© 2018 by 21Geo, Thomas Dobroth

Case Study:

Compressor Crankcase Replacement

An example MSB designed to mimic the motion a legacy crankcase.  

Currently, piston compressors use a crankcase to drive the piston.  The motion of the piston is sinusoidal up/down motion.   Pushing refrigerant from the low-pressure chamber to the high-pressure chamber takes three steps: 1) intake of the low-pressure fluid, 2) compressing the fluid to high pressure, and 3) injecting the compressed fluid into the high-pressure chamber.  Uneven injection into the high-pressure chamber spikes pressure.  Pressure becomes force on the cylinder head and force times distance is lost energy.  Modern high-efficiency compressors use four or more cylinders to reduce pressure spikes. 

The uneven injection is rectified through redundancy.  Even so, the crankcase injection is inherently uneven.  Energy is lost unnecessarily.  

 

By using an MSB instead of a crankcase, the optimal cycle can be “hard-coded” into the bearing.  In this case, the optimal cycle is to inject smoothly over 180 degrees of shaft rotation (Above).  Smooth injection keeps the pressure from spiking and using 180 degrees of shaft rotation keeps the number of cylinders down to just two. Two cylinders instead of four, six or eight means fewer valves, pistons, cams, manifolds and cooling infrastructure.  While the bearing is complex, the overall complexity is reduced.  The net costs will likely be lower.  The compressor MSB is shown below.  

Summary

 

The benefits of using this an MSB instead of a crankcase are:

 

  • Optimal efficiency. 

  • Energy use 20% to 50% lower. 

  • Lower upfront costs.  (CHEAPER)

 

Typically, energy efficiency cost more up front.  The costs limits adoption.  The MSB simultaneously finds optimal efficiency and lower upfront costs.  Adoption will likely be simplified.  

 

MSB’s show promise to produce cost-effective and optimal efficiency devices.  About 40% of worldwide electricity turns compressors for HVAC and refrigeration.  The improvements in operating efficiency will dramatically reduce greenhouse gas emissions.   The lower up-front costs expedite adoption.  Another goal for reducing global warming is to curtail the use of CFC refrigerants.  If implemented in conjunction with the changing of refrigerants, the adoption of the new refrigerants is simplified.