Inlet Angle Research Articles

Analyzing the impact of blade geometrical parameters on energy recovery and efficiency of centrifugal pump as turbine installed in the pressure-reducing station

Improving renewable energy efficiency has received great attention globally by increasing demand for energy supplies and air pollution issues. The Soft Pressure Regulation System (SPRS) as a potential technology provides the possibility of regulating pressure and energy recovery in pressure-reducing stations. Pump as Turbine (PAT) is a good choice for installation in Water Distribution Network (WDN) pipelines due to its availability and economic benefits, and it can play a key role in decreasing startup time and return on investment. In this paper, the performance of centrifugal PAT under WDN conditions has been numerically and experimentally evaluated, and simulation validation was performed, too. Analyzing the work conditions of the pressure reduction station shows that the hourly flow rate trend changes considerably based on end-user demand. A major portion of the SPRS's operation time occurs in off-design conditions of the PAT, and efficiency is drastically decreased considering the lack of flow control tools. The effect of blade inlet angle, blade warp angle, blade curvature, and change of these parameters simultaneously was investigated to increase the high-efficiency working range. Losses resulting from flow separation and formation of vortices are significantly decreased by simultaneous change of blade geometrical parameters in the range of design point and higher flow rates (Q ≥ 1.0QBEP). Since the highest frequency of flow rate based on statistical analysis occurs in this range, the total power generation of SPRS improves significantly. The PAT efficiency with the improved impeller at part-load condition (0.8QBEP), design condition (QBEP), and over-load condition (1.2QBEP) is improved by 0.83 %, 2.69 %, and 6.71 % in comparison with the original impeller, respectively.

Association Between Cervical Sagittal Alignment and Subaxial Paraspinal Muscle Parameters.

Retrospective review of prospectively collected data. The authors aim to investigate the association between muscle functional group characteristics and sagittal alignment parameters in patients undergoing anterior cervical discectomy and fusion. The relationship between the morphology of cervical paraspinal muscles and sagittal alignment is not well understood. Patients with preoperative cervical magnetic resonance imaging and cervical spine lateral radiographs in standing position who underwent anterior cervical discectomy and fusion between 2015 and 2018 were reviewed. Radiographic alignment parameters included C2 to 7 lordosis, C2 to 7 sagittal vertical axis (SVA), C2 slope, neck tilt, T1 slope, and thoracic inlet angle. Muscles from C3 to C7 were categorized into four functional groups: sternocleidomastoid group, anterior group, posteromedial group, and posterolateral group (PL). A custom-written Matlab software was used to assess the functional cross-sectional area (fCSA) and percent fat infiltration (FI) for all groups. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index. A total of 172 patients were included. Regression analyses demonstrated that a greater C2 to 7 SVA was significantly associated with a greater FI of the anterior group from C3 to C5 and with a higher fCSA of the PL group at C3 to C4, and C6 to 7. A larger C2 slope was significantly correlated with a greater FI of the anterior group at C3 to C4 and a higher fCSA of the PL group from C3 to C5. This work proposes new insights into the complex interaction between sagittal alignment and cervical paraspinal muscles by emphasizing the importance of these muscles in sagittal alignment. The authors hypothesize that with cervical degeneration, the stabilizing function of the anterior muscles decreases, which may result in an increase in the compensatory mechanism of the PL muscles. Consequently, there may be a corresponding increase in the C2 to C7 SVA and a larger C2 slope.

