bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Characteristics of a Small Fixed-Bed Gasifier Stove
Authors: Beedie D , Syred N , O'Doherty T 
Published: February 2007

This paper describes work directed at characterizing the dynamic behaviour of a small gasifying fixed-bed biomass stove. The system comprises a primary gasification chamber, followed by a multi-stage secondary combustor which can allow for the considerable variation in quantity and calorific value of fuel gas produced by forming a series of flamelets which move along the length of the secondary combustor as a function of the local mixture ratio. The typical cycle time is about 60 minutes and once warmed up the unit is capable of operating with low emissions, providing appropriate guidelines are followed. Correlation of temperature and gas concentration measurements on the unit with velocity and flow visualization measurements on a perspex model of the secondary combustor show that improvements can be made to the flow patterns in the bottom of the secondary combustion chamber by reducing the size and shape of the recirculation zones formed and revising the location of the mid-section secondary air inlet. Control of the system is indicated using a simple measurement of temperature in the secondary combustor to determine appropriate air supply rates.
The Use of Palm Oil as Diesel Fuel Substitute
Authors: Sapuan S M , Masjuki H H , Azlan A 
Published: February 2007

The high cost of energy supplies as well as the concern over the availability of oil have brought much pressure on many countries to search for renewable energy sources, especially after the oil crisis in 1973. Vegetable oil fuels such as palm oil fuel provide one of the alternative forms of energy that are currently being studied, particularly as a diesel fuel substitute. The purpose of this note is to review the potential of palm oil as an alternative fuel in automotive and industrial diesel engines with respect to its performance and tribological, environmental, economic and social implications.
Review of Sorbent Injection Processes for Low-Cost Sulphur Dioxide Control
Authors: Sage P W , Ford N W J 
Published: February 2007

Over recent years there has been growing public awareness world-wide that the use of fossil fuels can have damaging consequences for the environment. As a result increased efforts are being made to reduce such adverse effects. A range of low-cost sorbent injection techniques for abatement of sulphur dioxide applicable to combustion plant and other process operations are available and development is continuing. These techniques are generally characterized by modest SO2 removal and low capital cost. The potential for application depends on a range of plant specific factors, although their market niche is likely to be limited to smaller industrial scale plant or existing plant with a low residual lifespan. The main barrier to their exploitation on such plant is considered to be the general lack of operational experience, which does not help their acceptance by plant operators as an alternative to established techniques such as spray drying and wet flue gas desulphurization. This paper describes the options for sulphur dioxide abatement from combustion plant with particular reference to low-cost sorbent injection processes and discusses their applicability.
Sizing Ram Pumps
Authors: Young B W 
Published: February 2007

Although a method for the optimal design of ram pump systems using a pump of given size now exists, there is no simple procedure for selecting the proper size of pump to provide a specific duty. This Technical Note shows how pump size may be determined from the required output power. The finding is supported by existing results and further tests on a 53 mm Wilcox pump. Examples are given to illustrate the sizing of small to medium pumps. A cost analysis indicates that economy of scale applies to ram pumps and that the use of multiple pumps is not cost effective unless low drive heads have to be utilized.
Tadpole: A Design Problem in the Mechanics of the Use of Sea Wave Energy
Authors: French M J 
Published: February 2007

A study is made of a device for obtaining electrical energy from sea waves, in which the problem of providing a reaction against the wave forces is met by a combination of a pendulum and gyroscopes. The mechanics is developed in a logical manner which gives a clear insight into the function, the pendulum providing the reaction force, which leaves an unbalanced moment to be countered by the gyroscopes, which also constitute the power take-off. The result is a relatively small machine with no external moving parts. The treatment requires no understanding of wave hydrodynamics. It is felt this paper may be of special interest as a design study, in which the relation between the mechanics and the development of the concept is peculiarly cogent.
Simplified Analysis and Design of the Hydraulic Ram Pump
Authors: Young B W 
Published: February 2007

Hydraulic ram pumps are currently of interest because they make use of a renewable energy resource and are environmentally friendly. Ram pumps are particularly appropriate for use in the developing world as their construction is basic and robust and they are inexpensive and easy to install and maintain. Numerous attempts to analyse the complex behaviour of a ram pump system have been made in the past, but few have been successfully translated into simple design procedures and none have resulted in a general method for a ram pump of any size. The analytical approach adopted in the present paper assumes constant friction loss in the drive pipe during acceleration and concentrates on zero recoil conditions at which optimum pump performance occurs. Four simple and general design equations are derived which incorporate conservative assumptions for the critical velocity in the drive pipe and the effect of system losses. Design examples are given and design predictions compared with new and existing test results. Conclusions are drawn regarding the relevance of traditional drive pipe length–drive pipe diameter (L/D) and drive pipe length–supply head (L/H) ratios.
Phase-Averaged Temperature Characterization in Swirl Burners
Authors: Fick W , Syred N , Griffiths A J , O'Doherty T 
Published: February 2007

