Waterjet Pump Research Articles

Transient Hydrodynamic Characteristics of a High-Speed Axial Flow Water-Jet Pump during Variable Speed Process

To investigate the transient characteristics of high-speed axial flow water-jet pumps during start-up and emergency acceleration as well as to analyze how different accelerations affect the performance of internal flow, the k–ω turbulence model of the SST model and Zwart cavitation model were used to perform unsteady simulation on an impeller rotating at a speed of 1850. The steady-state numerical simulation method was verified by the experimental data, the numerical calculation results were basically consistent with the experimental data, the margin of error was within 5%, and the numerical simulation method was reliable. The results show that there was an obvious transient effect in the process of variable speed, and the thrust reached a stable state later than the speed. The buffer times for start-up times of 1 s, 2 s, and 3 s were 0.0394 s, 0.0375 s, and 0.0282 s, respectively, and the buffer times for the acceleration times of 0.5 s, 1.0 s, and 1.5 s were 0.0330 s, 0.0273 s, and 0.0230 s, respectively. The greater the acceleration, the more serious the flow rate and thrust lag behind the speed, and the greater the impact thrust. Under the same acceleration, the buffer time required in the start-up process was 19.3~22.6% longer than that in the acceleration process. During the change in speed of the high-speed water-jet pump, the vortex core area of the suction surface (SS) first appeared on the side of the shroud at the inlet, increased with the increase in the rotational speed, and developed toward the middle of the impeller. However, after the flow was stabilized, the vortex core region gradually shrank and eventually disappeared. When the rotational speed reached 0.6 times the design speed, cavitation occurred at the leading edge (LE) of the blade, and the cavitation area increased with the increase in the rotational speed. When reaching the same speed, the greater the acceleration, the more serious the cavitation. Under the design speed, that is, 6000 r/min, the cavitation volume fraction of the 1 s start-up process was 7.32%, the 2 s start-up process was 5.84%, the 3 s start-up process was 5.32%, and the 0.5 s acceleration process was 6.86%. The cavitation volume fraction of the 1 s acceleration process was 5.04%, and that of the 1.5 s acceleration process was 4.23%. Under the same acceleration, the cavitation volume fraction of the start-up process was 6.7~25% larger than that of the acceleration process. Compared with the start-up process and acceleration process under the same acceleration, the accelerated process had a smaller region of vortex core, stronger anti-cavitation ability, and more stable flow than the start-up process. During the actual operation process of the water-jet pump, it is advisable to use smaller accelerations and segmented accelerations as much as possible until the design speed is reached. The research findings serve as a foundation for future investigations into the transient characteristics of high-speed water-jet pumps operating under variable speed conditions.

Investigation on transition characteristics of laminar separation bubble on a hydrofoil

The phenomenon of water–jet pump stall can be ascribed to the development of blade boundary layer separation with the transition process playing a significant role in this separation. The hydrofoil is usually used as a simplified model of the water–jet pump impeller blade, and its flow field characteristics have important reference values for analyzing the impeller flow. Based on the transition model and the dynamic mode decomposition method, this article presents the results of a study that was carried out on the stall characteristics of the NACA0009 blunt trailing edge hydrofoil. The transition characteristics of hydrofoil surfaces at different angles of attack (AoA)and Chord-based Reynolds numbers (ReL) are obtained. The hydrofoil boundary layer transition is dominated by natural transition as the AoA is less than 4°, while the transition is dominated by leading-edge separation-induced transition as the AoA is greater than 4°. The investigation yields the dynamic properties of the LSB (Laminar Separation Bubble) as the AoA is varied. The phenomenon known as the deep stall is distinguished by the movement of the stall vortex toward the upstream direction near the trailing-edge region, where it merges with the LSB in the leading-edge region. This phenomenon leads to oscillations in the lift and drag coefficients. The relationship between the LSB and the trailing-edge stall vortex is established using DMD (Dynamic Mode Decomposition) methods. As the phenomenon of the deep stall occurs, it can be observed that the modal energy of the leading-edge LSB is comparatively higher than the modal energy of the trailing-edge stall vortex, inducing the dominant role of the LSB and the movement toward the trailing-edge region and, consequently, the phenomenon of trailing-edge vortex shedding in the hydrofoil. The findings of this study could be guidance for the design of fluid machinery blades.

