Load Ratio Research Articles

Finite element model analysis of long-term performance of composite anchorage based on double-material parameters

Carbon fibre-reinforced polymer (CFRP) tendons demonstrate the advantages of light weight, high strength, and superior corrosion resistance and have broad application prospects for long-span cable structures. However, given the low transverse shear strength of CFRP tendons, how to achieve long-term and reliable anchorage for CFRP tendons is a critical issue. The long-term performance (LTP) of a novel composite anchorage for CFRP tendon was assessed in this study. Then, a finite element model (FEM) with double-material creep parameters was established to reliably model the LTP experiment according to the creep parameters of the bonding medium and CFRP tendon. Finally, the effects of the free section tendon length, pre-tightening force, over-tensioning force, and elastic modulus of the bonding medium were analysed using the established FEM with double-material creep parameters. Results revealed no visible damage to the CFRP tendon and anchorage after the LTP experiment. The maximum tendon slippage was 0.054 mm, and the residual load ratio was 0.826. These phenomena indicate that the novel composite anchorage has excellent LTP. The FEM modelling results based on double-material creep parameters were in good agreement with the experiment results. The residual load ratio calculated by the FEM was 1% lower than the experimental value. Through the parameter analysis, the residual load ratio of the specimen was effectively improved under longer free section tendon condition, but tendon slippage increased to a certain extent. In addition, the LTP of the composite anchorage can be effectively improved by appropriately decreasing pre-tightening force and over-tensioning force. When the over-tensioning force was 1.4 times the test load, the tendon slippage was reduced by 34.2%, and the residual load ratio increased by 4.8%. The greater elastic modulus of the bonding medium in the range of 2.1 GPa–3.1 GPa, the worse the LTP of the composite anchorage.

Multi-objective optimization of the performance and emissions characteristics of a CI engine powered by Pyrus glabra biodiesel as a novel feedstock using response surface method

Finding new renewable sources for the production of biofuels has attracted a lot of attention in recent years due to the reduction of fossil resources. A new biodiesel feedstock as a renewable source is presented in this study. The purpose of this study was to evaluate the performance and emissions of diesel engines powered by diesel and biodiesel fuel blends by volume percentages of 5, 10, 15 and 20. The multi-objective optimization is applied to minimize engine emissions and maximize the performance of the engine. The obtained results revealed that engine load and biodiesel ratio have a significant effect on the engine emissions and parameters at the 5% level. The results revealed that when the diesel engine was operated with an engine load of 70% and biodiesel concentration of 9% as an optimal condition. The optimal value of the BTE, BSFC, brake power, and brake torque were 20%, 307 g/kW.h, 24 kW, and 94 Nm, respectively. The optimal value of engine-out emissions was 12 ppm, 9%, and 209 ppm for HC, CO2, and NOX emissions, respectively. The desirability value was found to be 73% at this optimal engine working condition.

Seismic performance and flexural strength prediction of high-strength bar reinforced UHPFRC walls under high axial load ratio

A new-type shear wall built with high-strength reinforcement and ultra-high performance fiber reinforced concrete (UHPFRC) is proposed in this paper, aiming to solve the problem of too large cross-section size of bottom shear wall members of high-rise and super high-rise buildings. Four UHPFRC wall specimens built with high-strength reinforcement were tested under cyclic loading to examine the influence of the parameters of fiber volume fractions (0 vs. 1.5% vs. 2.5%) and the spaces of horizontal distribution reinforcing bars (150 mm vs. 300 mm) on the seismic performance. In addition, a calculation method of flexural strength of UHPFRC shear wall is established. The research results show that: the UHPC wall specimen without fibers failed in the axial compression brittle mode, and the UHPFRC wall specimens with fibers failed in flexure-dominated ductile mode. The bridging effect of steel fibers at the cracks kept the integrity of the UHPFRC. The drift ratio capacities of the UHPFRC wall specimens under high axial compression ratio of 0.5 were 3.56%. Increasing the fiber volume fractions can improve the strength, initial stiffness, and cumulative energy consumption of the wall specimens, reduce the damage degree of the UHPFRC at the toes of the wall specimens, and can also reduce the reinforcement ratio of horizontal reinforcement without influence on the seismic performance. The proposed method of flexural strength of UHPFC walls shows reasonable prediction accuracy.

