Pump Performance Research Articles

Research on Prediction Methods for Eccentric Wear of the Slipper Pair in Axial Piston Pumps and Lubrication Performance Analysis

Abstract The axial piston pump (APP) is the core power component of hydraulic systems. Its friction pair wear can cause the degradation of piston pump performance until the function is completely lost or the service life is terminated. The slipper pair, prone to wear failure, is selected as the research object in this paper. The prediction method for the eccentric wear of the slipper pair is established, and the gradual change rules of the performance with wear accumulation are explored. The micro-surface rough peak contact and the stress state of the slipper pair are analyzed, and the mixed lubrication model of the slipper pair is established based on the elastohydrodynamic lubrication (EHL) model of the slipper pair. Grid discretization of a sealing belt of the slipper pair is carried out based on two-body abrasive wear and Archard adhesive wear models to improve the prediction method for eccentric wear of the slipper pair. The effectiveness of the proposed method is verified by a surface morphology analysis of the worn slipper. The results showed that the wear depth and wear width of the outer edge of the slipper bottom surface are positively correlated with the oil discharge pressure and the inclination angle of the swashplate, and negatively correlated with the rotational speed and the dynamic oil viscosity. The outer edge of the slipper is wedged after eccentric wear, and the hydrodynamic effect of the lubricating oil film of the slipper pair is enhanced. Hence, proper wear can improve the lubrication performance of the slipper pair.

Performance analysis of a novel air source ammonia/water cascade heat pump for heating buildings in subarctic climate

Performance of available air-source heat pumps (ASHP) for buildings is extremely influenced by the outdoor air temperature (OAT). When OAT falls below –20 °C, especially in subarctic climate, most commercially available ASHPs lose their defined functionality. To address this issue, a novel cascade heat pump (CHP) is proposed that utilizes two natural (with zero global warming index) refrigerants: ammonia, aka R717, as the low stage (LS) refrigerant, and water, aka R718, as the high stage (HS) working fluid. The proposed system is equipped with two rotary vane compressors for LS and HS. To desuperheat the compressor discharge temperatures and increase the HS heating capacity, liquid refrigerant is injected into the chamber of both LS and HS compressors. The wet compression is thermodynamically modeled and validated against experimental data available in the literature. Optimum design parameters such as the maximum allowable temperatures during compression and the minimum vapor quality after injection are obtained where the COP is maximized. Total exergy destruction, number/location of injectors and the injected amounts are also investigated. The proposed CHP can deliver 6.35 kW heating load at 50 °C with a COP of 1.985 when OAT is –40 °C. From a broader perspective, the proposed CHP not only proves its efficacy in extremely cold subarctic climates but also emerges as a pivotal player in addressing the global warming issue. This is accomplished through a dual approach to decarbonization—firstly, by electrifying heating processes and secondly, by substituting phased-out refrigerants with environmentally friendly natural alternatives.

Design and Performance of a Linear Flux Pump for the Frascati Coil Cold Test Facility

Design and Performance of a Linear Flux Pump for the Frascati Coil Cold Test Facility

Experimental characterization and numerical modelling of an air to water CO2 heat pump under different outdoor and operating conditions for domestic hot water generation

This work assesses the influence of different outdoor and operating conditions on the performance of an air-to-water CO2 heat pump for domestic hot water (DHW) generation. For that purpose, an air to water CO2 heat pump with internal heat exchanger (IHX) was developed and characterized in an experimental campaign under well-controlled lab conditions. The system includes an in-house control system implemented to operate at the optimal gas cooler pressure. The heat pump and the control system are tested for DHW generation. The heat pump uses a finned-tubes heat exchanger as evaporator and plate heat exchangers as gas cooler and internal heat exchanger. The numerical model used a 1dimensional, cell by cell discretization method to characterize the performance of both, the gas-cooler and the evaporator under a wide range of values of their key variables. The IHX is also modelled with the same strategy. ARHI equations are considered to describe the compressor performance. The experimental data obtained are used to validate a numerical model of the heat pump under different air velocities, air temperatures and air humidity at the evaporator. The effectiveness of the control system proposed is experimentally confirmed during the experimental tests. Results show a good agreement between the numerical simulations and the experimental data what permits to validate the model and to assess the performance of the transcritical heat pump under different climate conditions.