Critical State Calculation of Saddle-Shaped Unstable Region of the Axial-Flow Pump Based on Bifurcation SST k–ω Model

This study aims to investigate the critical state of the saddle-shaped unstable region of the axial-flow pump and propose a suitable criterion for identifying this state. The bifurcation SST k–ω model considered the rotation effect is used in the present work and verified in the numerical calculation of a water jet pump. Then, it is used to simulate the critical state of the axial-flow pump. Results show that the leading-edge separation vortex generates at 0.6Qd, while the head declines only at 0.55Qd. Therefore, using the inflection point of the head-flow curve as the critical state criterion is unsuitable. In addition, the fixed monitoring point is unsuitable for identifying the critical state due to the insensitivity to the amplitude, main frequency, and periodicity changes at the critical state. Finally, to identify the critical state, it is essential to arrange a monitoring point at the leading edge of the blade suction near the shroud, which should rotate with the impeller. The critical state criterion is that the main frequency position of the pressure fluctuation signal is offset at the monitoring point, and the amplitude is increased by 10 times.

Comparison of Cavitation in Two Axial-Flow Water Jet Propulsion Pumps

To investigate the appropriate design method of the water jet pump, numerical simulations are carried out to compare the cavitation in two pumps designed by the streamline method and the blade load method. Based on a brief description of the design methods, the internal flow fields and cavitation in the two axial flow water jet propulsion pumps are studied by using the SST k−ω turbulence model and barotropic law cavitation model. The cavitation location, disturbance velocity field, blade load, and their variations with the cavitation number are analyzed. The results show that the pump designed by the blade load method has a smaller cavitation bubble than the pump designed by the streamline method. With the decrease of cavitation number, the vapor bubbles first appear at the blade tip of the leading edge and then extend from the leading edge to the trailing edge. The bubble thickness and the area of the low pressure on the suction surface also increases. A whirl in the disturbance velocity is observed, which turns the direction of incoming flow to the cavitation area. Furthermore, the head drop of water jet pump is related to the decrease of blade load. The results also show that at the point of cavitation number equal to 0.319, an unexpected peak of head in the pump designed by the streamline method is observed, which indicates an unstable working point for the pump. If the priorities are anti-cavitation performance and high efficiency at the design condition, the blade load method is the first choice to design pumps. While the streamline method should be adopted if high efficiency at large flow rates is preferred.

Experimental study on thrust pulsation characteristics of water jet propulsion pump units

Due to the influence of the rotating impeller in the water jet propulsion pump, the thrust generated by the water jet propulsion pump unit has a time-series pulsation characteristic. Firstly, through theoretical derivation, it is found that the thrust of a water jet propulsion pump unit is related to the outlet flow rate of the nozzle, and there is a pulsating characteristic of the thrust. Secondly, a direct thrust measurement system for the water jet propulsion pump unit was designed to achieve direct thrust measurement, further verifying the pulsating characteristics of thrust. The experimental results show that the transient thrust of the water jet propulsion pump unit fluctuates with time in a distinctly periodic manner, with low-frequency pulsations dominating. As the rotating speed increases, the amplitude of the subdominant frequency of the pump unit thrust pulsation tends to increase, while the influence of the impeller and guide vane on the transient thrust pulsation decreases with increasing speed, and the high energy density region in the wavelet transform time-frequency data gradually concentrates to the low-frequency. The experimental results and the related analysis can provide an empirical basis for studying the hydrodynamic aspects of the water jet pump unit.

