Untitled record

The invention relates to an internal combustion engine with a medium or high pressure exhaust gas turbine (axial or radial), as well as a continuously operated burner, which according to the invention is charged with combustion air high pressure propulsion jet steam injector and whose motive steam is mainly generated in a recuperator (countercurrent heat exchanger) downstream of the exhaust gas turbine . In contrast to known applications of such a recuperator, not only the feed water for generating motive steam is fed to the exhaust gas in the heat exchanger, but also the fuel and also the combustion air.

The invention also relates to a method for operating an internal combustion engine with a medium or high pressure exhaust gas turbine, as well as a continuously operated burner, which according to the invention is charged with combustion air by a high pressure propulsion jet steam injector and whose motive steam is mainly generated in a recuperator downstream of the exhaust gas turbine. In contrast to known applications of such a recuperator, not only the feed water for generating motive steam is fed to the exhaust gas in the heat exchanger, but also the fuel and the combustion air.

The object of the invention is to provide an internal combustion engine of the type mentioned at the outset and to make a high-pressure steam propulsion jet pump applicable for compressing the combustion air for such a machine. The exemplary embodiments show two variants of the use of the high-pressure propulsion jet steam injector: In a first example, the burner is charged solely by the steam injector without any further moving components; in a second exemplary embodiment, an application of the steam injector with an additional upstream connection of a compressor stage driven by the turbine is shown.

Similar applications are known from the application DE 560 273 A, in which the combustion air is additionally compressed by means of steam and consequently a mixture of steam and combustion air reaches the burner.

It is known from application US Pat. No. 2,542,953 A that only the evaporated fuel is used in the injector to convey and compress the combustion air. The fuel is evaporated in a heat exchanger to the combustion chamber.

In an embodiment according to US Pat. No. 5,983,640, air is sucked in with the aid of the steam jet pump and subsequently also expanded in a turbine.

EP 0 462 458 A describes a method according to which high-pressure steam is generated in a waste heat steam generator of a gas turbo group, which steam is used for further compression of the air by means of a steam jet pump.

From GB 190 927 090 A it is known that by means of a steam generated in the exhaust gas heat exchanger, fuel and air are sucked in by a jet apparatus.

US Pat. No. 5,687,560 A1 shows an internal combustion engine with an exhaust gas turbine and an upstream, continuously operated combustion chamber. One version of this internal combustion engine has a heat exchanger connected downstream of the exhaust gas turbine, in which heat is supplied to the combustion air and a fuel / steam mixture in countercurrent. In a further embodiment of this internal combustion engine, part of the fuel / vapor mixture is compressed. This is a process for using the waste heat from an exhaust gas turbine because a heat exchanger is connected in the exhaust gas flow. It is therefore a two-stage gas turbine consisting of a low-pressure pre-compressor and an exhaust-gas turbine mechanically coupled to a low-pressure pre-compressor. In the first stage, the combustion air is preheated. This preheated fuel is then fed into the combustion section of the downstream exhaust gas turbine. At the outlet of the exhaust gas turbine, a second heat exchanger is arranged, which from the hot exhaust gas

AT 501 554 B1 is flowed through. In this second heat exchanger, the combustion air previously cooled by the first heat exchanger is passed through and correspondingly heated in order to be fed into the inlet stage of the exhaust gas turbine in the refreshed state. A feed water circuit is not shown in any way in the aforementioned provision. The disadvantage of this known internal combustion engine with exhaust gas turbine is that a total of two countercurrent heat exchangers are required, namely a first countercurrent heat exchanger for heating the fuel and a second countercurrent heat exchanger for heating the combustion air. The fuel is not fed in via a jet pump, but via a low-pressure compressor, which is also disadvantageous for efficiency.

US Pat. No. 5,845,481 A1 discloses an internal combustion engine with an exhaust gas turbine and a continuously operated combustion chamber, in which the heat of the exhaust gas is transferred to part of the fuel in a heat exchanger connected downstream of the exhaust gas turbine. It is therefore a simple heat transfer in a double gas turbine, which consists of a compressor stage and an expansion stage, with a second countercurrent heat exchanger being arranged in a waste heat countercurrent heat exchanger, which transfers heat to the combustion air from the compressor stage in order to preheat it and feed it into the expansion stage . This two-stage turbine arrangement also has the same disadvantages as those in US Pat. No. 5,687,560 A1.

