喷射染色机换热器的结构设计

喷射染色机换热器的结构设计的独特之处是：已知加热时间，要求所设计的换热器在一定时间内，将已知量的染液加热到预定的温度。本文讨论了这种换热器的设计方法及改进设计的途径。     

Study on flow force compensation characteristics and optimization design of jet guiding groove

A jet guiding groove is designed on the spool to compensate the steady-state flow force. The steady-state flow force model is analyzed and derived. The influence of structural parameters on steady-state flow force is studied by CFD simulation. The response surface method is used to construct the steady-state flow force polynomial regression model. The optimal structure size of the jet guiding groove is obtained. The steady-state flow force compensation coefficient is defined and calculated. Results show that the compensation effect decreases with the increase of pressure difference. However, at the same pressure difference, the absolute value of the compensation coefficient of the spool with jet guiding groove is less than that of the spool without jet guiding groove. The results show that the jet guiding groove can effectively compensate the steady-state flow force and improve the control accuracy of the valve.     

MATHEMATICAL MODELING OF FLUID SPRAY CURTAINS FOR MITIGATION OF ACCIDENTAL RELEASES

In this article experimental and theoretical investigations on liquid spray curtains are presented, in the context of absorbing and dispersing accidental releases of chlorine in air. A mathematical model of a two-phase jet is developed to evaluate the entrained air rate in connection with the liquid flow rate. The model was successfully compared by means of replicated wind tunnel experimental runs adopting spray nozzles suitable to create a two-blade barrier. The experimental work demonstrated that it is possible to distinguish two regions in the barrier. One region is dominated by the liquid inertia and is comparable to an airplane jet. The other region is dominated by gravitational effects, and its dimensions do not vary appreciably. An analytical solution to the problem is obtained, taking into account the instantaneous and nonreversible chemical reactions, i.e., chlorine absorption in alkaline solutions, in the case of still air. The developed methodology could be applied to more complex situations, allowing the attainment of a more generalized approach for the design of a curtain given the release parameters, the site layout, and vulnerable target specifications.     

DIMENSIONLESS PERFORMANCE AND DESIGN GUIDELINES FOR REVERSE-FLOW DIVERTERS DURING REVERSE-FLOW MODE

Pneumatic pulse jet pumps are air-powered, low-maintenance devices useful for delivering hazardous liquids. A key component in these pumps is the reverse-flow diverter (RFD), consisting of a nozzle and a diffuser. Despite several decades of practical application, no clear guidelines exist for RFD design during the reverse-flow portion of the pumping cycle. We experimentally investigated the effects of diffuser entrance/nozzle exit area ratio, suction gap length, and diffuser divergence angle on RFD flow and pressure. The results were used to derive two dimensionless performance coefficients (ξ_M = 0.50?^0.38 and q = A + B · exp[-Eu_out/(C · Eu₀)] + D · exp[-Eu_out/(E · Eu₀)]) and to develop a series of design guidelines for RFDs in reverse-flow mode.     

Numerical Study on the Effect of Cross-Flow on Turbulent Flow and Heat Transfer Characteristics Under Normal and Oblique Semi-confined Impinging Slot Jets

Abstract

Impinging jets are commonly used in industrial dryers and electronics chip cooling. Since in industrial practice it is necessary to use multiple jets, the interaction between jets can have important effect on their heat transfer performance. Hence, the study of cross-flow caused by the spent flow of upstream jets is obviously significant. In this study, a computational fluid dynamics simulation was carried out of the flow and heat transfer characteristics for a single semi-confined turbulent slot jet of air impinging normally or obliquely into an imposed air cross-flow of the same or different temperature. The standard k?ε and the Reynolds stress models were used. Effects of the various flow parameter (e.g., jet-to-cross-flow mass ratio) and geometric parameters (e.g., nozzle-to-target spacing and jet angle) were evaluated at a fixed Reynolds number (11,000 and 12,000) for equal and unequal temperatures of the jet and cross-flow. Results indicate the significant degradation of the impingement heat transfer rates due to cross-flow and a relatively minor influence of the temperature difference between the jet and cross-flow over the ranges of parameters studied. Both the turbulence models produced comparable Nusselt number distributions along the impingement surface.     

Kinco CD伺服成功应用于喷气织机

喷气织机是采用喷射气流牵引纬纱穿越梭口的无梭织机。Kinco伺服系统在喷气织机送机,卷取机构上优异的表现得到了客户的高度认可和肯定。     

Investigation of Chemical/Mechanical Polishing of Niobium

A chemical/mechanical method for polishing flat niobium sheets to a mirror finish was developed. Various polishing slurries with different open circuit potentials and pH values were considered. All slurries fell within the niobate region of the Pourbaix diagrams, indicating that slurries are in a thermodynamically stable region. Oxidation characteristics of the niobium in the various slurries were determined by XPS and confirmed previously published work that niobium forms various layers of stable niobium oxides roughly 4.5–4.7 nm in thickness on the surface. A multi-step polishing method that relies on mechanical abrasion of the surface proved to be effective, and particles of different hardness and size were explored. Niobium wafers with initial peak-to-valley (PV) surface roughness of 3 to 7 μm were polished. The multi-step process utilized a slurry containing 1 μm diameter alumina particles to polish this initial roughness down to a submicrometer level. The final polish was provided by a slurry containing smaller particles. The oxide slurry with 70 to 100 nm silica particles gave the best mirror finished surface, with PV = 235 nm, Ra = 32 nm, and RMS = 39 nm. While polishing caused some disorder in the niobium metal, using the oxide slurry gave results closer to those obtained by buffered chemical polish (BCP), which exhibits the highest degree of atomic order based on XPS studies. A polishing process starting with mechanical abrasion, followed by a two-step mechanical polish, is successful for obtaining smooth niobium surfaces on flat wafers.     

Surface Roughness Effect on Slider Bearing Lubrication

The effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force, is studied. The distinction is made between waviness and roughness, the latter being treated as a random quantity which may be characterized by a probability density function, determined experimentally. Results can be obtained in closed form suitable for calculation if a Beta distribution is assumed. Actually, this can approximate quite closely a Gaussian distribution, yielding quite accurate results. However, the procedure developed can be carried out for any desired distribution.     

Reaction‐Crystallization of Struvite in a Continuous Liquid Jet‐Pump DTM MSMPR Crystallizer with Upward Circulation of Suspension in a Mixing Chamber – an SDG Kinetic Approach

The experimental results concerning kinetic aspects of struvite precipitation in a continuous DTM‐type crystallizer with internal circulation of suspension forced by a liquid jet‐pump are presented and discussed. Nucleation and crystal growth rates of struvite during reaction‐crystallization processes in diluted water solutions of magnesium, ammonium, and phosphate ions were identified. Kinetic parameters were calculated on the basis of population density distributions adopting a simplified model of the mass crystallization process in a MSMPR crystallizer taking under consideration size‐dependent growth (SDG) mechanism. The Rojkowski hyperbolic SDG model has proved to be the equation best statistically fitted to our own data set.     

The influence of asymmetries in shaped charge performance

Numerical analyses have been performed to investigate the influence of shaped charge asymmetries in the jet characteristics. The shaped charge configuration employed in the numerical analyses has a trumpet copper liner and aluminum casing filled with PBXN-110 explosive charge. Four types of shaped charge defects have been analyzed within the scope of the work as off-center initiation of the explosive charge, detachment of the high explosive fill from the casing, air bubbles inside the high explosive fill and shaped charge liner dimensional inaccuracies. Response of the jet against each of the above defects has been determined in terms of off-axis velocities, named as radial drift velocities, induced throughout the jet.