High Propulsion Research Articles

Chemical Auxiliary for Photocatalytic Active Colloids.

Active colloids with the ability to self-propel and collectively organize are emerging as indispensable elements in microrobotics and soft matter physics. For chemically powered colloids, their activity is often induced by gradients of chemical species in the particle's vicinity. The direct manipulation of these gradients, however, presents a considerable challenge, thereby limiting the extent to which active colloids can be controlled. Here, we introduce a series of rationally designed molecules, denoted as chemical auxiliary (CA), that intervene with specific chemical gradients and thus unveil new capabilities for regulating the behaviors of photocatalytic active colloids. We show that CA can alter the diffusiophoretic and osmotic interactions between active colloids and their subsequent self-organization. Also, CA can tune the self-propulsion of active particles, enabling a record high propulsion speed of over 100 μm/s and endowing high salt tolerance. Furthermore, CA is instrumental in establishing dynamic, competing gradients around active particles, which signifies an in situ, noninvasive, and reversible strategy for reconfiguring between modes of colloidal activity.

Numerical Simulation and Experimental Study on the Aerodynamics of Propulsive Wing for a Novel Electric Vertical Take-Off and Landing Aircraft

The electric vertical take-off and landing (eVTOL) aircraft offers the advantages of vertical take-off and landing, environmental cleanliness, and automated control, making it a crucial component of future urban air traffic. As competition intensifies, demands for aircraft performance are escalating, including forward flight speed and payload capacity. The article presents a novel eVTOL design with propulsive wings and establishes methodologies for propulsive wing unsteady numerical simulation and wind tunnel experiments, analyzing its aerodynamic characteristics and lift enhancement mechanism. The results indicate that the cross-flow fan (CFF) provides unique airflow control capabilities, enabling the propulsive wing to achieve remarkably high lift coefficients (exceeding 7.6 in experiments) and propulsion coefficients (exceeding 7.1 in experiments) at extreme angles of attack (30°~40°) and low airspeeds. On the one hand, the CFF effectively controls boundary layer flow, delaying airflow separation at high angles of attack; on the other hand, the rotation of the CFF induces two eccentric vortices, generating vortex-induced lift and propulsion. The aerodynamic performance of the propulsive wing depends on the advance ratio and angle of attack. Typically, both lift and propulsion coefficients increase with the advance ratio, while lift and drag coefficients increase with the angle of attack. The propulsive wing shows significant advantages and prospects for eVTOL aircrafts in the low flight velocity range (0–30 m/s).

Analyzing the performance of hull and water jet propeller under mooring conditions: effects of shallow water depths and varying inflow speeds

PurposeWater jet propulsion is widely used in various military and civilian fields due to its advantages of simple structure and high propulsion efficiency. The process of mooring involves utilizing specially designed equipment to secure a ship at a designated berth. During the process of water jet propulsion, the single propeller operates within a complex and turbulent three-dimensional flow. Hence, studying the coupling between the water jet propeller and the hull is critical to comprehending the characteristics of the device and the distribution of the flow field in detail.Design/methodology/approachFirstly, we conducted computational fluid dynamics (CFD)-based self-propulsion calculations to evaluate the interaction between the hull and the propeller. We subsequently analyzed the propeller's performance and the forces acting on the hull to understand how the presence or absence of the hull influenced the water jet propeller. Finally, we performed calculations and analysis of the cavitation characteristics of the coupling between the hull and the water jet propeller, considering different rotational speeds and water depths at the bottom of the pool.FindingsThe study demonstrated that the presence of the hull boundary layer under the hull-propeller coupling condition led to reduced uniformity of propeller inlet flow and lower efficiency of the propulsion pump. However, it also increased the bias toward low-flow conditions. Additionally, increasing the impeller speed led to a gradual increase in the cavitation volume within the water jet propeller, resulting in a gradual decrease in the propeller's performance.Originality/valueThis research provides the technical support required for effective design and operation of water jet propulsion systems. This paper involves studying and analyzing the performance and flow field of the coupling between the hull and propeller under mooring conditions with a specified hull model.