A Method for Preliminary Design of Variable Geometry Vaned Diffuser for Centrifugal Compressor

Abstract Centrifugal compressors require a wide operating range as well as high efficiency. Typical active control forms to enhance the operating range are suction throttling with a valve in a suction line, discharge throttling with a ring installed in a vaneless diffuser, variable inlet guide vanes, and variable geometry vaned diffuser (VVD). This study focuses on the design of a VVD whose vane rotates around a pivot to adjust its opening and proposes a method to estimate the main parameters of the VVD at the preliminary design stage. The design method here is based on matching the diffuser vane inlet angles with the flow angles at the diffuser inlet. If the designed VVD can maintain low incidence at the diffuser vane leading edge over the whole movable range of the vane is evaluated. A graph, which indicates the relation between the diffuser vane inlet angles and the flow angles at the diffuser inlet at diffuser choking and diffuser stalling, makes the evaluation easy. The proposed procedures were applied to select the number of vanes of the VVD for a turbocharger compressor. Tests for the validation of the design procedures were conducted by using fixed vaned diffusers that simulated the VVDs installed on the turbocharger with an 85 mm-diameter impeller. The results showed the effectiveness of the proposed design procedures. This paper first presents examples of applications of the typical active methods extending centrifugal compressors’ operating range for real machines and then discusses the design of VVD.

Research on particle retention in continuous horizontal fluidized bed based on CFD-DEM method

Horizontal fluidized beds are widely used in continuous production lines due to their efficient heat and mass transfer mode. Continuous production goals require stabilized reaction systems, which can be achieved by controlling particle retention. But there is a lack of an effective means of controlling particle retention. In this paper, Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) method is applied to investigate the particle retention in different air inlet angles, which is characterized by the particle back-mixing degree, spatial and residence time distribution. The results show that at low air inlet angles, the system is effective in controlling particle retention. This is achieved through stronger particle back-mixing and more concentrated residence times, which are essential for maintaining reaction system stability. These findings provide guidance for controlling particle retention and enhancing continuous fluidization equipment efficiency.

Selecting the inlet configuration for gas-liquid cylindrical cyclone separator

Gas-Liquid Cylindrical Cyclone Separator (short for GLCC) is a compact separator that has been widely used in petroleum production. The inlet configuration has significant impact of the GLCC capacity separation. By utilization of both FEM simulation and practical experiments, three inlet configurations and twelve inclined angles are investigated to find the steadily operating inlet configuration for industrial applications. In this study, the flow pattern and kinematic behaviour of each configuration are thoroughly analysed. Besides, the distribution of three velocity components of the body flow in GLCC is compared with one of the practical experiments. The result shows that the current inclined-inlet angle of 27° is not the steadily operating angle for industrial applications. In steady, it is a range of inclined inlet angle from 0° to 35° for three inlet configurations. The dual-inlet configuration indicates better properties for separating efficiency.

Iliosacral Screws Can be Placed With Precision by Adjusting the Pelvic Inlet Between S1 and S2.

To determine: 1) the natural incidence of sacral inlet angle differences between S1 and S2 and 2) implications for iliosacral screw placement with a technique to improve the accuracy of the intraoperative fluoroscopic inlet for S1 and S2. Combined retrospective and prospective cohort reviews. Regional Level 1 trauma center. After exclusion criteria, 300 patients with uninjured pelvic rings to determine the natural incidence of S1 - S2 angle differences and 33 patients treated with iliosacral screws over the study period. None in the retrospective cohort. In the prospective cohort all patients underwent fluoroscopically assisted iliosacral screw fixation. Radiographic determination of S1 - S2 angle differences above 10 degrees in a natural population for the retrospective cohort. In the prospective, operative cohort the outcome of interest was the safety of iliosacral screws in S1 and S2 as determined on intraoperative fluoroscopy and postoperative CT scan.Results: In the retrospective cohort, 180/300 (60.0%) had S1 - S2 inlet angle differences above 10 degrees. In the operative cohort, 19/33 (57.6%) had S1 - S2 inlet angle differences above 10 degrees. Of the iliosacral screws in S1 and S2 placed using the described imaging technique, all (69/69, 100%) were safe. A normal population determined that differences in the inlet angle between S1 and S2 are common. An operative cohort was treated using preoperative CT-based planning to define different intraoperative fluoroscopic inlet views for S1 and S2, if a larger difference existed. Using this technique, 69/69 (100%) of iliosacral screws were either intraosseous or juxtacortical and safe. Level V. See Instructions for Authors for a complete description of levels of evidence.

