Blade Height Research Articles

Blade design and analysis of centrifugal compressors for the transcritical carbon dioxide refrigeration cycle

The compressor is one important component in the transcritical CO2 (carbon dioxide) refrigeration cycle. The CO2 compressor has a small volume at the same refrigeration capacity because its refrigeration capacity per unit volume is large. The radial compressor often used in the CO2 refrigeration cycle has complex internal flow and difficult blade modeling. The paper presented a new centrifugal compressor with radial flow, whose blades are straight and easy to process. Taking a single stage compressor blade for example, the effects of the velocity coefficient, energy head coefficient, rotational speed of the moving blade, blade height, inlet radius and radial distance of the blade on the efficiency and pressure ratio were studied. According to the conclusions, the paper designed and simulated the blades of two compressors of the transcritical CO2 two-stage refrigeration cycle. Simulation result showed that the efficiencies of the two compressors were respectively 84.97% and 87.23%.

Effect of blowing ratio, rotation, and film hole row location on film cooling on the suction surface of a rotating turbine blade

Experiments and simulations were performed to study the single-row film cooling performance on a turbine blade suction surface. Effects of blowing ratio, rotation, film hole row location, and the combine effects of the above three factors on single-row film cooling performance were studied. Totally three injection row locations of 12.4% S, 23.2% S, and 34% S were taken into consideration, where S refers to the suction side streamwise length. Experiments were carried out under turbine speeds of 400rpm, 600rpm, and 800rpm respectively with average blowing ratios change in the region of 0.5 to 1.5. Rotational Reynolds number corresponding to the turbine speeds was 3.57 × 105, 5.36 × 105, and 7.15 × 105. Pressure sensitive paint (PSP) technique was employed in obtaining film cooling effectiveness distribution. To assist explain the experimental results, numerical simulations were performed to acquire the mainstream and coolant jet flow field and local blowing ratio of each film hole. Results showed that film traces on the suction surface are bent toward the blade mid-span, and the downstream jet deflects more. Increasing blowing ratio and rotational Reynolds number will slightly reduce the inward film deflection. The local blowing ratios at hole exits are not evenly distributed along streamwise and spanwise direction under the combine effects of the three factors, which result in different film cooling performance at different streamwise locations and different blade heights.

Vortex structure and pressure fluctuation of a pump-turbine in pump mode using large Eddy simulation

Pump-turbines are usually used to ensure the stability of power system frequency and make up for the shortcomings of the intermittent nature of new energy such as wind energy. They are an important part of modern power systems. The Large Eddy Simulation (LES) method is used to study the vortex characteristics and pressure fluctuation intensity of the model pump-turbine working in pump mode. Results show that the wake vortex of the impeller has a great influence on the internal flow field of the pump-turbine, which is developed from the vortex structure near the suction surface of the blade. The distribution of trailing edge shedding vortex of guide vanes and shock vortex around tongue is closely related to the wake vortex of impeller. The wake vortex is divided into α and β according to the distribution range along the blade height. Their motion law and dissipation rate are different, and the influence of the α vortex on the flow field is greater. The distribution of pressure fluctuation intensity near the wall corresponds to the vortex structure, which indicated that the vortex is an important factor in pressure fluctuation. It is of great significance to improve the vortex structure inside the pump-turbine for safe and stable operation. The research in this paper can provide reference for the stable operation of the pump-turbine.

The influence of splitter blades and meridional profiles on the performance of small-scale turbopumps for ORC applications; analysis, neural network modeling and optimization

This work presents the influence of splitters on the performance of small-scale turbopumps for organic Rankine cycle applications numerically. Different design parameters, such as impeller diameter at the outlet, number of blades, blade angle at the trailing edge, and the length and location of the splitter blades, are studied for both shrouded and unshrouded impellers at tip clearance ratios of 0.05 and 0.10 (relative to blade height). The results suggest that splitter blades can increase impeller head coefficient and slip factors up to 10%–24% depending on the blade outlet angle. At the same time, the total efficiency is not influenced significantly. The CFD calculations predict that the placement of splitters in the middle of the blade channel leads to the maximum head coefficient for shrouded impellers. In contrast, for the tip clearance ratio of 0.10, a higher head coefficient is observed for placement closer to the suction side of the main blade. After that, different meridional profiles are studied to investigate their influence on the performance characteristics and mitigation of tip clearance effects. Profiles with a sharper change of cross-section area at the inlet rather than a linear change are found more advantageous, as higher head rise, total efficiency, and static efficiency are observed. In the end, the splitter blade profiles are optimized through techniques of design of experiments, leading to a 2.43% improvement in total efficiency. In contrast, the head rise remains constant, and static efficiency decreases by 0.49% for an impeller with a tip clearance ratio of 0.05.

