Table of Content

24 April 2017, Volume 38 Issue 4

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Contents

2017, 38(4):  0. 

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Paper

Influence of Rotating Speed on Local Lubrication and Friction Characteristics of Wet Clutch

ZHAO Er-hui, MA Biao, LI He-yan, DU Qiu, LI Hui-zhu, MA Cheng-nan

2017, 38(4):  625-633.  doi:10.3969/j.issn.1000-1093.2017.04.001

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This work focuses on the influence of rotating speed on local lubrication and friction charac- teristics of wet clutch. A thermal mixed lubrication model in plane contacts is developed, and the pin-on-disc tests are conducted on universal material tester (UMT). Local pressure distribution, load sharing ratio, contact area ratio, local temperature rise and friction coefficient are analyzed. The results show that, as the rotating speed rises, hydrodynamic pressure grows significantly, while real contact area of friction pair reduces obviously. The main normal load is supported by hydrodynamic film. The friction coefficient is mainly affected by the change of asperity contact area, and has rough congruent relationship with the real contact area ratio. Key

Research on Ammonia Slip and Control of Diesel Engine SCR System

YUE Guang-zhao， LIU Xing-hua， QIU Tao

2017, 38(4):  634-642.  doi:10.3969/j.issn.1000-1093.2017.04.002

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The prediction and control of ammonia slip are the key issues of selective catalytic reduction (SCR) system. A SCR sample test bench was built. The adsorption and desorption characteristics of ammonia in V₂O₅-WO₃/TiO₂ catalyst are studied, and the effects of NH₃/NO_x ratio and catalyst temperature on ammonia slip are analyzed. The results show that the ammonia slip increases rapidly once ammonia leaks. The prediction of critical point of ammonia slip is very crucial for the control of ammonia slip. When the ammonia slip reachs to a critical point, the ammonia storage saturation level is not changed with the change in NH₃/NO_x ratio and catalyst temperature. When NH₃/NO_x ratio is set to 0.7, 1.0 and 1.4, the ammonia storage saturation level is 79%, 75% and 76%. The value of ammonia storage saturation level maintains fluctuations in the rangg of about 76.7% when the ammonia slip reachs to the critical point. The ammonia storage saturation level is related to the ammonia slip critical point. The control method of ammonia slip is designed based on the correlation between ammonia saturation level and ammonia slip critical point. The control method was used for SCR, and the European transient cycle (ETC) test of engine was performed. The ETC test results show that the brake specific emission of outlet NO_x is reduced to 2.45 g/(kW·h), the average ammonia slip is 3.7 ×10^-6, and the peak ammonia slip is 12.8×10^-6, which meet the requirements of national IV emission regulations. Key

Effects of Driving Coil Connection Modes on Emission Efficiency of MFEL

FAN Guang-cheng， JIANG Ming-yang， LONG Xiao-fei， DENG Hui-min， YAN Zhong-ming， WANG Yu

2017, 38(4):  643-650.  doi:10.3969/j.issn.1000-1093.2017.04.003

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Multipole field electromagnetic launcher (MFEL) is a novel electromagnetic launching technology. MFEL has the numerous adjustable parameters and flexible driving coil connection modes, which can significantly affect the efficiency of system. The formula of repulsion force on armature and waveform matching problem are analyzed based on the equivalent circuit model, and the influence of driving coil connection mode on emission efficiency under different voltages (capacitances) and multi-stage electromagnetic launch is studied by using the electromagnetic finite element method. The simulated results indicate that different voltages (capacitances) need to match with different driving coil connection modes in order to achieve greater emission efficiency. In the case of multi-stage sextupole field electromagnetic launch, the driving coil connection modes also should be changed with armature speed, which can realize waveform matching well and improve the emission efficiency with the slight change of capacitance.Key

Dynamic Response of Composite Rail during Launch Process of Electromagnetic Railgun

