DE102012002566A1 - Heat engine, particularly four-stroke petrol and diesel engine for use with combustion air injection, has compressed air storage for cylinder filling, where variable compaction takes place based on filling degree at constant cylinder volume - Google Patents

Abstract

The heat engine has a compressed air storage for cylinder filling, an engine control device with a combustion air characteristic field. The purge air flow is passed into the inflation air flow by closure of the exhaust valve (4) for exhaust residue discharge. The combustion air injection takes place in the charge exchange stroke before the power stroke, in which the piston moves from the bottom to top dead center of the cylinder and the residual exhaust gases are flushed out by the inflowing combustion air. The variable compaction is carried out based on different filling degree at constant cylinder volume by variable activation periods of compressed air injectors (2) and variable opening cross-sections. An independent claim is included for an operating method for a heat engine.

Description

In a comparison of the reciprocating engine with the gas turbine, it can be seen that the processes in the reciprocating engine run sequentially in the same room, while they take place in a gas turbine simultaneously at different points of the engine. The gas turbine works in contrast to the piston engine with continuous combustion. This leads to a better use and thus to a smaller power mass of the gas turbine. By combining the characteristics of a compressor of a gas turbine with a piston engine omitted in a four-stroke engine, the two clocks suction and compression. This corresponds to a 360 ° rotation of the crankshaft and the elimination of the frictional losses of the crank mechanism and intake valve control as well as reduced heat losses. The disadvantages such as the decrease in torque at low or higher speeds, caused by lack of gas dynamics or shortening of Einströmzeiten, and rinsing losses omitted. Reason enough to rethink the now about 140 years old work process. The following describes an engine that can be classified as a two-stroke engine according to its working method.

The two-stroke engine requires two piston strokes or one crankshaft revolution for one working cycle. A working cycle describes the movement of the piston from top dead center (TDC) to bottom dead center (TDC) and vice versa. The new thing about it, in this engine, the entire combustion air is injected under pressure by means of a Druckluftinjektor in the cylinder. The blowing process takes place in the optimized exhaust stroke. The original exhaust stroke becomes the charge cycle cycle. Due to the changed gear ratio, crankshaft exhaust camshaft, from 2-1 to now 1-1, the exhaust timing adapts to this working method. Due to the positive purging gradient (increasing internal cylinder pressure higher than exhaust backpressure), the charge exchange work is much easier. The decoupling of the intake and compression stroke from the working process is characteristic of this engine. Over the entire operating range, from idling to full load, it works as a supercharged engine. So far, a conventionally charged engine in the idling and lower part load range was running in the suction mode. The system is structurally similar to common rail injection.

An air compressor fills a compressed air reservoir during operation. The compressed air reservoir replaces the intake manifold. The compressed air injectors are connected either directly or indirectly via pipes to the compressed air reservoir. The compressed air injectors replace the intake valves and are operated electromagnetically and controlled by the engine control unit. For this purpose, a separate map is stored. By means of a compressed air injector with variable nozzle different cylinder pressures in different load ranges can be driven. This equals a previously variable compression. The air exiting the compressed air injector at high pressure and pressure deprives the environment of much heat, which improves internal cooling and decreases the tendency to knock (in gasoline mode).

