乳胶泡沫引火位置对火蔓延特性的影响

利用自行搭建的小尺寸实验平台,开展了对不同点火位置的乳胶泡沫材料燃烧过程的对比实验,通过对火蔓延过程中的部分重要参数(如最大火焰高度、火蔓延速度和蔓延过程中样品表面温度变化等)的测定,分析了点火位置不同时,乳胶泡沫材料的火蔓延特性。结果表明:边缘点火和中间点火条件下,最大火焰高度分别为397和491 mm,火蔓延速度分别为1.8和0.97 mm·s~(-1);边缘点火时的乳胶泡沫材料表面火蔓延过程中的温度低于中间点火情况下。     

不同点火位置时乳胶泡沫火蔓延特性

在边缘点火和中间点火条件下对多孔乳胶泡沫进行小尺寸燃烧,研究了不同点火位置时火焰的蔓延过程和规律,考察了材料表面温度分布、火蔓延速率和火焰高度随时间的变化.结果表明,边缘和中间点火时,平均火蔓延速率分别为0.42和0.24cm/s,蔓延至整个材料表面的时间分别为84和74s,最大火焰高度分别为68.6和82.7cm.随火焰区不断增大,火焰温度不断升高,传递给未燃区的热量增多,加速了材料热解,火蔓延速率增大.     

点火位置对乳胶泡沫水平火蔓延规律的影响

为研究点火位置对乳胶泡沫材料水平方向火蔓延规律的影响。搭建小尺寸实验平台,在距离材料中心点0（x1）、3.54 cm（x2）、7.08 cm（x3）、10.62 cm（x4）、14.16 cm（x5）、17.70 cm（x6）位置处点火,研究了试样表面温度、质量损失、火焰高度、火蔓延速度等特性参数的变化规律。结果表明,随着点火位置由材料中心点向边缘点移动,平均火蔓延速度分别为0.24、0.23、0.19、0.31、0.42、0.51 cm·s^-1,呈现先减小后增大的规律;x3点火位置时的平均火焰高度较低,燃烧时间较长,平均质量损失速率较低,主要与火蔓延过程中的热量传递方式有关。研究结果显示了乳胶泡沫的火蔓延过程,得到了点火位置对火蔓延的影响规律。     

点火位置对乳胶泡沫水平火蔓延规律的影响

为研究点火位置对乳胶泡沫材料水平方向火蔓延规律的影响。搭建小尺寸实验平台,在距离材料中心点0(x1)、3.54 cm(x2)、7.08 cm(x3)、10.62 cm(x4)、14.16 cm(x5)、17.70 cm(x6)位置处点火,研究了试样表面温度、质量损失、火焰高度、火蔓延速度等特性参数的变化规律。结果表明,随着点火位置由材料中心点向边缘点移动,平均火蔓延速度分别为0.24、0.23、0.19、0.31、0.42、0.51 cm·s~(-1),呈现先减小后增大的规律;x3点火位置时的平均火焰高度较低,燃烧时间较长,平均质量损失速率较低,主要与火蔓延过程中的热量传递方式有关。研究结果显示了乳胶泡沫的火蔓延过程,得到了点火位置对火蔓延的影响规律。     

不同宽度及密度的保温材料EPS的火焰蔓延及燃烧特性

对密度为18和25 kg/m3的保温材料模塑聚苯乙烯(EPS),在不同宽度下进行小尺寸燃烧特性实验,考察了池火区长度、火焰高度及火蔓延速度等. 结果表明,EPS火焰蔓延过程中,火焰形态包括典型形态、逆向形态及重合形态;宽度为8 cm的试样火焰蔓延稳定性较差,逆向形态及重合形态更多. 不同宽度、密度18 kg/m3的EPS的平均池火长度均大于密度25 kg/m3的EPS,主要是由于EPS密度越小其火蔓延速度越大. 密度18 kg/m3的EPS由于孔隙中空气的助燃作用,火蔓延速度约为密度25 kg/m3的EPS的2倍. EPS材料表面火焰区平均火焰高度主要受宽度影响,而池火区平均火焰高度主要受池火区长宽比影响.     

