SOFC Turbocharger Start-Up Air Switching to Prevent Gas Flow Reversal

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In fuel cell systems combining solid oxide fuel cells (SOFC) and turbochargers, the turbocharger cannot be started independently, requiring external start-up gas, and there is a risk of gas flow reversal due to pressure differences, necessitating a stable method to switch between start-up gas and compressed gas.

Innovation Solution

A fuel cell system with a turbocharger, oxidizing gas supply line, control valve, blow line, and start-up air line, where the control unit gradually decreases the blow valve opening and increases the control valve opening to switch from start-up air to compressed oxidizing gas, ensuring stable start-up by preventing gas flow reversal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If start-up gas is supplied from outside to start the turbocharger, then the turbocharger can be started, but gas flow reversal may occur due to pressure differences during switching

Engineering Contradiction:

Improvestart-up stabilityVSAvoidgas flow reversal

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The blow valve is closed before the control valve is opened during the switching process. This preliminary action establishes a pressure barrier that prevents gas flow reversal when transitioning from start-up gas to compressed gas supply, ensuring stable start-up operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The blow valve serves as an intermediary component between the start-up gas supply and the compressed gas supply. By controlling the blow valve's opening and closing timing, the system mediates the pressure transition and prevents direct conflict between the two gas sources, eliminating flow reversal risks.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the control valve is opened early during switching, then gas supply continuity is maintained, but gas flow reversal occurs due to pressure imbalance

Engineering Contradiction:

Improvegas supply continuityVSAvoidpressure balance

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The blow valve is closed in advance before the control valve opening is increased. This preliminary pressure establishment ensures that when the control valve opens, the pressure balance is maintained and gas flow reversal is prevented, achieving both continuity and stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

By closing the blow valve beforehand, the system creates a pressure cushion that absorbs the pressure imbalance during switching. This cushioning effect prevents gas flow reversal while maintaining continuous gas supply to the cathode.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Object-affected harmful factors

If the blow valve is closed too early during switching, then gas flow reversal is prevented, but gas supply interruption occurs

Engineering Contradiction:

Improvegas flow reversal preventionVSAvoidgas supply interruption time

Core Design Contradiction:

Object-affected harmful factorsVSDuration of action of moving object

Solution Approach 1:

The blow valve is closed at an optimally timed moment before the control valve opens sufficiently to maintain pressure balance. This timing ensures that the blow valve provides its protective function just long enough to prevent flow reversal, then opens to maintain continuous gas supply.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The switching process is made dynamic by continuously adjusting both the blow valve and control valve openings during the transition. This dynamic control allows the system to prevent gas flow reversal at critical moments while maintaining gas supply continuity throughout the switching process.

Inventive Principle:

Principle #15Dynamics

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 method enables stable start-up of the fuel cell system by effectively managing gas flow transitions, preventing backward flow and ensuring reliable operation of the turbocharger.

Implementation Method 1

a turbine to which exhaust fuel gas and exhaust oxidizing gas discharged from the fuel cell are supplied as combustion gas

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 2

having a compressor driven by the turbine

Methodology Applied

Scientific EffectThermal energy conversion:

Implementation Method 3

oxidizing gas compressed by the compressor

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS11936078B2Fuel cell system and method for starting same

Publication Date: 2024.03.19 MITSUBISHI HEAVY IND LTD

AI summary

The purpose of the present invention is to provide fuel cell system capable of stable start-up and method for starting the fuel cell system. Fuel cell system includes SOFC, a turbocharger, oxidizing gas supply line, a control valve, oxidizing gas blow line, start-up air line for supplying the start-up air to the oxidizing gas supply line with a blower, and a control unit that, in state in which the control valve is closed and the blow valve is opened to supply the start-up air to the oxidizing gas supply line with the blower when the turbocharger is started, decreases the opening of the blow valve and, after the timing at which the opening of the blow valve starts to decrease, increases the opening of the control valve and then stops the supply of the starting air.