US2557198A - Gas turbine - Google Patents

Description

June 19, 1951 w, M, MCHQLS 2,557,19

l GAS TURBINE Filed uay 21, 1947 4 Shenets-Sheet 1 FIGJ.

June-19 1951 w. M. NICHOLS ,2,557,198

GAS mslm; Filed lmay 21. 1947 v 4 shuts-sheet 2 INVENToR W/LL/'AM M. NcHoLs June 19, 1951 w. M.' NICHOLS l 2,551,198

GAS TURBINE l Filed May 2]..A 1947 y 4 Sheets-Sheet 3 FIG -5- AlR /1\ 'l PRESSURE REACTION 1 STAGE INLET PRESSURE STAGE \2." STAGE INLET PRESSURE CONSTANT PRESSURE l STAGE 60 A/mscwuaoz nessuna l .INVENTOR WlLLiAM M'N/'cHoLs June 19, 1951 Filed May 2l. 1947 W. M. NICHOLS GAS TURBINE 4 Sheets-Sheet 4 F'IGZ INVENTOR WILL/'AM M-N/'cHoLs ATTO EY Patented June 19, 1951 GAS TURBINE William M. Nichols. Schenectady, N. Y., assignmto VAmericain Locomotive Company, New York, N. Y., a corporation of New York Application May 2l, 1947, Serial No. 749,433

1Claim.

This invention relates to gas turbines.

The object of the present invention is to obtain greater efliciency in a gas turbine, as well as to eliminate the need of a bulky heat exchanger in order to obtain this eflciency. Most gas turbines operate on either the constant volume (explosion) cycle or on the constant pressure (continuous process) cycle. 'I'he turbine of the present invention operates on a combination of both cycles,

, at full power, and mostly on the constant volume cycle at light load.

Other and further objects of this invention will panying drawings and the appended claim.

Referring to the drawings forming a part of this application:

Fig. 1 is a sectional view, on the line I-I of Fig. 2, of a gas turbine Vconstructed according to the present invention;

Fig. 2 is a section on the line II-II of Fig. 1;

Fig. 3 is a section on the line III-III of Fig. 1; Fig. 4 is a diagrammatic view of one type of turbine blading for the turbine of Fig. 1;

Fig. 5 is a diagrammatic view of another type of turbine blading for the turbine of Fig. 1;

Fig. 6 is a pressure diagram showing the relative work done by the turbine wheels;

Fig. 'I is a sectional view of a turbine constructed in accordance with a modification of this invention, taken through the combustion chambers and looking toward the inlet ports; and

Fig. 8 is a sectional view through the rotary inlet valve of the turbine of Fig. 7, looking in the opposite direction toward the inlet ports.

The gas turbine of Figs. 1-6 is indicated in the drawings by the reference numeral I, and includes a front wall 2 and a rear wall 3 spaced by an inner pipe 4 and an outer pipe 5. 'I'he inside of pipe 4 provides a chamber 6, and the space between the pipes 4 and 5 provides a chamber 1. The walls 2 and 3 and the pipes 4 and 5 are connected by tie rods 8 and spacers 9. 'I'he inside of the pipe 4 and the outside of the pipe 5 are protected by fire brick or some other like material IIJ retained by sleeves II. A shaft I2 is mounted axially in pipe 4 for rotation therein, this shaft I2 having an enlarged hub I3 at its rear end supported in a ball bearing I4 mounted in the pipe 4. A nozzle ring I5 is integral with the hub I3 and overlaps the outer face of the wall 3. The shaft I2 extends at its front end through a central orifice I6 in the wall 2.

A housing I1 is secured to the outer face of wall 2 in any desired manner. This housing has an inlet I8 and an orifice I9 in line with orifice I6, shaft I2 extending through orifice I9 and being journalled in a ball bearing mounted on the outer face of the housing I1. A circular valve 2| is keyed on shaft I2 in housing I1, the circumference of valve 2l beingv spaced from the appear from the following description, the accom-f 2 surrounding wall of the housing I1 to provide an annular chamber 22 in communication with the inlet I8.

The chamber 1 maybe divided by radial partitions into as many combustion chambers as desired. In the instant case three partitions 23 partition the chamber 1 into three combustion chambers. 24, 25 and 26. Each partition 23 extends from the wall 2 to the wall 3. However, since the flow of hot gases is toward the wall 3 the center portion of this wall is protected by a cone 21 of re brick or other material covered by a shield 28, and the partitions 23 are cut to t snugly against the outer face of the shield 29 and adjacent inner face of the wall 3. The partitions may be secured in place by welding.