Design of Savonius Double-Stage Wind Turbine, Capacity 300W

The use of fossil energy sources is increasing along with the increasing need to make reserves of fossil energy sources dwindling. Without the discovery of new reserves, oil in Indonesia will run out in the next nine years, natural gas will run out in 22 years, and coal will run out in 65 years. According to ESDM data, with current technology, the electricity potential from renewable energy reaches 432 GW, or 7-8 times the current total installed generating capacity. Wind energy (wind) is one of the renewable energy potentials, and the most widely available among all energy sources. Therefore, to anticipate the depletion of energy reserves that we have and to take advantage of the existing energy potential, research is being carried out on designing wind turbines so that we can take advantage of the existing energy potential, and not only depend on fossil energy which is depleting, and the main goal is know how to design and get the appropriate size and design of the turbine. From the design results obtained the value of the rotor diameter is 442 mm, the height of the rotor is 884 mm, the blade height is 439 mm, the diameter of the end plates is 486.2 mm, and the diameter of the shaft is 18 mm. As well as from the simulation, the maximum shaft stress value is 30,794 N/m2, the maximum displacement is 0.313 x10-4 mm, the minimum safety factor is 3.028, and the strain value is 0.114 x10-6, where these results can be used as a reference for the manufacture of this wind turbine later.

Aerodynamic Design Optimization and Analysis of Ducted Fan Blades in DEP UAVs

In order to reduce the dependence on fossil fuels, the concept of distributed electric propulsion (DEP) has been introduced. At present, there are a few studies on the small electric propulsion engines of DEP vertical take-off and landing (VTOL) UAVs. According to the design requirements of DEP VTOL UAV ducted fans, the aerodynamic design of a ducted fan is carried out in this paper. Firstly, the initial model is established by referring to theoretical derivations. Then, Bezier curves are used to control the mid-arc and thickness distributions of the blade profiles at different blade heights in order to realize the parameterization as design variables. Finally, the objective function that can represent the performance of the rotor is selected, and a multi-objective genetic algorithm is used to optimize the performance. The optimal results are obtained, and the aerodynamic characteristics are analyzed. Compared with the initial model, the total pressure ratio and isentropic efficiency of the optimized model are increased by 5.3% and 7.8%, respectively, reaching 1.20 and 90.37%. Meanwhile, the aerodynamic performance of the optimized model is improved, indicating that the performance of the rotor is significantly enhanced and that the design task is completed.

An Efficient Approach for Parametric Modeling and Prediction of the Hollow Blade Manufacture Shape

In recent years, hollow fan blades have been widely used to meet the requirements of aeroengines for lightweight and better performance. However, the hollow fan blade will change from the manufacture shape to the operating shape with large deformations during operation. This deviation, if neglected, will lead to deceptive results for structural and aerodynamic analysis. However, the existing methods have low prediction accuracy or require a lot of calculation in case of large deformations. In this paper, an iterative method for parametric modeling, automatic generation of finite element model, and hot-to-cold analysis of an H-shaped hollow fan blade are proposed. The accuracy and efficiency of the traditional uncoupling (UCM) and weak coupling methods (WCS), as well as the proposed strong–weak coupling method (SWCS), are compared with the strong coupling method (SCU) as a reference. Results show that improvements in the prediction accuracy can be made by the SWCS method, and the error of the maximum blade deformation is 2.3%, while the error of the UCM method and WCS method is 30% and 12%, respectively. An excellent agreement can be observed between the SWCS and SCU methods in the whole blade height with errors of 2%~5%, and the calculation time of the SWCS method is only 2.5% of the SCU method, which is reduced from 7200 min to 180 min, making it possible to conduct the hot-to-cold analysis at the design stage.