Postoperative quality of life in patients with ankylosing spondylitis and thoracolumbar kyphosis: risk factors and personalized sagittal reconstruction strategy.

The aim of this study was to investigate the factors affecting postoperative quality of life in patients with ankylosing spondylitis (AS) and thoracolumbar kyphosis (TLK), and establish a personalized sagittal reconstruction strategy. Patients with AS and TLK who underwent pedicle subtraction osteotomy (PSO) from February 2009 to May 2019 were retrospectively included. Quality of life and spinal sagittal radiographic parameters were collected before surgery and at the last follow-up. Patients were divided into two groups based on the attainment of minimal clinically important difference (MCID) on the Bath Ankylosing Spondylitis Functional Index and Oswestry Disability Index. Comparisons of radiographic parameters and clinical outcomes were conducted between and within groups. Regression analysis was used to identify the risk factors within the missing MCID cohort. Sagittal reconstruction equations were established using the pelvic incidence (PI) and thoracic inlet angle (TIA) in the reached MCID cohort. The study comprised 82 participants. Significant improvements were observed in most radiographic parameters and all quality-of-life indicators during the final follow-up compared with the preoperative measures (p < 0.05). Factors including cervical lordosis (CL) ≥ 18° (OR 9.75, 95% CI 2.26-58.01, p = 0.005), chin-brow vertical angle (CBVA) ≥ 25° (OR 14.7, 95% CI 3.29-91.21, p = 0.001), and pelvic tilt (PT) ≥ 33° (OR 21.77, 95% CI 5.92-103.44, p < 0.001) independently correlated with a failure to attain MCID (p < 0.05). Sagittal realignment targets were constructed as follows: sacral slope (SS) = 0.84 PI - 17.4° (R2 = 0.81, p < 0.001), thoracic kyphosis (TK) = 0.51 PI + 10.8° (R2 = 0.46, p = 0.002), neck tilt (NT) = 0.52 TIA - 5.8° (R2 = 0.49, p < 0.001), and T1 slope (T1S) = 0.48 TIA + 5.8° (R2 = 0.45, p = 0.002). PSO proved efficacious in treating AS complicated by TLK, yielding favorable outcomes. CBVA ≥ 25°, CL ≥ 18°, and PT ≥ 33° were the primary factors affecting postoperative quality of life in patients with AS. The personalized sagittal reconstruction strategy in this study focused on the subjective sensations and daily needs of patients with AS, which were delineated by the equations SS = 0.84 PI - 17.4°, TK = 0.51 PI + 10.8°, NT = 0.52 TIA - 5.8°, and T1S = 0.48 TIA + 5.8°.

Study of the short-circuit flow and circulation flow’s impact on separation performance of cyclone separator with volute-helical inlet

Short-circuit flow and circulation flow are important secondary flows in a cyclone, which have a negative impact on separation performance. This work proposed new cyclones (VH cyclone), incorporating volute-helical inlets with five tilt angles based on the characteristics of short-circuit flow and circulation flow, in order to enhance separation efficiency without a significant pressure drop compared to a Lapple-type cyclone with a tangential inlet (TI cyclone). The separation performance and Euler number of six cyclones are obtained by experiments and analytical models. The simulation is utilized to explore characteristics of short-circuit flow and circulation flow, with a focus on the impact of these flow patterns on particle motion. The result shows that proportion of short-circuit flow increases initially and then decreases with the increase of the tilt angle, while circulation flow is continually weakened. The cutoff diameter increases first and then decreases while the trend of Euler number is opposite for new cyclones. By considering both separation performance and Euler number, VH4 cyclone (Tilt angle of volute-helical inlet is 6.5°) exhibits optimal performance, with a cutoff diameter 20.41% lower than that of TI cyclone, while their Euler numbers are similar.

