Motor vehicle equipped with fuel cell with improved sound emission

Abstract

A motor vehicle comprising a fuel cell and a supply assembly providing a supply to the fuel cell wherein the supply assembly comprises a centrifugal compressor for compressing a reagent, the centrifugal compressor comprising an impeller having, in order: a shaft portion extending along an inlet axis; a circumferential edge extending annularly around the inlet axis; a connecting portion extending from the shaft portion to the circumferential edge; first and second vanes protruding from the connection portion, where each of the second vanes is arranged between two respective vanes to form two respective radial flow channels for the reagent; wherein the first blade and the second blade have respective contours along respective curvilinear abscissas, the contours having a shape equal to each other and being positioned to be uniformly distributed according to a periodic or angular step around the inlet axis, and wherein the contour of the second blade is shorter than the contour of the first blade.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102023000021351 filed on October 13, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The invention relates to a motor vehicle equipped with a fuel cell, in particular the fuel cell being supplied with hydrogen to generate electrical energy by electrochemical reaction with oxygen. Background Art

[0004] Some motor vehicles have a propulsion arrangement based on fuel cells.

[0005] The fuel cell is supplied with fuel, typically hydrogen, which passes in and out through the fuel cell via specific inlet and outlet openings.

[0006] Additionally, a reagent (usually oxygen) suitable for causing an electrochemical reaction with the fuel flows through the fuel cell such that the electrochemical reaction produces a flow of electrons, ie, electrical current, and waste products.

[0007] For example, when the fuel and reagent are hydrogen and oxygen, respectively, the waste material consists of water.

[0008] Like the fuel, the reagent enters and exits through specific inlet and outlet openings.

[0009] The fuel cell is usually connected to an electrical circuit comprising an electrical energy accumulator, usually a battery, which in turn can be used to power an electric motor of the motor vehicle.

[0010] In this field, the use of fuel cells is very attractive since they are able to generate sufficient electrical energy for the electric propulsion of motor vehicles.

[0011] In addition, for example, when the fuel and the reagent are hydrogen and oxygen, respectively, since the waste material is water, it is possible to obtain electricity without generating harmful emissions.

[0012] On the other hand, the lack of a thermal engine means that the sounds emitted by the use of a motor vehicle are generally considered unpleasant by the driver.

[0013] The reasons for dissatisfaction are essentially related to a reduction in driving pleasure and also to a reduction in the driver's perception of the operating conditions of the motor vehicle, for example with particular reference to acceleration and load on the electric motor.

[0014] In fact, in vehicles with thermal engines, drivers even just instinctively use the sound produced by the engine as a useful feedback signal for driving. In addition, it is well known that drivers experience a sense of pleasure associated with the sound consistent with the operation of the motor vehicle.

[0015] This is especially true for sports or luxury motor vehicles with higher performance.

[0016] In addition, the sound produced by the heat engine is often also used outside the motor vehicle, for example by drivers of nearby vehicles or pedestrians, as a sign of the presence of the motor vehicle.

[0017] Therefore, there is a need to improve the sound tolerance in general, or more specifically, the sound tolerance of a motor vehicle provided with a fuel cell.

[0018] In more detail, the same need is even stronger when the motor vehicle does not have a thermal engine.

[0019] The object of the present invention is to meet the above-mentioned need, preferably in a reproducible and simple manner. Summary of the invention

