bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of the unsteady aerodynamic characteristics of horizontal axis wind turbines including three-dimensional effects
Authors: Wang T , Coton F. N.
Published: October 2002

An unsteady aerodynamic model for horizontal axis wind turbine performance prediction has been extended to consider three-dimensional (3D) rotational effects. The method couples a prescribed wake vortex scheme with a semi-empirical unsteady aerofoil model to provide the unsteady response of the blades due to the cyclic variation of incidence. The wake geometry of the turbine and the basic aerodynamic parameters required by the unsteady aerofoil model are calculated from the prescribed wake model using two-dimensional aerofoil data. The 3D rotational effects are then taken into account by a series of corrections to the unsteady aerofoil model. Application of these corrections has yielded substantial improvements in the prediction of aerodynamic force and moment coefficients on inboard blade sections. This is illustrated by a series of comparisons with field data. In general, the method is shown to give accurate predictions over a range of operating conditions and inflow angles.
Conceptual design for the energy conversion system of a nuclear gas turbine cogeneration plant
Authors: Kikstra J. F. , Verkooijen A. H M.
Published: October 2002

The high-temperature gas-cooled reactor (HTGR) is a nuclear reactor which can be designed to be inherently safe. When the helium heated in the reactor is used directly in a closed-cycle gas turbine system, the excellent safety characteristics can be combined with a high efficiency. Because of the small scale and simple modular design (both a result of the inherent safety) the HTGR is suitable for combined heat and power (CHP) production. In this article an energy conversion system for a nuclear gas turbine cogeneration plant is designed. First, with help of a basic model, a cycle choice is made and some parameters such as pressure ratio and heat-power ratio are optimized. With a steady state model a conceptual design is made and a sensitivity analysis is carried out for a number of design parameters. Finally, the off-design behaviour is optimized.
Development of a novel gas turbine driven centrifugal compressor
Authors: Turner A. B. , Davies S. J. , Childs P. R N. , Harvey C. G. , Millward J. A.
Published: October 2002

The purpose of the paper is to provide design and operational information for the conversion of small turboprop engines into land-based shaft power drives. These can provide economical solutions to individual power requirements such as standby electrical generators, combined heat and power units, fan drives or centrifugal compressor drives. Considerable numbers of ex-military engines are currently becoming available at economical prices. One such engine is the Rolls-Royce Dart turboprop gas turbine which, although there are over 2000 still in civil and military service worldwide, is now being phased out of Royal Air Force operation. This paper describes the modification of a Dart RDa 12 engine to drive a centrifugal compressor from a smaller RDa 7, Mk 552, engine for a compressed air facility on a university campus.

The modified engine has a power of over 2400 hp (1790 kW) at 15000 r/min and the compressor was driven directly from the engine output shaft supplying 10.5 kg/s of air at a pressure ration of 3.3:1. To achieve this, the turboprop's main reduction gearbox was removed, the teeth on the engine drive pinion ground down and a flexible coupling fitted to it to drive the RDa 7 compressor which was flange mounted on the engine gearbox-air intake casing. The removal of the main gearbox removed the drives to the lubricating oil pumps the fuel pump and the engine control system. The manner in which these problems were overcome and the method of operating the system are described.

One of the most important considerations in starting such a direct drive system is the complete closing off of the air intake to the driven compressor and the design of an annular valve to perform this duty is described. The operating parameters including the flow, pressure ratio and engine turbine entry temperatures for this system are given.
A prototype of a fast cycle adsorption refrigerator utilizing a novel carbon—aluminium laminate
Authors: Critoph R. E. , Tamainot-Telto Z , Davies G. N L.
Published: October 2002

A laboratory prototype of a fast cycle adsorption refrigerator is presented: it uses a monolithic carbon-aluminium laminate adsorbent and ammonia refrigerant. The system has a high effective thermal conductivity and density bed and is powered by heat and designed to provide a specific cooling power up to 1 kW/kg adsorbent. There are two generators and each one consists of a tubular stainless steel shell containing a laminate of activated carbon discs and aluminium fins formed in situ. The full unit is designed for a power input up to 10 kW and a cooling power up to 3 kW. Preliminary results of the performance are presented and allow assessment of the intensification of heat transfer within the bed. At specific working conditions (evaporating and condensing temperatures, 7.5 and 32°C respectively; generating temperature, 140°C; half-cycle time, 620 s), the results have demonstrated the intensification of heat transfer within the generator through temperature and pressure profiles during the cycles. With an intrinsic heating power input of about 1.130 kW, the refrigerator produces continuously about 0.500 kW of cooling that corresponds to a specific cooling power of 0.180 kW/kg. The cooling coefficient of performance (COP) is about 0.44.
Evaluation of an above-ground installation control strategy using Simulink
Authors: Doonan A. F.
Published: October 2002