TIAN Zhen-guo, MENG Xiao-yong, AN Xue-yun, BAI Xiang-zhong

2017, 38(4):  651-657.  doi:10.3969/j.issn.1000-1093.2017.04.004

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Armature is subjected to an electromagnetic force to move along the composite rail when electric current flows into the electromagnetic rail. The inner surface of the rail may be worn and planed due to ampere force and armature pressure, which limits the service life of the electromagnetic rail gun. Copper-based composite rail has good conductivity, corrosion resistance and higher strength. The composite rail is simplified as an elastic foundation beam, and its mechanical characteristics are analyzed. The general solution of the dynamic deflection of composite rail under moving load is obtained by using the two- dimensional Fourier transform. The dynamic response of the composite rail under the launching of electromagnetic railgun is obtained. The influences of the geometrical dimensions of composite rail and the input voltage on the dynamic response of composite rail are analyzed. The results show that the influence of armature pressure on the rail deformation is much larger than that of the repulsive force, and the dynamic property of rail can be improved by using the reasonable proportion of composite layer thickness. Key

Application of Pulse Power Supply with RSD Switch in Electromagnetic Launch

ZHANG Ya-zhou, LI Zhen-xiao, TIAN Hui, LI Hai-yuan, LI Bao-ming

2017, 38(4):  658-663.  doi:10.3969/j.issn.1000-1093.2017.04.005

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A capacitor-based pulsed power supply (PPS) with reversely switched dynistor (RSD) is develop to study the launch mechanism of electromagnetic railguns. The RSD for which controlled plasma converter technology is used shows the following characteristics: simultaneous switching response in whole area, lower switch-on losses, higher power capacity, higher current transfer efficiency and long service life. A multi-module parallel structure with sixteen 64 kJ pulse power modules is applied. PPS adopts a compact and integrated design as well as built-in functions, such as charging, control, protection and measurement. Operational voltage of PPS is 18 kV, the stored energy is 1 MJ, the discharge waveform can be adjusted through the sequential control, and the short-circuit synchronization discharge peak current is 960 kA. Several launch tests were conducted on 20 mm caliber electromagnetic launching (EML) device with PPS, The experimental results show that the system has high reliability, and is capable of outputting adjustable current waveform. PPS can fulfill the research needs of hypervelocity launch experiment in EML. Key

Reliability Analysis and Improvement of MEMS-based Safety and Arming Device in Fuze

TU Hong-mao, SUN Zhi-li, QIAN Yun-peng , LIU Qin

2017, 38(4):  664-672.  doi:10.3969/j.issn.1000-1093.2017.04.006

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The quantitative reliability assessment of a MEMS-based safety and arming (MEMS S&A) device in fuze is performed based on the structural design and simulation. The structural design of MEMS S&A is then improved and verified through experiment. A primary design of MEMS S&A device is presented. The functional requirements of the key structures in the device are proposed according to the operating environment of small-caliber munition fuzes. Finite element (FE) simulation is adopted to evaluate the design. The structural reliability simulation method based on FE simulation and its implementation procedures are proposed, which can help to quantify the reliability of the device. An efficient CAE software integration method using ANSYS as an example is presented to facilitate the repetitive FE-based calculations. The reliability of the key structures of the device is evaluated, where the randomness of loading, geometric parameters and material properties are taken into account. The significant factors are also identified for further structural improvements. A prototype of MEMS-based S&A device is manufactured, which is delivered to centrifugal experiments. Experimental results demonstrate the feasibility of the design. Key

Design Method of Energy Isolation System for Fuze Setting via Primer

LIAO Xiang, LI Hao-jie, ZHANG He

2017, 38(4):  673-678.  doi:10.3969/j.issn.1000-1093.2017.04.007

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In-bore real-time fuze setting via primer is needed to increase the ammunition first round hitting probability of current large or middle caliber gun. The energy isolation system is designed for isolating the setting energy from the primer firing circuit and the firing energy from the setting circuit by establishing the boundary conditions of the isolation system and giving a set of functions that meets the boundary conditions. An energy isolation system for a specific kind of firing energy is designed by setting the parameter values of the functions. The isolation system has been experimentally proved to successfully isolate the firing energy and the setting energy. The firing energy loss on isolation system is very small. Key

