Browsing by Author "Alqallaf, Jasem"
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Item Open Access Blade roughness effects on compressor and engine performance—a CFD and thermodynamic study(MDPI, 2021-11-04) Alqallaf, Jasem; Teixeira, Joao AmaralDegradation of compressors is a common concern for operators of gas turbine engines (GTEs). Surface roughness, due to erosion or fouling, is considered one of the major factors of the degradation phenomenon in compressors that can negatively affect the designed pressure rise, efficiency, and, therefore, the engine aero/thermodynamic performance. The understanding of the aerodynamic implications of varying the blade surface roughness plays a significant role in establishing the magnitude of performance degradation. The present work investigates the implications due to the degradation of the compressor caused by the operation in eroding environments on the gas turbine cycle performance linking, thereby, the compressor aerodynamics with a thermodynamic cycle. At the core of the present study is the numerical assessment of the effect of surface roughness on compressor performance employing the Computational Fluid Dynamics (CFD) tools. The research engine test case employed in the study comprised a fan, bypass, and two stages of the low pressure compressor (booster). Three operating conditions on the 100% speed-line, including the design point, were investigated. Five roughness cases, in addition to the smooth case, with equivalent sand-grain roughness (ks) of 15, 30, 45, 60, and 150 µm were simulated. Turbomatch the Cranfield in-house gas turbine performance simulation software, was employed to model the degraded engine performance. The study showed that the increase in the uniform roughness is associated with sizable drops in efficiency, booster pressure ratio (PR), non-dimensional mass flow (NDMF), and overall engine pressure ratio (EPR) together with rises in turbine entry temperature (TET) and specific fuel consumption (SFC). The performance degradation evaluation employed variables such as isentropic efficiency (ηis), low pressure compressor (LPC) PR, NDMF, TET, SFC, andEPR. The variation in these quantities showed, for the maximum blade surface degradation case, drops of 7.68%, 2.62% and 3.53%, rises of 1.14% and 0.69%, and a drop of 0.86%, respectively.Item Open Access Numerical study of effects of solid particle erosion on compressor and engine performance(Elsevier, 2022-06-24) Alqallaf, Jasem; Teixeira, Joao AmaralSolid particle erosion (SPE) is a major source of damage to, and cause of failure of, turbomachinery, including centrifugal and axial compressors and gas turbines. There is considerable interest within the turbomachinery industry to develop the means to enhance durability and improve prediction of likely breakdowns of machinery operating in locations and conditions where ingestion of, for example, dust and sand grains is unavoidable during operation. The present study examines the implications of degradation of the compressor on gas turbine cycle performance, caused by operating in eroding environments, linking compressor aerodynamics with the thermodynamic cycle. The research engine employed in the study comprised a fan, bypass, and two stages of the low-pressure compressor (booster). A numerical simulation using Computational Fluid Dynamics (CFD) software was performed to predict the likely erosion patterns due to solid particles (SPs) impacting on the blades of the first two stages of an axial compressor. This study introduces a method that provides the freedom to apply roughness to a particular region of the blade following the SPE patterns identified as part of the CFD simulations so as to represent the effects of the erosion spots on the overall flow field. The localised roughness method employs a perturbation of the geometry of the blade in the regions corresponding to the location predicted by the SPE model. The intensity of the perturbation, which is governed by a “fraction factor” coded in a Matlab script, was calibrated by reference to a roughness case, applied over the entire blade surface, with equivalent sand-grain roughness () of 60 μm. Turbomatch, the Cranfield in-house gas turbine performance simulation software, was employed to model the degradation of engine performance. The research confirmed that SPE is linked with significant decreases in engine performance parameters such as isentropic efficiency (ηis) and pressure ratio (PR). These quantities showed, for the SPE cases considered, a drop of 8.8% and 5.2%, respectively. These findings are useful to link local SPE events to global GTE cycle performance.Item Open Access Solid particle erosion behaviour and protective coatings for gas turbine compressor blades—a review(MDPI, 2020-08-13) Alqallaf, Jasem; Ali, Naser; Teixeira, Joao Amaral; Addali, AbdulmajidGas turbines (GTEs) are often utilised in harsh environments where the GT components, including compressor vanes and rotor blades, are subject to erosion damage by sand and dust particles. For instance, in a desert environment, the rate of damage made by solid particles erosion (SPE) becomes severe, and therefore results in degradation to the GTE parts, lowering the cycle efficiency, reducing the device lifetime, and increasing the overall cost of the operation. As such, understanding the erosion mechanism caused by solid particles and the effects associated with it is crucial for selecting the appropriate countermeasures and maintaining the system performance. This review paper provides a survey of the available studies on SPE effects on GTEs and surface protective coatings. Firstly, the ductile and brittle SPE mechanism is presented, as well as the ductile-brittle transition region. Then, an in-depth focus on the parameters associated with the SPE, such as particles properties and impingement conditions, is introduced. Furthermore, the existing theoretical models are shown and discussed. Afterwards, erosion resistant coating materials for surface protection and their selection criteria are covered in the review. Finally, the gap in knowledge and future research direction in the field of SPE on GTEs are provided.