Backsweep Angle Research Articles

DEM simulation of subsoiling in tropical sugarcane fields: Effects of opposing subsoiler design and model parameters

During the subsoiling operation of clayey soil in sugarcane fields in tropical areas, there are key limitations such as high resistance caused by high adhesion and unsatisfactory subsoiling effects of machines and tools. To address these issues, this study first explored the machine's structural characteristics using a mechanism analysis method to identify key optimization parameters. Then, simulation tests were conducted based on the root-soil complex model. Single factor analysis was conducted to evaluate the effects of backsweep angle, plow spacing, and penetration angle on tillage resistance and soil disturbance, determining their optimal ranges. Finally, a multi-factor orthogonal rotation combination experiment was designed using Box-Behnken theory to optimize the subsoiler's structural parameters. The regression analysis results show that the optimized model significantly improves the reliability of simulation results. Field verification test results show that under the conditions of a sweep angle of 50°, a plow spacing of 60 cm, and a soil penetration angle of 45°, the average tillage resistance of subsoiling operations is significantly reduced to 76.2 kN, and the amount of soil disturbance is reduced to 1780cm². The optimization reduced tillage resistance and soil disturbance by 34.42% and 30.50% respectively, significantly improving the subsoiling performance. To our knowledge, this is the first work applying discrete element methods to subsoiling operations in red clay soils in sugarcane growing areas. The proposed machine structure has higher efficiency and better performance, providing an effective reference for the design and application of sugarcane field subsoiling machinery.

Data-Driven Radial Compressor Design Space Mapping

Abstract Estimates of turbomachinery performance trends inform system-level compromises during preliminary design. Existing empirical correlations for efficiency use limited experimental data, while analytical loss models require calibration to yield predictive results. From a set of 3708 radial compressor computations, this paper maps efficiency as a function of mean-line aerodynamics, and determines the governing loss mechanisms. An open-source turbomachinery design code creates annulus and blade geometry, then runs a Reynolds-averaged Navier–Stokes simulation for compressors sampled from the mean-line design space. Polynomial surface fits yield a continuous eight-dimensional representation of the design space for analysis, predicting efficiency with a root-mean-square error of 1.2% points. The results show a balance between surface dissipation in boundary layers and mixing loss due to casing separations sets optimum values for inlet Mach number, hub-to-tip ratio, de Haller number, and backsweep angle. Surface dissipation drives the effect of flow coefficient, with high surface areas at low values, and high velocities at high values. Compact compressor designs are achieved by increasing inlet Mach number, reducing hub-to-tip ratio, and minimizing the radial loading coefficient—all of which reduce efficiency approaching design space boundaries. An interactive web-based tool makes the results available to practising engineers, demonstrating large ensembles of automated designs and simulations as a higher-fidelity replacement for legacy empirical correlations in preliminary design.

Study on the Influence of Blade Outlet Backsweep Angle on Performance of Impeller

As an important parameter of compressor impeller, the design value of blade outlet backsweep angle has a great influence on the performance of impeller. In this paper, six impellers with blade outlet backsweep angle β2B equal to 0°, 10°, 20°, 30°, 40°, and 50° were designed to evaluate the influences of impeller backsweep angle β2B on the performance, characteristics of gas flow and equivalent stress using computational fluid dynamics (CFD) and finite element analysis (FEA). Results indicated that the performance curve for the outlet backsweep blade angle β2B of 50° has the largest stable operating range. The isentropic efficiency of the impeller with backsweep angle β2B equal to 40° is 16.8% - 25.9% higher than that of the impeller with backsweep angle β2B equal to 0°. When the blade outlet backsweep angle is 30°, the equivalent stress distribution of the impeller is more uniform, the maximum equivalent stress is the smallest.

НАПОРНАЯ ХАРАКТЕРИСТИКА ЦЕНТРОБЕЖНОГО КОМПРЕССОРА МАЛОРАЗМЕРНОГО ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ НА ОСНОВЕ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Shown the possibility of using the standard ANSYS CFX hydrodynamic software package for calculating the gasdynamic characteristics of the centrifugal compressor impeller of micro turbojet engines with different options for profiling blades which based on physical and numerical modeling. Presented a methodology for designing the impeller of a centrifugal compressor based on solving the inverse problem of gas dynamics. As a result of a numerical study, the head coefficient of various forms of the impeller was obtained and presented the dependences of the head coefficient and efficiency on the blade back sweep angle 2 β . b The article discusses the effect of the blade back sweep angle 2 β b on the compressor efficiency and the head characteristic for three different values of the blade back sweep angle 2 β b for example, the impeller with the back sweep angle  2 β b and with the radial blades  2 β 90 b and with blades bent forward  2 β b The centrifugal compressor was designed using Vista CCD programs in one-dimensional computing and Fluid flow CFX in three-dimensional computing. For blade profiling, the BladeGend program was used with different profiling options in order to improve compressor efficiency. The computational grid and the construction of a structured hexahedral mesh for the impeller was carried out in Ansys Turbogrid and the SST model of turbulence was selected in the calculation, which, with sufficient grinding of the mesh at the walls, adequately simulates separated flows at the channel walls, as well as the flow in the flow core. When constructing a grid along the walls between the channel blades, the parameter y + was controlled, which should not exceed 2. It is permissible to use a coarser grid in the flow core compared to the grid near the walls. The design grid of the impeller consists of 350000 elements.