[0020] The object is achieved by a motor vehicle, the motor vehicle comprising at least one fuel cell and a supply assembly, the supply assembly being configured to supply fuel and a compressible reagent to the fuel cell, the compressible reagent being used to react with the fuel in the fuel cell and generate electrical energy, wherein the supply assembly comprises a centrifugal compressor, the centrifugal compressor being configured to compress the reagent and the centrifugal compressor comprising an impeller, the impeller comprising, in sequence: a shaft portion extending along an inlet axis; a circumferential edge extending annularly around the inlet axis; a connecting portion extending from the shaft portion to the circumferential edge; a first blade and a second blade protruding from the connecting portion, wherein each of the second blades is arranged at two The invention relates to a method for preparing the first radial flow channel and a method for preparing the first radial flow channel. The method comprises: providing a first blade and a second blade respectively connected to the connecting portion of the first blade and a second blade respectively connected to the connecting portion, wherein the first blade and the second blade have respective profiles along their respective curved horizontal coordinates, the profiles having shapes equal to each other and being positioned to be evenly distributed around the inlet axis according to a period or an angular step; wherein the profiles of the first blade and the second blade have first lengths equal to each other and second lengths equal to each other, respectively, wherein the second length is smaller than the first length.

[0021] In one embodiment, the contour is defined by a base extending at least at the connecting portion and / or by a free end opposite the base, respectively.

[0022] In one embodiment, the contours each extend from the circumferential edge along a respective curvilinear abscissa.

[0023] In one embodiment, the profiles have respective ends at the shaft portion.

[0024] In one embodiment, the first blade and the second blade have respective leading edges, and the leading edges form substantially equal angles of attack with the shaft portion or the connecting portion, respectively.

[0025] In one embodiment, the motor vehicle also includes: a sensor configured to pick up the sound generated by the operation of the centrifugal compressor and generate a sound signal, wherein the sound signal includes information about the frequency of the sound; a processing device configured to process the sound signal by shifting the frequency of the sound signal downward; and a speaker device configured to receive the sound signal processed by the processing device and reproduce the shifted sound corresponding to the sound signal processed by the processing device.

[0026] In one embodiment, the processing device is configured to shift the frequency of the sound signal with a constant shift gain.

[0027] In one embodiment, the processing device is configured to transpose the frequency of the sound signal downward by at least three octaves, preferably at most four octaves.

[0028] In one embodiment, the processing device is configured to amplify the sound signal such that the pitch-shifted sound reproduced by the speaker device is amplified relative to the sound generated by the operation of the centrifugal compressor.

[0029] In one embodiment, the speaker arrangement is configured to reproduce the pitch-shifted sound within a passenger compartment of the motor vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Below, an embodiment of the present invention will be described by way of non-limiting example and with reference to the accompanying drawings for a better understanding of the present invention, in which:

[0031] Figure 1 is a perspective view of an impeller of a centrifugal compressor according to the prior art;

[0032] Figure 2 is a perspective view of a motor vehicle according to the present invention;

[0033] Figure 3 is a block diagram of a power generation assembly for a motor vehicle including a fuel cell and a centrifugal compressor for compressing a reagent supplied to the fuel cell;

[0034] Figure 4 is a front view of a centrifugal compressor, i.e., a view across a plane perpendicular to the inlet axis of the compressor;

[0035] Figure 5 yes Figure 4 A perspective view of an impeller of a compressor in an enlarged scale;

[0036] Figure 6 Yes means Figure 5 The impeller and Figure 1 A perspective view showing a comparison between known impellers in FIG.

[0037] Figure 7 It is shown from the front Figure 5 and Figure 1 A front view showing a comparison between the impellers in FIG.

[0038] Figure 8 is used to reproduce Figure 4 Schematic diagram of a sound reproduction device for the sound produced by the operation of a compressor. DETAILED DESCRIPTION

[0039] exist Figure 2 In the drawings, reference numeral 1 is used to denote a vehicle in general, in particular a motor vehicle, more particularly a sports car or racing car.

[0040] The motor vehicle 1 comprises a body 2 defining an interior passenger compartment or cabin for accommodating at least a driver and optionally one or more passengers.

[0041] The motor vehicle 1 further comprises at least one fuel cell 10 and a supply assembly 11 which is configured to supply the fuel cell 10 .

