WO2010009839A2

WO2010009839A2 - Steam circuit process device and method for controlling the same

Info

Publication number: WO2010009839A2
Application number: PCT/EP2009/005194
Authority: WO
Inventors: Jürgen Berger; Michael Bucher; Christian Bausch
Original assignee: Voith Patent Gmbh
Priority date: 2008-07-25
Filing date: 2009-07-17
Publication date: 2010-01-28
Also published as: WO2010009839A3; DE102008034977A1; US20110167823A1; EP2432973A2

Abstract

The invention relates to a steam circuit process device, comprising a reservoir for a liquid working medium; an evaporator in which the working medium is evaporated by heat supply, the vaporous working medium being fed to an expander for expansion and for carrying out mechanical work and being subsequently liquefied in a capacitor which communicates with the reservoir; a working medium pump for supplying working medium from the reservoir to the evaporator. The invention is characterized in that liquid working medium is supplied in the direction of flow of the working medium upstream or in the region of the capacitor to the working medium exiting the expander.

Description

Steam cycle process device and method for controlling the same

The invention relates to a steam cycle device and a method for controlling the same, wherein the steam cycle device in particular forms part of a vehicle drive or auxiliary drive in a vehicle.

Steam cycle processes, for example a Clausius-Rankine process, for generating mechanical power from a heat flow are known and can be driven, for example, by a separate burner unit in a combined heat and power device. For vehicles steam cycle processing devices are preferably used to use waste heat of an internal combustion engine, depending on the choice of the working fluid and the temperature control of the steam cycle as heat sources of the cooling water flow of the internal combustion engine or preferably their exhaust gas flow serve.

The CH 171813 describes a steam power plant with a steam cycle, in which, viewed in the flow direction of the working fluid, the following components are arranged one behind the other: a feed pump, an evaporator, a

Superheater, a steam turbine, a condenser and a working fluid container. In the flow direction in front of the steam turbine, a shut-off valve is arranged, by means of which the influx of vaporized working fluid to the steam turbine can be completely interrupted. Downstream of the feed pump, a first bypass is provided for branching off a partial flow of liquid working fluid. Furthermore, a second bypass is provided by means of which vaporous working fluid can be conducted past the steam turbine. Both bypasses can be connected to one another in a flow-conducting manner via corresponding control valves. In this case, the second bypass is always opened when the shut-off valve is closed in the supply line to the steam turbine and the steam turbine is to be stopped or when pressure peaks occur in the steam cycle as a result of closing the shut-off valve. Since in the case of closing the shut-off valve evaporated working fluid would rest in the supply line, the superheater would be destroyed due to the ever increasing heat input - because the heat energy to overheat the steam is not transmitted to the flowing working fluid and discharged from this. For this reason, when closing the shut-off valve, the control valves in the first and second

Bypass switched so that the vaporized working fluid remains in motion (flows) and is passed around the steam turbine. At the same time case is opened by opening corresponding control valves liquid working fluid from the first bypass downstream of the feed pump to the vaporized, guided past the steam turbine working fluid for cooling in the connecting line of both bypasses. The vaporized, bypassed working medium thereby collapses in the connecting line and is then fed via the second bypass to the condenser for further removal of heat. The two bypasses thus provide only a safety device to prevent the destruction of the superheater and continue to serve to reduce pressure peaks in the circuit due to the closing of the valve in the live steam supply to the expander. With this arrangement, no power control of the expander is expressly provided.

For power control of steam cycle processes, a regulation of the volume flow of the working fluid to the evaporator is proposed by DE 102 29 250 A1. This requires a working fluid pump with variable delivery volume to set a predetermined volume flow and / or pressure setpoint for the working fluid in the supply line to the evaporator. To realize this requirement, the working fluid pump can be assigned a variable-speed drive, which makes an electric motor necessary for an electrically operated pump, but which is disadvantageous for a vehicle drive due to the required Bauraumerfordemisses. Furthermore, this represents an additional electrical load. If the steam cycle process device is part of a vehicle drive with an internal combustion engine, then alternatively the working fluid pump can be driven by a variable speed clutch from the internal combustion engine. However, this is also Solution structurally complex, unfavorable in terms of efficiency and requires space for the additional control clutch.

