基于液流控集成芯片的总磷在线分析仪的研制

研制了一种基于液流控集成芯片技术的总磷在线分析仪,分别从液流控集成芯片、分析流路、电路控制等方面进行了设计及验证讨论,同时对分析仪的性能进行了测定。研究结果表明,在0~2mg/L的量程范围内,分析仪的标准曲线的R2值为0.9999;检出限为0.04mg/L;示值误差在0.75%以内;精密度为0.15%;量程漂移为0.05%F.S。分析仪体积小、重量轻、准确度高,精密度好,检出限低,可集成于户外的微型水站,使户外的微型站更小、更轻。

Semi-active control for vibration attenuation of vehicle suspension with symmetric MR damper

A semi-active force tracking PI controller is formulated and analyzed for a magnetorheological (MR) fluid-based damper in conjunction with a quarter-vehicle model. Two different models of the MR-damper are integrated into the closed-loop system model, which includes: a model based upon the mean force-velocity (f-v) behaviour; and a model synthesis comprising inherent nonsmooth hysteretic force and the force limiting properties of the MR damper. The vehicle models are analyzed to study the vibration attenuation performance of the MR-damper using the semi-active force tracking PI control algorithm. The simulation results are also presented to demonstrate the influence of the damper nonlinearity, specifically the hysteresis, on the suspension performance. The results show that the proposed control strategy can yield superior vibration attenuation performance of the vehicle suspension actuated by the controllable MR-damper not only in the sprung mass resonance and the ride zones, but also in the vicinity of the wheel-hop. The results further show that the presence of damper hystersis deteriorates the suspension performance.

Droplet Pattern Formation and Translation in New Microfluidic Flow- Focusing Devices

We conducted experiments on specially designed microfluidic chips that generate droplets through a microfluidic ow-focusing approach. The fluid flow in the microfluidic channel produced a shear flow field at low Reynolds numbers. The droplets in the microfluidic system exhibited special droplet pattern formations similar to periodic crystal-like lattices because of the competition between shear forces and surface tension. By adjusting the flow rate ratio of the water （droplet phase） to oil （continuous phase） phases and changing the outlet channel widths, the droplets formed monolayer dispersion to double-layer formation to monolayer squeezing when the outlet channel widths were 250 or 300 μm. We also obtained droplets with monolayer dispersion, three-layer arrangements, double-layer squeezing, and monolayer squeezing when the outlet channel width was 350 μm. The outlet channel width was increased to 400 μm, and four-layer arrangements were observed. We also studied the translation of droplet formation, which resulted in a detailed strategy to control drop size and droplet pattern formation for emulsi cation in microfluidic devices. We expect that our strategy can provide theoretical guidance to synthesize dispersion or polydisperse colloid particles.

Microfluidic technology for multiphase emulsions morphology adjustment and functional materials preparation

Multiphase emulsions could be used as templates in considerable fields such as coating, optical materials, stan- dard particles and biomedicine. Among various emulsion forming methods, microfluidic technology, with good monodispersity, high controllability and operation simplicity, has been widely used in the preparation of multi- phase emulsions with different systems. This review would focus on the basic principles of forming multiphase emulsions, the recent progress in controlling multiphase flow in microfluidics, and preparation of functional ma- terials with microfluidics mainly by the authors＇ research group. We believe that the review will contribute to the readers in this prospective area very well. ~ 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.

Experimental analysis on adjusting performance of vapor-liquid two-phase flow controller

The vapor-liquid self-adjusting controller is an innovative automatic regulating valve.In order to ensure adjusted objects run safely and economically,the controller automatically adjusts the liquid flux to keep liquid level at a required level according to physical properties of vapor-liquid two-phase fluid.The adjusting mechanics,the controller’s performance and influencing factors of its stability have been analyzed in this paper.The theoretical analysis and successful applications have demonstrated this controller can keep the liquid level steady with good performance.The actual application in industry has shown that the controller can satisfactorily meet the requirement of industrial production and has wide application areas.

Numerical Simulation on a Throttle Governing System with Hydraulic Butterfly Valves in a Marine Environment

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.

Fluid Flow Past a Circular Cylinder with Tandem Rod and Staggered Rod at Low Reynolds Number

The flow past a primary cylinder with one tandem control rod and one staggered control rod is simulated in this paper through solving the Navier-Stokes equations. Two examples are simulated to validate the model, and the results matched well with those of previous researches. The Reynolds number based on the diameter of the primary cylinder is 500. The diameter ratio between the control rod and the primary cylinder （d/D） is 0.25. It was found that the effect of the combination of one upstream tandem control rod and one staggered control rod on the hydrodynamics of the primary cylinder is a linear superposition of the effect of a corresponding single control rod, and the effect of the upstream tandem control rod is dominant at larger spacing ratios such as G/D=2. For the combination of a downstream tandem control rod and a staggered control rod, the effect of the control rods is different from that of the corresponding single control rod in the region of 0.2〈G/D〈0.5 ＆ 30°〈a〈120° and 0.9〈G/D〈1.4 ＆ 30°〈a〈50°, where the additional effect is obvious. In this case, the effect of the downstream tandem control rod is dominant at small spacing ratios （such as G/D=0.1）. At moderate spacing ratios such as G/D=0.4, the effects of the tandem control rod and the staggered control rod are comparable in both cases.

