FI108567B - Two-stroke engine - Google Patents

Abstract

in a two-stroke engine, two pistons 11a, 11b are coupled together in such a way that when one cylinder 15a has a compression stroke, the other cylinder has an expansion stroke. A shaft 13 interconnecting said pistons 11a, 11b is provided with dynamical magnetic bearings 12 and contact-less seals 14 such as labyrinth seals. <IMAGE>

Description

108567

Two-stroke engine

The invention relates to a two-stroke internal combustion engine according to claim 1.

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The best efficiency of internal combustion engines is usually achieved with large two-stroke diesel engines, so called crosshead engines. The net efficiency of such a turbocharged engine is about 50%. However, the crankshaft mechanism used in the engine with its bearings causes significant losses. Furthermore, the lubricating oil used to lubricate the bearings and piston causes significant operating costs. In addition, it contaminates the exhaust fumes so that the sludge oil deposit significantly increases the cost of cleaning the gas boiler. Of course, lubricating oil is also a significant environmental hazard. If no lubricating oil were needed, a two-stroke diesel engine with 15 natural gas high pressure injection would be quite environmentally friendly.

It is an object of the present invention to provide an improvement to the above problems. The object of the invention is mainly achieved by the features of patent claim 1.

The invention is illustrated in the following description and in the appended claims , in drawings with ί. * ·. Fig. 1 is a longitudinal cross-sectional view of the invention. 2 and Fig. 2 is a schematic perspective view of an embodiment using four two-stroke motors of Fig. 1 as a group.

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The principle of the motor according to the invention is shown in Fig. 1. The basic element is two interconnected pistons 11a, 11b (at opposite ends of the shaft 13), which are supported by active magnetic bearings (with feedback loops). the shafts 12 keep the shaft 13 connecting the pistons 11a, 11b in a continuous line at a desired accuracy of about 0.01 mm by means of a powerful, continuously adjustable magnetic field 2! UH 567. Non-contact Laby breast seals are used as seals 14 for pistons 11a, 11b and shaft 13 with respect to the frame structure 15. The entire piston mechanism moves without mechanical contact 5 to the frame structure 15 and thus no lubricating oil is required.

Power from the motor is obtained by a linear generator 16. With the pistons 11a, 11b, a movable rotor 17 interposed therebetween, mounted on a shaft 13, is magnetized, e.g., by a flexible cable 18, and the magnetization current is continuously adjusted by the regulator 28 a generator consisting of a rotor 17 and a stator 19 connected to the frame structure 15 surrounding it, to its inner surface, provides a suitable counter-force for the operation of the piston 11a, 11b. Linear generator 16 generates asynchronous, mainly high frequency, current that is transformed | drive 20 to a network-compatible, synchronized alternating current.

Let's take a closer look at the cycle. As the upper piston 20a of Fig. 1 moves upwards, it compresses the air in the cylinder 15a, the temperature of which increases as a result of the compression work. At the same time, the piston 11b performs a duty cycle, i.e. the combustion gas below it expands. Fr. the piston 11a is near the upper dead center, the lower piston 11b opens; in cylinder 15b, the exhaust valve 21b, and the exhaust gases can flow: 25 to turbine 23 of turbocharger 22. As the piston 11a has moved slightly 1 (· · upwards, the air * · passages 24b in cylinder 15b of lower piston 11b open and release piston 11b and Now, the upper piston 11a is at the dead center, and its cylinder 15a is injected with injection valve 30a for a fuel (liquid or gaseous, or a mixture of gas and air, so called pilot fuel), which ignites according to the principle of diesel. Now, the upper piston 11a begins to move downward, starting the stroke, while the lower piston 11b in the cylinder 15b has the exhaust valve 21b closed and therein begins the compression stroke described above with respect to the piston 11a. to the compressor 26 of the urban compressor 22.

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The cycle described above is the normal cycle of a conventional large two-stroke diesel engine, except that the piston movement is now not controlled by the crankshaft. When the pistons 11 are always moving in one of the cylinders 5a 15a or 15b, the work is in progress, which ensures the continuity of the process. The compression ratio of the engine is no longer determined by the crankshaft sizing, but by the timing of the injection and exhaust valves and the counter-force produced by the line generator 16.

10 As the pistons move back and forth, a moment of inertia swings up and down of the body structure 15. This can be compensated by placing the four units formed by the pistons 11a, 11b, the shaft 13, the linear generator 16 and the frame structure 15 into one interconnected group, as shown in Figure 2, with the axes 13 parallel. The movements of the pistons 15 in these are timed such that when the pistons move upwards in the cylinders a and b, they always move downwards in the cylinders c and d, and vice versa. In this way, the inertia forces are compensated and the motor is completely vibration free.

20 In large engines, piston cooling is traditionally done with lubricating oil. On the other hand, the need for cooling the piston is increased by the requirement for lightness, which usually results in poor material resistance to heat. (Aluminum alloy). In this case, the piston is not set to the same size: ·. *. 25, because the reciprocating motion is performed on a high load-bearing, articulated shaft 13. The piston could be made! heat-resistant, nickel-based alloy (eg Inconel series) and coated with ceramic material. Then the piston cools sufficiently through its bottom.

