CN105354354A - Method for calculating temperature field of main driving motor of electric aircraft - Google Patents

Abstract

The invention discloses a method for calculating a temperature field of a main driving motor of an electric aircraft. The method comprises: (1) in combination with a special structure of the main driving motor of the electric aircraft, setting a basic assumption of a solving process; (2) in combination with a practical working condition of the main driving motor of the electric aircraft, finishing the setting of boundary conditions of a fluid field and the temperature field; (3) establishing a mathematic model of the main driving motor of the electric aircraft; (4) establishing a physical model of the main driving motor of the electric aircraft, and finishing model network subdivision; and (5) based on a fluid-structure coupled differential equation, performing solving with a finite element numerical method to obtain temperature rise distribution of the main driving motor of the electric aircraft in different operation conditions. According to the method, the temperature field and the fluid field of the main driving motor of the electric aircraft are subjected to whole-field solving; the same mathematic model is adopted; and the method has the advantages of high solving speed, low iterative frequency and high calculation precision.

Description

A kind of electric airplane main drive motor Calculation Method of Temperature Field

Technical field

The present invention relates to the electric airplane main drive motor solution of Temperature method based on Fluid structure interaction, belong to high force-energy density electrical machine temperature field analysis technical field.

Background technology

Along with the continuous research with new energy technology of opening gradually of low altitude airspace, the positive fast development of civilian use electric aircraft industries.Electric airplane requires that main drive motor power density is large and torque density is large, and this makes the temperature rise of electric airplane main drive motor, and comparatively common electric machine is high.If main drive motor Temperature calculating is inaccurate, motor is by cisco unity malfunction, especially for the motor being applied in the main driving of electric airplane, its temperature rise value comparatively conventional motor is high, the general maximal value can born close to motor, need accurately to calculate electric airplane main drive motor temperature field, this electric airplane motor tool for design high-performance, high precision and special construction is of great significance, power density and the torque density of motor can be optimized further, make motor performance perform to ultimate limit state.

Present electric motor temperature field depends on numerical evaluation mostly, and computing method were all carried out respectively for motor stator or rotor in the past, suppose there is no heat transmission between stator, rotor in computation process, but the air gap in the middle of actual rotor exists Convective Heat Transfer, certain error can be caused to stator or rotor temperature field calculating obviously separately.Heat eliminating medium in air duct is converted to coefficient of heat transfer to temperature profile effect by some scholars, is loaded in the Temperature calculating of motor component as boundary condition.Such an approach achieves the weak coupling in fluid field and temperature field, but this coupling scheme still need that heat eliminating medium is converted to coefficient of heat transfer to temperature profile effect to be loaded, and think that heat eliminating medium temperature rise linearly changes, this also can calculate to electric motor temperature field and cause certain error.

Under in actual condition, electric airplane main drive motor is in strong cooler environment, the Reynolds number of stream air working medium reaches more than 10,000, belongs to strong turbulent category, and ordinary temperature Flow Field Numerical computing method are difficult to solving of competent nonlinear problem like this.The order of accuarcy that electric airplane main drive motor internal temperature field calculates, depend primarily on the affixed tactile coefficient of heat transfer of stream and fluid temperature (F.T.), the change solving cooling fluid flow velocity in territory is the principal element determining coefficient of heat transfer.Due to the lack of uniformity of electric airplane main drive motor internal flow flow velocity change, adopt Conventional wisdom formula to draw the boundary condition of coefficient of heat transfer as Temperature calculating, can solve to thermo parameters method and bring relatively large deviation.

Summary of the invention

Be difficult to solve to solve conventional motors temperature field coefficient of heat transfer, rotor temperature field solves separately the larger problem of error, the invention provides a kind ofly effectively to be applicable to electric airplane main driving high force-energy density electrical machine and the fluid structurecoupling solution of Temperature method that solving precision is high, iterations is few.

The general idea of fluid structurecoupling solution of Temperature method is by electric motor temperature field and fluid field integrated solution, the whole territory that solves adopts general control equation, the convection heat transfer state of fluid domain and solid domain coupling surface is without the need to relying on experience factor, this makes motor convection heat transfer' heat-transfer by convection face become inside, zoning, avoid and utilize experimental formula determination air duct, the coefficient of heat transfer of ventilation slot inside surface and the problem causing error larger, solve the problem that fluid structurecoupling face coefficient of heat transfer is difficult to determine, high force-energy density main drive motor each part temperatures field result of calculation can be calculated more accurately.

