The force of a marine diesel and its shafting are complex. With effects between structure assembly and hull deformation, shaft misalignment often occurs, which can lead to serious accidents such as bearing wear, coupling fracture, and crankshaft fracture. Due to the influence of structural and operational conditions, traditional vibration time-frequency analysis methods struggle to accurately detect and quantify shafting misalignment. Additionally, the characteristic of power and double frequency is easy to be aliased with other fault features and causes misjudgment. Therefore, a model for misalignment morphological characteristics is developed based on the structural features of misaligned shafting. An online detection scheme is proposed to account for misalignment patterns and mechanical structure effects. The research focuses on the diesel output shaft, and a six-degree-of-freedom fault simulation test bench is established for experimental verification of the misalignment detection method. Furthermore, a self-healing control scheme for shafting misalignment faults is proposed and validated through experiments, enabling online self-healing control of such faults. The data demonstrates that the misalignment detection method based on shafting morphological characteristics can achieve online detection of misalignment under different working conditions, with an accuracy rate exceeding 90%. The self-healing control device driven by servo electric cylinder can reduce the misalignment of shafting by more than 75% within 10 s.
Metallic sealing ring is a static sealing structure part widely used in aero-engine, and its profile forming accuracy is the key to the sealing performance, which is of great significance in reducing engine internal flow losses and improving engine thrust-to-weight ratio. Currently, the formed quality of metallic sealing ring mainly uses final destructive sampling inspection, and the lack of geometric quality inspection method in the forming process prevents timdy finding its forming defects. To address the above problems, an on-machine inspection research of geometric quality for metallic W-ring formed profile is carried out. A multi-level registration and distance thresholds based irregular section profile measurement point cloud preprocessing method is proposed, to solve the problem of serious outliers, missing and noise in the measurement point cloud. In order to realize the accurate extraction of complex geometric feature parameters, a minimum area bounding rectangle based profile geometric feature parameters extraction method, a medial axis based wall thickness extraction method, and a curvature and pre-location based circular feature parameters extraction method are proposed. Based on the dual laser scanners, an on-machine measurement system is built, and integrate the above methods, the hardware and software module are developed. Finally, the experimental results demonstrate the advantage of the method. Compared with the traditional destructive inspection results, the average relative error of 1.350% for the profile geometric feature parameters, 3.219% for the wall thickness and 1.372% for the circular feature parameters.
As pipelines take an increasingly important role in energy transportation, their health management is necessary. In-pipe inspection is a common pipeline life maintains method. The signal obtained through internal inspection contains strong noise and interference where the internal environment of the pipeline is extremely complicated. Thus, it is challenging to accurately identify the defect signal. A defect detection algorithm framework based on feature boosting is proposed by using the multi sensing pipeline pig as the detection signals. Through boosting construction of features and hierarchical classification, the framework can not only correctly classify various signals in the internal detection signals but also realize the accurate identification of defect signals. Concurrently, in order to demonstrate the high flexibility and robustness of the detection framework, experiments and verifications have been carried out on specimens in three different environments i.e. laboratory environment, simulated environment and actual environment. In the classification of actual environmental detection signals, comparisons with different algorithms have been undertaken and quantitatively evaluated using the F-score and demonstrated the effectiveness of the proposed framework.
