High Pressure Combustor Hot Surface Ignition
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Solution Overview
Problem
Traditional ignition methods fail at high pressures in oilfield downhole applications, with pyrophoric fuels being hazardous and costly, and hot surface ignition struggling to raise the temperature of oxidizer and gaseous hydrocarbon mixtures above auto-ignition temperatures efficiently.
Innovation Solution
A combustor system with an air/fuel premix injector, hot surface igniter, and insulation that mixes air and fuel into a single premixed stream, igniting the mixture at low velocities in an initial combustion chamber to create a deflagration wave that ignites the main combustion chamber, using minimal power and controlling air/fuel ratios for efficient combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pyrophoric fuels are used for ignition at high pressure, then ignition reliability is improved, but safety hazards and cost increase
Solution Approach 1:
The patent introduces an intermediary heating element (resistive heater or glow plug) that indirectly ignites the fuel-oxidizer mixture by heating it to autoignition temperature, rather than using pyrophoric fuels that directly ignite upon contact. This intermediary device eliminates the safety hazards of pyrophoric materials while maintaining ignition reliability at high pressures.
Solution Approach 2:
The patent replaces the chemical ignition mechanism of pyrophoric fuels with an electrical heating mechanism. The heating element converts electrical energy to thermal energy, which then ignites the mixture through thermal conduction and convection, substituting a mechanical/electrical system for a chemical one to eliminate safety hazards.
2Object-affected harmful factors
If hot surface ignition is used to raise temperature above auto-ignition, then safety hazards are reduced, but power consumption increases
Solution Approach 1:
The patent segments the combustion process into two distinct chambers: a small initial combustion chamber where a controlled amount of fuel-oxidizer mixture is ignited, and a larger main combustion chamber where the bulk fuel is combusted. The heating element only needs to ignite the small initial mixture, significantly reducing the total energy required compared to heating the entire fuel load.
Solution Approach 2:
The patent prepares a pre-mixed fuel-oxidizer mixture in advance and introduces it to the heating element at the optimal moment. This preliminary preparation ensures that the heating element only needs to provide enough energy to reach autoignition temperature, rather than continuously heating a large volume of fuel, thereby reducing overall power consumption.
3Device complexity
If traditional spark ignition is used at high pressure, then device simplicity is maintained, but ignition effectiveness decreases
Solution Approach 1:
The patent changes the ignition mechanism from spark discharge to thermal conduction and convection through a heated surface. The heating element is designed with high thermal conductivity and sufficient surface area to transfer heat efficiently to the fuel-oxidizer mixture, achieving reliable ignition at high pressures where spark ignition fails, while maintaining relative device simplicity.
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
Achieves reliable ignition at high pressures with reduced hazards and costs, using minimal power to maintain combustion, and effectively manages air/fuel ratios for efficient energy use and reduced heat loss.
Implementation Method 1
hot surface ignition has none of the chemical or cost drawbacks associated with pyrophorics, rather, the challenge is to utilize the limited power available downhole to raise and keep the temperature of the oxidizer (air) and gaseous hydrocarbon mixture above auto-ignition temperature
Implementation Method 2
raise and keep the temperature of the oxidizer (air) and gaseous hydrocarbon mixture above auto-ignition temperature
Implementation Method 3
The initial combustion chamber is deliberately lined with the insulation
Implementation Method 4
igniting the air/fuel mixture in the initial combustion chamber to create a deflagration wave that ignites the main combustion chamber
Data Source
AI summary
A combustor including a housing, an injector body, insulation, an air/fuel premix injector, a hot surface igniter, a fuel injector and a burner. The housing forms a main combustion chamber. The injector body is coupled within the housing and the injector body includes an initial combustion chamber. The insulation lines the initial combustion chamber. The air/fuel premix injector is configured and arranged to dispense a flow of air/fuel mixture into the initial combustion chamber. The hot surface igniter is configured and arranged to heat up and ignite the air/fuel mixture in the initial combustion chamber. The fuel injector dispenses a flow of fuel and the burner dispenses a flow of air. The flow of fuel from the fuel injector and the flow of air from the burner are ignited in the main combustion chamber by the ignition of the air/fuel mixture in the initial combustion chamber.