The gas turbine; progress in the design and construction of turbines operated by gases of combustion

Front matter

GIFT OF

ASSOCIATED ELECTRICAL AND MECHANICAL ENGINEERS

MECHANICS DEPARTMENT

Preface

THIS volume is intended to place in the hands of engineers and experimenters such theoretical and practical data as are now available in the solution of the problem of the gas turbine.

At the present time such machines are yet in the experimental stage, and it is still uncertain to what extent they may become generally practicable. There has, however, been expended much study and effort, both in the investigation of the theoretical principles upon which the gas turbine depends, and in the construction of machines intended to realize, more or less effectively, the possibilities which have been indicated /by such studies.

Much of the information contained in this book is included in the transactions of learned societies, in the pages of periodicals, and in the records of private experimenters, and it is believed that by gathering in one volume the results of the work of English, French, German, and other organizations, the engineers and mechanics who are investigating the subject may be assisted by perceiving what has already been accomplished, and thus avoid unnecessary repetition of work which is already on record.

The gas turbine need not be a machine of exceedingly high thermal efficiency in order to be available for many purposes. The advantages accompanying a continuous turning effort, instead of the intermittent impulses of the reciprocating gas or gasoline motor, may, in many instances, overbalance a somewhat lower fuel economy; while the reduction in weight, consequent upon the attainment of a very high rotative speed, may become of controlling importance. It is therefore of the utmost desirability that all the conditions be

i

PREFACE taken into account, and it is for this purpose that the present volume has been prepared, collecting together the relative influence of the various elements of which the problem is composed.

The author desires to acknowledge the assistance which has been freely rendered to him in the preparation of this volume. To the memory of his colleague in the Societe des Ingenieurs Civils de France, M. Rene Armengaud, he records his obligations for personal communications describing the experimental work conducted in the laboratory at St. Denis; and to M. Alfred Barbezat he desires to express his appreciation for the continuation of this most important work. To M. Armand de Dax, Secretaire Administratif of the Societe des Ingenieurs Civils de France, and to M. L. Sekutowicz, his colleague in the Societe, he acknowledges the kind permission to translate the important paper of the latter author; and to Mr. Edgar Worthington, Secretary of the Institution of Mechanical Engineers (London) as well as to the author, Mr. R. M. Neilson, he is indebted for permission to reproduce the paper of the latter, as well as the discussion which it elicited. The writer also wishes to express his indebtedness to Dr. Sanford A. Moss, Dr. Charles E. Lucke, Prof. Sidney A. Reeve, Prof. Lionel S. Marks, and Dr. H. N. Davis, for valued suggestions and assistance.

HENRY HARRISON SUPLEE.

NEW YORK, November, 1909

Contents

PAGE

INTRODUCTION 5

Chapter I. Historical . 9

The Smoke Jack, the First Gas Turbine; Barber's Turbine; Fernihough's Patent; Burdin's Experiments; Tournaire's Communication to the French Academy; Bourne's Suggestions; Boulton's Patents; the Stolze Hot- Air Turbine; Parsons's Patent; Laval, Lemale, Armengaud; Later Papers.

Chapter II

THE DISCUSSION BEFORE THE INSTITUTION OF MECHANICAL ENGINEERS. 28 Paper by R. M. Neilson, Discussing Various Available Cycles and their Merits and Disadvantages; Discussions by Messrs. Henry Davey, F. W. Burstall, James Atkinson, Col. R. E. B. Crompton, H. M. Martin, Robert H. Smith, and Mr. Neilson. Communications from Dugald Clerk, W. J. A. London, E. Kilburn Scott, and George A. Wigley.

Chapter VI. The Practical Work Of Armengaud And Lemale 227

The Explosion Gas Turbine; the Combustion Turbine; the Original Experimental Machine at St. Denis; Details of Combustion Chamber; Structural Arrangement of Parts; the Rateau Polycellular Air Compressor; the 300 Horse-Power Gas Turbine; Gas Turbines in Submarine Torpedoes; Data and Results of Tests; the Karavodine Turbine.

