Thrust Values Research Articles

The amplitude of low-frequency fluctuations is correlated with birth trauma in patients with postpartum post-traumatic stress disorder

Postpartum post-traumatic stress disorder (PP-PTSD) is a severe mental disorder worldwide. In recent years, some studies have reported that PP-PTSD stems from birth trauma. The present study was dedicated in finding ways to predict the occurrence of emergency caesarean section (ECS), trying to analyze the methods to reduce incidence of PP-PTSD on this basis, further exploring the neuroimaging changes in PP-PTSD. A total of 245 primiparas with intention of vaginal delivery were recruited. The internal tocodynamometry measurement was performed during labor for all mothers, and respectively taken at 3–5 cm, 5–8 cm, and 8–10 cm of cervical dilation. The receiver operating characteristic (ROC) curve and Binary logistic regression analyses were also performed to identify fetal head descending thrust that might help in the prediction of ECS. Resting-state magnetic resonance imaging (MRI) was performed on 26 patients diagnosed with PP-PTSD of 245 mothers, the amplitude of low-frequency fluctuations (ALFF) technology was used to observe the spontaneous neural activity of all PP-PTSD patients and correlation analyses were performed. We found that the natural delivery rate of mothers with fetal head descending thrust <16.29 N (5–8 cm), 26.36 N (8–10 cm) were respectively lower than other mothers with fetal head descending thrust ≥16.29 N (5–8 cm), 26.36 N (8–10 cm) (P < 0.05). The ROC curve analysis showed that the area under the receiver operating characteristic curve (AUC) value of thrust (5–8 cm) was 0.896 (95% CI: 0.854–0.938, p < 0.001), AUC of thrust(8–10 cm) was 0.786 (95% CI: 0.714–0.858, p < 0.001), which showed strong potential for predicting ECS. In addition, the Binary logistic regression analysis showed thrust (5-8 cm) and thrust (8–10 cm) were independent correlates of ECS. The resting-state functional magnetic resonance imaging (rs-fMRI) results indicated that PP-PTSD group showed decreased ALFF in the bilateral insula cortex (IC), right anterior cingulate cortex (ACC), and left midcingulate cortex (MCC) compared with healthy postpartum women (HPW) (false discovery rate (FDR) correction q-value < 0.05). The ALFF value of the right ACC was positively correlated with the Perinatal Post-traumatic stress disorder Questionnaire (PPQ) score (r = 0.4046 p = 0.0403) and Posttraumatic Stress Disorder Checklist–Civilian Version (PCL–C) score (r = 0.3909 p = 0.0483). The internal tocodynamometry measurement can serve as a predictive tool for ECS, on this basis, the implementation of effective emotional support may help to reduce the incidence of PP-PTSD. Besides, this study has verified the presence of altered ALFF in the brain regions of PP-PTSD patients, mainly involving the bilateral IC, right ACC, and left MCC, that might be associated with emotion, cognition, and memory disorders functions in PP-PTSD patients.

A novel simplified simulation method for the precooler based on the virtual source term: modeling, validation and application

Precooling technology is one of the promising approaches for expanding the flight envelope of conventional turbine engines and enhancing flight performance at high Mach numbers. Within this domain, a crucial challenge is to rapidly and accurately obtain the flow and heat transfer characteristics of the precooler. Currently, full-size simulation of the precooler is impractical, while simplified and fast simulation methods employed in previous research have exhibited certain deficiencies, including excessive simplification and unconvincing validation. In this study, a novel simplified simulation method for the annular precooler based on the virtual source term model was proposed. This method comprehensively considered the axial and radial non-uniformity of airflow caused by the coupling effect between the precooler and the inlet channel in the actual flow field. Subsequently, systematic validations of the reliability and superiority of this method were conducted, along with its application in the overall performance calculation of the precooled engine. The results demonstrate that the simplified method proposed in this paper showcases higher accuracy than the methods employed in previous research. Compared with the real model, the relative errors of the overall parameters are within ± 1 %, and the relative errors of the distortion indices for total temperature and total pressure are 5.1 % and −1.5 %, respectively. Meanwhile, the number of computational mesh cells is reduced by more than 95 %. Moreover, the first application of the simplified method in the overall performance calculation of the precooled engine reveals that the traditional low-dimensional model underestimates both the total pressure loss of the precooler and the fuel consumption for precooling, resulting in larger calculation deviations in the thrust and equivalence ratio, respectively. The values of thrust calculated with the high-dimensional virtual model show an average decrease of 2.01 % compared to those derived from the low-dimensional model. In addition, a higher Mach number results in lower effectiveness, higher air inlet temperature, and reduced resistance of the precooler to heat exchange imbalance caused by flow non-uniformity. These factors lead to an escalating relative deviation of the equivalence ratio between the two models, reaching 26.45 % at Mach 5.

