bluuebunny/crossref_metadata_2025 huggingface dataset:
Technological advances in high-efficiency particulate collection
Authors: Parker K R
Published: October 2002

Particulate control equipment for the larger industrial processes, which can effectively collect particles in the submicrometre range, is limited to the electrostatic precipitator and bag filter as cost effective methods. To meet ever decreasing emission levels, demanded by the Regulatory Agencies, the equipment suppliers and academics are involved in ongoing research and development activities in order to obtain a better understanding of the collection process itself, such as to achieve improved performance and, equally importantly, plant reliability and availability.

This paper reviews some of the activities in the electrical, microelectronics, material sciences, fluid flow and finite element analysis fields and indicates how the findings are leading to new designs that are more reliable and also how the improvements are making the equipment more cost effective while operating at a higher performance level.

Finally, with the concern over the emission of ‘air toxics’, while both the electrostatic precipitator and bag filter are established technology for effectively removing solid and liquid particulates with sizings well below 1 micrometre there is now an additional requirement for collecting vapour phase materials to meet the latest regulatory emission levels. Some ideas and approaches are examined which can prove effective in collecting the majority of materials classified as ‘air toxics’, such that the equipment will meet the existing and possible future emission standards.
Noise control in power plant
Authors: Snow D J
Published: October 2002

During the last decade the shape of the UK non-nuclear electricity generation industry has changed fundamentally from a stable monopoly providing power primarily from large coal-fired units to a rapidly developing competitive industry with a wide range of plant types. The removal of the restrictions on burning natural gas in power stations and the introduction of flue gas desulphurization on some of the traditional plants has highlighted the reduced cost and lower emissions of gas-powered generation, leading to a major increase in the use of this fuel in more efficient combined cycle gas turbine (CCGT) plant. Outside the United Kingdom, the economics and politics of fuel supply and electricity production may be different, and both traditional plant and new CCGT projects are being constructed in overseas markets by UK utilities, often in partnership arrangements with other companies. In parallel with these developments there is significant new effort expended on the development of combined heat and power (CHP) plant and renewable energy sources, especially wind power. Although relatively small in MW terms, the latter plant type presents significant and particular noise control requirements. On the horizon, new coal plant using coal gasification or fluidized bed technologies may be anticipated. At the same time as these major changes in plant selection are occurring there are simultaneous developments in the methods of environmental noise assessment. In this article the use of noise control within the electricity generation industry is reviewed and the influence of the changing trends in plant and environmental noise assessment are discussed.
Modelling of spanwise mixing in compressor through-flow computations
Authors: Dunham J
Published: October 2002

Although three-dimensional Navier-Stokes computations are coming into use more and more, streamline curvature through-flow computations are still needed, especially for multistage compressors, and where codes which run in minutes rather than hours are preferred. These methods have been made more realistic by taking account of end-wall effects and spanwise mixing by four aerodynamic mechanisms: turbulent diffusion, turbulent convection by secondary flow, spanwise migration of aerofoil boundary layer fluid and spanwise convection of fluid in blade wakes. This paper describes the models adopted in the DRA streamline curvature method for axial compressor design and analysis. Previous papers are summarized briefly before describing the new part of the model—that accounting for aerofoil boundary layers and wakes. Other changes to the previously published annulus wall boundary layer model have been made to enable it to cater for separations and end bends. The resulting code is evaluated against a range of experimental and computational results.
An experimental investigation of a centrifugal compressor with hub vane diffusers
Authors: Sitaram N , Issac J M
Published: October 2002

The present investigation reports results of experimental studies on a centrifugal compressor equipped with hub vane diffusers. The diffuser vane height ( h/b) is varied as follows: 0 (vaneless), 0.2, 0.3, 0.4 and 1 (vane). The experiments were carried out on a low specific speed centrifugal compressor with a radial tipped impeller with an inducer at the inlet. The measurements consist of determining performance characteristics, measuring static pressures on the hub and shroud and flow traverses with a precalibrated cobra probe at the diffuser exit over one passage at five flow coefficients, viz. φ = 0.23 (near surge), 0.34 (near peak pressure rise), 0.45, 0.60 and 0.75 (near maximum flow). The peak energy coefficient is maximum for the hub vane diffuser with an h/b ratio of 0.2. The hub vane diffusers have a wider operating range than the vane diffuser. At high flow coefficients, the static pressure rise is substantially low at the throat region of the vane diffuser as the incidence on to the vane leading edge is very high. The mass averaged static pressure coefficient is high in the low-volume range for the hub vane diffuser of h/b = 0.3, but in the high-volume range it is high for the vaneless diffuser.
Thermodynamic analysis of hydraulic air compressor-gas turbine power plants
Authors: Bidini G , Grimaldi C N , Postrioti L
Published: October 2002

Nowadays, the most common way to improve energy conversion efficiency is the integration of different systems, thus achieving a better exploitation of the available exergy potential (e.g. combined cycles, cogeneration, etc.). As a means of producing power in hydroelectric plants hydraulic energy is commonly considered to be almost completely exploited. The aim of this paper is to analyse the possible integration of hydraulic energy sources with conventional, fossil fuel based systems; in particular, power plants based on the combination of an hydraulic air compressor (HAC) and a gas turbine are considered.

