Volumetric Efficiency Research Articles

The Influence of the Intake Geometry on the Performance of a Four-Stroke SI Engine for Aeronautical Applications

In this work, the influence of plenum and port geometry on the performance of the intake process in a four-stroke spark ignition engine for ultralight aircraft applications is analyzed. Three intake systems are considered: the so-called “standard plenum”, with a relatively small plenum volume, the “V1 plenum”, with a larger plenum volume, and the “standard plenum” equipped with a large curvature manifold called the “G2 port”. Both measurements and 3D CFD simulations, by using Ansys® Academic Fluent, Release 20.2, are performed to characterize and analyze the steady-flow field in the intake system for selected valve lifts. The experimental data and the numerical results are in excellent agreement with each other. The results show that at the maximum valve lift, i.e., 12 mm, the V1 plenum allows an increase in the air mass flow rate of 9.1% and 9.4% compared to the standard plenum and the standard plenum with the “G2 port”, respectively. In addition, the volumetric efficiency has been estimated under unsteady-flow conditions for all geometries at relatively high engine rpms. The difference between numerical results and measurements is less than 1% for the standard plenum, thus proving the accuracy of the model, which is then used to study the other configurations. The V1 plenum shows a fairly constant volumetric efficiency as the engine speed increases, although such an efficiency is lower than that of the other two geometries considered in this work. Specifically, the use of the “G2 port” leads to an increase of 1.5% in terms of volumetric efficiency with respect to the configuration with the original manifold. Furthermore, for the “G2 port” configuration, higher turbulent kinetic energy and higher swirl and tumble ratios are observed. This is expected to result in an improvement of air–fuel mixing and flame propagation.

Research on leakage characteristics of working clearances of hydrogen circulation pump

The volumetric efficiency of the hydrogen circulation pump (HCP) is mainly affected by the amount of leakage in working clearances. Studying the leakage characteristics of working clearances is of great significance for optimizing the performance of the HCP. Therefore, this paper developed a three-blade elliptical conjugate rotor HCP, and compared the results of experiments and simulations for different working conditions. On this basis, the flow rate, pressure, and internal flow field changes of radial clearance models and axial clearance models with four different scales of 0.1mm, 0.14mm, 0.18mm, and 0.22 mm were studied. The results indicate that: under four different pressure ratios and rotational speeds, the simulation results using the overlapping grid method showed a maximum difference of 4.17% compared to the experimental results, verifying the reliability of the simulation calculation method; the average flow rate of the HCP is linearly inversely proportional to both the radial clearance and the axial clearance, with a decrease rate of 11.6 Nm3/h and 5.8 Nm3/h as the clearance size increases by 0.04 mm; the radial clearance leakage of the same size is higher than the axial clearance, the leakage value in the radial clearance between the rotors is higher than that between the rotor and the pump casing, and the internal leakage of axial clearance is not evenly distributed, with higher leakage value in the middle area than that in the left and right areas.

Flow characteristics of asymmetric plunger pairs in high-pressure plunger pumps

Abstract The deep-sea submersible is an essential piece of equipment for deep-sea development, serving as a crucial tool for conducting exploration and operations in the deep ocean. As the core component of the hydraulic system, the plunger pump is vital for ensuring the smooth lifting and lowering of the submersible. The plunger pair, which constitutes the most significant friction pair in plunger pumps, plays a pivotal role in determining both the service life and volumetric efficiency of the pump through its friction, lubrication, and sealing performance. This article proposes a flow model for the plunger pair in eccentric and inclined positions, considering its various orientations and placements. It elucidates the deformation and leakage characteristics of the plunger pair under different configurations, including various postures, material properties, and design parameters. The findings not only provide a theoretical foundation for the design of reciprocating seals and the evaluation of sealing performance but also contribute to the broader field of parameter design and performance assessment for other types of gap seals.

