Pericles Pilidis

Cranfield University, Cranfield, England, United Kingdom

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Publications (228)78.38 Total impact

  • Waleed Al Busaidi · Pericles Pilidis
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    ABSTRACT: The growing acceptability of the natural gas as an energy source yields to place a higher research concentration on improving the centrifugal compressor design and performance prediction techniques. This is the first part of a two-part study that aims to introduce a new integrated method for reliable performance prediction of multi-stage industrial centrifugal compressor based on stage stacking technique. In this part, two most common existing models are adapted to be valid for industrial centrifugal compressors and the predicted characteristics are evaluated against measured data. Based on the conducted evaluation, a new model will be derived in the second part which incorporates the advantages of both approaches with more accurate prediction. Lüdtke method predicts the compressor design efficiency based on the correction of the derived experimental set of data. This approach has been applied for a single stage centrifugal compressor at a single speed and flow values. Recently, Casey–Robinson method uses a new set of algebraic equations to obtain the compressor curve with less dependency on the geometrical features. This model has been tested with a single stage turbocharger compressor where the performance curve can be derived without considering the mechanical stages. This approximation will introduce a more significant impact when this method is used for large industrial compressors. Therefore, these models will be improved to be suitable for multi-industrial centrifugal compressors and their prediction capability to estimate the performance map will be examined in this paper.
    No preview · Article · Apr 2016 · Applied Thermal Engineering
  • Waleed Al-Busaidi · Pericles Pilidis
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    ABSTRACT: The high operating efficiency of centrifugal compressor is a basic requirement to maintain the gas productivity and machine availability. However, there are several factors influencing the stage efficiency in the operating environment leading to a deterioration in the compressor performance in addition to its impact on the mechanical integrity of the internal components. These variables can be classified into three main groups which are suction parameters variation, flow profile distortion, and compressor component damage. The determination of the root cause will help for a proper maintenance plan and to reduce the machine downtime. Hence, this paper will introduce a new approach to identify the inefficient compressor operation causes based on the available operation data. The investigated case is a three-stage gas transport centrifugal compressor driven by 2.9 MW two-shaft gas turbine. The outcomes from the conducted optimisation are compared with the measured discharge parameters and the findings from the internal inspection observation to emphasize the outcomes from the derived approach.
    No preview · Article · Jan 2016 · Journal of Failure Analysis and Prevention
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    ABSTRACT: The estimated life of gas turbines is expected to diminish over time when compared to the manufacturers’ estimated life, particularly when used as a back-up to Renewable Energy Sources (RES). As RES are been introduced into the grid, the gas turbines used in conjunction with them are operated in “Load-Following” modes to these RES which includes wind, thermal, solar, etc. As back-up plants, the start/stop and power settings are expected to be dictated by the response to grid requirements and need to compensate for the load shortfall attributable to unpredictable nature of RES. This mode of operation results in Gas turbine high pressure turbine blades experiencing low cycle fatigue and creep life failure over time. It is therefore of great importance to estimate the life consumed during this mode of operation to enable appropriate maintenance planning/repair action. In order to estimate the life consumed during adverse/cyclic operating regimes, a tool has been developed wherein different scenarios can be simulated and analyzed to obtain engine life consumption factors. The tool is capable of estimating life consumption based on seasonal power demand. For the purpose of study, an aero derivative power plant of 100MW power output was used as a reference engine. The paper provides an in-depth analysis of the study undertaken and it arrives at the conclusion that the operation of engine during summer contributes to a higher degree of LCF and creep life consumption in comparison to operations during other seasons.
    Full-text · Article · Dec 2015
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    Full-text · Dataset · Nov 2015
  • Waleed Al-Busaidi · Pericles Pilidis
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    ABSTRACT: The centrifugal compressor blockage is considered an important issue in compressor operation and one of the main causes of machine failure. This is normally initiated by the presence of deposits with the process gas yielding to reduce the effective flow area, increase the frictional losses and distort the pressure distribution profile. The influences of flow blockage cover the thermodynamic, aerodynamic and rotordynamic performance parameters of centrifugal compressor as will be investigated further in this study. Accordingly, this paper introduces a novel approach to model the impact of non-reactive deposits flow on the centrifugal compressor aerothermodynamics performance. The developed set of empirical equations in this study provides a new way to derive the equivalent compressor performance map at various degrees of fouling with a consideration of gas properties and stage efficiency variation and without a prior knowledge of the detailed geometrical features. In order to emphasize the validity of the new method, it has been tested with two operating cases and the obtained results were compared with the internal inspection findings from the stage overhauling process. Besides, this approach has been proven to be valid for the modelling of flow blockage effect at the suction side, compressor internals and downstream equipment. Furthermore, a new methodology has been established to assess the possibility of deposits accumulation in the gas path of the compression system based on the operational data of the discharge parameters.
