【正文】 載荷力 載荷力等于切向力和軸向力的合力，其表達式為： 為了求出因為氣流載荷所引起的彎矩，首先要確定葉片根部截面的法線與圓周切線之間的夾角θh，以及載荷力與圓周切線之間的夾角θp。在葉片長度方向上受到的彎矩為：在葉片根部出現最大彎曲應力為：其中 W—葉片根部斷面的彎曲斷面系數，m3。 則葉片根部總得應力為拉伸應力與彎曲應力之和，其表達式為： 強度校核是根據安全系數n來判斷，為： 當安全系數滿足時，葉片是安全的。在本設計中，葉輪直徑D2=，輪轂半徑dh=，葉片數z=12，功率p=450kW，空氣密度ρ=，轉速n=960r/min，葉片寬度b=，柵距t=，葉片全長=，重心rc=，選用Q235A號碳素結構鋼，單個葉片質量為m=8kg，氣流安裝角θ=35。要校核葉片的安全可靠，只要校核葉片根部能不能滿足要求就行了。 一、作用在葉片上的總離心力 由 帶入數據得： kN 二、葉片根部拉伸應力 Mpa 三、氣流流動壓力引起的切向力N 四、氣流動壓力引起的軸向力 N 五、載荷力N 六、載荷力引起的彎矩。 七、葉片根部的最大彎曲應力其中 所以 Mpa 八、葉片根部的總應力Mpa 九、強度校核﹥2 所以是安全的。當葉輪旋轉時，連接葉柄與葉片的鉚釘承受葉片的離心力［19］。鉚釘的最大切應力τ（N/m2或pa）其中 F—單個葉片離心力，N； d—鉚釘直徑，本設計中采用d=22mm； z—鉚釘數量，個； 由前面的計算可知 kN，在本設計每個葉片采用1個鉚釘，鉚釘的剪切力為： Mpa 查機械設計手冊可知，16Mn材料的鉚釘［τ］=480Mpa，所以能滿足強度要求。軸與軸套的傳動鍵選取平鍵，鍵的尺寸按照《機械設計手冊》5228頁表5318選取，尺寸如下：鍵高度h=14mm，軸深9mm，；鍵的寬度b=22mm；鍵長L=180mm。 驗算鍵的擠壓強度公式為： 式中 T—； d—軸的直徑，m； K—鍵與輪轂的接觸高度，可近似取k＝h/2，h為鍵的高度； L—鍵的計算長度m。因此 Mpa 查機械手冊可以知道，P[P]，所以鍵檢驗合格，滿足強度要求。 軸流通風機的效率是指氣體流經整個風機通道時，實際上獲得的有效能量與理論上輸入能量的比值，風機內的能量損失多指氣流流經集流器、轉子、定子、擴散器等主要部件的各種損失。已知帶有擴散筒和后導葉的軸流風機其全壓效率為：其中 — 理論總壓系數； — 葉輪損失系數 ； — 前導葉損失系數； — 后導葉損失系數 ； — 擴散筒損失系數。其中=0。 一、 計算葉輪平均直徑截面上的參數 二、理論總壓系數 三、葉輪相對損失系數其中 t/b= 所以 C= 平均直徑處 所以 =所以 四、葉輪效率五、全壓效率由=，==，=［20］為：=；。故風機效率為： η==，與校核的效率差距不大。結 論 （1）本設計選用了葉輪+后導葉軸流風機的設計方案，該方案具有體積小，壓力高、運行經濟好、調節(jié)效率高、應用廣泛的特點，較好地滿足了送風機的要求。 （2）選用了等環(huán)量流型，保證氣流在風機通道中是圓柱面流動，該流型具有效率高等特點。 （3）選用了在軸流風機設計廣泛應用的LS翼型，該翼型具有結構簡單，加工容易，升力大，阻力小，升阻比大，效率高的特點。 （4）升力系數、葉片弦長、葉片安裝角等設計參數分布合理。 （5）%，因此該風機為高效風機。 （6）選用了分段、剖分式結構，因而結構簡單、拆裝方便、維護容易。 （7）電機內置、獨立冷卻，具有結構簡單、占地面積小的特點。 （8）配有消聲器，降低了風機的噪聲。 （9）各分段之間采用螺栓連接，其拆裝方便，便于維護。 （10）在風機上有多種標識，提高了安全性。 （11）強度校核表明，葉輪、葉片、葉柄、鍵等均滿足要求，能夠可靠工作。參考文獻［1］［2］［3］［4］［應用科學］.紹興：紹興市新民新能 源工程技術有限公司，2009［5］何川，：中國電力出版社，2008［6］：機械工業(yè)出版社，1981.?。?］［本科學位論文］.徐州：中國礦業(yè)大學，2008［8］：中國礦業(yè)大學出版社出版［9］：機械工業(yè)出版社，1999［10］高中庸，陳迎春，2014［11］：機械工業(yè)出版社1983［12］［13］吳秉禮，：吉林大學出版社， 2007［14］張玉成，：化學工業(yè)出版社，2011［15］［16］單輝祖，：高等教育出版社，2003［17］楊可楨，程光蘊，：高等教育出版社，2006［18］：化學工業(yè)出版社，2007［19］：機械工業(yè)出版社，2005［20］：機械工業(yè)出版社，2000翻譯部分英文原文Mathematics modeling of the behavior in operation of induced draft fans for 350MW Fossil Power Units to predict its optimum maintenance timeAbstractMathematics modeling of processes and equipment behavior in operation at Fossil Power Units is a useful tool, because it let us predict the performance equipment during its operative life.With the help of modern statistical techniques, such as parametric and nonparametric models, it is possible to predict the optimum maintenance time intervals。 