DE102017116799A1 - Heat engine, method for operating such a heat engine, motor vehicle and combined heat and power plant - Google Patents

Abstract

A heat engine having an internal combustion engine (10) with improved efficiency will be described. The internal combustion engine has at least one volume-variable working space (16), which can be connected to an intake tract (20) and an exhaust gas tract (22). To improve the overall efficiency, a water supply is provided, which opens into the working space (16) and / or into the exhaust gas tract (22), and in the exhaust tract (22) is arranged with an electric generator (28) coupled turbine (26). Furthermore, preferred methods for operating such a heat engine are proposed (FIG. 1).

Description

The invention relates to a heat engine according to the preamble of claim 1, a method for operating such a heat engine according to claims 9 to 14, a motor vehicle, an aircraft and a watercraft with such a heat engine according to claims 15 to 17 and a combined heat and power plant with such a heat engine according to claim 18.

Combustion engines are used in today's technology in very large quantities. The main application of such internal combustion engines is in the vehicle sector, especially in the automotive sector. Furthermore, internal combustion engines are also used in the stationary area, for example in combined heat and power plants. Such internal combustion engines are usually designed as reciprocating engines and have at least one piston-cylinder unit with a defined by piston and cylinder, variable-volume working space. This working space is connected to an intake tract and an exhaust tract. The term "intake system" is to be understood in this context very broad, it also refers to engines with a turbocharger or a charge air compressor, each with or without intercooler.

A known problem of internal combustion engines is their poor mechanical efficiency. The majority of the chemical energy used is lost through heat, which is particularly disadvantageous when using internal combustion engines in motor vehicles. The fact that much of the primary energy used is converted into heat is even doubly unfavorable. On the one hand, the proportion of usable mechanical work is relatively low, on the other hand, additional energy must be expended for the cooling, which further reduces the overall efficiency. In particular, usually a water cooler must be used, which has a negative effect on the energy consumption (fuel consumption) of the vehicle just by increasing the air resistance. Often, even at full load, a lot of fuel is injected to prevent the engine from overheating and non-self ignitors to start knocking. This additionally increases the fuel consumption. This problem occurs especially in downsizing engines.

Although a part of the thermal energy can be used in cogeneration plants according to the principle of heat coupling, the efficiency is still in need of improvement, especially at times when little heat is needed, namely in summer.

In turbocharged engines, the exhaust gas flow is used to drive (set in rotation) the turbine of the turbocharger located in the exhaust tract. However, since hot exhaust gases have a very low density, the efficiency of such a high-temperature exhaust gas turbine is also low. The fact that the turbine sits as close to the outlet as possible in order to achieve a quick response, additionally worsens the efficiency, because a highly pulsed gas flow can be used less efficiently than a more uniform one. In addition, the exhaust back pressure is quite high, since turbochargers build up at high speeds unnecessarily much pressure, which is then discharged via a wastegate valve in the exhaust, which further increases the back pressure.

In turbo engines, it is also known to inject water between the compressor and the working space (i.e., into the intake pipe) for charge air cooling.

On this basis, the present invention has the object to develop a generic heat engine to the effect that their overall efficiency is improved.

This object is achieved by a heat engine having the features of claim 1. Preferred methods for operating such a heat engine are given in claims 9 to 14. Such an engine may in particular be part of a vehicle (claims 15 to 17) or part of a combined heat and power plant (claim 18).

The basic idea of the invention is to inject water into the working space and / or the exhaust tract so as to increase the total amount of exhaust gas / dry steam and thus its density, in order to more effectively use the exhaust gas / vapor mixture to drive a turbine, which in turn generates an electric power Generator drives. The electrical energy generated in this way can in principle be used as desired. In the case of a combined heat and power plant thus increases the total amount of electrically generated energy, in the case of a motor vehicle, the electrical energy thus obtained can be used in a known manner, for example for driving one or more electric auxiliary motors (hybrid vehicle) or charging the battery.

The invention can be used in principle in all types of internal combustion engines and it will generally be preferred to use four-stroke reciprocating engines. As fuel all common fuels such as gasoline, diesel, LPG, natural gas, alcohol and hydrogen come into consideration.

Liquid water is injected into the working space and / or the exhaust tract. This water evaporates taking pictures of energy so that the water injection in addition to the cooling of the engine contributes. This in turn implies that the water cooler can be dimensioned significantly smaller or that even can be completely dispensed with in some applications on a water cooler, which further increases the overall efficiency of the motor vehicle (ie with the same mileage fuel consumption is reduced) and reduces structural measures.

