High-power-density propelling device, high-power-density propelling assembly and aero-engine

Abstract

The invention provides a high-power-density propelling device, a high-power-density propelling assembly and an aero-engine, and relates to the field of aero-engines. The propelling device comprises a transmission shaft which is sleeved with a sun gear. And the multiple propelling units are distributed around the transmission shaft, each propelling unit comprises an outer gear ring, and the outer gear rings are driven by the propelling units to rotate. And the inner gear ring surrounds the multiple propelling units and the transmission shaft, and the outer gear rings on the multiple propelling units are meshed with the sun gear and the inner gear ring at the same time so as to drive the transmission shaft and the inner gear ring. The inner gear ring drives the fan blade disc to rotate. The harsh performance index requirements are met under the requirements of limited space and limited weight.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aero-engines, in particular to a high-power-density propulsion device, an assembly and an aero-engine. BACKGROUND

[0002] The megawatt electric drive assembly is the "heart" of a high-power electric aircraft, and its performance directly affects the safety, economy, environmental protection and comfort of the aircraft. Whether pure electric or hybrid architecture, a propulsion unit is needed.

[0003] It is crucial to master the core technology of electric machine design and develop new aircraft power industry layout represented by electric drive. The weight and size of each component in the aircraft electric propulsion assembly have very strict requirements, especially for aircraft electric machines. It is difficult to replace traditional gas turbines due to insufficient power density. High-power-density propulsion unit design is a key technology in electric machine design. SUMMARY

[0004] The purpose of the present application is at least to provide a high-power-density propulsion device under the premise of the demand for high power density of an aviation propulsion electric machine, which meets the strict performance index requirements under the demand of limited space and limited weight.

[0005] The following gives a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all contemplated aspects, and neither is it intended to identify key or critical elements of all aspects nor to delineate the scope of any or all aspects. Its only purpose is to give some concepts of one or more aspects in a simplified form as a prelude to the more detailed description given later.

[0006] One of the embodiments of the present application provides a high-power-density propulsion device, which comprises:

[0007] A transmission shaft, a sun gear is sleeved on the transmission shaft.

[0008] A plurality of propulsion units, the plurality of propulsion units are distributed around the transmission shaft, and the propulsion unit comprises an outer gear ring, which rotates under the drive of the propulsion unit.

[0009] An inner gear ring, the inner gear ring is arranged around the plurality of propulsion units and the transmission shaft, and the outer gear ring on the plurality of propulsion units is engaged with the sun gear and the inner gear ring at the same time to drive the transmission shaft and the inner gear ring.

[0010] The inner gear ring drives the fan disc to rotate.

[0011] One of the embodiments of the present application provides a high-power-density propulsion device, which comprises:

[0012] A transmission shaft, a sun gear is sleeved on the transmission shaft.

[0013] a plurality of propulsion units, the plurality of propulsion units are distributed around the transmission shaft, the propulsion units comprise an outer ring gear, the outer ring gear rotates under the drive of the propulsion units.

[0014] an inner ring gear, the inner ring gear is arranged around the plurality of propulsion units and the transmission shaft, the outer ring gears on the plurality of propulsion units are simultaneously meshed with the sun gear and the inner ring gear to drive the transmission shaft and the inner ring gear.

[0015] the transmission shaft drives the fan blade disc to rotate.

[0016] One of the embodiments of the present application provides a high-power-density propulsion device, the propulsion device comprising:

[0017] a transmission shaft, the sun gear is sleeved on the transmission shaft.

[0018] a propulsion motor, the transmission shaft is connected with the propulsion motor, and the transmission shaft rotates under the drive of the propulsion motor.

[0019] a plurality of propulsion units, the plurality of propulsion units are distributed around the transmission shaft, the propulsion units comprise an outer ring gear, the outer ring gear rotates under the drive of the propulsion units.

[0020] an inner ring gear, the inner ring gear is arranged around the plurality of propulsion units and the transmission shaft, the outer ring gears on the plurality of propulsion units are simultaneously meshed with the sun gear and the inner ring gear, the propulsion motor and the plurality of propulsion units jointly drive the inner ring gear to rotate.

[0021] the inner ring gear drives the fan blade disc to rotate.

