The Gas Position in France
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QLIET but intensive progress has been made in the use of gas-driven vehicles and marine motors in France during the past two years. The reasons for rapid advance have been considerations of economy and national defence, and the necessity of redressing the adverse French balance. The second dgmands greater independence from imported fuels and brought the support of Government and municipalities to all endeavours aiming at the perfection of gas equipment for coaches, lorries and agricultural and army tractors.
The two usual systems of employing gas for motors have developed side by side; one for the consumption of compressed coal gas (4,500 calories before compression), and the other for operation on gas generated from timber, coke or coal.
The second has the advantage of making the vehicles independent of compressing plant and filling stations. It needs no cylinders; it permits the running of the engines upon such material—whether it be coal or wood splinters— as can most easily be obtained in the districts where the vehicles operate, and it assists French forestry and mining. Its faults are that starting and acceleration are rather slow.
Promising Outlook for Compressed Gas.
Compressed gas does not suffer from this drawback and has other advantages explained below. With the growing provision of compressing and filling stations throughout the country, which will also be dealt with later, the importance of this type is on the increase. It has made most progress in the field of industrial and refuse lorries and et passenger buses.
Among some 400,000 heavy vehicles in France, only 3,000 to 4,000 are as yet running regularly on gas, and of these only 200-300 are on compressed gas, but the numbers will soon multiply as a result of the Government's recent legislation compelling all transport undertakings which include more than ten vehicles to equip at least 10 per cent, of their rolling stock for home-fuel use. Wheat alcohol may he available as fuel in the future, but as the distillation plants (at the time of writing) have not yet been started, the only home-produced fuel which, in fact, benefits by the decrees, is gas.
The self-generated variety, supported, of course, by the same laws, has, so far, found its principal application in farm tractors, marine transport and lorries. In the last B36 named field, therefore, the two types compete. Local conditions usually decide in favour of one or the other. Obviously, it will be more economical to use self-generated gas in wooded or in mining districts, whilst compressed gas will prove cheaper elsewhere, especially for 41 large vehicles formerly running on oil fuel.
Many leading motor manufacturers as well as concerns specializing in gas equipment have occupied themselves with the new opening. As a result numerous variations of the apparatus have been produced and patented. Nevertheless, it is possible to describe, in outline, the elements common to all equipment. Basically they resemble the plants which have been developed in this country and have been described from time to time in this paper.
In the case of compressed gas, there are, as a rule, five main units. The cylinders or other containers of compressed gas are made of light metal alloys and are tested to withstand pressures of 300-375 kilos. per sq. cm. A set, usually four, is mounted within the chassis frame. According to M. Tinard, the leading expert on the subject, they weigh, when fully charged and storing about eight cubic metres of gas, less than 80 kilos. for an average set and less than 54 kilos. for a light set. Each set will permit a run of 150-160 kiloms. before it need be refilletl, and this is sufficient, under the French system of transport localized by departments and in view of the existing network of filling stations. Then there is the extender or pressure-reducing valve, which will bring down the pressure of the gas to nearly that of the atmosphere; the mixer, which serves really as a carburetter; the three-way cock, permitting the driver to switch over from gas to petrol, or from petrol to gas, without having to stop the engine, and, of course, the cylindervalves and tube system, connecting all the above with the engine. The latter must have a compression ratio of 7.5-8 to 1, which will meet the requirements both of gas and benzol-alcohol mixture.
Vehicles thus equipped have now run for varying periods between six months and two years on the French roads, and have been found thoroughly satisfactory in performance. Many refinements which smooth out the performance have been effected, and it is claimed that the thermic output of the motors running on gas is 10 per cent. higher than that of an equivalent petrol motor.
Variety of Fuels.
In the case of self-generated gas the apparatus for adapting vehicles to gas consumption, consists, in most average equipments, of three essential parts. Chief of these is the generator, a kind of miniature furnace, into which any one of the following substances can be fed:—Ordinary wood pieces or splinters below 5 ins. by 2 ins.; coke, semicoke, coal or charcoal, or pure anthracite.
The driver fills the " foyer " or hopper before starting. Anthracite will give best results, and the longest runabout 200 Idioms., with a generator of standard size, but even wood splinters will produce enough gas for a run of about 150 kiloms. before refilling is necessary. Then there are a purifier, the so-called epurateur in which the gas is cleaned with the aid of filtration, cooling tubes, etc., which is preceded by a depoussiereur in which dust, etc., is deposited, and the suction or conduit system, which leads the gas to the engine carburetter.
The entire generating equipment is based upon the reverse combustion principle, and, in this case, too, there have been evolved many refinements ensuring nearly absolute purity of the gas. Some make it possible to use, at the driver's option, gas or petrol, or a gas-petrol mixture. By the turn of a single control he can put into operation any one of the three, again without stopping the engine.
Here it must be interpolated that, in all the cases above where petrol has been mentioned, vaporizing or oil fuel might be substituted where vehicles would normally run on such fuels.
Economy of Both Systems.
