Stepped Nozzle Bank for Accurate Mass Flow Measurement
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Solution Overview
Problem
Existing fluid flow measurement technologies, such as sonic nozzles and conventional de Laval nozzles, face inaccuracies due to fluid dynamic and thermodynamic calculations, and sensitivity to pressure changes caused by sub-sonic fluid flow boundary layers, which affect mass flow rate measurements.
Innovation Solution
A nozzle with a single step, approximately 1 throat diameter from the inlet, creating an oblique shock wave to account for boundary layer flow, and a nozzle bank comprising multiple stepped nozzles that partition fluid flow for direct measurement with mass flow devices, eliminating the need for thermodynamic or fluid dynamic calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional de Laval nozzles with smooth throat are used, then the device structure is simple, but measurement accuracy deteriorates due to sub-sonic boundary layer effects and sensitivity to pressure changes
Solution Approach 1:
The patent introduces a localized step feature at the nozzle throat region while maintaining smooth contours elsewhere. This local modification creates an oblique shock wave precisely where needed to eliminate boundary layer effects, improving measurement accuracy without requiring complete redesign of the entire nozzle structure.
Solution Approach 2:
The patent transitions from a smooth curved throat (spheroidal profile) to a stepped profile with sharp edges at the throat region. This geometric change from curved to angular geometry creates the necessary oblique shock wave while maintaining overall nozzle functionality, directly addressing the measurement accuracy issue.
2Measurement precision
If thermodynamic and fluid dynamic calculations are used to determine flow rate, then the measurement system is simple, but measurement accuracy deteriorates due to inherent uncertainties in calculations
Solution Approach 1:
The patent replaces the computational approach (thermodynamic and fluid dynamic calculations) with a direct mechanical measurement approach. By using the stepped nozzle to create choked flow conditions, the system directly measures mass flow rate through the nozzle rather than calculating it from pressure and temperature data, eliminating calculation uncertainties.
3Reliability
If differential pressure is applied to induce sonic flow rate, then flow measurement is enabled, but measurement stability deteriorates due to sensitivity to pressure changes across the nozzle bank
Solution Approach 1:
The patent divides the fluid flow into multiple separate streams by using multiple stepped nozzles arranged in a nozzle bank. Each nozzle independently measures a portion of the total flow, and the results are combined. This segmentation allows for more stable individual measurements and reduces the impact of pressure variations on any single nozzle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides accurate and stable mass flow rate measurements by closing off unaccounted boundary layer flow, ensuring consistent mass flow rates regardless of pressure changes, thus improving measurement accuracy and stability.
Implementation Method 1
A nozzle with a single step, approximately 1 throat diameter from the inlet, creating an oblique shock wave to account for boundary layer flow
Implementation Method 2
This sensitivity is due to the transfer of mass flow through the nozzle bank via a sub-sonic fluid flow boundary layer in each nozzle
Data Source
AI summary
A method for measuring fluid flow within a fluid flow pipe includes partitioning a fluid flow within a pipeline with a nozzle bank, wherein a predetermined number of stepped nozzles is open; measuring the fluid flow in at least one partitioned fluid stream with at least one mass flow device; and calculating a total fluid flow within the pipeline. The nozzle bank includes a plurality of nozzles, each nozzle having a single step at about 1 throat diameter from an inlet plane of the nozzle, wherein the single step is an increase corresponding to about 10% of the throat diameter and has a length of about throat diameter/2.