The identification of the fuel flow to shaft speed dynamics of a twin-shaft gas turbine is addressed, with the aim of validating thermodynamic engine models. A measured input signal must be used in estimation in order to exclude the fuel feed dynamics from the model. This has been shown to present problems when fitting discrete models to engine data, and this paper examines the direct estimation of s-domain models in the frequency domain. A number of different multisine test signals were applied to the engine for the purposes of model estimation and nonlinear detection. The use of frequency-domain techniques is shown to produce high-quality models, and the tests also yield information on the levels of noise and nonlinearity and the length of the pure time delay. This work illustrates the potential of frequency-domain techniques for modeling systems where a physical interpretation is to be made of the model and where the need for accuracy requires that a measured input signal be used in estimation.

Frequency-domain identification of gas turbine dynamics

Digital Computer Methods for Prediction of Gas Turbine Dynamic Response

Meta-heuristic global optimization algorithms for aircraft engines modelling and controller design; A review, research challenges, and exploring the future

The Hammerstein model configuration, which includes a nonlinear static block followed by a linear dynamic block, is applied to model the static and dynamic characteristics of a micro-turbine. The parameters in the model can be extracted from the measurements of physical engines or from the simulations of physics-based models. In this paper, a nonlinear model is used to assist in the dynamic performance of the micro-turbine when connected to the grid as a distributed generator. Copyright © 2005 John Wiley & Sons, Ltd.

Modelling micro-turbines using Hammerstein models

Modern system identification techniques allow dynamic models to be directly estimated from measured data and the design of the data gathering experiment is a key step in any identification procedure. This thesis deals with the design of test signals for both linear and nonlinear modelling and their application to an engineering problem. It is motivated by a desire to fully exploit the recent advances in computer technology, which make the design and application of complex multisine test signals a practical possibility. The thesis can be divided into two parts, the first dealing with test signal design and the second presenting a detailed study of the testing and modelling of an aircraft gas turbine. The main contributions of the first part deal with the influence of noise and nonlinearities on multisine test signals and the design of new types of multisines for testing nonlinear systems. The test times associated with single sine, multisine and maximum length binary signals are studied, with the aim of reducing test times while maintaining accuracy in the presence of noise. A novel methodology is presented for analysing the influence of system nonlinearities on multisines, with the aim of designing signals which are robust to nonlinear effects. This leads to the design of signals which can be used to identify the best linear approximation of block-oriented nonlinear systems of the Wiener-Hammerstein type. The design of signals which minimise the nonlinear distortion at the test frequencies is also studied, with the aim of identifying the underlying linear dynamics of the system. A scheme is proposed for the identification of linear systems in the presence of nonlinear distortions. The designs are then further developed to allow the direct measurement of points on the frequency-domain Volterra kernels (higher-order frequency response functions) of a nonlinear system. The second part of the thesis deals with gas turbine modelling, with the aim of estimating models which can be used to verify the linearised thermodynamic models derived from the engine physics. The design of appropriate test signals is discussed, a detailed analysis of the measured data is presented and engine models are identified. The influence of noise and nonlinearities on the estimated models is studied. It is shown that the use of multisine signals and frequency-domain techniques is particularly suited to this problem, since the continuous-time s-domain models needed to validate the thermodynamic models can be directly estimated. The problem of estimating discrete-time models which do not have a continuous-time counterpart is also discussed and some possible causes of this effect are investigated. This thesis is a contribution to the further application of multisine signals to the measurement and identification of linear and nonlinear systems. It also illustrates the potential of frequency-domain techniques for modelling gas turbine dynamics, where a physical interpretation of the model parameters is to be made. Table of

Identification of linear and nonlinear systems using multisine signals : with a gas turbine application

The paper gives details of the way in which servo-mechanism techniques have been applied to accessory control problems. The emphasis has been on the correlation of theory with practice and typical results are given from tests on some 15 British gas-turbine engines. For completeness a brief introduction to the basic concepts is first dealt with, then examples are given of linear and non-linear theories applied to typical working systems.It is pointed out that though the examples refer to hydraulic, mechanical, and thermodynamic processes the ideas may be carried forward into widely differing fields.