Modelling of the refrigerant distribution in a critically charged propane heat pump cycle for performance evaluation

The investigation of heat pumps employing natural refrigerants as working fluids has gained substantial momentum, driven by increasingly stringent regulations addressing the global warming potential (GWP) and ozone depletion potential (ODP) of refrigerants. Propane (R290) stands out as an attractive option due to its low GWP and zero ODP. However, a major drawback of propane lies in its flammability. When using propane as working fluid, it will therefore be necessary to limit the total refrigerant charge within the system, without compromising on the heat pump performance. This study endeavors to address this challenge by developing a model of the refrigerant charge distribution in a critically charged heat pump system consisting of an evaporator, a compressor, a condenser, and an expansion valve. In the model, the charge distribution in the two heat exchangers is modelled in detail using a suitable void fraction correlation. For the compressor and expansion valve, a simplified model is employed, in which no refrigerant charge is calculated. Using an iterative procedure, the model can then be used to determine the coefficient of performance (COP), evaporator- and condenser pressure for a heat pump with an established total charge and heat capacity. The influence of different design and operation parameters, such as the degrees of subcooling and superheat, the volume ratio of the evaporator and the condenser, etc., can be assessed.

Modeling and evaluation of centrifugal pump performance degradation model based on stochastic process

In order to clarify the performance degradation problem of fuel centrifugal pumps, a stochastic process-based performance degradation model modeling method is given with an aero-engine fuel centrifugal pump as the object of study, and the reliability assessment is carried out. First, the degradation modeling method based on stochastic process is given. Secondly, PumpLinx is utilized to obtain the performance degradation data of the centrifugal pump and perform data processing. Gamma and Wiener stochastic process models are given based on MATLAB. Finally, based on the centrifugal pump performance degradation data for centrifugal pump reliability assessment, and compare and analyze the advantages and disadvantages of the two modeling methods, and found that the degradation modeling method based on the Gamma process is more suitable for centrifugal pump reliability assessment.

Assessment of viscosity effects on high-speed coolant pump performance

The high-speed coolant pump facilitates thermal regulation in electric vehicle components, including batteries and motors, by circulating an ethylene glycol solution. This commonly used circulating fluid exhibits a notable negative correlation with temperature in terms of viscosity. Numerical simulations investigate the transient dynamics of a high-speed coolant pump operating at 6000 rpm, driving coolant flow at various temperatures. A high-speed coolant pump test rig is established, and the performance is evaluated under different temperature conditions. The numerical simulations at different temperatures align well with the experimental outcomes. Decreasing temperatures, from 100 to −20 °C, lead to reduced pump head and efficiency due to increased viscosity. Specifically, at a flow rate of 30 L/min, head decreases by 40.03% and efficiency by 44.19%. With escalating viscosity, the best efficiency point shifts toward lower flow rates. Notable impacts on both disk efficiency and hydraulic efficiency are observed due to viscosity fluctuations. It exerts minimal influence on volumetric efficiency at elevated flow rates but has a substantial impact on volumetric efficiency at lower flow rates. Increased fluid viscosity causes uneven pressure distribution within the pump, altering velocity profiles within the impeller. High-viscosity fluids tend to form large-scale vortex structures around the blades, reducing the thrust exerted by the blades on the fluid. Higher viscosity results in larger vortex structures around the blades, reducing thrust and increasing fluid frictional resistance. The study findings provide valuable insights for the advancement of high-efficiency, energy-saving, high-speed coolant pumps tailored for electric vehicles.

