CN110162863B - Thermal coupling design method of electric ducted fan - Google Patents
Thermal coupling design method of electric ducted fan Download PDFInfo
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Abstract
The invention provides a thermal coupling design method of an electric ducted fan, which is characterized in that the influence of a hub in the ducted fan on the actual efficiency and the actual thrust of fan blades and the influence on the heat dissipation requirement of a motor (the heat dissipation quantity of the surface of a motor shell is larger than the heat productivity of the motor) and the power of the motor are considered, and the hub ratio and the heat dissipation requirement of the motor are integrated into the design process of the ducted fan, so that the design result of the ducted fan can meet the use requirement of a multi-working-condition environment, the heat dissipation requirement of the motor (the heat dissipation quantity of the surface of the motor shell is larger than the heat productivity of the motor) is met, the volume of the motor is minimized, and the power-weight ratio of the motor in the ducted fan is improved.
Description
Technical Field
The invention relates to the technical field of aviation propulsion, in particular to a thermal coupling design method of an electric ducted fan.
Background
With the stricter requirements on safety, energy conservation, environmental protection, reliability and the like of airplanes, multi-electric airplanes, full-electric airplanes and hybrid airplanes gradually get attention of people and are rapidly developed. In these new types of airplanes, the design concept of wing body fusion is combined, so that the electric ducted fan becomes a very critical part. The traditional ducted fan is a propulsion form widely used in the field of aviation, and becomes a mainstream propulsion mode in the existing large passenger plane due to the advantages of high propulsion efficiency, low noise, good containment, large unit power thrust and the like. The electric ducted fan uses the motor to replace an aircraft engine in a traditional ducted fan, and can obtain quicker system responsiveness, lower noise pollution, more flexible traditional system arrangement and the like.
The power-to-weight ratio (power to mass ratio) is a very important and sensitive parameter in the field of aviation propulsion, since the weight of an electrically powered ducted fan directly affects the weight of a commercial load and the effective flight range of an aircraft. If the power-weight ratio of the motor for aviation needs to be improved, optimization needs to be carried out from three aspects: (1) the heat dissipation of the motor is enhanced; (2) optimizing the design of the electromagnetic structure of the motor; (3) the structure is light. In order to improve the power-weight ratio, two means can be used, namely, liquid hydrogen is used for cooling the motor, so that the heat dissipation requirement of the motor can be fully met, and the motor can even work under the condition of low-temperature superconductivity; secondly, some electromagnetic design schemes are tried, such as a switched reluctance motor, an axial air gap permanent magnet motor, a superconducting synchronous motor and the like are used as motors. However, in the field of small-sized aviation propulsion, the weight of the electric ducted fan is increased by excessively complicated heat dissipation modes and structures (such as oil cooling, liquid hydrogen cooling and the like), and meanwhile, the reliability problems of sealing and the like are caused. It is therefore an object of many researchers to provide a motor that minimizes the size of the motor to achieve a higher power-to-weight ratio.
The matching design of the prior ducted fan and the motor is mainly carried out through two indexes of power and rotating speed, and then temperature rise is checked and checked, so that the temperature rise on an operation working condition line of the airplane meets the safety requirement of the motor in the operation process of the airplane. However, this design approach has two major problems: the first is that the design process of the motor and the ducted fan is not considered in a coupling way, particularly the index of the hub ratio is the first parameter which needs to be determined in the whole design process and has great influence on the blades and the motor, such as the power-weight ratio of the motor; secondly, the influence of the thermal performance (such as the heat dissipation requirement of the motor) of the motor on the design process is not considered in the design process of the ducted fan, so that the power-weight ratio of the motor is not ideal.
Disclosure of Invention
In view of the defects in the prior art, the present invention aims to provide a thermal coupling design method for an electric ducted fan, which integrates the hub ratio and the heat dissipation requirement of a motor into the design of the ducted fan, and improves the power-weight ratio of the motor in the ducted fan.
