Volumetric Efficiency Research Articles

Suction and discharge flow controls of a co-rotating scroll hydrogen circulation pump

The purpose of this paper is to reveal the relationship between the suction, discharge flow control and self-designed co-rotating scroll hydrogen circulation pump (CSHCP) aerodynamic performance and irreversible flow loss. The effect of five suction angles and five discharge spoiler positions on the performance and flow loss of a CSHCP was firstly revealed using the computational fluid dynamics (CFD) three-dimensional numerical simulation method combined with entropy production (EP) theory and omega vortex identification methods. The optimized suction angle and discharge spoiler position of CSHCP were identified through comparing with isentropic and volumetric efficiency, EP, vortex distribution and flow pulsation intensity. Subsequently, the performance and flow loss difference of CSHCP are further distinguished before and after optimization of suction and discharge spoiler structure under designed or variable rotational velocities. The results demonstrate that the optimized suction angle and discharge spoiler position angle are 22.5° and 45°, respectively. After the combination optimization of suction and discharge spoiler structure, the total EP and discharge temperature pulsation intensity of CSHCP are reduced by about 13.2% and 67.5% respectively. The research results provide a reference for the efficient and stable operation of HCP for fuel cell system.

Development of maximum conical shock angle limit for osculating cone waveriders

Hypersonic waveriders are special shapes with leading edges coincident with the body's shock wave, yielding high lift-to-drag ratios. The waverider geometry results from streamline tracing using the solutions of a basic flow field such as the wedge or the cone for specified shock and base curves. The base and shock curves can be independently prescribed in the osculating cone method enabling a larger design space. Generally, low values of the conical shock angle (9∘−15∘) are used. The lack of any method to limit the maximum cone angle for osculating cone waverider motivates this study. Mathematical expressions are derived for geometrical conditions that result in successful osculating cone waverider generation. A power law curve and a Bézier curve are analyzed. Closed-form expressions for the maximum cone shock angle are obtained for the power law curve. A numerical procedure to solve the same for the Bézier curve is developed. The results, for a typical Mach number of 6.0, evidently show that the maximum cone shock angle for successful waverider generation is significantly lower than the maximum angle for attached shock solutions. The limiting conditions developed will be essential in constraining the waverider sample space for automated multi-objective optimization routines. CFD simulations were conducted on waveriders designed with traditional shock angle of 12∘ and near limiting shock angle of 18∘. The analysis revealed a substantial 50% increase in volumetric efficiency, albeit with a minor decrease in aerodynamic performance. This highlights the critical need for determining the maximum conical shock angle when aiming for specific high volumetric efficiency.

Study on pressurization characteristics of single-screw steam compressor with water spray cooling under fluctuating heat source operating conditions

For a water-injected single-screw steam compressor (SSSC), the performance of the compressor is significantly affected by the water spray rate. However, the precise relationship between the water injection parameters and the operating parameters of the heat source under fluctuating heat source operating conditions (FHSOC) has not been elucidated. This paper introduces a constructed thermodynamic analysis model for the wet compression process under FHSOC aiming to explore the impact of fluctuating heat source parameters such as inlet steam temperature (IST) and inlet steam dryness (ISD) on the thermodynamic performance parameters of the compressor. The operational performance of the SSSC is then analyzed and compared under two distinct conditions: optimal water spray rate (OWSR) and fixed water spray rate (FWSR). The results demonstrate that when the IST of the SSSC increases within the range of 375 K–400 K, there is an initial decline followed by an increase in both the leakage rate and volumetric efficiency. Simultaneously, displacement and power consumption decrease, while adiabatic indicated efficiency and OWSR increase. Within this range, an optimal synergy is observed between IST and water spray parameters enabling the compressor to exhibit superior lubrication, sealing, and pressurization performance. On the other hand, when the ISD increases within the range of 0.92–1, the total heat transfer in the compression chamber decreases, and the leakage, OWSR, displacement, power consumption, adiabatic indicated efficiency, and volumetric efficiency all show varying degrees of increase. Regarding the volumetric efficiency corresponding to the OWSR, the impact of ISD on volumetric efficiency surpasses that of IST to a significant degree.