凹型结构下保温材料EPS典型垂直火蔓延特性对比研究

本工作通过自主搭建小尺寸火蔓延的实验平台,研究了凹型结构中保温材料EPS垂直向上和向下火蔓延特性。对比分析了火焰结构特性、火蔓延速度、质量损失速率、火焰温度等参数的变化规律。结果表明,在垂直向上蔓延过程中,EPS出现短暂的停滞现象。一方面由于烟囱效应易形成一个大的浮力压力差,导致火焰不稳定性;另一方面由于凹型结构易于烟气的聚集,导致燃烧不充分。而在垂直向下蔓延过程中,由于逆向烟囱效应的影响,火蔓延速度明显加速。火蔓延过程中质量损失速率,很大程度上受其火焰高度的影响,呈现上下振荡的特性。未燃区域部分,火焰温度经历两个温度峰值,向上蔓延过程中第一个温度峰值大于第二个;而向下蔓延过程中第一个温度峰值小于第二个。这主要是由于火焰结构形态及烟囱效应的方向特点,导致产生两个不同大小的峰值。本研究结果可为实际凹型结构下火蔓延特性研究提供前期理论和参考价值。     

阻燃硬质聚氨酯泡沫塑料垂直火蔓延特性研究

通过一步合成法制备了阻燃硬质聚氨酯泡沫,自主搭建保温材料火蔓延实验台,采用中小尺寸实验对比研究了阻燃及非阻燃硬质聚氨酯的垂直火蔓延特性,分析了火焰结构特性、火蔓延速度、火焰温度、质量损失速率等参数的变化规律。结果表明,火蔓延过程中,材料表面均出现了炭化现象,垂直双面燃烧过程中聚氨酯纯样RPUF燃烧最剧烈,阻燃剂膨胀石墨(EG)、次磷酸铝(AHP)和二乙基次膦酸铝(ADP)的加入,抑制了材料的燃烧和蔓延,使材料燃烧的火蔓延速度、质量损失速率及温度等参数都相应降低。RPUF/AHP5垂直双面火蔓延过程中,火焰稳定性差,在20 s后出现熄灭现象,原因是阻燃剂次磷酸铝(RPUF/AHP5)受热挥发出难燃气体。AHP降解后形成的含磷化合物可促进聚氨酯分子链成炭,导致产生熄灭现象。而RPUF/ADP5火蔓延过程中,同样出现了熄灭现象,其熄灭的程度低于阻燃剂次磷酸铝(RPUF/AHP5)试样。RPUF/EG5火蔓延过程中试样表面温度存在两个峰值,由于RPUF/EG5燃烧生成的炭层不稳定所致。当温度高于400℃时炭层被迅速氧化,热量穿透炭层使内部未燃样品热解,生成温度的第二个峰值。     

倾斜角对液体燃料润湿条件下砂床表面火蔓延的影响

利用纹影系统、CCD相机以及K型热电偶对正丁醇润湿条件下不同角度的砂床表面火蔓延特性进行了研究,分析了不同砂床表面倾角对火蔓延的影响机理。研究结果表明:正丁醇润湿条件下变角度砂床表面火焰是稳定匀速蔓延的,向上蔓延时,火焰的高度、黄色发光区以及蔓延速度随着倾角的增加而增大;向下蔓延时,火焰的高度、黄色发光区以及蔓延速度随着倾角的增加而减小;蔓延火焰前方存在预热区,且预热区随表面倾角的增大而增大:砂层内部存在热边界层,且砂床热边界层厚度随表面倾角的增加而减小。得到的火蔓延特性及燃烧机理为此类液体燃料的储存、使用以及环境保护提供了一定的科学依据。     

旋转流中预混合火焰高速传播现象—II.点火位置与燃烧过程

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上,围绕燃烧器的点火特性,对旋流场中的点火位置和稳定火焰形成进行了数值分析.结果表明,不适当的点火位置会影响稳定火焰的形成,在相同的燃烧工况下,在流场中点火位置不同,火焰的发展出现不同的趋势.在靠近中心轴附近的低速区点火时,火焰能够稳定;在靠近管壁的高速区点火时,撤离点火源后,火焰吹熄.本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.     

