The Short Answer
Metal foam is used in aircraft engines today in gearbox air/oil separators, compact heat exchangers and environmental control systems, and it has been flight-engine tested as an acoustic liner over the fan. It is not used directly in the combustor flame, because combustion gas can exceed 1500 °C, hotter than the melting point of nickel. Research and patents explore two combustor-related roles: foam cores inside air-cooled combustor walls, and porous metal flame arrestors for hydrogen fuel systems.
As of September 2026 we found no announcement of a production engine using metal foam in its combustor. Claims that metal foam has "transformed" jet engine combustion are not supported by public evidence. The real opportunities are the cooler parts of the engine and the hydrogen transition.
Where Metal Foam Fits in a Jet Engine
| Engine area | Metal foam role | Status |
|---|---|---|
| Gearbox and bearing chamber breathers | Air/oil separation element | In service |
| Oil, fuel and air heat exchangers | High-surface heat transfer core | In service in aerospace thermal systems |
| Environmental control systems (ECS) | Heat exchangers, filters, diffusers | In service |
| Fan case | Acoustic liner and rub strip over the rotor | Engine-tested by NASA |
| Fan outlet guide vanes | Combined surface cooler and sound absorber | Patented concept |
| Combustor wall | Air-cooled foam core between metal and ceramic skins | Patented concept |
| Hydrogen fuel and premix systems | Flame arrestor, flashback barrier | Research |
| Combustor hot-gas path, turbine | None | Beyond metal foam temperature limits |
Air/Oil Separators: The Most Established Use
Engine gearboxes and bearing chambers are vented, and the vented air carries oil mist. Losing that oil costs money, adds emissions and can trigger maintenance. Metal foam separators, often mounted in a rotating breather, give oil droplets a huge internal surface to collide with and coalesce on. The oil returns to the system and clean air vents overboard. Aerospace foam makers list gearbox air/oil separators as a core application because foam delivers high separation in a compact, lightweight part.
Heat Exchangers and Environmental Control
Modern turbofans reject more heat from oil, generators and electronics than earlier engines, and they have less space to do it. Open-cell foam turns a small volume into a large heat transfer surface with modest pressure drop. One aerospace foam supplier reports that foam heat exchangers can deliver more than double the cooling effectiveness of a traditional fin design. A US patent goes further, placing a metal foam cooler on the fan outlet guide vanes so a single part both cools oil and absorbs noise.
Acoustic Liners and Rub Strips
Conventional fan liners use perforated sheet over honeycomb. Metal foam behaves as a bulk absorber that attenuates a broader band of noise. NASA installed a foam-metal liner close to the fan rotor of a Williams FJ44-3A turbofan to measure high-speed fan noise reduction, and a related NASA concept uses open-cell foam as the sacrificial rub strip within the fan containment system, adding noise reduction with little or no aerodynamic penalty.
The Combustor: What Research Actually Shows
The temperature problem. Combustion gas can exceed 1500 °C, above the incipient melting point of the metal parts it touches. Next-generation engines such as the CFM LEAP and Pratt & Whitney GTF run hotter and at higher pressure than their predecessors, and industry has turned to ceramic matrix composite (CMC) liners and single-crystal superalloys for the hottest parts. Nickel melts at about 1455 °C and copper at about 1085 °C, so standard nickel or copper foam cannot sit in the flame.
Foam-walled, air-cooled combustors. US Patent 7,263,772 describes a combustor built around an open-cell metal foam core with a thin metal outer skin and a ceramic inner skin. Compressor air flows through the foam, cooling it from the inside, then exits to form a protective film along the hot wall. The claimed benefits are a much lighter combustor and simpler manufacturing than machining the shell from a superalloy forging. The foam survives because it is cooled, not because it tolerates flame temperature.
Porous media combustion. Burning fuel inside a porous matrix gives stable, lean, low-emission flames and is studied for micro gas turbines and hydrogen-rich fuels. Most high-temperature porous burners use silicon carbide or other ceramic foams. Metal foam burners work where temperatures are lower, and pore size can be tuned so that flames either cannot propagate (preventing flashback) or burn inside the foam.
High-temperature alloy foams. Open-cell foams are commercially produced in oxidation-resistant alloys such as FeCrAlY and Inconel 625, which extend the usable temperature range for heat exchangers, catalyst supports and cooled structures, though still well below flame temperature.
Hydrogen Aviation: The Next Opportunity
Hydrogen burns fast and flashes back easily, so hydrogen fuel lines, vents and premixers need reliable flame barriers. Porous metal quenches flames by pulling heat from them in small pores, and research on hydrogen-blended gases in porous media shows how pore structure controls quenching and pressure suppression. This makes metal foam a strong candidate for flame arrestors and flashback protection in hydrogen fuel systems, alongside its role as the electrode material in the electrolyzers that produce green hydrogen. See our nickel foam electrolysis guide.
Choosing a Foam for Aerospace R&D
Nickel foam offers the best oxidation and corrosion resistance of the common foams and suits hot, oily breathers, filters and flame arrestor testing. Copper foam has the highest thermal conductivity and suits heat exchanger and thermal management prototypes, below its oxidation limits. Nickel-iron foam balances cost and durability for filtration rigs. Compare nickel and copper foam in detail.
What PrometheanFoam Supplies, and What It Does Not
Flight hardware must come from AS9100-qualified supply chains with full traceability. PrometheanFoam does not claim AS9100 certification, and we do not supply parts for installation on aircraft. We supply nickel, copper, iron and nickel-iron foam for research, prototyping and ground test rigs, from one of the largest non-aluminum metal foam production bases, with ISO 9001:2015 certified production, material certificates with every order, and custom PPI, thickness from 0.3 mm and custom alloys.