DE102016218937A1 - Method for operating a system for carrying out a thermodynamic cycle, system for carrying out a thermodynamic cycle and arrangement with such a system and an internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating a system (3) for carrying out a thermodynamic cycle, wherein an expansion device (13) of the system, a lubricant for lubricating the expansion device (13) is supplied, wherein one of the expansion means (13) supplied amount of lubricant by means of at least one Control valve means (33, 33 ', 33' ') is set, and wherein a lubricant quality of the lubricant on the basis of the expander (13) supplied amount of lubricant and a state of the at least one control valve means (33, 33', 33 '') is monitored.

Description

The invention relates to a method for operating a system for carrying out a thermodynamic cycle, a system for carrying out a thermodynamic cycle, and an arrangement with such a system and an internal combustion engine.

Such a system for carrying out a thermodynamic cycle process has an expansion device, which is supplied to the lubrication lubricant during operation of the system. It is possible that during operation of the system the lubricant is contaminated by a working medium flowing along a working medium circuit of the system, for example by condensing working medium in a separator for separating liquid lubricant from vaporous working medium, or by transferring and / or leaking working medium into the working medium Lubricant circuit in the area of the expansion device. If working medium enters the lubricant, its viscosity and thus its lubricating properties are reduced. It then threatens signs of wear or damage to the lubricated components. In order to avoid this as far as possible, it is desirable to be able to monitor lubricant quality of the lubricant during operation of the system and, if necessary, to be able to take measures to respond to reduced lubricant quality.

The invention has for its object to provide a method for operating a system for performing a thermodynamic cycle, such a system and an arrangement with such a system and an internal combustion engine, said disadvantages do not occur.

The object is achieved by providing the subject matters of the independent claims. Advantageous embodiments emerge from the subclaims.

The object is achieved in particular by providing a method for operating a system for carrying out a thermodynamic cycle with the following steps: a lubricant for lubricating the expansion device is fed to an expansion device of the system, wherein a quantity of lubricant supplied to the expansion device is adjusted by means of at least one control valve device, and wherein a lubricant quality is monitored based on the amount of lubricant supplied to the expansion device and a state of the at least one control valve device. Characterized in that the control valve means for adjusting the amount of lubricant which is supplied to the expansion device, is used, whose state is dependent in particular on the viscosity of the lubricant. In particular, the lower the viscosity of the lubricant to adjust the control valve means for supplying a certain amount of lubricant in the direction of a closed state must be set. Therefore, the amount of lubricant supplied to the expansion device in conjunction with the state of the at least one control valve device constitutes an indicator of the lubricant quality. The lubricant quality can thus be monitored in a very simple manner, particularly preferably with already existing sensors. In particular, it is possible to determine if the viscosity of the lubricant is reduced by proportions of working medium in the lubricant, wherein suitable measures can be taken preferably on such a state.

Lubricant quality is understood to mean, in particular, a property of the lubricant, very particularly preferably its viscosity and / or its content of working medium.

A quantity of lubricant supplied to the expansion device is understood in particular to be a quantity of lubricant supplied per unit time of the expansion device, very particularly preferably a volume flow of lubricant to the expansion device.

In order to monitor the quality of the lubricant, in particular a quantity of lubricant currently supplied to the expansion device and an instantaneous state of the at least one control valve device are used, wherein in particular the amount of lubricant supplied and the state are each considered for the same time.

The fact that the lubricant quality is monitored means, in particular, that it is explicitly or implicitly checked, based on the quantity of lubricant supplied to the expansion device and the state of the at least one control valve device, whether the lubricant quality is suitable for safely lubricating the expansion device or if it has decreased in a relevant manner , although this does not necessarily require an explicit determination or determination of a directly indicating the lubricant quality size. On the contrary, it is basically sufficient to monitor the quantity of lubricant supplied to the expansion device on the one hand and the state of the at least one control valve device on the other hand and to react if necessary in a suitable manner, if these - in particular in combination with each other - determined values that suggest a significantly reduced lubricant quality.

A state of the control valve device is understood in particular to mean an adjustment of the control valve device and / or a value of a control variable for the control valve device. It is therefore possible, in particular to monitor the instantaneous setting of the control valve device itself. Alternatively or additionally, a control variable which is used to drive the control valve device can be monitored, the value of which then represents the state of the control valve device. In particular, the state designates a position of the control valve device between a fully open and a fully closed functional position.

It is possible that the amount of lubricant supplied to the expansion device is controlled by means of the control valve device.

However, it is particularly preferably provided that the amount of lubricant supplied to the expansion device is regulated with the at least one control valve device as an actuator to a desired amount of lubricant. In this case, the lubricant quality is monitored in particular on the basis of the desired lubricant quantity and the state of the at least one control valve device. Preferably, a volume flow control for the lubricant is realized. An actual amount of lubricant supplied to the expansion device is preferably determined by a flow measurement and / or a volumetric flow measurement.

