GB2157833A - Testing oil for emulsion formation - Google Patents

Abstract

In order to assess how prone various types of engine lubricating oils are likely to be to formation of water-in-oil emulsions on the rocker covers of internal combustion engines, the engine operating conditions are simulated in a test rig (1) in which heated oil and heated saturated air (or raw steam) are directed by delivery pipes (18, 23) onto an inclined test plate (16) which is disposed inside a test cabinet (3) and cooled to a temperature below that of the heated oil and saturated air, so that water-in-oil emulsion formation occurs on the test plate. The test region inside the test cabinet can be evacuated by applying suction to a suction pipe (29), so as to simulate the effect of suction applied to the rocker cover breather pipe of an internal combustion engine. <IMAGE>

Description

SPECIFICATION Apparatus for testing oil This invention relates to apparatus for testing oil, and in particular though not exclusively to a test rig which is able to assess how prone an engine lubricating oil under test is likely to be to formation of a water-in-oil emulsion on an internal combustion engine rocker cover when actually used in that engine.

It is well known that water-in-oil emulsions form on the underneath surface of the relatively cool rocker covers of internal combustion engines under certain conditions. Such emulsions often have a somewhat creamy appearance and texture, similar to mayonnaise, and are undesirable in that they can lead to partial or complete blocking of the breather pipe leading through the rocker cover from the subjacent rocker chamber, or in extreme cases of the air filter in the engine carburettor.

Various factors affect the formation of the water-in-oil emulsions such as engine design, weather conditions and properties of the oil itself. In order to investigate these factors, it is conventional to run actual engine tests for different oils under test, after which the rocker cover is removed and tests carried out on the emulsions deposited on the rocker cover.

These engine tests are time consuming and very expensive to conduct and it would be highly desirable to be able to conduct equivalent tests on laboratory equipment which is comparatively simple and cheap to use.

According to the present invention there is provided apparatus for testing oil, which comprises a component having a test surface, means for directing oil to be tested and watercontaining fluid at test temperatures above ambient onto the said test surface, and means for maintaining said test surface at a further test temperature below the first-mentioned test temperatures to cause oil and water in contact with one another on said test surface to combine to form a water-in-oil emulsion.

The water-containing fluid will usually be saturated air but it could alternatively be raw steam.

In a particularly convenient arrangement, the component is arranged with its test surface as an underneath surface of the component such that excess oil and excess of any other liquid on said test surface drip from the component into an oil collection region of the apparatus. The oil collection region may comprise an inclined floor which drains into an oil reservoir from which the oil directing means is supplied. In this way, the oil is recycled which significantly reduces the quantity of oil which is used in the apparatus in any one test as compared with the quantity of oil which would otherwise need to be used.

Especially conveniently, the component comprises a test plate, having a plane test surface, which is arranged to be adjusted into a desired position of inclination about a horizontal axis of the apparatus. In this way, the apparatus can be adapted for simulating the effect of the oil under test for the particular angle of inclination of the underneath surface of any given rocker cover. The test plate is preferably removable, in order to enable a further test plate having different metallurgical surface properties to be exchanged for the first-mentioned test plate. This enables the effect of different metallurgical properties on the formation of water-in-oil emulsions for any given lubricating oil to be investigated. Especially conveniently, the test plate is secured in position by releasable clips.

The means for maintaining the test surface at the aforesaid further temperature can comprise a hair pin cooling tube arrangement mounted on an opposite surface of said component to the test surface.

In a preferred arrangement, the means for directing oil to be tested and water-containing fluid onto the test surface comprises respective oil and water delivery pipes, each pipe being closed at one end and formed with a line of orifices in its lateral wall which in each case direct oil or water-containing fluid onto the test surface.

The apparatus may further comprise programmable control means for supplying the oil and water delivery pipes alternately with oil and water-containing fluid. When using such an alternate-supply arrangement, it has been found that the emulsion thereby formed very closely corresponds with that produced in an actual engine run.