Methods have been developed to represent the rotating temperature fields associated with a three-dimensional, time-dependent coherent structure, the precessing vortex core (PVC), formed in the exit of swirl burners. In conjunction with laser sheet visualization of the phenomenon and phase-averaged rotating velocity measurements a description of the phase-averaged rotating temperatures and associated flow fields has been made for the flow in a 100 kW swirl burner (modelled on a 2 MW system for the efficient combustion of low calorific value gases), fired on premixed natural gas and air with some 10 per cent of the fuel used being injected on the central axis as a pilot. The resulting calibrated temperature maps show comparable patterns to the laser Doppler anemometry velocity measurements and some basic structures associated with the PVC can be identified. Past the burner exit the PVC is shown to precess about the central axis and create a crescent-shaped region of high-velocity flow close to the exit wall and extending over about 180°. This structure extends to about one exit diameter downstream. Two flame regions are formed in this system. An inner yellow diffusion flame forms on the boundary of the PVC due to its coherence as the 10 per cent of the gas introduced on the axis passes directly into this structure. A much larger diameter annular blue premixed flame forms, which encloses the inner flame, restricts the oxygen supply and gives good flow visualization. The inner flame surrounding the PVC only breaks up when it hits the side of the reversed flow zone (RFZ) and bursts with the PVC, then coalescing with the outer flame. As a result of the PVC, uneven burning results on the outside of the flame with hot and cold regions corresponding to low- and high-velocity regions respectively. The PVC was found to be helical in shape with the helix angle (140° from x/De = 0.13 to x/De = 039 above the burner exit) acting in the opposite sense to that of the flame. The work has relevance to many areas where swirl burners or swirl-assisted combustion devices are used. In particular, high levels of swirl are probably best used in primary stages of air-staged low NOx burners where high levels of flame stability are sought under fuel-rich conditions. Subsequent air stages at lower swirl levels will tend to even out the non-uniform burning processes. In terms of acoustic resonance care must be taken to mismatch the PVC frequency with any of the natural frequencies of the system, as otherwise large-scale pressure fluctuations can result.
Designing for Quality—An Integrated Approach for Simultaneous Quality Engineering
Authors: Braunsperger M 
Published: February 2007

Automobile industry practice has shown that it is not sufficient merely to apply familiar quality control methods such as FMEA (failure mode and effects analysis) or QFD (quality function deployment), to introduce development process (DP) systems or to adopt project management procedures when an improvement in product quality is required. More than this has to be done: the product development procedure must be better arranged and made capable of achieving preventive quality assurance. This paper presents an all-areas quality assurance concept as drawn up in the body development area of the BMW AG company and implemented successfully in the course of several pilot projects prior to general introduction. It is intended to provide stimuli and encouragement for similar measures to be taken in other areas, for example in the machinery construction industry.
Improvement of the Accuracy of a PUMA 560 Industrial Manipulator by Calibration
Authors: Greig A R , Lovell S P 
Published: February 2007

Compared to their repeatability, the accuracy of industrial manipulators is disappointingly poor. To permit off-line programming of manipulators and interaction with their local surrounds a high positional accuracy is required; this is particularly true for operation under supervisory control. The accuracy of a manipulator can be improved by calibration of its link lengths and joint angle measurements. This paper presents the results of the calibration of a PUMA 560 industrial manipulator and discusses simplifications to the procedure and theory which improve the practicality of the method without seriously compromising the results. Circle point analysis is used with data points being recorded by a pair of theodolites; the relevant theory is presented in the Appendix. A joint error correction function is produced for each joint. A fourfold improvement in accuracy is demonstrated without unduly increasing the complexity of the kinematics or requiring a sophisticated end effector.
A Study on Parameter Optimization for Circumferential Gas Tungsten Arc (GTA) Welding of Small Pipes considering Backing Gas Pressure: Part 1: Analysis of Weld Pool Surface Profile
Authors: Na S-J , Lho T-J 
Published: February 2007

