US160400A - Improvement in pyrometers for steam-engines - Google Patents

Description

G. B. DlXWELL.

Pyrometer for Steam-Eminem Patented March 2,1875.

% gaze/Af UNITED STATES PATENT FFICE.

GEORGE BASIL DIXVELL, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN PVROMETERS FOR STEAM-ENGlNES.

vSpecification forming pa rt of Letters Patent No. 160,40), dated March 2, 1875; application liled December 19, 1874.

@Asn B.

To all whom it maglfmucera:

Be it known that l, GEORGE BASIL DIX- WELL, at present a resident otl Boston, ot' the county of Suffolk and State ot' Massachusetts, have invented a new and useful Improvement in Steam-Engines, and do hereby declare the same to be fully described in the ollmving specilication and represented in the accompanying drawings, of which- Figure l is a top view, and Fig. 2 a trout elevation, ot' a steam-boiler and engine-cylinder with my invention applied thereto.

Such invention has for its object to obtain, with the smallest possible change ol" the existin form ot' steam-engines, the total suppression of cylinder condensation, and the `greatest amount of further advantage from superheating that is compatible with safety to the working parts. rlCliese have'been found, by long and carefullyconducted experiments, to be uninjured by a temperature a little above 40G@ Fahrenheit in the cylinder, but many engines have been ruined by the use ot' a much higher temperature. I assume, then, that for the present, until better lubricators are introduced, 4000 Fahrenheit is the limit for the heat ot' steam in the cylinder; but 4000 Fahrenheit in the cylinder imports a higher temperature in the superheater, because, even at full stroke, the entering steam must counterbalance radiation, and at shorter stroke it must also counterbalance the refrigeration arising out ofthe work done after the cut-oil", and this last increases with each increasing measure of expansion. n

Experiments have shown that the heat to counterbalance radiation, and the conversion ot' heat into power after the eut-off, is taken from the metal of the cylinder, which, in turn, upon the next stroke, absorbs the equivalent from the steam which enters up to the point of cut-oli.

if the steam be suiiiciently superlieated to balance radiation and the work done it will, at the point of ent-oli, be in a state of saturation, without any condensation or forination of mist; but in this case the full practicable advantage oi' superheating will not be obtained. rthis can only be donc by adding to the superheated steam in the heater such further temperature as will raise it at the point oi" cut-ott' to 4000 Fahrenheit. It is necessary, Y then, to superheat the steam by the amount of the difference between its temperature at saturation and 4000, and also by the equivalent of radiation, and also by the equivalent ot' the work done after the cut-oit". I say the work lone after the cut-ott', because the refrigeration caused by the work done up to that point takes place throughout the whole steam existing` in boilerspipes, and cylinder, and the proportion existing in the cylinder is, especiallyT at short cut-oli", an insigniiicant part of the whole.

Theory would lead us to expect this; and in experiments on a large scale, carefully oonducted and ot' long duration, the amount ot heat absorbed by the metal from the superheated steam agreed very closely at the different points ot' cut-oit' with the sum of radiation and the equivalent ot' the work done during expansion.

lt is evident, then, that to maintain the heat in the cylinder at 4G00 Fahrenheit requires at each cut-ott a different temperature in the snperheater, and, in fact, in the experiments above referred to, i000 Fahrenheit in the cylinder, at a cut-off ot' seventy per cent., required 5300 Fahrenheit in the superheater; 400@ Fahrenheit in Ithe cylinder, at a cut-ott' ot one-hall", required 5680 Fahrenheit; and 4000 Fahrenheit in the cylinder, at one-third cut-oli', required 6260 Fahrenheit in the superheater in the engines used. But these diii'erences between the cylinder and superheater temperatures will vary with different engines, because the amount of radiation varies greatly, and we cannot, therefore, rely upon the superheater temperatures to indicate the cylinder temperatures until we have ascertained by experiment the differences which actually exist in each particular engine.

Having thus premised, I now proceed to describe the nature or character of my present invention.

In the accompanying drawings, A denotes the cylinder, and B the boiler and furnace, oi" an ordinary steam-engine, the boiler heilig for the production ot superheated steam, to be used eXpansively in the cylinder, which is supposed to be provided with a cut-ott'. The pipe for conveyance of the steam from the geilerator to the steam-chest of the cylinder is shown at U. A pyrometer, D, is arranged in the lower part of the cylinder, its stem a being to project through the cylinder, and being jointed to an index-pointer, b, to operate with a graduated arc or scale, c, to indicate the temperature of the steam in the cylinder. Another such pyrometer, E, is similarly applied to the steamgenerator or superheater, and has its index-pointer d projected over a wooden scale or platform, e.

