Thermal Inertia Heat Exchanger for Turbomachinery in a Motor Vehicle

Abstract

A heat exchanger for a turbomachine, configured to heat a first fluid from a second fluid, comprising a shell delimiting an internal volume with a first internal circulation space configured to convey the first fluid, a second internal circulation space configured to convey the second fluid, the heat exchanger comprising a plurality of tubes, the first internal circulation space comprising an inner zone of the plurality of tubes (2), the second internal circulation space comprising an outer zone of the plurality of tubes, characterized in that the second internal space comprises a cellular or meshed material (3) having an average void ratio between 25% and 85%. Figure 5

Description

Title of the invention: THERMAL INERTIA HEAT EXCHANGER FOR A TURBOMACHINE IN A MOTOR VEHICLE

[0001] The present disclosure relates generally to the field of gas turbine cycle type turbogenerator devices and systems, otherwise known as "turbomachines". We are here in the context of a motor vehicle, where the turbomachine is involved in a range extender system of an electric or hybrid vehicle.

[0002] The present invention generally relates to a heat exchanger architecture for such turbomachines. The invention relates more particularly to a heat exchanger called a recuperator exchanger, which makes it possible to heat intake air by means of hot exhaust gases.

[0003] This recovery exchanger makes it possible to improve the overall efficiency of the turbomachine, particularly but not exclusively, in the case of a turbomachine with two compression stages.

[0004] Furthermore, during the start-up phase of the turbomachine, the efficiency of the turbomachine is degraded, until the moment when the temperatures have reached their nominal operating values.

[0005] The inventors sought to improve the efficiency of the turbomachine during the start-up phase of the turbomachine.

[0006] To achieve this objective, the invention proposes a heat exchanger for a turbomachine, configured to heat a first fluid from a second fluid, comprising a casing delimiting an interior volume with a first interior circulation space configured to convey the first fluid, a second interior circulation space configured to convey the second fluid, the heat exchanger comprising a plurality of tubes, the first interior circulation space comprising an interior zone of the plurality of tubes, the second interior circulation space comprising an exterior zone of the plurality of tubes, characterized in that the second interior space comprises a cellular or mesh material having an average void rate of between 25% and 85%, preferably with an average void rate of between 40% and 75%.

[0007] Thanks to these arrangements, the cellular or mesh material has significant porosity and acts as a thermal sponge. The material stores energy in the form of calories while the second fluid circulates in the second internal circulation space. In practice, the temperature rise of the gases is faster during a restart of the turbomachine because the honeycomb or mesh material has retained calories from the previous cycle, which it can release into the new cycle awaiting start-up. The transient effects of such a restart are shorter and the temperatures reach their nominal operating values ​​more quickly if we compare to the case of the first start-up or if we compare to the case of the known art.

[0008] Due to its function, the honeycomb or mesh material can also be called "thermal sponge effect material".

[0009] It should be noted that the thermal sponge material may occupy all or part of the second interior space. Only the second fluid bathes the thermal sponge material, but not the first fluid.

[0010] Furthermore, advantageously, the cellular or mesh material acts as a sound absorber, which reduces the noise generated at the exhaust of the second fluid from the turbomachine system.

[0011] However, thanks to the high void ratio, the presence of a thermal sponge effect material does not significantly degrade the flow of gases towards the outside and does not cause a significant loss of air pressure in the path of the second fluid towards the outside.

[0012] It is noted that the addition of the thermal sponge effect material is considered both for a single-stage compression turbomachine and for a two-stage compression turbomachine. The proposal also works for a three-stage or more turbomachine.

[0013] In this document, the term "average void rate" represents the proportion of space not occupied by the material. In other words, the "average void rate" is complementary to an average filling rate. The sum of the "average void rate" and the average filling rate is equal to 1. The notion of average is assessed over a volume where the configuration of the material is similar, for example over a volume of 5 to 10 mm3.

[0014] It should be noted that the tubes are the site of a significant heat exchange between the first fluid and the second fluid. The tubes thus form the main heat exchange interface.

[0015] According to an advantageous option, the cellular or mesh material is a metallic material. It withstands very high temperatures, for example up to 800°C, without melting or deteriorating, or degrading over the long term. Advantageously, such a metallic material has a high heat capacity and plays the role of a thermal sponge well.

[0016] According to one embodiment, the cellular or mesh material is steel wool or iron wool. This material is found as a semi-finished product and consequently the price The cost of this solution is competitive.

