GB1563003A

GB1563003A - Supercharged internal combustion engine

Info

Publication number: GB1563003A
Application number: GB39388/76A
Authority: GB
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1975-09-26
Filing date: 1976-09-22
Publication date: 1980-03-19
Also published as: DE2542970A1; NL7610588A; CH616207A5; FR2325814B1; FR2325814A1; JPS5256213A

Abstract

In the supercharged internal combustion engine (1) to which, in the event of an insufficient air supply, auxiliary air (16) can be fed by a turbocharger (8-10) by means of an injector (13) to which propellant air (15) can be admitted, it is intended by simple means to ensure an increase of the charger speed in the stationary partial load range and a shortening of the run-up time when accelerating. This is achieved in that the injector (13) is connected to a compressed air reservoir (14) and arranged outside the charging line (11) leading from the compressor (10) to the cylinders (2-5), in which line the auxiliary air delivered by the injector (13) can be introduced in the area downstream of the supercharger (10). This reduces the amount of air delivered by the compressor (10) and hence the power required for this, so that a greater part of the turbine power output is available for acceleration of the turbocharger. <IMAGE>

Description

(54) SUPERCHARGED INTERNAL COMBUSTION ENGINE (71) We, MASCHINENFABRIK AU GSBURG-NURNBERG AKTIENGESELLSCHAFT, a Germany company, 8900 Augsburg, Stadtbachstrasse 1, 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: This invention relates to a supercharged internal combustion engine having an arrangement by which auxiliary air can be supplied when there is insufficient air supply from the supercharger.

In arrangements of this type, particularly for an engine with an exhaust gas driven turbocharger, the supply of auxiliary air results in an improvement in the part load and acceleration behaviour of the whole engine-supercharger unit.

According to the present invention, there is provided an internal combustion engine having a supercharger connected for delivering a main air supply to the engine via a main air supply line, and means for supplying auxiliary air to the engine. which means comprises an injector which is connectible to a source of air under pressure and which is adapted to inject air into an auxiliary air supply line in such a way as to cause additional air to be drawn into the auxiliary air supply line from the surroundings, the auxiliary air supply line being discrete from the main air supply line and connecting into the latter at a location downstream of the supercharger. there being further provided a non-return valve in the auxiliary air supply line at a location between the injector and the connection into the main air supply line, and a shut-off valve disposed upstream of the injector so that. in use, the shut-off valve is located between the injector and the source of air under pressure, the shut-off valve being adapted to be actuated automatically in dependence upon changes in an operating variable of the engine, whereby auxiliary air can be supplied automatically to the engine during part load operating conditions and acceleration of the engine.

Advantageously, the shut-off valve is adapted to be actuated automatically in dependence upon changes in the charging air pressure or in the power output of the engine.

The non-return valve provided in the auxiliary air line between the injector and the opening into the main air supply line prevents any of the air supplied by the supercharger from being able to escape through the suction entry pipe of the injector when the injector is not being used to supply auxiliary la.that air.

It has been found that for the sustenance of operation of supercharged internal combustion engines under some conditions au xiliarv air at low pressure, but in large quantity, is necessary. In an engine according to the invention the pressure energy of the pressurised air fed to the injector, termed the drive air, is used in advantageous manner to convey a very considerable quantity of additional environmental air at low pressure. Even a small quantity of drive air is sufficient to obtain the desired inflow of additional air.Owing to the fact that the auxiliary air conveyed from the injector is introduced into the main air supply line downstream of the supercharger and is not sucked through the supercharger, the quantity of main air supplied by the supercharger is decreased and thus the power required for driving the supercharger to convey the main supply of air is also decreased. In the case of an exhaust gas driven turbocharger a larger proportion of the power supplied by the turbine therefore remains for the acceleration of the turbocharger. The invention thus provides for an increase in the supercharger speed in the part load range of the engine and for a reduction in the run-up time on acceleration of the engine.

Preferably, the injector comprises a nozzle, for example a convergent-divergent or Laval nozzle, and adjacent thereto a suction entry pipe through which, in use, the additional air is drawn freely from the surroundings by the action of the jet of air issuing from the nozzle, the nozzle and the suction entry pipe, which conveniently surrounds the nozzle, being directed into a mixer pipe-section in which the additional air and the drive air passing through the nozzle are mixed, the mixer pipe-section having at its downstream end a diffuser section leading into the auxiliary air supply line. Advantageously, the mixer pipe-section is a cylindrical tube having a length of approximately nine times its diameter or longer.

