HEAT ENGINE WITH STEAM SUPPLY DEVICE

Abstract

A heat engine, in particular an aircraft engine, having a first compressor for supplying a combustion chamber of the heat engine with air and a first turbine arranged downstream of the combustion chamber for driving the first compressor, wherein the heat engine also has at least one steam supply line for supplying steam from a steam source into the combustion chamber. The heat engine also has a steam supply device, which has a second compressor and is designed to compress the working gas further by the second compressor as a function of a mass flow conducted through the steam supply line, before the working gas flows into the combustion chamber.

Claims

1. A heat engine having a first compressor for supplying a combustion chamber of the heat engine with air and a first turbine arranged downstream of the combustion chamber for driving the first compressor, wherein the heat engine further has at least one steam supply line for supplying steam from a steam source into the combustion chamber, wherein a steam supply device, which has a second compressor arranged downstream of the first compressor and which is configured and arranged to operate the second compressor in such a way that it further compresses the air at least temporarily, as a function of a mass flow conducted through the steam supply line, before it flows into the combustion chamber.

2. The heat engine according to claim 1, wherein the steam supply device is configured and arranged in at least a first operating mode to operate the second compressor so that the pressure increase of the air is proportional to the change in mass flow due to the steam fed into the combustion chamber.

3. The heat engine according to claim 1, wherein the steam supply device is configured and arranged at least in a second operating mode to operate the second compressor so that the pressure increase of the air is not proportional to the change in mass flow due to the steam fed into the combustion chamber; wherein the pressure is more strongly increased than an increase in the mass flow.

4. The heat engine according to claim 1, wherein the steam supply device further has a steam turbine for driving the second compressor and at least a part of the steam from the steam supply line is conducted through the steam turbine and undergoes pressure release in the latter, before it flows into the combustion chamber.

5. The heat engine according to claim 1, wherein the steam source comprises an evaporator or a heat exchanger, which is configured and arranged to evaporate water and/or to heat it supercritically with the exhaust-gas heat of the heat engine.

6. The heat engine according to claim 5, further comprising a water recovery unit with at least one second heat exchanger for the recovery of condensed water from the exhaust gas of the heat engine.

7. The heat engine according to claim 1, wherein a part of the steam from the steam supply line flows through the steam turbine and another part of the steam is conducted via a bypass line past the steam turbine into the combustion chamber.

8. The heat engine according to claim 1, further comprising a steam control valve, which regulates the steam supply into the steam turbine and controls a mass flow ratio between the steam turbine and the bypass line.

9. The heat engine according to claim 1, wherein the second compressor and/or the steam turbine are not arranged coaxially with respect to the first compressor.

10. The heat engine according to claim 1, further comprising at least one third compressor and/or by a fan for supplying the combustion chamber and/or by at least one further turbine for driving the additional compressor and/or the fan via a transmission.

11. The heat engine according to claim 4, further comprising a second steam turbine, through which steam from the steam supply line flows and feeds the power to a shaft of the heat engine or to an auxiliary unit.

12. An aircraft, including at least one heat engine according to claim 1.

13. A method for operating a heat engine according to claim 1, wherein, at least temporarily, steam is conducted via the steam supply line into the combustion chamber and the second compressor is operated as a function of the supplied steam mass flow in order to further compress the air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES

[0025] Other advantageous further developments of the present invention ensue from the dependent claims and from the following description of preferred embodiments. Shown to this end in a partially schematic manner are:

[0026] FIG. 1 a heat engine in accordance with an embodiment of the present invention;

[0027] FIG. 2 a heat engine in accordance with another embodiment of the present invention.

DESCRIPTION OF THE INVENTION

[0028] FIG. 1 shows schematically a heat engine 1, which is based on the fundamental principle of the invention. The problem of the large working point shift or working line shift in the compressor 10 during the supply of steam from a steam source 25 to the combustion chamber 11 is solved by the heat engine 1 with a steam supply device 2. The steam supply device 2 has, as its main components, a second compressor 20, which is driven by a steam turbine 21.

[0029] Air that is conveyed from the compressor 10 of the heat engine 1 is conducted to the compressor 20 of the steam supply device 2. The steam turbine 21 feeds its power output to the compressor 20, which is designed in such a way that the pressure increase is proportional to the change in mass flow due to the steam. Accordingly present is a self-regulating mechanism, which ensures that the position of the working line in the compressors lying upstream does not change or does not appreciably change when steam is supplied into the combustion chamber 11. That is, in the absence of a steam supply to the steam turbine, the compressor 20 is not driven and does not bring about any pressure increase. For a steam supply of 30% of the air mass flow, for example, there is so much power output that the compressor achieves a pressure ratio of Pi = 1.3. In other words, the steam supply device 2 is designed in such a way that, when the mass flow in the turbine is 30% higher than the mass flow in the compressor, the second compressor 20 also increases the pressure in front of the combustion chamber by 30%.

