Cleaning Internal Combustion Engines Or The Like

Abstract

A method and apparatus for cleaning an internal combustion engine or the like so as to remove carbon deposits, coke sediments and the like. The method involves intermittently adding to the air feed system of the engine and optionally to the exhaust stream from the engine, fluid cleaning medium for a predetermined period of time at predetermined time intervals while the engine is in operation. The addition is effected via pressure diffusor jet means directly into the air stream and optionally the exhaust stream while the relative humidity of air and cleaning fluid is controlled. In the apparatus, the pressure diffusor means communicates via valve-controlled conduit means with a container for storing cleaning fluid under pressure. The jet means is arranged to discharge into the air feed system and optionally into the exhaust system, each system having a hygrometer inserted therein downstream relative to the jet means and for control of a dosing valve in said conduit means to maintain the humidity between 60 percent and 75 percent, measured at a temperature of 30.degree. C within said system.

Description

This invention relates to a method for the cleaning of an internal combustion engine or the like, so as to remove carbon deposits, coke sediments and the like, by adding intermittently during operation of the engine or the like a cleaning medium to the air feed system of the engine or the like and if desired also separately to its exhaust system. In addition, the invention includes an apparatus for carrying out this method.

The invention is employed first and foremost for internal combustion engines but can also be employed, for example, for the cleaning of smoke ducts and stoke holds in boilers.

The present invention has special significance for ships' engines but is also of interest for stationary engines or other engines where it is of importance to be able to maintain continuous operation over long periods of time. When there is discussion about engines herein, attention is first and foremost to diesel engines but it will be understood that turbine engines, petrol engines, jet engines and other engines will be able to draw advantage from the cleaning method of the invention.

As is known, slag will always be formed in connection with a combustion process and this slag, together with other materials which are left after the combustion, have always been a problem to remove from the engine and associated parts. Large portions of the slag flow out together with the exhaust gas or the expelled gas and, for example, by compressed air scavenging there is achieved a further, if not complete, cleaning. However, it appears to be almost impossible to remove all the residues after the combustion process and there occur gradually unavoidable deposits and permanently burned coke sediments in combustion chambers as well as on adjoining parts and in adjoining ducts. The deposits consist mainly of incombustible fuel portions, such as non-combustible carbon compounds, certain tar materials, ash materials, sulphur compounds and the like, which partly enter into chemical combination with each other and which partly form layers upon each other on the engine parts and gradually form permanent coatings, for example, in the form of coke sediments. Such deposits or sediments can be difficult to remove in an easy manner and, hitherto, it has been usual to remove such deposits and sediments by periodic engine overhauls in which the engine is dismantled and manual cleaning is effected by scraping-off and polishing together with a second cleaning of the sediments and deposits. Such an engine overhauling is rather demanding on labour and makes it necessary to stop the engine over a significant period of time. It is of the greatest importance to be able to avoid such engine overhauling of the driving engine while the ship is at sea since such engine overhauling means a substantial loss of time, something which can be rather costly, especially with large ships.

Routine overhauling with cleaning is necessary at predetermined time intervals, not only with a view to reducing the wear on the engine parts but as much for reducing the consumption of fuel. Preferably, the aim is to achieve the longest possible intervals between such engine overhauls so as to make thereby such an engine overhauling less dependent on time. With a dirty engine there occurs a marked increase in fuel consumption, partly as a result of the geometry of the combustion chamber and adjoining ducts being altered by the building up of the said sediments and deposits and partly as a result of the wear of the parts and from this the resulting leakages, but first and foremost as a result of the fouling of the valve parts which begin to leak and thereby overfeed the fuel or change the combustion process in another way. The permanent burning of the piston springs and from this the resulting increased wear on the cylinder lining has also occurred readily in dirty engines.