The testing apparatus may further comprise a steam generator arranged with its steam outlet connected to supply the water delivery pipe and selectively operable air supply means arranged for supplying air to the steam generator, whereby raw steam is supplied to the water delivery pipe when the air supply means is inoperative and saturated air is supplied to the water delivery pipe when the air supply means is operative.

Preferably, the component is arranged in an enclosed test region inside a test cabinet and means, including a suction line communicating with the test region, are provided for evacuating the test region. This arrangement simulates the effect of vacuum applied by the breather pipe in an internal combustion engine to the rocker chamber. A cold catchpot may be included in the suction line for collecting water-in-oil emulsion and preferably the hairpin cooling tube arrangement and a cooling region of said catchpot are connected in a common cooling circuit in which the coolant from the refrigerator of the cooling circuit passes firstly through the cooling region of the catch pot and then through the hairpin cooling tube arrangement.The quantity of emulsion collected in any measured time interval represents a measure of the probability in an actual engine that the breather pipe could become blocked. It is also preferred that the test cabinet be supported on an open framework which houses at least respective supply pumps, associated with the supply of the oil to be tested and the water-containing fluid.

This facilitates maintenance of the supply pumps. Preferably, as much of any other ancillary equipment that is employed is also housed in the same region for the same reasons.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a general perspective view of one form of test rig in accordance with the invention for simulating the conditions under which a water-in-oil emulsion is formed on the rocker cover of an internal combustion engine; Figure 2 is a front elevation, partly cut away, of the test rig; Figure 2A is an enlarged diagrammatic view showing a cold catchpot which accumulates water-in-oil emulsion forming in a suction line of the test rig; Figure 3 is a corresponding side elevation; and Figure 4 is a section taken along the line IV-IV of Figure 3.

Referring to Figure 1, there is shown a test rig, denoted generally by reference numeral 1 ,which comprises essentially a lower, open, framework 2 supporting an upper test cabinet 3, for enabling water-in-oil emulsion to be formed on the exposed surface of a test plate assembly (5 in Figures 2 and 3) to be described in further detail below. This arrangement is designed to simulate the build-up of water-in-oil emulsions on the rocker cover of an internal combustion engine, in order that test oils may be evaluated, qualitatively and quantitatively.

The test cabinet is in the form of a generally rectangular box having a lid 13, hinged at the rear to provide access to the inside of the test cabinet, with a rearwardly raked face at the front including an inspection window 4 so that the water-in-oil emulsion on the test plate assembly can be observed. Alternatively or in addition, a second observation window 6 can be provided in the front wall of the test cabinet.

The lower framework 2 is open to provide easy access for inspection of the auxiliary equipment which is required to support the simulated conditions in the test cabinet, this auxiliary equipment including an electrically heated oil reservoir 7 and pump 8 which deliver heated oil through a hose 9 (see Figures 2 and 3) to the test region of cabinet 3, and an air pump 10 for supplying air to a steam generator 11 mounted, externally of the framework 2, which can selectively deliver raw steam or saturated air to the test cabinet 3. A monitoring and control console 20 monitors certain operating parameters in the test rig and controls the operating conditions in accordance with the monitored parameters.

