US1888698A - Process and apparatus for operating turbines - Google Patents

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Nov. 22, 1932. w. SCHULE I PROCESS AND APPARATUS FOR. OPERATING TURBINES Fil ed Dec. 20, 1926 2 Shets-Shet 1 INVENTOR W/L HEL BY 1 Sch J45 ATTORNEYS NOV. 22, 1932. w, sc U 1,888,698

PROCESS AND APPARATUS FOR OPERATING TURBINES Filed Dgc. 20, 1926 2 Sheets-Sheet 2 Inventor: W/L HELM .5 01/025 FiI Q t W11.

flttom e ys Patented Nov. 22, 1932 1 UNITED STATES PATENT OFFICE.

WILHELM SCHULE, OF GORLITZ, GER-MANY, ASSIGNOB, TO HOLZWAB'IH GAS TURBmE 00., OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF DELAWARE PROCESS AND APPARATUS FOR OPERATING TURBINES Application filed December 20, 1926. Serial No. 155,849.

My invention relates to turbines which are operated by hot combustion gases and some other gaseous fluid of a lower temperature than such combustion gases.

It has been proposed to operate a high-- pressure turbine by combustion gases issuing from a combustion chamber or explosion chamber and to take the combustion gases exhausting from such highpressure turbine to a second turbine operating at a, lower pressure. Such exhaust gases have temperatures of from T to 1000 C. The combustion gases issuing from the high-pressure combustion chamber to operate a gas turbine under substantially constant pressure. have temperatures of the same order or even higher temperatures, especially when the turbine is constructed as a multistage action or reaction turbine in order to obtain as high a thermodynamic efficiency as possible.

actuating the turbine, it has been proposedto direct a flow of steam into the turbine simultaneously with the current of combustion gases but at a different point of the turbine. This arrangement of conveying the supply of combustion gases and steam sepa rately to different portions of the turbine presents certain difiiculties both as to construction and operation. and it is the object of my present invention to obtain the same advantages while avoiding the difiiculties just mentioned. I have found that this can be accomplished by causing the exchange of heat between the combustion gases and the steam to take place. not in the turbine rotor through the medium of the rotor itself, but before such gases and steam are admitted to the turbine blades. By such heat exchange the combustion gases are cooled to a point where their permanent admission to the turbine is permissible. that is to say. their temperature will not be injurious to the turbine even if they are adnntted continuously. The drop in temperature may be quite considerable; for instance,

the combustion gases may be brought from 1000 C. to 450 C. before they are admitted to the turbine. The question might be asked whether this would not reduce the etficiency of the two media (combustion gases and steam) to such an extent that the advantages of the new method of operation would be nullified or outweighed by too great a loss in the recovery of energy. It has been found, however, that such a loss in thermodynamic etliciency does not occur at all or only to a very slight extent, and my invention therefore enables a considerable improvement to be effected, since the turbine can be operated continuously and safely even with blades made of the usual material, without reducing the degree to which the heat of the combustion gases is utilized.

An explanation of the beneficial results of my invention will now be given with reference to the accompanying drawings, in which Fig. 1 is a diagrammatic elevation with parts in section, illustrating a turbine arrangement embodying my invention; Figs. 2 and 3 illustrate diagrammatically the pressurevolume relationships occurring in plants of the type shown in Fig. 1 for the first case described hereinbelow, wherein both gases or vapors I and II obey the general gas law, Fig. 2 showing the 721) diagram for steam and Fig. 3 for highly heated combustion gases; Figs. 4 and 5 show the pressure-volume relationships for the second case described hereinbelow, Fig. 4 showing the po diagram of the colder of the two heat exchanging bodies as being saturated or moderately superheated steam which no longer follows the general gas law, Fig. 5 showing the corresponding diagram for highly heated combustion gases; Figs. 6 and 7 show the pa diagramsfor steam and combustion gases, respectively, when the pressure of the cooler body (e. g. steam) is higher than that of the hotter body; and Fig. 8 is a view similar to Fig. 1 but shows a single turbine to which both of the gaseous media are conducted from the heat-exchanger. In Fig. 1. 10 indicates a combustion or explosion chamber having valves 11, 12 for periodically admitting air and fuel respectively. a suitable ignition device 13 and an outlet valve 14, all

of thesedevices being controlled to secure their proper timing in any well-known manner; see for instance the patent to Holzwarth No. 877,194. 15 indicates a heat-exchange apparatus having two paths. one of which, 16,

has its inlet connected as by a pipe 17 with erally use in'practice, I desire it to be understood that I might use as an equivalent therefor, other gaseous media of a temperature lower than that of the combustion gases flow ing through the path 16. For the purposes of my invention, as I have found, the cooling medium. that is the steam or its equivalent,

its original temperature t should be at the same pressure as the combustlon gases or at a higher pressure.

The advantages of my invention will be understood from the following considerations. reference being had to the diagrams, Figs. 2 to 5.