It has been proposed to reduce the deposition of slag materials and other coatings in internal combustion engines by effecting a constant and continuous supply to the fuel, to the intake air, to the combustion chamber separately or to other parts of the engine, of various agents, such as certain chemicals or quite simply normal water, oxygen-enriched water, steam carbon dioxide or carbon dioxide-containing gases and the like. For various reasons, such additions have not found particular application in practice and are not recognised as practically usable either. Firstly, it does not appear to be possible to supply the agent in such a manner that it acts equally effectively over all parts of the engine and therefore hitherto, one has only got a locally limited cleaning of the engine, while other parts of the engine can be largely unaffected by the cleaning. Secondly, such a mode of operation appears to demand a constant, precisely adjusted supply of the cleaning medium, without the proposal put forward indicating any such precise statement of the quantity supplied and other conditions. The result has been that the supply of cleaning medium and thereby the mode of operation of the cleaning medium has been rather arbitrary. If the cleaning medium is supplied in too small quantities, it will not be able to reach all regions of the engine in a strong enough concentration and hence in the intended manner and will not be able either, to prevent the local build up of sediments or deposits in certain regions of the engine. If the cleaning medium is supplied in too large quantities, it can, on the other hand, act negatively on the combustion process and reduce the effect of the combustion. The submitted proposals have not been able to make it possible to postpone the point of time for the otherwise conventional engine overhauling.

Intermittent cleaning has also been proposed in which the aim is to remove slag deposits on the engine by performing a shock-type treatment on the parts of the engine, especially by introducing water, steam or similar fluid medium into the internal combustion engine while the latter is in operation. In addition to the unfortunate influence such a shock treatment can have on the various highly heated parts of the engine, there is the undesirable effect of the sediments or deposits obtained loosening and then splitting off in flakes or pieces which are not necessarily blown out of the combustion chamber but can remain behind and increase the wear or possible stopping up of the valve passages and thereby produce leakages. A further disadvantage is that the effect of the engine is substantially reduced as long as the cleaning is carried on by such a shock-type action.

From Danish Pat No. 89,243, it is known to add intermittently a cleaning medium under pressure directly to the labyrinth seals between the stator and rotor parts of the motor, while the motor is in operation. As examples of cleaning means can be mentioned non-combustible, fat-dissolving means or steam or compressed air or a combination of these. However, there are not stated any definite quantities of cleaning means and no other special conditions are stated either. Tests have shown that steam or compressed air alone or in combination have little effect on the intermittent injection and that an arbitrary addition of fat-dissolving means does not have any noticeable effect alone or in combination with steam and/or compressed air. The action of the cleaning means according to the Danish patent must necessarily be rather arbitrary, since the patent specification does not disclose any clear solution to the problem.

According to the present invention a method of cleaning an internal combustion engine or the like so as to remove carbon deposits, coke sediments and the like comprises intermittently adding to the air feed system of the engine during operation of the latter fluid cleaning medium for a period of a few seconds to a couple of hours with time intervals of from one day to two weeks duration, said addition being effected via pressure diffusor jet means directly into the air stream while the relative humidity of air and cleaning fluid is adjusted to between 60 and 75 percent, measured at a temperature of 30.degree. C.

It has been found that in order to be able to obtain an intended cleaning effect, the relative humidity of the mixture ought to lie at about 70 percent. With a relative humidity of below 60 percent, the cleaning effect will be less satisfactory and with a relative humidity of above 75 percent, a condensation effect will readily take place which will act negatively on the combustion process. By carrying out the pressure spraying of the cleaning fluid, there is obtained a particularly precise distribution of the cleaning fluid and by adjusting the relative humidity of the mixture of air and cleaning fluid to about 70 percent an effective action is obtained on the coating in the air feed duct, as well as in the combustion chamber. In many instances separate feeding of the sprayed cleaning fluid in the exhaust ducts is preferred. It has been found that an action time of about 60 minutes during the course of a week's operation is satisfactory for routine cleaning of most engine types while the engine is in operation. However, it is apparent that the action time, especially for a "dirty" engine, can be extended or shortened according to need and can be effected correspondingly with a smaller or greater frequency, all according to the conditions.