Mass property estimation on TSE(3) via unscented Kalman filter using RCS thrusters

Estimation of spacecraft mass properties in the presence of noise is a nontrivial problem that, when properly addressed, can substantially reduce the crew time devoted to cargo management, control effort expended to manage fuel mass, or both. The estimation of such properties is treated here using a dual unscented Kalman filter (UKF) where the dynamics of the rigid-body spacecraft are formulated on the special Euclidean group SE(3) and its tangent bundle TSE(3) to avoid singularity and nonuniqueness issues found in attitude parameterization sets. The dual UKF on TSE(3) is developed, and a specific methodology is proposed for the estimation of the constant mass properties. An excitation approach is employed in the mass property estimation scheme. Arbitrary sensor suite placements are considered and implemented in the measurement model to capture real-world spacecraft behavior. Furthermore, a reaction control system with duty cycle constraints and noisy thrust values is implemented to account for uncertainty in the excitation inputs. With these features, the methods contained herein are found to be effective at estimating mass properties.

Experimental analysis and modeling of gas turbine engine performance: Design point and off-design insights through system of equations solutions

In this article, a systematic approach is presented for simulating turbojet engine performance at both design and off-design points. The construction of gas turbine engines involves a core, with additional components added based on the proposed methodology. Accurate formulation of component characteristics and their matching forms the basis for the system of equations needed for solving off-design engine performance. The developed algorithm's initial step involves comparing results with experimental data obtained from 230 N engines. Experimental testing utilizes a 780 N engine under diverse operating conditions, allowing determination of thrust values, fuel consumption, and outlet gas temperatures. An engine characteristic curve is derived under static conditions at ground level and validated against ground test results in Tehran. Unknown parameters are calibrated using a dedicated model, enabling the extraction of engine performance parameters across different corrected speeds. These results are then compared with GasTurb outputs. Comparative analysis between the proposed model's simulation and experimental data demonstrates high accuracy, affirming the reliability of the presented model.

Improved performance of linear induction motors based on optimal duty cycle finite-set model predictive thrust control

Linear induction machines (LIMs) find widespread adoption in various applications, owing to their inherent advantages such as low noise, compact turning radius, and excellent climbing capability. LIMs are extensively utilized in linear metro applications. However, in practical operations, the output thrust shrinks with the increase in speed, which is attributed to end effects. This phenomenon leads to a reduction in efficiency. In addition, fluctuations in the normal force impact system stability, posing disturbances to the suspension system. To address these challenges, this paper suggests a finite-set model predictive thrust control (FS-MPTC) for a drive system employing a linear induction motor (LIM). The FS-MPTC optimizes the duty cycle for the active voltage vector and allocates the remaining period to one of the zero voltage vectors. The selected zero voltage vector reduces the switching transition between it and the active voltage vectors. The duty cycle is calculated for the six voltage vectors by incorporating the deadbeat concept and the derivative value for the electromagnetic thrust. In the prediction stage of the FS-MPTC, the computed duty cycle and the corresponding voltage vector are used simultaneously and repeated for the six voltage vectors. The cost function comprises two terms: the error between the reference thrust and predicted thrust value as the first term and the error between the rated primary flux linkage and its predicted value as the second term. The reference thrust is generated from the outer speed control loop. To validate the effectiveness of the proposed control approach, Japanese 12000 linear induction machine parameters are employed for verification. Comparative analysis of the performance between the suggested control method with the optimal duty cycle and the same process with a fixed duty cycle demonstrates superior performance when utilizing the optimal duty cycle. Finally, the proposed FS-MPTC with the optimal duty cycle offers a promising solution to enhance the operational efficiency of the LIM-based drive systems.

