bluuebunny/crossref_metadata_2025 huggingface dataset:
On the performance of a cascade of turbine rotor tip section blading in nucleating steam Part 3: Theoretical treatment
Authors: Bakhtar F , Mahpeykar M R
Published: October 2002

During the course of expansion in turbines, steam first supercools and then nucleates to become a two-phase mixture. Formation and subsequent behaviour of the liquid lower the performance of turbine wet stages. This is an area where greater understanding can lead to improved design. This paper describes the theoretical part of an investigation into nucleating flows of steam in a cascade of turbine rotor tip section blading. The main flow field is regarded as inviscid and treated by the time-marching technique modified to allow for two-phase effects. The viscous effects are assumed to be concentrated in boundary layers which are treated by the integral method. Comparisons are carried out with the experimental measurements presented in the earlier parts of the paper and the agreement obtained is good.
Localization investigation of stationary random wave transmission along damped ordered substructural chains
Authors: Williams F W , Bennett P N , Lin J
Published: October 2002

Based on the symplectic eigensolution and the pseudo-excitation method, the localization of structural chains subjected to stationary random point excitation is investigated. The stiffness, mass and the hysteretic damping distributions are all continuously variable. The cause of the displacement and internal force localization is explained in terms of the symplectic eigenvalues and eigenvectors of a typical substructure of the structural chain. When duplicate symplectic eigenvalues occur, the degeneration of the stopband as well as the corresponding degeneration of the mode localization phenomenon are discussed.
Multilegged walker design—the joint torque versus workspace compromise
Authors: Howard D , Zhang S J , Sanger D J , Miao S
Published: October 2002

A machine's weight is directly related to the strength of the installed joint actuators, and it is reasonable to assume that minimizing the installed joint torques will minimize the machine weight. Unfortunately, the workspace area will also reduce with the installed joint torques; thus there must be a compromise between weight (joint strength) and workspace. Methods are presented to generate the set of static workspaces corresponding to a range of installed joint torques. In this way the relationship between the workspace area and installed joint torque can be established. A numerical example is presented which shows that a small reduction in the workspace area can lead to a substantial reduction in installed joint torque and hence machine weight.
On the performance of a cascade of turbine rotor tip section blading in wet steam Part 1: Generation of wet steam of prescribed droplet sizes
Authors: Bakhtar F , Mashmoushy H , Buckley J R
Published: October 2002

During the course of expansion in turbines steam nucleates to become a two-phase mixture consisting of a very large number of extremely small droplets carried by the vapour. Turbine stages operating in a two-phase regime have a lower efficiency than those working on superheated steam. To reproduce turbine two-phase flow conditions realistically requires a supply of supercooled steam which can be generated under blow-down conditions by the equipment employed. To generate wet steam the supercooled steam can be passed through a venturi. This paper is one of a set describing an investigation of the performance of a cascade of turbine rotor tip section profiles in wet steam and is concerned with the generation of a supply of wet steam of prescribed droplet sizes for admission to the cascade.
Geometrical design of cutting tools with surfaces of revolution for helical surfaces
Authors: Oancea N , Oancea V G
Published: October 2002

Machining of helical surfaces of constant pitch with tools bounded by surfaces of revolution is accompanied by generation errors due to imperfections of the effective cutting edge, relative positioning errors or kinematics of the machine tool. Therefore, the development of algorithms for the geometrical modelling of helical surfaces could be very useful. In fact, it is possible to model geometrically the effective generated surface on the workpiece when the cutting edge is known at discrete points, for instance, by physical measurement. Based on the principle of minimal distance first proposed in a previous work of the first author, a numerical method is developed that provides a very simple, yet very accurate, means to resolve both the direct and the inverse problem in the machining of helical surfaces with milling cutters and end mills. Thus, the profile of the cutting tool can be determined even for surfaces on the workpiece of arbitrary shape known either analytically or at discrete points. More importantly, it can be established either in the design or the exploitation stage what the accepted errors on the tool are (due to sharpening or wear), such that the tolerances on the surface to be machined are still met.
The effect of low-solidity vaned diffusers on the performance of a turbocharger compressor
Authors: Eynon P A , Whitfield A
Published: October 2002

The design of low-solidity diffuser vanes and the effect on the performance of a turbo-charger compressor is discussed. The effect of vane number and turning angle was investigated while maintaining a basic design with a solidity of 0.69 and a leading edge angle of 75°. This large leading edge angle was specifically chosen so that the vane would be aligned with the low flowrates close to surge. Tests were initially conducted with six, eight and ten vanes and a turning angle of 10°. Based on these results the ten-vane design was selected for further investigation with 15 and 20° of vane turning; this led to vane exit angles of 60 and 55° respectively. All results are compared with those obtained with the standard vaneless diffuser configuration and it was shown that all designs increased and shifted the peak pressure ratio to reduced flowrates. The peak efficiency was reduced relative to that obtained with the vaneless diffuser. Despite the low-solidity configuration none of the vane designs provided a broad operating range without the use of a variable geometry configuration. This was attributed to the selection of a large leading edge vane angle.
A study of the natural vibratory response of stator structures to improve condition monitoring strategies for induction motors
Authors: Lucas M , Thomson W T
Published: October 2002

