DE2654307C3 - Device for direct thermodynamic efficiency determinations on hydrostatic displacement machines - Google Patents

Description

10

a) The temperature difference measuring device has a switchable, adjustable gain element on;

b) The device contains two branches that are optionally acted upon by a switching valve with a pressure pot in at least one of the branches and a downstream choke in each branch or jointly for both Branches;

c) Temperature sensors are at least on the low-pressure side of the displacement machine and arranged in front of and behind the throttle or in the pressure pot.

2. Apparatus according to claim 1, characterized in that the changeover valve (5) is a pressure pot (6) and a throttle (7) connected in series upstream of the common drain (10) of both branches are.

3. Apparatus according to claim 1 or 2, characterized in that between the switching valve (16) with a high and a low pressure connection and the common adjustable throttle (21) of both branches each one branch with a pressure pot (14, 18) and one together with the Switching valve operated high pressure shut-off valve (19,20) is arranged.

4. Apparatus according to claim 3, characterized in that that the switching valve as a 4/2 way valve (16) with high pressure, low pressure and the two Branch connections in alternating connection, the high-pressure shut-off valves as non-return valves (19, 20) and the common adjustable throttle is designed as a flow control valve (21).

5. Device according to one of the preceding claims, characterized in that the circuit and their elements are arranged in or on a 5n common block (24), wherein alternately with the high or low pressure side connected bores (17, 18) and high pressure bores (27) close to one another but further away from Low pressure bores (10) are arranged. v>

6. Device according to one of the preceding claims, characterized in that a Recording (28) for the temperature sensor (31) on the low-pressure side of the displacement machine Switchable shut-off on the hydraulic fluid side (29) bo and a seal (30) and holder (32) for the partially inserted temperature sensor.

7. Device according to one of claims 1 to 5, -dadüfch characterized in that on the low-pressure side of the positive displacement machine in the flow area the hydraulic fluid is thermally insulated from other components and the environment The invention relates to a device for direct thermodynamic efficiency determinations on hydrostatic displacement machines with a temperature difference measuring and evaluation device for the high-pressure side taken from above the displacement machine and hydraulic fluid returned on the low-pressure side

One possibility for the thermodynamic determination of the effective wheel is in the journal »Ölhydraulik und Pneumatics 19 (1975) No. 2, pp. 91-95. There equations are given according to which from temperature and pressure differential measurements across the positive displacement machine the efficiency is calculated with the help of two material parameters of the hydraulic fluid used can be. Because the required values of the material parameters depend on the type, temperature, contamination and possibly also aging of the hydraulic fluid, a precise efficiency measurement is required a precise knowledge of these influencing factors is also required.

In DE-AS 12 26 334 a device is described with which the efficiency is measured according to a compensation method. Here, too, a partial flow of hydraulic fluid is taken from the displacement machine and passed through control valves, among other things, which have to be adjusted until the measuring device shows a zero value to be adjusted beforehand. Additional pressure measuring devices are used to determine the pressure present in the measuring device and the total pressure, the quotient of which is equal to the efficiency in the case of incompressible pressure fluids. With compressible hydraulic fluids, as practically imine. ¹ · are used in the field of oil hydraulics, additional significant corrections of the measurement result with the help of certain material parameters of the hydraulic fluid used are required. A certain period of time is also required for setting the zero value via the control valves, during which the operating state of the system must not change, otherwise a reliable compensation is not possible.

A disadvantage of the methods or devices mentioned is that the efficiency not only from the measurement results, but only with the help of other to be determined otherwise Material parameters can be determined. If these values are not known or not known reliably enough, is No or only an uncertain statement about the efficiency of the displacement machine is possible. Further the efficiency is not displayed directly, rather the measured values have to be converted or that Final result can be read from tables or diagrams.

A method and a device with a substance-independent determination of the efficiency direct display of the result is in the older, not yet pre-published German registrations P 25 43 237 and P 25 57 044 described. Then the efficiency is calculated as the quotient of two temperature differences determined the over the displacement machine and in the throttling and additional clockwise

Compression of hydraulic fluid taken on the high side can be measured.