A critical analysis and improvements of empirical models for predicting the performance of Electrical Submersible Pumps under viscous flow

One of the main challenges associated with Electrical Submersible Pumps (ESPs) system is the correct sizing of the pump. High viscosity fluids, emulsions, or compressible fluids significantly impact the pump’s ability to transfer energy to the fluid. Obtaining ESP characteristic curves in conditions resembling real applications is complex but essential for the correct design, operation, optimization, and safeguarding of ESP systems. The objective of this study is to critical assess the traditional methods for predicting the ESP performance under viscous flow. This study also improves these methods driven by ESP performance data. The results show that the original models have limitations because their databases are primarily based on data from conventional centrifugal pumps. Consequently, using these methods can result in significant errors in the sizing of the production system. The accuracy of the models improved significantly after modifying the methods. Reductions in errors were observed in all correction factors, and particularly in the prediction of global performance. The improvements were effective in mitigating the effects of increased deviations with the reduction in Reynolds number observed when applying the original models to predict flow rate and efficiency.

Analysis of the Cooperation of a Compressor Heat Pump with a PV System

The decarbonization of heating systems is one of the present political and legislative directions of the European Union and its Member States. The main activities concern the energy performance of buildings and energy efficiency. The mentioned UE directives are the basis for the financial support of high-emission fossil fuel thermal energy source replacement with emission-free ones, in particular heat pumps. Other aspects are the support of PV installations and the thermal insulation of buildings. 85% of EU buildings were built before 2000, and among those, 75% have poor energy performance. Therefore, a significant number of buildings have only high-temperature wall radiators, and this was a motivation to prepare this article. The main innovation of this research was a new theoretical design of a high-temperature heat pump based on ecological refrigerants. The presented solution allows wall radiators to receive a hot water supply with temperatures of up to 85 °C during external temperatures of up to −20 °C. Typical heat pumps do not have these kinds of parameters, so the authors decided to verify the possibility of operating this device in such a wide temperature range. Another important aspect was the analysis of PV support. Finally, this paper investigates the possibility of heating an energy-efficient house with the newly designed high-temperature heat pump. Depending on the location in Poland, i.e., Suwałki, Warsaw, and Wrocław, the total electric energy supplied to the compressors was 2538–3364 kWh. The energy provided by the PV to supply power to the compressors is 482–570 kWh. The achieved PV energy self-consumption is 16.9–19.0%. The Seasonal Coefficient of Performance (SCOP) of the heat pump is 1.825–2.038 without PV and 2.515–2.970 with PV.

Study on performance of direct-expansion heat pump water heater integrated uninsulated micro-channel PV/T solar collector

In this paper, a direct-expansion heat pump water heater system integrated uninsulated micro-channel PV/T solar collector (UMC-PVT-SC) is proposed. This system can realize storage for both thermal energy and electricity, ensuring the supply of domestic hot water. The theoretical models of micro-channel PV/T solar collector, hot water storage tank, compressor and electronic expansion valve are established to investigate the performance of the micro-channel PV/T heat pump water heater system. R134a is used as refrigerant. The system performance is numerically simulated using MATLAB for different solar radiation intensity, ambient temperature and wind speed. The results show that solar radiation intensity has the largest influence on the system performance, followed by ambient temperature and wind speed. The coefficient of performance of the heat pump (COPHP) and the overall coefficient of performance (COPpvt) of the integrated system increase while the required operating time reduces, as solar radiation intensity and ambient temperature increase. The uninsulated micro-channel PV/T solar collector (evaporator) can absorb thermal energy from both ambient air and solar radiation and therefore achieve high COPHP, electric efficiency and COPpvt. Even under cold weather conditions, the proposed solar collector and heat pump heater demonstrate high efficiencies, heating and power generation capacities. When ambient temperature is −18.6 °C and solar irradiance is 322 W/m2, the collector efficiency and electric efficiency of UMC-PVT-SC are still at 0.718 and 0.244, respectively, and the COPHP and COPpvt of the heat pump heater are 3.5, 5.63, respectively. The present work is of potential value for delivering net zero.

