GB1590369A

GB1590369A - Oil system

Info

Publication number: GB1590369A
Application number: GB2249078A
Authority: GB
Original assignee: Kuehnle Kopp and Kausch AG
Current assignee: Howden Turbo GmbH
Priority date: 1977-06-18
Filing date: 1978-05-25
Publication date: 1981-06-03
Also published as: DE2727432A1; DE2727432C3; DE2727432B2

Description

(54) AN OIL SYSTEM (71) We, AKTIENGESELLSCHAFT KUHNLE, KoPP & KAUSCH, of Friedrich-Ebert-Strasse 16, 6710 Frankenthal/Pfalz, Federal Republic of Germany, a joint stock company organised under the laws of the Federal Republic of Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a device for the limitation of rotational speed of an oil pump such as a turbine oil pump, which is driven by an auxiliary turbine and which generates preferably the control and/or lubricant pressure before and during the bringing up to speed as well as in a given case on the shutting down of a main turbine.

The protection of the oil supply is of decisive importance for the operational reliability of a steam turbine. Apart from the main oil pump, which is driven by the turbine shaft itself, an auxiliary oil pump is therefore provided, which secures the oil supply before and during the bringing up to speed as well as after the shuttingdown of the steam turbine. This auxiliary oil pump is as a rule constructed as a turbine auxiliary oil pump with a small steam turbine for its drive; this small turbine having permanent lubrication.Such a turbine oil pump, which maintains the oil pressure for bearing lubrication and in the hydraulic system for the opening of the steam valve only before and during the bringing up to speed as well as during the shutting-down of the turbine, as a rule generally has neither a rotational speed regulator nor a rotational speed trip mechanism to prevent excess rotational speed of the small steam turbine on a loss of load caused by a disturbance in the oil circuit.

A gearwheel oil pump, in which the conveyed quantity of oil is proportional to the rotational speed, is used in a conventional manner as an oil pump so that the steam feed and thereby the rotational speed of the driving turbine control directly the conveyed quantity and thereby the oil pressure. Apart from the control of the steam feed, it is also usual to limit the performance of the driving turbine by controlling the steam orifice. In oil pressure regulation by the steam feed as well as in performance regulation by controlling the steam orifice, over-rewing of the driving turbine cannot be avoided when the load from the gear wheel oil pump decreases and the driving turbine runs idle.This situation occurs when the oil pressure does not build up by reason of too large an oil delivery, which can for example be the case when a leakage is present in the oil circuit of the main turbine or too large a quantity of oil flows away in the case of bearing damage. This situation can also occur when an oil cooler is still empty while the turbine is up to speed or when the oil supply fails on the suction side of the oil pump.

According to the present invention, there is now provided an oil system comprising a rotary oil pump provided with a suction duct and a delivery duct, a turbine drivingly connected to the pump, and a Venturi in the delivery duct to limit the rotational speed of the turbine.

By incorporating the Venturi into the delivery duct, the pressure downstream of the Venturi falls off sharply, but the pressure upstream of the Venturi is maintained in the case of the oil delivery exceeding the normal conveyed quantity, be it through a leakage or through bearing damage or because the oil cooler is still empty.

Thereby, also the load conditions for the oil pump and the steam turbine driving it remain maintained.

The Venturi may be so dimensioned that the maximum quantity of oil conveyable through the Venturi exceeds the normal oil requirement by approximately 15%. Thereby, a relatively small pressure drop, which falls off sharply on the normal conveyed quantity being exceeded is maintained upstream of the Venturi and sets itself in normal operation downstream of the Venturi. Thereby, the oil pump is loaded by a load corresponding to the maximum conveyed quantity of oil so that the turbine runs on without the danger of over-revving only with a higher rotational speed corresponding with the increased decline of power.

A steam regulating valve may be arranged in a steam duct leading to the auxiliary turbine to throttle the steam feed with increasing pressure.

A control duct is connected between the steam regulating valve and the upstream side of the Venturi. If a fault such as an increased oil delivery on the delivery side and thereby a pressure drop should occur, the steam turbine is no longer acted upon by steam and cannot be driven at an excessive rotational speed.