Verification of Interface Compatibility Between Pcdu And High-power Hall Electric Propulsion

For the application of high power Hall electric propulsion system on satellites, a newly developed Power Control and Distribution Unit (PCDU) is applied which owns high voltage and high power. It is used to adjust the power of the solar array and battery to form a fully regulated 100V bus. Then the bus power is delivered to the Power Processing Unit (PPU). To verify the interface compatibility between the PCDU and the PPU load, as well as the rationality of the power supply architecture design, an integrated test of PCDU and PPU has been conducted. The test results shows that the compatibility meets the requirement.

Experimental optimization of a fish robot’s swimming modes: a complex multiphysical problem

Multiphysical optimization is particularly challenging when involving fluid–solid interactions with large deformations. While analytical approaches are commonly computational inexpensive but lack of the necessary accuracy for many applications, numerical simulations can provide higher accuracy but become very fast extremely costly. Experimental optimization approaches promise several benefits which can allow to overcome these issues in particular for application which bear complex multiphysics such as fluid–structure interactions. Here, we propose a method for an experimental optimization using genetic algorithms with a custom optimizer software directly coupled to a fully automatized experiment. Our application case is a biomimicking fish robot. The aim of the optimization is to determine the best swimming gaits for high propulsion performance in combination with low power consumption. The optimization involves genetic algorithms, more precise the NSGA-II algorithm and has been performed in still and running water. The results show a negligible impact of the investigated flow velocity. A subsequent spot analysis allows to derive some particular characteristics which leads to the recommendation to perform two different swimming gaits for cruising and for sprinting. Furthermore, we show that Exp-O techniques enable a massive reduction in the evaluation time for multiphysical optimization problems in realistic scenarios.

Enhancing efficiency and propulsion in bio-mimetic robotic fish through end-to-end deep reinforcement learning

Aquatic organisms are known for their ability to generate efficient propulsion with low energy expenditure. While existing research has sought to leverage bio-inspired structures to reduce energy costs in underwater robotics, the crucial role of control policies in enhancing efficiency has often been overlooked. In this study, we optimize the motion of a bio-mimetic robotic fish using deep reinforcement learning (DRL) to maximize propulsion efficiency and minimize energy consumption. Our novel DRL approach incorporates extended pressure perception, a transformer model processing sequences of observations, and a policy transfer scheme. Notably, significantly improved training stability and speed within our approach allow for end-to-end training of the robotic fish. This enables agiler responses to hydrodynamic environments and possesses greater optimization potential compared to pre-defined motion pattern controls. Our experiments are conducted on a serially connected rigid robotic fish in a free stream with a Reynolds number of 6000 using computational fluid dynamics simulations. The DRL-trained policies yield impressive results, demonstrating both high efficiency and propulsion. The policies also showcase the agent's embodiment, skillfully utilizing its body structure and engaging with surrounding fluid dynamics, as revealed through flow analysis. This study provides valuable insights into the bio-mimetic underwater robots optimization through DRL training, capitalizing on their structural advantages, and ultimately contributing to more efficient underwater propulsion systems.

Inhibited swimming capacity of fish entrained in wake vortices behind a semi-cylinder

The loss of fish swimming capacity induced by those energetic vortical structures is detrimental, and limited research on the mechanism of fish entrainment in the vortex has been reported. The present study investigated the entrainment of a fish in vortices generated in wake of a semi-cylinder. The swimming fish was modeled using an undulatory NACA0012 airfoil behind semi-cylinders with a diameter D from 0.1 to 2.4 times the fish body length (L). It was found that the fish couldn't get higher propulsion from the low momentum flow for D > 0.8L. The wake of the fish was distorted by the shedding vortices and trailing-edge vortices (TEVs) arose at fishtail. The length- and time-scale of TEVs were positive correlated with these of oncoming co-directional vortices. The uncontrollable hydrodynamics induced by TEVs could elucidate the disruption of fish stability by surrounding vortices, manifested as a loss of propulsion, the generation of a unidirectional torque, and increased power consumption. The fish head gradually got energy from the turbulent flow of oncoming vortices, but fails to compensate adverse effects of the TEVs. The recovery of swimming capacity occurred only in the less disturbed flow between the wake vortices.

