Abstract:In the current study, the effects of micro-vortex generators on the flow characteristics of a high-load compressor cascade are investigated, and four types of micro-vortex generators including “rectangular,” “curved rectangular,” “trapezoidal,” and “curved trapezoidal” are considered and named VGR, VGCR, VGT, and VGCT separately. The calculated results show that a rising reverse flow region, which is considered a main reason for occurring stall at +8° incidence, collapses rapidly from the leading edge in the c… Show more
“…It has been proved that the spatial positions and geometric parameters of LBs show significant effect on the cascade performance. 17 Therefore, the positions and geometric parameters need to be discussed in detail.Figure 13.Configuration and position of little blades.…”
Section: Numerical Resultsmentioning
confidence: 99%
“…In Figure 13, the distance between the two vanes ( S ) and the length ( L ) are defined according to some previous research studies focused on the effects of geometric parameters of the LBs on cascade performance. 17 Moreover, the stagger angle ( χ ) of the LBs at the stall condition (8° incidence) has been optimized by Guo, 21 and the optimal value is 1.29 γ . In the previous research studies, 17 the leading edge of the little blade with a smaller size shows an obvious superiority in reducing the total pressure loss at some larger incidence conditions; therefore, h L is lower than h T .…”
Section: Numerical Resultsmentioning
confidence: 99%
“…As the incidence is raised to 7°, the initial position moves upstream and arrives at the position near the LE. 17 In order to fully consider the effect of the LBs on the flow reversal regions, the longer axial range is considered. Therefore, the axial positions of 0%, 5%, 10%, 15%, and 20% are selected and named l 1 ∼ l 5 , respectively.…”
To reveal the importance of little blades’ spatial position to improve the cascade performance at different condition, the pitchwise and axial direction of the little blades on the end-wall are adopted as the optimization variables to complete a double-objective optimization. Meanwhile, the three-dimensional flow field characteristics of the cascade with and without little blades are analyzed comparatively. The study found that as the optimal solutions are obtained at the three bigger incidences (3°, 5°, and 7°), the optimal position is always close to the leading edge of blade and far away from the blade suction surface, and the more intuitive design suggestions are given in this article. Moreover, at the near design conditions (−1°, 0°, and 1°), little blades increase the total pressure loss and reduce the static pressure, which are considered unsuitable for improving the cascade performance. If the stable operation range are the main performance indicators, the optimization of the little blades’ spatial position should be completed at the near stall condition (7° incidence). If the conditions with mid-range incidences (2°< i <5°) are the main performance index, the parameter optimization of little blades should be achieved at 5°. Based on the further flow field analysis of the optimization results obtained at 3°, 5°, and 7° incidences (named Opt_Act3, Opt_Act5, and Opt_Act7), the induced vortices resist the effect of axial reverse pressure gradient and pass through the blade passage, which is the main reason for the total pressure loss reduction. Appropriate spatial position of little blades not only strengthens the capability to prevent the low-energy fluids accumulating in the corner region near the end-wall, but exhibits sufficient advantage to weaken the boundary layer.
“…It has been proved that the spatial positions and geometric parameters of LBs show significant effect on the cascade performance. 17 Therefore, the positions and geometric parameters need to be discussed in detail.Figure 13.Configuration and position of little blades.…”
Section: Numerical Resultsmentioning
confidence: 99%
“…In Figure 13, the distance between the two vanes ( S ) and the length ( L ) are defined according to some previous research studies focused on the effects of geometric parameters of the LBs on cascade performance. 17 Moreover, the stagger angle ( χ ) of the LBs at the stall condition (8° incidence) has been optimized by Guo, 21 and the optimal value is 1.29 γ . In the previous research studies, 17 the leading edge of the little blade with a smaller size shows an obvious superiority in reducing the total pressure loss at some larger incidence conditions; therefore, h L is lower than h T .…”
Section: Numerical Resultsmentioning
confidence: 99%
“…As the incidence is raised to 7°, the initial position moves upstream and arrives at the position near the LE. 17 In order to fully consider the effect of the LBs on the flow reversal regions, the longer axial range is considered. Therefore, the axial positions of 0%, 5%, 10%, 15%, and 20% are selected and named l 1 ∼ l 5 , respectively.…”
To reveal the importance of little blades’ spatial position to improve the cascade performance at different condition, the pitchwise and axial direction of the little blades on the end-wall are adopted as the optimization variables to complete a double-objective optimization. Meanwhile, the three-dimensional flow field characteristics of the cascade with and without little blades are analyzed comparatively. The study found that as the optimal solutions are obtained at the three bigger incidences (3°, 5°, and 7°), the optimal position is always close to the leading edge of blade and far away from the blade suction surface, and the more intuitive design suggestions are given in this article. Moreover, at the near design conditions (−1°, 0°, and 1°), little blades increase the total pressure loss and reduce the static pressure, which are considered unsuitable for improving the cascade performance. If the stable operation range are the main performance indicators, the optimization of the little blades’ spatial position should be completed at the near stall condition (7° incidence). If the conditions with mid-range incidences (2°< i <5°) are the main performance index, the parameter optimization of little blades should be achieved at 5°. Based on the further flow field analysis of the optimization results obtained at 3°, 5°, and 7° incidences (named Opt_Act3, Opt_Act5, and Opt_Act7), the induced vortices resist the effect of axial reverse pressure gradient and pass through the blade passage, which is the main reason for the total pressure loss reduction. Appropriate spatial position of little blades not only strengthens the capability to prevent the low-energy fluids accumulating in the corner region near the end-wall, but exhibits sufficient advantage to weaken the boundary layer.