Thrust Measurement of Liquid-fueled Rotating Detonation Engine under Two-wave Collision Mode

ZHENG Quan, LI Bao-xing, WENG Chun-sheng, BAI Qiao-dong

2017, 38(4):  679-689.  doi:10.3969/j.issn.1000-1093.2017.04.008

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The ring-shaped arrangement continuous rotating detonation engine, in which the mixture of gasoline/oxygen-enriched air is injected, is test. The propagation characteristics, time-domain characteristics, frequency-domain characteristics and detonation height of self-sustained detonation wave under two-wave collision mode are analyzed in detail. One-dimensional thrust of the engine model under two-wave collision mode is measured. The experimental results show that the detonation has an average frequency of 2.174 kHz and an average velocity of 1 051 m/s, the detonation wave height is between 55 and 70 mm, the effective thrust is 607.3 N, the thrust per unit area is 8.587×10⁴ N/m², and the fuel specific impulse is 735.1 s under the operating conditions of 0.82 equivalence ratio, 945.3 g/s oxygen-enriched air (34.3%O₂ and 65.7% N₂) and 84.3 g/s gasoline. It shows that the engine thrust under two-wave collision mode fluctuates obviously, the thrust oscillates around the average thrust, and the vibration frequency of engine and the propagation frequency of detonation wave are basically identical at the stable phase in the thrust curve. Key

Experimental Study of Critical Diameter of DNAN-based Aluminized Melt-cast Explosives

ZHANG Wei, ZHOU Lin, ZHANG Xiang-rong, YANG Yan-peng, CAO Tong-tang

2017, 38(4):  690-694.  doi:10.3969/j.issn.1000-1093.2017.04.009

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In order to reveal the detonation propagation characteristics of DNAN (2,4-dinitroanisole)-based melt-cast explosives, and speed up the application of the explosives, the critical diameter of DNAN-based aluminized melt-cast explosives is measured by continuous wire method. The measured results demonstrate that the critical diameter of DNAN-based aluminized melt-cast explosives decreases with the increase in wt% of aluminum (0~30wt%) and the decrease in particle sizes of both aluminum (d₅₀:6 μm, 12 μm, 31 μm) and RDX (d₅₀:19 μm, 147 μm, 751 μm), and increases with the decrease in crystal quality of RDX. The investigation can provide a basic reference for both the formulation of DNAN-based aluminized melt-cast explosives and the warhead design. Key

Workbench-based Simulation Analysis of Multi-perforated Gun Propellant in Extrusion Process

CHEN Fu-hua， HU Xiao-qiu， LIU Zhi-tao

2017, 38(4):  695-703.  doi:10.3969/j.issn.1000-1093.2017.04.010

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In order to obtain the structural parameters of specific multi-perforated gun propellant mould, the fluid-solid coupling module of Workbench is used to simulate the extrusion process of gun propellant slurry in the mold cavity and the deformation process of needle holder. The influences of shrinkage angle and length of molding on the extrusion molding pressure and the deformation of needle holder system are analyzed by the single factor method. The result shows that the compactness of extruded propellant and the deformation of needle holder system increase with the increase in length of forming segment and pressure. With an increase in contraction angle, the pressure and compactness of extruded propellant increase, but the deformation of needle holder system decreases gradually. At more than 55°, the pressure amplitude increases and the amplitude of the system deformation decreases. The pressure difference between the contracting segment and the forming segment is gradually reducedfrom the inlet to the outlet, and the final pressure distribution is uniform. Key

Influence of Organic Fluorine-contained Additives on Condensed Combustion Products of Aluminized Polyether Propellants