On-line condition monitoring is widely used to detect failure mechanisms in large highvoltage three-phase induction motors. The high-voltage winding is installed in a complex, stator core structure which vibrates due to electromagnetic forces. Insulation degradation can be diagnosed via on-line monitoring of partial discharges but the fundamental cause is often mechanical damage due to stator vibration. This paper presents results of an investigation into the natural vibratory response of the complete stator assembly. Results from finite element models of complex stator assemblies, including the frames, are supported by experimental measurements. These include freely suspended stator cores as in previous studies, and also now introduce the much more realistic condition of the complete stator assembly securely bolted on to a solid baseplate. The knowledge gathered in this study will aid the application of a vibration monitoring strategy to detect stator core vibration which can lead to winding insulation damage.
Closed-form and numerical solutions to the laser heating process
Authors: Yilbas B S , Sami M , Al-Farayedhi A
Published: October 2002

The laser processing of engineering materials requires an in-depth analysis of the applicable heating mechanism. The modelling of the laser heating process offers improved understanding of the machining mechanism. In the present study, a closed-form solution for a step input laser heating pulse is obtained and a numerical scheme solving a three-dimensional heat transfer equation is introduced. The numerical solution provides a comparison of temperature profiles with those obtained from the analytical approach. To validate the analytical and numerical solutions, an experiment is conducted to measure the surface temperature and evaporating front velocity during the Nd—YAG laser heating process. It is found that the temperature profiles resulting from both theory and experiment are in a good agreement. However, a small discrepancy in temperatures at the upper end of the profiles occurs. This may be due to the assumptions made in both the numerical and the analytical approaches. In addition, the equilibrium time, based on the energy balance among the internal energy gain, conduction losses and latent heat of fusion, is introduced.
Three-term control of lightly damped mechanical systems
Authors: Whalley R
Published: October 2002

Impedance, matrix quadratic models which arise from Lagrangian or Newtonian analysis are employed in the synthesis of controllers for lightly damped, series coupled mechanical systems having multiple outputs. Prescribed damping ratios and natural frequencies are generated by the closed-loop feedback scheme employing output measurements alone. The disturbance-rejection properties of the system are commented upon and a particular problem is presented for illustration purposes.
The vibration of ring-reinforced circular cylinders under external water pressure
Authors: Ross C T F , Richards W D
Published: October 2002

The paper reports on an experimental and a theoretical investigation into the vibration of three ring-stiffened circular cylinders under external water pressure. The theoretical analysis was via the finite element method, where both the structure and the surrounding water were modelled using finite elements. Comparison between experiment and theory was good, and showed that the resonant frequencies decreased with increasing external pressure. The results also showed that there was a possibility of a form of dynamic buckling, when the vibration eigenmodes became of similar form to the static buckling eigenmodes.
On the coupling of the elastohydrodynamic problem
Authors: Elcoate C D , Evans H P , Hughes T G
Published: October 2002

The paper presents the results of an investigation of methods of mathematically coupling the equations of elastohydrodynamic lubrication (EHL) that define the EHL line contact problem. The objective is to develop numerical solvers for use in the study of thin-film/rough surface contacts such as found in gears. It has been found that deformation behaviour of the surfaces is a dominant effect and that full rather than partial coupling is necessary for stable solutions. For cases considered using a Newtonian lubricant a first-order formulation of the Reynolds equation is required at high loads in the high-pressure part of the contact.

The fully coupled method is also applied to contact between a moving smooth surface and a stationary rough surface. The significant changes brought about by non-Newtonian oil behaviour are demonstrated, together with the ability of the method to provide solutions for cases where the λ ratio (of film thickness to surface roughness) is as low as 0.1.
Stokes flow in a double-lid-driven cavity with free surface side walls
Authors: Gaskell P H , Gürcan F , Savage M D , Thompson H M
Published: October 2002

Stokes flow is considered in a rectangular double-lid-driven cavity with free surface side walls, aspect ratio A and speed ratio S= U1/ U2, where U1 and U2 are lid velocities, as an idealized model for two-dimensional viscous flow in the ‘bead’ of a two-roll, meniscus coating system. For S ≤ 0 (> 0) there is one (two) large eddy (eddies) within the cavity with one (two) stagnation points on the centre-line between the free surfaces. Various transformations of flow structure arising as a result of flow bifurcations at these stagnation points are identified as the two control parameters A and S are continuously varied.

