EP3118424B1 - Control of orc processes by injection of un-vaporized fluids - Google Patents

Description

Field of the Invention

The invention relates to a thermodynamic cycle device, which can in particular be an ORC device, and a preheater for preheating a working medium; an evaporator for evaporating and optionally overheating a first mass flow of the preheated working medium; a volumetric expansion machine for expanding the vaporized and superheated mass flow of the working medium; a condenser for condensing and possibly supercooling the working medium emerging from the outlet; a feed pump for pumping condensed working medium to the preheater; and a first supply device for supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in an expansion chamber of the volumetric expansion machine between a closure and an opening of the expansion chamber. Furthermore, the invention relates to a corresponding method for operating a thermodynamic cycle, in particular an ORC process.

State of the art

If a power-generating process, such as the Organic Rankine Cycle (ORC), is operated in the environment of another unit, such as an internal combustion engine, both the direct integration of the generated energy and mechanical power into the external system (e.g. the expansion machine of the power-generating process can drive the third-party process at least in a supportive manner), as well as their provision for auxiliary units (for example, the third-party process can drive a pump in the force-generating process), since the conversion of mechanical energy into electrical energy leads to conversion losses. In addition, the saved motors for drive and generators for output also save costs and the compactness can be increased, both of which are critical factors for the integration of a force-generating process in the environment mentioned.

However, through a direct connection (for example a coupling via a rigid shaft) one of the processes loses the degree of freedom of the speed control (usually the downstream process). To avoid this, a connection can be made via a gearbox. This enables both a stepped and a stepless connection to control the speed. However, this regaining of speed control is accompanied by a number of disadvantageous properties. On the one hand, a gearbox represents an additional cost, which, depending on the application, has a significant impact on economic efficiency. This effect is reinforced by the fact that gearboxes (especially stepless ones) also lead to a loss in efficiency. Gearboxes are also subject to considerable stress and thus add additional maintenance and corresponding costs to the system. Last but not least, a transmission is also comparatively space-intensive, which is contrary to the goal of compactness in many motor integration applications.

The coupling of the expansion machine described here or the coupling of both the expansion machine and the feed pump of the ORC system to third-party processes without a transmission means that the degrees of freedom of the speed control are lost. As a result, no parameters that are favorable for ORC operation and required for the components can be regulated - especially volume flows, temperatures and pressure levels. This is particularly a problem for the operation, since the permitted temperatures of the components are limited, especially on the downstream side of the expansion machine.

In addition, due to the lack of speed control of the expansion machine, an expansion ratio cannot be made available that correlates with the volume ratio that is permanently installed in a volumetric expansion machine. The implementation of a variable volume ratio by means of a variable inlet or outlet window, which is customary in the prior art, represents a complex and expensive process which hinders the economy of ORC systems. However, an expansion that is not suitable for the expansion machine can result in efficiency levels falling too sharply and thus also making the overall system inefficient or, in extreme cases, exceeding the permissible maximum pressure. Exceeding the maximum permissible pressures and temperatures leads to a failure of the system with possible consequential damage.

US 6,035,643 A discloses an ORC system wherein the turbine has 21 successive stages in which the organic vapor expands and its pressure and temperature therein are reduced to generate mechanical energy from the thermal energy. On the way through the turbine, additional organic medium is added through valve-controlled injection nozzles on the way through the stages.

US 5,555,731 A discloses a preheated injection turbine cycle.

US 3,234,734 A discloses a process for converting heat into work using a working medium which is overheated and then expanded. An additional amount of liquid medium can be injected into a mixing chamber of the turbine, the injected amount mixing with a first expanded amount and expanding together in a second stage.

