Effects of Air Injection on Performance of Highly-Loaded Compressor Cascades

2007 ◽  
Author(s):  
Yanping Song ◽  
Huanlong Chen ◽  
Fu Chen ◽  
Zhongqi Wang
Keyword(s):  
Performance Improvement ◽  
Adverse Pressure Gradient ◽  
Air Injection ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Capacity Enhancement ◽  
Straight Blade ◽  
Flow Capacity ◽  
Blade Cascade ◽  
Highly Loaded

The effects of air injection on the performance of highly-loaded straight blade compressor cascade and compound lean blade cascade were investigated numerically. Air injection was implemented via the hole/slot penetrating through the pressure and suction surfaces under the effect of the pressure difference between the two sides. Various injection configurations including one-hole, multi-hole and slot configurations were studied in the straight blade cascade first to find the optimum injection configuration in this case. Then the mechanism of the injection slot on the performance improvement of the straight blade cascade was discussed in detail. The results show that air injection provides the low-momentum fluid near the suction surface with kinetic energy, to enhance its ability to withstand the adverse pressure gradient within the compressor cascade. Among the hole/slot configurations, the slot configuration (the radial width of 4.0mm) has the most favorable results in through-flow capacity enhancement and total loss reduction, and is used in the compound lean cascade study. The effects of air injection on the performance improvement in the compound lean blade cascade are less significant than those in the straight blade cascade though the compound lean blade cascade with the injection slot has the most improvement in the aerodynamic performance when the slot is placed at an appropriate location in this study.

The Effective Positions to Inject Water Into the Cascade of Compressor

2012 ◽  
Author(s):  
Jie Wang ◽  
Qun Zheng ◽  
Lanxin Sun ◽  
Mingcong Luo
Keyword(s):  
Kinetic Energy ◽  
Total Pressure ◽  
Lower Energy ◽  
Water Injection ◽  
Adverse Pressure Gradient ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Pressure Losses ◽  
Ansys Cfx ◽  
Highly Loaded

Generally, droplets are injected into air at inlet or interstage of a compressor. However, both cases did not consider how to utilize the kinetic energy of these moving droplets. Under the adverse pressure gradient of compressor, the lower energy fluids of blade surfaces and endwalls boundary layers would accumulate and separate. Kinetic droplets could accelerate the lower energy fluids and eliminate the separation. This paper mainly investigate the effective positions where to inject water and how to utilize the droplets’ kinetic energy. Four different injecting positions, which located on the suction surface and endwall, are chosen. The changes of vortexes in the compressor cascade are discussed carefully. In addition, the influences of water injection on temperature, total pressure losses and Mach number are analyzed. Numerical simulations are performed for a highly loaded compressor cascade with ANSYS CFX software.

Numerical Investigation of Passive Flow Control Using Wavy Blades in a Highly-Loaded Compressor Cascade

2018 ◽  
Author(s):  
Bo Wang ◽  
Yanhui Wu ◽  
Kai Liu
Keyword(s):  
Numerical Investigation ◽  
Flow Structure ◽  
Cross Flow ◽  
Leading Edge ◽  
Control Flow ◽  
Streamwise Vortices ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Highly Loaded

Driven by the need to control flow separations in highly loaded compressors, a numerical investigation is carried out to study the control effect of wavy blades in a linear compressor cascade. Two types of wavy blades are studied with wavy blade-A having a sinusoidal leading edge, while wavy blade-B having pitchwise sinusoidal variation in the stacking line. The influence of wavy blades on the cascade performance is evaluated at incidences from −1° to +9°. For the wavy blade-A with suitable waviness parameters, the cascade diffusion capacity is enhanced accompanied by the loss reduction under high incidence conditions where 2D separation is the dominant flow structure on the suction surface of the unmodified blade. For well-designed wavy blade-B, the improvement of cascade performance is achieved under low incidence conditions where 3D corner separation is the dominant flow structure on the suction surface of the baseline blade. The influence of waviness parameters on the control effect is also discussed by comparing the performance of cascades with different wavy blade configurations. Detailed analysis of the predicted flow field shows that both the wavy blade-A and wavy blade-B have capacity to control flow separation in the cascade but their control mechanism are different. For wavy blade-A, the wavy leading edge results in the formation of counter-rotating streamwise vortices downstream of trough. These streamwise vortices can not only enhance momentum exchange between the outer flow and blade boundary layer, but also act as the suction surface fence to hamper the upwash of low momentum fluid driven by cross flow. For wavy blade-B, the wavy surface on the blade leads to a reduction of the cross flow upwash by influencing the spanwise distribution of the suction surface static pressure and guiding the upwash flow.

