Exergetic, exergoeconomic and exergoenvironmental analysis of intercooled gas turbine engine

Exergetic and exergoeconomic and exergoenvironmental analyses have been performed for an advanced aero-derivative intercooled gas turbine engine. The proposed system was modelled using the IPSEpro software package and validated using manufacturer’s published data. The exergoeconomic model evaluates the cost-effectiveness of the gas turbine engine based on the Specific Exergy Costing [SPECO] method. The CO2 emissions per KWh were estimated using a generic combustor model, HEPHAESTUS, developed at Cranfield University. It is well known that the exergetic analysis can determine the magnitudes, locations and types of losses within an energy system. The effect of load and ambient temperature variations on gas turbine performance were investigated for two different configurations. The first system, Case-I, was a simple gas turbine (SCGT) engine, and the second, Case-II, an intercooling gas turbine (ICGT) system. The latter enhances gas turbine efficiency but, at the same time, has an adverse effect on the combustion chamber due to reduced compressed air temperature. It was confirmed that full load and low ambient temperature are preferable due to the low waste exergy. The unit exergy cost rate for both SCGT and ICGT have been calculated as 8.59 and 8.32 US$/GJ respectively. The exergoenvironmental results show the ICGT achieved lower emission levels and is more environmentally friendly than the SCGT

Energetic and exergetic analysis of combined cycle power plant: Part-1 operation and performance

Energetic and exergetic analyses are conducted using operating data for Sabiya, a combined cycle power plant (CCPP) with an advanced triple pressure reheat heat recovery steam generator (HRSG). Furthermore, a sensitivity analysis is carried out on the HRSG using a recent approach to differentiate between the sources of irreversibility. The proposed system was modelled using the IPSEpro software and further validated by the manufacturer’s data. The performance of the Sabiya CCPP was examined for different climatic conditions, pressure ratios, pinch point temperatures, high-pressure steam, and condenser pressure values. The results confirmed that 60.9% of the total exergy destruction occurs in the combustion chamber, which constitutes the main source of irreversibilities within a system. The exergy destruction was significantly affected by both the pressure ratio and the high-pressure steam, where the relation between them was seen to be inversely proportional. The high-pressure stage contributes about 50% of the exergy destruction within the HRSG compared to other stages and the reheat system, due to the high temperature difference between the streams and the large number of components, which leads to high energy loss to the surroundings. Numerous possibilities for improving the CCPP’s performance are introduced, based on the obtained results

Harmonics mitigation based on the minimization of non-linearity current in a power system

Harmonic issues in power systems are becoming an important topic for industrial customers and power suppliers alike due to their adverse effects in both consumer appliances as well as for utility suppliers. Consumers should seek to reduce harmonic pollution, regardless of voltage or current distortion already present in the network. This article suggests a new method for suppressing distortions by using the non-linearity current index (NLCI) to determine the shunt single-tuned passive filter (STPF) compensator value in non-sinusoidal power systems, with the objective of maintaining the power factor within desired limits. The objective of the proposed method is to minimize the nonlinear current of customer’s loads in the power system at the point of common coupling (PCC). Moreover, the proposed design takes into consideration other practical constraints for the total voltage and individual harmonic distortion limits, ensuring compliance with (Institute of Electrical and Electronics Engineers) IEEE 519-2014 guidelines, maintaining distortions at an acceptable level while also abiding by the capacitor loading constraints established in IEEE 18-2012. The performance of the optimally designed compensator is assessed using well documented IEEE standards based on numerical examples of nonlinear loads taken from previous publications

Resistance to ketolide antibiotics by coordinated expression of rRNA methyltransferases in a bacterial producer of natural ketolides

Significance Studies of antibiotic resistance are usually initiated in earnest only after resistance has become established in clinical pathogens. Here, we forewarn of a resistance mechanism to the novel antibiotics ketolides, which are only coming into broad medical practice. We show that the balanced activities and coordinated expression of two genes, pikR1 and pikR2 , provide efficient protection to Streptomyces venezuelae , a bacterial producer of natural ketolides. Expression of the more potent gene, pikR2 , is supported by pikR1 and specifically induced by ketolides. The resistance mechanism remains fully functional when pikR1 and pikR2 are transferred to other bacterial species and affords protection against clinical ketolides. These findings emphasize the need for the preemptive development of antibiotics that can overcome this resistance mechanism. </jats:p

