bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulated fuel feedback control of a fuel injection engine using a switch type oxygen sensor
Authors: Park K S , Park J , Kauh S K , Ro S T , Lee J
Published: October 2002

The jump—ramp control algorithm has been widely adopted for the air—fuel ratio control in a fuel injection spark ignition (SI) engine by using a conventional on—off type oxygen sensor. But the jump—ramp control method has limitations in improving the frequency and amplitude of the air—fuel ratio oscillation. This study suggests a new feedback control logic called modulated fuel feedback control, which has a concept of pretuned air—fuel ratio oscillation. In the modulation method, the oxygen sensor output is not treated as on—off but as an analogue for feedback. By using the modulation method, the frequency and amplitude of the air—fuel ratio oscillation can be controllable to some extent to improve the conversion efficiency of a three-way catalyst. The results show that the performance of the modulation method is better than that of the jump—ramp control method in reducing the amplitude of the air—fuel ratio oscillation as well as in increasing the frequency of the air—fuel ratio oscillation.
A two-degree-of-freedom ambulance stretcher suspension Part 1: System overview
Authors: Raine J K , Henderson R J
Published: October 2002

Ambulance suspensions often give a poor ride, which may result in deterioration in the condition of ill or injured patients. Suspension of the ambulance stretcher itself is a lower cost option than a purpose- built ambulance suspension and may offer superior isolation of the patient from road-induced disturbances. This paper describes the development of a pneumatic stretcher suspension offering both pitch and heave isolation. Design and theoretical considerations are outlined, and preliminary performance figures reported. Subsequent parts of this paper will explore the dynamics of the system with pneumatic damping and report on the performance of the prototype suspension for a range of patient masses, damping levels and floor vibration inputs.
Optimization of design parameters of rigid-link track systems using an advanced computer aided method
Authors: Wong J. Y.
Published: October 2002

This paper describes the applications of a computer aided method known as RTVPM to the selection and optimization of the basic design parameters of track systems with rigid links, commonly in use in agricultural and industrial vehicles. It is found that the ratio of roadwheel spacing to track pitch is a significant parameter that affects the tractive performance, particularly on soft terrain. For a given track system configuration and roadwheel spacing, it is important to select an appropriate track pitch to ensure good tractive performance on the one hand and minimal vehicle speed fluctuation on the other. It is also shown that the initial track tension has a considerable effect on tractive performance when the ratio of roadwheel spacing to track pitch is high and that its effect decreases with the decrease of the roadwheel spacing to track pitch ratio. The effect on tractive performance of the ratio of roadwheel spacing to track pitch becomes less significant with the increase of soil strength. It is demonstrated that by selecting the appropriate ratio of roadwheel spacing to track pitch, initial track tension, location of the centre of gravity and other design parameters, an optimum track system configuration for a given operating environment can be evolved.
Stresses and deformations in overlapped diesel engine crankshafts, Part 1: Experimental results
Authors: Bickley I , D'Olier V , Fessler H , Hyde T. H. , Warrior N. A.
Published: October 2002

Single-throw, epoxy resin models of five overlapped crankshafts with side-by-side connecting rods have been loaded in pure torsion or bending. Bending loads considered are those due to the radial or tangential components of the connecting rod force and those due to pure radial bending or radial bending due to journal displacement.

After the photoelastic frozen-stress cycle, deformations and stresses in the crankpin and journal fillets were measured. The principal stresses were determined over the whole highly stressed (toroidal) fillet surfaces. At each angular position around the crankpin and journal the magnitude, meridional position and direction of the greatest principal stress were obtained. In torsion these maxima were fairly constant with angular position, whereas in bending they varied linearly, as in a simple beam in bending. The results were expressed as stress concentration factors based on nominal stresses in a bar of the same diameter as the crankpin.
A compact particulate dilution tunnel for the characterization of diesel exhaust
Authors: Chan S. H. , Sun J. H. , Low S. C.
Published: October 2002

This paper presents the design of a compact particulate dilution tunnel used for characterizing diesel exhaust. Details of particulate mass concentration calculations based on various methods and the estimations of tunnel flow temperature and relative humidity due to psychrometric mixing between the extracted exhaust gas and diluting air are also elaborated.
V-ribbed belt design, wear and traction capacity
Authors: Yu D , Childs T. H. C. , Dalgarno K. W.
Published: October 2002