Apart from a load loss through increased oil delivery on the delivery side, a load loss can however also occur through inadequate oil supply on the suction side. In order to protect the steam turbine against over-revving in such a case, a further steam regulating valve may be arranged in the steam duct leading to the auxiliary turbine and which is connected by a control duct to the delivery duct upstream of the Venturi. On rising oil pressure the further steam regulating valve opens the steam feed from a low rotational speed opening cross-section.

By this manner, the steam turbine in the case of inadequate oil supply on the suction side, be it in consequence of an empty supply container or a leakage in the suction duct, can be acted upon only by such a quantity of steam that does not suffice to drive the steam turbine at an excessive rotational speed in the case of insufficient loading and that enables the steam feed to be increased when the oil pump, supplied with oil and driven by the turbine, builds up a pressure in the delivery duct.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings in which:- Figure 1 shows a turbine oil pump without oil-pressure-dependent regulation of the steam feed, provided with a Venturi connected in a delivery duct, Figure 2 shows a turbine oil pump with an oil-pressure-dependent regulation of the steam feed, provided with a Venturi connected in a delivery duct, Figure 3 shows a similar turbine oil pump to that shown in Figure 2 and provided with a second parallel oil circuit, Figure 4 shows a turbine oil pump provided with a Venturi connected in a delivery duct, oilpressure-dependent regulation of the steam feed being effected by the use of a further steam regulating valve with a low rotational speed opening cross-section, and Figure 5 shows a section through a Venturi.

Referring now to the accompanying drawings, Figure 1 shows a part of an oil circuit, in which a supply container 10 for the oil is connected through a suction duct 11 to the low pressure side of a gear wheel pump 12. The high pressure side of this gear wheel pump is connected to a delivery duct 13 in which a non-return valve 14 and a Venturi 15 are arranged. The drive of the gear wheel pump 12 takes place with the aid of a small steam turbine 16 to which the quantity of steam required for the drive of the turbine is fed through a steam duct 17. A blocking valve 18 is provided in the steam duct. The expanded steam is led away from the turbine through a waste steam duct 19.

The turbine is preferably limited in respect of its maximum performance by corresponding dimensioning of a steam orifice. The combination of the gear wheel pump 12 and the steam turbine 16 is designated as a turbine oil pump.

The Venturi incorporated in to the delivery duct is illustrated in detail in Figure 5. The basic construction and operation of the Venturi is known. The Venturi comprises a pipe which narrows then gradually widens in the direction of flow and acts as a diffuser. The through flow quantity Q is equal to the product of the flow speed c and the cross-sectional area F1 of the throat of the Venturi. The flow speed c is greatest when the entire pressure drop is converted into speed between the pipe cross-section F2 at the inlet side and the throat F1. In that case, the pressure in the throat is nearly reduced to zero.

When due to too large an oil delivery on the delivery side or a leak in the delivery duct 13, the oil flowing through the Venturi attains the maximum flow speed in the throat, the quantity of oil flowing through the Venturi is at a maximum i.e. the quantity of oil conveyed by the oil pump through the Venturi cannot be increased further.

Since the conveyed quantity is proportional to the rotational speed of the pump, it follows that the maximum rotational speed of the pump is fixed by the maximum quantity of oil conveyable through the Venturi. Thereby, the pump even in the case of a heavy oil loss in the delivery duct 13 cannot convey more oil than is fixed by the maximum flow speed in the Venturi.

For an expedient application the maximum conveyable quantity of oil is preferably about 15% above the normal quantity of oil so that the pressure drop across the Venturi is as small as possible in normal operation. On the normal conveyed quantity being exceeded, the pressure downstream of the Venturi falls off sharply, but the pressure upstream of the Venturi is maintained so that the loading of the steam turbine 16 by way of the gear wheel pump 12 is maintained and so when a fault occurs the turbine merely increases its speed by at most 1 5So when the pump by reason of the oil loss in the delivery duct 13 conveys the maximum quantity of oil.

In order to protect the turbine if a fault should occur the regulation of the performance of the steam turbine takes place by regulating the steam orifice.

The embodiment shown in Figure 2 differs from that shown in Figure 1 in that an oil pressure regulation by way of regulation of the steam feed is provided. For this purpose, the Venturi 15 upstream of the throat is connected with a control duct 20 which leads to a steam regulating valve 21. This steam regulating valve is arranged in the steam duct 17 and is so designed that the quantity of steam feed to the steam turbine is regulated in dependence on the oil pressure upstream of the Venturi orifice.