Each combustion chamber has an inlet port 29 in the Wall 2 and an outlet port 30 in the wall 3. The three ports 29 or the three ports 30 taken together form substantially 360 degrees leaving spacing webs 3l suiiicient for fastening to the partitions 23, as is clearly shown in Fig. 2, it being' understood that the ports 29 are similar in shape to the ports 30.

The rotary valve- 2l is provided with a single port 32 which will register, as the valve rotates, successively with each of the ports 29. Each of the combustion chambers is provided with fuel injection nozzles 33 and an igniter 34, the number of fuel injection nozzles being determined by the axial length of the combustion chamber so that an even distribution of fuel therein is obtained.

The nozzle ring I5 has a nozzle 35 provided with the usual vanes 36, nozzle 35 being substantially degrees in length, or, in other words, about the size and shape of a port 30. As nozzle ring l5 rotates to align its nozzle 35 successively with each of the outlet ports 30, gas leaves each of the combusion chambers in succession. In other words, ports 30 are controlled by nozzle 35 just as ports 29 are controlled by port 32. Since both nozzle ring I5 and valve 2l are rigidly connected to shaft I2, the control of the inlet ports is definitely controlled in relation to the control of the exhaust ports.

A rotor housing 31 is secured to the outer face ofthe wall 3. It is divided by a central partition 38 into a forward chamber 39 and a rear chamber 40, the nozzle ring I5 being housed in the chamber 39.

The rear wall 4I of housing 31 is provided with an interior hub 42, and hubs I3 and 42 form bearings for the turbine power shaft 43, this shaft 43 extending through a gland and thrust bearing 44 to the exterior of the housing 31. Power can be taken for the rear end of shaft 43 in any desired manner, and it may be geared by reduction gears in any desired manner to drive shaft I2, the gearing therefore being omitted for simplicity.

The nozzle ring I5 has a sealing margin 45 in close proximity with the adjacent wall of vthe housing 81, and has an inner rear chamber 46 in which is housed the rst-stage reaction wheel 41 of the turbine secured on shaft 43. Partition 38 is provided with a circular row of nozzles 48 which form the outlet ports of chamber 39. The partition 38 has a chamber 49 in its rear face housing a constant pressure turbine wheel 50 vhich may be either of the impulse or reaction ype- The hub 42 is shielded by iire brick or the like 5 i contained by a thin shielding member 52 similar to the shield 28. The chamber 39 is provided with a by-pass exhaust port 53 controlled by a valve 54.

The operation of the gas turbine is as follows:

The gas turbine must be started by rotation of shaft I2 in any desired well-known manner either mechanically or by iow of air to the turbine Wheels. Assuming therefore that the gas turbine is in operation, air under pressure will be flowing through the inlet i8 into the inlet chamber 22. The valve 2i will be rotated by the shaft I2 which can be driven by any desired means, or it can be connected to the turbine power shaft i3 by gears (not shown) in an obvious manner. As valve 2i rotates air from chamber 22 will iiow successively into the chambers 24, 25 and 26 through the port 32. The port 32 thus establishes communication with one combustion chamber for the inlet of air and then terminates communication so that combustion can take place in this combustion chamber. Fuel is injected into each combustion chamber by its injection nozzles 33 of which there are suiiicient to insure even dstribution of fuel throughout the combustion chamber. This injection takes place when the inlet port 29 of the combustion chamber is closed by a sealed portion of the valve 2i. Ignition is caused by the igniter 34. The expanding gases rush through the outlet 38 and through the vanes 36 of the nozzle 35 of the nozzle ring I5. The gases can only leave each combustion chamber as the nozzle 35 aligns with the port 3D thereof, and the nozzle ring I5 is accordingly timed with the injection and ignition so that the outlet port 30 of each combustion chamber is open at the proper time for the passage of the high pressure gas to the iirst-stage reaction Wheel 41. 41 receives the gas with iiuctuating pressure and the gas, after expansion in the wheel, enters the chamber 39 Where any fluctuations which are left are reduced so that the gas in chamber 39 iiows through the continuous nozzle 48 to the second-stage constant pressure turbine wheel 5l). The gas is expanded in the wheel 5U Aand enters the rear chamber 4U only after all the possible work has been taken out of this gas. It is exhausted from the chamber 48 through the outlet thereof.

l Should it be desired to operate the gas turbine only by the iiuctuating pressure cycle in the rststage reaction wheel 41, the valve 54 is turned to open position so that the gas is exhausted through the exhaust port 53 without passing through the second-stage wheel 5B. The exhaust port 53 will ordinarily be open only when the gas turbine is Wheel,

4 pressure to the combustion chambers that the constant pressure part ot the cycle by expansion in the second-stage wheel 58 becomes necessary.