Different initial magnetization states of ferromagnetic materials have large influence on stress magnetic detection, which needs to be overcome, to improve the robustness of the magnetic measurement. Through theoretical analysis of magneto-mechanical coupling, the initial magnetization state of ferromagnetic materials can be stable and controlled by appropriately increasing the external magnetic field strength H0. Furthermore, the rising section of the magnetization curve of ferromagnetic materials can be stably constrained within 40 MPa, which is far less than the general working load, and the falling section of the magnetization curve shows a nearly linear change with the increase of the stress. Based on this, uniaxial tensile magneto-mechanical coupling test of a Q235 low-carbon-steel specimen (with multiple cross-section mutations) was carried out, to clear the response of magnetic flux leakage signal of ferromagnetic material to tensile stress σt. The stress distributions of the specimen under different loads were obtained by finite element analysis, and then the effects of H0 and tensile stress σt on the normal component Hp(z) of magnetic flux leakage signal were analyzed. The results indicate that by locally enhancing H0, a relatively controllable and stable local magnetic flux loop can be formed at the examined part of the specimen, which can effectively overcome the problems caused by random and variable initial magnetization state, weak detection signal and low signal-to-noise ratio in metal magnetic memory detection. The influence coefficient φ was introduced to represent the correlative influence of σt on the characteristic parameter peak-peak amplitude S(z)p-p. Within the range of 0 MPa≤σt≤168 MPa, the maximum increase in φ was 18.4% with the increase of σt.
The three-roll skew rolling bonding process is proposed to solve the efficient continuous forming problems of seamless metal cladding tubes with high strength and corrosion resistance, which possess characteristics of high component melting point, large deformation resistance, and difficult interfacial bonding. Based on the ABAQUS software, a numerical simulation model is established for the three-roll skew rolling bonding process of 45/316L cladding tubes. The variation laws of the diameter reduction rate, wall reduction rate, elongation rate, component metal wall thickness ratio, etc. are studied under different diameter reduction rates and initial component metal wall thickness ratios. Finally, 45/316L cladding tubes were successfully prepared through the experiment, verifying the accuracy of the simulation analysis. The results show that 45 carbon steel and 316L stainless steel are forced to synchronously deform under multiple constraints of end welding, roll, and mandrel. The component metal wall thickness ratios are unchanged, laying a theoretical foundation for the accurate control of target size specifications. Tensile shear tests show that tensile shear fractures occur on the matrix of 45 carbon steel, and the bonding interface does not crack after the lateral bending test, proving that interfaces achieve high-strength metallurgical bonding. Therefore, the three-roll skew rolling bonding process provides a new method for realizing the precise control of component metal wall thickness, interfacial high-strength metallurgical bonding, and efficient continuous near-net forming of seamless metal cladding tubes with high strength and corrosion resistance.
12 mm medium-thick AA6061-T6 aluminium alloy and T2 pure copper was welded by double-sided stir friction welding, the influence of welding parameters on the microstructure and mechanical properties of the joint was investigated. It was found that there are significant differences in the weld formation between the first-pass and second-pass welds at both sides due to welding distortion even through the same welding parameters were used for those two welds at both sides, making it difficult to achieve excellent joint properties. In order to further improve the joint properties, the rotational speed and welding speed of the first-pass weld were fixed at 600 r/min and 400 mm/min respectively, while the welding parameters of the second-pass weld were investigated and optimized. On one hand, the rotational speed of the second-pass weld was fixed at 600 r/min while change the welding speed to 300 mm/min, 200 mm/min and 100 mm/min, respectively. A defect-free joint is achieved at the welding speed of 100 mm/min for the second-pass weld. On the other hand, the welding speed of the second-pass weld was fixed at 400 mm/min while change the rotational speed to 800 r/min and 1 000 r/min, respectively. The results showed that the defect-free joint with a maximum tensile strength of 151 MPa was obtained at the tool rotation speed of 800 r/min for the second-pass weld. This is because there isn’t any cavity defects and micro-cracks at the aluminium/copper interface, as well as the relatively thin intermetallic compound layer was formed at the Al/Cu interface under the optimized condition. The joint was fractured at the aluminium/copper interface and the fracture mode was classified as a ductile-brittle mixed fracture.