Description of the invention

1. 1. Absenken der Überhitzung (bei gegebenem Druck) um die Komponenten vor einem Betrieb bei Temperaturen oberhalb ihrer Limitierung zu schützen und/oder Absenken der Überhitzung um eine Wirtschaftlichkeit des Systems durch verbesserte Wirkungsgrade zu gewährleisten. Die Überhitzung bei trockenen Fluiden ist per se schädlich für den Wirkungsgrad, da sie Energie auf hohem Temperaturniveau darstellt, welche keinen zusätzlichen Beitrag zur Expansion leistet. Je weiter der Abdampf im überhitzten Bereich liegt, desto mehr Wärme muss vor der Verflüssigung im Kondensator abgeführt werden.
2. 2. Vermeidung von für den Betrieb uneffektiven Volumenverhältnissen auf Grund der nicht regelbaren Drucklagen bei festem Volumenverhältnis der Expansionsmaschine.
3. 3. Vermeidung von zu hohen Drücken (absolut oder auf die vom System erreichbare Verdampfungstemperatur bezogen), welche zu Schäden an der Anlage oder einer Nichtverdampfung des Fluides oder Teilen hiervon führen, was neben einem Wirkungsgradeinbruch ebenfalls Schäden verursachen kann.
4. 4. Vermeidung von zu großen Massenströmen des Arbeitsmediums, welche durch die zur Verfügung stehende Wärme nicht (in ausreichendem Maße) verdampft werden können.

The object of the invention is to at least partially overcome the disadvantages mentioned, and accordingly to at least partially solve the following four tasks:

1. 1. Lowering the overheating (at a given pressure) in order to protect the components from operating at temperatures above their limit and / or lowering the overheating in order to ensure that the system is economical due to improved efficiencies. Overheating in dry fluids is inherently detrimental to efficiency, since it represents energy at a high temperature level, which makes no additional contribution to expansion. The further the exhaust steam is in the overheated area, the more heat has to be removed in the condenser before liquefaction.
2. 2. Avoiding volume ratios that are ineffective for operation due to the non-controllable pressure levels with a fixed volume ratio of the expansion machine.
3. 3. Avoidance of excessively high pressures (absolute or based on the evaporation temperature achievable by the system), which lead to damage to the system or non-evaporation of the fluid or parts thereof, which can also cause damage in addition to a drop in efficiency.
4. 4. Avoidance of excessive mass flows of the working medium, which cannot be evaporated (to a sufficient extent) by the available heat.

The tasks 1 and 2 are solved by a device according to claim 1 and a method according to claim 11.

The thermodynamic cycle device according to the invention, which can in particular be an ORC device, comprises a preheater for preheating a working medium; an evaporator for evaporating and overheating a first mass flow of the preheated working medium; an expansion machine for expanding the vaporized and superheated first mass flow of the working medium; a condenser for condensing the working medium emerging from the expansion machine; and a feed pump for pumping condensed working medium to the preheater. The thermodynamic cycle device according to the invention is characterized by a first feed device for feeding a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in the expansion machine.

This enables the degrees of freedom of the lowering of the evaporation temperature and an adapted expansion ratio. The overheating can be reduced in this way and the volume ratio of the expansion can be reduced dynamically.

The device according to the invention can be further developed in such a way that the first feed device can comprise a feed inlet of the expansion machine and a first feed line between the preheater and the feed inlet.

According to the invention, the feed inlet is arranged in fluid communication with an expansion space of the expansion machine at a predetermined volume range of the expansion space, the expansion space expanding between an inlet and an outlet of the expansion machine.

A further development is that the first feed device comprises a first controllable throttle element, in particular a first thermostatic expansion valve, for regulating the second mass flow and / or the first feed device can comprise an injection device on the expansion machine, in particular on the feed inlet.

According to another development, the thermodynamic cycle device can further comprise a second feed device for feeding a third mass flow of the preheated working medium to the vaporized and overheated first mass flow of the working medium before it expands in the expansion machine. This enables temperature limits before direct injection into the expansion machine and a reduction in overheating, even if the real expansion ratio is not to be (further) reduced. This strategy allows the fresh steam temperature to be regulated quickly.

The second feed device can comprise a second feed line which is arranged between the preheater or the first feed line on the one hand and the inlet or a third line arranged between the evaporator and the inlet on the other hand.

The second feed device can comprise a second controllable throttle element, in particular a second thermostatic expansion valve, for regulating the third mass flow.

Another further development is that the feed pump can be coupled to a drive train operated via the expansion machine; and wherein the cycle process device may further comprise a controllable recirculation device for partially recirculating working medium from a high pressure side of the feed pump to a low pressure side of the feed pump. Fluctuations and instabilities in the evaporation zone can thus be avoided.

The controllable recirculation device can comprise a line from the high pressure side to the low pressure side of the feed pump, wherein the line can be provided with a third controllable throttle element.