Electric airplane Calculation Method of Temperature Field based on Fluid structure interaction of the present invention, mainly comprises the following steps:

Step one: according to electric airplane main drive motor special construction, actual condition, in conjunction with electric airplane aeration structure feature, arranges solution procedure basic assumption.

Step 2: the coupling boundary determining electric airplane main drive motor fluid, solid, temperature field, comprises inlet boundary, outlet border and wall border.

Step 3: set up electric airplane main drive motor solution of Temperature computation model, comprise mathematical model and physical model.

Step 4: mesh generation is carried out to electric airplane main drive motor model, is realized by finite element software.

Step 5: set up electric airplane main drive motor fluid-structure coupling system Flow-induced vibration characteristic differential governing equation, adopts Numerical Methods Solve, obtains electric machine temperature rise distribution.

In described step 3, electric airplane main drive motor solution of Temperature computation model adopts fluid and structural simulation model, and concrete mathematical model is as follows.

Electric airplane main drive motor three dimensional fluid mass-conservation equation is:

$\frac{\∂\mathrm{\ρ}}{\∂t}+\frac{\∂\left(\mathrm{\ρ}u\right)}{\∂x}+\frac{\∂\left(\mathrm{\ρ}v\right)}{\∂y}+\frac{\∂\left(\mathrm{\ρ}w\right)}{\∂z}=0$

Wherein, ρ is fluid density; T is the time; U, v and w are the component of velocity in x, y and z direction.

Electric airplane main drive motor Navier-Stokes equation is:

$\frac{d\left(\mathrm{\ρ}\stackrel{\‾}{U}\right)}{dt}=\mathrm{\ρ}\stackrel{\‾}{F}-\▿p+\mathrm{\μ}\mathrm{\Δ}\stackrel{\‾}{U}$

Wherein, for velocity; μ is fluid kinematic viscosity, and the kinematic viscosity of solid is infinitely great; P is hydrodynamic pressure; for acting on the mass force on fluid, in gravity field

Electric airplane main drive motor energy conservation equation is:

$\frac{\∂\left(\mathrm{\ρ}T\right)}{\∂t}+\▿\left(\mathrm{\ρ}T\right)=\▿\left(\frac{\mathrm{\λ}}{c}gradT\right)+\mathrm{\Φ}+S_h$

Wherein, c is the specific heat at constant pressure of fluid; λ is coefficient of heat conductivity; T is fluid temperature (F.T.); S _hfor fluid endogenous pyrogen; Φ is Dissipation Function of Energy.

At electric airplane main drive motor turbulent region, Turbulent Kinetic equation and the turbulent stress equation of the impact of reflection turbulence pulsation amount stream field obtain by standard equation k-ε equation, and its form is:

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{{\∂}_{x_i}}|\[\left(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_k}\right)\frac{{\∂}_k}{{\∂}_{x_i}}\]+G_k+G_b-\mathrm{\ρ}\mathrm{\ϵ}$

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{{\∂}_{x_i}}|\[\left(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_{\mathrm{\ϵ}}}\right)\frac{\∂\mathrm{\ϵ}}{\∂x_i}\]+G_{1\mathrm{\ϵ}}\frac{\mathrm{\ϵ}}{k}(G_k+G_{3\mathrm{\ϵ}}{G}_b)-G_{2\mathrm{\ϵ}}\mathrm{\ρ}\frac{{\mathrm{\ϵ}}^2}{k}$

Wherein, k is Turbulent Kinetic; ε is Turbulent Kinetic dissipative shock wave; μ is fluid kinematic viscosity; μ _tfor turbulent viscosity; G _kfor the Turbulent Kinetic k caused due to average velocity gradient produces item; G _bfor the generation item of Turbulent Kinetic k caused by buoyancy; σ _kfor the Prandtl number that Turbulent Kinetic k is corresponding; σ _εfor the Prandtl number that energy absorbing device ε is corresponding; G _{1 ε}, G _{2 ε}and G _{3 ε}be respectively empirical constant.

Electric airplane main drive motor solution of Temperature condition is as follows:

The temperature condition of continuity on coupling boundary:

T _w| _Ι＝T _w| _∏

The heat flow density condition of continuity on coupling boundary:

q _w| _Ι＝q _w| _∏

The 3rd class condition on coupling boundary:

$-\mathrm{\λ}{\left(\frac{\∂T}{\∂n}\right)}_w{|}_{\mathrm{\Γ}}=h(T_w-T_f){|}_{\mathrm{\Λ}}$

Wherein, T _w| be temperature profile function, q _w| be heat flux distribution function, Ι and Π is solid domain on fluid structurecoupling interface and fluid domain; H is surface coefficient of heat transfer, T _wfor solid wall surface temperature, T _ffor fluid temperature (F.T.), region Λ is that the fluid of electric airplane main drive motor solves territory, and region Γ is the solid domain of electric airplane main drive motor, and n is wall outer normal.