Method of pre-project selection of components for fpv uavs the quadropter type according to the set values of thrust, speed and flight time

Method of pre-project selection of components for fpv uavs the quadropter type according to the set values of thrust, speed and flight time

Free-Running tests for the rapidity of the aerodynamic lift-increasing planing craft

Free-running model test is one of the main test methods to study the performance of ships. In this study, a free-running test model was designed based on the planing trimaran model. The test model has a propulsion system and a data acquisition system, which can complete the functions of remote control, collecting thrust value and speed data and remote transmission data. Two kinds of wings were added to the test model, including the canard wing and the main wing. The test mainly studied the influence of the aerodynamic lift generated by the canard and the main wing on the rapidity of the planing trimaran. The test results show that with the increase of speed, the wing structure can produce considerable aerodynamic lift, and the purpose of reducing drag can be achieved by changing the pitch of the hull and lifting the hull. The test results verify the feasibility of using aerodynamic lift to improve the rapidity of high-speed planing craft. The combination of canard and main wing at the optimal attack angle can reduce hull resistance by 16.5 %.

Protuberance placement mastery: Shock wave control integration with Coanda effect to thrust vectoring on a sonic jet

Thrust Vector Control (TVC) is a technique that allows precise control over the direction and velocity of an aerial vehicle. This paper presents a novel approach combining shock wave control and the Coanda effect to apply this technique in sonic flows. The objective is to achieve more eligible and operational control over the deviation angles of the thrust vector. The research is conducted through numerical simulations and experimental tests to investigate the impact of protuberance location (1, 3.5, and 5 mm), protuberance width (1.5, 2 mm), depth of penetration (2, 6, and 10%), and nozzle pressure ratio (ranging from 2.1 to 4) on the flow field, thrust vector angle, and thrust value of the nozzle. The system's behavior depends on the protuberance location, pressure ratio, and penetration depth. The location of the protuberance influences the shocks and flow separation from the Coanda flap. Increasing the penetration depth up to 10% enhances system stability and reduces the protuberance location's influence on flow deviation. The study highlights the significant effect of protuberance placement on thrust loss, with higher penetration depths resulting in a more significant decrease. The system's behavior in terms of flow deviation is more stable at specific penetration depths and pressure ratios. The results show that the proposed technique achieves a maximum deviation angle of 83° for a sonic jet. In addition, the findings contribute to understanding TVC using protuberances and the Coanda effect. The proposed technique offers advantages in simplicity, reliability, and control performance. It opens possibilities for efficient and maneuverable aerospace vehicles, with applications in UAVs, surveillance, and search and rescue missions.

Transonic Flow Field Analysis of a Minimum Nozzle Length Rocket Engine

The aim of this paper is to develop a profile of axisymmetric minimum length nozzle giving a uniform and parallel flow at the exit section. The study is done at high temperature, lower than the dissociation threshold of the molecules. The design is made by the method of characteristics (MOC). The variation of the specific heats with the temperature is considered. The numerical results have been validated with CFD simulation Ansys-Fluent software. The second part of this study is to calculate and analyze the transonic flow field of this supersonic nozzle. The computation of the flow field characteristics at the throat is thus essential to the nozzle developed thrust value and therefore to the aircraft or rocket it propels. An investigation was conducted to analyze the effects of parameters on the position of the sonic line. These parameters include stagnation temperature T0, radius of the nozzle, types of gases, and exit Mach number ME.

Experimental analysis of propeller thrust in an undergraduate physics laboratory

As propulsive systems are challenging for undergraduates to understand, it is essential to design experiments that can help their visualization and testing. The development of digital technology (high-speed cameras, digital tracking software, or 3D printers) facilitates the implementation of such designs. We proposed to study the thrust produced by a propeller, whose operating principles are based on the conservation of linear momentum. The study was carried out on an air track to avoid frictional forces. Several system characteristics were established, such as the propellor’s rotation speed and angle of attack and different magnitudes were determined, including the dynamic thrust and static force values. 3D CAD software was used to design the propellers for the experiments, and 3D printers to produce them.