Engine Mass Flow Estimation through Neural Network Modeling in Semi-Transient Conditions: A New Calibration Approach

Nowadays, engine experimental research represents a very expensive field within the automotive industry, but it remains fundamental for engine and vehicle development. The present work aims to investigate a novel approach for engine control system calibration, by adopting machine learning techniques to model physical parameters of the engine starting from experimental data measured at the test bench. The main goal is to create a methodology which accelerates the calibration process without losing accuracy. A model that estimates air mass flow is created by adopting either a tree ensemble model or an artificial neural network trained on a small dataset, which was previously acquired at the test bench using a random calibration of the volumetric efficiency map. The model’s performance is first validated on a larger, random dataset. Then, the volumetric efficiency calculated from the air mass flow model estimation is used to calibrate the transfer function of the Engine Control Unit. Finally, the sensitivity of the model error correlated with the number of data points acquired is used in order to determine the best practice for a Design Of Experiment, which minimizes data acquisition. The methodology proposed can lead to reduced time and costs of the whole calibration process of the engine, without losing accuracy. The analysis was conducted on the entire vehicle, which is crucial for drivability, especially in motorcycles since they are highly sensitive to air-to-fuel ratio adjustments. This work demonstrates that machine learning models can be adopted for the fine-tuning of the calibration process, which is normally performed manually.

Research and clearance analysis on of steam twin-screw expander employed in indutrial waste heat recovery

In actual factories, screw expanders frequently operate under partial loads.To address the lack of theoretical research and the risks of errors in engineering design associated with steam pressure differential power generation under these conditions,a simulation of the twin-screw expander's working process was developed. The rotor profile was designed, geometric variables such as rotor mesh clearance were calculated, and models for leakage and heat transfer were established. A suction pressure correction model was proposed for the suction process under partial loads, along with correction parameters to simplify simulations.Experimental results demonstrate that the twin-screw expander operates stably under highly fluctuating conditions, demonstrating excellent variable load performance.As the load decreases, the loss of suction pressure reduces the expander's pressure differential, leading to lower leakage and improved efficiency. When the load is reduced from 100 % to 65 %, the volumetric efficiency increases from 78.87 % to 84.76 %, and the isentropic efficiency rises from 66.81 % to 74.25 %.Compared to experimental data, the flow calculation error of the suction pressure correction model presented in this study is controlled within 3 %.This model addresses performance calculations under partial loads, ensuring that theoretical models better align with real-world applications and supporting accurate selection of twin-screw expanders.This model enables appropriate selection of expanders to reduce pressure losses and enhance economic efficiency.

Solid-liquid flow characteristics of twin-screw pump under solid-containing transportation

Abstract Twin-screw pumps have the wear risk when the fluid contains particles. In order to clarify the flow characteristics of the twin-screw pump under solid-containing transportation, the solid-liquid flow characteristics research on a twin-screw pump are carried out using numerical simulation and experimental methods in this paper. The results show that the particle concentration has a small effect on the volumetric efficiency and hydraulic efficiency of the twin-screw pump under each differential pressure, but the presence of particles could increase the volumetric efficiency limitedly. The velocity of main flow and the turbulent kinetic energy have been restrained by the particles in the tooth chamber, and the inhibition phenomenon is more significant with the increase of particle concentration. The particles in the tooth chamber are inhaled by the leakage flow at the tooth-tip clearance. Some particles hit the tooth-tip and cause the abrasion, others flow into the tip clearances, which decreases the leakage flow velocity and results in a higher volumetric efficiency than that of the pure-liquid condition. The results of the study will provide a theoretical basis for the study of solid-containing transportation and particle wear in twin-screw pumps.

Effects of distribution valve spring stiffness and opening pressure on the volumetric efficiency of micro high-pressure plunger pump

With the rapid development of material science and manufacturing capabilities, hydraulic technology is increasingly high-pressure, lightweight and miniaturizing. Micro plunger pump is widely used in the field of deep-sea hydraulic equipment and advanced intelligent hydraulic equipment, owing to its high-power density, high output pressure and many other advantages. Its broad application aims to examine the inlet and outlet distribution valve spring parameters change on the micro high-pressure plunger pump volumetric efficiency, by changing the inlet and outlet distribution valve. This paper is based on the simulation of AMESim engineering software to derive multiple sets of data. It compared and analysed the specific effect of different spring stiffness and opening pressure on the volumetric efficiency of the micro high-pressure plunger pump which was then verified through experiment. Results of this study have certain reference significance for the design of the spring of the inlet and outlet distribution valve of the micro high-pressure plunger pump, which facilitates the optimization and improvement of the dynamic performance of the micro high-pressure plunger pump.

