Northwest Institute of Mechanical & Electrical Engineering
Northwest Institute of Mechanical & Electrical Engineering
Liu K.,Nanjing University of Science and Technology |
Yu Y.,Nanjing University of Science and Technology |
Zhao N.,Northwest Institute of Mechanical & Electrical Engineering
Journal of Harbin Institute of Technology (New Series) | Year: 2016
To investigate the spray characteristics of a new-type air-assist nozzle, three-dimensional laser phase Dopper analyzer (PDA) was used to measure the spray parameters. The external flow fields of the nozzle were simulated by means of computational fluid dynamics (CFD). The distributions of the diameter and the axial velocity for the droplets were analyzed respectively. The results indicate that, the mean diameter of the droplets fluctuates along the center axis. The distance between the measurement point and the nozzle increases, the axial velocity of the droplets decreases. The further the measurement point from the center axis is, the smaller the axial velocity of the droplets is. With the increase of the nozzle pressure drop, the axial velocity of the droplets improves while the mean diameter of the droplets is reduced, and the distribution uniformity of the droplets is better for the diameter. The simulation result agrees well with the experimental data. The average deviation ranges from 3.9% to 7.7%. © 2016, The Editorial Department of Journal of Harbin Institute of Technology. All right reserved.
Liu W.,Northwest Institute of Mechanical & Electrical Engineering |
Wei J.-G.,Northwest Institute of Mechanical & Electrical Engineering |
Wang Y.-W.,Northwest Institute of Mechanical & Electrical Engineering |
Zhang H.-H.,Northwest Institute of Mechanical & Electrical Engineering
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2016
A semi-closed pressure-loading vessel was designed to test the dynamic pressure bearing capacity of a laser ignition window. The mathematical model that describes the relationship between the propellant combustion and the pressure in the vessel was built and its validity was verified. The calculated results were fairly consistent with those achieved from tests. Then the vessel was used to test the bearing capacity of a sapphire window sample, the curves showing the pressure variation of the vessel were obtained and compared with those of the gun chamber. The results indicate that the sapphire window sample could satisfy the requirement of the gun's laser ignition. This vessel could simulate the actual dynamic pressure variation of the interior ballistic of the gun, which may provide a valid method for testing the dynamic pressure bearing capacity of the laser ignition window. © 2016, Editorial Board of Chinese Journal of High Pressure Physics. All right reserved.
Sun Y.-J.,Northwest Institute of Mechanical & Electrical Engineering |
Cui Q.-C.,Northwest Institute of Mechanical & Electrical Engineering |
Han X.-X.,Northwest Institute of Mechanical & Electrical Engineering |
Shi C.-M.,Northwest Institute of Mechanical & Electrical Engineering
Binggong Xuebao/Acta Armamentarii | Year: 2017
Solid-state phase transformation has significant effect on the evolution and magnitude of welding residual stress for armour steel during welding thermal cycle, while the current constitutive model can not take solid-state phase transformation into account. Based on heat transfer theory, solid-state phase transformation theory and continuum mechanics, a thermo-metallurgical-mechanical coupling constitutive model in which the effects of volumetric change, yield strength change and transformation induced plasticity(TRIP) on residual stresses due to solid-state phase transformation on welding residual stress are considered is established. The constitutive model is inserted into a general purpose implicit finite element program via user material subroutine UMAT. The change rules of temperature, microstructure and residual stresses are obtained for a butt welding of armour steel plates. The research results show that longitudinal residual stresses obtained from the coupling constitutive model are in good agreement with experimental results measured by X-ray diffraction perpendicular to weld centerline on the upper surface of the weldment. The correctness of developed computational method is confirmed, and TRIP has certain effects on the evolution of longitudinal residual stresses. For the magnitude of longitudinal residual stresses in the vicinity of weld zone, the fully-transformed region is less than partially-transformed region, and the partially-transformed region is less than untransformed region. © 2017, Editorial Board of Acta Armamentarii. All right reserved.
