Fuel-injection unit for testing the ignition quality of fuel

Precise quantities of fuel are injected repeatedly through a nozzle 30 under controlled conditions into a combustion chamber bombe (not shown) where the combustion is monitored. The unit comprises a pump block 5 having a bore 22 containing a barrel 20 and a plunger 21. Pump block 5 may contain heaters (27, fig.2) to ensure constant fuel viscosity. The nozzle 30 is attached to the barrel 20 by a clamp 3. Air under pressure in container 13 is released periodically into air cylinder 4 which causes piston rod 8 to strike a cam follower 2 driving the plunger 21 causing fuel to be injected. The test system can be used in an in-line feedback arrangement to permit the continual adjustment of a refining process to maintain the cetane number at a desired value.