The invention has for its object to provide a device that after connection to the Displacement machine to be measured directly evaluates the efficiency without additional evaluation or Corrective measures and regardless of the hydraulic fluid used and also indicates also allows completely delay-free continuous measurements and despite the simple structure high Reliability and accuracy guaranteed

According to the invention, this object is achieved by a device with the following features:

The temperature difference measuring device has a switchable, adjustable reinforcement element. the The device contains two branches with a pressure pot, which are optionally acted upon by a switching valve in at least one of the branches and a downstream Dr-jssel in each of the branches or jointly for both branches. The temperature sensors are at least on the low-pressure side of the displacement machine and arranged in front of and behind the throttle or in the pressure pot

In one embodiment of the invention, a switching valve, a pressure pot and a throttle are m series switched before the common flow of both branches, or it is between the switching valve with one High and a low pressure connection and the common throttle of both branches each with a branch a pressure pot and a high-pressure shut-off valve operated together with the switching valve arranged.

In a further embodiment of the invention, the switching valve is a 4/2 way valve with high pressure and Low-pressure and the two branch connections in alternating connection, the high-pressure shut-off valves as Check valves and the common adjustable throttle designed as a power source.

In one embodiment of the invention, the circuit and its elements are in or on a common block arranged, alternately connected to the high or low pressure side Wells and high pressure wells close together but further away from low pressure wells are.

The receptacle for the temperature sensor also has the low-pressure side of the displacement machine a switchable shut-off on the hydraulic fluid side and a seal and holder for the semi-inserted Temperature sensor on. or on the low-pressure side of the positive displacement machine in the flow area the hydraulic fluid is thermally insulated from other components and the environment Housing or conduit part that conducts heat to the hydraulic fluid and has a receptacle for one Temperature sensor disordered.

The advantages that can be achieved with the invention are siiid in particular the following:

The measurement result is immediate and independent of the respective hydraulic fluid without any further information Conversions or corrections are displayed as the actual efficiency of the displacement machine. the The entire measurement runs automatically from the acquisition of the measured values to the display of the result. Of the Connection of the measuring device is with only three connections - high and low pressure connection for the Removal of a partial flow of the hydraulic fluid and low-pressure side temperature sensor receptacle - quick and easy to manufacture. The high measuring frequency of the device with approx. 10 measurements per minute at intermittent and approx. 200 measurements per minute with continuous measurement is well above all bishcr known method and enables use even under highly fluctuating operating conditions.

Compared to the above-mentioned German applications P 25 43 237 and P 25 57 044 has a The device according to the invention also has the following advantages:

The starting temperature of the pressure change in the device is the same for motors and the same for pumps only by the amount of the loss-related temperature change different from the initial temperature on the displacement machine. Even with clearly temperature-dependent material parameters of the hydraulic fluid This means that there is none at all for motor measurements and only a negligibly small one for pump measurements Failure.

The alternating application of two branches within the device enables the closing and opening Shutdown of a branch with constant withdrawal of hydraulic fluid from the high pressure side of the System so that there are no pressure surges in this. Equipping the second branch with temperature sensors In addition, it allows the measurement frequency to be doubled, all other things being equal.

The arrangement of the temperature sensors on the low-pressure side of the displacement machine (A), in a pressure pot (B) and behind a throttle (C) provides the direct display of the sums of the temperature differences over the pump or motor (ATrm), over a throttle, required for the efficiency measurement (ATo) and with a throttle-free pressure change (ATKf) due to compression or expansion of the hydraulic fluid:

T ₁ 7, = I7 "+ 17p- \ T" - I7 "
7, 7 ,, = I7 "t lT _k . _t

As is well known, the temperature change of hydraulic fluids with throttling and pressure change in the pressure pot (A Tn or A Tk +) in the technically used pressure and temperature ranges is largely proportional to the pressure difference Ap applied. The parameter "starting temperature (T ^. 'Has in this case, although only a small one, but different for the two temperature changes to opposite influence on. For sufficiently small output temperature ranges (for. Example, for standard hydraulic oil T _n can) ± 5 K, this influence but at Efficiency measurements are practically neglected and the ratio A Th.iIA 77; can be regarded as constant.