Direction for High-Performance Supercritical CO2 Centrifugal Compressor Design for Dry Cooled Supercritical CO2 Brayton Cycle

To overcome the degradation of the cycle efficiency of a supercritical carbon dioxide (S-CO2) Brayton cycle with dry cooling, this study proposes an improved design of an S-CO2 centrifugal compressor. The conventional air centrifugal compressor can achieve higher efficiency as backsweep angle increases. However, the structural issue restricts the maximum allowable angle (−50~−56°). In this study, an S-CO2 centrifugal compressor performance was examined while changing the backward sweep angle at impeller exit to study if the previous optimum backsweep angle for an air centrifugal compressor is still valid when the fluid has changed. It is shown through an analysis that an S-CO2 centrifugal compressor can achieve the highest efficiency at −70° backsweep angle, which is greater than the typical design value. The S-CO2 centrifugal compressor is less restricted from a structural integrity issue because it has low relative Mach number regardless of the low sound speed near critical point (Tc = 304.11 K, Pc = 7377 kPa). It is also shown in the paper that the variation of compressibility factor does not impact on its total to total efficiency since its Mach number is still lower than unity. Finally, it is also shown that a backward sweep impeller can achieve higher pressure ratio and operate stably in wider range as the mass flow rate is decreased. As further works, the suggested concept will be validated by the structural analysis and the compressor performance test.

Numerical investigation & comparison of a tandem-bladed turbocharger centrifugal compressor stage with conventional design

Extensive numerical investigations of the performance and flow structure in an unshrouded tandem-bladed centrifugal compressor are presented in comparison to a conventional compressor. Stage characteristics are explored for various tip clearance levels, axial spacings and circumferential clockings. Conventional impeller was modified to tandem-bladed design with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison with conventional design. Performance degradation is observed for both the conventional and tandem designs with increase in tip clearance. Linear-equation models for correlating stage characteristics with tip clearance are proposed. Comparing two designs, it is clearly evident that the conventional design shows better performance at moderate flow rates. However; near choke flow, tandem design gives better results primarily because of the increase in throat area. Surge point flow rate also seems to drop for tandem compressor resulting in increased range of operation.

Performance Evaluation of Tandem Bladed Centrifugal Compressor

A tandem-bladed centrifugal compressor which may have better performance than the conventional designs has not yet been studied for its potential turbocharger application. In addition, no numerical study of the entire stage (including tandem impeller and volute) has been performed to fully exploit the benefits of such design with variation in axial clearance levels, circumferential clocking fractions, blade geometries/angles, number of inducer blades and the thickness of inducer blades. This paper presents a thorough experimental and numerical study on the performance of a moderate pressure ratio, unshrouded, tandem-bladed centrifugal compressor in comparison to a conventional compressor of commercial use in china for turbocharger application. The characteristics of a tandem compressor are investigated and compared for various parameters. Conventional impeller was first modified into tandem-bladed design but with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison. The tandem design was further modified and investigated by (1) narrowing down the meridional gas passage, (2) using straight or concave leading edge of exducer, (3) reducing the thickness and (4) the number of inducer blades. CFD and experimental results were found to be in good agreement. The study reveals a shift of surge point towards lower mass flow rate in all cases of tandem designs. A maximum of 25% increase in the range of operation is observed. All in all there is little influence of the different circumferential clocking fractions and axial spacings of the inducer. Computational investigations of a modified tandem compressor with 20% reduction in inducer thickness have shown better performance than the conventional design. Use of fourteen inducer blades with reduced blade thickness can further enhance the performance.

Flank Milling 공법적용을 위한 자동차용 터보차져 임펠러의 설계체험

The performance of small-size impellers with ruled surfaces was investigated for flank milling over a wide speed range, using computational fluid dynamics analyses and gas bench tests. An impeller with a ruled surface was designed, manufactured, and tested to evaluate the effects of blade loading, the backsweep angle, and the relative velocity distribution on the compressor performance. The simulations and tests were completed using the same compressor cover with identical inlet and outlet channels to accurately compare the performance of the abovementioned impeller with a commercial impeller containing sculptured blades. Both impellers have the same number of blades, number of splitters, and shroud meridional profiles. The backsweep angles of the blades on the ruled impeller were selected to work with the same pinched diffuser as for a sculptured impeller. The inlet-to-exit relative velocity diffusion ratio and the blade loading were provided to maximize the flow rate and to minimize the surge flow rate. The design flow rate, rpm, were selected same for both impellers. Test results showed that for the compressor stage with a ruled impeller, the efficiency was increased by 0.32% with an extended surge margin without a reduction in the pressure ratio as compared to the impeller with the sculptured design. It was concluded that an increased relative velocity diffusion coupled with a large backsweep angle was an effective way to improve the compressor stage efficiency. Additionally, an appropriate blade loading distribution was important for achieving a wide operating range and higher efficiency.