When the maximum quantity of oil conveyable by the gear wheel pump through the Venturi by reason of the limitation which in this embodiment is also about 15% above the normal quantity of oil, is reached, the pressure regulation is hardly influenced by the Venturi. On the normal conveyed quantity being exceeded, the pressure downstream of the Venturi greatly falls off, which, however, has no effect upstream of the Venturi, since the pressure is substantially maintained. As a consequence, the steam turbine is loaded just as before by the gear wheel pump conveying oil under load so there is no danger of over-rewing. The steam turbine in the case of a fault occurring, runs with an excess rotational speed of less than 15%. Thereby, damage to the steam turbine is avoided.

The embodiment shown in Figure 3 differs from that shown in Figure 2 in that in place of the gear wheel pump 12, there is a gear wheel pump 22 which is connected in two parallel oil circuits. The supply container 10 is connected through a further suction duct 23 with a second input of the pump which has a second output connected to a delivery duct 24 of the second oil circuit.

On a decrease in the oil pressure through too great an oil withdrawal in the delivery duct 24, there is only a small reaction on the steam turbine, since this is loaded through the first oil circuit and the pressure building up upstream of the constriction of the Venturi. In such a twocircuit arrangement, the Venturi is expediently mounted in the oil circuit which is designed to convey the greater quantity of oil.

Figure 4 shows a turbine oil pump with a Venturi connected downstream in the delivery duct with a steam regulating valve for oil pressure regulation. Connected to the steam duct 17 is a further steam regulating valve 31 which is connected through a control duct 30 to the pressure duct upstream of the constriction of the Venturi. This connection of the control duct lies between the pump 12 and the non-return valve 14. The steam regulating valve 31 has a minimum opening cross-section to drive the steam turbine at a lower rotational speed with a reduced quantity of steam. The steam regulating valve 31 is opened with increasing oil pressure through the control duct 30.

In this embodiment of the invention, care is also taken to prevent over-rewing of the steam turbine in a similar manner to that described with reference to Figure 2, not only in the case of too great an oil withdrawal on the delivery side, but also in the case of a lack of oil in the suction duct 11, should for example the oil supply container be empty or the suction duct have a leak.

The co-ordination of the two steam regulating valves is as follows: in the case of a lack of oil in the suction duct and accordingly a deficient pressure on the delivery side of the pump, the steam regulating valve 21 is driven open by the low pressure acting at the control duct 20. The steam regulating valve 31 remains in its most closed position so that only that quantity of steam flowing through the low rotational speed opening cross-section can act on the steam turbine 16. The steam turbine, due to the lack of adequate steam, cannot then be driven into the excess rotational speed range. When the pump conveys oil and a pressure builds up on the delivery side, the further steam regulating valve 31 is acted upon and opened by way of the control duct 30 so that steam regulating takes place only by way of the steam regulating valve 21.It is possible in this manner to protect the steam turbine against an excess rotational speed independently of whether the low load is caused by an oil deficiency on the suction side or too great an oil delivery through the delivery duct.

Shown in Figure 5 is a section through a Venturi inserted between two and flanges 35 of two pipe lengths connected to each other. The Venturi is machined into a cylindrical stub provided with a flange. The stub has an external diameter corresponding to the internal diameter of the pipe length to which it is connected so that the stub can be pushed into the pipe length.

The flange 37 lies between and is screwed to the end flanges 35.

WHAT WE CLAIM IS: 1. An oil system comprising a rotary oil pump provided with a suction duct and a delivery duct, a turbine drivingly connected to the pump, and a Venturi in the delivery duct to limit the rotational speed of the turbine.

2. An oil system as claimed in Claim 1, adapted to generate at least one of control and lubricant pressure for a main turbine.

3. An oil system as claimed in either Claim 1 or Claim 2, wherein the pump is arranged in normal operation to convey oil through the Venturi at a rate approximately 15% below the maximum rate conveyable through the Venturi.

4. An oil system as claimed in any one of the preceding claims, comprising a steam regulating valve disposed in a steam duct leading to the first-mentioned turbine, and a control duct connected between the upstream side of the Venturi and the steam regulating valve to cause the steam regulating valve to throttle steam conveyed to the turbine on an increase in pressure upstream of the Venturi.