In an HAC, air is entrained in the water flow in a downcomer pipe and compressed. Once separated from the water in a ‘stilling chamber’ at the bottom of the downpipe, the compressed air is supplied to a combustion chamber and then to a conventional gas turbine expander. An attractive characteristic of HACs is the capability, in principle, to perform an isothermal air compression instead of an adiabatic one, as in conventional compressors.

In the present work, a thermodynamic analysis is presented of HAC-gas turbine energy conversion systems, which are compared with conventional hydroelectric and gas turbine power plants. The calculated performance levels of such systems are comparable to those of combined cycle plants, making further technical and economical investigations quite interesting.
An experimental assessment of incidence losses in a radial inflow turbine rotor
Authors: Spence S W T , Artt D W
Published: October 2002

The non-optimum angle of incidence at the rotor inlet is the primary cause of reduced efficiency at off-design operating conditions in a radial turbine. Prediction of the complete performance characteristic, rather than just the design point, is desirable when considering the radial turbine as part of a dynamic system, such as a gas turbine engine, air cycle refrigeration plant or a turbocharger. The existing, rather unsatisfactory, incidence loss models are summarized and any published experimental information about the effect of incidence angle is reviewed. Through the analysis of data obtained from experiments conducted by the authors and reported elsewhere, correlations are drawn between the magnitude of the rotor loss and the gas incidence angle at the rotor inlet. As a consequence of the analysis, a negative value for the optimum incidence angle is confirmed and consistent trends are presented for the effects of varying incidence angle at different rotor speeds.
A computational and experimental evaluation of the performance of a centrifugal fan volute
Authors: Dilin P , Sakai T , Wilson M , Whitfield A
Published: October 2002

A detailed experimental study of the performance of two radial-flow fan volutes has been carried out at the Science University of Tokyo. This included a volute with a full tongue, such that no recirculating flow occurred, and the same volute but with the tongue cut back to allow flow recirculation. Detailed velocity and pressure distributions at a wide range of azimuth angles were obtained experimentally and are presented.

At the University of Bath a computational model, using the k-e turbulence model, has been used to predict the internal flow of both volutes, with particular attention given to the tongue flow. Predicted flow separation at the volute tongue has been demonstrated experimentally through laser sheet studies at the Science University of Tokyo.

The performance of the volutes is discussed and the computational fluid dynamics (CFD) analysis is used to recommend design improvements for the volute.
Prediction of the steady and non-steady flow performance of a highly loaded mixed flow turbine
Authors: Abidat M , Hachemi M , Hamidou M K , Baines N C
Published: October 2002

This paper describes a method for predicting the performance under both turbine inlet steady state and non-steady state flow conditions of a mixed flow turbine used for turbocharged internal combustion engines. The mixed flow turbine steady state performances computed with the steady state performance prediction method are in good agreement with the experimental results obtained in the Imperial College turbocompressor cold air test rig. The unsteady state performance is computed using a one-dimensional model based on the solution of the unsteady one-dimensional flow equations. These equations are solved in the volute by a finite difference method using a four-step explicit Runge—Kutta scheme. The instantaneous volute exit condition is provided by the steady state rotor performance prediction model with the assumption of a quasi-steady state flow in the rotor. The computed instantaneous performances are in reasonable agreement with published experimental data for the same mixed flow turbine. The unsteady flow model is also used to study the effects of the frequency and the amplitude of the pulse on the performances of the mixed flow turbine.
A new concept for squirrel-cage fan inlet
Authors: Montazerin N , Damangir A , Mirian S
Published: October 2002

The squirrel-cage fan with a newly introduced outward inlet lip is studied experimentally. Previous research has demonstrated the importance of inlet flow control on the general flow field and vortex generation of such fans. The bell-mouth inlet, which is the common industrial and academic practice, has drawbacks that result in flow separation and turbulence enhancement.