블레이드 후향각이 원심압축기의 성능과 유동에 미치는 영향

This paper presents a numerical investigation of the influence of the blade back sweep angle on the performance and flow characteristics in a centrifugal compressor with a vaneless diffuser. Five impellers with different back sweep angles were tested in the flow simulations. It was found that a low back sweep angle could improve the total-to-total pressure ratio and the work coefficient over whole operating ranges. However, the flow field in an impeller with a low back sweep angle produced a more non-uniform velocity distribution at the impeller exit because the wake region was significantly increased. As a consequence, the impeller with a low back sweep angle caused a low diffuser performance.

Effect of Impeller Blade Loading on Compressor Stage Performance in a High Specific Speed Range

The authors previously found that compressor stage efficiency in a high specific speed range was significantly improved by employing an increased relative velocity diffusion ratio coupled with a high backsweep angle (Shibata et al., “Performance Improvement of a Centrifugal Compressor Stage by Increasing Degree of Reaction Optimizing Blade Loading of a 3D-Impeller,” ASME Paper No. GT2009-59588). In spite of such a high relative velocity diffusion ratio, the same surge margin as with a conventional design was able to be achieved by using a special front loading distribution with a lightly loaded inducer. In the present study, the blade loading distribution was further optimized in order to achieve a larger surge margin than previously. Four types of fully shrouded impellers were designed, manufactured, and tested to evaluate the effects of blade loading, backsweep angle, and relative velocity diffusion ratio on compressor performance. The design suction flow coefficient was 0.125 and the machine Mach number was 0.87. Test results showed that the developed impeller achieved 3.8% higher stage efficiency and 11% larger surge margin than the conventional design without reducing the pressure coefficient and choke margin. It was concluded that aft loading coupled with a high degree of reaction was a very effective way to improve surge margin as well as stage efficiency. Stator matching was also investigated by changing the design incidence angle, which was shown to have a little influence on surge margin in the present test results.

Performance Improvement of a Centrifugal Compressor Stage by Increasing Degree of Reaction and Optimizing Blade Loading of a 3D Impeller

Performance improvement of 3D impellers in a high specific speed range was investigated using computational fluid dynamics analyses and experimental tests. In order to reduce the loss production within the stator passages, the backsweep angle of the impellers was increased. At the same time, the inlet-to-exit relative velocity diffusion ratio was also increased by increasing the impeller exit width to prevent the reduction in the pressure ratio. Moreover, the blade loading distribution at the impeller shroud side was optimized to suppress the surge margin reduction caused by the increased relative velocity diffusion ratio. Five types of unshrouded impellers were designed, manufactured, and tested to evaluate the effects of blade loading, backsweep angle, and relative velocity diffusion ratio on the compressor performance. The design suction flow coefficient was 0.125 and the machine Mach number was 0.87. Test results showed that the compressor stage efficiency was increased by 5% compared with the base design without reducing the pressure coefficient and surge margin. It was concluded that an increased relative velocity diffusion ratio coupled with large backsweep angle was a very effective way to improve the compressor stage efficiency. An appropriate blade loading distribution was also important in order to achieve a wide operating range as well as high efficiency.

Impeller Blade Unsteady Aerodynamic Response to Vaned Diffuser Potential Fields

To predict the unsteady aerodynamic response of centrifugal compressor impeller blades to the potential field generated by the downstream vaned diffuser, a small perturbation model is developed that considers the number of impeller blades and diffuser vanes, the impeller blade backsweep angle, the impeller rotational speed, and the mass flow rate. The unsteady flow is analyzed in the impeller exit region and the vaneless diffuser space between the impeller and the diffuser leading edge radius, where the unsteady flow generated by the diffuser vane potential field is most significant. The unsteady flow perturbations are superimposed on an irrotational two-dimensional steady flow model, resulting in an analysis that is consistent with the small perturbation velocity potential equation. This model is then applied to a representative modern high speed impeller-vaned diffuser configuration.

Surface pressure measurements on a pitching swept wing in a water channel

We present the results of surface pressure measurements on a swept wing of NACA 0015 profile and a back sweep angle of 15 deg, which was pitched at a uniform angular velocity. The pitching axis was perpendicular to the flow direction so that the experiment simulated the pitch-up maneuver of a fixed-wing aircraft. The experiments were performed in an open-surface water channel. The object of the study was to understand the mechanics of vorticity production and dynamic stall in three-dimensional unsteady flows. The phase-locked pressure data which were obtained at several closely spaced spanwise locations of the wing were used to obtain information on the fluxes of spanwise and chordwise vorticity components, in addition to the usual information on the aerodynamic coefficients. The study showed that the three-dimensional dynamic stall over the slightly swept wing is less catastrophic and more gradual than the two-dimensional process over an unswept wing. Other important effects observed were a spanwise variation of the aerodynamic coefficients and the presence of spanwise periodicity in the production of vorticity following the onset of dynamic stall.