Weft insertion guideway design based on high-temperature superconducting levitation

Abstract Wide-width weaving machines typically employ the method of increasing the shuttle’s initial speed to achieve a broader weft insertion. However, this approach not only leads to issues such as significant equipment vibrations, high noise levels, increased energy consumption, and reduced lifespan but also has limitations in achieving substantial increases in the fabric width. The article proposes a wide-width weft insertion method based on high-temperature superconducting magnetic levitation technology. It utilizes the levitation characteristics of high-temperature superconducting shuttles in a permanent magnet array’s magnetic field to levitate the shuttle. The shuttle is then propelled by a traveling wave magnetic field generated by an array of electromagnetic coils, enabling wide-width weft insertion. Based on the required thrust values and weaving speed for the shuttle insertion process, the structural parameters of the weft insertion guideway were calculated. A superconducting suspended weft insertion structure was designed, and a mathematical model between the weft insertion guideway and the shuttle was established. Subsequently, a simulation model of the weft insertion guideway was created using Simulink, and the model was simulated, verified, and analyzed using the field-oriented control algorithm. The simulation results indicate that the operating speed of the levitated shuttle and the driving force for weft insertion meet the requirements for high-speed wide-width weaving.

Analisis Perbandingan Penggunaan Pegas CVT Racing 1000 RPM 1500 RPM 2000 RPM terhadap Performa Sepeda Motor Honda Beat 110 CC

In the era of automatic transmission or automatic transmission motorbikes, many people enjoy doing it in various circles compared to manual transmission motorbikes, these automatic transmission motorbikes are indeed fuel efficient and agile, but automatic motorbike users are not satisfied with their less optimal power, seeing the problems in The use of springs is a factor that influences the performance of automatic transmissions. The purpose of this study is to analyze one of the components of the Continuously Variable Transmission, namely the CVT spring. then compare the power and torque values to find out the comparison of the use of the three springs on the vehicle and retrieve data through the dynotest process. Tests using this dynotest tool produce the values of power, torque, and engine speed produced by the vehicle, this test uses three springs with different constant values such as 1000 Rpm, 1500 Rpm, 2000 Rpm to retrieve table and graphic data values and then compare the data to be converted into thrust and vehicle speed values. To obtain the maximum speed of the vehicle. From the experimental results, each spring produces a different transmission ratio. This results in the value of power and torque, which is produced by each different spring.

Ramie Fiber Woven Composite: The Effect of Number of Layers of Woven Fibers on the Thrust Force in the Drilling Process

Composite material is a combination of two or more materials to obtain better properties and capabilities of the constituent materials. Applications for the use of composites can now be found in industrial equipment to household appliances. To produce these products required machining process. The aim of the study was to determine the effect of the number of layers of woven fiber and the diameter of the drill bit on the thrust of the ramie woven fiber composite in the machining process. The research method was based on ASTM D 5766/D 5766M-02 (Standard Test Method for Tensile Strength Open Hole Laminated Polymer Matrix Composites), the method of making composite material specimens using the hand lay-up method, and the drilling process was carried out with various machining parameters such as composite thickness with variations of 3 layers, 4 layers, 5 layers, and without layers (0 layers). The maximum thrust value obtained was 153.54 ± 3.3 N, with 5 layers of hemp fiber reinforcement, the highest feed rate was 0.15 mm/rev, and the lowest spindle speed was 88 rpm, while the minimum thrust value was 29.52. ± 3.12 N with 0 layers of ramie fiber reinforcement, and the lowest feed rate is 0.05 mm/rev with the highest spindle speed of 1500 rpm.

Investigation on Disaster Mechanism of Diversion Tunnel Induced by Gripper TBM in Hydrokarst Erosion Stratum and Engineering Measures