Further controls for the volume flow of the working fluid in the supply line to the evaporator are known from US 4,573,323 and US 4,020,637. From the first-mentioned document, an arrangement of several pumps is apparent, remove the working fluid from a reservoir or from an intermediate container, which is arranged between an evaporator and a superheater for the vapor phase of the working fluid. One of these pumps is designed as a controllable injector pump, which is preceded by a pump driven at a constant speed, the delivery volume is a function of the input-to-output pressure difference. Depending on the setting of the injector pump either working fluid from the intermediate container or the reservoir of the subsequent pump is supplied. With this particular intended for the start of operation of the steam cycle process device, it is not possible to precisely adjust the flow rate of the working fluid to the evaporator in terms of power control for the steam cycle.

From the aforementioned US 4,020,637 a steam cycle apparatus is known, which is driven by a burner unit. Part of the mechanical power generated at the expander is used to drive pumps for the working fluid to the evaporator and for the fuel supply to the burner unit. By this measure, there is a balance between the power output on the expander and the necessary steam supply in normal operation, which in turn depends on the pressure in the working fluid line and the burner temperature. If a disturbance of this equilibrium occurs, valves are opened in bypass lines on the pumps, which allow a recirculation of the working fluid or of the fuel to the pump input side. The valves in the bypass lines function as directional valves, that is, as switches that can assume an on and an off state. Furthermore, lie in the

Bypass lines restrictor to maintain the pressure drop across the pump. Due to the design of the disclosed bypass lines in the case of the opening of the bypass line, only a pressure peak degraded, so that the disclosed device does not allow control of the volume flow and / or pressure of the working fluid in the supply line to the evaporator along a setpoint curve, instead, the measures described above are taken only in the case of overpressure. The same applies to the pump device in the supply line to the burner.

The published patent application DE 195 24 171 A1 describes a low-temperature engine (refrigerating machine) for driving working machines with a gas as working fluid. In this case, liquid gas is conveyed by means of a pump and fed to an evaporator. The vaporized gas performs work in a flash machine and is subsequently cooled and liquefied in a flash (condenser). The liquefied working fluid is then fed to a fluid collector (tank) and conveyed from there via the pump again. Furthermore, a bypass is provided, seen in the flow direction of the working fluid behind the pump, branches off a part of the liquid working fluid and this the already relaxed, cooled and thus liquid working fluid flowing from the condenser, supplies. Thus, a portion of the working fluid flowing out of the pump is supplied directly to the fluid collector.

Alternatively, the working fluid pump rotatably from the

Internal combustion engine to be driven. In such a drive, the working fluid pump runs in response to the internal combustion engine speed, so that the funded working fluid flow is proportional to the speed of the internal combustion engine. In order to obtain a sufficiently high working medium volume flow for feeding the evaporator or the expander even at low to medium engine speeds, correspondingly larger-sized pumps are used. However, this also means that due to the torsionally rigid coupling at maximum speeds of the engine, a correspondingly high working medium volume flow to the evaporator is generated. The subsidized by the working fluid pump Working medium volume flow is thus significantly greater than the required volume flow for the evaporator or the expander.

Since thus the delivery volume flow is always proportional to the engine speed and not to the accumulating amount of heat, with this system no optimal management of the steam parameters possible. Due to the non-optimal process control, the amount of heat to be dissipated by the condenser increases in relation to the net power of the steam process. This is particularly disadvantageous in the use of the steam cycle device in a motor vehicle, since there the available space is limited and larger and heavier components lead to higher fuel consumption.

The invention has for its object to provide a Dampfkreisprozessvorrichtung and a method for controlling the same, which make it possible, especially for applications in a motor vehicle or its drive train, the capacitor smaller and lighter than previously run. Preferably, at the same time can be dispensed with a separate, variable-speed adjustable drive machine for the working fluid pump and yet the delivery volume of the evaporator or expander supplied working fluid for the purpose of power adjustment made variable, or the pressure of the working fluid in the supply line to the evaporator can be adjusted according to a target specification , In this case, a structurally and production-technically simple solution is sought, which takes up a small space and also works energy-efficient.

The object according to the invention is achieved by a steam cycle device and a method according to the independent claims. The dependent claims represent preferred embodiments of the invention.

The inventors have recognized that by branching off at least part of the working medium volume flow upstream of the working medium pump and feeding the diverted part to the working fluid leaving the expander downstream, reduces the Wärmeabführfläche and the capacitor can be structurally made smaller.

A steam cycle device according to the invention comprises a reservoir for a liquid working fluid and an evaporator in which the working fluid is vaporized by supplying heat, the vaporous working fluid being fed to an expander for relaxation and mechanical work and subsequently liquefied in a condenser communicating with the reservoir stands. According to the invention, a working fluid pump for supplying working fluid from the reservoir to the evaporator is provided. In this case, in the working fluid flow direction before or in the region of the condenser, liquid working fluid is supplied to the working fluid emerging from the expander.

