US48321A - Improvement in steam-engines - Google Patents

Description

0. M. STILLMAN.

STEAM ENGINE.

No. 48,321. Patented-June 20, 1865..

Wnviwsu. W/ w UNIT D STATES- (PATENT OFFICE.

0. M. STII LMA N,"OF WnsrERLY,n1-ioDE ISLAND."

l M-PROVEM'EN'T IN. STEAM-ENGINES. g

' Specification forming part of Letters Patent No. 48,321, dated une 20, 1865.

To all whom may concern;

Beit kno u that I, OLM. STILLMAN, of Westerly, in the county ofWashington and .State' of Rhode Island, have invented certain new and useful Improvements in Steam-Engines; and I do herebydeclare that the follow- .ing is a full and exact description thereof, reference being'had to the accompanying drawafter itsdisengagement from the water.

I conduct the steam from the boiler to the cylinder in a superheated condition and apply it, first, equally to theeutire exterior of the cylinder, and afterward, int-he usual manner, to the interior of the cylinder, realizing thereby advantagesiin the economy of fuel and modoration ofyheat 0n the working parts neverthefore so simply and cheaply attained.

Before proceeding to describe the details of my construction, 1 will briefly present" the theory onwhich my invention is based. This theory is not new.

Steam possesses the remarkable peculiarity of changing its temperature very greatly with changes of pressure. Steam at one or two pounds absolute pressure, which is far below thepressure of the'atmosphere, exists as steam, but is only about blood wa rm,.or 100 mm enheit. Thesame steam compressed to a small yolume, so that its pressure shall equal that of the atmosphere has a temperature of 212 Fah renheit, and. ifstill further compressed, so as to attain apres'sureof fifty pou nds per square inch above atmosphere it assumes a. temperature of a about 300 Eahrenheit. This'property induces .1 greatloss of effect insteam-engines as ordina-. iilyworkd. Thisloss occurs in thiswise Suppose the-stea'mto be thoroughly appliedto the met-1' of the cylinder until the latter attains the same temperature throughout as that of the steam at" full pressure; and suppose the cylinder to be so thicklyclothed that'no heat can escapefroin its exterior surface. Now, the.

admlsslon of steam through the steam-value? into one end of the cylinder'acts as desired to impel the piston to the end of the stroke. Then-the exhaust-valve opens and the steam is allowed to escape into the atmosphere or into thecondenser, as the case may be bm;

a certain quantity remains in theoylinder. because the space where it was retnains filled with steam, but at a much lower pressure than before. (The temperature of the remaining steam is very greatly lowered by reason of its. diminished'pressure.). Now, during this state of things the thin steamstands inclosed within a metallic cylinder of a much higher temperatureth'an itself. The naturat resultfollows': It absorbs heat from the metal and assumes acondition known to stcamengineers as superheated -that is to say, the thin steam which is tardily expelled from the cylinder assumes afltem'perature some ten or more degrees 7 above that corresponding to its pressure. Tbe

heat required to produce this condition is transferred from the, solid cylinder into the steam by a process known as convection. Theconvection is similar'to the conduction of heat between solids, except that the particlesof thefluid are in motion, and a great number are presented very rapidly to the metal to be heated. The heat is taken away by this process from the inner surface of the cylinder and diffused throughout the steam. After this rare and superheated steam' has been all driven out.

. into the condenser or into the atmosphere by the returning stroketof the piston, steam at full pressure is again admitted from the boiler' to impel the piston, and the round of opera-- tions above described commences to be :re- .peated; but now the condition of the cylinder is not the same as was supposed for the preceding stroke'. The metal of the cylinder in the preceding stroke wasassuined to he at exactly-thesametemperatureasthesteam. Now,

it is cooler, because heat has been abstracted fromthe innersurface of the cylinder andconveyed away with theexhaust-steamas above described. When the fresh steam at full temperature strikes the slightly-cooled interior of the cylinder it heats the metal again nearly or quite to its original temperature, but in doing so the steam is cooled. It necessarily parts with some of its own heat. The abstraction of thisheat from thesteam compels a small quantity of it to condense and assume the form of water. This water tends to adhere to the in nor wall of the cylinder, where the condensation has necessarily occurred. A portion will undoubtedly remain. like a tine dew,'a dherin g to the interior of the cylinder. Now, the moment the stroke is completed and theexhaustvalve again opens the same phenomenon is repeated asbefore, with the addition of the evaporation of this thin stratum of water.

