Shaft Power Research Articles

Energy-saving mechanism and dynamic characteristics of blade angle adjustment in low head pumping system

To investigate the energy-saving mechanisms and dynamic characteristics of blade angle adjustment, this study proposes a novel research method via simulations, prototype and model testing. For stable conditions, the internal field, the external and energy characteristics of the pumping system with different blade angle are examined. The dynamic characteristics of the pumping system and the blade force characteristics during the adjustment process are also studied. The research results show that, under a certain net head, an appropriate impeller blade angle improves the flow state in the pump and conduits, decreasing the entropy production and providing suitable inlet circulation to reduce the hydraulic loss of outlet conduit, thereby improving the pumping system efficiency by 5–10 percentage points. During the adjustment process, there is an approximate 20-s delay in dynamic characteristics. Additionally, with the increase of the blade angle, the hydraulic torques for blade axis and pump shaft increase, thus increasing the blade adjustment force and shaft power. The adjusting force is found to be underestimated in the adjustment processes of decreasing the blade angle. Achievements of this paper contribute to high efficiency of pumping system and high reliability of blade adjustment devices and pump units.

Study on the Influence of Tip Clearance on Working Characteristics of High-Altitude Fan

To study the influence of tip clearance on the working characteristics of high-altitude fans, this paper takes the MIX-140 high-altitude fan as the research object. Five different tip clearance (TC) models are selected. The CFD method is used to analyze the changes in the working characteristics of the fan under different flow rates and TCs in ground and high-altitude environments. The reliability of the numerical method is verified through a fan test bench. The results show that the tip leakage flow caused by the TC will continuously deteriorate the working characteristics of the fan. Under the rated flow rate in the ground environment, for every doubling of the blade’s TC, the static pressure difference will decrease by 5%, the efficiency will decrease by 2%, and the power will decrease by 3%. In a high-altitude environment, the flow rate corresponding to the maximum shaft power point of the fan will continuously increase with an increase in the tip clearance, which will bring about additional energy consumption. For high-altitude fans, the deformation caused by the high-speed rotation of the impeller needs to be taken into account. Undoubtedly, it is advantageous to choose the smallest possible tip clearance value. The results of the analysis and test methods in this paper will provide a basis for designing the tip clearance of high-altitude fans.

Guideline for Large-Scale Analysis of Centrifugal Blower Using Wall-Resolved Large Eddy Simulation

Abstract To reduce the number of prototypes during product design and accurately predict unsteady phenomena occurring at off-design points, a method for accurately predicting the performance of centrifugal blowers through numerical analysis is required. This article presents a guideline for accurately predicting the performance of centrifugal blowers using compressible flow analysis with large eddy simulation (LES). In LES analysis, it is important to have a grid resolution that resolves the minimum vortex scale near the wall (referred to as wall-resolved LES) and to consider detailed geometry such as the length of the suction pipe. The calculations in this study used a model blower, which is a scale model of a single-stage centrifugal blower for use in industrial plants. The model blower was experimentally measured for various parameters such as the blower pressure coefficient, the static-pressure-rise coefficients of the impeller and vane-less diffuser, the shaft power, and the pressure fluctuations at the inlet of the impeller and the inlet of the vane-less diffuser. The results of these measurements were compared with those obtained from the wall-resolved LES. The study confirmed that the accuracy of performance prediction can be improved to less than a 4.0% error in the blower pressure coefficient at both design and off-design operating points by resolving the minimum vortex scale with 14.6 billion-grid elements and considering the detailed geometry.

