Source : Appleton's Mechanics Magazine and Engineer's Journal, Vol 1, N°1
Title: Ericsson's Patent Caloric Engine
Date: January, 1851
This is a scheme which Mr. Ericsson tried some years since, but which, at the time, was not sucessful ; and his attention has boon directed to removing those practical difficulties which meet the experimentalist on this subject at every turn.
An engine of apparently 6 or 8 horse-power has been placed by him in the Exhibition building, and to obviate the difficulty of working it within the building, owing to the regulations as to fire, &c, one of 100 horses' power is now being constructed in the United States for exhibition, which was intended to be erected near the Exhibition boiler house, and set to work, to afford an opportunity of acquiring some experience of its powers and economy. The invention has been secured in England in the name of Captain Dunn, Mr. Ericsson's representative.
A moment's reflection will show that there is a possibility of effecting an immense saving on our present method of employing coal as a generator of power. In our most economical expansive engines, we recover nothing of that which we employ. The heat required to convert the water into steam is delivered by the air-pump, diluted, so to speak, with so much cold water, and the problem is, to concentrate that heat and render it again available for generating steam.
Whether that problem can ever be solved, whilst water is used as a medium, it is impossible to predict. The gases appear to offer a better chance of success, and accordingly Mr. Ericsson employs the expansive force of heated air in his engine instead of steam.
The engineer will perceive at a glance that the arrangement described is not such as would effect the greatest economy. The cylinders would doubtless be made double acting, more especially as the engine is essentially a low-pressure one, and the whole arrangement modified to save room and weight.
The principal novelty appears to consist in the employment of a condenser, which, when saturated with heat, is used as a regenerator or boiler, until it is sufficiently cool to act again as a condenser. It is proposed to have two of these condensers, to be used alternately, although we think it possible that in practice it will be found that there will be certain points of temperature between which these vessels will be too hot for condensers, and not hot enough for generators.
But this may be met by increasing the number of these vessels, and using them alternately. Probably, to lower their temperature quick enough, in order to convert them into condensers, a small jet of water might be used ; whilst, by having a succession of condensers, the air would first pass through the hottest, and so on in succession, till it was deprived of its remaining heat by the coolest of them ; a reverse action would take place with the generators.
But leaving these suggestions, which have probably occurred to the inventor equally with ourselves, we will proceed to quote the specification before us.
The invention consists in producing motive power by the application of caloric to atmospheric air or other permanent gases or fluids susceptible of considerable expansion by the increase of temperature. The mode of applying the caloric being such, that after having caused the expansion or dilatation which produces the motive power, the caloric is transferred to certain metallic substances, and again retransferred from these substances to the acting medium at certain intervals, or at each successive stroke of the motive engine, the principal supply of caloric being thereby rendered independent of combustion or consumption of fuel ; accordingly, whilst in the steam engine the caloric is constantly wasted by being passed into the condenser, or by being carried off into the atmosphere, in the improved engine, the caloric is employed over and over again, enabling me to dispense with the employment of combustibles, excepting for the purposes of restoring the heat lost by the expansion of the acting medium and that lost by radiation, also for the purpose of making good the small deficiency unavoidable in the transfer of the caloric.
Having thus stated the object and general character, I will now proceed to describe the structure of the improved engine for producing motive power, reference being had to fig. 1.
A and B are two cylinders of unequal diameter, accurately bored and provided with pistons a and b, the latter having air-tight metallic packing rings inserted at their circumferences.
Before describing the operation of the improved engine, it will be proper to observe that the piston-rod a' only receives and transmits the differential force of the piston b, viz., the excess of its acting force over the reacting force of piston a.
It will also be proper to observe that this differential force imparted to said piston rod may be communicated to machinery by any of the ordinary means, such as links, connecting-rods and cranks, or it may be transmitted directly for such purposes as pumping or blowing.
I have further to observe, that the conical valves K and J may be worked by any of the ordinary means, such as eccentrics or cams, provided the means adopted be so arranged that the valve K will commence to open the instant that the piston b arrives at the full up-stroke, and be again closed the instant the piston arrives at full down-stroke, whilst the valve J is made to open at the same moment, and to close shortly before, or at the termination of the up-stroke.
In like manner, the slide-valve N' is to open and close as the piston b arrives respectively at its up and down stroke, similar to the slide valve of an ordinary high-pressure engine.
Having thus described the construction of the engine, I will now proceed to describe the manner in which the same is to be put into operation.
Before starting, fuel is put into the fireplaces R R, and ignited, a slow combustion being kept up until the beaters and lower parts of the regenerators shall have been brought to a temperature of about 500°.