In using compressed coal-gas, an average engine with a compression ratio of about 7 to 1 will need only 1.8-1.6 cubic m. of gas to do the work of I litre of oil fuel. In the producer-gas equipment, the Societe d'Application des GazoOnes, for instance, will not only guarantee the apparatus for a considerable time, but also states that 1.1-1.3 kilos. of charcoal, according to its quality, will do the work of 1 litre of petrol, or rather, produce the quantity of gas equivalent to this performance.
Varying percentages are claimed for the saving in running costs obtained by the use of gas instead of petrol or oil fuel, going from 27 per cent, as high as 75 per cent. But even if this claim be not accepted, one fact is certain: there is complete agreement on the saving itself being considerable and paying for the installation of the equipment within a few months.
Recently a trial run of 28 vehicles, half of them being passenger vehicles of large size and half being lorries, was held at Tulle to show an average performance of these gasfed vehicles over an exceedingly difficult road. The route to Clermont which had to be taken abounds in steep gradients and ticklish bends. Yet all 28 machines ran without trouble and arrived to time, the coaches achieving an average speed of 50-53 kiloms. per hr., which accorded with the timetables for them, whilst the lorries made an average speed of 32-38 Idioms, per hr.
Ten municipalities in France, among them the important cities of Paris and Bordeaux, have installed refuse lorries working on compressed gas. In this line the Renault company has produced a model, which is in constant use in Bordeaux, so constructed that the gas furnishes not only the motive power, but also the power for tipping the plat form and for sliding a heavy steel door which seals the lorry hermetically. The producer-gas vehicles " coal" at home, or wherever wood, coke or coal are available. That means in effect that they can obtain their fuel in the smallest village. For the compressed-gas machines, however, stations are, of course, required. In the first place, the French engineers concentrated upon producing a quickly assembled compressing
plant at low cost, which can be installed easily. The establishment of such " pastes de compression" proceeds, in fact, all the time at various points in the country. The already existing plants are distributed as follows:—
In the gasworks, municipal and private, of nearly all departmental centres, and, of course, at the works of Gal de Paris. In addition, this organization has erected a filling station at the Porte d'Aubervilliers and another at the Plaine St. Denis. There exist 39 further filling stations in other towns throughout France, so that the country is well covered even now. The ideal aimed at is that eventually there should be stations everywhere at a distance of not more than 30 miles from each other. In the departments Nord, Pas de Calais, Somme, and Aisne, this ideal is near achievement.
Compressing-station Capacities.
The compression in the above stations varies from 600 cubic m. per hr. at Montpellier and 400 cubic m. per hr. at Paris, Dijon and certain other stations, to only 60 cubic m. per hr. at Waziers and 20 cubic m. per hr. at Marseilles, but the most popular and most frequently encountered are the 200-cubic-m.-per-hr. stations.
The price of the gas varies a little but will never exceed the equivalent of one penny per cubic m. Gas de Paris charges its normal industrial rate of 60 centimes, for instance (Id. equals 74 centimes at the present rate of exchange). The cost of equipping a lorry with the compressed-gas apparatus, including the adaptation of the engine to a higher compression than for liquid fuel and fitting it with cooling breech (culasse), etc., is given by the " Comae pour le Developpement de l'Emploi des Gas Comprimes " as 10,000 to 12,000 francs in all, which Means about £60 to £65.
The cost of equipping al lorry with the self-generating equipment amounts, for vehicles, up to 3 tons, to 8,000 francs, for larger ones up to 6 tons, to about 9,500 francs, and for still higher tonnages, to 10,500 francs. These quotations are from the S.A.G.
From the personal experience of the writer, it can he stated that vehicles by Ford (the 3-ton lorry), Renault, Panhard-Levassor, Delahaye, Latil, Rochet-Schneider and Laffiy have been successfully equipped with one or other variety of gas apparatus.
Numerous Inherent Advantages.
In conclusion, the advantages claimed for the use of compressed gas over liquid fuel may be summarized thus:— In the case of petrol, difficulties arise in attaining perfect atomization. These do not exist with gas which mixes better with air than any liquid fuel.
The relative proportion of gas and air remain practically the same, under all conditions. This is far from being achieved to the same extent by petrol. When the vehicle runs at low speed a bigger proportion of petrol will usually be consumed. In the case of gas there is no relative increase. Starting when the temperature is low is easier with gas than with liquid fuel.
Gas is an anti-detonation fuel in the sense in which this term is understood by the motor industry, whilst petrol will not lend itself to a higher compression than 5.5 to land even heavier liquid vaporizing fuels will take, at mast, 6.5-7.5 to I. Gas makes it possible to raise the ratio to 8 to 1, and thus improves the resulting thermic yield.
Exhaust products, in the case of gas, are without smell and have only a very low CO content. This is of evident importance in crowded towns. Lubricant is not diluted.
Even if all the claims be not accepted without criticism, and even if the possible enthusiasm of those who advocate the use of compressed gas be discounted, enough is left so far as the practical running of the vehicles in French transport and trade is concerned to designate gas at least as a
sound and economical alternative to petrol. P.S.