GB2125892A - Turbo-supercharging and resonance charging an I.C. engine - Google Patents

Abstract

A multi-cylinder engine (1) has combined supercharging by means of a turbo-supercharger (5-7) and a resonant intake system (8-12) connected to the exhaust system (2-4). The connection conduits 13, which are open at least when the charging pressure exceeds the exhaust pressure by the provision of non-return valves 14, provide for transmission of pressure pulses from the exhaust system to the intake system which increase the resonance charging effect. The engine may have various multi-cylinder arrangements (Figs. 2, 3 and 5). The intake and exhaust system connection may be opened at starting and/or low load for exhaust recirculation, a valve controlling the connection. <IMAGE>

Description

SPECIFICATION Turbo-supercharging an internal combustion engine The present invention relates to a method of, and apparatus for, turbo-supercharging an internal combustion engine.

Turbo-supercharging is probably the best known means for increasing the specific output or power of an internal combustion engine. However, due to the different absorption or intake characteristics of a turbo-supercharger and a fourcycie internal combustion engine rather complex matching or accommodation problems result, in particular if the internal combustion engine is designed for the largest possible range of higher mean pressures, as is required for modern vehicle engines. Each adaptation of a turbo-supercharger to a four-cycle vehicle engine, therefore, ultimately is a compromise between optimum operating values at a selected operating point and a useful operating range which is as wide as possible.

A number of measures have become known to counter such difficulties and to increase the useful operating range of turbo-supercharged engines as much as possible.

It is thus conventional practice, for example, for small engines, to arrange a vent valve downstream of the compressor or upstream of the turbine for regulating the maximum supercharging pressure.

It is furthermore known to combine turbosupercharging with supercharging by a resonance system. In the so-called resonance supercharging systems there are used fresh-gas oscillatory systems which are tuned to resonance and which comprise resonance tubes and, if desired, resonance containers. Such systems and their elements form an oscillatory system having a well definable natural frequency. The principle of resonance supercharging may be solely used as such or in combination with a turbo-supercharging system constituting a so-called combined supercharging system.When the oscillatory arrangement is connected between the turbosupercharger or the air intake pipe or tube and the cylinders and when the oscillatory arrangement is excited by a frequency approximating the aforementioned natural frequency due to the movement of the pistons during successive intake periods during operation of the engine, then resonance will occur and amplified pressure oscillations will originate, by means of which the volumetric efficiency of the cylinders is considerably improved in a desired range of rotational speeds under the action of the instantaneous oscillation-caused super pressures at intake valve closure as compared to internal combustion engines without such resonance supercharging.More detailed explanations thereof are published in, for example, "MTZ Motortechnische Zeitschrift", Volume 32 (1971), pages 368 to 373 and Volume 39 (1978), pages 447to451.

In addition to such arrangements on the intake side including an oscillatory system tuned to resonance, an arrangement of an oscillatory system on the exhaust side is also known as, for example, by German Patent Publication No.

2,914,691. The method described in the printed publication provides for decoupling the absorption or supply characteristic, respectively, of a fourcycle engine and of a turbo-supercharger to approximate the operating conditions of the latter to those of a plain gas turbine process. The decoupling is effected by connecting the intake collector downstream of the compressor to the exhaust collector upstream of the turbine by a connecting or by-pass line. This connecting line is connected parallel relative to the engine. A valve is located in the connecting line and permits the air flow through the connecting line to be regulated.

By utilising the pulsation energy generated by the charging change of the engine and originating, on the one hand, from the fluctuations in the pressure of the charging air on the intake side and, on the other hand, from the fluctuations in the pressure in the exhaust system on the exhaust side, it is intended to generate a pressure difference of such great magnitude at the connecting line that in the partial load range a large amount of air can flow through the connecting line, namely even then when the mean pressure upstream of the connecting line is smaller than the mean pressure downstream thereof. In addition to an increase in the supercharging air pressure there is intended to be attained an improvement in the acceleration characteristic of the thus equipped engine, preferably in the partial load range where the greatest deficiency of air is to be expected.