GB 642 118 A contains an internal combustion engine with continuously operated combustion chambers upstream of the exhaust gas turbines and heat exchangers downstream of the exhaust gas turbines, in which the combustion air is preheated and steam is generated. In this arrangement, several compressor stages are arranged one behind the other in order to achieve a relatively high degree of compression for the combustion air to be introduced into the combustion chamber. A first heat exchanger for cooling the combustion air is arranged in the space between the low-pressure compressor stage and the high-pressure compressor stage. However, it is not a counterflow heat exchanger. Another heat exchanger is arranged in the area between the high pressure compressor and the high pressure combustion chamber. There are also steam generators provided, the burner nozzles of the two combustion chambers work with a mixture of steam and oil. There is no jet pump and a counterflow heat exchanger that is suitable for extracting heat from the exhaust gas and for preheating the fuel, the combustion air and a feed water in counterflow.

No. 1,874,314 A1 shows an internal combustion engine with an exhaust gas turbine and a continuously operated combustion chamber and two steam injectors for additional compression of the combustion air, as well as recuperative heat exchangers for generating the steam. The turbine is designed in two stages, in that the exhaust gas turbine is mechanically coupled to a supercharger stage. In the mechanical pre-compression stage, the combustion air is pre-compressed and some of it is fed to the burner. Before it enters the burner, the combustion air is additionally compressed by two steam injectors that work one after the other. Another part of the combustion air is added to the exhaust gas after the burner, but before it enters the exhaust gas turbine. This form of secondary admixing of steam is necessary because the amount of steam in the burner would extinguish the flame.

All of the steam in the exhaust gas is condensed in a heat exchanger after passing through the exhaust gas turbine and is pre-evaporated again as a liquid in a heat exchanger to form the exhaust gas after the turbine and is superheated in a second heat exchanger in the burner. The disadvantage of this known internal combustion engine is that a total of three heat exchangers and three injectors are required. Although this is an additional constructive effort, the decisive factor is that in this internal combustion engine only a small part of the waste heat in the exhaust gas can be used recuperatively. The exhaust gas, which consists of the combustion gas - composed of burned fuel and "burned combustion air" - as well as the steam, is countered by the heat capacity of the recirculated feed water. However, this can never absorb the residual heat of the heat exchanger with its heat capacity

AT 501 554 B1

Absorb steam and exhaust gas.

Furthermore, the combustion air for the internal combustion engine shown is not preheated. In principle, this would also not be possible in the embodiment shown, since it makes it necessary to heat the combustion air upstream of a mechanical compressor stage, which would by far cancel out the benefits of heat recirculation. The internal combustion engine shown also dispenses with the recirculation of waste heat by means of the inflowing fuel.

The recuperative waste heat recirculation via the incoming feed water and the fuel and the combustion air makes it possible to provide an internal combustion engine according to the invention, which achieves a sufficient compression pressure in front of the burner with only one steam jet injector without a mechanical pre-compressor and, on the other hand, does not keep the flame from excessive steam clears.

To operate a heat engine, steam jet pumps for compressing the combustion air can only be used to a very limited extent, since extremely poor efficiencies are achieved. This poor efficiency results on the one hand from the fact that the high-pressure motive steam already changes into the state of wet steam in the motive nozzle, on the other hand, due to the mixing with the intake air, the steam in the injector chamber is almost completely liquefied, the efficiency ηθ «sinks to that to <5%!

The object of the invention is to provide a method which improves the efficiency of the high-pressure steam jet pump to such an extent that, given sufficient pumping ability of the steam, the inevitable liquid entry of the motive steam into the combustion air remains below a level that leads to the extinguishing of the flame. As a result, the feed water is heated in the counterflow heat exchanger at the physically highest possible pressure and then additionally overheated in the heat exchanger to the burner. As the steam passes through the Laval steam jet and the steam pressure changes to the supersonic speed of the driving steam flowing out, condensation water inevitably arises in the steam. This is why the combustion air sucked in in the recuperator is heated well above the condensation temperature of the steam, which means that when the wet steam is then mixed with this hot air, the water in the steam evaporates again. This improves the pumpability of the propulsion jet to a decisive extent.

For all media flowing through, the recuperator consists of a filigree, labyrinth-like channel system through which the media flow at subsonic speed. Only by flowing at subsonic speed can gases and liquids be conducted through labyrinthine, space-saving exchanger tubes and chambers without the occurrence of damaging compression surges.

The recuperator has an elongated shape in the main direction of the media and is thermally insulated from the outside on all sides. The metal used for the recuperator has sufficient thermal conductivity to gradually equalize the temperature gradient from one end of the deceiver to the other after the machine has been switched off. This equalization of the temperature leads to a uniformly high mixing temperature of the entire heat exchanger. This in turn has the consequence that soot and fuel deposits are burned afterwards at the cold points (during operation) of the heat exchanger on the exhaust gas side. .