[0042] The fuel cell 10 specifically includes:

[0043] a fuel circuit having an inlet point 14 for receiving fuel as input and an outlet point 15 for discharging unused fuel,

[0044] a reagent circuit, comprising: an inlet point 18 for receiving a suitable reagent as input to react with the fuel to generate electrical current and waste materials; and an outlet point 19 for discharging unused reagent and waste materials; and

[0045] The coolant circuit includes an inlet point 22 for receiving cool coolant as input to remove heat, and an outlet point 23 for discharging coolant heated by the removed heat.

[0046] In the operation of the fuel cell 10 , a portion of the fuel circulating in the fuel circuit is used as a result of undergoing an electrochemical reaction.

[0047] The electrochemical reaction occurs as a portion of the reagent circulates in the reagent loop and through the electrolyte of the fuel cell 10 .

[0048] An electrochemical reaction is required to separate the fuel into positive ions and electrons.

[0049] The positive ions pass through the electrolyte where they combine with the reagents to form waste products therewith.

[0050] Additionally, the electrolyte also prevents electrons from passing through.

[0051] The latter bypasses the electrolyte through the electrical circuit of the fuel cell 10 , thereby forming an electric current.

[0052] The portion of the reagent that actually reacts with the fuel is used up by the formation of waste products.

[0053] In detail, the reagent is a compressible fluid, in particular a gaseous state under ambient temperature and pressure conditions.

[0054] The electrolyte may include, for example, a proton exchange membrane disposed between the fuel circuit and the reagent circuit so as to be in contact with both the fuel and the reagent at respective opposing surfaces thereof.

[0055] For example, the fuel comprises or is defined by hydrogen.

[0056] In addition, for example, the agent comprises or is defined by oxygen. Oxygen may be only a part of the air surrounding the motor vehicle 1. Therefore, more generally, the agent may also be considered to comprise or be defined by air.

[0057] Additionally, for example, the coolant may include or be defined by water.

[0058] If the fuel and reagent are hydrogen and oxygen (or air) respectively, then the waste material will include or be defined by water, although specifically water as distinct from the coolant.

[0059] In any case, the operation of the fuel cell 10 is generally known and will not be described in further detail.

[0060] The supply assembly 11 supplies fuel and reagents to the fuel cell 10. More specifically, the supply assembly 11 supplies fuel and reagents to the inlet points 14, 18, respectively.

[0061] The reagents will react with the fuel in the fuel cell 10 to generate an electric current, thereby generating electrical energy.

[0062] The supply assembly 11 includes a centrifugal compressor 4 configured to compress the reagent.

[0063] In this case, the compressor 4 recovers the agent from the environment outside the motor vehicle 1. Specifically, the agent recovered by the compressor 4, ie at least a part of the air outside the motor vehicle 1, passes through the air filter 5 to purify the outside air.

[0064] The compressor 4 thus compresses the reagent and sends it to the fuel cell 10 , or more precisely to the inlet point 18 .

[0065] The reagent compressed by the compressor 4 preferably passes through an intercooler 6 which is configured to exchange heat between the compressed reagent and the external environment, so that the compressed reagent cools, transferring the heat to the external environment.

[0066] More preferably, the motor vehicle 1 comprises a humidifier 7 , which is arranged in particular between the intercooler 6 and the fuel cell 10 , in order to humidify the compressed reagent before it reaches the fuel cell 10 .

[0067] For example, the compressed reagent enters the fuel cell 10, or more precisely, the entry point 18, via the valve device 8, which is configured to regulate the flow of the reagent towards the fuel cell 10. Specifically, the valve device 8 is arranged between the humidifier 7 and the fuel cell 10.

[0068] Optionally, the reagent and waste materials leave the fuel cell 10 , or more precisely, the exit point 19 , via a further valve device 9 which is configured to regulate the exhaust flow of the reagent from the fuel cell 10 .

[0069] The reagent and waste material may pass through the humidifier 7. Specifically, the humidifier 7 is configured to transfer the humidity of the waste material to the compressed reagent coming from the compressor 4 and directed toward the fuel cell 10, or more precisely, toward the inlet point 18.

