Electric Propulsion Research Articles

Multi-objective design optimization and physics-based sensitivity analysis of field emission electric propulsion for CubeSat platforms

Field-emission electric propulsion is an electrostatic space electric propulsion technology that offers various advantageous features including efficient design, high specific impulse, and versatile thrust capabilities ranging from micro-Newton to milli-Newton levels. These characteristics make this type of propulsion a promising technology for small satellite platforms, enabling precise attitude control, orbit maintenance, and de-orbiting through ionization and acceleration of a liquid metal propellant. The growing demand for small propulsion systems in CubeSat platforms has spurred significant progress in modeling and characterizing field emission electric propulsion thrusters to enhance their overall performance. However, little study has been conducted to investigate the effect of geometric configurations on electric fields or expelled ion trajectories for design optimization. In this study, multi-objective design optimization is performed by incorporating electrostatic simulation coupled with an analytical performance model into evolutionary algorithms based on prediction from surrogate modeling, aiming to optimize the thruster emission design to maximize thruster performance. Physical insights into the key design factors influencing the performance of field emission electric propulsion have been gained by probing into the interaction between ion particles and electric field behavior within the thruster. It has been found that the length of the emitter tip has a significant effect on plume divergence, i.e., a longer emitter tip under the influence of electric field at higher emitter current tends to result in lower initial acceleration of emitted ions and subsequently wider spread or divergence of the ion beam. A shorter emitter tip, on the other hand, generates a sharper E-field gradient, resulting in a more focused and narrower ion beam. Additionally, sensitivity analysis has identified the mass flow rate and potential distributions as the most influential design factors on performance due to the active roles they play in the performance generation process.

Evaluation of a multiphase cascaded H-bridge inverter for induction motor operation

Multi-phase systems are becoming more popular for applications requiring high power and precise motor control, even if single-phase AC power is still frequently utilized in households and some enterprises. While both systems have benefits over single-phase, there are trade-offs associated with each. Because of its balanced operation and effective power transfer, the three-phase (3-Φ) system is the most widely used multi-phase system. Nevertheless, different phase values can be investigated for particular applications where reducing torque ripple and harmonic content is essential. Using odd numbers of phases (such as 5-Φ) that are not multiples of three is one method. This design has the ability to reduce torque ripple by producing a more balanced magnetic field as compared with even-numbered phases. But adding more phases also makes the system design and control circuitry more complex. Systems with five phases (5-Φ) provide a compromise between performance and complexity. Applications such as electric ship propulsion, rocket satellites, and traction systems may benefit from their use. Nevertheless, choosing a multi-phase system necessitates carefully weighing the requirements unique to each application, taking into account elements like cost, power transmission, control complexity, and efficiency. The increasing popularity of electric vehicles and renewable energy technologies has led to the need for inverters in current electric applications. Conventional inverters provide square wave outputs, which cause the drive system to become noisy and cause harmonics. Multi-phase multilevel inverters can be used to enhance inverter functioning and produce an improved sinusoidal output. This study focuses on an induction motor drive powered by a five-phase multilevel cascaded H-Bridge inverter. With less torque and current ripples in the motor rotor, the power conversion harmonics are reduced and the switching components of the inverter are under less stress. However, in comparison to traditional inverters, it does require a greater number of legs. Because the switches needed for the cascaded H-Bridge inverter are less expensive in five-phase systems, they are favoured over higher phase orders. Furthermore, the suggested inverter removes 5th order harmonics, something that is not possible with traditional inverters. A five-phase induction motor appropriate for variable speed driving applications is also suggested by this research. Lastly, utilizing pulse width modulation (PWM) converters and an FPGA controller, an experimental study is carried out to assess the dynamic performance of the suggested induction motor drive. Particular attention is paid to the In-Phase Opposition Disposition (IPD) PWM technique.

