Design And Research Of Axial Flux Doubly Salient Electromagnetic Generator For Automobile Exhaust Gas Energy Recovery

Internal combustion engines directly discharge high-temperature,high-pressure,and high-speed exhaust gases,leading to problems such as energy dissipation and low thermal efficiency.To recover the residual energy in the exhaust gas,this paper proposed an axial flux doubly salient electromagnetic generator(AFDSEG)suitable for high-temperature and high-speed operation,which converts the exhaust gas energy into electrical energy required by onboard equipment.Compared with the radial flux doubly salient electromagnetic generator(DSEG),the AFDSEG has the advantages of small axial length and low rotational inertia.The basic structure,parameter optimization,electromagnetic performance,and fault operation of the AFDSEG were studied as follows:By studying the number and structural form of the stator and rotor of the axial machine,this paper gave the basic topology of AFDSEG,determined the basic theory and design principles of generator operation,and analyzed the ideal induction electric potential and inductance curves for generator operation.The equivalent magnetic network model of the motor was established,the excitation self-inductance expression,the mutual inductance expression of the armature winding and excitation winding,etc.were derived,and the mathematical model of the motor,including the flux equation,voltage equation and power equation,was given.Analysis of the mechanism of induction electromotive force generation lead to the conclusion that the overlapping area of the stator-rotor was the main influencing factor.Under the premise of the same stator-rotor axial cross-sectional shape,the mathematical analytical model of the overlapping area of three stator slot tooth surface models was established.Under the double verification of the mathematical model and the finite element method,it was proved that only the sectorial teeth-surface sectorial slot-surface with a linear variation of the overlapping area can generate constant induction electric potential and can achieve the purpose of large amplitude and slight output pulsation.In order to wind more windings in the stator slots and also to improve the core utilization,a sectorial stator tooth parallel stator slot model that was different from the shape of the slot tooth surface was constructed,parameters such as the stator slot inner diameter angle and stator slot depth were dimensionally optimized using Taguchi algorithm,and an air gap performance evaluation function was established to optimize the two-layer air gap of the motor.To address the problem of inter-pole flux leakage generated by the centralized excitation winding,the coupling constraint equation of the number of stator-rotor poles and excitation span was derived by combining the excitation winding span.The magnetic circuit and electromagnetic performance of three winding forms,partition 1,partition 2and alternating type,were compared and analyzed by finite element simulation,and the number of winding layers and the matching of excitation winding and armature winding turns were parametrically simulated to obtain a winding form with small flux leakage and fewer harmonics.Based on the above analysis,the static and dynamic characteristics of AFDSEG were studied.The Fourier decomposition method was applied in combination with the radial flux DSEG to focus on the harmonic content of the induced electric potential,which was reduced by 7.37% and 3.41% for the former compared to the latter for the no-load and load generated electric potential harmonics,respectively.Using the Bertotti iron consumption separation model,the core losses of each part were calculated to obtain the distribution pattern of AFDSEG iron consumption and the percentage of fundamental and harmonic losses.The structural strength of the rotor assembly was calibrated by finite element software to ensure the stability of the motor operation.Four fault conditions were simulated and the results showed that the generator can run briefly with an open circuit fault,but the short circuit current may damage the machine.Finally,a prototype was fabricated,and no-load and load power generation were performed to verify the correctness of the model structure proposed in this paper and the theoretical and simulation analyses performed.