Modeling and analysis of 3D mixed lubrication in marine cam–tappet pair

During the operation of the marine cam–tappet pair, affected by periodic dynamic load, transient velocity, and micromorphology, it usually operates in a mixed lubrication state. Under extreme operational conditions, contact is likely to occur at the asperity of the interface, leading to problems such as stress concentration and dry contact. Considering the transient dynamics and three-dimensional roughness of cam–tappet pair, a mixed-elastohydrodynamic lubrication model is developed in this article, while the effects of surface waviness on the lubrication state are also investigated. The results show that the film thickness can be increased by 0.098 μm, and the coefficient of friction can be reduced by 10.6% when the wavelength ratio ranges from 1/6 to 6. However, when the amplitude exceeds 0.6 μm, the coefficient of friction may reach 0.10. Under conditions of low speed and high load, the film thickness decreases and contact load ratio increases. And about 30% reduction in film thickness is achieved on cam–tappet pair, potentially leading to increased wear or scuffing failure.

A simple method and prediction model for calculating the cooling load of impinging jet ventilation system in office buildings

An appropriate thermal stratification environment can be formed in impinging jet ventilation (IJV) cooling rooms. In this scenario, the well-mixing hypothesis provided by the conventional mixing ventilation is not applicable to calculate the cooling load of IJV systems. In the present study, a simple method using the cooling load ratio (CLR, α) is proposed for calculating the cooling load in the thermal stratification environment of IJV. Numerical simulations are applied to investigate the effect of several influencing factors on the CLR. Univariate analysis results indicate that the key influencing factors of α are the thermal length scale (Lm), supply airflow rate (L) and total heat gain (q*). A prediction model of α (CLR model) is developed related to the three influencing factors of Lm, L and q*. The CLR model has a high prediction accuracy in low q* situations (q* ≤ 2.5), with a slightly reduced accuracy in high q* situations. Overall, the maximum relative error of the CLR model is lower than 12%. Moreover, contour plots of α illustrate that α achieves a minimum level of 0.55, and the values of α vary between 0.55 and 1.0 for all the values of Lm, L and q*. The CLR model can provide a theoretical basis for the determination of cooling load and energy saving potential of IJV systems during the design stage.

Smart Vehicle to Grid Energy Management Algorithm for Electric Vehicle Supported by Photovoltaic Energy Sources

The paper demonstrates grid improvements with results considering the integration of smart charging algorithms of electric vehicles (EVs) and photovoltaic (PV) energy sources to effectively manage energy flow. It aims to minimize energy costs by leveraging the bidirectional energy transfer capability of EVs and optimizing their interaction with the grid and PV sources. The proposed algorithm takes into account various parameters such as transformer load ratios, solar power generation, and the state of charge of vehicle batteries. The algorithms are implemented by acquiring one year’s real-time data of a predetermined transformer in a neighborhood from the electricity distribution company. The number of EV is estimated for the years 2025 and 2030. Buildings with energy management systems (BEMS), which charge EV with a controlled charging algorithm, provide renewable energy support with PV and reduce the transformer load during peak hours with the V2G algorithm. BEMS is not applied in buildings without EV or PV. Simulation results demonstrate that as the number of EVs increases, renewable energy source support and controlled charging algorithm alone are not sufficient. However, it demonstrate that energy costs and grid stress are successfully minimized by using the V2G algorithm in addition to controlled charging algorithm and PV.

