Investigations on the use of pneumatic cross-flow nebulizers with dual solution loading including the correction of matrix effects in elemental determinations by inductively coupled plasma optical emission spectrometry

The use of a so-called trihedral and a T-shaped cross-flow pneumatic nebulizer with dual solution loading for inductively coupled plasma optical emission spectrometry has been studied. By these devices analyte clouds from two solutions can be mixed during the aerosol generation step. For both nebulizers the correction of matrix effects using internal standardization and standard addition calibration in an on-line way was investigated and compared to elemental determinations using a conventional cross-flow nebulizer and calibration with synthetic standard solutions without matrix matching. A significant improvement of accuracy, both for calibration with internal standardization and standard addition, was obtained in the case of four synthetic solutions containing each 40 mmol L^− 1 Na, K, Rb and Ba as matrix elements and 300 μg L^− 1 Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb as analytes. Calibration by standard addition in the case of dual solution loading has been shown to be very useful in the determination of elements at minor and trace levels in steel and alumina reference materials. The results of analysis for minor concentrations of Cr, Cu and Ni in steel as well as for Ca, Fe, Ga, Li, Mg, Mn, Na, Si and Zn in alumina powder certified reference materials subsequent to sample dissolution were found to be in good agreement with the certificates. Limits of detection were found to be only slightly above those for a conventional cross-flow nebulizer and a precision better than 3% was realized with both novel nebulizers.     

Time domain identification and ranking of noise sources in a pneumatic nail gun

This paper investigates the noise sources in a pneumatic nail gun. The study combines two complementary experimental approaches. The first uses simultaneous data observation, with sound, acceleration and air pressure signals simultaneously recorded in conjunction with a nail gun motion high speed video. This strategy allows the identification of the physical processes involved in the operation of the machine at different time instants, as well as the associated noise generation mechanisms. However, since multiple noise sources radiate at the same time, this observation technique is not sufficient for noise source identification and ranking. Thus, a second approach introduces a selective wrapping procedure, and the strategy assures a reliable classification of the noise sources. The investigation considers the following noise origins: the air exhaust, the machine body and the workpiece/worktable.     

Effect of moisture content on conveying characteristics of pulverized coal for pressurized entrained flow gasification

During the pneumatic conveying, pulverized coal with different moisture contents may develop substantial difference in flow characteristics, whose cause is not fully understood. This study focused on influence of moisture content on conveying characteristics in an experimental test facility with the conveying pressure up to 4 MPa. The experiments included soft coal and lignite with similar density and particle size. With the increase in moisture content, the mass flow rate decreased for lignite (3.24% < M < 8.18%) but increased at first and then decreased for soft coal (0.4% < M < 6.18%) at same operating parameters. The flowability of soft coal was worse than that of lignite at similar operating parameters and external moisture content. The extremal conveying moisture contents of two coal types were obtained. The particle charge and surface moisture content were investigated to indicate influence mechanism of moisture content on mass flow rate in pneumatic conveying at high pressure. Pressure drop of soft coal was greater than that of lignite for same test section. The conveying phase diagram of dense-phase pulverized coal at high pressure was obtained and the pressure drops through different test sections were compared and analyzed. The bend loss factor rose with the increase in moisture content and was independent of conveying velocity and solid-gas ratio in dense-phase pneumatic conveying at high pressure.     

Next-generation NATO reference mobility model complex terramechanics – Part 2: Requirements and prototype

In part 2 of this paper, the Complex Terramechanics (CT) software tools requirements recommended by the NATO research task group RTG-248 are presented along with example simulations from a CT prototype software tool which attempts to satisfy the requirements.     

Experimental and numerical study of installing a dune model in a 90° bend in the horizontal-vertical pneumatic conveying system

In the pneumatic conveying process, particles move to the bend under the influence of inertia to form a particle rope, which will cause serious wear between the particles and the pipe wall, and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this study. Firstly, the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental study. Then the energy saving mechanism of the dune model is studied by CFD-DEM coupling. The experimental results show that the installation of the dune model reduces the minimum pressure drop velocity. The numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model, which reduces the energy loss. Moreover, the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.     

