中大。     

点火位置对射流点火发动机燃烧特性的影响

射流点火可以有效提高发动机燃烧效率,抑制爆震,预燃室内部火花塞的点火位置对于点火成功率以及燃烧效果有较大影响。采用CFD仿真的方法,研究了被动式射流点火发动机预燃室内部火花塞点火位置对发动机缸内燃烧过程的影响,得到以下结论：适当的将预燃室内火花塞点火位置靠近预燃室喷孔可借助高湍动能气体实现火焰的加速传播;在气流作用下,火焰首先向预燃室末端传播,可减少高温燃气喷射前预燃室向主燃室回流的未燃混合气,提高预燃室内混合气的累计放热量,预燃室内可燃混合气累计放热率最高可提升14.9%。     

密闭燃烧性能试验台高压筒体研制

针对固体推进剂燃速测量设备不足的问题,设计了一种基于超声回波反馈的动态燃速测量系统。介绍了测试系统组成及其测试原理,设计了筒体的结构,并利用ANSYS软件对主筒体和上端盖进行了有限元分析及校核,证明了设计的安全性。依据设计进行了实物制造,试验表明,该系统可以满足预期的试验要求。     

调合生物柴油燃烧及颗粒物组分的试验研究

为深入研究不同比例调合生物柴油对发动机燃烧特性及颗粒物组分的影响,在一台单缸四冲程发动机上进行了调合生物柴油燃烧及颗粒物排放的试验研究。利用燃烧分析仪研究调合生物柴油对发动机燃烧过程的影响,利用热重分析仪(TGA)、气相色谱/质谱联用仪(GC-MS)研究调合生物柴油对颗粒物热重特性、挥发性有机物(VOCs)质量分数及有机可溶成分(SOF)和多环芳香烃(PAHs)组分的影响规律。研究表明:随着生物柴油掺混比的增加,发动机最高爆发压力及压力升高率峰值增加,压力曲线前移,预混放热率峰值随生物柴油掺混比增加而减小。与B0相比,燃用B20调合生物柴油,最高爆发压力增加了5.59%,对应的曲轴转角提前了3°CA。燃用调合生物柴油后VOCs及SOF组分略有增加,燃用B0、B5、B10及B20后颗粒物中VOCs组分的质量分数分别为12.28%、15.09%、23.06%和26.94%,SOF组分的质量分数分别为29.32%、32.08%、34.26%和35.67%,燃用B20后排放颗粒物中总PAHs降低了10.26%。     

“双碳”目标下零碳燃料基础燃烧特性实验教学平台开发及应用研究

“双碳”目标背景下,为满足燃烧类相关课程实验教学环节的需求,基于氢气预燃室射流点火引燃氨气这一燃烧模式,设计了零碳燃料基础燃烧特性实验教学平台。平台由定容燃烧实验教学平台与光学发动机实验教学平台组成,通过对火焰传播图片与燃烧压力数据的分析实现对不同参数条件下预燃室射流引燃特性和主燃室着火特性的评价。实验教学实践表明,该实验教学平台完全满足零碳燃料基础燃烧特性研究的目标,取得了良好的教学效果。     

固体火箭推进剂燃烧微粒场的激光全息诊断

大幅度提高金属燃料的含量是实现高能高效推进剂配方的一个发展方向。现针对含铝量2／%,粒度及含铝量6%,粒度15±2μm的两种推进剂展开了一系列的研究工作。应用离轴4F全息技术,进行了固体火箭推进剂燃烧流场的粒子分布研究。在常压、2MPa和4MPa实验工况下,获得了清晰的全息图。     

Simplified Modeling of Deflagration in Vessels

A simplified method that models the deflagration process occurring in closed or vented vessels is described. When combustion occurs within the spherical or cylindrical vessels, the flame moves spherically or segmentally to the vessel periphery. The volume and area of each element along the propagating flame front are calculated by using simple geometrical rules. For instabilities and turbulence resulting in enhanced burning rates, a simple analysis results in reasonable agreement with the experimental pressure transients when two burning rates (a laminar burning rate prior to the onset of instability and an enhanced burning rate) were used. Pressure reduction caused by a vent opening at predetermined pressure was modeled. Parameters examined in the modeling include ignition location, mixture concentration, vented area, and vent opening pressure. It was found that venting was effective in reducing the peak pressure experienced in vessels. The model can be expected to estimate reasonable peak pressures and flame front distances by modeling the enhanced burning rates, that is, turbulent enhancement factor.     

Accurate measurements of output characteristics and detonations of motorbike high-speed racing engine and their optimization at actual atmospheric conditions and combusted mixture composition

At a motorbike high speed racing engine there is very important an output engine characteristics which depends significantly on a detonation combustion rate, atmospheric conditions and a combusted mixture composition. The combustion process has got a relevant influence on a wear degree of main engine parts or on their damage eventually. The detonation combustion rate is very important because this kind of burning can be not only destructive but a useful phenomenon, as well. If the process of detonation burning is kept on a certain level, it can help significantly to the next increasing of an engine power output. In this article there is described the measurements of output characteristics of a high-speed racing engine which were performed by means of a data-recording system and the detonation combustion was evaluated using a quantitative method. The actual values of atmospheric conditions and the mixture composition were added to the measured values. Then the obtained values are compared visually with a damage degree of an engine piston caused by the detonation burning. The result is a limit value expressed in a number of detonation units related to a run distance interval of the vehicle driven by the high-speed racing engine. In framework of this run distance interval there is the process of detonation burning profitable. As well as it increases an engine power output and together it is not destructive with regard to engine design parts.     