A similar supercharging technique or method as described in the journal "Entropie" Volume 48 (1972), pages 5 to 12, contemplates additionally arranging a combustion chamber in the aforementioned connection line.

In the known resonance systems arranged at the side of the charging air the cyclically occurring suction strokes excite a standing wave in the intake system in the event of resonance. However, such systems have disadvantages which oppose any widespread application thereof. The excitation energy consumes charge changing power, so that the fuel consumption is increased. In many applications (cylinder number) the producible pressure amplitudes are too small to ensure effective recharging. The band width of the active frequencies is relatively small. Resonance systems arranged at the exhaust side, however, do not result in any improvement, in fact, such systems tend to have a negative effect.Additionally, it will have to be generally considered that the design of a resonance system always constitutes a compromise between optimum effectiveness, permissible component size and acceptable flow losses in the intake system. The dimensional considerations become more critical as the range of resonance frequencies is lowered.

Therefore, with the foregoing in mind the present invention seeks to make possible the provision of a method of, and apparatus for, turbo supercharging an internal combustion engine in which the pressure amplitudes at the intake side, and thus the recharging effect, are increased in comparison to prior art supercharging systems.

Another object that may be achievable with the present invention is the provision of a method of, and apparatus for, turbo-supercharging an internal combustion engine in which the absorption or consumption of charge alternating or changing power for excitation is reduced.

The invention may also enable the provision of a method of, and apparatus for, turbosupercharging an internal combustion engine in which the turbo-supercharger is decoupled from the engine in order to be able to operate the same in a more favourable operating range.

According to the present invention, there is provided a method of turbo-supercharging an internal combustion engine comprising intake means and a compressor arranged on an intake side of said engine, exhaust means and a turbine arranged on an exhaust side of said engine, and an oscillatory system for utilising gas oscillations, said method comprising the step of: interconnecting said intake means and said exhaust means of said engine by providing a connection therebetween so as to form an oscillatory system capable of resonance when the pressure downstream of said compressor is higher than the pressure upstream of said turbine.

In a second aspect the invention provides apparatus for turbo-supercharging a multi-cylinder piston-type internal combustion engine having an exhaust-type turbo-supercharging system and oscillatory or oscillatable intake means or elements, connecting means and exhaust means or elements. The intake means or elements, the connecting means and the exhaust means or elements are preferably matched to form an oscillatory system having a natural frequency effective for turbo-supercharging which is close to the excitation frequency. However, shutoff means are connected in said connecting means and serve to interconnect the intake and exhaust components of the intake means and exhaust means when the pressure on the intake side is greater than the pressure on the exhaust side.

In further aspects the invention provides (a) turbo-supercharging means comprising an exhaust-type turbo-supercharging system and said oscillatable intake, exhaust and connecting means; (b) an engine provided with such a turbosupercharging means; and (c) a method of operating an engine.

By additionally employing the exhaust side for the formation of the resonance oscillatory system as proposed in accordance with the invention considerable advantages may be achieved. Firstly, the aforementioned dimensioning problem is generally defused. The energy for exciting a standing wave is obtained from that location where it is present in abundance and in a useful cyclic sequence when suitably combined together.

By utilising the otherwise unused pressure pulsations in the exhaust for exciting the oscillatory system at the intake side thereof, there are attained increased pressure amplitudes. Due to the same effect the pressure will be lowered at the region between the pulsations, which again reduces the charge changing work, and thus, the fuel consumption. Simultaneously, the absorption or intake characteristics of the engine and the turbo-supercharger will be decoupled, with the advantages resulting therefrom.

The shutoff means may comprise a non-return or one-way valve connected in the connection or connecting means such that a throughflow only will be permitted from the intake side to the exhaust side. It may be so arranged that the turbosupercharger runs completely free and always adjusts to optimum efficiency in the static operating state.