Laboratory dynamometer experiments have been performed on the running-in of an automotive K-section V-ribbed belt. The rib shape has been found to change, owing to wear, in three regions. At the top of the rib, a shoulder develops; at the root of the rib, debris piles up; in between, the rib wears without change of slope. The main changes occur in the first 20 h of running-in conditions chosen to represent loads found in practice; after running for 250 h, further changes could hardly be observed. The measured rib profiles were input to finite element calculations of the contact pressures between the ribs and the pulley grooves. The purpose was to study the way in which load was shared between the rib flanks and the rib roots and further to study the reduction in traction capacity of the belt due to increased root loading as wear progressed. After running for 250 h, the belt was estimated to have about a 10 per cent lower maximum traction coefficient than when it was new. An improved belt design is suggested, to enable high traction capacity to be maintained for longer times.
Improvement in vehicle aerodynamic drag and rolling resistance determination from coast-down tests
Authors: Petrushov V. A.
Published: October 2002

The coast-down method is the way to determine the vehicle drag value and its relationship to the aerodynamic configuration and tyre parameters under conditions of real atmospheric turbulence and road covering. Since all coast-down techniques available are based on the measurements of the test object speed or its deceleration which are the main source of experimental data errors, it is of great importance to phase these variables out of use. This paper describes the method based on the time—distance function to be derived by a new solution of the coast-down equation that is free from speed and deceleration. This enables a considerable group of measurement error sources to be eliminated and the coast-down technique sensitivity to be increased; so the small drag alterations due to the changes in vehicle aerodynamic configuration or tyre parameters, such as load, inflation pressure and temperature, can be detected. Road—tunnel and road—bench correlation fields are essentially enriched for the vehicle design purposes.
Technical Note: A two-degree-of-freedom ambulance stretcher suspension: Part 3: Laboratory and road test performance
Authors: Henderson R. J. , Raine J. K.
Published: October 2002

Parts 1 and 2 of this paper gave a design overview and described the dynamics of a prototype two-degree-of-freedom pneumatic suspension for an ambulance stretcher. This concluding part briefly reviews laboratory shaker table and ambulance road test performance of the suspension with passive pneumatic damping. The suspension system is found to offer compact low-cost isolation with lower natural frequencies than achieved in earlier mechanical systems.
Effects of exhaust gas recirculation temperature on diesel engine combustion and emissions
Authors: Ladommatos N , Abdelhalim S. M. , Zhao H
Published: October 2002

When hot exhaust gas is mixed with inlet air, the charge to a diesel engine is modified in three ways: the charge temperature increases, the total charge mass is reduced and the charge composition changes. This paper is concerned with the effects on combustion and pollutant emissions of only the first two items. The last item has been investigated by the authors previously and reported in references [1-4]. The investigation was conducted on a high-speed direct-injection diesel engine at about 40 per cent of full load, 2000 r/min and constant fuelling rate. The investigation included in-cylinder heat release and exhaust gas analysis. It was found that increasing inlet charge temperature, at constant inlet charge mass and composition, increased oxides of nitrogen (NO x) and particulate exhaust emissions but reduced unburnt hydrocarbon (UHC) emissions. When the inlet charge mass was reduced at constant inlet temperature, the exhaust particulates and UHC emissions increased substantially, principally because the oxygen available for combustion was reduced. In contrast, NO x emissions increased only slightly, probably because the effects on NO x of a higher combustion peak temperature tended to be offset by substantially lower oxygen availability.
A study to investigate the capability of adsorbents for reduction of cold-start emissions
Authors: Miller A. L. , Ginter D , Seaba J. P. , Loyalka S. K. , Ghosh T. K.
Published: October 2002

Most of the emissions (about 60 per cent) from automobiles occur during a cold start before the catalytic converter becomes active. The use of an adsorbent trap for temporary storage of emitted hydrocarbons before catalysts attain the light-off temperature in the converter has been investigated as a means for reduction of cold-start emissions. The hydrocarbon emissions can be reduced significantly if the hydrocarbons are retained by the trap until catalysts reach the light-off temperature. The effect of engine speed on the emission of NO x, CO and hydrocarbons and their subsequent retention in the adsorption trap was studied. A hydrophobic adsorbent, Hisiv-1000, and molecular sieve 13X were used individually and in conjunction in the trap to adsorb hydrocarbons. Although significant amounts of hydrocarbons were adsorbed in the trap initially, they were released from the trap rather quickly even before catalysts reached the light-off temperature.
Robust adaptive control of an active vehicle suspension system
Authors: Ramsbottom M , Crolla D. A. , Plummer A. R.
Published: October 2002

This paper describes the development of an adaptive control scheme for an active vehicle suspension system. The proposed scheme comprises a variant of the self-tuning pole assignment algorithm and a simple fuzzy logic gain scheduling controller. In this work, the active suspension problem is interpreted as one of regulation and setpoint tracking and, as a consequence, combined ride and levelling control is realized. Simulation results for a quarter vehicle model indicate that ride performance benefits can be achieved in parallel with levelling control capabilities. Moreover, it is shown that this scheme retains good control performance even in the presence of vehicle configuration uncertainties and road disturbance changes.
An operating point optimizer for the design and calibration of an integrated diesel/continuously variable transmission powertrain
Authors: Brace C. J. , Deacon M , Vaughan N. D. , Horrocks R. W. , Burrows C. R.
Published: October 2002