The adapted experimental approach is a conceptual study. It is a combination of standard characteristic measurements and detailed laser Doppler anemometry. The measured flow pattern inside the volute demonstrates that the separated flow behind the inlet lip, which for an ordinary inward lip occupies a large part of the rotor blades, disappears. This is promising since removing this separated flow diminishes a major loss-making region in this fan and adds to the effective flow area. It also reduces noise and gives uniform blade loading. The results also show an improvement in performance in comparison with that of a fan with an ordinary inward inlet lip. This modification is industrially feasible with no extra manufacturing cost and therefore can represent a substantial advance over the current practice.
The performance and emission characteristics of C1-C5 alcohol-gasoline blends with matched oxygen content in a single-cylinder spark ignition engine
Authors: Yacoub Y , Bata R , Gautam M
Published: October 2002

Alcohols with carbon numbers ranging from C1 to C5 were individually blended with unleaded test gasoline. All the alcohol-gasoline blends had the same oxygen mass content. The performance characteristics of the blends were quantified using a single-cylinder spark ignition engine. The knock-limiting spark timing was determined by analysis of the third derivative of the measured in-cylinder gas pressure versus crank angle. The engine operating conditions were optimized for each (C1-C5) blend with two different values of matched oxygen mass content (2.5 and 5.0 per cent). Emission mass rates of carbon monoxide (CO), nitric oxides (NOx), total unburned hydrocarbons (THCs), alcohols and aldehydes were quantified. The brake power specific rate emissions were compared with that of neat gasoline. Adding lower alcohols (C1, C2 and C3) to gasoline improved the knock resistance. Further improvement was achieved by increasing the oxygen content of the fuel blend. Blends with higher alcohols (C4 and C5) showed degraded knock resistance when compared with neat gasoline. Generally, all alcohol-gasoline blends showed reduction in CO emissions. Higher alcohol-gasoline blends with an oxygen mass content of 5.0 per cent showed a pronounced increase in NOx emission rates when operating at high compression ratios and 5° before top dead centre timing. This is attributed to their lower enthalpy of vaporization and higher flame temperature. All blends tested at optimized operating conditions showed reduction in THC emission rates. Unburned alcohol emission rates were higher for blends with higher content of alcohol, and aldehyde emissions were higher for all blends with formaldehyde as the main constituent.
Measurement of the thermal resistance of paint coatings using a simple transient cooling method
Authors: Jackson J. D. , Hatchman J. C.
Published: October 2002

During the preliminary calculations of the overall heat transfer rates for some applications in marine systems, it became apparent that the controlling medium could be the thermal resistance of the paint film. A thorough literature search was carried out but no data could be found and as a consequence it was recognized that the properties would have to be determined experimentally. The approach adopted was to measure the rate of temperature fall of a body as it cooled by forced convection in an airstream.
Reliability and durability from large heat recovery steam generators
Authors: Pearson M , Anderson R. W.
Published: October 2002

Experience with heat recovery steam generators (HRSGs) designed for larger-heat-input and higher-steam conditions highlights limitations in some features of traditional designs extrapolated from smaller HRSGs that operated predominantly continuously. Many combined-cycle units may be subjected to periods of regular overnight shut-down much earlier than expected and, unless anticipated during the initial design, there will be significant adverse impact on reliability and durability. Very premature problems already experienced on large HRSG designs in combined-cycle and cogeneration applications give an early warning that more widespread problems will arise as HRSGs are subjected to more thermal cycling. Problems that arise when inadequate attention is given to transient conditions over the full range of operation of the combined-cycle gas turbine unit, including at part loads, during shut-downs and restarts from diverse pre-start conditions, are highlighted. The paper gives examples of how the damage to HRSGs during shut-down and starts can be mitigated by minor modifications and sympathetic operating procedures and suggests how prudent purchasers can enhance reliability and lower lifetime costs at a small premium in installed cost by specification of appropriate design features. Other weaknesses which cause problems for operation and maintenance are discussed.
Experimental performance evaluation of a 99.0 mm radial inflow nozzled turbine at larger stator-rotor throat area ratios
Authors: Spence S. W T. , Doran W. J. , Artt D. W.
Published: October 2002

Following on from experimental data already presented by Spence and Artt in 1997, further comprehensive performance tests were carried out on a 99.0 mm radial turbine with three larger vaned stators. The results have helped to confirm some of the trends noted in the earlier tests. Measurements of the efficiency, mass flowrate and rotor pressure ratio are presented together with the results of a simple loss analysis. For smaller stator sizes the turbine mass flowrate is shown to be proportional to the stator throat area. The significance of the stator-rotor throat area ratio is examined and its dependence on the stage pressure ratio is noted.
Time-resolved measurements with fast-response probes and laser Doppler velocimetry at the impeller exit of a centrifugal compressor: a comparison of two measurement techniques
Authors: Gizzi W. P. , Roduner C , Stahlecker D , Koppel P , Gyarmathy G
Published: October 2002

The goal of this work was the investigation of the unsteady flow field existing at the exit of the impeller of a centrifugal compressor and the critical comparison of velocity measurements with two systems based on totally different measurement principles. The paper focuses on the measurement concepts, the accuracy and the error quantification.

A one-sensor fast-response probe (FRAP® system) and a commercially available laser Doppler velocimetry (LDV) system were used to perform wall-to-wall traverses and to measure the two main time-resolved velocity components. The test rig was run at the best point of the operating line, at a tip Mach number of 0.75.

