C2H2-O2-Ar和C2H2-N2O-Ar直接起爆形成爆轰的临界能量

采用高压电点火进行直接起爆形成爆轰,起爆能量通过放电过程中电流的输出信号确定。首先通 过实验测定并对比C2H2-O2-Ar和C2H2-N2O-Ar等2种混合物在各种初始状态下直接起爆形成爆轰的临界 起爆能量。实验结果表明,在相同状态下C2H2-N2O-Ar混合物的临界起爆能量显著高于C2H2-O2-Ar混合 物的。进一步基于各物质爆炸特征长度和爆轰临界管径的参量关系对临界起爆能量差异性进行分析,得到了 C2H2-N2O-Ar混合气体的爆轰临界管径预测曲线,并在此基础上得出C2H2-N2O-Ar混合物爆炸特征长度 与临界管径的关系为r0=2.5dc,而C2H2-O2-Ar两者关系为r0=2dc。结果清晰地表明,使用N2O 作为氧化 剂,爆炸特征长度与爆轰临界管径之间的比例因数增大,表明该物质直接起爆形成爆轰所需的起爆源单位能 量增大,因而直接形成爆轰的临界能量相应提高。     

Mechanisms of detonation transmission in layered H2-O2 mixtures

When a plane detonation propagating through an explosive comes into contact with a bounding explosive, different types of diffraction patterns, which may result in the transmission of a detonation into the bounding mixture, are observed. The nature of these diffraction patterns and the mode of detonation transmission depend on the properties of the primary and bounding explosives. An experimental and analytical study of such diffractions, which are fundamental to many explosive applications, has been conducted in a two channel shock tube, using H₂-O₂ mixtures of different equivalence ratios as the primary and bounding or secondary explosive. The combination of mixtures was varied from rich primary / lean secondary to lean primary / rich secondary since the nature of the diffraction was found to depend on whether the Chapman-Jouguet velocity of the primary mixture,D _p, was greater than or less than that of the secondary mixture,D _s. Schlieren framing photographs of the different diffraction patterns were obtained and used to measure shock and oblique detonation wave angles and velocities for the different diffraction patterns, and these were compared with the results of a steady-state shock-polar solution of the diffraction problem. Two basic types of diffraction and modes of detonation reinitiation were observed. WhenD _p>D _s, an oblique shock connecting the primary detonation to an oblique detonation in the secondary mixture was observed. WithD _p<D _s, two modes of reinitiation were observed. In some cases, ignition occurs behind the Mach reflection of the shock wave, which is transmitted into the secondary mixture when the primary detonation first comes into contact with it, from the walls of the shock tube. In other cases, a detonation is initiated in the secondary mixture when the reflected shock crosses the contact surface behind the incident detonation. These observed modes of Mach stem and contact surface ignition have also been observed in numerical simulations of layered detonation interactions, as has the combined oblique-shock oblique-detonation configuration whenD _p>D _s. WhenD _p>D _s, the primary wave acts like a wedge moving into the secondary mixture with velocityD _p after steady state has been reached, a configuration which also arises in oblique-detonation ramjets and hypervelocity drivers.     

2:2:1 Resonance in the Quasiperiodic Mathieu Equation

In this work, we investigate regions of stability in the vicinity of 2:2:1 resonance in the quasiperiodic Mathieu equation $$\frac{{d^2 x}}{{dt^2 }} + \left( {\delta + \varepsilon \cos t + \varepsilon \mu \cos \left( {1 + \varepsilon \Delta } \right)t} \right)x = 0,$$ using two successive perturbation methods. The parameters ∈ andμ are assumed to be small. The parameter ∈ serves forderiving the corresponding slow flow differential system and μserves to implement a second perturbation analysis on the slow flowsystem near its proper resonance. This strategy allows us to obtainanalytical expressions for the transition curves in the resonantquasiperiodic Mathieu equation. We compare the analytical results withthose of direct numerical integration. This work has application toparametrically excited systems in which there are two periodicdrivers, each with frequency close to twice the frequency of theunforced system.     