Chapter VII. General Conclusions 251

INDEX . 255

Introduction

ALTHOUGH the gas turbine was one of the earliest forms of combustion motor it failed to attain practical or commercial importance, and it is only since the steam turbine has reached its present commanding position that the possibility of developing the gas turbine in similar manner has been seriously considered.

The practical difficulties in the way of the realization of a successful gas turbine are very great. The high temperatures involved demand especial care in order that the strength of the material may not be unduly affected. The high rotative speeds required, if high efficiencies are to be secured, render the mechanical problems connected with centrifugal action more serious even than with the steam turbine; while the doubt as to the action of hot gases in diverging nozzles renders an important element in the theory yet uncertain.

At the same time there has been going on, during the past few years, in Europe and in America, some very effective experimental work upon the gas turbine; while the theory has also been made the subject of elaborate study by English, French, German, and American scientists.

Most of the information regarding this work is in a form unavailable for the practical engineer and investigator. The theoretical discussions are, for the most part, contained in the transactions of professional societies; much of it in languages other than English. The practical experiments

GAS TURBINE.

are being conducted behind closed doors and reliable information is not generally attainable in detailed form.

It has therefore been thought desirable to gather under one cover the most important papers which have appeared upon the subject of the gas turbine in England, France, Germany, and Switzerland, together with some account of the work in America, and to add to this such information upon actual experimental machines as can be secured.

FIG. 1. — Scheme of gas turbine with reciprocating compressor.

In the present state of the art this is all that can be done, but it is believed that this will aid materially in the conduct of subsequent work, and place in the hands of the gas-power engineer a collection of material not generally accessible or available in convenient form.

The general lines along which the plans of the various gas turbines, now under experimental investigation, are con-

THE GAS TURBINE.

structed, will be understood from the accompanying schematic diagram. This is substantially as given by Dr. Sanford A. Moss in connection with his thesis upon the gas turbine presented to the faculty of Cornell University in 1903.

The fuel, in this case some form of liquid hydrocarbon, is forced into a combustion chamber, together with the proper amount of compressed air for its combustion. The products of combustion are discharged through a diverg-

CombusElon Chamber

Air Inlet

LJ

Compressor

Turbine & I

Exhaust

FIG. 2. — Scheme of gas turbine with multiple wheels and rotary compressor.

ing nozzle upon the buckets of an impulse wheel which is thus caused to rotate, a portion of the power developed being used to drive the compressor, and the remainder being available for external use.

Since one of the presumed advantages of the gas turbine over the ordinary gas engine is the substitution of continuous rotary motion for the reciprocating action of a piston in a cylinder, it is undoubtedly desirable that a rotary compressor be used, so that the reciprocating pump may be dispensed with. The general arrangement of such an apparatus, including also a multistage turbine, is here given, as devised by Mr. Rudolf Barkow (Fig. 2).

Here the air is drawn in and compressed by a rotary compressor, mounted on a continuation of the turbine shaft. The compressed air is delivered to the combustion chamber, into which the liquid fuel is also injected, and the combustion takes place under pressure, the gases and products of combustion passing through the diverging nozzle to the buckets and guide vanes of the turbine.

The extent to which these schematic forms have been developed from the earliest beginnings, and the lines along which theory and experiment have been pushed, will be seen in the following pages.

Chapter I. *

HISTORICAL.

THE use of the expansive action of heat upon elastic gases to operate a revolving wheel for the production of power is by no means recent; in fact it antedates the employment of a piston reciprocating in a cylinder for the same purpose. Considered in this broad sense there is no doubt that the windmill is entitled to be called a gas turbine, since the pressure of the moving air upon its sails can be traced to 'the currents produced by changes of temperature in the atmosphere.

Leaving aside the windmill, however, there can be little question as to the claims of the mediaeval "Smokejack" to be considered as a gas turbine. This machine, the origin of which it is impossible to trace, has been attributed to Leonardo da Vinci and illustrations of it are to be found in his engineering sketch books. A somewhat later form is shown in the illustration, this being taken from an engraving in Bishop Wilkins's book " Mathematical Magick," published in 1648, the present engraving and following description being found in the edition of 1680.

