Napier Nomad I, E125 NM.3 Engine




The Nomad 1 exhibited 1951 is a 12 cylinder liquid cooled horizontally opposed 2 stroke diesel with forced induction. It has a capacity of 41.131 litres (2,508 cu in), weighed 4,255 lbs (1,930 kg) and measured 10ft 6in (3.2m) long, 4ft 10in ( 1.5m ) wide and 1ft 1in ( 1.2m ) deep. It had a maximum power of 3125 ehp (2330 kW) and a specific fuel consumption of 0.36 lb/bhp/hour (0.34 kg/kW/hour).

The drawing above is simplified for the sake of explanation. The valveless cylinders seen at A in the diagram, the inlet aperture is the lower opening on the side of the cylinder and the exhaust is the upper aperture. The inner of the two contra rotating propellers B is geared to the crankshaft, its drive shaft is hollow with the drive to the outer propeller passing through it. The crankshaft also drives a large centrifugal supercharger C via step up gears, this supercharger is approximately the same width as the engine.

The engine is fitted with a complex exhaust driven turbine D, the driving exhaust gas energy being augmented by an additional combustion chamber J since there is still significant oxygen in the 2 stoke diesel exhaust. The turbine shaft passes forward to drive an axial compressor F then finally is geared to drive the first propeller G. Between the axial and centrifugal compressors is an intercooler with various controls for bypass as well as coolant control. A second turbine E could be switched in series with the primary one D via a valve L when maximum power was required in conjunction with the additional combustion chamber J.



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