Post-Mix Cutting Nozzle Geometry for Lower-Pressure Flame Stability
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Solution Overview
Problem
Prior post-mixed oxygen-fuel cutting nozzles have an inadequate preheat gas ratio, leading to inefficient combustion and increased gas pressures, resulting in higher consumption and waste.
Innovation Solution
The design features a cutting nozzle assembly with a 2:1 ratio of larger diameter oxygen bore holes to fuel gas bore holes, along with an angled shroud and flange, enhancing gas flow capacity and mixing efficiency by directing preheat oxygen and fuel gases for improved combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the preheat gas ratio is increased, then combustion efficiency is improved, but device complexity increases
Solution Approach 1:
The nozzle is divided into multiple functional sections with distinct bore configurations. The preheat section contains multiple preheat bores arranged in specific patterns, while the cutting section has separate cutting bores. This segmentation allows independent optimization of gas flow paths for preheating and cutting functions, achieving improved combustion efficiency through proper gas ratio control without requiring complete redesign of the entire nozzle structure.
Solution Approach 2:
Different sections of the nozzle have locally optimized bore diameters and arrangements. The preheat bores have specific diameter ranges (0.020-0.040 inches) while cutting bores have different dimensions. The shroud thickness varies along the length, being thicker in the preheat section and thinner in the cutting section. These local quality variations enable efficient combustion in the preheat zone while maintaining overall structural simplicity.
2Loss of substance
If gas pressure is reduced, then gas consumption is decreased, but flame stability deteriorates
Solution Approach 1:
The nozzle design changes the physical parameters of the gas flow path, specifically the bore diameters and their ratios. The preheat bores have diameters of 0.020-0.040 inches with a total cross-sectional area that creates an optimal mixing ratio with fuel gas. The cutting bores have diameters of 0.030-0.060 inches. These parameter changes enable stable combustion at lower pressures by optimizing the velocity and mixing characteristics of the gas streams.
Solution Approach 2:
The design replaces high-pressure mechanical forcing with optimized geometric configurations to achieve proper gas mixing and flame stability. Instead of relying on high pressure to maintain flame stability, the inverted cone shroud geometry and specific bore arrangements create natural flow patterns that stabilize the flame at lower pressures, reducing overall gas consumption.
3Quantity of substance
If the number of preheat bores is increased, then preheat gas volume is increased, but manufacturing complexity increases
Solution Approach 1:
The preheat gas delivery system is segmented into multiple individual bores rather than using a single large passage. This segmentation into 2-10 preheat bores with diameters of 0.020-0.040 inches distributes the gas flow more effectively, increasing the total preheat gas volume while maintaining manufacturability through standard drilling and tapping operations. The segmented approach is easier to manufacture than attempting to create equivalent flow through fewer, more complex passages.
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 configuration allows for lower gas pressure settings, reducing consumption and waste while producing a more focused, efficient flame, resulting in cost savings and improved performance.
Implementation Method 1
a cutting nozzle assembly with a 2:1 ratio of larger diameter oxygen bore holes to fuel gas bore holes, along with an angled shroud and flange, enhancing gas flow capacity and mixing efficiency by directing preheat oxygen and fuel gases for improved combustion
Data Source
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AI summary
A cutting nozzle assembly and associated method of making same includes a nozzle having a central bore extending therethrough along a longitudinal axis through which an associated cutting gas is discharged. A plurality of spaced fuel gas bores are arranged around the central bore, and preheat passages are arranged around both the central bore and the fuel gas bores. A retaining nut receives at least a portion of the nozzle therein, and the retaining nut includes a shroud extending axially outward from a discharge end of the nozzle. At least one of an inner surface of the shroud and the additional preheat passages are angled inwardly toward the longitudinal axis. The fuel gas bores and the preheat passages each have the same cross-sectional dimension, and twice the number of preheat passages as fuel gas bores are provided.