In recent years the emphasis within British Gas has moved from the construction aspects of the natural gas transmission system to one of investigating methods of optimizing the operational efficiency of the existing pipeline network. In particular, the developments which have taken place in the area of microprocessor technology have provided the opportunity to implement improved control strategies in areas where existing pneumatically based systems are somewhat limited in terms of performance. This paper describes how the simulation software package Simulink was used to evaluate safely the performance of an alternative control strategy whereby the pressure of the pipeline is measured a considerable distance downstream from the main pressure regulating station.
On appraising alternative power plant investment proposals: Part 2: Application
Authors: Roy-Aikins D J E A , Bohn D
Published: October 2002

This paper is an application of the economic model developed in Part 1 and programmed in the computer code PEACES (program for the economic analysis of combined energy systems). A case study is presented in which hypothetical energy requirements at an industrial site are considered and an exercise is conducted wherein cogeneration is considered as a means of improving the energy situation at the site. Appropriate technologies that can satisfy the cogeneration requirements are investigated and technical and economic evaluations are carried out for a feasibility assessment. Of the three proposals considered, the gas turbine with heat recovery steam generator and the gas/steam turbine combined cycle cogeneration plant were found to be economically viable, while the steam turbine was not. It was recommended that the gas/steam turbine combined cycle cogeneration proposal be adopted, as it was the most economical.
Thermodynamic analysis of a partial gasification pressurized combustion and supercritical steam combined cycle
Authors: De S , Nag P K
Published: October 2002

The aim of this paper is to study the thermodynamic performance of a new combination of a partial gasification pressurized combustion gas cycle and a supercritical steam cycle as a means of advanced ‘clean coal’ power generation. Energy and exergy analyses of the proposed power cycle are presented. The effects of pressure ratio of the gas cycle, the turbine inlet temperature (TIT) and amount of coal gasification on the thermodynamic performance of the combined cycle are discussed. The optimum pressure ratio has to be determined on the basis of a judicious compromise between the net power and the overall efficiency. Overall efficiency is the maximum for an optimum TIT. The relative coal feeds for partial gasification and pressurized combustion may be adjusted with a compromise between net power and overall efficiency. The power output of the cycle can be increased by more coal gasification. However, this yields a lower overall efficiency.
Computational studies of unsteady flows in a centrifugal compressor stage
Authors: Koumoutsos A , Tourlidakis A , Elder R L
Published: October 2002

This paper describes the flow analysis in a centrifugal compressor stage using a three-dimensional computational fluid dynamics (CFD) algorithm. The flow unsteadiness arising from the interaction between the impeller and the diffuser has also been analysed using an algorithm suitable for equal or multiple numbers of rotor and diffuser blades. The multi-block, structured grid CFD code TASCflow which provides an approximate solution to the Reynolds-averaged Navier-Stokes equations was used as a basis and algorithm development was undertaken to provide the required capability of modelling the unsteady interactions of the impeller and the diffuser.

The centrifugal compressor stage under investigation consists of 28 radial blades (of which 14 are splitter blades) in the impeller and 27 vanes in the diffuser. The presented results and analysis are for off-design flow conditions where experimental results were available for comparison. The results obtained for the steady-state model show a reasonable agreement with the measurements. In general the unsteady flow field obtained shows a reasonable agreement with experimental data and exhibits considerable differences when compared with the steady-state results.
Direct and reverse flow conditions in radial flow hydraulic turbomachines
Authors: Ventrone G , Ardizzon G , Pavesi G
Published: October 2002

Direct and reverse operation of radial flow turbomachines is examined. A runner momentum coefficient is defined which provides the means for correlating the ideal pump and turbine head-flow parameters in the region of optimum performance in both modes of operation. A theoretical procedure is thus arrived at by which turbine operation is predicted once the significant geometric parameters and the performance curves of a given pump are known. Tests on a number of machine configurations show that the results obtained at best efficiency operation by the present method are within ±4 per cent of observed values, while errors in the predictions of empirical formulations may be more than ±30 per cent. Furthermore, the present method gives a fairly accurate estimation of the range of flows for acceptable turbine operation, which is not considered by other procedures.
A dimensionaless number for the control of ultra-high-pressure water systems
Authors: Momber A W
Published: October 2002

An optimization procedure is developed for ultra-high-pressure water systems (UPWSs) based on an easily estimated control parameter. This parameter, ɛ, is a dimensionless number and, as a control condition, should always be unity. Any deviation from ɛ = 1 requires a system response to avoid efficiency losses. On the basis of the proposed procedure, any required change in the response parameters for UPWSs can be estimated quantitatively.
Development of novel intermetallic compounds and solid solution systems as hydrogen storage devices
Authors: Esayed A Y
Published: October 2002

