Research on the Performance of Pumpjet Propulsor of Different Scales

This study presents a numerical research on the open-water performance of a pumpjet propulsor at different scales. Simulations were performed by an in-house viscous CFD (Computational Fluid Dynamic) code. The Reynolds-averaged Navier–Stokes (RANS) method with SST k-w turbulence model is employed. A dynamic overset grid is used to treat the relative motion between the rotor and other parts. The numerical results are compared with the model test data and they agree well. Comparisons for the open-water performance between the pumpjet propulsors with two scales are carried out. The results indicate that the total thrust coefficient of the large-scale pumpjet propulsor is greater than that of the small-scale one while the torque coefficient is smaller. Therefore, the efficiency of the large-scale pumpjet propulsor is about 8~10% higher than that of the small-scale pumpjet propulsor. The open-water performance of the rotor, pre-swirl stator and duct is obtained separately to estimate the discrepancies on the thrust and torque coefficients between different scales. To analyze the scale effect from different parts, the research on flow field and pressure distribution are carried out. The variation of total thrust and torque coefficient comes mainly from the rotor, which is caused by the flow field, influenced by the duct and stator.

Distance and Rotational Speed Analysis of Coaxial Rotors for UTHM C-Drone

The prototype of UTHM C-Drone use a coaxial hexacopter concept for its propulsion system. A coaxial rotor consists of two motor and two propellers mounted above each other and aligned in relation to their axis of rotation. The propellers are based on the T-Motor U15XXL KV29 model used in UTHM C-Drone. The distance between the two propellers is usually relative to the radius of the propeller or can be lesser. The objectives for this study are to investigate the effect of distance between upper and lower propeller in a coaxial rotors system and the effect of rotational speed. This study is important to ensure the C-Drone power efficient and capable to lift 180 kg payload. The CAD model of the propeller and coaxial rotors system were designed based on the specification from T-Motor company by Solidworks software and the flow simulations were conducted using Solidworks Flow Simulation module. The total of six CAD models; one for a single propeller and five for coaxial rotors with five difference of distance cases were constructed. For each model, the total thrust was tested from 50% throttle power up to the 90% throttle power. It was found that the coaxial rotors system can generate more thrust than a single propeller but less than double. It was also found that if the lower propeller rotates faster than the upper propeller, the increment of total thrust is very small. However, if the upper propeller rotates faster than the lower propeller, the total thrust increase significantly. For the case of faster upper propeller, as the higher the throttle applied, the thrust increment ratio will decrease, and the efficiency of the thrust produced will be affected. In addition, for same rotation speed, the thrust generated was lesser when both propellers rotate in a same direction compared to when each propeller rotates in the opposite directions of each other.

Coupled Eulerian-Lagrangian Simulation of Indexable Drilling

This paper presents finite element simulations of indexable drilling of AISI4140 workpieces. The Coupled-Eulerian-Lagrangian framework is employed and the focus is to predict the drilling torque around the hole axis, thrust force, temperature distributions and chip geometries. The cutting process is modelled separately for peripheral and central insert. Then, the total thrust force and torque are predicted by superposing the predicted result for each insert. Experiments and simulations are conducted at a constant rotational velocity of 2400 rpm and feed rates of 0.13, 0.16 and 0.18 mm/rev. While the predicted torques are in excellent agreement, the thrust forces showed discrepancies of 12 - 20% to the experimental measured data. Effects of the friction modelling on the predicted torque and thrust force are outlined and possible reasons for the thrust force discrepancies are discussed in the paper. Additionally, the simulations indicate that the tool and workpiece temperature distributions are virtually unaffected by the feed rate.

