DE1451910A1 - Method for operating an internal combustion engine with exhaust gas turbocharging and device for carrying out this method - Google Patents

Description

Maschinenfabrik Augsburg-Nürnberg Aktiengesellschaft Augsburg, Stadtbachstrasse 1

P.B. 2365

Method for operating an internal combustion engine with exhaust gas turbocharging and device for implementation

this procedure

The invention relates to a method for operating an internal combustion engine with pre-compression of the charge air in at least one exhaust gas turbocharger operated by the engine exhaust gases and with a bypass line with an overflow valve connecting the charge air line to the turbine feed line, and also with a device for supplying an additional controllable amount of energy to the turbine, this device as well as the overflow valve can be controlled so that as the engine speed falls, both the amount of air flowing over and the additional amount of energy become larger. With this operating mode it is possible, e.g. to drive a vehicle to let the boost pressure and the torque increase with decreasing engine speed, so as to improve the torque characteristics of the to match the ideal traction force hyperbola.

They are internal combustion engines with exhaust gas turbocharging and regulation by blowing around part of the fuel supplied by the supercharger Air in the turbine feed line is known, in which the air diverted to the turbine is heated in a heat exchanger or in a combustion chamber arranged in front of the turbine serves as combustion air. In these arrangements, the heat transferred to the air circulation in the heat exchanger is or The heat released in the combustion chamber through the combustion of additional fuel is that which is additionally supplied to the turbine Amount of energy. The increase in output of the turbine is therefore no longer limited to the amount of air blown around, rather, an additional amount of energy is supplied to the turbine with the heat from the fuel.

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P.B. 2565

But it is now easy to prove that the efficiency "at the combustion of additional fuel in the recirculated air bad is. The total fuel consumption is thereby significantly increased, so that this method is limited to the cases in where high torque is rarely required at low engine speed. However, vehicle engines often need to be in be driven in this area.

In addition, however, the amount of heat that can be generated by combustion of additional fuel in the recirculated air is also essential depending on the amount of circulated air, which in turn - as with any other air circulation control - through the pressure gradient existing between the charging line and the turbine feed line is determined. If not enough If there is a pressure gradient, then no more air flows from the charging line into the turbine line, and one could with the introduction of additional fuel in the combustion chamber does not achieve the desired acceleration of the turbine.

The present invention is based on the object of designing an internal combustion engine with exhaust gas turbocharging so that them while avoiding costly devices for torque conversion is suitable for operation with heavily fluctuating loads. First and foremost, the well-known blow-through regulation should be used can be expanded in their scope.

This object is achieved according to the method according to the present invention in that the supply of additional energy to the exhaust gas turbine takes place independently of the supply of blown air. Due to the independent energy supply to the turbine, the charging fan is quickly accelerated to the required speed if the pressure in the charging line is too low, so that the excess amount of air can then be directed to the turbine. As will be explained in more detail in connection with the exemplary embodiment, the two measures complement one another

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in such a way that thereby the greatest possible freedom of interpretation an exhaust gas turbocharger is required. The charge fan can be designed, for example, so that its efficiency is at its optimum or is close to the engine absorption line at maximum engine speed, since you can by blowing and independent energy supply to Turbine can set practically any operating point in the map, with the additional amount of energy according to the requirements can regulate the amount of air blown around or the amount of air required by the engine.

It is particularly advantageous to use compressed air as a carrier for the additional amount of energy, which is known per se Way produced in a compressor mechanically driven by the engine and a special one through a special line The nozzle segment is fed to the turbine. Although the invention has the possibility of additional heating of the blown Does not exclude air volume, it should be said that only with the independent energy supply to the turbine with the help of a compressed gas A better degree of efficiency is achieved than if the blown air volume is heated up in the same way as a gas turbine section is, since it is known that the efficiencies of gas turbines are very low at such low pressures.

The drawings belonging to the exemplary embodiments described below show in FIG

Fig. 1 an-cylinder internal combustion engine with blow-by regulation and independent energy supply through compressed air to the turbine,

2 shows the subdivision of the nozzles on the turbine,

3 shows a reciprocating compressor with control of the delivery rate by moving the outlet slots,

Fig. 4 the explanation of the method according to the invention on the basis of a charger map.

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The driven by the exhaust gas turbine 1 blower 2 promotes, sucked from it the air through the duct 3 to the air distributor 4 · of the motor 5 · The three cylinders coming from $ e exhaust gases of the 6-cylinder engine are combined and are represented by the lines 6 7 fed to the separate nozzle chambers 8, 9 of the turbine 1.

For the blow-by operation, the line 10 and the branch lines 11 and 12 are provided, which into the turbine feed lines 6 and 7 open. Just before the mouths is in (each of the lines 11, 12 each have a Hückströmmsperrorgan 13 »14 and a blow-by valve 15 »16 arranged. With the valves 15 »16 open and with a sufficient pressure gradient between the charging line 3 and the feed lines 6, 7 thus flows part of the ter 2 conveyed air to turbine 1.

In order to be able to supply additional energy to the turbine 1 independently of the blown air, the motor 5 drives a compressor of the positive displacement type, e.g. the reciprocating compressor 17, whose compressed air flows through the line 18 into the nozzle chamber 19 of the turbine 1 is performed.

The blow-off valves 20, 21 are also connected to the lines 6, 7, when opened, engine exhaust gases can be blown off into the erection, which is particularly important at high engine speeds in This comes into consideration if there is a risk of the turbine "running away" due to excessively large "exhaust gas quantities," or if there is a drop of the boost pressure is desired.

