最新刊期
卷 50 ， 期 11 ， 2016
- 摘要：An efficient solution method based on wave propagation method, multi-harmonic balance method and Receptance method was developed to solve the problem with overlarge degrees of freedom and computational complexity in calculating the nonlinear vibration response of continuous covered blades with damped shroud. According to the cyclic symmetry property of blade, the vibration analysis of a whole blade can be reduced to one of its basic sector using wave propagation method and the nonlinear friction force can be solved from the displacement of the basic sector and friction contact model; the differential equations in time domain of the reduced basic sector can be transformed into algebraic equations in frequency domain by multi-harmonic balance method. The orthogonality of normalized modes is used to decouple the vibration equation of blade in frequency domain and the local nonlinear characteristics of the blade system are used to condense the linear DOFs in non-contact interfaces. So that the scale of nonlinear iteration can be effectively reduced and the computation efficiency is improved. The results showed that the relative error obtained with the developed method was 0.33% and the calculation time was reduced to 10%, which verifies the accuracy and efficiency of the proposed method. The nonlinear vibration response of a real shrouded blade was investigated by this method.关键词：whole blade;vibration response;shroud damper;order-reducing method864|4|2更新时间：2025-07-09
- 摘要：A numerical algorithm was employed to investigate the coupled flow behavior between gas flow and wall film. The air flow and wall film on a flat, and the water vapor flow and wall film in a turbine cascade were focused on. It is concluded that the film thickness is approximately proportional to the root of the inlet wall film Reynolds number, and inversely proportional to the mainstream flow Mach number. Film thickness and the outlet pressure have a weak negative exponential order relation, and the interface velocity is linearly related to the outlet pressure. The additional losses due to water film are sensitive to the change of water flow rate, but not sensitive to the flow Mach number. As for the turbine stator, the pressure surface film thickness is relative even, except that a film accumulation region appears at the tip corner region. In contrast, the suction side thickness changes obviously, and the film accumulation is observed at both the tip and root corner regions. The wall film distribution in a turbine cascade is affected by three factors. The wall curvature influences the film thickness and velocity by influencing the interphase shear force. The endwall secondary flow from the pressure side to the suction side leads to film accumulation near the suction surface. The radial pressure gradient caused by passage vortex and corner vortex results in film redistribution along the blade height. On the other hand, the film accumulation on the blade exerts a significant impact on the surface pressure and outlet flow angle.关键词：gas flow;wall film;coupling flow behavior;numerical investigation788|4|2更新时间：2025-07-09
- 摘要：So far in the simulation research of spiral-wound heat exchanger the space bars are rarely considered, the deviation between simulation results and actual situation is thus enlarged. This paper mainly studies the effects of the number and arrangement of space bars on the shell side's thermal and hydraulic performance with numerical simulation method. Numerical results showed that the space bars affect the axial flow rate of shell side and cause more vortexes in radial sections. Compared with the calculation results of the models without space bars under the same inlet condition the Nusselt number Nu of lined up-space bar models was decreased by 1.6%-2.5%; the pressure drop per heat exchanger length ΔPl was increased by 14.5%-17.0%; the performance evaluation criteria FP was decreased by 5.7%-5.9%; the Nu of staggered-space bar models was increased by 17.0%-18.1%; ΔPl was increased by 38.4%-39.9% and FP was increased by 13.7%-15.4%. Moreover, the staggered arrangement of space bars can further enhance the turbulence of shell side, compared with the lined up arrangement the Nu of staggered arrangement was increased and ΔPl was increased accordingly in the same working conditions. When the number of space bars was more than 12(13, 14 and 15), the number of space bars had little effect on the shell side performance. This paper provides a new approach for spiral-wound heat exchanger simulation and offers a theoretical reference for the performance optimization.关键词：spiral-wound heat exchanger;space bar;turbulence enhancement;pressure drop736|4|2更新时间：2025-07-09