Referring now to Figures 2 and 3, the test plate assembly comprises a backing plate 1 3 of heat conductive material such as copper which is pivotally mounted about a stationary pivot shaft 14 which is fixed at its two ends in the sidewalls of the test cabinet. The backing plate is provided on its rear surface with a hairpin cooling tube arrangement 21 whose tube ends are connected through flexible hoses 1 5 which pass through the rear wall of the test cabinet and are connected in a cooling circuit through which a cooling medium is circulated to maintain the test plate assembly 5 at a desired temperature. This temperature value is maintained by means of a temperature sensor 32, mounted centrally on the rear face of the backing plate 13, which controls the operation of the refrigerator unit in the coolant circuit.A preferred alternative arrangement is to use four temperature sensors which are arranged on respective corner regions of the backing plate and whose output signals are averaged. The front face of the backing plate 1 3 is covered by a flat test plate 1 6 whose metallurgy is chosen such that its exposed test surface on which the water-in-oil emulsion is produced has any desired metallurgical property. The test plate 1 6 is removably mounted on the backing plate 13, for example by means of clips or other suitable quick release means, to enable another test plate having different metallurgical properties to be exchanged for the initial test plate.The test plate assembly 5 can be pivotably adjusted about the axis of fixed pivot shaft 1 4 into any desired angular position between a substantially vertical position in which the test plate projects downwardly inside the test cabinet and a rearward position in which the test plate assembly is rearwardly downwardly inclined and extends back to the rear wall of the test cabinet. Thus, in the selected position, the test surface is an underneath surface of the test plate assembly. The selected angular position of the test plate assembly about the pivot shaft 14 represents the angle of inclination of the rocker plate which the test plate assembly represents and the test plate assembly is held clamped in that position by a screw clamp 1 7 which can be operated when the cover 1 2 is open. Oil and any small quantities of water dripping off the test plate assembly lands on the floor 34 of the test cabinet which, as Figure 3 shows, slopes downwardly towards the front of the test rig so that the oil and water drain back into the oil reservoir 7.

An oil spraying pipe 1 8 extends between the side walls of the test cabinet. One end of this pipe 1 8 passes through the cabinet wall at one side and is connected there with oil hose 9. Pipe 1 8 is closed at its other end and a line of orifices 1 9 is formed in the pipe wall over an axial extent which registers with the test plate 1 6 and these orifices direct jets or sprays of heated oil from the oil reservoir onto the exposed face of the test plate.The oil reservoir is heated by means of an electrical heater which is shown very diagrammatically at 22 in Figures 2 and 3 and is controlled in accordance with the output electrical signal from a temperature sensor 30 mounted in the reservoir wall with its temperature sensitive part in thermal communication with the hot oil. In this way, the oil temperature is maintained substantially constant. The oil spraying pipe 1 8 is arranged at a fixed location selected so that the oil spray will impinge upwardly onto the test plate 1 6 even in the rearward most position of the test plate assembly. A solenoid-operated valve 31 in hose 9 can be closed to shut-off delivery of oil to the oil spraying pipe 18, when required.

Similarly, a steam pipe 23, which is closed at one end and extends in parallel relationship with oil spraying pipe 1 8 between the two sides of the test cabinet 3, is supplied at its open end with steam (either as raw steam or saturated air) through hose 24 from steam generator 11 and the steam issues upwardly from orifices 25 in the steam pipe wall against the exposed surface of test plate 1 6.

A flow rate and temperature sensor 26 is connected in the outlet from the steam generator 11. Furthermore the steam delivery can be closed-off by shutting a solenoid-operated valve 33.

The steam generator 11 itself is an upright cylindrical vessel including an electric heater (not shown) which heats up water in the vessel which has a steam outlet at the top to which the inlet end of hose 24 is connected.

An inlet air pipe 27, supplied with air under pressure from the delivery side of air pump 10, enters the steam generator 27 through the bottom and causes air to bubbie through the water so that saturated air can be fed from the steam outlet of the steam generator to the steam pipe. A temperature sensor (not shown) monitors the temperature of the water inside the steam generator and the electric heater is controlled to maintain a desired water temperature inside the steam generator. The temperature measurements and control effected when delivering saturated air to the test region are essential for ensuring that the temperature and properties of the saturated air are appropriate for the tests being carried out.

Alternatively, when desired, raw steam can be delivered by the steam generator by shutting off a solenoid-operated valve 28 in inlet pipe 27 and raising the temperature of the water in the steam generator to boiling point. A sight glass 30 in the side wall of the steam generator serves to indicate the water level in the steam generator.

