In the last decade, fuel tank inerting systems have transcended from a niche market of military aircraft into wide scale proliferation on commercial airliners. In fact, almost all commercial airliners have a fuel tank inerting system onboard, many of which include systems and components supplied by Parker Aerospace. These systems reduce the flammability risk inside the fuel tank by supplying an inert gas into the space above the liquid fuel. These systems rely on a source of pressurized air, typically engine bleed air, to provide the feed stock for the inert gas.
As the airframers of commercial airliners move away from bleed air systems and toward more electric aircraft in the future, an opportunity is presented for a fuel tank inerting technology that does not rely on high pressure air. Moreover, this same inerting technology could be applied to other aircraft in which bleed air is in limited supply or unavailable altogether, such as military rotorcraft, small commercial transports, and business jets.
This opportunity is setting the stage for the next evolution in fuel tank inerting systems: catalytic inerting. In 2016, Parker Aerospace and Phyre Technologies, Inc. signed an exclusive agreement to develop Phyre’s patented ullage-recirculating catalytic inerting technology for aerospace applications. Since that time, Parker has been actively developing the system and its components for high performance, high durability, and low weight. Significant advancements have been made in the development of the catalytic reactor, condenser and other components. At the same time, Parker has grown its testing infrastructure and analytical capabilities to support a full-scale program.
Fuel tank inerting systems perform the critical function of reducing the flammability potential of the mixture of gases in the ullage space above the fuel in aircraft fuel tanks. Catalytic inerting advances fuel tank inerting technology beyond the current applications, in which inert nitrogen gas is generated from high-pressure engine bleed air inside of an air separation module (ASM).
Read our previous blog post that discusses how catalytic inerting technology differs from today’s traditional ASM-based method.
Most contemporary commercial airliners use engine bleed air for many purposes ranging from cabin pressurization and environmental control systems (ECS) to anti-icing, water and hydraulic system pressurization, and ASM-based fuel tank inerting. While an ASM-based inerting system uses far less bleed air than the ECS and anti-ice systems, the extraction of bleed air from the engine results in decreased engine efficiency. The larger engines of a typical commercial aircraft have the capacity to supply bleed air for these subsystems; but other aircraft types – helicopters, turboprop-powered transports, business jets, and newer more-electric aircraft – have less bleed air to spare.
A primary benefit offered by catalytic inerting technology is that it requires no engine bleed air. Circulation of ullage gas through the system and back to the fuel tank is provided by a low-power consumption electric blower.
The blowers and other electrically powered components in the closed-loop catalytic fuel inerting system call for only a modest amount of electricity. Although the electrical power required by the system is supplied by the engine generator, the relatively low power consumption of the catalytic inerting system results in less parasitic power loss to the engine than ASM inerting systems. This is a principal reason why catalytic inerting is ideally suited for aircraft applications where there is little or no engine bleed air available, especially rotary wing aircraft and more-electric commercial aircraft.
The demanding missions that helicopters fly – whether military or commercial – require the aircraft to have available as much power as possible. By eliminating the need for engine bleed air to drive fuel tank inerting, catalytic systems directly support the need for greater range as well as higher payload and takeoff weight.
A catalytic fuel inerting system is largely self-contained and can occupy a smaller envelope than its ASM-based counterpart. These features enable a catalytic inerting system to be neatly packaged as a line-replaceable unit (LRU) and facilitate ready integration within the airframes of both new helicopter platforms and existing ones. Furthermore, the general shape and positioning of helicopter fuel tanks enables close coupling of the catalytic inerting system with minimal external plumbing and structure.
As part of its future vertical lift (FVL) modernization efforts, the United States Army is developing its Future Attack and Reconnaissance Aircraft (FARA) and Future Long-Range Assault Aircraft (FLRAA) programs, targeted to be operational before 2030. Parker’s catalytic fuel inerting systems is ideally suited to such applications.
“Our development program for catalytic fuel inerting systems is proving that the technology will be a viable option for future aircraft programs, especially vertical lift platforms. We are looking at all options to successfully bring this technology to the marketplace.”
— John Hayden, business development director, Parker Aerospace Fluid Systems Division (FSD)
Parker Aerospace engineers have been maturing catalytic fuel inerting by iteratively proving and improving the technology. The Parker team is working to reduce system complexity, increase component durability, and fine-tune the catalytic reactor for maximum performance and life - all while keeping a close eye on procurement and maintenance cost targets.
Stay tuned to the aerospace blog for updates to the Parker Aerospace vision of the future for aircraft fuel tank inerting systems.
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This article contributed by Bryan Jensen, senior principal engineer, Parker Fluid Systems Division.