DE2413378A1 - Gas turbine for motor vehicles - has laval nozzle and a pressure reducing turbine but no heat exchanger - Google Patents

Abstract

The gas turbine is used basically but not exclusively as a motor vehicle prime mover, and does not have a downstream heat exchanger in the high temperature region. The gas turbine has downstream convergent divergent nozzle through which more than half of the working gas is passed and accelerated above sonic speed. Cold air is passed through convergent divergent nozzles held within the main nozzle in the diagram. This air is accelerated to about twice the sonic speed and cold and hot gases are mixed in the mixer. A downstream pressure is generated in a recompression unit. A decompression turbine is operated with gas drawn from the cycle. This turbine cycle can be operated with argon and a nuclear reactor.

Description

Gas turbine cycle, in particular for driving automobiles.

The invention relates to and to a gas turbine cycle is essentially, but not exclusively, intended to be the prime mover of Automobiles.

Gas turbine cycles are well known. But if you look at it For example, the cycle of Ackeret and Keller, it is found that expensive heat exchangers required are.

But heat exchangers not only have the disadvantage of being a relatively large one Consuming volume - a disadvantage, also due to an increase in the system gas pressure cannot be significantly mitigated wefl the exchange path length for heat transfer is determined by the Prandtl-see choice Pr - + and this is almost independent of pressure is - but because of their real job they can. at high temperatures also not be shielded against this.

The object of the invention is therefore to provide a gas turbine cycle indicate who can do without heat exchangers in the high temperature range and very high working gas temperatures can be achieved economically.

In order not to make the description too complicated, be the Main idea of the invention immediately at Ea-nd of the attached figure, a Functional diagram explained.

This functional diagram initially represents a main circuit, which consists of the components Laval nozzle (1), a re-sealing body (4), combustion chamber (5) and a main turbine (6). The main cycle is about a first Compressor (7) with a downstream cooler (8), a second compressor (9) with downstream cooler (110) and the Laval nozzle (2) fresh air is supplied. The corresponding The proportion of burned air is removed from the system via the discharge turbine (11) removed.

The central idea behind the arrangement can thus be characterized as follows: The compressor (7) increases the fresh air to a little more than the combustion chamber pressure compressed, which essentially results from the requirement on the unloading turbine Cii) to get a reasonable efficiency, determined and about 80 atm for maximum = operation may be. After recooling through the cooler (8), it continues to flow so compressed - for example by the factor tO - that they after recooling by the cooler (10) in the Laval nozzle (2) receives a supersonic speed that is approximately The overshoot speed that the hot gas reaches in the Laval nozzle (1) is the same static pressure is the same. The Mach number of the cold gas supersonic flow may then be about 2, while the unmixed hot gas supersonic flow is about the Mach number 1.1 may have. If the gases mix in the mixing path (3Y, so at - apart from friction losses - the same flow velocity decreases the temperature of the hot gas.

This means, however, that when the working gas is compressed, it becomes higher Pressure reached when it is behind the main turbine (6) and can make sense approximately Achieve a factor of 2, as a calculation of the processes shows.

The real aim of the invention is, of course, to obtain the highest possible overall efficiency with a small installation volume. According to one of the main equations in thermodynamics, the ideal efficiency is May be -example If T1 = 1600 ° K and T2 = 400 ° K, the ideal efficiency is = 75%. In order to be able to realize the gas temperatures that correspond to the ones indicated, the auxiliary circuit shown in dashed lines in the figure is required, which by means of the valve (14) provides forced circulation gas cooling of the main and discharge turbine rotor and guide vanes, as well as of the recompression body (4). - These.

Measure is of course to be understood as an example. If necessary further components can be recorded through the drawn cooling circuit. - In the cooler areas of the main circuit, e.g. in the Laval nozzle (1), the mixing space (3) and the 'recompression body (4) are now pressure-resistant Walls of the components lined with a chrome-aluminum-iron alloy, which is known to be corrosion-resistant to air up to temperatures of 1200 ° C is. One now provides at the same time by a (for example waffle-like) structuring and a suitable perforation (to prevent forced convection) for that a gap of a few tenths of a millimeter between the corrosion-resistant alloy and Structural material lying on the ground, this can result in a lowering of the structural material temperature can be achieved to reasonable values. This measure outlined in this way should certainly be that require the greatest care in the design of the part of the Laval nozzle (2), which still has the high static pressure, against the flow of hot gas from the Laval nozzle (1) shield.

