DE2745686A1 - IC engine with multistage compressor - uses compressed air to cool cylinders before combustion - Google Patents

Abstract

The IC engine includes a multi-stage compressor, it has intercooling to give nearly isothermal compression, and one or more working cylinders containing reciprocating or rotary pistons for intermittent combustion and expansion, together with a heat exchanger if necessary. When running, the combustion air emerging from the compressor (1) is guided round the cylinders and cylinder heads (1, 1b) to cool them, and then either directly or via a heat exchanger into the combustion chambers (7a).

Description

B r e nnkraftmaschin

The invention relates to improvements in the German Offenlegungsschrift No. 2 450 077 described internal combustion engine .

The aim of this proposal was to increase the thermal efficiency to approx. 80 # and the economic efficiency (overall efficiency) to 50 - 55 ° h.

This was achieved through approximately isothermal compression the combustion air and then preheating it in a regenerative heat exchanger.

The disadvantage of this proposal is that it is not yet possible to burn gasoline using this method, that the speed of the engine because of the type of cylinder charging proposed at the time by combustion air only low could be that the regenerative heat exchanger has large dimensions and that the difference between thermal Efficiency and overall efficiency of the engine because of the cylinder cooling losses is relatively large.

To avoid these disadvantages, an internal combustion engine is proposed which consists of at least one multi-stage compressor unit with intermediate cooling for approximately isothermal compression and one or more working cylinders (piston stroke cylinders or rotary piston cylinders) for intermittent combustion and expansion and possibly one or more regenerative heat exchangers, and which is characterized according to the invention that during operation the combustion air emerging from the compressor unit is passed around the working cylinders or their liners and / or through the cylinder heads for cooling purposes and, after absorbing the cooling heat there, is passed into the combustion chambers of the working cylinders .

This way of guiding the combustion air is

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This is preheated from the outlet temperature of the compressor unit (approx. 12O ⁰ C) by the cooling heat of the working cylinder to 300 35O ⁰ C and a considerable part of this cooling heat can be converted into mechanical energy in the subsequent expansion processes. This makes it possible to achieve an overall efficiency of the Internal combustion engine of over 60 # can be achieved. When burning gasoline (injection of the same in front of or into the suction lines of the working cylinder), this level is sufficient to preheat the combustion air and there is no need to arrange a separate regenerative heat exchanger.

When burning light or heavy oils (by direct fuel injection into the combustion chambers of the working cylinders), the combustion air exiting the cylinder heads is heated by at least one of the exhaust gases from the working cylinder or the exhaust gases from the expansion unit for the purpose of further heating before it enters the combustion chambers of the working cylinders regenerative heat exchanger passed and further heated (up to 750 ⁰ C). This enables a further increase in the overall efficiency.

According to another essential feature of the invention is used to achieve an approximate constant-space combustion (which is accompanied by a sharp rise in pressure in the combustion chambers of the Working cylinder is connected and thereby further increases the overall efficiency) the introduction of the by the compressor unit compressed combustion air into each working cylinder during the retraction of the piston from lower to upper Dead center, preferably carried out in the second half of the same. The inlet valve of each working cylinder is used for this purpose A maximum of 90 crank angle degrees, but preferably 60 - 45 crank angle degrees open before top dead center and 15-0 crank angle degrees closed before top dead center.

If very high engine speeds are required, before Introducing the compressed combustion air into a working cylinder it is flushed with low-compression purging air, mainly over the first Part of the piston decline. In this case the inlet valve

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of the working cylinder can even be opened 100 - 110 crank angle degrees before the upper (cylinder head side) dead center.

For flushing the working cylinder, the flushing air is expediently from a lower stage of the compressor unit taken. Or at least one separate scavenging air compressor is arranged on the shaft of the compressor unit .

According to another feature of the invention, the compressor unit in a manner known per se by means of an expansion unit (gas turbine, rotary piston cylinder, screw spindle expansion device) driven, which is acted upon by the exhaust gases of the working cylinder during operation. Through this Above all, a large overall expansion ratio can be achieved.