In the case of symmetric flow, S= -1, reducing A from A = 2.5 produces a sequence of pitchfork bifurcations at which a stagnation-saddle point changes to a centre (or vice versa) with the generation of two additional stagnation points. As A → 0 and the number of stagnation points increases, it is shown that the flow structure consists of a series of nested separatrices, each contained within the central section of the previous one. In the case of asymmetric flow, S ≠ -1, S < 0, the above pattern of behaviour is repeated as A is reduced from A = 2.5, apart from an initial saddle-node bifurcation at which a saddle and a centre annihilate each other. When the lids move in the same direction ( S > 0) bifurcations may arise separately or simultaneously in each of the two large eddies. Again as A → 0 with S constant, nested separatrices appear in both eddies. The key results are displayed via bifurcation curves in an ( S, A) control space diagram.
Theoretical and experimental simulation of accident scenarios of the Joint European Torus cryogenic components Part 2: The Lower Hybrid Current Drive cryopump
Authors: Ageladarakis P A , O'Dowd N P , Webster G A , Papastergiou S
Published: October 2002

A flexible mathematical model has been developed in Part 1 to simulate the transient thermal response of a number of nuclear fusion components, including cryogenic devices that operate inside the JET Tokamak. The present work reports on the simulation of an accident scenario, as well as further studies of hypothetical off-normal scenarios concerning an out-of-vessel cryopump (the LHCD cryopump). These studies resulted in a complete safety protection system for the cryopump, which has been implemented into the JET operating routines.
Gas-assisted laser repetitive pulsed heating of a steel surface
Authors: Shuja S Z , Yilbas B S
Published: October 2002

The present study is carried out to investigate the effect of the assist gas jet on the thermal integration due to repetitive pulsed laser heating. Air is considered as the assist gas, which impinges coaxially with the laser beam and orthogonal to a steel surface. The low Reynolds number k-ε model is introduced, based on previous studies, to account for the turbulence. A numerical scheme using the control volume approach is employed to solve the two-dimensional axisymmetric governing equations of flow and heat conduction. The transport properties of the assist gas and of the solid substrate are considered as variable. The study is extended to include two gas jet velocities and three laser pulse types. It is found that thermal integration in the solid substrate is possible for a low-intensity power ratio of the repetitive pulses and the influence of the assist gas jet on the temperature profiles is almost insignificant.
A new time integration method in structural dynamics using the Taylor series
Authors: Wang S M , Shenoi R A , Zhao L B
Published: October 2002

The paper presents a new method of time integration for structural dynamic responses. In comparison with well-known methods, it is advantageous in several aspects. It satisfies the governing equations in continuous intervals rather than at discrete time instants (collocation, SSpj) or in average form (weighted, GNpj). It approximates the structural response with user-controllable order of accuracy. It automatically controls the convergence and accuracy so that a correct answer can be assured via auto-adjusted stepping and expansion terms. As far as the accuracy of velocity and acceleration is concerned, the method is much better since rapid convergence can be obtained with ease. Like the explicit integration method, this approach does not demand solution of simultaneous equation sets, yet it can be used with a time increment much larger than that of the implicit methods.
Precision inspection of deviations of machined surfaces
Authors: Zhang J J , Gong D
Published: October 2002

The deviations of machined surfaces of high-precision mechanical components are one of the major error items that affect the precision, and hence the performance, of the components. However, industrial standards concerning profile deviations are still not available for many components with curved surfaces, due to lack of accurate inspection and error evaluation methods, although general purpose coordinate measuring machines are widely available. Proposed in this paper are two such methods that detect and process surface form deviations using coordinate measuring machines. Possible measurement error sources of these methods have been investigated and necessary remedies suggested. Both are seen to lead to higher inspection accuracy than the methods reported in the literature. Experiments were designed and carried out to confirm and illustrate the validity of these proposed methods.
On the role of three-dimensional inverse design methods in turbomachinery shape optimization
Authors: Zangeneh M , Goto A , Harada H
Published: October 2002

The application of a three-dimensional (3D) inverse design method in which the blade geometry is computed for a specified distribution of circulation to the design of turbomachinery blades is explored by using two examples. In the first instance the method is applied to the design of radial and mixed flow impellers to suppress secondary flows. Based on our understanding of the fluid dynamics of the flow in the impeller, simple guidelines are developed for input specification of the inverse method in order to systematically design impellers with suppressed secondary flows and a more uniform exit flow field. In the second example the method is applied to the design of a vaned diffuser. Again based on the understanding of the detailed flow field in the diffuser obtained by using 3D viscous calculations and oil flow visualizations, simple design guidelines are developed for input specification to the inverse method in order to suppress corner separation. In both cases the guidelines are verified numerically and in the case of the diffuser further experimental validation is presented.
The exploitation of three-dimensional flow in turbomachinery design
Authors: Denton J. D. , Xu L
Published: October 2002