Numerical study of the detonation structure in rich H2?NO2/N2O4 and very lean H2?N2O mixtures

In some mixtures and under certain conditions, detonation soot records show substructures. In nitromethane and nitrogen tetroxide mixtures, particular cellular structures can be observed. This kind of structures has been reported as the so-called double cellular structure. One- and two-dimensional simulations of detonation have shown that the double cellular structure is related to a non-monotonous energy release. Two-step energy release is also observed in rich H₂−NO₂/N₂O₄ and in very lean H₂−N₂O mixtures. The present study aims at the investigation of the effect of the energy release profile on the detonation structure in these two mixtures through numerical simulations. The origin of the non-monotonous energy release is explained in both mixtures using one-dimensional simulations with detailed chemistry. Reduced kinetic schemes are obtained and used to perform two-dimensional simulations. It is shown that in rich H₂−NO₂/N₂O₄ mixtures, the double cellular structure appears, whereas in very lean H₂−N₂O mixtures, classical substructures are observed. Both behaviours are explained based on ZND calculations and previous stability results. Phenomenological considerations led the authors to link the formation of the double cellular structure with the appearance of a large scale instability mode (a super cellular structure).     

Direct initiation of detonation in cryogenic gaseous H2-O2 mixtures

Critical conditions for the direct initiation of self-sustained detonation in cryogenic hydrogen-oxygen mixtures are examined experimentally. These initial conditions are expected to depend mainly on four parameters: the equivalence ratio of the mixture, the amount of the initial energy deposition, the initial temperature and pressure of the mixture. These critical conditions are determined by fixing alternatively three of these parameters and varying the fourth one from subcritical to supercritical detonation conditions. Results are presented for initial pressuresP _o and equivalence ratios ranging from 0.3 to 1 bar and from 1 to 2 respectively, for the two initial temperaturesT _o, 123 K and 293 K. These results indicate that for the lowest values of the initial pressure, a decrease of initial temperature may favour the onset of detonation. Whatever the initial conditions, the measured detonation pressures and velocities are in reasonably good agreement with the corresponding Chapman-Jouguet values computed using the ideal-gas equation of state.     

氨基乙酸-H2O2体系抛光液中铜的化学机械抛光研究

在CP-4型CMP试验机上采用5μm厚的铜镀层片研究了氨基乙酸-H2O2体系抛光液中铜的化学机械抛光行为,分别采用Sartorius 1712MP8型电子天平和WYKO MHT-Ⅲ型光干涉表面形貌仪检测抛光去除率和抛光后表面粗糙度,用CHI660A型电化学工作站的动电位极化扫描技术和PHI-5300ESCA型X射线光电子能谱仪分析抛光液中氧化剂和络合剂等化学组分对铜的作用机制.结果表明,由于氧化剂H2O2对铜的氧化作用使得氨基乙酸对铜的络合速率从1.4 nm/min提高到47 nm/min,进而提高了铜的化学机械抛光去除率.当抛光压力≤10.35 kPa时,抛光后铜表面出现腐蚀坑,腐蚀坑面积比率随抛光过程相对运动速度的增大而减小;当抛光压力≥17.25 kPa时,铜表面腐蚀坑消失,在相对运动速度≥1 m/s条件下,表面粗糙度为3-5 nm;当抛光压力〉6.9 kPa,在相对运动速度≤1 m/s条件下,随着相对运动速度增大,机械作用增强,抛光去除率增大;当相对运动速度〉1 m/s时,抛光界面区抛光液润滑效应增强,抛光去除率有所降低,化学机械抛光过程中这一临界相对运动速度为1 m/s.     

Theoretical investigation of nonequilibrium flow of a H2O-H2-O2 mixture in a profiled nozzle

In the approximation of a two-dimensional flow of a nonequilibrium gas, a study is made of inversion in the vibrational-rotational transitions of the H₂O molecule during expansion of a H₂O-H₂-O₂ mixture in a two-dimensional profiled nozzle. A comparison with the one-dimensional theory is made.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 106–111, January–February, 1982.     

Formation of inversion in jet of CO2-H2O-N2 gas mixture expanding through a slot

A calculation is made of the kinetics of vibrational relaxation of CO₂ molecules in a CO₂ -H₂O-N₂ mixture escaping into a vacuum from a slot. The examination of vibrational relaxation led to a solution of the kinetic equations corresponding to the most important channels of energy exchange in vibration-vibration and vibration-translation processes. It proved possible to consider the dynamics of a nonequilibrium gas in an approximation of the adiabatic motion of a medium with an effective adiabatic index corresponding to a certain degree of freezing in of the vibrational component of the heat capacity of the gas. The calculated values of the gain index agree well with experimental data. The gain index was calculated with allowance for Doppler and Lorentz mechanisms of line broadening. The results of the calculation were analyzed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 25–31, November–December, 1973.The authors thank A. S. Biryukov and N. N. Sobolev for advice and comments and É. A. Ashratov and G. K. Bunin for conducting the gasdynamical calculation on an electronic computer.     