According to an expedient development of the invention, the drive air is taken from a cylinder or other container containing compressed air; this is possible owing to the low consumption of drive air since much of the auxiliary air comprises the additional environmental air drawn in by action of the drive air. The use of a cylinder or other container containing compressed air ensures a high degree of operational reliability and continual readiness for use without considerable maintenance expenditure as compared with the use of an auxiliary blower.

In use, the drive air is expanded in the Laval nozzle to somewhat less than atmospheric pressure. the pressure energy being almost completely converted into kinetic energy. This air jet of high speed mixes with the freely sucked in air from the environment, and the auxiliary air is then slowed down in the diffuser and the pressure correspondingly increased. With suitable selection of the cross-sections which can be determined bv calculations and simple experiments for the conditions of each individual case, the pressure is increased to a degree necessarv for the sustenance of the operation of the engine.By being mixed with air from the surroundings the temperature of the resultant auxiliary air is considerably higher than the temperature of the expanded drive air at the downstream end of the nozzle, so that disadvantageous effects on the combustion process in the engine are avoided and the exhaust gas temperature can be kept high. If the drive air were to be injected directlv into the main air supply line. the auxiliary and main air supplies would be cooled, ignition and combustion would be impaired and the engine exhaust gas temperature would fall causing a reduction in the supercharger turbine output.

The invention may be put into practice in a number of ways but one specific embodiment will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 shows schematically a supercharged four-cylinder internal combustion engine, in accordance with the invention, having an injector for supplying auxiliary air to the engine, and Figure 2 shows the injector of the engine of Figure 1 in enlarged representation.

Figure 1 shows the internal combustion engine 1 with four cylinders 2 to 5 and an output shaft 6 to which a propeller, for example, can be fitted. The exhaust gases from the cylinders 2 to 5 are supplied via an exhaust gas manifold 7 to an exhaust gas driven turbine 8 of a turbocharger which drives, via a shaft 9, a supercharger compressor 10 the rotor of which is rigidly connected to the shaft 9, which compressor sucks air from the surroundings, compresses it and supplies it, via a main air supply line 11, under pressure to the engine cylinders 2 to 5. This main supply air which becomes heated during the compression process is cooled in a charging air cooler 12 located downstream of the compressor 10.

Particularly when starting the engine 1 and in the case of low load operation the energy of the engine exhaust gases does not completely meet the power required to drive the compressor 10 to supply the total amount of air needed by the engine 1. A certain amount of auxiliary air is therefore added to the main air supplied by the compressor 10. To supply such auxiliary air there is provided an injector 13 which can be fed, via a drive air line 15 connected in advantageous manner to a cylinder 14 of compressed air, with a small amount of drive air and which is adapted so that the drive air causes a fairly large amount of additional air to be sucked in from the environment. This additional air is mixed with the expanded drive air and is blown via an auxiliary air line 16 into the main air supply line 11, the auxiliary line 16 being connected into the latter at a location downstream of the compressor 10.

As indicated in Figure 1 by solid and broken lines, the auxiliary air line 16 can open into the main air supply line 11 either upstream or downstream of the charging air cooler 12; introduction of auxiliary air upstream of the charging air cooler 12 has the advantage that the cold auxiliary air can be heated somewhat by the relatively hot compressed main air supply flowing to the charging air cooler and, paradoxically, in the charging air cooler itself, since the temperature at the coolant outlet of the cooler may well be higher than the temperature of the auxiliary air coming from the injector 13.

This auxiliary air supply arrangement ensures that the cylinders 2 to 5 can always be supplied adequately with air, it being possible to convey the additional auxiliary air required for this with a very small amount of drive air. Introduction of the auxiliary air into the main air supply line at the location downstream of the compressor 10 permits a rapid acceleration of the engine 1, irrespective of the throughput quantity of the compressor.

To shut down the injector 13 in engine operating ranges in which the amount of air conveyed by the turbocharger is sufficient for the supply needs of the cylinders 2 to 5, a shut-off valve 17 is provided in the drive air line 15 upstream of the injector 13. The shut-off valve 17 is operable automatically.