Proper Orthogonal Decomposition Based Response Analysis of Inlet Distortion on a Waterjet Pump

This study addresses the challenge of performance degradation in waterjet pumps due to non-uniform suction flow. Utilizing the Proper Orthogonal Decomposition (POD) method, it decomposes and reconstructs the flow features within a waterjet pump under non-uniform inflow into a series of modes ranked in descending order of energy. By analyzing the modes with dominant energy, which contain complex information about the flow field, it is revealed that modes 1 and 2 predominantly represent the formation of a concentrated vortex, whereas modes 3 and 4 illustrate its spatial offset. Notably, in the hub section, mode 3 exhibits a delayed flow separation caused by the reduction of circumferential vortex (CV), with a consequent lift in blade loading at the leading edge and a higher head compared to mode 1. In the shroud section, the delayed flow separation in mode 3 suppressed reverse flow and the concentrated separation vortex (CSV) and then increased the blade loading, ultimately enhancing the pump head. The findings provide significant insights into optimizing waterjet pump performance by detailing the interactions between various flow structures and pump components, effectively filling a knowledge gap in applying dimensionality reduction techniques within the distorted flow fields of water jet pumps.

INVESTIGATING CAVITATION PHENOMENON IN EXTERNAL GEAR PUMPS

External gear pumps find widespread application across various industries owing to their simplicity, efficiency, and reliability in fluid transfer tasks. However, cavitation poses a significant challenge to these pumps, potentially impairing their performance and leading to premature failure. This article delves into innovative approaches for mitigating cavitation effects, with a specific focus on material selection and surface coatings. By harnessing advanced materials and coatings, enhanced durability of pump components can be achieved, minimizing cavitation-induced damage and ultimately improving pump performance and longevity. Keywords: cavitation, external gear pump, cavitation between gears, hydraulic equipments.

Real-time monitoring and optimization of a large-scale heat pump prone to fouling - towards a digital twin framework

Large-scale heat pumps are a promising technology for the decarbonisation of heat supplied in buildings and industries, provided they operate as expected. However, common faults like fouling and unplanned downtime periods can significantly affect their performance and availability. This could limit the widespread adoption of large-scale heat pumps over other heating technologies such as gas and electric boilers. Approaches described in the literature to optimize the operation of large-scale heat pumps often lack validation under real-world conditions and do not account for performance degradation due to faults. This work demonstrates a step towards utilizing digital twins to improve the energy performance of a commercial large-scale heat pump affected by fouling. A framework was proposed based on the real-time adaptation of digital twins, where a simulation model was calibrated online based on measurements from the heat pump in operation, which was then used for set point optimization. This enabled to determine optimal intermediate pressure set points in the heat pump operating under varying levels of fouling over time. The framework was tested on different periods of heat pump operation spread over ten calendar months. The results showed that the use of online calibration rather than a single calibration decreased performance estimation errors between 3 and 17 percentage points. Moreover, the set points determined by the online-calibrated model, along with a simpler polynomial model derived from it, showed improvements in the heat pump performance by up to 3%, depending on the level of fouling. The findings of this study demonstrated the potential to extend the proposed framework using digital twins to enhance the energy efficiency of large-scale heat pumps.