CONTROL OF DYNAMIC TRIM FOR PLANING VESSELS WITH INTERCEPTORS IN TERMS OF COMFORT AND MINIMUM DRAG

Nowadays, interceptors are often used to decrease total resistance and enhance comfort by reducing dynamic trim for high-speed planing vessels. They can be controlled manually as well as automatically by using a suitable closed-loop control system. Thus, in the present study, an automatically controllable system is presented to minimize the total resistance by reducing the dynamic trim in calm water. To reach this aim, a mathematical model which can represent the 2 degree of freedom vertical motion of a prismatic planing vessel is presented. The coefficients used in the model are calculated by using the Savitsky method. The standard dynamic trim angle and the optimum ones in terms of resistance are calculated by using the same method. For control action, a linear full state feedback control strategy (linear quadratic regulator) is applied, and instantaneous blade heights are found considering the change in forward speed. Therefore, the control-oriented model is able to change the blade height to reach the optimum trim angle in terms of the total resistance of the vessel for different forward speeds and speed profiles. The results show that the designed linear quadratic regulator control strategy is successful for reference trim tracking problems.

An Effective Impeller Design for Pump

The impeller of a centrifugal pump plays an important role because it determining the flow rate and efficiency of the pump. The efficiency of the pump is determined by the design of the impeller design. Under filing is one of the method for removing material from the underside of the impeller vane at the exit. Under filing also increases the pump head. The design involves having a blade height that is lower than the nominal impeller diameter, which can lead to reduced power consumption, improved flow characteristics, and decreased noise and vibration compared to traditional impellers. The design of under filing impeller vanes can be optimized by various parameters, such as the blade angle, blade thickness, and number of vanes. Computational fluid dynamics (CFD) simulations and experimental testing can be used to optimise the design and ensure proper performance. The modified impeller should then be installed in a test rig that replicates the operating conditions of the pump or compressor. The test rig should be equipped with suitable sensors to measure flow rate, pressure, temperature, and power consumption. The performance of the modified impeller should be compared to that of the baseline impeller, and the improvement in efficiency should be quantified.

Parameters of the soil-holding part of the slurry spreader

The aim of the study is the theoretical substantiation of the parameters of the soil-holding part of the slitter for manure incorporation into the soil. A slitter with soil-holding part to the tool for application of organic fertilizers was developed. The basic principles and methods of classical mechanics, mathematical analysis and statistics were used in this study. The analytical dependences for determining the parameters of the soil-holding part of the creeper were obtained. The length of the soil-holding part of the creeper depends on the speed of the machine, the angle of installation and the height of the jogger blade, the angle of the natural slope of the soil, the coefficient of friction of the soil and manure, and also their fall height. It is set that at an angle of friction of soil 23-37º, an angle of a natural slope of soil 30-41º and speed of unit movement 1,4 m/s, the length of a soil-holding part is equal 0,15-0,25 m.

Effect of Interstage Pipeline on the Performance of Two-Stage Centrifugal Compressors for Automotive Hydrogen Fuel Cells

At present, two-stage centrifugal compressors based on air bearing and high-speed motor technology are widely used in automotive hydrogen fuel cells. The low-pressure stage and high-pressure stage of the compressor are directly connected through an interstage pipeline, thus the structure of the interstage pipeline has an important influence on the aerodynamic performance of the compressor. In this work, a two-stage compressor with three different interstage pipelines were investigated experimentally and numerically. Results show that affected by the interstage pipeline bend section, the flow distortion will be induced at the impeller inlet of the high-pressure stage, and the distortion intensity changes with the pipeline structure. Among the three models, the EPC (elbow pipe change) model induces the most intense total pressure distortion at the condition of 80 kr/min and 130% mass flow rate, resulting in an efficiency reduction of 2 and 1.5 percentage points compared with the SPC (straight pipe change) and the TPC (total pipe change) model, respectively. Further research indicates that the upstream distortion has obvious influence on the downstream rotor blades. As the blade height decreases, the load becomes more uniform on the main blades, while the load extremum migrates to the trailing edge on the splitter blades. Finally, three models are tested, and their performance is compared at three typical rotational speeds., It is recommended that interstage pipelines similar to SPC models should be chosen to improve the two-stage compressor efficiency in the design.

