THE D. J. SMITH SUCTION-GAS PRODUCER.
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First Published Particulars of the Drawings from which this Plant is to be Produced in Quantities.
Wg HAVE frequently given expression to the opinion that Colonel D. J. Smith's portable gas producer plant has proved its value as a fuel provider for motor vehicles, and particularly for all those types in which this journal is especially interested, without any limitation as to either size or type.
Indeed, the question of the moment, in this regard, is whether we shall see first on the road a producergas-equipped Ford or a five-tonner of more or less equal renown so fitted. Specially-designed plants are now nearing completion which are suitable, one type for the smallest of. four-wheeledocommercials, the other for the largest of those.i.in regular use. Actually it has become a matter for further speculation as to whether there is a type of mechanicallypropelled road vehicle to which the.plant.may not suitably and with advantage be fitted. Some very startling developments indeed are forecasted in this
. and other directions.
Our own experience of the working of the plant on an old Belsize lorry, and 'using an experimental equipment, built, as it were, from whatever could be spared at a time when every factory of importance was devoting all its energies to direct war work, went to confirm practically all the claims which had been made for it. Improvements which suggested themselves to us were all of a mechanical nature, which would naturally be incorporated in a carefully-designed plant intended for commercial exploitation.
There was one outstanding exception to this rule. It was apparent, in the varying circumstances which were, and are, continuously to be met with in ordinary road work that some efficient means were required for securing inter-relation of the engine's demand for gas and the feed of the coal into the furnace. Even this desideratum had been foreseen by the inventor, and was:, incorporated in ,his patent. It had not been found convenient to include such a provision in the rough experimental plant, but it is actually embodied in the more complete equipments, One of which.' we are now about to examine, and which it is hoped will shortly, in several exarripleS; be at work on the road.
This article should, in the main, be descriptive of detail, that is to say of the mechaalical improvements which have been made to the plant as it was originally described in these pages. For the benefit of any new readers, however, and also to refresh the memories of others, we will briefly review its general principles and mode of operation. In the following it is assumed that the fire is already lighted and the engine running. On the firebars is a glowing mass of incandescent fuel, kept constantly in that state by the continuous supply of warm air and steam which is drawn through and from the boiler or vaporizer situated at the top of the plant, 'through the air and vapour supply pipe to the underside of the bars, through the fire, where it undergoes'chemical changes and emerges as the combustible gases, carbon monoxide (CO) and hydrogen (11), together with that inert constituent of atmospheric air—nitrogen (N).
These gases emerge from the producer at the opening marked on the drawing as outlet to engine, and between these and the engine cylinder they are cooled and cleaned in the dry scrubber, which is illustrated in detail*esides being indicated on the Separate drawing which shows the general arrangement of the plant. This scrubber is of special design and quite
new; we shall refer to it again later. A simple mixing valve' easily controlled by the driver, provides for suitable dilution of the gases by admission of air in correct proportion.
An engine-driven shaft, known as the feed-gear driving shaft, drives, through worm-and-wheel gearing, two other shafts which have several functions to perform. The feed-gear countershaft has, at the end opposite to the driving shaft, an eccentric. Two coupling rods run, one upwards and the other downwards from the eccentric, and these drive, through ratchet gear, rotary valves. The upper valve receives and discharges, once each revolution, a charge of fuel from the hopper which delivers to the upwardly-projecting pipe on the top of the plant. The lower valve similarly receives and discharges the ash from the fire.
The pump-driving countershaft is also fitted with an eccentric at its outer end, and, by this means, drives a small water pump. Drawing its supply from a conveniently-situated tank on the chassis, this pump delivers water to the boiler or vaporizer, the overflow thence passing to a trough below the firebars, where it affords additional steam for conversion, in the fire, to combustible gases. An opening into the ashpan, normally closed by a valve, allows of a small fan being used to blow up the fire, either at starting or after an engine stoppage of more than five minutes' duration. During the operation of this Ian,. the gas formed is driven off. through a convenient vent.