点火位置对氢气/甲烷/空气预混气体爆燃特性的影响

为研究不同点火位置下氢气/甲烷/空气预混气体的爆燃特性,改变点火位置IP和氢气添加比例φ,在100mm×100 mm×1000 mm方形透明管道实验平台上开展爆燃实验。实验结果表明:火焰结构向泄爆端和封闭端传播时受点火位置和氢气添加比例的控制,当火焰向泄爆端传播时,郁金香火焰的形成因素由IP主导,当火焰向封闭端传播时,IP及φ共同作用于郁金香火焰的形成;IP和φ对火焰前锋演化的作用模式可以分为3类;当混合气体中φ小于0.25时,氢气添加对火焰传播速度的影响不明显;当φ不超过0.75时,仅当IP位于管道中后部时,超压出现周期性振荡,且点火位置距泄爆端越近,振荡时间越长;当为纯氢爆炸时,不同点火位置下压力振荡消失且到达最大压力峰值的时间基本一致;当φ不同时,最大压力峰值随点火位置的变化规律不同。     

Experimental investigation into the influence of ignition location on flame spread and heat release rates of polyurethane foam slabs

This study presents the results from a set of 11 large‐scale open fire tests performed on flexible polyurethane foam slabs/mattresses. The purpose of the study was to investigate the influence of the ignition location on the fire behaviour of the foam slabs and to generate data on a highly characterised material that could be used for modelling work in the future. A method for obtaining spatially resolved flame spread data for this type of material was presented using a gridded array of 5 × 10 thermocouples placed on the underside the foam slab and from this, flame spread was examined using three different approaches. The heat release rate (HRR) results showed clear shapes forming that were dependent on the ignition location, with two distinct behaviours being observed between the various different ignition locations, this was also observed in the calculated flame spread rate (FSR) data. Results within an individual test, showed the calculated range of FSRs over the geometry of the slab varied between approximately 1 and 8 mm/s depending on the ignition location. The average FSR values between tests varied between 3 and 7 mm/s and the maximum and minimum values were calculated to be approximately 11 and 2 mm/s respectively.     

浓度和点火位置对氢气-空气预混气爆燃特性影响

开展了氢气-空气预混气在透明方管内的爆燃实验研究,分析在一端开口一端封闭的狭长空间内,浓度和点火位置对氢气-空气预混气爆燃特性的影响。实验结果表明：氢气浓度和点火位置对火焰锋面结构以及发展有重要影响;各当量比条件下,均在距封闭端100 mm位置点火时反应最为迅速;在极贫燃或极富燃条件下,点火位置对火焰发展影响更大。氢气浓度与点火位置共同作用于压力波形,以距封闭端300 mm点火位置为界,分别在管道前后两段点火时,不同当量比条件下超压波形呈现复杂变化。超压峰值对氢气浓度具有极强依赖性,并且浓度对爆燃超压的影响程度远大于点火位置;在各点火位置下,均在Φ = 1.25时获得最大超压;最大超压对应的点火位置取决于当量比。     

旋转流中预混合火焰高速传播现象-II. 点火位置与燃烧过程

在前期关于Vortex-bursting旋流式预混燃烧器的燃烧效率及其进口混合气速度分布对燃烧效率的影响实验基础上，围绕燃烧器的点火特性，对旋流场中的点火位置和稳定火焰形成进行了数值分析. 结果表明，不适当的点火位置会影响稳定火焰的形成，在相同的燃烧工况下，在流场中点火位置不同，火焰的发展出现不同的趋势. 在靠近中心轴附近的低速区点火时，火焰能够稳定；在靠近管壁的高速区点火时，撤离点火源后，火焰吹熄. 本结果对于强化预混合燃烧的稳定性具有理论和工程指导意义.     

Fire-performance of a ventilated facade insulated with a B2–classified rigid polyurethane foam

A two-storey test rig was used to investigate how an insulated facade would react to the impingement of a simulated room fire. In particular, whether or not a facade insulated with polyurethane foam would promote vertical flame spread. Wooden cribs weighing 40 kg were used as fire sources. One set of tests was run without any steel cladding to study the behaviour of the polyurethane foam alone. In a wall-configuration test as well as under a conrner-configuration one limited vertical and horizontal flame propagation were found. The degree of damage was to some extent, greater under the corner-test conditions than with the wall tests. A ventilated facade construction with the profiled steel cladding fixed to vertical support-work was used for the second set of tests. In order to simulate repair conditions, the outer metal cladding was completely removed from the lower 1.5 m of the facade. In Both tests a strong chimney-effect behind the cladding was observed. This intensification of the flame impingement led to a flame spread up the top of the facade. The tests indicated that the vertical flame spread would continue unless the method of construction incorporated vertical fire stops.     