According to another development, a rotation of the expansion machine can be coupled to a rotation of an externally running process; in particular, a shaft of the expansion machine can be coupled to an external drive train of an engine, either directly or indirectly via a transmission.

The object of the invention is further achieved by a method according to claim 11.

The method according to the invention for operating a thermodynamic cycle, in particular an ORC process, comprises the following steps: preheating a working medium by means of a preheater; Evaporating and overheating a first mass flow of the preheated working medium through an evaporator; Expanding the vaporized and superheated first mass flow of the working medium in an expansion machine between an inlet and an outlet of the expansion machine; Condensing the working medium emerging from the outlet through a condenser; and pumping condensed working medium to the preheater with a feed pump; the method being characterized by supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in the expansion machine.

Unless otherwise stated, the advantages of the method according to the invention and its developments correspond to those of the device according to the invention.

According to a development of the method according to the invention, the following further step can be provided: regulating the second mass flow and / or injecting the second mass flow into an expansion space of the expansion machine.

Another development is that the method can further comprise: supplying a third mass flow of the preheated working medium to the vaporized and superheated first mass flow of the working medium before it expands in the expansion machine.

According to another development, the third mass flow can be regulated.

Another development is that the following further step can be provided: coupling a rotation of the expansion machine with a rotation of an externally running process; in particular by coupling a shaft of the expansion machine to an external drive train of an engine, either directly or indirectly via a transmission.

The further developments mentioned can be used individually or, as claimed, can be suitably combined with one another.

Further features and exemplary embodiments and advantages of the present invention are explained in more detail below with reference to the drawings. It is understood that the embodiments are not exhaustive of the scope of the present invention. It is further understood that some or all of the features described below can also be combined with one another in other ways.

drawings

Fig. 1

shows a first embodiment of the thermodynamic cycle device according to the invention.

Fig. 2

shows a second embodiment of the thermodynamic cycle device according to the invention.

Fig. 3

shows a third embodiment of the thermodynamic cycle device according to the invention.

Fig. 4

qualitatively shows the relationship between expansion ratio and expansion efficiency.

Fig. 5

is an exemplary representation of the relationship between pressure and enthalpy in the direct injection of preheated working medium into the expansion machine.

Embodiments

Fig. 1 shows a first embodiment of the thermodynamic cycle device 100 according to the invention in the form of an ORC device (Organic Rankine Cycle). The cycle process device comprises a preheater 10 for preheating a working medium; an evaporator 20 for evaporating and overheating a first mass flow of the preheated working medium; an expansion machine 30 for expanding the vaporized and superheated first mass flow of the working medium; a condenser 60 for condensing the working medium exiting the expansion machine 30; and a feed pump 70 (with motor M) for pumping condensed working medium to the preheater 10. According to the invention, a first feed device 40 is provided for supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in the expansion machine 30.

The first feed device 40 comprises a feed inlet 48 of the expansion machine 30 and a first feed line 47 between the preheater 10 and the feed inlet 48. The feed inlet 48 is arranged in fluid communication with an expansion space of the expansion machine 30 at a predetermined volume range of the expansion space, the expansion space between one Inlet 32 and an outlet 34 of the expansion machine 30 expanded.

The first feed device 40 further comprises a first controllable throttle element 45, in particular a first thermostatic expansion valve, for regulating the second mass flow and / or wherein the first feed device 40 comprises an injection device 41 on the expansion machine 30, in particular on the feed inlet 48.

The regulation can take place on the basis of the measured temperatures T, which are shown as examples. In particular, the throttle element 45 can be controlled accordingly.

The rotation of the expansion machine 30 can be coupled to a rotation of an externally running process; in particular, a shaft 31 of the expansion machine 30 can be coupled to an external drive train of a motor 90, either directly or indirectly via a gear 91, which can include a freewheel or shifting options.

Injecting the preheated working medium into the expansion that has already partially taken place has the effect shown below.