The highest temperatures occur in the combustion chamber (5).

This is why it is advisable to line them with a suitable ceramic. The measure just described for the alienation of the chromium-Al-Fe alloy can be used can be used to store the ceramic elastically and not to have too high temperature gradients in: to let it arise.

High centrifugal forces now also occur in the turbine blades on. Therefore, it is considered here, for example.

made of a sintered chrome alloy with suitable porosity. This possibility and the fact that the compressor (l, the fresh air on a higher pressure than the static pressure on the turbine blades is achieves that cold air enters the flow boundary layer of the turbine blades and so lowers the turbine blade temperature.

Bs it goes without saying that the described cooling and Heat shielding measures are to be understood as examples and, if so, better solutions exist, can be replaced by them.

The gas turbine cycle described is primarily used to drive automobiles is thought to be ee as automobiles to a crude percentage. operated with partial load will have, moreover, great re-acceleration ability and easy braking must, of course, the control and regulation problem of the arrangement great attention to dedicate. In order to avoid excessive material stresses due to excessive temperature fluctuations z; ti obtained, one will rely on the well-known: quality or mixture = regulation only If necessary, fall back as far as it is based on the heat transfer key figures to compensate conditional temperature fluctuations applies and essentially with the also known quantity or filling regulation work. This is in the Figure shows the throttle (12), which is still used to avoid excessive pressure Intake subcooling the back throttle (13) was switched on.

At this point there is now a very important advantage of the arrangement clear. In principle, one can create a cycle - as is well known ' - imagine, which only consists of the components (5), (7), (8), (9), (11) and t12). Using the listed technical cooling and heat shielding measures This would mean that e-Tn would already be relatively more useful even at maximum operation Result in efficiency. Due to the throttling control, however, you can now get away with it assume that the performance of the compressors (7) 'and (9) is approximately proportional to the system reference pressure, which is defined, for example, as a static combustion chamber = pressure may be, while the line of the turbine (11) due to the changing adiabatic gradient varies disproportionately to the reference pressure. That is, at part load the efficiency drops sharply. However, this is not the case with the arrangement according to the invention. Because the units (1), (2), (3) and (4) have an almost constant compression ratio supply, the output of the turbine (6) is also proportional to the system = reference pressure. May the performance ratio at maximum operation Turbine (6) closed Turbine (11) should be about one, but it rises sharply at part load, d0h., the high degree of efficiency of the system is largely retained even at part load. at Based on these considerations, it was assumed that only axial compressors were used which results in a high indexed efficiency in a large speed range achievable ift with almost no speed-independent power.

Before we begin oiniga essential action that the figure are not to be found, is received, it should be noted briefly that the figure Of course, no statement on the detailed quantitative definition of the arrangement power. With the general level of awareness of all components used - with the recompression body (4) at the latest since the work of Ludwieg and Oswatitsoh but this is also not necessary. The same also applies to the figures. A respective purpose = adapted optimization with mainframe computers does not represent any today Problem 'more.

Regarding the mixing section (3) it should be mentioned that as! primary mixing power the turbulence induced by wall friction is to be considered. If you superimpose the one from Laval nozzle (2) Exiting air flow a suitable swirl, so one becomes thereby the required Can reduce the length of the mixing path and this measure will also prove to be advantageous affect the efficiency of the diffusers.

To the cooling flow through the blades compared to the other cooling flows To increase the cooling gas inlet into the blades in the turbines, as is known place radially further inwards than # the outlet.

It goes without saying that when designing compressor (9) and cooler (10) care is taken that no unacceptable air condensation in Laval nozzle (2) occurs.

In the case of the burned numerical values, the cooler (10) and the neighboring Apparatus parts pressures of up to 800 atmospheres occur. With the smallness of this However, this does not represent components and the maximum temperatures present here Problem dare From a safety point of view, one can think of it; think these components in a steel tube with a reinforcement made of fiberglass = reinforced Store plastic and foam lining.

The latter measure is of course also applicable to all other components Applicable if: the necessary cooling measures are not disregarded leaves.

That the recompression body (4) in the figure in the diffuser = part is shown with a tapering inner delimitation, is only for reasons of clarity happen. In practice, you will most likely use this diffuser with an external extension interpret.

In the Atbildung the air passage is shown so that fresh air at (12) and the exhaust gas exits at (15). To avoid corrosion with smaller To be able to work with excess air, one can think of a part of the exhaust gas fed back via a cooler from (15) to (12). It should be noted here that (15) represents a starting throttle.