Simulasi Graphical User Interface Analisis Termodinamika Mesin Turboprop Menggunakan Perangkat Lunak Matlab R2020a

A turboprop engine is a hybrid engine that delivers thrust or jet thrust and also drives the propeller. This is basically similar to a turbojet except the turbine works through the main shaft which is connected to the reduction gear to rotate the propeller in front of the engine. This research was conducted to determine the development of engine performance in thermodynamic analysis so as to know the value of each parameter on a engine that has been developing for 20 to 50 years with different engine manufacturing. So that in this study a comparison of the thermodynamic analysis of the TPE-331, PT6A-42 and H85-200 engines was carried out. In the TPE331-10, PT6A-42, and H85-200 turboprop engines the value of fuel to air ratio and shaft work increases with increasing altitude while compressor work, fuel flow rate, shaft power, propeller thrust, jet thrust, total thrust, equivalent engine power and ESFC decrease with increasing altitude. Furthermore, the turbine's working value is relatively stable as the altitude increases. After that, the value of compressor work and turbine work on the PT6A-42 engine was greater than that of the TPE331-10, and H85-200 engines. However, the value of the fuel to air ratio, fuel flow rate, shaft power, jet thrust, equivalent engine power and ESFC on the H85-200 engine was greater than the TPE331-10 and PT6A engines. Furthermore, at sea level, the value of the axle, propeller thrust, and total thrust on the H85-200 engine is greater than that of the TPE331-10 and PT6A-42 engines but at an altitude of 25,000 ft, the PT6A-4 engine has a greater value than that of the TPE331-10 and PT6A-42 engines. TPE331-10, and H85-200 engines.

Optimization of the trimming tilting angle of the electric tiltrotor propeller group

The paper examined the possibility of improving the energy efficient performance of an electric tiltrotor with a lift-propulsion propeller group for a steady flight mode by reducing the energy consumption of the propeller group per unit of time or per unit of the path traveled by the electric tiltrotor. This is achieved by selecting the optimal tilting angles of the electric tiltrotor total thrust vector. In the proposed approach, the trimming tilting angle of the propeller group is variable, depending on the aerodynamic characteristics of the electric tiltrotor, its propeller group. Since the propeller group is equipped with the drives for tilting them, this approach is easily implemented by the conventional facilities of the electric tiltrotor. The tilting of the total thrust vector, on the one hand, leads to an increase in the effective value of the aerodynamic lift coefficient and, on the other hand, it is accompanied by a decrease in the projection of the total thrust vector on the flight speed vector, a change in the drag and power required to create the thrust of the propeller group. This circumstance makes it necessary to solve the optimization problem in order to increase the maximum endurance and long-range capabilities in the cruise mode of the electric tiltrotor flight. The paper presents a method for calculating the optimal tilting angles of the total thrust vector based on the equations of steady motion of the electric tiltrotor in the cruise flight mode, the expression for the total power required for the rotation of the propellers of the propeller group. The analytical dependences for the optimal tilting angles of the total thrust vector are obtained depending on the ratio of the wing area to the total propeller-disk area of the propeller group and the aerodynamic quality of the electric tiltrotor.

A CFD Research on the Effect of Pre-Swirl Stator Blades Number on a Pumpjet Propulsor

In this paper, effect of different pre-swirl stator number on open water performance of a pumpjet propulsor was studied. The pumpjet propulsor consists of shaft system, pre-swirl stator, rotor and duct. The numerical simulations were based on HUST-Ship, a series of inhouse codes, solving the Reynolds Averaged Navier-Stokes (RANS) equation. The computational region was discretized by structured grids and SST k-ω turbulence equations was discretized by finite difference method. The performances of rotor, pre-swirl stator and duct were monitored separately in order to understand the effect in the thrust and the torque. It was found that with the increase of the number of pre-swirl stator blades, the thrust produced by rotor blades increased. However, the number of pre-swirl stator blades influences the thrust of stator, and may have negative effect on the total thrust. In the meantime, thrust of duct also has a little increase. With the increase of the number of pre-swirl stator blades, the propulsion efficiency increases first and then decreases.