It is particularly advantageous if the drive of the Compressor unit takes place exclusively through one or more relaxation sag units, so that the compressor unit with the relaxation unit driving it is designed as a unit mechanically separated from the block of the working cylinder. In this way, for example, the speed of the compressor unit can be selected to be higher than the speed of the actual reciprocating piston motor. The limit measurement of the actual reciprocating engine can also be increased as a result.

When cooling the working cylinder, it is advantageous that when the working cylinder is designed as a reciprocating piston cylinder the combustion air coming from the compressor unit first enters the cooling spaces (cooling channels) around the liners and then the Flows through cylinder heads. This makes it possible to keep the parts of the liners wetted by the lubricating oil in a particularly cool manner keep.

According to another feature of the invention, the Exhaust gases exiting the working cylinders for the purpose of further cooling via at least one regenerative heat exchanger to the Relaxation unit or the relaxation units passed. This allows the heating surface of the heat exchanger to be kept smaller because the pressure of the exhaust gases is still considerably above atmospheric pressure and therefore higher heat transfer on the exhaust gas side numbers can be achieved. It is advantageous to

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regenerative heat exchanger at least one with a shut-off valve provided bypass duct on the exhaust gas side in order to apply hotter exhaust gases to the expansion unit if necessary and thereby, for example, the engine speed radch increase.

In order to improve the cooling of the liners, they are provided with cooling fins on their outer surfaces, which are preferably are designed as single or multiple screw ribs or as ribs parallel to the longitudinal axis of the liner. For education ■ «η cooling channels, these cooling fins extend to the inner surfaces the actual working cylinder. These cooling channels are to be designed in such a way that, with regard to the speed of the combustion air, whose pressure loss and cooling effect are balanced.

In the execution of the internal combustion engine for gasoline combustion - i.e. without regenerative heat exchanger - flows through the combustion air exiting the cylinder head is fed into an expansion tank before it enters the intake port of the cylinder head, in order to ensure almost steady flow conditions in the cooling channels of the liner. Behind this A gasoline injection nozzle is used in a known manner in front of or in the intake duct of the working cylinder (cylinder head) arranged.

In order to largely reduce the heat loss of the internal combustion engine, the working cylinders are individually or in blocks Surrounded by thermal insulation in a manner known per se.

In order to significantly improve the acceleration ability of the internal combustion engine for operation, it has for the Relaxation unit at least one with a drainage valve equipped pressure storage boiler, which is charged from the pipe network of the combustion air via a throttle orifice. Through open the drain valve can temporarily connect to the expansion unit additional working medium supplied.

Purely the application of the intercooler of the compressor, unit with cooling air, at least one cooling air fan is arranged on the shaft of the compressor unit. The intercooler but can also be acted upon by means of cooling water.

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If the working cylinders of the internal combustion engine are designed as rotary piston cylinders (as in the Wankel engine), then The combustion air also flows through the eccentric shaft for the purpose of cooling. In such an internal combustion engine, the compressor unit for the combustion air and / or the expansion unit for the exhaust gases of the working cylinder on the eccentric shaft arranged, preferably coupled.

In the drawings are two embodiments of the subject invention and two temperature-entropy diagrams. It shows

1 shows a sketch of a first embodiment for gasoline combustion without a regenerative heat exchanger.

FIG. 2 shows a section through a working cylinder along the line A-B of FIG. 1.

3 that for the first embodiment of the internal combustion engine corresponding temperature-entropy diagram.

4 shows a sketch of a second embodiment for the combustion of light or heavy oil with a regenerative heat exchanger and a compressor unit mechanically separated from the working cylinder.

5 that of the second embodiment of the internal combustion engine corresponding temperature-entropy diagram.