The desired lubricant quantity is preferably determined as a function of an operating state of the expansion device, the operating state prescribing the lubricant requirement. The desired lubricant quantity can be determined in particular as a function of a rotational speed, a load and / or a temperature of the expansion device, preferably from a characteristic map.

Which state the at least one control valve device has, in particular how far it must be closed in order to regulate a certain setpoint lubricant quantity, depends very substantially on the viscosity of the lubricant. In particular, the at least one control valve device must be closed more and more with decreasing viscosity of the lubricant in order to regulate a certain setpoint lubricant quantity. Namely, the more intensively the highly viscous lubricant is mixed with the low-viscosity working medium, the more must the control valve device taper a flow cross section in order to maintain the required setpoint lubricant quantity, in particular a setpoint volume flow.

According to one embodiment of the invention, it is provided that a lubricant warning is output when the state of the at least one control valve device exceeds a first predetermined limit state in the direction of a closed control valve device. The lubricant warning may serve as an indication to an operator of the system that the lubricant will be diluted and reduced in viscosity. The lubricant warning may in particular be emitted optically, for example by a light signal, a symbol or a warning on a screen, acoustically, in particular by a warning tone, and / or in another suitable manner. Alternatively or additionally, it is preferably provided that a cleaning measure for cleaning the lubricant is initiated when the state of the at least one operating device has exceeded the first predetermined limit state in the closing direction.

The cleaning measure is preferably initiated automatically when the condition provided for this is met, or an operator of the system is issued a message on which this can perform the cleaning action manually. When comparing the state of the control valve device with the first specific limit state, the amount of lubricant supplied to the expansion device, in particular the desired lubricant amount, is preferably taken into account, since the state of the at least one control valve device, in particular in connection with the amount of lubricant to be adjusted or regulated, makes a statement with regard to Contamination and in particular the viscosity of the lubricant allowed. In order to take this into account, the first specific limit state is preferably determined, in particular in each case instantaneously, as a function of the lubricant quantity or desired lubricant quantity supplied to the expansion device, in particular instantaneous, in which case it can be read out in particular from a characteristic field.

According to one embodiment of the invention, it is provided that, when the state of the at least one control valve device exceeds a second specific limit state in the direction of a closed control valve device, the expansion device is shut down or the system is turned off. The fact that the system is shut down means, in particular, that a supply of heat to the working medium cycle is stopped and the system is completely shut down and put out of operation. In contrast, a shutdown of the expansion means in particular means that their speed is reduced to zero, wherein the working fluid circuit can be maintained otherwise. For example, it is possible that the working medium along a Bypassing path is passed around the expansion device, so that the expansion device itself is no longer supplied with working fluid. Incidentally, however, the working medium cycle is maintained, in particular, the working medium continues to be supplied with heat in the evaporator and withdrawn in the condenser heat. In this case, the lubricant can be cleaned, wherein the expansion device can be put back into operation when the lubricant is sufficiently cleaned. If this does not succeed within a predetermined time, the system can be shut down.

As has already been described for the first specific limit state, the second specific limit state is preferably also determined, in particular in each case instantaneously, as a function of the quantity of lubricant supplied to the expansion device or of the desired lubricant quantity, in particular read out from a characteristic field. The second specific limit state is in each case selected such that there is the risk of damaging the expansion device if it continues to be operated with the lubricant quality reduced according to the second specific limit state.

Preferably, in the context of the method, first a lubricant warning is issued, and / or a cleaning measure for cleaning the lubricant initiated when the state of the control valve means exceeds the first predetermined limit state, in which case, quasi in a further escalation stage, the expansion device is shut down or the system is turned off when the state of the control valve means exceeds the second predetermined limit state. In this case, it is also clear that the second specific limit state preferably corresponds to a more closed state of the control valve device than the first specific limit state, which in this respect rather corresponds to a further open position of the control valve device than the second specific limit state. This in turn corresponds to the consideration that the control valve device must be closed the further with a given lubricant volume flow, the lower the viscosity and therefore the higher the contamination of the lubricant with the working medium.

According to one embodiment of the invention, a lubricant warning is issued when the state of the at least one control valve device exceeds a third specific limit state in the direction of a closed control valve device. As already explained for the first and the second specific limit state, the third specific limit state is preferably determined as a function of the lubricant quantity or the desired lubricant quantity, in particular read out from a characteristic field. The third specific limit state preferably corresponds to a further open state of the control valve device as the first specific limit state, which in turn corresponds to a more open state than the second predetermined limit state. Thus, it is possible to realize the following escalation stages with the three different specific limit states: Preferably, a lubricant warning is first issued when the state of the control valve means exceeds the third predetermined limit condition, then a cleaning action for cleaning the lubricant is initiated in a next escalation stage, if the state of the control valve means exceeds the first predetermined limit condition, the expansion means then being shut down or the system shut down in a subsequent escalation stage when the condition of the control valve means exceeds the second predetermined limit condition. In this way, it is possible to react in a stepped manner and adapted to the particular operating situation of the system to a deterioration of the lubricant quality, in particular to an increasing proportion of working medium in the lubricant.