WANG Wei-lun, LI Jian-min, YANG Rong-jie, LIU Zhu, LI Shi-peng

2017, 38(4):  704-710.  doi:10.3969/j.issn.1000-1093.2017.04.011

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To explore the influence of organic fluorine-contained additives on aluminum agglomeration during combustion of the aluminized polyether propellants, a high-speed video camera is used to monitor the combustion process of propellants, and the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), laser particle size analyzer, X-ray diffractometer and real-time particle size analyzer are used to analyze the morphology, size, composition and real-time particle size of condensed combustion products of propellants. The results show that the organic fluorine-contained additives contribute to reduce the size of burning aluminum particles. The coarse agglomerate size is reduced obviously after adding 2% organic fluorine-contained additives. The average diameter of condensed combustion products is decreased from 5.83 μm to 3.06 μm at 7 MPa. XRD results show that α-Al₂O₃ and θ-Al₂O₃ are nearly disappeared in condensed combustion products due to addition of organic fluorine-contained additives, in which δ-Al₂O₃ and γ-Al₂O₃ are generated. Key

Integrated Fault Detection and Fault Tolerant Control for Morphing Aircraft

CHENG Hao-yu, DONG Chao-yang, JIANG Wei-lai, WANG Qing, SUI Han

2017, 38(4):  711-721.  doi:10.3969/j.issn.1000-1093.2017.04.012

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Considering the state delay and missing measurements in the network environment, the closed-loop fault detection for the morphing aircrafts with alterable sweep wings is investigated based on the switched system theory. The morphing aircraft is modeled as switched system which takes the altitude, Mach and wing sweep angle as parameters. Based on the integrated design method, the mode-dependent observer-based filter and the state estimation feedback controller are derived to ensure that the fault signal can be detected efficiently and the output can track the command signal accurately. The stability of the system is guaranteed by Lyapunov-Krasovskii functional method and average dwell time method. The sufficient existing conditions of filter and controller are given in the form of linear matrix inequalities (LMI). The simulated results show that the proposed method can detect the fault signal efficiently, the output can be used to track the command signal, and the system is robust to parameter uncertainties. Key

Experimental Study of Pressure Characteristics during Deflagration Venting in a Square Vessel

ZHAO Tian-hui, GAO Kang-hua, WANG Ming-yang, LI Bin, SUN Song, GUO Qiang

2017, 38(4):  722-727.  doi:10.3969/j.issn.1000-1093.2017.04.013

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Experiments were conducted to study the explosion venting process of the ethylene-air mixtures in a square vessel with an open at one end. The influences of venting area,venting pressure and gas concentration on the development and distribution characteristics of pressure in the explosion venting process are studied, and some empirical formulas are discussed with the change of peak pressure in the vessel. Results show that, for small venting area, the pressure shows obvious double peak phenomenon in the vessel, and the gas concentration mainly influences the second peak value; for large venting area, the gas concentration has little influence on the peak pressure; for small venting area and premixed gases closed to optimum concentration, the distribution of gas pressure in the vessel has remarkable gradient, and the distribution of pressure in the vessel is uniform; the error between the calculated value and experimental value varies greatly under different operating conditions. Key

Experimental Research on Transmission Accuracy of Multi-cable Drive

XIE Hong-wei, TAO Zhong, HOU Jun-zhan, ZHANG Wei-guo

2017, 38(4):  728-734.  doi:10.3969/j.issn.1000-1093.2017.04.014

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In order to determine the effects of preload force, load, rope number and rotate speed on cable drive transmission accuracy, an experiment is conducted to measure the transmission error under the condition of different cable numbers. The results show that the transmission error is composed of transmission backlash and slip error. When cable number remains constant, the transmission backlash decreases and the slip error increases with the increase in preload force. The transmission error increases with the increase in preload force. The transmission backlash and slip error increase with the increase in load, which causes a larger transmission error. When cable number is increased, the transmission backlash decreases slightly while the slip error decreases significantly. The influence of rotate speed on the transmission error can be ignored. What is proved to be an effective way for improving transmission precision is to increase rope number or decrease preload force under the condition of given load. Key