Numerical studies for effect of geometrical parameters on water jet pump performance via entropy generation analysis

This paper presented an implementation of entropy generation analysis in the main flow field of a water jet pump via the CFD method. This study aimed to identify the inefficient location of energy conversion and to analyse entropy generation sources in each region of the water jet pump. The 2D-axisymmetric model and realisable k-ε (RKE) turbulence model at steady-state conditions were performed to validate jet pump performance and to assess the entropy generation. Likewise, the effects of the projection ratio and throat-aspect ratio as independent parameters were investigated. As a result, the throat is the most inefficient part due to the high total entropy generation rate, following by diffuser part. Also, the entropy generation rate was assessed dominant than viscous dissipation due to the turbulent dissipation, which was caused by a turbulent shear stress layer of mixing the streams. In conclusion, the projection ratio influenced the growth of the shear stress layer as well as the entropy generation. Further, the throat-aspect ratio affected the distribution of entropy generation in the throat section. An appropriate combination of both parameters has an impact on the jet pump performance improvements reducing the entropy generation rate in the future.

Vortex-induced energy loss of a mixed-flow waterjet pump under different operating conditions

Vortex-induced energy loss of a mixed-flow waterjet pump under different operating conditions

SU JET POMPALARININ PERFORMANSI VE KATI-SIVI KARIŞIM TAŞIMACILIĞINDA UYGULANMASI

This present work is focused firstly on an experimental investigation for the optimum design of water jet pumps to be used in the hydrotransport of solid particles through pipeline systems. Experiments were conducted in a closed test loop using five types of jet pumps with various dimensions of the driving nozzle, suction nozzle, mixing chamber, and diffuser employing water as driving and suction fluid. The efficiency of each water jet pump element was analyzed and interpretations of results related to each water jet pump were made about the parts to be considered in the optimum design of a water jet pump. From the experimental results, the water jet pump having the optimum mixing chamber, suction nozzle, driving nozzle location, and cross-sectional dimensions produced a maximum efficiency of about 33%. In the second part of the study, the solid particle carrying capacity of water jet pumps in a pipeline system was studied under saltation, moving bed, and heterogeneous flow regimes by introducing seven different types of solid particles having various concentrations into the closed test loop. The effect of jet pumps on separating solid particles from flow in a region was investigated. A curved form of a by-pass system called the ‘flow division unit’ was added to the main pipeline system and through the flow division unit, then most of the solid particles in the flow were forced to flow towards the suction pipe of the jet pump. As a result of this, only water with very small particle concentrations passed through the centrifugal pumps, and in this way, the wear risk of the centrifugal pump was reduced considerably.

Research on Cavitation Wake Vortex Structures Near the Impeller Tip of a Water-Jet Pump

Cavitation can cause noise in the water-jet pump. If cavitation occurs in the water-jet pump, the hydraulic components in the pump are prone to erosion. The surface erosion reduces energy delivery efficiency and increases maintenance costs. The decline in pump performance will lead to the instability of the entire energy system. In this paper, the cavitation flow structure of the water-jet pump is studied by the method of numerical simulation and experiment, which provides a reference for the prediction and improvement of cavitation. Based on the closed test platform, in order to reveal the physical process of cavitation evolution, high-speed photography is used to capture the complex cavitation flow phenomenon in the pump. After that, the cavitation vortex structure was further explored by numerical simulation. Through the simulation of the impeller blade tip leakage flow and the Tip Leakage Vortex Cavitation (TLVC) characteristics under different cavitation conditions, the flow mechanism of the impeller blade tip leakage flow and the separation vortex induced by the cavitation region under different cavitation conditions were revealed. The main factors affecting the development of the cavitation wake vortex structures were summarized.

