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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク degree of reaction ： ウィキペディア英語版 degree of reaction Degree of reaction or reaction ratio (R) is defined as the ratio of static pressure drop in the rotor to the static pressure drop in the stage or as the ratio of static enthalpy drop in the rotor to the static enthalpy drop in the stage. Degree of reaction (R) is an important factor in designing the blades of a turbine, compressors, pumps and other turbo-machinery. It also tells about the efficiency of machine and is used proper selection of machine for the required purpose. Various definitions exist in terms of enthalpies, pressures or flow geometry of the device. In case of turbines, both impulse and reaction machines, Degree of reaction (R) is defined as the ratio of energy transfer by the change in static head to the total energy transfer in the rotor i.e. :$R\; =\; \backslash frac\; \}$.〔Peng, William W., Fundamentals of turbomachinery, John Wiley, 2008〕 For a gas turbine or compressor it is defined as the ratio of isentropic heat drop in the moving blades (i.e. the rotor) to the sum of the isentropic heat drops in the fixed blades(i.e. the stator) and the moving blades i.e. :$R\; =\; \backslash frac\; \}$. In pumps, degree of reaction deals in static and dynamic head. Degree of reaction is defined as the fraction of energy transfer by change in static head to the total energy transfer in the rotor i.e. :$R\; =\; \backslash frac\; \}$. ==Relation== Most turbo machines are efficient to a certain degree and can be approximated to undergo isentropic process in the stage. Hence from $Tds\; =\; dh\; -\; (\backslash frac)dp$, it is easy to see that for isentropic process ∆H ≃ ∆P. Hence it can be implied :$R\; =\; \backslash frac\}$ The same can be expressed mathematically as:〔S.M,Yahya, Turbines, Compressors and Fans, 4th ed. McGraw,2011〕 :$\backslash \; R\; =\; \backslash frac\; \backslash textrm\}\}\; \backslash ,\backslash \; \backslash textrm\; \backslash ,\backslash \; \backslash frac\; \backslash textrm\; \}\}$ Where 1 to 3ss in Figure 1 represents the isentropic process beginning from stator inlet at 1 to rotor outlet at 3. And 2 to 3ss is the isentropic process from rotor inlet at 2 to rotor outlet at 3. The velocity triangle〔 (Figure 2.) for the flow process within the stage represents the change in fluid velocity as it flows first in the stator or the fixed blades and then through the rotor or the moving blades. Due to the change in velocities there is a corresponding pressure change. Another useful definition used commonly uses stage velocities as:〔 :$\backslash ,\; h\_2\; -\; h\_3\; =\; ^2\; -\; V\_^2)\; +\; -h\_\; =\; h\_\; -\; h\_\; =\; (\; U\_2\backslash ,V\_-\; U\_1\backslash ,V\_)$ is the total enthalpy drop. The degree of reaction is then expressed as〔Dixon, S. L., Fluid Mechanics and Thermodynamics of Turbo-machinery, 5th ed. Elsevier,2011.〕 :$R\; =\backslash frac^2\; -\; V\_^2)\; +\; )\}$ For axial machines $U2\; =U1=\; U$, then〔 :$R=\backslash frac^2)\})\}$ The degree of reaction can also be written in terms of the geometry of the turbomachine as obtained by〔 :$R=\; (\backslash frac)(\backslash tan\; -\; \backslash tan)$ where $\backslash beta\_3$ is the vane angle of rotor outlet and $\backslash beta\_2$ is the vane angle of stator outlet. In practice $(\backslash frac)$ is substituted as ϕ and $(\backslash tan\; -\; \backslash tan)$〔 as $\backslash tan$ giving$R=\; \backslash phi\; \backslash tan.$ The degree of reaction now depends only on ϕ and $\backslash tan$ which again depend on geometrical parameters β3 and β2 i.e. the vane angles of stator outlet and rotor outlet. Using the velocity triangles degree of reaction can be derived as:〔 :$R=\backslash frac+\backslash frac(\backslash tan\; -\; \backslash tan)$ This relation is again very useful when the rotor blade angle and rotor vane angle are defined for the given geometry. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「degree of reaction」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.