When recirculation of the exhaust gas is desired e.g. for reasons of exhaust gas composition at very low load and/or for improving the cold start behaviour of the engine it is convenient to design the shutoff means as an adjustable flap member or flap valve, the position of which is regulatable as a function of load, power output and rotational speed of the internal combustion engine.

Some embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a sixcylinder in-line engine equipped with a combined supercharging apparatus embodying the invention; Figure 2 is an illustration, similar to that of Figure 1, of a four-cylinder engine equipped with a combined supercharging apparatus embodying the invention; Figure 3 is an illustration, similar to that of Figure 1, of a five-cylinder engine equipped with a combined supercharging apparatus embodying the invention; Figures 4a and 4b show possible arrangements of a supercharger cooler in a combined supercharging apparatus embodying the invention; and Figure 5 is a schematic illustration, similar to that of Figure 1, of an eight-cylinder V-engine illustrating the use of a combined supercharging apparatus embodying the invention for engines of higher cylinder number in a double-arrangement of such supercharging apparatus.

Referring to the drawings, it is to be understood that only enough of the construction of the supercharging apparatus and related engine has been shown as needed for those skilled in the art to readily understand the underlying principles and concepts of the present development while simplifying the showing of the drawings. Turning attention now specifically to Figure 1, there has been schematically illustrated therein a sixcylinder engine. The engine cylinders 1 a, 1 b, 1 c, 1 d, le, 1f are arranged in a conventional cylinder block, thus not here shown in greater detail, and each contains a standard and thus not particularly illustrated intake valve and exhaust valve.In correspondence with the usual mode of operation of such an engine the order of working cycles is such that the cylinders la, 1 b, Icand id, 1 e, if, respectively, follow each other with a crank angle of 2400 and that a crank angle difference of 1 200 exists between the two aforementioned groups of cylinders. Such an order results in a division into two groups of the intake means or elements and the exhaust means or elements as shown in Figure 1. The exhaust valves of the group of cylinders 1 a to 1 c each open via an exhaust passage or channel 2 into a common exhaust gas receiver 3.

An analogous arrangement is provided for the exhaust valves of the group of cylinders id to if which open into an exhaust gas receiver 3 associated therewith via exhaust passages 2. The exhaust gases are directed to an exhaust gas turbine 5 from each of the two exhaust gas receivers 3 by means of a respective exhaust pipe or conduit 4 prior to reaching the atmosphere. The exhaust gas turbine 5 is driven by the exhaust gases and in turn drive a compressor 7 by means of any suitable driving connection 6 which thus has only been schematically shown by a broken line. The exhaust gas turbine 5 and the compressor 7 collectively form the turbosupercharger of the engine depicted in Figure 1.

Analogous to the just described arrangement at the engine exhaust side, the intake valves of the group of cylinders 1 a to 1 c each open into a common resonance container 9 by means of a respective intake passage or channel 8 and, correspondingly, intake, passages or channels 8 of the other group of cylinders id to 1 f open into a second such resonance container 9. The two resonance containers 9 are each connected to a balancing or compensation container 11 via a respective resonance tube or pipe 10. The balancing or compensation container 1 1, in turn, is connected by means of an air supply line or conduit 12 to the outlet side of the compressor 7 of the turbo-supercharger.The two resonance containers 9 at the intake side are crosswise connected, as will be seen in Figure 1, to the exhaust gas receivers 3 located at the exhaust side by means-of respective connecting conduits or pipes 1 3. In these connecting conduits 13 between the intake side and the exhaust side, there are arranged shutoff means 14 which in this case each consist of, for instance, a non-return or one-way valve which blocks gas throughflow from the exhaust side to the intake side.

The mode of operation and the effect of the heretofore described turbo-supercharger 5, 7 is assumed to be well known in this technology.