Optimization study of low lateral force in eccentric ball-piston pumps

Eccentric ball piston pump is a high power density hydraulic component. In this paper, a low lateral force design method for an eccentric ball-piston pump is proposed to reduce the lateral force between the ball and the cylinder by slightly inclination of the cylinder, and a mathematical model of the method is established. An experimental platform of eccentric ball-piston pump for evaluating the performance of cylinder block slightly inclination was established to verify the effect of slightly inclined cylinder block on the volumetric efficiency and mechanical efficiency of the pump. According to the experimental results of the prototype, the tilting angle from 0° to 3°, the lateral force between the ball piston and the cylinder decreases and then increases, the volumetric efficiency of the pump increases and then decreases, and the mechanical efficiency improves continuously. 3° of cylinder tilting angle reduces the friction torque by 2.63 Nm compared with the un-tilted cylinder, and the mechanical efficiency improves by 7.12%. 2° of cylinder tilting angle reduces the leakage volume by 0.475 L/min compared with the un-tilted cylinder, and the volumetric efficiency improves by 3.67%. This study is instructive for the study of high efficiency of eccentric ball piston pumps.

Unsteady internal flow characteristics study of a hydrogen circulation pump under different pressure differential conditions

The purpose of this paper is to investigate the flow and pressure pulsation characteristics of hydrogen circulation pump under varying pressure differences. A dynamic mesh technology was employed to conduct an unsteady numerical simulation of the interior of the hydrogen pump. The pressure pulsation within the pump cavity area was analyzed using fast Fourier transform, and the unevenness of pressure and flow inside the pump under varying pressure differential conditions was specifically studied. The results reveal that interference between dynamic and static in the pump cavity, caused by meshing clearance between rotors and radial clearance between the rotor and pump cavity, leads to pressure pulsation peaks occurring at twice the rotational frequency at all monitoring points. Additionally, as the pressure difference increases, the exhaust flow rate at the outlet of the pump cavity decreases from 49.237 m3/h to 12.392 m3/h, while volumetric efficiency decreases from 85.95% to 32.3%.

Modeling and experimental validation of twin lip balanced vane pump considering micromotions, contact mechanics, and lubricating interfaces

This paper presents a model formulation for balanced twin lip vane pumps and an experimental activity to validate the model. The simulation model begins with a geometrical module that preprocesses the CAD drawings of a given unit. The model then performs a fluid dynamic analysis using a lumped-parameter formulation to solve for the pressures inside properly defined control volumes within the unit. The fluid dynamic model is solved simultaneously with a motion module that evaluates the planar motions of the vanes using Newton’s law of motion and with a lubricating interface solver based on the Reynolds equation. Contact dynamics formulations and elastohydrodynamic relations are applied at the vane locations in contact with the cam ring. The comparison with experimental results highlights a good match in volumetric and hydromechanical efficiencies. The measured outlet pressure ripple matches the simulated one for all tested speeds and pressures. The paper also shows a breakdown of the distribution of volumetric and power losses arising from various components of the machine. The proposed methodology is computationally inexpensive, so it can be used in future design and optimization studies aimed at improving the performance of such units.

Optimization and experiment research of the cylinder block of the roller piston pump

The roller piston pump is a new type of axial piston pump. The pump has the advantages of high limiting speed, low noise, and vibration compared to the traditional axial piston pump. However, the structure and flow channel of the cylinder block of the roller piston pump are more complicated. When the cylinder block is subjected to high hydraulic pressure, its radial compressive deformation is large, which will lead to wear of the cylinder block and distribution shaft. For this problem, the paper will optimize the structural parameters of the cylinder block. Eight key parameters of the cylinder block are selected as the design variables, and the maximum radial deformation and mass of the cylinder block are taken as the optimization objectives. The central composite design method is used to generate 81 sets of sample data, and the second-order response surface model is obtained by regression analysis. The optimal structural parameters of the cylinder block are obtained through multi-objective optimization, and the material of the cylinder block is optimized. Finally, an experiment bench was built for experimental validation, and the efficiency of the pump was further investigated. The optimization results show that the maximum compression deformation of the inner diameter surface of the cylinder block decreases from 15.865 to 4.903 µm, and the mass of the cylinder block increases from 434.951 to 489.892 g. The experimental results show that the load-bearing pressure of the optimized roller piston pump increases from less than 15 to 35 MPa, and compared with the traditional axial piston pump, there is an increase in both mechanical efficiency and volumetric efficiency.