The injection of water into the working space is, according to current knowledge, the most important embodiment of the invention. The mode of action will now be explained using a simple model. It is assumed that the ideal gas equation applies: $$\text{pV}=\text{NKT}$$

By evaporating the water, the number of gas particles N increases as the temperature decreases. That is, it can be achieved that the pressure remains constant at a given volume. Or in other words: The water injection leads by cooling to a pressure drop of the combustion gas, which is compensated at the same time by the formation of steam. Thus, the density of the turbine driving gas increases, which increases their performance / efficiency.

If the heat engine has a catalytic converter, the exhaust gas temperature should not fall below 400 ° C before this in regular operation to ensure that the catalyst continues to operate properly. In the case, the exhaust gas-steam mixture after the catalyst, before the turbine, further cooled to about 200 ° C and compressed by the forming dry steam. If no catalyst is present, for example, hydrogen as fuel, the exhaust gas temperature can be lowered directly after complete combustion in the combustion chamber, for example, 200 ° C. The pressure / temperature ratio should be designed so that the steam remains dry (dry steam) and not yet condensed (wet steam).

The beginning of the exhaust tract is preferably formed by a widening Auspuffvortopf that is formed by the resonance behavior that the (due to greater density) sluggish exhaust gas vapor mixture quickly escapes and the piston in the upward movement as little resistance opposes (smoothing of the exhaust back pressure).

Since the catalyst requires a minimum temperature to work effectively, it is preferably located in front of the turbine driving the generator. The combination of suitably dimensioned exhaust pre-well and catalyst smoothes the exhaust gas steam flow, which additionally increases the efficiency of the exhaust gas steam turbine. In order to keep the pressure loss by cooling over the outer walls of the exhaust tract low, this can be preferably isolated.

Since the exhaust steam turbine does not need to be trimmed to good responsiveness like a turbocharger, it can be optimized for high efficiency in the most common engine load conditions. The significantly higher density (at the same pressure) of the exhaust gas-vapor mixture significantly increases the efficiency of turbines, which is the gist of the invention. The proposed combination is well above the efficiency of, for example, a pure exhaust gas turbocharger with attached generator. Temperatures of only about 200 ° simplify high-efficiency turbine designs and significantly reduce the use of materials.

The main advantage of the invention is the generation of additional electrical energy, which is implemented with full (or missing) batteries directly via electric drive motors (which directly reduces consumption) or stores energy in the battery charging mode, which is used later (which indirectly reduces the consumption) ,

In embodiments where water is injected into the working space, the circuit water cooling can be significantly reduced or, for example, in freestanding cylinders even a simple air cooling soft, since the cooling / conversion of the heat takes place where it arises. A slightly larger sized oil cooler with a narrow circulation cooling in the upper area of the cylinder can also replace a circuit water cooling. This reduces the weight, the energy expenditure for cooling and the flow resistance, which makes up approximately 20% of the air resistance in water-cooled cars. The maximum heat is only a quarter turn instead of a whole and no longer flows through the cylinder head.

If a water injection is provided in the exhaust tract, this can be done before and / or after the turbine. A water injection in front of the turbine should be designed so that the steam in the exhaust-steam mixture remains dry, so it does not come to a condensation of the water vapor. As a result, the density of the exhaust gas-steam mixture is further increased, which further increases the performance / efficiency of the turbine. A possible water injection after the exhaust gas turbine serves another purpose, namely, by the evaporation of the hitherto dry steam of the exhaust gas-steam mixture to a temperature when he begins to condense. The then wet steam can then further condense in a (not shown here) condenser, settle and be recovered together with the injected water behind the turbine and fed to the water tank. Since conventional exhaust gas, for example, a gasoline combustion, already contains about 25% water vapor, an excess of water is present, so that not even 100% of the water must be recovered to obtain the required amount of water. The water tank can be kept very small and ideally, or rarely, refilled. If the cooling condenser is flat, designed as a large part of the subfloor, it has no negative effects on air resistance.

All types of water injection just described can be used individually or in any combination with each other.

Since less must be cooled in the usual way, the cooling over the cylinder walls is lower, whereby the pressure during the power stroke in the relevant range is better preserved, which increases the efficiency.

By cooling via the water injection, an increased mixture enrichment at full load is no longer necessary, which further reduces fuel consumption and promotes lean burn engines.

The water injection quantity, duration, pulse, and time is adjusted by the engine management of the load situation, which is cooled due to the situation.

