Two-Stage Combustor for Stirling Engine Heat Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing combustor designs face challenges in achieving stable, clean, and efficient combustion of hydrocarbon fuels at high temperatures, as they often result in excessive NOx and hydrocarbon emissions, and catalyst degradation or volatilization, while also requiring materials that can withstand high temperatures and efficiently transfer heat to downstream applications.
Innovation Solution
A two-stage combustor system is introduced, comprising a partial oxidation reactor with a catalytic partial oxidation process and a deep oxidation reactor that operates non-catalytically at higher temperatures, using a porous heat spreader to efficiently transfer heat to a heat acceptor, allowing for durable construction materials and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-stage combustor uses near-stoichiometric oxidant-to-fuel ratio to achieve stable combustion, then complete combustion is improved, but flame temperature exceeds 1,200°C causing material durability issues and heat transfer inefficiency
Solution Approach 1:
The combustor is divided into two separate stages: a first-stage combustor that operates at controlled temperatures below 1,200°C with a catalyst, and a second-stage combustor that handles remaining combustibles. This segmentation allows each stage to operate under optimal conditions, preventing excessive temperatures while maintaining combustion stability.
Solution Approach 2:
A catalyst is introduced as an intermediary substance in the first-stage combustor to promote complete combustion at lower temperatures. The catalyst enables the combustion reaction to proceed efficiently without requiring near-stoichiometric oxidant ratios, thus controlling flame temperature while maintaining combustion reliability.
2Temperature
If combustor materials are designed to withstand temperatures above 1,200°C, then temperature resistance is improved, but heat transfer efficiency to downstream applications decreases
Solution Approach 1:
The combustor system is segmented into two stages with different temperature regimes. The first stage operates below 1,200°C where efficient heat transfer materials can be used, while the second stage handles any remaining high-temperature combustion. This allows optimization of heat transfer efficiency in the primary combustion zone.
Solution Approach 2:
The operating temperature parameter of the primary combustor is changed from above 1,200°C to below 1,200°C through catalytic combustion. This parameter change enables the use of materials with superior heat transfer properties while maintaining combustion effectiveness.
3Productivity
If an oxidation catalyst is used in a single-stage combustor to promote complete combustion, then conversion efficiency is improved, but catalyst lifetime is greatly reduced due to volatilization at temperatures exceeding 1,200°C
Solution Approach 1:
The combustion process is segmented into two stages, with the catalyst placed only in the first stage where temperatures are controlled below 1,200°C. This protects the catalyst from thermal degradation and volatilization, extending its lifetime while maintaining high conversion efficiency for the majority of fuel combustion.
Solution Approach 2:
The catalyst serves as an intermediary that enables efficient combustion at lower temperatures. By mediating the combustion reaction in the first stage, it allows complete combustion to occur without requiring temperatures that would cause catalyst volatilization, thus preserving catalyst integrity and extending service life.
4Productivity
If near-stoichiometric oxidant-to-fuel ratio is used in single-stage combustion, then complete combustion is achieved, but NOx emissions increase due to high flame temperatures
Solution Approach 1:
The combustion process is segmented into two stages, with the first stage performing the majority of combustion at controlled temperatures below 1,200°C using a catalyst. This temperature control prevents the formation of thermal NOx, while the second stage completes combustion of any remaining combustibles, achieving both completeness and low emissions.
Solution Approach 2:
The temperature parameter of the primary combustion zone is changed from above 1,200°C to below 1,200°C through catalytic combustion. This parameter change suppresses thermal NOx formation mechanisms while maintaining combustion completeness through the catalytic reaction pathway.
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 two-stage combustor design achieves stable and complete combustion with minimal emissions, extends catalyst longevity, and enables efficient heat transfer to downstream applications like Stirling engine heater heads, using suitable materials for each temperature range to maintain durability and efficiency.
Implementation Method 1
a partial oxidation reaction zone comprising a porous substrate having a partial oxidation catalyst supported thereon
Implementation Method 2
a porous heat spreader being capable of retaining combustion therein and transmitting heat to a heat acceptor
Implementation Method 3
burning a hydrocarbon fuel with an oxidant for the purpose of producing a clean and durable combustion process while providing heat efficiently
Data Source
AI summary
A two-stage combustor having as constituent parts: a partial oxidation reactor, which catalytically converts a hydrocarbon fuel and a first supply of oxidant into a gaseous partial oxidation product; and a deep oxidation reactor having a premixer plenum fluidly connected to a porous heat spreader, which converts the gaseous partial oxidation product to deep oxidation products. In one embodiment, the premixer plenum provides an empty space wherein combustion occurs in flame mode. In a second embodiment, the premixer plenum contains a high pore density foam matrix, absent catalyst, which facilitates holding a flameless combustion downstream within the porous heat spreader. In both embodiments heat produced during combustion is transmitted from the heat spreader to an associated heat acceptor, such as a heater head of a Stirling engine.