In order to achieve the above object, the present invention provides a thermal coupling design method of an electric ducted fan, for designing a ducted fan including fan blades, a motor, and a duct, the thermal coupling design method of an electric ducted fan including steps S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, and S11. S1, trying to obtain the hub ratio r of the ducted fan to be designed, and setting the thrust requirement T of the ducted fan to be designed under one working condition in the multi-working-condition environment|rustThe size requirement, the exit parameters of the ducted fan and the blade tip Mach number of the ducted fan are estimated to obtain the estimated efficiency of the ducted fan under the working condition and calculate to obtain the axial speed V of the airflow at the exit of the ducted fanoutThe dimensional requirements include axial length L of the ducted fanductRadius R of ducted fanductThe ducted fan outlet parameters comprise the ratio of the outlet airflow cross section area to the inlet airflow cross section area of the ducted fan and the airflow density rho of the ducted fan outlet, and the multi-working-condition environment comprises a plurality of working conditions; s2, according to the axial velocity V of the ducted outlet airflowoutRadius R of ducted fanductAnd the ducted fan outlet parameters, and calculating to obtain the performance parameters of the ducted fan according to the excited disc theory of the ideal gas, wherein the performance parameters comprise thrust T and power consumption P; s3, according to the hub ratio r of the ducted fan and the axial length L of the motormotorCalculating the volume V of the motormotor(ii) a S4, obtaining the volume V of the motor according to the given rotation speed omega of the motor and the step S3motorCalculating the power P of the motormotor(ii) a S5, obtaining the efficiency value eta of the motor by initial estimationmotor(ii) a S6, according to the efficiency value eta of the motormotorAnd power consumption P of the ducted fan, and calculating to obtain the heat productivity W of the motorH(ii) a According to the axial length L of the motormotorCalculating the known surface area of the motor shell, the temperature difference of the surface of the shell and the flow velocity of the airflow at the shell to obtain the heat dissipation W of the surface of the motor shellC(ii) a S7, judging whether the heat dissipation quantity of the surface of the motor shell obtained in the step S6 is larger than the heat productivity of the motor, if not, executing the step S8; if yes, go to step S9; s8, checking the efficiency value eta of the motormotorIf it can be raised, the motor efficiency value eta is increasedmotorAnd returning to the step S6, executing the steps S6-S7; if not, increasing the hub ratio of the ducted fan, returning to the step S3, and executing the steps S3-S7; s9, checking the power P of the motormotorIf the redundancy exists, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, otherwise, determining the hub ratio of the ducted fan and the thrust requirement T of the ducted fan under the working condition|rustSubstituting the thrust T into a fan design program to carry out fan blade design and simulation calculation to obtain the blade profile, the performance data and the 3D simulation model of the fan blade of the preliminarily designed ducted fan and executing the step S10; the performance data includes actual efficiency, actual thrust of the ducted fan; s10, giving an efficiency error value and a thrust error value, judging whether the actual efficiency of the preliminarily designed ducted fan is too high, namely whether the actual efficiency of the ducted fan is higher than the estimated efficiency and whether the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual efficiency of the preliminarily designed ducted fan is too low, namely whether the actual efficiency of the ducted fan is lower than the estimated efficiency and the absolute value of the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, increasing the hub ratio of the ducted fan and returning to the step S3 and executing the steps S3-S7, if not, judging whether the actual thrust of the preliminarily designed ducted fan is too high or not, namely whether the actual thrust of the ducted fan needs to be higher than theFinding T|rustHigh and actual thrust and thrust demand T|rustIf yes, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual thrust of the primarily designed ducted fan is too low, namely the actual thrust ratio of the ducted fan is higher than the thrust requirement T|rustLow and actual thrust and thrust requirement T|rustIf the absolute value of the difference value is larger than the thrust error value, increasing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, otherwise, outputting the actual efficiency and the actual thrust of the ducted fan and executing the step S11; s11, judging whether the actual thrust of the preliminarily designed ducted fan under the working condition is larger than the thrust requirements of the ducted fan under other working conditions in the given multi-working condition environment, if so, outputting the blade profile, the performance data and the 3D simulation model of the fan blades of the preliminarily designed ducted fan to serve as the final design result of the ducted fan meeting all the working conditions; if not, the thrust requirement of the ducted fan under other working conditions is taken as the thrust requirement T in the step S1|rustAnd returning to the step S1, and re-executing the steps S1-S7 until the actual thrust of the ducted fan obtained by the primary design is greater than the thrust requirements under the other residual working conditions in the multi-working-condition environment, and outputting the final design result of the ducted fan meeting all the working conditions.
In one embodiment, the value of the hub ratio r of the ducted fan obtained in step S1 is in a range of 0.2 to 0.4.
