DE1020645B - Process for the carnotization of steam cycle processes - Google Patents

Description

Process for the Carnotization of steam cycle processes Carnotization of the steam cycle process is known to mean the adjustment to the Carnot process with the efficiency (Ql-Q2) : Qi = (TI-T2) : Ti, where Q1 is the heat supplied, Q2 the heat removed and Tl the highest, T2 is the lowest temperature of the process.

In the steam cycle, the lowest temperature T2 depends on the temperature of the cooling water for the condenser i. On the other hand, the temperature T, in the sense of a Carnotization, depends on various circumstances. If the heat is not only supplied at a maximum temperature T, as in the Carnot process, but within a temperature range as usual (evaporation, overheating and also feed water preheating), an average heat supply temperature T. < Ti applies. The efficiency is now 7 / _ (Tm - T2) : T ..

The ratio T., : T, can be described as the degree of carnotization. With complete Carnotization, T., = Ti, so that the interrelation 27 = (Tm - T2) : T. changes into 77 = (T, - T2) : TI. So that the working medium can perform a cycle in the Carnot process, it must then be brought from T to T2 or from T2 to T between heat supply and removal. If a process is equivalent to the Carnot process in terms of efficiency, i.e. if it is to be addressed as carnotized, then these two temperature changes of the medium must be covered by internal energy circulation without any external influence.

This inner circulation takes place in the actual Carnot process mechanical transmission, in which internal energy is turned into work during isentropic expansion transformed, which is used by mechanical means to compress the work equipment, whereby it transforms itself back into internal energy.

In the Ericson process, this internal circulation takes place in the form of heat instead, that in a perfect counterflow heat exchanger without any mechanical Aid is implemented. This process has the same efficiency as the Carnot process.

It is therefore the one necessary to carry out a full Carnotization internal circulation of energy both mechanically and by heat transfer possible. One can of course also achieve full Carnotization by that the internal circulation takes place partly as mechanical energy, partly in the form of heat. Is only part of this inner circulation covered in itself, but part of warmth supplied from the outside, one has it with a degree of Carnotization less than 1 to do, and the mean temperature Tm denotes the upper temperature of the Carnot process, which has the same efficiency as the partially carnotized process.

When considering a Carnotization of the steam cycle depends on the individual phases of heat supply, such as preheating, evaporation and overheating, to go out. From this it follows that the Carnotisierung, related to the whole Process, imperfect and perfect, depending on how many phases of the process be included in the carnotization in whole or in part. The degree of carnotization depends on it.

A known method for a limited carnotization of the preheating is the regenerative feed water preheating. Here is partially expanded steam taken from various pressure stages of the turbine and fed to the preheating stages. Cycle processes with camotization of evaporation differ from those described in that not the whole amount of the working medium is between its physical state liquid and gaseous changes, but always only a part. The other part remains always vapor or gaseous. For this reason it is also not the solution to the problem possible without the use of a compressor.

The procedure described below is used to carnotize preheating, Evaporation and part of superheating.

The Ts diagram in Fig. 1 shows the cycle to be carnotized (I) adeghitm n. If the preheating from a to o 'is carnotized by regenerative preheating, the process changes to a' o 'd eg 1a il in n. Without a final ZGvischen overheating the process is represented by a 'o' d eg k i n '. A second cycle (II) is superimposed on this cycle, with the course o p i k. This process only takes place in the overheating area, i.e. without changing the aggregate state of the working medium. Along the lines hi and ik , the state variables and changes in state are the same as in the process to be carnotized. Both processes can therefore be brought together on these routes. The waste heat from the cycle (II) is used in cycle (I) to preheat from o 'to d, vaporize at pressure p, from d to e and superheat from e to f. For this purpose, the amount of steam GI in the cycle (II) must be related to the amount of steam GI in the cycle (I) as Gji: GI = (2 - 4): (6 - 8). With a correspondingly changed entropy scale, but with the same temperature scale, the process (II) o p i k changes over to the cycle o ' p ' i ' k' of Fig. 1. The arrangement corresponds to the intended heat transfer in the drawing. The heat for preheating up to the evaporation temperature at the pressure P 1 is transferred along o 'd. This happens in countercurrent. The transfer of heat 3 d k'4 from process (II) to process (I) takes place with an increase in entropy of 4 s, since the evaporation and overheating heat 3 def 5 is equal to the amount of heat 3 d k'4. From f to g and from l_ to m , superheat is supplied in a special superheater, while the superheats from P 'to i' and 1a to i take place together in one superheater, since the steam pressures are the same and these two sections of the processes (II ) and (I) are merged.

