Browsing by Author "Szymanski, Artur"

Now showing 1 - 6 of 6
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    Aeroderivative gas turbine back-up capability with compressed air injection
    (Elsevier, 2020-08-08) Abudu, Kamal; Igie, Uyioghosa; Roumeliotis, Ioannis; Szymanski, Artur; Di Lorenzo, Giuseppina
    The transition to more renewable energy sources of power generation is associated with grid instability and the need for backup power, due to their intermittency. This provides an opportunity for gas turbine engines, especially the aeroderivative (AD) types that generally have higher ramp rates than heavy-duty engines. Nonetheless, higher ramp rates are still necessary to meet more stringent grid requirements, with increased renewables subscription. The study examines ramp rate improvements and performance enhancement through compressed air injection at the back of the high-pressure compressor (HPC). Two configurations of AD engines are considered in the investigation. In-house gas turbine performance simulation software has been used to simulate the steady-state and transient operations for design and off-design performance. Compressed air injection in the study is facilitated by an assumed compressed air storage or an external compressor. The steady-state analysis for power augmentation shows that for the two-spool engine with fixed speed low-pressure compressor (LPC), a 16% increase in power is obtained with 8% of flow injection. The other engine that is intercooled and consists of a variable speed LPC with power turbine shows a 21% increase in power for the same injection amount. Above 8% injection, the HPC of both engines tends towards an adverse rise in pressure ratio. However, up to 15% of flow injection is allowed before the surge point. It is seen generally that the operating point of the LPC moves away from surge, while the opposite is the case for the HPC. For transient simulations focused on ramp rates, the better improvements are shown for the intercooled engine that runs at variable speed. This is a ramp rate improvement of 100% with air injection, while that of the other engine increases by 85%
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    Aerodynamic limits air injection for heavy-duty gas turbine: compressor aerodynamic limits for power augmentation and ramp-up capabilities
    (SAGE, 2022-04-24) Szymanski, Artur; Igie, Uyioghosa; Hamilton, Richard
    Improved operational flexibility of gas turbines can play a major role in stabilising the electric power grid, by backing up intermittent renewable power. Gas turbines offer on-demand power and fast dispatch of power that is vital when renewable power reduces. This has brought about increasing demand to improve the ramp-up rate of gas turbines. One approach is through the injection of compressed air from energy storage or an auxiliary compressor. This method is the focus of the present work, which shows for the first time, the implications and limits of compressor air injection in a high-fidelity Computational Fluid Dynamics model (CFD). The 3D multi-stage model of the compressor was developed in ANSYS CFX v19.2, while the boundary conditions related to the injection cases have been obtained from a corresponding 0D engine model. The upper limits to air injection determine how much air can be injected into the engine, providing indicative values of power augmentation and ramp-up rate capabilities. These have been previously addressed by the authors using 0D models that do not consider the compressor aerodynamics in great detail. The CFD study has shown that for power augmentation, 16% of compressed air (based on compressor exit) is allowed based on the onset of stall. It also shows that increasing air injection amplifies losses, blockage factor and absolute velocity angle. Also, about 30% of the blade span from the hub is dominated by a rise in the total pressure loss coefficient, except the outlet guide vane for which separation occurs at the tip. For the ramp-up rate analysis, up to 10% air injection is shown to be sustainable. The work shows that the improvements in the 0D analytical engine model are plausible, in addition to demonstrating similar limits at different ambient temperatures.
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    Aerodynamic limits of gas turbine compressor during high air offtakes for minimum load extension
    (Elsevier, 2021-02-18) Szymanski, Artur; Igie, Uyioghosa; Abudu, Kamal; Hamilton, Richard
    Renewable energy sources (RES) have become a favoured alternative to fossil fuel energy generation that has been driven by environmental concerns. Their intermittent nature has meant that gas turbines have remained relevant to support them as a backup. Current grid operation requires gas turbines to operate at as low power as possible when their demand drops, and also ramp-up quickly when power generation from renewables declines. Air extraction from a gas turbine compressor can address the first requirement, as this mechanism reduces the load or power of the engine while storing the air for further pressurised reinjection, related to ramp-up rate improvements. This study demonstrates the aerodynamic implications and the limits to air extraction behind the last stage of the compressor, to achieve further minimum load reduction. To achieve this, a zero-dimensional (0D) analytical model of an engine at design and off-design conditions (air extraction) has been used to determine the boundary conditions for a 3D compressor Computational Fluid Dynamics (CFD) model. The multi-stage CFD model shows the aerodynamic implications of low to high air extractions that are limited by choke, high flow separation, and loss in the pressure at the hub region of OGV and last stage stator. As such, the back of the compressor was more affected than the earlier stages. Based on these, the limit of flow extraction is 18% (of the compressor discharge). The compressor of the analytical engine model showed similarity in trends for comparable conditions with the stand-alone 3D compressor, however, more optimistic than the latter. The work has shown that the compressor is capable of high airflow extractions to reduce the minimum load further.