Construction of data base containing flow field information under different blade placement of pumping station in digital twin

Abstract The data base in digital twin technology includes various data such as the structure, performance, and operating status of the physical object. And the data base is the key point for the construction of the digital twin system. However, the data bases of different digital twin systems usually contain different information. In this paper, the flow state of the pumping station under different angles of four blades is selected as the research object. The research methods in this paper mainly include Latin hypercube sampling, numerical simulation and neural network prediction. The Latin hypercube sampling is used to select the typical Angle difference model. The numerical simulation is used to obtain flow field information. The neural network prediction method is used to construct a complete data base. The study incorporates an actual large-scale mixed-flow pump station to head, efficiency, and shaft power as the prediction targets. It utilizes the different angle difference data of ten sets of four blades as the training set, forty sets of remaining samples as the experiment set, and employs the backpropagation neural network method for constructing the prediction network. By changing the experiment set and test set, the method can efficiently complete the construction of data base including actual test and numerical simulation, which provides a solid foundation for the construction of digital twin platform.

Effect of Axial Clearance Between Turbine and Guide Wheel on Hydraulic Performance of Mine Borehole Turbo Generator

Abstract In order to study the influence law of axial clearance between turbine and guide wheel on the performance of mine turbine generator. The three-dimensional unsteady internal flow and external characteristics of 8 kinds of turbine generator models with different coaxial clearance are calculated. The results show that: As the axial clearance coefficient between the turbine and the guide wheel increases, the pressure loss at the inlet and outlet of the guide wheel and turbine increases gradually, the torque and shaft power of the turbine are reduced, the hydraulic efficiency of turbine generator decreases gradually; The hydraulic efficiency of the turbine increases first and then decreases. Considering the external and internal flow characteristics comprehensively, the axial clearance coefficient between the turbine and the guide wheel is between 0.12 and 0.15, and the turbine generator performance is the best. It can provide some reference for the design optimization of Mine Borehole Turbo Generator.

Fault Detection on Short-Haul or Highly Dynamic Flights Using Transient Flight Segments

Abstract A machine learning-based approach is presented, which allows to detect persistent engine faults after a single flight. It utilizes transient in-flight measurements and a transient engine model. The time series of the residuals between the measured data and the data resulting from performance synthesis is evaluated using moving windows containing at least one transient segment. A continuous wavelet transformation and a pretrained convolutional neural network are utilized on the residuals for feature extraction. The fault detection is carried out via a one-class support vector machine, trained exclusively on nominal engine operation data. Therefore, the approach requires no a-priory knowledge of the effects of engine faults on the in-flight measurements. Under the assumption of persistent faults, all windows of a single flight, which contain at least one transient segment, are considered in order to improve the reliability of the fault detection. This approach is validated using measured data of a small helicopter engine that replicates the dynamic flight of the corresponding model helicopter on a ground test bed. Consequently, step changes as well as complex variations of the shaft power output are considered. Four standard gas path sensors are considered. The one-class support vector machine is used successfully to detect two types of total pressure sensor anomalies. Assuming a typical number of transient segments for an average short haul flight, it turns out that persistent faults can be detected within one flight with a probability of above 90%.

Data-driven approach for design and optimization of rotor–stator mixers for miscible fluids with different viscosities

Rotor–stator mixers (RSMs) are essential equipment used in the food, pharmaceutical, and cosmetic industries. The performance of RSMs is conventionally analyzed using three approaches based on empirical correlations and experimental and numerical analyses. This paper introduces a new approach based on a multifidelity data-driven framework for designing and optimizing RSMs that systematically combines elements of experimental and high-resolution computational fluid dynamics (CFD) models to train a machine learning model to predict RSM performance. It was subsequently coupled to an optimization solver based on a genetic algorithm. The developed framework was applied to a small-scale RSM with variable rotor blade radius, rotor speed, stator mesh width, and mass flow rate that is operated to mix two miscible fluids with different viscosities. The RSM was optimized at two regimes of low and high viscosities to achieve the best performance in terms of shaft power and mixing indices. The results demonstrate the successful application of the developed frameworks. The optimization of the mixing of high-viscosity fluids yielded a higher improvement than that for low-viscosity fluids. A decrease in shaft power of approximately 50% was obtained for the high-viscosity fluids, whereas the mixing indices increased up to 20% by the optimization of the geometrical input design parameters. The proposed framework can be advantageous for designers and operators at the industrial scale.