Advantage of the present invention is mainly: the fluid structurecoupling mathematic model of temperature field 1, setting up electric airplane main drive motor, electric motor temperature field and the whole field of fluid field is solved, avoids the correction of traditional heat-dissipating coefficient, drastically increase the precision that Numerical Temperature solves; 2, the integrated solution such as electric airplane main drive motor rotor, stator and casing, reduces the error relying on experimental formula to bring.

Be applied to the main propulsion motor on electric airplane, very high power energy density be possessed, mean and under limited weight demands, Driving Torque and the power of motor will be improved.Electromagnetic load is the key index of design of electrical motor, decides the manufacturing cost of motor, serviceable life, performance and operational reliability.Electromagnetic load is high, and motor volume can be little, but temperature rise will be high, and temperature rise can make the permanent magnet of motor demagnetize, and this seriously reduces the fault-tolerant ability of main drive motor, brings danger even to aircraft and pilot.Adopt the electric airplane main drive motor temperature field analysis method that the present invention proposes, the solution of Temperature precision of motor can be improved, this, under guarantee motor safety service condition, can make motor produce larger power and torque, increases power density and the torque density of motor.

Accompanying drawing explanation

Fig. 1: based on the electric airplane main drive motor analysis of heat transfer method flow diagram of fluid structurecoupling;

Fig. 2: electric airplane main drive motor Numerical Temperature solves process flow diagram;

Fig. 3: the bilateral coupling analysis figure in electric airplane main drive motor electromagnetic field-temperature field;

Fig. 4: electric airplane main driving high force-energy density electrical machine magnetic flux density waveforms figure.

Embodiment

Below in conjunction with Fig. 1-Fig. 4 accompanying drawing content, the present invention is further elaborated.

Composition graphs 1 motor analysis of heat transfer process flow diagram, described electric airplane main drive motor fluid structurecoupling Calculation Method of Temperature Field comprises the following steps:

Step one: according to electric airplane main drive motor special construction, actual condition, in conjunction with electric airplane aeration structure feature, arranges solution procedure basic assumption.

Step 2: the coupling boundary determining electric airplane main drive motor fluid, solid, temperature field, comprises inlet boundary, outlet border and wall border.

Step 3: set up electric airplane main drive motor solution of Temperature computation model, comprise mathematical model and physical model.

Step 4: mesh generation is carried out to electric airplane main drive motor model, is realized by finite element software.

Step 5: set up electric airplane main drive motor fluid-structure coupling system Flow-induced vibration characteristic differential governing equation, adopts Numerical Methods Solve, obtains electric machine temperature rise distribution.

In present embodiment, basic assumption and boundary condition in conjunction with the special construction of electric airplane main drive motor, actual condition and aeration structure feature, need be determined.

Main drive motor model modeling basic assumption is as follows: when considering stator winding copper loss, think that the impact of eddy effect on every root strand is identical, get its mean value; The impact of turn-to-turn insulation on heat transfer of stator winding is answered in the comprehensive coefficient of heat conductivity of winding in reduction to groove; Rate of flow of fluid is less than the velocity of sound, fluid is used as incompressibility gas and considers, ignores physical parameter change; Thermal source thermal value keeps being uniformly distributed, and disregards heat radiation effect; Ignore the impact that airflow fluctuation produces.

Main drive motor model modeling boundary condition is determined as follows: air inlet place plane is fluid intake border, and air outlet place plane is fluid egress point border; Top hole pressure is standard atmospheric pressure; Except outlet and inlet boundary condition, all the other fluids and solid interfaces are without slip boundary; Models for temperature field inlet velocity is determined according to the sliding actual condition running, take off, cruise and land.

Under running status, main drive motor heat eliminating medium is by the domination of three physics laws, i.e. the mass conservation, momentum conservation and energy conservation.Because the fluid motion solving territory is turbulent motion, in numerical simulation calculates, the differential equation of equal form when turbulence model adopts.

Three dimensional fluid mass-conservation equation, also referred to as continuity equation, its equation is as follows:

$\frac{\∂\mathrm{\ρ}}{\∂t}+\frac{\∂\left(\mathrm{\ρ}u\right)}{\∂x}+\frac{\∂\left(\mathrm{\ρ}v\right)}{\∂y}+\frac{\∂\left(\mathrm{\ρ}w\right)}{\∂z}=0$

Wherein, ρ is fluid density; T is the time; U, v and w are the component of velocity in x, y and z direction.