According to one development of the invention, it is provided that at least one viscosity parameter characteristic of the viscosity of the lubricant is detected, the at least one viscosity parameter being used in a comparison of the state of the at least one control valve device with at least one of the determined limit states.

This approach takes into account that the viscosity of the lubricant depends not only on the working fluid content in the lubricant, but also on other parameters, in particular a pressure and a temperature of the lubricant. Accordingly, the at least one viscosity parameter is used as a measure of what viscosity the working medium should have in the uncontaminated state under currently present conditions, on the basis of which information then actual contamination of the lubricant can be detected and detected with particular certainty and accuracy. Preferably, the at least one specific limit state is determined as a function of the at least one viscosity parameter. This represents a particularly simple, rapid and elegant possibility of taking into account the at least one viscosity parameter. In this case, it is possible, in particular, for the at least one specific limit state to be read from a characteristic field as a function of the at least one viscosity parameter. In particular, the at least one particular limit state then determined depending on the amount of lubricant, in particular the desired amount of lubricant, and the at least one viscosity parameter, in particular read out of a map.

The viscosity parameter used is / are preferably a pressure and / or a temperature of the lubricant, these values being particularly preferably detected in the immediate vicinity of the control valve device or on the control valve device itself. Alternatively or additionally, it is also possible to indirectly determine the at least one viscosity parameter, for example by detecting a pressure and / or a temperature of the working medium in the region of the expansion device as a measure of the viscosity parameter. It turns out that at the expansion device, the pressure and the temperature of the lubricant substantially coincide with the pressure and the temperature of the working medium.

According to one embodiment of the invention, it is provided that as a cleaning measure for cleaning the lubricant, a collecting container for the lubricant is at least partially emptied via a purge line in the working fluid circuit of the system. The collecting tank is fluidically connected via a filling line with a separator, which is adapted to separate liquid lubricant from vaporous working fluid in the working fluid circuit and supply the collecting container via the filling line. The expansion device is supplied in particular from the reservoir with lubricant, which serves in particular as a buffer for the lubricant. The separation device is preferably arranged downstream of an evaporator in the working medium circuit, and preferably upstream of the expansion device, that is to say in a region of the working medium cycle in which the working medium is preferably completely vaporous and particularly preferably superheated. This allows separation of liquid lubricant conveyed along with the working medium along the working fluid circuit from the vaporous working medium in the separation device. However, it is possible that in certain operating conditions, portions of the working medium are also liquid at the location of the separating device, for example when heating the system or sudden load jumps, which in particular lead to an increase in pressure and thus to a boiling point increase of the working medium, wherein condensate working fluid in the separator and can get into the collection container. In this way, the lubricant is contaminated by the working fluid. A cleaning of the lubricant is then possible by this is emptied from the reservoir via the purge line in the working fluid circuit, wherein the lubricant is performed together with the working fluid along the working fluid circuit, wherein the working fluid is re-evaporated in the evaporator. If there are operating conditions in the system again in which the working medium downstream of the evaporator is almost completely or completely vapor-shaped, preferably superheated, the purity of the liquid lubricant deposited in the collecting container increases successively, so that it is successively cleaned. The emptying of lubricant from the collecting container via the purge line can then be terminated preferably when the lubricant has been sufficiently cleaned.

It is particularly preferably provided that the cleaning measure is terminated depending on the state of the at least one control valve device. The expansion device is namely preferably also supplied during the cleaning measure with lubricant, wherein the viscosity increases successively due to the cleaning measure, so that the control valve device is opened again at a given lubricant volume flow. It is then possible, based on the state of the control valve device to determine when the lubricant has reached a sufficient lubricant quality, so that the cleaning measure can then be terminated.

The purge line preferably opens upstream of the evaporator, preferably upstream of a working medium conveyor, more preferably upstream of a condenser in the working medium circuit. It is then ensured that the liquid working medium reaching from the collecting container into the working medium circuit is again evaporated in the evaporator, so that it can be separated from the lubricant in the separating device.

The object is also achieved by providing a system for carrying out a thermodynamic cycle having a working fluid circuit with an expansion device. The system also includes a lubricator configured to supply lubricant to the expander. The system is characterized in that it is designed to carry out a method according to one of the previously described embodiments. In particular, the advantages that have already been explained in connection with the method are realized in connection with the system.