[0017] According to one embodiment, the steel wool or iron wool is made of stainless steel wire. The metal wire does not oxidize, and it does not degrade over time.

[0018] According to one embodiment, the cellular or mesh material is in contact with the tubes. The calories stored in the material are returned by conduction and convection to the first fluid which licks the interior of the tubes, without excluding radiative transmission elsewhere.

[0019] According to one embodiment, the heat exchanger is of the counter-current type. This maximizes the heat transfer between the second fluid and the first fluid.

[0020] According to one embodiment, the inlet of the first fluid occurs at a temperature between 100°C and 200°C, the outlet of the first fluid occurs at a temperature between 600°C and 700°C, the inlet of the second fluid occurs at a temperature between 750°C and 820°C, the outlet of the second fluid occurs at a temperature between 200°C and 300°C. As a result, the thermal sponge effect material operates over a wide temperature range, it is the seat of a spatial temperature gradient of a few hundred degrees over the path of the fluids.

[0021] According to one embodiment, the tubes are arranged parallel to each other, either as a single group or as several groups arranged in cascade, i.e. in series. There may be, for example, four groups of tubes, each group forming a cascade stage relative to the other groups.

[0022] According to one embodiment, the flows are generally perpendicular. In other configurations, the flows in question may be oblique to each other, or even parallel.

[0023] Indeed, in the heat exchange zones, at the level of the tubes, the path of the first fluid is substantially perpendicular to the path of the second fluid.

[0024] According to one embodiment, there is provided for the first fluid: a first inlet orifice for the first fluid, an upstream collector zone serving all or part of the plurality of tubes, a downstream collector zone, and a first outlet orifice. Between the upstream collector zone and the downstream collector zone, there may be one or more groups of tubes.

[0025] The first internal circulation space may comprise one or more distribution spaces at the ends of the tubes for directing the first fluid from the interior of a subassembly or group of tubes to the interior of another subassembly or group of tubes. The distribution spaces are located between the upstream collector zone and the downstream collector zone on the path of the first fluid.

[0026] According to one embodiment, a second inlet orifice for the second fluid and transfer ports, a second outlet orifice are provided for the second fluid.

[0027] The present invention also relates to a turbomachine system configured to provide electrical energy in a motor vehicle, as a range extender, and comprising a heat exchanger as defined previously.

[0028] According to one option, the turbomachine system comprises two compression stages.

[0029] The present invention also relates to a motor vehicle comprising a turbomachine system as defined above.

[0030] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a turbomachine system for a motor vehicle; - [Fig.2] schematically illustrates an example of a heat exchanger, for turbomachine, seen in perspective; - [Fig.3] schematically illustrates an example of a heat exchanger, with a view from the front in section along section line III visible in [Fig.2], with only around fifteen tubes represented per heat exchange zone, the others not being represented; - [Fig.4] schematically illustrates an example of a heat exchanger, with a view from above section along section line IV visible in [Fig.2], with only a few tubes represented per heat exchange zone; - [Fig.5] illustrates in more detail a first example of configuration with the tubes and the thermal sponge effect material installed between the tubes; - [Fig.6] illustrates in more detail a second example of configuration with the tubes and the thermal sponge effect material installed between the tubes.

[0031] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0032] Gas turbine type energy converters are currently being studied as range extenders in electric or hybrid vehicles. They are also more simply called “turbomachines” or “electricity turbogenerators” if we include their functional output.

[0033] This type of converter can operate in APU mode (for Auxiliary Power Unit) where its role is to recharge the batteries of an electric vehicle. It is thus mechanically decoupled from the powertrain and operates at its maximum efficiency point.

[0034] Several cycles are studied, including simple recuperative cycles (RGT for recuperative gas turbine or “Recuperative Gas Turbine”), but also recuperative cycles regenerative chiller (IRGT) and cycles with chiller, recuperator and reheater or "Intercooled Recuperative Reheat Gas Turbine" in English).

[0035] The refrigerated, recuperated and reheated gas turbine (IRReGT) cycle is a cycle with high potential for automotive applications. This cycle allows for high efficiency and high power density (high net specific work) to be achieved.

[0036] This technology has the following advantages: low emission level, low emission noise level, ability to operate with several types of fuels.

[0037] Heat exchangers exist on the market and several types are offered: a tube and fin exchanger, a plate and fin exchanger, a plate exchanger, and a 3D printed metal micro-channel exchanger.

[0038] In [Fig.l] is shown a system diagram of a turbomachine of interest according to the present invention.