    No preview · Article · Nov 2015 · Engineering Failure Analysis
  • Waleed Al Busaidi · Pericles Pilidis

    No preview · Article · Sep 2015
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    ABSTRACT: The life cycle estimation of power plants is important for gas turbine operators. With the introduction of wind energy into the grid, gas turbine operators now operate their plants in load-following modes as back-ups to the renewable energy sources which include wind, solar, etc. The motive behind this study is to look at how much life is consumed when an intercooled power plant with 100MW power output is used in conjunction with wind energy. This operation causes fluctuations because the wind energy is unpredictable and overtime causes adverse effects on the life of the plant – The High Pressure Turbine Blades. Such fluctuations give rise to low cycle fatigue and creep failure of the blades depending on the operating regime used. A performance based model that is capable of estimating the life consumed of an intercooled power plant has been developed. The model has the capability of estimating the life consumed based on seasonal power demands and operations. An in-depth comparison was undertaken on the life consumed during the seasons of operation and arrives at the conclusion that during summer, the creep and Low cycle life is consumed higher than the rest periods. A comparison was also made to determine the life consumed between load-following and stop/start operating scenarios. It was also observed that daily creep life consumption in summer was higher than the winter period in-spite of having lower average daily operating hours in a start-Stop operating scenario.
    No preview · Article · Aug 2015 · Journal of Propulsion and Power
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    Waleed Al Busaidi · Pericles Pilidis
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    ABSTRACT: This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor’s performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties’ variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties’ variation to the inefficient and unstable compressor performance based on the available operational data.
    Preview · Article · Aug 2015 · Energies
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    Waleed Al Busaidi · Pericles Pilidis
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    ABSTRACT: This paper introduces a new iterative method to predict the equivalent centrifugal compressor performance at various operating conditions. The presented theoretical analysis and empirical correlations provide a novel approach to derive the entire compressor map corresponding to various suction conditions without a prior knowledge of the detailed geometry. The efficiency model was derived to reflect the impact of physical gas properties, Mach number, and flow and work coefficients. One of the main features of the developed technique is the fact that it considers the variation in the gas properties and stage efficiency which makes it appropriate with hydrocarbons. This method has been tested to predict the performance of two multistage centrifugal compressors and the estimated characteristics are compared with the measured data. The carried comparison revealed a good matching with the actual values, including the stable operation region limits. Furthermore, an optimization study was conducted to investigate the influences of suction conditions on the stage efficiency and surge margin. Moreover, a new sort of presentation has been generated to obtain the equivalent performance characteristics for a constant discharge pressure operation at variable suction pressure and temperature working conditions. A further validation is included in part two of this study in order to evaluate the prediction capability of the derived model at various gas compositions.
    Preview · Article · Aug 2015 · Energies
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    DESCRIPTION: Through Life Engineering Conference
    Full-text · Research · Aug 2015
  • Waleed Al Busaidi · Pericles Pilidis

    No preview · Article · Aug 2015
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    Gbanaibolou Jombo · Pericles Pilidis · Suresh Sampath · David Mba
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    ABSTRACT: The paper presents a methodology for estimating the fatigue life of rolling-element bearing under irregular loading conditions. This method overcomes the limitations encountered by rolling-element bearing lifing models based on a constant bearing load assumption, when used in applications where bearing load varies over time with also changes in rotational speed. To include these irregular loading effects, a load-slice averaging methodology is applied to the loading history; in which the loading history is assumed to be composed of many thin slices of loading conditions. The operating conditions within each loading slice are averaged, and with the aid of linear damage rule and Lundberg-Palmgren load-life correlation for rolling-element bearings, each loading slice fatigue damage contribution is determined. The cumulative loading slice fatigue damage is used to estimate rolling-element bearing life. This approach can also be used as a tool for real-time life prognosis of rolling-element bearings. The method is demonstrated with simulated loading histories acting on a Cooper split cylindrical roller bearing and life prediction comparison is made between several approximate closed form bearing life expressions for different types of loading.