Study of Quick Prediction Method for Ship Corrosion Related Static Electric Field Based on Point Charge Source Model

JIANG Run-xiang， ZHANG Jia-wei， LIN Chun-sheng

2017, 38(4):  735-743.  doi:10.3969/j.issn.1000-1093.2017.04.015

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A method of rapidly establishing the prediction model based on the point charge source is proposed for the prediction of ship corrosion related static electric field. The reasonable division of ship structure is set, and the mixed potential of ship is calculated based on mixed electrode potential. The functional relationship between potential and current of point electrode is established based on the material polarization curve and the electrochemical system’s current sum which is zero. The current of point electrode is calculated using least squares method, and the ship corrosion related static electric field is predicted using the potential calculation method of point charge under three-layered medium. The effectiveness of the proposed method is verified by using the surface ship simulation data and the ship model test results. The results show that the proposed method can be used for fast prediction of ship corrosion related static electric field. Key

Synchronous Design of Electrode and Its Feeding Path in EDM for Cowled Integral Impeller

ZHAO Jian-she， ZHOU Xue-de， ZHOU Xu-jiao， WANG Wen-feng

2017, 38(4):  744-749.  doi:10.3969/j.issn.1000-1093.2017.04.016

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Electrical discharge machining (EDM) is an important process technique to machine the cowled integral impeller, and the processing quality and efficiency are directly influenced by the design of electrode and its feeding path. The design of electrode and its feeding path is very complicated because of the narrow and twisted channel between two blades. A synchronous design method of electrode and its feeding path is put forward to get a maximum stiffness electrode with complete forming surface corresponding to the blade's surface, and its implement method is also studied based on UG software. The design efficiency, machining accuracy and stability are all improved significantly. A cowled integral impeller's EDM experiment is verified. Key

Optimization Priority Analysis of Precision Gear Manufacturing Process Based on AHP Fuzzy Comprehensive Evaluation Method

LI Qiang, XIE Li-yang, LI Hai-yang, ZHANG Fang-min, SONG Jia-xin

2017, 38(4):  750-757.  doi:10.3969/j.issn.1000-1093.2017.04.017

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The traditional failure mode effect and criticality analysis (FMECA) is often used in product risk analysis of failure mode, which does not involve the technological parameter optimization priority analysis of product manufacturing process, and the unreasonable weight distribution of the severity, probability of occurrence and detective difficulty exists in risk priority number (RPN) analysis. A process optimization priority number (POPN) analysis method is proposed by referring to the RPN method of traditional FMECA, taking the manufacturing process of a precision gear as the research object, in which the current technology level and technology improvement cost are considered. And then the optimization priority levels of all technology parameters are evaluated and sequenced based on the analytic hierarchy process fuzzy comprehensive evaluation method. According to the evaluated results, the improvement projects of important technology parameters are presented to increase the reliability and supportability of precision gear products. Key

Improved Cuckoo Search Algorithm for Reliability Sampling Inspection Program in Binomial Case

GUO Zhi-ming, LI Chang-fu, JI Guang-zhen, LIU Qin, QIAN Yun-peng, HU Bing-su

2017, 38(4):  758-765.  doi:10.3969/j.issn.1000-1093.2017.04.018

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The design of reliability sampling inspection program for the success or failure products is an issue to be solved in reliability test. Meta-heuristic algorithm provides a new idea to solve the problem. Cuckoo search algorithm is a new meta-heuristic algorithm, and has been widely used in many fields because of its simplicity but efficiency. A model for reliability sampling inspection program is developed to minimize the risk. The mechanism of the cuckoo search algorithm is expounded. For the local search efficiency of the algorithm, an adaptive detection probability is proposed to balance the global search and local search efficiencies. The result of a case study reveals that the proposed method is feasible and effective. Key