Laser directed energy deposition (DED) is a manufacturing technology for producing high performance fully dense near-net metallic components, which is melting metal powders point by point and stacking them layer by layer. Since the microstructure of DEDed TC4 titanium alloy is different from that made by traditional forging, selecting appropriate heat treatment process can improve its mechanical properties significantly. The effects of three different heat treatment on microstructure morphologies and tensile properties of DEDed TC4 alloy were investigated. The results show that after 600 ℃ and 800 ℃ annealing treatment, the α lamellae coarsens to different degrees, and the volume fraction of α phase increases slightly. The double annealing heat treatment at 975 ℃ results in the appearance of equiaxed α phase, improving room-temperature plasticity with about 26.1% higher in average transverse reduction of area than that after 800 ℃ annealing treatment. After double annealing heat treatment at 975 ℃, TC4 alloy has the highest transverse average elongation at high temperature tensile test at 400℃, showing excellent high temperature strength-plastic balance.
The vibration theory of strip rolling mill is very important to the quality of sheet metal and the stable operation. Considering the influence of the horizontal dynamic excitation of rolling force, the nonlinear damping, the nonlinear stiffness and the gap between the work roll bearing seat and the bridge, the fractional order dynamic model of the horizontal nonlinear vibration of the work roll is established. The amplitude-frequency characteristic curve equation of the horizontal nonlinear vibration of the upper work roll is obtained by average method. The effects of the horizontal dynamic excitation amplitude, stiffness coefficient, nonlinear damping coefficient and fractional differential coefficient and order of the rolling force on the principal common amplitude-frequency characteristic curve of the system are analyzed. A hydraulic intelligent liner plate is designed to be installed between the mill yard and the bearing seat of the upper work roll. The amplitude-frequency characteristic equation of intelligent liner installation system is obtained by using multi-scale method. The influence of stiffness coefficient and damping coefficient of liner on amplitude-frequency characteristics is analyzed, and the control effect of intelligent liner on horizontal nonlinear vibration is studied by numerical simulation. Finally, the correctness and feasibility of intelligent liner design are verified by experiments, which provides a new idea for nonlinear dynamic analysis and stability control of rolling mill, and has important guiding significance for practical production.
The high-cycle fatigue cracks of metal components start from some internal grains. The classical phenomenological damage theory can not reveal the damage morphology and evolution process on the micrograin scale, and it is difficult to establish a true description of the damage. Based on the intrinsic dissipation theory of phenomenological damage mechanics and the Lin-Taylor hypothesis, a microplastic dissipation potential was established to characterize the irreversible strain dissipation of grains, and the macroscopic equivalent characterization of the cumulative plastic strain of grain size was obtained by using the microscopic integral idea, and a two-scale model of high-cycle fatigue damage evolution was further established. The model is suitable for uniaxial, multi-axial proportional and multi-axial non-proportional loading conditions, considering both the cyclic characteristics of damage driving force and the single-bilateral effect of crack closure behavior. The load condition of the component is realized by ABAQUS, and the damage driving force is calculated by UMAT subroutine. Finally, the experimental data of aluminum alloy LY12CZ, 5% chromium steel and C35 steel used in aviation industry under different loading paths are used to evaluate and verify the proposed two-scale model. The results show that the new model has a good life prediction effect. The new model reveals the main relationship between micromechanical behavior and phenomenological damage evolution, and provides a new way to solve complex mechanical problems involving multi-scale behavior such as fatigue damage and failure of metal materials.
CoCrFeNiMn high-entropy alloy (HEA) generally exhibits outstanding ductility and fracture toughness properties, however its low strength and hardness limit its application potential in the field of structural materials. There are few reports on the effect of Al content on microstructure and properties of CoCrFeMnNi HEA fabricated by powder metallurgy at present. CoCrFeMnNi HEAs with different Al content were prepared by hot-pressing sintering method using gas-atomized HEA powder and Al powder as raw materials. The effect of Al content on microstructure and properties of HEAs was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), nanoindentation experiment, vickers hardness, compression at room temperature and polarization curves. The results show that with the increase of Al content from 0 to 5 wt.%, the relative density and the volume fraction of reticular Cr-rich BCC phase precipitated in the FCC matrix of as-prepared HEAs increase. When the Al content increases to 5 wt.%, the nano-indentation hardness and elastic modulus of the FCC phase in fabricated HEA increase slightly and the mentioned performance of BCC phase is significantly higher than that of FCC phase, the vickers hardness increases from 248.4 to 508.3 HV and the compression strength at room temperature is also greatly improved mainly due to the precipitation strengthening effect; At the same time, the minimum corrosion current density is obtained, confirming the improved corrosion resistance. However, the addition of excessive Al leads to the segregation of Al element, and a sharp increase in the volume fraction of BCC structure and microstructural heterogeneity of as-fabricated HEA, which deteriorates the hardness, elastic modulus and corrosion resistance.