[0022] In some embodiments, the high-power-density propulsion device comprises a planet carrier, the planet carrier is used for fixing a stator part of the propulsion unit, and the planet carrier is connected with a rotor part of the propulsion unit through a bearing.

[0023] In some embodiments, the propulsion unit comprises a slotless permanent magnet synchronous motor based on a Halbach array, and the outer ring gear is sleeved on the outer side of the motor.

[0024] In some embodiments, the propulsion device comprises 2-8 slotless permanent magnet synchronous motors.

[0025] In some embodiments, the high-power-density propulsion device comprises an outer rotor, the outer rotor is sleeved on the outer side of the inner ring gear, and the center of the outer rotor is connected with the fan blade disc through an output shaft to drive the fan blade disc to rotate.

[0026] In some embodiments, the high-power-density propulsion device comprises an energy storage unit, the energy storage unit is power-connected with the transmission shaft, and the energy storage unit is used for converting and storing kinetic energy generated by the transmission shaft.

[0027] One of the embodiments of the present application provides a high-power-density propulsion assembly, the propulsion assembly comprising the high-power-density propulsion device in the above-mentioned embodiments and further comprising a coordination controller.

[0028] The propulsion unit comprises a unit controller capable of monitoring operating state data of the propulsion unit.

[0029] The coordination controller is in signal connection with the unit controller, and is configured to control the propulsion unit according to the operating state data.

[0030] One of the embodiments of the present application provides an aero-engine comprising the high-power-density propulsion device of the above embodiments or the high-power-density propulsion assembly of the above embodiments.

[0031] The high-power-density propulsion device relates to the application, the rotor part of the propulsion unit is highly integrated with the gear, which can consider variable speed and directly couple the output torque of multiple propulsion units to the same port, and the port directly drives the propeller, the duct fan and the like, and is suitable for low-speed and large-torque application scenarios. Meanwhile, the propulsion unit is integrated in the planetary gear transmission box, which can realize ultra-short shaft design and further reduce the weight of the high-power-density propulsion device.

[0032] The high-power-density propulsion device relates to the application, the rotation speed of the propulsion unit is controlled within 20000 rpm, the rotation speed can be matched with the low-pressure shaft to high rotation speed through the outer gear ring radius, and the high rotation speed design is helpful to the increase of the power-to-weight ratio of the motor. Meanwhile, the research on one super-power high-rotation-speed aero-megawatt motor and its transmission box is converted into the research on multiple smaller-power propulsion units, which has higher maturity and lower cost.

[0033] The high-power-density propulsion device relates to the application, which can be applied to future megawatt commercial aviation electric propulsion devices, because the power of the large-bypass-ratio turbofan engine is mainly generated by the fan outer duct, and the direct replacement of the low-pressure shaft, the high-pressure shaft, the combustion chamber, the turbine and the like with the megawatt electric propulsion device is the inevitable development trend of future large-bypass-ratio aero-engines in the process of electrification development. The high-power-density propulsion device can be applied to megawatt aviation electric propulsion systems, megawatt low-speed and large-torque wind power generation systems, hundred-kilowatt propulsion motors adapted to low-altitude economic small aircraft (eVTOL, eCTOL, UAM), tens of kilowatt new energy automobile hub motor assemblies and robot high-compact shutdown motor assemblies, and the like, and has a wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0034] The above features and advantages of the present application can be better understood after reading the detailed description of embodiments of the present application in conjunction with the following drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related properties or features can have the same or similar reference numerals. Among them:

[0035] Figure 1is a schematic diagram of the internal structure of a high power density propulsion device according to some embodiments;

[0036] Figure 2 is a schematic diagram of a high power density propulsion device connected with a fan according to some embodiments;

[0037] Figure 3 is a schematic diagram of the structure of a high power density propulsion device according to some embodiments;

[0038] Figure 4 is a side view of a high power density propulsion device according to some embodiments;

[0039] Figure 5 is a three-dimensional view of a propulsion unit according to some embodiments;

[0040] Figure 6 is a top view of a propulsion unit according to some embodiments;

[0041] Figure 7 is a schematic diagram of a high power density propulsion assembly according to some embodiments. DETAILED DESCRIPTION

[0042] The present application is described in detail below with reference to the attached drawing figures and specific embodiments. It should be noted that the aspects described below with reference to the drawing figures and specific embodiments are merely exemplary and should not be understood to limit the scope of the present application in any way.

