Effects of Excess Air Coefficients on Combustion Characteristics of N-butanol by a Constant Volume Combustion Bomb

The effects of excess air coefficients on the combustion characteristics have been experimentally investigated by means of a constant volume combustion bomb.N-butanol was tested as the research fuel at different air-fuel equivalence ratios.Through the discussion of the combustion pressure,the combustion temperature,accumulated heat release,ignition delay and combustion duration,the effects of the excess air coefficient on combustion characteristics is clarified.Experimental results show that near the theoretical air-fuel ratio,the combustion rate is the fastest accompanying with shorter combustion duration while the combustion pressure and temperature reach the maximum.With increase or decrease of the excess air coefficient the combustion pressure,the temperature and the heat release reduce.Simultaneously,the combustion timing is deferred and the combustion duration becomes longer.

DAMAGE OF A HIGH-ENERGY SOLID PROPELLANT AND ITS EFFECTS ON COMBUSTION

In order to improve the safety of high-energy solid propellants, a study is carried out for the effects of damage on the combustion of the NEPE (Nitrate Ester Plasticized Polyether) propellant. The study includes: (1) to introduce damage into the propellants by means of a large-scale drop-weight apparatus; (2) to observe microstructural variations of the propellant with a scanning electron microscope (SEM) and then to characterize the damage with density measurements; (3) to investigate thermal decomposition; (4) to carry out closed-bomb tests. The NEPE propellant can be considered as a viscoelastic material. The matrices of damaged samples axe severely degraded, but the particles are not. The results of the thermal decomposition and closed-bomb tests show that the microstructural damage in the propellant affects its decomposition and burn rate.

Effects of Medium temperature on lean burn combustion duration of n-butanol

In this study,we did exploratory tests on the combustion duration of n-butanol,of which the object was lean mixture whose excess air ratio is 1.6,the independent variable was the initial temperature of combustion bomb.We did combustion tests on constant volume combustion bomb by changing the boundary conditions of the medium temperature.And we got its influence rules on the combustion duration of n-butanol,analyzing the combustion characteristic parameters about cylinder pressure,pressure rise rate,the combustion temperature,temperature rise rate,heat release and heat release rate.The results show that: With the increasing of medium temperature,the combustion duration is shortened significantly.

Burning characteristics of microcellular combustible objects

Microcellular combustible objects for application of combustible case,caseless ammunition or combustible detonator-holding tubes are fabricated through one-step foaming process,in which supercritical CO_2 is used as foaming agent.The formulations consist of inert polymer binder and ultra fine RDX.For the inner porous structures of microcellular combustible objects,the cell sizes present a unimodal or bimodal distribution by adjusting the foaming conditions.Closed bomb test is to investigate the influence of both porous structure style and RDX content on burning behavior.The sample with bimodal distribution of cell sizes burns faster than that with unimodal distribution,and the concentration of RDX can influence the burning characteristics in a positive manner.In addition,the translation of laminar burning to convective burning is determined by burning rate versus pressure curves of samples at two different loading densities,and the resulting transition pressure is 30 MPa.Moreover,the samples with bigger sample size present higher burning rate,resulting in providing deeper convective depth.Dynamic vivacity of samples is also studied.The results show that the vivacity increases with RDX content and varies with inner structure.

振荡提取-氧弹燃烧-离子色谱法测定纺织品中的可吸附有机卤化物

采用振荡提取、氧弹燃烧以及离子色谱定量检测等步骤测定纺织品中可吸附有机卤化物(AOX)。将纺织品加入到适量的提取液中,通过振荡使AOX充分溶解并富集在活性炭上,使用酸性硝酸钠溶液处理以去除无机卤化物。采用氧弹燃烧方式对可吸附AOX的活性炭进行裂解、燃烧及气化,采用离子色谱法测定。结果发现,在标准溶液0.02~2.50mg/L范围内,Cl^(-)、Br^(-)和I^(-)的线性相关系数R2在0.999以上,AOX的定量限为7.58~8.67mg/L,在不同的加标水平下AOX的平均回收率在83.1%~98.1%,相对标准偏差RSD(n=7)为2.1%~5.9%,表明方法具有良好的回收率和精密度。