Since the generator constantly supplies power while the engine is running, the capacities of the batteries can be significantly reduced or even completely dispensed with. Both reduce costs and weight, which in turn reduces fuel consumption and increases maneuverability.

Long charging times, such as plug-in hybrids or electric vehicles, can be shortened considerably or completely eliminated.

The generator can also be taken from the electrical system voltage, which saves the alternator.

The electrical energy can be used for an electric compressor that responds faster than a turbocharger and can be regulated better. It can also be used for electromagnetic valve control, which saves weight and eliminates the need for air cooling unfavorable (because insulating) chain case and a closed cylinder head camshaft housing.

Since water is already on board anyway, this can also be used to cool charge air.

• 1 ein Ausführungsbeispiel einer erfindungsgemäßen Wärmekraftmaschine in einer stark schematischen Darstellung,
• 2 den Motor der Wärmekraftmaschine der 1 während eines ersten Ausführungsbeispiels des erfindungsgemäßen Betriebs derselben,
• 3 das in 2 Gezeigte während eines zweiten Ausführungsbeispiels des erfindungsgemäßen Betriebs,

The invention will now be described with reference to preferred embodiments with reference to the figures. Hereby show:

• 1 An embodiment of a heat engine according to the invention in a highly schematic representation,
• 2 the engine of the heat engine the 1 during a first embodiment of the operation according to the invention,
• 3 this in 2 Shown during a second embodiment of the operation according to the invention,

The 1 shows an embodiment of a heat engine according to the invention. The basis of this heat engine is an internal combustion engine 10 , which may be designed in particular as a four-stroke internal combustion engine. This internal combustion engine 10 can have a piston-cylinder unit or any number of piston-cylinder units. Shown is merely a piston-cylinder unit with a piston 12 and a cylinder 13 , The piston 12 is in the usual way with a crank gear 18 coupled, so that piston 12 and cylinders 13 a variable volume workspace 16 define. This workroom 16 is the Otto or diesel engine via at least one inlet valve 14 with an intake tract 20 and at least one exhaust valve 15 with an exhaust tract 22 connected. The combustion engine side beginning of the exhaust tract 22 is preferably as Auspuffvordopf 23 educated. In the case of the internal combustion engine 10 a diesel or gasoline powered engine 10 is the Auspuffvortopf 23 usually in the flow direction of a catalyst 24 downstream. Furthermore, in the exhaust system 22 a turbine 26 arranged, which by means of a shaft 27 , directly or through a translation, with an electric generator 28 connected is. This generator 28 feeds the electrical energy generated by him either in an electrical storage, in an electrical load or (in the case of a stationary heat engine) in a power grid (generally with the reference numeral 30 designated).

Is a catalyst 24 provided, there is the turbine 26 preferably downstream of the catalyst.

There is one or more water supplies provided, each in one Injector end. In the exemplary embodiment shown, three water feeds are provided, each in one (shown) or several injection nozzles 40a . 40b . 40c lead. Im in 1 embodiment shown, a first injection nozzle opens 40a in the workroom 16 , a second injection nozzle 40b between catalyst and turbine and a third injection nozzle 40b behind the turbine. Preferably, the injection nozzles 40a . 40b . 40c designed to nebulize the injected under pressure liquid water to fine droplets. It is possible that the injectors inject pulsed.

It is first on the water injection into the working space by means of the first injection nozzle 40a received: According to a first method is one of the water injections, as in 2 shown during the intake stroke with the inlet valve open 14 and closed exhaust valve 15 , The injected water creates evaporative cooling which cools the charge air in turbocharged engines. This increases the density of the air and thus the amount of oxygen and reduces the tendency to knock in Nichtselbszündern in the subsequent compression stroke. The maximum pressure of compression before ignition can be higher, resulting in increased efficiency. A charge air cooling by water injection in the intake system is known and already in use. In this invention, as only one of a plurality of injections, it serves primarily to impart a higher density to the exhaust gas, and therefore, is to be regarded primarily as an enhancement / combination that supports this objective. Since it is only one of several injections at other times, the injection also takes place directly into the combustion chamber. Furthermore, it supports the effort to completely dispense with a water cooling.

For non-auto-igniters, such as a gasoline engine, one or more pulsed injections may be made during the compression stroke to further reduce knock (auto-ignition) at full load. This allows to further increase the compression ratio and to use cheaper regular gasoline. This injection is not shown in any figure.