The compound bowing design in a highly loaded linear cascade with large turning angle

2020 ◽  
Vol 234 (16) ◽  
pp. 2323-2336
Author(s):  
Xingxu Xue ◽  
Songtao Wang ◽  
Lei Luo ◽  
Xun Zhou
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Side Effect ◽  
Adverse Pressure Gradient ◽  
Suction Surface ◽  
Turning Angle ◽  
Linear Cascade ◽  
Velocity Triangle ◽  
Highly Loaded

Numerical simulation was carried out to study the influences of blade-bowing designs based on a highly loaded cascade with large turning angle, while the compound bowing design showed much lower endwall loss than the conventional design in this study. Generally, it showed that the increased turning angle would strengthen the adverse pressure gradient on the suction surface, so the side effect of negative blade bowing angle would be enhanced because of the reduced flow filed stability near suction–endwall corner. However, the positive corner bowing angle that applied in the compound bowing design would enhance the flow field stability near the suction–endwall corner by adjusting spanwise pressure gradient and velocity triangle, so the side effect of negative blade bowing angle would be suppressed and lead to weaker secondary flow. In detail, the blade bowing angle (as well as the corner bowing angle in the conventional bowed cascades) was varied from −5° to −30° in this study, while the reductions of the loss coefficient in the compound bowed cascades were about 0.662.16 times higher (the absolute differences were about 0.0067 0.0097) than the corresponding conventional bowed cascades. Moreover, the Reynolds number and Mach number at the outlet plane were kept at 2.4 × 105 and 0.6, respectively, during the bowing design to ensure the comparability.

Investigation on the Highly Loaded Helium Compressor Based on Helium Thermophysical Properties: Part B — The Loss Analysis of Highly Loaded Axial Helium Compressor

2017 ◽  
Author(s):  
Zhitao Tian ◽  
Qun Zheng ◽  
Bin Jiang ◽  
Qingfang Zhu
Keyword(s):  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Tip Clearance ◽  
Specific Power ◽  
Compressor Cascade ◽  
Loss Mechanism ◽  
Air Compressor ◽  
Loss Analysis ◽  
Profile Loss ◽  
Highly Loaded

Helium compressor is a main component of high temperature gas reactor (HTGR) helium power conversion unit, and its performance has significant effects on the power output and cycle efficiency. In this paper, the flow loss analysis of highly loaded axial helium compressor is carried out using a computational fluid dynamics (CFD) program at both design and off-design point. To understand the loss mechanism of the highly loaded helium compressor, special attention is paid to the tip clearance loss, profile loss and the end wall loss. As is well-known, when increasing the backpressure, the specific power and adverse pressure gradient of general air compressor cascade increase as well. But the specific power and adverse pressure gradient of the highly loaded design helium compressor in this paper will decrease with the backpressure increasing due to the new velocity triangle. So the loss characteristics of the highly loaded helium compressor are different from that of air compressor. From the three-dimensional viscous numerical results, the profile loss is the most important loss source of the highly loaded helium compressor. The proportion of the highly loaded helium compressor profile loss is more than 50%.

Vortex Structures for Highly-Loaded Subsonic Compressor Cascades With Slot Injection

2017 ◽  
Author(s):  
Huanlong Chen ◽  
Huaping Liu ◽  
Dongfei Zhang ◽  
Linxi Li
Keyword(s):  
Suction Side ◽  
Compressor Blade ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Vortex Control ◽  
Analysis Theory ◽  
Numerical Simulation Methods ◽  
Linear Compressor Cascade ◽  
Highly Loaded

A promising flow analytical way to offset the respective shortcomings for the experimental measure and numerical simulation methods is presented. First, general topological rules which are applicable to the skin-friction vector lines on the passage surface, to the flow patterns in the cross-section of the cascade as well as on the blade-to-blade surface were deduced for the turbomachinery cascades with/without suction/blowing slots in this paper. Second, the qualitative analysis theory of the differential equation was used to investigate the distribution feature of the flow singular points for the limiting streamlines equation. The topological structure of the flow pattern on the cascade passage surfaces was discussed in detail. Third, the experiment and numerical simulations results for a linear compressor cascade passage with highly-loaded compound-lean slotted blade, which were combined to topologically examine the flow structure with penetrating slot injections through the blade pressure side and suction side. The results showed that the general topological rules are applicable and effective for flow diagnosis in highly-loaded compressor blade passage with slots. Finally, an integrated vortex control model, in which the blade compound-lean effect and the injection flow through the slots were coupled, was presented. The model shows that reasonable slot injection configurations can effectively control the concentrated shedding vortices from the suction surface of a highly-loaded compressor cascades passage, thereby the aerodynamic performance for the blade passage is remarkably improved. The present work provides a novel theoretical analysis method and insights of the flow for the turbine blade passage with cooling structures, aspirated compressor blade passage and other applications with new flow control configurations in turbomachinery field.