As ordinary steam engines are actually started and operated the cylinder never at tains the full temperature of the steam in the boiler. It is always cooler, and when the steam is admitted a portion is condensed and gives 'heat to the metal, and when the steam is exhausted the temperature of the metalof the cylinder, although insufficient before to equal that of thestrong steam, now exceeds that of the weak cool steam whichis presented to the interior surfaces of the cylinder during the return-stroke; and always under this latter condition (while the metalis hotter than the waterand steam which is presented to it) it gives off heat to the particles ofwater and re-evaporates them into steam, and that steam flows away with the rest through the open exhaust-valve. This process is. repeated at each stroke, and the quantity of heat thusstealing away from the boiler into the exha'ustpipe without having performed its proper work in the engine has been estimated by some French and other careful experimenters as high as one-third of all the heat used. It is important to understand this,and 1 will repeat. The heatenters vwith the steam through the steam-port in the other particles of steam, which remain. ex-

panded by the remaining heat,- are compelled to do thework of pushing the piston alone;

but immediately on the-ste'am-pressure being reduced in the interior of the cylinder by the opening of the exhaust-valve, the heat which had thus enteredthe metal returns and again enters the water, causing it to assume the condition of steam and leave the surface of the metal in time to pass off with the exhaust. In short, whenthe steam is admitted to the cylinder, a portion is condensed, adhering to the inner surface of the cylinder until the exhaust is opened,when the'heat of the cylindercauses the condensed particles" to evaporate and pass off with the other steam, but having done no part of the labor. In order to obviate this difficult-y, steam direct from the boiler was at an I 2 as es early date introduced into a jacket to assist in maintaining the requisite heat in the metal of the cylinder, the water condensing in the jacket flowing back to the boiler or escapingthrongh a trap. Although this was of advantage,vyet, owing to the resistance of themetal of. the'oylind-er, the heat was not transmitted with suificient rapidity to maintain the interiorsurfaca of the cylinder at a temperature sufficiently high to prevent all internal condensation; More recently common steam on its way from the'boiler has been allowed to flow in aconstant stream through the jacket, and thence into the steam-chest; but in suchcases little advantage resulted, because as the-heat imparted to the outside of the cylinder, by its absence from the steam, allowed a portion of the steam to condense, the resulting water was carried along with the current of steam into' the cylinder and deposited on the interior surface, where, upon the opening of the exhaust, it lie-evaporated and absorbed the heat it had just before imparted to the exterior surface.

Later experimenters have recognized these facts, and some have jacketed their cylinders with stronger steam, or steam at higher pressme than that admitted into the cylinder. Haycraft, in Great Britain, and E. 'W. Smith, in our own country, have published plansfor effooting this. Both use an-additional boiler, in which steam-is maintained at a higher pressare than thatin the'working-boiler. Haycraft placed his extra boiler lower than the steamcylinder, and allowed the steam as it condensedin the jacket to trickle down in the form of water and return to the same boiler to bereevaporatcd. Smith, whoseinvention was patented in this country in 1861, improved upon Haycrafts by placing the high-pressure boiler where he pleased, or employing the common donkey-boiler on shipboard to supply the high-pressure steam, and be discharged the same in the form either of, steam or water, or

of the two coin'mingled,from the lower part of his jacket into his working-boiler. My invention is superior to either, by avoiding the necessity for any extra boiler, and yet obtaining the same desirable end of heating the exterior of the cylinder to a sufficiently high temperaturn to allow the heat to travel inward through its thickness, and maintain the interiorsnrface ofthe cylinder at such a condition that the working-steam will not condense thereon.

In my engine the jacket is so arranged and combined that the steam from the boiler is first carried through .a superheating apparatus,

w here its temperatureis raised; thence through v a. pipe, where it acts on a device which regulates the amount of the superheating; next into the jacket, where it is distributed equally over all the surface of thc exterior of the cylinder (including the ends) which can be made available, and it is afterward introduced directly into the steam-chest, and admitted into the cylinder in the ordinary manner to operate the engine. It comes from the superheater at about 450- Fahrenheit, quay be perhaps'cooled a few I degrees in the'transfe'r through the pipe to the jacketythen gives up its surplus heat rapidly by conveetioiuto all parts of the exterior of the cylinder, holding the entire exterior of the latter at about 350 Fahrenheit; and lowering its own heat nearly to that point; then it enters the cylinder at the proper time and urges the piston, resentin itself to the rubbing surfaces. at a temperature which those surfaces -thereto,-and aids the heat which is tra\-'eling through the metal from the outside in raising its temperature a gain without any steam being condensed. I prefer that the steam, after performingits' work in driving the piston, shall be reduced to a condition verynear that of saturated steam, but if it'is still something hotter no evil results follow.

I have experimented with my inventionseveralmonths, and found a marked economy of fuel to result the refrom. p

I employ a steam-pressure of sixty pounds per square inch above atmosphere. The'temperature due to this pressure is 311 Fahrenheit. I raise the steam by superheating to a temperature varying from 4 007 Fahrenheit to 450 Fahrenheit. The temperature is' regulated and kept within these limits by the thermostat. V 1

To guard against risk of fire from any derangement of the regulating apparatus. or any other cause, 1 inclose my jacketed cylinder and most of the other parts in a stratum of plaster, which is applied by pouring the plaster-in a fluid state into a casin'gof thin metal previs ously provided around the" exterior of the.

jacketfl Outside of this I use wooden lagging with ohe or more layers of i'elt, if desired.

Topnableothers skilled in the art to make and use my invention, 1 will proceed to briefly describe its construction and operation by the aid of thedrawings, and of the letters of ref erence marked thereun.

