Greater Efficiency for Producer-gas Operation
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Two New Ideas Tried Out by Bradford Corporation with a View to Securing More Satisfactory Performance r-rVO new devices, which Bradford 1 Corporation passenger transport department has introduced for use on its vehicles running on producer gas, were referred to by Mr. John Harrison, assistant works superintendent of the undertaking, when he gave a talk on producer-gas traction at a recent meeting of the Yorkshire Transport Society, at Bradford Technical College.
The devices, in question have been applied to oil-engined buses which have been converted to use producer gas on the pilot-injection system but one of them is applicable to either petrol or oil engines operating on producer gas. It is an additional gas falter, which takes the form of a tube, covered. with • a. high-temperature grease on the inside, and-Which is fitted in the gas pipe-line under the bonnet. The gas, as it passes through this tube, and just before entering the engine, is agitated by means of a swirling attachment, so that any ash or other suspended matter in the gas tends to become embedded in the grease which, because of its special heat-resisting quality., retains its glutinous characteristic despite the Warmth from the engine.
Mr. Harrison said it had been found that this supplementary filter extracted quite a lot of dirt from the gas, thus . helping to reduce cylinder wear. With an eye to accessibility, it was originally fitted at the rear of the bus as an inner tube pushed inside the pipe-line at the point where the flexible tube from the trailer-producer was attached. Experience showed, however, that the smaller diameter, necessary for this inner-tube • arrangement, so increased gas pressure at this point that the filter-oil was carried away by the 'gas.
In the position it now occupied, the filter was not inserted a,s an innea tube, but as a section having the same diameter as the rest of the pipe-line. This forward location did not involve much disadvantage from the accessibility standpoint; the tube could, with little trouble, be taken out for weekly • cleaning, regreasing, and replacement. .
The other new device, mentioned by Mr. Harrison, is applicable to oil engines running on producer gason thepilot-injection system. It has been -introduced with a view to obtaining greater elasticity in the mechanism for dual control—through 'theaccelerator pedal—of the gas throttle and the injection pump. The device, for the purpose of allowing full range to the gas throttle while, the range of oil fuel injection is restricted, comprises a telescopic arrangement of levers and springs.
When the aecelerator pedal has been pressed to a point where the predetermined maximum of oil injection is reached, any further pressure is absorbed by _the springs, except in so far as • it ,continues to open the -gas throttle, but when, full throttle is
reached the device permits of a fractional increase in the quantity of oil injected, which had been found necessary to cover the time lag in the flow of gas after a period of closed-throttle running; it is also a help in hillClimbing.
Mr. Harrison, who had referred to the greater efficiency obtained' through the G.M. -automatic gas mixer, which obviates, the need for the, driver to control the air, valve manually, stressed the desirability of niaking the oil fuel injection completely automatic. At , present, he remarked, the amount ofoil fuel saving was dependent on the driver in that, by keeping the accelerator pedal hard down, be could obtain the injection of additional oil when that might not be .necessary. Efforts were now being made to achieve a method of control whereby extra oil would be given to' increase the rate of acceleration, but would be automaticallycut out when the engine had attained a certain speed and no further increase was necessary.
There were limits, however, to the amount of oil-fuel saving which it was
practicable. to effect. For, instance, the more liquid fuel saved the greater the consumption of producer gas,, with a consequent invease .in the amount of ash takenthrough the filters to the engine. Whilst all extra engine wear, throukh.operation on producer gas, was not attributable to grit—some being' cauSed by ammonia and sulphur compounds—it was reasonable to assume that any increased suction effect on the ' producer opened the possibility of greater cylinder wear.