Browsing by Author "Brighenti, Giovanni D."

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Advanced gas turbine cycle performance modelling using response surface methods
    (Cambridge University Press, 2018-10-26) Seetharama-Yadiyal, V.; Brighenti, Giovanni D.; Pavlos, Zachos
    Surrogate models are widely used for dataset correlation. A popular application very frequently shown in public literature is in the field of engineering design where a large number of design parameters is correlated with performance indices of a complex system based on existing numerical or experimental information. Such an approach allows the identification of the key design parameters and their impact on the system’s performance. The generated surrogate model can become part of wider computational platforms and enable optimisation of the complex system without the need to run expensive simulations. In this paper a number of design point simulations for a combined gas-steam cycle are used to generate a response surface. The generated response surface correlates a range of cycle’s key design parameters with its thermal efficiency while it also enables identification of the optimum overall pressure ratio and the high pressure level of the raised steam across a range of recuperator effectiveness, pinch temperature difference across the heat recovery steam generator and the pressure at the condenser. The accuracy of a range of surrogate models to capture the design space is evaluated using root mean square statistical metrics.
  • Thumbnail Image
    ItemOpen Access
    Design point performance and optimization of humid air turbine power plants
    (2017-04-20) Brighenti, Giovanni D.; Orts-Gonzalez, Pau Lluis; Sanchez-de-Leon, Luis; Zachos, Pavlos K.
    With the recent drive towards higher thermal efficiencies and lower emission levels in the power generation market, advanced cycle power plants have become an increasingly appealing option. Among these systems, humid air turbines have been previously identified as promising candidates to deliver high efficiency and power output with notably low overall system volume, weight and emissions footprint. This paper investigates the performance of an advanced humid air turbine power cycle and aims to identify the dependencies between key cycle design variables, thermal performance, weight and cost by means of a parametric design optimization approach. Designs of the main heat exchangers are generated, aiming to ascertain the relationship between their technology level and the total weight and acquisition cost of them. The research outcomes show that the recuperator and the intercooler are the two components with the largest influence on the thermal efficiency and the total cost. The total weight of the power system is driven by the technology level of the recuperator and the economizer. Finally, the effectiveness of the aftercooler seems to have the greatest impact in reducing the total acquisition cost of the system with minimum penalty on its thermal efficiency.
  • Thumbnail Image
    ItemOpen Access
    The impact of heat exchanger degradation on the performance of a humid air turbine system for power generation
    (Elsevier, 2018-12-13) Orts-Gonzalez, Pau Lluis; Zachos, Pavlos K.; Brighenti, Giovanni D.
    This paper aims to analyse the impact of air-water heat exchanger’s degradation on the performance of a reheated humid air turbine system for power generation applications. A number of thermal models to simulate the performance of the various sub-systems was put together and validated against experimental data. The performance degradation of the heat exchangers is characterised by means of a degradation coefficient, which is used to drive the cycle into off-design and part-load conditions when degradation is accounted for. Three heat exchanger design scenarioswere investigated, namely a low, a medium and a high effectiveness in order for the impact of the degradation penalties on cycle thermal efficiency to be determined. The performance deterioration of the heat exchangers is also analysed from an exergetic point of view in order to identify the key sources that penalise the thermal efficiency of the humid air turbine system. The degradation analysis shows that typical levels of intercooler deterioration cause notable penalties in the cycle performance, reducing its thermal efficiency and power output by 1.8 percentage points and 28% respectively compared to the un-degraded operation. The exergy analysis showed that the deterioration of the intercooler also penalises the efficiency of the low pressure compressor and reheater, which contribute to the performance penalty of the cycle too. It is also found that the degradation of the intercooler can also lead to operability penalties at the low pressure compressor by reducing its surge margin. The effects of the deterioration of the aftercooler and economiser were found to only have a weak effect on the system’s performance. The outcome of the work constitutes a step forward in understanding of the performance behaviour of an advanced cycle when heat exchanger degradation is present.