Design and numerical analysis of supersonic radial-inflow turbines for transcritical ORC processes

Radial inflow turbine design was investigated for ORC systems having transcritical and close to critical point expansion. The analysis was carried out by combining the turbine design and turbine loss analysis with a thermodynamic cycle analysis. Six fluids were investigated, including three hydrocarbons and three fluorocarbons. The objective is to investigate in detail the design and efficiency of ORC turbines designed for transcritical cycles and close to the critical point expansions, where the real gas effects and the density changes along the expansion are significant. The results of the efficiency predictions gained by using the existing enthalpy loss correlations were compared against computational fluid dynamics simulations. It was revealed that using supercritical inlet state leads to more compact turbine wheel dimensions, increased turbine power, as well as increased rotational speed, when compared to subcritical processes. On the other hand, higher turbine efficiencies were reached with subcritical turbine inlet conditions. This is mainly because of the increased stator outlet Mach number, increased expansion ratio, and lower blade height at the rotor inlet with supercritical turbine inlet conditions, resulting into higher losses along the expansion.

Effect of Flow Rate on Regular Patterns of Pressure Load Distribution on Helico-Axial Pump Impeller Blade Surface

In this paper, the k-ω SST (Shear Stress Transport) turbulence model is employed to study the effect of flow rate on regular patterns of pressure load distribution characteristics on the helico-axial pump impeller blade surface. The results show that all the curves of pressure load distribution of helico-axial pump impeller blade surface at different blade heights under different flow rates show a similar trend of increasing first and decreasing then. At the impeller blade inlet area, with the increase of flow rate, the range of negative blade pressure load in this area gradually increases. When the pump runs under small flow rate conditions, within the range of relative position from 0 to 0.2 of the hub, the work capacity of the hub is obviously stronger than that of other areas of the impeller, while within the range of relative position from 0.2 to 1, the work capacity from hub to rim gradually enhances. With the increase in flow rate, the area with a strong work capacity of the hub gradually expands while the area with a strong work capacity of the rim gradually narrows. The research results can provide a theoretical reference for the optimization design of pump supercharging performance.

Dynamic response of turbine blade considering a droplet-wall interaction in wet steam region

The high-speed impact of liquid droplets on blades in wet steam region seriously affects the safe operation of steam turbine. For blade stability and response characteristics, most studies utilized ideal gas as working medium and few studies focused on the role of droplets in the flow field. In this study, both the distribution information of droplet particles in the flow field and the impact of droplet particles on blades were comprehensively considered. First, the droplet distribution at the last stage inlet was calculated, and then the droplet-wall interaction model was determined and loaded into calculation process. The pressure distribution on blade surface, blade force variation, mechanical properties, and further dynamic response characteristics of blade were analyzed with ideal gas and wet steam models, respectively, by using one-/two-way fluid-structure interaction. Results show that the blade displacement of leading and trailing edges under wet steam model reaches the maximum at near 80% blade height, and there is a low frequency amplitude corresponding to 460 Hz–470 Hz with the peak value in the range of 22Pa–26Pa. The variations of the maximum displacement and maximum equivalent stress of the blade with time are more intense under wet steam model compared with those under ideal gas model.

Thermodynamic performance of a radial-inflow turbine for ocean thermal energy conversion using ammonia

Aiming at the high-efficiency OTEC application, a 30 kW radial-inflow turbine using ammonia was constructed via the one-dimensional design. In addition, a 3D CFD simulation was carried out to research the turbine performance. Furthermore, the effects of blade tip clearance on the flow characteristic in turbine were elucidated and the turbine performance under the off-design conditions was examined. It is indicated that the performance of the designed turbine is satisfactory with a theoretical isentropic efficiency of 85.2% under the design condition. The leakage flow encounters the scraping flow after leaving the tip clearance, forming the vortexes in the cross-section of the flow passage, which decreases the turbine efficiency, and the best ratio of blade tip clearance to inlet blade height is suggested to be 0.04–0.06. When the rotational speeds deviated from the design value, the vortexes appear in the flow passage of the turbine, resulting in non-negligible impact loss of blade and the consequent efficiency reduction. At the design rotational speed, the turbine shows a good adaptability to the inlet temperature variations with the inlet temperature varying from T0 = 296K to T0 = 304K. When the inlet pressure increases, the rotational speed corresponding to the maximum efficiency is also increased.