In one embodiment, the axial velocity V of the ducted outlet airflow in step S1outIncludes steps S111, S112, and S113. S111, according to the radius R of the ducted fanductAnd a hub ratio r of the ducted fan, by:
wherein r represents the hub ratio of the ducted fan, AinRepresenting the inlet airflow cross section of the ducted fan, and calculating to obtain the inlet airflow cross section A of the ducted fanin(ii) a S112, according to the inlet airflow cross-sectional area A of the ducted faninAnd the outlet airflow cutoff of the ducted fanThe ratio of the area to the inlet airflow cross-sectional area is calculated to obtain the outlet airflow cross-sectional area A of the ducted fanout(ii) a S113, according to the outlet airflow cross section area A of the ducted fanoutThrust demand T|rustAnd an airflow density ρ at the ducted fan outlet by:
where ρ represents the airflow density at the ducted fan outlet, AoutThe sectional area of the outlet airflow of the ducted fan is represented, and the axial velocity V of the outlet airflow of the ducted fan is calculatedout。
In one embodiment, the calculation of the fan performance parameter in step S2 includes steps S21, S22 and S23. S21, according to the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutAnd axial velocity V of the ducted outlet air streamoutBy the following formula: m ═ Vout·AoutRho, where m represents the gas mass flow, the gas mass flow m is calculated; s22, according to the gas mass flow m and the axial velocity V of the bypass outlet gas flowoutAnd calculating to obtain the thrust T of the ducted fan as m multiplied by Vout(ii) a S23, according to the thrust T of the ducted fan, the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutCalculating the power consumption of the ducted fan
In one embodiment, the volume V of the motor in step S3motorThe calculation process of (2) is as follows: according to the ratio R of the hub of the ducted fan and the radius R of the ducted fanductAnd obtaining the radius of the hub by the relationship of the radius of the hub, and assuming that the radius of the hub and the radius R of the motor are RmotorSame according to the radius of the hub and the axial length L of the motormotorCalculating the volume V of the motormotor。
In one embodiment, the power P of the motor in step S4motorThe calculation process of (2) is as follows: pmotor＝ω·kτVmotorWherein k isτIs the motor torque coefficient.
In one embodiment, the efficiency value η of the motormotorThe value range of (A) is between 85% and 90%.
In one embodiment, the heat generation amount W of the motor in step S6HThe calculation process of (2) is as follows: wH＝P/ηmotor(1-ηmotor)。
In one embodiment, the heat dissipation amount W of the motor casing surface in step S6CThe calculation process of (2) is as follows: wC＝hAΔT，
In the formula, h represents the convection heat transfer coefficient, A represents the surface area of the motor casing, Delta T represents the surface temperature difference of the casing, v represents the flow velocity of the air flow at the casing, the flow velocity v of the air flow at the casing is obtained by the quotient of the air volume flow at the casing and the surface area of the motor casing, and the air volume flow at the casing is obtained by the sectional area A of the air flow at the outlet of the ducted fanoutAnd axial velocity V of the ducted outlet air streamoutThe product is obtained.
The invention has the following beneficial effects:
in the thermal coupling design method of the electric ducted fan, the influence of the actual efficiency and the actual thrust of the fan blades by the hub in the ducted fan, the influence of the heat dissipation requirement of the motor (the heat dissipation quantity of the surface of the motor shell is larger than the heat productivity of the motor) and the power of the motor are considered, the hub ratio and the heat dissipation requirement of the motor are integrated into the design process of the ducted fan, the design result of the ducted fan can meet the use requirement of a multi-working-condition environment, meanwhile, the motor can meet the heat dissipation requirement (the heat dissipation quantity of the surface of the motor shell is larger than the heat productivity of the motor), the volume of the motor is minimized, and the power-weight ratio of the motor in the ducted fan is improved.
Drawings
Fig. 1 is a flow chart of a thermal coupling design method of an electric ducted fan of the present invention.
Fig. 2 is a schematic view of a ducted fan in the thermal coupling design method of an electric ducted fan of the present invention.
Wherein the reference numerals are as follows:
1 Fan blade
2 electric machine
3 duct
Detailed Description
The accompanying drawings illustrate embodiments of the present invention and it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms, and therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.
The thermal coupling design method of the electric ducted fan according to the present invention is explained in detail below with reference to the accompanying drawings.
Referring to fig. 1 and 2, the method for thermally coupling design of an electric ducted fan according to the present invention is used for designing a ducted fan including a fan blade 1, a motor 2, and a duct 3, and includes steps S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, and S11.
S1, trying to obtain the hub ratio r of the ducted fan to be designed, and setting the thrust requirement T of the ducted fan to be designed under one working condition in the multi-working-condition environment|rustThe size requirement, the exit parameters of the ducted fan and the blade tip Mach number of the ducted fan are estimated to obtain the estimated efficiency of the ducted fan under the working condition and calculate to obtain the axial speed V of the airflow at the exit of the ducted fanoutThe dimensional requirements include axial length L of the ducted fanductRadius R of ducted fanductThe ducted fan outlet parameters include a ratio of an outlet airflow cross-sectional area to an inlet airflow cross-sectional area of the ducted fan and an airflow density ρ of the ducted fan outlet, and the multi-operating-condition environment includes a plurality of operating conditions.