Friction pull plug welding (Friction pull plug welding, FPPW) is a high efficient solid-state repair welding technology widely used in the aerospace field. In this study, 12mm thick aluminum alloy plates were selected to carry out FPPW trails. The method of emergency stop at different welding stages was applied to explore the forming process. The full-process welding was used to analyze microstructure and properties. According to the change of pull force, FPPW process could be divided into pre-friction stage, loading stage, constant force welding stage and forging stage. The results of emergency stop at different welding stages showed that in the early stage of welding, the sliding friction was the main friction mode and preheated the interface. The heat increased as the welding process progresses, and local bonding occurred at the interface. In the later stage of welding, adhesive friction played a dominant role so that the interface bonding condition emerged and then bonded well during the forging stage. The results of full-process welding showed that when the welding tensile force was 50 kN, a brittle second-phase continuously distribute on the bonding interface which lowered the bonding strength. As the welding tensile force was increased to 60 kN, the strength increased with the decreasing of the second phase in the bonding interface. However, when the welding tensile force rose to 70 kN, necking occurred at the joint and continuous tiny pores appeared on the bonding interface, resulting in a significant decrease in strength. These research results can provide a good reference for medium-thick plate FPPW forming.
The fusion welding methods play an important role in joining aluminum alloys, but the resulting welds suffer from a number of metallurgical issues. Therefore, it is particularly urgent to develop the effective modification/repair processes with high machining flexibility margin for aluminum alloy fusion welded joints, which is of great engineering significance for them to improve the service performance and extend the service life. A typical AA2024 aluminum alloy TIG welded joint using ER4043 wire was subjected to friction stir processing (FSP). The effect of FSP on the microstructure and properties of TIG joint was investigated. The results show that the fusion zone consists of coarse cast dendrites, Al-Si eutectic network and metallurgical defects; after FSP, the cast structure in the fusion zone is completely eliminated and transformed into a dense, uniform and fine-grained aluminum matrix composite reinforced with Si particle, resulting in a simultaneous improvement in strength-ductility synergy and corrosion resistance of TIG joint. The constitutive relationship between the microstructure evolution and property improvement of TIG joint before and after FSP is established, which reveals the microstructural origin of the performance improvement for the TIG joint after FSP, and provides new insights into the modification/repair of fusion welds of many metallic systems for enhanced performance.
The buckling and wrinkling phenomena in the process of tube manufacturing are predicted and studied by taking the tube formed by free bending as the research object. Firstly, the analysis model of free bending tube is established through the research of wrinkle prediction of pure bending tube forming, and the ripple function of free bending tube forming is deduced. Secondly, combined with the calculation formula of bending deformation energy of tube and the prediction formula of pure bending tube, the calculation formula of critical energy is obtained. Then, ABAQUS finite element simulation software is used for simulation calculation, and free bending critical energy calculation formula is used to predict the buckling and wrinkling phenomenon of tube and verify it. Finally, the prediction method of free bending buckling wrinkling is used to explore several factors affecting the free bending buckling wrinkling of pipe fittings. The results show that the bending radius, relative pipe diameter and unit length twist angle are the factors that affect the occurrence of buckling and wrinkling in the precision forming process of thin-walled tube NC bending. The research results have created conditions for the determination and optimization of parameters in the free bending forming process.