Because of the combining of two turbine wheels, the iirst taking care of the expansion of the iiuctuating pressure gas, and the second taking care of the expansion of the constant pressure gas, the instant gas turbine will have a greater efficiency than has been obtained in previous gas turbines. It will be noted, by reference to Fig. l, that the second-stage turbine is a smaller turbine than the first-stage turbine. The cycle is completed without any need for a bulky heat exchanger such as is customarily used in prior art cycles.

The cycle of the instant gas turbine has both a constant volume (explosion) part and a constant pressure (continuous process) part. At light loads the turbine operates mainly on the constant volume part, and at heavy loads most of the work is done by the constant Ypressure part.

While, as aforesaid, atmospheric air may be admitted at the inlet I8, it is contemplated that air will be delivered to the inlet I8 at constant pressure, but this pressure will be varied with the load so that at very light loads this pressure is practically atmospheric.

The valve 2| is sealed in the housing I1 so that, as is obvious from Fig. l, leakage is impossible except through the ball bearings 2i, and the housing containing thisbearing can be packed in any well-known marmer to prevent any leakage of air from the chamber 22. Some leakage may occur from the combustion chambers backed into the chamber 22, but this is where air under pressure is admitted to the inlet I8.

Since the nozzle ring I5 only contains a short nozzle 35, the remainder of the nozzle ring acts as a rotating outlet valve sealing off the ports 30 except when it is desired that gas pass therefrom to the turbine wheels. c

'I'he work done by the gas turbine is indicated diagrammatically in Fig. 6. The first-stage turbine wheel 41 is designed primarily to convert the variable explosion pressure into work with maximum efficiency. In Fig. 6, the work of one combustion chamber is shown in solid lines. It has two peaks 55 and 55. These peaks indicate part of the work being done by the gases of the combustion chamber 24. The work done by the combustion gases of chambers 25 and 26 is indicated by dotted lines. The air pressure at the inlet I8 is indicated by a dot-dash line 51. The pressure in the chamber -39 is indicated by the line 58.

The peaks 55 and 56 rise above the ordinary inlet pressure of the :first-stage turbine wheel 41, this inlet pressure being designated by the line 59 extending on opposite sides of the peaks. Therefore the work done by the rst-stage reaction turbine Wheel is plotted between the lines 58 and 59 including the peaks 55 and 56. The gas enters the second-stage turbine wheel at the constant pressure indicated by the line 58 and is expanded down to the discharge pressure in chamber 40 indicated by the line 6I). This diagram of Fig. 6 shows afull load running condition, and it will be seen that more work is done by the constant pressure second-stage turbine wheel than is done by the uctuating pressure rststage reaction turbine wheel. It should, however, be noted that the inlet pressure of the secondstage turbine wheel (line 58) is only slightly less than the air pressure at the inlet I8 (line 51) The rst-stage wheel must be a reaction wheel and the blading oi.' this wheel 41 is so shown in Figs. 4 and 5 which show diagrammatically two possible arrangements of rstand second-stage turbine wheels. The second-stage or constant pressure turbine wheel 50 can be a reaction wheel 58a, as shown in Fig. 4, or an impulse wheel 50h, as shown in Fig. 5. The reaction blading in all cases has very little curvature at the inlet, as is clearly shown in Figs. 4 and 5. ' Ihe combustion chambers 24, 25 and 26 are indicated as pipes, and the stationary nozzles 35 and 48 have the same vaning in both cases. It is to be remembered, when referring to Figs. 4 vand 5, that the nozzle 35 is relatively short.

For very iight loads it has been stated that the inlet pressure at the inlet i8 would be only slightly above atmospheric pressure. Therefore there would be no pressure drop available for the constant pressure stage of the expansion, and if this stage were not eliminated it would result ,in undesirable losses. Thus at light loads, the Valve 5l is turned to open the by-pass exhaust port 53.