Design and performance study of a novel variable cross-sectional rotor for twin-screw vacuum pumps

The variable cross-sectional rotor is considered as a potential technology to further improve the performance of twin-screw vacuum pumps, due to its remarkable advantages of large internal volume ratio. In this study, a mathematical model of variable cross-sectional rotors was established to obtain its generation method. A novel type of variable cross-sectional rotor was constructed by using the proposed method, and this rotor exhibits superior sealing performance. The variable cross-sectional rotor was geometrically compared with the traditional equal cross-sectional rotor. Then the accuracy of the proposed generation method as well as the advance of the generated variable cross-sectional rotor were verified by experimental test results. Results show that this design method achieves the construction of high accuracy variable cross-sectional rotors by generating 3-D helical surfaces. Compared with the traditional equal cross-sectional rotor, the geometric pumping speed and internal volume ratio of the variable cross-sectional rotor are increased by 7.57 % and 10.45 %, respectively. The volumetric efficiency of the variable cross-sectional rotor is increased by 6.52 % and the time to reach the ultimate pressure is reduced by 9.42 %, demonstrating superior pumping and sealing performance.

Experimental and Numerical Study on Scroll Compressor under Different Profile Correction and Discharge Ports Shapes

The scroll compressor is an essential component in air conditioning and heat pump systems. This study examined an electric scroll compressor using R22 refrigerant, focusing on how modifications in the scroll head profile and discharge structure affect its performance. Initially, a semi-empirical model based on mathematical formulas was developed to predict the performance improvements of the updated scroll compressor. Three-dimensional simulation software was then used to illustrate changes in the internal flow dynamics before and after enhancements. The predictions were validated through experimental testing. Both the semi-empirical model and the three-dimensional unsteady numerical calculation model analyzed the effects of modifications to the tooth head profile and discharge port shape on compressor performance. The adoption of a PMP profile correction delayed the compressor discharge process, shifting the starting discharge angle from 315°to 344°, thereby reducing under-compression occurrences during operation and increasing volumetric efficiency by 1.31%. Additionally, mathematical formulas correlating temperature with compressor performance were developed from fitting data, predicting compressor behavior under various conditions. Moreover, replacing a circular discharge port with a waist-shaped port reduced power consumption by 0.59 kW, resulting in a more uniform temperature distribution and enhanced mass flow rate during compressor operation.

Thermodynamic performance and compression characteristics analysis of low GWP refrigerant in compressors: Experimental investigation and 0-D/3-D simulation

The utilization of low global warming potential (GWP) refrigerants is crucial for reducing greenhouse gas emissions. Among these alternatives for hydrofluorocarbons (HFCs), R290 stands out as a natural refrigerant with a low GWP value of 3. Therefore, it is beneficial to promote its widespread adoption and enhance the efficiency of compressors and their systems that utilize R290 to mitigate the greenhouse effect. The present study investigates and compares the thermodynamic performance and compression characteristics of a high-speed compressor employing R290 as a refrigerant with those of an R32 compressor. In contrast to previous studies, this paper presents a novel approach by developing validated the zero-dimensional (0-D) and three-dimensional (3-D) simulation model, along with experiments, to investigate the distribution of performance loss and suction-compression characteristics in high-speed R290 compressors. The results demonstrate that the R290 compressor exhibits superior volumetric efficiency, while excessive compression at high speeds leads to a noticeable reduction in indicated power. The combination of increased over-compression loss and motor loss at high speeds resulted in a 11.7% rise in input power, leading to an 8.4% decline in thermodynamic performance for the R290 compressor under standard heating compared to the R32 compressor.

