本文選題：網(wǎng)格絮凝池　切入點：PIV測量　出處：《蘭州交通大學》2017年碩士論文　論文類型：學位論文

【摘要】：本文以網(wǎng)格絮凝池模型為試驗研究對象,采用粒子成像速度場儀(PIV)對網(wǎng)格絮凝池流場進行測量,獲得不同網(wǎng)孔尺寸網(wǎng)格板在不同進水流量條件下的流場信息�；赑IV測試結(jié)果,按變化規(guī)律信息將速度場劃分區(qū)域,結(jié)合大渦PIV方法探求網(wǎng)格絮凝池內(nèi)湍動能k及湍動耗散率ε的分布情況,找尋其與速度場劃分區(qū)域間的聯(lián)系。同時在相同的前提條件下,進行絮凝實驗,深入的研究網(wǎng)格絮凝池流場的水力特性與絮凝效果之間的關系。通過對網(wǎng)格絮凝池模型進行流場PIV測量及絮凝實驗研究,可以得出以下主要結(jié)論:1.對不同網(wǎng)格板后各向速度進行全面分析,得出水流過網(wǎng)格板后速度變化以縱向速度為主,距網(wǎng)格板越近,縱向速度與橫向速度的比值越大;距網(wǎng)孔中心越近,縱向速度與橫向速度的比值越大;距格擋中心越近,縱向速度與橫向速度的比值越小。2.分析特定網(wǎng)格板(6×6mm)后各特征截面的各向速度,得出水流通過網(wǎng)格板后速度的變化規(guī)律基本呈現(xiàn)為三類:加速區(qū)、摻混區(qū)、穩(wěn)定區(qū),若改變水力條件,區(qū)域劃分范圍會有弱小的波動。本次試實驗中1號網(wǎng)格板(4×4mm)和2號網(wǎng)格板(6×6mm)獲取的流場中速度變化規(guī)律經(jīng)歷三個過程,加速區(qū)、摻混區(qū)、穩(wěn)定區(qū),3號網(wǎng)格板(10×10mm)獲取的流場中速度變化規(guī)律只經(jīng)歷了加速區(qū)和摻混區(qū)。3.進水流量越大,水流過網(wǎng)格板后的流速越大,顆粒碰撞的幾率隨之增大,從而引起湍動能增大,湍動能耗散率增大。利用大渦PIV方法分析流場,距網(wǎng)格板距離一定,在相同進水流量條件下,不同網(wǎng)格板對應的湍動能及湍動能耗散率的波動幅度不同,分析得出,湍動能的波動幅度在加速區(qū)、摻混區(qū)較大,穩(wěn)定區(qū)較小;湍動能耗散率的波動幅度在加速區(qū)較大,摻混區(qū)、穩(wěn)定區(qū)較小。4.根據(jù)絮凝實驗可以得出,改變水力條件對絮凝效果具有明顯影響。網(wǎng)孔尺寸過小時,進水流量小,水流過網(wǎng)格板后的流速可以達到設計流速范圍,絮凝效果較好;進水流量過大,水流過網(wǎng)格板后流速過大,對流場引起的紊動較大,會破壞已形成的絮體結(jié)構(gòu),使細小絮體的數(shù)量逐漸增加,絮凝效果反而變差。網(wǎng)孔尺寸過大時,隨進水流量的改變,水流通過網(wǎng)格板后流速達不到設計流速范圍,生成的絮體顆粒相互碰撞幾率低,絮凝劑只會局部發(fā)生微團內(nèi)高濃度反應,不能充分與更多懸浮物接觸生成絮體并進行沉降,致使絮凝效果差。綜合對比得出,2號網(wǎng)格板(6×6mm)的絮凝效果更好。
[Abstract]:In this paper, the flow field of grid flocculation tank is measured by particle imaging velocity field analyzer (PIV), and the flow field information of grid plate with different mesh size under different influent flow rate is obtained. Based on the results of PIV measurement, the flow field of the grid flocculating cell model is studied in this paper. The velocity field is divided into regions according to the changing law information, and the distribution of turbulent kinetic energy k and turbulent dissipation rate 蔚 in the grid flocculation cell is studied by using the large eddy PIV method, and the relation between the velocity field and the velocity field is found. At the same time, under the same premise, the distribution of turbulent kinetic energy k and turbulent dissipation rate 蔚 in the grid flocculation cell is studied. The relationship between hydraulic characteristics and flocculation effect of grid flocculation tank was studied in depth. The flow field PIV measurement and flocculation experiment were carried out on the model of grid flocculation tank. The main conclusions are as follows: 1. The following conclusions can be drawn: 1. The overall analysis of the velocity of different grid plates shows that the variation of water velocity after flowing through the grid plate is mainly the longitudinal velocity, the closer to the grid plate, the greater the ratio of longitudinal velocity to transverse velocity; The closer it is to the center of the mesh, the bigger the ratio of longitudinal velocity to transverse velocity is, and the closer it is to the center of the grid, the smaller the ratio of longitudinal velocity to transverse velocity is. It is concluded that the variation law of the flow velocity after passing through the grid plate is basically presented as three categories: acceleration zone, mixing zone, stable zone, if hydraulic conditions are changed, In this experiment, the velocity variation law in the flow field obtained from the 1 grid plate 4 脳 4 mm and 2 mesh plate 6 脳 6 mm) experienced three processes: acceleration zone, mixing zone, In the stable region, the velocity variation law in the flow field obtained by the No. 3 grid plate 10 脳 10mm only experienced the acceleration zone and the mixing zone .3.The larger the influent flow rate, the greater the velocity of water flowing through the grid plate, and the probability of particle collision increases, thus causing the increase of turbulent kinetic energy. The turbulent kinetic energy dissipation rate is increased. The large eddy PIV method is used to analyze the flow field with a constant distance from the grid plate. Under the same influent flow rate, the turbulence kinetic energy and turbulent kinetic energy dissipation rate of different grid plates are different. The fluctuation amplitude of turbulent kinetic energy is in the acceleration region, the mixing region is larger, the stable region is smaller, the fluctuation range of turbulent kinetic energy dissipation rate is larger in the acceleration zone, the mixing zone and the stable region are smaller. Changing hydraulic condition has obvious influence on flocculation effect. When the size of mesh hole is too small, the flow rate of water can reach the design velocity range, the flocculation effect is better, the influent flow rate is too large, the flow rate of water can reach the design velocity range after flowing through the grid plate, the flow rate of the inlet water is too large, When the velocity of water flows through the grid plate is too large, the turbulence caused by the flow field is larger, which will destroy the structure of the floc that has been formed, and make the quantity of the fine floc increase gradually, and the flocculation effect becomes worse. When the size of the mesh hole is too large, the flow rate changes with the influent. The velocity of flow through the grid plate can not reach the designed velocity range, and the probability of collision between the generated floc particles is low. The flocculant can only produce high concentration reaction in the micro-agglomeration, and can not fully contact with more suspensions to form the floc and make the floc settle. The result shows that the flocculation effect is better than that of No. 2 grid plate (6 脳 6 mm).
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU991.2

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本文編號：1589139