As 3 shows, a water injection can also be done during the power stroke. The water evaporates, which leads to a cooling of the combustion gases, since the evaporation energy must be expended. In return, the total amount of gas is increased as described above. This denser, because cooler mixture of combustion exhaust gas and additional steam (exhaust gas-steam mixture) leaves in the exhaust stroke ( 1 ) the working space and then enters the exhaust tract 22 , In the illustrated embodiment, first in the Auspuffvortopf 23 ,

The three methods just described are preferably combined, for example, in that a part of the water in the intake stroke, a part in the compression stroke and a part of the water is injected in the power stroke. The injection quantity distribution between the cycles can be load-dependent. The duration of injection (s) after complete combustion can also extend from the power stroke to the exhaust stroke.

After flowing through the catalyst 24 compress further (pulsed) water injections by means of the second injection nozzle 40b the exhaust-vapor mixture again, so that the high-density cooled exhaust-vapor mixture then the turbine 26 drives.

Basically it is possible to use water via the water supply 40 in the also hot Auspuffvortopf 23 to inject in order to increase the amount of gas. However, this injection does not support the engine cooling and is not shown in any figure.

The water injection into a section of the exhaust tract behind the turbine by means of the third injection nozzle 40c serves to cool the exhaust gas vapor mixture to prepare it for condensation in a subsequent condenser. The condensed water can be collected and reused.

The combination of all three measures described will often be ideal in terms of the maximum efficiency of the heat engine, but it is at this point again to emphasize that the three measures described (water injection into the working space, water injection into the exhaust system before the turbine, water injection into the exhaust system behind the turbine) can also be used individually or in any "two-person combinations".

In principle, it is also possible for the water to mix quickly evaporating liquids such as alcohol.

The invention has been explained with reference to a heat engine whose internal combustion engine is a four-stroke reciprocating engine. This is the preferred but not the only possible embodiment. The internal combustion engine could also be a two-stroke reciprocating engine or a rotary engine (Wankel engine).

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

piston

13

cylinder

14

intake valve

15

outlet valve

16

working space

18

crank mechanism

20

intake system

22

exhaust tract

23

Auspuffvortopf

24

catalyst

26

turbine

27

wave

28

generator

30

electrical storage, electrical consumer or network

40a, b, c

injection

Claims (18)

Heat engine with an internal combustion engine (10) with at least one volume variable working space (16) which is connectable to an intake tract (20) and an exhaust tract (22), characterized in that at least one water supply is provided in the working space (16) and / or into the exhaust gas tract (22) and that in the exhaust tract (22) with a with an electric generator (28) coupled turbine (26) is arranged. Heat engine after Claim 1 , characterized in that the internal combustion engine (10) has at least one piston-cylinder unit whose variable-volume working space (16) by the piston (12) and the cylinder (13) is defined. Heat engine after Claim 1 or Claim 2 , characterized in that in the exhaust gas duct (22) in front of the turbine (26) at least one catalyst (24) is arranged. Heat engine according to one of Claims 1 to 3 , characterized in that at least one water supply in the working space (16) ends. Heat engine according to one of Claims 1 to 4 , characterized in that at least one water supply (40) in the exhaust tract between a catalyst (24) and the turbine (26) ends. Heat engine according to one of Claims 1 to 5 , characterized in that at least one water supply in the exhaust tract ends after the turbine (26). Heat engine according to one of Claims 1 to 6 , characterized in that at least one water supply ends in the exhaust tract in Auspuffvortopf. Heat engine according to one of Claims 1 to 7 , characterized in that a plurality of water supply in the working space (16) and in the exhaust gas tract (22) are distributed. Method for operating a heat engine after Claim 4 or Claim 8 , characterized in that one or more water injections in the working space (16) during the intake stroke of the internal combustion engine (10). Method for operating a heat engine after Claim 4 or Claim 8 , characterized in that one or more water injections in the working space (16) during the compression stroke of the internal combustion engine (10). Method for operating a heat engine after Claim 4 or Claim 8 , characterized in that one or more water injections in the working space (16) during the working cycle of the internal combustion engine (10). Method for operating a heat engine after Claim 4 or Claim 8 , characterized in that one or more water injections in the working space (16) during the exhaust stroke of the internal combustion engine (10). Method according to one of Claims 9 to 12 , characterized in that further takes place a water injection into the exhaust system upstream of the turbine. Method according to one of Claims 9 to 13 , characterized in that further takes place a water injection into the exhaust tract after the turbine. Motor vehicle with a heat engine according to one of Claims 1 to 8th , Aircraft with a heat engine according to one of Claims 1 to 8th , Watercraft with a heat engine according to one of Claims 1 to 8th , Combined heat and power plant with a heat engine according to one of Claims 1 to 8th ,

Images