[0070] Furthermore, the motor vehicle 1 comprises a separation device 25 which is configured to separate reagents and waste substances leaving the fuel cell 10 . The separation device 25 is preferably arranged downstream of the humidifier 7 .

[0071] The waste materials separated using the separation device 25 reach an outlet towards the external environment.

[0072] The supply assembly 11 includes a turbine 26 configured to receive a reagent flow leaving or discharged from the fuel cell 10 (ie, in detail, a reagent separated using the separation device 25 ) and generate mechanical power through the reagent flow.

[0073] The compressor 4 uses the mechanical power generated by the turbine 26 to compress the reagent recovered by the compressor 4. Therefore, the turbine 26 may be connected to the compressor 4 so as to supply the generated mechanical power to the compressor 4.

[0074] Optionally, the motor generator unit 27 is placed between the turbine 26 and the compressor 4. The motor generator unit 27 is connected to the turbine 26 and the compressor 4 to convert the mechanical power generated by the turbine 26 into electrical energy and use the electrical energy to drive the compressor 4. Alternatively, the motor generator unit 27 and the turbine 26 may be connected in parallel with the compressor 4 to drive the compressor 4 according to a parallel structure.

[0075] The compressor 4 , the motor generator unit 27 and the turbine 26 are therefore part of a turbocharger assembly.

[0076] The supply assembly 11 also includes a fuel supply line, which in turn includes a tank 28 for containing fuel, an injection device 29 configured to inject the fuel into the fuel cell 10, and an optional recirculation device 30 (such as a pump or a fan) configured to redirect the fuel leaving the fuel cell 10 (because it is not used by it) to the tank 28.

[0077] The coolant is preferably circulated from the outlet point 23 to the inlet point 22 through a cooling line, which passes through a radiator 31 of the refrigeration line. The radiator 31 is configured to exchange heat between the coolant and the external environment, so that the coolant cools, transferring heat to the external environment. The circulation of the coolant from the outlet point 23 to the inlet point 22 is preferably in a closed loop and occurs by a pump not shown.

[0078] The motor vehicle 1 further comprises at least one electrical energy storage device 32 , such as a battery, which is configured to store the electrical energy generated by the fuel cell 10 .

[0079] Furthermore, the motor vehicle 1 comprises an electric motor, not shown but configured to propel the motor vehicle 1. The electric motor is connected to the device 32 in order to be supplied with stored electrical energy.

[0080] For the sake of clarity, Figure 3 Any component schematically depicted in FIG. 1 may be considered as part of the motor vehicle 1 independently of the other components.

[0081] Go to Figure 4 , the compressor 4 includes an impeller 35 .

[0082] More specifically, the compressor 4 further includes a casing 36 accommodating the impeller 35 .

[0083] The impeller 35 rotates relative to the housing 36 about an inlet axis A (in detail, a linear axis).

[0084] The housing 36 has an inlet opening 37 at the axis A. Specifically, the inlet opening is defined by a through hole of the housing 36 along the axis A.

[0085] The reagent enters the compressor 4 through the opening 37 and reaches the impeller 35 .

[0086] Furthermore, the housing 36 defines internally a stator channel 38 having at least one portion 39 and a portion 40. The at least one portion 39 extends substantially in a circumferential direction about the axis A and extends around the impeller 35 at a position radially further outward than the impeller 35, the portion 40 extending tangentially from the portion 39 along the tangential axis B and terminating in an outlet opening 41, which is specifically defined by a through hole of the housing 36 along the axis B.

[0087] The rotation of the impeller 35 about the axis A radially pushes the reagent entering axially through the inlet opening 37, thereby increasing its kinetic energy.

[0088] The reagent is thus compressed through the stator channel 38 until it flows out through the outlet opening 41. Thus, the stator channel 38 has a shape configured to convert the kinetic energy of the reagent into an increase in the pressure of the reagent.

[0089] The impeller 35 comprises a shaft portion 42 extending along the axis A and a circumferential edge 43 extending annularly, in particular circularly, around the axis A (in detail, across a plane orthogonal to the axis A).

