Design and Optimization of Fluid Machinery

Abstract

Fluid machinery plays an indispensable role in fundamental human activities and is widely used in areas such as desulfurization in coal-fired power plants, power generation in hydropower stations, water transmission, and agricultural irrigation. Due to the expanding range of applications, there are increasingly higher demands for the performance of fluid machinery in practical engineering. There is an urgent need to design and optimize high-performance fluid machinery to address current issues such as instability, low efficiency, and complex structures in fluid machinery operation. This Special Issue focuses primarily on the design and optimization of fluid machinery. The issue goes through a thorough peer review process, with a total of 21 articles accepted. These articles align with the theme of the Special Issue and cover the following categories.

1. Optimization Method of Fluid Machinery

The traditional orthogonal experimental method has been widely used due to its short optimization cycle and significant optimization effects. Cao et al. [Contribution 1] employed an orthogonal decomposition approach to study the inflow distortion of a water jet pump. They compared the effects of various inflow methods on pump performance and found that the delayed flow separation in Mode 3 of the proper orthogonal decomposition could suppress reverse flow and concentrated separation vortices, then increasing the blade load and ultimately improving the pump head. Of course, innovations have also emerged based on traditional methods. Gao et al. [Contribution 2] combined orthogonal experiments with gray relational analysis to optimize the auxiliary blades of a centrifugal pump. They found that the primary and secondary factors affecting the pump head were the inner diameter, width, and number of auxiliary blades. Additionally, Wang et al. [Contribution 3] used Plackett–Burman experimental design to screen the factors influencing the hydraulic performance of a spiral centrifugal pump. Their results indicated that blade thickness and impeller outlet width were significant influencing factors. With the rapid development of computer technology, a new generation of efficient optimization methods has emerged. Zhang et al. [Contribution 4] optimized the hydraulic efficiency of a multistage pump using a radial basis function (RBF) neural network. They found that impeller outlet width, impeller blade wrap angle, blade exit angle, and diffuser inlet width were key factors influencing hydraulic efficiency. The optimization model resulted in a 4.35% increase in efficiency under design conditions. Zhang et al. [Contribution 5] optimized the inlet channel of the elbow of a pipeline pump using the sand cat swarm algorithm to optimize the backpropagation (SCSO-BP) neural network. The optimized inlet model minimized the impact losses on the inlet wall and improved the uniformity of the velocity distribution at the inlet impeller. As a result, the pump efficiency increased by approximately 5% near the design flow rate. Gong et al. [Contribution 6] conducted an optimization study on water distribution in large irrigation districts, using the Hengliu Main Canal in the Zhouqiao Irrigation Area of Jiangsu Province as a case study. Based on the dynamic programming (DP) method, the optimization results indicated that, during moderately dry and particularly dry years, the minimum water shortage in the controlled irrigation area of the horizontal-flow main canal during the rice growing period was 2.57 × 10⁴ m³ and 23.31 × 10⁴ m³, respectively. Tian et al. [Contribution 7] reviewed the application of ISIGHT software in the optimization of hydraulic machinery design, focusing on its advantages in solving optimization problems.

2. Effect of Geometric Structure on Internal Flow Characteristics of Fluid Machinery

The impeller is the key component that determines the performance of a pump. Han et al. [Contribution 8] studied the impact of the blade exit angle on the performance and internal flow patterns of high-speed electric submersible pumps. They found that at both low and high flow conditions, a small exit angle of 10° resulted in higher efficiency for the high-speed submersible pump compared to other configurations. In addition, Gao et al. [Contribution 9] reduced the leakage flow through the impeller by adding a set of auxiliary blades to change the direction and magnitude of the leaking fluid flow. Compared to the original structure, the leakage at the throat ring was reduced by approximately 28.99%, significantly improving the pump’s head and overall efficiency. The impeller clearance is also a key factor affecting pump performance. Cao et al. [Contribution 10] proposed a tandem cascade design based on the existing single-stage cascade design, and they conducted a comparative analysis of the effects of both designs on various flow losses under the same operating conditions. The results showed that, compared to the single-row blade configuration, the tandem-row design better reduces blade losses and increases the pressure difference across the upper and lower surfaces of the blades, thereby improving the blade’s load-bearing capacity and stability. Bionic methods have been shown to produce positive results when applied to fluid machinery. In order to further enhance the drag reduction and noise reduction performance of a marine centrifugal pump with a Space-V groove bionic surface, Li et al. [Contribution 11] employed the response surface method to establish a regression equation between the total sound pressure level and the height, width, and spacing of the bionic groove structure. They analyzed the interactive effects of each parameter on the total sound pressure level. The results indicated that, as the groove height increased, the total sound pressure level initially decreased and then increased. Similarly, as the groove width increased, the total sound pressure level decreased first and then increased.