Post-damage recovery of substandard RC columns by CFRPs

Cyclic response of substandard reinforced concrete (RC) columns and structural repair of pre-damaged columns by carbon-fiber-reinforced polymers (CFRPs) were investigated through combination of experimental and advanced numerical modeling methods. The specimens, representing typical RC columns in substandard buildings, were constructed from low-strength concrete, plain round bars, and nonconforming reinforcement details. The key parameters under investigation included the lap-splice, hook detail in the longitudinal reinforcement, and axial load ratio. First, the RC columns were subjected to cyclic loading until the attainment of their heavy damage state. The failure mode was dominated by the flexural response alongside significant reinforcement slip and axial damage, involving concrete crushing and reinforcement buckling. Subsequently, the severe cracks and concrete damage were repaired by the externally wrapped CFRP sheets. The former load-carrying capacities of the repaired RC columns were recovered. The damage formation in the concrete and reinforcement was transferred to CFRP sheets. The final failure mode was characterized by local deformations in the CFRP, with minimal damage observed in the concrete and reinforcement bars. Furthermore, the numerical solution effectively reproduced the nonlinear behavior of the as-built specimens. The crack patterns and capacities observed in the numerical solutions align with the responses observed in the experimental tests.

Evaluation of human papillomavirus type 16 viral load and genome physical status in Iranian women with cervical disease.

This study examined the viral load and physical status of the human papillomavirus 16 (HPV-16) genome in non-cancerous, precancerous and cancerous cervical lesions. Quantitative real-time PCR was performed to determine HPV-16 E2 and E6 viral load in 132 cervical specimens. E2/E6 viral load ratio was used to determine the physical status of HPV-16 genome. E2 gene viral load was a significant (P < 0.001) predicting biomarker in differentiating non-cancerous from precancerous and cancerous samples. E6 gene viral load was significantly different between the groups (P < 0.001). The specificity and sensitivity of E2 and E6 in distinguishing SCC samples were 100% and 95% respectively. HPV-16 viral load measured through E2 and E6 genes is a reliable indicator of lesion type.

OPTIMAL DESIGN OF THE TRADITIONAL CHINESE WOOD FURNITURE JOINT BASED ON EXPERIMENTAL AND NUMERICAL METHODS

In this study, computer aided technology was utilized to improve the traditional grid shoulder mortise-and-tenon joint (GSMTJ). Firstly, the traditional GSMTJ was redesigned through using separated loose tenon by the computer aided design (CAD) software called AutoCAD. And then the mechanical strengths of the traditional GSMTJs and the improved GSMTJs were compared and analyzed using the experimentally validated finite element method (FEM) based on the computer aided engineering (CAE) software called ABAQUS. Finally, the GSMTJs were further investigated from perspective of manufacturing efficiency using the computer aided manufacturing (CAM) software called JDSoft SurfMill. Based on the above simulation analysis, the improved GSMTJ was validated to be equivalent strength, high manufacturing efficiency increasing by 11.5%, low processing load ratio decreasing by 30%, as well as less wood material cost reducing by 3.6% compared with the traditional GSMTJ. The proposed improved GSMTJ was validated to be more suitable to modern wood processing machines. In addition, the methodology of combining the CAD, CAE, and CAM to wood products design was proofed efficient, economic, and feasible, and can be also used in design of other products.

Assessing fatigue crack growth thresholds for a Ti-6Al-4V (STOA) alloy using two experimental methods

