- Reaction score
A remarkable experimental Italian jet aircraft from the WW II era. Some of this tech might return (say electric motors driving the compressor fan) since there is a promise of high fuel efficient flight:
Caproni-Campini N.1 (CC.1 & CC.2)
The Caproni-Campini N.1 used an ingenious way of propelling itself. The piston engine inside the fuselage drove a ducted fan and fuel was bled and ignited in the compressed air emitted through the tailpipe. With a maximum speed of only 375 km/h (233 mph), the N.1 served only to prove its propulsion concept was possible. The design limitations meant that development would be fruitless, and as Italy’s war effort gained momentum, thoughts turned to more immediate problems.
It is perhaps surprising at first sight that, having been the second nation to fly an air-breathing jet-propelled aeroplane, Italy did not feature among the leading nations in this field of technology. But in truth the Caproni-Campini N.1 was no more than an ingenious freak which employed a conventional piston engine to drive a variable-pitch ducted – fan compressor with rudimentary afterburning. As such it did nothing to further gas turbine research, and was to all intents and purposes a technical dead-end. The engineer Secondo Campini had created a company in 1931 to pursue research into reaction propulsion and in 1939 persuaded Caproni to build an aircraft to accommodate the fruits of this work, namely the adaptation of an Isotta- Fraschini radial engine driving a ducted-fan compressor; the compressed air was exhausted through a variable-area nozzle in the aircraft’s extreme tail, and additional fuel could be ignited in the tailpipe to increase thrust.
The real innovation of Caproni Campini jet was not in the main engine (a normal piston engine) but in the Jet after-burner. A ducted propeller worked as an air compressor pumping fresh air in a Venturi duct: the injection of fuel worked as the first afterburners used on F-100 Super Sabre during 1950’s. There were not annular combustion chambers and the ducted propeller was unable to change hydraulically the inclination of the blades (pitch). Also the jet exhaust had no flux adjustment by changing the outer diameter of the outlet, like it happens on modern jets. These were the reasons of the too long venturi duct crossing the fuselage. Now try to imagine, as a never built CC2, a turbo-diesel engine moving hydraulically an adjustable pitch fan in a short duct having annular combustion chamber and a variable geometry outlet…this never to be produced evolution of Caproni Campini could fly at low speed with the lowest consumption possible of vegetable oil (colza, sesami ect) closest as possible to the Allied bomber “boxes” and after attacking – by using the afterburner!
The CC1 solution was totally different from both other jet solutions (Axial and Centrifugal) because the thermodynamic performance of any engine is linked to entropy (dQ/dt°C). The higher the temperature in the combustion chamber the more the energy really useful for weight of fuel burned per second: internal combustion engines (piston engines) have an internal “flame” temperature varying from 900 °C to 1400°C in the while jet engines never exceed 700°C-750°C.
But a jet theoretically can exceed the speed of the exhausted gases (rule of parallelogram of forces plus reaction): an after-burner can push out gases with a speed largely supersonic. With a sudden injection of methyl alcohol into the after burner this CC2 could have a good chance to reach or pass Mach1 during a climbing high Mach strafing attack to the allied close bomber box-formations, to be repeated till end of alcoholic fuel. Finally this strange half-jet would have the possibility to reach its own landing-site by mean of the diesel engine at “cruise economical” speed and without burning a litre of rare petrol… This was the real final target for the Caproni-Campini project: the first supersonic “no-petrol” interceptor. The only competitors were the German rocket fighter Me-163, Me-263, Ju-248. Stupidly this intrepid and successful development program was stopped at the very beginning: with the death of Italo Balbo the genius of Prof. Campini was forgotten.
The two-seat low-wing N.1 (sometimes referred to as the CC.1) was first flown at Taliedo on 28 August 1940 by Mario de Bernadi. A number of set-piece demonstration flights was undertaken, including one of 270 km (168 miles) from Taliedo to Guidoma at an average speed of 209 km/h (130 mph), but it was clear from the outset that use of a three-stage fan compressor driven by a piston engine would limit further development, and the experiment was abandoned early in 1942 when Italy was faced with sterner priorities. The only other developer of Campini type jet was Japanese Navy, who used this type engine on their Ohka 22 kamikaze planes. The N.1 survives today in the Museo della Scienza Technica at Milan as a monument to ingenuity if not sophisticated technology.
Type: two-seat research aircraft
Powerplant: one 900-hp (671-kW) Isotta-Fraschini radial piston engine driving a three-stage ducted-fan compressor
Performance: maximum speed 375 km/h (233 mph)
Ceiling: 13,000 feet
Range at cruising speed: 168 miles
Time to climb to 13,000 feet: 53 minutes!
Weights: empty 3640kg (8,025 lb); maximum take-off 4195 kg (9,248 lb)
Dimensions: span 15.85m (52ft 0 in); length 13,10 m (43 ft 0 in); wing area 36.00m2 (387.51sqft)