Laser Drilling Head Cooling via Liquid Nitrogen Phase Transition
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Solution Overview
Problem
Existing laser drilling methods for rock formations face challenges in achieving rapid drilling advancement in deep boreholes without overheating issues at the laser-drilling head or drill rod, due to high power density requirements and thermal management limitations.
Innovation Solution
The method involves guiding the laser beam through a laser-guide tube within the drill rod, where nitrogen is supplied in a liquid state and changed to gas at the laser-drilling head, with a heating-gas stream and cooling-gas stream being branched off to manage heat and enhance drilling efficiency, and using a specialized drill rod configuration for efficient energy and signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a glass-fiber cable is used to transmit the laser beam over long distances (2,000 m to 10,000 m), then the laser beam can be guided to the borehole bottom, but the beam intensity is significantly attenuated and inadequate for effective drilling
Solution Approach 1:
The patent changes the physical state of nitrogen from gas to liquid for transmission through the drill rod. Liquid nitrogen has much lower attenuation for laser beams compared to gaseous nitrogen, enabling high-power laser transmission over long distances (2,000-10,000 m) while maintaining adequate beam intensity at the borehole bottom
Solution Approach 2:
The patent utilizes phase transition of nitrogen between liquid and gaseous states. Nitrogen is supplied as liquid through the drill rod to minimize laser attenuation, then converted to gas at the laser-drilling head where it serves as protective and conveying gas. This phase transition enables both long-distance transmission and effective drilling functions
2Productivity
If the laser beam power is increased to more than 500 kW to bombard the entire borehole bottom simultaneously, then drilling advancement can be improved, but thermal problems occur due to overheating of the laser-drilling head and drill rod
Solution Approach 1:
The patent uses the phase transition of nitrogen from liquid to gas as a cooling mechanism. Liquid nitrogen is supplied through the drill rod and evaporates at the laser-drilling head, absorbing large amounts of heat during vaporization. This phase change effectively removes excess heat from the high-power laser system, preventing overheating while maintaining high drilling productivity
Solution Approach 2:
The patent converts the harmful thermal energy that would cause overheating into a beneficial cooling effect. The nitrogen gas, after absorbing heat during phase transition and cooling the drill components, continues to serve its dual function as protective gas for the laser beam and conveying gas for removing detached rock material
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 allows for the unattenuated transmission of high-power laser beams and effective cooling, preventing overheating and thermal short circuits, enabling efficient rock detachment and removal while maintaining drilling advancement.
Implementation Method 1
The energy of the laser beam arriving at the borehole bottom detaches the rock material present there and does so specifically—depending on rock material—by melting, evaporation and/or by spalling.
Implementation Method 2
nitrogen is supplied to the laser-drilling head via the drill rod in liquid state of matter and in the region of the laser-drilling head is changed into the gaseous state of matter
Implementation Method 3
a further partial stream serving as heating-gas stream is additionally branched off from the supplied nitrogen, and is heated by means of an electrical heating device associated with the laser-drilling head and is directed toward the borehole bottom being bombarded by the laser beam
Data Source
AI summary
There is a method for drilling a borehole in a rock formation by bombarding the borehole bottom with a laser beam, which is generated by a laser-beam generator situated outside the borehole and is guided by means of suitable auxiliary devices to a laser-drilling head situated at the borehole bottom. The drilling head is coupled with a drill rod, wherein nitrogen, supplied to the laser-drilling head via the drill rod, is split into a partial stream serving as protective gas, which protects the transmitted laser beam from interfering suspended particles. There is a further partial stream, serving as a conveying-gas stream, which transports the rock material detached from the borehole bottom out of the borehole via an annular space remaining between drill rod and borehole wall. The laser beam is guided to a laser drilling head by extending through a laser guide tube.