In case you haven’t noticed, we like bizarre powerplants on this blog. We’ve discovered nuclear-powered jets and missiles. This morning we saw (and heard!) a two-stroke, 6 piston, 3 cylinder horizontally opposed diesel engine that has made more than one head explode. Well, Black Steelies reminded me of a bizzare powerplant that just might make your head implode back to normal…behold, the diesel/turbine Napier Nomad!
In 1945, the UK government looked across The Pond and saw those wacky Americans at the Curtiss-Wright factory working on a combination gas and turbine engine. The Brits, in their haughtiness, thought they could do better. And they almost did.
The Air Ministry wanted an engine rated at 6,000 hp and with good fuel economy. Sir Harry Ricardo suggested that a diesel engine would meet this objective. British engine builder Napier already had some experience with diesel aircraft powerplants. Prior to WW2, Napier had licensed the Junkers Jumo 204 design and called it the Napier Culverin. With the onset of the war, though, Napier & Son focused on its Saber engine. When they heard the boys at Adestral House were discussing a high horsepower, efficient engine they jumped at the chance.
Napier origianlly started off by putting two Culverins together in an H-block formation. This resulted in a 75-liter engine…a bit bigger than anything could handle. So, they reverted to what they learned from ze Germans and applied it in a race against the ‘Mericans. The result was the horizontally-opposed 12 cylinder Nomad. It bested the Curtis-Wright design, and was competitive with the early jet engines. But, it had issues.
Napier’s idea was to use the high thermal efficiency of a piston engine, the fuel efficiency of a diesel engine, and the power of a turbine engine. The concept was to replace the combustion chamber of the turbine engine with the diesel engine. However, they had problems coupling the diesel engine back into the turbine. By the time they started making progress on figuring out these problems, jet engines had advanced and the Boeing 707 was on its way with 4 shiny new jet engines ready for service.
Two Nomads were designed. The first, called Nomad I, was intended to drive contra-rotating props. It was essentially two engines in one, with a turbo-supercharged diesel engine driving one prop, and a complete Napier Naiad turboshaft engine below it driving another prop AND the compressor for the supercharger. It would also have a sort of afterburner capability with additional fuel being dumped into the turbine during takeoff. So, it was a supercharged diesel with a turboshaft and an afterburner. The Nomad I was tested in the nose of an Avro Lincoln bomber and, when operating properly, provided 3,000 hp with a very good specific fuel consumption.
Even before Nomad I was complete, Napier began work on Nomad II. In the Nomad II configuration the engine was greatly simplified. An additional compressor stage was added to the turboshaft engine to act as a turbocharger on the diesel engine with the diesel exhaust gases driving the turbine. Rather than two separate engines, the system behaved more like a diesel engine with a big ass turbo-supercharger…which also provided some thrust. One set of props was removed and the engines now were coupled via a hydraulic clutch. This configuration resulted in an engine that was half a ton lighter and produced about 3,100 hp. It was tested in an Avro Shackleton.
A third variant was in the works when the Ministry of Defence decided to cancel the Avro Shackleton IV, the only planned aircraft to use the Nomad III. This bizarre engine breathed its last breath in 1955 after over 5 million pounds sterling were spent on its development.
[Photo Credits: Public Domain via Wikimedia Commons]