Numerical Investigation of Corner Separation on Compressor Cascade

2013 ◽  
Author(s):  
Jing Ling ◽  
Xin Du ◽  
Songtao Wang ◽  
Zhongqi Wang
Keyword(s):  
Pressure Gradient ◽  
Pressure Distribution ◽  
Separation Zone ◽  
Adverse Pressure Gradient ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Corner Separation ◽  
Pressure Point ◽  
Static Pressure Distribution ◽  
Blade Thickness

This paper studied the effects of suction surface corner separation on the aerodynamic performance and the effects of the blade parameters on suction surface corner separation in rectangular cascade. Corner separation alters the static pressure distribution on the suction surface, establish a C-Shape pressure distribution along spanwise, compared with open separation, closed separation intensifies the C-Shape pressure distribution, increases the streamwise adverse pressure gradient on the suction surface after the lowest pressure point. The diffusion capability in a closed separation was significantly lower than in an open separation on the separation zone, loss was larger than open separation. The changes of blade parameters have great effects on corner separation, not only affect the scale of separation zone, even they will change the separation form. This study show that with the increase of the blade thickness, the maximum thickness position moving afterwards and the increase of the deflection of mean camber line, the streamwise adverse pressure gradient on the suction surface after the lowest pressure point increase, the scale of separation zone increase, even the separation type changes from open separation to closed separation.

The Influence of Blade Negative Curving on the Endwall and Blade Surface Flows

1995 ◽  
Author(s):  
Zhongqi Wang ◽  
Wanjin Han
Keyword(s):  
Static Pressure ◽  
Adverse Pressure Gradient ◽  
Vortex Sheet ◽  
Front Part ◽  
Blade Surface ◽  
Suction Surface ◽  
Turning Angle ◽  
Pressure Surface ◽  
Low Aspect Ratio ◽  
Blade Cascade

In order to explore the mechanism reducing the energy losses by use of negative curved blades, an experiment was carried out on turbine rectangular cascades with straight and negative curved blades of high turning angle and low aspect ratio. Ink trace technology was employed to show the flows on the endwalls and blade surfaces. The pressures were measured in detail with static pressure taps on the endwalls and blade surfaces. Experimental results indicate that when negative curved blades are used, a separating saddle of inlet boundary layers goes forward into the passage and approaches the pressure surface, as the streamwise adverse pressure gradient on the cascade inlet endwall becomes lower, compared with that of straight blade cascade. In addition, the static pressure contours are almost parallel lines perpendicular to the endwall on the front part of the suction surface and the curves which internal normals with the positive slopes near the endwall direct to the midspan from high pressure to lower pressure on the middle, this leads to the separation of free vortex sheet pattern on the suction surface. As a result, it is delayed that the separation lines converge towards midspan.

Flow physics of highly loaded tandem compressor cascade with non-axisymmetric endwall profiling

2020 ◽  
pp. 095765092098310
Author(s):  
Zhiyuan Cao ◽  
Wei Guo ◽  
Cheng Song ◽  
Bo Liu
Keyword(s):  
Static Pressure ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Blade Loading ◽  
Tandem Configuration ◽  
Blade Passage ◽  
Corner Separation ◽  
Axial Location ◽  
Highly Loaded

Tandem configuration is an effective methodology to reduce flow separation on compressor blade suction surface and to improve blade loading. However, in modern highly loaded cases, corner separation remains as its single blade counterpart. In this study, non-axisymmetric endwall profiling (NAEP) was utilized in a highly loaded tandem cascade (diffusion factor D = 0.69), aiming at reducing its severe corner separation and revealing the unique flow mechanism while NAEP is utilized in tandem cascade. NAEP was designed in both forward (F) blade and rare (R) blade separately, and was investigated numerically in tandem environment. Results show that, NAEP in F blade passage can effectively eliminate the corner separation and reduce loss generation, whereas NAEP in R blade passage has no positive effect on corner separation and even promotes loss production. The optimal NAEP approximately removes the corner separation completely, with loss coefficient reducing by as much as 37.8%. The optimal NAEP for the tandem cascade features optimal axial location at the origin of corner separation. There is an optimal NAEP height (0.02 of blade height), under which NAEP can achieve pretty good control effect while the peak of NAEP varies in a large axial location range. In the tandem configuration, it is found that NAEP transfers blade loading from R blade to F blade; the static pressure increases significantly for the entire cascade, but the static pressure distribution of F blade does not exhibit as the design intent of NAEP. In addition, it is interesting to find that the flow turning near endwall reduces after endwall profiling, which is unique in tandem cascade and is contrast to the view on conventional configuration. On the contrary, NAEP in R blade has no influence on the corner separation of the tandem cascade; due to the decrement of cross-passage pressure gradient for R blade, the flow overturning near endwall reduces.