Shock wave ignition in N2O-CO(N2)-He mixtures

The behavior of the pressure behind shock waves in N₂O-CO-He mixtures is investigated. The pressure can be relatively easily measured and, at the same time, reflects the general influence of the experimental conditions on flow formation in the shock tube. Shock-wave mixture ignition effects and, moreover, hydrogen combustion in the contact zone are analyzed from the standpoint of their influence on the stagnation parameters and the optical properties of the flow in the shock tube nozzle. The correctness of modeling the conditions behind the reflected wave by means of mixtures similar in composition to the equilibrium products of the N₂O-CO reaction [1] is discussed in the same context.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 164–170, September–October, 1989.The authors wish to thank G. D. Smekhov for calculating the equilibrium compositions of the mixtures behind the shock waves and A. P. Zuev for stimulating discussions.     

H2O and CO2 Dilution in MILD Combustion of Simple Hydrocarbons

MILD combustion is a very attractive technology because of its intrinsic features for energy production from diluted gas deriving from bio- or thermochemical degradation of biomass. An effective use of such a technology for diluted fuel requires a thorough analysis of ignition and oxidation behavior to highlight the potential effects of the different fuel components on the basis of temperature and diluent/oxygen/fuel mixture composition. In this work, ignition and oxidation of a model gas surrogate for the gaseous fraction of biomass pyrolysis products containing C₁-C₂ species, CO and CO₂ were experimentally and numerically studied over a wide range of temperature and overall composition in the presence of large amounts of CO₂ or H₂O. Experimental results showed that such species significantly alter the evolution of the ignition process in dependence on temperature range and mixture composition. Several kinetic models were tested to simulate experimental results. Significant discrepancies occur, especially in the case of steam dilution. Numerical analyses suggested that such diluents acted mainly as third body species at low temperatures, conditioning both radical production pathways and the relative weight of C₁ oxidation/recombination routes, while strongly interacting with the H₂/O₂ high temperature branching mechanisms at high temperatures. Further analyses are mandatory to improve the predictability of the models and extend the applicability of the chemical schemes to non-standard conditions.     

Numerical simulation of detonation reignition in H $_2$-O $_2$ mixtures in area expansions

Time-dependent, two-dimensional, numerical simulations of a transmitted detonation show reignition occuring by one of two mechanisms. The first mechanism involves the collision of triple points as they expand along a decaying shock front. In the second mechanism ignition results from the coalescence of a number of small, relatively high pressure regions left over from the decay of weakened transverse waves. The simulations were performed using an improved chemical kinetic model for stoichiometric H-O mixtures. The initial conditions were a propagating, two-dimensional detonation resolved enough to show transverse wave structure. The calculations provide clarification of the reignition mechanism seen in previous H-O-Ar simulations, and again demonstrate that the transverse wave structure of the detonation front is critical to the reignition process. Received 16 July 1998/ Accepted 17 November 1998     

Detailed flowfields of a RAMAC device in H2−O2 full chemistry

Numerical simulations of a RAMAC device were performed for a range of speeds and grid densities. For certain initial conditions the detonation was unstable and propagated ahead of the projectile in a normal detonation wave, similar to the experimental phenomenon of unstart. The unstart was observed to develop within the narrow space between projectile and tube wall (the throat), so we focus on that area. Detailed flowfield views of the throat reveal a separated flow rotating in one large vortex. The detonation is overdriven but steady for fast enough upstream velocities. The vortex has an important role in triggering off the unstart by creating a condition at the throat whereby the detonation can propagate against the flow. An abridged version of this paper was presented at the 15th Int. Colloquium on the Dynamics of Explosions and Reactive Systems at Boulder, Colorado, from July 30 to August 4, 1995.     

绿色润滑油的发展概况

概述了绿色润滑油的发展状况     

Wheel slip measurement in 2WD tractor

A microcontroller-based slip sensor was developed for a 2WD tractor to indicate slip values during on-farm use. The ‘zero condition’ considered for the development of slip sensor was – tractor supplied with a driving torque to propel any device across a tarmacadam surface while delivering zero net traction (self-propelled condition). This sensor comprised of four components: power supply; sensing of throttle position, gear position, and wheel rpm; processing of collected data; and display unit. Power was taken from the tractor battery. Rotary potentiometer and proximity switches were installed on the tractor to measure throttle position and wheel revolution, respectively. The performance of developed slip sensor was evaluated both on tarmacadam surface as well as in the field. The variations between indicated and actual slip were found to be within 0–5% for both the surfaces, thus indicating the accuracy of slip measurement by the developed slip sensor.