Along the working medium circuit are - especially in the order given in the flow direction of the working medium seen - a working media conveyor, a Evaporator, the expansion device and a capacitor arranged. In a manner known per se, the liquid working medium conveyed by the working medium conveying device is preferably vaporized in the evaporator, wherein it flows in vapor form to the expansion device, in which it is expanded, thereby performing mechanical work on the expansion device, so that in particular an output shaft the expansion device is driven. In particular, thermal energy, pressure energy and / or flow energy of the working medium are converted into mechanical work. From the expansion device, the expanded working fluid continues to flow to the condenser, where it is preferably re-liquefied. From the condenser, it then returns to the working fluid conveyor, so that the working fluid circuit is closed.

Downstream of the evaporator, and preferably upstream of the expander, there is preferably disposed a separator arranged to separate liquid lubricant from vaporous working medium, the separator being fluidly connected to a sump into which the liquid lubricant is directed. The expansion device is supplied by the lubricating device in particular from the reservoir with lubricant. The collecting container is in turn connected via a purge line to the working medium circuit, preferably upstream of the working medium delivery device, particularly preferably upstream of the condenser.

The lubricating device has in particular at least one control valve device which is set up to adjust, preferably to regulate, one of the expansion devices, in particular per unit of time supplied lubricant quantity - preferably a volume flow. For this purpose, a control device is preferably provided, which is operatively connected to the at least one control valve device for the control thereof, wherein in particular the control device is set up to carry out a method according to one of the previously described embodiments. Preferably, the at least one control valve device is associated with a volumetric flow meter, so that the volume flow of the lubricant can be measured by the control valve device and in particular can be used as an actual variable for the control. Furthermore, the system preferably has at least one viscosity parameter sensor, in particular a pressure sensor and / or a temperature sensor for detecting a measure of the viscosity of the lubricant, wherein in particular the pressure and / or the temperature of the lubricant can be detected as a measure of its viscosity.

It is possible that the lubricant is supplied to the expansion device in more than one lubricant flood, in particular in a plurality of separate lubricant floods. In this case, it is possible for a lubricant quantity fed in particular per unit time of the expansion device to be adjusted separately for each lubricant flow. In this case, preferably each flood is associated with a separate control valve device.

The system is preferably set up to carry out an organic Rankine cycle process (ORC process). Particularly preferably, the system is set up for the use of waste heat, in particular of industrial waste heat, very particularly preferably for the use of waste heat of an internal combustion engine. The system can be set up in particular for stationary use or for mobile use, for example in a motor vehicle.

The working medium used is preferably ethanol, an ethanol-water mixture, or an organic working medium other than ethanol, for example a fluorohydrocarbon or a chlorofluorocarbon.

As the lubricant, a synthetic ester is particularly preferably used.

The expansion device is preferably designed as a turbomachine, in particular as a turbine. Alternatively, the expansion device is preferably designed as a displacement machine or as a volumetric expansion device, in particular as a reciprocating piston engine, as a scroll expander, as a vane machine, or as a Roots expander. Particularly preferably, the expansion device is designed as a screw expander, in particular as an unsynchronized screw expander. Alternatively, it is also possible that the expansion device is designed as a synchronized or overhung screw expander.

The separation device is preferably oriented as a cyclone separator, wherein it particularly preferably has baffles through which the working medium and lubricant flow in the separation device can be deflected so that liquid portions bounce off the baffles and in this way can be separated from the vaporous medium flow. A cyclone ensures an efficient separation of liquid components while at the same time very low pressure loss.

It is possible that the output shaft of the expansion device is operatively connected to an electric machine, in particular a generator, so that the electric machine, in particular the generator, through which Expansion device is driven. Alternatively or additionally, it is also possible for the output shaft of the expansion device to be mechanically connected to an internal combustion engine, in particular a crankshaft of the internal combustion engine, in order to be able to supply mechanical power to the internal combustion engine from the expansion device.

Finally, the object is also achieved by providing an arrangement which has a system for carrying out a thermodynamic cycle according to one of the previously described embodiments and an internal combustion engine, wherein the internal combustion engine and the system are thermally connected to each other, so that waste heat of the internal combustion engine in the system can be used for the thermodynamic cycle. In particular, the internal combustion engine is preferably thermally connected to the evaporator of the system, so that this waste heat of the internal combustion engine can be supplied, in particular in the form of waste heat from the exhaust gas and / or from a coolant circuit of the internal combustion engine. The output shaft of the expansion device can be mechanically operatively connected to an electric machine or to the internal combustion engine, in particular its crankshaft.

In particular, with the method, the system and the arrangement, it is possible to reduce the performance-specific costs of such a system. In this case, damage to the expansion device by insufficient lubricant quality, in particular by insufficient lubricity of the lubricant can be avoided, the lubricity of the lubricant for all operating ranges of the expansion device can be ensured. It is implemented as a protection mechanism for maintaining the life of the expansion device, and there is a lower maintenance requirements and / or an increase in maintenance intervals for the internal combustion engine. The system and maintenance costs can be reduced.

