As a widely used protection device, the radiation blockage ability of water spray curtain to high temperature heat source is influenced by a number of elements, of which spray dynamics characteristic of nozzles is an important factor. An experimental study on radiation attenuation ability of water sprays has been carried out in laboratory. Droplets diameters and distributions of varied positions have been measured by laser particle sizer at different pressures. The position range varies from 25 to 175 cm and pressure changes from 1 to 3 bars. The attenuated radiation fluxes are measured by radiation heat flux meters to analyze the transmissivity of sprays. The results clearly indicate that the spray dynamic characteristic can severely affect the blockage ability of thermal radiation. The variation tendency of particle mean diameter can directly reflect the change trend of attenuation efficiency. Characteristic of droplets and relative positions of protected objects are two significant factors for affecting attenuation efficiency. These factors should be considered when water spray curtains are to be used in industrial and building fire protection. Furthermore, different nozzles with different characteristics, which should be measured firstly when they are used to discharge the water sprays.

Fire extinction in a closed ship cabin is one of the efficient measures for fire fighting. It would be of significant values for engineering application to study the smoke characteristics of a fire within a closed cabin. This paper constructs a fire model with analyses of smoke height, self-extinction time, the cabin temperature at the quenching time and CO density based on the study of the fire behavior and the smoke characteristics in a confined cabin. It also presents a simulation verification for the theoretical model. The results demonstrates that this model does well to study the characteristics of smoke production and flow in a closed cabin. So it could be a good reference for crews to control damage while suppressing fire in closed cabins.

在剖析电缆火灾原因的基础上,利用实验方法对阻燃电缆的阻燃性能进行了研究,得出了其在火焰中具有良好的抗火能力.之后利用破坏性实验进一步证明了阻燃电缆的良好抗火性能,利用FDS火灾模拟软件对无电缆参与的火灾和有电缆参与的火灾进行了仿真研究,得出了电缆在火灾中是否被引燃主要取决于是否与火焰直接接触的结论.最后,建议人们在电缆防火设计时,重点关注那些容易接触火焰的电缆.

目前池火灾热辐射大小基本使用经验公式进行计算.由于耗资和安全考虑,实验研究基本集中在小尺度火灾上,难以得到大尺度火灾热辐射特性.本文使用工程计算中的常用理论模型,计算了大型池火灾下的热辐射大小.分析了不同距离和高度下的热辐射通量大小,为防火灭火提供理论和实际指导.

针对消防灭火过程中雾状水滴喷射位置对灭火效率的影响问题,基于火灾动力学理论,分析灭火过程中的传热传质过程,构建了消防人员灭火过程的模拟环境和仿真模型,根据人员灭火过程中可能采取的灭火动作,运用火灾动力学软件对15种典型行为状态下灭火过程进行数值仿真,绘制针对具体火源的灭火动作与灭火效率关系图谱,并结合消防人员实际灭火训练数据分析水枪位置、入射角度、入射高度以及火源位置等因素耦合作用对灭火效率的影响,给出验证消防人员灭火行为和灭火战术有效性的仿真计算方法.

In order to analyze the atomization characteristics of flat fan nozzles using for water spray curtain, the DPM model was used for simulation. The results showed a longer atomization process with more pressure. The mean diameter of droplets decreased first, then increased. The velocity of droplets attenuated according with exponential decay model. Relatively small particles had faster velocity attenuation and more residential time that is important for heat shielding ability of spray curtain.

利用不同羽流模型对封闭空间火灾进行建模,在结合实验测出的热释放速率基础上,计算了不同羽流模型下的烟气填充时间和温度变化情况.将计算结果和实验数据进行了对比,分析了不同羽流模型的适用性.结果表明:火灾初期,4种羽流模型下的烟气填充速度相近,其中McCaffrey羽流模型与实际烟气填充过程最为接近;火灾后期,Zukoski羽流模型最接近实际烟气填充过程;火灾过程中,Thomas羽流模型和Zukoski模型计算结果非常接近,Thomas羽流模型更适用于一般的工程计算;4种羽流模型下的烟气层温度和实验结果有很大差异,实际工程中均不建议用来预测烟气温度.

The pool fire mathematical model of hermetically closed room is built by different plume models, the time of smoke filling and smoke layer temperature are calculated combined with experimental heat release rate. Theoretical calculations are compared with the experimental results to verify the usefulness of different plume models. The results indicate that: in initial period of fire, the smoke filling speeds of four plume models are similar, and McCaffrey plume model is most close to physical processes; in later period of fire, Zukoski plume model is most close to physical processes of smoke filling; during the fire, the results of Thomas plume model and Zukoski plume model are almost identical, and Thomas model is more suitable for engineering application; the smoke layer temperature discrepancy between theoretical calculation and experimental data is huge, and the theoretical calculation method of temperature is not recommended for predicting temperature in engineering.