Evaluation of CI Engine Performance Using Compression Ratio for Palm Oil Biodiesel

The experiment explores vegetable oils as potential future fuels for internal combustion engines, particularly compression ignition engines designed for diesel. However, these oils have distinct properties from diesel, requiring modifications for direct use. Integration approaches include adjusting oil properties or adapting engines. Commonly, transesterification aligns oil properties, but using biodiesel often affects engine performance. In this study palm oil biodiesel as a diesel substitute, evaluating engine performance and emissions. In a short-term test, engine performance and emission traits by employing biodiesel compression ratio of 12:1, 14:1 and 18:1 with diesel at full load. Findings indicated that 14:1 and 18:1 exhibited 1.01 % and 1.02 % higher brake power than pure diesel. Volumetric efficiency percentages were 82.33 for 14:1, 82.36 for 18:1, and 82.30 for 12:1. Notably, 14:1 and 18:1 showed 5.44% and 10.90 % increased brake thermal efficiency compared to diesel. Interestingly, 14:1 and 18:1 displayed 2.35 % and 2.61 % higher mechanical efficiency than diesel. The exhaust gas temperature was notably decreased in 12:1 to 18:1 compression ratio. Nitric oxide concentrations were 65.07 ppm for 12:1, 124.44 ppm for 14:1, and 126.48 ppm for 18:1. Carbon dioxide levels increased by 9.79 % for 14:1 and 62.47 % for 18:1 relative to diesel. Carbon monoxide concentrations were 0.07 % for 14:1 and 0.05% for 18:1, in contrast to diesel's 0.12%.

Experimental study and model optimization of thermodynamic performance of a single screw water vapor compressor

Single screw water vapor compressor has greater advantages under conditions of low suction temperature and high compression ratio, however, the current study has the following limitations: (1) the volumetric and isentropic efficiency were substituted as a fixed value into the models of compressor, (2) The suction temperature is concentrated in the medium-high region, (3) The compression ratio is concentrated in the medium-low range, which failed to accurately describe the water vapor compression process. Therefore, the relationship between the volumetric efficiency, isentropic efficiency and key characteristic parameters of compressor is studied experimentally, the mathematical models of the volume flow and compression power are established and verified by experiments, the changes of the mass flow, compression power, COP and SMER with suction temperature, discharge pressure and compression ratio are analyzed, the operation process parameters of the single-screw water vapor compressor are optimized.

Predict the characteristics of diesel engine using glycine max oil biofuel

Significant research is devoted to the transformation of Glycine max oil (soybean oil) into biofuel. An exhaustive investigation into the performance, combustion and emission analyses of glycine max oil biofuel (GMOB) in the context of optimization studies involving variable engine factors such as load, injector timing and so forth, has yet to occur. This study endeavors to fill the gap in the academic literature regarding comprehensive engine investigations of GMOB. In this study, five distinct mixtures of GMOBs are combined with diesel: DS1—0% biofuel with 100% diesel, DS2—5% biofuel with 95% diesel, DS3—20% biofuel with 80% diesel, DS4—40% biofuel with 60% diesel and DS5—100% biofuel and 0% diesel. Using standard ASTM limits, the properties of the biodiesel samples were evaluated and confirmed (the kinematic viscosity at 40°C for GMOB is 4.6 mm2/s, whereas that of unadulterated diesel is 3.0 mm2/s). Utilizing the combustion, emission and performance characteristics of a compression ignition engine, the blend, load and injection timing (IT) were optimized. At 100% load, an upward trend in indicated thermal efficiency is observed for both diesel and biofuel blends. Furthermore, the volumetric efficiency of all biofuel blends was enhanced through the implementation of advanced IT (24.5° b TDC). Additionally, smoke emission is observed to increase by 18.5°–24.5° b TDC across all mixtures. Biofuel mixtures exhibit a negligible minimum rate of pressure increase per degree.

