"INTRODUCTION Design and performance analysis methods for ducted flow systems often involve an explicit or implicit assumption that the flow is uniform across a section. In practice@ some degree of spatial non-uniformity is present in all real ducted flow systems and@ consequently@ it is often necessary to formulate a set of representative mean properties to describe a non-uniform flow and to use in the analysis methods. The use of appropriate mean values is important@ for example@ in the calculation of component performance when the inlet and outlet profiles are significantly different and in cases where the variation of properties across a profile is large. Mean values are often used to provide a simplified flow description at component interfaces and an appropriate choice is particularly important in ensuring consistency between calculations for separate components of a system@ such as a gas turbine engine@ that may be analysed independently by different groups. This Data Item complements a group of Items concerned with the definition of mean values and mean-value sets for the one-dimensional representation of steady@ spatially non-uniform flows and their use in the analysis of system performance. References 5 and 7 are concerned primarily with definition of the reference-mean mean-value-set for compressible flow*. If there are no constraints on the choice of mean values@ use of the reference-mean set is recommended . Its principal advantages over historical approaches to flow averaging are that it is thermodynamically-consistent@ it retains the correct sectional entropy and therefore allows a true measure of efficiency for processes in which profiles change@ it is application-independent@ providing a universal definition across component interfaces and it avoids attributing hypothetical losses to the flow upstream or downstream of the measurement station. It requires no more input information than that required for any mass-flow based method. The Data Item provides information on the use of@ and background to@ a computer program for calculation of mean-value properties at a section in a duct flow. The methods are applicable to steady@ spatially non-uniform (profiled) compressible flows@ assumed to be essentially axial@ i.e. free from significant crossflows such as radial flow and swirl. The flow property profiles may be derived from experimental measurements@ in which case measurement uncertainties on the raw measurements are assumed to be accounted for separately so that the calculation starts with a ""corrected"" set of measurements. Alternatively@ the flow property profiles may be derived from computational fluid dynamics analysis methods or specified as analytical power-law profiles. Section 2 relates the notation used in output files from the program to notation used in the text of the Data Items. Some specific terminology used to describe gas property calculations is also explained. Section 3 describes access to the program@ which is available as an executable file. The input data required by the program are described in Section 4. The program requires input of profile information for static pressure@ total pressure or axial velocity and total temperature or profile definition by input of power-law parameters. The principal application is to radial profiles in circular or annular ducts and profiles across one direction only of rectangular ducts. However@ a more general input option is included that allows for profiles varying in two dimensions and for other duct shapes. Output from the program is described in Section 5. The program calculates local property values across the profile and uses these to derive sectionally-integrated values and mean values. Although use of the reference-mean-set is recommended@ the program calculates a wide range of mean-value properties from other definitions for comparison with the reference-mean set and for continuity with previously-used methods. The calculated mean values fall into one of several groups as described below. ? Mean property values that form part of thermodynamically self-consistent mean-value-sets@ notably the reference-mean values (Appendix A.3). ? Mean-set factors allowing the derivation of sectionally-integrated extensive properties of the profiled flow from the mean property values (Appendix A.3). A minimum number of these factors forms an essential part of any complete mean-value-set. ? Mean values that are part of groups for which@ historically@ only a few basic mean properties have been used@ such as mass-derived mean values. These groups have@ where possible@ been extended to cover a full set of mean flow properties. Often the original derivations were restricted to isenergic (uniform total temperature) flows of calorically-perfect gases. Again the methods have been extended to cover the more general case with total-temperature profiles and for thermally-perfect gases where this is feasible (Appendix A.4). ? Miscellaneous mean values that are derived from particular mean-specific extensive properties@ such as enthalpy-derived mean values (Appendix A.5). ? Profile factors relating two different mean-value definitions of a particular property. These are useful in indicating the magnitudes of differences between definitions. In this program these profile factors nearly all use the reference-mean-set values as the comparison (Appendices A.3@ A.4@ A.5). Two worked examples are described in Section 6@ for which input and output files are listed in Appendix D. Appendix A gives brief descriptions of the mean-value properties calculated. Appendix B lists the unit sets allowed in the program and gives conversion factors and other default parameters included within the program. Appendix C gives a glossary of some terms used in the Item and related terms that may be encountered in the literature. * Reference 9 considers the application of the same methodology to incompressible flows."
ESDU 03012 B-2010 history
2010ESDU 03012 B-2010 Computer program for calculation of mean value properties for non-uniform compressible flows