Effects of Boundary Layer Suction on the Performance of Compressor Cascades

2006 ◽  
Author(s):  
Fu Chen ◽  
Yanping Song ◽  
Huanlong Chen ◽  
Zhongqi Wang
Keyword(s):  
Boundary Layer ◽  
Flow Rate ◽  
Flow Behavior ◽  
Aerodynamic Performance ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Boundary Layer Suction ◽  
Suction Flow ◽  
Suction Slot ◽  
Highly Loaded

The effects of boundary layer suction on the aerodynamic performance of compressor cascade are mainly determined by: (1) the location of the suction slot; (2) the suction flow rate; (3) the suction slot geometry; and (4) the aerodynamic parameters of the cascade (e.g. solidity and incidence). In this paper, an extensive numerical study has been carried out to investigate the effects of these influencing factors in a highly-loaded compressor cascade by comparing the aerodynamic performance of the cascade in order to give guidance for the application of boundary layer suction to improve the performance of modern highly-loaded compressors. The results show that boundary layer suction alleviates the accumulation of low-energy fluid at suction surface corners and enhances the ability of flow turning, and this improvement in flow behavior depends on the location of the suction slot and the suction flow rate. When the location of the suction slot and the suction flow rate are fixed, as the cascade solidity decreases from 1.819 to 1.364 and 1.091, the cascade total pressure loss is reduced at most by 25.1%, 27.7% and 32.9% respectively, and the cascade exit flow deviation is decreased by 3.1°, 4.2° and 5.0° accordingly. Moreover, boundary layer suction also has the largest effect in the cascade with smaller solidity at large positive incidences, which means that boundary layer suction is an effective way to widen the stable operating range of the highly-loaded compressor cascade. The suction slot geometry is described by the suction slot width and the suction slot angle with respect to the direction normal to the blade suction surface. The results show that the flow behavior is improved and the endwall loss is reduced further as the increase of the suction slot width. The suction slot angle has an obvious influence on the pressure inside the slot, therefore, should be considered in the design of the suction slot since the maximum pressure inside the slot is usually required.

Effect of Boundary Layer Suction on the Corner Separation in a Highly Loaded Axial Compressor Cascade

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Tian Liang ◽  
Bo Liu ◽  
Stephen Spence
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Axial Compressor ◽  
Compressor Cascade ◽  
Flow Uniformity ◽  
Suction Surface ◽  
Corner Separation ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Highly Loaded

Abstract Control of corner separation in axial compressor blade rows has attracted much interest due to its potential to improve compressor efficiency and the energy utilization in turbomachinery. This paper investigates the effectiveness and mechanisms of boundary layer suction in controlling the corner separation of a highly loaded axial compressor cascade. Numerical simulations have been carried out to investigate the effect of different suction schemes on the loss downstream of the cascade and the change in incidence characteristics with the variation of the suction flowrate. The results show that the effectiveness of flow suction in controlling the flow separation depends heavily on the proportion of the blade for which it is applied. It was found that suction along part of the blade span on the suction surface could effectively remove the separation at the region of the span influenced by the suction slot. However, this resulted in a deterioration of the flow field at other parts of the span. The full-span suction scheme on the suction surface not only eliminated the separation of the boundary layer in the middle of the blade but also significantly improved the flow uniformity near the end-wall. Despite the improvement in flow uniformity using the full-span suction scheme, a three-dimensional (3D) corner separation still existed due to the strong cross-passage pressure gradient. To improve the flow field uniformity further, two combined suction schemes with one spanwise slot on the suction surface and another slot on the end-wall were designed in order to fully remove both the separated flow on the blade suction surface and the 3D corner separation. It was found that the total pressure loss coefficient was reduced significantly by 63.8% with suction flowrates of 1.88% and 0.82% for the slots on the suction surface and the end-wall, respectively. Further work showed that the behavior of the loss coefficient is different as the combination of suction flowrates is changed for different incidence. The cascade loss at high incidence operation can be more effectively reduced with suction control on the end-wall. When implementing combined suction, it is necessary to determine the best combination of suction flowrate according to the incidence level.

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