I. Provision of a direct injection of preheated fluids into the ongoing expansion according to the process control in FIG. 1 to solve tasks 1 and 2:

$${\dot{Q}}_{\mathit{VW}}=\left(h_2-h_1\right)\ast {\dot{m}}_{\mathit{AM},\mathit{VW}}=\left(T_2-T_1\right)\ast {\bar{c}}_{p,1-2}\ast {\dot{m}}_{\mathit{AM},\mathit{VW}}$$

$${\dot{Q}}_{\mathit{VD}}=\left(h_3-h_2\right)\ast {\dot{m}}_{\mathit{AM}.\mathit{VD}}=\mathrm{\Delta }{h}_{\mathit{evap}}\ast {\dot{m}}_{\mathit{AM}.\mathit{VD}}$$

$${\dot{Q}}_{\mathrm{Ü}H}=\left(h_4-h_3\right)\ast {\dot{m}}_{\mathit{AM},\mathrm{Ü}H}=\left(T_4-T_3\right)\ast {\bar{c}}_{p,3-4}\ast {\dot{m}}_{\mathit{AM},\mathrm{Ü}H}$$

During the processes of preheating VW (Q̇ _VW ), evaporation VD ( Q̇ _VD ) and overheating ÜH ( Q̇ _{Ü H} ), which are common for the ORC circuit, part of the fluid ( ṁ _{AM, DE} ) is removed before evaporation. The total energy input into the system, which can take place directly or via an intermediate circuit, can be determined as follows: $${\dot{Q}}_{\mathit{total}}={\dot{Q}}_{\mathit{VW}}+{\dot{Q}}_{\mathit{VD}}+{\dot{Q}}_{\mathrm{Ü}H}$$

$${\dot{Q}}_{\mathit{VW}}=\left(H_{\mathrm{2nd}}-{\mathrm{<figure-callout\; id="1"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}_1\right)\ast {\dot{m}}_{\mathit{AT\; THE},\mathit{VW}}=\left(T_{\mathrm{2nd}}-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">T</figure-callout>}}_1\right)\ast {\bar{c}}_{p,1-\mathrm{2nd}}\ast {\dot{m}}_{\mathit{AT\; THE},\mathit{VW}}$$

$${\dot{Q}}_{\mathit{VD}}=\left(H_{\mathrm{3rd}}-H_{\mathrm{2nd}}\right)\ast {\dot{m}}_{\mathit{AT\; THE}.\mathit{VD}}=\mathrm{\Delta }{H}_{\mathit{evap}}\ast {\dot{m}}_{\mathit{AT\; THE}.\mathit{VD}}$$

$${\dot{Q}}_{\mathrm{Ü}H}=\left(H_{\mathrm{4th}}-H_{\mathrm{3rd}}\right)\ast {\dot{m}}_{\mathit{AT\; THE},\mathrm{Ü}H}=\left(T_{\mathrm{4th}}-T_{\mathrm{3rd}}\right)\ast {\bar{c}}_{p,\mathrm{3rd}-\mathrm{4th}}\ast {\dot{m}}_{\mathit{AT\; THE},\mathrm{Ü}H}$$

mit $${\dot{m}}_{\mathit{AM},V\ddot{\mathrm{U}}}={\dot{m}}_{\mathit{AM},\mathit{VD}}={\dot{m}}_{\mathit{AM},\ddot{\mathrm{U}}H}$$

ferner gilt: $${\dot{m}}_{\mathit{AM},\mathit{VW}}-{\dot{m}}_{\mathit{AM},V\ddot{\mathrm{U}}}={\dot{m}}_{\mathit{AM},\mathit{DE}}$$

Here h ₁ , h ₂ , h ₃ and h ₄ denote the enthalpies at the respective in Fig. 1 specified positions. For the consideration of the branching of working medium (AM) after preheating, no further division of the mass flow is considered and the evaporation and overheating can be summarized as evaporation with overheating ( Q̇ _{V Ü} ): $${\dot{Q}}_{V\mathrm{Ü}}={\dot{Q}}_{\mathit{VD}}+{\dot{Q}}_{\mathrm{Ü}H}=\left(H_{\mathrm{4th}}-H_{\mathrm{2nd}}\right)\ast {\dot{m}}_{\mathit{AT\; THE},V\mathrm{Ü}}$$

With $${\dot{m}}_{\mathit{AT\; THE},V\ddot{\mathrm{U}}}={\dot{m}}_{\mathit{AT\; THE},\mathit{VD}}={\dot{m}}_{\mathit{AT\; THE},\ddot{\mathrm{U}}H}$$

the following also applies: $${\dot{m}}_{\mathit{AT\; THE},\mathit{VW}}-{\dot{m}}_{\mathit{AT\; THE},V\ddot{\mathrm{U}}}={\dot{m}}_{\mathit{AT\; THE},\mathit{DE}}$$