The use of a continuously variable transmission (CVT) with an integrated engine controller allows great freedom of choice of the engine operating point to deliver the power demanded by the driver. This flexibility places even greater emphasis on the requirement to locate an appropriate engine operating point. A technique has been developed that locates the ideal instantaneous engine operating point by minimizing a simple weighted sum of exhaust emissions and fuel consumption predicted by an artificial neural network. This process may be configured automatically to take account of varying operating or environmental conditions, allowing the optimum performance to be returned by the powertrain controller at all times. The structure has been implemented for a turbocharged and intercooled direct injection diesel engine used as the prime mover in an integrated powertrain. Results are presented that demonstrate the use of the optimizer to derive widely varying operating schedules for the engine, each with associated emissions and economy implications. The optimizer code is sufficiently compact to be incorporated into a practical powertrain control strategy. Experimental work presented in a companion paper has confirmed that this ‘systems’ approach to powertrain control allows the emissions and economy performance of the vehicle to be tailored to suit the particular requirements of the installation.
Prediction of the performance of a split/circulated power transmission
Authors: Jo H-S , Lim W-S , Park Y-I , Lee J-M
Published: October 2002

A method for the prediction of performance is presented in this paper for the design of a vehicle having a split/circulated power transmission with slip elements and planetary gears. Internal power flow patterns of such systems are also theoretically analysed using mathematical modelling. To estimate the usefulness of the designed power transmission, a geometrical approach is proposed by the performance locus diagram which presents the overall characteristics of the system. This enables complete prediction of the qualitative performance and the effect of design factors. These factors are the system layout, the types and gear ratios of the planetary gears and the design parameters of the slip elements. The predicted results of the power transmission are compared with those of experiments using a dynamometer.
The influence of the interface coefficient of friction upon the propensity to judder in automotive clutches
Authors: Centea D , Rahnejat H , Menday M. T.
Published: October 2002

This paper presents an investigation of the driveline torsional vibration behaviour, referred to as judder, which takes place during the clutch engagement process, particularly on small trucks with diesel engines. A non-linear multibody dynamic model of the clutch mechanism is employed to study the effect of various clutch system and driveline components on the clutch actuation performance. The paper demonstrates that judder is affected by driveline inertial changes, variation in the coefficient of friction, μ, of the friction disc linings with slip speed, v, and the loss of clamp load. The results of the simulations show that various friction materials with different μ- v characteristics produce torsional self-excited vibrations of the driveline. The results also show that loss of clamp load relating to the speed of clutch actuation also contributes to judder. Furthermore, it is shown that the simulation results conform closely to the experimental findings.
Mathematical modelling of precious metals catalytic converters for diesel NOx reduction
Authors: Kandylas I. P. , Koltsakis G. C. , Stamatelos A. M.
Published: October 2002

Precious metal catalysts for NO x reduction in lean diesel engine exhaust conditions are characterized by a narrow temperature range of efficient operation and require high availability of reducing species in significant concentration. Consequently, there exists a large optimization potential in the design and control of lean-NO x catalytic conversion systems. A mathematical model of the transport and chemical phenomena in platinum-based lean-NO x catalysts was formulated, based on the experience with analogous models for gasoline three-way catalysts. A simplified four-reaction scheme is employed, considering the oxidation of CO, H2 and hydrocarbons (HCs), as well as the reaction between NO x and HCs. Results are compared with previously published laboratory and engine data in order to assess the capacity of this approach in representing real-world behaviour of Pt-based lean-NO x catalysts. Initial results illustrate the power and flexibility of the model, which is able to predict the NO x conversion characteristics in model gas tests as well as in full-scale engine tests with reasonable accuracy.
A theoretical analysis for the dynamic axial crushing of top-hat and double-hat thin-walled sections
Authors: White M. D. , Jones N
Published: October 2002

An approximate theoretical analysis is presented for the mean crushing forces generated during the dynamic axial loading of top-hat and double-hat sections. The theoretical predictions compare favourably with experimental results reported in a companion article on spot-welded mild steel sections and with the empirical equations and theoretical predictions of other authors.
Thermodynamic modelling of complete engine systems—a review
Authors: Chow A , Wyszynski M. L.
Published: October 2002

