分层反压注射成型厚壁光学透镜的工艺分析

为了研究反压压力对成型厚壁光学透镜的影响,利用自行开发的分层反压注射成型厚壁光学透镜的实验方案,通过正交实验优化设计开展了工艺参数优化实验,研究了在不同分层方式下内外层反压压力对对厚壁光学透镜光学性能的影响,从而根据正交优化参数组合成型具有优异光学性能的理想厚壁光学透镜。正交实验研究结果表明,使用聚甲基丙烯酸甲酯(PMMA)为厚壁光学透镜的原材料进行分层反压注射成型,能够有效减少厚壁光学透镜收缩率,同时随着内外层反压压力的提高,厚壁光学透镜的透光率和折射率均不同程度的得到提高,透镜光学性能优异。     

Investigation of smoke gases and temperatures during car fire – large‐scale and small‐scale tests and numerical investigations

The hazards for passengers during vehicle fires result from the increasing temperature and the emitted smoke gases. A fire was set on a car to investigate the development of temperature and of gaseous fire products in the passenger compartment. The study was based on a full‐scale test with a reconstructed scene of a serious car fire. The aim of this work was to identify the conditions for self‐rescuing of passengers during a car fire. A dummy, equipped with several thermocouples, was placed on the driver's seat. Also, the smoke gases were continuously collected through a removable probe sensor corresponding to the nose of the dummy in the passenger compartment and analyzed using Fourier transform infrared spectroscopy. Additionally, several car components were investigated in the smoke density chamber (smoke emission and smoke gas composition). It was found that the toxic gases already reached hazardous levels by 5 min, while the temperatures at the dummy were at that time less than 80 °C. The toxicity of smoke gases was assessed using the fractional effective dose concept. The various experimentally parameters (temperature and smoke gas composition) were implemented into numerical simulations with fire dynamics simulator. Both the experimental data and the numerical simulations are presented and discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

浅谈化工区稳高压消防水系统设计

文章结合工程设计实例针对大庆石化公司化工区消防水现状,论证了增设稳高压消防水系的必要性和紧迫性。在通过对比稳高压与临时高压消防水系统的基础上,提出将现有装置的临时高压改造为稳高压系统的设计思路,在装置改造量最小的情况下,完善整个化工区的稳高压消防水系统,不但满足安全生产的要求同时也满足了现行规范的要求。同时针对现有消防水系统存在的腐蚀和冻涨的问题提出了解决措施以保证改造后稳高压消防水系统的正常运行。     

Influence of longitudinal fire location on smoke characteristics under the tunnel ceiling

The critical ventilation velocity is almost the most well‐investigated fire phenomenon in the tunnel fire research field whereas previous studies have always investigated it when the fire source is distant from the downstream tunnel exit. Fortunately, a recent study provided a set of data on the critical ventilation velocity for tunnel fires occurring near tunnel exits by small‐scaled experiments, nevertheless, with a lack of further analysis. To demonstrate the relationship of the critical ventilation velocity and the distance between the fire and tunnel exit more explicitly and detailedly, a quantitative and graphical study was carried out and a correlation was presented in this paper. Inspired by this, a set of small‐scaled experiments were carried out to investigate the influence of different longitudinal fire locations on maximum smoke temperature under the tunnel ceiling. Results show that unlike the critical ventilation velocity, the maximum smoke temperature was not obviously affected by longitudinal fire location. Copyright © 2014 John Wiley & Sons, Ltd.     

The burning behaviors of pool fire flames under low pressure

To investigate the influence of low pressure on pool fire behaviors, liquid n‐heptane pool fires with the diameters of 6, 8, and 10 cm were tested in a low‐pressure altitude chamber. The tests were conducted under different static chamber pressures, ranging from 40 to 60 to 80 to 101 kPa. Fuel mass loss and high‐speed flame video were recorded during the whole burning process of each test. The mass burning intensity is determined by the convective and radiative heat feedback to the fuel, and analysis shows that the convective part is the major contributor to fuel evaporation. Video recordings show that flame height increases with the reduction of pressure, as supported by the dimensionless analysis. The flame puffing amplitude increases under low pressure, resulting in a portion of the flame being quenched. A special phenomenon was observed from the flame videos in that flame rotation emerged at the ending burning stage, which was attributed to the Coriolis force effect. Copyright © 2014 John Wiley & Sons, Ltd.     

