Why FeTu

Fetu Concept

FeTu have created a new, novel positive displacement device with compression and expansion capabilities;

a compact four-chamber, single-rotor design of two  halves, bound by a single set of mechanical constraints. Two entry and two exit ports are each served by a pair of positive-displacement chambers. These dual-acting chamber pairs operate in anti-phase; in 180º rotation two chambers draw in fluid through the inlet ports to the point of maximum volume, whilst their opposed partners simultaneously compress and displace air out the discharge ports to a point of zero volume.

“I have never monitored or witnessed an Innovate UK funded project which has over deliver on expectation by such an amount as this”

Bruce Blackburn, Innovate UK monitoring officer

The system is made up of a single drive-shaft which runs through the device carrying a spherical rotor. The rotation of the shaft causes the rotor to ‘roticulate’™ in 3D space (simultaneously rotate and articulate). The rotor follows a defined path, operating the chambers formed in the space separating the two parts. The chambers are configured in such a way that the inlet and discharge ports each receive continuous flow.

The chambers rotate with the rotor, meaning they spend equal time in the compression and induction phase; this imparts a cooling effect on the internals. The proximity of the chambers as they rotate is local to the inlet during induction and local to the discharge during compression. The design makes it impossible for a chamber to be in communication with both suction and discharge ports at the same time, meaning it can operate normally and effectively in a valveless state. 

The dynamic parts do not make contact but run in close proximity, sufficient to affect a seal. The leakage path lengths are long and stagnate flow through them to assist sealing. The only contact points within the device are by means of frictionless bearings.

The architecture can be built a different volume chamber on top and bottom giving the effect of compressing and expanding at different rates.

The Device can be run as:

Compressor / Vacuum Validation:

Testing of Evolution II was completed in collaboration with the University of Bath. The FeTu device was ran within a compression cycle and a vacuum cycle. A Paper has been written on test findings and is to be presented at the 11th ICCS 2019 event:


 “The roticulating concept air compressor: experimental and numerical investigation”


The aim of this was to take the concept from TRL 3 to TRL 5.
A variable-speed test-rig was designed for the FeTu concept to allow pressure, temperature, torque and mass flow data to be captured as a continuous-flow process using a data acquisition and control system, recording a wide range of pressure and speed conditions.

Rig to design

A FeTu unit is fitted to the test rig, fully instrumented, leak-tested and lagged. Tests typically start with the gate valve fully open at 100 rpm, data is captured after system stabilisation then the pressure is increased via the gate valve, stabilised and recorded at the new pressure. A full range of pressure ratios are collected before the gate valve is fully opened once again, unit depressurised, and the speed indexed by 100 rpm. This process continues to up to 1500rpm. Therefore, there is a wide range of performance data at different pressure ratios and speeds.

Variations in clearance, NRV cracking pressure and the addition of contact seals were explored in pursuit of an optimal configuration to maximise volumetric efficiency and performance.