This paper gives an overview of engine systems modelling by first and second law analysis. Complex engine systems are becoming more commonly implemented to meet the increasing demands of fuel efficiency and emission legislation. Future engine systems may also include both exhaust gas treatment and fuel processing devices. This leads to complex interactions within the thermodynamics and chemistry of powerplant systems. There is therefore a need to improve the systems modelling methods. This concerns first of all the composition tracking and the models of three-way catalytic exhaust converters and fuel processors. The applicability of gas dynamics modelling to chemically complex systems is also discussed. All these processes need to be modelled as interacting parts of one system.
A centralized hydraulic system for passenger cars
Authors: Darling J , Tilley D. G. , Hickson L. R.
Published: October 2002

The majority of passenger vehicles use separate hydraulic circuits to drive and control high-power components such as the braking and steering systems. While this approach is acceptable, it is possible for significant improvements in effficiency to be achieved using a centralized system. In order to establish the advantages and disadvantages of the distributed and centralized approaches, a simulation-based feasibility study of the pressure, flow and power requirements of the individual engine cooling, anti-lock braking system (ABS), semi-automatic transmission, active roll control and power assisted steering subsystems was carried out.

Using a realistic drive and load cycle together with simulation models accounting for component non-linearities and dynamics, the flow requirements of an integrated hydraulic system were established. It was shown that the steering and roll control suspension requirements were complementary. The steering system requires high flow at low forward speeds, while the suspension requires high flow during conditions of high speed. In addition it was shown that, although the peak flow requirements of an integrated system were high, the mean flow was moderate and the high demands could be met using small accumulator units, suggesting that the system would be feasible for use in passenger cars. Finally, an energy efficient integrated hydraulic circuit including some degree of safety back-up is proposed.
Effect of the suspension structure on equivalent suspension parameters
Authors: Kim C , Ro P. I. , Kim H
Published: October 2002

This paper examines the uncertainties in modelling a real suspension system that are due to the effect of suspension linkage layout (or structure) on the equivalent suspension parameters of a corresponding mathematical model. In most research on active suspension systems, a quarter-car model of two masses is very often used. However, without considering the influence of the suspension kinematic structure, the simple model may not be as effective as might be expected because of the uncertainties in the suspension parameters. Two sets of identified parameters for different suspension systems are compared to show the effect of suspension structure on the equivalent parameters. The relationships between specific parameters and changes in certain suspension linkage layouts are also investigated. The benefits of the parameter identification are demonstrated in the process of designing two active systems (one using a sky-hook control law and the other using a sliding mode control technique). The results show that suspension structure has a strong effect on the equivalent suspension parameters and this relationship becomes more important as the structure of suspension increases in complexity. The advantage of the identification process is crucial in designing both linear and non-linear active suspension systems.
Dynamic response of the Hybrid III three year old dummy head and neck during side air bag loading
Authors: Duma S. M. , Crandall J. R. , Pilkey W. D. , Seki K , Aoki T
Published: October 2002

This paper presents the results from 14 tests designed to evaluate the response and injury potential of a Hybrid III three year old dummy subject to loading by a deploying seat mounted side air bag. An instrumented Hybrid III three year old dummy was used for tests in two different occupant positions chosen to maximize head and neck loading. Four seat mounted thoracic side air bags were used that varied only in the level of inflator output. The National Highway Traffic Safety Administration's neck injury criteria for complex loading were modified to include moment values for both anterioposterior and lateral directions. The results indicate that side air bags may be designed so that the forces and moments in the child dummy's neck are below injury threshold values during a side air bag deployment. While there is considerable uncertainty as to the validity of published injury criteria owing to the lack of child biomechanical data, this study demonstrates the sensitivity of child response to initial position which provides insight into placement and geometry of side airbag systems. Furthermore, the data indicate a relationship between airbag inflator properties and child dummy response for a given airbag geometry.
Observer-based control of vehicle semi-active suspensions
Authors: Yi K , Song B. S. , Park J. H.
Published: October 2002

This paper presents an observer-based controller for vehicle semi-active suspensions. Vehicle suspensions are disturbance-affected dynamic systems and semi-active suspensions can be represented as a bilinear model. A new methodology for designing observers for vehicle semi-active suspensions has been proposed. The proposed methodology simplifies the observer design process and is convenient for implementation. An observer is formulated such that the estimation error is independent of unknown road disturbances. The proposed observer uses easily accessible measurements, such as accelerations, and guarantees exponentially convergent state estimations for suspension deflections and velocities. The absolute sprung mass and unsprung mass velocities can be estimated using the proposed observer. Simulations and experimental rig tests show that all states of a semi-active suspension can be estimated only with acceleration measurements. The estimated states are used to improve ride quality in a semi-active suspension. It has been shown that the performance of the observer-based controller is comparable to that of a controller using measured states.
A new concept of misfire detection using a wide-range oxygen sensor in a spark-ignition engine
Authors: Chung Y , Choi S , Bae C , Yoon K
Published: October 2002