It is well known that the weld bead becomes wider and the weld pool hangs down as the circumferential welding of small-diameter pipes progresses, if constant welding conditions are maintained over the entire joint length and/or no appropriate backing gas is supplied into the pipe. In order to obtain a weld bead which is uniform in width and does not hang down over the whole circumference of the pipe, the welding parameters such as welding current, welding velocity and backing gas pressure should be optimized as the welding progresses. In order to optimize the welding parameters, a mathematical model for determining the temperature distribution in the pipe workpiece and the surface profile of the resultant weld pool is indispensable. An efficient finite difference model was adopted for calculating the three-dimensional transient temperature distribution in circumferential gas tungsten arc (GTA) welding of pipes. Its solution was obtained by employing the alternating direction implicit (ADI) finite difference method, in which a periodic boundary condition and a periodic cubic spline function were used. For calculating the weld pool surface profiles in full penetration circumferential welding of pipes, a governing equation was derived in the cylindrical coordinate and solved using a simple finite difference model with the ADI scheme. In Part 2 of this paper, an efficient parameter optimization method is used to evaluate the optimal welding current for a required bead width when the welding velocity is given.
Analysis and Computer Simulation of the Electrochemical Machining Process: A Stepped Moving Tool Eroding a Plane Surface
Authors: Hardisty H , Mileham A R , Shirvani H 
Published: February 2007

This paper presents a theoretical and computational investigation of the electrochemical machining (ECM) process, for the important practical case of a stepped tool eroding an initially flat work surface. A fully automatic computer package based on the finite element method (FEM) has been developed which simulates the two-dimensional ECM process. To provide theoretical benchmarks for the computer simulation, differential erosion of a step has been analysed in terms of the one-dimensional processes on either side of it. To facilitate this analysis, the basic erosion equation has been approximated by a simple exponential relation, which becomes increasingly exact as time increases. This has enabled explicit equations for the time required to machine a step to be developed. This simple theoretical model both provides insight into the ECM process and facilitates design estimates of the time required to erode a step to a given tolerance. Five characteristic cases of erosion with a stepped tool have been summarized in parametric form. For one of these cases, results from the two-dimensional computer simulation have been compared with theory; there is good agreement. It is intended that the computer results from the four remaining cases will be presented in a later companion paper which will provide additional information on the computer package and the two-dimensional results from it.
Shot Peen Forming Sheet Metal: Finite Element Prediction of Deformed Shape
Authors: Grasty L V , Andrew C 
Published: February 2007

Shot peen forming is a production process used to create curved metal parts from sheet. It is commercially important despite the fact that its mechanisms are not fully understood; peen forming programmes are currently generated using experience and trial and error. The purpose of this work is to increase the predictability and range of application of the process by advancing its understanding. Finite element analysis proved to be a satisfactory procedure for studying shot peen forming. The stress distribution in a sheet arising from multiple indentations, as occur in shot peen forming, was modelled. A technique of squeezing the upper layers of a finite element model was shown to be a good simulation of the stress distributions resulting from shot peen forming, and provided a much more tractable analysis with respect to computing time and resources.
Criterion for the Locality of a Manipulator Arm with Respect to an Operating Point
Authors: Abdel-Malek K 
Published: February 2007

Criteria for determining an optimum locality of a manipulator arm are developed. In many cases, in a manufacturing environment, the tools, fixtures and targets that a manipulator has to deal with cannot be relocated. Thus, the choice of the manipulator locality is important. The method presented in this paper uses the notion of a service sphere to determine required orientability at an operating point. The boundary surfaces to the wrist-accessible output set is determined and positioned such that the service sphere is inside the wrist-accessible output set. To determine boundary surfaces of the wrist-accessible output set, manipulator singularities (internal boundary, and higher order) are computed and substituted into the constraint equation to parameterize singular surfaces. Part of these surfaces may lie internal to the boundary while other parts are a subset of the boundary. Singular surfaces are then intersected to determine second-order singularities. Second-order singularities partition surfaces into subsurfaces. Those subsurfaces on the boundary are determined by perturbing a point on the surface and concluding whether the perturbed point satisfies the constraint equations. The boundary to the wrist-accessible output set is then located with respect to the service sphere. The locality of the manipulator is determined for maximum orientability.
Rotational Moulding of Liquid Polymers
Authors: Harkin-Jones E , Crawford R J 
Published: February 2007

The vast majority of rotationally moulded articles are produced from powdered polymers. However, the moulding process developed originally from the use of liquid polymers and nowadays there is a renewed interest in such systems because of some unique advantages that they offer. This paper compares the behaviour of three different liquid polymer systems—nylon 6 by ring-opening caprolactam, polyvinyl chloride plastisol and polyurethane. The flow behaviour of each material is examined with particular reference to wall thickness distributions and bubble formation in the product. On the basis of this, criteria for the production of fault-free mouldings have been established. The interrelationships between mould shape and resin viscosity are also examined and an ideal viscosity—time—temperature profile is proposed for liquid polymer systems. Finally, a general comparison of the materials is made with regard to material handling, safety, cycle times, etc.
Robotic Assembly Operation Strategy Investigation Without Force Sensors Through the Research on Contact Point Location and Range of Peg Movement
Authors: Qiao H , Dalay B S , Knight J A G 
Published: February 2007