Data Science and Machine Learning Processes for IoT Based Pulsed Plasma Thruster Research

Pulsed Plasma Thrusters (PPT) are very high specific impulse but low efficient electric propulsion engine which are being used as primary or secondary propulsion mechanism for spacecrafts (cube, micro, nano or pico satellites). PPTs are used in academic and/or industrial research from decades, but its experimental data collection methods are normally offline, analysis methods are conventional, and data interpretation lies in electromagnetic, physical, and chemical domain. It is inadequate to explain PPT generated data in few specific domains only and it may prone to inadequate explanations which can hide vast insights of data. Actually, PPT generated data are usually big data. It is essential to analyze and explain PPT data in data science and machine learning domain to get keen insights from the data. To this date no such complete solution exists for PPT either in industrial arena or academia to use all these three technologies. To meet the gap, we propose and implement an Internet of Things (IoT) based architecture for PPT experimental facility to collect, accumulate, and process PPT data intelligently. This architecture yields some machine learning (ML) models with prediction accuracy above 93%. This architecture is a complete IoT and big data based Artificial Intelligence (AI) implementation on PPT data through data science and ML processes. This architecture is capable to contribute in both academic as well as industrial research, development and deployment.

Experimentally backed model of bubbly flow in a CNTP reactor

Centrifugal Nuclear Thermal Propulsion is a second-generation propulsion concept currently being researched to succeed traditional solid core nuclear thermal propulsion. Current efforts across the space industry are focusing on development of technologies for enabling manned flight to Mars and scientific missions to the outer planets. To enable these types of mission's direct injection trajectories are needed to decrease exposure to astronauts and scientific payloads to the harsh environment of space. Current efforts in nuclear thermal propulsion have shown great promise in higher specific impulses ∼900 s, but even these levels of specific impulse fall short for manned Mars missions with durations less than two years or direct injection to orbit of the outer ice giants Uranus and Neptune without the use of gravity assists. High performance nuclear thermal propulsion has been proposed using bubble through nuclear reactors to reach specific impulses as high as 1800 s, however significant challenges exist to prove the feasibility of such a system. One of the major challenges is the fluid mechanics within the core of the engine since little is known about uranium in the liquid phase. An experimental study has been conducted to better understand the fluid dynamics to better inform the thermodynamic and nucleonic models. Using the data from the experiment, high-fidelity simulations have been developed to predict the fluid dynamics of the uranium fuel. This information can then be further fed into thermodynamics models in development to predict core temperatures and system behaviour. The validated models show that small bubbles reach thermal equilibrium, and high centrifugal forces and surface tension assist in confining the molten uranium within the reactor core. Injector methods suggest feasible configurations to encourage bubble flow while minimizing backflow of the propellant, motivating further study of Centrifugal Nuclear Thermal Propulsion based systems.

Numerical Analysis of The Effects of Propeller High Thrust Distribution on Propulsion System Performance

High ship propulsion performance is the main goal of designers, propeller is one component of the propulsion system that also affects the performance of the propulsion. In propeller planning, it is necessary to pay attention to the efficiency of the propeller, in addition to reducing ship operating costs and reducing CO2 gas emissions which is one of the requirements for ships built above 2013, the rules have been made into the Energy Efficiency Design Index (EEDI) standard. At this time the propeller that is widely used is the B Series propeller including the propeller design used on mini LNG ships, namely the B6.40 propeller, the B Series propeller has a pitch character from the Wageningen Propeller Series study. Innovations are made to get better propeller efficiency by varying the pitch distribution. The B6.40 propeller of the standard constant pitch type was modified to B6.40 variable pitch (high thrust). Propellers with high thrust have better efficiency especially for non-fast boats. This study was conducted to obtain the best propeller efficiency of a constant pitch propeller and three high thrust propeller units using Numeca's Computational Fluid Dynamics (CFD) numerical self-propulsion test. For validation of the simulation program by comparing the results of the open water test B6.40 Wageningen while resistance validation by comparing the ship resistance model test. The results of the self-propulsion test using Disc Actuator show that the propulsion coefficient (PC) of Modified-2 and Modified-3 high thrust propellers is better when compared to constant pitch. The magnitude of the increase in PC value reaches ± 4% higher than the constant pitch type on the Modified-3 propeller.