Numerical investigation on the interactions between rotating detonation wave complex and planar turbine cascade

AbstractDue to pressure gain characteristics, the rotating detonation combustor (RDC) can be integrated into gas turbines by further improving the system's performance. The matching of unsteady flows in the RDC and turbine is a key challenge. Here, interactions in an RDC and planar turbine cascade are investigated using the unsteady Reynolds time‐averaged Navier‐Stokes method. The effects of the blade profiles on interactions between the oblique shock wave (OSW) and turbine cascade are analyzed, and the suppression effect of the turbine cascade on high‐frequency pressure oscillations is evaluated. The results show that the OSW interacts with the leading edge, pressure side, suction side, and trailing edge of the turbine stator and rotor blades, which generates complex wave systems in the cascade passage. The opposite propagation direction causes the OSW to be aligned or misaligned with the stator blade. The position of the OSW that operates on the turbine cascade changes, and two different wave system structures appear. The various pitches of the turbine cascade at different blade heights cause differing intensities and propagation directions in the reflected wave as generated by the action of the OSW and turbine cascade and the variable flow fields at different blade heights. The turbine cascade can significantly suppress the high‐frequency pressure oscillations, while the pressure amplitude attenuation rate can reach over 80% when the OSW propagates through the turbine cascade. These findings expound on the interaction mechanism between the rotating detonation wave complex and the turbine stator and rotor blades.

Study on Distribution Law of Gas Phase and Cavitation in the Pressurization Unit of Helical Axial Flow Multiphase Pump

Due to the irregular change of gas void fraction (GVF) in multiphase pumps, the pressure distribution in the pump is often uneven, which leads to the formation of low-pressure area and thus the occurrence of cavitation. In order to study the gas phase and cavitation distribution in the impeller region of a multiphase pump under different cavitation stages and GVF conditions, this study used numerical calculations as the main method and experimental verification as a secondary method to investigate the cavitation phenomenon in the pump under different stages and GVF conditions. The results showed that at different stages, both the volume fraction and the covering area of the gas phase were reduced to a certain extent with the increase in blade height, and the distribution law of the gas phase on the blade changed with the development of the cavitation stage, especially on the blade surface. At different GVFs, cavitation first occurred at the inlet of the blade SS and then extended along the blade streamline from the inlet to outlet, with the volume fraction and distribution of cavitation gradually increasing and then extending to the blade PS. The results showed that the presence of the gas phase inhibited the development of cavitation in the multiphase pump to some extent, and the cavitation performance of the multiphase pump was better in the presence of the gas phase than in pure water conditions. The results of this study provide a theoretical basis for improving the cavitation performance of multiphase pumps.

A novel damage identification method for flue gas turbine blades based on tip timing

Tip timing signal analysis has been applied to the online condition monitoring of high-speed blades. However, traditional tip timing analysis methods are not suitable for low-speed flue gas turbines. Therefore, this paper proposes a novel blade tip timing signal analysis method based on an investigation of the dynamic response characteristics of low-speed blades. First, the finite element modal theory is introduced to analyze the characteristics of blade damage. Second, an equivalent cantilever beam analysis model of flue gas turbine blades is established under complex environment and working conditions. In order to monitor the variation of local stiffness, a damage identification method based on the variation of the free end deflection of the equivalent cantilever beam is proposed. Finally, a rotating blade tip timing monitoring testing rig is established to verify the feasibility of the proposed method. The results show that the cracks originating at about 80% of the blade height have the greatest influence on blade stiffness, followed by blade root. The calculated blade damage parameters are 4.8464 mm and 3.7588 mm, and the crack influencing factors are 4.7476 and 3.6822, respectively, indicating that the change trend is consistent with the blade damage rules.

