Computer program for calculation of mean value properties for non-uniform compressible flows.
Abstract:ESDU 03012 provides background to and guidance on the use of a computer program for calculation of mean-value properties for ducted flows. Use of mean values is necessary when variation of properties across a section of the flow is large and, for example, in the calculation of component efficiencies when inlet and outlet property profiles are significantly different. Mean values are often used to provide a simplified flow description at component interfaces and an appropriate choice is important in ensuring consistency between calculations for separate components in a system, such as a gas turbine, that may be analysed by different groups. By offering the calculation of mean values from a variety of definitions, ESDU 03012 also allows evaluation of the consequences of different mean value choices. The program requires input of local values of static and total pressure and total temperature or static pressure, axial velocity and total temperature in one of three formats. Firstly, as values applicable for elemental areas across the flow, for which any duct section is covered; secondly, as property profiles across the flow for axisymmetric flow in circular or annular ducts and two-dimensional flow in rectangular ducts or thirdly, in terms of analytical power-law profiles.
Gas property data are required as a single value of specific constant-pressure heat capacity for a calorically-perfect gas or as polynomial equations or tabulation for specific constant-pressure heat capacity, specific enthalpy and specific constant-pressure entropy function for a thermally-perfect gas. Default properties giving a good approximation for air are provided.
The program output includes a summary of the input data with a user-defined selection of calculated mean-property values and local property values across the profiles. Mean value sets included are; the reference-mean set (ESDU 95011 and ESDU 97029, this conserves mass flow and entropy and defines an isentropic reservoir value of mean total pressure and is recommended in the absence of other requirements), the momentum-mixed mean set (conserving mass flow and absolute stream force), the enthalpy-mixed mean set (conserving mass flow and enthalpy) and the pseudo-mixed mean set (conserving mass flow, enthalpy and entropy but consequently representing a compressed state). Also calculated are area-weighted and mass-flow-weighted mean values, mass-derived mean values and a number of miscellaneous mean properties derived from internal energy and mean enthalpies.
|Data Item ESDU 03012
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