Momentum conservation equation, is also called Navier-Stokes equation:

$\frac{d\left(\mathrm{\ρ}\stackrel{\‾}{U}\right)}{dt}=\mathrm{\ρ}\stackrel{\‾}{F}-\▿p+\mathrm{\μ}\mathrm{\Δ}\stackrel{\‾}{U}$

Wherein, for velocity; μ is fluid kinematic viscosity, and the kinematic viscosity of solid is infinitely great; P is hydrodynamic pressure; for acting on the mass force on fluid.

Energy conservation equation is:

$\frac{\∂\left(\mathrm{\ρ}T\right)}{\∂t}+\▿\left(\mathrm{\ρ}T\right)=\▿\left(\frac{\mathrm{\λ}}{c}gradT\right)+\mathrm{\Φ}+S_h$

Wherein, c is the specific heat at constant pressure of fluid; λ is coefficient of heat conductivity; T is fluid temperature (F.T.); S _hfor fluid endogenous pyrogen; Φ is Dissipation Function of Energy, and its computing formula is as follows:

$\mathrm{\Φ}=2{\mathrm{\μ\ϵ}}_1^2$

Wherein, ε ₁for the Deformation tensor of fluid, represent fluid and overcome the mechanical energy that viscosity consumes, it will irreversibly be converted into heat and dissipate.

At full-blown turbulent region, the Turbulent Kinetic equation of reflection turbulence pulsation amount stream field impact and turbulent stress equation obtain its form by standard k-ε equations and are:

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{{\∂}_{x_i}}|\[\left(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_k}\right)\frac{{\∂}_k}{{\∂}_{x_i}}\]+G_k+G_b-\mathrm{\ρ}\mathrm{\ϵ}$

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{{\∂}_{x_i}}|\[\left(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_{\mathrm{\ϵ}}}\right)\frac{{\∂}_{\mathrm{\ϵ}}}{{\∂}_{x_i}}\]+G_{1\mathrm{\ϵ}}\frac{\mathrm{\ϵ}}{k}(G_k+G_{3\mathrm{\ϵ}}{G}_b)-G_{2\mathrm{\ϵ}}\mathrm{\ρ}\frac{{\mathrm{\ϵ}}^2}{k}$

Wherein, k is Turbulent Kinetic; ε is dissipation turbulent kinetic energy; μ is viscosity coefficient; μ _tfor turbulent viscosity; G _kfor the Turbulent Kinetic k caused due to average velocity gradient produces item; G _bfor the generation item of Turbulent Kinetic k caused by buoyancy; σ _kfor the Prandtl number that Turbulent Kinetic k is corresponding; σ _εfor the Prandtl number that dissipation turbulent kinetic energy ε is corresponding; G _{1 ε}, G _{2 ε}and G _{3 ε}be respectively empirical constant; G _{1 ε}=1.44, G _{2 ε}=1.92, G _{3 ε}=0.09, σ _k=1.0, σ _ε=1.3.μ _t, G _k, G _bfollowing formula is adopted to calculate respectively:

${\mathrm{\μ}}_t={\mathrm{\ρC}}_{\mathrm{\μ}}\frac{k^2}{\mathrm{\ϵ}}$

$G_k=-{\mathrm{\ρ\μ}}_i{\mathrm{\μ}}_j\frac{{\∂}_{{\mathrm{\μ}}_j}}{{\∂}_{x_i}}$

$G_b={\mathrm{\βg}}_i\frac{{\mathrm{\μ}}_i}{P_{r_i}}\frac{\∂T}{{\∂}_{x_i}}$

$\mathrm{\β}=-\frac{1}{\mathrm{\ρ}}\frac{\∂\mathrm{\ρ}}{\∂T}$

Wherein, μ _i, μ _jfor the fluctuation velocity of turbulent flow; for turbulence Prandtl number, desirable g _ifor the component of acceleration of gravity on the i-th direction, β is thermal expansivity, C _μfor empirical constant.

In fluid structurecoupling Temperature calculating k-ε model, the computing method forming the dissipation turbulent kinetic energy ε of k equation source item are as follows:

$\mathrm{\ϵ}=\frac{C_{\mathrm{\μ}}^{\frac{3}{4}}{k}_p^{\frac{3}{2}}}{{\mathrm{k\Δy}}_p}$

Wherein, k _pfor the tubulence energy of node p; Δ y _pfor node p is to the distance of wall.

