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Scramjet MHD System Generates Electrical Power

A modified scramjet ground demonstrator with a magnetohydrodynamic generator installed downstream of the combustor

A modified scramjet ground demonstrator with a magnetohydrodynamic generator installed downstream of the combustor

WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- An inherent limitation of scramjets [supersonic combustion ramjets] is their inability to provide air vehicle systems--especially future air vehicles that use high-power directed energy weapon systems--with electrical power using conventional generators.

Conventional gas turbine engines produce electrical power via mechanically rotating generators, but scramjets have no rotating parts to provide this function. 

AFRL sponsored the Hypersonic Vehicle Electric Power Systems program to develop a solution to this problem. Through this effort, AFRL researchers worked with partners in industry and academia to demonstrate that magnetohydrodynamic generators can extract electrical power directly from scramjets and generate it on demand and nearly instantaneously (within a response time of milliseconds).

Researchers modified a scramjet ground demonstrator by installing an MHD generator downstream of the combustor. The principal components of the MHD generator are an electrode-lined channel inside a superconducting magnet. 

For this demonstration, the system employed a helium-cooled superconducting magnet borrowed from the National Aeronautics and Space Administration's Marshall Space Flight Center. The interaction of the magnetic fields with the scramjet's electrically conducting exhaust gas flow creates the ability to produce electrical power.

The concept demonstrated simulated speeds of Mach 8 and produced 2-10 kW of electrical power. The power output was limited only by the mass flow rate of the scramjet test rig.