Office for Technology Commercialization

Inverted Liquid Piston Compressor/Expander

Technology #20150203

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Liquid PistonGas Compression
James Van de Ven, PhD
Assistant Professor, Mechanical Engineering, College of Science and Engineering
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Managed By
Kevin Nickels
Technology Licensing Officer 612-625-7289
Patent Protection

US Patent Pending US20170002803

Efficient Gas Compression and Expansion

Using a liquid piston that’s inverted solves some of the traditional problems prone to mechanical gas compressors. This new invention uses liquid as a static piston and moves the gas chamber relative to the liquid, thus eliminating mechanical sliding seals and subsequent gas leakage found in typical mechanical compressors. Moving the cylinder relative to the stationary liquid piston allows for high frequency operation without an unstable liquid-gas interface. In addition, a porous media used in combination with the liquid piston provides a large surface area that increases heat transfer. The inverted liquid piston compressor further improves performance by using a ferrofluid for the liquid piston along with a magnetic field to create a downward force, which increases the maximum frequency of operation and improves drainage of the porous media.

Liquid Piston Challenges

Mechanical methods of compressing or expanding a gas, such as reciprocating pistons, screw compressors and vane motors, suffer from poor heat transfer, gas leakage and high sealing friction. As a result, more energy is required to compress the gas, which reduces the efficiency of the overall cycle. Current liquid piston systems face challenges with the stability of the liquid-gas interface during acceleration of the liquid piston, which may result in gas bubbles penetrating the liquid and/or liquid drops being ejected into the gas. This new inverted liquid piston compressor/expander design features increased heat transfer, improved efficiency (via reduced friction), cohesive gas-liquid interface and high frequency operation.


  • Increased heat transfer
  • Improved efficiency through reduction in friction
  • High frequency operation
  • Increased power density
  • Eliminates mechanical sliding seals
  • Cohesive gas-liquid interface

Phase of Development Concept