Fuel-economy-optimal power regulation for a twin-shaft turboshaft engine power generation unit based on high-pressure shaft power injection and variable shaft speed

Due to the high power-to-weight ratio characteristic of turboshaft engines, the power generation unit based on it holds immense potential in the hybrid electric propulsion system (HEPS) of flying cars. To mitigate environmental pollution and reduce fuel consumption, while enhancing the fuel economy of turboshaft engine power generation unit (TEPGU) across the entire power output range, this paper investigates a dual-motor electronic regulation architecture for twin-shaft TEPGU. According to the different variable combinations of TEPGU architecture, two modes and their respective fuel-economy-optimal power regulations are proposed. Initially, by considering the efficiency distribution of motors, we construct an Extended co-working balance model based on the Newton-Raphson method. Subsequently, different operating modes are proposed and discussed, studying the characteristic laws of the power generation unit under each mode. For the variable speed mode and the power split mode, this article proposes a shaft-speed-feature-projective searching (SFPS) method and a multi-dimensions-feature-projective searching (MFPS) method based on characteristic dimensionality reduction projection. Finally, a comparative analysis of the fuel-saving effects of the SFPS and MFPS regulation methods is conducted, and the reasons for enhancing fuel efficiency are discussed. The simulation results show that the model of TEPGU is in good agreement with the experimental data, and the error of specific fuel consumption(SFC) in the full power range is less than 5.7 %. Besides, comparative results indicate that the strategies based on MFPS and SFPS can achieve a maximum instantaneous fuel consumption reduction of 14.38 % and 10.82 %, respectively. The MFPS strategy exhibits a fuel consumption saving of 12.69 % throughout the driving cycle, demonstrating superior performance in fuel economy.

Performance enhancement on the three-port gas pressure dividing device by flow channel optimization of wave rotor

Wave-rotor-based gas pressure dividing (GPD) is a potential technology that can synchronously conduct gas compression and expansion. This study, proposes a novel curving flow channel of wave rotor (C-FCWR) for the three-port GPD device, aiming to settle the technical problem of traditional width-constant straight flow channels (WS-FCWR). A series of comparative hydrodynamics and thermodynamic analyses are conducted. For the optimized C-FCWR with a forward-curving angle of +10°, the flow vortex generation in the medium-pressure (MP) and low-pressure (LP) ports is rather limited, the shaft power is as low as -0.45 kW, the shock wave efficiency is beyond 99.8 %, and the expansion depth remains above 26.4 K, proving a great technical advantage. For the application feasibility of the optimized C-FCWR to working conditions, a compression ratio below 1.2 and an expansion ratio of 1.8 are conducive to the overall performance of the GPD device.

Fast and accurate modelling of twin-screw compressors: A generalised low-order approach

Twin-screw compressors (TSC) are commonly used in heat pump processes due to their robustness and flexibility. They exhibit two core properties, i.e. the swept volume and the built-in volume ratio (BVR), which heavily influence their capacity limits and off-design efficiency. This work presents a new low-order model (i.e. a polynomial model), which can accurately predict a TSC’s behaviour. The model uses the external pressure ratio and volumetric compressor inlet flow rate to calculate isentropic efficiency and compressor speed. The input parameters are normalised with a reference flow rate (calculated from the swept volume) and the BVR, respectively. This results in a generalised model of low numerical cost, which can be used for explorative studies independent of the specific machine size and BVR. A gain in computational speed by a factor of 375 is achieved compared to a semi-empiric reference model. The model displays very good predictive accuracy when used to predict the performance of machines with similar BVRs, but different sizes. A mean deviation from the manufacturer data of 4.29%, 0.88°C and 1.38% for the shaft power, the outlet temperature and the compressor speed can be observed, respectively. When there is a difference in size and BVR, the prediction accuracy is still reasonable but significantly declines for small and very large pressure ratios. Nevertheless, the proposed new approach extends the state-of-the-art by introducing a low-order model, which combines the advantages of low computational cost, high accuracy, physically correct predictions over a wide operational range and scalability to different machine capacities and BVRs. The validation for different fluids indicates a good general prediction accuracy relatively independent of the used fluid.