One of the limitations surrounding the exploitation of hydrogen as a fuel is the difficulty in storing it economically and conveniently. At present, hydrogen is typically stored as a compressed gas or as a cryogenic liquid. However, neither method is very appealing. Gaseous storage requires a large volume and/or weight of storage vessels, while liquid hydrogen requires a rather expensive liquification process and some energy as well. Another possibility for storage that is currently being studied and utilized is metal hydrides. The hydrogen reacts with the metals and forms metal hydrides. Storing hydrogen as a metal hydride has many advantages. Firstly, hydrogen can be stored in metal hydrides more efficiently (in terms of volume) than as liquid, or even solid, hydrogen. Secondly, the formation reaction is easily reversible. The formation of the hydride is an exothermic and usually spontaneous reaction, but the hydrogen can easily be recovered by heating the hydride. Therefore, the metal hydride can be classified as a safe method of storing hydrogen since the hydrides are generally stable below their dissociation temperatures. Moreover, the self-cooling effect will slow down and eventually stop any loss of hydrogen if a leak is developed in the storage system.

Several metal hydrides have been developed, but none of them satisfies all these requirements. Some of the more common drawbacks of the currently available materials are that (a) hydrogen-metal ratios are too low, (b) metals involved are too costly, (c) the absorption or release of hydrogen is difficult, slow or sensitive to poisoning phenomena and (d) significant hysteresis is exhibited. The available materials for hydrogen storage are briefly reviewed and a more detailed overview is given of two classes of materials that are being developed in the author's laboratory, namely zirconium-based Laves phase intermetallic compound and body-centred cubic solid solutions based on niobium.
Modelling of the droplet size distribution in a low-pressure steam turbine
Authors: Petr V , Kolovratnik M
Published: October 2002

Realization of numerous tests on the droplet size measurement with extinction probe, in a 200 MW low-pressure steam turbine, provides necessary experimental data for testing the theoretical models of the droplet nucleation process in steam turbines. The earlier computational model accounting for the unsteady and viscous effects given by Bakhtar and Heaton and by Guha and Young, where the steam particles follow randomly chosen different streamlines within the blade rows with prescribed polytropic efficiency distribution in the pitchwise direction, thus undergoing various nucleation conditions, has been extended in this paper to consider to some extent two-dimensional effects. Because several uncertainties still exist in the inversion methods, predicting the size distribution of droplets, this contribution is aimed at direct comparison of the computed and measured transmittance data I/I0.
Emissions characteristics of higher alcohol/gasoline blends
Authors: Gautam M , Martin D W , Carder D
Published: October 2002

An experimental investigation was conducted to determine the emissions characteristics of higher alcohols and gasoline (UTG96) blends. While lower alcohols (methanol and ethanol) have been used in blends with gasoline, very little work has been done or reported on higher alcohols (propanol, butanol and pentanol).

Comparisons of emissions and fuel characteristics between higher alcohol/gasoline blends and neat gasoline were made to determine the advantages and disadvantages of blending higher alcohols with gasoline. All tests were conducted on a single-cylinder Waukesha Cooperative Fuel Research engine operating at steady state conditions and stoichiometric air-fuel (A/F) ratio. Emissions tests were conducted at the optimum spark timing-knock limiting compression ratio combination for the particular blend being tested. The cycle emissions [mass per unit time (g/h)] of CO, CO2 and organic matter hydrocarbon equivalent (OMHCE) from the higher alcohol/gasoline blends were very similar to those from neat gasoline. Cycle emissions of NOx from the blends were higher than those from neat gasoline. However, for all the emissions species considered, the brake specific emissions (g/kW h) were significantly lower for the higher alcohol/gasoline blends than for neat gasoline. This was because the blends had greater resistance to knock and allowed higher compression ratios, which increased engine power output. The contribution of alcohols and aldehydes to the overall OMHCE emissions was found to be minimal.

Cycle fuel consumption (g/h) of higher alcohol/gasoline blends was slightly higher than with neat gasoline due to the lower stoichiometric A/F ratios required by the blends. However, the brake specific fuel consumption (g/kW h) for the blends was significantly lower than that for neat gasoline.
Modelling of cogeneration systems Part 3: Application of steam turbine cogeneration analysis to Auckland Hospital cogeneration utility system
Authors: O'Brien and J M , Bansal P K
Published: October 2002