    Full-text · Conference Paper · Jun 2015
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    Cesar Celis · Vishal Sethi · Riti Singh · Pericles Pilidis
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    ABSTRACT: In this work, the Techno-economic Environmental Risk Analysis framework, a multi-disciplinary optimisation tool developed by Cranfield University, is utilised in conjunction with an in-house optimiser to carry out aircraft engine cycle optimisation processes. The central point here is the evaluation of the capabilities of the in-house optimiser for performing this type of optimisation processes. Simplifying hypotheses are thus considered when both defining the aircraft flight trajectory and modelling the different engine configurations analysed. Accordingly, several optimum engine cycles minimising separately three objective functions, (i) specific fuel consumption in cruise (ii) fuel burned, and (iii) oxides of nitrogen emitted, are determined. The cycle optimisation processes carried out yield results reflecting the general trends expected when optimising according to these objective functions. It follows then that the in-house optimiser is suitable for carrying out gas turbine power plant optimisation processes. It is expected that this optimiser be utilised in future for both optimising the preliminary design of gas turbine engines and determining optimum and “greener” aircraft engine cycles.
    Full-text · Article · May 2015 · Journal of Aerospace Technology and Management
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    Barinyima Nkoi · Pericles Pilidis · Theoklis Nikolaidis
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    ABSTRACT: The aim of this paper is to assess and compare techno-economic viability of large-scale simple cycle (SC) and advanced cycles aero-derivative industrial gas turbines combined-heat-and-power (ADIGT-CHP) generation in the petrochemical industry in terms of net present value (NPV), internal rate of return (IRR), and simple-payback-period (SPBP). To achieve this, a techno-economic assessment method was applied using a case study of a large-scale Refinery CHP. Parameters of technical performance of the ADIGT-CHP such as fuel flow, power output, emissions, heat recovery, and steam flow, in conjunction with various cost elements were made inputs in an economic module utilising a 20 years life-cycle. Economic principles were applied to predict the NPV, IRR, and SPBP of the three ADIGT-CHP cycles over conventional case (Grid electricity plus on-site boiler). The advanced cycles considered are intercooled (IC) cycle and intercooled-recuperated (ICR) cycle. The result shows that all three ADIGT–CHP cycles exhibit positive NPV, good payback-period and internal-rate-of-return, which is an indication that all are viable, though the SC ADIGT–CHP was found to be more profitable than the others. The percentage savings in operational cost of SC, IC, and ICR cycle ADIGT–CHP over the conventional case were obtained as 21.1%, 20.5%, and 19.7% respectively. More so, SC ADIGT–CHP was found to exhibit higher CHP efficiency and steam flow than IC and ICR cycles. This sort of assessment would aid decision makers to make good choice of large-scale ADIGT-CHP cycle option in the petrochemical industry.
    Full-text · Article · Apr 2015
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    Ioannis Goulos · Vassilios Pachidis · Pericles Pilidis
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    ABSTRACT: This paper presents the development of a mathematical model for the implementation of flexible rotor blade dynamics in real-time helicopter aeromechanics applications. A Lagrangian approach is formulated for the rapid estimation of natural vibration characteristics of nonuniform rotor blades. A matrix/vector formulation is proposed for the treatment of elastic blade kinematics in the time-domain. In order to overcome the classical hurdles of time-accurate simulation and establish applicability in real-time, a novel, second-order accurate, finite-difference scheme is employed for the numerical discretisation of elastic blade motion. The proposed rotor dynamics model is coupled with a finite-state induced flow and an unsteady blade element aerodynamics model. The combined formulation is implemented in a helicopter flight mechanics simulation code. The integrated approach is deployed in order to investigate rotor blade resonant frequencies, trim control angles, oscillatory blade loads and induced vibration for a hingeless and an articulated helicopter rotor. Extensive comparisons are carried out with wind tunnel and flight test measurements, and non-real-time comprehensive analysis methods. Good agreement with measured data is exhibited considering primarily the low-frequency harmonic components of oscillatory loading. It is shown that, the developed methodology can be utilised for real-time simulation on a typical computer with sufficient modelling fidelity for accurate estimation of oscillatory blade loads.
    Full-text · Article · Mar 2015 · Aeronautical Journal -New Series-
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    Full-text · Dataset · Feb 2015
  • R. Agbadede · P. Pilidis · U.L. Igie · I. Allison
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    ABSTRACT: The effectiveness of online compressor washing is site specific and it is determined by several factors, amongst which is liquid injection droplet size that relates to the nozzle orifice diameter and injection pressure. To investigate the influence of liquid injection droplet size on the effectiveness of online compressor washing, three elliptical flat fan nozzles with different orifice diameters were selected, followed by ascertaining the mean droplet sizes for each of the nozzles with the Malvern Spraytec Particle Analyzer. Two of the three nozzles that generated droplet sizes of 55 and 80μm were employed to investigate the influence liquid injection droplet on the online compressor washing effectiveness. Prior to the washing effectiveness investigations, the three middle blades of the cascade were fouled in a uniform and repeatable manner, after which washing was conducted with different injection droplet sizes. When the washing effectiveness for droplet sizes of 55.1 and 80.24μm were compared on the aerodynamic performance plots of exit flow angle, total pressure loss, and non-dimensional velocity; a slight difference was observed for the two droplet sizes. The washing effectiveness of using liquid injection droplet size of 80.24μm produced a lower exit flow angle and total pressure loss coefficient than the droplet size of 55.1μm. This implies that the droplet size of 80.24μm has a higher momentum, thereby dislodging the particles more easily than the 55.1 μm droplet size. The reduction in isentropic efficiency and flow capacity obtained from the experimental data for the fouled and washed cases were used as input into Turbomatch to simulate the effects of washing with different fluid injection droplet sizes. Blades washed with a droplet size of 80.24μm produced a higher recovery of power output and efficiency from the fouled case than the ones washed with a droplet size of 55.1μm.