The ducted fan is applied to an airplane in a complex multi-working-condition environment, and at the beginning of the design of the ducted fan, the thrust requirement T of each working condition stage on the ducted fan needs to be determined by general designers according to flight tasks and flight envelope lines|rustAnd size requirements, etc. The multiple working conditions comprise a takeoff working condition, a climbing working condition, a descent working condition and a descent working conditionUnder the flying working condition, the heat dissipation difficulty of the ducted fan is the largest, so the ducted fan is preferably designed under the takeoff working condition firstly. Before designing the ducted fan, the thrust requirement T of the ducted fan under all working conditions is given according to actual requirements|rustSize requirements, ducted fan exit parameters, and ducted fan tip mach number. The performance of the ducted fan is preliminarily known through the Mach number of the blade tip. The value of the hub ratio of the ducted fan is to take into account, on the one hand, the size of the electric machine 2 etc. which the hub can accommodate and, on the other hand, the consistency of the blade root of the fan blade 1 is not too great. The hub ratio of the fan is generally smaller, and the hub ratio of the ducted fan can be generally between 0.2 and 0.4. The airflow density ρ of the ducted fan outlet in the ducted fan outlet parameters may be assumed to be the ambient density at the corresponding operating conditions.
Axial velocity V of bypass outlet airflow in step S1outIncludes steps S111, S112, and S113. S111, according to the radius R of the ducted fanductAnd a hub ratio r of the ducted fan, by:
wherein r represents the hub ratio of the ducted fan, AinRepresenting the inlet airflow cross section of the ducted fan, and calculating to obtain the inlet airflow cross section A of the ducted fanin(ii) a S112, according to the inlet airflow cross-sectional area A of the ducted faninAnd the ratio of the outlet airflow cross section area to the inlet airflow cross section area of the ducted fan is calculated to obtain the outlet airflow cross section area A of the ducted fanout(ii) a S113, according to the outlet airflow cross section area A of the ducted fanoutThrust demand T|rustAnd an airflow density ρ at the ducted fan outlet by:
where ρ represents the airflow density at the ducted fan outlet, AoutThe sectional area of the outlet airflow of the ducted fan is represented, and the axial velocity V of the outlet airflow of the ducted fan is calculatedout。
S2, according to the axial velocity V of the ducted outlet airflowoutHalf of ducted fanDiameter RductAnd calculating performance parameters of the ducted fan according to the excited disc theory of the ideal gas, wherein the performance parameters comprise thrust T and power consumption P.
The calculation process of the fan performance parameters in step S2 includes steps S21, S22, and S23. S21, according to the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutAnd the axial velocity V of the ducted outlet gas flowoutBy the following formula: m ═ Vout·AoutRho, where m represents the gas mass flow, the gas mass flow m is calculated; s22, according to the gas mass flow m and the axial velocity V of the bypass outlet gas flowoutAnd calculating to obtain the thrust T of the ducted fan as m multiplied by Vout(ii) a S23, according to the thrust T of the ducted fan, the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutCalculating the power consumption of the ducted fan
The excitation theory in the step S2 is to regard the wind turbine (i.e. ducted fan) as an excitation disk, extract wind energy through the excitation disk, regard the excitation disk as incompressible, model the flow passing through the ducted fan and make the following assumptions: 1) assuming the mach number is low, such that the flow appears as an incompressible fluid; 2) assuming that the flow outside the ducted fan flow tubes has a constant stagnation pressure (no effect on it); 3) assuming that the flow is stable; (4) on the swash plate, it is assumed that the pressure varies discontinuously, but the speed varies in a continuous manner. And the design of inner and outer diameters such as the inlet and the outlet of the ducted fan is assumed, so that the gas mass flow m is rho A through modelingdisk[(Vout+Vin)/2]And a thrust force
Wherein, VinAxial velocity of the ducted inlet air stream, AdiskRepresenting the swash area (i.e., the area at the fan blades 1), and thus allowing an approximation of the gas mass flow m and thrust T of the ducted fan to be obtained by modelingThe formula is m ═ Vout·Aoutρ and T ═ mxvout。
S3, according to the hub ratio r of the ducted fan and the axial length L of the motor 2motorThe volume V of the motor 2 is calculatedmotor。
Volume V of motor 2 in step S3motorThe calculation process of (2) is as follows: according to the ratio R of the hub of the ducted fan and the radius R of the ducted fanductAnd the radius of the hub is obtained according to the relation of the radius of the hub, and the radius R of the motor 2 is assumedmotorSame according to the radius of the hub and the axial length L of the motor 2motorThe volume V of the motor 2 is calculatedmotor. The motor 2 is assumed to be a cylinder, so the outer diameter of the motor is the same as the hub radius of the motor, and the axial length L of the motor 2 is determined according to the hub radiusmotorThe volume V of the motor 2 is obtained by calculationmotor。
S4, obtaining the volume V of the motor 2 according to the given rotating speed omega of the motor 2 and the step S3motorCalculating the power P of the motor 2motor。
Power P of the motor 2 in step S4motorThe calculation process of (2) is as follows: pmotor＝ω·kτVmotorWherein k isτIs the motor torque coefficient. Under the condition that the motor 2 is directly connected with the fan blades 1, the rotating speed omega of the motor 2 is the same as that of the ducted fan.