Steam turbine cogeneration analysis (STuCA) is a quasi-static steam cogneration plant modelling tool, which has been developed and applied to the Auckland Hospital energy centre at Auckland, New Zealand. The STuCA code consists of four submodels, namely a load, a system, a plant and an economic model. The load model was developed using historical data and drove the system model, which consisted of heat exchangers. The system model output was then used to drive the plant model that modelled the turbine and boiler and predicted the primary energy flows and cash flows at the site. Economic analysis tools including thermodynamic, thermoeconomic and economic performance measures such as the payback period and the net present value used these data to analyse the economic performance measures such as the payback period and the net present value used these data to analyse the economic performance of the site. The STuCA model output correlated to site data to within 10 per cent and provided data that could be used by the economic analysis tools. The application of the STuCA model to the hospital site proved that it could be used to design cogeneration plants, to analyse retrofit, to upgrade proposals and to study the effects of changing site loads on plant performance.
Pump efficiency testing by the thermodynamic method—an independent view
Authors: Thorne E W , Neal A N
Published: October 2002

This note summarizes the development of a code of practice on pump efficency testing by the direct thermodynamic method, and a temperature probe calibration procedure. A series of comparative on-site pump tests are analysed, highlighting areas of agreement and aspects requiring further research.
Computational fluid dynamics applied to a cement precalciner
Authors: Giddings D , Eastwick C N , Pickering S J , Simmons K
Published: October 2002

This paper describes a study of the use of computational fluid dynamics (CFD) to investigate the performance of a precalciner vessel at a cement works, In this vessel, limestone, held in suspension, is calcined to calcium oxide and the endothermic reaction is supported by the combustion of coal.

Results are presented from a CFD model that contains all the essential features of the precalciner as operated when burning coal. The model fully represents the reactions and fluid dynamics of the precalciner. Previously unidentified features are illustrated. Certain key features at points in the precalciner, where some limited measurements can be made, are compared with the parameters indicated by the computational model. The measurements are consistent with the results calculated by the model indicating fair validation. The CFD data show the following

1 The gases undergo distinct recirculation.

2 The coal particles entering at one inlet have significantly different trajectories and temperature histories from those entering at the second diametrically opposed inlet.

3 There is 90 per cent completion of coal combustion at the exit.

4 73 per cent limestone in the raw meal is calcined to calcined to calcium oxide at the exit from the precalciner.

5 The highest reaction rate of the raw meal is closer to one side of the vessel due to interaction with the gas flows.

Future work is proposed which, firstly, will provide further validation of the results so far attained by selective measurements on the precalciner and, secondly, will model the combustion and aerodynamic behaviour of waste-derived fuels in the precalciner vessel, commencing with shredded car tyre chips.
Stabilization of the Chernobyl Shelter
Authors: Heriot I. D.
Published: October 2002

The Shelter enclosing the wrecked Chernobyl Unit 4 reactor continues to deteriorate posing an increasing environmental threat due to structural degradation and the ingress of water. The uncertain nature of the wreckage within the Shelter combined with structural instability and high radiation fields make the remediation a very challenging task. A decision-based approach known as the Shelter Implementation Plan (SIP) has been adopted as a way of resolving the many difficulties. This plan has the financial support of more than 20 nations under the Chernobyl Shelter Fund (CSF) which is administrated by the European Bank for Reconstruction and Development (EBRD). Project execution will pose a number of unique problems in technology, project management, contracting, nuclear regulation and risk management.
Numerical investigation into the effects of a radial gap on hydraulic turbine performance
Authors: Sato K , He L
Published: October 2002

The effects of the rotor/stator blade row interaction on the performance of radial turbine stages are investigated numerically. A three-dimensional unsteady incompressible Navier-Stokes method based on the dual-time stepping and the pseudocompressibility method is developed for the performance prediction. A centrifugal pump with a vaned diffuser is calculated for validation purposes, and the predicted unsteady flow results show reasonable agreement with the experimental data. The method is applied to analysis of hydraulic turbine stages. A generic turbine rotor is combined with a row of nozzle guide vanes with three settings of radial gap and numerical flow simulations are conducted for the performance evaluations. The predicted efficiency of the hydraulic turbine stages deteriorates if the radial gap between blade rows is reduced although the difference is very small. The entropy rises along the streamlines suggest that the differences in the stage efficiency level can be largely attributed to the loss generated in the nozzle vane passages.
Conceptual design optimization of mixed-flow pump impellers using mean streamline analysis
Authors: Oh H. W. , Kim K-Y
Published: October 2002

A conceptual design optimization code for mixed-flow pump impellers has been developed to determine the geometric and fluid dynamic variables under appropriate design constraints. In the present study the optimization problem has been formulated with a non-linear objective function to minimize the fluid dynamic losses. The optimal solution is obtained by means of the Hooke-Jeeves direct search method. Computations are performed using mean streamline analysis and the present state-of-the-art loss correlations. Changes in the optimized efficiency and design variables of mixed-flow pump impellers are presented in this paper as a function of non-dimensional specific speed in the range 1.9 ≤ Ns ≤ 2.5. The diagrams presented herein can be used efficiently in the preliminary design phase of mixed-flow pump impellers.
Real gas Brayton cycles for organic working fluids
Authors: Angelino G , Invernizzi C
Published: October 2002