Improving flow and noise performances of centrifugal pump in dishwasher through impeller design optimization

Noise and performance are critical factors in the customer's selection of dishwashers. The centrifugal pump, which circulates water for washing dishes, dominantly influences the performance and noise of a dishwasher. This study aims to improve the performance and reduce the noise of a centrifugal pump by modifying its impeller design. Priorly, the flow and noise characteristics of the target pump were experimentally characterized. Then, the flow performance of the pump was predicted using a virtual pump performance tester based on the computational fluid dynamics techniques to solve the three-dimensional unsteady incompressible Reynolds Averaged Navier-Stokes equations. The noise radiation generated by the impeller was predicted using the Ffowcs Williams-Hawkings equation. The results were validated by comparing the predicted with the measured. The Response Surface Method, where the blade inlet and outlet angles at the hub and shroud locations were used as design variables, was applied to improve the flow and noise performance of the pump. The optimized impeller design increased the pump flow rate by 17.5% and reduced the flow noise level by 3.5 dB at the same flow rate, as per the fan law predictions.

Analysis of vortex characteristics and energy losses in a cryogenic hydrogen turbo-expander for a 5 t/d hydrogen liquefier

The cryogenic hydrogen turbo-expander (CHTB) is the most core component which determines the dependability and efficiency of hydrogen liquefiers. In present study, CFD method are adopted to simulate the internal flow field inside a CHTB for a 5 t/d hydrogen liquefier. The Ω method and entropy generation method are implemented to identify vortex structures and calculate energy losses. The results show tip leakage vortex is the primary vortex and causes energy losses through strong fluid shear but not rotation effect. The turbulent dissipation is the main energy dissipation. The total entropy generation of CHTB impeller is significantly higher than nozzle because of tip clearances. As tip clearances increase from 0% to 1.6%, total entropy generation increases by 83%, and output shaft power and isentropic efficiency reduce by 9% and 6% respectively. Working conditions mainly affect the inlet angle of attack and significantly impact vortex characteristics and energy losses in the CHTB.

Investigation of Energy Loss Mechanism and Vortical Structures Characteristics of Marine Sediment Pump Based on the Response Surface Optimization Method

Marine sediment pumps are extensively applied in marine engineering fields with complex media and harsh flow conditions. Therefore, this study conducts a multi-factor optimization design for a marine sediment pump. The response surface optimization method is utilized to improve the efficiency by optimizing the number of impeller blades, the blade inlet angle, the blade outlet angle, and the blade wrap angle. Next, a response surface regression model is created, and the influence of geometric parameters on the efficiency is determined. Meanwhile, the energy loss mechanism and vortical structure characteristics after optimization are analyzed by applying entropy production and the method for identifying Omega vortices. The findings suggest a 6.33% efficiency enhancement in the optimized model under the design conditions. The impeller’s internal flow field is enhanced, and the entropy generation rate is significantly diminished. The fluid flow adhered more closely to the blade profile, and the velocity and pressure distribution exhibit better uniformity. The presence of large-scale vortices and occurrences of flow separation within the impeller passage experience a notable decrease, and the overall fluid pressure fluctuation amplitude decreased, resulting in a more stable flow. Therefore, the discoveries from the research offer references for the design and selection of marine sediment pumps.

CFD-DEM study on the synergistic effect of coke consumption and particle dynamics in the blast furnace raceway

In this study, the gas-solid flow process in the blast furnace raceway is numerically simulated using coupled computational fluid dynamics and the discrete element method (CFD-DEM). The coke reaction kinetics data are imported into the DEM model to reproduce the consumption process of each coke particle. The effects of inlet gas velocity and angle on the morphology of the raceway, coke consumption rate, coke bed temperature, and particle size distribution in the blast process are systematically investigated and analyzed. The results show that the consumption of coke particles promotes the formation of raceways during the blast process. At the same time, a coke mixture layer is produced at the edge of the raceway. The higher the inlet gas velocity, the thicker the coke mixture layer in the middle and upper parts of the raceway region, and the larger the proportion of small particles in the coke mixture layer. The effect of the inlet gas angle on the raceway region is less than the inlet gas velocity. However, with the increase in the inlet gas angle, the high-temperature region of the coke bed extends downward gradually, which is conducive to activating the hearth.