The description of the method on the one hand and the system and the arrangement on the other hand are to be understood as complementary to each other. Features of the system or arrangement that have been explicitly or implicitly described in connection with the method are preferably features of a preferred embodiment of the system or arrangement, individually or in combination with each other. Procedural steps that have been explicitly or implicitly described in connection with the system or arrangement are preferably individually or in combination with each other steps of a preferred embodiment of the method. This is preferably characterized by at least one method step, which is due to at least one feature of an inventive or preferred embodiment of the system or the arrangement. The system and / or the arrangement is / are preferably distinguished by at least one feature which is caused by at least one method step of a method according to the invention or a preferred embodiment of the method.

The invention will be explained in more detail below with reference to the drawing. The single figure shows a schematic representation of an embodiment of an arrangement with a system for performing a thermodynamic cycle.

The single FIGURE shows a schematic representation of an embodiment of an arrangement 1 which is a system 3 for carrying out a thermodynamic cycle and an internal combustion engine 5 having, wherein the internal combustion engine 5 so thermally with the system 3 is operatively connected, that waste heat of the internal combustion engine 5 in the system 3 can be used to carry out the thermodynamic cycle.

The system 3 has a working media cycle 7 on, in which - seen in the order specified in the flow direction of a working medium - in succession a working media conveyor 9 , an evaporator 11 , an expansion device 13 and a capacitor 15 are arranged.

Liquid working fluid is removed from the working fluid conveyor 9 to the evaporator 11 promoted, where the working medium absorbs heat and is evaporated. The vaporous working medium flows from the evaporator 11 to the expansion device 13 where it is relaxed, where there is mechanical work on the expansion device 13 performed, which in particular an output shaft 17 the expansion device 13 is driven. The relaxed working fluid passes from the expander 13 to the capacitor 15 where it is cooled and in particular liquefied again. The working medium then flows from the condenser 15 back to the working media conveyor 9 so the working media cycle 7 closed is.

The working media cycle 7 is in the embodiment shown here with a surge tank 19 in fluid communication with the surge tank 19 preferably a pressure relief valve 21 assigned.

The internal combustion engine 5 is in particular with the evaporator 11 thermally connected, the evaporator 11 preferably, waste heat from exhaust gas and / or a coolant circuit of the Internal combustion engine 1 can be fed. It is possible that the evaporator 11 of exhaust gas and / or of coolant of the internal combustion engine 5 is flowed through.

The output shaft 17 here is mechanical with an electric machine 23 connected, so the electric machine 23 through the output shaft 17 that is, by the expansion device 13 , is drivable. The electric machine 23 is preferably designed as a generator. Thus it is ultimately with the arrangement 1 and in particular the system 3 possible, via the thermodynamic cycle electrical power from the waste heat of the internal combustion engine 5 to win.

The system 3 is in particular designed for carrying out an organic Rankine cycle (Organic Rankine Cycle - ORC). In this case, the working medium used is preferably an organic fluid, in particular ethanol, an ethanol-water mixture, or another organic fluid which is not ethanol, for example a fluorohydrocarbon or a chlorofluorohydrocarbon.

The system 3 has a lubrication device 25 which is set up to the expansion device 13 to supply with a lubricant, in particular to lubricate. Here are in particular three lubricant flooding 27 . 27 ' . 27 '' provided over which three different lubrication points, in particular two bearings 29 and a workroom 31 the expansion device 13 , Lubricant is supplied.

Each of the lubricant floods 27 . 27 ' . 27 '' is a control valve device 33 . 33 ' . 33 '' assigned, via which one of the expansion device 13 per unit of time over the respective lubricant flood 27 . 27 ' . 27 '' supplied amount of lubricant, in particular in the volume flow of the lubricant along the corresponding lubricant flood 27 . 27 ' . 27 '' set, preferably to a desired amount of lubricant, in particular a desired volume flow is controlled.

It is possible that the lubrication device 25 has only a single lubricant flood with a single control valve device. But it is also possible that the lubrication device 25 has two lubricant floods, or more than three lubricant floods, wherein each lubricant flow is preferably associated with a control valve device.

The control valve devices 33 . 33 ' . 33 '' are each variable with respect to a passage cross-section for the lubricant from a maximum open state to a maximum closed state. The state of the control valve devices, which is also referred to below as the opening state 33 . 33 ' . 33 '' also by a drive signal for the control valve devices 33 . 33 ' . 33 '' can be represented is for a given volume flow of lubricant depending on an instantaneous viscosity thereof. The lower the viscosity of the lubricant, the more fluid it is, the farther the control valve devices must be 33 . 33 ' . 33 '' be closed to set a given volume flow.

The state of the control valve devices 33 . 33 ' . 33 '' can therefore be used as a measure of the lubricant quality of the lubricant, especially since its viscosity may be reduced by contamination with working fluid.