浅谈建筑工程防排烟系统设计中容易忽视的几个问题

根据实践经验,总结出若干建筑工程防排烟系统设计中容易忽视的问题,提出值得借鉴的经验和需要吸取的教训,以便引起广大审核人员特别是初学者的注意,防止类似的错误发生。     

Experimental and numerical study of interactions between sprinklers and natural smoke vents

Real scale experimentations have been conducted in order to investigate interactions that may occur in a compartment where sprinklers and Smoke and Heat Exhaust Vent Systems coexist. Fuel oil spray was used as fire source with steady heat release rate of 400 and 800 kW. Both sprinkler system and natural Smoke and Heat Exhaust Vent Systems were designed according to the French standards. Effect of vent on sprinkler activation time was studied. An analysis of the temperature field inside the compartment was conducted while vent was opened prior or after sprinkler activation. Simulations of the experiments were also carried out with Fire Dynamics Simulator v.6 for validation purpose and also to provide supplementary data regarding soot flow rate and energy extracted at the vent.     

Fire effluent component yields from room‐scale fire tests

Estimation of the time available for escape (ASET) in the event of a fire is a principal component in fire hazard or risk assessment. Valid data on the yields of toxic smoke components from bench‐scale apparatus is essential to accurate ASET calculations. This paper presents a methodology for obtaining pre‐flashover and post‐flashover toxicant yields from room‐scale fire tests. The data are to be used for comparison with bench‐scale data for the same combustibles: a sofa, bookcases, and electric power cable. Each was burned in a room with a long adjacent corridor. The yields of CO₂, CO, HCl, HCN, and soot were determined. Other toxicants (NO₂, formaldehyde, and acrolein), whose concentrations were below the detection limits, were of limited importance relative to the detected toxicants. The uncertainty values were comparable to those estimated for calculations used to determine ASET and were sufficiently small to determine whether a bench‐scale apparatus is producing results that are similar to the real‐scale results here. The use of Fourier transform infrared spectroscopy was useful for obtaining toxicant concentration data; however, its operation and interpretation are not routine. The losses of CO, HCN, and HCl along the corridor were dependent on the combustible. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental study of the burning behavior of n‐heptane pool fires at high altitude

The same configured calorimeters were built in Hefei (99.8 kPa) and Lhasa (66.5 kPa), respectively. Four sizes of round pans with diameters of 10, 15, 20, and 25 cm were adopted to study the effect of high altitude on the burning behavior of liquid pool fires. Analysis on the burning rate obtained in this study and in the literature at different altitudes indicates that pressure fire modeling performs better than radiation fire modeling in correlating the burning intensity (burning rate per unit area) with pressure and pool diameter for cases under low ambient pressure. The study also shows that heat release rate and combustion efficiency decrease at higher altitude. For medium pool fires, the burning intensity and heat release rate are proportional to D^5/2, thus the combustion efficiency being independent on pool sizes but decreases at higher altitude by a factor approximate to the pressure ratio. Copyright © 2014 John Wiley & Sons, Ltd.     

Hazards of combustion products: Toxicity,opacity, corrosivity,and heat release: The experts' views on capability and issues

The science of understanding how fires burn and how heat smoke and gases are generated and affect people has progressed substantially in the last half century. The principles of facility design for life safety in fires have reached a degree of maturity. Standards and code provisions for fire detection, suppression and control have become the norm. Real‐scale (or nearly real‐scale) test methods for the flammability of furnishings and interior finish have been established. In addition, some tests have been developed that measure the results of the burning of a small sample from the finished product. Yet, while there have been numerous small‐scale apparatuses developed for assessing the generation of heat, toxic gases, and visible or corrosive smoke, these facets of life and property safety have not found widespread inclusion in building and fire codes. There has been an invigorated effort in ISO TC92 SC3, Fire Threat to People and the Environment, to develop a coherent and comprehensive set of fire safety standards and guidance documents for life safety. Smaller efforts are ongoing within some national and regional standards bodies. In November 2008, experts in this field gathered at The Royal Society in London to hear papers that captured the state of the art and to discuss where we might go from here. This paper summarizes the papers and the discussion from that meeting. Copyright © 2010 John Wiley & Sons, Ltd.