DEM PARAMETERS CALIBRATION OF MIXED BIOMASS SAWDUST MODEL WITH MULTI-RESPONSE INDICATORS

Taking hybrid biomass sawdust as the material, carry out the simulation calibration experiment with JKR contact model based on DEM principle. The Plackett-Burman factorial experiment is carried out by Design-Expert for 10 related factors. Combined with the steepest climbing test scheme, according to the Box-Behnken experiment, the parameter calibration of the multi-response Indicators is completed. The results are as follows: the Poisson's ratio of hybrid sawdust is 0.30, the density is 399.22kg·m-3, the recovery coefficient between sawdust particles is 0.47, the rolling friction coefficient between sawdust particles is 0.39, and the parameter of surface energy density between sawdust particles (JKR) is 0.29J·m-2. Through the comparative verification experiment, it can be seen that the relative error of the repose angle is 3.41%, and the relative error of the stress-time response curve is less than 6.36%, which verifies the reliability of the calibration method, and provides a theoretical reference for the study of the constitutive characteristics of biomass materials and the densification mechanism.

Reliability Test Plan Based on Logistic-Exponential Distribution and Its Application

In this article, a reliability test plan is developed for Logistic-exponential distribution (LoED) under time truncated life test scheme. The distribution has been chosen because it can used to model lifetime of several reliability phenomenon and it performs better than many well known existing distributions. With the discussions of statistical properties of the aforesaid model, the reliability test plan has been established under the assumption of median quality characteristics when minimum confidence level P* is given. To quench the objective of the paper i.e; to serve as a guiding aid to the emerging practitioners, minimum sample sizes have been obtained by using binomial approximation and Poisson approximation for the proposed plan. Further, operating characteristic (OC) values for the various choices of quality level are placed. Also, minimum ratio of true median life to specified life has been presented for specified producer’s risk. Important findings of the proposed reliability test plan are given for considered value of k=0.75,1,2. To demonstrate the appropriateness of suggested reliability test plan is achieved using four real life situation.

Analysis of transmission box vibration characteristics under random road torsional excitation

Random road torsional excitation is a key excitation condition for transmission box vibration of tracked vehicles. In order to accurately analyze influences of random road torsional excitation on the vibration characteristics of the transmission box, a calculation method of this excitation for tracked vehicle is proposed based on the random expression of the roughness of standard road surface. Furthermore, random road torsional excitations under different road grades and vehicle speeds are simulated. With the finite element method and modal superposition method, the box body is discretized, and the elastic characteristics of the box body are characterized to explore the dynamics coupling mechanism of gear shafting and the box body. By considering bending-torsional coupling vibration of gear shafting under multi-source excitations, such as the fluctuated torque of engine and dynamic meshing stiffness of gears, dynamic coupling model of gear shafting and box body under random road torsional excitation is established. The dynamic response of the gearbox under random road torsion excitation is obtained by co-simulation with the variable step length Runge-Kutta method. Influences of different road grades, track preload and vehicle speeds on dynamic response characteristics of the gearbox are analyzed. Real vehicle road test scheme is designed to obtain surface acceleration response of the box body at different speeds on the cement road surface. Both test and simulation results are compared and analyzed to verify the accuracy of the simulation method, which provides a theoretical reference for dynamic optimization of the transmission box.

Investigation of the axial force on a varying-speed centrifugal pump impeller

Centrifugal impeller has high efficiency but obvious axial force problems because of the axial-to-radial flow direction change. It is easy to cause the over loading of thrust bearing and damage shaft system. Especially in varying-speed centrifugal pumps, the mechanism, characteristics, and influence of impeller axial force is complex. Therefore, experimental and numerical studies are conducted to resolve these problems in this case. The impeller axial force is comparatively investigated by analyzing zonal components, visualizing internal flow, and resolving pressure attenuation law in clearances. This study provides a new test scheme based on force sensors for measuring the impeller axial force. The results show that the variation tendency of impeller axial force is similar to that of pump head. Flow patterns show that streamline-rotation angle decreases with the increase of flow rate in clearances. As the key factor affecting impeller axial force, the static pressure distribution in the clearances can be divided into specific variation stages to specify the mechanism. Specially in this varying-speed case, the blade axial force shifts from positive to negative with the decrease of rotation speed from high to low. This study provides a good reference for solving the axial force problems for centrifugal pumps.