Time dependent full-core multiphysics analysis of nuclear thermal propulsion reactors

Nuclear thermal propulsion is the high thrust, high specific impulse rocket engine technology for future crewed missions to Mars and beyond. This paper presents a full-core multiphysics analysis approach that accounts for thermal–hydraulic and thermo-mechanical feedback while adjusting control drum position during operation. This time-dependent coupled multiphysics approach is then compared to previously adopted decoupled analysis. The results demonstrate that neglecting multiphysics feedback and control drum rotation introduces significant errors into the spatial power distributions, which subsequently cause significant errors in the prediction of thermal and mechanical safety margins during engine operation. Finally, the multiphysics approach is applied to design the fuel orificing pattern for an engine that can provide a specific impulse of 900 s while maintaining acceptable maximum fuel temperatures throughout a 60-minute main-stage burn. The analysis presented in this paper conclusively demonstrates the benefits of adopting a multiphysics approach to design high specific impulse nuclear thermal propulsion reactors.

Analysis on Performances and Flow Fields of a Single Waterjet Propeller Based on SST k −ω Model

As a special method of ship propulsion, waterjet propeller has been widely used in military and civilian fields due to its advantages of simple structures and high propulsion efficiency. Affected by waves of sea and rotation of impeller, the internal flow of waterjet propeller is extremely complex on three dimensions. When waterjet propeller works, its turbulent flow is often accompanied with unstable phenomena like flow separation, secondary flow, and backflow. On the other hand, the impeller of the propeller will be easily cavitated if it runs at high speed. That has a serious impact on performance and structure of the propeller. Therefore, understanding the open water performance and cavitation characteristics is imperative. In this study, we analyze the performance and flow field of a single marine external waterjet propeller based on the SST k−ω model. We focus on examining its performance under various advance coefficients in open water conditions. The experimental results show that the distributions of streamline and inlet velocity are more uniform at the highest efficiency point than other operating conditions. The loss for the generation of entropy is relatively low at the same time. The analysis on cavitation shows that the volume of the cavitation bubble will increase gradually as the cavitation number of the propeller decreases. Meanwhile, the performance of the propeller decreases obviously at the blade tip extending from the rim to the hub.

Fundamentals and recent progress of additive manufacturing-assisted porous materials on transpiration cooling

The requirements for new generation vehicles in terms of the flight speed, thrust–weight ratio, and maneuverability necessitate the development of high performance and reliable propulsion systems where active thermal protection technology plays a crucial role. Transpiration cooling based on a microporous structure is considered as one of the most promising techniques for protecting the high heat flux walls from ablation in aerospace applications. Unlike conventional fabrication methods, additive manufacturing (AM) has been applied to fabricate three-dimensional (3D) porous structures with customized geometries that are specific to applications, i.e., in terms of the design of features such as the pore diameter, pore density, porosity, and pore morphology. Three major AM technologies (selective laser melting, inkjet, and stereolithography) followed by a post-printing process have been proposed for the additive manufacture of porous structures. In particular, 3D-printed porous structures have great promise for transpiration cooling applications. In this review, we discuss the detailed steps of porous structure topology design and a general framework is presented for AM. The heat transfer and strength performance are also provided for porous parts fabricated by AM. Furthermore, the applications of 3D-printed porous media in transpiration cooling with different regimes are described. This review concludes by explaining the current challenges and prospects for the next generation of 3D-printed porous structures in transpiration cooling systems.

Investigation of wt.% Si and Heat Treatment on the Mechanical Properties of Al6063 Aluminum Alloy by the Casting Product Propeller Shaft Model