Even if the invention can be used particularly advantageously in motor vehicles, especially rail, truck or passenger cars, it is also conceivable to use the steam cycle apparatus according to the invention or the control method according to the invention in other mobile devices or stationary systems, in particular for exhaust gas energy recovery in industrial plants. For example, the expander could then be used to drive aggregates.

Particularly advantageous is a bypass line for supplying the liquid working fluid is provided, which establishes a connection between an output side of the working fluid pump and an input side of the capacitor. In this case, the bypass line, for example, open directly in the pressure chamber of the working fluid pump, so be disposed within the working fluid pump or in a connecting line to the evaporator. Likewise, the other end of the bypass line may open directly in the condenser or in a line in the working direction before the condenser.

A further, preferred embodiment provides that the bypass line opens with its one end in a line between the expander and the condenser. Such an orifice may for example be designed as a T-shaped connecting pipe. But other forms are conceivable.

Furthermore, an embodiment is preferred in which the bypass line opens with its one end directly in the expander. The mouth can, for example, in

Outlet area, so be provided downstream of the expansion space of the expander, so that the supply of liquid, passed by the evaporator working fluid takes place in the expander.

According to the above embodiments, the working medium supplied via the bypass line to the outlet of the expander or to the inlet of the condenser is essentially in a (single) physical state, namely the liquid state. In this case, a single state of aggregation means that it is assumed that the state variables of the working medium can not change suddenly, as described e.g. in the case of cavity. The mixture of the liquid phase of the branched off via the bypass line working fluid with the vaporous phase of the exhaust steam of the expander takes place only in the exhaust steam of the expander leading line or in the condenser.

The supply of liquid, diverted from the evaporator working fluid to the expander leaving, usually completely vaporous working fluid has the advantage that the steam is condensed or at least partially liquefied. The collapse of the vapor at the point of supply of the liquid working fluid results in an improved heat transfer and a reduced volume of working fluid flowing from the expander into the condenser, so that the heat transfer surface can be made smaller to dissipate the waste heat in the condenser. As a result, at least the same amount of heat as in conventional larger capacitors without supply of liquid working fluid can be dissipated in the capacitor despite smaller dimensions. Particularly advantageously, in the region of the supply of the liquid working medium to the expander leaving working medium, the liquid surface of the liquid working medium is increased. An enlargement of the liquid surface can be done for example by atomizing the branched liquid working medium. For this purpose, for example, air can be supplied to the liquid working medium in the manner of an aerosol, so that a spray mist is formed. Such atomization can be done for example by means of a Venturi nozzle. Also, only by means of high pressure, the liquid working fluid can be transferred through a suitable nozzle in a kind of spray. The advantage of atomization also lies in the fact that the working fluid leaving the expander is better mixed with the supplied liquid working fluid.

It is also conceivable to wet the tube carrying the vapor in the region of the merging of liquid and vaporous working medium on the inside with liquid working medium.

In the bypass line, a controllable valve may be provided, by means of which the pressure and / or flow rate of the working medium in the supply line to the evaporator (indirectly) is controlled / controlled. In this case, the amount of working fluid, ie, the volume flow of the (liquid) working medium flowing into the evaporator is varied as a function of the temperature of the (vaporous) working medium leaving the evaporator, by diverting a certain partial volume flow of liquid working fluid, bypassing the evaporator and bypassing the evaporator, the outlet of the expander or the inlet of the capacitor is supplied. The diverted volume flow can be adjusted, for example, by changing the opening cross-section of the controllable valve. In other words, the opening cross section of the valve in the bypass line is varied as a function of the temperature of the working fluid leaving the evaporator in order to evaporate more or less liquid working fluid. As a result, an inflow control, ie an indirect Adjustment of the pressure or volume flow of the vaporized working fluid as a function of the liquid working medium achieved.

For this purpose, appropriate sensors may be provided, the (current) sizes of the working fluid (pressure, temperature, subsidized or on the

Bypass line diverted volume or mass flow) of the working fluid in the flow direction of the working fluid before and / or after the evaporator or in front of the expander record and transmit them for evaluation via suitable lines to a corresponding control / control device. Of course, these sensors can be in the evaporator, expander or the corresponding

Connecting lines to the evaporator or expander itself be introduced.

