Results presented at 2016 European Fluid Machinery Congress

A paper on Vert’s technology and latest results of the water-injected compressor was presented by Olly Dmitriev, CEO of Vert Rotors, at 2016 European Fluid Machinery Congress in The Hague, The Netherlands 

You can download a research paper showing how the Conical Rotary Compressor works, and what results have been achieved by the company. In brief, here are a few main points:

  • Tests of the CRC.80 have demonstrated that the novel conical screw profile improves volumetric efficiency of the machine to 86.90% at 9 bar(a) discharge pressure, which is comparable or slightly better than a state-of-the-art, oil-injected twin-screw compressor of similar displacement.
  • The overall size of the CRC.80 package (without pressure vessel) was 40% smaller than an oil-injected twin-screw compressor from a leading



Olly Dmitriev said:

“For an end-user looking for an oil-free compressor, water-injected screw is a much better alternative to the dry-running screw. It is not noisy, and most importantly does not produce the uncomfortable high-pitch “screaming” noise, which is typical of dry-running screw compressors. Injection of water instead of oil removes the risk of contamination, producing high quality air, compliant with ISO 8753-1 “class 0”. A major difficulty has been that, to operate with water, twin-screw compressors have to be re-engineered from corrosion-free materials. Before it was too expensive, and for economic reasons only larger, more expensive compressors were available on the market. Our work shows that we have solved this problem.”

The paper shows the progress, how the team solved the technical problems moving step-by-step.


The first fundamental problem was the impact of poor sealing properties of water on the compressor’s volumetric efficiency. The authors have shown that the conical screw profile improves volumetric efficiency of a compressor by reducing the clearance between the rotors, and eliminating the leakage path from the high-pressure side to the low-pressure side. Vert’s conical machine has a novel 2+3 conical screw profile, with the male conical rotor positioned inside the female conical rotor, which reduces the leakage flow.

Screw rotors in twin-screw compressors are typically manufactured from carbon steel, which was not an option for the CRC.80, because of accelerated corrosion with water. Vert produced its screw rotors from a combination of materials running at low friction: brass and composite polymers.

The test results of the conical screw compressor demonstrate that such a compressor can achieve significant volumetric efficiency, even with water injection.

What’s next?  

The company is preparing a 2.5kW new generation water-injected compressor, based on all hard lessons learned through the last three years of R&D. This new compressor will provide oil-free compressed air, at very high energy efficiency, and with low noise. We believe that water in compressors provides the same benefits as oil (low-noise, high efficiency), but is an ecologically clean and sustainable media.