Misfiring in spark-ignition engines can cause immediate damage to the catalyst and increase emissions since it brings unburned fuel and oxygen into the catalyst, resulting in an increase in temperature owing to subsequent combustion. Therefore, misfirings must be detected, as specified in the on-board diagnostics (OBD) regulations. One of the common methods of misfire detection is to detect the fluctuation in angular velocity of the crankshaft, which can be misdetected under conditions of high speed and low load and under conditions of rough road driving. An alternative method of misfire detection is suggested here, which utilizes the signal fluctuation of a wide-range oxygen sensor installed at the confluence point in the exhaust manifold. To understand the fluctuation in the wide-range oxygen sensor signal caused by a misfiring, the fluctuation in oxygen concentration in an exhaust manifold was estimated by measuring the hydrocarbon concentration. The effect of the transient response of a wide-range oxygen sensor on misfire detection performance was also investigated. It was found that differentiation of the sensor signal gives the criteria for misfire detection. The misfiring can be detected by monitoring the amplitude of the fluctuation in the differentiated signal, and the misfired cylinder can be identified by monitoring the phase delay between the peak point of the differentiated signal and a reference signal. This scheme has been shown to detect the misfiring condition reliably and to identify the misfiring cylinder up to an engine speed of 5000 r/min.
Study of combustion characteristics of a compression ignition engine fuelled with dimethyl ether
Authors: Huang Z. H. , Wang H. W. , Chen H. Y. , Zhou L. B. , Jiang D. M.
Published: October 2002

This paper presents the combustion characteristics of a light-duty direct-injection diesel engine operating on dimethyl ether (DME). The indicated pressure diagrams and injector needle lifts are recorded and the combustion characteristics are demonstrated and compared with those of an engine operated on diesel fuel. The experimental and calculated results show that the DME engine has a longer delay of injection and duration of injection, a lower maximum cylinder pressure and rate of pressure rise, as well as a shorter ignition delay compared with those of a diesel engine. The DME engine has a low mechanical load and combustion noise, a fast rate of diffusion combustion and a shorter combustion duration than that of a diesel engine. It has the ideal pattern of compression ignition engine heat release.
Dynamic measurements of particle concentration in solid-liquid slugging suspensions
Authors: Fossa M , Di Felice R
Published: October 2002

Experiments have been carried out to analyse the characteristics of liquid suspensions which exhibit a non-uniform solid concentration. In order to investigate the bed behaviour, a new probe was developed and tested to measure the instantaneous concentration of solid particles. Attention is focused on slugging solid-liquid fluidized beds, where regions of low solid concentration alternate with regions of high solid concentration. The analysis of the results allowed some relevant flow characteristics (slug frequencies and slug velocities) to be recognized.
Scale, order and complexity in polymer processing
Authors: Bush S F
Published: October 2002

From slow beginnings in the 1860s, the evolution of the polymer industry has been marked in the second half of the twentieth century by rapid increases in the scales of production, by increasing power to control order at the molecular level, and by the variety and complexity γ of the resultant processes and products. The paper reviews some of the key developments over the last 100 years or so with a view to identifying themes likely to be of continuing importance in the new century.

A general model for the cost of a processing technology is proposed in terms of the factors Q and γ involved in producing a given artefact. Particular technologies are discussed in terms of the order in which basic processing functions are carried out. A major trend likely to continue into the twenty-first century is the way in which the supramolecular organization of the polymer chains is increasingly being brought under control, either directly by processing or indirectly by self-ordering properties of the polymers themselves. Self-organization of reinforcing fibres during processing to produce optimal performance of polymer composites is a parallel trend also likely to develop further into the next century. To illustrate these ideas the paper draws on examples from major polymer processes: extrusion, injection moulding, film blowing, reaction moulding, thermoforming, fibre making and coating.
Process system regulation with minimum control effort
Authors: Whalley R , Ebrahimi M
Published: October 2002

The regulation of process systems which may be described by linear multi-variable Laplace-transformed models having finite time delays is considered. Conventional frequency response methods are employed to assess relatively stability. A feedback strategy which will minimize the control effort required to confine output changes following disturbance inputs is employed. Typical process system models are investigated using output feedback. Computer-simulated response characteristics are presented.
Offshore technology—advances at the dawn of the new millennium reviewed from a UK perspective
Authors: Lyons G J
Published: October 2002

This paper considers the technologies that have enabled offshore hydrocarbons production to reach the existing limits, and what may be required realistically to extend these limits further at the beginning of the new millennium.

