Ultrasonic Sensor Fouling Reduction via Intermittent Cavitation
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Solution Overview
Problem
Sensors used in water quality measurement, such as the Nalco 3D fluorometer, face significant fouling issues due to contaminants in water, leading to rapid degradation and reduced effectiveness, especially in highly contaminated fluids like wastewater, with existing mechanical and ultrasonic solutions proving inadequate.
Innovation Solution
The method employs high-intensity ultrasonic technology by using a transducer and probe connected to an optical sensor, submerged in the liquid medium, to induce cavitation through cyclic sound pressure waves, effectively reducing fouling by utilizing the natural piezoelectric properties of quartz to resonate and create cavitation within the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If low power and low intensity ultrasound is used to prevent sensor breakage, then sensor safety is improved, but fouling prevention effectiveness deteriorates
Solution Approach 1:
The system applies ultrasonic cleaning in periodic cycles rather than continuously. During cleaning cycles, high intensity ultrasound is applied to remove fouling, then the sensor operates normally for measurement. This periodic approach allows effective fouling removal while giving the sensor rest periods to avoid cumulative stress and potential damage.
Solution Approach 2:
The system dynamically adjusts ultrasonic parameters (intensity, frequency, duration) based on sensor position, fouling level, and material properties. By changing these parameters appropriately, the system can apply high intensity ultrasound when needed for effective cleaning while using lower intensity or no ultrasound during measurement phases, thus preventing both fouling and sensor damage.
2Reliability
If high intensity ultrasonic technology is used to effectively reduce fouling, then fouling prevention effectiveness is improved, but interference with sensor measurements worsens
Solution Approach 1:
The system alternates between measurement phases and cleaning phases. During measurement phases, the sensor operates normally without ultrasonic interference. During cleaning phases, high intensity ultrasound is applied to remove fouling. This temporal separation ensures that measurements are not interfered with by ultrasonic waves while still achieving effective fouling prevention.
Solution Approach 2:
The system performs preliminary cleaning before measurements are taken by detecting fouling levels and initiating cleaning cycles in advance. This ensures the sensor surface is clean before measurement begins, eliminating the need to apply ultrasound during measurement and thus avoiding measurement interference.
3Reliability
If mechanical wiper mechanisms are used to remove foulants, then fouling removal capability is improved, but device complexity and points of failure increase
Solution Approach 1:
The system replaces mechanical wiper mechanisms with an ultrasonic cleaning system. Instead of using motors, seals, and moving parts to physically wipe the sensor surface, the system uses high intensity ultrasonic waves to create cavitation in the liquid medium, which mechanically removes fouling through acoustic pressure. This eliminates complex mechanical components while achieving effective fouling removal.
Solution Approach 2:
The ultrasonic cleaning system is self-regulating and requires no external mechanical actuation. The control system monitors sensor conditions and automatically activates ultrasonic cleaning when fouling is detected, eliminating the need for mechanical wipers, motors, and associated control mechanisms. The system serves itself by using the liquid medium already present in the measurement chamber.
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 significantly reduces fouling by using high-intensity ultrasonic waves intermittently, minimizing interference with sensor measurements and extending the operational lifespan of sensors, even in highly contaminated fluids, while allowing for easy integration with existing systems.
Implementation Method 1
a transducer and a probe, wherein the probe and the transducer are operably connected to each other so that the transducer receives a signal from a source, translates the signal to mechanical energy
Implementation Method 2
operating the ultrasound technology by sending the signal to the transducer so that the probe ultrasonically vibrates causing cavitation in the liquid medium
Implementation Method 3
applying the current to the quartz flow cell with opposing polarity, the current causing the quartz flow cell to resonate, the resonation causing cavitation within the liquid medium
Data Source
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AI summary
A device and method for reducing and/or preventing fouling of a sensor is disclosed. The method comprises operating ultrasound technology that is submerged or partially submerged into a liquid medium that is responsible for the fouling. The device comprises the ultrasound technology itself. The ultrasound technology may be operated intermittently at high intensity to advantageously provide cavitation of the liquid medium, while avoiding the disadvantages typical of continuously operating ultrasound technology at high intensity. Additionally, the method may be carried out by taking advantage of the piezoelectric property of quartz.