Organizing a closed Brayton cycle in such a way that the compression process is performed in the vicinity of the critical point where specific volumes are a fraction of those of an ideal gas yields performance indices particularly attractive, mainly at moderate top temperatures. Cycle thermodynamic analysis requires the development of adequate methods for the computation of thermodynamic properties above the vapour saturation curve about the critical point. Working fluids suitable for the proposed cycle can be found in the class of organics, in particular among the newly developed, zero ozone depletion potential, chlorine-free compounds. The numerous technical and environmental requirements which a fluid must meet for practical use combined with the peculiar thermodynamic restraints limit the number of suitable fluids. Mixing two substances of different critical temperatures yields an indefinite number of fluids with tailor-made thermodynamic properties. One such mixture 0.93 HFC23 + 0.07 HFC125 (molar fraction), having tcr = 30°C, at tmax = 400°C, pmax = 150 bar, gives an efficiency above 27 per cent with heat rejection temperatures between 89 and 33°C. With a different mixture composition with a 50°C critical temperature, at the same tmax and pmax, an efficiency of 25.1 per cent is attained in a combined heat and power generation cycle with heat available in the range 53-103°C. An experimental programme to test the thermal stability of organic fluids showed that top temperatures of 380-450°C are achievable with some commercially available fluoro-substituted hydrocarbons. In view of practical applications a conversion unit based on a reciprocating engine could handle without problems the pressures and temperatures involved. The use of turbomachinery would lead to power plant of large capacity for the usual rotor dimensions or to micro-turbines at high rotating speed in the low power range.
An experimental and analytical examination of the combustion period for gas-fuelled spark ignition engine applications
Authors: Shrestha Bade S. O. , Karim G. A.
Published: October 2002

A predictive procedure is described for determining the effective time period needed to complete the energy release by combustion from the moment of flame initiation by a spark to the completion of flame propagation in a spark ignition engine while using a number of gaseous fuels and some of their mixtures. These predicted values of the combustion period when used in a relatively simple modelling procedure can produce predicted values of key engine performance parameters that compare well with the corresponding experimentally obtained values.
An experimental study of low-pressure filmwise condensation on a small in-line tube bank
Authors: McNeil D. A. , Cuthbertson G , Burnside B. M.
Published: October 2002

A purpose-built test facility has been constructed and used to produce data for filmwise condensation from steam, and steam-air mixtures, flowing downwards across a 15 row by 5 column bundle of tubes. Data were obtained at conditions typical of those found in the UK electricity generating industry. Steam was supplied at pressures of 50, 75 and 100 mbar, at velocities of 10,20 and 33 m/s and with air concentrations of 0 and 10000 ppm. Steam to cooling water temperature differences of 5, 10 and 15 K were used to generate heat fluxes of up to 90 kW/m2. The data were used to investigate the application to tube bundle design. It is shown that the selection of an appropriate steam velocity allows good agreement between some shell-side heat transfer correlations and the experimental data, and that existing correlations for inundation and air-concentration effects are sufficient.
Thermal field structures in low Damkôhler reacting flows
Authors: Bounif A , Tabet-Hellal F , Gökalp I
Published: October 2002

This paper is mainly concerned with the regime of distributed reaction zones of a well-stirred reactor, where the Damköhler number is below unity. It is an original study compared with the majority of work done in the field of the interaction between combustion and turbulence in premixed flames. The turbulent structures are subjected to opposing effects, i.e., reduction induced by chemical effects and expansion induced by the increase in mean temperature due to exothermic reactions. When Da >1, the first effect due to the chemistry can scarcely outweigh the expansion of the turbulent structures caused by the exothermic effect. This result is the major contribution of the present study. This phenomenon is not sufficiently known, both in terms of mechanism and quantitative effects. The first objective of this work is to try to provide a qualitative explanation, using an experimental and computational analysis based on certain hypotheses. These assumptions will then explain the difference observed between the behaviour of the temperature fluctuations in the case of reacting and non-reacting turbulent flow in low Damköhler number situations, where the exothermic effect is negligible. The present paper analyses and compares the fluctuating temperature structures inside this reactor for various mean temperature situations. The experimental study is conducted using fine-wire thermoanemometry. The results of numerical simulations obtained using the Navier-Stokes energy equations and the chemical species transport equations associated with a turbulence model are compared with available measurements. The predictions were within engineering accuracy of experimental data.
Off-design performance prediction for diffuser pumps
Authors: Sun J , Tsukamoto H
Published: October 2002

This paper presents a numerical methodology developed for predicting off-design performance of diffuser pumps. In off-design conditions, the effects of rotor/stator interaction and the pump system characteristics become significant, and both need to be taken into account. The pump computational fluid dynamics (CFD) model and the system characteristic equation were incorporated to allow for flow dynamics in the duct. Flow analysis was applied to an entire circumference to capture the asymmetric flow feature at part-flow caused by rotating stall. An arbitrary sliding interface was exploited to consider the influence of rotor/stator interaction.