Advances are considered which relate to many parts of the world. Each has its own particular challenges. The viewpoint presented here is, however, from the United Kingdom.
The characteristics of rotary feeders used for the flow control of particulate materials
Authors: Reed A R , Bradley M S A , Pittman A N
Published: October 2002

Rotary feeders are one of the most widely used devices for regulating the flow of powdered and granular solid materials from storage facilities such as hoppers, silos, bins and bunkers. In this paper the performance characteristics of such feeders are examined, from both model and experimental standpoints, with a view to enhancing understanding of the operation of these devices. Through understanding the way in which materials flow through the inlet port and into the rotor pockets a model is developed that describes how the feed rate varies with the rotor speed. Experimental work confirms the general form of the characteristics predicted by the model studies. An approach is developed for predicting the feed rate characteristics when handling free-flowing materials having particle sizes greater than 5 mm. Further work is necessary to predict these characteristics when handling materials have particles smaller than this size.
Milling, mixing and tempering—an engineering view of chocolate
Authors: Beckett S T
Published: October 2002

The confectionery market in the UK is larger than that of tea, newspapers and bread put together. Chocolate accounts, to some degree, for nearly two-thirds of this market and, as its manufacture is relatively complex, carefully controlled processing is required. These processes include, grinding, mixing and crystallization. This review outlines the most common methods of making chocolate by describing the machines that are used and explaining what the individual processes are designed to achieve.
It's not what you do, it's why you do it that makes the difference between engineering and science: The strategy and structure of process engineering in the United States
Authors: Axon C J , Howell J A
Published: October 2002

The dramatic changes to academic process engineering by the UK's largest competitor, the USA, has led them to be stronger, more successful and more vibrant. It is advocated here that unless the UK also makes appropriate changes, it will not survive in the global process engineering marketplace.

This paper reports on some of the conclusions of a study carried out last year by a group of young academics who visited the USA in late 1998. The report's findings have significance beyond chemical process engineering and touch all areas of engineering research in the UK (and further afield). It is concluded that universities must change the way that they develop the careers of younger staff, train students (under- and postgraduate) and promote collaboration between the different pure sciences and engineering. In addition, ideas are presented for both the Funding Councils and industry for ways in which they might change to meet the challenges just around the corner.
Thermodynamic performance simulation of a twin-screw multiphase pump
Authors: Feng C , Yueyuan P , Ziwen X , Pengcheng S
Published: October 2002

A twin-screw pump is a positive displacement pump widely used in various applications such as the petroleum, shipbuilding and foodstuff industries. It can pump some special fluids, such as multiphase fluids and non-Newtonian fluids, which cannot be boosted by other kind of pumps. Profile generation, rotor geometry characteristics and mathematical models to predict the backflow within twin screw multiphase pumps are presented in this paper. On the basis of this analysis, the fundamental equations are provided to simulate the working process of the pump. Also presented is a discussion on the relationship between the slippage rate and the differential pressure, suction pressure, gas void fraction and the rotor rotational speed. In order to verify the mathematical model, performance data of a prototype multiphase pump are measured and the pressure generation process is recorded by using a signal analyser. From the comparison between the simulation result and experimental data, it is shown that the model can simulate the working process of a twin-screw multiphase pump successfully.
Aspects of the elastic stability of walls in rectangular planform steel silos
Authors: Brown C J
Published: October 2002

This paper deals with the use of light stiffeners to prevent elastic instability in the walls of rectangular planform steel silos and offers advice about their most effective use. It shows that significant potential material savings can be achieved if reduced silo wall thickness is used with torsionally stiff ring beams or with stiffeners placed on the surface of the plate to increase flexural stiffness. Vertical stiffeners are more effective than horizontal stiffeners in resisting elastic buckling.
The effect of change in flow rate on the vibration of double-suction centrifugal pumps
Authors: Hodkiewicz M R , Norton M P
Published: October 2002

This investigation identifies changes in the character of vibration measured on a pump bearing housing resulting from flow below the best efficiency point for industrial double-suction single-stage units with different wear conditions. The paper develops a set of vibration features that will assist in identifying low flow conditions in double-suction pumps.
Monitoring the lubricant condition in a low-speed rolling element bearing using high frequency stress waves
Authors: Jamaludin N , Mba D , Bannister R H
Published: October 2002

This paper presents the results of an investigation into the development of a reliable, nonintrusive and effective technique capable of accessing the lubrication condition within a low-speed rotating bearing. This unique monitoring system is known as pulse injection technique (PIT) and involves transmitting a Dirac pulse through a bearing via a stress waves (SW) sensor. Analysis of measured stress wave signatures differentiated between a properly and poorly lubricated bearing. This method was found to be effective as stress wave propagation is sensitive to the transmission path, which in turn is affected significantly by the type and amount of grease present in the vicinity of the working elements of a bearing.