The cycle (I) takes place between the pressures @ 1 and Po, at which the condensation occurs. The cycle (II) works with the pressures p2 and p3. Expansion i ' to k' and compression o 'to P' have the pressure ratio P2: p3.

While Fig. 1 in the Ts diagram according to the invention shows a Carnotization for the subcritical pressure area, the same method is shown in Fig. 2 for vapor pressures that can be arbitrarily high above the critical pressure. Process (I) a ' m def g i k L and process (II) m 3a g h., Which, according to the circulating steam quantity ratio GII: GI = (2-4): (6-8), changes into ne 'n' g ' h' if the entropy scale is changed in the same ratio. From cycle process (II), the amount of heat 2 m 'lt' 4 is given off to cycle process (I) as far as possible in countercurrent from 1a to na '. Here it appears as the amount of heat 2 na 'd 5, with an increase in entropy A s occurring. This is less than in the example in Fig. 1. Accordingly, when the pressure P is increased, the heat transfer from process (II) to process (I) becomes more favorable. The heat is supplied via n 'to ``', d to e, f to g and i to k, whereby n 'to g' and f to are also carried out together, since the pressures are the same. The heat is dissipated along the condensation path l to a '. As in the example according to Fig. 1, the pressure limits for process (I) are P, and f ", while process (II) works between pressures P2 and p3. Hence, expansion g 'to h' and compression m ' up to n 'the pressure ratio p2: p3.

If the last reheating is avoided, the last section of the process in Fig. 1 runs from i to n '(expansion) and from n' to a '(condensation). Correspondingly, this section in Fig. 2 is g to L '(expansion) and l' to a ' (condensation). It is known to use bleed steam, which is recompressed, to preheat and evaporate. In all of these known processes, the generated steam is fed to the process directly before or / 'and after the compression. Furthermore, the compression is carried out by means of a turbo compressor, the work of which is diverted from the main turbine.

In contrast, in the present case, such a high pressure P, chosen that by the expansion to the pressure P2 (see Fig. 1 and 2) a performance is achieved that the power requirement of the compression of the bleed steam from the pressure P, on the pressure p, covers. The inlet pressure at the engine is p.-Regenerative preheating In this process, it takes place in the well-known manner by means of taps on the main turbine and / or a preheating turbine, the amount of steam supplied to it prior to compression is taken from the circulation steam, so that previously heat for further preheating, evaporation and overheating of the condensate was released. The preheating takes place with smallest increase in entropy by means of saturated steam due to the lack of overheating. With this arrangement, there are none of the usual devices such as desuperheaters etc., required.

The inventive novelty of the invention is that two amounts of gas different thermodynamic states in nozzles to the same supercritical Velocities are brought, then a pressure equalization in the space behind the nozzles takes place transversely to the direction of flow, with the compensation space in the direction of the flow such a cross-sectional change after a small final value has that the Compensation work is converted into pressure, the axial velocity of the gas flow from the beginning to the end of the compensation space and the kinetic energy remains constant of the total gas quantities only in the following #_, diffusers kept the missing pressure difference delivers up to the desired medium pressure.

As in some cases of technology, so is also in the present for Carnotization of the steam cycle is given the task of producing two different amounts of gas Pressure and possibly also different temperatures, if possible without an increase in entropy to a common mean pressure ß "Z and possibly also to a mean pressure Temperature t, bring.