These are the primal and functional necessities or the plant, if it is to be suitable for vehicle propulsion :---Mechanically-operated and easily regulated fuel feed, ash discharge and water feed ; a suitable boiler and connection to the underside of the fire ; and communication above the lire, through an efficient scrubber, with, the engine induction pipe. The secondary mechanical details, and the refinements in design throughout, are worthy of careful study.
The fuel and ash valves are alike, being merely short hollow cylinders to which are secured suitable driving spindles. They revolve in chambers which they closely fit, and each has one circular port cut in its wall. This port registers at one time wita an opening of the same size in the top of the chamber, and again, after it has moved through half a revolution, with a similar opening in the bottom. With the port registering with the upper opening the valve fills with fuel or ash as the case may be, emptying itself again when the port faces the lower opening. Accessibility to the valves and ports for cleaning is attained by making them hollow and open at the end remote from the spindle. iA. hand hole with a quickly-removable cover closes this outer end of he valve chamber and gives access to the valve for cleaning or allows of its complete removal, an operation which should very rarely be require& •
The valves are driven, as has been stated, b_y an eccentric on the feed-gear countershaft, and adjustment of the rate of feed, which is from time to time necessary owing to occasional variation in the quality of the fuel, is providedfor by utilizing a frictionpawl, and allowing for the alteration of the length of the driving lever. The latter is for this purpose .made in two parts ; one, a casting with a projecting stem, carries the spring-actuated rollers which serve as pawls, the.other is a plain bar with a slot near one end and an eye for receiving the eccentric rod pin through the other. These two parts are nipped together by a couple of bolts through the slot in the outer portion of the lever, and by moving the slotted portion against the other, variation in total length of the lever is quite readily attained ' The interoonnected throttle and fuel-feed gear calls for mention at this juncture. It is unfortunately omitted from the drawing. A slotted and ficiating link which, according to its position determines, the effective leverage of the eccentrio rod, is controlled as to that position by the throttle connection.
One ether point about these valves. It is occasionally neeessary, as when starting, to accelerate the fuel feed by hand. In order to pro
risTery-54 vide for this operation, each valve is I Fleeter J fitted with a handle, and to guide the
i driver, it is erected on the spindle so that it is in line with the port opening in the valve. He can thus ascer. .fain whether the port is uppermost, and the valve accepting fuel, or at its lowest point, and discharging.
The feed-valve casing and its pipe are pivoted on a pin which is co-axial with the pipe. In the normal running position, as Shown in the drawing, it is secured by a wing-nut-and eye-bolt. Slacking this,off frees the casing so that it can be swung side ways and allow egress to the gases [Handle for evolved when lighting the fire or
cperation when blowing up after an engine
Below this component will be seen the boiler, and the reader will im media.tely, no doubt, notice its peculiar shape, with the dependent tube for the fuel, surrounded by a conical space between it and the boiler. This should be considered
in conjunction, with the delivery passage to the engine, which opens into the cone-soaped i space. The object is to eliminate, so far as possible, the risk of carrying over in the gas as it passes to the engine' dust from the luel. By carrying the lower edge of -the cone below the level of the boiler proper, a small reserve of water is retained so as, in the event of a shortage, to delay the excessive heatingof that portion which is nearest the fire.
The main body of the furnace is in duplicate, having an inner and outer wall, both of sheet metal, with a narrow passage between the two. Holes in the outer one—they dO not appear in the drawing— serve as inlets for the air supply, which is thus drawn past the hot inner wall 'of the furnace on its way to the fire, achieving in one operation the twin objects of cooling the furnace and heating the incoming air. The iirebrick lining is el special material, marvellously light, and is made in one piece. It does not reach to the ?op of the inside of the furnace, being bevelled off so as to -allow a maximum of heating surface to the boiler.
Particularly interesting is the design of the firebars. The circular grate s divided into six parallel sections, about equal in width, each section being made up of the equivalent of four bars I in. wide, with spaces of the same width. Each section has a half bearing at one end and a plain projecting arm at the other. They are assembled so that three of the sections have, their bearing ends at one side of the grate, and three at the other, and they alternate, a, bearing end being cheek by jowl with a plain end at the same side.