- 摘要：Increasing the turbine inlet temperature is a feasible method to improve the cycle thermal efficiency and power output of a gas turbine. The heat transfer and flow characteristics of air and air/mist cooling in the trail edge path of a gas turbine stator are numerically investigated with ANSYS-CFX. The simulations for different working fluids(air and air/mist)are carried out to find their cooling performance difference. The changes of mist distribution, Nusselt number, flow friction factor and thermodynamic efficiency are analyzed in the cases of different Reynolds number and different initial diameter of mist. The results show that the mist flow distance goes up when Reynolds number and mist initial diameter increase. At the same Reynolds number, the bottom averaged Nusselt number increases when spraying mist with different initial diameter into cooling air. The enhancement of the bottom averaged Nusselt number is related to Reynolds number and the initial mist diameter. To reach the highest cooling performance, the evaporating and disturbance effects of mist ought to be taken into consideration. Spraying mist into cooling air slightly affects the friction factor, but the increase of thermodynamic efficiency can reach up to 26% considering both heat transfer and flow friction.关键词：gas turbine;air/mist cooling;cooling performance;numerical simulation800|4|1更新时间：2025-07-09
- 摘要：In order to deal with the increasingly severe climate change and energy crisis, explore efficient energy conservation and GHG emission reduction policies and complete the quantitative evaluation of relevant policies, the LEAP model of Shaanxi Province is established according to the Shaanxi statistical yearbook and combined with the actual situation of Shaanxi Province. This LEAP model includes four parts: energy demand module, energy transformation module, resources supply module and GHG emission module. And based on the forecast of the development in population and economy of Shaanxi Province this paper has made a prediction on the energy consumption and GHG emission of Shaanxi Province in different policy scenarios, and conducted an analysis of the energy conservation and GHG emission reduction potential of the relevant policies. The results show that with the implementation of various policies, Shaanxi Province's energy consumption and GHG emission will be decreased with the implementation of various energy conservation and emission reduction policies. The primary energy consumption of Shaanxi Province in 2030 is expected to be decreased by 20.35% compared with the baseline scenario; the GHG emission will be reduced by 27.29% The renewable energy generation technology has made a great progress in energy conservation and GHG emission reduction, and most contribution to energy conservation and emission reduction was made in industry, transportation and power generation. So, generally speaking, Shaanxi Province has enormous potential in energy conservation and GHG emission reduction.关键词：energy conservation;emission reduction;LEAP model716|4|7更新时间：2025-07-09
- 摘要：To solve the problem that the complex optical path of projector and the large deflection of main point are difficult to meet the requirement of high-precision calibration, a wholly parametric plane linear estimation algorithm of the projector was put forward to determine the initial deviation value of main point. Thus, the wholly parametric high precision calibration of the projector can be fulfilled. Firstly, the projector is treated as a virtual camera to obtain the coordinates of the projector and the calibration board through multiple frequency phase shift principle. Secondly, a two-step method is utilized to solve the nonlinear equations. To obtain the stable direct parameter estimation, a vector parameter is introduced to solve the linearization of the nonlinear equation and an optimal point set is selected by affine transformation relationship. Finally, a global bundle adjustment algorithm is developed to implement high precision calibration of the projector. After the calibration of single camera system, the standard balls are measured to verify its accuracy. The experimental results showed that the average value of the projector-camera system's re-projection error is 0.04 pixel, and the average deviation is less than 0.1 mm in diameter and 0.05 mm in distance acquired by the standard balls. The results further indicate that the algorithm model is simple, stable and accurate. Above all, the projector calibration algorithm can be applied to the situation that the displacement of main point has a large deviation and focal length is unknown.关键词：structured light measurement;projector calibration;plane model;wholly parametric1100|4|0更新时间：2025-07-09
