Effective strategy of non-axisymmetric endwall contouring in a linear compressor cascade

2021 ◽  
pp. 095441002110375
Author(s):  
Yuchen Ma ◽  
Jinfang Teng ◽  
Mingmin Zhu ◽  
Xiaoqing Qiang
Keyword(s):  
Pressure Gradient ◽  
Pressure Loss ◽  
Cross Flow ◽  
Operating Conditions ◽  
Control Effect ◽  
Corner Separation ◽  
Aerodynamic Pressure ◽  
Compressor Performance ◽  
The Cross ◽  
Endwall Contouring

The corner separation and the related secondary flow have great impact on the compressor performance, and non-axisymmetric endwall contouring is proved effective in improving compressor efficiency. The aim of the study is to improve the compressor performance by two local endwall contouring strategies at the design and off-design conditions. The endwall is parameterized and the Bezier curve is used to loft the endwall surface. The design of the contoured endwall is based on a multi-point optimization method to minimize the aerodynamic pressure loss. In order to identify the influence of the contoured endwall, a detailed flow analysis is conducted on four effective contoured endwall designs. The selected endwall geometries exhibit great control ability on the corner separation and significantly reduce the pressure loss at the two operating conditions. The directional concave near the leading edge can induce strong streamwise pressure gradient and accelerate the endwall flow, greatly reducing the cross-passage pressure gradient. The convex structures near the concave edge and at the outlet can block the cross-flow and prevent the interaction between the cross-flow and the suction corner flow. The benefit of the contoured endwall is mainly due to the re-distributed endwall static pressure and blocking of the cross-flow movement. In terms of the control effect, the shape of the concave also matters and better control effect is observed on the deep and wide concave. The flow will be guided by the concave, and the best suppression on corner separation is observed on the concave which follows the suction side. The results also indicate that the relief of the hub corner separation slightly increases the shroud pressure loss.

scholarly journals Enhancement of Impingement Heat Transfer With the Crossflow Normal to Ribs and Pins Between Each Row of Holes

2018 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Pressure Loss ◽  
Cross Flow ◽  
Experimental Results ◽  
Hole Density ◽  
Impingement Heat Transfer ◽  
The Cross ◽  
Flow Maldistribution

Impingement heat transfer investigations with obstacle (fins) on the target surface were carried out with the obstacles aligned normal to the cross-flow. Conjugate heat transfer (CHT) computational fluid dynamics (CFD) analysis were used for the geometries previously been investigated experimentally. A 10 × 10 row of impingement jet holes or hole density, n, of 4306 m−2 with ten rows of holes in the cross-flow direction was used. The impingement hole pitch X to diameter D, X/D, and gap Z to diameter, Z/D, ratios were kept constant at 4.66 and 3.06 for X, D and Z of 15.24, 3.27 and 10.00 mm, respectively. Nimonic 75 test walls were used with a thickness of 6.35 mm. Two different shaped obstacles of the same flow blockage were investigated: a continuous rectangular ribbed wall of 4.5 mm height, H, and 3.0 mm thick and 8 mm high rectangular pin-fins that were 8.6 mm wide and 3.0 mm thick. The obstacles were equally spaced on the centre-line between each row of impingement jets and aligned normal to the cross-flow. The two obstacles had height to diameter ratios, H/D, of 1.38 and 2.45, respectively. Comparison of the predictions and experimental results were made for the flow pressure loss, ΔP/P, and the surface average heat transfer coefficient (HTC), h. The computations were carried out for air coolant mass flux, G, of 1.08, 1.48 and 1.94 kg/sm2bar. The pressure loss and surface average HTC for all the predicted G showed reasonable agreement with the experimental results, but the predictions for surface averaged h were below the measured values by 5–10%. The predictions showed that the main effect of the ribs and pins was to increase the pressure loss, which led to an increased flow maldistribution between the ten rows of holes. This led to lower heat transfer over the first 5 holes and higher heat transfer over the last 3 holes and the net result was little benefit of either obstacle relative to a smooth wall. The results were significantly worse than the same obstacles aligned for co-flow, where the flow maldistribution changes were lower and there was a net benefit of the obstacles on the surface averaged heat transfer coefficient.

Three-dimensional laminar boundary layers in crosswise pressure gradients

1974 ◽  
Vol 66 (4) ◽  
pp. 641-655 ◽  
Author(s):  
J. H. Horlock ◽  
A. K. Lewkowicz ◽  
J. Wordsworth
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Free Stream ◽  
Three Dimensional ◽  
Cross Flow ◽  
Free Stream Velocity ◽  
Stream Velocity ◽  
Laminar Boundary Layers ◽  
The Cross

Two attempts were made to develop a three-dimensional laminar boundary layer in the flow over a flat plate in a curved duct, establishing a negligible streamwise pressure gradient and, at the same time, an appreciable crosswise pressure gradient.A first series of measurements was undertaken keeping the free-stream velocity at about 30 ft/s; the boundary layer was expected to be laminar, but appears to have been transitional. As was to be expected, the cross-flow in the boundary layer decreased gradually as the flow became progressively more turbulent.In a second experiment, at a lower free-stream velocity of approximately 10 ft/s, the boundary layer was laminar. Its streamwise profile resembled closely the Blasius form, but the cross-flow near the edge of the boundary layer appears to have exceeded that predicted theoretically. However, there was a substantial experimental scatter in the measurements of the yaw angle, which in laminar boundary layers is difficult to obtain accurately.