The two countershafts, pump drive and feed-gear drive, are each formed with three cams, and the sections of the grate are so laid that a bearing end of a section rests upon a shaft between two cams, while its opposite plain end rests upon a cam. As the two shafts are constantly in motion, the effect
• is a continuous undulating motion to the bottom of the fire; practically, no part of the grate is ever still. The ash is, therefore, never allowed to lodge anywhere on the bars, and the formation of clinker, which is fused ash, is to all intents and purposes prevented entirely.
Of the two pipes which may be noted to the left of the right-hand view of the generator, and also to the top of the plan view, the short one conveys warm air from the. interior of the jacket to the vaporizer,the long one is the medium for the trans ference of a mixture of air and water vapour from the boiler to the underside of the grate through which it is drawn by the suction of the engine. The proportions of air and vapour, upon which depend
the thermal value of -the ensuing gas, are automatically regulated in conj increases, with the throttle open
ing. As the latter a valve in the air to boiler" pipe closes correspondingly, causing increased suction in the boiler and a consequent freer formation of steam. afire steam in proportion to air gives a richer gas. In order to prevent too rapid a' consumption of the water, this special valve is never allowed entirely to close, but is prevented from so doing by a suitable stop.
The Novel Design of the Scrubbing Plant.
The scrubber on the new plant is entirely novel, and forms the subject of independent patents. It is a combined water heater (and gas cooler) and. scrubber, and may be said to censist of three parts. The hot gas enters at the top left-hand side (see drawing) and passes down the inner of two tubes seen there. It emerges at the lower end of this tube into a large expansion box where, as a result of the sudden change in velocity, it drops all the heavier particles of dust. In its passage down the tube the gas is also cooled by water ascending in the outer tube. This is the water which subse quently passes to the vaporizer of the gas generator itself, so that the heat which it receives while cooling the gas is of considerable benefit. The water is pumped by the small pump shown on the, generator drawing, as the scrubber, as will be under stood by again referring to the arrangement draw ing is placed in the pump delivery circuit. Leaving the expansion box, the gas passes up inside half of the many small vertical tubes, and down. the other half, losing particles of dirt all the way. It is finally, in the third part of the scrubber, relieved of
any solid matter still remaining in it, by 'being passed through inverted cones of .fine gauze, whileh are held in spring clips inside two larger tubes, which appear at the right hand of our drawing.
An important feature of this component is the ease with which it can be completely cleansed. There are three swing doors at the top and two at the bottom. Each is secured by one nut only. The fire doors need only to be thrown open, when the whole scrubber can be sluiced through in the space of a couple of minutes.
We have by no means exhausted the interesting features and good points of this plant, but we have, to write truly, more than exhausted our space. .
Details, of construction, such as the method of securing all handholes, the design of -the friction
pawls, the arrangement of the pump drive,' the
complete enclosure and thorough lubrication of all -working parts, etc.. etc., must be left for disclosure
by the drawings. They are of particular interest to designers,. though not falling entirely outside the concern of the user. The design is good, the plant, already proved in respect of its practical utility, now appears as a sound engineering proposition. It only remains to add that the patentee himself is not directly, we understand, concerned in its commercial exploitation, and that all inquiries should be addressed to Major Tulloch, Bank Chambers, King Street, St. James's, London, S.W. In addition to the applications of this plant which we have foreshadowed in our opening paragraphs, we understand that arrangements have been made at the request of an,important firm to design a 500 h.p. set for aeroplan€ ,purposes. Colonel Smith thinks that this can be achieved within the limits of weight ; if so, it will have a very important bearing on the future of commercial aviation, serving almost entirely to eliminate the danger of fire which exists in petrol. Yet other applications which are foreshadowed are in connection with self-contained electric lighting sets for farm tractors. Official trials have shown that, with the Smith producer plant, electricity can be generated at a price considerably lower than if town gas is used. The increase in bus faros, due largely to high price of liquid fuel, calls for the adoption of some new source of fuel supply, and if producer gas were adopted not only the bus company but the bus user should materially 'benefit. 'Several sets of the plant built to the new designs are expected to be running towards the end of this month or early in June.