The pure tungsten plate and the CLF-1 reduced activation ferritic/martensitic (RAFM) steel was welded successfully based on the Joule heat generated by the constant current output from the resistance seam welding, named resistance diffusion welding. Meanwhile, the graphite with high resistivity and the pure Fe foil were proposed as the thermal compensated auxiliary electrode and the interlayer in the welding process, respectively. The interfacial structure, joint strength, and fracture form of the obtained W/steel and W/Fe/steel welded joints were compared to reveal the role of the interlayer in the welding process. The results indicated that：due to the introduction of the interlayer between tungsten and RAFM steel, the interfacial structure of the obtained W/Fe/steel welded joint was changed significantly. The original W/Fe connection interface was replaced by two interfaces of W/Fe and Fe/steel. In addition, the addition of the interlayer led to an increase in the resistance of the entire welded joint, which improved the Joule heat generated in the welding process. Hence, the interdiffusion distance at the interface increased from 2 μm to 4 μm, and the obtained shear load of the W/Fe/steel welded joint reached 12 313.3 N, which was about 30.82% higher than the former. The real-time temperature field of the W/Fe/steel welded joint surface showed that the temperature of the auxiliary electrode graphite was the highest in the whole welding process. The highest temperature was 910 ℃ but was lower than the melting point of the base metal. This indicated that the mechanical properties of the welded joints were dominated by the interdiffusion of different elements, which was resistance diffusion welding. Moreover, the fracture morphology sketched that the addition of the interlayer resulted in the increase in the reaction area at the fracture surface, and the main fracture position was located at the W side, indicating that a good metallurgical bond was formed between tungsten and RAFM steel.
With the rapid development of battery electric vehicles, there has been a higher demand for increased energy density and safety in power batteries. The blade battery has significantly enhanced space utilization and addressed the issue of low energy density in conventional Lithium iron phosphate batteries(LFP). A model combining 1D electrochemical with a 3D thermal model is developed to investigate the following three aspects. Firstly, the effect of environmental temperature, charge rate, and heat transfer coefficient on the electrochemical properties of blade batteries with varying lengths is studied. Through the use of the DC impedance decomposition method(DCR), the primary physicochemical process that affects the electrochemical performance of the long/short blade battery is identified and traced. Secondly, the influence of the above three variables on temperature distribution and temperature rise process at the end of charging of the long/short blade batteries is investigated. Furthermore, a heat production decomposition (HPD) study is carried out to demonstrate the heat production of each component. Thirdly, the influence of battery size and heat transfer coefficient on battery temperature uniformity is explored, and several helpful proposals that benefit to temperature uniformity are suggested. The main results are as follows ① The effect of blade battery length on electrochemical performance is attributed to the different collector resistance, and the resistance increases as the length of the battery increases. Additionally, the thermal performance is affected by the length of the blade battery, which is dependent on internal heat production, conduction, and surface dissipation. According to the results, as the length increases, there will be a corresponding increase in heat production and temperature difference of the battery. ② The three factors mentioned above displayed varying effects on electrochemical and thermal properties. On the one hand, the environmental temperature and heat transfer coefficient have little influence on electrochemical properties and heat production constitution. On the other hand, as the charging rate increases, the capacity declines noticeably because of the rise in overpotential, and heat production increases considerably both reversible heat and irreversible heat. Additionally, the temperature uniformity improves in length direction with the increasing heat transfer coefficient. Moreover, improving thermal conductivity is proven another effective way to temperature uniformity. According to the simulations, the L400 shows the best temperature consistency among the three different battery sizes, containing the L400, L800, and L1200. In summary, decreasing the length of the battery and improving the thermal conductivity of the material are effective methods to enhance temperature uniformity in each direction of the batteries.