The mean levels and fluctuations of the velocity vector components were compared. Over the middle, 70 per cent of the channel width, the FRAP® and LDV measurements typically agree within 2–5 per cent of the momentary local flow velocity in terms of both the radial and the circumferential velocity components. The time-mean distributions agree within typically 0–4 per cent.

Attention was focused on the near-hub and near-shroud layers where both measurements are affected by wall proximity errors. Largest discrepancies (of 10 per cent) in the time-mean velocity occurred at the shroud where velocity component values could differ by as much as 20 per cent momentarily. These discrepancies should be viewed in relation to the peak-to-peak amplitude of the ensemble-averaged velocity fluctuations which was of the order of 25 per cent in the present compressor.
Tip-clearance-affected flow fields in a turbine blade row
Authors: Sell M , Treiber M , Casciaro C , Gyarmathy G
Published: October 2002

For effective validation of computational fluid dynamics (CFD) codes for design, numerical simulations must be compared and contrasted with experimental data sets which are well posed and measured. This paper presents, with the emphasis placed primarily upon the description and explanation of the experimental results, a test case designed for CFD validation concerning the flow field generated by the presence of tip clearance in an annular cascade turbine blade row.

The test case is based upon a moderately loaded prismatic blade profile, operating with axial inflow and a nominal mid-span exit Mach number of 0.5. In addition to the case with no clearance, three gap heights, representing 1, 3 and 5 per cent of chord length have been selected. These tip clearances were chosen because they represent three conditions where the tip clearance is below, approximately equal to and substantially larger than the inlet boundary layer displacement thickness. At the leading edge this produces different behaviours, with the smallest gap producing a stagnation point, equivalent to the case without tip clearance, while the largest clearance allows throughflow over the leading edge into the tip gap.

In the presence of larger tip clearances, the tip leakage flow induces a stagnating flow in the trailing-edge region, which results in a large area of blocked flow in the blade passage downstream of the trailing edge.
Calculation of transition in turbine cascades by conditioned Navier-Stokes equations
Authors: Steelant J , Dick E
Published: October 2002

To simulate transitional heat transfer in turbine cascades, the conditionally averaged Navier-Stokes equations are used. To cover both the physics of free-stream turbulence and the intermittent flow behaviour during transition, a turbulence weighting factor τ is introduced. A transport equation is presented for this τ factor including convection, diffusion, production and sink terms. In combination with the conditioned Navier-Stokes equations, this leads to improvements in the calculation of flow characteristics in both the transitional layer and the free stream. The method is validated on transitional heat transfer measurements in a linear turbine cascade at typical operational conditions.
Experimental investigation of the unsteady rotor aerodynamics of a transonic turbine stage
Authors: Dénos R , Sieverding C. H. , Arts T , Brouckaert J. F. , Paniagua G , Michelassi V
Published: October 2002

This paper describes some results of a large experimental programme on unsteady flow through the rotor of a transonic turbine stage in the large Compression Tube Turbine Facility at the von Karman Institute for Fluid Dynamics. The tests were carried out as part of a Brite EURAM project. The test programme covered the investigation of the effects of a variation in the rotational speed of the rotor, the axial stator-rotor distance and the stator trailing-edge coolant flow ejection. The paper aims at presenting the measurements of the relative inlet total pressure and the rotor blade surface pressure at rotor mid-span.
Improving gas turbine power plant safety: the application of computational fluid dynamics to gas leaks
Authors: Gilham S , Cowan I. R. , Kaufman E. S.
Published: October 2002

Gas-fired power stations have recently come under the scrutiny of the UK Health and Safety Executive who have raised concerns over potential explosion risks. The gas turbines are usually housed within acoustic enclosures to protect the turbine and to reduce environmental noise. However, in the event of a gas leak, such enclosures may promote a build-up of gas and thus give rise to an explosion risk. This paper describes how General Electric, working with W. S. Atkins, have responded to these concerns. Examples are given of how computational fluid dynamics simulations and field measurements have been used to study the effectiveness of gas turbine compartment ventilation and gas detection systems. Developments of the modelling techniques to allow additional safety and operational efficiency issues to be considered are also described.
Induced flow reciprocating pumps Part 1
Authors: Burton J. D. , Short T. D.
Published: October 2002

A water column, contained in a rigid pipe equipped with a foot valve, may be set in oscillation and bounced against a hydraulic spring at the lower end. In this way, water may be lifted inertially. The use of such induced flow pumping stretches back to at least the eighteenth century. After exploring these roots the paper proceeds to illustrate modern applications, mainly for hand-and wind-operated water-lifting systems in remote areas. Two arrangements for maintaining the water column in oscillation are examined. By analysis and experiment it is shown that greatly improved performance is achieved by permitting the water column to rebound freely.
Transportation fuel from cellulosic biomass: a comparative assessment of ethanol and methanol options
Authors: Borgwardt R. H.
Published: October 2002