After referring to the action of windmills and to Eolipiles, the learned bishop continues: "But there is a better invention to this purpose mentioned in Cardan,* whereby a spit may be turned (without the help of weights) by the motion of the air that ascends the Chimney; and it may be useful for the roasting of many or great joynts : for as the fire must be increased according to the quantity of meat, so the force of the instrument will be augmented proportionably to the fire. In which contrivance there are these conveniences above the Jacks of ordinary use :

* Cardan. De Variet. Rerum. I. 12, c. 58.

THE GAS TURBINE.

"1. It makes little or no noise in the motion.

"2. It needs no winding up, but will constantly move of itself, while there is any fire to rarifie the air.

"3. It is much cheaper than the other instruments that are commonly used to this purpose. There being required with it only a pair of sails, which must be placed in that part of the Chimney where it begins to be straightened, and one wheel, to the axis of which the spit line must be fastened, according to the following Diagram.

FIG. 3. — The smoke jack. The first gas turbine. From Bishop Wilkins's "Mathematical

"The motion to these sails may likewise be serviceable for sundry other purposes, besides the turning of a spit, for the chiming of bells or other musical devices; and there cannot be any more pleasant contrivance for continual and

•cheap music. It may be useful also for the reeling of yarn, the rocking of a cradle with divers the like demestick occasions. For (as was said before) any constant motion being given, it is easie for an ingenious artificer to apply it unto various services.

"These sails will always move both day and night, if there is but any fire under them, and sometimes though there be none. For if the air without be much colder than that within the room, then must this which is more warm and rarefied, naturally ascend through the chimney, to give place unto the more condensed and heavy, which does usually blow in at every chink or cranny, as experience shews."

After the smoke jack, the next proposition for a gas turbine appears to be that of Barber, who took out a British patent in 1791, No. 1833, which seems like a very complete .anticipation of nearly all the most recent developments in this line. Barber's patent includes the distillation of the gas from wood, coal, or oil, its delivery, with the proper amount of air into a combustion chamber, and the discharge of the products of combustion upon the buckets of a turbine wheel.

He even went so far as to inject water into the combustion chambers to reduce the temperature, the mixed steam and gases acting upon the wheel.

The illustration, Fig. 4, gives an idea of Barber's patent.

The vessels marked 1, 1, are retorts for the production of the gas to be used, these being intended for the distillation of coal, wood, etc., by means of an external flame. When it is remembered that Murdock did not begin his experimental investigations into the manufacture of coal gas until 1792, one year after Barber's patent, and only made his results public in 1797, it will be seen that Barber was distinctly in advance of his time. The retorts shown in Barber's drawing are in duplicate, for alternate charging

THE GAS TURBINE.

FIG. 4. — Barber's gas turbine, 1791.

and discharging, the' gas being delivered into a cooling chamber B, from which it is drawn by one of the compressing pumps C, D, and delivered to the receiver 4, from which it passes to the triangular-shaped combustion cham-

THE GAS TURBINE.

bers. The other compressing pump delivers air and vapor of water into the combustion chamber, and the products of combustion are discharged upon the buckets of the wheel to effect its rotation. The drawing shows the reducing gearing for operation of the compression pumps, the power to be taken from the upper gear shaft.

It is evident that Barber's machine involved constructive problems altogether unsolved in his time, but the apparatus was surprisingly complete in its conception, including combustion at constant pressure, with pumps for the supply of air and fuel, together with the use of vapor of water for the reduction of temperature, and a train of gear wheels for the reduction of the speed.

FIG. 5. — Fernihough's turbine, 1850.

Nothing seems to have been done for more than fifty years after the patent of Barber, but in 1850 a mixed steam and gas turbine was proposed by W. F. Fernihough, and patented in Great Britain, No. 1328, of 1850. This apparatus, Fig. 5, consisted of a chamber A, lined with refractory material, and fitted with a grate B, on which the fuel was ignited. Air was supplied under pressure through E, whilewater was sprayed from above at H, and the mixture of steam and the gases of combustion were delivered through the nozzle I upon the wheel L, L.