Electric airplane main drive motor solution of Temperature condition is as follows:

The temperature condition of continuity on coupling boundary:

T _w| _Ι＝T _w| _∏

The heat flow density condition of continuity on coupling boundary:

q _w| _Ι＝q _w| _∏

The 3rd class condition on coupling boundary:

$-\mathrm{\λ}{\left(\frac{\∂T}{\∂n}\right)}_w{|}_{\mathrm{\Γ}}=h(T_w-T_f){|}_{\mathrm{\Λ}}$

Wherein, T _w| be temperature profile function, q _w| be heat flux distribution function, Ι and Π is solid domain on fluid structurecoupling interface and fluid domain; H is surface coefficient of heat transfer, T _wfor solid wall surface temperature, T _ffor fluid temperature (F.T.), region Λ is that the fluid of electric airplane main drive motor solves territory, and region Γ is the solid domain of electric airplane main drive motor, and n is wall outer normal.

Governing equation on control volume in electric airplane main drive motor Temperature calculating region is as follows:

Wherein, Γ _Φfor the diffusivity of Φ; ▽ Φ is the gradient of Φ; S _Φfor the source item of Φ on unit volume; V and for control volume; A is chain of command.Main drive motor Numerical Temperature solution procedure as shown in Figure 2.

The thermal source of solution of Temperature comprises copper loss, core loss and mechanical loss, the way of the electromagnetic field in Fig. 3-temperature field coupling need be adopted to solve, take into full account the coupled relation between main drive motor electromagnetic field and temperature field, carry out the couple solution of polygon physical field, the accuracy of calculating can be improved.

In electric airplane main drive motor fluid and structural simulation process, the loss calculating motor is accurately very useful, this is because loss is the necessary condition of main drive motor solution of Temperature, is also the boundary condition in solution procedure.

The copper loss of main drive motor is dominant loss, and electric airplane main drive motor electromagnetic load is high, and running frequency is large, winding is in the magnetic field work condition environment of complicated alternation, in order to accurate Calculation copper loss, must consider the impact that kelvin effect produces, the copper loss computing formula adopted in the present invention is:

Wherein, m is the driver motor alternating current number of phases, gets 3 herein; k _rfor the circulation coefficient between strand in parallel; k _efor eddy current loss factor; N is the number of lead wires on coil width; B is coil width; b _sfor the width of groove; f _nfor frequency; for phase current; R _sfor time-varying reactance.K _rand k _eaccount form is as follows:

$k_r=\frac{0.019}{N_s^2}{h}_{cu}^4{\left(\frac{l_t}{l_t+l_e}\right)}^2\×{10}^8$

$k_e=0.107N_s^2{h}_c^4\frac{l_t}{l_t+l_e}\×{10}^8$

Wherein, N _sfor coil turn; h _cufor the overall height of wire in groove; h _cfor strand is high; l _tfor overall length unshakable in one's determination; l _efor winding overhang half turn.

Traditional motor iron loss generally only considers magnetic hysteresis loss and eddy current loss, and the deviate of loss is joined in the experience factor that the factor such as rotary magnetization, processing makes iron loss increase, and these needs are by a large amount of motor empirical data.And for electric airplane main drive motor, belonging to specific type of electric machine research category, this motor experiment data are little, and the core loss value therefore calculated by the experience factor of iron loss difference is infeasible.In addition, electric airplane main drive motor electromagnetic property is special compared with conventional motor, and electromagnetic load is high, increase in magnetic field or there is fluctuation in minimizing process, form little hysteresis ring in magnetic fluctuation process in this process, as shown in Figure 4, this will inevitably have an impact to magnetic hysteresis loss.Therefore, the calculating of core loss should consider local magnet ring magnetic hysteresis loss impact.Wherein core loss is divided into magnetic hysteresis loss, eddy current loss and abnormal wear.Consider that the total magnetic hysteresis loss under hysteresis ring is calculated as follows:

$P_h=K_{h}K\left({\mathrm{\ΔB}}_T\right)B_m^a$

Wherein, K _hhysteresis loss coefficient, K (Δ B _t) local hysteresis loss correction coefficient, for the close value of motor magnetic.

The computing method of electric airplane main drive motor iron loss are as follows:

$P_{core}=K_{h}K\left({\mathrm{\ΔB}}_T\right){\mathrm{fB}}_m^a+{\mathrm{Gk}}_{e1}\underset{k=1}{\overset{\mathrm{\∞}}{\Σ}}{\left(k_a{\mathrm{fB}}_k\right)}^2+\frac{k_{e1}}{T_1}{\∫}_0^{T_1}{\[{\left|\frac{B_k}{dt}\right|}^2\]}^{\frac{3}{4}}dt$

Wherein, k _e1for iron core vortex loss factor, G is teeth portion or yoke portion quality, and f is fundamental frequency, T ₁for the electricity cycle, B _kfor node magnetic is close, k _afor positive integer, k _a=0,1,2,3.