[0043] It should be understood that the use of “system,” “device,” “unit,” and / or “module” herein is a method of distinguishing different components, elements, parts, sections, or assemblies from one another. However, if other expressions can achieve the same purpose, the expressions can be replaced by other expressions.

[0044] It can be understood that the technical terms involved in the description of the present specification, such as “center”, “longitudinal”, “transverse”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, etc. The orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments, and does not indicate or imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the application.

[0045] It should be noted that the terms "first", "second", etc. used in the specification are used to distinguish features only, and do not have special meanings unless otherwise stated. As shown in the specification and claims, the terms "a", "an", "one", and / or "the" do not refer to a single number, but also include a plurality, unless the context clearly indicates otherwise. Generally, the terms "include" and "contain" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list. The method or device can also include other steps or elements.

[0046] In the description of the specification, it should be noted that unless otherwise explicitly specified or limited, the terms "mount", "connect", "connection" should be understood broadly, for example, it can be fixedly connected, integrally connected, or detachably connected; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements, etc. For those skilled in the art, the specific meaning of the above terms in the specification can be understood according to the specific circumstances.

[0047] Figure 1 is a schematic diagram of the internal structure of a high-power-density propulsion device according to some embodiments.

[0048] The embodiments of the specification propose a high-power-density propulsion device, as shown in Figure 1 The propulsion device 1 includes a transmission shaft 11, a propulsion unit 12, and an inner ring gear 13.

[0049] The transmission shaft 11 is located at the center of the propulsion device 1. A sun gear 111 is sleeved on the transmission shaft 11, and the sun gear 111 is fixed relative to the transmission shaft 11.

[0050] The number of propulsion units 12 is multiple, and the multiple propulsion units 12 are distributed around the transmission shaft 11. In some embodiments, according to the actual power requirement, 2-8, or even more or fewer propulsion units 12 are provided. Figure 1 The three propulsion units 12 shown in the figure are only examples. For ease of description, the following description of the specification will continue to take three propulsion units 12 as an example.

[0051] Referring to Figure 1 , the propulsion unit 12 can output power, and the power output by the propulsion unit 12 provides the propulsion force of the entire propulsion device 1. The propulsion unit 12 includes an outer ring gear 121, which rotates under the drive of the propulsion unit 12 to transmit the power of the propulsion unit 12 outward.

[0052] The internal gear ring 13 has a ring-shaped structure and surrounds multiple propulsion units 12 and the drive shaft 11. The internal gear ring 13 and the drive shaft 11 are coaxially arranged. Multiple propulsion units 12 are arranged between the internal gear ring 13 and the drive shaft 11. The external gear rings 121 on the multiple propulsion units 12 simultaneously mesh with the sun gear 111 and the internal gear ring 13.

[0053] Figure 2 This is a schematic diagram showing the connection between a high power density propulsion device and a fan, according to some embodiments.

[0054] In some embodiments, the rotation of multiple external gear rings 121 can simultaneously drive the sun gear 111 and the internal gear ring 13 to rotate, and the sun gear 111 drives the drive shaft 11 to rotate. When the external gear rings 121 simultaneously drive the sun gear 111 and the internal gear ring 13, the fan impeller 22 can be driven by either the drive shaft 11 or the internal gear ring 13, thereby driving the rotation of the fan blades 21. In some embodiments, the drive shaft 11 is connected to the fan impeller 22 to drive the fan blades 21 to rotate. (The following is a continuation of the previous paragraph.) Figures 3-4 This describes the structure by which the internal gear ring 13 drives the fan impeller 22 to rotate. The fan casing 23 encloses the propulsion device 1 and the entire fan assembly.