The Application of Servo-Mechanism Analysis to Fuel Control Problems

The study comprises the effect of natural/free convection on an MWCNT–water nanofluid‐filled cavity. The porous cavity is heated/cooled to the left/right walls and the horizontal wall is maintained adiabatically. The flow behavior and entropy analysis are evaluated numerically using the finite difference approximation techniques. This study is bounded with various dimensional parameters such as ϕ $\phi $ —nanoparticle concentration, Ha—Hartmann number, Ra—Rayleigh number, and Da—Darcy number. The results of the study are illustrated using ψ $\psi $ —streamlines or stream function, θ $\theta $ —isotherms, Π $\Pi $ —heatlines or heat function, S ψ ${S}_{\psi }$ —fluid friction irreversibility, S θ ${S}_{\theta }$ —heat transfer irreversibility, Θ cup ${{\rm{\Theta }}}_{\mathrm{cup}}$ —cup‐mixing temperature, and Θ RMSD ${{\rm{\Theta }}}_{\mathrm{RMSD}}$ —root‐mean‐square deviation. Also, Nu ${Nu}$ —average Nusselt number and Be ${Be}$ —average Bejan number are used to represent the transfer rate of heat and irreversibility of fluid friction/heat transfer, respectively. The domination of conduction on lower Ra and Da are noticed and, domination of convection on higher Ra and Da are observed using a heatline map. The fluid friction and heat transfer irreversibilities are highly noted near the vertical boundaries for increasing Rayleigh number and Darcy number.

Fluid friction/heat transfer irreversibility and heat function study on MHD free convection within the MWCNT–water nanofluid‐filled porous cavity

Nitrate transport in a fracture-skin-matrix system under non-isothermal conditions

Exploring the potential of third-generation microalgae bio-alcohol and biodiesel in arresting particulate smoke emissions and greenhouse gases using CART

Abstract The heat transfer between ambient medium and moving material can be examined by the fluid flow past an impulsively started vertical plate (ISVP). In manufacturing processes such as wire/fiber drawing, hot rolling, continuous casting, and hot extrusion can be related to the hot moving material and heat transfer to the ambient medium. Also, a similar type of study addresses the understanding of aerospace engineering applications. This present study considers a mathematical model which describes the hybrid nanofluid past the ISVP by considering the transient term as a fractional derivative. The fractional order of flow governing equations is derived to enhance the heat transfer predictions with real-world problems by considering viscous dissipation, applied magnetic field, and radiation effects. Such a mathematical model is discretized by a finite difference technique and solved by a computational algorithm using FORTRAN. The findings of the study are illustrated using the velocity and temperature profiles. Also, the heat transfer and fluid friction against the boundary are interpreted using the Nusselt number and skin-friction coefficient, respectively. The results are examined under the variation of dimensionless parameters such as Eckert number, time-fractional order, Grashof number, the fraction of nanoparticles, suction, magnetic, and radiation parameters. It is observed that the heat transfer and fluid flows are affected by changing the time-fractional order. Also, a transition in the distribution of velocity and temperature is detected with varying time-fractional order.

Numerical study of heat transfer between hot moving material and ambient medium using various hybrid nanofluids under MHD radiative-convection, viscous dissipation effects, and time-fractional condition

J. O. N. Lawrence

Papers

The Application of Servo-Mechanism Analysis to Fuel Control Problems

Fluid friction/heat transfer irreversibility and heat function study on MHD free convection within the MWCNT–water nanofluid‐filled porous cavity

Nitrate transport in a fracture-skin-matrix system under non-isothermal conditions

Exploring the potential of third-generation microalgae bio-alcohol and biodiesel in arresting particulate smoke emissions and greenhouse gases using CART

Numerical study of heat transfer between hot moving material and ambient medium using various hybrid nanofluids under MHD radiative-convection, viscous dissipation effects, and time-fractional condition