In order to again allow the degrees of freedom of temperature and adapted expansion ratio, the branched-off liquid working medium is supplied to the expansion machine via a suitable feed after a certain proportion of the expansion and is injected directly (process control according to Fig. 1 ). In order to achieve thermal equilibrium as quickly as possible during the injection (heat input until there is a uniform temperature in the expansion chamber), the injection device must be designed accordingly and ensure good distribution with high fluid surfaces (e.g. fine atomization). For the controllability of the parameters, a throttle element, in particular a controllable or a passive throttle element (for example a thermostatic expansion valve) is used in the feed line.

For injection into the expander, an inlet hole must be made in a suitable place in the housing. This must be determined depending on the volume ratio of the expansion machine. The still high pressure of the chamber has a limiting effect in the direction of the start of expansion, which hinders the entry of liquid fluid. In addition, overheating can also increase during the course of the expansion, so that more liquid fluid can also be evaporated at a later point in time of the expansion. On the other hand, there should be enough time to open the chamber to maintain thermal equilibrium with complete evaporation. Furthermore, participation in a large expansion share of the overall expansion is positive for the generation of benefits.

Various positive effects can be achieved in this way:

a. Volume ratio adjustment

$$v_{K,\mathit{ein}}=\frac{V_{K,\mathit{ein}}}{m_{\mathit{AM},K,\mathit{ein}}}$$

$$v_{K,\mathit{aus}}=\frac{V_{K,\mathit{aus}}}{m_{\mathit{AM},K,\mathit{aus}}}$$

$$V_i=\frac{V_{K,\mathit{aus}}}{V_{K,\mathit{ein}}}=\mathit{konstant}$$

mit den Kammervolumina am Ein- und Auslass V _K,ein/aus sowie der Masse des in der Kammer eingeschlossenen Arbeitsmediums m _{AM,K,ein/ aus}. Da im Standardfall ohne Kammereinspritzung die Masse des Arbeitsmediums in der Kammer konstant ist, ergibt sich Φ _EX = V_i. The volume ratio of the expansion (Φ _EX ) can be reduced dynamically (see also Fig. 5 ), the following relationship applies to the specific volumes at the time the chamber is closed when entering the expansion machine ( v _{K, on} ) and at the moment of opening the chamber at the outlet of the expansion machine ( v _{K, off} ) with the fixed volume ratio of the expansion machine V _i : $${\mathrm{\Phi }}_{\mathit{EX}}=\frac{v_{K,\mathit{out}}}{v_{K,\mathit{a}}}$$

$$v_{K,\mathit{a}}=\frac{V_{K,\mathit{a}}}{m_{\mathit{AT\; THE},K,\mathit{a}}}$$

$$v_{K,\mathit{out}}=\frac{V_{K,\mathit{out}}}{m_{\mathit{AT\; THE},K,\mathit{out}}}$$

$$V_i=\frac{V_{K,\mathit{out}}}{V_{K,\mathit{a}}}=\mathit{constant}$$

with the chamber volumes at the inlet and outlet V _{K, on / off} and the mass of the working medium m _{AM, K, on / off} enclosed in the chamber . Since the mass of the working medium in the chamber is constant in the standard case without chamber injection, Φ _EX = V _i results .

The actual expansion ratio (Φ _real ) is determined from the live steam parameters and the evaporation parameters and is determined by pressure and temperature before and after the expansion machine.

In the case of Φ _real <Φ _EX one is in the area of post-compression. In this case, the fluid is brought to a lower pressure level during expansion in the expansion machine (chamber closed) than is actually present after the expansion machine. This leads to the fact that the fluid is compressed after opening the chamber, which has very negative effects on the efficiency due to the increased push-out work to be carried out by the expansion machine. In the area of post-expansion (Φ _real > Φ _EX ), the increased outlet pressure from the chamber has a positive effect. The pressure level in the expansion chamber at the end of the expansion is still higher than that after the Expansion machine. As a result, the fluid expands further when the chamber is opened, and the post-expansion generates additional power due to the lower push-out work to be performed by the expansion machine.