Jin Q.-M.,Northwest Institute of Mechanical & Electrical Engineering
Guti Huojian Jishu/Journal of Solid Rocket Technology | Year: 2017
In order to investigate the mechanical properties under different loading conditions of modified double-base propellants, some groups of tests at different strain rates and creep tests at different temperatures under tensile and compressive loads were done. The stress factor and strain factor of asymmetric effects are used to demonstrate the mechanical properties. The results show that the modified double base propellant has asymmetric mechanical effects in tension and compression loads, which are dependent on the strain rate and temperature. Expansion of the origin defects in materials, change of moving space of molecular chains and different mechanical properties between matrix and particle are considered to be the main inherent factors that lead to the asymmetric mechanical effects of modified double base propellants. © 2017, Editorial Dept. of JSRT. All right reserved.
Wang G.,University of Science and Technology of China |
Li K.,Northwest Institute of Mechanical & Electrical Engineering |
Li R.,Northwest Institute of Mechanical & Electrical Engineering
Bandaoti Guangdian/Semiconductor Optoelectronics | Year: 2016
Starting from the equations describing the relationship between the intracavity Iav, the incident Iin and the output beam Iout of a FPSOA, it is demonstrated that Iin is a single valued function of Iav. After expanding Iin into a third-order Taylor's series in terms of Iav approximately, the derivative of Iin with respect to Iav can be expressed as a quadratic equation in terms of Iav. Furthermore, it is verified that only when the quadratic equation owns two real roots, the FPSOA enters into bistable operation region. In other words, the discriminant of the quadratic equation being positive can be described as the necessary condition of bistability in FPSOAs. Numerical results agree well with the analytical formula. The results will afford a novel way for studying the bistability in other devices owning similar structures. © 2016, Editorial Office of Semiconductor Optoelectronics. All right reserved.
PubMed | Northwest Institute of Mechanical & Electrical Engineering, China Aerospace Science and Technology Corporation and Northwestern Polytechnical University
Type: Journal Article | Journal: Sensors (Basel, Switzerland) | Year: 2014
A dynamic attitude measurement system (DAMS) is developed based on a laser inertial navigation system (LINS). Three factors of the dynamic attitude measurement error using LINS are analyzed: dynamic error, time synchronization and phase lag. An optimal coning errors compensation algorithm is used to reduce coning errors, and two-axis wobbling verification experiments are presented in the paper. The tests indicate that the attitude accuracy is improved 2-fold by the algorithm. In order to decrease coning errors further, the attitude updating frequency is improved from 200 Hz to 2000 Hz. At the same time, a novel finite impulse response (FIR) filter with three notches is designed to filter the dither frequency of the ring laser gyro (RLG). The comparison tests suggest that the new filter is five times more effective than the old one. The paper indicates that phase-frequency characteristics of FIR filter and first-order holder of navigation computer constitute the main sources of phase lag in LINS. A formula to calculate the LINS attitude phase lag is introduced in the paper. The expressions of dynamic attitude errors induced by phase lag are derived. The paper proposes a novel synchronization mechanism that is able to simultaneously solve the problems of dynamic test synchronization and phase compensation. A single-axis turntable and a laser interferometer are applied to verify the synchronization mechanism. The experiments results show that the theoretically calculated values of phase lag and attitude error induced by phase lag can both match perfectly with testing data. The block diagram of DAMS and physical photos are presented in the paper. The final experiments demonstrate that the real-time attitude measurement accuracy of DAMS can reach up to 20 (1) and the synchronization error is less than 0.2 ms on the condition of three axes wobbling for 10 min.
Hu Z.-T.,Nanjing University of Science and Technology |
Yu Y.-G.,Nanjing University of Science and Technology |
Cao Y.-J.,Northwest Institute of Mechanical & Electrical Engineering
Hanneng Cailiao/Chinese Journal of Energetic Materials | Year: 2016
To explore the expansion characteristics of multiple wall combustion-gas jets which uniformly distributed along the circumferential direction under high temperature and high pressure in confined liquid working medium, the combustion gas generator and cylindrical filling liquid chamber were designed. The expansion processes of multiple wall jets were recorded by high-speed digital photographic system. The average axial displacements of multiple wall jets at different time were achieved by disposing the expansion sequence diagrams. It shows that the irregular interface induced by the Kelvin-Helmholtz instability exists in the entire jets expansion process. The effects of the number of orifices and the blasting injection pressure on expansion characteristics of multiple wall jets are discussed. The experimental results indicate that, as the number of orifices increase from four to eight, the axial expansion displacements of multiple jets decrease, at t=5 ms, the number of orifices increase from four to six, the axial expansion displacements decrease 8.3 percent, and it decrease 3.1 percent when the number of orifices increase from six to eight. The larger the blasting injection pressure, the greater the axial expansion velocity, the earlier jets get to the top of liquid filling chamber, at t=5 ms, the blasting injection pressure increase from 12 MPa to 20 MPa, the axial expansion velocity increase 20.1 percent, and it increase 19.9 percent when the blasting injection pressure increase from 20 MPa to 28 MPa. © 2016, Editorial Board of Chinese Chinese Journal of Energetic Materials. All right reserved.