In main drive motor rotary course, also can produce the mechanical loss of small scale.Mechanical loss comprises bearing friction loss and draft loss.

Bearing friction loss is calculated as follows:

$P_f=0.15\frac{F}{d}{v}_1\×{10}^{-5}$

Wherein, F is bearing load; D is ball (or roller) center diameter; v ₁for ball center circumferential speed.

Draft loss computing method are as follows:

P _g＝k _sk ₁C _fπρ _gω ³r ⁴l

Wherein, k _sfor the external arc situation of rotor surface; k ₁for rotor surface roughness; C _ffor windage coefficient, relevant with rotor surface shearing force; ρ _gfor atmospheric density; ω is the angular velocity of rotor; R is rotor radius; L is rotor axial length.

Electric airplane main drive motor total losses are:

P＝P _cu+P _core+P _f+P _g

Grid is the carrier of simulation and analysis.As the product that zoning is discrete, the quality of grid is not only directly connected to the stability of numerical evaluation, convergence and counting yield, but also is related to correctness and the resolution of result of calculation.The present invention mainly adopts unstrutured mesh subdivision, and compared with structured grid, it abandons the structural requirement of any inherence.Unstrutured mesh is non-finite difference somatotype, mainly preserves the information of related network and grid node by tabulating method.

Unstrutured mesh method advantage is the stress and strain model being suitable for complex region, very simple to the process of singularity point especially; Its random data structure is easier to do mesh adaption, to catch the material resources characteristic in flow field better.

Electric airplane main drive motor model more complicated, is difficult to the requirement reaching " thinner the closer to wall grid ", wall-function method should be adopted to be solved during grid division.

Wall-function method is actual is one group of semiempirical formula, for unknown quantity to be asked in the physical quantity on wall and turbulent core district is contacted directly, its basic thought is: the flowing for turbulent core district uses k-ε model solution, directly uses semiempirical formula to be connected by the variable that solves in the physical quantity on wall and turbulent core district.

Electric airplane main drive motor temperature field thermal boundary condition is dynamically determined by heat exchange process, and Coupled Heat Transfer problem that can not be prespecified, interactional restriction between fluid and wall can be subject to.Temperature now on interface or heat flow density all should regard a part for result of calculation as, instead of known conditions.

Solution of Temperature process is as follows: assuming that the Temperature Distribution on motor coupling boundary, one of them region Γ is solved, draw the local heat flux density on coupling boundary and thermograde, then apply above-mentioned mathematical formulae and solve another region Λ, to draw Temperature Distribution new on coupling boundary.Distribute as the input of region Γ using this again, repeat above-mentioned calculating until convergence.Discrete, whole field, whole field solves, and the heat transfer process in zones of different is combined, and solves as a unified heat transfer process.Different region adopts general control equation, and difference is only the difference of generalized diffusion process coefficient and broad sense source item, coupled interface the is become inside of zoning.

When adopting control volume integral method to derive discrete equation, the condition of continuity on interface can meet in principle, eliminates the process that iterates between zones of different, computing time is significantly shortened.

It is one of predominant methods calculating coupled problem that discrete, whole field, whole field solves, temperature field in the solid existed in coupled problem and fluid zone needs couple solution, at this moment the interphase of solid and fluid just becomes the interface controlling volume, and the equivalent coefficient of diffusion on this interface should adopt the method for harmonic average to be determined.Coefficient of heat conductivity in solid and fluid zone takes respective actual value, but the specific heat capacity in solid area then should adopt the value of fluid zone specific heat capacity, and on such guarantee coupled interface, physical thermal current density is continuous.

In the present invention, solution of Temperature needs to set up three-dimensional physical model in advance, and three-dimensional graphics software need be adopted as realizations such as Solidwork; Carry out fluid structurecoupling Numerical Temperature when solving, need, by finite element software as Ansys arranges thermal source and boundary condition, to carry out subdivision etc.