Economic Aspects of Aircraft Propulsion Electrification

Aircraft propulsion electrification is currently being considered by industry and academia as one of the most promising strategies to reduce air transport emissions and increase overall efficiency levels. In the past decade, several papers were published on this subject, with the majority indicating encouraging fuel burn benefits versus conventional, fossil-fuel-based propulsion systems when future technologies, novel aircraft configurations, and synergistic propulsive-airframe integration are employed. However, a much smaller effort has been applied to the economic aspects of hybrid and fully electric propulsion, which are crucial for a successful product introduction. The present paper describes the modeling of a baseline general-aviation-type aircraft and its propulsion system retrofit with electrified architectures, exploring different electrification strategies for a fixed airframe design. Analyses are performed at the aircraft level, comparing recurring and cash operating costs for several cost and durability scenarios. While considerable CO2 reductions may be achieved in some electrification strategies, aircraft performance is significantly penalized, and important improvements in economic figures of merit are needed in order to make electrified propulsion cost-competitive. Electrified architectures tend to increase costs: turboelectric increases recurring equipment costs, while hybrid-electric increases recurring and direct maintenance costs, especially at higher degrees of energy hybridization.

Hybrid electric aircraft design with optimal power management

The aviation industry has continuously improved its fuel efficiency over the last decades with innovations in technology, design and operation. Further improvements are becoming more difficult as current technology reaches complete maturity. Electrification of road vehicles is predicted to completely replace combustion engines in vehicles. As the efficiency and reliability of electric batteries and motors improve, so does the case for electric propulsion systems in aircraft. Jet fuel carries significantly more energy per weight than current state of the technology batteries, making complete replacement of fuel challenging. Hybrid electric propulsion, where both fuel and batteries are used to power propulsion systems could be feasible and improve fuel efficiency. Hybrid electric powertrains use electric power to reduce the power demands from the combustion engine. Electric batteries are discharged and charged during the operation based on power requirements.This paper presents an aircraft design method that includes optimized power management in the design loop. Power management determines battery discharging and charging throughout the design mission to reduce overall fuel consumption. Power management optimization provides the necessary feedback on battery and fuel performance to design battery pack size. This method is applied to regional aircraft, which typically fly the shortest routes of a commercial airline fleet. These short routes have proportionally longer climb and descent segments. These characteristics of regional aircraft routes lead to wider variations in power during operation, where hybrid electric powertrains are the most beneficial.The proposed hybrid electric aircraft design method finds that a serial hybrid electric regional aircraft could achieve significant fuel efficiency improvements to current regional aircraft. This result is in contrast of the current literature, which requires significant improvements to battery energy density, power distribution efficiency and electric motor efficiency to achieve similar fuel performance results. The hybrid electric regional aircraft does not outperform a traditional turboprop aircraft designed with identical objectives. The turboprop aircraft design improves even greater fuel efficiency improvements over current regional turboprop aircraft. This suggests two pathways are possible; the propulsion system of the next generation of regional aircraft could still be non-electric and achieve improved fuel burn improvements considering current technology or serial hybrid-electric powertrains configurations could be adopted in an expanded time horizon if optimistic technology development is done on battery power density to match the possible improvements of the proposed turboprop aircraft.

Classification, military applications, and opportunities of unmanned aerial vehicles

Unmanned aerial vehicles (UAVs) are cutting-edge technologies used for military purposes world-wide at tactical, operational, and strategic levels. This study provides an overview of the history and current state of military drones, considering a global and Ecuadorian background. Then, a classification of the UAVs developed and built in Ecuador is conducted based on their endurance, altitude, and wing span to understand the national context and progress. The research also delves into the applications of UAVs in several military operations and missions, aiming to create a framework that aligns UAV capabilities with specific operational needs; this permits the identification of the challenges and opportunities the country faces. Unmanned aerial systems have changed the battlefield, and the government needs to adapt to a national strategy that incorporates this technology; this research analyzes and provides insights to improve military capabilities such as exploring modern UAV military applications, technical updates in communication, navigation, and data acquisition systems; and the integration of emerging technologies like smart materials, artificial intelligence, and electric propulsion systems. This study provides valuable insights into the Ecuadorian UAVs that enhance the country’s military operations and offer some applications and uses of this technology for national security.