CO2 capture in a novel rotating spiral contactor with hydraulic seal: Hydromechanics, mass transfer and modeling

The efficient capture of CO2 has always been a goal pursued by people. However, low gas handling capacity and low gas–liquid ratio restricts existing gas–liquid contactors, especially for non-rotating ones. In this study, a gas–liquid contactor with high gas handling capacity and high gas–liquid ratio, the rotating spiral contactor, was developed. Hydrodynamic properties of the contactor were experimentally or theoretically investigated. A novel interface model was developed to describe gas–liquid interface shape. CO2 capture using MEA/DMEA aqueous solution were evaluated in terms of space–time yield (τ), overall volumetric mass transfer coefficient (KGae) and CO2 capture efficiency (η). A rate-based model was developed and applied for the first time to predict CO2 capture in the rotating spiral contactor. The hydrodynamic results showed that liquid layer thickness was below 400 μm for the liquid with viscosity of 14.5 mPa.s. Under the rotational speed of 1200 rpm, the gas–liquid ratio ranged from 525 to 2700, while the gas–liquid surface area remained around 667 m2/m3. The interface model predicted interface thickness within a relative deviation of ± 20 %. The results also showed that τ, KGae and η respectively were 3428–17021 h−1, 1.0–6.4 kmol.m−3.h−1.kPa−1 and 38–98 % at the gas–liquid ratio range of 200–1000. The predicted KGae and η by rate-based model agreed well with the experimental data within a relative deviation of ± 15 %. This rotating spiral contactor is ideally suitable for the scenarios with large gas handling requirement and high gas–liquid ratio.

Investigation of the leakage in the flow distribution pair of radial piston hydraulic motors through CFD analysis and experiments

The internal leakage of a radial piston motor (RPM) is an unavoidable structural characteristic, and the amount of internal leakage has a critical effect on the volumetric efficiency of the motor. Using the distribution plate as the force body, an equation for the balance between the preload spring force and the hydrodynamic force is analytically derived, the variation range of the clearance of the flow distribution pair (FDP) is determined, and a model for the internal leakage flow of the FDP is developed. Based on computational fluid dynamics (CFD) simulations, the effects of the oil film thickness, inlet pressure, motor speed, and oil temperature on the leakage volume are investigated. An efficiency test system for RPMs is built and tests are performed on motor prototypes. The experimental results show that the error between experimental and simulation results decreases gradually with increasing motor speed. When the motor runs at the rated speed, the error is stable within 5%. The experimental results verify the correctness of both the theoretical and CFD models. The CFD analysis method can be used as a technical means to optimize the motor volumetric efficiency and the preload spring design.

Research and design of internal meshing gear pump separating crescent plate

The design of the crescent block is a key factor in the high-pressure operation of the internal meshing gear pump. In order to increase the output pressure of the pump, this article designs a new type of separable crescent plate. Then, taking a certain type of high-pressure internal meshing gear pump as the research object, a nonlinear differential equation for the internal flow field of the gear pump was established, and the pressure distribution law in the transition zone of a cycle was derived. A mathematical model of the device was established based on the equilibrium conditions of the internal and external crescent block forces. Finally, experimental research was conducted on the design parameters of the separation crescent plate. The results showed that under the conditions of displacement of 100.5 ml/r, pressure of 20.5 MPa, and rotational speed of 1800 RPM, the compensation chamber angle range was 31.23°, and the pump's volumetric efficiency could reach 94.6%. There were no abnormal phenomena during the entire operation of the pump, and there was no jamming or jamming of the friction pair.

Rotor profile improvement by optimizing meshing curve for helical roots blowers in HFCV application

This paper introduced a novel design and optimization method of the Roots profile to enhance the performance of helical Roots blowers in Hydrogen Fuel Cell Vehicle applications. The proposed profile was generated based on defined meshing curves, and thus the shape of meshing curves can be explicitly optimized. First, the mathematical models for Roots profile generation based on meshing curves were presented. Next, the influence of the shape of meshing curves on the geometric performance of Roots rotors was investigated, and the meshing curve was further optimized using a genetic algorithm. Finally, the CFD method was employed to identify the specific performance enhancement brought by the optimized Roots profile. Results showed that the proposed profile design method could flexibly adjust the shape of meshing curves so as to intuitively control the spatial leakage channels formed by helical rotors. The optimized profile boosted the volumetric and adiabatic efficiency of the Roots blower up to 2.87%, and 1.89%, respectively, compared to the original one. The leakage analysis indicated that the performance improvement was attributed to the reduction of the leakage rate caused by the blow-hole and contact line. The conclusions obtained could effectively support the development of high-efficiency helical Roots blowers.