In the gasoline engine according to FIGS. 1 and 2, the working cylinder (reciprocating piston cylinder) 1 consists of the actual working cylinder 1a and the cylinder head 1b with the intake valve 2 and the exhaust valve 3 and the spark plug 4. Furthermore, a Purge air valve 21 arranged. The working cylinder 1 is clad on the outside with thermal insulation 1c. In the actual working cylinder 1a is the liner 5 with helical cooling fins 5a arranged. The likewise helical cooling air ducts 6 are located between the cooling ribs 5a. The piston 7 is delimited the combustion chamber 7a below and transmits the force of the working gases via the connecting rod 8 to the crankshaft 9

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The top of the liner 5, the bottom of the cylinder head 1b and the top of the piston 7 are with inner Quartz glass insulation 10 lined in order to extract less heat from the combustion gases in the combustion chamber 7a.

A shaft 12 is mechanically articulated to the crankshaft 9 via the transmission 11, which the compressor unit 13, the relaxation sag unit 14 (designed as a gas turbine) and the cooling air fan 15 carries. The compressor unit 13 consists of three connected in series on the combustion air side Screw screw compressors 13a, 13b and 13c, between which intercoolers 16a and 16b for the combustion air are arranged are. The intercoolers 16a and 16b are operated by the cooling air fan 15 applied with low pressure cooling air.

The combustion air emerges from the compressor unit 13 and flows into the working cylinder via the connecting line 17a 1, through its cooling air ducts 6 in the cylinder head 1b and from this via the expansion tank 17b and the intake duct into the combustion chamber 7a. In front of the intake channel 18 is the gasoline injection nozzle 19 arranged.

After ignition and combustion of the gasoline-air mixture in the combustion chamber 7a, the exhaust gases from the working cylinder 1 landed on the Outlet channel 20 and the connecting line 17c to the expansion unit 14 (gas turbine), where they complete a residual expansion and do additional mechanical work.

In Pig. FIG. 2 also shows the control diagram for the inlet valve 2, the outlet valve 3 and the purge air valve 21 of the working cylinder 1 of the internal combustion engine. (Direction of rotation crankshaft counterclockwise.)

The working cycle is comparable to that of a conventional two-stroke engine, as it happens with every revolution of the crankshaft a work cycle takes place.

During the piston swing from the cylinder head side to the crank side dead center, the expansion takes place via the crank angle # " of the combustion gases with the release of mechanical work. During this phase are inlet valve 2, outlet valve 3 and Purge air valve 21 closed. That is via the crank angle cT Exhaust valve 3 open and the exhaust gases leave during the

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Piston decrease from the crank side to the cylinder head side Dead center the combustion chamber 7a of the working cylinder 1. With high-speed In engines, the exhaust gases are also scavenged via the crank angle £ while the piston is falling the purge air valve 21 is open.

During the subsequent crank angle oO (ie a maximum of 90 degrees, but preferably 60-45 degrees of winding before the cylinder head-side dead center opening and 15-0 degrees before the cylinder head-side dead center), the inlet valve 2 is open and the combustion chamber 7a is charged by compressed combustion air.

In the vicinity of the top dead center, the crank angle β causes ignition and combustion of the gasoline-air mixture (in light oil or heavy oil engines, injection and combustion of the fuel). As a result of the approximate constant-space combustion achieved in this way, a strong pressure increase is achieved in the combustion chamber 7a, which considerably improves the overall efficiency.

The purge air is after the first stage 13a of the compressor unit 13 taken. However, a separate scavenging air compressor can also be arranged on the shaft 12.

That in Pig. The temperature-entropy diagram shown in FIG. 3 shows the thermodynamic changes in state of the combustion air or the combustion gases in the internal combustion engine according to FIG. 1 and Pig. 2. The strong rise in pressure is particularly important remarkable by realizing an approximate constant-space combustion.

The second embodiment of the internal combustion engine according to Pi «. 4 has a fuel injector 22 for the combustion of light or heavy oil, and a regenerative heat exchanger 23 in. Is further heated to exiting the Zylinderkpf 1b combustion air by the exhaust gases of the Arbeitszylinüers 1 (up to about 75O ⁰ C). The exhaust gases emerging from the heat exchanger 23 still have a pressure of 3-6 bar and then expand in the expansion unit 14.

