Wind Tunnel Vehicle Drag Measurement Using Running Belt Platform
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Solution Overview
Problem
Existing methods for measuring propulsive power in vehicles with wind-exposed wheels are inaccurate due to the magnified drag forces on upper wheel surfaces, which are not properly accounted for in traditional wind tunnel measurements, leading to inaccuracies in propulsive efficiency assessment.
Innovation Solution
A running belt platform driven by a universal dynamometer and controlled by a closed-loop servo control system is used inside a wind tunnel to measure the propulsive power required to overcome net drag forces on vehicles, maintaining the vehicle centered under varying operating speeds and headwind conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional force-measuring instrumentation on pedestal mounts is used to measure net drag force on vehicles, then the measurement setup is simple and adaptable from aircraft testing, but the measurement accuracy deteriorates due to magnified upper wheel drag forces that are not properly accounted for
Solution Approach 1:
The patent segments the measurement system into two independent parts: (1) a pedestal mount that measures only the aerodynamic drag force on the vehicle body, and (2) a separate wheel assembly with force transducers that measures the propulsive force at the wheel axles. This segmentation allows each measurement to be optimized independently, eliminating the error where wheel drag forces contaminate the body drag measurement.
Solution Approach 2:
The patent introduces an intermediary element - a set of stationary rollers or belts positioned beneath the vehicle wheels - that allows the vehicle to roll freely while the wheel axles remain constrained for force measurement. This intermediary setup isolates the propulsive force measurement from the aerodynamic drag measurement, enabling accurate separation of these two force components.
2Stability of the object's composition
If the vehicle is immobilized on a running floor mounted on a pedestal mount, then the force measurement setup is stable, but the propulsive efficiency assessment becomes inaccurate under rising headwinds due to magnified upper wheel drag forces
Solution Approach 1:
The patent transitions from a static immobilized vehicle setup to a dynamic rolling setup. The vehicle is allowed to roll freely on stationary rollers or belts that simulate road conditions, while the wheel axles remain constrained for force measurement. This dynamic setup better replicates actual driving conditions and accurately captures the interaction between wheel rotation and aerodynamic forces under headwinds.
Solution Approach 2:
The patent extracts the wheel assembly from the pedestal mount system, allowing the wheels to roll independently on stationary rollers while the vehicle body remains suspended from the pedestal for aerodynamic drag measurement. This extraction separates the measurement of propulsive force at the wheels from the measurement of aerodynamic drag on the body, eliminating the contamination effect.
3Ease of operation
If direct force-measurement methods are used to determine overall vehicle drag, then the measurement method is straightforward and commonly employed, but substantial inaccuracies occur in propulsive power measurement when wheels are exposed to headwinds
Solution Approach 1:
The patent segments the force measurement into two separate measurement systems: one measuring aerodynamic drag force on the vehicle body via the pedestal mount, and another measuring propulsive force at the wheel axles via force transducers. This segmentation maintains operational simplicity while dramatically improving measurement accuracy by preventing cross-contamination of force measurements.
Solution Approach 2:
The patent replaces the traditional mechanical pedestal mount system with a hybrid system that combines aerodynamic suspension (for body drag measurement) with direct force transducer measurement at the wheel axles. This substitution eliminates the mechanical coupling that causes measurement errors while maintaining the simplicity of force measurement.
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 a more accurate measurement of propulsive power and force used to overcome drag, significantly improving the assessment of propulsive efficiency, especially under increasing headwind conditions.
Implementation Method 1
Drag force on exposed wheels increases more rapidly on upper wheel surfaces than on vehicle frame surfaces, causing a non-linear relation from rising wind speeds between net drag forces on vehicle frame surfaces versus net drag forces on vehicle wheel surfaces.
Implementation Method 2
The running belt is driven by a universal dynamometer and controlled by a closed-loop servo control system, which maintains the vehicle centered on the running belt under varying operating speeds and headwind conditions.
Data Source
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AI summary
A method and apparatus for measuring the propulsive power required to overcome net drag forces on a vehicle mounted within a wind tunnel. The apparatus includes a running belt platform driven by a dynamometer and supporting the vehicle, to be placed inside a wind tunnel and controlled by a closed-loop servo control system, which maintains the vehicle centered on the running belt under varying operating speeds and headwind conditions.