[0039] A first stage called low pressure comprises a low pressure compressor CLP and a low pressure turbine TLP, these two entities being linked together via a first shaft AL. This first shaft Al drives a first electrical machine MGLP, which is used essentially as a generator and secondarily as a motor for the start-up phase of the first stage.

[0040] A second stage called high pressure comprises a high pressure compressor CHP and a high pressure turbine THP, these two entities being linked together via a second shaft A2. This second shaft A2 drives a second electrical machine MGHP, which is used essentially as a generator and secondarily as a motor for the start-up phase of the second stage.

[0041] The MGLP and MGHP electric machines are electric generators whose electrical power output can be used directly by a vehicle traction motor or the output can be injected into the main traction battery.

[0042] In addition, an air filter AF is arranged upstream of the low pressure compressor. In addition, a cooling exchanger IC cools the air taken from the outlet of the low pressure compressor and brought to the inlet of the high pressure compressor.

[0043] A first combustion chamber CCLP supplies hot gases to the low pressure turbine TLP. The first combustion chamber CCLP is supplied with air by the high pressure turbine outlet THP.

[0044] A second CCHP combustion chamber supplies hot gases to the high-pressure turbine THP1. The second CCHP combustion chamber is supplied with air by the high-pressure compressor CHP via a heat exchanger which is the main object of the present invention.

[0045] The first combustion chamber and the second combustion chamber are each furthermore supplied with a hydrocarbon fuel. The hy- A hydrocarbon is for example methanol or ethanol.

[0046] The air leaving the high-pressure compressor CHP passes through a heat exchanger marked 1, before joining the second combustion chamber CCHP to supply air to said second combustion chamber CCHP. This air flow forms the first fluid F1 which will be discussed in connection with the heat exchanger described in detail below.

[0047] Furthermore, the heat exchanger 1 receives as second fluid F2 air at the outlet of the low pressure turbine TLP via the pipe 18.

[0048] As visible in Figures 2 to 5, the heat exchanger 1 comprises a casing 6 delimiting an interior volume denoted E0.

[0049] An XYZ reference is defined for the heat exchanger. The X direction corresponds to the longitudinal direction of the vehicle. The Y direction corresponds to the transverse direction of the vehicle. The Z direction may correspond substantially to the vertical.

[0050] The heat exchanger 1 is, in the example presented, the largest component of the turbomachine system. The heat exchanger 1 has a generally parallelepiped shape, which promotes good integration into the architecture of the vehicle, in particular in the lower part of the chassis. The longest dimension LY extends in the transverse direction Y. According to one example, the length LY extends along almost the entire width of the vehicle, for example at least 100 cm. The other dimensions LX and LZ, according to the other two dimensions, can typically be between 10 cm and 20 cm.

[0051] The casing 6 comprises a front wall 10, a back wall 15, a bottom wall 13, an upper wall 11, a left side wall 12 and a right side wall 14. These walls delimit the interior volume E0, in a hermetic manner, except for the fluid inlets and outlets provided for their respective purposes.

[0052] Arranged on the front wall 10 of the heat exchanger 1 are: the inlet of the first fluid EF1, the outlet of the first fluid SF1, and the inlet of the second fluid EF2.

[0053] The outlet of the second SF2 fluid is located on a side wall or on both side walls. Curved return vents may be provided on the sides of the front face, so that all the fluid inlets and outlets are on the same side of the heat exchanger 1, for optimal integration into the vehicle architecture.

[0054] Inside the exchanger, there is provided a first heat exchange zone Z1, a second heat exchange zone Z2, a third heat exchange zone Z3 and a fourth heat exchange zone Z4.

[0055] The order of the heat exchange zones follows the path of the second fluid F2, namely the hot gases which come out of the exhaust of the first stage, i.e. of the stage low pressure via the TLP low pressure turbine then via line 18.

[0056] In contrast, the path of the first fluid first passes through the fourth heat exchange zone Z4, then the third heat exchange zone Z3, then the second heat exchange zone Z2 and finally the first heat exchange zone Z1.

[0057] Consequently, the heat exchanger considered here is a so-called counter-current exchanger or a so-called cross-flow exchanger.

[0058] The path of the first fluid Fl zigzags as illustrated by the arrowed path PI in dashed lines shown in [Fig.4].

[0059] Inside the heat exchange zones, the first fluid circulates in tubes 2. Here the tubes 2 are of round section but they could have another shape of section.