[0090] In addition, the impeller 35 includes a connecting portion 44 extending from the shaft portion 42 to the circumferential edge 43 .

[0091] More specifically, the shaft portion 42 and the connecting portion 44 are both axially symmetric with respect to the axis A and are coaxial with each other.

[0092] Specifically, along the axis A, the shaft portion 42 maintains a constant radial extension (i.e., radius) relative to the axis A, while the connecting portion 44 has a steadily increasing, more specifically, gradually increasing radial extension starting from the shaft portion 42 until it encounters the circumferential edge 43, thereby radially connecting the shaft portion 42 with the circumferential edge 43.

[0093] Thus, the connecting portion 44 is substantially radial, ie it has a radial extension from the lateral outer surface of the shaft portion 42 to the circumferential edge 43 .

[0094] The connecting portion 44 is preferably formed in one piece with the shaft portion 42 and the circumferential edge 43. More generally, the entire impeller 35 is preferably made in one piece.

[0095] The impeller 35 further comprises a first blade 45 and a second blade 46 protruding from the connection portion 44. Each of the blades 46 is arranged between two corresponding blades 45, in particular angularly around the axis A, so as to form two respective radial flow channels 47 for the reagent.

[0096] In practice, the rotation of the impeller 35 about the axis A forces the reagent to flow radially, i.e. in a centrifugal manner, along the channels 47. Thus, each channel 47 delimited by one of the blades 46 and one of the other blades 45 defines a centrifugal path, i.e. having at least a radial component, for the axial entry of the reagent along the axis A.

[0097] Optionally, the impeller 35 includes splitter baffles 48 , each of which protrudes from the connecting portion 44 and is arranged to further divide a portion (or, more preferably, only a portion) of a corresponding one of the channels 47 into two portions.

[0098] Specifically, the impeller 35 includes a splitter baffle 48 for each of the channels 47 .

[0099] The flow dividing baffle 48 preferably extends only to the connecting portion 44 , not far from meeting the circumferential edge 43 .

[0100] Furthermore, the flow splitter baffles 48 preferably extend to the circumferential edge 43 , ie they terminate at the circumferential edge 43 .

[0101] Considering that the radial path starts from an end closer to the shaft portion 42 than to the circumferential edge 43 and ends at an end closer to the circumferential edge 43 than to the shaft portion 42, the diverter baffle 48 extends along the radial path defined by the channel 47, particularly along the terminal portion of the radial path.

[0102] The subsections divided by each of the flow dividing baffles 48 are adjacent to each other in the circumferential direction relative to the axis A.

[0103] In practice, each of the flow dividing baffles 48 is disposed in the middle of the corresponding channel 47 , thereby dividing the channel 47 into two halves, with the two halves being adjacent in the circumferential direction.

[0104] The flow splitter baffles 48 should not be confused with the blades 45, 46, since they have a different shape, arrangement, extension and function than the blades 45, 46. In particular, the flow splitter baffles 48 are known components for increasing the compression ratio of the compressor 4 and for avoiding the so-called "choked flow" phenomenon at the leading edge of the main blades (here defined by the blades 45, 46).

[0105] For example, the splitter baffle 48 has an axial extension (along the axis A), in particular starting from the circumferential edge 43, which is less than or equal to half or more generally three quarters of the axial extension of the impeller 35. On the other hand, the main blades defined here by the blades 45, 46 have an axial extension (along the axis A), in particular starting from the circumferential edge 43, which is greater than half or more generally three quarters of the axial extension of the impeller 35.

[0106] The blades 45 , 46 have respective base portions 50 that extend at least to the connecting portion 44 , although they may also extend to the shaft portion 42 .

[0107] The blades 45 , 46 extend from a base portion 50 , with a configuration that overhangs the connecting portion 44 and possibly the shaft portion 42 , until they terminate at a free end 51 opposite the base portion 50 .