Also according to the invention is an apparatus for carrying out this method which comprises pressure diffusor means such as a jet including a control valve communicating via valve-controlled conduit means with a container for storing the cleaning fluid under pressure, said jet being arranged to discharge into the air feed system to the engine or the like which system has a hygrometer inserted therein downstream relative to said jet and for control of a dosing valve in said conduit means.

In order that the invention can be more clearly understood, a convenient embodiment thereof will now be described, by way of example, with reference to the accompanying drawing.

Referring to the drawing, a diesel engine 10 is shown in plan with six cylinders 11-16 supplied in a manner not shown with combustion air, via a common air feed duct 17, from a supercharger 18 having an air filter 19. The cylinders can correspondingly be supplied with scavenge air from the supercharger 18 via a common scavenge air duct (not shown) which can extend parallel to the air feed duct 17. From the six cylinders there extend exit ducts (not shown) to a common exhaust duct 20 having an associated exhaust turbine 21 for operation of the supercharger.

At 22, there is shown a compressed air conduit having a branch 23 via a check valve 24 and a relief valve 25 to a container 26 for cleaning fluid, and from the container 26 passes a conduit connection 27 via a dosing valve 28 to a pressure diffusor jet 29 which projects inwards into the air stream in the air feed duct 17. A branched conduit connection (not shown) runs to a pressure diffusor jet which projects inwards into the air stream in the scavenge air duct.

In the drawing, there is shown a construction in which jets are utilised in the combustion air duct and the scavenge air duct, but alternatively these can be replaced by a single jet located in front of the air filter to the supercharger.

In addition to the said branches to the combustion air duct and the scavenge air duct, there can also be utilised a branch line 31 to the exhaust duct 20. If desired, there can further be utilised several jets including stop valves 32 in the exhaust duct 20 for spraying cleaning fluid, for example one for each cylinder 11-16 so as to obtain the best possible cleaning for each cylinder's exhaust exit openings.

In order to obtain the intended precise cleaning, it is important that the cleaning fluid be sprayed before it enters into the combustion chamber and that the humidity of the mixture of air and cleaning fluid be adjusted to about 70 percent relative humidity (measured at 30.degree. C). In order to avoid condensation, care must be taken that it at any rate does not substantially exceed 75 percent relative humidity and so as to obtain some effect from the cleaning, not exceeding 60 percent relative humidity either. According to the invention, this is achieved by controlling the dosing valve 28 relying upon a hygrometer 30 which is inserted in the air feed duct 17 a distance downstream relative to the pressure diffusor jet 29. alternatively, or in addition, a corresponding hygrometer can be inserted in the scavenge air duct. The hygrometer can, if desired, be adapted by means of a control system known per se to effect electro-control of the dosing valve or, by means of various hygrometers, there can be controlled automatically and individually various dosing or stop valves in the various ducts which are to be supplied with cleaning fluid so that there is obtained an automatic feeding of cleaning fluid in exactly suitable amounts and thereby a constant, desired relative humidity can be ensured during the whole of the cleaning process. In the illustrated embodiment, there is only shown an installation in which manual regulation of the dosing valve is effected relative to the hygrometer reading.

Practical tests have been carried out with the aforementioned apparatus while employing various cleaning fluids, and in particular there will be described an experiment undertaken with a cleaning fluid produced on the basis of 95 weight percent water.

Prior to the practical experiment cleaning was carried out by manual overhauling of the engine.