[0055] Traditional aircraft engines cause air pollution (CO2, NO) due to combustion. X Emissions will exacerbate global environmental pollution, and the electrification of aircraft engines is an inevitable trend in green development. This specification's embodiments transform the study of a single ultra-high-power, high-speed megawatt-class aircraft motor and its gearbox into a study of a bundled combination of multiple smaller-power propulsion units 12, with multiple propulsion units 12 providing power to the fan. The power-to-weight ratio of the propulsion unit 12 has reached at least 3 kW / kg, meeting the high power density requirements for replacing traditional gas turbines. In some embodiments, the power-to-weight ratio of the propulsion unit 12 has reached 3.8 kW / kg.

[0056] Figure 3 This is a structural schematic diagram of a high power density propulsion device according to some embodiments. Figure 4 This is a side view of a high power density propulsion device according to some embodiments.

[0057] like Figure 3 and Figure 4 As shown, the propulsion device 1 includes an outer rotor 14, which is divided into upper and lower sections (relative to the upper and lower sections). Figure 3The outer rotor 14 is fixed relative to the inner ring 13. In some embodiments, the outer rotor 14 wraps around the sun gear 111, the inner ring 13, and the propulsion units 12. The outer rotor 14 rotates with the inner ring 13. The outer rotor 14 has an output shaft 141 extending outwardly from the center of the outer rotor 14. The output shaft 141 is connected to the fan disk 22. The outer rotor 14 drives the fan disk 22 to rotate through the output shaft 141. It is understood that there is no connection between the transmission shaft 11 and the output shaft 141.

[0058] In some embodiments, as shown in FIG. 1, the transmission shaft 11 and the output shaft 141 extend in opposite directions from opposite sides of the outer rotor 14. Figure 4

[0059] In some embodiments, the propulsion units 12 drive the transmission shaft 11 and the inner ring 13 to rotate simultaneously. The transmission shaft 11 is connected to the energy storage unit. The energy storage unit converts the kinetic energy generated by the rotation of the transmission shaft 11 into electrical energy for storage.

[0060] In some embodiments, the transmission shaft 11 also provides propulsion for the propulsion device 1. The transmission shaft 11 is connected to the propulsion motor or the energy storage unit. The transmission shaft 11 rotates under the drive of the propulsion motor or the energy storage unit. The energy storage unit releases the stored electrical energy to convert into kinetic energy for the rotation of the transmission shaft 11. The transmission shaft 11 drives the inner ring 13 to rotate together with the plurality of propulsion units 12. This improves the fault tolerance of the propulsion device 1. Even if there is damage or failure in the propulsion motor or the propulsion units 12, the propulsion device 1 can still operate normally under the joint work of the remaining propulsion components.

[0061] In some embodiments, as shown in FIG. 1, the high-power-density propulsion device 1 includes a planet carrier 15. The planet carrier 15 is used to fix the stator part of the propulsion unit 12. The planet carrier 15 is connected to the rotor part of the propulsion unit 12 through a bearing. Figure 1

[0062] In some embodiments, the propulsion unit 12 includes a slotless permanent magnet synchronous motor based on a Halbach array. The outer ring 121 is sleeved on the outer side of the rotor of the permanent magnet synchronous motor. The structure of the propulsion unit 12 will be described below with reference to Figures 5-6

[0063] Figure 5 FIG. 2 is a three-dimensional view of the propulsion unit according to some embodiments. Figure 6 FIG. 3 is a top view of the propulsion unit according to some embodiments.

[0064] FIG. 4 is a three-dimensional view of the propulsion unit according to some embodiments. Figure 5 Figure 6 ​​​​As shown, the rotor part of the propulsion unit 12 includes a Halbach permanent magnet 124. The Halbach permanent magnet is a kind of high magnetic load design at present, and the use of the material can further reduce the amount of permanent magnet, thereby achieving the effect of lightweight of the propulsion unit 12.

[0065] In some embodiments, the rotor part of the propulsion unit 12 further includes an outer shell 122 and a rotor yoke 123, and the Halbach permanent magnet 124, the rotor yoke 123, the outer shell 122 and the outer gear ring 121 are sequentially arranged in the radially outward direction of the propulsion unit 12, that is, the rotor yoke 123 is wrapped outside the Halbach permanent magnet 124, the outer shell 122 is wrapped outside the rotor yoke 123, and the outer gear ring 121 is wrapped outside the outer shell 122. Specifically, the rotor yoke 123 is fixed on the outer shell 122 by winding technology, so that the rotor yoke 123 is tightly attached to the outer shell 122. By arranging the rotor yoke 123 and the outer shell 122 outside the Halbach permanent magnet 124 to form a protective structure, the protective structure is light and thin, has sufficient pre-tightening force and containment effect, and can effectively avoid the disastrous consequences caused by the flying loss of the rotor components contained therein under high-speed rotation.