The ability of this technique to monitor the lubrication condition within a bearing whilst in operation could be utilised to determine the appropriate time for grease replenishment or addition.
Submicrometre particle separation via high-speed gas centrifuges
Authors: Hitchings A , O'Doherty T , Syred N
Published: October 2002

The separation of submicrometre particulate matter from gases is a problem that has attracted much interest over the years. Filter systems require low face velocities and hence tend to be of large size, while also requiring sophisticated, bulky, regeneration systems. A high-speed centrifuge which can be linked with a turbocharger has been developed which can remove particulates well into the submicrometre range in diameter. The centrifuge operates at speeds of up to 60 000 r/min, with the assistance of both axial thrust air bearings and radial foil bearings.

Experimental analysis of the centrifuge using particle sizing techniques etc. has shown the effectiveness of the system operating at a range of different flowrates. This has been done by comparing the relative effectiveness of the system for the different flowrates.

The paper discusses the analysis of the separative efficiency (i.e. the ability to concentrate particles into a small proportion of the gas) of the present system and the predicted efficiencies of future systems.
Modelling incompressible flow in a pressure relief valve
Authors: Francis J , Betts P L
Published: October 2002

Lift, blowdown and discharge of pressure relief valves depend ultimately on the flow structures generated within those valves. A report is made of an enquiry into the incompressible flow structure within such a valve. Commercial software is used to predict axisymmetric flow patterns inside a model of a real valve, and comparisons are made with the pressure distribution and force imposed on the real valve disc. The reliability of the simulation is further assessed using the oil-film technique to record reattachment lengths of separated shear layers. Results of the simulation are encouraging and have enabled flow regimes visible in the valve flow characteristic to be identified with the transition between separated flow patterns inside the valve.
Local flow characteristics and its effect on cowled finned systems
Authors: Lin S , Griffiths A J
Published: October 2002

An experimental study of local flow characteristics within cowled finned systems has been carried out using laser Doppler anemometry (LDA). Such systems are used to control axial temperature profiles within the barrel of an extrusion process. During the experiments, a perspex model was used to simulate the actual system. The inlet Reynolds number within the air cowl was 1.72 × 104. The local flow between fins was characterized by the flow in the curved duct formed by the fin base tube, fin surfaces and air cowl around the outer diameter of the fins.

The flow pattern between the fins was measured at the sight windows on the air cowl wall. The local flow characteristics and its effect on heat transfer behaviour on fin surfaces were discussed. It was highlighted that the heat transfer through fin surfaces can be greatly influenced by the local flow characteristics. The mean heat transfer coefficient in the curved duct was estimated using both empirical equations and experimental results. The mean coefficient was also predicted using a computational fluid dynamics (CFD) package, and was underestimated by 12 per cent when compared with that found using the empirical relationships.
A computerized fault tree construction methodology
Authors: Andrews J D , Henry J J
Published: October 2002

A new approach to automating the fault tree construction process is proposed. The methodology has features which make it applicable to binary state systems and also to process control systems. Previous attempts to model the failure generation in systems have worked well on only a small sub-class of system types and have failed to produce a generally applicable method. Thus in some previous approaches there are desirable features which are worth retaining in a new construction method. The new method is based on the flexibility of the decision table method but incorporates a way of detecting, classifying and analysing control loops, similar to that used with operators in the digraph approach. As well as using operators to deal with control loops a new operator is introduced that deals with two-state circuits. This will mean that when constructing the fault trees, the difficulty of handling repeated events will be eliminated and the size of the tree structures will be significantly reduced. The developed algorithm can produce a tree format appropriate for direct input to an analysis code. The method is demonstrated in this paper by its application to a simplified safety system from the railway industry. This system has been selected as it exhibits features that are typical of two-state circuitry but is also small enough to illustrate the new developments introduced.
Identification of strength parameters for a high-pressure vessel wound by fibre reinforced composite materials
Authors: Qian L , Yuan R
Published: October 2002

In this paper a high-pressure vessel (HPV) is assumed to be wound by a set of macro-scopically orthotropic layers constructed respectively from unidirectional laminae. The formulae for the three-dimensional stress fields in the vessel are established. In the light of the Tsai-Wu failure criterion, the first ply failure internal pressure (FPFP) is calculated. Using this measured FPFP, the vessel strength parameters are identified by Bayesian methods.
Fracture of glass-reinforced plastic pipes of mixed wall construction under pressure loading
Authors: Kitching R , Hose D R , Priestner R , Hashemizadeh S H
Published: October 2002