It should also be noted that it can be useful to use the compressor (7) Split into two units and provide an intercooler. Even this option has not been shown in the figure for reasons of clarity shown.

As a result of the penultimate measure, the arrangement can also become a closed one Circuit can be redesigned if it is possible to find a suitable one for the combustion chamber (5) other heat source, e.g. a nuclear reactor, to find the appropriate heat transfer properties owns. Argon can then be used as the working gas.

The contradiction to the above-mentioned remarks about heat exchangers can be mitigated here by the fact that, in contrast to recuperators, here a Pressure adjustment between primary and secondary side is possible and large units how nuclear reactors also justify the use of rare metals such as molybdenum.

In this context, it is permissible to point out that this leads to an overestimation however, there is certainly no reason, as the explanations are merely a possible one Show advantage over alternative concepts for peak load power plants.

Finally, with regard to the cycle with internal combustion, that the arrangement according to the invention here is certainly a high-quality air filter system Requires, but this is no problem for the current state of the art represents and possibly this system can be useful with an intake = silencer be combined.

Claims (12)

Expectations Ii. G, a turbine cycle - essentially, but not # exclusively to drive automobiles - that is behind a turbine (6) relatively low decompression more than half of the Working gas fed to a Laval nozzle (1í) and slightly above a Mach number 11 is accelerated by one or more Laval nozzles embedded in Laval nozzle (1) (2) cold working gas at almost the same speed, almost the same static pressure, but a Mach number around 2, is introduced into a vermiscer (3) is mixed, so 'that in a subsequent recompression by means of a Recompression body (4) creates a total gas pressure which is greater than the total gas pressure behind the turbine (6) and through an unloading turbine connected downstream of the turbine (6) (11) as much gas is withdrawn from the circuit in stationary operation as it is on Cold gas is supplied in the same time unit. 2. Gas turbine cycle according to claim 1, characterized in that the working gas is air, the fresh air by a throttle control (12) and possibly (13), the compressors (7), (9) and the coolers (8), (10) of the Laval nozzle (2) of claim 1 is fed and the combustion chamber (5) is arranged behind the recompression body (4) will. 3. Gas turbine cycle according to claim 1l, characterized in that that the working gas is not air - but bapw. Argon - is through the combustion chamber (5) a heat exchanger - for example a nuclear reactor - is replaced and the cycle below Retaining the compressors and coolers of claim 2 is redesigned that »the working gas from (1-5) to (12) is recirculated via a cooler. 4. Gas turbine cycle according to claims 1 and 2 or 3, daurch characterized in that the turbine blades not only through an auxiliary gas circuit be cooled, but also made of a metal of suitable porosity, for example Sinter = chrome-based alloy and another one through the passage of cold gas Experience cooling. 5. gas turbine cycle according to at least 2 'of the preceding claims, characterized in that a swirl is superimposed on the cold gas flow in Laval nozzle (2) will. 6. Gas turbine cycle according to at least 2 of the preceding claims, characterized in that the structural materials in the hot gas areas through a corrosion-resistant alloy made of, for example, chromium-Al-Fe with perforation and a Gas intermediate layer of a few tenths of a millimeter against the high temperatures be shielded. 7. Gas turbine cycle according to at least 2 of the preceding claims, characterized in that the combustion chamber (5) is additionally lined with ceramic will. S-. Gas turbine cycle according to at least 2 of the preceding claims, characterized in that the turbines (6) and (11 ') and the compressors (7) and (97 are designed so that they are almost independent of power over a wide speed range are and by means of the throttle valves (12) and possibly (13) a throttling, Have quantity or filling regulation. 9. Gas turbine cycle according to at least 2 of the preceding claims, characterized in that the compressor (7) is in at least 2 units with an intercooler is split up. 10. Gas turbine cycle according to at least two of the preceding claims, characterized in that the recompression body (4) has an oblique shock supersonic compression head un includes a diffuser. 11. Gas turbine circuit according to at least claim 2, characterized in that that a til of the exhaust gases from (15) to (12) is returned via a cooler, to reduce the excess air ratio. 12. Gas bucket cycle after at least. 2 of the preceding claims, characterized in that, for safety reasons, the under high pressure Components in a steel housing or the like 'and / or glass fiber reinforced plastic be embedded with a foam lining or the like. L e r s e i t e