Single-Mode Cavity Resonator Heating for Uniform Magnetic Field

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Solution Overview

Problem

In microwave heating using cavity resonators, maintaining uniform heating of objects requires adjusting the position of the object to align with the maximum magnetic field strength, which complicates the apparatus design and reduces practicality.

Innovation Solution

A cylindrical or rectangular tubular cavity resonator is used to maintain a standing wave with its maximum magnetic field at the central axis, allowing objects to be heated uniformly by passing through this region, and the microwave frequency is adjusted to match the resonance frequency based on the object's placement for efficient heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the position of the object to be heated is adjusted to align with the maximum magnetic field strength in a cavity resonator, then heating efficiency is improved, but the apparatus complexity and positioning mechanism requirements increase

Engineering Contradiction:

Improveheating efficiencyVSAvoidapparatus complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

Instead of moving the object to align with the maximum magnetic field position, the invention inverts the approach by positioning the object at a fixed location and adjusting the microwave frequency to match the resonance frequency of the cavity with the object in place. This eliminates complex positioning mechanisms while maintaining high heating efficiency through frequency tuning rather than positional alignment.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the control parameter from positional alignment to frequency adjustment. By tuning the microwave frequency to match the resonance frequency of the cavity resonator when the object is in its fixed position, the system achieves maximum magnetic field strength at the object's location without requiring mechanical positioning mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If the supply position of the object is changed to follow the maximum magnetic field strength position, then heating uniformity is improved, but the apparatus size increases

Engineering Contradiction:

Improveheating uniformityVSAvoidapparatus size

Core Design Contradiction:

Manufacturing precisionVSVolume of stationary object

Solution Approach 1:

Rather than moving the object to track the maximum magnetic field position, the invention fixes the object at a predetermined position and inverts the approach by adjusting the microwave frequency to ensure the maximum magnetic field occurs at the object's fixed location. This eliminates the need for large positioning mechanisms while maintaining heating uniformity.

Inventive Principle:

Principle #13The other way round (Inversion)

3Adaptability or versatility

If dielectric or metal pieces are inserted into the cavity to adjust resonance frequency, then the resonance frequency is adjusted, but the magnetic field strength distribution shifts causing misalignment with the object position

Engineering Contradiction:

Improveresonance frequency adjustmentVSAvoidmagnetic field alignment

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The invention changes the approach from physically inserting dielectric or metal pieces to adjust resonance frequency to electronically tuning the microwave frequency. By adjusting the microwave source frequency to match the cavity's resonance frequency (which naturally includes the object), the system achieves both frequency adjustment and magnetic field alignment without disturbing the field distribution.

Inventive Principle:

Principle #35Parameter changes

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 method enables efficient and repeatable uniform heating of magnetic or conductive materials without the need for complex positioning mechanisms, improving heating efficiency and reducing apparatus size.

Implementation Method 1

forming a standing wave whose maximum magnetic field portion is always at the central axis of the cavity resonator

Methodology Applied

Scientific EffectStanding wave: Resonance

Implementation Method 2

heating the object to be heated by magnetic heat generation by magnetic loss

Methodology Applied

Scientific EffectMagnetic loss heating: Magnetic Hysteresis

Implementation Method 3

heating the object to be heated by induction heating by an induced current generated in the object to be heated

Methodology Applied

Scientific EffectInduction heating: Electromagnetic Induction

Data Source

PatentUS11883789B2Microwave heating method, microwave heating apparatus, and chemical reaction method

Publication Date: 2024.01.30 NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE & TECHNOLOGY

AI summary

A microwave heating method using a microwave, including: controlling a frequency of the microwave, to form a single-mode standing wave; disposing an object to be heated in a magnetic field region where a strength of a magnetic field formed by the single-mode standing wave is uniform and maximum; and heating the object to be heated by magnetic heat generation by magnetic loss caused by an action of the magnetic field of the magnetic field region, and/or induction heating by an induced current generated in the object to be heated due to the magnetic field of the magnetic field region.