Experimental study on fire hazard of typical curtain materials in ISO 9705 fire test room

Curtain materials are commonly used as decoration, shade, or screen. They are flammable and are usually across a large part of a room, leading to the risk of a high fire hazard. Once ignited, the upward fire spread would accelerate the fire development in an enclosure. In this paper, fire hazard of three typical curtain materials with different pleat rates were tested in an ISO 9705 fire test room. Fire parameters such as temperature field, flame spread rate, heat release rate (HRR), and emitted gases, and the influences of pleat rate and cotton content on flame spread rate were investigated. The correlation between flame spread rate and HRR was discussed. The results show that the upward flame spread has an accelerating rate, and an inverted‐triangle burning area would emerge during the combustion. Some horizontal fibrillar structures appear in this burning area. Pleat rate and cotton content have considerable influence on the curtain fire behavior. The flame spread rate shows a linear response to HRR at the early stage. In addition, a function between average flame spread rate and pleat rate for engineering estimation is proposed, and a linear relationship between HRR/m_CO and m/m_CO has been obtained. The study results provide valuable reference to building fire simulation and safety design. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of variations in incident heat flux when using cone calorimeter test data for prediction of full‐scale heat release rates of polyurethane foam

The development of methods to predict full‐scale fire behaviour using small‐scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data were obtained using cone calorimeter tests and infrared video‐based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests and in predicting results for thinner foams. Results indicated that because of sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Fire spread from an open‐doors electrical cabinet to neighboring targets in a confined and mechanically ventilated facility

Electrical cabinet fire is one of the main fire hazards in nuclear power plants. As part of the OECD PRISME‐2 programme, four fire tests were carried out to investigate the fire spread from an open‐doors electrical cabinet to overhead cable trays and adjacent cabinets in a confined and mechanically ventilated facility. These tests, named CFS‐5 to CFS‐7 and CORE‐6, used same both cabinet (fire source) and three overhead cable trays. The trays were filled with a halogenated flame‐retardant cable‐type for CFS‐5 and one halogen‐free for the three other tests. Moreover, fire dampers were used for CFS‐7 test while CORE‐6 test implemented two additional cabinets adjacent to the fire source. Measurements such as flame and gas temperature, gas concentration, mass loss rate, and heat release rate were performed for investigating the fire spread. Cabinet fire spread to the cable trays for CFS‐5 and CFS‐6 tests. Three fast and short cable tray fires were shown for CFS‐5, while a slow and long cable tray fire was highlighted for CFS‐6. In contrast, the fire dampers shutdown for CFS‐7 test prevented ignition of the overhead cables. Furthermore, for CORE‐6 test, cabinet fire spread to the adjacent cabinets, but the upper cables were not ignited.     

Bedding ignition,vertical flame spread and subsequent thermal impact on underlying mattress

The ignition of bedding and subsequent vertical spread of fire along the side of a noncombustible surrogate bed set was investigated. One‐hundred‐eight (108) tests were conducted to assess the ignition timeline and subsequent vertical flame spread of bedding up the side of a bed along with the thermal impact of the bedding fire on the underlying bed set. The ignition source for all tests was comprised of the flame from a book of matches placed on bedding at floor level at the base of the bed. The bedding consisted of combinations of a cotton/polyester blend sheet and bedspread. Ignition occurred in 3 to 10 seconds for the majority of the test. The speed of subsequent vertical flame spread, assessed through video frame analysis tools, was dependent on the exposed bedding material with an exposed sheet exhibiting faster spread. Thermal exposure from the burning bedding to the vertical sides of the bed set was assessed with an array of thermocouples embedded at the surface of the sides of the underlying bed set. The time to thermal exposure was found to be a function of the vertical flame spread and thickness of the bedding material(s).