“…The distance between the two little blades (S), the height (h T ) and the length (L) are defined according to previous researches focused on the effects of geometric parameters of the little blade on cascade performance. 37 The height of the little blade trailing edge is defined as 0.2d, here d means the thickness of boundary layer. In the previous research, leading edge with a smaller size shows an overwhelming superiority in reducing the total pressure loss at the large incidence conditions, therefore the h L is lower than h T .…”
Section: Effects Of Little Blades On Compound Lean Compressor Cascadementioning
The development of boundary layer affects the compressor cascade performance to a certain extent. Therefore, the compound lean and little blades are selected to redistribute the boundary layer, and the influences of these two flow control technologies on the axial compressor cascade performance are further studied. The calculated results showed that appropriate high pressure region on the blade suction surface near the end-wall is helpful to reduce the total pressure loss of compressor cascade, which can be achieved by positive lean technique. Meanwhile, the maximum stable operation boundary can be expanded by the application of positive leaned blade. On the other hand, the introduction of negative lean angle not only increases the total pressure loss of cascade, but reduces the stable operation range. As the little blades are introduced in the negative lean compressor cascade, the stable operation range is significantly improved by the introduction of little blades. Especially the cascade with −10° lean angle, the maximum stable operation boundary is increased from 1° to 6°. In the positive lean compressor cascade, although more low-energy fluid is accumulated on the blade suction surface near the mid-span, the little blades still show an active role in reducing the total pressure loss and expending the stable operation range, because the influence range of induced vortex reaches 30%span. The results provide a reference for improving the aerodynamic performance of compressor stator, especially when more low-energy fluid is blocked in the range near the mid-span.
“…Therefore, researchers have conducted a large number of flow control experiments and numerical studies on the end wall of the compressor. Passive end wall control methods include casing treatment (Chen et al 2019), end wall profiling (Li et al 2014;Li et al 2016), and vortex generator (Ma et al 2018), etc. Because of the lack of controllable variables related to compressor operating conditions and speed changes, passive control methods usually can only optimize the performance of the compressor under individual operating conditions, therefore, it cannot guarantee that the performance of the compressor will be improved in the full range of operating conditions.…”
In order to improve the performance of a high-load transonic axial compressor, this paper proposes a method of applying endwall synthetic jet to the casing for active flow control. Taking NASA Rotor35 as the research object, the aerodynamic performance of the compressor is numerically calculated by applying three sets of synthetic jets with different excitation parameters at five different axial positions of 0%Ca, 25%Ca, 50%Ca, 75%Ca and 96.15%Ca. The results show that the three parameters of excitation position, jet peak velocity and jet frequency all have an effect on the performance of the compressor. The excitation position has the greatest influence on the flow margin of the compressor, and the best position is 25%Ca. After the jet peak velocity is increased from 100m/s to 150m/s, the flow margin, total pressure ratio and efficiency of the compressor are not greatly improved, which shows that the impact of the jet peak velocity is not as good as the excitation position. After continuing to increase the excitation frequency of the synthetic jet from 600Hz to 1200Hz, although the flow margin of the compressor is slightly reduced, the total pressure ratio and efficiency are further improved. This shows that there may be a threshold for the jet frequency, and only when the jet frequency is greater than the threshold can the overall aerodynamic performance of the compressor be improved.
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