Stirling Engine Heater Head in Fluidized Bed

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Solution Overview

Problem

Incinerator systems with Stirling engines, particularly those used in residential settings, face premature heater head failure due to high temperature fluctuations and corrosive exhaust gases when burning biomass, leading to reduced durability and frequent expensive repairs.

Innovation Solution

Incorporating a fluidized bed of solid particles, such as quartz sand, in the combustion chamber and positioning the Stirling engine's heater head within it, along with a heat exchanger to preheat combustion air and a control system for air pressure, ensures consistent temperature and reduces corrosive exposure, while a control unit manages air flow to efficiently start and maintain the combustion process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the heater head is arranged directly in the combustion chamber, then the system structure is simple, but the heater head is exposed to high temperature peaks and corrosive substances, leading to reduced service life

Engineering Contradiction:
Improvesystem structureVSAvoidheater head service life
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

A fluidized bed made of solid particles (preferably quartz sand) is introduced as an intermediary medium between the combustion chamber and the heater head. The fluidized bed absorbs temperature peaks and prevents direct contact between the heater head and corrosive combustion products, thereby protecting the heater head while maintaining system functionality.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The fluidized bed creates a protective environment around the heater head by maintaining a controlled atmosphere of inert or less reactive particles. This inert environment reduces the exposure of the heater head to corrosive substances generated during biomass combustion, extending its service life.

Inventive Principle:
Principle #39Inert atmosphere (Inert environment)

2Power

If wood pellets are burned in the combustion chamber, then energy is generated, but large temperature fluctuations and peaks up to 1100°C occur, damaging the heater head surface

Engineering Contradiction:
Improveenergy generationVSAvoidtemperature peaks
Core Design Contradiction:
PowerVSTemperature

Solution Approach 1:

The introduction of the fluidized bed changes the thermal parameters of the combustion system. It acts as a thermal buffer that absorbs temperature peaks and reduces temperature fluctuations, maintaining a more stable temperature environment for the heater head while preserving the energy generation capability of the combustion process.

Inventive Principle:
Principle #35Parameter changes

3Speed

If combustion air is supplied directly to the combustion chamber, then the combustion process starts quickly, but the combustion efficiency is reduced and energy is wasted

Engineering Contradiction:
Improvecombustion start-up speedVSAvoidcombustion efficiency
Core Design Contradiction:
SpeedVSLoss of energy

Solution Approach 1:

A heat exchanger is introduced to preheat the combustion air before it enters the combustion chamber. This preliminary heating action improves combustion efficiency by reducing the energy required for ignition and maintaining higher combustion temperatures, thereby reducing energy losses while preserving quick start-up capability.

Inventive Principle:
Principle #10Preliminary action

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 extends the service life of the heater head by maintaining a consistent temperature, reducing corrosive damage, and optimizing energy use by preheating combustion air, thereby enhancing the overall durability and efficiency of the incinerator system.

Implementation Method 1

A fluidized bed generally refers to a bed of solid particles, for example quartz sand, which is brought into a fluidized state by an upward flow of a fluid, in the present case air

Methodology Applied
Scientific EffectFluidized bed combustion: Fluidisation

Implementation Method 2

The arrangement of the heater head of the Stirling engine in the fluidized bed therefore means that temperature peaks are avoided and operation takes place at a constant temperature

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a heat exchanger is provided between the combustion air supply and the combustion chamber, whereby the combustion air is preheated

Methodology Applied
Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 4

a Stirling engine for generating electrical energy, the heater head of the Stirling engine being in the combustion chamber

Methodology Applied
Scientific EffectStirling cycle: Stirling Cycle

Data Source

PatentEP2827059B1Incinerator installation
Publication Date: 2020.02.19 BEILSCHMIDT ALFRED
  • EP2827059B1 patent drawingFigure 1
  • EP2827059B1 patent drawingFigure 2

AI summary

The invention relates to a combustion furnace system, preferably for the combustion of biomass, in particular wood pellets, comprising an ignition unit (11), a combustion chamber with a fuel supply (3), combustion air supplies (12, 13), an exhaust gas system (7) equipped with a heat exchanger (8) for heating water preparation, and a Stirling engine (1) for generating electrical energy, wherein the heater head (2) of the Stirling engine (1) is arranged in the combustion chamber. A fluidized bed (5) consisting of a bed of solid particles, preferably quartz sand, is arranged in the combustion chamber, and the heater head (2) of the Stirling engine (1) is arranged in the fluidized bed (5).