Future sources of renewable fuel energy will be needed to supplement or displace petroleum. Biomass can be converted to ethanol or methanol, both having good properties as a motor fuel, but requiring distinctly different production technologies. Those technologies are compared in terms of production cost, potential for petroleum displacement and effectiveness for management of greenhouse gas emissions. Supply curves that relate the crop price to the national biomass production potential are crucial to the comparison. The higher delivered cost of biomass that would be acceptable as feedstock for methanol production, plus the increased conversion efficiency and lower production cost that can be obtained by use of natural gas as a co-feedstock, are major factors favouring methanol. The overall net carbon dioxide emission reduction and petroleum-displacement potential of methanol produced in a single process from biomass and natural gas in the United States are nine times those of two separate processes that would produce ethanol from the same amount of biomass and methanol from the same amount of natural gas.
Fuzzy logic controller for a retrofitted closed-loop injection moulding machine
Authors: Huang S-J , Lee T-H
Published: October 2002

For the purposes of producing precise products and providing the flexibility for products variation, an open-loop control commercial injection moulding machine is retrofitted into a closed-loop control system for monitoring the filling and post-filling phases of the injection processes. The hydraulic control unit, control and interface circuits, safety limit switches and personal-computer-based controller were redesigned and constructed. Since the injection moulding processes have complicated non-linear dynamics and model uncertainty, the application of a classical proportional-integral-derivative controller has adaptivity and robustness problems, especially with regards to the pressure control during compression phase. Here, an intelligent fuzzy controller is employed to adjust the injection speed of the filling phase and to control the nozzle pressure of the post-filling phase. The experimental results show that this controller has good performance in actual injection moulding processes.
Non-fragile H∞ flight controller design for large bank-angle tracking manoeuvres
Authors: Yee J-S , Yang G-H , Wang J L
Published: October 2002

This paper is concerned with the design of non-fragile H∞ output feedback control of a high-performance aircraft similar to F-16 in executing a large bank-angle tracking manoeuvre. The non-fragile H∞ flight controllers are designed to tolerate multiplicative gain variations in the controller matrices. The designs are based on three linear trim models of the high-performance aircraft. From the linear and non-linear simulations, the results show that the resulting closed-loop systems using the non-fragile H∞ flight controllers are robustly stable and have H∞ disturbance attenuation bounds with respect to some admissible controller gain variations. Corresponding performance comparisons with the standard robust design approach show that the resulting closed-loop systems using the standard H∞ flight controllers are unstable under the same controller gain variations.
The robustness of reduced order minimal controller synthesis control in the plastic region
Authors: Bulut S
Published: October 2002

In this paper, the stability of the reduced order minimal controller synthesis (ROMCS) algorithm is investigated by comparative robustness tests. Both, ROMCS control and the proportional plus integral (P +1) controller are implemented in the case of aluminium alloy specimens of 10 mm diameter. Three other different specimens are controlled under the same controller implementations. Hence, the unmodelled dynamics and disturbances are introduced as a natural consequence of these test conditions.
Evolutionary L∞ identification and model reduction for robust control
Authors: Tan K C , Li Y
Published: October 2002

An evolutionary approach for modern robust control oriented system identification and model reduction in the frequency domain is proposed. The technique provides both an optimized nominal model and a ‘worst-case’ additive or multiplicative uncertainty bounding function which is compatible with robust control design methodologies. In addition, the evolutionary approach is applicable to both continuous- and discrete-time systems without the need for linear parametrization or a confined problem domain for deterministic convex optimization. The proposed method is validated against a laboratory multiple-input multiple-output (MIMO) test rig and benchmark problems, which show a higher fitting accuracy and provides a tighter L∞ error bound than existing methods in the literature do.
Linearization techniques in fault diagnosis of non-linear systems
Authors: Lin W , Wang H
Published: October 2002

In this paper it is shown how the well-known linearization technique can be used to solve the problem of fault diagnosis, for non-linear systems subject to actuator failures. An exponential adaptive observer is designed on the basis of the first approximation approach, achieving locally exponential convergence of observation error as well as unbiased fault diagnosis. A link between linear fault diagnosis and its non-linear counterpart is explored. The effectiveness of the proposed non-linear fault diagnosis scheme is illustrated through a simulation example.
Inversion control of non-linear systems with an inverse NARX model identified using genetic algorithms
Authors: Luh G-C , Wu C-Y
Published: October 2002