Carbody vertical abnormal vibration of light rail transit during operation seriously impact the passengers’ ride comfort. To address this issue, carbody vertical vibration characteristics of light rail transit is studied through field test, theoretical analysis and simulation reproduction and the causes of abnormal vibration are clarified. The results show that the carbody vertical vibration frequency with 7.5 Hz is the main reason for the deterioration of the light rail transit ride comfort. The trailer of the light rail transit exhibits a vibration mode of floating up and down, while the adjacent vehicles pitch in the opposite direction. The frequency of carbody pitching motion is significantly affected by the longitudinal stiffness of the elastic articulation, while the secondary vertical stiffness of the bogie and the longitudinal deviation from carbody gravity to the bogie have a minor impact. The insufficient stiffness of the elastic articulation is the preliminary cause, with a measured hinge stiffness of 11.87 MN/m, which is far below the design value. A simulation model based on the measured data reproduces the carbody abnormal vibration and confirms that the insufficient longitudinal stiffness of the elastic articulation is the root cause. This relevant research provides technical support for addressing abnormal vibration problems and enhancing the performance of light rail transit.
Addressing the insufficient safety and poor interactivity issues at unsignalized intersections with multiple vehicles, a distributed autonomous driving multi-vehicle cooperative control method is proposed. Firstly, a trajectory prediction model is utilized to obtain the future 3-second motion trajectories of all vehicles within the intersection as input for conflict screening. Secondly, a safety assessment model based on the responsibility-sensitive safety(RSS) model is established to evaluate the interaction between vehicles by assessing their predicted trajectories. Thirdly, a multi-vehicle cooperative control framework based on game theory and the intelligent driver model(IDM) is constructed. The interaction process between conflicting vehicles is modeled as a Nash equilibrium problem, and cooperative control strategies for multiple vehicles are generated by solving optimization problems. Vehicles that do not interact with other vehicles are controlled by IDM, thereby achieving separate control and joint action for all vehicles. Finally, the proposed method is validated in a simulated scenario of an unsignalized intersection. Experimental results demonstrate that compared to baseline methods, the proposed approach effectively enhances safety, real-time performance, and traffic efficiency.
The polygonal wear of high-speed train wheels occurs commonly and can increase the wheel-rail interaction force dramatically and have a bad effect on the operation safety and comfort of the train. The mechanism on initiation and development of the polygonal wear deserves further study. A high-speed rolling test is performed based on the full-size wheel-rail roller test rig and reproduced the whole process of the initiation and development of the polygonal wear in the laboratory. The mechanism of the initiation and development of the polygonal wear is clearly demonstrated. The evolution progress of the polygonal wear is detailed investigated under different test speed conditions. The effective countermeasures to suppress the polygonal wear development are proposed. The results obtained in the research will be helpful for the further study on the mechanism and countermeasures of the polygonal wear.
Vehicle collision warning is the core technology of vehicle active safety control. It is often necessary to use accurate vehicle state information to precisely predict the motion trajectory, and then determine whether there is a collision risk within the safe collision warning time by the motion trajectory prediction module. To improve the accuracy of collision warning, a state estimation method using constant turning rate and acceleration model as the state transition equation, and square root volume Kalman filter as the estimation algorithm is established first, which is beneficial to improving the estimation accuracy of the relative motion state of the target vehicle. A relative motion trajectory prediction method integrated with grey prediction is then proposed. The measured variables are predicted in multiple steps through the grey prediction model and are corrected by the square root volume Kalman filter to improve the prediction accuracy of the relative motion trajectory of the target vehicle. Considering the influence of road adhesion coefficient on the safe collision warning time, a vehicle lateral collision warning method is proposed at last. The numerical simulation results show that the warning methods proposed can accurately predict the collision time of the vehicle under different road conditions, and the early warning time is greater than the safe collision warning time, so as to ensure that the driver or the active obstacle avoidance control system can control the vehicle timely and improve the safety of vehicle driving.