Hand laid-up straight pipes of 250 mm inside pipe diameter, constructed from polyester resin matrix and E-glass reinforcement supplied in two different combinations of chopped strand mat (CSM) and woven rovings (WR) have been tested to destruction under internal hydraulic pressure. Results are compared with those from a similar pipe constructed from CSM only and one constructed by wrapping CSM layers on a PVC (polyvinyl chloride) liner. Failure pressures for the different constructions are compared with each other and with design pressures associated with two design codes. Features of the fracture patterns are noted, following an extensive microscopic examination of the straight pipes.
A process for the manufacture of cold, clean, dry air at temperatures down to 173 K and its application in the forced cooling of high-pressure rubber hose prior to wire braiding
Authors: Liu S Y , Wang P , Yan S P
Published: October 2002

This paper describes a new technique for freezing braided wire rubber hose with cold air produced by refrigeration using an air turbine. This work details the whole refrigeration system and the procedure, highlights the characteristics of the refrigeration cycle and the design of the freezing chamber and also discusses the present situation of the technique in a wide range of applications. It has been proved in the production practice of the rubber hose that this new technique is a pioneering and effective achievement with low production costs.
Pressures beneath the disc of a compensated pressure relief valve for gas/vapour service
Authors: Betts P L , Francis J
Published: October 2002

In this work, the pressure distribution was measured on the underside of a commercial valve disc ( in situ) when the relief valve was subject to choked compressible flow. The results indicate the limits of three-dimensional effects on the substantially axisymmetric flow. The results also show the position of the minimum section (throat) and shock wave; their behaviour with changing lift is seen to match that inferred from previous work.
Application of risk-based inspection for pressurized HC production systems in a Brunei petroleum company
Authors: Hagemeijer P M , Kerkveld G
Published: October 2002

A large number of ageing oil and gas production and evacuation facilities are owned and operated by BSP (Brunei Shell Petroleum). The company is facing the challenge of optimizing the return on inspection efforts in a period of time when more production is required and operating costs have to be minimized. Over recent years significant improvements have been made to BSP's system of planning and performing offshore inspection, in particular concerning the management of hydrocarbon process containment integrity, via a change from a periodic return inspection approach to a risk-based inspection (RBI) approach. This article presents the quantified benefits achieved to date, and the way this process of change has been/is being managed, firstly, to yield the major savings today, and secondly to sustain these gains by setting up processes and systems to support the new way of working.

The value of the RBI approach, in terms of its contribution to the company's business drivers, is summarized thus. Cost optimization—the implementation of RBI principles in BSP has reduced the inspection effort (per platform) significantly to a level, which only involves the ‘minimum required’. The move has been to invest more in planning, thereby reducing (eliminating some) offshore execution of work. These benefits have been quantified in Section 3.1. In addition, increased production availability—the approach has assisted in reducing planned shut down times and minimizing unexpected shut downs due to failures. The move has been from shutdown inspection to onstream inspection. These benefits have been quantified in Section 3.2. Finally, safety—has been improved primarily by reducing the likelihood of failures and having fewer inspectors commuting to and working offshore. The move has been to perform focused inspection on hot spots in the system to reduce HC losses. These benefits have been quantified in Section 3.3.
A method of plant design evaluation featuring maintainability and reliability
Authors: Thompson G , Geominne J , Williams J R R
Published: October 2002

This paper presents an evaluation method for plant systems that comprise many parts, typically systems that are formed by the synthesis of proprietary equipment. The evaluation method is intended for use in a design review exercise before construction or when considering plant enhancement. Maintainability and reliability considerations are integrated with plant performance parameters in the assessment method. Plant performance is assessed with respect to the proximity of the expected performance to the performance capability limits of equipment. Maintainability and reliability are assessed with respect to expected reasonable performance and by extensive check-lists. The principles of the method are given and supported by case studies.
Analysis and collapse of thick composite torispheres
Authors: Dong L , Blachut J
Published: October 2002

A drape algorithm for a torispherical shape was developed and used to predict the distortion of woven fabric and its influence on the last ply failure load in externally pressurized composite dome closures. Two 50-ply carbon-fibre-reinforced plastic domes were manufactured and collapsed. Progressive failure analysis was carried out and comparisons with experimental data are provided.
Reliability prediction procedures for mechanical components at the design stage
Authors: Warburton D , Strutt J E , Allsopp K
Published: October 2002

This paper reports progress towards the development of procedures and techniques for assessing the reliability of components at the design stage. From a fundamental understanding of the degradation and failure processes and their relation to the underlying operational, environmental, materials and design variables, the paper develops procedures to support reliability prediction of mechanical devices using an electro-mechanical actuator as a case study. The methodology is illustrated by particular reference to the process of sliding wear leading to jamming of the actuator.