THE FRENCH PARAFFIN VAPORIZER TRIALS.
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A Description of the Winning Device. The _ Efficiency of the Bellem Apparatus.
T11E FRENCH motor authorities have on fre: quent occasions shown their interest in substi: tides for petrol, and have done not a. little to encourage all movements having for their object the liberation of the industry from the petrol ring.
A. little more than a year ago the Automobile Club of France announced that it would hold a competition for appliances making possible the use of paraffin in internal-combustion motors, and particularly in those motors used in commercial vehicles. With the battle front so near Paris, conditions were not ideal for trials of this nature ; therefore, it was not surprising that the competition had to be postponed. The second date happened to coincide with the last German drive towards Paris, but, notwithstanding this, the event went through without a hitch. The number of competitors was small, consisting of Bellem and Bregeraa with two motors, e-Aldo with one, and Genault with one ; three others withdrew at the last moment.
The competition only served to prove the practicability of the Bellem system, which was the only one to fulfil all the conditions, viz., not exceed 350 grammes per hbrse-power, not weigh more than 33 lb. per horse-power, and to travel a distance of 634 miles on the road at a minimum average of 18 miles an hour. In consequence, No. 1 Bellem system won the first Prize of £2000, and No. 2 Bellem was awarded the second prize of £400 cash. The test opened at the Automobile Club of France laboratory with a three hours brake test under full load and, at full speed. The Bellem system, which had been applied to two Unie four-cylinder motors of 101 mm. 'by 150 mm. bore and stroke, developed, re. spectively, 32 h.p. and 33 h.p. and consumed 334 grammes and 297 grammes per horse-power hour. Each engine maintained an average speed of a little more than 1100 revolutions a minute. It was permissible to make use of petrol for starting, providing a special tank was not required. One of the Bellems took advantage of this and was running satisfactorily on paraffin in one minute. The other, which started up from cold direct on paraffin, ws.s.iu perfect running
condition in 45 seconds. The Aldo and the Genault both made use of petrol, the former being very slow in getting into condition, and both of them exceeded the maximum allowance of 350 grammes per horsepower hour.
The second test comprised running under full load at half-speed for two hours, when both the Bellem motors were started up from cold on paraffin, and both were running perfectly almost immediately. The best filel consumption under this test was by No. 2 Bellem, which showed 353 grammes per horse-power hour. One of the competitors ran as high as 714 grammes. The third test was under half-load at full speed. Finally, there was a two-hour test running light at full speed.
Owing to their high fuel consumption, the Aldo and the Genault were not entitled to start in the second stage of the competition. This left the two Bellems with an open field. These two Unic motors were put into slightly different Unic chassis, No. 1 motor going into a pre-war type chassis with a full touring body, thetotal weight of the vehicle being 3782 lb., and No. 2 being put into a new type chassis, carrying a tester's body and loaded with sand, the total weight being 3977 lb.
Under these regulations the cars had to leave the A.C.F. laboratory on four successive mornings and cover a circuit to the north-west of Paris, the return . each evening being to the Club laboratory. This necessitated travelling over very rough roads and negotiating a considerable, amount of traffic—conditions which are not ideal for fuel economy. A military observer was carried on each car and tanks were sealed. No. 1 Bellem covered 15.5 miles to the gallon, had a total fuel consumption of 228.4 lb. of paraffin, consumed 85.2 grammes per ton-kilometre, and averaged 25.4 miles per hour for the total distance of 634 miles. There was no engine trouble of any kind, the only stops being for a seized brake and a broken pipe.
The second car did equally well.Its average speed was 24.9 miles per hour : total fuel consumed, 271 lb. ; miles per gallon, 18.8; consumption per ton-kilometre 67.2 grammes. The engine was never touched, the only road stops being for loose steering column, a broken pipe, and the loss of an oil tank cap.
The successful Belem system has developed beyond the experimental to the practical stage. It-was intro
duced some time before the war, was held back owing to hostilities, but recently has been taken up by a French syndicate and has been applied to a number of engines, particularly lorry engines in French civilian and military service.
This system 'necessitates some changes in the design of the motor. The intake valve remains closed during the major portion of the intake stroke. The piston descends and produces a vacuum in the cylinder. This vacu'uni causes a power aspiration of a small quantity of air through a pulverizing apparatus to which the required quantity of paraffin has been fed by an automatic measuring instrument. The pulverizer valve may be placed in the valve caps or "in the cylinder head, and can be either automatic or mechanically controlled by means of an overhead camshaft which had been added to the standard engine. About 45 degrees before lower dead centre the ordinary intake valve opens and admits pure air; it closes again 45 degrees after lOwer dead centre. The pure air being drawn in while a considerable vacuum exists in the cylinders, the short time during which the valve remains open is sufficient to obtain a complete filling of the cylinders. The charge is compressed in the ordinary way to 4 kilos. or 5 kilos. per square centimetre, and is fired, as usual, by a spark from a high-tension magneto.
This method of spraying the fuel into a partial vacuum is the essential feature of the Bellem system, and explains
the ease with which the engine can be started up from cold. The writer has had an opportunity of test ing this on a Ford engine, in mid-winter. On
a very cold morning, after the engine had been standing all night in an unheated garage, it was pos
sible to start up on paraffin quicker than could be done with petrol fed through the usual Ford carburetter. Also the engine ran perfectly within a few seconds of being cranked. As a simple experiment will readily show, there is no condensation of fuel in the engine cylinder, the mixture being a very fine vapour.
The French censor having forbidden publication, we are not able to show the construction of the pulverizer valve by means of which the measured quantity of paraffin and a small amount of air are admitted into the cylinder. But we are permitted -to illustrate the second additional apparatus, which is a small metal box within -which are four measuring pumps, with a pipe from each going to one of the pulverizer valves. This measuring pump is usually driven off the• water pump and magneto shaft. The amount of fuel to be delivered at each stroke. varies with the engine speed and load, and this is obtained by varying the stroke. The cylinders are movable by means of a control brought .up to the driver's head. Thus, by raising them or lowering them, the effective length of stroke is decreased or increased, and the quantity of fuel varied in the same ratio. Merely from a description, the apparatus is apt to be considered complicated, but, in reality, it is no more delicate or more liable to get out of order than the average carburetter.