As a result of the cyclical switching of both branches to r ^ inui flow or to additional pressure change in the pressure pot, only the throttle temperature ATo or the sum of the temperature changes ATi, + ATkt are present above the temperature sensors ß and C , here the former in the switching valve position I. the latter in the Position II. The amplification element according to the invention, connected in position 1 in each case, in the measuring device for the temperature difference Tc-Tb can now be set so that the following applies:

-T ₈ ), - (7V-Te) ₁

/ c = 1 + 1 IT ₁ ;.,;! / IT ".

This setting can be done manually, but also automatically by using the efficiency indicators the positions 1 are brought to match those of positions II. With already at the beginning With the adjustable measuring amplifiers, this setting can of course also be made on these themselves.

Then the efficiency is continuously in the position I only from the temperature differences Measured above the displacement machine and a throttle. These measurements are valid as long as how no impermissible parameter deviations occur. However, this can easily be done through short-term control measurements can be determined in a clocked process or by monitoring the inlet temperature or the like.

Efficiency measurements with a known k-factor are advantageously carried out with a simplified measuring device carried out without switching valve etc. with otherwise the same sensor arrangement.

The adjustability of the throttle enables the case by case or automatic adjustment of the hydraulic fluid flow, so that the pressure change over the Throttles and in the expansion device according to theory is equal to the change in pressure across the displacement machine.

The pressure pot is easily inserted between the switching valve and the throttle. If this Branch is separated from the high pressure side by actuating the switching valve, the between expands Switching valve and throttle located hydraulic fluid through the throttle, which because of the occurring very low volume flow no longer represents a flow resistance. The expansion effect will also achieved when, together with the switching valve, a high-pressure shut-off valve in front of the common Throttle of both branches is actuated and the hydraulic fluid in the pressure pot between the changeover and shut-off valve by means of a very small throttle that is constantly open or a switchable valve to the low-pressure side of the Displacement machine expands.

Such a circuit can be particularly advantageous with a 4/2 way valve as a switching valve and

form. The required joint actuation results from the function of the directional control valve and through the pressure change at the check valve automatically and the branch in question is also activated by the Check valve as a seat valve hermetically sealed on one side, so that regardless of the leakage of the Switching valve, no fault flow can occur in the pressure pot. With that all requirements are below Use simple and reliable standard components met

A flow control valve acting as a common throttle causes that the measuring current is kept constant regardless of the system pressure, so that it is reproducible Measurement conditions are possible without additional measures.

The described arrangement in a common block results in the shortest possible connections, low ones Masses and in the area of the expansion devices minimal temperature differences and thus negligible Heat transfers even without additional hydraulic fluid withdrawal. The pressure pots are included simply executed as bores in the block, the diameter of which is the same or - to take advantage of the low thermal conductivity of hydraulic fluids - greater than that selected for the connecting bores.

In addition, such a block is easier and more thermally insulated than a piped circuit.

The special design of the temperature sensor holder on the low rear allows the introduction of the sensor while the system is running, since in a first position the receptacle is blocked from the system while the probe is inserted and sealed up to a first stage and a second Position, the shut-off on the hydraulic fluid side is open and the sensor is fully inserted. the Conversely, withdrawal is also possible without interrupting operations.

Another possibility is the arrangement of the sensor on the outer wall, with input and Removal or replacement of the sensor is possible while the system is running.

If the hydraulic fluid connections are equipped with shut-off valves, plug-in couplings or the like are, is in connection with one of the described guide recordings of the total diuie Aiiseiiluß the device Possible at any time without interrupting operation while the system is running and at any operating pressure.

Several exemplary embodiments of the invention are illustrated in the drawings and are described below described in more detail. It shows

F i g. 1 shows a basic circuit diagram of a two-circuit alternating expansion device with switchover for continuous efficiency measurements,

F i g. 2 shows a circuit diagram of a device according to F i g. 1 with 4/2 way valve, check valve and flow control valve,

F i g. 3 shows a schematic embodiment according to FIG. 2 in block construction,

Fig. 4 an example of a low-pressure sensor holder according to FIG. 1 with barrier, and

5 shows an example of a low-pressure sensor holder according to FIG. 1 on the outside wall.