5. An oil system as claimed in Claim 4, comprising a further steam regulating valve disposed in the steam duct, and a further control duct connected between the upstream side of the Venturi and the further steam regulating valve to cause the further steam regulating valve to open to allow an increase in the steam fed to the turbine on an increase in pressure upstream of the Venturi.

6. An oil system substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

7. An oil system as claimed in Claim 6, and modified substantially as hereinbefore described with reference to Figure 2 of the accompanying

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. When the maximum quantity of oil conveyable by the gear wheel pump through the Venturi by reason of the limitation which in this embodiment is also about 15% above the normal quantity of oil, is reached, the pressure regulation is hardly influenced by the Venturi. On the normal conveyed quantity being exceeded, the pressure downstream of the Venturi greatly falls off, which, however, has no effect upstream of the Venturi, since the pressure is substantially maintained. As a consequence, the steam turbine is loaded just as before by the gear wheel pump conveying oil under load so there is no danger of over-rewing. The steam turbine in the case of a fault occurring, runs with an excess rotational speed of less than 15%. Thereby, damage to the steam turbine is avoided. The embodiment shown in Figure 3 differs from that shown in Figure 2 in that in place of the gear wheel pump 12, there is a gear wheel pump 22 which is connected in two parallel oil circuits. The supply container 10 is connected through a further suction duct 23 with a second input of the pump which has a second output connected to a delivery duct 24 of the second oil circuit. On a decrease in the oil pressure through too great an oil withdrawal in the delivery duct 24, there is only a small reaction on the steam turbine, since this is loaded through the first oil circuit and the pressure building up upstream of the constriction of the Venturi. In such a twocircuit arrangement, the Venturi is expediently mounted in the oil circuit which is designed to convey the greater quantity of oil. Figure 4 shows a turbine oil pump with a Venturi connected downstream in the delivery duct with a steam regulating valve for oil pressure regulation. Connected to the steam duct 17 is a further steam regulating valve 31 which is connected through a control duct 30 to the pressure duct upstream of the constriction of the Venturi. This connection of the control duct lies between the pump 12 and the non-return valve 14. The steam regulating valve 31 has a minimum opening cross-section to drive the steam turbine at a lower rotational speed with a reduced quantity of steam. The steam regulating valve 31 is opened with increasing oil pressure through the control duct 30. In this embodiment of the invention, care is also taken to prevent over-rewing of the steam turbine in a similar manner to that described with reference to Figure 2, not only in the case of too great an oil withdrawal on the delivery side, but also in the case of a lack of oil in the suction duct 11, should for example the oil supply container be empty or the suction duct have a leak. The co-ordination of the two steam regulating valves is as follows: in the case of a lack of oil in the suction duct and accordingly a deficient pressure on the delivery side of the pump, the steam regulating valve 21 is driven open by the low pressure acting at the control duct 20. The steam regulating valve 31 remains in its most closed position so that only that quantity of steam flowing through the low rotational speed opening cross-section can act on the steam turbine 16. The steam turbine, due to the lack of adequate steam, cannot then be driven into the excess rotational speed range. When the pump conveys oil and a pressure builds up on the delivery side, the further steam regulating valve 31 is acted upon and opened by way of the control duct 30 so that steam regulating takes place only by way of the steam regulating valve 21.It is possible in this manner to protect the steam turbine against an excess rotational speed independently of whether the low load is caused by an oil deficiency on the suction side or too great an oil delivery through the delivery duct. Shown in Figure 5 is a section through a Venturi inserted between two and flanges 35 of two pipe lengths connected to each other. The Venturi is machined into a cylindrical stub provided with a flange. The stub has an external diameter corresponding to the internal diameter of the pipe length to which it is connected so that the stub can be pushed into the pipe length. The flange 37 lies between and is screwed to the end flanges 35. WHAT WE CLAIM IS:

1. An oil system comprising a rotary oil pump provided with a suction duct and a delivery duct, a turbine drivingly connected to the pump, and a Venturi in the delivery duct to limit the rotational speed of the turbine.

drawings.

8. An oil system as claimed in Claim 6, and modified substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

9. An oil system as claimed in Claim 6, and modified substantially as hereinbefore described with reference to Figure 4 of the accomapnying drawings.

10. An oil system as claimed in any one of Claims 6 to 9, substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.