Compressor Performance Map Interpolation Using Exit Mass Flow
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Solution Overview
Problem
Existing methods for creating compressor maps that extend to zero speed are limited by the need for arbitrary beta lines, which lack physical meaning and result in inconsistent and variable interpolation, especially in the choking region, leading to significant variations in predicted performance data used for design, health monitoring, and control of flow machines.
Innovation Solution
The method involves using lines of constant exit corrected mass flow instead of artificial beta lines for interpolation, providing a physical basis for interpolating compressor performance data, ensuring consistent and accurate predictions across the operational range, including sub-idle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arbitrary beta lines are used for interpolation to extend compressor maps to zero speed, then performance data can be obtained across the full operating range, but the interpolation becomes inconsistent and variable, especially in the choking region
Solution Approach 1:
The patent changes the interpolation parameter from arbitrary beta lines to lines of constant exit mass flow. This parameter change provides a physical basis for interpolation that is consistent across the entire operating range including the choking region, eliminating the variability and inconsistency associated with arbitrary beta line selection while maintaining methodological simplicity.
2Ease of operation
If beta lines are used to tabulate data for interpolation, then data can be organized for computational use, but the lines lack physical meaning and require user judgment for placement
Solution Approach 1:
The patent replaces the arbitrary geometric construction of beta lines with a physically meaningful parameter-based approach using lines of constant exit mass flow. This substitution eliminates the need for user judgment in placing interpolation lines while retaining the computational tabulation capability, as the physical parameter (exit mass flow) naturally defines the interpolation paths without requiring subjective placement decisions.
3Reliability
If extrapolation methods are used to extend compressor performance data to lower speeds, then sub-idle characteristics can be obtained, but the accuracy and reliability of the predicted data deteriorates
Solution Approach 1:
The patent applies preliminary action by establishing lines of constant exit mass flow across the entire operating range before performing interpolation to obtain sub-idle characteristics. This preliminary structuring of the data with physically meaningful parameters ensures that when extrapolation is performed to lower speeds, the results remain accurate and reliable because the interpolation framework is based on fundamental flow physics rather than arbitrary geometric constructions.
Data Source
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AI summary
A method of determining performance characteristics of a flow machine having a rotor interacting with a flow field. The method comprises: receiving performance data for the flow machine comprising data values of a performance parameter of the rotor and mass flow for the flow machine at one or more defined rotor condition, the performance data defining a two-dimensional array of data in which points for a common rotor condition are identifiable; determining or receiving exit mass flow values for the flow downstream of the rotor; and identifying one or more point in the received performance data and interpolating from said one or more point to a corresponding one or more point at a different rotor condition based on a correlation of the exit mass flow values for said points.