Direct Drill Bit Drive Using a Stirling Cycle for Deep Hard-Rock Drilling
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Solution Overview
Problem
Deep drilling technologies face challenges in efficiently penetrating hard rock formations due to the limitations of existing percussion drilling methods, which suffer from decreased energy efficiency and increased wear at great depths, especially under high hydrostatic pressures, and the difficulties in supplying and managing gaseous fuels and oxidizers.
Innovation Solution
A direct chisel drive utilizing a heat engine operating on a quasi-closed Stirling cycle, where the working gas is continuously heated and cooled, decoupling mechanical work into an oscillating stroke movement, and using a thermoacoustic or free-piston Stirling engine design that eliminates exhaust gases and manages pressure through pre-compressed reservoirs or gas-generating chemical reactions, allowing operation at high depths with conventional drilling fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional hydraulic percussion drill hammers use water hammer effect with mud column acceleration, then impact energy can be generated for rock penetration, but energy efficiency decreases significantly with increasing borehole depth due to larger mud mass requiring acceleration
Solution Approach 1:
The patent replaces the hydraulic water hammer system with a thermal engine system. Instead of accelerating large masses of drilling fluid to generate impact, the invention uses a closed-cycle thermal engine (Stirling or Otto cycle) that converts thermal energy directly into mechanical impact motion of a piston and chisel assembly. This substitution eliminates the fundamental limitation of hydraulic systems where energy efficiency degrades with depth.
Solution Approach 2:
The invention changes the working medium from liquid drilling fluid to gaseous working medium (air or other gases) in a closed thermal cycle system. This parameter change allows the system to operate independently of the overburden pressure and mud column weight, maintaining consistent performance at great depths where hydraulic systems fail.
2Length of stationary object
If down-the-hole hammers generate impact energy directly above the chisel, then drilling depth can be increased, but supply of compressed air and fuel at great depths becomes problematic due to performance limitations of above-ground compressors
Solution Approach 1:
The patent changes the working medium from liquid drilling fluid to gaseous working medium (air or other gases) in a closed thermal cycle system. This parameter change allows the system to operate independently of the overburden pressure and mud column weight, maintaining consistent performance at great depths where hydraulic systems fail.
Solution Approach 2:
The thermal engine system is designed to be largely self-contained, using a closed cycle where the working gas is compressed and heated within the system itself. The compression is achieved through the engine's own mechanism rather than requiring external compressors, reducing the operational complexity of supplying compressed air and fuel to great depths.
3Reliability
If percussion drills operate with conventional drilling fluid throughput, then cooling and lubrication can be provided, but premature wear occurs due to solids contained in the drilling fluid
Solution Approach 1:
The patent extracts the thermal engine and working gas system from the conventional drilling fluid circulation system. By separating the power generation function into a closed thermal cycle system, the invention eliminates the interaction between the impact mechanism and the abrasive solids in the drilling fluid, thereby preventing premature wear while still allowing drilling fluid to perform its cooling and lubrication functions.
4Length of stationary object
If heat engine uses gaseous working medium at great depths, then operation under high hydrostatic pressure can be achieved, but pressure differential between inside and outside of engine can cause failure of impact mechanism or collapse of working volume
Solution Approach 1:
The patent changes the working medium from liquid drilling fluid to gaseous working medium (air or other gases) in a closed thermal cycle system. This parameter change allows the system to operate independently of the overburden pressure and mud column weight, maintaining consistent performance at great depths where hydraulic systems fail.
Solution Approach 2:
The engine is designed with a pre-compressed working gas volume that can withstand the external hydrostatic pressure at great depths. The closed thermal cycle system maintains internal pressure to counterbalance the external pressure, preventing collapse of the working volume and failure of the impact mechanism.
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
The solution provides a low-maintenance, high-efficiency drive for percussion drilling in crystalline hard rock, maintaining functionality under extreme pressures and reducing wear, while eliminating the need for exhaust gases and ensuring uninterrupted operation at great depths.
Implementation Method 1
The direct chisel drive works according to a real Stirling cycle of a quasi-closed gaseous working medium. The working gas is continuously heated and cooled, decoupling mechanical work into an oscillating stroke movement
Implementation Method 2
The mechanical useful work results from a phase shift between heating and expansion or cooling and contraction of the working gas
Implementation Method 3
A further and particularly advantageous way of supplying heat is the generation of frictional heat from a rotary motion generated, for example, by a pneumatic or hydraulic turbine or a displacement motor, by means of a suitable pair of friction
Implementation Method 4
The cooling is carried out by the drilling fluid, which flows through channels in the heat exchanger
Implementation Method 5
The heat is dissipated by the drilling fluid flowing through channels in the heat exchanger
Implementation Method 6
gas-generating or gas-consuming chemical reactions of solids with a high molar conversion of gas molecules
Implementation Method 7
The preferred working gas in these cases is therefore nitrogen
Data Source
Figure 1(a)~1(f)
Figure 2(a)~2(d)
Figure 3(a)~3(e)
AI summary
In a direct drill bit drive for tools for comminuting brittle materials and penetrating into brittle materials by percussive impact on the basis of a heat engine operated with a gaseous working medium, the heat engine is a hot gas engine operating in accordance with a real Stirling cycle process.