Many of the phenomena involved in turbomachinery flow can be understood and predicted on a two-dimensional (2D) or quasi-three-dimensional (Q3D) basis, but some aspects of the flow must be considered as fully three-dimensional (3D) and cannot be understood or predicted by the Q3D approach. Probably the best known of these fully 3D effects is secondary flow, which can only be predicted by a fully 3D calculation which includes the vorticity at inlet to the blade row. It has long been recognized that blade sweep and lean also produce fully 3D effects and approximate methods of calculating these have been developed. However, the advent of fully 3D flow field calculation methods has made predictions of these complex effects much more readily available and accurate so that they are now being exploited in design. This paper will attempt to describe and discuss fully 3D flow effects with particular reference to their use to improve turbomachine performance. Although the discussion is restricted to axial flow machines, many of the phenomena discussed are equally applicable to mixed and radial flow turbines and compressors.
Variable step Rosenbrock algorithm for transient response of damped structures
Authors: Piché R , Nevalainen P
Published: October 2002

A Rosenbrock algorithm with varying time step is adapted for transient analysis of damped second-order differential equations. The time step adjustment is based on an embedded local truncation error estimation formula. An interpolation formula can be used for intermediate output. The stepping formula is L-stable and the error estimation formula is bounded for large time steps. The Rosenbrock algorithm is compared with the Thomas—Gladwell STEP34 algorithm, which is found to be only conditionally stable. Numerical results are given for two linear examples: a stiff, linear, two-degree-of-freedom system and a non-proportionally damped plate.
The behaviour of heavily loaded line contacts with transverse roughness
Authors: Hooke C. J.
Published: October 2002

In heavily loaded, piezoviscous contacts the surface roughness tends to be flattened inside the conjunction by any relative sliding of the surfaces. However, before it is flattened, the roughness affects the inlet to the contact, producing clearance variations there. These variations are then convected through the contact, at the entrainment velocity, producing a clearance distribution that differs from the original surface. The present paper explores this behaviour and establishes how the amplitude of the convected clearance varies with wavelength and operating conditions. It is shown that the primary influence is the ratio of the wavelength to the inlet length of the conjunction. Where this ratio is large, the roughness is smoothed and there is little variation in clearance under the conjunction. Where the ratio is small, significant variations in clearance may occur but the precise amplitude and phasing depend on the ratio of slide to roll velocities and on the value of a piezoviscous parameter, c. The numerical results agree closely with existing solutions but extend these to cover the full range of operating conditions.
Self-induced vibration of bandsaw blades during cutting
Authors: Le-Ngoc L , McCallion H
Published: October 2002

A new interpretation of the washboarding phenomenon found in bandsawing of wood is given in this paper. A theoretical model of the washboarding pattern was derived by considering the motion of the teeth during cutting. The theory of machine tool chatter was adapted to illustrate the mechanism of self-induced vibration in bandsawing and to provide a criterion for its existence. It was found that the whole cutting span of the band should be used to determine the vibration characteristics instead of the previous practice of using the section between the workpiece and the top wheel. It has been found that the frequencies responsible for washboarding are all torsional frequencies and physical explanation for this is suggested by considering the squeeze film damping effect of the air gaps between the blade and the sawn surfaces.
Bidimensional strain measurement using digital images
Authors: Vacher P , Dumoulin S , Morestin F , Mguil-Touchal S
Published: October 2002

This paper proposes a method that allows a strain field on plane samples to be determined using the digital image correlation method. The displacement field is approximated by an iterative process attempting to optimize the correlation between two pictures, the first one before strain and the second one after strain. The precision obtained on the displacement field can be better than 0.01 pixel. This precision makes it possible to calculate the strains in a large range, from elastic strains (>0.01 per cent) to large strains (>200 per cent), with or without a strain gradient.
A model of liquid outflow from single-outlet vessels
Authors: Kubie J
Published: October 2002

This paper analyses the outflow of liquids from single-outlet vessels. In such vessels the liquid leaving the vessel through the outlet is replaced by another fluid, which enters the vessel through the same opening. A theoretical model is developed for the general case of gas—liquid systems. The model, based on a simplified description of the system, is derived from first principles, and contains one adjustable parameter. Irrespective of the numerical value of this parameter the model describes qualitatively the various phenomena observed experimentally, such as the linear variation between the large-scale gas void fraction in the vessel and the elapsed time. A correlation for the adjustable parameter is presented and its significance discussed. The model is in excellent agreement with the available experimental data on the variation of the large-scale gas void fraction in the vessel and the large-scale gas pressure in the vessel with elapsed time. The application of the model is also discussed.
Analysis of the vibration of pipes conveying fluid
Authors: Zhang Y L , Gorman D G , Reese J M
Published: October 2002