Optimal fault-tolerant flight control for aircraft with actuation impairments

Current trends towards greater complexity and automation are leaving modern technological systems increasingly vulnerable to faults. Without proper action, a minor error may lead to devastating consequences. In flight control, where the controllability and dynamic stability of the aircraft primarily rely on the control surfaces and engine thrust, faults in these effectors result in a higher extent of risk for these aspects. Moreover, the operation of automatic flight control would be suddenly disturbed. To address this problem, different methodologies of designing optimal flight controllers are presented in this thesis. For multiple-input multiple-output (MIMO) systems, the feedback optimal control is a prominent technique that solves a multi-objective cost function, which includes, for instance, tracking requirements and control energy minimisation. The first proposed method is based on a linear quadratic regulator (LQR) control law augmented with a fault-compensation scheme. This fault-tolerant system handles the situation in an adaptive way by solving the optimisation cost function and considering fault information, while assuming an effective fault detection system is available. The developed scheme was tested in a six-degrees-of-freedom nonlinear environment to validate the linear-based controller. Results showed that this fault tolerant control (FTC) strategy managed to handle high magnitudes of the actuator’s loss of effciency faults. Although the rise time of aircraft response became slower, overshoot and settling errors were minimised, and the stability of the aircraft was maintained. Another FTC approach has been developed utilising the features of controller robustness against the system parametric uncertainties, without the need for reconfiguration or adaptation. Two types of control laws were established under this scheme, the H∞ and µ-synthesis controllers. Both were tested in a nonlinear environment for three points in the flight envelope: ascending, cruising, and descending. The H∞ controller maintained the requirements in the intact case; while in fault, it yielded non-robust high-frequency control surface deflections. The µ-synthesis, on the other hand, managed to handle the constraints of the system and accommodate faults reaching 30% loss of effciency in actuation. The final approach is based on the control allocation technique. It considers the tracking requirements and the constraints of the actuators in the design process. To accommodate lock-in-place faults, a new control effort redistribution scheme was proposed using the fuzzy logic technique, assuming faults are provided by a fault detection system. The results of simulation testing on a Boeing 747 multi-effector model showed that the system managed to handle these faults and maintain good tracking and stability performance, with some acceptable degradation in particular fault scenarios. The limitations of the controller to handle a high degree of faults were also presented

Quality Measurements on Quantised Meshes

In computer graphics, triangle mesh has emerged as the ubiquitous shape rep- resentation for 3D modelling and visualisation applications. Triangle meshes, often undergo compression by specialised algorithms for the purposes of storage and trans- mission. During the compression processes, the coordinates of the vertices of the triangle meshes are quantised using fixed-point arithmetic. Potentially, that can alter the visual quality of the 3D model. Indeed, if the number of bits per vertex coordinate is too low, the mesh will be deemed by the user as visually too coarse as quantisation artifacts will become perceptible. Therefore, there is the need for the development of quality metrics that will enable us to predict the visual appearance of a triangle mesh at a given level of vertex coordinate quantisation

Development of a survey instrument for measuring the perceptions and attitudes of the managers of Saudi public organisations on the benefits of Saudi labour rights and laws

The procedure adopted for development of a survey instrument to measure the perceptions and attitudes of Saudi managers on the benefits laws has been described in this paper. The commonly adopted procedure of determining the scales and items for the survey was followed. The context-specific requirements were considered in determining the items to be included in the two scales. The full questionnaire contained relevant demographic items, eight items each for perceptions and attitudes measurement and a final open question for whatever the survey participants wished to say about the topic of survey. A pilot trial was done using the developed survey instrument to measure perceptions and attitudes of Saudi public sector managers on the benefits enjoyed by their workforce due to favourable labour laws. The results showed both perceptions and attitudes of managers to be positive. The results were explained in a number of different ways with the support of literature. Some limitations of this research, as scope for further research, have also been listed

Managing security and compliance risks of outsourced IT projects

PhD ThesisSeveral sources of constraints, such as business, financial and legal, can lead organisations to outsource some of their IT services. As a consequence, different security risks may be introduced, such as confidentiality, integrity and availability risks. Analysing and managing the potential security risks in the early stages of project execution allow organisations to avoid or mitigate the impact of these security risks. Several organisations have adopted ISMS standards and frameworks in an endeavour to manage outsourced IT project security risks. In this thesis, existing ISMS standards and frameworks have been reviewed and analysed to assess their ability to effectively manage the security and compliance risks of outsourced IT projects and satisfy their security needs. The review reveals that existing ISMS standards and frameworks represent only general security recommendations and do not consider variation in security requirements from one organisation to another. There is also a lack of adequate guidance for implementing or complying with these standards and frameworks, and they are not designed to manage the security and compliance risks of outsourced IT projects. To overcome these weaknesses, a new framework has been introduced. The framework is a structured approach that is designed to manage variation in security requirements, as well as provide a methodology to guide organisations for the purpose of security management and implementation. The framework was evaluated using different evaluation methods including a focus group, questionnaire, and case study, which were also used to generate recommendations and suggestions for improvements. The evaluation results confirmed that the framework provided the participants with an effective approach for managing security and compliance risks in the outsourcing context. It was understandable, easy to use, and independent from different constraints such as project size, cost or execution time. The framework is now ready to be put into practice by organisations that intend to outsource their IT services partially or totally