By means of the regulating / control device, the pressure and / or volume flow of the vaporous working medium produced in the evaporator can be adjusted or varied to the expander depending on the power requirement on the expander. In this case, the volume flow and / or pressure profile of the working fluid in the supply line to the evaporator (and thus the flow and / or pressure profile of the vaporized working medium to the expander) follow a predetermined setpoint curve, which can be adjusted via the control / regulating device. As a result, the waste heat utilization of the internal combustion engine for each operating point of the

Internal combustion engine can be optimally used. For example, at an operating point of the internal combustion engine in which relatively much heat is obtained (high engine load, high engine speed) of bypassed via the bypass liquid working fluid flow to the expander emerging from the working medium (steam) are supplied, whereby the vapor collapses and liquefied.

Such a regulation / control can preferably always, ie during operation of the internal combustion engine and especially when relatively particularly much waste heat, take place. In a method according to the invention for controlling a steam circuit process device, the working medium volume flow conveyed by the working medium pump varies independently of a desired value for the pressure and / or the volume flow of the working medium to the evaporator, and the working medium volume flow supplied to the evaporator and / or expander is regulated and / or controlled by a part of the working medium volume flow from the working fluid pump is supplied to the emerging from the expander working fluid and thus does not enter the evaporator.

Preferably, the amount of the part of the working medium volume flow

(Partial volume flow) from the working fluid pump, which is supplied to the emerging from the expander working fluid is adjusted in dependence on the temperature of the exiting the evaporator working fluid. This means that the height of the partial volume flow can be adjusted by means of the opening cross section of the controllable control valve and depending on the temperature of the vaporized or superheated working fluid after the evaporator.

The invention will be explained below by way of example with reference to embodiments and the accompanying figures.

Show it:

FIG. 1 schematically simplifies an embodiment of a steam cycle device according to the invention.

Figure 2 shows a further embodiment of an inventive

Dam pfkreisprozessvorrichtu ng.

FIG. 1 shows schematically the basic components of a steam cycle device. From a reservoir 5 liquid working fluid is pumped by means of a working fluid pump 1 to the evaporator 2. In the evaporator 2, the evaporation of the working fluid, wherein the necessary for this thermal energy is supplied from a burner unit, not shown in detail. Particularly preferably, the steam cycle device is part of a vehicle drive with an internal combustion engine whose waste heat heats the working fluid in the evaporator 2. In particular, the exhaust gases of an internal combustion engine come into consideration, wherein the components necessary for the simplification of the representation are not shown in detail in Figure 1. The evaporator 2 can be constructed in several stages, in particular, a superheating unit for the vapor phase can be provided.

The working fluid is supplied in the vapor state from the evaporator 2 to the expander 3 via a line 8 in which this performs mechanical work under relaxation. Following the expander 3, the working fluid in the condenser 4 is liquefied and returned to the reservoir 5.

The expander 3, which can also be generally referred to as a steam-driven engine, is designed, for example, as a piston engine, steam turbine or centrifugal machine.

As a preferred working fluid pump 1, an internal gear pump is used, the speed of which is set independently of the volume flow specification in the supply line to the evaporator 2.

In the region of the output side of the working fluid pump 1, a bypass line 7 is provided, which opens with its one end in the condenser 4 and thus mixes liquid working fluid with the flowing from the expander 3 in the condenser 4 vaporous working fluid. The bypass line 7 comprises a valve 6, which may be designed, for example, as a controlled overflow valve or pressure relief valve. It may also be an electrically, electromagnetically, pneumatically or mechanically operable Proportional valve act. The valve 6 can be actuated, for example, by a central control unit, such as an on-board computer.

Also, suitable sensors may be arranged for receiving pressure in the valve 6 and / or in the bypass line 7, which send signals for control or control to a central control unit.

FIG. 2 shows a further exemplary embodiment of a steam cycle device according to the invention, wherein the same reference numerals as in FIG. 1 are used for matching components. For the illustrated

Embodiment empties the bypass line 7 in a line 8, which expander 3 and capacitor 4 connects working medium conducting each other. Thus, in the present case, the bypass line 7 discharges directly into the line 8 leading from the expander 3, where the liquid phase from the bypass line 7 mixes with the substantially vaporous phase of the working medium (exhaust steam from the expander 3). The connection point can be designed, for example, as a T-shaped connecting tube. In the bypass line 7 facing part of the connecting tube, a nozzle may be provided which atomizes the liquid working fluid from the bypass line 7. The nozzle may also be arranged in the bypass line 7. Through the nozzle should a

Magnification of the liquid surface of the liquid working fluid take place, so that the expander 3 leaving, the vaporous working fluid cools faster when it hits the liquid droplets of the atomized working fluid. Atomization can be carried out, for example, by sucking in or supplying air, such as ambient air. It is of course also conceivable to apply the branched liquid working fluid from the bypass line 7 in the connecting pipe or in the feed line by wetting on the inner sides of the line 8 or the connecting pipe.