The methodology was applied to a diffuser pump stage which includes a suction pipe, impeller, diffuser, U-bend, return channel and discharge pipe. Predicted results of the head-flow curve, pressure field and impeller radial forces were validated by the experimental data over the entire flow range. Back flow in the shroud region at small flowrates (from 0 to 40 per cent of design flow) was realistically exhibited. Flow in the region of 81 per cent of design flow displayed unstable features being caused by the occurrence of rotating stall in the impeller, such unsteady phenomena manifest themselves as a drop in the pump head rise, and larger fluctuations in impeller inlet pressure and radial forces.

The present study has demonstrated that incorporation of the pump system characteristic equation and the pump CFD model produces a good prediction of pump off-design performance. The developed methodology can provide an alternative to dealing with pump off-design performance.
A preliminary study of the use of genetic algorithms in flowfield numerical analysis
Authors: Fan H-Y , Yam R , Dang C
Published: October 2002

In this paper, a new computational fluid dynamics (CFD) method, genetic-algorithm-based numerical analysis method, is developed to solve a flowfield problem based on an analogue between the evolution of living organism systems in nature and inanimate physical systems governed by laws of conservation. The new methodology is demonstrated with an analysis of a simple two-dimensional circular diffuser cascade. The computational results obtained are encouraging.
An efficient generic method for calculating the properties of combustion products
Authors: Guha Abhijit
Published: October 2002

A simple method for calculating the properties of combustion products is presented. The method is generic: the same equations apply to any fuel for any fuel—air ratio and temperature. The equations are suitable for both hand calculation and computer applications requiring repetitive property evaluations. The present equations offer accuracy comparable with the most elaborate method available but at a significantly reduced computational cost. The theory should find direct use in design-point and off-design performance calculations and optimization of internal combustion engines, e.g. gas turbine plants, calculation of the three-dimensional flowfield within a multistage turbine, and other applications requiring properties of combustion products.
Theoretical determination of effectiveness for heat pipe heat exchangers operating in naturally ventilated tropical buildings
Authors: Yua Y. H.
Published: October 2002

The thermal performance of wickless thermosyphon based heat pipe heat exchangers (HPHEs) for naturally ventilated buildings was simulated using a computer simulation program. This computer program utilizing Microsoft Visual Basic 6.0 software was developed on the basis of the effectiveness—number of heat transfer units (NTU) method and uses the concept of iteration to predict the temperature distribution across the HPHE and its thermal performance. The overall effectiveness of HPHEs was also studied in this research.
Integrated modelling of internal combustion engine intake and exhaust systems
Authors: Chiavola O
Published: October 2002

This paper presents a new method to analyse the unsteady gas flow in both intake and exhaust systems of internal combustion engines. Such a method is based on the simultaneous use of a one-dimensional model applied to describe the phenomena in ducts, together with a lumped parameter scheme to investigate the cylinder or other volume behaviour, coupled with a three-dimensional model, able to guarantee detailed information on flow behaviour in complex geometry, retaining the advantages of all methods, accuracy as well as fast processing and high flow pattern resolution. The description of the one-dimensional model developed with an example of its application is presented. The integrated approach with the coupling procedure is then described. Finally the results of a multicylinder exhaust system simulation are illustrated.
Mean streamline performance analysis of mixed-flow fan impellers covering the low flowrate characteristics
Authors: Oh H. W. , Kim K-Y
Published: October 2002

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and a suction recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.
Power pipe: An algorithm for analysis for single-phase, steady state, pipe networks with second-degree boundary conditions
Authors: Desideri U , Di Maria F
Published: October 2002

In this paper, an algorithm is described for the resolution of pipe networks with input and output conditions defined by pressure-flowrate correlations. The procedure and the main characteristics of the software are described. The method is particularly suited for solving pipe networks with boundary conditions defined by pressure-flowrate second-degree curves and during off-design operation. The code works with single-phase compressible and incompressible flow and a variety of fluids, including steam-gas mixtures. Heat transfer is also calculated for pipe elements and controls for steam condensation in steam or steam-gas networks are present. An application to a geothermal steam network power plant is included with comparison with experimental data.
Power and desalination in the Arabian Gulf region: An overview
Authors: Azoury P. H.
Published: October 2002