The inverse dynamics approach has been widely utilized in the control problem of various practical non-linear systems in recent years. This paper demonstrates a feedforward-feedback controller scheme of a non-linear plant whose dynamics are unknown and uncertain. The feedforward controller, an inverse NARX model (non-linear autoregressive model with exogenous inputs), provides only coarse control, whereas the feedback controller is used to handle unmodelled dynamics and disturbance. The inverse NARX model is derived by inverting the forward NARX model identified using genetic algorithms. A parallel-type NARX model whose outputs of the identification model are fed back into the identification model is adopted in the identification procedure to include the stability examination numerically. Both experimental and simulation results demonstrate that the proposed controller provides very good performance in the problems of input estimation and output tracking.
Optimum regulation of process systems with particular reference to an industrial boiler
Authors: Whalley R , Ebrahimi M
Published: October 2002

The regulation of process systems which are represented by linear multi-variable time-invariant Laplace-transformed models is considered. Procedures which are based on the use of controller-generated functions are presented, enabling feedback control investigations to be made. Simple scalar-system frequency-domain design techniques are used, in conjunction with polynomial functions, to distort the characteristic equation-root locus to desirable areas of the complex plane. Commensurate with this constraint, a feedback strategy is presented which minimizes the control effort required, for arbitrary disturbance variations. A typical process system model is employed to illustrate the procedure. Thereafter, an industrial model of a boiler-furnace system is outlined, and an optimum minimum control effort regulator is derived.
Gradient-based control and optimization of boundary layer transition
Authors: Tutty O R , Hackenberg P , Nelson P A
Published: October 2002

In flow past bodies, small amounts of surface suction can delay the transition from laminar to turbulent flow. Suction therefore has significant potential to reduce the drag and hence the operating costs of aircraft. To obtain best results the suction distribution must be optimized, and, if necessary, should be adjusted to take account of changing conditions. Here distributed suction is used through a number of independently controlled discrete suction panels, with transition maintained at a desired location while an automatic adaptive control feedback loop regulates the suction flowrates. The combination of minimum suction effort with constant transition position is expressed as a constrained optimization problem. A gradient-based algorithm is used to perform the control and optimization. Up to six suction panels are used, and flows both with and without an imposed pressure gradient are considered. In simple cases the method converges rapidly, but in other situations there is no single optimum solution within the numerical tolerance of the method. There are also cases in which an optimum solution exists but cannot be achieved as it occurs at a discontinuity in the relationship between the transition position and the suction flowrates. Similar problems could occur with other cost functions and formulations, and when using different solution algorithms.
Non-linear process modelling based on a Wiener approach
Authors: Ikonen E , Najim K
Published: October 2002

The identification of multiple-input single-output Wiener models is considered in this paper. The non-linear memoryless part is described by a parametrized steady state model. In this paper two representations for the linear dynamic part that preserve the unit steady state gain are discussed and compared: finite step response and transfer function with a feedback polynomial. The steps necessary for estimating the parameters of the Wiener model are presented. In the simulation examples with data from a pneumatic valve model, distillation column model and a pilot pump-valve system, the performance of the approach is examined, and the use of various kinds of non-linear black-box and grey-box structure for the modelling of the static part is illustrated.
An architecture for system-wide fault detection and isolation
Authors: Dassanayake H P B , Roberts R , Goodman C J
Published: October 2002

A novel approach to distributed fault detection and isolation (FDI) is presented. Consideration is given to an appropriate architecture and communication method for a truly distributed FDI system. As part of the discussion on system architecture, regard is given to the correct level at which fault detection, diagnosis and isolation should be carried out.

The case study of an automatic door as part of a building automation system is presented. Recognized faults are induced on the asset and detection methods formulated. It is demonstrated that, by implementing the fault detection algorithms at a lower level, it is possible to carry out FDI over a system consisting of many assets. This allows maintenance staff more precise information regarding the health of the whole system and allows system-wide isolation and in-depth diagnostics to be applied in the event of a fault being detected. The architecture discussed allows the implementation of system-wide FDI at a fraction of the cost of stand-alone systems.
Physical model-based inversion in control systems design using bond graph representation
Authors: Ngwompo R F , Ngwompo R F , Scavarda S , Thomasset D
Published: October 2002

In Part 1, a graphical and physical approach to the inversion of dynamic systems using the bond graph representation was presented. Two applications of inverse bond graph models are presented in this paper: the sizing of actuators for the control of a given system with pre-defined output performance specifications and the zero-dynamics analysis of a system from a physical viewpoint.
Hydraulic anti-lock braking control using the hybrid sliding-mode pulse width modulation pressure control method
Authors: Wu M-C , Shih M-c
Published: October 2002