The dynamic equilibrium matrix equation for a discretized pipe element containing flowing fluid is derived from the Lagrange principle, the Ritz method and consideration of the coupling between the pipe and fluid. The Eulerian approach and the concept of fictitious loads for kinematic correction are adopted for the analysis of geometrically non-linear vibration. The model is then deployed to investigate the vibratory behaviour of the pipe conveying fluid. The results for a long, simply supported, fluid-conveying pipe subjected to initial axial tensions are compared with experimentally obtained results and those from a linear vibration model.
On the tuning pipe of a two-stroke engine for scooter-type motorcycles
Authors: Huang R F , Hsu M-P , Chen W L , Lee K
Published: October 2002

Engine performance and simultaneous pressure wave histograms in the cylinder and exhaust port were studied in this experiment. The performance of two-stroke engines for scooter-type motorcycles depended greatly on the length and expansion angle of the tuning pipe. The length of the lead-in pipe dominated the phase of the starting point of reflected expansion waves. The full length determined the timing of reflected expansion waves. The first expansion angle of the exhaust pipe must be limited to a small value and then expanded gradually to give the desired diameter. The effect of the muffler was also discussed. There was an optimal distance between the end of the tuning pipe and the spacer of the muffler to obtain a maximum power output.
A systematic approach to profile relief design of low and high contact ratio spur gears
Authors: Yildirim N , Munro R G
Published: October 2002

This is the first of a series of papers on the design of the tooth profile relief of both low and high contact ratio spur gears and its effects on transmission error (TE) and tooth loads. A systematic approach to profile relief design is introduced. The process of profile relief analysis is based on a number of simplifying assumptions to ease the understanding of the relief design. Useful relief cases determined during the simplified analysis are further investigated, with realistic parameter values such as variable stiffness, manufacturing tolerances and so on, in other papers of the series. Experimental validation of the cases proven to be good are also given in forthcoming papers.

In the present paper, the systematic approach is applied to low contact ratio (LCR) spur gears first with some design regions and to high contact ratio (HCR) spur gears with some new and promising design regions and rules. Several smooth transmission error curves at different loads are shown to be possible for the relief designed, hence allowing a range of loads with uniform motion transfer. The advantages of HCRG over LCRG in terms of smooth TE curves and tooth load values are noted.
A new type of profile relief for high contact ratio spur gears
Authors: Yaldirim N , Munro R G
Published: October 2002

The second of a series of papers on the systematic approach to the profile relief design of both low contact ratio (LCR) and high contact ratio (HCR) spur gears and its effects on transmission error (TE) and tooth loads. Basics of the approach are given in the previous paper of the series. Application of the approach to HCR spur gears has produced two promising design cases, namely the short and long reliefs, with advantages and disadvantages. In this paper a new relief type, double relief, is introduced by making use of the two promising cases. Advantages of the two are brought together, with some compromise. The overall performance of the new relief type, however, is superior to the others in terms of peak-to-peak TE value, maximum tooth load value, rate of tooth loading and number of smooth TE curves, and hence in terms of the range of transmitted load with nearly uniform motion transfer. A procedure for compensation for adjacent pitch error (PE) with smooth TE curve at off-design load is also included.
Evaluation of spur gear mesh compliance using the finite element method
Authors: Arafa M H , Megahed M M
Published: October 2002

This paper presents a finite element (FE) modelling technique to evaluate the mesh compliance of spur gears. Contact between the engaging teeth is simulated through the use of gap elements. Analysis is performed on several gear combinations and the variation in tooth compliance along the contact location is presented in a non-dimensional form. Results are compared with earlier predictions based on analytical, numerical and experimental methods. Load sharing among the mating gear teeth is discussed, and the overall gear mesh stiffness together with its cyclic variation along the path of contact is evaluated.
Influence of form on surface temperatures in form grinding
Authors: Walsh D , Torrance A A
Published: October 2002

Although the temperature rise in the arc of cut during grinding may be calculated with some confidence for simply shaped workpieces (cylinders and flats), there is little or no way of allowing for the way grinding temperatures may vary locally when a complex form is ground. In this paper, dimensional analysis is used to develop a formula for calculating a temperature concentration factor at geometric discontinuities in workpieces. The numerical factors in the formula are supplied by fitting it to results of a large number of finite element calculations, with examples of its application to two types of industrial process.
A novel thick-film strain transducer using piezoelectric paint
Authors: Hale J M , Tuck J
Published: October 2002