Design and Verification of Flush Air Data Sensing Module with Navigation and Temperature Information

For aircraft which move in the atmosphere, the angle of attack and angle of sideslip cannot be measured precisely. This limits the precision of guidance and control systems, so the flush air data sensing system module with navigation and temperature information is designed for atmosphere parameter calculation. In this work the traditional parameter calculation method is improved, and a new algorithm which combines pressure data, temperature data and navigation data to calculate the atmosphere parameters is proposed. A ground experiment test scheme with a simulated flight environment is designed and the measured data is fitted and filtered to complete the experiments. The flush air data sensing module gets pressure data and temperature data of the atmosphere with sensors, and the measured data is integrated with navigation information to calculate the aircraft parameters of the angle of attack, angle of sideslip, dynamic pressure, static pressure, Mach number and so on. Calculated parameters can be transmitted to guidance and control systems to improve the attitude and trajectory precision for an aircraft. Experimental results show that the software and hardware of the flush air data system module with navigation and temperature information work well, and communication of various devices is normal. The flight status of aircraft can be precisely calculated online, which provides a useful reference for prospective wind tunnel experiments and flight tests.

Fruit Processing Equipment based on Model Processing

The technology and equipment of this study can improve the technical level of the equipment for peeling and cleaning of Camellia oleifera fruit. Based on the biological characteristics of Camellia oleifera fruit, the size distribution model of Camellia oleifera fruit was established, and the equipment structure and key parameters were determined based on the working principle and design method of the shelling and cleaning mechanism. Based on the analysis of the movement track of the shell stripping and cleaning executive parts, the test scheme is established, and it is optimized that when the crankshaft speed is 240-260r/min and the track speed is 0.4-0.6m/s, the treatment capacity can reach the level of 2000kg/h, and the purification rate is more than 99%. When the vibration frequency of the vibrating motor is set to 50Hz and the horizontal inclination of the separation belt is 50 ° ∼ 55 °, the cleaning effect of the equipment is the best.

Intelligent Parameter Inversion of Fractional-Order Model Based on BP Neural Network

To explore creep parameters and creep characteristics of salt rock, an Ansys numerical model of salt rock sample was established by using fractional creep constitutive model of salt rock, and an orthogonal test scheme was designed based on uniaxial compression test of salt rock samples. A large number of training data were obtained by combining the numerical model with the experimental scheme, and the model parameters were inverted by using the BP neural network. The model parameters are used for forwarding calculation, and the results are in good agreement with the measured strain data. This shows that the model parameter inversion method proposed in this paper can obtain reasonable parameter values and then accurately predict the creep behaviour of salt rock, which provides a good technical basis for related engineering practice and scientific research in the future.

Investigation on Clocking Effect of Diffuser in a Multi-Stage Centrifugal Pump

The clocking effect is an important phenomenon in the multi-stage Rotating machinery. In order to master the rules and mechanism of diffuser clocking effect on the performance of multi-stage centrifugal pump, the orthogonal tests were applied to design the test scheme. The energy performance and outlet pressure pulsation of a multi-stage centrifugal pump with different diffuser clocking positions were synchronously measured. It was found that the diffuser clocking position had little influence on the energy performance, but had an obvious effect on the outlet pressure pulsation. When the diffuser clocking positions were 0°, 30°, 30° and 30° (CL4), the effective value of outlet pressure pulsation and its amplitude at the main frequency (Impeller Rotation Frequency) were decreased the most, approximately 27.2 % and 38.5 % ,respectively. The CFD method was used to simulate the unsteady flow in the pump with the optimal diffuser clocking position (CL4) and without diffuser clocking position (CL1) respectively to reveal the mechanism of diffuser clocking effect. The simulation results showed that the change of diffuser clocking position can improve the inlet and outlet velocity distribution and reduce the area of high turbulent kinetic energy and the number of cores in the outlet flow passage, which is beneficial to the operation stability of the pump. Compared with the CL1, the hydraulic loss in the four diffusers was reduced by 2.43 %, 12.15 %, 11.43 % and 13.19 % respectively under the optimal diffuser clocking scheme (CL4), and the total reduction of hydraulic loss is about 1.11 % of the pump head.