Furthermore, a variety of embodiments are conceivable, the basic principle remains the same: The working fluid is at the outlet of the working fluid pump 1 or downstream of the working fluid pump 1, before or in the area branched off the evaporator 2 and fed to the vaporous working fluid of the expander 3 for cooling.

LIST OF REFERENCE NUMBERS

Working medium pump

Evaporator

expander

capacitor

reservoir

Valve

bypass line

management

Claims

claims

A steam cycle apparatus comprising 1.1 a reservoir (5) for a liquid working fluid; 1.2 an evaporator (2) in which the working fluid is evaporated by supplying heat, wherein the vaporous working fluid is supplied to an expander (3) for relaxation and performance of mechanical work and subsequently liquefied in a condenser (4) connected to the reservoir (5) communicates; 1.3 a working fluid pump (1) for supplying working fluid from the reservoir (5) to the evaporator (2); characterized in that

1.4 in the working fluid flow direction before or in the region of the condenser (4) liquid working fluid is supplied to the expander (3) exiting working fluid.

2. Dampfkreisprozessvorrichtung according to claim 1, characterized in that for supplying the liquid working fluid, a bypass line (7) is provided which a connection between the output side of the working fluid pump (1) and the input side of

Condenser (4) produces.

3. steam cycle device according to claim 2, characterized in that the bypass line (7) opens with its one end in a line (8) between the expander (3) and the condenser (4).

4. steam cycle device according to claim 2, characterized in that the bypass line (7) opens with its one end in the condenser (4).

5. steam cycle device according to claim 2, characterized in that the bypass line (7) opens with its one end in the expander (3).

6. steam cycle device according to one of claims 2 to 5, characterized in that in the bypass line (7), a valve (6) is arranged, by means of which by changing the working medium volume flow through the bypass line (7) of the pressure and / or flow of not through the bypass line (7) diverted working fluid to the evaporator (2) is controllable or controllable.

7. steam cycle device according to claim 6, characterized in that a control / control device is provided, by means of which the opening cross section of the valve (6) is adjustable, such that the

Volume flow and / or the pressure profile in the supply line to the evaporator (2) follows a predetermined setpoint curve, which results from the power requirement on the expander (3).

8. Dampfkreisprozessvorrichtung according to claim 6 or 7, characterized in that at least one pressure, volume, mass flow and / or temperature sensor is provided which receives the corresponding size of the leaving the evaporator working fluid and at least one line to the rule / Transmitted control device, so that the volume flow and / or the pressure curve in the supply line to

Evaporator (2) in dependence of the temperature of the evaporator (2) leaving working fluid is adjustable.

9. A method for controlling a Dampfkreisprozessvorrichtung according to at least one of claims 1 to 8, characterized in that the of the working fluid pump (1) funded working fluid flow independently of a setpoint for the pressure and / or the flow rate of the working fluid to the evaporator (2) varies, and the working medium volume flow supplied to the evaporator (2) and / or expander (3) is regulated and / or controlled by a part of the

Working fluid flow from the working fluid pump (1) from the expander (3) exiting working fluid is supplied.

10. The method according to claim 7, characterized in that the liquid working fluid is atomized before or during the supply to the expander (3) emerging working fluid.

11. The method according to claim 7, characterized in that at the point of merging liquid and the expander (3) leaving the working medium, the inside of the line (8), which carries the working fluid from the expander (3), takes place with liquid working fluid.

12. The method according to any one of claims 9 to 11, characterized in that the amount of the part of the working medium volume flow from the working fluid pump (1), which is supplied to the expander from the expander (3) emerging working fluid, depending on the temperature of the evaporator ( 2) exiting working fluid is set.

13. Drive unit for a vehicle, comprising

13.1 a steam cycle device according to one of claims 1 to 6;

13.2 an internal combustion engine whose exhaust gases are supplied to the evaporator (2) for heating and / or evaporation of the working fluid; characterized in that

13.3 the internal combustion engine, the working fluid pump (1) at least indirectly drives.