The assembly operation plays an important role in manufacturing industry. The robotic peg-hole insertion operation, the most widely used assembly model, has been heavily studied due to its widespread application. The purpose of the research in this area is to design techniques that enable the robot to perform assembly operations with high speed, high accuracy and low cost. The key problems of strategy investigation research include: (a) designing a series of sub-goals through which the peg-hole system can achieve the insertion operation from any point in the initial area, (b) calculating the allowable range for the initial area, (c) determining the values and duration of the control inputs and (d) analysing the robustness of the strategy. There are many strategies given to perform the assembly operation with the assistance of specially designed force sensors or flexible wrists. In this paper: 1. The map from the position of the peg in the coordinate frame attached to the hole and the location of the contact point in the frame attached to the peg was analysed. This provided the basis for the identification of the position relationship between the peg and the hole using a force sensor signal. 2. The range of peg movement was analysed and found to be useful in the selection of the sub-goals for the insertion operation. 3. A deficient and yet precise hardware strategy, characterized by not requiring force sensors or flexible wrists, was analysed. 4. The validity of the deficient hardware strategy was demonstrated through experiments with the UMI-RTX robot. The results were further confirmed through simulation. The allowed initial area, the control input design and the robustness of the strategy were analysed in detail. A constant cycle time of 2.5 s was achieved during the ten trials in which the diameters of the pegs were selected from a choice of 29.99, 31.98 or 31.99 mm with a clearance between the hole remaining at 0.02 mm and a common peg legnth of 41 mm.
Removal of Pinholes and Bubbles from Rotationally Moulded Products
Authors: Spence A G , Crawford R J 
Published: February 2007

The rotational moulding processing method for plastics is steadily expanding its product range and market areas. However, a drawback of the process has always been the surface pinholes and internal bubbles which occur in the products due to the inherent nature of the process. In an attempt to alleviate this problem, a programme of research has been carried out to investigate the factors that affect the formation of the bubbles and more importantly influence their removal. This paper describes how bubbles in rotationally moulded products can be removed by pressurizing the inner atmosphere of the mould. It has been shown that bubbles were successfully removed from MDPE (medium density polyethylene) by introducing a low pressure (0.5 bar) inside the mould after the polymer had melted. The removal of bubbles using pressure was shown to increase the impact properties (25 per cent) and the tensile properties (5 per cent) of the moulding while also reducing the cycle time. Pressure was successfully used to remove bubbles from other rotational moulding materials, such as polypropylene, Nylon 12, polycarbonate, ethylene vinyl acetate and ethylene butyl acetate.
The Characterization of Mixed-Mode Energy Release Rates in Orthotropic Materials
Authors: Walker C A , Jamasri  
Published: February 2007

The aim of this work was to predict, from the material constants, mixed-mode energy release rates in orthotropic materials, in particular the general cases in which the crack is aligned at a random angle to the principal material direction, normal to the plane of orthotropy. Two-dimensional finite element models with various fibre orientations were generated. The finite element models were validated by comparing two sets of contour plots of deformation, one resulting from the finite element analysis and the other from moiré interferograms of the experimental work. On comparison there was shown to be a strict similarity between experimentally determined and computational deformation fields. Variations of the energy release rates were investigated for both rapid and stable crack growth. This was accomplished by generating two-dimensional stable crack growth finite element models. In general, energy release rates were found to be strongly affected by the fibre orientation. An increase of the angle of the crack growth direction caused a decrease of the mode I energy release rate and, by contrast, an increase of the mode II energy release rate, but the mode II energy release rate was always a small fraction of the mode I value. Crack extension caused a gradual increase of the mode I energy release rate both for coplanar and non-coplanar crack growth. However, there was no significant effect found on the mode II energy release rate.
A Technique for Experimental Acoustic Modal Analysis
Authors: Whear F R , Morrey D 
Published: February 2007

A technique developed to carry out experimental acoustic modal analysis using commercially available structural modal analysis software is described. This uses a finite difference calculation to determine the spatial variation in pressure. In order that the resulting function exhibits the same nodes and antinodes as the actual pressure distribution at resonance, a second-order finite difference calculation is performed to obtain the second spatial derivative. This is implemented in practice using a three side-by-side microphone probe with an analogue differential amplifier. The technique is verified by measuring the natural frequencies and mode shapes of a bare rectangular office. These results are compared with analytical calculations and output from a finite element model. The results show very good agreement for all modes in the frequency range of interest.