- 摘要：The symmetric discrete-event systems(DES)consist of groups of identical components. For such DES, the supervisor in the form of automata synthesized by the supervisory control theory often has large number of state and is nontransparent in control logic. Thus a computational approach of abstract control function is proposed. This approach fully exploits the symmetry of the system. For the performance index to avoid the underflow or overflow of buffers, the number of components in the status of processing finish is extracted with event relabeling map, thereby the processing details of each component are omitted. Then the abstract control functions are computed with the state tree structures(STS)based on the abstract status information. Finally, by illustrating examples of components working in parallel and serial, the invariance property of control functions are analyzed. Namely, with fixed buffer sizes, the status information required by the control function is irrelevant to the total number of components. The experimental results showed that by utilizing the invariance property of control functions, the repeated computation of control functions is avoided when identical components are added or deleted. Meanwhile, all controllable events relabeled by the same symbol can be enabled by one abstract control function; thus the number of control functions is reduced. Moreover, compared with the controller represented by automata, the control functions have fewer states and are more transparent in control logic.关键词：discrete-event systems;supervisory control theory;state tree structures;control functions;predicate logic644|4|0更新时间：2025-07-09
- 摘要：To investigate the stability parking of an underwater glider, a numerical simulation is carried out. Two types of instability states of the underwater glider are defined, namely, “when the fluid drag exceeds the friction between the hydraulic support and the seabed, sideslip occurs” and “when the fluid torque relatively to the fulcrum exceeds the restoring torque from net gravity, side roll occurs”. The mathematical models of the instability state are established. Considering the coupling of the underwater glider between flow field and seabed, the numerical simulation is carried out with ANSYS-CFX. Under the conditions of different flow velocities(0-2 m/s), distances(0.15-0.5 m)and attitude angles, the curves of the fluid force and torque are completed. It reveals that when the distance between the buoyant and seabed is smaller than 0.3 m, wall effect is obvious, which is helpful in the stability of the glider, and attack angle of the glider greatly reduces the stability of the whole system; when azimuth angle is at 150°-155°, the disturbance of fluid is most obvious. The results can be used for practical design and parking experiment for a new underwater glider.关键词：underwater glider;stability parking;numerical simulation636|4|1更新时间：2025-07-09
- 摘要：To satisfy the manipulation requirement of auxiliary droplets release aiming at micro-objects, a droplet dispensing method based on piezoelectric drive is presented. The dispenser of piezoelectric micro-jet, which employs piezoelectric actuator to achieve non-contact dispensing, is designed. Accordingly, the formation condition of single droplet is analyzed. Subsequently, a multi-physics coupled model of piezoelectric micro-jet, including piezoelectric device model, fluid-solid interaction model, laminar flow model, and two-phase flow model, is established to simulate the process of droplets formation and analyze the factors affecting the droplet formation capacity. Experimental tests were conducted on a customized micromanipulation platform to verify the performance of the micro-dispenser. Experimental results indicate that the droplet volume increases with the driving voltage and pulse width. Meanwhile, the single droplet forms more easily with higher driving voltage and larger pulse width, and the results are consistent with simulation. Through the comprehensive adjustment of control parameters, the minimum drop volume of 3.5 nL, which is sufficient for micro-object auxiliary release, can be obtained using the designed micro-dispenser. The feasibility of the proposed method and the fabricated micro-dispenser were verified by the manipulation of tin and polystyrene microspheres with a diameter of 200 μm.关键词：micromanipulation;piezoelectric drive;micro-jet;droplet;multi-physics674|4|0更新时间：2025-07-09
- 摘要：In order to obtain all geometric errors of numerical control(NC)machine tool, according to the 3D measurement characteristic of laser tracker, the pose measurement principle for geometric accuracy detection of machine tool and separation principle for geometric error are developed. By means of NC precise turntable fixed on machine tool and a laser tracker, the pose information of translational axis can be calculated, then the geometric errors are determined. First, the pose measurement principle and measurement mathematical model of linear axis are developed in details, including calibration principle of measuring points and base stations, and the acquisition procedures of pose deviation. Then, the three angular errors and three linear errors are identified successively and geometrically, and the comprehensive error identification model for single axis is determined. At last, the feasibility and veracity are verified by simulation experiment, measurement experiment and comparative experiment. Results of experiments show that the proposed method is able to complete the precision detection of a 3-axis milling machine within 2 h, and the errors are identified successfully. This measurement principle has short measurement time and high precision, and solve the calibration problem of base station with higher precision. The pose measurement principle provides a new method for machine tool error detection with an extensive application prospect.关键词：pose measuring principle;geometric accuracy detection;numerical control precision turntable;laser tracker842|4|6更新时间：2025-07-09