Wind Load Distribution in Float Photovoltaic System

This paper investigates wind load distribution in float PV plants. Wave and wind load are dominant environmental load factors in determining design load in float PV plants. In particular, wind load is determined based on the numerical analysis results. The literature indicates that several input parameters exist, such as inlet angle and space between PV modules. An exemplary structure with ten arrays of PV modules was generated in this study. To investigate the wind load distribution in a float PV plant, the computational fluid dynamic (CFD) analysis was conducted with variables including wind direction (inlet angles) and three wind speeds (36.2, 51.7, and 70 m/s) in PV modules in the floating structure. Based on the numerical analysis, the wind load distribution of PV modules can be characterized with respect to the inlet angle and wind speed. The numerical results show that the wind loads in the central arrays are dominant.

Precise regulation of the multicolor spectrum of carbon dots based on the bionic leaf vein ultrasonic microreactor

Carbon dots (CDs) are a fascinating new type of fluorescent carbon nanomaterial with excellent photoelectric properties. However, preparing long-wavelength and multicolor-emitting CDs has been challenging, limiting their large-scale applications. Fortunately, a new efficient method has been proposed to co-regulate CDs' multicolor spectra using an ultrasonic microreactor. Inspired by plant leaves, a bionic vein microchannel was designed with good fluidity and high energy transfer efficiency. The optimal microchannel structural parameters were determined after investigating the effects of fractal angle, depth-to-width ratio, and inlet angle on the flow uniformity of the microchannel using numerical simulations. The efficiency of ultrasonic energy transfer was improved by directly coupling the microreactor and the sandwich transducer to fabricate the ultrasonic microreactor. Simulation results showed that the ultrasonic microreactor's vibration resonated along the longitudinal direction, and the ultrasonic intensity of the microreactor was maximal and uniform. A high-efficiency and controllable ultrasonic microreactor system was built to synthesize the CDs in situ. The influence of the ultrasound field intensity on CDs' preparation in a microreactor was simultaneously investigated to verify the ultrasound enhancement, and the PLQY of the high-performance CDs was found to be 83.1%. The CDs' multicolor spectra from the blue to the red region can be precisely tuned by adjusting key reaction parameters such as reaction temperature, flow rate, and precursor concentration. This new method shows promising applications in lighting, display, and other fields, making CDs a versatile and exciting new material to explore.

Numerical study on aerodynamic performance improvement of the straight-bladed vertical axis wind turbine by using wind concentrators

The present study proposes a new concept of Straight-bladed Vertical Axis Wind Turbines (SB-VAWTs) with convex-shaped wind concentrator. The wind concentrator is installed up and down the rotor, which is designed to capture more airflow and improve the flow characteristics inside the rotor. The profile of the wind concentrator is generated based on the B-spline, the quadratic rotational orthogonal combination design method is used to study the effects of bottom radius R1, top radius R2, inlet angle α1, and outlet angle α2 of the concentrator, and the distance ΔL between the concentrator and the rotor on the aerodynamic performance of the SB-VAWT by numerical simulation. It is found that the installation of the wind concentrator improves the flow characteristics inside the rotor and enhances the aerodynamic performance of the SB-VAWT, particularly at lower wind speeds. Under the condition of this study, the average torque coefficient and maximum power coefficient of the SB-VAWT with the wind concentrator are enhanced by up to 24.7 % and 52.7 %. This study can provide a reference for using a wind concentrator to improve the aerodynamic characteristics of SB-VAWTs and demonstrate the potential of using this kind of SB-VAWT for wind energy utilization systems.