Fabrication of controllable porous tungsten tips for indium FEEP by dynamic reciprocating electrochemical etching combined with ultrasonic cleaning method

The porous tungsten emitter is a core component of field emission electric propulsion (FEEP). It combines the advantages of sharp tip and internal propellant transport. The emission performance of a FEEP thruster is highly depended on the emitter's tip apex radius. Traditional processing methods for solid tungsten tips are unsuitable for porous tungsten due to its unique structure and electrochemical properties. This paper introduces a novel approach combining dynamic reciprocating electrochemical etching with ultrasonic cleaning to fabricate cone-shaped porous tungsten tips with controlled apex radii. By alternating between 5 cycles of etching and an ultrasonic cleaning, a 1.9 μm apex radius is achieved after 90 repetitions. The etching current waveform reveals the material dissolution mechanism. The electrochemical characteristics of porous tungsten are investigated, with an optimal processing voltage of 2 V identified. To refine the apex radius and prevent tip collapse, a 1.9 V etching voltage is used in the final stages, maintaining the apex within 2 μm. The effectiveness of the fabricated tip is confirmed through wetting in indium and ignition tests.

The Challenges of Naval Electromobility in Amazônia

Introduction: This study aims to assess the feasibility of replacing a diesel-powered tourist boat with a Solar Electric Hybrid Catamaran with a capacity for fifty people to promote sustainable tourism in the Amazon, specifically in the Belém-Pará region. The initiative seeks to take advantage of the opportunity presented by COP 2030 to innovate in the waterway transportation matrix through renewable energy sources. The research is based on sustainability concepts, the environmental impacts of using fossil fuels and the advantages of using solar energy for waterway transportation. The methodology includes a comparative analysis of diesel-powered vessels' operational and environmental costs and a Hybrid Electric system based on data compiled from a master's thesis. The expected results include identifying significant benefits in terms of reduced carbon emissions. The discussion will address the challenges faced in implementation, such as the initial investment costs, the maintenance of the new technologies, and the adaptation of operators and tourists to the latest transportation conditions. The implications of this research are vast; it can serve as an incentive for energy transition in the river transportation sector. Furthermore, this research pioneers the proposal of replacing diesel-powered tourist boats with solar electric hybrid models in the Amazon region. The study adds value by presenting a practical and sustainable solution to the environmental challenges the tourism sector faces, in line with the global sustainability goals set by COP 2030. Objective: This research outlines the importance and potential of naval electric mobility in the Eastern Amazon region, highlighting its relevance within COP 2030 and the SDGs for promoting ecotourism for the Amazon region. Theoretical Framework: The research is based on sustainability concepts, the environmental impacts of using fossil fuels, and the advantages of using solar energy for water transportation. In addition, previous experiences of implementing similar technologies in other regions and the potential for replicability in the Amazon are considered, focusing on environmental conservation and economic development. Method: This research is a compilation of the master's thesis entitled "Waterway electric propulsion technologies: conceptual design of a hybrid vessel with a focus on meeting environmental, social and Governance (ESG) practices," where the study was carried out in the municipality of Belém, Pará in the year 2023. Results and Discussion: The expected results include identifying significant benefits in terms of reduced carbon emissions, lower noise pollution and improved air quality. The discussion will address the challenges faced in implementation, such as initial investment costs, maintaining the new technologies and adapting operators and tourists to the new transportation conditions. Social acceptance and the potential for a positive impact on local tourism will also be assessed. Research Implications: This research has vast implications, ranging from contributing to climate change mitigation to promoting more sustainable tourism practices in the Amazon. Adopting the Solar Electric Hybrid Catamaran can serve as a model for other areas with similar geographical characteristics, encouraging public policies aimed at using renewable energies in the transportation sector. Originality/Value: This research pioneers the proposal of the replacement of diesel-powered tourist boats with a solar electric hybrid model in the Amazon region. The study adds value by presenting a practical and sustainable solution to the environmental challenges faced by the tourism sector, which is in line with the global sustainability goals set by COP 2030.