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.

     

氧—液化石油气焊技术研究

通过分析氧液化石油气火焰的燃烧过程,计算火焰的理论燃烧温度后认为,氧液化石油气火焰的温度可以进行焊接,但是火焰的内焰具有氧化性,不能很好保护熔池金属,通过改变焊嘴的结构,使火焰内焰在燃烧时处于中性就可以进行气焊,通过采用高锰高硅填充丝进行焊缝填充和脱氧,保证接头质量.     

Combustion dynamics in a model lean-premixed gas turbine with a swirl stabilized injector

Unsteady numerical study has been conducted on combustion dynamics of a lean-premixed gas turbine with a swirl injector. A three-dimensional computation method utilizing large-eddy-simulation (LES) technique with finite rate chemical reaction was applied with the message passing interface (MPI) parallel architecture. The unsteady turbulent flame dynamics are carefully simulated so that the flow motion can be characterized in detail, showing fairly comparable results with the experimental data. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots and large vortical structures in the azimuthal direction. The correlation between pressure oscillation and unsteady heat release is examined by the spatial Rayleigh parameter. In addition, it is shown that the complicate heat-release-structure can be precisely regenerated by means of modal analysis using proper orthogonal decomposition (POD).     

Modeling of aluminum particle combustion with emphasis on the oxide effects and variable transport properties

A simplified analytical modeling of single aluminum particle combustion was conducted. Ignition and quasi-steady combustion (QSC) were separately formulated and integrated. Both the heat transfer from the hot ambient gas and the enthalpy of heterogeneous surface reaction (HSR) served to cause the particle ignition. Conservation equations were solved for QSC parameters in conjunction with conserved scalar formulation and Shvab-Zeldovich function. Limit temperature postulate was formulated by a sink term pertinent to the dissociation of the aluminum oxide near the flame zone. Effective latent heat of vaporization was modified for the thermal radiation. Ignition and QSC of the aluminum particle were predicted and discussed with emphasis on the effect of the aluminum oxide and variable properties. The model was validated with the experiments regarding ignition delay time, burning rate, residue particle size, flame temperature, QSC duration, and stand-off distance of the envelop flame. Agreement was satisfactory and the prediction errors were limited within 10%.     

炉底漏风对炉内燃烧及NOx生成排放特性的影响

干式排渣系统的冷却风会影响炉内燃烧的组织,现有研究多采用现场试验的方法,研究对象多为排烟温度或锅炉效率。以一台湿渣机改干渣机的660 MW超临界机组为研究对象,采用数值模拟的方法,研究了干渣机漏风对炉内燃烧和NO_x生成排放特性的影响,对比分析了不同炉底漏风来源时,炉膛火焰中心、飞灰含碳量、NO_x排放浓度等关键参数的变化。研究结果表明,炉底漏风量为燃尽风减量的工况对于炉内燃烧影响不明显;炉底漏风量全部或部分为燃烧器二次风减量时,随着漏风量占二次风比例的增大,主燃区氧量水平、出口飞灰含碳量、NO_x排放浓度均随之增高。从冷却风量对炉内燃烧及NO_x排放特性的角度分析了干渣机不同冷却风来源对机组运行的影响,为干式排渣机设计、改造及运行提供理论指导。     

基于彩色相机的运动燃煤颗粒温度测量研究

基于McKenna燃烧器的平面火焰携带流燃烧器系统的燃烧环境,采用彩色相机测温系统对运动中的燃煤颗粒进行拍摄。彩色相机测温系统经过黑体炉进行温度测量标定后,利用其r、g波段的响应,采用双色法对燃煤颗粒的温度进行测量。测温系统的标定采用基于BP神经网络训练的方法进行,通过对蜡烛燃烧火焰的拍摄,将得到的颗粒温度与热电偶数据进行对比,验证了测温系统的可靠性。实验研究了燃烧器出口不同距离处燃煤颗粒的温度信息,结果表明,燃煤颗粒温度随颗粒到喷嘴出口距离的变化整体呈先上升后下降趋势。该结果为研究煤粉燃烧过程及着火机理提供了参考。     

隔板应用于发动机燃烧室不稳定燃烧抑制中的二维数值计算分析

针对某水下航行器的燃烧室,用有限元的方法对隔板抑制燃烧不稳定性的声学机理进行了初步研究。利用ANSYS软件数值计算了隔板长度变化以及隔板数目变化时,对应的燃烧室声模态,并比较了它们的变化对燃烧室声模态造成的影响。计算表明:隔板抑制燃烧不稳定主要是通过对燃烧室腔体的声学共振频率进行平移,避开了与其相耦合的频率,从而达到抑制燃烧不稳定的目的。同时随着隔板长度的增加,靠近隔板处的声腔部分的切向声模态轴向化会逐步加剧,这样就可以得到更好的抑制作用。