The heat exchanger 23 has on the exhaust gas side one with a

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Shut-off valve 24 provided bypass channel 25, above which when required sf all hotter exhaust gases are directed to the expansion unit 14 can be used to increase its performance.

If necessary, the heat exchanger 23 can also be switched on the exhaust gas side in such a way that it is acted upon by the exhaust gases emerging from the expansion unit 14.

The compressor unit 13 is only used by the expansion unit 14 and is mechanically separated from the Karbeiwelle 9 of the working cylinder 1.

The expansion unit 14 has a drain fitting 26 provided pressure storage tank 27, which is charged via a throttle orifice 28 from the pipe network 17 of the combustion air will. Due to the contents of the pressure storage tank 27, the expansion unit 14 can temporarily receive additional working medium and its performance can be increased as a result.

Otherwise, identical parts in FIG. 4 have the same reference numbers as in Pig. 1 and 2.

In the temperature-entropy diagram according to FIG. 5, the thermodynamic changes of state are plotted that the combustion air or the combustion gases in the internal combustion engine of the second embodiment (according to FIG. 4).

The lines A-B, C-D and E-F represent the partial compressions in the compressor unit 13. The lines B-C and D-E show the intercooling in the intercoolers 16a and 16b. The distance F-G shows the heating of the combustion air in the cooling channels 6 and in the cylinder head 1b. The section G-H shows the heating of the combustion air in the regenerative heat exchanger 23. The segment H-J shows the increase in temperature and pressure as a result of the constant-space combustion. J-K shows the expansion during the working stroke. K-L shows the cooling of the exhaust gases from the working cylinder 1 in the regenerative heat exchanger 23.L-M shows the post-expansion of the working cylinder exhaust gases in the expansion unit 14

Instead of one working cylinder 1, the internal combustion engines according to FIGS. 1, 2 and 4 can also have several working cylinders own.

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L e r s e i t e

Claims (21)