• – Betrieb mit Benzin, Gas und Diesel
• – Innere Gemischbildung Während des Ladungswechseltaktes gelangt das Abgas vom Zylinder in den Abgaskrümmer und Verbrennungsluft über den Druckluftinjektor in den Zylinder. Das Kraftstoffluftgemisch wird durch Einspritzen von Kraftstoff in den Zylinder während des Ladungswechseltaktes gebildet.
• – Gleichraumverbrennung bei Benzin und Gasbetrieb
• – Gleichdruckverbrennung bei Dieselbetrieb
• – Quantitätsregelung Die Menge der Verbrennungsluft regelt nicht mehr die Drosselklappe, sondern die zeitliche Ansteuerung der Druckluftinjektoren sowie deren Öffnungsquerschnitt. (Abweichung vom Ottomotor)
• – Qualitätsregelung Die Menge des eingespritzten Kraftstoffes wird durch die Ansteuerzeit der Einspritzventile verändert (wie beim Dieselmotor).
• – Druckluftinjektoren als Ersatz für Einlassventil
• – Druckluftspeicher mit Sensoren
• – Motorsteuergerät mit Verbrennungsluftkennfeld
• – Zylinderkopf mit drei Auslassventilen (Regelfall)
• – Abgasturbolader mit zusätzlichen Axialverdichter
• – Mehrstufiger Abgasturbolader
• – Abgasturbolader mit Elektroantrieb

The engine with combustion air injection has the following features:

• - Operation with gasoline, gas and diesel
• - Internal mixture formation During the charge cycle, the exhaust gas passes from the cylinder into the exhaust manifold and combustion air via the Druckluftinjektor in the cylinder. The fuel-air mixture is formed by injecting fuel into the cylinder during the charge cycle cycle.
• - Equilibrium combustion in gasoline and gas operation
• - Constant pressure combustion in diesel operation
• - Quantity control The amount of combustion air no longer regulates the throttle valve, but the timing of the compressed air injectors and their opening cross-section. (Deviation from gasoline engine)
• - Quality control The amount of injected fuel is changed by the actuation time of the injectors (as with the diesel engine).
• - Compressed air injectors as a replacement for intake valve
• - Compressed air storage with sensors
• - Engine control unit with combustion air map
• - Cylinder head with three exhaust valves (standard case)
• - Exhaust gas turbocharger with additional axial compressor
• - Multi-stage turbocharger
• - Exhaust gas turbocharger with electric drive

1. Operation of the internal combustion engine with combustion air injection gasoline operation

Charge cycle clock:

The outlet valve opens approx. 40-90 ° before UT. As a result of the residual combustion pressure of 3-5 bar remaining at the end of the power stroke, the exhaust gases, which are up to 900 ° C, puff out of the cylinder at the speed of sound. In the area of the bottom dead center, the compressed air injector opens and blows a short but powerful purging air flow downwards to the piston crown, through the shape of which it is deflected and guided in the direction of the outlet valve. The exhaust valve closes approx. 20-40 ° KW to UT. When now going up piston opens the Druckluftinjektor a second time and fills the cylinder with only so much combustion air, that depending on the speed and torque an ignitable mixture of rich over Stoichiometric to lean sets. After the compressed air injector is closed, fuel is sprayed into the resulting air vortex in a finely atomized state. The then forming fuel air mixture is ignited by spark depending on the speed 0-40 ° CA (crank angle) before TDC. The control of the compressed air injector is shifted at ever higher speeds and thus ever shorter periods of time up to a control. The scavenging air flow then passes by closing the exhaust valve in the filling air flow.

Power stroke:

The combustion is initiated by the skipping of the spark at the electrodes of the spark plug. The expansion of the up to 2500 ° C hot gases drives the piston to the bottom dead center, the heat energy is converted into mechanical energy. The maximum combustion pressure of 30-60 bar is available 4-10 ° CA after TDC.

1.1. Starting process with the engine with gasoline operation (multi-cylinder engine)

After switching on the ignition, an electric motor starts, the z. B. drives a two-stage axial compressor. The axial compressor sits directly in front of the radial compressor of an exhaust gas turbocharger and can be coupled with it via an overrunning clutch. This axial compressor now conveys combustion air into the compressed air reservoir for a few seconds up to the stuffing limit. The engine control unit uses the compressed air sensor on the accumulator to recognize the preprogrammed value (nominal / actual comparison), actuates the corresponding compressed air injector (piston in the power stroke), measures the fuel and triggers the ignition. The compressor, which is arranged in front of the turbocharger and possibly multistage, is always switched on when the pressure in the compressed air reservoir falls below a certain value. This will usually be the case, for example, at idle with insufficient exhaust gas flow rate. The crankshaft position must be made before the restart so that the piston has the highest combustion pressure in the power stroke before or with the tangle of the connecting rod.

