APU Fuel System Oxygen-Enriched Combustion Ignition
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Solution Overview
Problem
Low temperatures at high altitudes hinder the startup and sustained operation of auxiliary power unit (APU) gas turbine engines due to increased fuel viscosity and the large temperature gap required for ignition, leading to impaired operability and reduced efficiency.
Innovation Solution
A fuel system that includes an air separation module to supply oxygen-enriched air and a heating element to pre-heat the fuel, along with a barbotage system that feeds hydrogen to the combustor, enhancing combustion ignitability and efficiency by increasing oxygen and hydrogen concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional fuel injection is used at high altitudes, then the APU can operate with simple fuel system, but low fuel temperatures cause increased fuel viscosity and larger droplet formation that impede combustion ignition
Solution Approach 1:
The patent changes the chemical composition parameter of the combustion environment by introducing oxygen-enriched air and hydrogen into the combustor. This alters the combustion parameters to achieve reliable ignition and sustained operation in cold, high-altitude conditions where traditional fuel injection fails.
Solution Approach 2:
The patent introduces oxygen-enriched air as an intermediary substance between the fuel and the combustion process. This intermediary provides additional oxygen to facilitate complete and reliable combustion of the fuel droplets in cold conditions where normal air would be insufficient.
2Reliability
If oxygen-enriched air is supplied to the combustor, then combustion ignition is improved, but device complexity increases due to the air separation module
Solution Approach 1:
The air separation module serves multiple functions: it separates oxygen from air to create oxygen-enriched combustion air, provides nitrogen for fuel tank inerting, and manages fuel tank atmosphere. This multi-functionality justifies the added complexity by delivering multiple benefits from a single system component.
Solution Approach 2:
The patent applies the principle of strong oxidants by using oxygen-enriched air in the combustor. The increased oxygen concentration accelerates the oxidation (combustion) process, enabling reliable ignition and sustained operation in cold conditions where normal air would be insufficient.
3Productivity
If hydrogen is added via barbotage system, then combustion efficiency is enhanced, but device complexity and hydrogen storage requirements increase
Solution Approach 1:
The patent changes the chemical composition parameter of the fuel by introducing hydrogen through the barbotage system. This alters the fuel's combustion characteristics to achieve higher combustion efficiency and better performance in cold, high-altitude conditions.
4Reliability
If fuel is pre-heated, then fuel viscosity is reduced and atomization is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-heating the fuel before it reaches the injectors. This preliminary heating action reduces fuel viscosity and improves atomization quality before combustion, ensuring reliable operation in cold conditions.
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 system facilitates ignition and improves sustained operation by reducing the energy required for engine startup and operation, mitigating the effects of low temperature conditions at high altitudes, and enhancing fuel efficiency.
Implementation Method 1
a heating element configured to pre-heat the fuel
Implementation Method 2
a barbotage system configured to feed hydrogen to the injector
Implementation Method 3
an air separation module configured to supply oxygen-enriched air into the combustor via the injector for combustion
Implementation Method 4
fuel injected into an APU combustor to form larger-than-usual droplets
Data Source
AI summary
A fuel system for a gas turbine engine comprises an injector disposed to inject fuel and air into a combustor of the gas turbine engine. In a first embodiment, the fuel system further comprises an air separation module configured to supply oxygen-enriched air into the combustor via the injector for combustion. In a second embodiment, the fuel system further comprises a barbotage system and a heating element. The barbotage system is configured to feed hydrogen to the injector, and the heating element is configured to pre-heat the fuel.