  • Thumbnail Image
    ItemOpen Access
    Part-load performance modelling of a reheated humid air turbine power cycle
    (Elsevier, 2018-04-11) Brighenti, Giovanni D.; Zachos, Pavlos K.; Orts-Gonzalez, Pau Lluis
    Humid air turbines have previously demonstrated the potential to deliver high efficiency and power output combined with low emissions. This paper investigates the part-load performance of a 40 MW class advanced humid air turbine for power generation applications across a range of operating conditions. The paper investigates the impact of the main burner and reheater burner on the system’s part-load power output and thermal efficiency and provides insights into the behavior of the key modules across the power spectrum of operation including the saturator tower which was never reported previously. The impact of the ambient air and sea water temperature on the cycle’s performance are also investigated. The outcome of the research shows that the thermal efficiency if the system is less than 0.26% penalized when operating down to 50% of the design power output. Sea water temperature was found to have a more notable impact than ambient air temperature on both power output and thermal efficiency Overall, this work constitutes a step ahead in understanding the potential benefits of an advanced humid air turbine system for power generation applications across a range of operating conditions which is not previously shown.
  • Thumbnail Image
    ItemOpen Access
    Performance and techno-economic analysis of humid air turbines for commercial marine applications
    (2018-05) Brighenti, Giovanni D.; Zachos, Pavlos K.
    The curb in SOᵪ and NOᵪ emissions, led by legislation both globally and in emission controlled areas, could eventually result in a ban of heavy fuel oil (HFO) for commercial marine applications. This could end in a window opening for advanced gas turbine-based power plants in the market of deep sea propulsion, currently dominated by slow-speed two-stroke diesel engines. Previous studies have identified humid air turbine (HAT) as promising gas turbine- based cycles, able to compete with diesel engines in terms of maximum thermal efficiency. However, no emphasis has yet been given to the identification of the potential of the reheated HAT cycle. This cycle features notably better performance relatively to a single burner system, and may promote the exploitation of humid cycle power plants in applications where high thermal efficiency and high power-to-plant size rations are of importance. This thesis presents an analysis of the impact of the technology level of the main component on the performance of the HAT cycle. Part-load performance analyses of the humid air cycle as a whole system is performed. Moreover, a techno-economical study of a commercial vessel powered by a HAT cycle for a given commercial route is used to directly compare the annual cost of machinery of the cycle with a diesel engine. The research outcomes confirm the higher thermal efficiency of the reheated HAT cycle and show the impact of technology level of the heat exchangers on the performance of the cycle. The part-load analyses of the HAT cycle show low penalties in performing away from the design condition. The comparison between the HAT and diesel engine, and advanced diesel engines, demonstrate the potential of the HAT cycle as prime mover of commercial marine vessels. Overall this research is a step forward towards the understanding of the feasibility of humid air turbines for replacing diesel engines in commercial marine applications or for applications where the density of power is of competitive advantage.
  • Thumbnail Image
    ItemOpen Access
    Techno-economic analysis of a reheated humid air turbine
    (Elsevier, 2018-03-30) Orts-Gonzalez, Pau Lluis; Zachos, Pavlos K.; Brighenti, Giovanni D.
    The purpose of this paper is to identify the economic potential of a reheated humid air turbine system for power generation applications. A parametric analysis is performed to correlate the technology level of the system with the required cost of the electricity for economic viability. The effect of fluctuations of the main cost drivers is evaluated via an uncertainty analysis. The performance of the studied reheated humid air turbine is compared against previously studied humid configurations and well established gas-steam combined cycles. The fuel cost is found to be driving the cost of electricity. The uncertainty analysis also shows the dependency of the optimum cycle design parameters upon the market prices. The analysis reveals the capability of the reheated humid air turbine to be an economically viable option for the power generation sector featuring an estimated cost of electricity 2.2% lower than simpler humid cycles, and 28% lower than established combined cycles currently in service. The outcome of the work constitutes a step forward in the understanding of the economic performance of advanced complex cycles and proves the potential of such systems for applications where high efficiency and economic performance is jointly required.