A Novel Multi-Stage Impingement Cooling Scheme—Part I: Concept Study

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Kexin Liu ◽  
Qiang Zhang
Keyword(s):  
Cross Flow ◽  
Target Surface ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Single Stage ◽  
Impingement Cooling ◽  
Flow Effect ◽  
Multi Stage ◽  
Cooling Design ◽  
The Cross

Abstract The impingement cooling for a modern gas turbine component, either a combustor liner or a high-pressure turbine blade, is often not as efficient as required due to strong cross-flow effect and coolant maldistribution. This paper reports a novel multi-stage impingement cooling scheme to effectively use the coolant and minimize the cross-flow effect. The design concept and general working mechanism are introduced in this Part I paper. The extra design flexibilities and optimization strategies are reported in Part II. Numerical simulations on conjugate heat transfer (CHT) were carried out to assess the flow structure and thermal performance between a typical single-stage cooling design and a three-stage cooling design at typical operating conditions. It has been observed that the novel multi-stage cooling design can reinitiate impingement jets at each stage, which greatly reduces the cross-flow impact and local thermal gradient. The staging of cooling air for the target surface also offers better utilization of the cooling capacity. Even by using 50% of the coolant designed for the single-stage impingement cooling, the multi-stage case can still sufficiently cool the target surface. The additional pressure loss penalty introduced in multi-stage design needs further efforts on design optimization.

Transverse Injection Into a Supersonic Cross Flow Through a Circular Injector With Chevrons

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Anand Raj Hariharan ◽  
V. Babu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Performance Metrics ◽  
Cross Flow ◽  
Operating Conditions ◽  
The Other ◽  
Total Pressure Loss ◽  
Minimal Impact ◽  
Transverse Injection ◽  
Flow Through

Results from 3D, compressible, unsteady Favre-averaged calculations of transverse injection into a supersonic cross flow are reported. Four injector geometries, namely, circular, wedge, diamond, and chevron, have been investigated. The effectiveness of the chevron injector is demonstrated by comparing performance metrics, such as degree of mixing and total pressure loss, against those of the other injectors. The results show that the chevron injector provides better mixing and spreading compared to other injectors, with almost the same total pressure loss. Furthermore, for the operating conditions studied, the chevron-penetration angle is shown to have a minimal impact on the mixing and the total pressure loss.

Corner Separation Control in a Highly Loaded Compressor Cascade Using Plasma Aerodynamic Actuation

2012 ◽  
Author(s):  
Yun Wu ◽  
Xiao-hu Zhao ◽  
Ying-hong Li ◽  
Jun Li
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Separation Control ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Corner Separation ◽  
Pressure Loss Coefficient ◽  
Highly Loaded

Corner separation, which forms over the suction surface and endwall corner of a blade passage, causes significant total pressure loss in highly loaded compressors. Plasma flow control, based on the plasma aerodynamic actuation, is a novel active flow control technique to improve aircrafts’ aerodynamic characteristics and propulsion efficiency. This paper reports computational and experimental results on using three types of plasma aerodynamic actuation (PAA) to control the corner separation in a highly loaded, low speed, linear compressor cascade. Reynolds-Averaged Navier-Stokes simulations were performed to optimize the PAA arrangement. The PAA was generated by a microsecond or nanosecond dielectric barrier discharge in wind tunnel experiments. The total pressure loss coefficient distribution was adopted to evaluate the corner separation control effect. The control effect of pitch-wise PAA on the endwall, in terms of relative reduction of the pitch-wise averaged total pressure loss coefficient in the wake, is much better than that of stream-wise PAA on the suction surface. When both pitch-wise PAA on the endwall and stream-wise PAA on the suction surface are turned on simultaneously, the control effect is the best among all three types of PAA. The main effect of pitch-wise PAA on the endwall is to inhibit the crossflow from neighboring pressure surface to the suction surface, whilest the main effect of stream-wise PAA on the suction surface is to inhibit the boundary layer accumulation and separation. Compared to microsecond discharge PAA, nanosecond discharge PAA is more effective at higher freestream velocity. The mechanisms for nanosecond discharge and microsecond discharge PAA are different for corner separation control.