Shaft propeller is one of the most important parts of ship propulsion installations. To produce a good quality shaft propeller, the ship propeller designer must consider various parameters, in order to produce the type and size of the propeller that has the value of effectiveness and high propulsion efficiency. Shaft propellers are usually made of steel but, in this study the propeller shaft model is made of Aluminum Alloy base material. So the material must have good mechanical properties. The purpose of this study is to see the mechanical properties of the sheller propeller with aluminum alloy base material with the addition of silicon elements and magnesium by going through the heat treatment process. The main base material used is 6063 aluminum alloy, with variations in the addition of Si (1, 2, 4 wt%). The addition of Mg can improve the mechanical properties of the casting. Alloy Al6063 is heated to a temperature of 790°C to reach a complete liquid state. Then the temperature is lowered to 645°C, then the Si element is inserted into the heating furnace and stirred. Then the temperature is lowered to 615°C, then the Mg element is added, then stirred thoroughly by a mechanical stirrer. The rotational speed of the stirrer is 70 rpm and the stirring time is 240 seconds. Then heated to a pouring temperature of 670°C. The mold is heated to a temperature of 265°C. Then poured into the mold and pressed 7 MPa. After that, it was allowed to stand for 600 seconds, and then removed from the mould. The cast propeller shaft is cooled at room temperature. Then the propeller shaft was heat treated with a solution treatment temperature of 485°C for 3600 seconds and then quenched using a fluid. After that, the casting products were treated with artificial aging. The results of the study are, Porosity will decrease along with the addition of Silicon elements. The lowest porosity level is in addition of 3% wt Silicon that is equal to 1.15%. Tensile test with the addition of 1% wt Silicon ie, 106.882 MPa, in addition of 2% wt Silicon that is, 128.713 MPa, and in addition of 3% wt Silicon ie 132.668 MPa. So the highest tensile stress value is at 3% wt. Hardness values will increase with the addition of Silicon elements. The highest hardness value found in the variation of 3% wt Silicon ie, 69.9 HB. While in the variation (0, 1, 2% wt) that is, 43.75 HB, 51.24 HB and 56.45 HB. So this study, proving that the addition of silicon elements can improve the mechanical properties of the shaft propeller.

Numerical Study of Kaplan Series Propeller using CFD: Effect of Angle of Attack and Number of Blade Variations

Kaplan series propeller has the potential to improve ensuring the high ship propulsion performance of the operation. In this study, a Kaplan propeller is evaluated with a Controllable Pitch Propeller (CPP) behavior such as angle of attack and the number of blades. The propeller blades which are studied are 3, 4, and 5 blades with the angle of attack about 10.3⁰, 15.3⁰, and 20.0⁰. The method in this study is using Computational Fluid Dynamic (CFD) simulations. Moreover, surface pressure, thrust, torque, and efficiency are evaluated due to the influence of the angle of attack variations. It has been found that varying the angle of attack significantly affects the distribution of the pressure surface of the propeller. The pressure gradually increases at the higher level of the angle of attack. Furthermore, it is well known that variations in the angle of attack and the number of blades significantly affect propeller performance as expressed by propeller thrust and torque values. Thrust and efficiency tend to increase at higher levels of the angle of attack. However, it tends to decrease at the propeller with more blades on it

PMSM Speed Control using SVPWM Technique

A simulation analysis of a voltage source inverter using Space Vector Pulse Width Modulation (SVPWM) to control the speed of a Permanent Magnet Synchronous Motor (PMSM) has been presented in this research. PMSM is an AC drive that widely helps in high power propulsion systems. SVPWM is one of the best PWM techniques. The SVPWM is powered by a voltage source inverter connected to the PMSM. Space vector modulation is responsible for developing pulses to control the switches of the inverter. This research introduces an SVPWM-fed three-phase voltage source inverter for controlling the speed of PMSM drives using MATLAB/Simulink.

Adaptive Modification of TBM Tunneling in Coal Mine Roadway and Disaster Control Technology for Complex Geological Conditions

Many mines have introduced the tunnel boring machine (TBM) to improve the efficiency of rock tunneling because of its high propulsion capacity, safe working space, and intelligent equipment. In contrast, the operating environment of coal mines is often under complex geological conditions such as high ground stress, large depth of burial, high temperature, water damage, and large construction angles, making it difficult to apply traditional TBMs in coal mines. Taking the TBM of Gaojiapu Coal Mine of Zhengtong Coal Industry as an example, this paper introduces the coal mine adaptability transformation and construction technology optimization of the equipment, optimizes the design of the roadheader department of the equipment, increases the support operation space and reduces the empty roof distance, shortens the length of the whole machine and transforms the walking structure to enhance its maneuverability and convenience, and applies the monorail crane to the auxiliary transportation system of TBM. This paper proposes the theory of TBM tunneling disaster control in complex geology, research and discussion on TBM jamming, impact pressure, cooling prevention and control, and water damage in complex geological conditions. The results obtained were applied at the Zhengtong Coal Industry in engineering practice, resulting in an average monthly progress of more than 200 m, which is more than three times more efficient than full rock heaving, and also reduces the work intensity of tunneling personnel and promotes the development of coal mining. The final part of the article looks at the future application of TBMs in coal mining.