Research on Phased-mission Success Probability Assessment under Random Common Cause Failures

CAO Wen-bin， HU Qi-wei， SU Xu-jun， ZHAO Jian-min

2017, 38(4):  766-775.  doi:10.3969/j.issn.1000-1093.2017.04.019

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Common cause failure exists in the performing process of military equipment mission. The reasonable modeling of the common cause failure events is of great significance to the accurate assessment of mission success probability. A kind of random common cause failure has not been considered in the existing mission success probability assessment models for phased-mission system. The implicit BDD (binary decision diagrams) method is used to model the phased-mission success probability when the occurrence of the random common cause failure event follows a certain distribution. A real example is used to verify the validity of the proposed model. The results show that the proposed model can be used to assess the phased-mission success probability considering random common cause failure, and the reasonable modeling mission profile contributes to the accurate evaluation of mission success probability. Key

Reliability Analysis of Phased-mission System with Multiple States Based on Discrete Event Simulation

SU Xu-jun, LYU Xue-zhi

2017, 38(4):  776-784.  doi:10.3969/j.issn.1000-1093.2017.04.020

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An algorithm of phased-mission system with multiple states is presented. The concepts of phased-mission system and its features are discussed, and an active standby (AS) tree structure method is proposed to depict the system structure of each phase. The behaviors of phased-mission system with multiple states are discussed based on state chart. According to discrete event simulation concept,a simulation algorithm is presented to estimate the reliability parameters of phased-mission system with multiple states. A case-study is introduced to verify the algorithm. The proposed simulation algorithm is very practical and versatile. The algorithm can be used to describe the complex behaviors of phased-mission system flexibly and obtain the more reliability parameters to understand the system operation. Key

Fractional Order Discrete Grey Model and Its Application in Spare Parts Demand Forecasting

PAN Xian-jun, ZHANG Wei, ZHAO Tian, GUO Xiao-Qiang

2017, 38(4):  785-792.  doi:10.3969/j.issn.1000-1093.2017.04.021

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A method of applying fractional GM(r,1) to forecast the demand of the spare parts is proposed for a new concept weapon because of the lack of comparable existing equipment, less historical data on spare parts demand, and the lack of understanding the supportability of equipment. The perturbation bound of GM(r,1) is proven to be smaller than the perturbation bound of GM(1,1) by using the matrix perturbation theory. p-order cumulative matrix is obtained by the first-order cumulative matrix and its matrix multiplication. Based on fractional order differential equation theory, the p-order accumulative matrix is extended to the r fractional order accumulative matrix, and a fractional accumulative gray model GM(r,1) is established. r fractional order difference matrix is obtained by matrix inversion, and the calculation method of r fractional difference is simplified. The optimal value of r in GM(r,1) is determined through genetic algorithm (GA). The GM(r,1) model is applied to forecast the demand of spare parts. The experimental results show that GM(r, 1) model has better prediction performance than GM (1,1) model. Key

Sliding Mode Control of Cascade Pneumatic Muscles of Elbow Joint Based on Disturbance Observer

WANG Bin-rui， SHEN Guo-yang， JIN Ying-lian， WANG Ling

2017, 38(4):  793-801.  doi:10.3969/j.issn.1000-1093.2017.04.022

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The design and control of elbow joint are the research priorities of humanoid arm. To obtain the elbow joint model, a test platform is constructed for static modeling of a single pneumatic muscle,and then a nominal model of cascade elbow joint is established. The least square parameter identification is used to obtain the parameters of model. A sliding mode control law is designed based on Luenberger disturbance observer. The elbow joint location tracking with proportion integration differentiation (PID) control, sliding mode control (SMC) and sliding mode control based on disturbance observer (SMCDO) are simulated. Three control algorithms are tested by taking half a bottle of mineral water held at the end of humanoid arm as a load and uncertain outside disturbance. The simulated and experimental results show that the location tracking accuracy and robustness of sliding mode control based on disturbance observer are better than those of sliding mode control and PID control. Key