Fatigue crack growth rate behavior in the threshold and near-threshold regimes for a Ti-6Al-4V solution-treated and over-aged (STOA) alloy was investigated using two test procedures: i) accelerated load reduction (ALR) utilizing faster load-shed rates than recommended in the ASTM standard E647 load-reduction (LR) test procedure, and ii) compression pre-cracking constant-amplitude (CPCA) or load-increasing (CPLI) and load-reduction (CPLR). Fatigue crack growth tests were conducted on compact, C(T), specimens (B = 6.35 mm) with two different widths (W = 51 and 76 mm) at two stress ratios (R = 0.1 and 0.7). The crack-growth-rate test data were compared to previous test data produced from the same batch of material using the ASTM LR and CPCA test procedures that were tested on C(T) specimens (W = 25, 51 and 76 mm) over a wide range in stress ratios (R = 0.1, 0.4, and 0.7).Although none of the load-reduction test procedures provided a good representation of the threshold value (ΔKth) at low R, the CPCA test procedure was the most promising. The LR, ALR, and CPLR test procedures were influenced by prior loading history, leading to higher ΔKth values and slower crack growth rates in the threshold regime due to a rise in the crack-opening loads. The LR and ALR tests at R = 0.1 and shed rates of −0.08, −0.32, and −0.95 mm−1 yielded ΔKth values that were 15 to 38 % higher than the estimated threshold stress-intensity factor range (ΔK*th)R=0.1 based on the crack-closure model (FASTRAN). The compression pre–cracking test procedures are more accurate alternatives for developing threshold and near-threshold fatigue crack growth rates. Specifically, the CPLR test procedure produced a ΔKth value that was 8–18 % higher than (ΔK*th)R=0.1. Additionally, LR and ALR tests produced different ΔKth values as a function of the specimen width for a given load ratio, which violates classical fracture mechanics principles. In addition, the spread in the ΔK-rate data in the low-rate regime was larger than the spread in the mid-rate regime as a function of R, a term referred to as “fanning”. In contrast, the CPCA test procedure produced consistent crack growth rates over the same range of ΔK values examined, independent of the specimen width and these data did not exhibit “fanning” with R. Further research is necessary to develop standard test procedures capable of providing a more definitive representation of the ΔKth value in the threshold regime. However, FASTRAN can serve as a crucial tool in aligning the actual ΔKth values with those obtained through CP testing, thereby bridging the gap and enhancing the reliability of the results.

Study on load allocation of land-based total nitrogen in the Bohai Sea

Total nitrogen (TN) is one of the terrigenous pollutants in the Bohai Sea. A reasonable releasing scheme can effectively improve the seawater quality. Based on the observed TN concentrations and the national pollution control requirements, the TN load ratios of four major rivers around the Bohai Sea are adjusted in multiple levels within the range of 50 %–200 % in the frame of total control. Then, a pollutant transport model is used to evaluate each load allocation scheme by calculating the area of different seawater qualities. The optimum scheme is loads of the Yellow River and Luan River are set to 50 % and 200 % of the levels in 2018, and thus the area of heavily polluted seawater can be decreased by 33.14 %. Additionally, the reasonable TN reduction amounts of four major rivers in 2018–2020 are calculated according to the optimum scheme, which can be provided as a decision-making basis of marine managements.

Matrix-based predictive model of residual drift and analytical resilience design approach for self-centering columns

Residual displacement serves as a crucial indicator in evaluating the safety and reparability of structures following seismic events. As a novel self-centering structure, the unbonded prestressed reinforced concrete (UBPRC) column has demonstrated its effectiveness in reducing residual displacement. However, there remains a lack of quantitative research concerning the influence of various structural and material parameters on residual displacement. For the quick and convenient evaluation of the seismic performance and resilience of UBPRC columns, in this paper, the influence of various parameters on the residual drift ratio of UBPRC columns was investigated by establishing a logarithmic linear relationship between the parameters and the residual drift ratio. These parameters include the longitudinal reinforcement and concrete strength (fy and fc), reinforcement ratio of longitudinal and transverse (ρl and ρs), prestressed strand ratio (ρp), aspect ratio (Ar), axial load ratio (αc), and prestressing force ratio (αps). Among the two parameters related to prestressed strands, increasing the prestressing force ratio significantly reduces RDr, while the influence of the prestressed strand ratio on RDr is relatively small. On this basis, a matrix-based probabilistic predictive model for the residual drift ratio was established. According to various physical parameters, the proposed mathematical model accurately predicts the residual drift ratio and describes the influence of each parameter on it. Furthermore, an analytical resilience design approach was proposed, and an analytical expression in matrix form for a multi-parameter resilience design was derived. Lastly, the impact of parameters on the damage state was investigated, and the range of parameter values under investigation was established, according to the analytical resilience design approach.