Development of inverted pendulum thrust stand with spring-shaped wire for high power electric thrusters.

Pendulum thrust stands are used to measure the thrust of electric propulsion systems for spacecraft. A thruster is mounted on a pendulum and operated, and the pendulum displacement due to thrust is measured. In this type of measurement, the pendulum is also affected by nonlinear tensions due to wiring and piping that deteriorate the accuracy of the measurement. This influence cannot be ignored in high power electric propulsion systems because complicated piping and thick wirings are required. Therefore, to reduce the influence of tension due to wires and tubes, we developed an inverted pendulum-type thrust stand with pipes and wirings as springs. In this paper, we first derive the design guidelines for spring-shaped wires; the necessary conditions for sensitivity, responsivity, spring shape, and electric wire were formulated. Next, a thrust stand was designed and fabricated based on these guidelines, and the performance of the stand was evaluated through calibration and thrust measurements using a 1 kW-class magneto-plasma-dynamics thruster. The sensitivity of the thrust stand was 17 mN/V, the normalized standard deviation of the variation of the measured values owing to the structure of the thrust stand was 1.8 × 10-3, and the thermal drift during the long-time operation was ∼4.5 × 10-3 mN/s.

Dynamics and hydrodynamic efficiency of diving beetle while swimming

Diving beetle, an excellent biological prototype for bionic underwater vehicles, can achieve forward swimming, backward swimming, and flexible cornering by swinging its two powerful hind legs. An in-depth study of the propulsion performance of them will contribute to the micro underwater vehicles. In this paper, the kinematic and dynamic parameters, and the hydrodynamic efficiency of the diving beetle are studied by analysis of swimming videos using Motion Capture Technology, combined with CFD simulations. The results show that the hind legs of diving beetle can achieve high propulsion force and low return resistance during one propulsion cycle at both forward and backward swimming modes. The propulsion efficiencies of forward and backward swimming are 0.47 and 0.30, respectively. Although the efficiency of backward swimming is lower, the diving beetle can reach a higher speed in a short time at this mode, which can help it avoid natural enemies. At backward swimming mode, there is a long period of passive swing of hind legs, larger drag exists at higher speed during the recovery stroke, which reduces the propulsion efficiency to a certain extent. Reasonable planning of the swing speed of the hind legs during the power stroke and the recovery stroke can obtain the highest propulsion efficiency of this propulsion method. This work will be useful for the development of a bionic propulsion system of micro underwater vehicle.

Aerospace Environmental Challenges for Electrical Insulation and Recent Developments for Electrified Aircraft.

The growing trend towards high voltage electrical assets and propulsion in the aeronautics and space industry pose new challenges in electrical insulation materials that cannot be overlooked. Transition to new high voltage electrified systems with unprecedented high levels of voltage, power, and efficiency must be safe and reliable. Improvements in both performance and safety of megawatt power systems is complicated because of the need for additional power transmission wiring and cabling and new safety requirements that have the potential of making the resulting systems heavier. To mitigate this issue, novel lightweight materials and system solutions are required that would result in lower specific weights in the insulator and conductor. Although reduced size and weight of system components can be achieved with new concepts, designs, and technologies, the high voltage (≥300 V) operation presents a significant challenge. This challenge is further complicated when considering the extreme operating environment that is experienced in aircraft, spacecraft, and targeted human exploration destinations. This paper reviews the extreme environmental challenges for aerospace electrical insulation and the needs associated with operating under high voltage and extreme environments. It also examines several recently developed robust lightweight electrical insulation materials that could enhance insulation performance and life. In aerospace, research must consider mass when developing new technologies. The impact of these recent developments provides a pathway which could enable next generation high altitude all electric aircraft, lightweight power transmission cables for a future sustained presence on the Moon and missions to Mars using HV propulsion, such as spacecraft with Nuclear Electric Propulsion systems.