Alan R. Reed

On-line flicker measurement of gaseous flames by image processing and spectral analysis

The flicker of a flame is an important physical parameter associated with the characteristics of a combustion process. This paper presents a novel instrumentation system developed for on-line continuous flicker measurements of combustion flames. The system comprises a high-speed CCD camera, a frame grabber and associated image processing software. The flicker signal was obtained by processing the radiation intensity of individual pixels within the luminous region of a flame image. Power spectral density analysis was performed to obtain the frequency components of the flicker signal. The quantitative flicker of a flame is defined in terms of weighted spectral components in the frequency domain and this definition has been proven to be well suited to quantification of the flickering characteristics of a flame. A tungsten lamp driven by a frequency-varying power supply was employed to calibrate the measurement system. The calibration results show that the system is capable of measung the flicker of an unknown light source with a relative error no greater than 3% . The system developed has been utilized to investigate the relationship between the flicker of a diffusion flame and the burner diameter, and to study the effect of the equivalence ratio on the flicker of a premixed flame under a range of combustion conditions. The experimental results obtained by both motion image analysis and spectral analysis have demonstrated that the flicker of a diffusion flame depends predominantly on the burner diameter. It has also been found that the flicker of a premixed flame varies with the equivalence ratio and a peak flicker exists for a given air flow rate.

Constructing an engineering model for moisture migration in bulk solids as a prelude to predicting moisture migration caking

The aim of this study was to examine one of the mechanisms behind moisture migration caking, where liquid solution bridges form between particles in a bulk solid system because of an increase in local relative humidity, and then solidify as the local relative humidity drops - the effect being increased as more cycles occur. The goal was to develop a one-dimensional model for the heat and mass transfer processes involved, based on established physics and the characteristic moisture sorption curve of the solid (in this case sugar). The model was verified using scaled-down equipment (a caking box) to simulate the caking in a big bag. The results of this study will assist in the prediction of caking produced in this way.

A hybrid numerical model for predicting segregation during core flow discharge

A continuum numerical model is presented that parameterizes the interactions between particles at the microscopic level and predicts the development of moving stagnant zone boundaries during core flow discharge of granular material. The model is then employed for the prediction of segregation of multi-component granular mixtures during discharge from core flow hoppers and its capability to accurately simulate the behavior of the granular mixture is demonstrated through comparisons with experimental data.

Assessing the potential of a fine powder to segregate using laser diffraction and sieve particle size measuring techniques

Abstract This paper describes a research programme undertaken with a view to solving a serious industrial powder handling problem. The aim of this research was to rationalize three grades of an additive fine powder used in the manufacturing of a mixed product to one grade, with the aim of reducing or eliminating the potential risk of particle segregation within the product. The use of a segregation tester, specifically to quantify the propensity of a sample of bulk solid to segregate when poured on to a heap, was central to this research. Particular attention was paid to the particle size distribution curves of the final product within different areas of the segregation tester. Two different techniques for characterizing particle size were used in the investigation — one based on size separation using sieving analysis and the other based on the laser diffraction technique. These techniques yield different measures of particle size distribution, resulting in different conclusions as to the feasibility of particle size analysis being a useful indicator of the propensity of a powder to segregate.

An investigation into the effect of product type when scaling for diameter in vertical pipelines

The prediction of pressure drop is important to pipeline design and it is often necessary to use data from one pipeline size to predict what will happen in another pipeline size. This paper looks at the effect of two different products when scaling for diameter in vertical pipelines. Data has been measured for cement and flour in two bore sizes. A means of modelling has been established to allow prediction of the operation of a pipeline of one bore size, from trials on another bore size in vertical sections. The model used to correlate pipeline diameter with pressure gradient data in vertical pneumatic conveying pipelines will be discussed along with the general data trends for the two materials.

The dependence of power consumption of pneumatic conveying systems upon bulk material properties, pipeline bore and routing, and mode of flow

In this paper the dependence of the power consumption of pneumatic conveyors upon conveyed materials, pipeline route and bore, and mode of flow has been examined. The findings are that, with different materials and modes of flow, not only is the amount of power consumed very different but it varies in different ways with pipe bore and routing. Additionally it has been found that, for any given conveying system, the choice of air mover also has a strong influence on the power requirement.

Original paperAssessing the potential of a fine powder to segregate using laser diffraction and sieve particle size measuring techniques

Abstract This paper describes a research programme undertaken with a view to solving a serious industrial powder handling problem. The aim of this research was to rationalize three grades of an additive fine powder used in the manufacturing of a mixed product to one grade, with the aim of reducing or eliminating the potential risk of particle segregation within the product. The use of a segregation tester, specifically to quantify the propensity of a sample of bulk solid to segregate when poured on to a heap, was central to this research. Particular attention was paid to the particle size distribution curves of the final product within different areas of the segregation tester. Two different techniques for characterizing particle size were used in the investigation — one based on size separation using sieving analysis and the other based on the laser diffraction technique. These techniques yield different measures of particle size distribution, resulting in different conclusions as to the feasibility of particle size analysis being a useful indicator of the propensity of a powder to segregate.