S5, obtaining the efficiency value eta of the motor 2 by initial estimationmotor. Efficiency value eta of the electric machine 2motorThe motor 2 can be a permanent magnet motor according to empirical estimation, and the efficiency values eta of the motor 2 can be initially estimated if the efficiencies of the permanent magnet motors are similarmotorThe value range of (A) is between 85% and 90%. S6, according to the efficiency value eta of the motor 2motorAnd the power consumption P of the ducted fan, and the heating value W of the motor 2 is obtained by calculationH(ii) a According to the axial length L of the motor 2motorCalculating the known surface area of the motor shell, the temperature difference of the surface of the shell and the flow velocity of the airflow at the shell to obtain the heat dissipation W of the surface of the motor shellC。
Heat generation amount of motor 2 in step S6WHThe calculation process of (2) is as follows: wH＝P/ηmotor(1-ηmotor)。
Heat dissipation amount W of the motor case surface in step S6CThe calculation process of (2) is as follows:
WC＝hAΔT，
in the formula, h represents the convection heat transfer coefficient, A represents the surface area of the motor casing, Delta T represents the surface temperature difference of the casing, v represents the flow velocity of the air flow at the casing, the flow velocity v of the air flow at the casing is obtained by the quotient of the air volume flow at the casing and the surface area of the motor casing, and the air volume flow at the casing is obtained by the sectional area A of the air flow at the outlet of the ducted fanoutAnd axial velocity V of the ducted outlet air streamoutThe product is obtained. The maximum temperature of the surface of the motor shell can be obtained by inquiring international standards according to different grades of the motor.
S7, judging whether the heat dissipation quantity of the surface of the motor shell obtained in the step S6 is larger than the heat productivity of the motor 2, if not, executing the step S8; if yes, go to step S9.
S8, checking the efficiency value eta of the motor 2motorIf it can be raised, the motor efficiency value eta is increasedmotorAnd returning to the step S6, executing the steps S6-S7; if not, the hub ratio of the ducted fan is increased and the process returns to step S3 to execute steps S3-S7.
S9, checking the power P of the motor 2motorIf the redundancy exists, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, otherwise, determining the hub ratio of the ducted fan and the thrust requirement T of the ducted fan under the working condition|rustSubstituting the thrust T into a fan design program to carry out fan blade design and simulation calculation, outputting the blade profile and performance data of the fan blade 1 of the ducted fan obtained by primary design and a 3D simulation model, and executing the step S10; the performance data includes actual efficiency, actual thrust of the ducted fan.
The fan design in step S9 has been designed by various well-established design methods in the prior art. The fan design program in the thermal coupling design method of the electric ducted fan uses the fan design program written based on the design method of the equivalent ring capacity along the blade height to design the ducted fan, so as to obtain the design result of the fan blade 1, such as the blade shape of the fan blade 1 of the ducted fan, and according to the design result of the fan blade 1, the design is divided into grids and the flow field is set, and the three-dimensional simulation calculation is carried out by using the commercial fluid calculation software such as NUMCIA software and ANSYS software, so as to obtain the 3D simulation model and the performance data of the ducted fan, wherein the performance data comprises the actual efficiency and the actual thrust of the ducted fan, and also comprises the related data of the ducted fan such as gas volume flow, total pressure rise and the like. The method used by the fan design program is not limited to the method based on equal ring number along the blade height, and the fan design program can also be realized by using other fan design methods. Steps S7 to S9 are a process of combining the heat dissipation requirement of the motor 2 of the ducted fan and the influence of the hub ratio on the fan blades 1 and the motor 2 into the design of the ducted fan, so that the motor 2 of the ducted fan meets the heat dissipation requirement (the heat dissipation amount of the surface of the motor casing is greater than the heat generation amount of the motor 2) and the power of the motor is efficiently utilized, and the volume of the motor 2 is reduced as much as possible by reducing the hub ratio, thereby achieving a higher power-to-weight ratio by making the motor 2 meet the heat dissipation requirement and reducing the volume of the motor 2.