In the mean time Burdin, in France, had proposed, in 1847, to make a hot-air turbine, using a multiple-wheel rotary compressor to deliver air through a heating chamber to a corresponding rotary motor. This plan was included in the remarkable communication of Tournaire, presented to the Academic des Sciences in 1853. The original memoir of Tournaire is remarkable in many ways, both for the breadth of its conception of the problem, and also because it refers to " elastic fluid turbines," not limiting the action to steam, but including hot air and gases, and thus distinctly including the gas turbine. In view of the importance of this communication it is here translated entire, from the Compte Rendu des Seances de V Academic des Sciences of March 28, 1853, pp. 588-593.

"APPLIED MECHANICS. — Note upon multiple and successive-reaction turbine devices for the utilization of the motive power developed by elastic fluids; by M. Tournaire, Ingenieur des Mines. Commission: MM. Poncelet, Lame, Morin, Combes, Seguier:

" Numerous attempts have been made to cause the vapor of water or other gaseous substances to act by reaction upon the blades or passages of rotative apparatus similar to turbines or other hydraulic wheels; but down to the present time these inventions have not been crowned with practical success. The economical application of the principle of reaction to machines operated by elastic fluids would nevertheless be of a very high degree of interest, since the moving portions would thereby be reduced to very small dimensions, and, in the great majority of cases, the transmission of the motion would be lightened and simplified. In a word, such machines would enable the same advantages to be realized as are found with hydraulic turbines compared with waterwheels of large diameter.

" Elastic fluids acquire enormous velocities, even under the influence of comparatively low pressures. In order to utilize these pressures advantageously upon simple wheels analogous to hydraulic turbines, it would be necessary to permit a rotative motion of extraordinary rapidity, and to use extremely minute orifices, even for a large expenditure of fluid. These difficulties may be avoided by causing the steam or gas to lose its pressure, either in a gradual and continuous manner, or by successive fractions, making it react several times upon the blades of conveniently arranged turbines.

1 'We must attribute the origin of the researches which we have made upon this subject to the communications which M. Burdin, Ingenieur en Chef des Mines, and membre Correspondant de I'lnstitut, has had the courtesy to make to us, and which go back to the close of 1847. M. Burdin, who was then engaged upon a machine operated by hot air, desired to discharge the compressed and heated fluid upon a series of turbines fixed upon the same axis. Each one of these wheels was placed in a closed chamber, the air to be delivered through injector nozzles and discharged at a very low velocity. The author proposed to compress the cold air by means of a series of blowers arranged in a similar manner. This idea of employing a number of successive turbines in order to utilize the tension of the fluid a number of times seemed to us a simple and fertile one; we perceived in it the means of applying the principle of reaction to steam and air engines.

"Since the differences in pressure, as used in steam engines, are considerable, it became evident that a large number of turbines would be required to give a sufficient reduction in the velocity of the fluid jet. The lightness and small dimensions of the moving parts permits of very high rotative speeds compared with those of ordinary engines.

" Notwithstanding the multiplicity of parts, it is essential that the apparatus should be simple in its action, susceptible of a high degree of precision, and that adjustments and repairs should be readily made. We believe that we have fulfilled these essential conditions by means of the following arrangements :

"A machine is composed of several independent motor axes, connected by means of pinions to a single wheel for the transmission of the motion. Each of these axes carries several turbines; these receive. and discharge the fluid at the same distance from the axis.

" Between two turbines is placed a fixed ring of guide blades. The guides receive the discharge from one reaction wheel and give to it a direction and velocity suitable to act upon the following wheel. Each of these systems of fixed and moving organs is to be enclosed in a cylindrical case. The guide blades will form portions of rings or annular pieces placed in the fixed cylinder, and these should be fitted very exactly the one to the other. The turbines should also have the form of rings, and should be fitted to a sleeve attached to the shaft. Projections fitting into grooves secure the guides to the cylindrical case, and fasten the turbines to the shaft. The first set of guides, which act simply as injector nozzles, may be made in one solid piece, carrying the journal of the shaft. Nothing could be easier than to erect or dismount such an apparatus. In order to transmit the motion it is necessary that the shaft should pass through the end of the cylindrical case through an opening fitted with a tight packing; such a single stuffing box will answer for each series of reaction wheels.