[0108] The bases 50 extend along respective directions or curvilinear abscissae with the same shape. This means that there is at least one rigid rotational translation that allows two separate bases 50 to perfectly overlap. In other words, ideally, the curvilinear abscissae can overlap, even if they are located individually on the impeller 35.

[0109] More specifically, the curvilinear abscissa is not unlimited but extends between two opposite ends, thereby defining a corresponding curvilinear segment.

[0110] The base 50 or the corresponding curvilinear abscissa is located on the impeller 35, uniformly distributed around the axis A according to at least one angular period. This means that the curvilinear abscissa has corresponding points (e.g. even only one point for each curvilinear abscissa) distributed around the axis A, for example according to the angular period, in a circular direction on a plane perpendicular to the axis A. In particular, these points are all located at the same position and have the same shape of the corresponding curvilinear abscissa. In other words, these points all have the same coordinates along the corresponding curvilinear abscissa. For example, these points coincide with the ends of the curvilinear abscissa, in particular those ends that are closer to the circumferential edge 43 than to the shaft portion 42.

[0111] In the embodiment shown, these points are exactly on a circumferential edge 43 which extends in a circular manner between the other objects in a plane perpendicular to the axis A.

[0112] The angular period may also be defined as a blade step or angular step of the blades 45 , 46 , where the blades 45 , 46 define in detail or specifically the main blades of the impeller 35 .

[0113] The bases 50 of the blades 45 have equal respective first lengths (notably along or according to the corresponding curved abscissa). Similarly, the bases 50 of the blades 46 have equal respective second lengths (again along or according to the corresponding curved abscissa).

[0114] The second length is shorter or smaller than the first length.

[0115] Specifically, the base 50 with the first length occupies the entire extension of the corresponding curve segment or curve abscissa. Therefore, the base 50 with the second length is substantially slightly shorter than the base with the first length, although the curve segment or curve abscissa along the extension is equal to the curve segment or curve abscissa along the extension of the other bases 50.

[0116] In any case, all base portions 50 preferably have respective ends 50 b at the shaft portion 42 .

[0117] Furthermore, all bases 50 preferably extend from the circumferential edge 43 , ie they have an end 50 a at the circumferential edge 43 .

[0118] Similar to the base 50 , the free end 51 extends along a corresponding curvilinear abscissa having the same shape. Again, similar to the base 50 , the length of the free end 51 of the blade 46 is shorter than the length of the free end 51 of the blade 45 .

[0119] More generally, the base 50 or the free end 51 can more generally be considered as specific profiles of the blades 45, 46, wherein the expression "profile" is not necessarily specifically limited to the base 50 or the free end 51 (which are specifically two opposite end profiles of the blades 45, 46), but covers, for example, the intermediate cross-sectional profile of the blades 45, 46, such as the intermediate profile of the blades 45, 46 between the two end profiles.

[0120] The blades 45 are identical to the other blades 46 , although they are distributed at different positions on the impeller 35 .

[0121] exist Figure 6 and Figure 7 In the comparison, the slight difference between blade 45 and other blades 46 is clearly visible, wherein impeller 35 is different from the impeller 35 according to Figure 1 The prior art impeller 101 shown in FIG. Figure 6 , Figure 7 , the differences between the impellers 35, 101 are highlighted in grey. This shows how the impeller 101 has main blades 102 that are all identical.

[0122] exist Figure 7 In FIG. 1 , the leading edges 24 of the blades 45 , 46 and the leading edge of the blade 102 are projected onto a plane perpendicular to the axis A. FIG.

[0123] Conveniently, the leading edges 24 of the blades 45, 46 form substantially the same respective angles of attack or incidence with the shaft portion 42 (or with the connecting portion 44 according to an embodiment not shown). Here, the term "substantially" means that the difference in the leading angle or pitch may range from -15 degrees to 15 degrees, more preferably from -10 degrees to 10 degrees.

[0124] As in Figure 7 The projection of the leading edge 24 onto a plane perpendicular to the axis A is preferably radial, or extends radially relative to the axis A, as seen in FIG.