Experimental and numerical investigations of circular concrete filled steel double-skin and double-tube columns exposed to fire

Circular concrete-filled steel double-tube (CFSDT) columns have shown excellent ductility and load-carrying capacity. However, research on the fire resistance of CFSDT columns is still limited. This paper presents the fire tests, finite element (FE) modeling, behavior, and design of circular CFSDT columns and concrete-filled steel double-skin (CFSDS) columns exposed to fire. The fire resistance tests of one CFSDS and six CFSDT columns are described. Analysis is given on the effects of the material strength, the thickness of the inner steel tube, and the load ratio on the fire resistance of the specimens. Finite element models are developed that simulate the fire behavior of filled composite columns with double tubes and are verified by fire test results. The verified FE models are employed to undertake parametric studies on the structural responses of CFSDS and CFSDT columns under fire exposure. A design model is proposed for calculating the fire resistances of CFSDT columns. The results show that the load ratio and the column slenderness ratio have the most significant effect on the fire resistance of CFSDT columns; the cross-sectional parameters remarkably affect the fire resistance; and the material strength has a moderate impact on the fire resistance of CFSDT columns. Compared with CFSDS specimens, the existence of the core concrete significantly increases the fire resistance of CFSDT columns. The proposed design model for fire resistance can yield a safe prediction.

Experimental study of concrete-filled stainless steel tubular stub columns with circular and square cross-sections subjected to combined compression and bending

This paper presents an experimental study into the structural behaviour and strength of concrete-filled stainless steel tubular stub columns with circular and square cross-sections subjected to combined compression and bending moment. A total of sixteen concrete-filled stainless steel tubular (CFSST) stub columns were tested, including two section types (circular and square hollow sections), two grades of concrete infill (C30 and C60), two thicknesses of tube wall for each cross-section (6 and 10 mm), and five loading eccentricity ratios (0, 0.2, 0.3, 0.4 and 0.5). The CFSST stub column specimens were loaded in compression, with different loading eccentricities applied to achieve a wide range of axial load-to-bending moment ratios. This research provides a comprehensive report on the experimental methodology and subsequent observations, including the failure modes, load-deformation curves, axial load-bending moment curves, strain development at the key locations and values of ductility index. It can be observed that for circular CFSST columns, ultimate load decreased by roughly 70% with an increase in loading eccentricity ratios from 0 to 0.5, while for square columns, the reduction was about 50% under same conditions. The experimental results were used to evaluate if the existing design provisions for carbon steel-concrete composite structures is capable of designing the investigated CFSST stub columns. It was found that the mean ultimate load to predicted failure load ratios are 1.25, 1.32, and 1.36, with coefficients of variations (COV) equal to 0.08, 0.09 and 0.11, for the European, American, and Chinese codes, respectively. Consequently, the design approach specified in the Chinese code led to the most conservative and scattered strength predictions among the three codified design approaches. In contrast, the European code provides the most precise predictions of the test results, though there still remains scope for improvements in the ultimate resistance predictions of CFSST stub columns subjected to combined compression and bending.

Cyclic creep strain rate criterion for short-fibre reinforced thermoplastics: Validation of creep and fatigue performance across a wide range of load ratios

The fatigue and creep responses of short-fibre reinforced thermoplastic matrix composites are influenced by numerous parameters such as load ratio for fatigue. Fatigue criteria, based solely on the evolution of the cyclic creep of the mean strain, are effective for load ratios greater than zero (tension/tension) but have limitations for negative load ratios (tension/compression).The aim of this study was to propose a unified creep and fatigue criterion, based on the evolution of the cyclic creep of the maximum strain, that allowed both load ratio domains to be covered. To investigate a wide range of load ratios (-1 to 0.8), an existing creep and fatigue database was augmented with purely alternated tension/compression tests. This database, which included 489 tests, considered the variations in parameters that influence the creep and fatigue responses, such as fibre orientation, water content and specifically for fatigue load ratio and frequency. This was used to validate a unified criterion based on the cyclic creep of the maximum strain. This criterion improved fatigue life prediction compared to existing criteria and allowed fatigue and creep results to be unified with 87% of estimated lifetimes within a scatter band of factor two.