This paper describes the manufacture and testing of a novel strain transducer for use in structural vibration monitoring, based on piezoelectric paint. The materials selection and development of application techniques are outlined for the three principal components of the transducer (paint binder, piezoelectric material and electrode). The final design comprised a suspension of milled lead zirconate/lead titanate (PZT) ceramic powder in lacquer with a gold electrode formed by vapour deposition. The transducers were tested for variability and for dynamic properties (bandwidth and dynamic range). It was found that there is considerable scatter between the output sensitivities of individual transducers, but that the dynamic properties are very consistent. It is shown that the techniques developed form the basis for a viable vibration transducer in the range 20–600 Hz.
A measure of utility of parts of plane frames
Authors: French M
Published: October 2002

This study was undertaken because of a paper by Croll [4] showing that the basic structural economy of suspension bridges was inferior to that of cable-stayed ones. While agreeing with this result, the present author sought for an insight that would make it plain that this was so, and why, and developed a quantitative measure of utility u for any element of such a structure. This utility factor gives an immediate indication of the relative usefulness of an element of given direction at a given point in a plane structure carrying a given system of loads and confined to a certain area of its plane. It confirms Croll's result by inspection, and is offered as an aid to designers concerned with structural economy. Its derivation and examples of its use are given.
Transonic fan and compressor design
Authors: Calvert W. J. , Ginder R. B.
Published: October 2002

Transonic fans and compressors are now widely used in gas turbine engines because of their benefits in terms of compactness and reduced weight and cost. However, careful and precise design is essential if high levels of performance are to be achieved. In this paper, the evolution of transonic compressor designs and methods is outlined, followed by more detailed descriptions of current compressor configurations and requirements and modern aerodynamic design methods and philosophies.

Current procedures employ a range of methods to allow the designer to refine a new design progressively. Overall parameters, such as specific flow and mean stage loading, the axial matching between the stages at key operating conditions and the radial matching between the blade rows are set in turn, using one- and two-dimensional techniques. Finally, detailed quasi-three-dimensional and three-dimensional computational fluid dynamics (CFD) analyses are employed to refine the design. However, it is important to appreciate that the methods all have significant limitations and designers must take this into account if successful compressors are to be produced.
Regular and chaotic dynamics of a simplified fly-ball governor
Authors: Ge Z-M , Chen C-S , Chen H-H , Lee S-C
Published: October 2002

The dynamics of a simplified model of a fly-ball speed governor undergoing a harmonic variation about its rotational speed is studied in this paper. This system is a non-linear damped system subjected to parametric excitation. The harmonic balance method is applied to analyse the stability of period attractors and the behaviour of bifurcations. The time evolutions of the response of the non-linear dynamic system are described by time history, phase portraits and Poincaré maps. The regular and chaotic behaviour is observed by various numerical techniques such as power spectra, Lyapunov exponents and Lyapunov dimension. Finally, the domains of attraction of periodic and stranger attractors of the system are located by applying the interpolated cell mapping (ICM) method.
Fuzzy ignition timing control for a spark ignition engine
Authors: Wang W , Chirwa E. C. , Zhou E , Holmes K , Nwagboso C
Published: October 2002

It is well known that the optimum ignition timing, which gives the maximum brake torque (MBT) for a given engine design, varies with the rate of flame development and propagation in the cylinder. This depends, among other factors, on engine design and operating conditions, and on the properties of the air-fuel mixture. In modern engines the ignition timing is generally controlled by fixed open-loop schedules as functions of engine speed, load and coolant temperature. It is desairable that this ignition timing can be adjusted to the optimum level producing the best torque to obtain minimum fuel consumption and maximum available power. This paper presents an ignition timing control system based on fuzzy logic theory. A pressure sensor system ws developed for the determination of combustion parameters and ignition control on a Ford 1600cm3 four-cylinder engine fuelled with natural gas. Several tests were carried out in optimizing the pressure detection system. The results obtained provide important information compatible with intelligent control of the engine using fuzzy logic technology. Moreover, tests carried out to date using this technology show good results that fit quite well with the original engine output torque characteristics.
Driver visual allocation and the introduction of intelligent transport systems
Authors: Lansdown T. C.
Published: October 2002

The introduction of intelligent transport systems may affect the driver's ability safely to control the vehicle by distracting him/her from the roadway. These systems must therefore be evaluated to ascertain whether they impose an unreasonable demand on the driver. This paper discusses issues surrounding the use of visual allocation measures for the evaluation of driver information systems in a road trail setting. It explores their value in differentiating between different levels of imposed visual demand. An investigation was made of the visual demand and subjective mental workload resulting from the use of a congestion warning device, an in-car entertainment system and driving without these (the control). The results of the study suggest that the congestion warning device imposed significantly greater visual demand and subjective mental workload than either the in-car entertainment system or the control condition. Difficulties in comparing empirical data with other reported work are highlighted.
Light-duty diesel exhaust after-treatment by a multicyclone particulate separator with an oxidation catalyst
Authors: Crane R. I. , Wisby P
Published: October 2002