Numerical Study of the Evaporation Effects on the Microdroplet Dynamics in Digital Microfluidic Biochips

In this paper, an electrohydrodynamic approach is used to model and study dynamics of evaporating microdroplets in digital microfluidic systems. A numerical eleetrohydrodynamic approach is used to calculate the driving force and shear force （due to the walls）. Effects of contact line pinning is considered by adding a three-phase contact line force, and also considering dynamic contact angle which modifies the mierodroplet boundary conditions. Since air is used as the filler fluid, the drag force is neglected. Although energy equation is not solved （constant temperature assumption）, effects of the evaporation is considered from two aspects： It is shown that an additional force is needed to balance the dynamic equation of the mierodroplet motion. Also, at each time step the microdroplet interface has to be deformed due to the change in the microdroplet radius. Important findings of the proposed model includes the transient velocity and displacement of the microdroplet as well as the driving and opposing forces acting on the microdroplet as functions of time. It is shown that mass loss due to evaporation tends to accelerate the droplet; whereas the competitive effect of the reduced driving force decelerates the droplet at the end of motion. The modeling results indicate that evaporation plays a crucial role in microdroplet motion by changing the force balance and the microdroplet boundary condition.

Design and application of a multi - function combined hydraulic oil cylinder

Hydraulic equipment in engineering, in different working stages, different speed, load, variable load and variable speed is one of the most frequently encountered problems, to solve this problem is usually used to continuously adjustable pressure, adjustable flow control to achieve. In this paper, the structure design of a combination of oil tanks, combined with oil circuit examples in the case of no need to adjust the pressure, adjust the flow rate, to achieve the high speed, light load of the typical operating requirements and hydraulic servo feedback.

Liquid metal-integrated ultra-elastic conductive microfibers from microfluidics for wearable electronics

Liquid metal(LM) has shown potential values in different areas. Attempts to implement LM are tending to develop new functions and make it versatile to improve its performance for practical applications.Here, we present an unprecedented LM-integrated ultra-elastic microfiber with distinctive features for wearable electronics. The microfiber with a polyurethane shell and an LM core was continuously generated by using a sequenced microfluidic spinning and injection method. Due to the precise fluid manipulation of microfluidics, the resultant microfiber could be tailored with tunable morphologies and responsive conductivities. We have demonstrated that the microfiber could act as dynamic force sensor and motion indicator when it was embedded into elastic films. In addition, the values of the LMintegrated ultra-elastic microfiber on energy conversions such as electro-magnetic or electro-thermal conversions have also been realized. These features indicate that LM-integrated microfiber will open up new frontiers in LM-integrated materials and the wearable electronics field.

Dielectrophoresis Flow Control of Volatile Fluids in Microchannels

In recent years the microchannel heat exchangers have been applied in a great variety of technical areas. One of the problems, which exist in the microcharmel technology is the flow instabilities, including fluid maldistribution in the microcharmels array for the case of two-phase flow especially in micro-evaporators. One of the ways to solve this problem is flow rate control at the microcharmel inlet. However, due to very small inlet to the array of microchannels the classic flow restriction device （with moving mechanical parts） will be difficult to apply. The new device for the flow rate control based on the dielectrophoresis force was presented in the paper. Experimet^tal research results of using this device for refrigerant flow control was presented in the paper. The experimentally obtained relationships between applied voltages and frequencies and flow rates were presented showing opportunity for applying such method for refrigerants and other volatile fluids.

Bioinspired perovskite quantum dots microfibers from microfluidics

As perovskite quantum dots(PeQDs)are performing their outstanding characteristics,incremental efforts have been devoted to such materials.Here,inspired by the spider spinning process,we present novel PeQDs microfibers with tailorable morphologies and functions from a multi-injection microfluidic approach.The microfibers were generated by introducing PeQDs precursors into each barrel of the inner capillary array and mixing them in the spindle middle channel,where the poly(vinylidene fluoride)(PVDF)dissolved in N,N-dimethyl formamide(DMF)was also injected as their sheath fluid.During this process,the PeQDs were in situ synthesized with the connection of precursor cations and anions in the core fluid;while the PVDF formed solidified microfibers to encapsulate PeQDs with the fast dispersion of DMF into the outer aqueous solution.Thus,the good encapsulation of PeQDs was achieved in PVDF microfibers,which effectively protected them from different hostile environments.Because of the highly tunable spinning processes,the microfibers exhibited controllable diameters and helical geometric structures,and the encapsulated PeQDs could yield adjustable emission peaks.Based on the PeQDs microfibers,we have explored their potential as luminescent materials in barcodes and as flexible photodetectors,which make such microfibers highly versatile for different areas.