在国民经济中我国化工产业地位突出，其发展规模和速度对各个行业有直接、间接影响。同时，危化品所引起的火灾也越来越难以控制，波及面广，施救难度大。因此，研究新型高效、环境友好的灭火材料，对于保护人民生命财产安全具有重要意义。干水粉体是一种具有核壳结构的新型灭火材料，由疏水型二氧化硅包裹水溶液呈现粉末状态，有较强的流动性和分散性，稳定性较差。本文在普通干水粉体的基础上加入胶凝剂和有效灭火组分，使其兼有较强的物理冷却及化学灭火协同作用，测试分析了流动性、松密度、粒径大小和耐压性，并以理论、实验及数值模拟相结合的方法对改性干水粉体的灭火性能进行深入研究。

本文通过查阅文献研究干水粉体制备及改性机理，利用高速剪切搅拌法，制备以去离子水和强疏水型二氧化硅为基料的干水粉体。采用正交试验法，通过表观观察和偏光显微镜法，研究不同的固液配比、搅拌转速、搅拌时间等参数对制备干水粉体的影响，确定了最佳制备条件。制备了含有0.5%ZFA、1.5%ZFB、2.0%ZFC有效灭火组分的改性干水粉体，添加0.3g结冷胶以增强粉体的核壳结构强度，并测试对比了不同粒径粉体的流动性、松密度、粒径分布及耐压性等物性参数，以满足后期粉体充装需求。研究结果表明：M_SiO2:M_H2O=9：100，搅拌转速为4000r/min，搅拌时间为3min时制备所得的粉体结构较为稳定，分散性最好；干水粉体的松密度均分布在0.419~0.569 g·mL^-1范围以内，ZFB凝胶干水的流动性最好，流出速率为3.71 mL·s^-1，休止角均≤28°；粉体颗粒粒径大部分在300μm以内，粉体颗粒所能承受的最大压力为1.4MPa左右。

为研究改性干水粉体的灭火有效性，自行搭建扑灭油池火实验平台，开展不同驱动压力工况条件下对粉体灭火有效性的影响研究，进行了不同组分、不同粒径粉体对火焰温度的影响，并与ABC类、BC类干粉灭火剂进行了灭火效果对比。研究结果表明：在1.0MPa、1.2MPa的驱动压力下，干水粉体的灭火效率较高，其降温冷却速率分别为11.5℃/s、11.3℃/s。驱动压力过大或过小，灭火效能均不理想；添加了化学组分的改性干水粉体的灭火有效性有显著提高，效果最好的是ZFB凝胶干水粉体，冷却速率为13.9℃/s；粒径200~300μm的干水粉体冷却速率为17.1℃/s，高于其他粒径范围的粉体颗粒；与ABC类、BC类干粉灭火剂相比，ZFB凝胶干水的热电偶记录温度与时间曲线下降速率更明显，说明降温效果更佳。

为了更好地研究喷射粉体灭火过程中干水粉体与火焰羽流的相互作用，通过ANSYS Fluent数值模拟受限空间内粉体颗粒在不同驱动压力下的浓度分布情况。模拟结果表明：灭正庚烷火过程中，干水粉体受驱动气体喷射获得动能，随距离不断增加，粉体颗粒动能不断损耗，还受到火焰羽流阻力，从而迫使火焰羽流形状发生变化；在1.4MPa的驱动压力下，粉体颗粒最先穿透火焰羽流，到达火源区域抑制火焰所需要的时间也最少。在相同时刻，驱动压力不断增大，火焰羽流高度不断减小，火焰羽流宽度增大。

The chemical industry in China has a prominent position in the national economy and the scale and speed of its development has a direct and indirect impact on various industries. At the same time, the fire caused by dangerous chemicals is becoming more and more difficult to control, covering a wide range of areas, and difficult to rescue. Therefore, it is of great significance to study new efficient and environmentally friendly fire extinguishing materials to protect people's life and property safety. Dry water powder is a new fire extinguishing material with core-shell structure, which is composed of hydrophobic silica coated aqueous solution. Powder state, strong liquidity and dispersion, poor stability. In this paper, on the basis of ordinary dry water powder, gelling agent and effective fire extinguishing components are added to make it have a strong synergistic effect of physical cooling and chemical fire extinguishing. The fluidity, bulk density, particle size and pressure resistance are tested and analyzed. The fire-extinguishing performance of the modified dry water powder was studied in depth by a combination of theory, experiment and numerical simulation.

This paper studied the preparation and modification mechanism of dry water powder by referring to the literature, and prepared dry water powder with deionized water and strong hydrophobic silica as the base material by using high-speed shear agitation method. Orthogonal test method was used to study the effects of different solid-liquid ratio, stirring speed, stirring time and other parameters on the preparation of dry water powder by apparent observation and polarizing microscope, and the optimal preparation conditions were determined. A modified dry water powder containing 0.5% ZFA, 1.5% ZFB, 2.0% ZFC effective fire extinguishing components was prepared, and 0.3 g gellan gum was added to enhance the core-shell structural strength of the powder. In addition, the physical parameters such as fluidity, bulk density, particle size distribution and pressure resistance of powders with different particle sizes were tested and compared to meet the needs of later powder filling. The research results show that: M_SiO2:M_H2O=9:100, when the stirring speed is 4000r/min, and the stirring time is 3min, the structure of the powder prepared is relatively stable and the dispersibility is the best. The bulk density of dry water powder was 0.419-0.569 g· ml^-1, and the fluidity of ZFB gel was the best, with an outflow rate of 3.71 mL·s^-1 and Angle of rerest ≤28°. The particle size of powder particles is mostly within 300μm, and the maximum capacity that powder particles can withstand is about 1.4MPa.

In order to study the fire extinguishing effectiveness of modified dry water powder, an experimental platform for extinguishing oil pool fire was built. The effects of different driving pressures on the fire extinguishing effectiveness of powder were studied, and the effects of different components and different particle sizes of powder on the flame temperature were studied. And the fire extinguishing effect is compared with that of ABC and BC dry powder fire extinguishing agents. The research results show that: under the driving pressure of 1.0MPa and 1.2MPa, the fire extinguishing efficiency of dry water powder is higher, and the cooling rate is 11.5℃/s and 11.3℃/s, respectively. If the driving pressure is too large or too small, the fire extinguishing performance is not ideal. The fire extinguishing efficiency of the modified dry water powder added with chemical components was significantly improved, and the ZFB gel dry water powder had the best effect, with a cooling rate of 13.9℃/s. The cooling rate of dry water powder with a particle size of 200~300μm is 17.1℃/s, which is higher than that of powder particles in other particle size ranges. Compared with ABC and BC dry powder fire extinguishing agents, the temperature and time curve recorded by the thermocouple of ZFB gel dry water has a more obvious decrease rate, indicating that the cooling effect is better.

In order to better study the interaction between dry water powder and flame plume in the process of jet powder fire extinguishing, the concentration distribution of powder particles in a closed space under different driving pressures was numerically simulated by ANSYS Fluent. The simulation results show that in the process of extinguishing the heptane fire, the dry water powder is injected by the driven gas to obtain kinetic energy. With the increasing distance, the kinetic energy of the powder particles is continuously lost, and it is also resisted by the flame plume, which forces the shape of the flame plume to change. Under the driving pressure of 1.4MPa, the powder particles penetrate the flame plume first, and the time required to reach the ignition source area to suppress the flame is also the least. At the same time, the driving pressure keeps increasing, the flame plume height decreases, and the flame plume width increases