A particulate after-treatment system has been developed and applied to a 2.51 direct-injection diesel engine. The base exhaust system configuration included an oxidation catalyst; to this has been added a compact heat exchanger believed to have the potential for promoting particle growth, followed by four inclined reverse-flow cyclones in parallel. Emission measurements have shown that the system is capable of reducing exhaust particulate mass concentrations by up to 70 per cent compared with the base configuration. For the same engine speed and load, and with uncooled or cooled exhaust gas recirculation levels from zero to 50 per cent, particulate reductions were achieved without an increase in NOx emissions. Only a modest deterioration in particulate separation was found on bypassing the heat exchanger; this result might be explained by processes in the catalyst and adjacent muffler leading to significant particle growth, although no direct evidence of this is yet available. Measurements of the change in unburned hydrocarbon (HC) vapour concentration through the exhaust system components indicated that HC adsorption or condensation onto particulates is unlikely to be the predominant growth mechanism which allows inertial separation by cyclones. The feasibility of a cyclone-based after-treatment system for production vehicles is discussed.
Heat transfer and chemical kinetics in the exhaust system of a cold-start engine fitted with a three-way catalytic converter
Authors: Chan S. H. , Hoang D. L. , Zhou P. L.
Published: October 2002

Modelling of cold-start engine exhaust behaviour is a difficult task as it involves complicated heat transfer processes associated with water condensation and evaporation at the walls of the exhaust manifold/pipe and monolith cells, and the chemical reactions of CO/HC/NO in the three-way catalytic converter. This paper presents a model that is capable of predicting the exhaust gas temperatures along the exhaust system and across the catalyst monolith, both spatially and temporally, from the moment when the engine is cranked. The conversions of CO/HC/NO to harmless carbon dioxide, water and nitrogen at the catalytic converter downstream have been validated satisfactorily by the experimental data. The distortion of measured NO emission data/signals due to the dynamic behaviour of the chemiluminescence analyser has been reconstructed by means of a signal inference technique before these signals were used to validate the predictive capability of the model developed.
Technical Note: Investigation on emission characteristics of a compression ignition engine with oxygenated fuels and exhaust gas recirculation
Authors: Wang H. W. , Huang Z. H. , Zhou L. B. , Jiang D. M. , Yang Z. L.
Published: October 2002

Investigations of emission characteristics were carried out on a compression ignition, dimethyl ether engine (DME) with exhaust gas recirculation (EGR) and on a diesel engine with a dimethyl carbonate (DMC) additive. The experimental results show that the DME engine with EGR can simultaneously reduce smoke and NOx emissions. The NOx can be reduced by about 20 per cent for every 10 per cent of EGR introduction, while smoke remains at zero. The diesel equivalent brake specific fuel consumption (b.s.f.c.) shows a slight decrease when DMC is added, while the effective thermal efficiency shows a slight improvement. It is found that the smoke reduction rate and smoke show a linear relationship with DMC percentage or oxygen mass percentage in the diesel fuel. For the specific brake mean effective pressure (b.m.e.p.), smoke will be reduced by 20 per cent for every 10 per cent DMC added and by 40 per cent when the oxygen mass percentage in the fuel reaches 10 per cent. The CO decreases when DMC is added, while NOx shows an increase. This difference is pronounced at a high b.m.e.p. For the specific b.m.e.p., CO and NOx show a linear relationship with DMC mass percentage in the fuel; CO will be reduced by 20 per cent while NOx will be increased by 20 per cent for every 10 per cent DMC added.
Epicyclic gear trains for automotive automatic transmissions
Authors: Hsu C-H , Hsu J-J
Published: October 2002

Epicyclic gear trains, which contain at least four coaxial links, are widely used in automatic transmissions. This paper presents a systematic methodology for the synthesis of epicyclic gear trains for automotive automatic transmissions. The graph representation of epicyclic gear trains is applied to develop an approach for the structural synthesis of the graphs of admissible epicyclic gear trains. Next, for each admissible graph the adjacency matrix of an epicyclic gear train is defined to develop an algorithm for the configuration synthesis of epicyclic gear trains. Using the proposed algorithm, all possible epicyclic gear trains for automotive automatic transmissions are systematically synthesized. In this paper, admissible epicyclic gear trains with up to ten links have been successfully synthesized. The results of work will lead to the creation of new multispeed automotive automatic transmissions.
Agile control systems
Authors: Young K W , Muehlhaeusser R , Piggin R S H , Rachitrangsan P
Published: October 2002

To cope with unpredictable demand and a wide variety of products, future production systems require agility. To realize manufacturing agility, the control system has to respond and adapt to variations in real-world, dynamic production environments. The control system has to promote requirements such as reduced complexity, increased flexibility, adaptation in real time, extensibility, heterogeneity and autonomous operation. A control system architecture is proposed ensuring manufacturing agility by adapting quickly and cheaply to changes in the production environment.
Technical Note: Some limitations of the chassis dynamometer in vehicle simulation
Authors: Plint M. A. , Martyr A. J.
Published: October 2002