Cao Y.-J.,Northwest Institute of Mechanical & Electrical Engineering |
Zhang X.-M.,Northwest Institute of Mechanical & Electrical Engineering |
Li Z.-F.,Northwest Institute of Mechanical & Electrical Engineering
Dandao Xuebao/Journal of Ballistics | Year: 2016
In order to achieve the safety launch of recoilless guns in the confined space,a new charge structure containing liquid balance body was designed.The interior ballistic experiment was carried out based on the new charge structure,and the interior ballistic model was established.The calculated results are in good agreement with the experimental results.On this basis,the effects of the initial liquid balance body mass,the liquid density,the propellant web size,the nozzle throat diameter and the engraving pressure on the interior ballistic performance were analyzed.Results show that the balance body mass has remarkable effect on the maximum chamber pressure and the muzzle velocity,while the effect of the liquid density is little.Larger propellant web size,smaller nozzle throat diameter and lower engraving pressure are in favor of improving the overall interior ballistic performance.The results can offer theoretical guidance for the interior ballistics and charge-structure design of new recoilless gun based on the liquid balance body. © 2016, Editorial Board of Journal of Ballistics. All right reserved.
Li C.,Northwest Institute of Mechanical & Electrical Engineering |
Chen M.,Northwest Institute of Mechanical & Electrical Engineering |
Han Y.,Northwest Institute of Mechanical & Electrical Engineering
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2015
For those position servo systems having time delay element, a design method is presented that the system possesses maximum phase margin under the same length of mid-frequency interval. Open loop gain crossover frequency is determined by letting the derivative of phase to angular frequency to zero. As a result, characteristics of phase margin and gain crossover frequency versus mid-frequency interval width are obtained. A new design method of position controller parameters is given and the designed system dynamic performance can be within the expected range. The robustness to open loop gain variation can be improved significantly. Moreover, in order to guarantee the servo system tracking precision, feedforward compensation to the servo system with time delay is executed. Through establishing position differential observer, numerical feedforward compensation with high signal to noise ratio is achieved. At last, a control platform based on permanent magnet synchronous motor (PMSM) position servo system is developed. Simulation and experimental results verify the effectiveness of the proposed approach, which can also apply to industry process control. © 2015, The editorial office of Transaction of China Electrotechnical Society. All right reserved.
Yongshou L.,Northwestern Polytechnical University |
Xindang H.,Northwestern Polytechnical University |
Xiaojun S.,Northwest Institute of Mechanical Electrical Engineering |
Jun L.,Northwestern Polytechnical University |
Zhufeng Y.,Northwestern Polytechnical University
Engineering Failure Analysis | Year: 2010
Load-transferred experiments and fatigue tests of the anti-double dog-bone riveted joints were carried out, and the fracture surfaces were observed by scanning electron microscopy (SEM) in this paper. Based on the finite element analysis (FEA), the multi-axial fatigue life of the anti-double dog-bone riveted joints has been predicted by Smith-Watson-Topper (S-W-T) method and Wang-Brown (W-B) method respectively. And the results of FEA were compared with the experiment results. The results show that because of the deformation of the rivets and the holes, the load transferred by the rivets decreases with external load increase. The fracture of joints all occur at rivet holes, and the crack initiates at the dog-bone specimen closed to the rivet head. Compared with the result of W-B method, the result of S-W-T method is more conservative and reliable. © 2010 Elsevier Ltd.