The best known method is the use of a turbo compressor, with p, the inlet pressure and P2 the outlet pressure of the turbine and p3 the Inlet pressure and f., Is the outlet pressure of the compressor. However, this requires a corresponding expenditure on machines. In addition, the achievable efficiency with low throughput volumes left a lot to be desired. The carnotization process can then adversely affected by this «-erden.

To explain the nozzle method, the following considerations are assumed: In Fig. 3, a cylinder 1 closed on all sides is shown with a piston 2 which divides the cylinder space into two unequal spaces. In the small space v, let the gas pressure be P, and in the large space r; let the gas pressure f.,. v, - v., is equal to your entire cylinder volume. If P,> p2, piston 2 is pushed to the right. Until the pressure is equalized on both sides of the piston, work is transferred to the outside of the piston rod. If the piston were suddenly released without loss of work, it would perform a damped oscillation in the direction of the cylinder axis. When the piston is at a standstill, the work released to the outside in the first case now appears as heat in the entire amount of gas in the cylinder. This means an increase in entropy. The second case is therefore irreversible. In Fig. 4, a cylinder 1 is shown which, in addition to that of Fig. 3, has a second piston 3 which allows the total cylinder content to be changed. The second piston 3 is connected to the piston 2 located inside the cylinder 1 via an imaginary mechanism 4 with a variable transmission ratio such that the forces are in equilibrium in any position. Piston 2 delivers work to piston 3, which is used for compression, and vice versa, piston 3 delivers work to piston 2, depending on the direction of movement of the piston. Obviously, pistons 2, 3 are now in equilibrium in every position. The pressures p1 and p2 in the two cylinder chambers can now be set in any ratio p1: p2. This process is reversible, i.e. without a change in entropy. If p, > p2, the cylinder volume v becomes smaller as p,: p2 becomes smaller. decrease. With pressure equalization (p1 ° p2) vm it is always <than the sum of the initial volumes vl @ - v2.

A comparison of the examples shows that a pressure equalization of two amounts of gas if the total volume remains constant, a work transfer to the outside is conditional or an increase in entropy either by throttling or by a damped oscillation the amount of gas, whereby the work that can otherwise be dissipated to the outside is transformed into heat. However, the total volume of both gas quantities becomes due to the resulting equalization work reduced accordingly, no oscillation can arise in the gas quantities, ie there is also no increase in entropy. It is expressly of a volume reduction the total amount of gas spoken, because of a compression of the total amount of gas during there can be no question of compensation, because a part expands, whereby at the same time the other part is compressed.

Fig. 5 shows in section the example of a nozzle 5, which alone through Flow processes allow the pressure equalization to be carried out. In Part I, both will Gas quantities with pressures p1 and p2 with a pressure drop to p1 'and p.,' Are the same Brought speed. In order to avoid shock losses, the speeds must be equal. In addition, at least the speed of the gas volume must correspond to the pressure p2 ' be supercritical, so that a kickback of the higher pressure p1 'into the nozzle is excluded is. So there is a "lock speed" to be maintained. A displacement of the jet in the nozzle over the boundary layer is not to be expected, because also the high pressure gas flows at the same speed, in contrast for example to Laval nozzles that blow into a dormant gas with high counter pressure.

In part 1I of the nozzle 5, the pressure is equalized by a pressure wave runs transversely to the direction of flow of the gas quantities. From cross section 1 to cross section 2, the speed distribution across the axis of the nozzle follows a sine function (0 - max. - 0). The gas guide F is formed according to a sine function, the Cross-section 2 to cross-section 1 of the nozzle 5 behaves like vm: (v1 -f- v2) according to the cylinder example with two pistons. An oscillation perpendicular to the direction of flow, for example when blowing out a Laval nozzle in a room with lower pressure as the nozzle end pressure can therefore not take place here, theoretically therefore also none Entropy increase.

