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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 Rayleigh flow ： ウィキペディア英語版 Rayleigh flow Rayleigh flow refers to frictionless, non-Adiabatic flow through a constant area duct where the effect of heat addition or rejection is considered. Compressibility effects often come into consideration, although the Rayleigh flow model certainly also applies to incompressible flow. For this model, the duct area remains constant and no mass is added within the duct. Therefore, unlike Fanno flow, the stagnation temperature is a variable. The heat addition causes a decrease in stagnation pressure, which is known as the Rayleigh effect and is critical in the design of combustion systems. Heat addition will cause both supersonic and subsonic Mach numbers to approach Mach 1, resulting in choked flow. Conversely, heat rejection decreases a subsonic Mach number and increases a supersonic Mach number along the duct. It can be shown that for calorically perfect flows the maximum entropy occurs at M = 1. Rayleigh flow is named after John Strutt, 3rd Baron Rayleigh. ==Theory== The Rayleigh flow model begins with a differential equation that relates the change in Mach number with the change in stagnation temperature, T0. The differential equation is shown below. :$\backslash \; \backslash frac\; =\; \backslash frac\backslash left(1\; +\; \backslash fracM^2\backslash right)\backslash frac$ Solving the differential equation leads to the relation shown below, where T0 * is the stagnation temperature at the throat location of the duct which is required for thermally choking the flow. :$\backslash \; \backslash frac\; =\; \backslash frac\backslash left(1\; +\; \backslash fracM^2\backslash right)$ These values are significant in the design of combustion systems. For example, if a turbojet combustion chamber has a maximum temperature of T0 * = 2000 K, T0 and M at the entrance to the combustion chamber must be selected so thermal choking does not occur, which will limit the mass flow rate of air into the engine and decrease thrust. For the Rayleigh flow model, the dimensionless change in entropy relation is shown below. :p, remains constant. :$\backslash begin$ H &= \frac = \frac = \frac \\ \frac &= \left(subsonic Mach number until M = 1.0 and the flow chokes. Conversely, adding heat to a duct with an upstream, supersonic Mach number will cause the Mach number to decrease until the flow chokes. Cooling produces the opposite result for each of those two cases. The Rayleigh flow model reaches maximum entropy at M = 1.0 For subsonic flow, the maximum value of H occurs at M = 0.845. This indicates that cooling, instead of heating, causes the Mach number to move from 0.845 to 1.0 This is not necessarily correct as the stagnation temperature always increases to move the flow from a subsonic Mach number to M = 1, but from M = 0.845 to M = 1.0 the flow accelerates faster than heat is added to it. Therefore, this is a situation where heat is added but T/T * decreases in that region. 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「Rayleigh flow」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.