- 摘要：According to the lightweight and heavily loaded characteristics of spiral bevel gear, spiral bevel gears with tooth edge contact were analyzed by finite element processing batch, and the change regulation of tooth edge contact as load increases was quantitatively discussed. On the basis of tooth contact analysis, gear meshing processions were divided into several steps to calculate. Each step was combined to describe the gear meshing processions. Taking a pair of spiral bevel gears as an example, tooth edge contact is analyzed under different load conditions. The contact stress, contact pattern and contact trajectory were obtained by post-treatment, which well coincide with tooth contact analysis and loaded tooth contact analysis. The result shows that three tooth edge contact parameters listed above steeply rise as loads passing beyond the critical value. And the change characteristics can be obtained by quantitative calculation and parameter comparison.关键词：spiral bevel gear;tooth edge contact;contact stress;contact pattern;finite element method721|4|10更新时间：2025-07-09
- 摘要：To obtain the type synthesis of three-translational and one-rotational(3T1R)hybrid mechanisms, an efficient synthesis methodology is proposed based on fractal theory and topological graph. The major concept of this method is to transform the hybrid mechanism into linkage mechanism, whose main frame is determined by topological graph and whose links are composed of the assignment of kinematic pairs. Fractal theory is applied to the topological graph, and the permutation and combination of output displacement set and selecting suitable kinematic pairs are conducted to achieve the configuration diversity of hybrid mechanisms. The route rule for dealing with the topological graph is proposed, and the calculation rule of union-intersection-preserving for deriving the kinematic pair's output is presented. According to fractal theory and topological graph, the hybrid mechanism is classified into two types. Thereafter, a relationship model of hybrid mechanism and fractal theory is established, so the mechanical design and fractal theory are unified in mathematics and logic. Matlab is utilized in type synthesis of 3T1R hybrid mechanism, and one of the configurations is achieved, demonstrating the validity of the proposed methodology.关键词：hybrid mechanism;type synthesis;fractal theory;3T1R745|4|2更新时间：2025-07-09
- 摘要：Switched reluctance motor with double salient structure and nonlinear inductance characteristics may be subject to torque ripple when working in the states of switching and single-phase conducting. In view of this, a fuzzy sliding-mode multiplex-loop control system with control quantities of speed, torque and current is designed, in which fuzzy sliding-mode control is adopted for speed loop and the speed difference is transformed into given torque through integral transformation. By comparing instantaneous torque with the given torque, switching tubes will be controlled to realize torque's closed-loop control. The torque is distributed to the windings of two simultaneously conducted phases during the commutation of motor and the equations of torque, current and rotor position angle are established. The winding currents will be obtained via the distributed torque to realize current's closed-loop control. Therefore, the torque ripple can be depressed effectively during the commutation and single-phase conducting. Simulation and experimental results show that the proposed method has a better control effect than the direct instantaneous torque control(DITC)with PID at low speeds, and the torque ripple can be stabilized within ±0.3 N·m, while becoming slight greater at medium speeds but within the range of ±0.8 N·m. So the torque ripple is depressed effectively by the proposed method.关键词：switched reluctance motor;motion equation;torque ripple;multiple-loop control;fuzzy sliding mode control663|4|3更新时间：2025-07-09