The dimensioning of part I of the nozzle 5 results from the known aspects. The ratio of the cross-sections 1 and 2 depends on the pressures p1 'and p2' and the ratio of the two gas flows. The axial length of the nozzle part II depends on the speed of the gas quantities and the maximum speed of the equalizing pressure wave transverse to the gas flow, taking into account the sinusoidal speed distribution. In the axial direction, the gas velocities in cross-section 1 and in cross-section 2 are theoretically equal to one another. The volume reduction, i.e. the compression, is not disputed from the kinetic energy of the gases, but from the work of expansion of the amount of gas with the higher initial pressure, analogously to cylinder example 2 from the work transferred from piston 2 to piston 3. In part III, the convergent diffuser reduces this speed with an increase in pressure to the critical limit. The divergent diffuser IV reduces the gas velocity further in the subcritical area, the pressure increasing from pm '(after the equalization in part 11) to the desired equalization pressure p "m the nozzle is fully balanced, as the times for this in parts II and III are much too short.

In Fig. 5, the nozzle 5 is designed asymmetrically to the direction of flow, to represent the process in the simplest form. The nozzle can constructively under Maintaining the desired function can be designed differently. This is how, for example, when the flat Fig. 5 is rotated around the axis a-u, Fig. 6 and when rotated around the Axis b-b Fig. 7. In Fig. 6 the high pressure steam flows as a central ring, so that the pressure equalization takes place radially towards the axis, while in the case of Fig. 7 the pressure equalization of the high pressure steam flowing inside here radially from the Axis away happens.

The specified dimensioning conditions for parts I and II of the nozzle show that the pressures p1 and p2 also increase the gas flow rate a certain nozzle is fixed within certain limits when shock losses and gas oscillations should be avoided. Therefore, if necessary, several can be connected in parallel Provide nozzles. With nozzles according to Fig. 5, to achieve a higher throughput a row arrangement similar to a paddle grid can also be developed. This however, it will be more of a concern at lower pressures. At high and maximum pressures the nozzles that are rotationally symmetrical to the axis will be used. This should be just a few examples from the range of possible arrangements for practical Implementation of the method forming the invention by means of pure flow processes two gas quantities of different pressures in nozzles (theoretically without increase in entropy) to bring to a medium pressure pnt.

Fig. 8 shows the processes in the nozzle in detail in an is diagram Phases broken down. Losses are not taken into account here. It was also disregarded let the phases flow into one another in individual points by processes are shown separately in time, but simultaneously in certain areas happen.

Fig. 9 shows a circuit diagram that shows the Carnotization process using the AD compensating nozzle. The regenerative preheating Vwl takes place by means of taps on the low-pressure turbine Tn and via a preheating turbine Tv, whose operating steam is branched off in front of the equalizing nozzle _4D, i.e. after its remaining superheat has been given off. The power of the turbine T ,, is used to drive auxiliary machines, etc.

Due to the overheating heat of the bleed steam from the pressure p2 from the turbine T, the condensate, which has already been highly preheated by Vwl, is evaporated in the evaporator Vd at the pressure p1 and is superheated in the heat exchanger Ü. The residual overheating heat of the bleed steam is given off to the preheated condensate in the heat exchanger Vw. Hereinafter, this extraction steam enters from the pressure p2, reduced by the Vorwärmturbine T, given amount of steam into the AD Ausgleichdüse a. After the heat exchanger Ü, the steam from the pressure p1 in the superheater U1 is further superheated by means of flue gas heat before it enters the equalizing nozzle AD . As already described, the pressures P1 and p2 are balanced in this nozzle, so that the combined steam quantities of the high and low pressure leave the compensation nozzle AD with the mean pressure P. the turbine T to enter.

After this turbine T, the steam flow is divided into the amount of bleed steam from pressure P2 and a part that flows through the medium and low pressure turbine. Less the amount drawn off for the first stages of preheating Vwl, the remainder this amount of steam is precipitated in the condenser and fed by the feed pump Sp fed back into the circuit via the preheating Vwi.

In Fig. 9, between the turbine T "" and the turbine T "is a Intermediate overheating indicated by dashed lines. This should show that depending on the pressure and temperature conditions of the steam process here, d. H. behind the turbine TI, a single or multi-stage reheating is provided can be.