Release Operation Method and Experiment of Micro Objects Based on Vibration Effect

HU Jun-feng, CAI Jian-yang

2017, 38(4):  802-809.  doi:10.3969/j.issn.1000-1093.2017.04.023

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A release operation method based on piezoelectric vibration control is proposed to solve the adhesion problem of micro gripper in the process of clamping tiny objects. It is proved by the theory of elastic adhesion that the inertia force caused by the piezoelectric vibration effect can be used to overcome the adhesion between the micro gripper and small object. And it is illustrated that the proposed method is feasible. A dynamic model for illustrating the vibration characteristics of the piezoelectric micro-gripper is established by using the experimental method. The conditions on the amplitude and frequency of input voltage of the actuator during the stable release of the micro objects are obtained based on the proposed model. An experimental platform with a micro gripper is built in order to carry on the experiments on the release of small objects. The experimental results show that the proposed method is feasible, and the smaller the sizes of the tiny objects are, more difficult the release is. The greater inertia force is needed to overcome the adhesion force. Key

Research Notes

Testing Method for Relative Activation Time of Fuze Chemical Battery Based on Geomagnetism Turns-counting

YANG Wen-zhong， DING Li-bo， ZHANG He

2017, 38(4):  810-816.  doi:10.3969/j.issn.1000-1093.2017.04.024

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A method to use the memory testing technology for the simultaneous record of the voltage curve of chemical battery and the geomagnetic signal in the trajectory is presented for the test requirement of activation time of small-caliber fuze chemical battery. The relative activation time of chemical battery and the testing principle are given. The generation method of mutation magnetic field and the distortion performance of local magnetic field are analyzed, and a dynamic recovery test method and the experimental data are given. The experimental results show that the proposed method can be use to get the voltage curve of chemical battery, the time when a projectile passes a muzzle, and the relative activation time of chemical battery, which has an important significance to optimize the cell performance and improve the precision of fuze. Key

Method for Evaluating Angle Measurement Uncertainty of Gun Clinometer

WEN Hai, CHENG Bin, ZHANG Kai-wei

2017, 38(4):  817-823.  doi:10.3969/j.issn.1000-1093.2017.04.025

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In order to facilitate understanding, exchange and comparison, a clinometer is asked to provide an uncertainty in the competition task. In the actual measurement, the evaluation of class A is difficult when the sample size is small.A laboratory calibration process is proposed to approximate the actual measurement process. The historical calibration data and linear regression are used to establish a class A evaluation method based on statistical process control technology. The method is proved to be feasible by using the historical calibration data of a certain type of clinometer and the MATLAB tool. The GUM me- thod is used to obtain the extended uncertainty curve at any angle. This conclusion is verified by Monte Carlo method. Key

Study of Leakage Flow Boundary Model-based Sealing Labyrinth Analysis Method

FU Xin， CAO Yong-hua， ZHANG Yi-bin， ZHU Chao

2017, 38(4):  824-832.  doi:10.3969/j.issn.1000-1093.2017.04.026

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In view of the complex structure of labyrinth channel, changing sealing gap and a large amount of grids in numerical simulation calculation domain, a high-speed straight-through sealing labyrinth structure adopting different sealing configuration parameters is investigated. A labyrinth leakage flow boundary model is established based on test results, which can reveal the effects of environmental parameters and sealing configuration parameters on sealing property. The results show that the proposed model can be used to repeat the experimental rule and reliably simulate the labyrinth leakage flow in multistage compressor. The calculated sresult shows that 0.5% flow leakage would result in decreasing the flow, pressure ratio and efficiency of a three-stage compressor by 1.4%, 0.3% and 1.1%, respectively. Key