[0125] For the configuration of the impeller 101, ie, having six blades 102 that are all identical, the periodicity of the impeller 101 is six.

[0126] Generally speaking, the periodicity of an impeller of a general centrifugal compressor affects the sound produced by the same general centrifugal compressor during use.

[0127] More specifically, the sound will have a fundamental frequency that is proportional to the angular rotational speed of the impeller, according to a proportionality factor equal to the periodicity of the impeller. The more significant frequencies of the sound are generally multiples of the fundamental frequency.

[0128] Thus, the presence of blades 45 , 46 that differ according to the length of base 50 ensures that the periodicity of impeller 35 is halved, specifically three, relative to the periodicity of impeller 101 .

[0129] Thus, the sound spectrum of the compressor 4 will be enriched relative to known compressors, in particular by multiples of half the fundamental frequency.

[0130] By this enrichment, the sound spectrum will have more significant frequencies, or better yet, twice as many significant frequencies, in particular a number equal to that of a heat engine.

[0131] On the other hand, the natural frequency of the sound produced by the operation of the compressor 4 will remain well above the natural frequency of the sound produced by the heat engine.

[0132] Thus, the motor vehicle 1 advantageously comprises ( Figure 8 ) A sensor 55 is configured to pick up the sound generated by the operation of the compressor 4 and generate a sound signal containing at least information about the frequency of the generated sound.

[0133] The sensor 55 may be coupled to the compressor 4 . Specifically, the sensor 55 is fixed to the housing 36 .

[0134] The sensor 55 may be arranged at the inlet opening 37 .

[0135] For example, the sensor 55 is configured to measure the pressure of the sound wave or to measure a quantity indicative of said pressure. Thus, the sound signal may indicate the pressure. The frequency of the sound signal will be substantially the same as the frequency of the sound produced by the compressor 4.

[0136] In detail, the sensor 55 may be a microphone.

[0137] Furthermore, the motor vehicle 1 comprises a processing device 56, such as a control unit. The control unit comprises in particular an electronic computing unit. The processing device 56 is configured to process the sound signal by transposing the frequency of the sound signal downward.

[0138] In other words, the processing device 56 extracts the information about the frequency, modulates the frequency downward, and generates a new sound signal to replace the previous sound signal, that is, it updates the sound signal, introducing the information about the modulated frequency into the new signal or updated signal. Therefore, the updated signal carries or contains the information about the modulated frequency.

[0139] In practice, the processing device 56 applies a pitch conversion technique to the vocal signal to adjust the vocal signal, thereby producing an updated or adjusted vocal signal.

[0140] Specifically, the transposition of the frequencies occurs with a constant transposition gain. For example, each of the frequencies is transposed at least three octaves lower, preferably to a maximum of four octaves lower.

[0141] The updated sound signal is also preferably amplified by the processing device 56 relative to the original sound signal.

[0142] In more detail, the amplification of the sound signal includes an increase in the amplitude of the sound signal associated with the pitch-shifted frequency.

[0143] Furthermore, the motor vehicle 1 comprises a speaker device 57 which is configured to receive the updated or processed sound signal from the processing device 56 and to reproduce a pitch-shifted sound corresponding to the received signal.

[0144] Therefore, the pitch-shifted sound will have a pitch-shifted frequency. In addition, if the original sound signal is amplified, the pitch-shifted sound reproduced by the speaker device 57 will be amplified, that is, with a larger amplitude, i.e., with a greater volume or intensity, relative to the sound originally produced by the operation of the compressor 4.

[0145] The loudspeaker device 57 is preferably designed to reproduce the pitch-shifted sound in the passenger compartment of the motor vehicle 1 .

[0146] From the above, the advantages of the motor vehicle 1 are evident.

[0147] Although the motor vehicle 1 does not have a heat engine or an internal combustion engine, the sound of the heat engine or the internal combustion engine is in any case similarly obtained from the supply assembly 11 , ie from the compressor 4 .