Due to the injection of fluid during expansion, the following applies: m _{AM, K, off} > m _{AM, K, on} , which leads to a reduction in Φ _EX according to the relationship shown above, so that Φ _EX < V _i : $${\mathrm{\Phi }}_{\mathit{EX}}=\frac{v_{K,\mathit{out}}}{v_{K,\mathit{a}}}=\frac{V_{K,\mathit{out}}}{m_{\mathit{AT\; THE},K,\mathit{out}}}\ast \frac{m_{\mathit{AT\; THE},K,\mathit{a}}}{V_{K,\mathit{a}}}=\frac{V_{K,\mathit{out}}}{V_{K,\mathit{a}}}\ast \frac{m_{\mathit{AT\; THE},K,\mathit{a}}}{m_{\mathit{AT\; THE},K,\mathit{out}}}=V_i\ast \frac{m_{\mathit{AT\; THE},K,\mathit{a}}}{m_{\mathit{AT\; THE},K,\mathit{out}}}<V_i$$

This shift is due to the qualitative course of the isentropic expansion efficiency Fig. 4 shown.

Furthermore, the principle of internal recuperation (as in Fig. 5 shown) integrated into the process.

This leads to an improvement in the performance of the system in two ways. On the one hand, the overheating of the dry fluid, which increases during the expansion, is used to evaporate additional preheated AM for the expansion and thus to increase the mass flow of the AM participating in the expansion. Otherwise the energy of the overheating of the exhaust steam would have to be dissipated through the condenser. In addition to this, the low-temperature heat source of the preheater is usually not fully utilized and can be better used due to the increased amount of fluid in the preheating.

Internal recuperation avoids two problems that normal recuperation has after the expansion. On the one hand, there is no additional pressure loss through internals after the expansion, which reduces the pressure level available for the expansion. Furthermore, a subsequent recuperation corresponds to a preheating of the AM, for which, however, there is usually already sufficient heat available at a low temperature level, which is why this reduces the amount of heat used compared to the available one.

b. Reduction of overheating of the exhaust steam

In addition to the positive effect on performance, it can also be achieved by limiting the components, e.g. of the steam-cooled generator, it may be necessary to lower the steam temperature. An increase in the mass flow would reduce the overheating of the AM, but cannot influence the fluid already present as live steam and thus represents a relatively sluggish control intervention. On the other hand, this can be achieved very quickly by the injection.

Since the overall heat balance is not affected by the bypass, this rapid regulation of the fresh steam temperature also requires readjustment by the mass flow. This is done by regulating the speed of the pump (on pumps that cannot be regulated in speed is related to Section III Fig. 3 received).

This cannot guarantee the temperature limits of components that are in the current expansion prior to direct injection (see Section II.)

c. Measurement of the parameters

1. 1. Vor der Einspritzstelle: modellprädiktive Ermittlung der einzuspritzenden Menge an AM anhand eines gemessenen Ist-Wertes. Es wird nicht gemessen, inwiefern sich nach der Einspritzung der geforderte Sollwert (=Maximalwert) auch einstellt.
2. 2. Nach der Einspritzstelle: "klassische" Regelung der einzuspritzenden Menge an AM durch Vergleich von Soll- und Istwert.

Two control strategies are conceivable for this:

1. 1. In front of the injection point: predictive determination of the amount of AM to be injected on the basis of a measured actual value. It is not measured to what extent the required setpoint (= maximum value) is also set after the injection.
2. 2. After the injection point: "classic" regulation of the amount of AM to be injected by comparing the setpoint and actual value.

Fig. 2 shows a second embodiment of the thermodynamic cycle device 200 according to the invention, the further compared to the first embodiment Features. The same reference numerals mean the same elements. A second supply device 50 is provided for supplying a third mass flow of the preheated working medium to the evaporated and superheated first mass flow of the working medium before its expansion in the expansion machine 30. The second feed device 50 comprises a second feed line 57 which is arranged between the preheater 10 or the first feed line 47 on the one hand and the inlet 32 or a third line 17 arranged between the evaporator 20 and the inlet 32 on the other hand. wherein the second feed device 50 comprises a second controllable throttle element 55, in particular a second thermostatic expansion valve, for regulating the third mass flow.

This measure has the effect described below.