Performance characteristics of two-phase impulse turbines for energy recovery in thermal systems

The two-phase impulse turbine (TPIT) can improve the efficiency and economy of various thermal systems, because it can directly convert the internal energy of thermal fluids into the shaft power of the turbine with no needs of additional low-temperature sub-systems. However, current efficiency of reported TPITs is much lower than gas or water turbines, due to unknown characteristics of the two-phase flow in TPITs. This paper comprehensively analyzed the performance characteristics of a TPIT, which was used in the refrigeration system. CFD methods were employed to analyze the two-phase flow based on flashing models and validated with experimental results. Three average methods were used to derive the Euler power and compared with the output power derived by the torque on each blade, while the average method based on the modified factor can evaluate the Euler power accurately. The non-uniform flow caused by the nozzle position was significant, while the liquid film near pressure side and the shroud were also three dimensional and affected by wall effects. The liquid layer on the shroud was related to the negative torque on blade tips. Results presented in this paper are constructive for designing efficient thermal systems without additional energy recovery devices.

Energy characteristics of a deep-sea mining pump under solid-phase interaction

Deep-sea mining pumps (DMPs) are the crucial power equipment for the hydraulic lift deep-sea mining system. The efficiency and sustainability are greatly affected by the particle conveyance capacity and erosion pattern. To investigate the energy performance, particle conveyance capacity, and erosion pattern of the DMP, different inlet particle volume fraction (IPVF) schemes are investigated using the Euler-Euler method. The data indicates that as the IPVF increases, the head and shaft power increase gradually, and the flow rate at the highest efficiency is consistently 1.5Qd. Additionally, the fluctuation range of the conveyance capacity index decreases as the flow rate increases. At an IPVF of 15%, the particles exhibit a backflow phenomenon, resulting in poor particle conveyance capacity. As the flow rate increases, the erosion rate (ER) of the impeller (IMP) decreases and then increases, and the ER of the space guide vane (SGV) gradually decreases, resulting in a more stable flow state. The erosion distribution of the IMP blades is mainly concentrated on the suction surface. The erosion distribution on the SGV blades is primarily concentrated on the middle and rear of the pressure surface, as well as the middle and front of the suction surface.

Artificial Neural Network Model for Estimating the Pelton Turbine Shaft Power of a Micro-Hydropower Plant under Different Operating Conditions

The optimal performance of a hydroelectric power plant depends on accurate monitoring and well-functioning sensors for data acquisition. This study proposes the use of artificial neural networks (ANNs) to estimate the Pelton turbine shaft power of a 10 kW micro-hydropower plant. In the event of a failure of the sensor measuring the torque and/or rotational speed of the Pelton turbine shaft, the synthetic turbine shaft power data generated by the ANN will allow the turbine output power to be determined. The experimental data were obtained by varying the operating conditions of the micro-hydropower plant, including the variation of the input power to the electric generator and the variation of the injector opening. These changes consequently affected the flow rate and the pressure head at the turbine inlet. The use of artificial neural networks (ANNs) was deemed appropriate due to their ability to model complex relationships between input and output variables. The ANN structure comprised five input variables, fifteen neurons in a hidden layer and an output variable estimating the Pelton turbine power. During the training phase, algorithms such as Levenberg–Marquardt (L–M), Scaled Conjugate Gradient (SCG) and Bayesian were employed. The results indicated an error of 0.39% with L–M and 7% with SCG, with the latter under high-flow and -energy consumption conditions. This study demonstrates the effectiveness of artificial neural networks (ANNs) trained with the Levenberg–Marquardt (L–M) algorithm in estimating turbine shaft power. This contributes to improved performance and decision making in the event of a torque sensor failure.