- 摘要：Aiming at the problem of multiple switches simultaneous turning on or off in single-phase three-level neutral point clamped(NPC)rectifiers, we put forward a space vector pulse width modulation(SVPWM)method. This method can reasonably design the modulation sequences inside each sector, and add transition modulation sequences in sector switch, so as to ensure the continuity of switching states. On the basis of analyzing the influence of each switching state on the neutral point voltage, this method selects appropriate redundant small vector according to the neutral point voltage and grid current, so as to achieve the neutral point voltage control. In addition, by using redundant zero vectors, this method can achieve the effect of frequency doubling. For this SVPWM method, a prototype was built to carry out experimental research. The experimental results showed that the proposed SVPWM method can guarantee only one switch turning on or off at one time, and the change of the output voltage is always half the DC side voltage, and that the phase of the grid voltage is the same as that of the grid current, with good dynamic performance. This method can realize the neutral point voltage control with fast dynamic response speed and accurate steady control.关键词：single phase three-level neutral point clamped(NPC)rectifier;sector transition;neutral pointvoltage control757|4|1更新时间：2025-07-09
- 摘要：A numerical simulation method was adopted to study the pressure change and fluid thermal stratification in liquid oxygen tank during the ascent process by a user-defined function(UDF)considering the aerodynamic heat and space radiations. The influences of atmosphere physical parameters, flight acceleration and phase change occurring in the liquid-vapor interface on the tank pressure and fluid temperature distribution were taken into account in the present numerical model. The calculation results showed that aerodynamic heat has great influence on the tank pressurization frequency and with the increase of aerodynamic heat flux, the tank pressurization time increases and depressurization time reduces gradually. After 120 s flight, the aerodynamic heat flux reaches its maximum value, and its influence on the tank pressurization behavior becomes most prominent. At this moment, the minimum tank pressure rise time and the maximum tank pressure reduction time are 4 s and 13 s, respectively. During the pressurization process without outflow, the tank pressure fluctuates within the set pressure range, and the phase change is condensation at the interface. The liquid mass increases about 11.05 kg while the ullage mass decreases about 1.52 kg in this process. When it is in the outflow period, the tank pressure decreases with the continuous injection of pressurized gas, and the ullage mass shows a fluctuating increase. Both the gas and liquid temperatures boost to higher temperatures with time. As the space radiation leakage leads to the temperature increase of drainage liquid, and hence resulting in safety issues for the rocket engine, some effective measures should be taken to reduce the space leakage.关键词：ascent process;aerodynamic heat;space radiation;tank pressure change;thermal stratification713|4|2更新时间：2025-07-09
- 摘要：To quickly analyze the flutter boundary condition and response characteristics of transonic nonlinear aeroelastic systems, a CFD based aeroelastic reduced order model(ROM)was built in this paper through a proper orthogonal decomposition(POD)method. To implement this process, a full order linearized time domain model was built firstly by Taylor expression on the nonlinear steady CFD flow field; then a fluid ROM was obtained through the POD method Afterwards, an aeroelastic ROM was built by coupling the fluid ROM with structural dynamic equations. An international standard model AGARD 445.6 wing was taken as the test case to illustrate the results. Some important parameters in ROM establishment such as steady flow field, time step and the process of generation of sample dates were systematically studied. The research indicates that if the steady flow field doesn't have good convergence performance, the linearized model may have unstable and that the responses may have numerical oscillation and become unstable as the large time step is selected in the ROM calculation. In order to capture more flow characteristics of the flow field, the generation of POD sample dates should ensure adequate response time. The ROM built in this paper has the same accuracy with the nonlinear CFD/CSD coupling system and it is a low order state space model which can be applied to system characteristics analysis and flutter suppression design. Compared with CFD/CSD coupled method, the computational efficiency can be improved about 3 to 6 orders.关键词：CFD/CSD coupling;reduced order model;proper orthogonal decomposition;flutter693|4|3更新时间：2025-07-09