乙醇-氢气-空气混合燃气的层流燃烧速度测定

为了研究乙醇的层流燃烧特性,在定容燃烧弹内,分别研究了初始压力为0.3 MPa,氢气比例为50%时,不同初始温度(370 K和450 K)和当量比(0.7~1.4)下,氢气-乙醇混合燃气的火焰传播规律。计算得到了混合燃气的层流燃烧速度和马克斯坦长度,分析了拉伸率对火焰传播速度的影响,同时将研究结果与文献数据进行了比较,验证了计算模型的可靠性。结果表明:随着初始温度的增加,混合燃气的层流燃烧速度也会随之提升;当量比的增加也会提升混合燃气的层流燃烧速度,在当量比为1.2时达到了峰值,随后开始降低。初始温度的增加会在一定条件下会导致火焰的不稳定;在初始温度370 K下,马克斯坦长度始终大于0,火焰一直处于稳定状态;初始温度450 K、0.7~0.9当量比下的马克斯坦长度小于0,火焰出现了不稳定状态,因为较高的初始温度会产生强烈的对流和湍流效应,这些效应会使火焰的边界层受到扰动,造成火焰不稳定;不同初始温度下的马克斯坦长度都随当量比的增加而增加,火焰的稳定性不断提升。对计算得到的层流燃烧速度进行数据拟合,得到了计算乙醇-氢气-空气混合气层流燃烧速度的关系式。

大空间尺度下预燃室射流火焰发展历程的光学诊断和模拟研究

基于定容燃烧弹,在与大型低速预燃室式双燃料船机相似的空间和热力学条件下,采用相似的点火过程,对主燃烧室内的射流火焰发展和引燃预混火焰的扩展历程进行光学测试;提出一种基于全网格映射,分阶段采用不同的燃烧模型的方法模拟不同燃烧阶段的火焰发展过程。基于定容装置试验数据验证了模型对燃烧火焰扩展速度预测的适用性和准确性。研究结果表明:预燃室燃油喷射量直接影响射流火焰的最大贯穿距离和火焰强度;主燃烧室内的混合气需要达到一定浓度才能被引燃。对燃烧过程的模拟,第一阶段燃烧采用均质搅拌反应器(well-stirred reactor,WSR)模型可以较为准确地模拟不同燃油喷射量下的射流发展速度和火焰射流的最大贯穿距离;第二阶段燃烧采用G方程可以较为准确地模拟火焰在各方向上的扩展速度。采用Mapping方法连接的两个模型对燃烧两个阶段的火焰扩展的整体速度具有较高的预测精度。

Numerical evaluation of acoustic characteristics and their damping of a thrust chamber using a constant-volume bomb model

In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation（FFT）, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal（1L） acoustic mode can be excited easily and is hard to be damped. The axial position of the central constantvolume bomb has little influence on the amplitude and damping capacity of the First Radial（1R） and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential（1T） mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber.

Spray,atomization and combustion characteristics of oxygenated fuels in a constant volume bomb:A review

Biofuels have extensive available resources and have an immense potential as promising alternative fuels for automobile.The application advantages of biofuels are mainly reflected as particulate matter(PM)reduction,carbon neutral,greenhouse gases reduction,waste utilization,energy and economic security,and fuel pluralism.Based on the understanding of molecular structure effects of biofuels on soot formation and particles morphology,the effects of alcohols,ethers,esters and biodiesel on spray and combustion process in constant volume bomb in recent years are retrospectively analyzed in this paper.For the mixture,macromolecular ester fuels and polyoxymethylene dimethyl ether(PODE)are conducive to the improvement of liquid spray,while biodiesel,small molecules,dimethyl ether(DME)and alcohols are reversed.Alcohols are advantageous to the extension of mixing time and the increasing of vapor-phase mixture.Through the influence integrated assessment,alcohols show the best performance on the spray,atomization and combustion,while biodiesels show the worst.But in terms of combustion,PODE is the best choice without considering spray and atomization.For binary alternative-diesel fuel blends,methanol or butanol is the best additive based on synthetically considerations on spray,atomization and combustion.To meet the requirements of the fuel application of diesel engine,ternary fuel or even quaternary fuel have been proposed and explored.This review can help to form a systematic understanding on fuel recombining and obtain the guide of clean and efficient fuel formulation for diesel engine.