DESIGN OF PUMPING INSTALLATIONS: DEVELOPMENT OF AN EXCEL WORKBOOK FOR HYDRAULIC MACHINES LECTURES

Nowadays, pumps are used worldwide in a very wide range of facilities and for countless purposes, including HVAC, domestic and commercial buildings, district energy, industrial processes and water treatment, municipal wastewater and water supply, agriculture and irrigation, among others. Accordingly, the number of applications is also very diverse. The purpose of present contribution is to introduce an Excel Workbook that represents a friendly easy to use tool that enables the design of pumping systems. It was first thought for Hydraulic Machines Master lectures, but its use might be looked at in a wider perspective. The Workbook includes 17 worksheets (Figure 1), all linked to each other, addressing different aspects of the design. Special attention is paid to the major and minor head losses calculation, the cavitation phenomenon, the use of dimensionless coefficients to determine the rotation speed to obtain a specific operating point and to the calculation of the system curve. Energy efficiency represents today an important goal in every pumping facility; therefore, one of the objectives of this tool is to enable the user to quantify both the shaft power and the efficiency of different operating points thus allowing a sustained definition of the best solution.

Semi-empirical model of the twin-screw refrigeration compressor with capacity control devices

Adopting twin-screw refrigeration compressors with capacity control devices has become the dominant trend to meet varying cooling demands. To analyze the compressor performance with different capacity control methods and further explore the potential, a semi-empirical model with 16 characteristic parameters is proposed. Detailed working processes under the part-load condition (PC) are considered and the corresponding calculations, including pressure loss, power loss, and leakage are innovatively refined. Subsequently, a prototype experiment was carried out for parameters identification and model validation. A good agreement between the experimental and simulated values is attained, with average relative errors of 3.46 % and 1.15 % for shaft power and mass flow rate under the variable frequency condition (VFC) and 3.18 % and 4.63 % under the PC. Thermodynamic simulation results indicate that both shaft power and mass flow rate are linearly correlated with frequency and the efficiencies are nearly stable over the whole interval. However, as the load decreases, the performance decays significantly and the most remarkable change occurs at a position of between 0.9 and 1. The volumetric and adiabatic efficiencies of the VFC are 3.65 and 2.26 times higher than that of the PC when the mass flow rate reaches the lower limit.

A sensorless centrifugal pump operation states estimation method based on HSSA-BPNN

As a liquid transportation equipment, centrifugal pumps find extensive use in industrial process control. Certain environments involving high temperature, high pressure, and highly corrosive media may not permit the installation of flow and pressure sensors. Consequently, accurately estimating the operating status of centrifugal pumps in the absence of sensors has become a prominent research focus. However, the precision of existing sensorless estimation methods remains a concern. This study introduces a HSSA-BPNN model utilizing valve opening degree, motor rotational speed and shaft power as input variables. A hybrid strategy improved sparrow search algorithm (HSSA) is developed to optimize the back propagation neural network (BPNN). Experimental results demonstrate a low mean absolute percentage error (MAPE) of the test data, which are 2.2741% and 1.6502%, respectively. The absolute errors of flow rate and head are below 0.3 m3/h and 0.5 m, respectively, with relative errors less than 4% and 3%, meeting practical applications.

Off-design performance and economic analysis in coupled binary cycle with geothermal reservoir and turbo-expander

This study presents a thermo-hydro-mechanical reservoir model of the Chingshui geothermal field, coupled with a thermodynamic model of the binary cycle. A one-stage axial turbo-expander was designed and analyzed in three dimensions using ANSYS-CFX. The results were used to train the artificial neural network model, providing the mass flow rate of the working fluid, isentropic efficiency (ηis,exp), and shaft power of the turbo-expander under off-design conditions to the thermodynamic model of the binary cycle. When the mass flow rate of the geofluid (m˙geo) exceeded 30 kg/s, ηis,exp gradually increased from its lowest value over the operation time and approached the design value. The performance of the power cycle degraded substantially owing to the decrease in the production temperature and considerable increase in the power consumption of the injection pump (W˙pgeo). Owing to effect of W˙pgeo, the decrease ratios of the first- and second-law efficiencies at m˙geo = 40 kg/s from the 1st to the 30th year were 5.7 % and 4.2 % for the cycle, and 23.2 % and 21.9 % for the total system, respectively. Finally, six scenarios of decreased m˙geo were examined. The decreased m˙geo had a relatively small impact on the payback period, and significantly affected the electricity production cost.