The lubricant quality is therefore within the scope of a preferred embodiment of the method proposed here on the basis of the expansion device 13 Currently supplied amount of lubricant, in particular the flow rate, and a current state of at least one of the control valve means 33 . 33 ' . 33 '' supervised. In this way, it is easy, fast and with preferably already existing sensors possible to monitor the lubricant quality of the lubricant and to respond to a decreasing lubricant quality.

The control valve devices 33 . 33 ' . 33 '' are preferred as actuators of a control of the expansion device 13 over the lubricant floods 27 . 27 ' . 27 '' per unit time supplied amounts of lubricant, in particular the corresponding volume flows used. The setpoint lubricant quantities provided for this purpose are preferably dependent on an operating state of the expansion device 13 determined, in particular depending on their speed and their temperature. The lubricant quality is in particular based on the desired lubricant quantities and the states of the control valve devices 33 . 33 ' . 33 '' supervised. This can in particular for each of the lubricant floods 27 . 27 ' . 27 '' be carried out separately. In particular, a redundancy with regard to the monitoring of the lubricant quality can be achieved in this way. It is also possible that from the individual lubricant floods 27 . 27 ' . 27 '' ascertained information combined in a suitable manner, for example, be averaged to make a reliable statement regarding the lubricant quality.

In particular, an actual value for the expansion device 13 per unit of time supplied amount of lubricant, in particular for the volume flows in the lubricant floods 27 . 27 ' . 27 '' to obtain is preferred in every flood of lubricants 27 . 27 ' . 27 '' a volumetric flow meter 35 . 35 ' . 35 '' arranged. The Flow measuring devices 35 . 35 ' . 35 '' can be designed in particular as a flow meter. The measured values determined by them can in particular be used as actual values for controlling the expansion device 13 supplied quantity of lubricant used, but also to monitor the lubricant quality by these measurements with the respective states of the associated control valve devices 33 . 33 ' . 33 '' be compared. The monitoring of the lubricant quality can therefore be carried out additionally or alternatively to the determination of the setpoint values on the basis of the actual values.

On a decreasing lubricant quality can be reacted in various ways. In particular, it is possible to provide different escalation levels. So it is particularly possible that a lubricant warning is issued when the state of at least one of the control valve devices 33 . 33 ' . 33 '' exceeds a first predetermined limit state in the direction of a closed control valve device. The lubricant warning may in particular be issued optically, for example in the form of a warning light, in the form of a screen message, or in another suitable manner, or acoustically, for example as a warning tone, or in any other suitable manner. Alternatively or additionally, a cleaning measure for cleaning the lubricant can be initiated.

It is also possible that the expansion device 13 shut down or the system 3 is turned off when the state of at least one of the control valve means 33 . 33 ' . 33 '' exceeds a second specific limit state in the direction of a closed control valve device, wherein the second specific limit state, in particular a more closed state, ie a smaller passage cross-section, corresponds to the first predetermined limit state.

The expansion device 13 in particular, can be shut down by a first shut-off valve 37 closed and a second shut-off valve 39 is opened so that the working medium is no longer on the expansion device 13 but along a bypass path 41 is guided, in particular, the speed of the expansion device 13 can be lowered to zero. The working media cycle 7 but can be maintained otherwise, the working medium, bypassing the expansion device 13 along the bypass path 41 from the evaporator 11 to the capacitor 15 flows.

It is also a triple escalation stage possible, wherein first, when the state of at least one of the control valve device 33 . 33 ' . 33 '' exceeds a third predetermined limit state toward a closed control valve means, only a lubricant warning is issued, wherein when the state exceeds the first predetermined limit state, a cleaning action for cleaning the lubricant is initiated. If the state then also exceeds the second specific limit state, the expansion device becomes 13 shut down, or the system 3 will be turned off. The third specific limit state is further open, so has a larger passage cross section, as the first certain limit state. The first certain limit state is thus further closed, that is, has a smaller passage cross-section than the third certain limit state, but it is more open, so has a larger passage cross-section than the second certain limit state. Thus, with the three escalation stages mentioned here, it is possible in particular to graduate to an ever decreasing viscosity of the lubricant and react to the situation.

However, the viscosity of the lubricant does not depend solely on the contamination with working fluid, but on further viscosity parameters, so that preferably at least one characteristic of the viscosity of the lubricant viscosity parameter is detected, the viscosity parameter in a comparison of the state of at least one of the control valve means 33 . 33 ' . 33 '' is used with at least one of the specific limit states. In particular, the pressure and / or the temperature of the lubricant is / are preferably used as the viscosity parameter, preferably both the pressure and the temperature of the lubricant, which are preferably by means of a pressure sensor 43 and a temperature sensor 45 - here for all lubricant floods 27 . 27 ' . 27 '' be recorded together. But it is also possible that the individual lubricant floods 27 . 27 ' . 27 '' or groups of lubricant floods 27 . 27 ' . 27 '' separate pressure and / or temperature sensors are assigned. With the aid of the at least one viscosity parameter, influences on the viscosity of the lubricant, which are not attributable to contamination with working medium, can be observed and, in particular, calculated out, so that ultimately the contamination of the lubricant with working medium can be more accurately recognized.