Influence of Mixture Gas Conditions on the Laminar Combustion Characteristics of Natural Gas

Natural gas is a promising alternative fuel for the internal combustion engine,and natural gas engine has become an efficient and feasible measure to deal with the energy shortage and climate change.Since the laminar flame characteristics are the foundation of the turbulent flame,the laminar flame characteristics of natural gas have a significant impact on the combustion status and efficiency of the engine.A visual constant volume bomb was used to study the influence of the gas components,different excess air coefficient(λ),and initial conditions on the laminar combustion characteristics of natural gas.The experimental results showed that when the initial pressure and temperature were 0.1 MPa and 300 K respectively,compared to propane,ethane had a remarkable influence on the equivalent-combustion laminar-combustion-speed,with an average increase of approximately 5.1%for every 2.5%increase in the ethane proportion.The laminar combustion velocity of the natural gas under different excess air coefficients had a maximum value at aboutλ=1.0,and the Markstein length of the flame decreased with the increase of theλ.The increase in the initial pressure of the mixture resulted in a decrease in the equivalent-combustion laminar-combustion-speed of the flame,a significant decrease in the Markstein length.The increase of the initial temperature of the mixture led to a rapid increase of the equivalent-combustion laminar-combustion-speed,but the effect on the flame Markstein length was not dominant.

氧弹燃烧离子色谱法同时检测焚烧废弃物中氟、氯、溴、硫多元素含量

采用氧弹燃烧离子色谱法同时检测焚烧废弃物中氟、氯、溴、硫含量。进行了方法检出限测试、标准物质测试、实际样品测试、标准样品加标回收实验验证方法准确度和精密度研究。4种元素的方法检出限在1.4~13.8 mg/kg、方法加标回收率在91.4%~105.5%、测定值的相对标准偏差<4.5%。氧弹燃烧离子色谱法检测焚烧废弃物中氟、氯、溴、硫含量准确度高,方法可行。

纳米CuBi_(2)O_(4)/G复合增强AP/nAl复合物燃烧和释压研究

为了显著提高AP/nano-Al(nAl)复合物的压力释放效率,降低燃烧时间,提出了一种制备AP/nAl/G/CuBi_(2)O_(4)(CBO)复合物的策略。密闭爆发测试结果表明,复合物的压力释放率和压力达到峰值时间都得到了显著改善;当添加石墨烯(G)(2 wt%)/CBO(5 wt%)时压力增加13.5%,增压速率增加51.1%。此外,利用激光点火装置和高速摄像系统对制备复合物的点火和燃烧性能进行了评估,结果表明G和CBO的引入成功降低了点火延迟并缩短了20 ms燃烧时间。综上所述,添加CBO和G能显著改善AP/nAl燃烧放热、峰值压力与最大增压速率。

水蒸气稀释条件下NH_(3)/H_(2)层流燃烧特性研究

通过定容燃烧弹试验结合一维层流预混火焰数值计算的方法,在初始压力为101.3 kPa,化学当量比为0.8~1.4,掺氢比为0.3~0.7的条件下,探究水蒸气含量(0~50%)对NH_(3)/H_(2)燃烧特性的影响机制。研究结果表明:随着当量比的增加,NH_(3)/H_(2)层流火焰速度先增大后减小,其峰值出现在当量比1.2左右。随着水蒸气稀释比增大,NH_(3)/H_(2)层流火焰速度线性降低,其峰值向当量比1.1偏移,且受当量比影响的敏感度降低。化学动力学分析表明在水蒸气的物理化学作用中,稀释作用的影响最大。主要基元反应中R1、R3、R68等支链反应对层流火焰传播具有促进作用,而R16、R58、R60等支链反应具有抑制作用。提高水稀释比会增加关键支链反应对层流火焰速度的敏感性系数,并且其增加的幅度不断变大。随着水稀释比不断增加,反应区的NO、N_(2)O、OH等自由基的物质的量分数显著降低,导致NH_(3)/H_(2)层流火焰速度降低。

氧弹燃烧-离子色谱法测定助焊剂中的碘

采用氧弹燃烧-离子色谱法测定助焊剂中的碘。使用NaOH-抗坏血酸(AA)复合成分作为吸收液有效成分,可将氧弹燃烧对碘的吸收率达到90%左右,并且能有效解决以单一AA成分作为吸收液有效成分氧弹燃烧后,样品在进行离子色谱测试时基线过高而不能准确识别碘的问题。实现碘含量在50~1000μg范围内助焊剂样品碘的高效吸收以及准确测定。方法安全,环保,操作便捷,在助焊剂中碘含量的准确测定方面可发挥重要作用。