The oscillatory system capable of resonance and intended for the additional resonance supercharging operation is formed by the two resonance tubes or pipes 10, the balancing or compensation container or receptable 1 the resonance containers 9 and the intake passages 8 at the intake side as well as by the connecting or connection conduits 13 and by the elements or components located at the exhaust side, namely the exhaust passages or channels 2, the exhaust gas receivers 3 and the exhaust pipes 4. The oscillatory system thus comprises elements located at the intake side as well as elements located at the exhaust side and the interconnection elements located therebetween.

The oscillatory system is tuned or matched such that the natural frequency thereof is in a desired rotational speed range of the engine when the connecting means 1 3 are in their open state.

During operation of the engine the gas oscillations are excited by the cyclic sequence of exhaust pulses originating from the group of cylinders 1 a to 1 c and id to if, respectively, and produce the charging or re-charging operation at the end of the intake strokes or cycles at the intake sides of the groups of cylinders 1 d to 1 f and 1 a to 1 c, respectively, these intake sides being connected by the connecting or connection conduits 1 3 with the exhaust side of the engine.

Figures 2 and 3 show a four-cylinder in-line engine and a five-cylinder in-line engine, respectively, in a representation which is the same as in Figure 1. The components of the oscillatory system have been illustrated to be adapted to the mode of operation of such engines, in particular to the ignition sequence, the valve control and the overlap of the intake and exhaust cycles thereof; thus identical or analogous components or parts have been conveniently designated with the same reference characters.The oscillatory system, in this case, encompasses, downstream of the compressor 7 and the air supply line or conduit 12 leading to this resonance container 9, the resonance container 9 itself as well as, in the embodiment of Figure 2, four intake passages 8 and, in the embodiment of Figure 3, five such intake passages 8 for connecting the resonance container 9 to the cylinders 1 a to id (Figure 2) and 1 a to 1 e (Figure 3), on the intake side and, on the exhaust side, an exhaust gas receiver 3, the respective four or five exhaust passages or channels 2 of the cylinders 1 a to id (Figure 2) and 1 a to 1 e (Figure 3), respectively, opening into the exhaust gas receiver 3, as well as the exhaust pipe or conduit 4 and the connecting or connection conduit 1 3 which connects the resonance container 9 to the exhaust gas receiver 3 and in which again there is arranged a shutoff means 1 4 like, for example, a non-return or one-way valve.

In this case the oscillatory system is also tuned or matched such that the natural frequency thereof is at a desired engine rotational speed when the connecting arrangement or conduit means 1 3 is in the open state. The gas oscillations are excited by the cyclic sequence of exhaust pulses. The air supply line or conduit 12 has to be designed such that the natural frequency thereof is outside of the excitation frequency as governed by the engine.

The arrangements as described hereinbefore can be augmented at any time by a supercharger cooler. In the case of a six-cylinder engine according to the embodiment as shown in Figure 1, such a supercharger cooler or intercooler 1 5 is advantageously connected immediately forwardly or upstream of the balance container ii and following the air supply line or conduit 12 as has been illustrated in Figure 4a. In the embodiments as shown in Figures 2 and 3 the supercharger cooler or intercooler 1 5 is analogously connected in the air supply line or conduit 12 as shown in Figure 4b.

The embodiment shown in Figure 5 illustrates as an example an advantageous construction for internal combustion engines having a greater number of cylinders than the engines shown in Figures 1 to 3. This construction is basically a duplication of the arrangement shown in the lastmentioned Figures 1 to 3. Of course, systems based on higher multiples can be readily devised.

However, generally only one turbo-supercharger, i.e. only one compressor 7 and only one turbine 5, is provided for each engine with corresponding manifolds following the same. In detail, such multiplication will be evident from the eightcylinder engine shown in Figure 5 and the arrangement will be seen to constitute a doubling of the arrangement shown in Figure 2 for a fourcylinder engine. Again, identical or analogous parts are designated with the same reference numerals. In analogous fashion and in accordance with the invention, ten-cylinder engines can be designed with twice the arrangement shown in Figure 3 for five-cylinder engines, and similarly twelve-cylinder engines can be designed with twice the arrangement shown in Figure 1 for sixcylinder engines.