A High-Performance piezoelectric micropump designed for precision delivery

A piezoelectric micropump (PE pump) was proposed featuring a multi-plate cantilever valve (MPCV) and a ramp channel (RC) to deliver high performance in a compact design. Both the MPCV and RC underwent thorough theoretical, simulation-based, and experimental evaluations. A specialized driver plate was then developed to precisely control the PE pump. Key parameters of the PE pump were optimized based on test results. The final phase involved assessing the PE pump's output performance through tests, including a simulated insulin infusion scenario. The findings revealed that the MPCV exhibited a pronounced rectification capability, significantly enhancing the pump's operational efficiency over traditional designs. The RC, on the other hand, effectively minimized fluid resistance, capitalizing on the fluid inertia effect for improved performance. Integrating the MPCV and RC aligned the fluid path from inlet to outlet closely parallel to the PE vibrator. This alignment reduced backflow, thereby improving the micropump's output efficiency. Operating at 240 voltage peak-to-peak (Vpp) and 230 Hz, the PE pump demonstrated a flow rate of 6.8 ml/min and an output pressure of 68.6 kPa while maintaining a compact size of merely 10 × 10 × 1.5 mm3. The precision in flow rate adjustment was refined to 0.15 μl, with the deviation in insulin delivery being approximately ± 3 %. The study presents a prototype for a continuous subcutaneous insulin infusion protocol, leveraging the PE pump's advanced features.

Seasonal COP of a residential magnetocaloric heat pump based on MnFePSi

The performance of a magnetocaloric heat pump (MCHP) consisting of active magnetocaloric regenerators (AMR) of 12 layers of MnFePSi magnetocaloric materials (MCM) with a linear distribution of Curie temperatures was investigated using a 1D numerical model. The model predicted the heating power and coefficient of performance (COP) of the AMR for a fixed temperature span of 27K, between 281K and 308K, and variable flow rate and AMR cycle frequency. A maximum applied magnetic field strength of 1.4T was used. A well-insulated house with a maximum heating power demand of 3kW (under quasi steady state conditions) was considered. Ambient temperature in The Netherlands was taken as a reference for the estimation of the seasonal heating power demand. Without optimizing the design of the AMR, the model predicts a maximum single-AMR heating power equal to 43.5W when the AMR operates at 3Hz and 3Lmin-1, and a maximum COP equal to 5.8 when it operates at 1.5Hz and 1Lmin-1 Considering the maximum heating power of a single AMR, approximately 69 AMRs are needed to provide the design heating power demand of the house. It was found that it is possible to achieve an AMR seasonal COP of 5.6 by continuously adjusting the flow rate and frequency of operation of the MCHP along with the ON/OFF switching of some groups of AMRs in order to adjust the heating power of the MCHP to the heating power demand of the house.

Characterization of organic fouling on thermal bubble-driven micro-pumps

Thermal bubble-driven micro-pumps are an upcoming micro-actuator technology that can be directly integrated into micro/mesofluidic channels, have no moving parts, and leverage existing mass production fabrication approaches. These micro-pumps consist of a high-power micro-resistor that boils fluid in microseconds to create a high-pressure vapor bubble which performs mechanical work. As such, these micro-pumps hold great promise for micro/mesofluidic systems such as lab-on-a-chip technologies. However, to date, no current work has studied the interaction of these micro-pumps with biofluids such as blood and protein-rich fluids. In this study, the effects of organic fouling due to egg albumin and bovine whole blood are characterized using stroboscopic high-speed imaging and a custom deep learning neural network based on transfer learning of RESNET-18. It was found that the growth of a fouling film inhibited vapor bubble formation. A new metric to quantify the extent of fouling was proposed using the decrease in vapor bubble area as a function of the number of micro-pump firing events. Fouling due to egg albumin and bovine whole blood was found to significantly degrade pump performance as well as the lifetime of thermal bubble-driven micro-pumps to less than 104 firings, which may necessitate the use of protective thin film coatings to prevent the buildup of a fouling layer.