Strong transient characteristics in axial flow waterjet pump during rapid starting period with special emphasis on saddle zone

Strong transient characteristics in axial flow waterjet pump during rapid starting period with special emphasis on saddle zone

Implementasi Alat Penjernih Air Tanah (Artesis) Menjadi Air Layak Pakai Pada Gedung Elektro Politeknik Negeri Bengkalis

Meeting the need for clean water has become a very common problem and has not been resolved in most parts of the Indonesian state in general, especially in coastal areas. Even though artesian well water is available, the condition of the water is generally slightly yellowish in color and has a high acid content. The same thing happened to the Electrical Building of the Bengkalis State Polytechnic, so that the toilet, ceramics and some equipment in the toilet quickly turned yellow and corroded due to the high acid content in the water and could create a dirty/dirty impression on the toilet. The method implemented is to create a water purification system using a media tube sourced from bore well water (artesian) which is yellow in color and has a high acid content, which can produce clear water and low acid levels so as to avoid yellowing in the toilet and equipment in the toilet. The stages carried out are installing water purification installations (installation of water jet pump machines, media tubes and piping systems), installing electrical installations for water purification systems, testing water purifiers, and making iron cages for media tubes. (artesian) which is yellow in color and has high acid content can become clear water and low acid content, so that it can overcome the problem of the need for clear water suitable for use at the Bengkalis State Polytechnic Electrical Building. Based on the results of the activity, which is made capable of producing water that is fit for consumption with no odor and the color is clearer than before, and this water purifier has been submitted to the Department of Electrical Engineering at the Bengkalis State Polytechnic through the Head of the Electrical Engineering Department on August 19, 2022Amri, H., & Syaiful, A. (2018). Implementasi Teknologi Pengolahan Air Tanah Artesis Menjadi Air Layak Minum Di Desa Buruk Bakul. Jurnal Pengabdian DIKEMAS, 2(1), 1-4.Yaqin, R. I., Ziliwu, B. W., Demeianto, B., Siahaan, J. P., Priharanto, Y. E., & Musa, I. (2020). Rancang Bangun Alat Penjernih Air Portable Untuk Persediaan Air Di Kota Dumai. Jurnal Teknologi, 12(2), 107-116Wan M. F.(2015).“Implementasi Teknologi Pengolahan Air Gambut Menjadi Air Layak Konsumsi Bagi Masyarakat Desa Sungai Alam, BengkalisIndra, S.,T., Mulyono,R.,A., Suprawihadi,R. (2019). Alat Pengolah Air Tanah Menjadi Air Bersih dengan Proses KombinasiAerasi-Filtrasi Upflow (Desain Rancang Bangun). Jurnal Kesehatan,10(1), 53-60.

Nonlinear dynamic characteristics of suction-vortex-induced pressure fluctuations based on chaos theory for a water jet pump unit

To improve the effective use of ocean energy by water jet propulsion pump, it is necessary to study the underwater suction vortex (USV), which affects the propulsion and stealth performance of water jet propulsion pump. This paper analyses the time-frequency and nonlinear dynamic characteristics of the pressure fluctuation induced by USV through high-speed photography and high-frequency pressure fluctuation tests. The nonlinear characteristics of pressure fluctuations under the conditions with and without USV are compared and analyzed based on the chaotic time series analysis theory. The results show that the chaotic characteristics of the pressure fluctuation signal are unaffected by the occurrence of USV. However, the singular attractor structure of the pressure fluctuation signals induced by USV is highly complex, and the largest Lyapunov exponent increases. Therefore, the pressure fluctuation signals induced by USV have stronger chaotic characteristics. Note that the saturation correlation dimension of the pressure fluctuation signal in the period without USV is larger than that with USV, mainly because the influence factor of the pressure fluctuation signal in the USV period is relatively single, which is primarily induced by USV. The nonlinear characteristics analysis of the pressure fluctuation signal can effectively identify the presence of USV.

Incremental residual learning-based dynamic modeling and stability analysis for multipower underwater vehicles

Dynamical modeling is the basis of state prediction, motion control, and performance analysis for underwater vehicles. Existing dynamic modeling methods were derived from physical principles, less considering the modeling reality gap caused by environmental uncertainty. Therefore, an incremental residual learning-based dynamic model is proposed for a novel multipower underwater vehicle with strengths of the water-jet pump and buoyancy drives. First, the multimodal physical dynamic model is derived from multibody systems, including driving forces and hydrodynamics. Then, the continuous residuals caused by the environmental uncertainty are compensated by the incremental residual learning. After that, multimodal stability criteria are established based on the hydrodynamic equilibrium equation. Finally, experiments on Computational Fluid Dynamics and lake trials are conducted to demonstrate the effectiveness of the proposed method.

