Coal Gas as Motor Fuel
Page 50
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Interesting Experiments Carried Out in France with Buses and Lorries
TN France a good deal of atten-Ition is being devoted to the use of coal gas on motor vehicles, particularly by the Societe du Gaz de Paris and the S.T.C.R.P., the latter being the short name of the company which operates the buses in Paris.
Following experiments with a lorry, the S.T.C.R.P. has since December, 1928, been running two of its motorbuses on coal gas, these vehicles operating on the route between the Road Point de la Villette and the Gare de Luxembourg. We are indebted to M. L. Bacqueyris,se, the engineer of the company, for the latest particulars of the results obtained.
The vehicles are of the company's standard Single-deck 38-passenger type having the usual four-cylindered engine, except that the bore has been increased from 105 mm. to 110 mm., the stroke being 150 mm. and the compression ratio raised from 4.25 to 5.4 to 1.
The necessary supply of gas is stored in six steel cylinders, each having a capacity of 45 litres (equivalent to a total of 9,535 cubic ft.of free gas) at a pressure of 2,133 lb. per sq. in. The cylinders employed, which are laid horizontally under the floor of the bus, are of a specially light kind, their weight being about only one-third that .of the ordinary type, the necessary strength having been ob c28 tamed by winding their exteriors with piano wire.
The six cylinders are connected by a pipe, one extremity of which is provided with a union for joining up to the source of compressed gas and the other to an expander or pressure reducer mounted at the side of the engine. Each cylinder is also equipped with its own shutoff valve.
The Passage of the Gas.
The gas from the cylinders first passes t6 the expander, where the pressure is reduced, 'to a point slightly higher than that ,of the atmosphere. From the expander the, gas is drawn by engine suction to an automatic gas and air mixer and thence to one branch of the main inlet pipe. This has two branches, the second of them being connected to an ordinary liquidfuel carburetter. The engine is caused to run on one or other fuel by means of a' two-way valve at the junction of the admission-pipe liranches.
Before starting on their day's work, the two buses are driven to the Villette gasworks, where they receive their charge of compressed gas, on which they are run until the gas supply is exhausted, when the engines are turned over on to the ordinary motor spirit, consisting of 40 per cent, commercial petrol and 60 per cent. benzole.
When running on liquid fuel the engines normally develop 35 b.h.p. at 1,200 r.p.m. M. Bacqueyrisse reports that, speaking generally, the two buses are giving satisfactory results and states that the consumption of gas amounts to approximately 48.5 cubic ft, or 6,169 calories, per vehicle-mile, and on the petrol-benzole mixture to 1.286 pints, or 6,054 calories, per mile.
The Societe du Gaz de Paris has for some time also been running three lorries on coal gas, two of the vehicles being 21-tonners having four-cylindered sleeve-valve engines, having a bore and stroke of 85 mm. and 130 mm. respectively. The expander or the pressure-reducing device and air and gas mixer are designed on the same general lines as are those on the two Paris buses.
With 'load, the large vehicle weighs just over 9 tons and the two others 5 tons 12 cwt. and 6 tons 9 cwt., the respective consumption per, mile averaging 27.4 cubic ft. for the first machine and 21.46 cubic ft. for the othera.
No information is available as to the mileage run on one charge by the buses, but in a series of tests with the gas company's lorries distances up to 50 miles have been covered.