Dynamic Compressor Mass Flow Interpolation for Surge Avoidance
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Solution Overview
Problem
Dynamic compressors, such as centrifugal compressors, face inefficiencies and instability issues like choked flow and surge, which can damage components, and existing methods lack cost-effective means to accurately measure mass flow rate for real-time control.
Innovation Solution
A controller with a memory storing a map of predetermined operating points and instructions to interpolate mass flow rates using nearest data points, allowing operation without a mass flow sensor, and adjusting parameters to maintain efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mass flow sensor is installed to measure mass flow rate, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual copy of the mass flow sensor by generating a lookup table with predetermined operating points and their corresponding mass flow rates. This virtual copy allows the system to determine mass flow rate through interpolation of stored data rather than using physical sensor instrumentation, thereby achieving measurement capability without the complexity and cost of actual mass flow sensors.
Solution Approach 2:
The patent introduces an intermediary approach by using a processor to interpolate mass flow rates from predetermined operating points stored in memory. This intermediary computational method bridges the gap between available sensor data (rotational speed, pressure) and the required mass flow rate information, eliminating the need for direct mass flow measurement hardware.
2Device complexity
If real-time mass flow data is obtained through interpolation, then device complexity is reduced, but measurement precision may worsen
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing mass flow rates for multiple predetermined operating points in a lookup table during system initialization or offline calibration. This advance preparation enables the system to quickly interpolate accurate mass flow rates during real-time operation without requiring complex computational models or additional sensors, thereby maintaining precision while reducing device complexity.
3Device complexity
If the compressor operates without real-time mass flow monitoring, then device complexity is reduced, but reliability worsens due to inability to detect surge or choke conditions
Solution Approach 1:
The patent implements feedback by continuously calculating current mass flow rate through interpolation and comparing it against predetermined operating points stored in the lookup table. This feedback mechanism enables the control system to detect when the compressor is approaching surge or choke conditions by monitoring deviations from expected operating characteristics, thereby improving reliability without requiring additional mass flow sensors.
Data Source
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AI summary
A method for determining a mass flow of a dynamic compressor that does not include a mass flow sensor while the compressor is operating to compress a working fluid includes determining, by a processor, a current operating point of the compressor. If the current operating point is the same as one in a map of a plurality of predetermined operating points stored in a memory, the mass flow of that predetermined operating point is retrieved as the mass flow of the current operating point. Otherwise, the processor calculates the mass flow at the current operating point from the mass flows of a subset of the predetermined operating points nearest the current operating point. The dynamic compressor continues to operate to compress the working fluid based at least in part on the calculated mass flow rate for the current operating point.