In gripper tunnel boring machine (TBM) tunneling through complex geological formations, the safe and efficient recovery from large-scale collapses remains a formidable challenge. In this study, we investigate the causes of a 1246 m3 collapse that occurred during the gripper TBM tunneling in the diversion tunnel in Xinjiang, China. Various techniques including TSP seismic waves, CFC advanced water exploration, laboratory point load tests and packer permeability tests were employed for thorough research. The examination discloses that the water softening in biotite-quartz schist in fractured zones contributes significantly to the loosening and dislocation of rock layers along joints. The gripper TBM’s cutterhead exacerbates this process through cutting action and vibrations, causing large-scale instability and eventual rock mass collapse. To tackle this engineering problem, we propose a three-step treatment scheme comprising “Reinforcement-Backfill-Re-excavation”. Furthermore, we propose a technique to handle TBM collapses by creating a “protective shell” within the cavity. The safety and feasibility of these proposed solutions were thoroughly validated through numerical simulations. Also, we utilized the Hoek-Brown theory and Rostami prediction formula to establish recommended values for the total thrust and total torque of the TBM during the collapsed section. The proposed treatment scheme and estimated parameters were successfully applied, resulting in a comprehensive solution from collapse handling to tunneling. This study offers valuable details on effectively managing large-scale collapses in gripper TBM tunneling, which can be useful for similar tunnel engineering and improve safety and efficiency.

Development of a steady-state computational fluid dynamics solver for transonic rotorcraft flows

The capability for solving compressible fluid flows in the rotating frame of reference is added to an existed open-source CFD solver, namely, HiSA solver. The new implementation is explained and validated using the experimental data of the Sikorsky S-76 rotor. A comparison is presented between the moving mesh results obtained from the original HiSA code and the single rotating frame results achieved through the new implementation. The comparison includes an analysis of torque and thrust values, as well as computational costs. The results imply that, for evaluating the performance of an isolated rotor or for shape optimization purposes at the transonic regime, the single rotating frame method, like the one introduced in the current work, can provide accurate results within an acceptable computational budget. Furthermore, the results show that, at least 25 revolutions are required for the transient analysis to reach an acceptable steady-state converged solution like the one obtained by the single rotating frame method.

Experimental Study of a 3D Printing Strategy for Polymer-Based Parts for Drone Equipment Using Bladeless Technology.

The present study focuses on an up-to-date topic regarding flying equipment identified within the category of drones that use, for propulsion and air movements, the power generated by electric motors. In this paper, researchers focus on implementing bladeless technology to calculate, develop, and construct flying equipment known in the literature as drones. The entire structure of the prototype, all the needed parts, is to be obtained using additive manufacturing technologies, which assumes practical realization using 3D-printing equipment. Nowadays, the 3D-printing process has been proven to be a reliable solution when it comes to manufacturing complex shape parts in quite a short time and with reduced costs. The practical study within the present research aims to obtain polymer-based, lightweight parts with complex shapes inside to be implemented in the propulsion of a drone. The complex surface geometry of the parts that this research used is influenced by the ventilation technology offered by the "Air Multiplier" technology. The entire structure of the final drone equipment, all the parts, is to be manufactured using fused filament fabrication (FFF). The main purpose of the fusion is to use the advantages offered by this technology in drones to obtain advantages such as augmented values of thrust, a more agreeable and muffled sound signature, or an increased level of safety.

Multi-objective optimization of a hypersonic airbreathing vehicle

Multi-objective optimization of a hypersonic airbreathing engine (scramjet technology) was carried out with the aim of maximizing thrust and minimizing drag while satisfying a series of design constraints, such as avoiding unstart (blockage of supersonic flow within the combustion chamber) by ensuring that the pressure ratio across the shock waves remains below the adverse pressure gradient given by the Korkegi limit, geometry correction to achieve shock on-lip condition, and temperature and pressure requirements at the inlet exit. Using the relations presented in the literature, pressure and viscous drag are estimated analytically. The analytical approach is verified against computational fluid dynamics data from Ansys Fluent to solve two-dimensional compressible Reynolds-averaged Navier–Stokes flow equations, with transition shear stress transport as the turbulence closure model. Comparing the total drag and the flow properties at the combustion chamber entrance shows the model's feasibility for the optimization approach. Three different approaches were conducted to formulate the multi-objective function to determine the one that can find the highest number of geometries satisfying the Korkegi limit with the highest net thrust. The best approach was the multi-objective function formulated with the uninstalled thrust, total pressure recovery, and pressure drag, concentrating the search in the region with greater uninstalled thrust and lower drag and nearly doubling the value of net thrust compared to the first formulation, which uses the uninstalled thrust, pressure drag, and viscous drag.