If not all of the condensate is caused by the overheating of the Bleed steam is to be evaporated in front of the equalizing nozzle AD, the rest of the Part can be evaporated in a normal boiler K in parallel. In the circuit diagram Fig. 9 is this separately fired evaporator K, the one with the superheaters Ü1 and Ü2 can be combined constructively, along with its connecting lines dashed drawn.

This circuit diagram Fig. 9 gives only one of the many possible examples of a system that is possible according to the inventive concept of Carnotization of the steam cycle when using the compensating nozzle AD in a wide variety of designs and applications.

The advantages of the method are that once for the same Maximum temperatures compared to the normal Rankine steam cycle significantly higher efficiency is achieved under the same other conditions. Furthermore, with the new method, the main engine becomes the same maximum pressures with much lower pressure and a much larger inlet volume for the amount of steam operated. This enables a higher degree of machine efficiency than in the normal process is achievable. The investment costs are still lower because instead of the The high pressure turbine enters the much cheaper equalizing nozzle and the enlargement the absorption capacity of the main turbine in the first turbine section by no means the savings outweighs. So the whole process allows the creation of a cheaper and at the same time much more economical power plant.

The process is suitable for the highest and lowest pressure areas, so that all service areas are included. So it is possible to use steam power plants low power with relatively high efficiency for any purpose, for example also ship drives etc. to build.

Starting the nozzle is done by first reducing the amount of gas with the low Pressure P2 is brought to lock speed. Only then will the amount of gas begin with admitted to the high pressure p1 and adjusted to the same speed. The for this The necessary auxiliary and control devices result from the respective type of application the nozzle and its classification in the power plant. This compensation nozzle adjusts new method represents in the application of supercritical flows for implementation a shock-free and vibration-free pressure equalization of two different gas quantities State. No comparison can therefore be made with the known jet compressors etc., which are all based on the injector principle, i.e. always two very different media Bringing together speed. Therefore, here are the expected efficiencies in any case low.

Claims (6)

PATENT CLAIMS-1. Process for the carnotization of steam cycle processes to compensate for the different thermodynamic states of two gas quantities, mainly different pressure, on a mean value, characterized by that both amounts of gas are brought to the same supercritical velocities in nozzles then in the space behind the nozzles a pressure equalization transversely to the direction of flow takes place, wherein the compensation space in the direction of the flow such a change in cross-section after a small end value shows that the work of compensation is converted into pressure is the axial speed of the gas quantities from the beginning to the end of the equalization chamber remains constant and the kinetic energy of the total gas quantities only in downstream Diffusers supplies the missing pressure difference up to the desired mean pressure. 2. The method according to claim 1, characterized in that for catnotizing the Preheating, evaporation and part of the superheating in steam cycle processes in the middle pressure area a cycle with slight expansion and compression Pressure ratio is superimposed, the waste heat of which the already preheated condensate still further preheated, evaporated and overheated, mainly at a much higher level Pressure as the initial pressure of the superimposed process, so that the result of this the condensate generated steam after further overheating by means of flue gases during expansion the circulating steam after this in a correspondingly designed flow device Heat release so condensed that both quantities of steam are superimposed on the initial pressure of the Achieve process and together after further heating in a flue gas superheater are supplied to the engine. 3. The method according to claims 1 and 2, characterized characterized that the regenerative preheating of the steam cycle to be carnotized partly or wholly fed from taps known per se on a preheating turbine whose vapor is branched off from the superimposed cycle before compression will. 4. The method according to claims 1 to 3, characterized in that the Power control at constant temperatures by changing the pressures of the Gas quantities and the most approximate preservation of the pressure conditions takes place. 5. Process according to claims 1 to 4, characterized in that, if temporary or only part of the condensate is constantly evaporating through the superimposed circuit the remaining part in a parallel-connected, heated with flue gases Evaporator (boiler) is brought to evaporation, which may be necessary for start-up the system can be used. 6. Implementation facility of the method according to claims 1 to 5, characterized in that a division takes place in a ballast and a back-up system, the back-up system is also newly created or already exists and then a ballast is added according to the new procedure. Considered publications: German patent specifications No. 931 655, 890 190, 556 034.