Rapid Compression Machine (RCM)
Simulating an Internal Combustion Engine
- What? An instrument designed to simulate a single engine cycle of an internal combustion engine.
- Why? Allows the study of self-ignition of fuel + air mixes under easily controlled conditions and in a cleaner environment than the traditional i.c. engine.
- Can I buy one?
Yes [2005]; but most of the dozen or so RCMs in the world were home-made:
- Massachussetts Institute of Technology, USA
- University of Leeds, UK (Prof. John Griffiths)
- National University of Ireland, Galway
- CNRS Institutes at Lille & Poitiers, France
- Germany
- Institute for Combustion Technology, University of Stuttgart
- Technical University, Munich
- Japan
- Gifu University (Prof. Kazunori Wakai)
- Hosei University
- Nagoya Institute of Technology
- Tokyo University
- Seoul National University, Korea Digital Engine Laboratory [KSME International Journal 16:1127-1134, 2002].
- University of New South Wales, Australia
- Tashkent, USSR (as it then was)
- Warsaw University of Technology
Galway RCM
We acquired (thanks to Dr. Chris Morley) the rapid compression machine built by Shell UK Ltd.
at their Thornton Research Centre; it needed upgrading and modernising but is a superb piece of machinery
which allows us to explore pressure and temperature regions which are not readily accessible to our
shock tube. It also means that we can study the oxidation of low volatility
fuels as the chamber can be preheated to 373K
The Shell/Galway RCM has a unique design; all the other RCMs use a single-piston to compress a gaseous fuel-oxidant mix,
the Galway RCM uses twin opposed pistons. The compression ratio can be varied whilst the
combustion chamber volume is 45 cm3. The initial chamber pressures can range from sub-atmospheric,
0.3 bar, to above atmospheric, 3 bar.
We have:
- ongoing studies of the autoignition of hydrogen, methane, propane and methane/ethane/propane mixtures under gas turbine conditions
- carried out measurements on all 9 isomers of heptane
- measured the impact of water vapour on the ignition of dimethyl ether, 2,3-dimethylpentane and toluene
- studied the behaviour of a 'virtual' RCM via CFD calculations; the model has been built with Star-CD and has answered
questions which are extremely difficult to measure experimentally. Detailed chemistry is being added via Chemkin-III.
- re-designed the reaction chamber to reduce the dead volume to a minimum,
- re-designed the piston heads to minimise the formation of corner vortices during compression by machining grooves or crevices
in the piston sidewall, and,
- using a rapid sampling system, and,
- measuring the auto-ignition of model biofuels.