[0148] In any case, the compressor 4 is an important component of the supply assembly 11 , so that the sound of a fossil fuel vehicle is obtained without including additional machines than those already required for the overall operation of the fuel cell 10 and therefore of the motor vehicle 1 .

[0149] In addition, the field of fuel cell technology is extremely attractive due to its virtually non-existent environmental impact and high efficiency.

[0150] Finally, it is clear that modifications may be made to the motor vehicle 1 according to the invention, without the resulting variations departing in any case from the scope of protection defined by the technical solution.

[0151] In particular, each of the details schematically represented in the drawings is independent of the other details and, in particular, is designed to solve a specific technical problem independently of the other details.

[0152] Additionally, the number or shape of each of the components shown may differ from that described and shown in the drawings.

Claims

1. A motor vehicle (1) comprising at least one fuel cell (10) and a supply assembly (11), wherein the supply assembly (11) is configured to supply fuel and a compressible reagent to the fuel cell (10), wherein the compressible reagent is used to react with the fuel in the fuel cell (10) and generate electrical energy, in, The supply assembly (11) comprises a centrifugal compressor (4), which is configured to compress the reagent and comprises an impeller (35), which in turn has: The shaft portion (42) extends along the inlet axis (A), a circumferential edge (43) extending annularly around said inlet axis (A), a connecting portion (44) extending from the shaft portion (42) to the circumferential edge (43), First and second blades (45, 46) protrude from the connecting portion (44), wherein each of the second blades (46) is arranged between two corresponding first blades (45) to form two respective radial flow channels (47) for the reagent, and optional flow divider baffles (48), each of which protrudes from the connecting portion (44) and is arranged to further divide a portion of a corresponding one of the radial flow channels (47) into two parts, The first blade and the second blade (45, 46) have respective profiles (50, 51) along respective curvilinear abscissas, the profiles (50, 51) having mutually equal shapes and being positioned so as to be evenly distributed according to periods or angular steps around the inlet axis (A), wherein the contours (50, 51) of the first blade (45) and the second blade (46) respectively have first lengths and second lengths that are equal to each other, Wherein, the second length is smaller than the first length.

2. A motor vehicle according to claim 1, wherein: The contours (50, 51) are respectively defined by a base (50) extending at least at the connection portion (44) and / or by a free end (51) opposite the base (50).

3. The motor vehicle according to claim 1, wherein: The contours (50, 51) each extend from the circumferential edge (43) along a respective curvilinear abscissa.

4. The motor vehicle of claim 1, wherein: The profiles (50, 51) have respective ends (50b) at the shaft portion (42).

5. The motor vehicle of claim 1, wherein: The first blade and the second blade (45, 46) have respective leading edges (24), and the leading edges (24) form substantially equal angles of attack with the shaft portion (42) or the connecting portion (44), respectively.

6. The motor vehicle of claim 1 further comprising: a sensor (55) configured to pick up the sound generated by the operation of the centrifugal compressor (4) and generate a sound signal containing information about the frequency of the sound, a processing device (56) configured to process the sound signal by down-shifting the frequency of the sound signal, and The speaker device (57) is configured to receive the sound signal processed by the processing device (56) and reproduce the pitch-shifted sound corresponding to the sound signal processed by the processing device (56).

7. A motor vehicle according to claim 6, wherein: The processing device (56) is configured to shift the frequency of the sound signal with a constant shift gain.

8. The motor vehicle of claim 6, wherein: The processing device (56) is configured to shift the frequency of the sound signal downward by at least three octaves, preferably at most four octaves.

9. The motor vehicle of claim 6, wherein: The processing device (56) is configured to amplify the sound signal so that the pitch-shifted sound reproduced by the speaker device (57) is amplified relative to the sound generated by the operation of the centrifugal compressor (4).

10. The motor vehicle of claim 6, wherein: The speaker device (57) is configured to reproduce the pitch-shifted sound within a passenger compartment of the motor vehicle.

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