This study integrates the discrete on-off operation of hydraulic high-speed solenoid valves and the pulse width modulation (PWM) method to achieve a quasi-continuous braking pressure control. Sliding-mode control is applied here due to the non-linear nature of the solenoid valve. The hybrid compensating method presented here compensates for the mechanical and electrical delay of solenoid valves, obtaining more precise control results and keeping the robustness of the sliding controller. Following verification of the braking pressure controller on a test stand, an anti-lock braking controller of a passenger car is designed by use of tyre tangential deceleration feedback. This anti-lock braking controller is also verified on a dynamic test stand. Braking experiments on both dry and wet road surfaces are simulated.
Adaptive fuzzy throttle control for an all-terrain vehicle
Authors: Trebi-Ollennu A , Dolan J M , Khosla P K
Published: October 2002

This paper describes an adaptive fuzzy throttle control for an all-terrain vehicle (ATV) powered by internal combustion engine. The design objective is to provide smooth throttle movement and zero steady state speed error, and to maintain a selected vehicle speed over varying road slopes for a 2–30 mile/h speed range. Unlike modern production vehicles which have microprocessor-based engine management systems, the ATV's engine is mechanically controlled via a carburettor.

A complete mathematical model of the engine is not available, making it very difficult to apply conventional control techniques. Using experience and data collected from extensive experiments conducted on the ATV throttle mechanism, an adaptive fuzzy throttle control algorithm is designed. A candidate Lyapunov function is employed in the adaptive law synthesis to ensure convergence. Experimental results are presented showing the effectiveness of the control algorithm at speeds below 2.74 mile/h (1.2m/s).
Experimental validation of a damage detection technique for helicopter main rotor blades
Authors: Kiddy J , Pines D
Published: October 2002

This paper experimentally validates the feasibility of an on-line damage detection capability for helicopter main rotor blades. A previously developed modal-based damage detection methodology is implemented to detect, locate and characterize simulated ballistic damage. The damage detection algorithm is based on an extension to eigenstructure assignment methods which were developed for non-rotating structures. Validation is performed on two separate test structures. The first is a long slender beam rotated in a vacuum. This captures the centrifugal effects while eliminating the aerodynamic loads that are found on an actual blade. The second involves a non-rotating test of full-scale main rotor blades from a Hughes TH-55A helicopter. The combined results demonstrate the possibilities and limitations of a modal-based approach for damage detection of a helicopter rotor blade. In general, it is shown that it is possible to detect damage in the blade if the damage occurs in a region of high modal energy. However, damage in regions of low modal energy are not easily detected with a modal-based approach.
On the singular perturbation approach to trajectory control of a multilink manipulator with flexible links and joints
Authors: Subudhi B , Morris A S
Published: October 2002

The singular perturbation approach has been shown to be successful in controlling both flexible link manipulators and flexible joint manipulators. In this paper, the technique is extended to control both link and joint flexibility of a multilink manipulator simultaneously while a desired trajectory is being tracked. A comprehensive, closed-form, Euler-Lagrange, assumed-mode model of a multilink manipulator has been formulated in which the effects of the link and joint flexibility are incorporated. This is then converted into a two-time-scale, state-space, singular perturbation model where the slow subsystem involves the link angles and the fast subsystem consists of the joint deflection and the link deflection variables. A composite controller is designed based on the two-time-scale model of the flexible link and joint manipulator. Numerical simulation results confirm that the proposed controller satisfactorily suppresses the tip deflection and joint flexibility of the manipulator while very good trajectory tracking is achieved.
Robust position control of a transportation carriage directly driven by a linear brushless d.c. motor
Authors: Shieh N C , Tung P C
Published: October 2002

This study proposes robust position regulation and output tracking controllers for a transportation carriage directly driven by a linear brushless d.c. motor. System identification for the linear motor and driver is performed using a dynamic signal analyser, thus providing a linearized model for the system. According to the selected nominal parameters, an optimal linear quadratic solution with a prescribed degree of stability is obtained. Owing to inaccuracies in the identification procedures and possible payload variations, system parameter uncertainties exist. In addition, time-varying disturbances corrupting the motor driver are also considered. Thus, an auxiliary input, connected to the nominal optimal control, is introduced to guarantee robustness for the control of the transportation carriage. Computer simulation and experimental implementation are completed and compared. These results demonstrate the effectiveness of the proposed approach for the position regulation and output tracking control within the linear brushless d.c. motor and also confirm the feasibility of its implementation in manufacturing systems.
Non-iterative evaluation of multiphase thermal compliances in bond graphs
Authors: Brown F. T.
Published: October 2002

The practical use of bond graphs to organize the efficient simulation of multiple-phase thermodynamic systems is perhaps the most significant piece of unfinished business regarding the evolution of bond graphs. The most widely recognized form for these cases, called the pseudo bond graph, dictates particular causalities that require iteration, assuming the use of available state equations. This paper shows how the alternative convection bond graphs can direct non-iterative evaluation of state properties of multiphase thermal compliances. The state variables of a compliance become temperature, mass and volume. A refrigeration cycle is used as an example.
HYBRSIM—a modelling and simulation environment for hybrid bond graphs
Authors: Mosterman P. J.
Published: October 2002