Experimental and numerical investigation of the flexural behavior of one–way RC slabs strengthened with near–surface mounted and externally bonded systems

This study investigated the flexural performance of one-way reinforced concrete (RC) slabs strengthened with two distinct strengthening systems: near–surface mounted (NSM) bars and externally bonded (EB) carbon fiber-reinforced polymer (FRP) strips. The NSM bars comprised four types: carbon FRP (CFRP), basalt FRP (BFRP), glass FRP (GFRP), and stainless–steel (SS) bars. The NSM–strengthened slabs showcased substantial enhancements in yield and ultimate load capacity, ranging from 20 % to 55 % and 59–123 %, respectively. In comparison, those strengthened with EB–CFRP strips displayed increases from 46 % to 107 % and 45–177 %, respectively, depending on the axial stiffness ratio of the strengthening system provided. Furthermore, the slabs reinforced with NSM–BFRP bars showed an 11–25 % improvement in their ductility indices. In contrast, the slabs reinforced with EB experienced a decrease in ductility ranging from 38 % to 50 %. This reduction was attributed to the differences in the modes of failure observed in both strengthening systems. The rupture of the NSM–FRP bars and the strain readings associated at the end of testing confirmed that the tensile strength of the NSM–FRP bars was fully exploited whereas the EB–CFRP strips utilized only 29–36 % of their ultimate tensile strain due to debonding. A finite element (FE) model was formulated to anticipate the behavior of the strengthened slabs. A strong correlation between the numerical predictions and the experimental outcomes was observed. The experimental–to–numerical ratios of the ultimate load ranged between 1.0 and 1.08 for the NSM–strengthened slabs and between 0.98 and 1.38 for the EB–strengthened slabs. This validated the FE models’ ability to capture the nonlinear performance of the strengthened slabs.

The Ratio between Weekly Training and Match External Physical Loads in U17 Elite Youth Soccer Players: Implications for the Training Process.

Research on the external physical load on elite youth soccer players during the weekly training microcycle in competitive periods and official matches is limited. The aims of this study were twofold: a) investigate possible differences in external physical load (PL) across player positions in U17 elite youth soccer players during official matches; b) determine the weekly training to match physical load ratio (WTMLr) across player positions. The sample included 20 outfield players from an elite soccer academy (mean age 15.94 ± 0.25 years) playing in four positions: central defender (CD), full-back (FB), central midfielder (CM) and Striker (S). Data were collected during the spring in-season period for 17 official matches played in a 4-3-3 game format. Indicators of external physical load monitored were: total distance (TD); total distance in high-speed running (HSR; > 16.1 km.h-1); total distance in sprint running (SPR; > 21.6 km.h-1); and relative physical load intensity (%HSR). The WTMLr was calculated for TD, HSR, SPR and %HSR as the ratio of the average weekly sum of training PL to the average sum of PL in an official match for a given players' position. Collectively, the training intensity during a one-week microcycle (%HSR in WTMLr) achieved only 76 % of match demands. CD performed significantly lower in all measured indicators of external PL during the official match than all other positions (p < 0.05; g > 0.80) except for TD in S. S achieved significantly higher SPR during official matches compared to CD (p < 0.05; g > 0.80), CM, and FB (g > 0.80). In contrast, CD reported higher WTMLr (medium-large effect size) in HSR and SPR indicators than all other positions. CM performed significantly higher %HSR in WTMLr than S and FB (p < 0.05; g > 0.80). Results revealed insufficient training intensity relative to match demands and, at the same time, weekly training PL did not meet match demands (especially in HSR and SPR) for players across the different positions. Therefore, practitioners should select appropriate training methods (drills and games) to ensure sufficient training intensity (HSR and SR metrics) and consider using the WTMLr, which can be used to help optimise and individualise training PL for different player positions.