A qualitative study on the pulsatile flow phenomenon in a dense fly ash pneumatic conveyor

Understanding of the dynamic particulate flow structures within a dense gas-fly ash pneumatic conveyor must be improved in order to better aid its design guidance.The complex pulsatile movement of the gas-fly ash mixture dominates the flow performance within the pipeline,and historically,non-invasive measurement devices such as the electrical capacitance tomography（ECT） were often used to sufficiently capture the flow dynamics.However,inadequate studies have been conducted on the pulsatile flow phenomenon,which directly relate to the gas-fly ash two-phase flow performance.This paper aims to investigate the pulsatile flows using an ECT device.Initially,pulsatile flow patterns under various experimental conditions were obtained through ECT.Pulses within a flow were then characterised into pulse growth and decay segments,which represent the superficial fluidisation and deaeration processes during conveying.Subsequently,structural and statistical analyses were performed on the pulse growth and decay segments.Results suggested that the increasing air mass flow rate led to the decrease of the superficial fluidisation/deaeration magnitude,however,the increase of the superficial fluidisation/deaeration durations.Also,the air mass flow rate was indicated as the dominant factor in determining the pulsing statistical parameters.This research provides fundamental insights for further modelling the dense fly ash pneumatic flows.     

Predicting the mode of flow in pneumatic conveying systems-- A review

An initial prediction of the particulate mode of flow in pneumatic conveying systems is beneficial as this knowledge can provide clearer direction to the pneumatic conveying design process. There are three general categories of modes of flow, two dense flows： fluidised dense phase and plug flow, and dilute phase oniy. Detailed in this paper is a review of the commonly used and available techniques for predicting mode of flow. Two types of predictive charts were defined： basic particle parameter based （e.g. particle size and density） and air-particle parameter based （e.g. permeability and de-aeration）. The basic particle techniques were found to have strong and weak areas of predictive ability, on the basis of a comparison with data from materials with known mode of flow capability. It was found that there was only slight improvement in predictive ability when the particle density was replaced by loose-poured bulk density in the basic parameter techniques. The air-particle-parameter-based techniques also showed well-defined regions for mode of flow prediction though the data set used was smaller than that for the basic techniques. Also, it was found to be difficult to utilise de-aeration values from different researchers and subsequently, an air-particle-based technique was developed which does not require any de-aeration parameter in its assessment.     

Characterization of the gas pulse frequency, amplitude and velocity in non-steady dense phase pneumatic conveying of powders

Current modelling techniques for the prediction of conveying line pressure drop in low velocity dense phase pneumatic conveying are largely based on steady state analyses.Work in this area has been on-going for many years with only marginal improvements in the accuracy of prediction being achieved.Experimental and theoretical investigations undertaken by the authors suggest that the flow mechanisms involved in dense phase conveying are dominated by transient effects rather than those of steady state and are possibly the principal reasons for the limited improvement in accuracy.This paper reports on investigations on the pressure fluctuation behaviour in dense phase pneumatic conveying of powders.The pressure behaviour of the gas flow in the top section of the pipeline was found to exhibit pulsatile oscillations.In particular,the pulse velocity showed variation in magnitude while the frequency of the oscillations rarely exceeded 5 Hz.A wavelet analysis using the Daubechie 4 wavelet found that the amplitude of the oscillations increased along the pipeline.Furthermore,there was significant variation in gas pulse amplitude for different types of particulate material.     

用低功率微波热雾化器与十字交叉气动雾化器作为ICP-AES进样装置的比较

在 ICP- AES中 ,最常用来引入液体样品的方法是雾化法 .因此 ,雾化器雾化效率的高低直接影响到 ICP- AES的分析性能 [1,2 ] .目前 ,在 ICP- AES中最常用的雾化器是气动雾化器 (PN) .它的优点是简单、稳定性好 ;缺点是产生的雾滴的直径范围很宽 (一般为 1～ 50 μm) ,进样效率低 ,一般仅为 1 %～3% [3] .热雾化器是近年发展起来的一种雾化效率较高的雾化法 ,已被越来越多地用于 ICP- AES[4～ 7] .热雾化法的雾化原理与同轴气动雾化法类似 ,不同之处在于 :对于热雾化法来说 ,(1 )雾化所需的气体来自于液体样品本身而不是外加的惰性…