    No preview · Article · Dec 2014 · Journal- Energy Institute
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    ABSTRACT: A large variety of promising power and propulsion system concepts are being proposed to reduce carbon dioxide and other emissions. However, the best candidate to pursue is difficult to select and it is imperative that major investments are correctly targeted to deliver environmentally friendly, economical and reliable solutions. To conceive and assess gas turbine engines with minimum environmental impact and lowest cost of ownership in a variety of emission legislation scenarios and emissions taxation policies, a tool based on a techno-economic and environmental risk assessment methodology is required. A tool based on this approach has been developed by the authors. The core of the tool is a detailed and rigorous thermodynamic representation of power plants, around which other modules can be coupled (that model different disciplines such as aircraft performance, economics, emissions, noise, weight and cost) resulting in a multidisciplinary framework. This approach can be used for efficient and cost-effective design space exploration in the civil aviation, power generation, marine, and oil and gas fields. In the present work, a conceptual intercooled core aeroengine design was assessed with component technologies consistent with 2020 entry into service via a multidisciplinary optimisation approach. Such an approach is necessary to assess the trade-off between asset life, operating costs and technical specification. This paper examines the influence of fuel consumption, engine weight and direct operating costs with respect to extending the engine life. The principal modes of failure such as creep, fatigue and oxidation, are considered in the engine life estimation. Multidisciplinary optimisation, comprising the main engine design parameters, was carried out with maximum time between overhaul as the objective function. The trade-off between minimum block fuel burn and maximum engine life was examined; the results were compared against the initial engine design and an assessment was made to identify the design changes required for obtaining an improved engine design in terms of direct operating costs. The results obtained from the study demonstrate that an engine optimised for maximum time between overhaul requires a lower overall pressure ratio and specific thrust but this comes at the cost of lower thermal efficiency and higher engine production costs.
    Full-text · Article · Oct 2014 · Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering
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    ABSTRACT: Industrial gas turbines are susceptible to compressor fouling, which is the deposition and accretion of airborne particles or contaminants on the compressor blades. This paper demonstrates the blade aerodynamic effects of fouling through experimental compressor cascade tests and the accompanied engine performance degradation using TURBOMATCH, an in-house gas turbine performance software. Similarly, on-line compressor washing is implemented taking into account typical operating conditions comparable with industry high pressure washing. The fouling study shows the changes in the individual stage maps of the compressor in this condition, the impact of degradation during part-load, influence of control variables, and the identification of key parameters to ascertain fouling levels. Applying demineralized water for 10 min, with a liquid-to-air ratio of 0.2%, the aerodynamic performance of the blade is shown to improve, however most of the cleaning effect occurred in the first 5 min. The most effectively washed part of the blade was the pressure side, in which most of the particles deposited during the accelerated fouling. The simulation of fouled and washed engine conditions indicates 30% recovery of the lost power due to washing.
    No preview · Article · Oct 2014 · Journal of Turbomachinery
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    Ioannis Goulos · Vassilios Pachidis · Pericles Pilidis
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    ABSTRACT: This paper presents a mathematical model for the simulation of rotor blade flexibility in real-time helicopter flight dynamics applications that also employs sufficient modeling fidelity for prediction of structural blade loads. A matrix/vector-based formulation is developed for the treatment of elastic blade kinematics in the time domain. A novel, second-order-accurate, finite-difference scheme is employed for the approximation of the blade motion derivatives. The proposed method is coupled with a finite-state induced-flow model, a dynamic wake distortion model, and an unsteady blade element aerodynamics model. The integrated approach is deployed to investigate trim controls, stability and control derivatives, nonlinear control response characteristics, and structural blade loads for a hingeless rotor helicopter. It is shown that the developed methodology exhibits modeling accuracy comparable to that of non-real-time comprehensive rotorcraft codes. The proposed method is suitable for real-time flight simulation, with sufficient fidelity for simultaneous prediction of oscillatory blade loads.
    Full-text · Article · Oct 2014 · Journal of the American Helicopter Society