Considering that axle box bearing is susceptible to long-term disturbances from track irregularities, lines, wheel-rail nonlinear contact, and vibration of the bogie frame and carbody, it is one of the components that are prone to damage in the rotating system of high-speed trains. In order to better analyze the interaction between the interior of the axle box bearings, a vehicle-track coupled dynamics simulation model including the axle box bearing subsystem is established using multi-body dynamics simulation software Recurdyn and Simpack. The influence of different line conditions on the load characteristics of axle box bearing under complex track excitation is investigated. The results show that: on the straight line, the peak value and trend of the contact load between the two rows of tapered rollers and the outer ring, as well as the large retaining edge of the inner ring, are basically consistent. At the beginning of the transition curve, the main load is borne by the first row of rollers, and the auxiliary load is borne by the second row of rollers. The first row of rollers enters the bearing area earlier than the second row of rollers. In the stage when the transition curve is about to leave, the main load is borne by the second row of rollers, the auxiliary load is borne by the first row of rollers. The second row of rollers enters the bearing area earlier than the first row of rollers. On the curve line, the load law is the same as that of the transition curve when it is about to depart, and the fluctuation of contact load tends to stabilize. In addition, on the transition curve and the curve line, the number of rollers in a row of rollers responsible for the main load entering the bearing area at the same instant is increased compared with that of the linear line rollers. The contact load between the two rollers and the cage is more complicated than the condition fluctuation of the straight line, and there is no obvious chronological order in the time dimension. In general, compared with the straight line, the more severe and more complex periodic impact is borne by the axle box bearing on the curve line, which will make the bearing more prone to damage.
A hybrid analytical modeling method for moving coil electromagnetic linear drive device is proposed. The model is used to further improve the electromagnetic field analytical model accuracy of the drive device. The hybrid analytical model combines the magnetic potential model and the equivalent surface current model to research the electromagnetic characteristics of the driving device. Define radial flux density correction coefficient to modify the single magnetic potential vector model. Use electromagnetic field boundary conditions of moving coil electromagnetic linear drive device to establish a more accurate electromagnetic characteristics mathematical model. Finally, obtain the distribution law of magnetic field in the air gap and the electromagnetic force - travel function. The FEM and experimental results show that the hybrid model is more accurate compared with the single magnetic potential model. After modification, the maximum error of thrust solution is reduced from 6.9% to 2.8% and the solution accuracy is improved by 4.1%, which prove the validity of the modified method. The error between the experiment and the analytical results is less than 2.5%, which verifies the correctness and accuracy of the analytical model. This method provides a theoretical basis for the modular design of electromagnetic linear drive device and the sensorless control, and enrich the control method of all-electric integrated drive system.
Oil and gas are mostly used as fuel for aggregate drying. Compared with oil and gas, the pulverized coal is also suitable for aggregate drying as the operating costs is dramatically reduced. In order to improve the combustion efficiency of pulverized coal and reduce NOXemissions, the benign development of pulverized coal combustion behavior needed to be effectively controlled. So the grading air distribution was applied to the pulverized coal combustion system of aggregate drying. The LB2000 aggregate drying equipment was taken as a study case, and the numerical model of the pulverized coal combustion system for aggregate drying was established. The influence of graded air distribution parameters on the combustion efficiency and NOXemissions was investigated. A response surface model was proposed, the graded air distribution parameters were comprehensively optimized by means of non-dominated sorting genetic algorithm II (NSGA-II). The results indicated that the pulverized coal combustion can be promoted and the NOX emission can be regulated when the air supply is increased properly. The highest temperature zone is cooled down and the temperature of back of the drying drum is rose with better aggregate drying effect and quality, and an anoxic environment is formed in local area of the combustion zone, which reduced the amount of NOX production with the increase of over-fire air within limits. Appropriate air staging depth is in favor to slowing down the combustion of pulverized coal. In addition, the mixing effect of pulverized coal and air can be improved by secondary air, so as to the full combustion of pulverized coal can be promote. The value ranges of the graded air distribution parameters are achieved according to the combustion efficiency and emission characteristics, which excess air coefficient is 1.25～1.35, over-fire air rate is 0.6～0.7, air staging depth is 0.4～0.6. The excess air coefficient is 1.337 5, the over-fire air rate is 0.647 7, and the air staging depth is 0.599 9 through optimization.