In all cases the shutoff means or elements 1 4 can be simple non-return or one-way valves as shown which, as already mentioned, are connected in the connecting conduit or connection arrangement between the intake side and the exhaust side such that a throughflow is only permitted from the intake side to the exhaust side. As concerns the technical design it will have to be observed that flow losses in the shutoff means 14 are kept very low.

When some circulation of the exhaust gas is desired for reasons of the exhaust gas composition at very low load and/or for improving the cold start behaviour of the engine, then each shutoff means or element 14 can be constituted by a controllable flap member or flap valve according to a further development of the invention. Regulation of such shutoff means, then, can be effected in dependence upon diverse engine parameters such as, for example, injection pumps, governor rod position and/or engine rotational speed, exhaust gas temperature, and so forth.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the it Invention is not limited thereto, but may be otherwise variously embodied and practised, as will be apparent to the skilled reader.

Claims (12)

1. A method of turbo-supercharging an internal combustion engine comprising intake means and a compressor arranged on an intake side of said engine, exhaust means and a turbine arranged on an exhaust side of said engine, and an oscillatory system for utilising gas oscillations, said method comprising the step of: interconnecting said intake means and said exhaust means of said engine by providing a connection therebetween so as to form an oscillatory system capable of resonance when the pressure downstream of said compressor is higher than the pressure upstream of said turbine.

2. An apparatus for turbo-supercharging a multi-cylinder piston-type internal combustion engine containing an exhaust-type turbosupercharging system, comprising: oscillatable intake means; oscillatable exhaust means; oscillatable connecting means interconnecting said intake means and said exhaust means; said intake means, said connecting means and said exhaust means being matched to form an oscillatory system having a natural frequency effective for turbo-supercharging which is close to an excitation frequency; said oscillatory system comprising intake components of said intake means and exhaust components of said exhaust means; and shutoff means arranged in said connecting means for interconnecting said intake components and said exhaust components when the pressure on the intake side is higher than the pressure on the exhaust side.

3. The apparatus as defined in claim 2, wherein said shutoff means comprise non-return valve means.

4. The apparatus as defined in claim 2, wherein said shutoff means comprise controllable flap means, the position of said controllable flap being regulatable as a function of the load, and/or power output and/or rotational speed of said internal combustion engine.

5. The apparatus as defined in claim 2, 3 or 4, wherein said intake means comprises a supercharger intercooler.

6. The apparatus as defined in any of claims 2 to 5, wherein said shutoff means comprise controllable shutoff means which can be controlled such that a predetermined amount of exhaust gas is recirculated.

7. Apparatus according to any of claims 2 to 6, wherein said intake means includes at least one resonance container for connection to respective engine cylinders, and said exhaust means includes at least one exhaust receiver for connection to respective engine cylinders.

8. Apparatus according to claim 7, wherein there are two each of resonance containers and exhaust receivers for connection to respective ones of two groups of engine cylinders; and said connecting means connect the resonance container associated with one group of cylinders to the exhaust receiver connected with the other.

9. Turbo-supercharging means comprising an exhaust-type turbo-supercharging system and apparatus according to any of claims 2 to 8.

10. A multi-cylinder piston-type internal combustion engine provided with apparatus according to any of claims 2 to 8 or turbosupercharging means according to claim 9.

ii. A method of operating a multi-cylinder piston-type internal combustion engine comprising providing it with turbo-supercharging means according to claim 9 such that the oscillatory system is matched to a desired operating speed range of the engine when said connecting means effect connection.

12. A method of turbo-supercharging and/or operating an internal combustion engine substantially as any exemplified herein with reference to any of the accompanying drawings.

1 3. Apparatus for turbo-supercharging an engine, turbo-supercharging means comprising a turbo-supercharging system and such apparatus, or an internal combustion engine substantially as herein described with reference to and as illustrated in any of Figures 1, 2, 3 and 5 optionally as modified by Figure 4a or 4b.