Two difl'erent gaseous bodies I and II (gases or vapors) having the weights G and G the same initial pressure p, and different initial temperatures t and tfi will, if expanded to the same final or counter-pressure p (for instance, atmospheric pressure), have difl'erent temperature drops or capacities for performing work, as indicated by the areas L, and L in Figs. 2 and 3 respectively, assuming that as in my invention these two media or bodies perform work independently of each other, for instance, one of them in a steam turbine and the other in a gas turbine. If. however, the hotter body H (for instance, combustion gases) and the relativelv cooler body I for instance, steam) before their admission to the two turbines are caused to pass in heat exchange relation to each other without, however, allowing them-to become mixed with each other (as by passing them through the heat exchanger 15 of Fig. 1) the hotter medium II will give of part of its heat to the cooler medium I and therefore the hotter medium, when it reaches the turbine 21, will have a temperature t which is lower than its original temperature t while the other and cooler medium for instance,

steam),'when it reaches the turbine 23, will have a temperature t which is higher than The heat exchange has reduced the energy contained in the hotter medium by an amount which we may call AL and has increased the energy contained in the cooler medium by an amount which we may call AL It will be evident that as long as AL is not smaller than AL the aggregate available energy contained in In this 'case the increase in volume AV which the cooler gas I undergoes by-the heat exchange, is equal to the decrease in volume AV which the warmer gas II undergoes owing to-the cooling; thus AV w-Av i This, however, -is correct only when within the temperature limits under consideration, t and t or t and t both gases have equal specific molecular heats C and C or equal,

specific heats Km and Kpn referred to the mass unit of 1 cubic meter at 0v C. and 760 mm. pressure. It can be shown readily that AL1=AL11 In other words, the increase in available enin this caseergy given to the cooler body by the absorption of heat is equal to the decrease in available energy which the warmer body surfers owing to lesser heat. The-heat exchange.

will therefore not alter the sum of the energies of these two bodies, for instance if both bodies are two-atomic gases and their limit I temperatures are not very far apart.

If, however, the specific heats K and K are difi'erent (for. instance, if II is'a twoatomic gas while I is superheated steam or carbonic acid or any combustion gas) then we have the relation AV K, and therefore Ave-wai If, for instance, in this case K,Ii K, then it .follows that AV AV In this case the increase in volume of the colder body I will be greater than the decrease in volume of the warmer body, and from thisit follows that v saturated or moderately superheated steam;

the other (warmer) I body II is any combustion gas. Such steam does not follow the law of gases, and with constant pressure its specific heat varies with the temperature. The combustion gas does, indeed, conform to the law of gases, but its specific heat becomes less with decreasing temperature. In this case the results are obtained by consulting the well-known tables giving the heat of steam and combustion gases, the available energies L L' L and L' being calculated in the well-known manner.

A special investigation shows that according to the steam pressure and the temperature of the steam and of the combustion gas, the sum of the energies available after the heat exchange, will be greater or smaller thanbefore the heat exchange or stay the same. For instance, with combustion gas derived from oil and having a temperature of 900 0., which is caused to interchange heat with dry saturated steam' of a pressure of either 3, 6 or 10 atmospheres until such combustion gas. is cooled to 450 C. while the steam is heated up to 400 (1., it has been found that the sum of available energy, figured from said initial pressures of 3, 6 or 10 atmospheres to a counter-pressure of 1 atmosphere absolute, is increased by .572 if the initial pressure was 3 atmospheres, while if the initial pressure was 6 atmospheres or 10 atmospheres, said sum is decreased by 2.5% or 4.5% respectively, so that in this case the heat exchange causes a slight reduction of the available energy when relatively high initial pressures are employed. I Conditions are diflerent, however, if we as sume that the steam pressure drop is utilized not only down to 1 atmosphere as in the case of combustion gases, but down to a vacuum of say .06 atmospheres absolute as is done in the case of steam turbines. Under this assumption, we shall obtain in each of the three cases referred to above, an increase amounting to 13%, 5.2% and 1.4% respectively. In other words, under these assumptions there will always be a more or less material increase of the entire available energy, as a result of the heat exchange. This may be understood readily by referring to the diagram in Fig. 4, which shows that the surface AL representing the additional energy, is continued below the line indicating atmospheric pressure. Finally, there is also the possibility of having the steam premure higher during the have been described as operating on sepa-* rate turbines or rotors, they might be caused to actuate the same turbine or the same rotor as indicated at 21' in Fig. 8.

I claim: I 1. In a turbo-engine, the combination of an explosion chamber adapted to be intermittently charged with an explosive mixture of air and fuel for explosion therein under con stant volume, whereby explosion gases of high temperature and pressure are produced, a nozzle valve at the outlet end of such chamber adapted to be opened after each explosion to discharge such gases under pressure, means whereby said gases are expanded without the performance of external work to increase their velocity and simultaneously to reduce their temperature, a heat exchanger, a' conduit for leading the high velocity gasesinto said heat exchanger, a conduit for conducting into the latter a fluid in heat exchange relation with said gases to be heated by the latter, a turbine arrangement, and means for conducting to the latter the cooled gases and the heatedfluid to perform work therein.

2. The combination with an explosion chamber adapted to be intermittently charged with an explosive mixture of air and fuel for explosion therein under constant volume, whereby explosion gases of high temperature and pressure are produced, said chamber having a nozzle valie at its outlet end adapted to be opened after each explosion to discharge such gases under pressure, of means whereby said gases are expanded withoutthe performance of external work to increase their velocity and simultaneously to reduce their temperature, a heat exchanger connected with said means to receive the expanded, high velocity gases, a

conduit for conducting into said heat exchanger a fluid in heat exchange relation with said gases to be heated by the latter, and means for conducting the heated fluid to a place of use.

W'ILHELM SCHULE.

heat exchange than the pressure of the com- I bustion gases, as indicated in the diagrams, Figs. 6 and 7. Investigation of the conditions obtaining in this case shows, as was to be expected, that in this case also a gain in energy is obtained by the heat exchange, since AL, A'L,

From the above explanations it will be evi-

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