When charging in the so-called burst mode, it is well known that an essential part of the exhaust energy is in the form of pressure peaks fed to the exhaust gas turbine at the speed of sound. At a junction, part of this pressure energy enters the Branch line over and here too moves at the speed of sound away. Although in the lines 11 »12 just before the mouths 22, 23 backflow blocking devices 13, 14 are arranged are which, when the valves 14-, 15 are open, the overflow of exhaust gas from the line 6 into the line 7 or vice versa

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prevent, so can additionally or as a replacement of the locking members 13, 14 a coordination of the exhaust lines 6 and 7 as well as the Blow-in lines 11 and 12 are made in such a way that a e.g. Pressure mountain, which reaches the mouth 22 through line 12, arrives there at the point in time when a through line 6 hurrying pressure mountain has reached the mouth 22. So a pressure mountain shouldn't coincide with a pressure valley like that the pail would be if short connecting lines to the both exhaust pipe strings were made. In this way, the pulsation energy is not lost.

Fig. 3 shows a schematic representation of a reciprocating compressor, the cylinder 31 of which is arranged axially displaceably with the aid of the mechanism indicated at 32, whereby the outlet openings 33 can be set at different distances s from the bottom dead center T. The outlet openings 33 are controlled by the upper edge of the piston 35. In the right half of the drawing, the cylinder 31 is shown in its lower position with the extension path s ^ and in the left half in the upper position with the extension path S2. On the one hand, the air sucked in through the suction valve 34 is displaced out of the cylinder 31 only on the path at Pressure line 18 (Fig. 1) is connected. The air remaining after the outlet openings have been pushed out then expands again at the beginning of the following suction stroke.

In Fig. 4 · is illustrated in a charger map, how Advantageously supplement the recirculation control and the control through independent energy supply.

On the ordinate is - as usual - the adiabatic head H _{ad of} the charge blower in mkp / kg and on the abscissa it is

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Secondary delivery rate Q is plotted in nr / see. The surge line L shown in dashed lines separates the instabi len working area (left) from the stable area (right) of the fan. T ^, # ₂ , f? - * are lines of equal efficiency. denotes the point of maximum efficiency (optimal operating point).

The diagram also shows the absorption lines s, s-, Sp of the motor at different engine speeds, namely s = * full speed, S ^ ■ 3/4 of the full speed and Sp = 1/2 of the full speed registered.

At full engine speed, the supercharger works at operating point P on absorption line s and delivers the quantity Qp with the pressure Hp. This point is in the stable range, so that control interventions are not required.

For half the engine speed, this charger would have to be designed so that it works at point P ₂ on absorption line S ₂ , supplying quantity Q ₂ at the significantly lower pressure EL ·, which is extremely unfavorable for vehicle propulsion.

By circulating charge air, the turbine is now supplied with more energy, so that the charger _{reaches the operating point P 2} *, at which it supplies _{the larger quantity Q 2} * with the already higher pressure H ₂ ^1. The quantity qA_ is fed to the engine and the quantity q _{2 to} the turbine. However, the pressure H ' ₂ is still lower than the pressure Hp at full speed. Without recirculation control, one could now adjust the charger by supplying energy independently to the turbine so that it reaches point P. at a higher speed, at which point it should deliver _{the amount of air q 2} 'with the pressure HL ^1. However, this point lies in the unstable working range, ie the flow rate is no longer constant and the fan pumps. Only by circulating the charge air with a slightly reduced air supply to the air nozzle of the turbine is it possible to set the operating point PU, which in turn is in the

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stable operating range of the charger is · Bainit is at the same time. proved that there is a direct functional connection between the steps "supply of energy to the turbine by blowing around part of the charge air" and "energy supply ¹¹ independent of blown air, with compressed air being used as the energy carrier for the latter with a special gate part.

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Claims (9)

Patent claims 1. Method for operating an internal combustion engine with precompression the charge air in at least one exhaust gas turbocharger operated by the engine exhaust gases and with a charge air line with the bypass line connecting the turbine feed line with overflow valve, furthermore with a device for supplying an additional controllable amount of energy to the turbine, this device as well as the overflow valve being controlled so that with falling engine speed both the amount of air flowing over and the additional amount of energy increase, characterized in that that the supply of additional energy to the exhaust gas turbine takes place independently of the supply of blown air. 2. The method according to claim 1, characterized in that compressed air is used as a carrier of the additional amount of energy is generated in a manner known per se in a compressor (17) mechanically driven by the motor (5) and by a special line (18) is fed to a special nozzle segment (19) of the turbine (1). 3. The method nach'Anspruch 2, characterized by the use a compressor of the displacement type (17) driven by the motor (5) »its delivery rate by changing the Position of its inlet or outlet openings (33) is regulated. 4. Device for performing the method according to one of claims 1 to 3 in an internal combustion engine with subdivided exhaust lines, characterized in that the blow-by lines (11, 12) are connected to one another and their lengths and the lengths of the turbine feed lines (6, 7 ) up ^to the mouths (22, 23) of the blow-in lines (11, 12) are matched so that when the blow-in valves (15t 16) are open, the pressure mountain entering through them arrives at the other mouth at the time when the feed line passes through there Druckberg has arrived. V. 909828/0436 5. Device for carrying out the method according to a of claims 1 to 3, characterized in that before ■ the mouths (22, 23) of the Umblaseleitüngen (11,12) in Eückströmmsperrorgane (13, 14) are arranged in a manner known per se. 6. device according to claim 4 or 5, characterized in that that blow-off valves (20, 21) are connected to the turbine feed lines (6, 7) in a manner known per se. BATH 9 09828/0436