Study on the performance and emissions of compression ignition engine powered by diesel and biodiesel blends

This research tested all specifications of synthesized biodiesel according to the American Society for Testing and Materials (ASTM). The spirulina micro-algae synthesized biodiesel is mixed with conventional diesel in different blends named B0, B10, B20, and B30. The number after the letter “B” indicates the ratio of (biodiesel/diesel blend), which will be used instead of net diesel for experimental purposes. Those blend specifications are investigated, and results are tabled. The variable compression ratio, single-cylinder, water-cooled, and compression ignition engine, were utilized to study the effect of algae biodiesel/diesel blends on engine performance and its exhaust emission constituents. No hardware modification was required, and the blends directly injected in the combustion chambers. The experimental investigation showed that B10 with 14.5 CR and 25 % load -as compared with net diesel- enhances almost all performance parameters more than other blends (1.7 % more brake efficiency, 12.7 % less brake specific fuel consumption, 3.45 % less in exhaust temperature, 6.7 % more in A/F ratio, and volumetric efficiency was nearly the same). It also enhances some emission parameters more than other blends (12 % less in unburned hydrocarbons (UHC′s) emissions), but with a slight increase in nitric oxides (NOX) emissions (2.4 % more than net diesel) with nearly the same values of carbon dioxide (CO2) and carbon monoxide (CO) emissions. In general, in comparison with net diesel and with icreasing blend ratio, the following results are observed: the volumetric efficiency results fluctuated with a slight difference. Both brake thermal efficiency, air/fuel ratio, and exhaust temperature were enhanced with a slight increase in brake-specific fuel consumption. For emissions: The carbon dioxide and nitrogen oxides emissions both are reduced significantly, while there was a slight increase in CO and UHC′s levels. Finally, this work recommends using the algae biodiesel as clean and substitution fuel.

Flow characteristics and factors affecting flow pulsation of external meshing herringbone gear pump

To enhance the outlet flow stability of the external herringbone gear pump, an analysis was conducted on the main influencing factors, key geometric parameters were identified, and a numerical model was developed for fluid analysis. A numerical model was then established for fluid analysis. The accuracy of the numerical model was verified by comparing it with experimental results, with simulation errors of displacement and volumetric efficiency being < 5%, ensuring the simulation's accuracy. The simulation results indicated that the pump's head (49.7808 m) and outlet pressure (4.9285 bar) remained stable. At 700 rev/min, the simulated volumetric efficiency was 82.94%. Subsequently, the impact of helix angle, changes in center distance, and tip clearance on outlet flow stability were analyzed. The analysis revealed that increasing the helix angle from 27° to 30° could reduce flow pulsation. A slight reduction in center distance from 180.3 (δ = +0.3 mm) to 179.9 mm (δ = −0.1 mm) effectively decreased mass flow difference and outlet pressure pulsation, enhancing outlet output stability. Reducing tip clearance from 0.25 to 0.12 mm, while meeting design requirements, resulted in more stable pressure and lift output. These results ensured smooth pump operation, improved outlet output stability, and met low-flow pulsation requirements. This study offered valuable insights into the design and production of the external meshing herringbone gear pump.

Synchronously Consolidating Li, Se, S, and C for Robust Li-SeS Batteries.

S-redox involving solvated polysulfides is accompanied by volumetric change and structural decay of the S-based cathodes. Here, we propose a synchronous construction strategy for consolidating Li, Se, S, and C elements within a composite cathode via a paradigm reaction of 8Li+2Se+CS2 = 2Li4SeS+C. The obtained composite features crystalline Li4SeS encapsulated in a carbon nanocage (Li4SeS@C), exhibiting ultrahigh electrical conductivity, ultralow activation barrier, and excellent structural integrity, accordingly enabling large specific capacity (615 mAh g-1) and high capacity retention (87.3% after 350 cycles) at 10 A g-1. TOF-SIMS demonstrates its superior volumetric efficiency to a similar derivative SeS@C (2Se+CS2 = 2SeS+C), and DFT reveals its lower activation barrier than Li2S@C and Li2Se@C. This consolidation design significantly improves the electrochemical performance of S-based cathodes, and the paradigm reaction guarantees structural diversity and flexibility. Moreover, employing a synchronous construction mechanism to maximize the synergistic effect between element consolidation and carbon encapsulation opens up a new approach for developing robust S or chalcogenide cathodes.