" After having acted upon the turbines on the first shaft, and thus parted with more or less of its elasticity, the fluid is caused to act upon the turbines of the second series, and so on. For this purpose large openings connect the end of each case with the beginning of the one which follows.

These cases and passages may form portions of the same casting. Since the steam or gas expands in proportion to its passage through the blades of the turbines and the guides, it is necessary that these blades should offer passages of continually increasing size, and the last portions of the apparatus will have much greater dimensions than the first.

uAs in the case of hydraulic reaction wheels, the last turbine on each shaft should discharge the fluid with a very low velocity. At its flow from the other turbines the fluid should have a velocity best adapted to its entrance into the passages between the guide blades. The motive power developed by these wheels will be produced, in great part, not by the extinction of the actual velocity of the fluid, but from the differences in pressures in entering and leaving the blades. This difference in pressures will produce a great excess in the relative velocity of discharge over the relative velocity of entrance, and, in order that this effect may be obtained, it will suffice, by reason of the continuity of the motion, for the orifices of discharge of the passages to be of smaller area than the entrance orifices; this corresponds, in general, to the arrangement in most hydraulic turbines. Considered with regard to the relative velocity of rotation, the velocity of flow through the passages of our turbines will be much greater than in the passages in ordinary reaction wheels, and, in consequence, they will be capable of utilizing a much greater proportion of motive power.

uAs is the case in all kinds of machinery, there are many causes tending to dimmish the useful effect of our apparatus, and to render it lower than the theoretical effect.

"One portion of the fluid will escape through the clearance intervals which must be left between the fixed and moving portions, and will have no effect upon the turbines and will not be directed by the guide blades. There will be produced shocks and eddies at the entrance and discharge 2 of the buckets. The considerable friction, due to the narrowness of the passages, will absorb a considerable portion of the theoretical work.

"All these injurious effects are produced in hydraulic turbines, some with an intensity almost equal in degree, others, such as the frictional resistances, to a much less extent. These reaction wheels are, nevertheless, excellent machines. In order that our steam or hot-air machines should equal them in respect to the effective power utilized, a very perfect construction will be necessary, which it will perhaps be difficult to attain, because of the small size of the parts. But if we consider the results obtained with piston engines operated by steam we see that we may make a large allowance for losses before our turbines fail to give equally good results. Many of the causes of loss inherent in the use of pistons and cylinders will be avoided. Thus, the cooling effect due to radiation from the exterior walls in contact with the surrounding medium will become negligible, since our cylindrical casings offer a very small mass and volume, traversed by a very large flow of heat.

"In order that the application of our principles may be successfully applied to engines operated by elastic fluids it is necessary that great care and a very high degree of precision be given to the construction and erection of the parts, and that the dimensions and curves of the blades be carefully studied.

"It is necessary that the teeth of the gear wheels, which are operated at very high speeds, should run with great smoothness, without shock or vibrations; the helicoidal system of gearing of White will probably be found desirable. The shafts should also be held by outside collars in order that the metallic stuffing boxes may not be subjected to heavy pressures. The journals will receive the pressure parallel to the axis; this, however, will be small, on account of the small dimensions of the turbines.

11 As for the regulators of the flow of the fluid, their functions will be performed by two slides or valves, one placed in the pipe connecting the engine to the generator, and the other in the opening through which the exhaust is discharged into the atmosphere.

"The principal advantage offered by the motors which we propose lies in the extreme lightness and small size which they offer. This is a point upon which we believe it unnecessary to insist at length. The present engines are too heavy and cumbersome, and are yet incapable of application to many purposes which are still accomplished by the physical effort of man. Without doubt the realization of our projects would extend widely the domain of mechanical power.