Preferably, the at least one specific limit state is determined as a function of the at least one viscosity parameter, in particular read out from a characteristic field.

The determined limit states then shift properly with the pressure and / or the temperature of the lubricant to the due to these parameters changed viscosity of the same to take into account.

A once initiated cleaning measure is preferably dependent on the state of at least one of the control valve devices 33 . 33 ' . 33 '' ended, based on this state in particular also a re-increasing lubricant quality, that is, in particular a re-rising viscosity of the lubricant, in particular due to decreasing working media shares in the lubricant, can be detected.

It turns out that the lubrication device 25 here a collection container 47 for the lubricant from which the expansion device 13 is supplied with lubricant. This collection container 47 is fluidically with a separator 49 connected, which is set up to operate the system 3 to separate liquid lubricant from vaporous working medium, wherein the separating device 49 here downstream of the evaporator 11 and upstream of the expansion device 13 in the working media cycle 7 is arranged. Here is the sump 47 via a filling line 51 with the separator 49 fluidly connected.

For lubricating the expansion device 13 is a lubrication circuit 53 provided over which the lubricant from the sump 47 over the lubricant floods 27 . 27 ' , 27 '' the expansion device 13 is supplied. In this case, a first lubricant conveyor 55 , preferably a lubricant pump, which is then arranged and arranged to supply the lubricant along the lubrication circuit 53 to promote. Depending on the pressure conditions in the sump 47 on the one hand and at the lubrication points of the expansion device 13 on the other hand can also on the first lubricant conveyor 55 be waived. The lubrication circuit 53 also has a return path 57 on, over the lubricant from the expansion device 13 in the collection container 47 is traceable. For this purpose, preferably a second lubricant conveyor 59 in the return path 57 arranged. Downstream of the second lubricant conveyor 59 is in the return path 57 a check valve 61 arranged, which is in particular adapted to prevent lubricant in an undesirable manner from the collecting container 47 over the return path 57 to the expansion device 13 flows.

It is possible that in the lubrication circuit 53 cooling equipment 63 are arranged for cooling the lubricant.

In certain operating conditions of the system 3 For example, when heating the Arbeitsmedienkreislaufs 7 or in load jumps, which may in particular lead to a sudden increase in pressure and thus boiling point of the working fluid, it is possible that working fluid downstream of the evaporator 11 proportionally liquid present and thus in the separator 49 is separated together with the liquid lubricant of vaporous working media portions, whereupon it into the collection container 47 arrives. The lubricant is then mixed with working medium and diluted, whereby its viscosity decreases. At the same time, this also reduces the lubricating and sealing capability of the lubricant, leading to vapor breakdown and thus to a loss of power in the expansion device 13 can come, which is also threatened by damage due to lack of lubrication due to the reduced viscosity of the lubricant.

As a cleaning measure for cleaning the lubricant is preferably the collecting container 47 at least partially via a purge line 65 in the working media cycle 7 emptied, with the purge line 65 in the embodiment shown here upstream of the capacitor 15 in the working media cycle 7 opens. From the collection container 47 in the working media cycle 7 effluent liquid lubricant with liquid working media proportions thus becomes along the working fluid circuit 7 in particular to the evaporator 11 promoted, where the working medium is evaporated again, so it then in turn of the liquid lubricant in the separator 49 can be separated. It is possible, the collection container 47 successively to rinse and to clean the lubricant of Arbeitsmedien- shares.

In the flushing line 65 is preferably a first valve device 67 arranged over which the purge line 65 lockable and is releasable. By means of the first valve device 67 can the cleaning measure, thus flushing the sump 47 be initiated and terminated, in particular by the first valve means 67 first opened and later closed. It is preferably possible that the first valve device 67 is variable continuously or discretely between a fully opened state and a fully closed state.

The first valve device 67 Can also be used to provide a level control for the sump 47 to implement, in particular, lubricant from the sump 47 in the working media cycle 7 is drained when the level in the sump 47 exceeds a certain limit level.

Preferably, in the filling line 51 a second valve device 69 arranged through which the collecting container 47 with the separator 49 connectable and separable from this. The second valve device 69 is preferably designed as a three-way valve, through which the separator 49 alternatively to the collection container 47 also with a bypass 71 connectable, the downstream of the separator 49 back into the working media cycle 7 empties. It is then possible in certain operating states of the system 3 in the separator 49 separated liquid not the collection container 47 but immediately downstream of the separator 49 again the working media cycle 7 supply. This can happen especially when the working fluid in the working fluid circuit 7 for the most part or completely liquid, for example when starting the system 3 or when cooling the working fluid circuit 7 if the system 3 is turned off. Thus, in particular, an excessive contamination of the lubricant in the collecting container 47 be avoided with working medium.

