Method for operating a combustion engine

Abstract

A method for operating a combustion engine having a crankcase, a piston group and a crankshaft, wherein the crankcase has an oil reservoir and an operational amount of lubricating oil is provided, wherein i) a partial amount of the lubricating oil is continuously discharged from the crankshaft and ii) a refill amount of new lubricating oil is continuously supplied, so that the operational amount of lubricating oil remains essentially the same; as well as a combustion engine for carrying out the method.

Claims

1. A method for operating a combustion engine having a crankcase, a piston group and a crankshaft, wherein the crankcase has an oil reservoir and an operational amount of lubricating oil is provided, the method comprising: i) continuously discharging a partial amount of the lubricating oil from the crankcase; and ii) supplying a refill amount of new lubricating oil to the crankcase, wherein the operational amount of lubricating oil remains essentially the same, wherein an airflow is moved via an inlet into the crankcase and moved via an outlet out of the crankcase, wherein the airflow is moved in the crankcase so that it is diverted about a rotational axis of the crankshaft in a corresponding rotational direction of the crankshaft, wherein, for this purpose, the inlet is arranged underneath a height of the crankshaft on one side of the crankcase and the outlet is arranged above the height of the crankshaft on a same side of the crankcase.

2. A method according to claim 1, wherein the partial amount of the lubricating oil that is discharged is selected so that the lubricating oil of the operational amount in total lies within a tolerance range of a quality parameter, wherein the partial amount discharged lies outside of the tolerance range of the quality parameter.

3. A method according to claim 2, wherein the quality parameter is selected from the group consisting of viscosity, TBN (total base number), TAN (total acid number), oxidation and nitration.

4. A method according to claim 3, wherein the amount of lubricating oil that is discharged is present in the airflow vented as an oil drop fraction, wherein the droplets have a diameter of less than 0.2 mm.

5. A method according to claim 1, wherein the airflow loaded with an oil drop fraction is mixed with a further airflow from the crankcase, wherein the further airflow differs from the loaded airflow by a smaller oil load.

6. A method according to claim 1, wherein a gas portion, which flows into the crankcase via the piston group (blow-by gas), will be discharged with the airflow.

7. A method for operating a combustion engine having a crankcase, a piston group and a crankshaft, wherein the crankcase has an oil reservoir and an operational amount of lubricating oil is provided, the method comprising: i) continuously discharging a partial amount of the lubricating oil from the crankcase by means of airflow moving via an inlet into the crankcase and moving via an outlet out of the crankcase; ii) supplying a refill amount of new lubricating oil to the crankcase; and iii) discarding the partial amount of the lubricating oil discharged from the crankcase, wherein the operational amount of lubricating oil remains essentially the same.

8. A method according to claim 7, wherein discarding the partial amount of the lubricating oil discharged from the crankcase includes conducting to a waste oil container.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In the following, the method for operating a combustion engine and stationary combustion engines will be illustrated in schematic figures and exemplary embodiments.

(2) FIG. 1 shows a sketch of a cross-section of an embodiment variant of a combustion engine according to the invention.

(3) FIG. 2 shows a sketch of a cross-section of an embodiment variant of a combustion engine according to the invention.

(4) FIG. 3 shows a chart of the course of limiting oil parameter in full load operation without application of a method according to the invention.

(5) FIG. 4 shows a chart of the course of limiting oil parameter in full load operation with application of a method according to the invention.

(6) FIG. 1 schematically shows a simplified cross-section through a part of the crankcase 1 of a combustion engine according to the invention. In the upper area, there is situated the piston group 2 having two cylinders that are schematically depicted. The crank cavity 3 constitutes the lower part of the crankcase 1 and shows the crankshaft 3, which would extend beyond the figure or the figure plane, respectively, with the longitudinal axis thereof. Underneath the crank cavity there is situated the oil sump 5, wherein the solid area represents the oil reservoir 6. At the right side wall of the crank cavity 3, openings are visible. The inlet 7 and the outlet 8 may be in a multiple-arrangement along the crank cavity 3.

(7) The depicted embodiment variant aims at discharging those oil droplet fractions, which are the most subject to degradation, together with the chemically reactive blow-by gases quickly out of the crankcase 1 and reducing the temperature around the oil drops in the engine compartment of the combustion engine. Arrows indicate fluid movements, which are relevant for the method according to the invention. The flushing of the oil droplets with cool air will reduce the surface reactions and the ageing rate of the oil. This is realized by cool fresh air being blown into the oil reservoir 6 at several position as close above the oil level as possible through the respective inlet 7. The inflow direction thus is tangential to the direction of movement of the crankshaft 4, so that the purging air will be supported and, fluidized by the movement of the crankpins between crankshaft 4 and oil reservoir sump 6, will flow from there up to the opposite side of the crank cavity 3. Finally, the airflow will be again discharged out of the crankcase 3 through the outlet 8, entraining the blow-by gases flowing out of the piston group 2 or the cylinder sleeves, respectively, into the crank cavity 3.