The investigation into the stability of a spray curtain atomizer is based on the discrete phase model (DPM)of Fluent.The spray particle size distribution under different pressures and the defor-mation caused by airflow are calculated,and the particle velocity attenuation characteristics of diffe-rent diameters are also analyzed.Studies show that the stability of spray curtain is affected greatly by airflow,especially the particle of diameter size under 200 μm,that increasing working pressure at a certain height can make the mean diameter of spray particles smaller and the size distribution more u-niform,which will improve the heat-shielding performance of spray curtain and that when the height exceeds a certain range,the water spray particle velocity will decrease so sharply as to reduce the sta-bility while pressure increases.

Using FDS software the paper simulates and researches the pool fire water spray extinguishing process.By large eddy simulation calculation it shows that the extinguishing process exists the optimal angle of incidence,increasing the distance from the fire source can't enhance fire-fighting efficiency,instead increases the firefighter danger,and provides the theory basis for fire drill and practice fire-fighting action.

Three radiation models are discussed in the present paper. The heat fluxes vary considerably between different methods. In all models, fluxes vary highly on the position of nearing the flame and are almost identical on the far away position. Heat fluxes calculated from point source model is less than other two models, and Shokri-Beyler model is highest. Shokri-Beyler method is most applicable at heat fluxes greater than 5 KW/m2 and recommended in engineering design, and Mudan model is not applicable for calculating the heat flux nearing the flame.

The signal of gear face fault is very weak in gear body vibration and the fault characteristic frequency is difficult to be found in Fourier spectrum.A new gear fault diagnosis method based on ensemble empirical mode decomposition(EEMD)and instantaneous energy density spectrum is proposed here.The intrinsic mode functions (IMFs)generated by EEMD can alleviate the problem of mode mixing and approach the real IMFs.The rotating frequency and its doubling are found in the instantaneous energy density of Hilbert spectrum.Meshing frequency can be clearly seen in modulated condition.The effectiveness of this method is demonstrated by analysis real gear fault signal.

In order to study the remaining problems of image processing method used in diesel engine fault diagnosis,a new method is presented based on time-frequency distribution image processing.The vibration signals of cylinder head surface are obtained and decomposed into a finite number of intrinsic mode function components by the EMD method.Using the reconstruct vibration signals by IMF1 and IMF2,the analytic signals are got by Hibert-Huang transform.Experimental results show that selecting the appropriate time-frequency distribution analysis and obtaining time-frequency distribution of analytic signal can distinguish the diesel engine fault conditions effectively.

Wave could easily cause large-scale and flexible hull deformation and great impact on the shaft system.The program composition of ship FE model with PCL(Patran command language) was used to generate mesh automatically near the waterline,efficiently calculate and wave loading.A large bulk carrier FE model was loaded with Ariy wave loading at different head sea angles and different phases to analyze the influences of wave loadings upon the the shaft system.

The misfire of one or more diesel cylinder and the abnormal clearance in the intake valve train of cylinder are common faults which affect the safety and the performance of the engine seriously. A new fault diagnosis method based on EEMD and instantaneous energy density spectrum is proposed here. The IMFs generated by EEMD can alleviate the problem of mode mixing and approach the reality IMFs. The instantaneous energy density of these IMFs can distinguish the faulty impacts clearly. The effectiveness of this method was demonstrated by analysis the vibration signals of misfire fault and abnormal clearance in the intake valve train of 3110 diesel.

Proper shaft line alignment is one of the most important actions during the design of the propulsion system.Usually,one dimensional beam model of the shaft system is isolated from the ship hull.The stiffness of the ship,bearing and oil film were calculated by a three-dimensional FE model in this paper.The crankshaft element was created based on crank elements.Some properties were considered,including rotating and oscillating mass for each cylinder,main bearing stiffness and thrust bearing stiffness,bearing clearance,ship construction flexibility and deformations,bearing thermal deformation,bending moment that acts on propeller shaft and thrust shaft.Achieving a more accuracy result is possible by the mentioned method.

The 2-D plane method is not accurate enough to analyze the effect on propulsion shaft system by hull deformation,therefore,the 3-D FE model of a bulk carrier was conducted.The wave pressure was calculated and loaded automatically based on Patran command language(PCL).The deformations of ship construction in various sea waves were calculated and the effect on bearing load was analyzed.The result shows that the deflection of hull under shaft line is small in and under the sea state 4.The deflection of hull under shaft line is increased by sea state.And it is more than 4 mm in the sea state 8, affecting the shaft bearing load enormously.The deflection of hull under shaft line in vertical,horizontal and longitudinal directions is increased when the course heading is 30°.