Artificial neural network based forecasting of diesel engine performance and emissions utilizing waste cooking biodiesel

Ecological and environmental problems resulting from fossil fuels are due to the harmful emissions released into the atmosphere. The rising interest in searching for alternative fuels like biodiesel is growing to solve these problems. Waste cooking oil (WCO) is transformed into methyl ester and combined with biodiesel in percentages of 25, 50, 75, and 100%. Research is done on the impacts of methyl ester blends on engine performance and emissions. Compared to diesel, the methyl ester combination showed 25% lower brake power and 24% loss in thermal efficiency at maximum load and 1500 rpm. However, diesel fuel showed 23% lower specific fuel consumption increase than biodiesel. Compared to diesel, methyl ester exhibits 15% lower air-fuel ratio and 4% volumetric efficiency. Biodiesel lowers CO, HC, and smoke concentrations by 12, 44, and 48%, respectively, compared to diesel. Biodiesel emits 23% higher NOx at 1500 rpm and 100% engine load. To predict the emissions and performance of different percentages of biodiesel at engine speed variation, an artificial neural network (ANN) model is presented. ANN modeling minimizes labor, time, and finances and uses nonlinear data. Predictions were produced about the brake output power, specific fuel consumption, thermal efficiency, air-fuel ratio, volumetric efficiency, and emissions of smoke, CO, HC, and NOx as a function of engine speed and blend ratio. All correlation coefficients (r) over 0.99 and R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R^{2}$$\\end{document} values were beyond 0.98 for all variables. There were low values of MSE, MAPE, and MSLE with significant predictive ability. WCO’s biodiesel is a viable diesel engine replacement fuel.

Novel rate-based modeling and mass transfer performance of CO2 absorption in rotating spiral contactor

For the process of CO2 absorption, existing gas-liquid contactors suffer from low mass transfer performance and low gas-liquid ratios. In this study, a rotating spiral contactor was developed to overcome these drawbacks and a novel rate-based model was developed to predict the CO2 absorption performance. The effective interfacial area (ae), overall volumetric mass transfer coefficient (KGae) and CO2 absorption efficiency (η) were investigated. The results showed that the ae was 913–1125 m2/m3 superior to the conventional contactor. In the range of gas–liquid ratio of 200–1800, the KGae and η were 1.4–10.1 kmol.m-3.h-1.kPa-1 and 40.5–99.6 %, respectively. The rate-based model predicted the KGae and η with the AARD of 6.71 % and 1.90 %, respectively. Also, it has better robustness even in highly nonlinear temperature and composition distributions. This study provides a potential contactor and a new modeling tool for CO2 capture and other gas-liquid separation.

Enhancing commercial check valves in downhole pump applications through laboratory testing system development

In this study, we aim to enhance the performance and longevity of downhole pumps employed in crude oil extraction in the oil industry. Downhole pumps play a pivotal role in the rod-pump system, comprising traveling and standing valves that function similarly to ball check valves. However, these valves often experience premature wear and tear. To address this concern, we embarked on experiments involving various check valve alternatives to conventional ball valves within downhole pumps. The testing conditions were controlled precisely. Furthermore, we evaluated four distinct check valve types, the original (representing the incumbent ball valves), spring-poppet (C), spring-ball (CB), and spring-poppet with soft-seated (S6C) check valves, within a controlled laboratory environment. We employed a TEXAPON N70 solution to replicate the properties and temperature conditions of crude oil. A portable ultrasonic flow meter was used to quantify the pump flow rate and assess its volumetric efficiency. In addition, we recorded data on the polished-rod load and plunger displacement to generate dynamometer cards, thereby enabling a comprehensive evaluation of the operational performance of the pump. Furthermore, we conducted a vacuum test to scrutinize valve leakage, which is a crucial indicator of the operational lifespan of a downhole pump. Our findings show that incorporating the CB check valve with the RHB pump in oil wells operated by the PTT Exploration and Production Public Company Limited (PTTEP) could result in a 15 % increase in volumetric efficiency and a remarkable 160 % improvement in durability compared to the original ball check valve.