[0060] The tubes 2 are arranged parallel to each other. The axes of the tubes are parallel to the longitudinal direction X.

[0061] More precisely, the heat exchanger 1 comprises a plurality of tubes, the first interior circulation space E1 is defined which comprises the interior zone of the plurality of tubes 2.

[0062] The number of tubes can range from 1000 tubes to 3000 tubes.

[0063] The tubes 2 are formed from copper, aluminum or an alloy resistant to temperatures of 800°C or more.

[0064] The internal diameter of the tubes 2 is between 1 millimeter and 3 millimeters.

[0065] According to the illustrated example, we have here four cascade stages for the path of the fluid FL. Of course, the number of cascade stages could be different: less than four or even more than four.

[0066] A first group of tubes is arranged in the first heat exchange zone ZL. A second group of tubes is arranged in the second heat exchange zone Z2. A third group of tubes is arranged in the third heat exchange zone Z3. A fourth group of tubes is arranged in the fourth heat exchange zone Z4.

[0067] Partitions are provided which delimit the distinct heat exchange zones.

[0068] A first partition 51 comprises four faces (as visible in [Fig. 3]) and delimits the first heat exchange zone ZL. A second partition 52 also comprises four faces and delimits the second heat exchange zone Z2, with the first partition 51. A third partition 53 also comprises four faces and delimits the third heat exchange zone Z3 with the second partition 52.

[0069] In these partitions are arranged lights 8 which allow the second fluid to flow from one heat exchange zone to the next (from Z1 to Z2, from Z2 to Z3 and from Z3 to Z4).

[0070] The interior volume 6 comprises a first interior circulation space denoted El configured to convey the first fluid F1, and a second interior circulation space denoted E2 configured to convey the second fluid F2.

[0071] For the first fluid F1, a first inlet orifice EF1, an upstream collector zone 42 serving all or part of the plurality of tubes, a downstream collector zone 41, and a first outlet orifice SF1 are provided.

[0072] On the path PI of the first fluid F1, between the upstream collector zone and the downstream collector zone, one can find, as in the example illustrated in the figures, one or more distribution spaces at the ends of the tubes making it possible to direct the first fluid from the inside of a subset of tubes to the inside of another subset of tubes. The distribution spaces act as a plenum which collects the output of a group of tubes and distributes the first fluid to another group of tubes.

[0073] A first distribution space D34 connects the tubes of the fourth heat exchange zone Z4 with the tubes of the third heat exchange zone Z3. A second distribution space D23 connects the tubes of the third heat exchange zone Z3 with the tubes of the second heat exchange zone Z2.

[0074] A third distribution space D12 connects the tubes of the second heat exchange zone Z2 with the tubes of the first heat exchange zone Z1.

[0075] In the illustrated architecture for the changer exchanger, a front hole plate 71 and a rear hole plate 72 are provided.

[0076] The front and rear perforated plates support and hold the tubes 2 and act as a sealed separation between the heat exchange zones and the distribution spaces.

[0077] It is noted that the second fluid does not circulate in the distribution spaces, the second fluid circulates only in the heat exchange zones and passes from one to the other through the ports 8.

[0078] The second interior circulation space denoted E2 comprises the exterior zone of the plurality of tubes, for their parts located in the heat exchange zones Z1 to Z4.

[0079] Advantageously according to the invention, the second interior space is not empty but contains a cellular or mesh material generically noted by the reference 3, also called thermal sponge effect material.

[0080] Generally, the thermal sponge effect material is in contact with the tubes which promotes a good heat exchange coefficient between the sponge effect material thermal and the first fluid via the material of the tubes.

[0081] According to an example of a turbomachine for range extender application, the inlet of the first fluid occurs at a temperature between 100°C and 200°C, the outlet of the first fluid occurs, after heating by the second fluid to a temperature between 600°C and 700°C.

[0082] In this same example, the entry of the second fluid occurs at a temperature between 750°C and 820°C, the exit of the second fluid occurs at a temperature between 200°C and 300°C.

[0083] It is noted that the flows are generally perpendicular, more precisely in each heat exchange zone, the path PI of the first fluid is substantially perpendicular to the path P2 of the second fluid.

[0084] According to an illustrated option, the thermal sponge effect material 3 is a metallic material. According to an illustrated option, the thermal sponge effect material 3 may be steel wool or iron wool. The steel wool or iron wool may be made of stainless steel wire or Inconel alloy (registered trademark) or equivalent. Advantageously, this material is a material with a high thermal capacity.