Numerical Investigation of Tip Leakage Vortex Cavitating Flow in a Waterjet Pump with Emphasis on Flow Characteristics and Energy Features

The Delayed Detached Eddy Simulation (DDES) turbulence model was coupled with a homogeneous cavitation model to analyze the tip-leakage vortex (TLV) cavitating-flow characteristics in a waterjet pump. The numerical results agree well with experimental data. The results show that the vortex evolution in the waterjet pump has three stages, which is similar to that around a hydrofoil, but the vorticity variations in the waterjet pump are more complicated. The relative-vorticity-transport equation was then applied to find the reason for the differences between the vorticity variation observed in the waterjet pump and that around a hydrofoil. The results indicate that the drastic fusion process of the TSV cavity and the TLV cavity in the waterjet pump resulted in the formation of triangular cavitation region near the blade tip that is difficult to reproduce by stationary hydrofoil simulation. This fusion process caused the local variation of fluid volume and further affected the vorticity transport. The entropy-production evaluation method considering the phase transition was then used to analyze the dissipation losses in the complex cavitation region. The results indicate that the drastic fusion process of the TSV cavity and the TLV cavity significantly influenced the entropy production rate distributions and enhanced the disturbance of the flow field. In addition, severe phase transition occurs in the drastic fusion region accompanied by huge phase-transition losses.

Study on noise of an axial flow waterjet pump with wavy leading edge

The effects of wavy leading edge on noise of an axial flow waterjet pump are investigated by using numerical simulation method. Based on bionics, five wavy leading edges with different combinations of wavenumber and amplitude are proposed. The physical mechanism is also revealed. The results show that the rotor with wavy leading edge does not change the dominant frequency of the noise, but reduces the amplitude. The optimal combination of wavenumber and amplitude in the study is 4/s (s is spanwise length) and 0.12C (C is the averaged chord length). The reason is that the wavy leading edge changes the pressure distribution of the blade, resulting in a radial pressure gradient. Meanwhile, vortex pairs around the leading edge of the blade occur. The vortex pairs cause the momentum exchange of the fluid in the boundary layer and outside the boundary layer, which makes the velocity distribution more uniform. In view of turbulent kinetic energy, the wavy leading edge can greatly reduce the turbulent kinetic energy in rotor under large mass flow rates. Therefore, the wavy leading edge may be applied to design the rotor of the axial flow waterjet pump to reduce its pressure pulsation and noise.

Numerical investigation and experimental observation of unsteady tip leakage cavitating flow for the axial waterjet pump

ABSTRACT In this paper, experimental observation and numerical calculation are applied to investigate the vortex-cavitation interactionin the blade tip region. Calculated performances have good agreement with experimental results. The evolution of TLVC is analysed byHigh-speed photography (HSP) at the selected cavitation condition. Liutex method was adopted to identify the tip leakage vortex (TLV)core centre. According to the radial location of the TLV core centre and the development of TLVC, the flow along the blade can bedivided into three regimes: stable cavitation, unstable cavitation and non-cavitation flow. Tip leakage flow (TLF) and main flow haveeffects on the TLV intensity and trajectory. Finally, different terms of vorticity transport equation were used to analyse the contributionof cavitation to the production and reallocation of vorticity in a rotating frame. It shows that circumferential dilatation and axial vortexstretching terms mainly contribute to vorticity production and its relocation.