Bond graphs are a powerful formalism to model continuous dynamics of physical systems. Hybrid bond graphs introduce an ideal switching element, the controlled junction, to approximate continuous behaviour that is too complex for numerical analysis (e.g. because of non-linearities or steep gradients). HYBRSIM is a tool for hybrid bond graph modelling and simulation implemented in Java and is documented in this paper. It performs event detection and location based on a bisectional search, handles run-time causality changes, including derivative causality, performs physically consistent (re-)initialization and supports two types of event iteration because of dynamic coupling. It exports hybrid bond graph models in Java and C/C++ code that includes discontinuities as switched equations (i.e. pre-enumeration is not required).
Algorithmic, physically based mode initialization when simulating hybrid systems
Authors: Edström K , Glad S. T.
Published: October 2002

In the simulation of hybrid systems, discontinuities can appear at mode changes. An algorithm is presented that gives initial values for the continuous state variables in a new mode. The algorithm is based on a switched bond graph representation of the system, and it handles discontinuities introduced by a changed number of state variables at a mode change. The algorithm is obtained by integrating the bond graph relations over the mode change and assuming that the physical variables are bounded. This gives a relation between the variables before and after the mode change. It is proved here that the equations for the new initial conditions are solvable. The algorithm is related to a singular perturbation theory by replacing the discontinuity by a fast continuous change. The action is considered of a single switch and the corresponding continuous change, tuned by a single parameter. By letting this parameter tend to zero, the same initial state values are achieved as those derived by the presented algorithm. The algorithm is also related to physical principles such as charge conservation.
Bond graph based frequency domain sensitivity analysis of multidisciplinary systems
Authors: Borutzky W , Granda J
Published: October 2002

Multidisciplinary systems are described most suitably by bond graphs. In order to determine unnormalized frequency domain sensitivities in symbolic form, this paper proposes to construct in a systematic manner a bond graph from another bond graph, which is called the associated incremental bond graph in this paper. Contrary to other approaches reported in the literature the variables at the bonds of the incremental bond graph are not sensitivities but variations (incremental changes) in the power variables from their nominal values due to parameter changes. Thus their product is power. For linear elements their corresponding model in the incremental bond graph also has a linear characteristic. By deriving the system equations in symbolic state space form from the incremental bond graph in the same way as they are derived from the initial bond graph, the sensitivity matrix of the system can be set up in symbolic form. Its entries are transfer functions depending on the nominal parameter values and on the nominal states and the inputs of the original model. The sensitivities can be determined automatically by the bond graph preprocessor CAMP-G and the widely used program MATLAB together with the Symbolic Toolbox for symbolic mathematical calculation. No particular program is needed for the approach proposed. The initial bond graph model may be non-linear and may contain controlled sources and multiport elements. In that case the sensitivity model is linear time variant and must be solved in the time domain. The rationale and the generality of the proposed approach are presented. For illustration purposes a mechatronic example system, a load positioned by a constant-excitation d.c. motor, is presented and sensitivities are determined in symbolic form by means of CAMP-G/MATLAB.
A high-level technique for diesel engine combustion system condition monitoring and fault diagnosis
Authors: Twiddle J A , Jones N B
Published: October 2002

This paper presents a technique for diagnosis of a class of engine faults, which adversely affect the combustion efficiency of a diesel generator set. The diagnosis is made by combining the evidence of two separate estimations of engine load with the outputs from a predictive fuzzy model of engine speed.

Certain faults affect the periodicity of the engine speed signal. The variation in periodicity means that the load estimation from power spectral density of the speed signal is not robust. This problem is countered by implementing a reference model to predict speed fluctuations with respect to crank angle. This model has the additional benefit that its output may be used to detect periodic fault symptoms in the speed signal, thereby leading to identification of the individual cylinder affected by the fault.

A fuzzy rule based system has been developed to diagnose faults based on the load estimations and the residuals obtained from the reference model. Testing the diagnostic system with data from the normal, and two other separate engine fault conditions, resulted in a classification success rate greater than 90 per cent in each case. A further benefit is reported where the combination of evidence from the three sources effectively validates the load estimation, which may then be used to infer faults in other subsystems.
Extracting symptoms of bearing faults from noise using a non-linear neural filter
Authors: Shao Y , Nezu K
Published: October 2002

Improving the signal-to-noise ratio is an important feature for the early detection of faults in bearings subject to large amounts of environmental noises. A method is proposed for improving the signal-to-noise ratio by adaptive neural filtering (ANF). A comparison of failure detection capabilities of a linear adaptive filter using the least mean square (LMS) algorithm and a non-linear adaptive filter using the ANF algorithm in conditions of large amounts of environmental noise is made. Experimental results show that an adaptive filter using a neural filtering algorithm is an effective means for extracting the symptoms of a bearing fault under such conditions.