Research on the Prediction Model of Shield Advancement Rate in Sandy Cobble Ground of Beijing

The long distance and tight construction period of the earth pressure balance shield tunneling in Beijing sandy cobble ground have a very positive impact on grasping the construction progress and improving the organization efficiency. Based on the real-time monitoring data of on-site earth pressure, cutter head speed, total thrust, screw conveyor speed, and cutter head torque, this study investigated the correlation between the shield advancement rate and the above parameters based on multiple nonlinear regression analysis method, which lay down the foundation of shield advancement rate prediction. The prediction model achieved satisfactory results and was further applied to an airport project. The results show that it is of guiding significance to use multiple regression method to establish shield prediction model and put forward the best advancement parameters to ensure the construction progress. The order in which the four operational parameters affect the advancement rate is total thrust, cutter head torque, screw conveyor speed, and cutter head speed. When the advancement time is greater than 57 min, the average advancement rate and daily progress are highly positively correlated. The research provides a reliable basis for the advancement rate prediction, safety control, and parameter optimization of shield advancement in similar ground.

Aerodynamic and Aeroacoustic Performance of Tail Rotor Investigation and Modification

With the increasingly stringent airworthiness standards, the noise generated during the rotorcraft flight is gradually attracting people’s attention. It widely operated helicopters at low altitudes because of their maneuverability. The way to reduce the noise caused by the complex airflow of the helicopter rotor system has progressively become a hot topic for researchers. Using a hybrid acoustic analysis method, this paper investigates the improvement of the noise and thrust of the helicopter’s tail rotor through the tail rotor structural parameters. For the basic model, the turbulence simulation is performed using an incompressible detached eddy simulation (DES) method, and the Lighthill acoustic analog equation is calculated using the finite element method (FEM). We verified the accuracy of the method through wind tunnel tests. We chose a series of structural parameters for sound simulation and fluid simulation calculations. The results indicate that the modified tail rotor noise reduced by 16.5 dBA and the total thrust increased by 19.9% from the prototype model. This work can enhance the duct tail rotor design to improve aerodynamic and aeroacoustic performance.

Quadrotor Drone Hovering in Ground Effect

A variable-pitch-controlled quadrotor drone was simulated in the ground effect using a high-fidelity CFD solver. In contrast to a single rotor in the ground effect, which has been extensively studied for conventional helicopters, the flow fields around multiple rotors are complex. In this study, the rotating speed of the rotors was maintained constant, and the blade pitch angles were adjusted so that the total thrust of the multicopter was the same regardless of the rotor height from the ground. It was observed that the power required for the quadrotors, which generate the same thrust, decreases when the rotors are approaching the ground from the height where they can be considered to be out of the ground effect, but increases locally when the rotor height is approximately the rotor radius, owing to flow recirculation into the rotor, and then decreases abruptly when the rotors further approach the ground. The outwash from the quadrotors depends heavily on the direction relative to the quadrotor layout. Along the plane crossing the diagonal rotor centers, the outwash velocity profiles resemble those of a single rotor; however, the outwash from the rotor gaps is stronger and extends to a much higher altitude.

Utilization of Open-Source OpenFOAM Code to Examine the Hydrodynamic Characteristics of a Linear Jet Propulsion System with or without Stator in Bollard Pull Condition

With the development of high-speed crafts, new propulsion systems are introduced into the marine industry. One of the new propulsion systems is linear jet which is similar to pump jet and has a rotor, a stator, and a duct. The main difference between this system and pump jet is the placement of linear jet system under the hull body and inside a tunnel. Since this system, like a water jet, is inside the tunnel, the design idea of this system is a combination of a water jet and pump jet. In this paper, hydrodynamic performance of linear jet propulsion system is numerically investigated. To this end, the OpenFOAM software is utilized and RANS steady equations are solved using a k - ε turbulent model. The linear jet geometry is produced by assembling a Kaplan rotor, stator with a NACA 5505 cross section, and a decelerating duct. The results of numerical solution in the form of thrust, torque coefficient, and efficiency are compared with available experimental data for a ducted propeller, and good agreement is displayed. Subsequently, the hydrodynamic parameters are computed in two conditions: with a stator and without a stator. By comparing the results, it is observed that the total thrust coefficient of the propulsion system with a stator at all advance ratios increases by at least 40%. It is further observed that addition of a stator also improves its efficiency.