S10, giving an efficiency error value and a thrust error value, judging whether the actual efficiency of the preliminarily designed ducted fan is too high, namely whether the actual efficiency of the ducted fan is higher than the estimated efficiency and whether the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual efficiency of the preliminarily designed ducted fan is too low, namely whether the actual efficiency of the ducted fan is lower than the estimated efficiency and the absolute value of the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, increasing the hub ratio of the ducted fan and returning to the step S3 and executing the steps S3-S7, if not, judging whether the actual thrust of the preliminarily designed ducted fan is too high or not, namely whether the actual thrust of the ducted fan is higher than the thrust requirement T|rustHigh and actual thrust and thrust demand T|rustIf yes, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual thrust of the primarily designed ducted fan is too low, namely the actual thrust ratio of the ducted fan is higher than the thrust requirement T|rustLow and actual thrust and thrust requirement T|rustIf the absolute value of the difference is greater than the thrust error value, the hub ratio of the ducted fan is increased and the process returns to step S3, and steps S3-S7 are executed, otherwise, the actual efficiency and the actual thrust of the ducted fan are output and step S11 is executed. The efficiency error value and the thrust error value may be set according to a specific design task, and the efficiency error value and the thrust error value may be set to 2%.
After obtaining the blade profile, the performance data and the 3D simulation model of the fan blade 1 of the preliminarily designed ducted fan, the actual efficiency and the actual thrust of the preliminarily designed ducted fan, and the estimated efficiency and the thrust requirement T need to be determined|rustAnd if the deviation is overlarge, the blade profile, the performance data and the 3D simulation model of the fan blade 1 of the preliminarily designed ducted fan are regenerated by adjusting the hub ratio. Therefore, the importance of the hub ratio in the design of the ducted fan can be reflected, and the hub ratio is also an important element to be considered.
S11, judging whether the actual thrust of the preliminarily designed ducted fan under the working condition is larger than the thrust requirements of the ducted fan under other working conditions in the given multi-working condition environment, if so, outputting the blade profile and performance data of the fan blades (1) of the preliminarily designed ducted fan and a 3D simulation model as the final design result of the ducted fan meeting all the working conditions; if not, the thrust requirement of the ducted fan under other working conditions is taken as the thrust requirement T in the step S1|rustAnd returning to the step S1, and re-executing the steps S1-S7 until the actual thrust of the designed ducted fan is greater than the thrust requirements under the other residual working conditions in the multi-working-condition environment, and outputting the final design result of the ducted fan meeting all the working conditions.
After the blade profile, the performance data and the 3D simulation model of the fan blade 1 of the ducted fan under the working condition are designed, whether the ducted fan under the working condition can be used under other working conditions needs to be judged, so whether the actual thrust of the ducted fan under the working condition obtained by primary design is larger than the thrust requirements of the ducted fan under other working conditions in a given multi-working condition environment is judged, if the actual thrust is not larger than the thrust requirements under other working conditions, the steps of the thermal coupling design method of the electric ducted fan are executed in a recycling mode according to the thrust requirements under other working conditions until the final blade profile, the performance data and the 3D simulation model of the fan blade 1 of the ducted fan under all working conditions are obtained.
In the thermal coupling design method of the electric ducted fan, the influence of the actual efficiency and the actual thrust of the hub in the ducted fan to the fan blades 1 and the influence of the heat dissipation requirement of the motor 2 (the heat dissipation capacity of the surface of the motor shell is larger than the heat productivity of the motor 2) and the power of the motor 2 are considered, and the hub ratio and the heat dissipation requirement of the motor 2 are integrated into the design process of the ducted fan, so that the design result of the ducted fan can meet the use requirement of a multi-working-condition environment, meanwhile, the motor 2 can meet the heat dissipation requirement (the heat dissipation capacity of the surface of the motor shell is larger than the heat productivity of the motor 2) and the volume of the motor 2 is minimized, and the power-weight ratio of the motor 2 in the duct.