A short suction pipe 29 extending through one side wall of the test cabinet 3 is connected to a suction pump (not shown) which applies a suction pressure to the inside of the test cabinet through suction line 40 to simulate the effect of the suction induced in the air breather pipe connected to the rocker chamber beneath the rocker plate cover of an actual internal combustion engine. Again, a solenoid operated valve (not shown) can be closed to remove the suction when required.

Preferably, and with particular reference to Figure 2A, a cold catchpot 41 is connected in suction line-40 for accumulating water-in-oil emulsion which forms in the suction line. The cold catchpot is essentially of double-walled construction, comprising an inner vessel 42 enclosed in a coolant jacket 43 and having an emulsion drain line 44 including an on-off valve 45 for periodically discharging from inner vessel 42 the emulsion which has collected there. The vessel 42 has a coolant inlet 46 and a coolant outlet 47 which are connected in the cooling circuit of the test plate in such manner that the coolant passes from the refrigerator unit firstly through the cooling region (defined between vessel 42 and jacket 43) of the cold catchpot and then through the hairpin cooling arrangement of the test plate assembly.An orifice plate 48 in the portion of suction line 40 leading from the cold catchpot 41 to the suction pump serves to encourage formation of emulsion in the suction line but prevent emulsion from being sucked from the catchpot 41 into the suction pump.

Finally, the monitoring and control of the test rig is managed by the console 20 which monitors and displays the temperature and flowrate output signals generated by the sensors 26, 30 and 32. It also controls the operation of the various solenoid operated valves 28, 31 (and the valve in the suction line to breather pipe 29), and the supply of electrical power to the heaters of the oil reservoir and steam generator, to the refrigeration unit and to the air and oil pumps. The console contains a programmable device for preselecting different modes of operation.For example, one mode might be to direct both oil and raw steam continuously onto the test plate assembly with suction applied, another mode might involve the substitution of saturated air for the raw steam of the first mode, and further modes could involve the alternation of the steam and oil delivery in the first and second modes. These last two modes have been found to produce very similar effects to those found to prevail in a real operating situation in which, during each cycle of the internal combustion engine, blow by and oil splash occur at different times, although the rate of alternation in the test rig is very much longer (e.g. the time period for supply of each of the oil and steam can be set in the range from just above 0 to 1 80 secs).

In operation, the test rig and console are switched on to allow the oil, steam and test plate operating temperatures to be reached and then a selected operating program can be followed. In this program hot oil and raw steam (or saturated air) are directed onto the cooled plate assembly, either simultaneously or alternately. The oil film which establishes itself on the exposed cool surface of the test plate 1 6 is exposed to the saturated air, allowing water vapour to condense in the oil film, thereby forming a water-in-oil emulsion.

This emulsion tends to build up in a thickening and spreading layer until emulsion drips off the test plate. In practice, however, the test would normally be completed before sufficient emulsion has formed that excess emulsion starts to drip from the test plate. As the emulsion layer grows, hot oil, water and possibly water-in-oil emulsion drips onto the inclined floor 33 of the test cabinet and runs back down into the oil reservoir for recycling.

The low vacuum, when applied to the breather pipe 29, causes the oil/saturated air mist to be drawn off into the cold trap catchpot in the suction line placed in front of a variable restriction orifice (none of these is shown). Emuision formation occurs in the catchpot. This simulates breather pipe/air filter conditions in an internal combustion engine.

As an example of how the invention can be put into operation, the following operating parameters are typical for the test rig described hereinabove: - Methanol coolant refrigerator and pump capable of maintaining coolant temperature in the coolant circuit in the range of + 10 C to - 20"C + 2"C.

- Air pump passes heated air into steam generator in which the water bath is maintained at a temperature between + 50 C and + 90"C +2 C.

- Raw steam/saturated air delivery rate to be between 0.1 and 10 litres/minute.