The system 3 preferably has a control device, not shown here, which is configured to carry out one of the previously described embodiments of the method. The control device is preferably at least with the control valve devices 33 . 33 ' . 33 '' and the volumetric flow meters 35 . 35 ' . 35 '' , and preferably the pressure sensor 43 and the temperature sensor 45 operatively connected. It can also with the first valve device 67 , the first shut-off valve 37 , the second shut-off valve 39 , and / or the second valve device 69 be operatively connected so that they can be controlled by the control device.

The collection container 47 is preferably used in particular as a buffer for the lubricant to at any time a sufficient amount of lubricant for the lubrication of the expansion device 13 to provide.

The system 3 as well as the internal combustion engine 5 are preferably set up for stationary use, or for mobile use, in particular in a motor vehicle.

Overall, it turns out that with the method proposed here and the system 3 and the arrangement 1 It is possible to reduce the performance-specific costs of such a system. In particular, damage to the expansion device 13 be avoided by insufficient lubricating oil quality or lubricity of the lubricant. A lubricity of the lubricant can be used for all operating ranges of the expansion device 13 be ensured. It becomes a protection mechanism to maintain the life of the expander 13 provided. In addition, a lower maintenance susceptibility and an increase in the maintenance intervals for the system 3 and in particular the expansion device 13 realized. This also reduces the system and maintenance costs.

Claims (9)

Method for operating a system ( 3 ) for carrying out a thermodynamic cycle, wherein - an expansion device ( 13 ) of the system a lubricant for lubrication of the expansion device ( 13 ), wherein - one of the expansion means ( 13 ) supplied by means of at least one control valve device ( 33 . 33 ' . 33 '' ), and wherein - a lubricant quality of the lubricant based on the expansion device ( 13 ) and a state of the at least one control valve device ( 33 . 33 ' . 33 '' ) is monitored. Method according to claim 1, characterized in that that of the expansion device ( 13 ) supplied amount of lubricant with the at least one control valve device ( 33 . 33 ' . 33 '' ) is controlled as an actuator to a desired amount of lubricant, wherein the lubricant quality based on the desired amount of lubricant and the state of at least one control valve device ( 33 . 33 ' . 33 '' ) is monitored. Method according to one of the preceding claims, characterized in that when the state of the at least one control valve device ( 33 . 33 ' . 33 '' ) a first predetermined limit state towards a closed control valve device ( 33 . 33 ' . 33 '' ), a) issuing a lubricant warning, and / or b) initiating a cleaning action to clean the lubricant. Method according to one of the preceding claims, characterized in that when the state of the at least one control valve device ( 33 . 33 ' . 33 '' ) a second predetermined limit state towards a closed control valve device ( 33 . 33 ' . 33 '' ), the expansion device ( 13 ) shut down or the system ( 3 ) is turned off. Method according to one of the preceding claims, characterized in that at least one for the viscosity of the lubricant Characteristic viscosity parameter is detected, wherein the viscosity parameter in a comparison of the state of the at least one control valve device ( 33 . 33 ' . 33 '' ) is used with at least one specific limit state, wherein preferably the at least one specific limit state is determined as a function of the at least one viscosity parameter. Method according to one of the preceding claims, characterized in that as a cleaning measure for cleaning the lubricant, a collecting container ( 47 ) for the lubricant at least partially via a purge line ( 65 ) into a working medium cycle ( 7 ) of the system ( 3 ) is discharged, wherein the collecting container ( 47 ) fluidically via a filling line ( 51 ) with a separating device ( 49 ) arranged to deliver liquid lubricant from vaporous working medium in the working medium circuit ( 7 ) and the collecting container ( 47 ) via the filling line ( 51 ). Method according to one of the preceding claims, characterized in that the cleaning measure depends on the state of the at least one control valve device ( 33 . 33 ' . 33 '' ) is terminated. System ( 3 ) for carrying out a thermodynamic cycle, comprising - a working medium cycle ( 7 ), which is an expansion device ( 13 ), and with - a lubricating device ( 25 ) arranged to supply the expansion device ( 13 ) with lubricant, characterized in that the system ( 3 ) is arranged for carrying out a method according to one of claims 1 to 7. Arrangement ( 1 ), with a system ( 3 ) according to claim 8 and with an internal combustion engine ( 5 ), wherein the internal combustion engine ( 5 ) with the system ( 3 ) is thermally operatively connected, so that waste heat of the internal combustion engine ( 5 ) in the system ( 3 ) is usable for the implementation of the thermodynamic cycle.

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