Where the rotary valve 2| is driven by the power shaft 43, reduction gearing must be employed since the valve 2| does not rotate at the same speed as the turbine wheels but need only rotate fast enough so that the combined volume of all of the combustion chambers times the number of revolutions is equal to the total volume of air used. The injection and ignition of fuel is timed to give maximum explosion pressure in the combustion chambers at a time when the valve 2| and nozzle ring I5 have sealed ofi' the ports 29 and 30.

No attempt has been made in the drawings to show a gas turbine as it would actually be constructed, but the gas turbine has been shown more or less diagrammatically for simplicity. While expansion of the fluctuating gases has been shown taking place in a single stage rotor l1, and expansion of the constant pressure gases has been shown taking place in a single stage rotor 50, each of the rotors 41 and 50 may be divided into multi-stages in a well-known manner if desired.

Valve 2| may also have incorporated in it a back track duct whose purpose is to allow the flow of gases from a combustion chamber having a slightly higher pressure linto a combustion chamber just filled with clean air, thereby preeompressing this air before the fuel is burned in this second combustion chamber. Such back track duct precompression gives more prompt burning of low grade fuel, as well as effecting an increase in the net cycle eiliciency. Such a back track duct would not ordinarily be employed in a gas turbine having only three combustion chambers as shown in Figs. 1 to 5. vIt is therefore shown in Figs. 7 and 8 in connection with a gas turbine having six combustion chambers. Parts of the modification of the invention shown in Figs. 7 and 8 which correspond to similar parts of the gas turbine of Figs. 1 to 5 are indicated by like references with an accent added.

The only actual change has been an increase in the number of combustion chambers to provide six combustion chambers 8| to I8 inclusive, and the inclusion of a back track duct 81 in the valve 2|', the back track duct having an inlet port ll and an outlet port 89 where the direction of rotation of the shaft I2' is in the direction of the arrow.

In Fig. 8 ports 68 and 89 are shown closed by valves 10, valves 10 being formed by the portions of the front wall 2 between ports 29' thereof. Assuming that chamber 6| has already fired and the gas therein has expanded to the turbine then this chamber will contain residual gas under pressure. Chamber -62 will then be firing and chamber 83 will contain a fresh charge of air. Rotation of the valve 2|' will connect chambers 6| and 63 so that the residual gas in chamber 6| can iiow backwards through the port 29 into chamber 63 where the residual gas will precompress the charge of air in combustion chamber 63 prior to fuel injection therein. This precompression cycle will be repeated for each of the six combustion chambers.

While there have been hereinbei'ore described approved embodiments of this invention, it will be understood that many and various changes and modifications in form, arrangement of parts and details of construction thereof may be made without departingr from the spirit of the invention, and that all such changes and modifications as fall within the scope of the appended claim are contemplated as a part of this invention.

The invention claimed and desired to be secured by Letters Patent is:

In a gas turbine of the class wherein expanding gas is transmitted under fluctuating pressure from a plurality of combustion chambers through outlet ports in the housing of the combustion chambers to a turbine housing, such ports being controlled by a rotary nozzle ring. in combination, a turbine housing; a turbine shaft in the housing; a first stage reaction turbine on the shaft at the outlet side of the nozzle' ring, said turbine being adapted for actuation by variable pressure gas flowing successively from the combustion chambers through the outlet ports into the nozzle ring; a constant pressure chamber at the outlet side of the ilrststage wheel: a second nozzle ring at the outlet side of the constant pressure chamber; a discharge chamber at the outlet side of the constant pressure nozzle ring; a second stage constant pres- 'sure turbine wheel on the shaft in the discharge chamber adapted to be driven by the gas passing through the constant pressure nozzle ring; and a by-pass port in said constant pressure cham` ber for cutting out said second-stage wheel when said turbine is running at a predetermined load.

WILLIAM M. NICHOLS.

REFERENCES CITED The following references are of record in the file of this patent: v

UNITED STATES PATENTS Number Name Date 1,714,549 Cooper May 28, 1929 1,854,615 Lasley Apr. 19,1932 1,858,322 Cooper May 17, 1932 1,931,545 Holzwarth Oct. 24, 1933 2,418,911 Smith Apr. 15, 1947 FOREIGN PATENTS Number Country Date 174,179 Great Britain Jan. 19, 1922 319,903 Great Britain Oct. 3, 1929 564,171 Germany Nov. 14, 1932 631,898 France Dec. 28. 1927

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