Experimental and Numerical Evaluation of Equivalent Stress Intensity Factor Models under Mixed-Mode (I+II) Loading

This study determines the equivalent stress intensity factor (SIF) model that best fits the experimental behavior of low-carbon steel under mixed modes (I and II). The study assessed Tanaka, Richard, and Pook’s equivalent SIF models. The theoretical values used for comparison correspond to the experimental results in a modified C(T) geometry by machining a hole ahead of the crack tip subjected to fatigue loads with a load ratio of R = 0.1. The comparison involved the SIF for six experimental points and the values computed through the numerical simulation. The Paris, Klesnil, and Modified Forman–Newman crack growth models were used with each equivalent SIF to analyze the prediction in the estimated number of cycles. The Klesnil model showed the closest prediction since the error between the calculated and experimentally recorded number of cycles is the lowest. However, the material behavior reflects a reduced crack propagation rate attributed to plasticity in the crack tip. The results suggest that Asaro equivalent SIF conservatively estimates the element lifespan with increasing errors from 2.3% at the start of growth to 27% at the end of the calculation. This study sheds light on the accuracy and limitations of different equivalent SIF models, providing valuable insights for structural integrity assessments in engineering applications.

A Quantitative Investigation on the Effects of Flexure-Dominated Reinforced Concrete Column Characteristics on the Dissipated Energy

This paper presents the effects of fundamental member and loading parameters on total dissipated energy capacity of RC columns in quantitative way by using an experimental database. Specifically, concrete compressive strength, yield strength of reinforcing bars; shear span-to-depth ratio, reinforcement ratios; peak drift ratio, and axial load ratio, are considered as influencing factors. Pearson’s correlation coefficients are utilized as dependency indicators to construct a correlation matrix where the effect of each factor on dissipated energy level is quantified. Results show that the effective factors among selected features are peak drift ratio, transverse reinforcement volumetric ratios of a member, and yield strength of rebars whereas the most influencing factors are the first two.

Calculation of Mixed Oil Volume for Sequential Transportation of Crude Oil Pipelines with Variable Temperature and Low Reynolds Number

In order to meet the differentiated demand of oil refiners for crude oil, improve the operating load ratio of long-distance pipelines, and reduce one-time investment, sequential transportation process has been widely used in long-distance crude oil pipelines in China. There are many studies on the calculation method of the mixed oil quantity of sequential transportation of refined oil, but due to its complex influencing factors, there is no general calculation model accepted by everyone. For the sequential transportation of crude oil pipelines, most of them have the characteristics of variable temperature and low Reynolds number, and it is more difficult to accurately calculate the mixed oil quantity than the refined oil pipeline. Through the analysis of the characteristics of oil mixing and hydraulic characteristics of sequential oil transportation, combined with the operation example of an oil pipeline in China, the calculation results of the diffusion theory formula, the Austin-Palfrey empirical formula and the equivalent pipeline length formula were compared and analyzed. The results show that the “equivalent pipeline length method” considers the influence of flow, pipe diameter and conveying distance on oil mixing, and takes into account the oil mixture caused by the change of initial oil mix and Reynolds number, which is more suitable for calculating the mixed oil quantity of sequential transportation of crude oil pipelines. However, for the sequential transportation of crude oil pipelines with low Reynolds number and variable temperature, the amount of oil mixed will be increased. According to the comparative analysis of actual cases, the correction coefficient is increased by 1.5 times on the basis of theoretical calculation, and the calculated value is in good agreement with the actual value, and the deviation is within 5%. It can be used as a reference for the design and operation management of variable temperature and low Reynolds number crude oil sequential transportation pipeline.