Mating Season Influences Placental Characteristics, Plasma IGF Concentration, and mRNA Expression without Affecting Lamb Birth Weight in Akkaraman Ewes

Seasonal variations significantly impact lambs’ birth weight and post-natal growth of lambs, yet the underlying physiological mechanisms remain insufficiently explored. Therefore, this study examined the effects of mating season on lamb birth weight, placental characteristics, maternal concentrations of insulin-like growth factors (IGFs) in plasma, and placental mRNA expression levels of IGFs in Akkaraman ewes reared under extensive conditions. Ewes were mated in the breeding season (September; n = 35) and out-of-breeding season (April; n = 27). Blood samples were taken from the jugular vein of all ewes using a vacutainer in sterile heparin tubes every month from mating to parturition. Post-lambing, both dam and lamb weights were recorded, and placental characteristics were documented within 12 hours of parturition in both seasons. The number and weight of cotyledons were higher (P<0.05) in ewes mated during the breeding season than those mated during the out-of-breeding season. Also, ewes mated during the breeding season demonstrated thicker large cotyledons (P<0.05). Although placental and cotyledonal efficiencies were similar in both mating seasons, volumetric cotyledon efficiency was higher (P<0.05) in ewes mated during the out-of-breeding season than in those bred during the breeding season. Additionally, ewes mated in the breeding season exhibited higher plasma concentration of IGF-I at three months of gestation than ewes mated in the out-of-breeding season (123.8 ± 9.8 vs. 99.3 ± 11.4 ng/ml, respectively; P<0.05). Although the mating season did not affect the IGF-I gene’s placental mRNA expression levels, the IGF-II gene’s expression level was notably higher (P<0.05; fold change: 2.84) in ewes mated during the breeding season. The results suggest that mating season influences placental characteristics, maternal plasma IGF-I concentrations, and IGF-II gene expression levels of cotyledons due to alterations in cotyledon numbers and size on the surface of the placenta.

Recalculation of Pump Speed and Stroke Length to Increase Production Rate and Volumetric Efficiency of HPU Well BTN-01

In the "BTN-01" well, one of the wells is owned by KSO PT PERTAMINA EP PT Sarana GSS Trembul. The "BTN-01" well is installed with a hydraulic pumping unit pump that experiences decreasing production, and based on tests on January 30, 2023, the output of the "BTN-01" well produces only 216 bfpd with 98% of water cut. The pump operates on 8 SPM of pump speed and 74-inch stroke length, with 43% of volumetric efficiency. As per theory, a proper design of hydraulic pumping unit pump will produce a volumetric efficiency value above 70%. To overcome this problem, it is necessary to perform research, started with an evaluation on the existing design and continue to quantitative research by recalculating the optimum production rate from IPR calculation, recalculating pump speed, recalculating pump stroke length, and recalculating volumetric efficiency to achieve higher value on both production rate and volumetric efficiency of the pump. In the "BTN-01" well, IPR was calculated by the Wiggins method, and it is known that the oil production rate is 5.53 bopd, 421.96 bwpd of water rate, and the fluid production rate is 427.5 bfpd. Based on the results of HPU redesign and recalculation of the optimum production rate, the new value of pump speed is 7 SPM (existing 8 SPM), the pump stroke length is 70 inches (existing 74 inches) with a volumetric efficiency of 78.45% (existing 43%) that can be called optimal.

Spatial Distribution of Heterogeneity of the AB Reservoir Unit of Zubair Formation in the South Rumaila Oilfield, Southern Iraq

Reservoir heterogeneity, a critical factor in fluid flow and recovery processes, manifests at various scales and is influenced by depositional facies, diagenesis, and structural features. This study aims to quantify and map the spatial heterogeneity within Unit AB of Zubair Formation, south Rumaila oilfield, utilizing the Lorenz coefficient (Lk ) for vertical heterogeneity and ordinary kriging for spatial interpolation. Analyzing porosity and permeability data from 44 boreholes using the Lk coefficient revealed that the AB reservoir unit is primarily homogeneous, with 65% of boreholes exhibiting homogeneity. However, heterogeneity is present in the central and southeastern portions of the oilfield. Without considering the reservoir’s heterogeneity, placing injection wells along the eastern flank could lead to increased water production and reduced volumetric sweep efficiency.