氧弹燃烧-离子色谱法测定4种再生醇溶剂中总氯、氮和硫的含量

建立并优化了甲醇、乙醇、异丙醇与正丁醇等4种再生一元醇中总氯、总氮与总硫含量的测定方法。采用氧弹燃烧的样品前处理方法,以25 mmol/L的氢氧化钠溶液为氧弹内吸收液,目标物转化为相应的离子化合物,使用离子色谱法进行定量。结果表明,方法中总氯、总氮与总硫拟合的标准曲线,其线性相关系数均大于0.999;样品取样量为1.5 g时,总氯、总氮与总硫的检出限分别为4.79 mg/kg、15.0 mg/kg与6.33 mg/kg,测定下限分别为19.2 mg/kg、60.0 mg/kg与25.3 mg/kg,RSD在2.58%~3.05%之间,加标回收率在70.6%~119%之间。该方法操作简单、准确度较高,实现了甲醇、乙醇、异丙醇与正丁醇等4种再生产品中总氯、总氮与总硫含量的同步快速测定。

外部环境对建筑材料热值检测结果的影响研究

燃烧热值是评估建筑材料火灾危险性的重要指标,其测定精度对消防设计和火灾风险评估至关重要。为了研究环境温度对热容量标定和燃烧热值的影响,通过氧弹量热法在不同温度条件下进行试验。结果表明,环境温度升高会导致热容量标定值和燃烧热值下降,且温度波动显著影响结果的稳定性。建议在测定过程中严格控制环境温度,以提高结果的准确性和可靠性。

氧弹燃烧-离子色谱法测定精馏残渣中硫的含量

水泥窑协同处置危险废物精馏残渣中硫元素含量的常用测定方法存在操作繁琐、灵敏度低、测试条件要求高、环境污染严重等问题。采用“氧弹燃烧—离子色谱法”测定精馏残渣中硫元素含量,克服了常规检测方法的不足,提高了检测结果的准确性及重现性。硫含量分析检测实验表明,在氧弹燃烧压力3MPa,吸收液为0.5mol/L NaOH溶液,吸收液作用时间20min,流动相流速100mL/min的条件下,硫酸根的质量浓度在0.5~50mg/L范围内表现出了较好的线性关系,相关系数均>0.999,平均加标(添加标准溶液)回收率达96.8%。

氧弹燃烧——分光光度法测定危险废物中总磷的含量

采用氧弹燃烧—分光光度法测定危险废物中总磷含量,利用耐卤素氧弹富氧、充分燃烧对废物进行预处理,以超纯水为吸收液、冲洗液,通过酸化、微沸将目标物转化为正磷酸根,并用分光光度法对吸收冲洗液中正磷酸根含量进行测定,通过计算可得到总磷的含量。结果表明:该方法定量检测限为36.0 mg/kg,在0~0.6 mg/L线性范围良好,相关系数大于0.999,精密度为11.46%。用99%磷酸三丁酯进行了方法验证,准确度在97.51%~101.20%。此方法具备较好的准确度、精密度,快速安全,适合危险废物总磷的测定,并可在焚烧设备防腐蚀控制和危险废物焚烧配料方面提供实际指导。

天然气-氢气-空气混合气的层流燃烧速度测定

在定容燃烧弹内研究了常温常压下天然气-氢气-空气混合气的火焰传播规律，得到了不同掺氢比例（氢气在天然气中的体积掺混比例为0％～100％）和燃空当量比（0．6～1．4）下混合气的层流燃烧速率和马克斯坦长度，通过对马克斯坦长度的测量，分析了拉伸对火焰传播的影响。结果表明，随着天然气中掺氢比例的增加，混合气的燃烧速率呈指数规律增加，马克斯坦长度值减小，火焰的稳定性下降。各掺氢比例下，随当量比的增加，马克斯坦长度值增加，火焰的稳定性增强。通过对试验结果的数据拟合，得到了计算天然气-氢气-空气混合气层流燃烧速率的关系式。

多功能燃烧弹试验系统的研究与开发

为了获得燃烧边界条件的精确控制及发动机多种内特性测试仪器设备的使用,同时改善定容燃烧弹的局限性,本研究进行了多功能燃烧弹的研制。多功能燃烧弹试验装置主要由燃烧弹部分、混合气配给系、燃料/空气混合系、喷油系、点火系、控制系统和数据采集分析等系统组成。多功能燃烧弹不仅具备良好的边界条件可控性,而且具备定压燃烧、复合燃烧过程以及定容燃烧过程的试验功能。它可对多种燃料、多种点火方式进行试验研究,并可对动态信号、光谱信号及其稳态参数信号进行采集。同时,该燃烧弹可以按照试验者的边界条件要求较准确地将燃烧边界条件控制在理想的状态,并可全面地进行发动机的工作过程研究。