In Fig. 1, a switching valve 5 is connected to a high pressure side 1 of any displacement machine 2 with an internal leakage oil line 3 via a high pressure branch 4. Behind this lie in parallel an expansion device (not shown) with oin # »r vArctpllharpn nroosel 7 and a line 8 with an adjustable throttle 9, which have a common outlet 10 with a low-pressure connection 11 or a tank return 12.

Temperature sensor receptacles 13, 14, 15 for temperature sensors A, B, C are arranged on the low-pressure side of the displacement machine 2, in the expansion device 6 and behind the throttles 7, 9. The outputs of the temperature sensors A, B, C are at the inputs of the measuring amplifier 40, 41. The output of the measuring amplifier 41 is connected directly and the output of the measuring amplifier 40 is connected to a divider 44 with a display 45 via an adjustable amplifier 43 which can be connected to a relay 42. A control device 46 is connected to the relay 42 and the switchover valve 5.

In the illustrated position I of the switching valve 5, hydraulic fluid flows from the high pressure side 1 via the high pressure branch 4 and the switching valve 5 through the expansion device 6 and the throttle 7 and via the outlet 10 to the low pressure connection 11 or the tank return 12. Above the temperature sensors A and C is located where the temperature difference sum

ATd +

- AT _M

After switching the switching valve 5 into the

In position It, the expansion device 6 is disconnected from the high-pressure branch 4 and the hydraulic fluid contained in it expands via the throttle 7. At the same time, the hydraulic fluid now flows via the switching valve 5 through the line 8 and the throttle 9 to the outlet 10. Via the temperature sensors D and C is the temperature difference JTb + ATr.

■ Iber the MeO amplifiers 40, 41 and the divider 44 the efficiency is shown in the display 45 according to the following equations:

I '/' /, t 17,

17 ,, + 17 ,.

17 «l / u
I 7 "<17,

k \ T "
i / "ι i / ,,

I7 "I7 \,
k I7 "

II)

In the new position I of the switch-over valve 5> u is the expansion device 6 again flows through and thereby brought back to the temperature and filled with the hydraulic fluid, corresponding to the current plant condition. This process is referred to as rinsing in the following. Theoretically, thermal insulation would be required for the entire area from the temperature sensor receptacle 13 via the displacement machine 2 to the temperature sensor receptacle 15. Experience has shown that the heat transfers in the area of flowing hydraulic fluid are usually negligible. On the other hand, they must be strictly observed in the area of static hydraulic fluid.

For continuous measurements, the control device 46 initially prescribes further measurements Measuring clocks by adjusting the amplifier 43, the values of the display 45 in the positions I those adjusted to positions II. The control unit 46 is then switched off in position I and now continuously the efficiency according to the equations

50

4 (1

displayed.

The validity of the setting "k" of amplifier 43 can be checked at any time by temporarily switching on the control unit and comparing the efficiency values for positions I and II.

2 shows, behind the high pressure branch 4, a directional valve 16 (4/2 way valve with changeover circuit and actuation not shown in detail), two branches each consisting of a heat-insulated pressure pot 17, 18 and a check valve 19, 20 with a downstream common flow control valve 21 and in the pressure pot 18 an additional temperature sensor receptacle would take 14a. In addition, a return line 22 leads from the directional valve 16 to a connection 23 in the drain 10 behind the receptacle 15. The function of this device differs in the following points from the device according to FIG. B. from position I to position !! closes the check valve 19 and the expansion in the pressure pot 17 takes place via the directional valve 16 and the return line 22 to the outlet 10. The same applies when switching the directional valve 16 from II to I for the pressure pot 18 and the check valve 20. In this two-circuit ^ change The circuit is always on a defTeinpefaturfühler-Aüfhmen 14 or 14a'urid 15, the temperature difference ATp + ATr, while flushing is carried out in the other branch. The required common switchover (high pressure to - low pressure to - shutoff valve or high pressure to - low pressure to - shutoff valve open) takes place here by combining the high and low pressure control in the directional valve 16 and the pressure change at the check valves 19, 20 automatically Actuation of the directional control valve 116. The Stromrcgclvcntil 21 keeps the flow constant at a pressure drop-free value regardless of the pressure difference present. Continuous measurements according to FIG. 1 are possible in both valve positions.