2. Operation of the internal combustion engine with combustion air injection diesel operation

Power stroke:

The combustion is triggered by reaching the autoignition temperature of the diesel fuel in the high density air. Due to the high combustion pressure of up to 160 bar, the piston moves to UT. Heat energy is converted into mechanical work.

Charge cycle clock:

The outlet valve opens 30-60 ° before UT. By still at the end of the power stroke existing pressure of 4-6 bar puffing the 550-750 ° C hot exhaust gases from the cylinder. In the area of the bottom dead center, the compressed air injector opens and blows a short but powerful purging air stream downwards to the piston crown, through the special shape of which it is deflected and guided in the direction of the outlet valve. The outlet valve closes 20-40 ° CA to UT. When now going up piston opens the Druckluftinjektor a second time and fills the cylinder with combustion air. When now closed Druckluftinjektor the trapped combustion air is compressed by the upward piston after. The control of the compressed air injector is shifted at ever higher speeds and thus ever shorter periods of time up to a control. In other words, the scavenging air flow passes into the filling air flow by closing the outlet valve. Shortly before top dead center, the air on the 14-24. Part of the original cylinder space after compressed. The air heats up to 600-900 ° C. Since the air at the high temperature and piston position can not expand immediately before TDC, the compression pressure increases to double (30-55 bar). About 15-30 ° CA before TDC diesel fuel is injected under high pressure finely atomized. In the hot air, the fuel evaporates and mixes with the air. Since the temperature of the compressed air is higher than the auto-ignition temperature of the diesel fuel of 320-380 ° C, the combustion is triggered. The mixture formation lasts over the beginning of combustion.

2.1. Starting procedure for the engine with diesel operation (multi-cylinder engine)

After switching off the engine, the crankshaft swings out. The piston of the cylinder with charge cycle and closing the exhaust valve comes to about 2/3 to 3/4 of the lifting height by the compression work now stopped. The piston of the cylinder with power stroke would be 1/3 to 1/4 before the bottom dead center. When restarting this constellation would be conceivably unfavorable. Therefore, the crankshaft position must either be taken when the engine is stopped or when restarting so that the piston comes to rest from the cylinder with power stroke immediately after top dead center. Babel can fix the crankshaft either with programmed Verbrennungslufteinblasung or shutdown via a grid gear. The now optimal for a restart piston in the cylinder with power stroke could exert enough force on the crankshaft and now generate a torque at the onset of working. The injected combustion air would heat up quickly in this small volume through the glow plug to autoignition temperature and ensure ignition of the injected diesel fuel.

Claims (13)

Heat engine with combustion air injection by means of compressed air injector. Compressed air cylinder for cylinder filling. Combustion air map in the engine control unit. Purge air flow for the purpose of exhaust residue emptying. Filling air flow for cylinder filling. Charge cycle cycle (combined exhaust stroke with residual compression stroke). Charged engine also in the idling and lower part load range up to the full load range. Variable compression based on different degree of filling with constant cylinder volume due to variable actuation times of the compressed air injectors and variable opening cross sections. Working procedure consisting of charge cycle with combustion air injection and conventional fuel injection and ignition triggering by means of spark plug and subsequent power stroke (gasoline operation). Working process consisting of charge cycle with combustion air injection and conventional fuel injection with high residual compression and thus ignition triggering (diesel operation) and subsequent power stroke. Starting function: with introduction of the working procedure. Quantity regulation in gasoline and gas operation by variable actuation times of the compressed air injectors and optionally variable opening cross-section. Charging with turbocharger (single or multi-stage) as well as electric drive or mechanical charger, both in connection with combustion air injection.

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