Unsteady flow and thermal dynamic performance of pre-compression characteristics in variable-speed scroll compressors

In the suction process of scroll compressors, a special thermodynamic phenomenon occurs, known as pre-compression, which significantly affects the inhalation capacity, volumetric efficiency, and thermal characteristics of scroll compressors. To explore its generation and impact, unsteady flow field distributions of the pre-compression phenomenon were obtained by numerical simulations. The pressure variation of the pre-compression phenomenon in air was analyzed, and the power consumption caused by pre-compression during the working process was investigated. Study results indicated that the pre-compression phenomenon is mainly produced by the geometric structure and operating features of the scroll compressor. The initial angle of the pre-compression phenomenon decreases by 31° as the rotational speed ranges from 3000 to 7000 r/min. The generation of the pre-compression phenomenon induces eddies in the suction chamber. Additionally, it was demonstrated that during the suction process, mass flow rate increases owing to the pre-compression phenomenon. The study is helpful for analyzing the suction process and improving operating efficiency of scroll compressors.

Evaluation of self-repair efficiency of polymers containing microcapsules using optical coherence tomography

Self-healing polymers are used to improve the durability and strength of materials and provide them with a longer service life. The authors propose a new optical method for evaluating the self-repair efficiency in polymers containing microcapsules. The non-destructive method measures spatial profiles of a hole series obtained after a material puncture. Spatial images of holes acquired by optical coherence tomography were processed to get a surface profile. The reduction of the average volume or depth of the holes compared to the reference material allows self-healing efficiency calculation. For the presented method, tests were carried out to measure the self-repair efficiency of test materials with 5% and 10% mass of repair capsules compared to Ethe reference polymer without capsules. The volumetric efficiencies of self-repair obtained from 30 holes of each material, acquired 8 h after the puncture, were computed as 51.6% and 58.3% for the two repaired material types, respectively.

Volumetric efficiency degradation prediction of axial piston pump based on friction and wear test

The axial piston pump (APP) is being developed towards higher pressure and higher rotational speeds to enhance operational power density. The piston-cylinder friction pair is a critical component of the APP. Due to its lack of self-compensation capability, the leakage of the piston-cylinder friction pair escalates rapidly under increasingly severe wear conditions. An innovative method for predicting the performance degradation and lifespan of APPs based on friction and wear tests has been proposed. This method can effectively predict the performance degradation trends of APPs under different operating conditions. The actual contact force on the piston pair (PP) during operation is determined through dynamic analysis. Friction and wear tests were conducted on 38CrMoAl piston and ZCuPb15Sn8 cylinder materials under various conditions using a testing apparatus. Utilizing friction and wear theory, the volumetric efficiency of APP under various operating conditions was derived as a function of operational time. The reliability of the theoretical analysis was validated through leakage tests on the APP. The results indicate that volumetric efficiency decreases exponentially with increasing working pressure at rated speed. This research provides theoretical guidance and an experimental foundation for the failure prediction of volumetric efficiency degradation in APP.

Variable leading-edge cone method for waverider design

The optimization of the waverider is constrained by the reversely designed leading edge and the constant shock angle distribution. This paper proposes a design method called the variable Leading-Edge Cone (vLEC) method to address these limitations. In the vLEC method, the waverider is directly designed from the preassigned leading edge and the variable shock angle distribution based on the Leading-Edge Cone (LEC) concept. Since the vLEC method is an approximate method, two test waveriders are designed and evaluated using numerical simulations to validate the shock design accuracy and the effectiveness of the vLEC method. The results show that the shocks of the test waveriders coincide well with the preassigned positions. Furthermore, four specifically designed application cases are conducted to analyze the performance benefits of the vLEC waveriders. The results of these cases indicate that, due to their variable shock angle distributions, the vLEC waveriders exhibit higher lift-to-drag ratios and better longitudinal static stability than conventional waveriders. Additionally, the vLEC waveriders demonstrate superior volumetric capacities near the symmetry plane, albeit with a minor decrease in volumetric efficiency.