taking ahead of breakdowns or decrements in Fossil Power Units, letting us keep equipment and processes inoperation for the predicted time. (Working them nearby their optima points of its characteristic curves.)Finally, the above situation results in a better performance of equipment and processes, failure reductions (or elimination), and reaching us more and more to equipment replace for natural aging of equipment.A technical problem that was studied and analyzed in USA during the eight ies, is now present in M233。xico, this is the random high vibration in induced draft fan (ID FAN) in 350MW Fossil Power Unit.At that time, remendations about how to avoid high vibrations were omitted, however, at the time, it did not exit puter tools and mathematical models as we have today。 and they let us model the ID FAN operative performance and predict, how many operating hours without failure can be accumulated with a reliability determined previously. And besides they give us elements for programming maintenance activitties.Among the types of failures studied in ID FAN are the random high vibrations, which are manifested by the erosion process at blades,mainly in these called “air foil”.1 ObjectiveThe objective is to show the mathematical model of ID FAN in operation, using statistical techniques and with them we may avoid forced out of service.With mathematical modeling we can determine optimum operation hours and then take the decision to stop for maintenance, or replace any part or damaged ponent.2 Data needed for the modelationIn order to model the operating behavior of equipment and processes, it is necessary to keep a historical record of every event that occurs during its life cycle. With this information the following may be determined with more precision: the event failure time, what the causes of failures,and which maintenance activities needed to be done to keep the equipment in service.Likewise, a register must be kept for every part replaced with additional in formation about what the damage was, how the damage is described by the operators, the involved cost in rehabilitation, and the nonproduction cost due to the the present time, in a Fossil Power Unit, it is not easy to concentrate all this data for analysis, because there are several Departments and personal that audit an event and, in the majority of cases, some data is lost, not collected, or not recorded correctly, with the precision that it is needed for modeling. In spite of this, we must recognize that work in Fossil Power Units is done better every time. People at power plant are collecting data (and more general the information), in the way that is required for operative behavior modeling, in the majority of cases with the help of puter systems.It must bee mon practice to know the total cost of new equipment, because it is possible that in some situations,it is economically spea