Napier (UK)

Napier engines were designed and built by D. Napier & Son, Limited of London, Acton, and Liverpool, UK. This firm was founded in 1808 when David Napier moved from Scotland to London to make printing machines. The factory was moved to Acton in 1903, after which time Napier became famous for their automobiles. This led to manufacturing aircraft engines under license at the beginning of WWI, followed by designing and building their own WWI aircraft piston engines, which continued between the wars through WWII into the post-WWII years. The late 1940s and the 1950s also saw extensive aircraft gas turbine development by the firm. The company remained independent until it was divided up in 1960, with Napier Aero Engines, Ltd. becoming part of Rolls-Royce, Ltd. in 1962. The Napier Nomad compound engine described below was a truly remarkable attempt to provide the 1950s with a highly-economical, efficient aircraft engine for long-range operations. It was developed under the leadership of Napier Chief Engineer, Ernest E. Chatterton, from about 1945 to 1955. The original version of the basic engine, the Nomad 1, was a twelve-cylinder, turbocharged, two-stroke, direct fuel-injection, compression-ignition (diesel) engine that was geared by helical spur reduction to drive the rear blade row (in tractor configuration) of a contra-rotating (C-R) propeller. The compounding was accomplished by driving a turbine with the exhaust gas of the basic engine, in principle the same as in the Curtiss-Wright R-3350 Turbo-Compound engine. However, the exhaust-driven turbine also drove an axial-flow compressor, the output of which passsed through an intercooler, and through a centrifugal compressor which combined to provide the turbocharging for the basic diesel. The turbine shaft also drove, through gearing, the front blade row of the propeller. Additional short-term power to improve take off (TO) could be implemented by the option of passing the diesel exhaust gas through two fuel-injected combustion chambers (essentially, afterburning of the diesel exhaust) and through another turbine in series on the same compressor/turbine shaft. The entire compounding system of the Nomad 1 engine is described in a simplified schematic drawing and discussion contained in Bill Gunston's piston engine book (BGP). Herschel Smith's book (S) reproduces a highly-detailed cutaway drawing (which initially appeared in "Flight" magazine for 4/30/54) of the Nomad 2. The Nomad 2 had some simplifications (noted below) to the original engine system. The Nomad never reached service after cancellation in 1955. Engines such as the R-3350 Turbo-Compound, the Pratt & Whitney R-4360 Wasp Major, the Bristol Centaurus, and the Rolls-Royce Griffon powered the last of the long-range piston military and civilian transport aircraft before the introduction of gas turbines for this class of aircraft.

OL-2500 (2-Stroke Diesel) -- {6.000 / 7.375 / 2502.3} / {152.4 / 187.3 / 41,003}

12cyl; Nomad 1, Nomad E 125, NNm.3; 2248shp@N/Arpm; 3000shp plus 320# residual thrust (for an equivalent shp of 3125) (TO); 1945-1953; Wt = 4200-4225#.
Liquid-cooled, two-stroke cycle, turbocharged, direct fuel injection, compound diesel engine system geared to N/A as described above.
BGE; BGP; J51-52toJ52-53; S; W52toW53.
Applications: (UK) Avro Lincoln (testbed), Shackleton (proposed); Blackburn and General Beverley (proposed).

12cyl; Nomad 2, Nomad E 145, NNm.6; Equivalent shp of 3135@N/Arpm or 4095 with water injection (TO); 1953-1955; Wt = 3580#.
Same as Nomad 1, but without the afterburning system (combustion chambers and auxiliary turbine) and the centrifugal compressor. However, variable gearing was added so that both the turbine and diesel-engine output drove a single propeller shaft, which replaced the C-R propeller. Also, provision for water injection was added to increase TO power. Later NNm.7 and NNm.8 versions are described in W55&W56 and have minor differences from the NNm.6, but the compiler does not know if they were built and tested after cancellation in 1955.
"Aeroplane" 4/30/54; BGE; BGP; "Flight" 4/30/54; J53-54toJ54-55; S; W53toW54.
Applications: (UK) Airspeed Ambassador freighter (proposed); Avro Shackleton (proposed); Blackburn and General Beverley (proposed).


Updated 2/19/08