A novel classification that defines the normal cervical spine: an analysis based on 632 asymptomatic Chinese volunteers

PurposeThe “normal” cervical spine may be non-lordotic shapes and the cervical spine alignment targets are less well established. So, the study was to propose novel classification for cervical spine morphologies with Chinese asymptomatic subjects, and to address cervical balance status based on the classification.MethodAn overall 632 asymptomatic individuals on cervical spine were selected from January 2020 to December 2022, with six age groups from 20–30 year to 70 plus group. Cervical alignment contained C2-7 cervical lordosis (C2-7 CL) and T1 slope (T1S), together with C1-2 CL, C2-4 CL, C5-7 CL, C2S, cervical sagittal vertical axis (CSVA), thoracic inlet angle (TIA) and neck tilt (NT). C2-7 cervical lordosis was regarded as primary outcomes. To identify groups with similar cervical alignment parameters, a 2-step cluster analysis was performed.ResultsC2-7 CL, T1S, CSVA, TIA and NT increased by age and mean value of them were larger in male than female group. Four unique clusters of female lordotic cluster, female kyphotic cluster, male lordotic cluster and male kyphotic cluster were classified mainly based on gender and C2-C7 CL. T1S was the independent influencing factor for C2-7 CL in all individuals and C2-7 CL = -28.65 + 0.57 × TIA, which varied from clusters. Although interactions among cervical parameters, it showed the alignment was more coordinated in lordotic groups.ConclusionsThe cervical sagittal profile varied with age and gender. Four clusters were naturally classified based on C2-7 CL and gender. The cervical balance status was addressed by C2-7 CL = − 28.65 + 0.57 × TIA.

Mean S1 inlet and outlet view angles are not safe for all individuals according to three-dimensional tomographic measurements.

Although there are many studies evaluating optimal inlet and outlet angles required for the correct placement of S1 iliosacral screws, there is no study evaluating reliability and feasibility of these angles for all individuals on three-dimensional (3D) anatomical models. A total of 100 women and 100 men were selected randomly. A vertical line was created according to long axis of the tomography device on which patient was lying in supine position. The automatized best-fit planes were created on superior and inferior endplates, anterior cortex including notch region and posterior cortex of first sacral vertebrae using 3D imaging software to measure mean inlet and outlet angles. We observed no statistically significant difference between gender groups in terms of inlet and outlet angles. Mean inlet view is obtained for anterior cortex of S1 in 22.5 ± 9.5° and for posterior cortex in 46.5 ± 9.3°. Mean fluoroscopic view angle of S1 for superior outlet is 40.3 ± 7.6 and for inferior outlet is 46.9 ± 8.8. Mean anterior and posterior S1 inlet view angles do not accurately visualize anterior cortex of 74 (37%) and posterior cortex of 66 (33%) individuals. Mean superior and inferior S1 outlet view angles do not accurately visualize superior endplate of 74 (37%) and inferior endplate of 56 (28%) individuals. Due to individual alterations of spatial position of sacrum, mean inlet and outlet view angles of S1 are not sufficient to visualize the iliosacral screws under fluoroscopy in many individuals.

Investigating the effects of air inlet jet on the performance of solar still: A comprehensive numerical study

Solar stills are a simple method of producing potable water, but their low efficiency makes them insufficient for meeting daily water needs. This study aims to improve the efficiency of simple solar stills (simple SS) by investigating the effect of an air inlet jet. Factors such as air velocity, entrance angle, and inlet and outlet location were studied. The effect of inlet velocity was studied for air inlet velocities of 1, 2, 3, 4, 5, and 9 m/s, and the effect of inlet angle was studied under six different angles ranging from −45 to +45 degrees. Results showed at Uin=5m/s for the case where the glass cover and basin water were in the highest temperature difference when the inlet was located on the left wall (left-inlet mode), water production rate (ṁ) and heat transfer rate (Nu) improved by %125 and %126, respectively, and for the right-inlet mode, ṁ and Nu improved by %209 and %205, respectively. For an angled inlet, at Uin=9m/s with inlet angle of +15 degrees, for left-inlet mode, ṁ and Nu improved by 211 % and 207 %, respectively, And for right-inlet mode, the ṁ and Nu improved by up to 264 % and 257 %, respectively.