Further advantages and details of the invention are explained below using an exemplary embodiment of the invention shown in the drawings. In this shows:

Fig. 1 is a schematic view of the machine with only injector compression (without an upstream compressor stage)

Fig. 2 is a schematic view of the machine with additional drives 5 from the turbine

AT 501 554 B1 nen pre-compressor stage for the combustion air.

In the heat engine according to the invention, a high-pressure steam jet pump (31) with its Laval propellant steam nozzle (1) and the mixing chamber (10) and the injector diffuser (12) are followed by an adiabatic burner (15) after the subsequent fuel injection (13). The exhaust gas from this continuously operated pressure burner (15) flows via the preferably multi-stage exhaust gas turbine (16) (either axially or radially) at predominantly subsonic speed and with constant expansion of the compressed gas into the recuperator (4). In the exhaust gas turbine (16) the pressure of the gas is completely released and the rotation of a shaft (17) is converted. The still very hot exhaust gas from this turbine (16) then flows in countercurrent to the inflowing fuel (25), to the feed water (26) and to the combustion air (24) at subsonic speed through the recuperator (4) designed as a countercurrent heat exchanger. The exhaust gas loses its entire residual heat due to the heat given off to the opposing flowing media (with the appropriate quality and sufficient exchange surface), except for the heat that cannot be recovered from the condensation heat of the steam. Since the vapor pressure of the outflowing mixture is around atmospheric pressure, that of the inflowing feed water is pressures of approx. 500 bar, the inflowing water cannot absorb the heat of condensation (the inflow evaporation temperature is significantly higher than the outflow condensation temperature).

The combustion air (24) flows through the heat exchanger (4) and the combustion air line (21) to the injector of the high-pressure steam jet pump (31). At the same time, water is pumped out of the feed water tank (23) by the feed water pump (22) and is pressed into the steam-side heat exchanger part (26) with the highest possible physical pressure. The feed water is heated in the steam exchanger (26). It is then fed to the steam superheater (14) on the burner (15). Heat is supplied via the steam superheater (14) so ​​that superheated superheated steam is produced. The superheated superheated steam with the highest possible physical pressure then flows via the high-pressure steam line (2) to the Laval steam propulsion nozzle (1), where it is blown into the injector at supersonic speed.

At the outlet of the steam propulsion nozzle (1) there is a negative pressure of a few 1/10 bar below atmospheric pressure. This negative pressure conveys the combustion air into the injector (31). In a second exemplary embodiment of this invention it is shown that it is possible to increase the pressure of the incoming combustion air above atmospheric pressure by means of a compressor (28) driven by the turbine (16).

In the injector (9-12) there is an intensive mixing of the supersonic steam and the preheated combustion air. Steam molecules collide with air molecules. The high momentum of movement of the vapor molecules is transferred to the air molecules in a predominantly elastic collision. The volume proportions of combustion air to motive steam can be many times over due to the maximized temperature of the motive steam and the maximized pressure of the motive steam. With a sufficient length of the injector mixing tube (10), both substances gradually and advantageously adopt a homogeneous speed and a homogenized mixing temperature.

The combustion air (24) is heated in the recuperator (4) to such an extent that its temperature is well above the condensation temperature of the steam. Water droplets that arise in the motive steam as a result of its work in the steam propulsion nozzle (1) are evaporated again due to the intensive mixing in the injector (9-12). This increases the efficiency of the steam jet pump (31) to the decisive extent that makes it applicable for this purpose in the first place. If a steam jet pump (31) were to supply the combustion air at normal ambient temperature, not only would the water droplets already present be retained as wet steam, but so much heat would be extracted from the motive steam that it would almost completely condense. It is therefore of indispensable importance for the functioning of the steam jet pump (31) according to the invention,

AT 501 554 B1 to generate superheated superheated steam at the highest possible pressure and to heat the combustion air far above the steam condensation temperature.

The fuel fed to the burner (15) is also heated in the counterflow heat exchanger (25) provided for this purpose by the recuperative heat from the exhaust gas. Temperatures are reached which can exceed the auto-ignition temperature of the fuels and many liquid fuels are also already evaporated in the heat exchanger (25).

So that the burner (15) can perform adiabatic combustion, it must also be encased on the outside with high-temperature insulation. If the burner (15) is not yet at the operating temperature at which fuel is self-igniting, an electric spark plug (30) is used to ignite. This spark plug (30) therefore only needs to be active when the machine is starting up.

The burner (15) is, as usual in such devices, conical in shape, it represents a diffuser. The mixture of steam, preheated combustion air and the fuel (13) just injected, flowing into the burner under pressure, is gradually expanding burner (15) decelerated to approx. 25 m / s.