A COMMERCIAL TURBOFAN ENGINE MODELING AND EXERGY ANALYSIS

Turbofan engines are one of the most common types of engines used in modern commercial and military aircraft due to their efficiency and performance characteristics. In this study, a thermodynamic model is generated using GasTurb 14 software for a commercial two-spool, unmixed flow, and booster turbofan engine (CFM56-5A3) used in Boeing A320-212. Besides, an exergy analysis of the modeled turbofan engine is performed. Exergy performance criteria such as exergy efficiency, exergy development potential, exergy destruction ratio, productivity lack ratio, and fuel depletion ratio are evaluated for the engine components. In addition, how bypass ratio (BPR) affects net thrust and specific fuel consumption (SFC) for the modeled turbofan engine is investigated. As a result, the net thrust and SFC values of the modeled engine and the actual engine are overlapped with 14.0% and 7.2% deviation, respectively. The maximum exergy efficiency occurs at the high-pressure turbine as 0.992. When the bypass ratio is minimum, the maximum net thrust and SFC occur as 62.24 kN and 24.08 g kN-1 s-1, respectively. High pressure turbine has the minimum exergy development potential of 1528.5 kW.

NUMERICAL INVESTIGATION ON PULSE DETONATION ENGINE PERFORMANCE UNDER DIFFERENT EQUIVALENCE RATIO

Detonation-based engines have a higher thermal efficiency than deflagration-based engines and are therefore widely studied. In this study, the effect of initiation conditions on the detonation wave propagation and the performance of a pulse detonation engine, one type of detonation-based engine, was numerically investigated. Hydrogen-oxygen mixtures with equivalence ratios of φ=0.8, 1.0, and 1.2 were defined as initiation conditions with constant pressure and temperature. The numerical simulations were conducted using the transient explicit density-based solver in the ANSYS Fluent commercial software. The adaptability of the adaptive mesh refinement method in detonation-based engines was explored in the numerical studies, reducing the average total cell count by a factor of 2.617, and obtaining consistent results according to validation studies. The adaptive mesh refinement method was also used in numerical simulations where different equivalence ratios were defined. It was determined that an increase in the equivalence ratio resulted in an increase in the detonation wave velocity. Also, an increase in thrust distribution at the nozzle exit was observed before the blowdown stage, and the calculated thrust values for φ=0.8, φ=1.0, and φ=1.2 were 248.28 N, 264.5 N, and 270.83 N, respectively.

Deep learning-based forecasting modeling of micro gas turbine performance projection: An experimental approach

Performance forecasting of aeroengines is crucial for achieving better operational efficiency, ensuring safety, reducing costs, and minimizing environmental impact in the aviation industry. It enables engineers and researchers to make informed decisions, leading to advancements in technology and the overall evolution of aviation. This study is focused on the effects of flight conditions on the performance of a turbojet, which in consequence affects the environmental aspect of operation. By investigating the relationships between aeroengine efficiency and performance indicators such as thrust, shaft speed, and exhaust gas temperature (EGT), and flight characteristics expressed in terms of environmental and operational conditions, the study seeks to elucidate these connections. The article's significance lies in its successful application of Long Short-Term Memory (LSTM) networks to predict thrust, shaft speed, and EGT variations in turbojet engines under varying flight conditions. Experimental data from a turbojet test bench is processed with deep learning, specifically LSTM recurrent neural networks that are developed based on Matrix Laboratory (MATLAB). The model inputs are free stream air speed, compressor inlet pressure, combustor inlet temperature, combustor inlet pressure, turbine inlet temperature, turbine inlet pressure, nozzle inlet pressure and fuel flow, and the outputs are thrust, shaft speed and EGT. Predicted thrust closely aligns with actual thrust values, though with minor discrepancies. Shaft speed predictions exhibit a similar trend, while EGT predictions showcase a comparable pattern with slight variations. Despite the prediction errors, a thorough evaluation of median values, box plots, and probability density functions confirms that the models effectively capture available information, though discrepancies may arise from measurement inaccuracies and initial engine conditions. These results show that it is possible to accurately predict turbojet performance using LSTM recurrent neural network. This research paves the way for enhanced aeroengine performance prediction, particularly in scenarios requiring off-board or high-performance applications.