3. Influence of Flow Conditions on Hydrodynamic Characteristics of Fluid Machinery

During the operation of fluid machinery, its dynamic characteristics significantly influence both overall operational stability and service life. Zhu et al. [Contribution 12] analyzed the pressure pulsations and structural characteristics of a coaxial cross-flow pump. They found that the maximum pressure pulsation amplitude occurred at the interface between the impeller and the guide vanes. The unevenness of the stress distribution at the impeller position decreased gradually with increasing radial distance. The high-stress and high-strain regions of both the impeller and guide vanes were primarily concentrated at the root of the blades. In addition, Yan et al. [Contribution 13] conducted a study on the coupled vibration and optimization of a parallel dual-stage ultra-high-speed centrifugal pump. They found that, under design conditions, the minimum values of the maximum average deformation and maximum average stress were both less than 0.31 mm and 245 MPa, respectively. The position of the bearing near the multistage impeller had the greatest impact on the deformation and stress of the rotor system, with both deformation and stress increasing as the distance from this point increased.

4. Internal Flow Mechanism and Energy Loss Analysis of Fluid Machinery

In the study of flow mechanisms in fluid machinery, Ma et al. [Contribution 14] studied the effect of inlet pre-swirl on pressure pulsations in a mixed-flow centrifugal pump using a combination of numerical simulation and experimental validation. The results showed that as the inlet pre-swirl angle increased, the intensity of pressure pulsations significantly decreased. Song et al. [Contribution 15] used a square cavity jet model to study the nozzle leakage phenomenon in an axial flow pump. Their research showed that the interaction between the main flow and the jet is the primary source of the leakage vortex formation. Kan et al. [Contribution 16] studied the effect of non-uniform inflow on the internal flow mechanisms of an axial flow pump. The results showed that uneven inflow leads to uneven pressure distribution within the impeller, imbalance in radial forces, and a shift in the center of radial forces. Additionally, low-frequency, high-amplitude pressure fluctuations were observed near the hub. In the study of energy losses in fluid machinery, Yang et al. [Contribution 17] conducted an energy loss analysis based on wave-passing theory for optimizing the axial matching dimensions between the inducer and impeller. They found that, in high-speed vehicle-mounted fire pumps, the impeller exhibits the lowest energy loss and best performance at an axial distance of 0.2D. Tang et al. [Contribution 18] analyzed the energy conversion characteristics of multiphase pumps based on energy transfer theory. They found that the flow rate primarily affects the vortex entropy dissipation within the impeller, particularly near the pressure side of the blade in the middle of the impeller. As the flow rate increases, the vortex entropy dissipation in the impeller’s pressure-boosting device also increases, with the vortex entropy dissipation in the front half of the impeller becoming more chaotic.

5. Fluid Machinery Design and Multiphase Flow Applications

In the design of novel fluid machinery, Kondus et al. [Contribution 19] developed a high-speed submersible pump for water supply, achieving a higher level of energy efficiency while reducing costs due to lighter weight and smaller size. In their study, by increasing the rotational speed from 3000 rpm to 6000 rpm and designing the pump for this specific rotational frequency, they achieved a significant increase in the pump’s head, from 15 m to 65 m. This reduced the need for multistage pumps, lowering the overall weight of the pump from 200 kg to 45 kg. Furthermore, the pump design resulted in a 5% improvement in energy efficiency. In the application of multiphase flow in fluid machinery, Wen et al. [Contribution 20] analyzed the effect of tip gap sizes on the dynamic and static head of a screw axial-flow impeller pump, revealing the variations in absolute velocity, relative velocity, and dynamic–static head under different cavitation stages. In the impeller, the absolute velocity typically decreases as the tip gap size at the front and rear of the flow direction increases, while it increases as the tip gap in the middle section enlarges. The larger the tip gap size in the impeller, the faster the dynamic head increases. In the diffuser, during the critical and severe cavitation stages, the absolute velocity decreases as the tip gap size increases. As the guest editor [Contribution 21] of this Special Issue, we also contribute a review paper of the advances in pump design methods, numerical simulations, and experimental techniques in deep-sea resource development. We discuss the application of various design optimization techniques in deep sea pumps, providing a detailed overview of commonly used multiphase flow numerical algorithms and their improved models in deep-sea pumps. Additionally, we summarized some of the experimental methods used in this field.

In summary, this Special Issue encompasses a diverse range of topics, including the application of optimization methods in fluid machinery, advancements in mechanisms, analysis of dynamic characteristics, internal flow mechanisms, energy loss assessment, structural design, and multiphase flow research. They provide valuable references for the ongoing optimization and design of fluid machinery. Notably, as interdisciplinary fields converge, leveraging computer technology has emerged as a key approach for enhancing the performance of fluid machinery. The papers featured in these Special Issues will significantly contribute to the rapid advancement of the fluid machinery field and promote progress in industrial society. Additionally, we are pleased to announce that contributions for the third volume of the Special Issue are now being solicited, and we encourage experts and scholars in the field to participate actively. For more information, please visit the following link: https://www.mdpi.com/journal/water/special_issues/2BGP3XJNER.