The above detailed description describes exemplary embodiments, but is not intended to limit the combinations explicitly disclosed herein. Thus, unless otherwise specified, various features disclosed herein can be combined together to form a number of additional combinations that are not shown for the sake of brevity.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (9)
1. A thermal coupling design method of an electric ducted fan is used for designing the ducted fan comprising fan blades (1), a motor (2) and a duct (3), and is characterized by comprising the following steps:
s1, trying to obtain the hub ratio r of the ducted fan to be designed, and setting the thrust requirement T of the ducted fan to be designed under one working condition in the multi-working-condition environment|rustThe size requirement, the exit parameters of the ducted fan and the blade tip Mach number of the ducted fan are estimated to obtain the estimated efficiency of the ducted fan under the working condition and calculate to obtain the axial speed V of the airflow at the exit of the ducted fanoutThe dimensional requirements include axial length L of the ducted fanductRadius R of ducted fanductThe ducted fan outlet parameters comprise the ratio of the outlet airflow cross section area to the inlet airflow cross section area of the ducted fan and the airflow density rho of the ducted fan outlet, and the multi-working-condition environment comprises a plurality of working conditions;
s2, according to the axial velocity V of the ducted outlet airflowoutRadius R of ducted fanductAnd the ducted fan outlet parameters, and calculating to obtain the performance parameters of the ducted fan according to the excited disc theory of the ideal gas, wherein the performance parameters comprise thrust T and power consumption P;
s3, according to the hub ratio r of the ducted fan and the axial length L of the motor (2)motorAnd calculating to obtain the volume V of the motor (2)motor；
S4, according to the given rotation speed omega of the motor (2) and the volume V of the motor (2) obtained in the step S3motorCalculating the power P of the motor (2)motor；
S5, obtaining the efficiency value eta of the motor (2) by initial estimationmotor；
S6, according to the efficiency value eta of the motor (2)motorAnd the power consumption P of the ducted fan, and the heating value W of the motor (2) is obtained by calculationH(ii) a According to the axial length L of the motor (2)motorCalculating the known surface area of the motor shell, the temperature difference of the surface of the shell and the flow velocity of the airflow at the shell to obtain the heat dissipation W of the surface of the motor shellC；
S7, judging whether the heat dissipation quantity of the surface of the motor shell obtained in the step S6 is larger than the heat generation quantity of the motor (2), if not, executing the step S8; if yes, go to step S9;
S8，checking the efficiency value eta of the electric machine (2)motorIf it can be raised, the motor efficiency value eta is increasedmotorAnd returning to the step S6, executing the steps S6-S7; if not, increasing the hub ratio of the ducted fan, returning to the step S3, and executing the steps S3-S7;
s9, checking the power P of the motor (2)motorIf the redundancy exists, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, otherwise, determining the hub ratio of the ducted fan and the thrust requirement T of the ducted fan under the working condition|rustSubstituting the thrust T into a fan design program to carry out fan blade design and simulation calculation to obtain the blade profile and performance data of the fan blade (1) of the preliminarily designed ducted fan and a 3D simulation model, and executing the step S10; the performance data includes actual efficiency, actual thrust of the ducted fan;
s10, giving an efficiency error value and a thrust error value, judging whether the actual efficiency of the preliminarily designed ducted fan is too high, namely whether the actual efficiency of the ducted fan is higher than the estimated efficiency and whether the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual efficiency of the preliminarily designed ducted fan is too low, namely whether the actual efficiency of the ducted fan is lower than the estimated efficiency and the absolute value of the difference value between the actual efficiency and the estimated efficiency is larger than the efficiency error value, if so, increasing the hub ratio of the ducted fan and returning to the step S3 and executing the steps S3-S7, if not, judging whether the actual thrust of the preliminarily designed ducted fan is too high or not, namely whether the actual thrust of the ducted fan is higher than the thrust requirement T|rustHigh and actual thrust and thrust demand T|rustIf yes, reducing the hub ratio of the ducted fan and returning to the step S3, executing the steps S3-S7, if not, judging whether the actual thrust of the primarily designed ducted fan is too low, namely the actual thrust ratio of the ducted fan is higher than the thrust requirement T|rustLow and actual thrust and thrust requirement T|rustIf the absolute value of the difference is greater than the thrust error value, increasing the hub ratio of the ducted fan and returning to step S3, executing steps S3-S7, if so, executing step S3-S7Otherwise, outputting the actual efficiency and the actual thrust of the ducted fan and executing the step S11;
s11, judging whether the actual thrust of the preliminarily designed ducted fan under the working condition is larger than the thrust requirements of the ducted fan under other working conditions in the given multi-working condition environment, if so, outputting the blade profile and performance data of the fan blades (1) of the preliminarily designed ducted fan and a 3D simulation model as the final design result of the ducted fan meeting all the working conditions; if not, the thrust requirement of the ducted fan under other working conditions is taken as the thrust requirement T in the step S1|rustAnd returning to the step S1, and re-executing the steps S1-S7 until the actual thrust of the ducted fan obtained by the primary design is greater than the thrust requirements under the other residual working conditions in the multi-working-condition environment, and outputting the final design result of the ducted fan meeting all the working conditions.