The chassis dynamometer is the standard tool for legislatively prescribed emission tests. For emission testing and many other vehicle test purposes the dynamic response is an adequate approximation to ‘on road’ conditions. This is not necessarily true if the requirement is to study vehicle driveline dynamics. The present analysis arose from two quite separate requirements to study driveline oscillations and ‘judder’ using chassis dynamometers of the same eVective inertia as the vehicle. During the studies by the authors it became clear that the dynamics of the vehicle-dynamometer combination diVer in important respects from those of a vehicle on the road. As the eVective inertia of the dynamometer falls the natural frequency of the engine-driveline-vehicle system rises while the oscillatory energy imparted to the vehicle falls rapidly. For reasonably accurate simulation of driveline vibration the roll inertia should be some five times that of the vehicle. It is shown that electrical simulation of inertia, as employed in most modern chassis dynamometers, is unsatisfactory where oscillatory phenomena are being studied.
Power split continuously variable transmission systems with high efficiency
Authors: Mantriota G.
Published: October 2002

Continuously variable transmissions (CVTs) have developed notably in different applications over the past years. This is especially true in the automobile field because of advantages in terms of car handling and efficiency on urban roads. In this work an original functional solution of a power split CVT system is described. The proposed solution allows the generation of a power flow without recirculation. Kinetic characteristics of single-component devices are obtained and the power split CVT system's efficiency is determined by considering how the efficiency of the component devices changes as a function of operating conditions. The advantages for the power split CVT system are therefore shown in terms of power and efficiency in comparison with the single CVT.
Hydrogen enrichment: A way to maintain combustion stability in a natural gas fuelled engine with exhaust gas recirculation, the potential of fuel reforming
Authors: Allenby S. , Chang W-C. , Megaritis A. , Wyszyński M. L.
Published: October 2002

An experimental study was carried out to evaluate the potential of hydrogen enrichment to increase the tolerance of a stoichiometrically fuelled natural gas engine to high levels of dilution by exhaust gas recirculation (EGR). This provides significant gains in terms of exhaust emissions without the rapid reduction in combustion stability typically seen when applying EGR to a methane-fuelled engine. Presented results give the envelope of benefits from hydrogen enrichment. In parallel, the performance of a catalytic exhaust gas reforming reactor was investigated in order that it could be used as an onboard source of hydrogen-rich EGR. It was shown that sufficient hydrogen was generated with currently available prototype catalysts to allow the engine, at the operating points considered, to tolerate up to 25 per cent EGR, while maintaining a coefficient of variability of indicated mean effective pressure below 5 per cent. This level of EGR gives a reduction in NO emissions greater than 80 per cent in all test cases.
Tracking the two-phase flow through a vehicle cowl box
Authors: Ghani S. A A. Abdul , Aroussi A. , Rice E.
Published: October 2002

The penetration of rainwater through the heating, ventilation and air conditioning (HVAC) system of a vehicle directly affects the provision of thermal comfort within the vehicle passenger compartment. Present vehicle designs restrict considerably the air management processes owing to reduced space and tighter packaging. In this study, a cowl box, the first element of the vehicle HVAC system, is examined through the scrutiny of the flow field prevailing within it. Particular attention is paid to the effects of cowl flooding on water ingress. The work described is both experimental and computational. An optical anemometer is used to acquire the experimental data within a transparent model of a cowl box. The results are then used to validate and tune the computational fluid dynamics (CFD) calculations performed on the same cowl geometry as well as to perform parametric studies of the features that affect the rainwater penetration. The phenomenon of rainwater ingress has integrated factors with the overall vehicle geometry, body seals at the cowl space, wipers set-up, HVAC blower set-up, rain intensity and road conditions. Therefore, in addition to the model- scale experiments, a full-scale vehicle is examined in the Flow Diagnostics Laboratory (FDL) climatic wind tunnel. The results obtained, using non-intrusive instrumentation, are also used to verify the computational model.
Geometry of hob and simulation of generation of the cylindrical gears by conventional or climb hobbing operation
Authors: Kim D. H.
Published: October 2002

This paper illustrates a method of representing the geometry of a hob tooth profile in parametric form and of determining the surface equation of a generated gear as a function of hob design parameters and generating motion specifications through a mathematical model of the generation process. The described method permits the effect of hob profile deviations and hob alignment errors on the generated gear to be observed precisely. Hence, the tolerances on hob design parameters and allowable alignment errors can be effectively specified. This approach can be applied in any axial hobbing operations-conventional or climbing-for generation of helical or spur gears.