- Test plate assembly cooled to within the range -5'Cto +10'C + 2"C.

- Oil reservoir temperature heated to +50'Cto + 90 C j3'C.

A specific example is as follows. The oil reservoir temperature is maintained at 80"C and the test plate, consisting of mild steel, is cooled to + 4"C. A saturated air delivery at 80"C is maintained. Oil is sprayed by the oil spraying pipe continuously during a 10 second interval in every minute. Saturated air is directed at the test plate throughout the remaining 50 seconds. This sequence is repeated for, say, 1 5 to 30 minutes. The actual timing is best determined experimentally, as are the optimum temperature values. At the end of each test program, the emulsion produced in the catchpot is weighed. In addition, the test plate is removed from the test cabinet and the depth and area of the emulsion layer are measured using any suitable technique.

The emulsion is weighed and photographed.

The test plate can then be stored on a rack and the rate of any emulsion breakdown can be observed.

It will be appreciated that with the test rig described above, comparative tests as between different oils for rocker covers at different inclinations and of different metallurgical properties can be made.

Claims (11)

1. Apparatus for testing oil, which comprises a component having a test surface, means for directing oil to be tested and watercontaining fluid at test temperatures above ambient onto the said test surface, and means for maintaining said test surface at a further test temperature below the first-mentioned test temperatures to cause oil and water in contact with one another on said test surface to combine to form a water-in-oil emulsion.

2. Apparatus according to claim 1, wherein said component is arranged with said test surface as an underneath surface of said component such that excess oil and excess of any other liquid on said test surface drip from said component into an oil collection region of the apparatus.

3. Apparatus according to claim 2, wherein said oil collection region comprises an inclined floor which drains into an oil reservoir from which said oil directing means is supplied.

4. Apparatus according to any preceding claim, wherein said component comprises a test plate, having a plane test surface, which is arranged to be adjusted into a desired position of inclination about a horizontal axis of the apparatus.

5. Apparatus according to claim 4, wherein said test plate is removable to enable a further test plate having different metallurgical surface properties to be exchanged for the firstmentioned test plate.

6. Apparatus according to any preceding claim, wherein said means for maintaining said test surface at said further temperature comprises a hairpin cooling tube arrangement mounted on an opposite surface of said component to said test surface.

7. Apparatus according to any preceding claim, wherein said means for directing oil to be tested and water-containing fluid onto said test surface comprises respective oil and water delivery pipes, each pipe being closed at one end and formed with a line of orifices in its lateral wall which in each case direct oil or water onto said test surface.

8. Apparatus according to claim 7, further comprising programmable control means for supplying said oil and water delivery pipes alternately with oil and water.

9. Apparatus according to claim 7 or 8, wherein a steam generator is arranged with its steam outlet connected to supply the water delivery pipe and selectively operable air supply means is arranged for supplying air to the steam generator, whereby raw steam is supplied to the water delivery pipe when the air supply means is inoperative and saturated air is supplied to the water delivery pipe when the air supply means is operative.

10. Apparatus according to any preceding claim wherein said component is arranged in an enclosed test region inside a test cabinet and means, including a suction line communicating with said test region, are provided for evacuating said test region.

11. Apparatus according to claim 10, wherein a cold catchpot is included in said suction line for collecting water-in-oil emulsion.

1 2. Apparatus according to claim 11 as appended to claim 6, wherein said hairpin cooling tube arrangement and a cooling region of said catch pot are connected in a common cooling circuit in which the coolant from the refrigerator of the cooling circuit passes firstly through the cooling region of the catch pot and then through the hairpin cooling tube arrangement.

1 3. Apparatus according to claim 10 11 or 1 2 wherein said test cabinet is supported on an open framework which houses respective supply pumps, associated with the supply of the oil to be tested and the water-containing fluid.

1 4. Apparatus for testing oil, substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.