By means of a hand-pump, or other similar means, atmospheric air is then to be forced into the receiver G through the pipe Q, until there is an internal pressure of some 8 or 10 pounds to the square inch. The valve J is then to be opened, as shown in the drawing; the pressure entering under the piston b will cause the same to move upwards, and the air contained in A will be forced through the valve F into the receiver.
The slide valves N N being, by means of the two stems n n, previously so placed that the passages l l are open, the air from the receiver will pass through the wires in L into the heater H, and further into C, the temperature of the air augmenting, and its volume increasing as it passes through the heated wires and heaters.
The smaller volume forced from A will, in consequence thereof, suffice to fill the larger space in C.
Before the piston arrives at the top stroke, the valve J will be closed, and at the termination of the stroke the valve K will be opened; the pressure from below being thus removed, the piston will descend, and the heated air in C will pass through k' p P and m into the regenerator M, and in its passage through the numerous small spaces or cells formed between the wires, part with the caloric, gradually falling in temperature until it passes off at o', nearly deprived of all its caloric.
The commencement of the descent of the piston a will cause the valve F to close and the valve E to open, by which a fresh charge of atmospheric air is taken into the cylinder A. At the termination of the full down stroke, the valve K is closed and the valve J again opened, and thus a continued reciprocating motion kept up.
It will be evident, that after a certain number of strokes the temperature of the wires or other matter contained in the regenerators will change; that of M will become gradually increased, and that of L diminished.
The position of the slide-valves N N should, therefore, be reversed at the termination of every fifty strokes of the engine, more or less, which may be effected either by hand, or by a suitable connection to the engine. The position being, by either of these means, accordingly reversed to that represented in the drawing, the heated air or other medium passing off from C will now pass through the partially cooled wires in L, whilst the cold medium from the receiver will pass through the heated wires of M, and on entering H will have attained nearly the desired working temperature.
In this manner the regenerators will alternately take up and give out caloric, whereby the circulating medium will principally become heated, in dependently of any combustion, after the engine shall have been once put in motion.
It is particularly worthy of notice, that the relative diameter of the supply and working cylinder will depend on the expansibility of the acting medium employed; thus, in using atmospheric air or other permanent gases, the difference of the area of the pistons may be nearly as 2 to 1, whilst in using fluids, such as oils, which dilate but slightly, the difference of area should not much exceed one tenth.
I have next to notice that in employing any other medium than atmospheric air, it becomes indispensable to connect the outlet pipe o' and the valve box e of the outlet valve E, as indicated by dotted lines in the drawing, these dotted lines representing the requisite connecting-pipe.
The escaping air or fluid at o' will, when such a connecting-pipe has been applied, furnish the supply cylinder independently of other external communication, and the acting medium will perform a continuous circuit through the machine under this arrangement ; the operation being in other respects as before described.
It is evident that the several parts composing the improved engine may be arranged in various ways, and the external form thereof may be greatly changed, whilst its principle of operation remains substantially as I have ascertained and described.
It is also evident that the working cylinder may be placed horizontally or otherwise, and that it may be made double acting ; and that a heat-intercepting vessel may be applied at each end of the working piston, an also an expansion heater at each end of the working cylinder.
I do not, therefore, confine myself to the exact form represented in the drawing, but I claim as the invention the substantial features of the devices I have described as new, and by which I secure great and beneficial results.
1st. I claim the structure which I call the regenerator, by which I effect a transfer of the caloric contained in the air, or other circulating medium that passes off from the working cylinder to a series of disks of wire-net, or to other minute metallic or mineral substances, for the purpose of being again retransferred to the air or other circulating medium that enters the working cylinder, whether said structure be so arranged that the metallic or mineral substances are made to take up and again return the caloric at each successive stroke of the working piston, or whether it is so arranged that the transfer and retransfer of the caloric takes place at intervals, or whether said structure is arranged in any other manner for the purpose of accomplishing substantially the purposes herein before mentioned.
2d. I claim the combination of the expansion heater with the working cylinder, by which the fall of temperature consequent upon the expansion of the air or other circulating medium during the upward movement of the working piston becomes restored, and by which also the force of said piston becomes augmented beyond what it would be if the accession of caloric effected by the expansion heater did not take place.
3d. I claim the heat-intercepting vessel attached to the working piston, by which any injuriously high temperature is prevented from reaching the packing of said piston, and by which also the very desirable end is attained of presenting at all times surfaces of uniform high temperature to the acting medium under the working piston.
4th. I claim the inverted position and open ends of the working and supply cylinders, as represented in the drawing.
5th. I claim the direct attachments of the working and supply pistons, by which not only the acting and reacting forces may be uniformly distributed over the area of each piston, but by which also the entire differential power of the working piston is rendered available, less only the friction of the packings.