Generator with free pistons Pescara

History

The principle of the generating with Piston S free is resulting from work in Thermodynamique of Raul Pateras Pescara, marquis de Pescara, as from 1935. It needed compressed air for the orders of its helicopters. Its research mainly aimed at obtaining:

a specific power higher than that of a Diesel engine,
a better output
the use of a fuel less refined and thus less expensive.

Principle

The generator with free pistons functions as a diesel engine 2 times which do not transform the alternative linear movement of its pistons into continuous circular motion, because it has neither rods nor of crankshaft. It thus results from it only from the cycles compression-relaxation. The admission and the exhaust are done via lights which are discovered in end of the road.

It consists of two double pistons which approach and deviate one from the other. The first part of the piston, of lower diameter, is the driving left . The second part, of a largeer diameter and located behind, is the compressive left . On its face it postpones compresses air in a volume called mattress , whose vocation is on the one hand, to limit the race of the unit and on the other hand, to return the pistons one towards the other as soon as the driving pressure falls after the exhaust ports opened. On its front face, it compresses air in the compressing cylinder. This compressed air will be used either to inflate bottles of air of reserve, or to ensure the sweeping of the driving Cylindre after the phase of exhaust and overfeeding at the time of the phase of admission.

The mattresses communicate between them so as to balance the pressures and the races of the two whole of pistons. During the starting of the generator, a strong air pressure compressed, caused thanks to a distributer, launches the units pistons one towards the other to generate a compression in the drive roll making it possible the combustive air to reach at least 600°C.This moment the fuel pulverized by an injector is consumed and caused the strong rise in pressure of gases which will drive out the pistons units towards the dead bottom center; the cycle is started.

Operation

The combustion of the carburizing mixture (Fuel) - combustive (air) is done with constant pressure. Indeed, as long as the injection lasts, the pressure on the operating piston remains quasi-constant whereas the volume occupied by gases increases consecutively with the distance of the pistons towards their dead bottom center. When the best performance is reached, the air pressure in the mattresses is equal to that exerted by combustion in the drive roll.

Use

From 1936 various models of generators were studied by the Pescara research department which had produced free piston compressors for public works (Demolition of Trocadéro). An engine of test in which the Alsacienne company of Mechanical engineering in 1936 replaced according to the indications of Raoul Pateras Pescara the steam boiler by free piston car-compressors providing of the compressed air to the same pressure as that of the vapor. First model GS30 was integrated in a generator which included/understood two generators GS30 and a turbo-dynamo of 350 kw. This group functioned until 1939 with the Alsthom factories of Belfort. A vertical industrial generator of a power of 700 ch and a weight of approximately 6 tons, oscillating with 500 impulses per minute, and functioning between 1,5 and 4,5 kg/cm ². The brilliant idea of the marquis de Pescara was to sweep the engine part by the compressed air and thus to feed from the turbines thanks to the recuperation of the energy contained in exhaust fumes. Thus was born starting from the compressors the generators with free pistons (communication from Mr. R. from Pescara “Generators with free pistons and gas turbine” page 211 N° 225 January 1939 HEAT and INDUSTRY: the day of organized combustion on December 16th, 1938) At the end of the Second world war, the National marine received under war damagees of the submarines of German construction which were equipped with compressing of air Junker functioning according to this system.

To the same time, the tendency being to replace the piston engines by rotary engines of the gas turbines kind, engineers of the company Sigma and company Rateau applied the idea of the Marquis the exhaust fumes of this system to make function a gas turbine; the device was then called “ Générateur of gas with free pistons ”.

With the beginning of the year 1950, the National Governed of the Factory Renault in its workshops of Choisy-the-King, built a prototype of engine driven by this material: March 15th, 1952, the 040 GA 1 left the engineering departments. It could develop a power of 750 kw (1 020 ch) in continuous mode and had very good performances.

the SNCF having announced its intention to replace its park vapor entirely, the National Control of the Renault Factory associated with the Company with the Workshops and Forges with the Loire (CAFL) undertook of launching the construction of another more powerful prototype, the 060 GA 1 . It was equipped with two groups made up each one of a gas generator with free pistons Sigma-Pescara GS 34 and of a gas turbine Rateau on 6 floors. The power of the machine was announced for 1 770 kw (2 400 ch). The generator “beat” between 350 and 600 cycles per minute for a travel of the piston ranging between 400 and 500 Misters the exhaust gas temperature of exhaust was about 2 000 °C, but this temperature was lower (T° < 1000 °C) during the admission in the turbine. The number of revolutions of the latter was of 12 280 t/mn. A second prototype, the 060 GA 2 was put in building site.

These machines, DC 80001 and DC 80002 , of which speed on rail lay between 74 and 128 km/h, will be built with only two specimens. Actually power of 1 100 kw (1 500 ch) was never exceeded and the breakdowns followed one another not without having with the passage broken some panes in the crossed stations…

This type of propulsion was not especially a success for the rail-bound transport.

Also in the current of the years 1950, the National marine put in building site a series of minesweepers (M701 with M759) carrying names of constellations or stars, whose propulsion was ensured by gas generators free pistons Sigma-Pescara coupled with gas turbines developing 2 000 CH. These ships, pertaining to the 10th division of minesweepers, were based in the military port of Cherbourg. They were so noisy during the cold start (because it was necessary to keep the purgings of sweeping opened long enough), which they had the reputation, undoubtedly overrated, “ to awake any Cherbourg ” but also to be very painful with the ears of the mechanics of quarter. Some of these reallocated ships as patrol coastal (as P741 Eridan enter others) were then attached to the underwater base of Pallice and operations managers in the the Bay of Biscay for the Center of Tests of the Moors.

These buildings remained in service until the end of the years 1970. Twenties and one ships of the type “Sirius” were brought into service by the Navy Main road of 1953 to 1956; the coaster “Cantenac” and “Mérignac” were brought into service in 1953. The Liberty Ship “William Patterson” was modernized by a propelling free piston apparatus which changed its power from 2400 to 6000 CV. November 8th, 1962, during his voyage in Corsica, the de Gaulle general visited the morning the thermo plant of Électricité de France in Apreto (Corsica), which was equipped with GS34. In 1963 Christian de Pescara student in engineering wrote an article on the generators with free pistons Pescara in the technical review n° 69 of the fourth quarters 1963 in the review of the former engineers of the school Breguet Paris. 500.000 CV of GS34 associated with turbines allow the production of electrical energy, the propulsion of 47 ships, the drive of compressors in eleven different industries representing thirty terrestrial groups. The sale was done in 40 countries.

Some achievements: power station of 600 KW with Mellaoui, central EDF. of 6000 KW of Cherbourg, power station of Chartres, station of water of pumping of the town of Paris, power station of cements Lebanese with Chekka, power station of the S.N. Repal, power station of 1500 KW Redeyef, central E.D.F of 1250 KW Kidneys, power station of 1500 KW Noumea, power station of Hassi-Messaoud, Machines Japanese Kokan Kabushiki Kaisha, power station of Cuba. Power station of 15000 CV of Imperial Chemical etc. An experimental car was built by General Motors. These apparatuses are built according to a technology of before the war of 1939 (foundry). The excellent output of these generators with free pistons would deserve a new glance by employing new materials and an electronic regulation. It is integrated perfectly in a new type of airship patented in 2002 by Christian de Pescara. In 1964 of the novel methods are prepared by Christian and his Father Raul Pateras Pescara who will die in 1966 in Paris. This research led to the creation of an important industry which disappeared for lack of modernism and which could not profit from an electronics of regulation which starts to be used about 1970 in the industrial turbines.

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