(8) The exiting mixture of oil droplets, purging air and blow-by gas is moved directly from the outlet 8 to an oil separator 9. A continuously inclined connection of the outlet 8 with the oil separator 9 is indicated in FIG. 1 by dashed lines. In the oil separator 9, the oil is separated and supplied to a waste oil container (not illustrated) via the oil outlet 15. The gas, from which waste oil has been removed, is returned to the suction pipe of the combustion engine via a gas pipe (16). By means of the method according to the invention, the oil discharged from the oil outlet 8 is mainly lubricating oil, which is more subject to degradation than the oil in the oil sump. According to the invention, hence, there is made the provision that the partial amount of oil discharged will not be reused. The oil discharged from the combustion engine in total is replaced by fresh oil from a not-depicted fresh oil container by means of the automatic refilling device.

(9) FIG. 2 shows some further details of an embodiment variant of a combustion engine according to the invention. The illustration of the crankcase 1 corresponds to the one in FIG. 1, wherein the illustration of already discussed elements and the reference numbers for a better understanding thereof have been omitted.

(10) At the upper end of the crankcase 1, a partial flow is removed at a further outlet 10 of the crankcase gas. This partial flow is connected with the airflow from the first outlet 8 via an adjustable throttle 11. A throttle device 12 is preferably installed also for the airflow from the outlet 8. The gas exiting at the upper and slow-flow end of the crankcase (further outlet 10) has a significantly lower oil load than the gas exiting laterally at the crank cavity (outlet 8). Due to appropriate positions of the throttle components, the mixed gas 14 composed of the two partial flows may be adjusted to the desired oil load. In order to prevent that large oil drops or splash oil portions are entrained with this laterally exiting gas, there are provided the appropriate selecting devices such as, e.g., a cyclone-like droplet separator 13.

(11) The FIGS. 3 and 4 show charts regarding the temporal course of an oil parameter according to the state of the art in practice (FIG. 3) as well as upon application of the method according to the invention (FIG. 4).

(12) The dotted line 1 indicates the respective value of a relevant quality parameter, for example, derived from viscosity, total base number (TBN), total acid number (TAN), oxidation and nitration. For the oil parameter used applies that higher values represent a higher quality of the oil. At the start of operation, the oil parameter has the value of 8, then dropping over the full load operation. The tolerance range for the oil parameter is indicated by the lower threshold value of 4.5, which is depicted in the figure by the dashed line 2. In FIG. 3, the oil parameter lies under this limit after 1,500 hours of operation, as depicted by the horizontal line 3. For this reason, for a corresponding engine there has to be performed an oil change after 1,500 hours of service life. FIG. 4 shows that in operation with a method according to the invention, however, the value will not drop below the threshold value. The values for the oil parameter remain well above the threshold value, as indicated by line 1. Data relate to an oil discharge of 0.05 g/kWh in addition to a specific oil consumption of 0.15 g/kWh.

(13) The situations depicted in FIGS. 3 and 4 relate, for example, to a stationary combustion engine, which upon standard application exhibits the following features:

(14) TABLE-US-00001 Engine performance. 1000 kW Specific lubricating oil 0.15 g/kWh consumption: Oil sump content: 300 1 Oil service life: 1500 hrs of operation Suction air amount: 4,110 m.sup.3/h Blow-by volume flow: 26 m.sup.3/h Oil load in the blow-by: 11.7 g/h

(15) The saving potential as a result of the method according to the invention is to be illustrated by way of concrete numbers in a simplified way. In normal operation, within an oil service life of 1,500 hours of operation, the engine will have a consumption of 225 kg oil. The amount of oil, which is entrained in the blow-by within this period, corresponds to about 18 kg. On the occasion of an oil change, about 220 kg oil have to be disposed of.

(16) In order to reach a constant oil quality near the limit of usability, by way of an additional oil discharge according to the invention, there have to be discharged, for example, in addition 0.05 g/kWh with an airflow. In this way, there may be reached, as shown in FIG. 4, a stable equilibrium of the oil quality within the acceptable threshold values. The maximum oil load possible of the purging air with an oil droplet fraction of less than about 10 m amounts to about 1.0 g/m.sup.3; accordingly, the airflow has to have a purging air amount of about 50 m.sup.3/h, which corresponds more or less to the double of the blow-by volume flow.

(17) Over a course of 6,000 hours of operation, according to prior art, there has to be performed an oil change four times, so that four times the oil sump content, i.e. 1,200 l, have to be provided, in contrast to which, over a course of 6,000 hours of operation according to the method proposed, only a refill amount of fresh oil of about 400 l will be required. Compared to the oil change, the oil costs for providing usable oil will be reduced to one third.

(18) Positive for the cost-effectiveness will also be the omission of downtime and the reduction of the waste oil to be disposed of, wherein the aspect last mentioned also has to be considered an advantage due to environmental reasons.