2. The method for thermally coupling a ducted electric fan according to claim 1, wherein the value of the hub ratio r of the ducted electric fan obtained in step S1 is in a range of 0.2 to 0.4.
3. The thermally coupled design method of an electrically powered ducted fan in accordance with claim 1, wherein the axial velocity V of the ducted outlet airflow in step S1outThe calculation process of (a) includes the steps of:
s111, according to the radius R of the ducted fanductAnd a hub ratio r of the ducted fan, by:
wherein r represents the hub ratio of the ducted fan, AinRepresenting the inlet airflow cross section of the ducted fan, and calculating to obtain the inlet airflow cross section A of the ducted fanin；
S112, according to the inlet airflow cross-sectional area A of the ducted faninAnd the ratio of the outlet airflow cross section area to the inlet airflow cross section area of the ducted fan is calculated to obtain the outlet airflow cross section area A of the ducted fanout；
S113, according to the outlet of the ducted fanCross sectional area of the outlet air stream AoutThrust demand T|rustAnd an airflow density ρ at the ducted fan outlet by:
where ρ represents the airflow density at the ducted fan outlet, AoutThe sectional area of the outlet airflow of the ducted fan is represented, and the axial velocity V of the outlet airflow of the ducted fan is calculatedout。
4. The thermally coupled design method of an electric ducted fan in accordance with claim 3, wherein the calculation process of the fan performance parameter in step S2 includes the steps of:
s21, according to the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutAnd axial velocity V of the ducted outlet air streamoutBy the following formula: m ═ Vout·AoutRho, where m represents the gas mass flow, the gas mass flow m is calculated;
s22, according to the gas mass flow m and the axial velocity V of the bypass outlet gas flowoutAnd calculating to obtain the thrust T of the ducted fan as m multiplied by Vout；
S23, according to the thrust T of the ducted fan, the airflow density rho of the outlet of the ducted fan and the outlet airflow cross section area A of the ducted fanoutCalculating the power consumption of the ducted fan
5. Thermally coupled design method of an electric ducted fan according to claim 1, characterized in that the volume V of the electric machine (2) in step S3motorThe calculation process of (2) is as follows:
according to the ratio R of the hub of the ducted fan and the radius R of the ducted fanductAnd the radius of the hub is obtained according to the relation of the radius of the hub, and the radius of the hub and the radius R of the motor (2) are assumedmotorSame according to the radius of the hub and the axial length L of the motor (2)motorAnd calculating to obtain the volume V of the motor (2)motor。
6. Method for the thermal coupling design of an electrically powered ducted fan in accordance with claim 1, characterised in that the power P of the electrical machine (2) in step S4motorThe calculation process of (2) is as follows:
Pmotor＝ω·kτVmotorwherein k isτIs the motor torque coefficient.
7. The method for the thermal coupling design of an electrically driven ducted fan according to claim 1, characterized in that the efficiency value η of the electrical machine (2)motorThe value range of (A) is between 85% and 90%.
8. The method for thermally coupling a motor-driven ducted fan in accordance with claim 1, wherein the heat generation amount W of the motor (2) in step S6HThe calculation process of (2) is as follows: wH＝P/ηmotor(1-ηmotor)。
9. The method for thermally coupling a motor-driven ducted fan in accordance with claim 3, wherein the heat dissipation amount W of the motor casing surface in step S6CThe calculation process of (2) is as follows:
WC＝hAΔT，
in the formula, h represents the convection heat transfer coefficient, A represents the surface area of the motor casing, Delta T represents the surface temperature difference of the casing, v represents the flow velocity of the air flow at the casing, the flow velocity v of the air flow at the casing is obtained by the quotient of the air volume flow at the casing and the surface area of the motor casing, and the air volume flow at the casing is obtained by the sectional area A of the air flow at the outlet of the ducted fanoutAnd axial velocity V of the ducted outlet air streamoutThe product is obtained.
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