[0085] The iron wool can have a regular or irregular structure, the tangle of the threads can have an orderly or unorderly appearance.

[0086] This material stores thermal energy in the form of calories, i.e. in enthalpic form.

[0087] The thermal sponge effect material has an average void ratio of between 25% and 85%.

[0088] A high average vacuum rate of between 40% and 75%, for example around 60 to 70%, makes it possible not to create a substantial air pressure loss.

[0089] It is not necessary for the thermal sponge material 3 to fill the entire interstitial space between the tubes.

[0090] For example, in a particular embodiment illustrated in [Fig.6], the thermal sponge effect material 3 can be arranged in layers 30. The assembly can thus provide an alternation of spaced parallel tubes and a layer 30 of thermal sponge effect material 3.

[0091] The layers 30 may extend in the XY plane between two rows of tubes. In a variant, the layers could be arranged differently and extend in the XZ plane, between two columns of tubes.

[0092] Instead of a mesh material as illustrated, a macroporous material could be used, with a significant average void ratio as mentioned above.

[0093] The macroporous material in question may be a cellular material obtained by 3D printing or any form of process.

[0094] According to one example, the thermal sponge effect material 3 can occupy at least 50% of the volume of the second interior space E2 of the heat exchange zones Z1 to Z4.

[0095] The thermal sponge effect material 3 also acts as a sound attenuator. In practice, it reduces the level of sound emissions due to the exhaust of burnt gases to the outside through the SF2 orifice.

[0096] The first fluid F1 is air in the illustrated example, but the first fluid could be any gas or any assembly of gases. Similarly, the second fluid F2 is air in the illustrated example, but it could be any gas or any assembly of gases, hence the generic term "fluid" in this document.

[0097] It is noted that in the illustrated turbomachine, the first stage is started a few moments before starting the second stage, i.e. the high pressure stage, so that the second fluid is preheated before starting the second stage. The fluid at the outlet of the low pressure compressor is already hot and heats the first fluid via the heat exchanger, so that the start of the high pressure stage is already closer to the nominal operating conditions.

[0098] Thanks to the present invention, from the second start-up of the turbomachine, the time required to reach the nominal operating conditions can be reduced, for example to the point of being divided by two, if compared to the same heat exchanger configuration without thermal sponge effect material.

Claims

Claims

1. Heat exchanger (1) for a turbomachine, configured to heat a first fluid (F1) from a second fluid (F2), comprising a casing (6) delimiting an interior volume (EO) with a first interior circulation space (El) configured to convey the first fluid (F1), a second interior circulation space (E2) configured to convey the second fluid (F2), the heat exchanger comprising a plurality of tubes, the first interior circulation space comprising an interior zone of the plurality of tubes (2), the second interior circulation space comprising an exterior zone of the plurality of tubes, characterized in that the second interior space comprises a cellular or mesh material (3) having an average void rate of between 25% and 85%, preferably with an average void rate of between 40% and 75%.

2. Heat exchanger (1) according to claim 1, characterized in that the honeycomb or mesh material is a metallic material.

3. Heat exchanger according to claim 2, characterized in that the cellular or mesh material is steel wool or iron wool.

4. Heat exchanger according to any one of claims 1 to 3, characterized in that the cellular or mesh material (3) is in contact with the tubes.

5. Heat exchanger according to any one of claims 1 to 4, characterized in that the heat exchanger is of the countercurrent type.

6. Heat exchanger according to any one of claims 1 to 5, characterized in that the inlet of the first fluid occurs at a temperature between 100°C and 200°C, the outlet of the first fluid occurs at a temperature between 600°C and 700°C, the inlet of the second fluid occurs at a temperature between 750°C and 820°C, the outlet of the second fluid occurs at a temperature between 200°C and 300°C.

7. Heat exchanger according to any one of claims 1 to 6, characterized in that there is provided for the first fluid: a first inlet orifice (EF1) for the first fluid, an upstream collector zone serving all or part of the plurality of tubes, a collector zone downstream, and a first outlet orifice (SF1).

8. Heat exchanger according to any one of claims 1 to 7, characterized in that a second inlet orifice (EF2) for the second fluid and transfer ports, a second outlet orifice (SF2) are provided for the second fluid.

9. A turbomachine system (8) configured to provide electrical energy in a motor vehicle, as a range extender, comprising a heat exchanger according to any one of claims 1 to 8.

10. A motor vehicle comprising a turbomachine system according to claim 9.

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