II. Providing a direct injection of preheated fluids before expansion according to FIG. 2 to solve the remaining part of problem 1 (temperature limitation before expansion): a. Reduction of overheating of live steam

In addition to direct injection into the expansion machine (process control according to Fig. 1 ) a direct injection of preheated fluid into the live steam upstream of the expansion machine may be necessary - for example, if the temperature limits before the direct injection into the expansion machine are not otherwise ensured (process control according to Fig. 2 ) or if a reduction in overheating is necessary, but the real expansion ratio (through process control according to Fig. 1 ) should not be (further) lowered.

This strategy allows rapid regulation to the fresh steam temperature, which, as already described, would be too slow by the pump.

However, since the overall heat balance is retained through this measure, the regulation of the total mass flow must also take place, for example by increasing the pump output.

b. Measurement of the parameters

1. 1. Vor der Einspritzstelle: modellprädiktive Ermittlung der einzuspritzenden Menge an AM anhand eines gemessenen Ist-Wertes. Es wird nicht gemessen, inwiefern sich nach der Einspritzung der geforderte Sollwert (=Maximalwert) auch einstellt.
2. 2. Nach der Einspritzstelle: "klassische" Regelung der einzuspritzenden Menge an AM durch Vergleich von Soll- und Istwert.

Two control strategies are conceivable for this:

1. 1. In front of the injection point: predictive determination of the amount of AM to be injected on the basis of a measured actual value. It is not measured to what extent the required setpoint (= maximum value) is also set after the injection.
2. 2. After the injection point: "classic" regulation of the amount of AM to be injected by comparing the setpoint and actual value.

Fig. 3 shows a third embodiment of the cycle device 300 according to the invention. The feed pump 70 is coupled to a drive train operated via the expansion machine 30, namely to the external motor 90; wherein the cycle process device further comprises a controllable recirculation device 80 for partially recirculating working medium from a high pressure side of the feed pump 70 to a low pressure side of the feed pump 70. The controllable recirculation device 80 comprises a line 81 from the high pressure side to the low pressure side of the feed pump 70, the line 81 being provided with a third controllable throttle element 82.

This measure has the effect described below.

III. Providing an adjustable recirculation around the feed pump in the event of an additional coupling of the feed pump to the external process according to FIG. 3 to solve the above-mentioned tasks 3 and 4:

In the event that the pump is also permanently linked to the process, the pump must be designed with a recirculation circuit (process control according to Fig. 3 ).

The disadvantage of this connection is that additional losses are generated by the recirculation around the pump. However, this is necessary in order to maintain the regulation of the mass flow with a fixed connection.

The pump must be dimensioned so that the lowest possible losses occur in the case of full load and sufficient control power is available at part load. Control power is necessary both for increasing the mass flow through the ORC circuit (e.g. in the event of excessive overheating) and for lowering the mass flow (e.g. available heat quantity is smaller than the heat quantity dissipated by AM or the fresh steam pressure that is set is above the evaporation pressure at the available one Temperature level).

There is also a division into a control with two components, in which the first bypasses the evaporator (bypass branches off before VD and feeds the fluid back to VD + ÜH), and the second, which regulates the mass flow (either by pump with a speed-adjustable motor or via recirculation control) by the evaporator, the advantage that sudden fluctuations and instabilities in the evaporation zone are avoided. This influence is briefly explained using the example of excessive overheating with the need to increase the mass flow:
The regulation of the pump / recirculation increases the mass flow, at the same time the direct injection is increased. As a result, the flow through the evaporator and superheater experiences only a small change in mass flow. As the different heat transfers in the evaporator / superheater react sensitively to changes in level, this measure helps to stabilize the process. In the event that only or also litigation according to Fig. 2 is used for control, their share of ṁ _{AM, DE is} slowly brought back to zero, so that overall a quick control intervention with rel. slow rates of change in the evaporator flow is achieved.

The illustrated embodiments are merely exemplary and the full scope of the present invention is defined by the claims.