- 摘要：In order to meet the requirements of low dispersive and low dissipative numerical discretization schemes in computational aero-acoustics, the spectral element method combined with Lighthill's acoustic analogy theory for the simulation of aeroacoustic problems is investigated. Taking the second temporal derivative of pseudopressure as the source of the inhomogeneous wave equation, and space discretization using spectral element method time discretization using implicit Newmark method, under the C-E-M absorbing boundary condition the acoustic field generated by a co-rotating spinning vortex pair is solved. This co-rotating vortex pair consists of two point vortices separated by a fixed distance of 2r0 with a circulation intensity Γ. The incompressible flow field is obtained using the complex potential theory, and the acoustic source terms are computed using these hydrodynamic quantities. The acoustic pressure results are evaluated by comparing them with the analytical solution obtained from the matched asymptotic expansion(MAE)method The numerical solutions are in good agreement with the analytical solutions. The results show that the spectral element method can obtain high accuracy using only eleven grids in one wavelength. In the case of the same number of grids, the smaller the time step, the smaller the error between numerical solution and analytical solution. Finally, it is proved that the aero-acoustic problems induced by incompressible flows can be solved with high accuracy by using the second temporal derivative of the pseudopressure as the acoustic source.关键词：computational aero-acoustics;spectral element method;acoustic analogy theory;absorbing boundary condition;finite element method;co-rotating spinning vortex pair709|4|1更新时间：2025-07-09
- 摘要：No baseline exists to evaluate the contact characteristics for deterministic contact model owing to the discontinuity, overlapping and missing of the asperity-peak. Based on the criteria of 3-point peak and 3-point valley, the middle higher peak or lower valley can be firstly identified as the true one in the three continuous peaks or valleys, and then a new asperity-peak of “valley-peak-valley” mode is defined. The proposed criterion is validated through a set of different surface profiles, and compared with other criteria found in the literature. The results show the huge influence obtained after using these different criteria. The number of asperity peaks decreases obviously with the increasing sampling interval, however, the mean asperity-peak radii and heights increase. The effects of different criteria on the calculated asperity-peak properties become almost negligible when the sampling interval is below 0.5 μm. The number of asperity peaks increases slightly with the decreasing surface roughness, and a similar tendency is found for the mean radii while the mean heights have an opposite effect. This criterion can provide a baseline for the evolution of the contact characteristics.关键词：rough surface;asperity peak;identification criteria;asperity-peak radius654|5|5更新时间：2025-07-09
- 摘要：A laser rotary grooving method on metal bar for low-stress shearing was developed to improve the precision of billets. A mathematical model was established through theoretical analysis on the laser rotary grooving process of 40Cr bars, and then L25(56)orthogonal tests were conducted to study the influence of factors including the laser parameters such as peak power(Pk), pulse width(τ)and pulse frequency(f), and the processing parameters such as processing speed(n), defocusing amount(s)and repeat turns(N). The influence order and optimum range of these factors were obtained by means of ANOVA analysis, and further shearing experiment was carried out on 40Cr bars. The results indicate that the influence order of the factors is N>s>Pk>f>τ>n, and the F values of N and s are 11.925 and 5.268 respectively, both of which have remarkable effects. The optimum ranges of these influencing factors are: Pk≥9.6 kW, τ≥0.3 ms, 3≤N≤10, 10 r/min≤n≤25 r/min, and s=0 mm. The sum of squares of errors(ε)between theoretical depth and real depth is 0.112 mm2 which proves that the calculation formula of theoretical groove depth h is accurate. Compared with the 40Cr billets processed by traditional shearing, the sheared surface inclination is 0.3°, and the weight tolerance is only 0.35%, resulting in an accuracy improvement of more than 13 times and 8 times, respectively.关键词：metallic bar;laser rotary grooving;low-stress shearing;annular groove617|4|2更新时间：2025-07-09
- 摘要：To avoid frequent mode switching and optimize the system control parameters for multi-mode hybrid energy storage system(HESS), a mode switch strategy with double parameter optimization(DPO)is proposed. Combining the state of charge(SOC)of ultra-capacitor(UC), power demand and the component efficiency, the DPO is integrated with the hysteresis control based on the real-time average power. The frequent mode switching can be effectively avoided and the system stability of the multi-mode HESS can be improved via the hysteresis control. To achieve the optimization of the overall system efficiency, the goal function of the simulated annealing optimization is established. The simulations and experiments verify the effectiveness of the DPO switch strategy. A comparison shows that the DPO switch strategy enables to reduce the frequencies of mode switching and of battery power output. The system stability and the battery safety are effectively guaranteed, and the overall system efficiency is improved and the battery life is extended simultaneously. Compared with the rule-based strategy, the overall system efficiency is improved up to 1.8%.关键词：electric vehicles;hybrid energy storage system;double parameter optimization;switch control strategy661|4|0更新时间：2025-07-09
