【摘要】：自從人們發(fā)現(xiàn)傳統(tǒng)的哈龍滅火劑對(duì)臭氧層有著不可修復(fù)的破壞性之后,細(xì)水霧滅火技術(shù)越來越受到重視。細(xì)水霧滅火技術(shù)不僅在民用建筑、公共建筑和船用領(lǐng)域上受到廣泛應(yīng)用,在能源領(lǐng)域和工業(yè)領(lǐng)域中更是發(fā)揮了重要作用。一直以來,人們都致力于提升細(xì)水霧滅火性能的研究。但噴霧速度過低,流量過小,噴頭尺寸過大等問題仍然沒有得到解決。本文將針對(duì)以上問題,對(duì)壓力式細(xì)水霧噴頭進(jìn)行結(jié)構(gòu)優(yōu)化,將優(yōu)化后的細(xì)水霧噴頭應(yīng)用到室內(nèi)泄漏的天然氣所引起的火災(zāi)中去,并對(duì)其滅火有效性進(jìn)行探究。采用FLUENT數(shù)值模擬軟件對(duì)壓力式細(xì)水霧噴頭進(jìn)行內(nèi)部流場(chǎng)數(shù)值模擬,分析該噴頭的霧滴粒徑分布情況,檢驗(yàn)粒徑是否符合正態(tài)分布,完成結(jié)構(gòu)準(zhǔn)確性判定。劃分網(wǎng)格并進(jìn)行無關(guān)性驗(yàn)證,討論分析噴頭幾何結(jié)構(gòu)參數(shù)對(duì)細(xì)水霧噴霧效果的影響。著重考察出口數(shù)量,進(jìn)口直徑比和出口長徑比對(duì)噴霧速度以及噴霧壓力的影響。經(jīng)模擬發(fā)現(xiàn),三者均對(duì)噴霧效果產(chǎn)生影響,進(jìn)口直徑比對(duì)噴霧效果的影響尤為突出。對(duì)優(yōu)化后的壓力旋流式細(xì)水霧噴頭進(jìn)行外部流場(chǎng)數(shù)值模擬研究。打開離散相追蹤模型,完成湍流模型、邊界條件、初始條件以及求解方法的選擇和設(shè)置。捕捉噴霧形態(tài)隨時(shí)間的變化,對(duì)比分析不同截面處、不同壓力下細(xì)水霧液滴的粒徑分布情況和速度變化規(guī)律。經(jīng)模擬發(fā)現(xiàn),提高噴霧壓力,不僅有利于擴(kuò)大噴霧保護(hù)范圍,還可以提高液滴穿透火焰的能力;在距離噴嘴出口豎直距離30mm處,細(xì)水霧液滴的破碎已基本達(dá)到平衡狀態(tài);當(dāng)噴射壓力達(dá)到0.5MPa時(shí),液滴接近完全破碎。建立細(xì)水霧作用于室內(nèi)泄漏的天然氣所引發(fā)火災(zāi)的氣/液兩相數(shù)值計(jì)算模型。采用通用有限速率燃燒模型和渦耗散湍流與化學(xué)反應(yīng)相互作用模型模擬火焰的穩(wěn)定燃燒,開啟細(xì)水霧DPM離散相模型,對(duì)細(xì)水霧與火焰之間的相互作用過程展開分析和記錄。對(duì)比分析細(xì)水霧作用前后火焰的動(dòng)態(tài)變化以及流場(chǎng)溫度、生成物濃度的變化情況。討論細(xì)水霧粒徑、流量和速度對(duì)滅火效果的影響。經(jīng)模擬發(fā)現(xiàn),優(yōu)化后的細(xì)水霧噴頭可以有效抑制室內(nèi)天然氣泄漏引發(fā)的火災(zāi),合理設(shè)置細(xì)水霧粒徑、流量和速度對(duì)滅火至關(guān)重要。
[Abstract]:Since it was found that the traditional halon extinguishing agent has irreparable damage to the ozone layer, water mist fire extinguishing technology has been paid more and more attention. Water mist fire extinguishing technology is not only widely used in civil buildings, public buildings and marine areas, but also plays an important role in the field of energy and industry. All along, people are devoted to improving the performance of water mist fire fighting. However, the spray speed is too low, the flow rate is too small, the nozzle size is too large and other problems have not been solved. In view of the above problems, the structure optimization of pressure water mist sprinkler is carried out in this paper. The optimized water mist nozzle is applied to the fire caused by indoor leakage of natural gas, and the fire extinguishing effectiveness of the optimized water mist sprinkler is discussed. The internal flow field of the pressure water mist nozzle is simulated by using FLUENT numerical simulation software. The droplet size distribution of the nozzle is analyzed, and whether the particle size conforms to the normal distribution is checked, and the accuracy of the structure is determined. The effects of nozzle geometry parameters on the spray effect of water mist are discussed and analyzed. The effects of outlet quantity, inlet diameter ratio and outlet length to diameter ratio on spray velocity and spray pressure were investigated. The simulation results show that all of them have influence on the spray effect, especially the inlet diameter ratio. The external flow field of the optimized pressure swirl water mist nozzle is numerically simulated. The discrete phase tracking model is opened to complete the selection and setting of turbulence model, boundary condition, initial condition and solution method. After capturing the change of spray morphology with time, the particle size distribution and velocity variation of water mist droplets at different cross sections and under different pressures were compared and analyzed. The simulation results show that increasing spray pressure can not only enlarge the spray protection range but also improve the ability of droplets to penetrate the flame. At the vertical distance from the nozzle outlet 30mm the breakup of water mist droplets has basically reached the equilibrium state. When the injection pressure reaches 0.5MPa, the droplet is nearly completely broken. A numerical model of gas / liquid two-phase fire caused by natural gas leakage caused by water mist is established. The steady combustion of flame was simulated by general finite rate combustion model and interaction model of vortex dissipation turbulence and chemical reaction. The DPM discrete phase model of water mist was opened and the interaction process between water mist and flame was analyzed and recorded. The dynamic change of flame, the temperature of flow field and the concentration of product before and after the action of water mist were compared and analyzed. The effects of particle size, flow rate and velocity of water mist on fire fighting effect are discussed. It is found by simulation that the optimized water mist nozzle can effectively restrain the fire caused by natural gas leakage in the room, and it is very important to set the particle size, flow rate and speed of water mist to extinguish the fire.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU892

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