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    Design of a high-speed intake distortion simulator for propulsion integration research
    (AIAA, 2023-01-19) Migliorini, Matteo; Szymanski, Artur; Zachos, Pavlos K.; MacManus, David; Martin, Peter G.
    High levels of inlet flow distortion can be a critical aspect in supersonic air induction systems due to the complex spatial nature and notable temporal unsteadiness. This can affect the operability and performance of the propulsion system. Simulation of the intake shock system in a relatively less expensive, lower technology readiness level experimental facility can be an important element to mitigate a significant part of the risk that industrial and certification testing carries. The work described in this paper is part of a programme that aims to develop such a distortion simulation test rig where the capability of advanced non-intrusive measurement techniques would be applied in propulsion integration research. The paper describes the concept, preliminary design and sizing of the working section of the rig, the exhaust system design and the integration of the test model. A brief summary of the rig architecture is provided along with details of the high-pressure system that drives the supersonic flow. The work indicates that careful design of the working section is required to ensure sufficient operating range and representative aerodynamics of the test model. It is also shown that the working section wall interference on the test model is tightly linked with the type and size of the aircraft intake to be tested. Ways to mitigate this interference are herein explored.
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    Entropy generation and efficiency of a transonic rotor with water injection - a numerical study
    (American Society of Mechanical Engineers, 2021-01-11) Zawadzki, Natan; Szymanski, Artur; Block Novelo, David Alejandro; Igie, Uyioghosa
    The application of compressor water injection in aeroengines is of renewed interest in the civil aviation industry. Water due to its unprecedented heat capacity has the potential to cool the engine air through evaporation and thus reduce the NOx emissions formed in a combustion process. It is well known that the evaporative cooling increases thermodynamic cycle efficiency and thus improves the fuel economy. A relatively unexplored area, however, is the entropy generation due to water phase change as well as the balance between the corresponding entropy yield and the savings from the cooling of the core compressor flow. Hence, little consensus in the literature exists on the ultimate effect of water injection on compressor efficiency. In this study, a numerical analysis of water injection on an axial transonic rotor was carried out. The compressor model was tested at near-peak efficiency conditions with and without water injection. The flow was analysed using the Eulerian-Lagrangian approach with two-way coupling and the k-ω Shear Stress Transport turbulence model with Reattachment Modification. A universal, second thermodynamic law approach to quantify the entropy generation is proposed and used to evaluate the compressor flow. Results show that evaporation can facilitate the compression process and does not impair the compressor efficiency if applied at favourable conditions. The entropy generation in droplet-laden flow scales according to the gains from cooling effect and losses due to the evaporation and increased friction in the fluid. Some of the discrepancies in the public domain could be addressed, showing that the observed improvement in compressor efficiency is highly sensitive to the entropy flux measurement location. Most benefits from water injection were observed at the rotor tip proving the case for part-span injection from an entropy balance perspective.
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    Power augmentation and Ramp-Up rate improvement through compressed air Injection: a dry low NOx combustor CFD analysis
    (Elsevier, 2024-02-09) Wiranegara, Raditya Yudha; Igie, Uyioghosa; Szymanski, Artur; Abudu, Kamal; Abbott, David; Sethi, Bobby
    Gas turbines play a key role in accelerating the transition towards more environmentally friendly power generation. This role includes backup of renewable generation that is intermittent, providing grid inertia as well as other ancillary services for grid stability. For quick backup power, the ramp-up rate of gas turbines can be improved through air injection at the back of the compressor, facilitated by integrating compressed air energy storage. Published works have mostly focused on low-fidelity engine system analysis of air injection overall effects. No study has focused on the detailed combustor performance presented in this study. The work shows the impact of air injection on the emissions, thermoacoustic stability and liner wall durability. These yardsticks in assessing the operability of the combustor have also been used for air power augmentation and ramp-up analysis. ANSYS software was used in the computational fluid dynamics (CFD) analysis of the three-dimensional dry low NOx combustor. Low-order models were used for the thermoacoustic stability and durability analysis. For the power augmentation study, the NO and CO emissions produced at 15 % air injection are below the maximum values of the combustor in design operations. Also, the stability and durability were within limits. The ramp-up investigation indicates up to 10 % air injection is allowed and the emissions are similarly acceptable. However, the thermoacoustic analysis shows a potential for combustion instabilities at high frequencies above 1800 Hz. Generally, there was no unusual wall liner durability in these two studies. When benchmarked against previous engine-level analysis, the ramp-up rate can be potentially improved by 54 % if the small concern on thermoacoustic instability is resolved.