A newly developed hydrogen compressor has a linear motor design and is hermetically sealed to increase the efficiency of H2 compression while avoiding potential problems associated with H2, such as leaks and embrittlement. The linear motor-driven reciprocating compressor (LMRC), developed by a team at Southwest Research Institute (SwRI; San Antonio, Tex.; www.swri.org), is designed to compress H2 for refueling H2-powered vehicles, such as fuel-cell electric vehicles, but can also be adapted for other gas-compression applications that require hermetic sealing, such as hazardous gas compression or flare-gas recovery.
The small size of H2 molecules makes leakage a key challenge, and hydrogen can also be absorbed by steel and other metals, leading to a loss of ductility (hydrogen embrittlement).
The new LMRC features an airtight compressor, hermetically sealed using a combination of SwRI-developed solutions. Coatings protect magnets from hydrogen incursion and embrittlement, while improved valve designs minimize leaks, SwRI says. It also utilizes a ceramic piston to minimize heat expansion and lower stress on its seal.
Linear actuation is also a critical aspect of the LMRC. “Typical compressors have a piston and crank mechanism that requires them to make the same motion every time, with every revolution of the motor that is driving it. SwRI’s LMRC is linearly actuated, so we can change the linear motion profile to optimize the compression process,” explains SwRI principal engineer and project lead investigator Eugene Broerman. The vertical motion of the compressor means that seals and bearings experience less friction, negating the need for traditional lubrication, as required for traditional reciprocating compressors, Broerman says.
Project engineers plan to modify different aspects of LMRC design to further increase efficiency and boost flowrates, as well as apply the LMRC to other compression applications.