- 摘要：To comprehensively coordinate tracking capability, fuel economy, driver comfortable response and car-following safety, a vehicular multi-objective adaptive cruise control(ACC)algorithm is designed, and an integrated longitudinal kinematic model of ACC system including vehicle model and its relationship with preceding vehicle is established. The quadratic objective functions that consider the contradictions between minimal tracking error, low fuel consumption and driver dynamic car-following behavior are developed, and the linear constraints that ensure dynamic car-following, desired comfortable response and driving safety are designed. Following model predictive control theory, the design of multi-objective ACC algorithm can be transformed into an online quadratic programming problem with multi-constraints. Adopting feedback correction mechanism, the modeling mismatch and external disturbances are greatly weakened to improve the control system robustness. Vector relaxation factors are introduced to deal with the non-feasible solution from hard constraints in the optimization process. The simulations show that the proposed algorithm can reduce fuel consumption by 9.3% and decrease tracking error index by 21.7% compared with LQR case in preceding vehicle cycle scenario, thus a good vehicle tracking is realized and the driver desired car following characteristics are satisfied.关键词：adaptive cruise control;multi-objective;model predictive control;feedback correction;vector relaxation factors759|4|9更新时间：2025-07-09
- 摘要：To reveal the vibration and acoustic radiation mechanism of propeller-shaft-hull coupled system in low-frequency, the three-dimensional sono-elasticity theory and acoustic analysis software is applied to analyze the relationship between the individual structural modal frequency and the propeller-shaft-hull coupled structure response frequency by the transfer characteristics of the propeller, propulsion shafting and hull. And the dominant modes corresponding to the peaks of vibration and acoustic radiation of the propeller-shaft-hull system under the longitudinal exciting and the lateral exciting are obtained. The results show that the oscillations of the blades have a great influence on the propeller-shaft system, especially the umbrella-form bending oscillation of the blades contributed significantly to longitudinal vibration and sound radiation of the propeller-shaft-hull system. The longitudinal peaks of vibration and acoustic radiation of the propeller-shaft-hull are interrelated to the 1st and 2nd longitudinal modes of the hull, the 1st longitudinal mode of the propeller-shaft system and the 1st umbrella-form bending mode of the propeller blades. The lateral peaks of vibration and acoustic radiation of the propeller-shaft-hull are interrelated to the bending modes of the hull and the propeller-shaft system. The total acoustic power under longitudinal exciting is significantly higher than that under lateral exciting.关键词：propeller-shaft-hull;vibration;acoustic radiation;dominant mode695|4|1更新时间：2025-07-09
- 摘要：To satisfy the requirement for environmental control of relics preservation in archaeology museums a preservation strategy for reintegrating primitive environment is proposed, in which some environmental parameters are strictly restricted in the soil-air coupled environment. In order to verify this technique, a laboratory room with a funerary pit was constructed to simulate a large open exhibition hall of archaeology museums, and a capillary radiant system was built to perform the environmental control for relics preservation. The field test showed that the capillary radiant system provided a more stable condition for the unearthed relics in the funerary pit. Experimental results proved that the temperature fluctuation of preservation area was reduced from 3.6 to 1.6 ℃, the average temperature difference of soil-air coupled environment decreased from 2.1 to 0.3 ℃, and the average temperature difference across the relic decreased from 3.8 to 0.8 ℃. Meanwhile, the air velocity in the preservation was controlled within 0.06 m/s, which is well below the upper limit value of 0.15 m/s prescribed for museums. The proposed preservation method is effective in mitigating heat and mass transfer and creating a more balanced environment for relics preservation.关键词：archaeology museum;relics preservation;in-situ environment;environmental control671|4|1更新时间：2025-07-09
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