Browsing by Author "Mwinuka, Tito E."

Now showing 1 - 8 of 8
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    Effects of Process Parameters on the Density and Durability of Biomass Briquettes Made from Wet Method
    (2015-02) Mwinuka, Tito E.
    This work aimed at improving the density and durability of biomass briquettes made by composting and pressing biomass (wet method). Though this type of briquettes requires much less energy to form, they are usually of much lower density compared to briquettes made from dry biomass. In this experimental work three parameters were considered, which are type of biomass, composting time, and moisture content. Biomass samples were mixed with water and left to decompose for varying number of days. The moisture content of samples was conditioned accordingly and briquettes were made from these samples using a die and a pressing machine. Briquettes were tested for density and durability. Results show that among saw dust, groundnut shells and rice husk briquettes, rice husk briquettes attain highest density (up to 0.47g/cm3). For all three biomass types, durability index tend to increase with an increase in moisture content. Durability of groundnut shells and rice husk briquettes tend to decrease with an increase in composting time while that of saw dust increase with composting time. For all the three biomasses, the apparent density decreases with an increase in moisture content. For groundnut shells and rice husks the density increases with compositing time while for saw dust the change in density is negligible. In general it can be concluded that better and denser briquettes can be obtained by as long as possible composting time and as low as possible moisture content (but sufficient for bonds formation). However the lower moisture content will decrease durability. Also, saw dust is not recommended for wet briquettes unless long composting time is available. It can be recommended that briquettes which may be subjected to harsh handling and transportation be made using higher moisture content.
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    Experimental Determination of the Effect of Number of Impeller Blades on the Air Flow Rate and Power Consumption of Centrifugal Blowers
    (2016) Mwinuka, Tito E.
    Design parameters for a centrifugal blower includes, power of a motor, impeller diameter, impeller width, impeller rotational speed, volume flow rate and number of blades in an impeller, while relationship among several of this parameters are well defined in literature, it is unclear as to how the number of impellers blades affect the performance of a blower. In this work, an experimental method to determine the effect of number of blades in an impeller is described. The blower has been tested at three different speeds using five fabricated impellers with 4, 5, 6, 7 and 8 blades respectively. It is found that, for all 3 selected blower speeds, air flow rate increase by about 19% by increasing the number of impeller blades from 4 to 8. It is also found that increasing blower speed has a significant increase in flow rate; that is, more that 80% increase upon doubling the number of impeller blades. It is also found that there is slight variation in power consumption due to change in number of blades. It is therefore proposed that changing the number of impeller blades can only be applied to fine tune the blower design within 15-20% flow rate variation. However nominal flow rate has to be established using blower speed and dimensions. Power consumption if found to increase slightly with maximum variation of 3% on increasing blade number from 4 to 8. The results are useful in the design or re-design of fabricated blowers and selection of suitable speed. When space is a constraint, increase in the number of blades or blower speed can respectively be applied to increase air flow rate depending on the magnitude of the increase required.
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    Extendible Operation Sequencing for Turn-Milled Components
    (Elsevier, 2007) Mwinuka, Tito E.; Hinduja, S.; Owodunni, O. O.
    Research in operation sequencing has hitherto been based on fixed heuristics with no obvious scientific basis. Often, the heuristics contain no technological considerations. This paper provides a scientific approach for the sequencing of features based on maximising the stiffness of the intermediate component. In the case of intersecting feature volumes, preference is given to a feature with a lower machining cost. This scientific approach is embedded within a flexible environment in which heuristic rules can be constructed from a rich vocabulary covering geometric and technological attributes, without the need for additional programming. Examples illustrating the capabilities of the system are described.
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    Extraction of 2D AutoCAD Geometric Data and Post-processing for Numerical Control
    (2013-06) Mwinuka, Tito E.; Mutagahywa, B.
    This paper presents some considerations regarding the extracting of geometrical data from CATIA models with the aim of using this data to program computer numerical control machine tools that do not have postprocessors integrated in the CATIA environment. This data usually represents holes and plane contours defined by their characteristic points. The paper defines how the information is organized in files and how these files can be used by postprocessor applications. A postprocessor that uses such information is also presented
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    Tool Selection for Rough and Finish CNC Milling Operations Based On Tool-Path Generation and Machining Optimisation
    (2015-03) Mwinuka, Tito E.; Mgwatu, Mussa I.
    Most of CAD/CAM systems lack fully‐automated process planning capabilities and depend on semi‐automatic capabilities that necessitate the traditional selection of tools and cutting parameters. This paper attempts to determine proper combinations of cutting tools through the generation of tool paths and optimisation of machining parameters using an example of the CNC milling process. Several machining simulations with different combinations of tool sizes were performed using MasterCAM software. Based on these simulations, substantial variations in tool paths were observed for different tool combina‐ tions and as such the optimum tool combination could only be obtained arbi‐ trarily. The tool paths derived from machining simulations were used to opti‐ mise machining parameters, that is, cutting speed, feed rate and depth of cut with the objective of minimising production time. In this case, an optimisation model was developed as a nonlinear programming problem and solved using extended LINGO nonlinear software. The results show that the subjectivity when selecting cutting tools can be avoided when appropriate tools are chosen alongside with the generation of a tool path within a CAD/CAM system using optimised machining parameters. As a consequence, CNC machine tools could be effectively utilised and the productivity significantly improved at shorter production time and cost.