Claims (15)

1. Thermodynamic cycle device (100, 200, 300), in particular an ORC device, comprising:

   a preheater (10) for preheating a working medium;

   an evaporator (20) for evaporating and superheating a first mass flow of the preheated working medium; and

   a volumetric expansion machine (30) for expanding the evaporated and superheated first mass flow of the working medium;

   a condenser (60) for condensing the working medium exiting said expansion machine (30); and

   a feed pump (70) for pumping condensed working medium to said preheater (10);

   characterized by

   a first supply apparatus (40) for supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in an expansion chamber of said volumetric expansion machine (30) between an opening and a closing of said expansion chamber.
2. Thermodynamic cycle device according to claim 1, where said first supply apparatus (40) comprises a supply inlet (48) of said expansion machine (30) and a first supply line (47) between said preheater (10) and said supply inlet (48).
3. Thermodynamic cycle device according to claim 2, where said supply inlet (48) is disposed in fluid communication with an expansion space of said expansion machine (30) at a predetermined volume range of said expansion space, and where during operation of said thermodynamic cycle device, working medium in said expansion space expands between an inlet (32) and an outlet (34) of said expansion machine (30).
4. Thermodynamic cycle device according to one of the claims 1 to 3, where said first supply apparatus (40) comprises a first throttle element (45), in particular a first thermostatic expansion valve, for controlling the second mass flow and/or where said first supply apparatus (40) comprises an injection device (41) at said expansion machine (30), in particular at said supply inlet (48).
5. Thermodynamic cycle device according to one of the claims 1 to 4, further comprising:
   a second supply apparatus (50) for supplying a third mass flow of the preheated working medium to the evaporated and superheated first mass flow of the working medium prior to its expansion in said expansion machine (30).
6. Thermodynamic cycle device according to claim 5, where said second supply apparatus (50) comprises a second supply line (57) arranged between said preheater (10) or said first supply line (47), on the one hand, and said inlet (32) or a third line (17) arranged between said evaporator (20) and said inlet (32), on the other hand.
7. Thermodynamic cycle device according to claim 5 or 6, where said second supply apparatus (50) comprises a second throttle element (55), in particular a second thermostatic expansion valve, for controlling the third mass flow.
8. Thermodynamic cycle device according to one of the claims 1 to 7, where said feed pump (70) is coupled to a drive train driven via said expansion machine (30); and where said cycle device further comprises:
   a controllable recirculation apparatus (80) for partially recirculating working fluid from a high pressure side of said feed pump (70) to a low pressure side of said feed pump (70).
9. Thermodynamic cycle device according to claim 8, where said controllable recirculation apparatus (80) comprises a line (81) from the high pressure side to the low pressure side of said feed pump (70), and where said line (81) is provided with a third throttle element (82).
10. Thermodynamic cycle device according to one of the claims 1 to 9, where a rotation of said expansion machine (30) can be coupled with a rotation of an externally running process; where, in particular, a shaft (31) of said expansion machine (30) can be coupled to an external drive train of a motor, either directly or indirectly via a transmission which can have freewheeling or shifting options.
11. Method for operating a thermodynamic cycle, in particular an ORC process, where said method comprises the following steps:

    preheating a working medium with a preheater (10);

    evaporating and superheating a first mass flow of the preheated working medium with an evaporator (20);

    expanding the evaporated and superheated first mass flow of the working medium in a volumetric expansion machine (30);

    condensing the working medium exiting said outlet (34) with a condenser (60); and

    pumping condensed working medium to said preheater (10) with a feed pump (70);

    characterized by

    supplying a second mass flow of the preheated working medium to the partially expanded first mass flow of the working medium in an expansion chamber of said volumetric expansion machine (30) between an opening and a closing of said expansion chamber.
12. Method according to claim 11, comprising the further step of:
    controlling the second mass flow and/or injecting the second mass flow into an expansion space of said expansion machine (30) between an inlet (32) and an outlet (34) of said expansion machine (30).
13. Method according to claim 11 or 12, further comprising:
    supplying a third mass flow of the preheated working medium to the evaporated and superheated first mass flow of the working medium prior to its expansion in said expansion machine (30); optionally with the further step of controlling the third mass flow.
14. Method according to one of claims 11 to 13, comprising the further step of:
    reducing a volume ratio of the expansion of the working medium expanded in the expansion machine by supplying the second mass flow of the preheated working medium in the expansion chamber.
15. Method according to one of the claims 11 to 14, comprising:
    coupling a rotation of said expansion machine (30) with a rotation of an externally running process; in particular by coupling a shaft (31) of said expansion machine (30) to an external drive train of a motor, either directly or indirectly via a transmission.

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