[0030] In the example illustrated, it is thereby taken into account that, in the case of steam-free operation, air conveyed through the first compressor 10 flows through the compressor 20. This causes pressure losses, which are not relevant, however, because what is involved in the case of these operating points is a partial load point.

[0031] By use of the exhaust-gas energy of the heat engine 1 in the present exemplary embodiment, water that is pumped from a feed water pump 26 to the steam source 25, namely, in this case, to a steam generator (an evaporator/heat exchanger), is evaporated and subsequently conducted through the steam line 24 to the steam turbine 21. In this case, the steam is brought to a pressure that is very much higher than the pressure in the combustion chamber 11. In this way, the utilizable thermal gradient is increased. After the expansion of the steam in the steam turbine 21, the pressure in the exhaust steam line 23 has to be greater than or at least equal to the pressure in the combustion chamber 11.

[0032] The energy flow in the steam supply line 24 is greater than the power required for driving the compressor 20. For this reason, the steam turbine 21 is supplied only with enough energy so that the power is sufficient in order to achieve the desired pressure increase in the compressor 20. The remaining steam is conducted via a bypass line 22 directly to the combustion chamber 11.

[0033] The air from the compressor 20 and the exhaust steam from the steam turbine 21 can be supplied directly to the combustion chamber 11. It is also possible for both streams to be mixed beforehand in full or in part. In the combustion chamber, the incoming air and the steam are mixed with fuel (K). The energy-rich working gas resulting from the combustion undergoes pressure release in the turbines 12 and 13.

[0034] FIG. 2 shows an exemplary aircraft engine 3 having the heat engine 1 with the supply device 2 shown in FIG. 1 as well as some reasonable augmentations. It could also be stated that the heat engine 1 in FIG. 1 forms the core engine of the aircraft engine 3 (with some minor adaptations). Functionally identical elements have the same reference numbers as in FIG. 1.

[0035] In addition, there is a propulsor, namely, a fan 30, in the example shown, which is driven by a low-pressure turbine 13 and, optionally, is driven via an intervening transmission 31. It is likewise possible to arrange an additional compressor (low-pressure compressor or booster) 32 in the flow direction between the fan 30 and the first compressor 10.

[0036] In FIG. 1 and FIG. 2, the steam supply device 2 is arranged adjacent to or offset with respect to the main axis of the heat engine 1 or of the aircraft engine 3. It is thereby fundamentally irrelevant whether the arrangement is chosen to be parallel, at an angle, or transverse. In an alternative exemplary embodiment, which is not shown here, it would also be conceivable to have a coaxial arrangement. Because an engine with steam in the working gas achieves a very high specific power output, there results a reduced mass flow for the compressor. In the case of a coaxial arrangement of the steam supply device 2, this would result in very small vane heights in the compressor 20. High gap losses and the danger of pumping would be the consequence hereof. The offset arrangement has the great advantage that the compressor 20 can be designed with a small hub ratio and thereby with large vane heights. In addition, the turbomachine part of the aircraft engines can be constructed to be axially short.

[0037] As described further above, the energy flow in the steam supply line 24 is greater than the power required for driving the compressor 20. For this reason, it can be advantageous to reduce the excess energy in an (optional) second steam turbine 28. Illustrated schematically in FIG. 2 is a possible embodiment. Here, the second steam turbine 28 is arranged coaxially with respect to the engine axis and feeds its power via an optional transmission 27 to a shaft of the aircraft engine. In the illustration, the steam turbine 28 is connected in series to the steam turbine 21; that is, the steam from the steam source 25 (here the steam generator) first flows through the second steam turbine 28 and afterwards flows through the first steam turbine 21. Also conceivable is a parallel connection of the steam turbines 21, 28 (not depicted). Instead of feeding the power to an engine shaft, the steam turbine 28 could also be used to drive auxiliary units or, for example, a generator.

[0038] On the basis of the heat engine in FIG. 1, it is shown how, by way of the steam supply device, the position of the working line or the working point in the compressor characteristic diagram can be kept constant. In the case of a corresponding design, the steam supply device 2 can also be utilized, however, in order to influence the position of the working point in a specific manner. To this end, a steam control valve 29 is integrated in the steam supply line 24. This steam control valve 29 can be used to vary the quantity of steam of the steam turbine 21. In the case of an unchanged steam mass flow to the combustion chamber, it is accordingly possible to regulate the pressure buildup in the compressor 20. The larger the bypass quantity is, the smaller is the pressure buildup in the compressor 20. As a result, the compressor 10 is throttled and the working point thereof moves in the direction of the pumping limit. In the case of smaller bypass quantities, exactly the opposite behavior is observed.

[0039] This can be a great operational advantage. For example, when the engine is accelerated, it is possible to lower the working line in the compressor characteristic diagram and thus to prevent “pumping.” In this way, the engine concept in accordance with the invention makes possible a very large working range, because, besides the turbine inlet temperature, also the mass flow rate can be utilized for adjustment of the power output. By way of influencing the working point in the compressor characteristic diagram, it is possible to improve the dynamic behavior.