Ultrasonic Waveguide for Hot Melt Flow Measurement
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Solution Overview
Problem
Existing ultrasonic sensors face challenges in measuring flow velocities in hot melts due to high temperature limitations, material degradation, and transmission losses, particularly in non-transparent fluids, where the piezoelectric transducer overheats and ultrasonic waveguides experience significant damping and dispersion.
Innovation Solution
An ultrasonic sensor with an ultrasonic waveguide made from materials like iridium, molybdenum, or stainless steel, with a layered structure and a chemically resistant protective jacket, ensuring low acoustic damping and effective wetting by the melt, along with a piezoelectric transducer housed in a thermally insulated protective housing and connected via capacitors and coils for signal adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the ultrasonic waveguide is made of material with high thermal resistance to protect the piezoelectric transducer from overheating, then the temperature at the transducer is limited, but the acoustic damping and transmission losses increase significantly
Solution Approach 1:
The waveguide is divided into multiple thin layers (foil structure) rather than using a single thick material. This segmentation allows the waveguide to maintain low acoustic damping while providing thermal protection, as the thin layered structure minimizes ultrasonic attenuation while the overall waveguide design limits heat transfer to the transducer.
Solution Approach 2:
The waveguide uses composite material construction with specific material selection (such as metal foils with appropriate acoustic and thermal properties) to achieve a balance between thermal resistance and acoustic transmission. The composite structure allows optimization of both thermal protection and ultrasonic signal transmission.
2Loss of energy
If the ultrasonic waveguide structure is made thin to minimize scattering and dispersion losses, then transmission losses are reduced, but the thermal protection capability is compromised
Solution Approach 1:
The waveguide is constructed as a thin-walled structure or multiple thin layers, segmenting the protective function across multiple thin components rather than relying on a single thick barrier. This maintains low acoustic damping while the cumulative thermal resistance of the layered structure provides adequate protection.
3Reliability
If the piezoelectric transducer is protected from the hot melt environment, then the transducer reliability is improved, but the ultrasonic signal transmission quality deteriorates
Solution Approach 1:
The waveguide acts as an intermediary element between the protected transducer and the hot melt environment. It provides the necessary acoustic coupling while maintaining the thermal barrier, allowing the transducer to remain protected while still transmitting ultrasonic signals effectively through the waveguide structure into the melt.
4Reliability
If a protective jacket is added to the ultrasonic sensor, then the chemical resistance and thermal protection are improved, but the device complexity increases
Solution Approach 1:
The protective jacket is designed to serve multiple functions simultaneously: thermal insulation, chemical protection, and mechanical protection. By integrating these multiple protective functions into a single component, the design avoids the need for separate protective systems for each function, thereby limiting the increase in device complexity.
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
Enables reliable, continuous, and accurate speed measurements in melts above 200°C by minimizing thermal damage to the transducer and reducing transmission losses, ensuring stable acoustic coupling and high-frequency signal integrity.
Implementation Method 1
The main component of the measuring device is the ultrasonic transducer in the form of a piezoelectric oscillator (also called a piezoelectric crystal or piezoelectric transducer)
Implementation Method 2
The ultrasonic waves are transmitted into the fluid to be examined from the ultrasonic transducer directly into the fluid or via the outer wall of the container enclosing the fluid
Implementation Method 3
the flow velocity can be determined based on the frequency shift of the ultrasonic measurement signals coupled in and out
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an ultrasonic sensor for measuring flow rates in liquid melts at high temperatures. The aim of the invention is to provide an ultrasonic sensor for carrying out local, continuous, reliable rate measurements in hot melts (T > 200°C). To achieve this, the ultrasonic sensor contains an ultrasonic waveguide (2) that is connected to the piezoelectric transducer (1) and consists of a material with low acoustic damping properties in a temperature range relevant for the area of application of above 200 °C, said material being chemically resistant to the melt. In addition, the end face of the ultrasonic waveguide (2) facing the melt is closed and can be wetted by the melt.