Non-axisymmetric endwall profiling in a highly loaded compressor cascade

2018 ◽  
Vol 233 (3) ◽  
pp. 275-292 ◽  
Author(s):  
Zhiyuan Cao ◽  
Bo Liu ◽  
Ting Zhang ◽  
Yibing Xu ◽  
Hang Zhao
Keyword(s):  
Flow Field ◽  
Pressure Gradient ◽  
Position Effect ◽  
Suction Side ◽  
Axial Position ◽  
Design Strategies ◽  
Compressor Cascade ◽  
Control Effect ◽  
Corner Separation ◽  
Highly Loaded

Very few studies of non-axisymmetric endwall profiling in compressor have been conducted in published literatures. This study investigates the control mechanism of non-axisymmetric endwall on the flow field of a highly loaded compressor cascade and the guidelines for the design of non-axisymmetric endwall. First, CFD method was validated with existing experimental data. Then, the design method of non-axisymmetric endwall based on trigonometric function and Bezier curve was introduced. The design strategies of non-axisymmetric endwall considering axial position effect, height effect and different patterns of concave/convex were investigated in detail. Results show that non-axisymmetric endwall is an effective way to control the near endwall flow field of the compressor cascade. With the optimal non-axisymmetric endwall in this study, the loss coefficient of the cascade is reduced by 5.5%, and the cascade exhibited suppressed corner separation, reduced passage vortex and more uniformly distributed outflow angles. The optimal axial position of the concave was at 0.22 axial chord, which was near the onset of corner separation, so the best control effect was obtained. There is an optimal height for the concave of the non-axisymmetric endwall. A lower concave will not have sufficient effect on the cascade, whereas a higher concave will be detrimental on the contrary. It is indicated that the influence mechanism of non-axisymmetric endwall on the compressor cascade is basically derived from the superimposed effect of reduced cross-passage pressure gradient and increased spanwise inward pressure gradient. The cross-passage pressure gradient can be reduced by both concave on the suction side and convex on the pressure side of the endwall. However, concave can introduce spanwise inward pressure gradient, whilst convex can introduce spanwise outward pressure gradient. For better improving the performance of compressor cascades, non-axisymmetric endwall is suggested to be a concave on the entire endwall, which introduces both reduced cross-passage pressure gradient and increased spanwise inward pressure gradient.

Effect of operational modes on the removal of a synthetic organic chemical by powdered activated carbon during ultrafiltration

2001 ◽  
Vol 1 (5-6) ◽  
pp. 39-47
Author(s):  
Y. Matsui ◽  
A. Yuasa ◽  
F. Colas
Keyword(s):  
Activated Carbon ◽  
Cross Flow ◽  
Powdered Activated Carbon ◽  
Organic Chemical ◽  
Filtration Cycle ◽  
Dead End ◽  
Synthetic Organic Chemical ◽  
The Cross ◽  
Short Time ◽  
Operational Modes

The effects of operational modes on the removal of a synthetic organic chemical (SOC) in natural water by powdered activated carbon (PAC) during ultrafiltration (UF) were studied, through model simulations and experiments. The removal percentage of the trace SOC was independent of its influent concentration for a given PAC dose. The minimum PAC dosage required to achieve a desired effluent concentration could quickly be optimized from the C/C0 plot as a function of the PAC dosage. The cross-flow operation was not advantageous over the dead-end regarding the SOC removal. Added PAC was re-circulated as a suspension in the UF loop for only a short time even under the cross-flow velocity of gt; 1.0 m/s. The cross-flow condition did not contribute much to the suspending of PAC. The pulse PAC addition at the beginning of a filtration cycle resulted in somewhat better SOC removal than the continuous PAC addition. The increased NOM loading on PAC which was dosed in a pulse and stayed longer in the UF loop could possibly further decrease the adsorption rate.

Cake Formation in Cross-Flow Microfiltration Systems

1992 ◽  
Vol 25 (10) ◽  
pp. 149-162 ◽  
Author(s):  
V. L. Pillay ◽  
C. A. Buckley
Keyword(s):  
Cross Flow ◽  
Operating Conditions ◽  
Waste Waters ◽  
Domestic Waste ◽  
Time Curve ◽  
Good Correspondence ◽  
Operating Variables ◽  
Start Up ◽  
Turbulent Flow Regime ◽  
Cake Formation

Cross-flow microfiltration (CFMF) has potentially wide application in the processing of industrial and domestic waste waters. Optimum design and operation of CFMF systems necessitates a knowledge of the characteristic system behaviour, and an understanding of the mechanisms governing this behaviour. This paper is a contribution towards the elucidation and understanding of the behaviour of a woven fibre CFMF operated in the turbulent flow regime. The characteristic flux-time curve and effects of operating variables on flux are presented for a limestone suspension cross-flow filtered in a 25 mm woven fibre tube. The phenomena contributing to the shape of the flux-time curve are discussed. A model of the mechanisms governing cake growth and limit is presented. Predicted steady-state fluxes show a notably good correspondence with experimentally measured values. It is also found that the flux may not be uniquely defined by the operating conditions, but may also be a function of the operating path taken to reach the operating point. This is of significance in the start-up and operation of CFMF units.

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