Surrogate-Based Multi-Objective Optimization of Flux-Focusing Halbach Coaxial Magnetic Gear

Due to their contact-free and low-maintenance features, magnetic gears (MGs) have been increasingly investigated to amplify the torque of electric motors in electric vehicles (EVs). In order to meet the requirements of propelling EVs, it is essential to design an MG with a high torque density. In this paper, a novel flux-focusing Halbach coaxial MG (FFH-CMG) is proposed, which combines the advantages of flux focusing and Halbach permanent magnet (PM) arrays. The proposed structure has a higher torque performance and greater efficiency than conventional structures. A multi-objective design optimization based on a surrogate model is implemented to achieve the maximum volumetric torque density (VTD), torque-per-PM volume (TPMV), and efficiency, as well as the minimum torque ripple, in the proposed FFH-CMG. The employed optimization approach has a higher accuracy and is less time-consuming compared to the conventional optimization methods based on direct finite-element analysis (FEA). The performance of the proposed FFH-CMG is then investigated through 2D-FEA. According to the simulation results, the optimized FFH-CMG can achieve a VTD of 411 kNm/m3, and a TPMV of 830 kNm/m3, which are significantly larger than those of the existing MGs and make the proposed FFH-CMG very suitable for EV applications.

Performance analysis and emission characteristics of VCR diesel engine using palm stearin oil biodiesel as fuel

Abstract The increasing depletion of fossil fuels has prompted international efforts to search for diesel substitutes. One way to considerably reduce fuel shortages would be to use bio-derived fuels as replacements. Transesterification of edible or nonedible vegetable oils yields biodiesel, which is one example of a bio-origin fuel and a workable solution. Biodiesel’s characteristics are often more advantageous than those of diesel. One well-known example of a nonedible vegetable oil is palm stearin. In this work, we investigate the potential use of transesterified palm stearin methyl esters (PSME) as a substitute fuel. A rated compression ratio (CR) of 17.5 and 210 bar of fuel injection pressure were employed in the experimental investigations, which were carried out at a constant speed of 1500 rpm. Our main goals were to reduce emissions and improve engine performance. The evaluation parameters encompassed brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), and emission indices. It was observed that using PSME led to better performance and fewer emissions when compared to using conventional diesel, especially when the CR was 17.5. Increased BTE, decreased BSFC, lower air–fuel ratios, and decreased volumetric efficiencies were all correlated with higher CR. As a byproduct of palm oil, PSME shows promise as a seasonally and geographically specific feedstock for biodiesel production, providing benefits over conventional diesel fuels in terms of performance and the environment.

Design and experimental validation of a valve-distributed water radial piston pump

In underground coal mining, there is an urgent need for reducing the noise, hydraulic shock, and leakage of reciprocating pumps. Flow pulsation is strongly dependent on the number of pistons for single-acting reciprocating pumps. Water hydraulic radial piston pumps (RPPs) allow the pistons to be radially distributed, which makes the multi-piston design easier compared to traditional single-acting reciprocating piston pumps. In this study, a novel valve-distributed water RPP was developed in which the star wheel assembled on the camshaft is used to drive the connecting rod-crosshead-piston assembly and realize the reciprocation of the piston and suction-discharge of the pump check valves. Mathematical and numerical models representing the RPP were built using MATLAB and AMESim, respectively. Three-dimensional computational fluid dynamics analyses were performed to investigate the internal flow field of the suction and discharge circuits as well as the flow characteristics of the discharge valve opening. A prototype pump was manufactured and tested for 200 h and then disassembled to evaluate the wear condition. The tested instant flow rates were lower than those obtained from the theoretical and simulation analyses. The experimental results also revealed that the average flow rates were almost independent of the output pressure and that the volumetric efficiency decreased with increasing rotational speed when the output pressure was larger than 25 MPa. Inspecting the disassembled water RPP revealed that scuffing problems occurred in the pistons, whereas the other components remained intact. The findings of this study offer a reference for water hydraulic power units in various applications and for investigating the intensity of water hydraulics.