The present invention proposes a kind of research method of electric airplane main drive motor temperature field, be particularly useful on high force-energy density electrical machine, adopt the algorithm of fluid structurecoupling, motor solid domain and the whole field of fluid domain are solved, there is the advantage that conventional motor temperature field method is incomparable.Compared with the method for conventional motor temperature field, present method avoids and adopt coefficient of heat transfer load temperature field and produce error, there is higher solving precision.In the present invention, solve in the process of motor total losses, consider the kelvin effect on motor winding surface and the local magnet ring magnetic hysteresis loss impact in magnetic field, it is more accurate that boundary condition loads.The very applicable specific type of electric machine field being applied to conventional motor temperature field method and can't resolve of research method of the present invention.

Claims (9)

1. an electric airplane main drive motor Calculation Method of Temperature Field, is characterized in that, comprises the following steps:

Step one: according to electric airplane main drive motor special construction, actual condition, in conjunction with electric airplane aeration structure feature, arranges solution procedure basic assumption.

Step 2: the coupling boundary determining electric airplane main drive motor fluid, solid, temperature field, comprises inlet boundary, outlet border and wall border.

Step 3: set up electric airplane main drive motor solution of Temperature computation model.

Step 4: mesh generation is carried out to electric airplane main drive motor model.

Step 5: set up electric airplane main drive motor fluid-structure coupling system Flow-induced vibration characteristic differential governing equation, adopts Numerical Methods Solve, obtains electric machine temperature rise distribution.

2. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, the solution procedure basic assumption of described step one is:

When considering stator winding copper loss, think that the impact of eddy effect on every root strand is identical, get its mean value; The turn-to-turn insulation of stator winding affects in the comprehensive coefficient of heat conductivity of winding in reduction to groove on what conduct heat; Rate of flow of fluid is less than the velocity of sound, fluid is used as incompressibility gas and considers, ignores physical parameter change; Thermal source thermal value keeps being uniformly distributed, and disregards heat radiation effect; Ignore the impact that airflow fluctuation produces.

3. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, the concrete boundary condition of described step 2 is:

Air inlet place plane is the inlet boundary of fluid, and air outlet place plane is fluid egress point border; Top hole pressure is standard atmospheric pressure; Except outlet and inlet boundary condition, all the other fluids and solid interfaces are without slip boundary; Models for temperature field inlet velocity is determined according to the sliding actual condition running, take off, cruise and land.

4. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, the electric airplane main drive motor solution of Temperature mathematical model of described step 3 is:

Three dimensional fluid mass-conservation equation, also referred to as continuity equation, its equation is as follows:

$\frac{\∂\mathrm{\ρ}}{\∂t}+\frac{\∂\left(\mathrm{\ρ}u\right)}{\∂x}+\frac{\∂\left(\mathrm{\ρ}v\right)}{\∂y}+\frac{\∂\left(\mathrm{\ρ}w\right)}{\∂z}=0$

Wherein, ρ is fluid density; T is the time; U, v and w are the component of velocity in x, y and z direction.

Momentum conservation equation, is also called Navier-Stokes equation:

$\frac{d\left(\mathrm{\ρ}\stackrel{\‾}{U}\right)}{dt}=\mathrm{\ρ}\stackrel{\‾}{F}-\▿p+\mathrm{\μ}\mathrm{\Δ}\stackrel{\‾}{U}$

Wherein, for velocity; μ is fluid kinematic viscosity, and the kinematic viscosity of solid is infinitely great; P is hydrodynamic pressure; for acting on the mass force on fluid.

Energy conservation equation is:

$\frac{\∂\left(\mathrm{\ρ}T\right)}{\∂t}+\▿\left(\mathrm{\ρ}T\right)=\▿\left(\frac{\mathrm{\λ}}{c}gradT\right)+\mathrm{\Φ}+S_h$

Wherein, c is the specific heat at constant pressure of fluid; λ is coefficient of heat conductivity; T is fluid temperature (F.T.); S _hfor fluid endogenous pyrogen; Φ is Dissipation Function of Energy, and computing formula is as follows:

$\mathrm{\Φ}=2{\mathrm{\μ\ϵ}}_1^2$

Wherein, ε ₁for the Deformation tensor of fluid, represent fluid and overcome the mechanical energy that viscosity consumes, it will irreversibly be converted into heat and dissipate.