Patent claims fly internal combustion engine, consisting of at least one multi-stage Compressor unit with intermediate cooling for approximately isothermal compression and one or more working cylinders (Piston stroke cylinder or rotary piston cylinder) for intermittent combustion and expansion and possibly one or more Heat exchangers, characterized in that the combustion air emerging from the compressor unit (s) (13) during operation for cooling around the working cylinder (1) or their liners (5) and after absorbing the cooling heat there directly or optionally via one or more heat exchangers (23) into the combustion chambers (7a) of the working cylinder (1) to be led. 2. Internal combustion engine according to claim 1, characterized in that the exiting from the cylinder head (Ib) or the cylinder heads Combustion air for the purpose of further heating before entering the combustion chambers (7a) of the working cylinder or the combustion chamber of the working cylinder via at least one of the exhaust gases of the working cylinder (s) (1) or of the exhaust gases of the expansion unit (H) or the expansion units are heated regenerative heat exchanger (23) is passed. 3. A method for operating one of at least one compressor unit and one or more working cylinders (piston stroke cylinders) and optionally one or more heat exchangers and / or an exhaust gas expansion unit (gas turbine, rotary piston cylinder, etc.) existing internal combustion engine, thereby characterized in that, in order to achieve an approximate constant-space combustion, the introduction of the by the compressor unit (13) compressed combustion air into each working cylinder (1) during the retraction of the piston (7) from the crank-side to the cylinder head-side dead center, preferably in the second Half of the same, takes place. and cylinder heads (1b) 909815/0574 4. A method for operating an internal combustion engine according to claim 3, characterized in that the inlet valve (3) of each working cylinder (1) a maximum of 90 degrees of crank angle, preferably but 60 - 45 degrees of crank angle before the cylinder head-side dead center opens and 15-0 crank angle degrees in front of the cylinder head Dead center closes. 5. A method for operating an internal combustion engine according to claim 3, characterized in that in order to achieve high engine speeds before the introduction of the compressed combustion air in a working cylinder flushing the same with low pressure scavenging air, mainly via the first part of the crank return (Crank angle £) takes place. 6. A method for operating an internal combustion engine according to the claims 3 and 5, characterized in that the scavenging air is taken from a lower stage (13a) of the compressor unit (13) will. 7. Internal combustion engine according to claim 1, as well as claims 3 and 5f, characterized in that on the shaft (12) of the compressor eraggregat there (13) at least one separate scavenging air compressor is arranged. 8. Internal combustion engine according to claim 1, characterized in that the drive of the compressor unit (13) is known per se Way through an expansion unit (gas turbine, rotary piston cylinder, Screw-spindle expansion device) (14) takes place, which during operation of the exhaust gases of the working cylinder (1) or the working cylinder is acted upon. 9. Internal combustion engine according to claims 1 and 8, characterized in that that the compressor unit (13) is driven exclusively by one or more expansion units (14), and that the compressor unit (13) with the (s) it drive expansion unit (s) (14) as one of the block of the working cylinder (1) a mechanically separated unit. 909815/0574 10. Internal combustion engine according to claim 1, characterized in that "when the working cylinder (1) is designed as a piston-stroke cylinder the combustion air coming from the compressor unit (13) first enters the cooling spaces (cooling channels 6) around the liner (5) and then the Cylinder head (1b) flows through each working cylinder (1). 11. Internal combustion engine according to claims 1 and 2, characterized that the exhaust gases emerging from the working cylinders or the working cylinder (1) for the purpose of further cooling at least one regenerative heat exchanger (23) are passed to the relaxation unit (H) or the relaxation units. 12. Internal combustion engine according to claims 1 and 11, characterized characterized in that for the regenerative heat exchanger (23) or for the regenerative heat exchangers at least one with a shut-off valve (24) provided exhaust-side bypass channel (25) is arranged. 13. Internal combustion engine according to claim 1, characterized in that that when the working cylinder (1) or the working cylinder is designed as a piston stroke cylinder, the liner (s) (5) at their (s) Outside (s) is or are provided with cooling fins, which are preferably are designed as single or multiple screw ribs or as ribs parallel to the longitudinal axis of the liner. 14. Internal combustion engine according to claims 1 and 13 »characterized in that the cooling fins (5a) of the liner (s) (5) for the purpose of forming cooling channels (6) on the inner surface (s) of the actual working cylinder (s) (1a) close or approximately fit tightly. 15. Internal combustion engine according to claim 1, characterized in that the cylinder head (1b) of each working cylinder (1) exits Combustion air flows through an expansion tank (17b) before it enters the intake duct (18) of the cylinder head (1b) . 16. Internal combustion engine according to claim 1, characterized in that in front of "or in the AnJigkanal (18) of each working cylinder in A gasoline injection nozzle (19) is arranged in a manner known per se 909815 / Ö57A ^it 17. Internal combustion engine aach claim 1, characterized in that the working cylinder (1) individually or in blocks in itself
are surrounded in a known manner by thermal insulation (1c). 18. Internal combustion engine according to claims 1 and 8, characterized in that the expansion unit (14) has at least one with a drain valve (26) provided pressure storage tank (27) from the pipe network (17) of the combustion air
a throttle screen (28) is charged. 19 · Internal combustion engine according to claim 1, characterized in that at least one cooling air fan (15) is arranged on the shaft (12) of the compressor unit (13), which is the
Intercooler (16a, 16b) of the same supplied with cooling air. 20. Internal combustion engine according to claim 1, characterized in that when the working cylinder (1) is designed as a rotary piston cylinder (Wankel engine) during operation, its eccentric shaft also flows through its eccentric shaft for cooling of compressed combustion air will. 21. Internal combustion engine according to claim 1, characterized in that when the working cylinder (1) is designed as a rotary piston cylinder #as compressor unit (13) for the combustion air and / or the expansion unit (14) for the exhaust gases from the working cylinder (1) arranged on the eccentric shaft, preferably coupled
is. 909815/0574