CFR Cetane Rating Engine


Fig. 1 Set-up of engine measuring cetane number

The CFR engine used for measurements is a single cylinder, four-stroke cycle pre-chamber type diesel engine. The displacement volume is 610 cm³, rev runs to 900 1/minute which is the value determined at the ASTM standard, the adherence of which is ensured by an asynchronous electric engine belt connected to the engine. The engine can be started with the help of this electric engine.
The main characteristic of the engine is that its compression ratio can be modified, and changing the preinjection timing and the fuel dose. The compression ratio modification be realized by the compression setting piston observable at the cylinder head shown at Figure 2.


Fig. 2. Combustion Chamber of the Cetane Rating Engine

The dose is a value determined at the standard either, its setting at 13 cm³/60±1 sec. follows according to the volume of fuel consumed in one minute. The value of pre-injection timing determined for measurement is 13° ± 0,2 measured at the main axis.
In case of the measuring method used by us – which essentially corresponds with the measuring method of cetane number ASTM D 613-93 – the main point is that having set the dose and the pre-injection timing to the mentioned point, modification of compression ratio takes place until ignition delay becomes 13° ± 0,2 measured at the crank shaft. At this point the engine works optimally, the start of burning will be at the TDC (Top Dead Center). (In case of measuring cetane number the compression hand wheel set up registered in this way has to be compared with a value belonging to a reference fuel of a known cetane number so the sample’s cetane number can be determined.)


  • Pressure Ratio: 8-36

  • Speed: 900 rpm

  • Injection Pressure: 103 bar

  • Cooling Water: 100 °C

  • Intake Air temp.: 66 °C

  • Injector Temp.: 38 °C

  • Pre-injection ang.: 13° BTDC

  • Ignition Delay: 13°

  • Fuel Cons.: 13 ml/min.