30 Conventional engines use oil-lubricated piston rings to seal the piston. The multi-stage labyrinth seal 14 used herein achieves sufficient sealing when the clearance between the labyrinth ridge and the frame structure 15 can be kept sufficiently low. This one. For this purpose, active clearance control can be performed in the same way as. 35 other applications, such as modern jet engines. The sensors then continuously measure the clearance between the piston 11a (11b) and the cylinder 15a, (15b), and adjust accordingly the rotation of the coolant media in the cooling sols 28a, 28b, which are placed in the frame structure 15 of the cylinders 15a, 15b. 15a, 15b.

The cooling of the linear generator 16 can be treated, at least in some cases 5, by the air flow generated by the reciprocating motion of the rotor 17 without a separate fan.

The motor can be started, for example, by compressed air or by using the generator 16 as a linear motor. Compressed air actuation 10 may be effected, for example, as follows: Compressed air is supplied to the lower cylinder 15b through the compressed air valve 29 so as to cause the upper piston 11a to rise to the upper dead center, and to inject fuel into the upper cylinder 15a. At the same time, the exhaust valve 21b of the lower cylinder 15b is opened so that the pressure 15 of the lower cylinder 15b decreases sufficiently so that the stroke of the upper cylinder 15a can lead to the upper dead center of the piston 11b. Fuel injection into the lower cylinder 15b is then performed and the engine continues to operate normally.

By way of example, the engine according to the invention is compared with a pe-20 slope engine. The application is primarily intended to be a large two-stroke engine, with power per megawatt per cylinder. Compared to a conventional engine, there are far fewer parts; mm. crankshaft, connecting rod and crankshaft bearings missing. In addition, the entire lubricating oil system is missing (the turbocharger can also easily be equipped with magnetic bearings). Thus, it can be estimated that despite the more complex control systems and the frequency converter, the motor of the invention would become the same. smaller than a conventional engine in the size class. The simple design allows for a higher average piston speed than the traditional engine, which further reduces the specific investment.

The efficiency of a modern large two-stroke diesel engine is about 50%. Because the motor of the invention is completely devoid of bearings. and lubricating oil losses, the efficiency can reach up to 55%.

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By eliminating the consumption of lubricating oil and the cost of processing it, operating costs are significantly reduced. In addition, the contamination of a potential gas boiler is reduced, as noted above.

Since only two cylinders are connected together in the engine according to the invention, the engine of the desired size can be easily assembled without any design. Of course, the cylinder blocks can also be placed horizontally.

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Claims (10)

108567 A two-stroke engine, wherein two pistons (11a, 11b) are coupled together such that when one of the cylinders (15a) has a compression stroke and the other has a stroke (15b), characterized in that the shaft (11a, 11b) 13) are provided with active magnetic bearings (12) and non-contact seals (14), such as labyrinth seals. A two-stroke motor according to claim 1, characterized in that the net power of the motor is arranged to be supplied by a linear generator (16) on the shaft (13) between the pistons (11a, 11b) whose current is arranged to be transformed by a frequency converter (20) 15 Motor according to Claim 2, characterized in that the magnetization of the rotor (17) of the linear generator (16) is arranged to be adjustable by the regulator (28) such that the linear generator (16) produces an optimum for the movement of the pistons (11a, 11b) 20 counterattacks. A two-stroke engine according to any one of claims 1 to 3,. characterized in that four units formed by two pistons (11a, 11b) are formed as an interconnected assembly such that when: in the first and second units (a and b), the pistons (11a, 11b) move upwards, the pistons in the second and in the third unit (c and λ · * d) downwards so that the counter forces and moments are compensated and the assembly becomes vibration-free. A two-stroke motor according to claim 4, characterized in that the movement of the pistons (11a, 11b) of the units is coordinated by a group controller acting on the controller (28) of the linear generator (16). Two-stroke engine according to one of Claims 1 to 5, characterized in that the engine is a diesel engine fueled by natural gas .1 · ·. j 7 108567 Two-stroke engine according to one of Claims 1 to 6, characterized in that the clearance between the piston (11a, 11b) and the cylinder (15a, 15b) is arranged to be adjustable in the body cooling sol (28) by a filing 5 cooling medium circulation. A two-stroke engine according to any one of claims 1 to 7, characterized in that the reciprocating motion of the rotor (17) of the linear generator (16) is arranged to provide air circulation for cooling the linear generator (16). A two-stroke motor according to any one of claims 1 to 8, characterized in that the motor is arranged to be started by using a linear generator (16) as a linear motor which produces sufficient movement of the pistons (11a, 11b) to start the process. Two-stroke engine according to one of Claims 1 to 8, characterized in that the engine is arranged to be started by supplying compressed air to the second cylinder (15a, 15b) by means of a valve (29) in the body (15) so that the piston (11a, 11b) sufficient movement. t I 1 • tl · t t »t» «« I »•» * · »· · 3 1 0 8 5 67