[0066] In some embodiments, the stator part of the propulsion unit 12 adopts a slotless structure, that is, the permanent magnet synchronous motor of the propulsion unit 12 adopts an outer rotor Halbach slotless topology structure. Specifically, the stator part of the propulsion unit 12 includes a Litz wire winding 126, a stator yoke 127 and a stator core 128. The Litz wire winding 126, the stator yoke 127 and the stator core 128 are sequentially arranged in the radially inward direction of the propulsion unit 12, the stator yoke 127 has a slotless structure, and the stator yoke 127 and the stator core 128 are connected through a bearing 129. The Litz wire winding 126 is arranged on the radially outer side of the stator yoke 127 and on the radially inner side of the Halbach permanent magnet 124, and an air gap 125 is formed between the Halbach permanent magnet 124 and the Litz wire winding 126. The use of the shaped Litz wire to form the stator winding can effectively suppress the alternating current loss of the permanent magnet synchronous motor at high frequency. The structure of the propulsion unit 12 can make the size of the air gap 125 as small as possible, for example, less than 2.5 mm, thereby improving the output torque of the permanent magnet synchronous motor and the output torque of the plurality of propulsion units 12.

[0067] The stator core 128 is arranged on the radially inner side of the stator yoke 127. The stator yoke 127 forms a slotless structure between the Litz wire winding 126 and the stator core 128, and the use of the slotless structure can maximize the reduction of torque ripple, and compared with the slot structure, the space occupied by the stator slot of the slot structure can be used to lay more windings, thereby improving the full slot rate to a certain extent.

[0068] The specific power density of a permanent magnet synchronous motor can be expressed as:

[0069] (1)

[0070] In equation (1), K Ø is the ratio of electrical load on the rotor and stator, m is the number of phases, m1 is the number of phases per stator, K e is the EMF factor, K i is the current waveform factor, K p is the electrical power waveform coefficient, η is the motor efficiency, B g is the air gap flux density, A is the total electrical load of the motor, f is the converter frequency, p is the number of motor pole pairs, D g is the air gap diameter, L e is the effective part of the stack length, and M is the mass of the motor.

[0071] (2)

[0072] In equation (2), and are proportional to the rotational speed and volume of the motor, respectively. Therefore, the specific power density of the motor is proportional to the air gap flux density, electrical load, and rotational speed. The electrical load or linear current density of the motor is closely related to the heat dissipation capacity and the current density in the slot. High electrical load increases the air gap flux density, but also heats the winding, requiring a larger cooling assembly.

[0073] (3)

[0074] Equation (3) is a hypothetical simplification based on equation (2), in which the electromagnetic load and air gap flux density are constant within a certain rotational speed range. When the power is constant, the motor with high rotational speed has a smaller size; when the size is the same, the motor with high rotational speed has a larger power, and the volume and weight of the motor can be reduced by increasing the rotational speed. The above formula and theory are used to illustrate the key design dimensions of the motor. The transmission shaft 11 shown in the specification directly drives the fan blade disc 22, which is essentially a low-speed large-torque, and through design, the rated rotational speed of the propulsion unit 12 matched therewith can be designed at a high rotational speed state. According to the derivation of the above formula, high-speed design can greatly improve the weight of the motor itself, and thus the power density of the motor.

[0075] Figure 7 is a schematic diagram of a high-power-density propulsion assembly according to some embodiments.

[0076] The embodiments of the specification also provide a high-power-density propulsion assembly 100, which includes the high-power-density propulsion device 1 described in the above embodiments, and further includes a coordination controller 30.