Most of the states constituting the Arabian Gulf region are so deficient in renewable water resources that they now rely almost exclusively on seawater desalination. The present overview considers the various options that are used to link together electric power production and desalination. The benefits and shortcomings of these options are outlined and the influence of the relative demand for electricity and water on the optimum type of plant is examined. The operational and commercial characteristics of the various desalination processes are summarized. The future prospects of both power and desalination production are discussed and the subsequent paths that desalination technology will follow in the region are suggested. The environmental impacts of power generation and desalination are explored and possible mitigating measures covering each type of impact are proposed. Finally, it is submitted that the social benefits of power and desalination in the area cannot be considered as having been truly realized unless regulatory standards relevant to these impacts are set up and adhered to.
Thermal performance study for the coal-fired combined cycle with partial gasification and fluidized bed combustion
Authors: Cai N , Yu T , Xiao J , Welford G
Published: October 2002

The coal-fired combined cycle with partial gasification and fluidized bed combustion (PGFBC-CC), also referred to as a hybrid cycle, has advantages of staged energy conversion and utilization, which can attain high thermal efficiency with low emissions. Four kinds of PGFBC-CC are studied in this paper, two based on pressurized fluidized bed combustion (PFBC) and two on atmospheric fluidized bed combustion (AFBC). Thermal performance calculations and parametric analyses were performed. On the basis of the results from the above analyses, the best integration system for China is suggested. In addition, a preliminary exergetic analysis is carried out for three of the PGFBC-CC variants.
Simulation of the performance of alternative refrigerants in liquid chillers
Authors: Grace I. N. , Tassou S. A.
Published: October 2002

The impact of refrigeration systems on the environment can be reduced by (a) the use of alternative refrigerants which are less harmful to the environment and (b) the optimization of systems and control strategies to deliver increased levels of energy efficiency. Mathematical modelling offers the opportunity to test the performance of systems under different operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady state behaviour and this is of particular importance for liquid chillers since these systems can operate under transient conditions for long periods. This paper covers the development of a general dynamic model for the simulation of liquid chillers. Brief descriptions of the system component models are given, including a semihermetic reciprocating compressor and thermostatic expansion valve as well as a shell-and-tube evaporator and condenser. The paper demonstrates the application of the model to simulate the performance of a liquid chiller retrofitted with a range of alternative refrigerants. The performance of the system is determined in terms of cooling capacity, power consumption and coefficient of performance for a range of different operating conditions. The relative performance of each refrigerant is discussed and the preferred alternative identified for typical applications.
Flow characteristics in the liner of a reverse-flow gas turbine combustor
Authors: Bharani S , Singh S. N. , Agrawal D. P.
Published: October 2002

Investigation carried out in a plane model of a reverse-flow gas turbine combustor under isothermal flow conditions has shown that the bulk of the flow remains close to the outer liner wall between the rows of primary and dilution holes, while it shifts towards the liner mid-plane after the row of dilution holes. At the combustor outlet, the bulk of the flow remains towards the inner wall of the outlet duct, with a uniform flow distribution. At the outlet of the combustor model, turbulence intensity was approximately three times higher than that at the inlet plane.
A parametric method for optimal design of two-dimensional cascades
Authors: Benini E , Toffolo A
Published: October 2002

A parametric method for optimal design of two-dimensional cascades, based on the coupling between a genetic algorithm and a commercial computational fluid dynamics code, is introduced. The results of cascade geometry optimization for a large range of inlet and outlet flow angle pairs are presented. The method is a simple as well as effective tool for the optimal design of cascades for axial flow pumps.
A comparative study of incompressible and compressible design approaches of radial inflow turbine volutes
Authors: Gu F , Engeda A , Benisek E
Published: October 2002

The one-dimensional design approaches of radial inflow turbine volutes can be catalogued into incompressible and compressible. This paper investigates the degree to which they differ from each other in terms of design parameters, such as the distribution of ratio of area to radius A/ r and radius r, and in terms of flow deviation from the free vortex pattern. Theoretical analysis proves that the incompressible approaches failed to provide free vortex and uniform flow for the wheel in compressible flow regimes. A numerical simulation on a previously designed and tested volute shows that the wake flow of the tongue and the boundary layer on the wall cause the tangential velocity of the volute flow to deflect from the free vortex design downstream and upsteam respectively of the tongue. The radial velocity component is higher at first, then lower than the free vortex design, owing to the significant pressure gradient around the tongue.
Influence of deterministic stresses on flow prediction of a low-speed axial flow compressor rear stage
Authors: Li Y. G. , Tourlidakis A
Published: October 2002

Deterministic stresses are used to describe the unsteady effects on the flow field in multistage axial flow compressors. In this paper, a circumferentially non-uniform mixing plane method implemented with deterministic stresses is used for the flow prediction inside the rear stage of an axial flow compressor in a multistage environment. The deterministic stress field is calculated with an overlapped solution approach for the same flow passage and implemented with the Navier-Stokes equations in order to provide continuous interfaces. The aerodynamic boundary condition is simplified with the application of a repeating stage model where only the mass flowrate and stage exit average static pressure are required. Two computational cases for the third stage of the Cranfield low-speed research compressor, one with the mixing plane model and the second with the mixing plane model in combination with deterministic stresses, are examined and compared with each other and also with corresponding experimental data. It is shown that the implementation of the deterministic stresses is beneficial for the flow prediction but the improvement in accuracy for low-speed axial flow compressor rear stages is not significant.
An experimental investigation into the effect of rotor blade sweep on the performance of the variable-pitch Wells turbine
Authors: Gato L. M C. , Webster M
Published: October 2002