For the measurement of the required temperature differences by means of tempera connected in pairs temperature sensor such as 13. Thermocouples, of course instead of the one receptacle 15 for each pair of sensors, a receptacle (not shown here) behind the Be arranged throttle

In Fig. 3, an embodiment in block design with a measuring block 24, a directional valve block 25 and a throttle valve block 26 is shown with unspecified thermal insulation. The circuit otherwise corresponds to Fig. 2. A particularly low-mass block design results if, instead of the separate directional valve block 25, the slide of the directional valve is arranged in the measuring block 24 and operated hydraulically. The pressure pots 17, 18 formed here by widened bores and a high-pressure feed bore 27 guided parallel to them are arranged close to one another. Due to the circuit, hydraulic fluid always flows into two of these bores (27 and 17 or 27 and 18), whereby, in conjunction with the thermal insulation (not shown), the measuring block 24 is largely kept at the inlet temperature of the hydraulic fluid. Between the expanded pressure fluid in the pressure pot bores 17 or 18 and iilici wiugcuuug lsi uic ιιιαΛίιΠύΐ

1 ci'iip'Ci aiut -

difference therefore only equals the expansion temperature difference and thus so small that during a measuring cycle only very low heat transfers and so that temperature changes of the expanded and static hydraulic fluid take place in the pressure pot.

Through a suitable coordination of the bore diameter and arrangement as well as the thermally conductive and insulating cross-sections can be achieved that result from the remaining heat transfers with the environment, the high pressure supply bean 27 and the throttle block 26, the walls of the Pressure pot bores 17 and 18 to a temperature that is only slightly different from the expansion temperature set so that practically no heat transfer takes place.

One of the pressure pot bores 17 or 18 is expedient for predominantly continuous measurements only designed as a simple hole

In Fig. 4 the low-pressure connection does not carry the displacement machine 2 shown in more detail, a connecting piece 28 with a ball plug 29 and a Seal 30. A temperature sensor 31 is in the illustrated half-inserted position by a Upper nut 32 held. The ball plug 29 can now be opened because the hydraulic fluid in the

Connection piece 28 is separated from the environment via the seal 30 and the inserted temperature sensor 31. By screwing in the union nut 32, the temperature sensor 31 is now brought into the measuring position, not shown in detail. The sensor is removed in the opposite direction. The same effect of installing and removing sensors while the system is running can of course also be achieved with other elements not shown in detail, such as ι. IJ. Rotary or sliding sleeves with double sealing can be achieved.

In FIG. 5, between a low-pressure connection 33 the displacement machine 2, not shown in detail, and a low-pressure line 34 each via one

10

Heat insulation ring 35 flanged to a pipe section 36 which is as thermally conductive as possible and on the surface of which a preferably flat temperature sensor 37 is arranged. The pipe piece 36 is surrounded by an insulating jacket 38 which can be axially divided 1, 13. For use in pump measurements, a suitable swirl device 39 can be arranged in front of the measuring point in the low-pressure line 34, which then forms the feed line, in the flow direction in front of the measuring point in order to avoid disruptive wall influences. This is not necessary for engine measurements, since in this case the hydraulic fluid flows in a sufficiently swirled manner from the low-pressure connection 33 to the measuring points.

I liciv.ii 2 sheets of 'drawings

Claims (1)

Patent claims: 1. Device for direct thermodynamic efficiency determinations on hydrostatic Displacement machines with a temperature difference measuring and evaluating device for the over Hydraulic fluid withdrawn from the displacement machine on the high-pressure side and returned on the low-pressure side, characterized by the following features: Housing or line part (36) with a receptacle is arranged for a preferably flat temperature sensor (37).