For automatic operation of the auxiliary air supply and to obtain a sensitive control of the air supply, an adjusting member 18 is provided which is operated in dependence on the valve of an engine operating variable as measured by a sensing element 19, which value is converted to an actuating signal in a regulator 20. In the illustrated embodiment the sensing element 19 picks up the power requirement of the engine 1 as the operating variable, as measured at the output shaft 6 for instance. Other embodiments are also conceivable, however; for example. advantageously, the charging air pressure in the charging air line 11 can be picked up as measured value for the sensing element 19, since this measured value gives direct information about the air supply of the engine.

In periods in which the injector is not to be used to supply auxiliary air, escape of any main charging air, supplied by the compressor 10, out through the injector 13 is effectively and simply prevented by means of a non-return valve 21 provided in the auxiliary air line 16 at a location between the injector 13 and the opening into the main air supply line 11. The shut-off valve 17 can also be automatically closed by a signal which is given when the automatic non-return valve 21 closes.

The construction and method of operation of the injector 13 will now be explained with reference to Figure 2. To the drive air line 15 connected to a compressed air cylinder 14, is attached a Laval-type convergent-divergent nozzle 22, by means of which drive air taken from the compressed air cylinder 14 is expanded to somewhat less than atmospheric pressure. The pressure energy in this drive air is thereby almost completely converted into kinetic energy.

The Laval nozzle 22 is surrounded bv a suction entry pipe 23 affording an annular suction port through which, as indicated by arrows, air from the environment is freely sucked into the low-pressure region at the downstream end of the nozzle 22. The suction entry pipe 23 can advantageously be constructed as a frusto-conically-shaped pipe section. To the suction entry pipe 23 is connected a mixer pipe-section 24 in which the air sucked in from the environment and the drive air stream issuing from the Laval nozzle 22 are mixed. Good results can be achieved by using a cylindrical mixer pipesection having a length of at least nine times its diameter.Owing to the mixing of the drive air, which is cooled quite considerably during the expansion through the nozzle, with the relatively warm air sucked in from the environment, the temperature of the resultant auxiliary air is brought to a level which ensures good combustion in the cylinders.

At its downstream end there is connected to the mixer pipe-section 24 a diffuser 25 in which the mixed, auxiliary air passing through the mixer pipe-section 24 is slowed down with accompanying increase of pressure. By suitable selection of the crosssections, which can be determined for each individual case by way of simple tests, a suitable pressure level of the auxiliary air for the sustenance of the engine operation can be achieved. The diffuser 25 opens out into the auxiliary air line 16 which is continued with the same cross-section as that of the downstream end of the diffuser 25.

WHAT WE CLAIM IS: 1. An internal combustion engine having a supercharger connected for delivering a main air supply to the engine via a main air supply line, and means for supplying auxiliary air to the engine, which means comprises an injector which is connectible to a source of air under pressure and which is adapted to inject air into an auxiliary air supply line in such a way as to cause additional air to be drawn into the auxiliary air supply line from the surroundings, the auxiliary air supply line being discrete from the main air supply line and connecting into the latter at a location downstream of the supercharger, there being further provided a non-return valve in the auxiliary air supply line at a location between the injector and the connection into the main air supply line, and a shut-off valve disposed upstream of the injector so that, in use, the shut-off valve is located between the injector and the source of air under pressure, the shut-off valve being adapted to be actuated automatically in dependence upon changes in an operating variable of the engine, whereby auxiliary air can be supplied automatically to the engine during part load operating conditions and acceleration of the engine.

2. An engine as claimed in claim 1, in which the shut-off valve is adapted to be actuated automatically in dependence upon changes in the charging air pressure or in the power output of the engine.