PERBAIKAN DAN PEMELIHARAAN MOTOR LISTRIK PENGGERAK WATER JET PUMP DI AREA WASTE HEAT RECOVERY SYSTEM PT CEMINDO GEMILANG

Electricity is one of the vital needs that is indispensable for all humans and other places, one of which is PT. Cemindo Gemilang, engaged in the cement-producing industry, requires a huge electricity capacity. To reduce or reduce the cost of electrical energy, a power plant unit and a WHRS (waste heats recovery system) were made to supply electrical energy to the cement plant area. PT. Cemindo Gemilang and the Power Plant rely heavily on electric motors, almost all of which operate using electric motors. The electric motor is a single-phase or three-phase type with a voltage of 11 KV, 6.6 KV or 400 volts. When all generating units operate, all electric motors that play an essential role will continue to be active so that damage is often caused by operation and service life therefore in the power plant department, and there is an electrical and mechanical maintenance division to maintain the continuity of the power plant operational system. This study's aim 1). Explain about electric motors, 2). Explain the definition of the water jet pump, 3). Explain how the water jet pump works 4). Explain the components used in electric motors and their repair and maintenance.

Numerical analysis of the cavitating flow in an axial flow waterjet pump with special emphasis on the tip leakage flow and tip leakage vortex

Abstract Due to the structural design requirements, tip leakage flow is a common phenomenon in the field of axial flow rotating machinery. The tip leakage flow interacts with the mainstream and induce complex tip leakage vortex. When the local pressure drops to the saturation pressure, cavitation may occur in flow passage and the vortex core. The tip leakage cavitating flow has a huge effect on the flow stability, which may reduce the efficiency of the waterjet pump. In the present study, Zwart cavitation model and SST k-ω turbulence model are employed to simulate the cavitating flow. The new proposed Liutex criterion has been used to capture the vortex structures in the flow passage and the tip gap. The vorticity transport equation in cylindrical coordinates is also used to discuss the variation tendency of the vorticity in the vicinity of the gap region under cavitation condition. The evolution of the cavitation is proved to be vital important for the formation and the breakdown of the tip leakage vortex. By analyzing the vorticity transport equation, the stretching term is shown to be the decisive factor.

Cavitating flow investigation in low specific speed axial flow waterjet pumps

Abstract In this paper, the cavitating flow in low specific speed axial flow waterjet pumps are treated at different cavitation conditions. In order to analyze the cavitating turbulent flow comprehensively, three axial flow waterjet pumps with the specific speed less than 650 min-1·m3s-1·m are chosen to compare the internal flow phenomenon. The investigations are conducted by numerical simulation, where RANS method is applied with k-ω SST turbulence model and homogeneous cavitation model. The results show that there are several types of cavitation such as tip leakage vortex cavitation, sheet cavitation attached on blade suction surface, and shedding cavity in the pumps. The vortex structure in the low specific speed waterjet pump contains tip leakage vortex, shedding vortex downstream of the sheet cavitation and perpendicular cavitation vortex. It is noted that the cavity firstly occurs at the leading edge near blade tip, and the sheet cavity covering the blade suction surface extends from leading edge to the middle part, while the tip leakage vortex cavitation develops with the decreasing cavitation number. Further analysis using relative vortex transport equation depicts that the vortex stretching term is the main contributor for the vorticity production in the pump, and the vortex dilation and baroclinic torque occur at the interface between cavity and water.

Investigation on performance in water jet pump under turning conditions

Turning has a significant effect on the performance of water-jet pump. Here, the axial flow water-jet pump was used as the research object, the performance and inner flow characteristics of water-jet pump under different turning angle were simulated through numerical simulation. The thrust, vorticity, bubbles in impeller, vapor volume fraction and surface load of blade were analyzed in detail when the turning angles were ±10°, ±20°, and ±30°, respectively. The results demonstrate that the thrust of the water-jet pump decreases linearly with the increase of the turning angle. At the same angle, the thrust of the water-jet pump when turning right is larger than that when turning left, and the maximum thrust difference is 9.14% of that without the turning angle. As the turning angle increases, the overall pressure of the water-jet pump decreases and the streamline distribution gets turbulent gradually. The vortex direction is the same as the turning direction basically. And the vortex distribution range is smaller when turning right under the same turning angle. The cavitation bubbles in the impeller occur firstly at the rim of the blade inlet and develop to the middle of the blade as the turning angle increases. The cavitation area is concentrated on the blade at turning side and the cavitation area when turning right is smaller than that when turning left.