Influence of the Hydraulic Circuit Setup on the Dynamic Performance of an Axial Piston Pump by Numerical and Experimental Analysis

Influence of the Hydraulic Circuit Setup on the Dynamic Performance of an Axial Piston Pump by Numerical and Experimental Analysis

Experimental investigation on the space heating performance of air source heat pump with vapor injection under frosting condition

For air source heat pump with vapor injection (ASHPVI), the vapor injection can improve its heating performance of ASHPVI at non-frosting low temperature condition. However, its effect under the frosting condition is still unclear. To improve the heating performance of ASHPVI under frosting condition, a test rig for the frosting of ASHPVI was built in a psychrometer testing room. Then, a new control strategy for vapor injection was proposed to ensure its safety, and two groups of frosting experiments with and without vapor injection were conducted. Results showed that under frosting condition, vapor injection can still improve the heating capacity of ASHPVI by 11.31 %. It can also make the outdoor coil surface temperature decreased by 0.8–4.6 °C, and further result in a faster frosting speed. Compared with the frosting duration without vapor injection (64 min), the frosting duration with vapor injection is shortened by 14 min. Owing to the faster frosting speed, the average COP with vapor injection decreases by 0.17, with a decrease rate of 6.03 %. When the heating capacity of AHSPVI without vapor injection under frosting condition can meet the building heating load, the vapor injection should not be adopted.

The effect of non-uniform inlet boundary conditions on the performance of the multiphase pump

Multiphase pump is an important equipment for oil and gas transportation. The gas-liquid distribution pattern at the inlet of a multiphase pump is crucial to its performance. We propose through an experiment that slug flow and annular flow are the main forms of gas-liquid distribution at the inlet of multiphase pumps. The effects of different flow patterns on the performance of multiphase pumps were investigated through numerical simulations and experimental tests. The results show that the multiphase pump is best adapted to the homogeneous bubble model, followed by the elastic flow and poorly by the annular flow. The energy conversion characteristic of annular flow is poor, and the higher the GVF is, the more obvious this characteristic is. The pressure distribution in the outlet region of the guide vane of the slug flow model is the most inhomogeneous, thus creating a larger vortex scale. The decrease in pressurization of the annular flow is most obvious with increasing GVF. At 30 % GVF, it decreased by 43 kPa compared to the uniform bubble flow model. The different flow patterns have a large effect on the impeller performance, but the distribution of the gas-liquid two-phase at the guide vane outlet tends to stabilize. The significance of this study is to further understand the performance of the first stage impeller of multiphase pumps under special working conditions, and then provide reference for the overall design of multistage pumps to broaden the scope of multiphase pump applications.

Comprehensive performance evaluation method of working fluids for high temperature heat pump based on multi-objective optimization

The working fluid has garnered significant attention as a critical factor influencing the efficiency of high-temperature heat pumps. A novel method based on multi-objective optimization has been introduced for assessing the performance of heat pump working fluids. The method enhances the clarity of the objective and flexibility in addressing various operating conditions, which helps to improve the efficiency of working fluid screening, especially for the complex mixture system. This study utilizes eight pure refrigerants as the initial fluid set and evaluates 560 binary mixtures with a 5% composition variation. The NSGA-II algorithm is combined with the theoretical heat pump cycle model to obtain Pareto optimal solutions regarding the mixtures, with the coefficient of performance and volumetric heating capacity as the objective functions. Then the evaluation of the optimal solutions is conducted by considering their flammability, toxicity, environmental performance, and temperature glide properties. Subsequently, a comprehensive performance index is derived. The evaluation reveals the dominant solution set for each pure refrigerant. The findings suggest that the blend R142b/R1233zd(E) with a mass fraction of R142b between 0.15 and 0.25 demonstrates a comprehensive performance index of 0.322–0.350, indicating superior performance during the basic cycle. Furthermore, various cycle configurations have been investigated. In the vapor injection configuration, R600a/R601(0.6/0.4) shows good performance in all aspects except flammability. The mixture R245fa/R601(0.2/0.8) exhibits superior overall performance in the internal heat exchanger configuration. It displays excellent temperature glide matching characteristics and good environmental performance. Nevertheless, it shows suboptimal performance in terms of toxicity and flammability. This approach replaces the previous qualitative comparison-based decision making methods, offering high efficiency and practicality.