At full-blown turbulent region, the Turbulent Kinetic equation of reflection turbulence pulsation amount stream field impact and turbulent stress equation obtain its form by standard k-ε equations and are:

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{\∂x_i}|\[(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_k})\frac{{\∂}_k}{\∂x_i}\]+G_k+G_b-\mathrm{\ρ}\mathrm{\ϵ}$

$\mathrm{\ρ}\frac{d\mathrm{\ϵ}}{dt}|=\frac{\∂}{\∂x_i}|\[(\mathrm{\μ}+\frac{{\mathrm{\μ}}_t}{{\mathrm{\σ}}_{\mathrm{\ϵ}}})\frac{{\∂}_{\mathrm{\ϵ}}}{\∂x_i}\]+G_{1\mathrm{\ϵ}}\frac{\mathrm{\ϵ}}{k}(G_k+G_{3\mathrm{\ϵ}}{G}_b)-G_{2\mathrm{\ϵ}}\mathrm{\ρ}\frac{{\mathrm{\ϵ}}^2}{k}$

Wherein, k is Turbulent Kinetic; ε is dissipation turbulent kinetic energy; μ is viscosity coefficient; μ _tfor turbulent viscosity; G _kfor the Turbulent Kinetic k caused due to average velocity gradient produces item; G _bfor the generation item of Turbulent Kinetic k caused by buoyancy; σ _kfor the Prandtl number that Turbulent Kinetic k is corresponding; σ _εfor the Prandtl number that dissipation turbulent kinetic energy ε is corresponding; G _{1 ε}, G _{2 ε}and G _{3 ε}be respectively empirical constant.

Governing equation on control volume is as follows:

Wherein, Γ _Φfor the diffusivity of Φ; ▽ Φ is the gradient of Φ; S _Φfor the source item of Φ on unit volume; V and for control volume; A is chain of command.

5. the electric airplane main drive motor Calculation Method of Temperature Field according to claim 1 or 4, in described electric airplane main drive motor solution of Temperature model, loss computing method is as follows:

Copper loss computing formula is:

Wherein, m is the driver motor alternating current number of phases, gets 3 herein; k _rfor the circulation coefficient between strand in parallel; k _efor eddy current loss factor; N is the number of lead wires on coil width; B is coil width; b _sfor the width of groove; f _nfor frequency; for phase current; R _sfor time-varying reactance.

Iron loss computing formula is:

$P_{core}=K_{h}K\left({\mathrm{\ΔB}}_T\right){\mathrm{fB}}_m^a+{\mathrm{Gk}}_{e1}\underset{k=1}{\overset{\mathrm{\∞}}{\Σ}}{\left(k_a{\mathrm{fB}}_k\right)}^2+\frac{k_{e1}}{T_1}{\∫}_0^{T_1}{\[{\left|\frac{B_k}{dt}\right|}^2\]}^{\frac{3}{4}}dt$

Wherein, K _hhysteresis loss coefficient, K (Δ B _t) local hysteresis loss correction coefficient, for the close value of motor magnetic, k _e1for iron core vortex loss factor, G is teeth portion or yoke portion quality, and f is fundamental frequency, T ₁for the electricity cycle, B _kfor node magnetic is close, k _afor positive integer, k _a=0,1,2,3.

Bearing friction loss is:

$P_f=0.15\frac{F}{d}{v}_1\×{10}^{-5}$

Wherein, F is bearing load; D is ball (or roller) center diameter; v ₁for ball center circumferential speed.

Draft loss is:

P _g＝k _sk ₁C _fπρ _gω ³r ⁴l

Wherein, k _sfor the external arc situation of rotor surface; k ₁for rotor surface roughness; C _ffor windage coefficient, relevant with rotor surface shearing force; ρ _gfor atmospheric density; ω is the angular velocity of rotor; R is rotor radius; L is rotor axial length.

Electric airplane main drive motor total losses are:

P＝P _cu+P _core+P _f+P _g

6. electric airplane main drive motor Calculation Method of Temperature Field according to claim 5, must consider the impact of electric airplane main drive motor electromagnetic field local magnet ring magnetic hysteresis loss in described iron loss computing method.Wherein, consider that the total magnetic hysteresis loss under hysteresis ring is calculated as follows:

$P_h=K_{h}K\left({\mathrm{\ΔB}}_T\right)B_m^a$

Wherein, K _hhysteresis loss coefficient, K (Δ B _t) local hysteresis loss correction coefficient, for the close value of motor magnetic.

7. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, described step 4 adopts unstrutured mesh to carry out network subdivision to electric airplane main drive motor model; When grid division is close to wall, if grid precision does not reach requirement, then wall-function method is adopted to be solved.

8. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, during described step 5 Modling model, needs to complete by softwares such as Solidwork and Ansys.

9. electric airplane main drive motor Calculation Method of Temperature Field according to claim 1, is characterized in that, Flow-induced vibration characteristic differential governing equation is:

Wherein, Γ _Φfor the diffusivity of Φ; ▽ Φ is the gradient of Φ; S _Φfor the source item of Φ on unit volume; V and for control volume; A is chain of command.