The paper describes an experimental investigation into the effect of rotor blade sweep on the performance of the variable-pitch Wells turbine. The blades tested included two sets of eight symmetrical constant chord NACA 0015 blades (one set had 30° backward sweep, while the other was unswept), two rotor solidities and blade pitch angles of 0° and 20°. The aim of the present experiments was to investigate and compare the aerodynamic performance of the backward swept and unswept blades for different rotor solidities and pitch angles. The measurements covered flowrate, pressure drop, torque and rotor speed. Traversing work with the aid of a directional total static pressure probe yielded more detailed information on the performance of each set of rotor blades. Experimental results have shown that the swept back design of the blades produces a positive value of efficiency and torque over a much wider operating range than the standard unswept NACA 0015 blades, but at the expense of peak efficiency.
Model-based predictive control using genetic algorithms
Authors: Ichikawa A , Vardy A. E. , Brown J. M B.
Published: October 2002

A predictive method of process control is developed by combining process simulators with genetic algorithm routines. The theoretical basis of the method is described and its use is illustrated for two examples involving unsteady fluid flows. In the first, a valve is to be closed as rapidly as possible without causing a storage tank to overflow. In the second, fan settings are to be chosen in a road tunnel to maintain an acceptable balance between the power consumption of the fans and pollution concentrations experienced by drivers. In both cases, the optimum control actions cannot be known in advance. Instead, the consequences of many alternative actions are explored using process simulators and the most suitable alternative is selected for implementation. The methodology is shown to be effective even when a vast range of potential actions is possible. Instead of seeking an ultimate optimum, the aim is to provide a selection of ‘good’ options from which the process operator (human or machine) can make an informed choice. A disadvantage of the method is a relatively large demand for central processing unit time, making it unsuitable for processes where very small response times are of the essence.
Single-passage solution of three-dimensional unsteady flows in a transonic fan rotor
Authors: Li H. D. , He L
Published: October 2002

Calculations of unsteady turbomachinery flows using conventional time domain methods typically would lead to the use of multiple passages/whole annulus owing to the required direct periodic condition. This makes conventional unsteady solutions extremely time consuming and is one of the major difficulties in applying unsteady calculations in a blading design environment. A single-passage approach to three-dimensional unsteady Navier-Stokes calculations using the Fourier series based shape correction method has been developed. The shape correction method gives a single-passage solution to unsteady flows in blade rows under multiple disturbances with arbitrary interblade phase angles. Therefore the computing time can be dramatically reduced. A case study for a transonic fan rotor subject to long-scale circumferential inlet distortions shows that a factor of 5 speed-up could be achieved. Detailed comparisons in both unsteady and time-averaged flow results between the single-passage and multiple-passage solutions demonstrate the validity and effectiveness of the present single-passage approach. A further calculation of a transonic rotor simultaneously under the influences of both upstream and downstream blade rows also shows the capability of the shape correction method in dealing with multiple disturbances.
Steady-unsteady measurements of the flow field downstream of a transonic high-pressure turbine stage
Authors: Paniagua G , Dénos R , Arts T
Published: October 2002

The three-dimensional flow field of a transonic high-pressure turbine stage has been studied experimentally in the von Karman Institute short duration compression tube facility. The test programme encompasses two Reynolds numbers ( Re2, c = 1.0 × 106, 1.26 × 106) and three different pressure ratios ( Po1/ Ps3 = 2.3, 3.1, 4.1). The steady flow angle, pressure and temperature measurements rely on five-hole pneumatic probes and micro-thermocouples. Fast response pressure and cold wire resistance thermometer probes measure the unsteady pressure and temperature. The experimental time-averaged spanwise distributions are compared with steady state three-dimensional Navier-Stokes stage simulations; zones of secondary flows are identified in the spanwise distributions. The stage exit pitchwise traverses show that the stator exit flow field affects the stage exit flow. Downstream of the stator vane, large time-resolved static pressure fluctuations are identified, attributed to the variation of the origin, the incidence and strength of the stator trailing edge shock. At the stage outlet, large total temperature fluctuations appear owing to the periodic passage of the tip leakage flow. For the high-pressure ratio, the rotor is choked and large pressure and temperature fluctuations are recorded owing to the rotating rotor trailing edge shock system. Zones of high mixing (secondary flows) tend to attenuate these fluctuations.