Effect of variable conditions on transient flow in a solid–liquid two-phase centrifugal pump

To investigate the influence of altering operational parameters on the transient flow characteristics within the flow channel of a solid–liquid two-phase centrifugal pump, this study employs a particle model based on the Euler–Euler method. Utilizing the standard k–e model, flow field simulations are conducted using the ANSYS-CFX software. Specifically, the study focuses on throttle regulation scenarios, monitoring and comparing the external and internal flow parameters of the solid–liquid two-phase pump with those of a clear water medium centrifugal pump. The results indicate notable modifications in head, efficiency, and shaft power due to the presence of solid particles in the two-phase flow. Decreasing flow rates during throttle regulation lead to fluctuations in pressure and turbulence energy distribution. Furthermore, under identical operational conditions, the variable working conditions of the solid–liquid pump result in increased flow rates of solid-phase particles near the impeller's outer edge, with particles shifting toward the middle and tail of the vane suction surface. This phenomenon exacerbates wear on the vane tail of the suction surface. Moreover, the study identifies that changing operational conditions in the solid–liquid dual-flow centrifugal pump contribute to increased axial forces, consequently leading to pump vibrations. Overall, this research elucidates the transient flow characteristics within the flow channel of solid–liquid two-phase centrifugal pumps under varied operational conditions, serving as a foundational reference for assessing the stability of such pumps.

Power Density Analysis of Wind Turbine Main Bearing Units by Holistic Optimization of Material, Manufacturing and Design of the Main Shaft

Given the continuous increases in wind turbine (WT) rated power and size, the nacelle weight and logistic handling costs increases significantly. To support heavier nacelles, stronger towers are needed which again increases material costs, so a need for nacelle power density increase arises. One solution to this problem is to increase the power density of the cast or forged WT main shaft. The power density in cast main shafts is limited by the low tensile strength of cast iron. High tensile strength steels, which theoretically increase power density, are used in state-of-the-art forged main shafts. However, their inner shaft diameter is kept small to reduce drilling costs. Since the loads of WT main shafts are dominated by the bending moments of the rotors, a high section modulus corresponds to a high power density. Material near the centre of the shaft therefore decreases the shaft power density. Hollow forging combines high tensile strength steel with a variable inner shaft diameter, enabling shaft designs with increased power density. Additionally, the use of air-hardening ductile (AHD) steel eliminates the need for costly heat treatment if the wall thickness is thin enough. The paper presents a holistic system model for the predesign of main bearing units (MBU) considering various materials and manufacturing methods. The model enables a feasibility assessment of hollow forged main shafts by comparing the resulting MBU weights across a wide range of WT power ratings. The MBU is selected instead of solely analysing the main shaft to account for the bearing and bearing housing weights, which depend on the main shaft geometry. The results show increased MBU power density of up to 23% for hollow forged shafts compared to forged shafts of the same material. Furthermore, when the shaft is hollow forged from AHD steel, the increase is even greater, up to 52%.

The Effects of Blade Height on the Efficiency of Gravitational Water Vortex Turbine

This paper presents the results of a study on the effect of blade height on the efficiency of a free-vortex water turbine. Laboratory experimentation was conducted to find the shaft power generation and the efficiency of the turbine. Water turbines with six blades and four different heights (208 mm, 248 mm, 288 mm, and 320 mm) were built and tested to determine the most appropriate blade height. The turbines were tested in a conical basin with inlet and outlet diameters of 600 mm and 100 mm and a height of 800 mm, at volume flow rates of 0.0088 m³/s, 0.0105 m³/s, and 0.0108 m³/s. The results showed that the turbine with a blade height of 288 mm was the most appropriate, yielding the highest efficiency of 30,46% at a water flow rate of 0.0108 m³/s.