I work the engine at a given cut-ott, say, (for instance,) one-third, and note the temperature indicated by the pyrometer in the cylinder, noting, a-lso, at the same time, the temperature in the superheater. It I tind the temperature in the cylinder to be 4000 Fahrenheit, while that of the superheater is, say, (5000 Fahrenheit, I make upon the pyrometer scale-board of the superheater, against 6000 Fahrenheit, the words one-third cut off.77 I next work the engine at another cut-ott', (say, for instance, one-half,) and if I find that with 4000 Fahrenheit in the cylinder the p vrometer of the superheater shows, say, 5600 Fahrenheit, I mark against 5G00 Fahrenheit of thc pyrometer-sez le of the superheater the words one-halt' cut off.7 And so I proceed until the pyrometer of the superheater is, so to speak, graduated for the diiferent cut-offs. I next, it' disposed, withdraw from the cylinder the pyrometer placed in it, and rely thereafter upon the p vrometer of the sul'ierheater, graduated as described.

Fig. 3 denotes the pyrometer-scale, provided with the divisions for tempera-tures, and the marks to indicate the cylinder temperatures for diiferent cut-offs, as set forth.

In order to audibly indicate the temperature ofthe superheater I apply to the scale of the pyrometer an adjustable metallic slide, f, fixed to the scale by a elampserew, g, going through a slot in the slide. To the said slide j' I attach a wire, h, of an electro-magnetic eurrent, whose electro-magnet is shown at c' and battery at 7U'. The armature Z has an elevating-spring, m, and is, `in effect, a hammer to strike a bell, n, arranged over it, as shown. From'the bell a circuit-wire, lL', extends to and through an electro non-conductor, m', xed upon the index-pointer of the pyrometer of the superheater, and thence is turned toward the slide j".

\Vhen the index-pointer may arrive at the position for which the slide is to be touched by the end of the current-wire carried by the said index-pointer, a galvanic circuit will be completed, and the alarm-bell will be rung. Vhen the engine may have been set to work at a particular cut-oft', the adjustable slide f is to be arranged so that before the circuit may be completed the index-pointer may have passed a little beyond the indicating division of the cut-ott, and whenever this point is reached the electric bell will give the alarm and the temperature ot` the superheater will be easily diminished by partly closing the damper, or by diminishing` the lire, or by opening the door ot' th efurnace, or any other of the usual means.

There is also applied to the pyrometer-scale another such adjustable slide, j", arranged as shown. Its purpose may be thus explained:

To this auxiliary slide j", and to the non-conductor m of the index-pointer, circuit-wires o p are attached, and arranged as shown, they leading to the electro-magnetic ala-rm apparatus, or another such having a bell of a tone differing from that of the other bell.

Then it may be desired to have au alarm indicate that the heat in the superheater has descended below the equivalent of a previously-selected minimum, (say, for instance, 3700 Fahrenheit,) the auxiliary slide f is to be adjusted properly to the scale, so that when the degree of temperature may have been reached the Wire of the index-pointer maybe brought into contact with the auxiliary slide, and thus create closure of the circuit and the sounding of an alarm.

My invention is based upon four facts, which I have discovered lfrom experiments. rIhe first is that superheated steam, unlike the gases, gives up its heat to metallic surfaces, and receives heat from them with great rapidity. The second is that the metallic surfaces of the cylinder and piston take up with immense rapidity the excess of heat existing in superheated steam brought near them, and by their great weight couvert a high temperature ot' steam into a much lower temperature of metal. It' we suppose the temperature of the entering steam to exceed the temperature of the cylinder by, say, 200O Fahrenheit, a very thin film of the cylinder and piston will sut'iice to reduce this excess from 2000 Fahrenheit to 200 Fahrenheit over the original temperature ot' the internal surfaces. rlhe third is that the said metallic surfaces give back to the expanding steam the heat previously absorbed, in such a manner as to supply the heat which is converted into work, and the heat withdrawn b v radiation. The fourth is that diiferent quantities of heat are thus absorbed and given out with diiierent measures of expansion, so that the steam must, and safely may, be superheated to temperatures proportioned to the said measures of expansion plus the heat withdrawn by radiation.

I claim as my invention as follows, viz:

1. The combination otl the two pyrometers D E with the superheater B and the enginecylinder A, to be operated by such, as and for the purpose specified.

2. In combination with the two pyrometers D E, superheater B, and the engine-cylinder A, applied as described, one or more adjustable slides,ff, and one or more electro-magnetic alarms, applied thereto, and to the pyrometer of the superheater, all substantially as and for the object and purposes as explained and represented.

GEO. BASIL DIXWELL.

Witnesses:

R. H. EDDY, J. It. SNOW.

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