A is an ordinary boiler. B is the chimney,

and U is' a vessel filled with tubes, through' whiclrtubes a portion of the products ofcombastion from thp furnace (not represented) is conducted. The steam generated in the boiler A is received into the superheater O at a point near the chimney B. It traverses the spaces in the snperheater between the hot tubes, and

rises in a superheated condition into the pipe D, which is thickly clothed to prevent the escape of heat. This pipe D delivers the superheated steam into a jacket, E, which surrounds the workingcylinder G. The superheated steam is distributed over both theends and over the entire cylindrical surface of the cylinder, except the necessary spaces for the parts on the upper side.

His a steam-chest,and h the steam-valve.

From the steam-jackefiE the steam is admitted into the steam-chest H through small holes e.

"These holes eare so distri hn ted, as represented,

that the steam is compelled to flow equally, or almost equally, over every part of the exterior or the cyl nder G. The working-cylinder G contains a piston, I, and'piston-rod '5, as usual.

The valve h is opera-ted by the.j.tod h. in the ordlnary manner, and the connections from piston'rod t and the valve-stem h to the main shaft J are of the usual character.

Exterior to the'easing G, which incloses the steam-jacket E and steam-chest H, is a thick stratum of plaster, K. This non-combustible and noucondueting stratum is" kept in place by an'exterior casing, L, as represented. I make this exterior casing of iron or other 'sn1t-,

able metal, and surround it finally by felting and wooden laggingof the usual character.

M is a damper, whichmay be adjusted, by

the aid of the lever at, so as to allow more or,

less of the products of combustion to pass into the superheater G from the furnace. V

"N is'a casing in whichis inclosed a loaded diaphragm of vulcanized indie-rubber. The under side of this diaphragm is in communication with a i'essel of water, I, which is'immersed in the superheated steam in the superheater 0, orin the pipe D. The upper side ot' the diaphragm is connected-by the. pipe 0 to the interior of the super-heater O in the manner represented. The lover a, turning on the fixed fulcrum a and caused to move up and.

down with the movements of the loaded diaphragm, is connected by the slight rod it to the lever m, and thus turns the damper M.

The operation of my invention is as follows:

The superheated steam flows through the. pipe D into the jaeketE,and ispresented uniformly, or nearly so, to the exterior of the workingpylinder G, and imparts a temperature .toQSaid exterior considerably higher thauthat dueflto the pressure of the steam. The heat thusimparted travels inward through the metal of the cylinder G, and is expended in maintaing the temperature of the interior surface of the cylinder G. ''A sufficient quantity is so transmitted to keep the extreme inner surface of the cylinder nearly or quite up to, or, in most cases, slightly above the temperature of saturated steam of the same pressure. The considerable amount of heat abstracted from thesteamin the jacketE, to be'thus transferred th'rou gh the metal'ot' the cylinder, lowers its temperature, so that it passes, into the steam-chest H, and from thence into the cylinder, only moderately superhea ted,where, afterimparting the, necessary amount of heat'to the inner surface of the cylinder, it is discharged through the exhaust-port g at just about the heat of satin rated steam'of the same pressure. At no time is any part of the steamcondensed in its passage through the engine; consequently. the great loss due inordinary engines to the condensation and're-evaporation is avoided by my invention and without the necessity 'for any additional boiler, or for subjecting the steamjacket toany higher pressure of steam than that to which the working parts of ,the apparatusare exposed.- The water under the diaphragm inthe casing N changes from the vaporous to the'dense fluid condition in proporlion as'the extent of the superheating of the steam is incrrased and diminished beyond properlimits. If the degree of superheati-ng becomes too high, the water boils with-such force as to raise the diaphragm, and through the connection n lever n, and connection 19?, ra ses the lever in and closes, or nearl y closes, the damper M, and thus, by excluding the productsof combustion from the superheater, soon reduces the extent of the-superheating.

but'the incombustible and non-conducting.

character of this envelope euablesit to withstand any required amount of heat and avoids the chance of suchaceident. v

L propose to inease the pipe D and the super-heater O in' a similar manner.

Having now fully described my invention,

what lelahn as new therein, and desire to secure by Letters Patent, is asvfollows:

1. The jacket E and cylinder G, constructed and arranged as described, in combination with the superheater 0, through which the steam passes on its way to thejacket, substantially as and for the purpose herein set forth.

2. The within-described arrangement of the steam-jacket E and cylinder G, whereby the steam is compelled to flow uniformly, or nearly so, over the cylindrical surface and through one or both heads of the cylinder, in the manner and for the purpose substantially as here in set forth.

3. The within-describedarrangement of the superheater G, the automatic regulator N, and its connections, the steam jacket E, and the cylinder G, soas to operate together in the 'manner and for the purpose substantially as herein set forth.

4. The incombustible clothing K, the-jacket E, cylinder G, and superheater 0,- arranged to operate together, substantially in the manner and for the purpose herein set forth.

In testimony whereof I have hereunto set my hand in the presence of twosubscri-bing witnesses.

v M. STILLMAN.- Witnesses: I I

' WILLIAM P. 00y,

S. W1 LooX, .Ir.

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