3. An engine as claimed in claim 1 or

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ensures that the cylinders 2 to 5 can always be supplied adequately with air, it being possible to convey the additional auxiliary air required for this with a very small amount of drive air. Introduction of the auxiliary air into the main air supply line at the location downstream of the compressor 10 permits a rapid acceleration of the engine 1, irrespective of the throughput quantity of the compressor. To shut down the injector 13 in engine operating ranges in which the amount of air conveyed by the turbocharger is sufficient for the supply needs of the cylinders 2 to 5, a shut-off valve 17 is provided in the drive air line 15 upstream of the injector 13. The shut-off valve 17 is operable automatically. For automatic operation of the auxiliary air supply and to obtain a sensitive control of the air supply, an adjusting member 18 is provided which is operated in dependence on the valve of an engine operating variable as measured by a sensing element 19, which value is converted to an actuating signal in a regulator 20. In the illustrated embodiment the sensing element 19 picks up the power requirement of the engine 1 as the operating variable, as measured at the output shaft 6 for instance. Other embodiments are also conceivable, however; for example. advantageously, the charging air pressure in the charging air line 11 can be picked up as measured value for the sensing element 19, since this measured value gives direct information about the air supply of the engine. In periods in which the injector is not to be used to supply auxiliary air, escape of any main charging air, supplied by the compressor 10, out through the injector 13 is effectively and simply prevented by means of a non-return valve 21 provided in the auxiliary air line 16 at a location between the injector 13 and the opening into the main air supply line 11. The shut-off valve 17 can also be automatically closed by a signal which is given when the automatic non-return valve 21 closes. The construction and method of operation of the injector 13 will now be explained with reference to Figure 2. To the drive air line 15 connected to a compressed air cylinder 14, is attached a Laval-type convergent-divergent nozzle 22, by means of which drive air taken from the compressed air cylinder 14 is expanded to somewhat less than atmospheric pressure. The pressure energy in this drive air is thereby almost completely converted into kinetic energy. The Laval nozzle 22 is surrounded bv a suction entry pipe 23 affording an annular suction port through which, as indicated by arrows, air from the environment is freely sucked into the low-pressure region at the downstream end of the nozzle 22. The suction entry pipe 23 can advantageously be constructed as a frusto-conically-shaped pipe section. To the suction entry pipe 23 is connected a mixer pipe-section 24 in which the air sucked in from the environment and the drive air stream issuing from the Laval nozzle 22 are mixed. Good results can be achieved by using a cylindrical mixer pipesection having a length of at least nine times its diameter.Owing to the mixing of the drive air, which is cooled quite considerably during the expansion through the nozzle, with the relatively warm air sucked in from the environment, the temperature of the resultant auxiliary air is brought to a level which ensures good combustion in the cylinders. At its downstream end there is connected to the mixer pipe-section 24 a diffuser 25 in which the mixed, auxiliary air passing through the mixer pipe-section 24 is slowed down with accompanying increase of pressure. By suitable selection of the crosssections, which can be determined for each individual case by way of simple tests, a suitable pressure level of the auxiliary air for the sustenance of the engine operation can be achieved. The diffuser 25 opens out into the auxiliary air line 16 which is continued with the same cross-section as that of the downstream end of the diffuser 25. WHAT WE CLAIM IS:

1. An internal combustion engine having a supercharger connected for delivering a main air supply to the engine via a main air supply line, and means for supplying auxiliary air to the engine, which means comprises an injector which is connectible to a source of air under pressure and which is adapted to inject air into an auxiliary air supply line in such a way as to cause additional air to be drawn into the auxiliary air supply line from the surroundings, the auxiliary air supply line being discrete from the main air supply line and connecting into the latter at a location downstream of the supercharger, there being further provided a non-return valve in the auxiliary air supply line at a location between the injector and the connection into the main air supply line, and a shut-off valve disposed upstream of the injector so that, in use, the shut-off valve is located between the injector and the source of air under pressure, the shut-off valve being adapted to be actuated automatically in dependence upon changes in an operating variable of the engine, whereby auxiliary air can be supplied automatically to the engine during part load operating conditions and acceleration of the engine.

3. An engine as claimed in claim 1 or

claim 2, in which the injector comprises a nozzle and adjacent thereto a suction entry pipe through which, in use, the additional air is drawn freely from the surroundings by the action of the jet of air issuing from the nozzle, the nozzle and the suction entry pipe being directed into a mixer pipe-section in which the additional air and the air passing through the nozzle are mixed, the mixer pipe-section having at its downstream end a diffuser section leading into the auxiliary air supply line.

4. An engine as claimed in claim 3, in which the mixer pipe-section is a cylindrical tube having a length which is approximately nine times its diameter or longer.

5. An engine as claimed in claim 3 or claim 4, in which the suction entry pipe surrounds the nozzle thereby to provide an annular entry port for the additional air.

6. An engine as claimed in any one of claims 3 to 5, in which the nozzle is a convergent-divergent nozzle.

7. An engine as claimed in claim 6, in which the nozzle is a Laval nozzle.

8. An engine as claimed in any one of the preceding claims, in which the injector is connected to a source of air under pressure.

9. An engine as claimed in claim 8, in which the source of air under pressure comprises a cylinder or other container containing compressed air.

10. An engine as claimed in any one of the preceding claims, in which the supercharger comprises an exhaust gas driven turbocharger.

11. A supercharged internal combustion engine substantially as specifically described herein with reference to the accompanying drawing.