Abstract:Numerical simulations have been performed to study the effect of the circumferential single-grooved casing treatment (CT) at multiple locations on the tip-flow stability and the corresponding control mechanism at three tip-clearance-size (TCS) schemes in a transonic axial flow compressor rotor. The results show that the CT is more efficient when its groove is located from 10% to 40% tip axial chord, and G2 (located at near 20% tip axial chord) is the best CT scheme in terms of stall-margin improvement for the … Show more
“…The rotor performance is maximally improved at the near-stall point that the isentropic efficiency and TPR can be increased by 3.3% and 7.2%, respectively. Moreover, the stall margin improvement ( SMI ) of the rotor calculated according to equation (4) 30 is about 2.0%.Figure 20.The effect of combined suction slots on rotor performance. (a) total pressure ratio-mass flow, (b) isentropic efficiency-mass flow.…”
Large-scale corner separation is one of the key factors that limit the performance improvement of high-load compressors. In this paper, the hub aspiration method was applied to a supersonic shock-in type compressor rotor with negative inlet pre-whirl to suppress the hub corner separation. Six suction schemes composed of aspiration slots with different locations and orientations have been designed and numerically tested. The results revealed that the aspiration location is better to be placed starting from the post-shock point and extending to the deep separation zone. The streamwise slot satisfying such conditions could effectively suppress corner separation but narrows the rotor stable mass flow range by increasing the pitchwise secondary flow. The circumferential skew slot could exactly remedy such defects. The streamwise slot combined with a downstream skew slot is the optimal aspiration strategy that effectively improves the rotor performance without reducing mass flow range. At the design and near-stall operating point, the rotor efficiency (EF) and total pressure ratio (TPR) could be improved by 1.3% and 5.0%, 3.3% and 7.2%, respectively. Consequently, the stall margin was increased by 2.0%. According to the flow loss analysis, the combined aspiration scheme mainly alleviated losses from hub to middle span by reducing the shock strength and the magnitude of separation as well as its radial migration. But in the tip region, it strengthened the leakage flow and its interaction with shock waves, thus increasing the flow losses.
“…The rotor performance is maximally improved at the near-stall point that the isentropic efficiency and TPR can be increased by 3.3% and 7.2%, respectively. Moreover, the stall margin improvement ( SMI ) of the rotor calculated according to equation (4) 30 is about 2.0%.Figure 20.The effect of combined suction slots on rotor performance. (a) total pressure ratio-mass flow, (b) isentropic efficiency-mass flow.…”
Large-scale corner separation is one of the key factors that limit the performance improvement of high-load compressors. In this paper, the hub aspiration method was applied to a supersonic shock-in type compressor rotor with negative inlet pre-whirl to suppress the hub corner separation. Six suction schemes composed of aspiration slots with different locations and orientations have been designed and numerically tested. The results revealed that the aspiration location is better to be placed starting from the post-shock point and extending to the deep separation zone. The streamwise slot satisfying such conditions could effectively suppress corner separation but narrows the rotor stable mass flow range by increasing the pitchwise secondary flow. The circumferential skew slot could exactly remedy such defects. The streamwise slot combined with a downstream skew slot is the optimal aspiration strategy that effectively improves the rotor performance without reducing mass flow range. At the design and near-stall operating point, the rotor efficiency (EF) and total pressure ratio (TPR) could be improved by 1.3% and 5.0%, 3.3% and 7.2%, respectively. Consequently, the stall margin was increased by 2.0%. According to the flow loss analysis, the combined aspiration scheme mainly alleviated losses from hub to middle span by reducing the shock strength and the magnitude of separation as well as its radial migration. But in the tip region, it strengthened the leakage flow and its interaction with shock waves, thus increasing the flow losses.
“…For instance, in the case of predicting hub corner separation, consideration of secondary flow, and adverse pressure gradient, as applied in a study (Lei, 2006), intelligent approaches can be useful to develop a model based on intelligent techniques. Casing treatment and applying slots (Lu et al, 2023), grooves (Wu et al, 2021), or both of them on the casing (Li et al, 2019), is one of the techniques used by the scholars to modify the stability of compressors. It is can be helpful to develop intelligent models for the modified compressors, e.g., the compressors with casing treatment (Vuong and Kim, 2021).…”
A compressor is one of the key components of a gas turbine engine and its performance and characteristics significantly affect the overall performance of the engine. Axial flow compressors are one of the most conventional types of compressors and are widely used in turbine engines for large-scale power generation. Intelligent techniques are useful for numerical simulation, characterization of axial compressors, and predicting their performance. The present work reviews studies applying different intelligent methods for performance forecasting and modeling different aerodynamic aspects of axial compressors. Corresponding to the outcomes of the considered research works, it can be expressed that by using these methods, axial compressors can be characterized properly with acceptable exactness. In addition, these techniques are useful for performance prediction of the compressors. The accuracy and performance of these methods is impacted by several elements, specifically the employed method and applied input variables. Finally, some suggestions are made for future studies in the field.
“…The results are listed and compared in Table 3. To the authors' acknowledgment, the most commonly used two ways to calculate the stall margin improvement are listed in this paper and represented by formulas (9) [31][32][33] and (10) 34 . The former one takes both the performance variation at the peak efficiency (or design) and the near-stall operating point into consideration, while the latter one concentrates on the near-stall point.…”
Shock wave/boundary layer interaction (SWBLI) is one of the key factors that limits the improvement of aerodynamic performance and stability for supersonic/transonic compressors. In this research, a combined flow control device (CFCD) was designed for controlling SWBLI in the NASA transonic compressor Rotor 35. The original flow fields for Rotor 35 were numerically analyzed first. The results show that the SWBLI is severe, resulting in much flow loss and partly leading to the compressor instability. Based on this phenomenon, the CFCD was designed with a novel three-dimensional passive self-recirculation flow channel and an active suction slot. The flow channel is mounted on the rotor blade suction surface to connect the low- and high-pressure regions ahead of and behind the shock, respectively. The effect of the CFCD on the rotor performance and corresponding working mechanism are then researched as well. With the help of CFCD, the rotor-achieved total pressure ratio (TPR) is maximally increased by 3.0%, and the stall margin (SM) is improved by 4.1% as well. But the rotor isentropic efficiency (IE) considering additional energy expenditure caused by active suction flow has the maximum increment at choke point of 0.27% and highest reduction at near-stall point of 0.54%. The working mechanisms of CFCD include two aspects: one is forming a stable and low-entropy generated lambda shock wave and the other one is reducing the magnitude of flow separation. The dominant mechanism varies with the rotor working condition and depends on whether the leading-edge shock moves upstream of the passive bleed slot.
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