[0077] The propulsion unit 12 comprises unit controllers, i.e. Figure 7 P1 controller, P2 controller and P3 controller as shown. The unit controllers are capable of controlling the electrical power output of the propulsion unit 12, i.e. the P1 controller is capable of controlling the electrical power output of the P1 gear motor (a first permanent magnet synchronous motor), the P2 controller is capable of controlling the electrical power output of the P2 gear motor (a second permanent magnet synchronous motor), and the P3 controller is capable of controlling the electrical power output of the P3 gear motor (a third permanent magnet synchronous motor).

[0078] The coordination controller 30 is in signal connection with the P1 controller, the P2 controller and the P3 controller, and is configured to control the operation of the propulsion unit 12, i.e. the P1 gear motor, the P2 gear motor and the P3 gear motor, according to the operation state data transmitted by the P1 controller, the P2 controller and the P3 controller. The P1 gear motor, the P2 gear motor and the P3 gear motor convert electrical energy into mechanical energy and output through the output shaft 141 to provide power for the operation of the fan 20. The essence of the coordination controller 30 is a health management assembly, which timely stops a motor in a damaged or fault state among the P1 gear motor, the P2 gear motor and the P3 gear motor, so that the fault of the motor does not continue to worsen and affect the safety of the entire high-power-density propulsion assembly.

[0079] The embodiments of the present specification also provide an aero-engine comprising the high-power-density propulsion device 1 of the above embodiments or the high-power-density propulsion assembly 100 of the above embodiments.

[0080] The above has described the basic concept, and it is obvious that the above detailed disclosure is only taken as an example for the person skilled in the art, and does not constitute a limitation on the present specification. In addition, unless explicitly stated in the claims, the order of the processing elements and sequences in the present specification, the use of numerals and letters, or the use of other names, is not used to limit the order of the processes and methods of the present specification. Although some currently considered useful embodiments of the application are discussed in the above disclosure through various examples, it should be understood that such details are only for the purpose of illustration, and the additional claims are not limited to the disclosed embodiments, on the contrary, the claims are intended to cover all modifications and equivalent combinations that meet the spirit and scope of the embodiments of the present specification.

Claims

1. A high power density propulsion device, characterized in that, The propulsion device includes: A drive shaft, on which a sun gear is mounted; Multiple propulsion units are distributed around the drive shaft, and each propulsion unit includes an external gear ring that rotates under the drive of the propulsion unit. An internal gear ring surrounds the plurality of propulsion units and the drive shaft, and the external gear rings on the plurality of propulsion units simultaneously mesh with the sun gear and the internal gear ring to drive the drive shaft and the internal gear ring; The internal gear ring drives the fan blades to rotate, or the transmission shaft drives the fan blades to rotate.

2. The high power density propulsion device according to claim 1, characterized in that, The high power density propulsion device includes a planetary carrier for fixing the stator portion of the propulsion unit, and the planetary carrier is connected to the rotor portion of the propulsion unit via bearings.

3. The high power density propulsion device according to claim 1, characterized in that, The propulsion unit includes a slotless permanent magnet synchronous motor based on a Halbach array, with the external gear ring fitted on the outside of the motor.

4. The high power density propulsion device according to claim 3, characterized in that, The propulsion device includes 2 to 8 slotless permanent magnet synchronous motors.

5. The high power density propulsion device according to claim 1, characterized in that, The high power density propulsion device includes an outer rotor, which is sleeved on the outside of the inner gear ring. The center of the outer rotor is connected to the fan blade disk through an output shaft to drive the fan blade disk to rotate.

6. The high power density propulsion device according to claim 1, characterized in that, The high power density propulsion device includes an energy storage unit that is poweredly connected to the drive shaft. The energy storage unit is used to convert and store the kinetic energy generated by the drive shaft.

7. A high power density propulsion assembly, characterized in that, The propulsion assembly includes the high power density propulsion device according to any one of claims 1 to 6, and further includes a coordination controller; The propulsion unit includes a unit controller, which is capable of monitoring the operating status data of the propulsion unit; The coordination controller is signal-connected to the unit controller, and the coordination controller is used to control the propulsion unit according to the operating status data.

8. An aircraft engine, characterized in that, It includes the high power density propulsion device as described in any one of claims 1 to 6 or the high power density propulsion assembly as described in claim 7.

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