Numerical evaluation on the effects of interceptor layout and blade heights for a prismatic planing hull

Planing hulls are exposed to effects such as trim and resistance that have a negative impact on their hydrodynamic performances. Interceptors are one of the systems to find solutions to reduce these negative effects. In this study, the effects of the interceptor layout and blade height on the hydrodynamic characteristics of a planing hull were investigated numerically, at varying speeds. The hydrodynamic behaviors of the interceptor at a selected case were also investigated in regular head waves. To reach this aim, a scaled prismatic planing hull form equipped with an interceptor which is suitable for planing vessels 4–10 m in length was selected for all analyses. The numerical study was performed by using the CFD (Computational Fluid Dynamics) approach which uses a finite volume method to discretize the RANS (Reynolds Averaged Navier Stokes) equations. The uncertainty of the numerical study was also performed to show the credibility of numerical results. According to the results of the current study, it is found that the most proper location of the interceptors for lower resistance is between the chine and the centerline of the selected planing hull. It is also understood that the effects of the blade height are directly related to the forward speed. Besides, the resistance values can be decreased by using interceptors up to FnB =2.5, while the presence of the interceptor has a negative effect on resistance after this speed regardless of the layout and selected blade height. In addition to this, the best interceptor blade heights for lower resistance at different forward speeds of the planing hull form were found for the tested cases. For the selected case, it is shown that interceptors are also useful in regular waves in terms of reducing dynamic trim, sinkage and resistance.

Blade optimal design parameters determination

Introduction. In Kazakhstan in present time there is a large number of earthmoving works, which leads to an increase in the demand for earthmoving-transport machines (ETM), in particular bulldozers of different types. In various industries and construction projects, the fleet of foreign-made ETM is operated and constantly updated, including the CIS countries (Russia, Belarus, Ukraine, etc.) in various type-sizes. So at construction sites, including the construction of roads and railways, bulldozers are widely used: Caterpillar Corporation such as Cat (USA), Liebheer (Germany), Xuanhua Construction machinery Co, Ltd (HBXG) and ZoomLion and Shehwa (China); bulldozers ChTZ-UralTRAK (Russia), etc.The construction of roads and railways with a length of several thousand kilometers is impossible to imagine without the participation of a universal bulldozer. One of the most important components of the bulldozer is the working organ (WO) of the bulldozer.The performance of the bulldozer largely depends on what type of blade is installed on it. Capacity (maximum prism of drawing the soil) is one of the main characteristics determined by the height and width of the blade, and most manufacturers offer add-ons (visor) that makes it possible to increase the height of the blade. Increasing the blade height allows more material to be moved and reduces spillage through the top of the blade. On the other hand, increasing the volume of the drawing prism along the width of the blade is offered by the side cheeks, giving the blade the shape of a bucket. They do not allow the moving soil to fall out on the sides of the blade (side rollers), thereby increasing the volume of material being moved. However, an excessive increase in blade capacity will require additional power costs of the bulldozer during operation, which will cause an increase in loads on the machine components and accelerate the intensity of their wear, especially when the bulldozer moves up the slope.The volume of material moved by the blade in one pass depends, in addition, on the possibility of changing the angle of the blade relative to the vertical and horizontal plane. In modern blade designs, the positions of the angle of inclination are regulated by 4 or 6 positions, depending on the category of soil being developed. The purpose of this study is to optimize the geometric parameters and establish the trapezoidal shape of the blade, taking into account the interaction of its frontal surface with the formed maximum prism of drawing the soil.Materials and methods. As materials, the developed soil and the bulldozer blade were used, the process of their interaction was investigated with the maximum formation of the prism of drawing the soil before the dump, using the graphic-analytical method of research.Results. The process of interaction of the blade with the soil has been optimized by graphic-analytical means, the maximum (maximum permissible) parameters of the blade have been determined, taking into account the traction factor of the bulldozer and the category of the soil being developed.Discussion and conclusion. Until now, the geometric shapes of promising designs of the bulldozer blade were installed mainly by experimental means, without taking into account the contact of the blade area with the ground. Methods for determining the rational shape of the blade have not been developed, especially the theoretically grounded optimal parameters of the WO, taking into account the touch of the longitudinal section of the soil from the frontal surface of the blade. Methods for determining the optimal (adapted) shapes and geometric parameters of the WO were not developed, taking into account the contact of the frontal surface of the blade with the maximum drawing prism. Methods for calculating the optimal parameters of the perspective blade design adapted to the developed soil are proposed:– rational geometric shapes of both the frontal and cross-section of the blade are determined;– mathematical formulas for determining the optimal parameters of the new blade design are presented, namely:the height of the blade and the visor; width of the blade, visor and additional knife-extender;– defined: the perimeter of the blade, the width and height of the side roller, when forming the maximum prism of drawing the soil in front of the blade.