11 Applied to steam motors we believe that our multiple turbines would permit a reduction in the dimensions of the reservoirs or generators of the fluid; because, the consumption of the motive material being continuous, the ebullition will be effected very regularly in the boiler, and there will be much less danger of the entrainment of a large proportion of water. If hot air be substituted for steam, as we may hope from the beautiful and fertile experiments of Ericsson, our turbines will replace, very happily, the enormous cylinders and pistons used by the Swedish engineer to receive the action of the compressed air. It remains to be seen if similar rotative apparatus may not be usefully employed for the compression of cold air. In case of success a complete mechanical revolution will be effected not only with regard to the quantity of combustible consumed but also in the matter, not less important, of the masses and volumes which enter into machine construction."

It seems surprising that the clearly expressed ideas of Tournaire failed of immediate realization, especially as they were passed in review under the eyes of such a committee of mechanical specialists as Morin, Lame, and Poncelet; but it is probable that constructive difficulties, the extent of which was fully realized by Tournaire, stood in the way. His work seemed to have been almost entirely overlooked until recently, but there is no doubt that he fully grasped the problem, as the text of his communication to the French Academy shows.

At the present time the term " elastic-fluid" turbine appears in nearly all patent specifications for such machines, their scope not being limited to steam alone. Tournaire not only used this very expression, but also foresaw the application of the multiple-turbine principle to pressure blowers as well.

He further saw that high fuel economy, while probably attainable with the turbine, was not the only advantage, but that material reduction in weight and in bulk might also be attained, points which to-day are of even more importance than they were fifty years ago.

An interesting forecast of the practicability of the gas turbine appears in the fifth edition of Bourne's large treatise on the steam engine, published in 1861. Discussing the advantages of superheated steam, Mr. Bourne says:

" Steam of a high temperature will, therefore, be more economical in its use than steam of a lower temperature, and surcharged steam being much hotter than common steam is consequently more advantageous. After all, however, the temperatures which it is possible to use with any kind of steam in an engine are too low to render any very important measure of economy possible by their instrumentality. We are, therefore, driven to consider the applicability of other agents, the most suitable of which appears to be air, and this brings us back to the point from whence we started at the commencement of the present chapter. Small measures of improvement are worth very little consideration when great and important steps of progress are apparently within our reach, and to us it appears quite clear that the prod-

THE GAS TURBINE.

ucts of combustion may be employed to produce motive power, not through the instrumentality of a cylinder and piston, but rather by means of a turbine or an instrument like a smoke jack or Barker's mill, and which may be made to work in water or some other liquid. In this way very high temperatures may be dealt with, and it is only by employing very high temperatures that any very great step of improvement is to be attained."

FIG. 6. — Boulton's multiple jet system

In 1864 the problem of combustion at constant pressure, in connection with the operation of a gas turbine, was investigated by M. P. W. Boulton, and his British patent, No. 1636 of 1864, contains some points of interest, in the light of what has been done since. He realized that the high velocity of the jet of gases issuing from the nozzle offered a practical difficulty, and proposed to remedy this by the use of successive induced jets of increasing volume and consequently lower velocity. This is shown in Fig. 4, the gases being delivered through the nozzle A, inducing a current in B, and this again in C. The turbine is represented at D, operated by the increased volume of fluid at the reduced velocity.

THE GAS TURBINE.

Another method proposed by Boulton for maintaining combustion at constant pressure is shown in Fig. 7. The gas is burned at A, in a chamber C, under water, the products of combustion passing up through the water between the baffle plates E, E, and the mixed gases and steam being delivered to the turbine from the top of the chamber B.

FIG. 7. — Boulton's constant-pressure combustion chamber.

The idea of combustion at constant pressure to furnish an elastic fluid composed of hot air and products of combustion for use in a turbine appears to have occupied the attention of a number of engineers from 1870 onward. John Bourne, the well-known British engineer and writer on the steam engine, took out two patents, one in 1869 and the other in 1870, relating to the combustion of coal dust for the production of gases for use in a turbine. His plans included the dilution of the gases with air and with the vapor of water, and involved the use of high pressures, up to 1,000 pounds per square inch. Bourne's patents refer entirely