While the engine was in operation, the cleaning fluid was set at a feed pressure of 5 kp/cm.sup.2 and the dosing valve 28 was gradually regulated up to a feed quantity corresponding to 70 percent relative humidity in the mixture of air and sprayed cleaning fluid in the air feed duct. In the actual case there was added cleaning fluid in an amount of 3 litres/hour. The feeding of the cleaning fluid took place over a time period of about 10 minutes without a noticeable decline in the performance of the engine, and the compressed air feed to the container for cleaning fluid was thereafter closed off simultaneously with the shutting off of the dosing valve 28. Afterwards the engine was allowed to run a week at a time at full power before a fresh cleaning operation was undertaken, which was also allowed to have a duration of about 10 minutes under conditions corresponding to those mentioned above. After a couple of months operation with routine cleaning as stated above and just after a previous cleaning operation the top cover was removed, and the cylinder walls, scavenge air and exhaust openings, scavenge air ducts together with piston tops and top covers, valve parts and the like were inspected. It was found that there was no occurrence of any coke coating or other deposition of slag on the inspected parts, and the engine appeared just as clean as after the manual engine overhauling which was undertaken before the practical test was started. In the exhaust duct the cleaning was not completely satisfactory but on subsequent tests with the separate feeding of sprayed cleaning fluid to the exhaust duct, satisfactory cleaning of the latter was also achieved. Satisfactory cleaning of the exhaust duct was also achieved on subsequent testing, where cleaning fluid was supplied only to the air intake side, by increasing the action time to 60 minutes.

Claims

What I claim is:

1. A method of cleaning an internal combustion engine or the like so as to remove carbon deposits, coke sediments and the like which comprises intermittently adding to the air feed system of the engine during operation of the latter fluid cleaning medium including water as a fluid carrier vehicle for a period of a few seconds to a couple of hours with time intervals of from one day to two weeks duration, said addition being effected via pressure diffusor jet means directly into the air stream while the relative humidity of air and cleaning fluid is adjusted to between 60 and 75 percent, measured at a temperature of 30.degree. C.

2. A method according to claim 1, wherein a similar intermittent addition of fluid cleaning medium is made via the pressure diffusor jet means to the exhaust stream from the engine or the like while the relative humidity of exhaust gas and cleaning fluid is adjusted to between 60 and 75 percent, measured at a temperature of 30.degree. C.

3. A method according to claim 1, wherein the addition of fluid cleaning medium takes place for approximately 60 minutes with a time interval of 1 week.

4. A method according to claim 2, wherein the addition of fluid cleaning medium takes place for approximately 60 minutes with a time interval of 1 week.

5. A method according to claim 1, wherein the relative humidity is adjusted to 70 percent.

6. A method according to claim 2, wherein the relative humidity is adjusted to 70 percent.

7. A method of cleaning an internal combustion engine having an air feed system for delivering combustion air thereto, said method comprising the steps of

intermittently spraying a fluid cleaning medium into said air feed system during operation of said engine to form a mixture of combustion air and cleaning fluid, said fluid cleaning medium including water as a fluid carrier vehicle; and

maintaining the humidity of the mixture of combustion air and cleaning fluid between 60 and 75 percent measured at a temperature of 30.degree. C within said air feed system.

8. A method as set forth in claim 7 wherein the fluid cleaning medium is sprayed at a feed pressure of 5 kp/cm.sup.2 in an amount of 3 liters/hour.

9. A method as set forth in claim 7 wherein said humidity is 70 percent.

10. An apparatus for cleaning an internal combustion engine having an air feed system for delivering combustion air thereto, said apparatus comprising

a container containing a supply of cleaning medium including water as a fluid carrier vehicle,

a conduit connection connected between said container and said air feed system,

a dosing valve in said conduit connection for controlling the flow of cleaning medium from said container to said air feed system,

a pressure diffusor means communicating said conduit connection with said air feed system for discharging a spray of cleaning medium into a stream of combustion air flowing through said air feed system during operation of said engine

a hygrometer in said air feed system downstream of said diffusor means to measure the humidity of the cleaning medium containing air stream, and

said hygrometer being connected to said dosing valve to control said valve in response to the measured humidity to maintain the humidity between 60 and 75 percent at a temperature of 30.degree. C.

11. An apparatus as set forth in claim 10 wherein said engine has an exhaust duct and said apparatus further comprises a branch line connected between said conduit connection and said exhaust duct, and at least one jet in said exhaust duct for spraying cleaning fluid thereinto.