Dynamic characteristics analysis of an aeroengine rotor system subjected to aerodynamic excitation

This paper aims to investigate the dynamic characteristics of an aeroengine rotor subjected to aerodynamic excitation. Firstly, the dynamic model of the turbo-shaft engine rotor system is established by means of finite element (FE) method, taking into account the blade-tip clearance-induced aerodynamic force and oil-film force induced by squeeze film damper. Next, the critical speeds and mode shapes of the rotor are achieved by calculation, simulation and experiment to illustrate the validity of the established model. Then, using bifurcation diagram, rotating orbit and time-domain waveform, the dynamic responses of the turbo-shaft engine high-pressure (HP) rotor with aerodynamic excitation are analyzed, and the effects of blade-tip clearance, inlet and outlet angles on the dynamic responses of the rotor are discussed, respectively. The numerical results reveal that the system maintains a stable-periodic motion at low-speed region. In contrast, at high-speed region, there is a noticeable appearance of instability. Besides, the magnitude of the response decreases with the growth of the blade-tip clearance. The growth of the inlet angle will result in an increase of the magnitude of the response, and the magnitude of the response reduces with the growth of the outlet angle. The aerodynamic force at resonance is greater than that at non-resonance. The research results can assist in understanding the dynamic characteristics of the rotor subjected to aerodynamic excitation, and provide theoretical guidance for the structural design of an aeroengine rotor system.

Magnetic resonance imaging pelvimetric measurements as predictors for emergent cesarean delivery in obstructed labor.

This study aimed to investigate the usefulness of various magnetic resonance imaging (MRI) pelvimetric parameters for predicting emergent cesarean delivery due to obstructed labor. This was a prospective observational study. MRI pelvimetry was performed in cases of a clinically suspected maternal narrow pelvis, maternal short stature, fetal overgrowth, and abnormal placental position. MRI pelvimetry was performed at 34.7±4.2 gestational weeks using a 1.5T MRI system. The pelvic inlet angle, pelvic inclination, obstetric conjugate, sacral outlet diameter (SOD), and coccygeal pelvic outlet were measured in the sagittal section. The interspinous diameter and intertuberous diameter were measured in coronal sections. Fetal anomalies, cesarean deliveries before the onset of labor, and non-reassuring fetal status were excluded from the analysis. MRI pelvimetry was performed in 154 patients. After excluding 76 cases, including 19 cases of absolute cephalopelvic disproportion, 78 cases of trial of labor were included. Of these, 63 were vaginal deliveries and 15 were emergent cesarean deliveries due to obstructed labor. The cut-off value for body mass index (BMI) was 22.2, with an area under the curve (AUC) of 0.69, for predicting obstructed labor. The cut-off value for the SOD was 10.7cm with an AUC of 0.69. BMI alone had a sensitivity of 80%, specificity of 66%, positive predictive value (PPV) of 36%, and negative predictive value (NPV) of 93%. When BMI and SOD were combined, sensitivity was 53%, specificity was 90%, PPV was 57%, and NPV was 89%. The odds ratio for emergent cesarean delivery was 5.42 (95% confidence interval 1.06-27.6, p=0.041) if the SOD was less than the cut-off value in the binomial logistic regression analysis in cases with an BMI >22. We confirmed that MRI pelvimetry was a reliable tool for better patient selection for obstructed labor. The SOD was the best predictor of obstructed labor, with a cut-off value of 10.7cm for women with a low BMI.