Electric Taxiing System. Kinetic Energy Recovery System as an Electric Taxiing Solution: Economic and environmental analysis: Phenom 300 case study

The aviation industry has thrived in recent years, with a significant increase in passenger numbers, leading to the development of larger aircraft fleets and the expansion of airport infrastructure. In 2019, more than 4.5 billion passengers traveled by airplane, which represents an 80% increase compared to 2009. As a consequence, this growth has also resulted in longer taxiing times for aircraft, increasing fuel consumption and operational costs. The industry's CO2 emissions have quadrupled since the 1960s, with over 1 billion tons released in 2019, contributing to global warming. Given that the improvements being made to current propulsion systems and the production of over 600 million liters of SAF (Sustainable Aviation Fuel) in 2023 do not seem sufficient to meet the ambitious goals set by regulators and operators, the logical solution would be to develop a system capable of moving the aircraft on the ground using alternative, cleaner, and cheaper energies, such as electric power. This paper explores the latest advancements in electric propulsion systems, specifically focusing on external and onboard systems. After the state of the art is established, this paper will cover a case study and propose a new alternative for an onboard system called ETS – Electric Taxiing System. The ETS is a 100% electric system for ground handling operations designed to use only the kinetic energy stored in a battery pack, which is recovered during aircraft landing and braking events. Although there are some studies on this topic, the author considers this paper to be more comprehensive as the results computed here take into account 96 variables, 60 simulations, several flight plans, and real-world data. The case study focuses on the implementation and dimensioning of the ETS, considering electric motor power and torque, and battery capacity for the Embraer Phenom 300. A brief economic and environmental analysis was also conducted, considering the operation of NetJets Europe, the world's leading and largest private jet company.

Ground test protection strategy for the 100 kW series hybrid electric propulsion system

With the goal of lower emissions, hybrid electric propulsion (HEP) aircraft is considered to be a promising solution, with the advantages of being more environmentally friendly and efficient. Moreover, superior reliability and good safety of the HEP systems is vital to ensure a safe flight. For this purpose, this article presents several successful case studies on overspeed, overvoltage/overcurrent, and communication protection with the combination of theory and experimental data. Given the practical application capability of fault protection, this article established a 100 kW HEP platform and designed an effective system level fault protection architecture, which consists of physical layer, decision layer and execution layer. Experimental studies have been conducted on the turboshaft engine overspeed, electrical architecture overvoltage/overcurrent, communication faults to verify the effectiveness of the proposed fault protection scheme. The test results have shown that the proposed strategy can effectively deal with various fault situations mentioned above to prevent the entire HEP aircraft system from becoming paralyzed, thus improving the reliability and safety of the system.

Soft lenses with large focal length tuning range based on stacked PVC gel actuators

A novel tunable lens with large focal length change and driven by stacked polyvinyl chloride (PVC) gel actuators is designed and characterized in this study. The lens rigid parts are 3D-printed and commercially available, whereas the PVC gel membrane is in volume production. Under electrical actuation, the lens attains focal length ranges from 30 to 217 mm within 400 V. A manual regulating mechanism is proposed for the finished lens that dexterously adjusts the initial focus and focal length ranges. In the compound actuation mode, large focus variation over 950% is achieved within 250 V. Under 250 V step input, the lens exhibits practical response time around 291 ms. Focal length tuning ability of the lens is also demonstrated by capturing the images of objects placed in different positions. This tunable lens is promising for various smart optics.

Fault diagnosis method for redundancy sensors of electric actuator

In order to solve the singular fault modes of redundant position sensors in electric actuators, a fault diagnosis method based on Hall sensor analytical model is proposed on the basis of traditional redundancy comparison algorithm. Through the complete self-monitoring design of Hall sensor and the analytical model design, non-similar redundancy signals of sensors are formed. At the same time, a hypothesis testing method based on sliding data window is adopted, and by adjusting the width of the sliding window to meet the indicators of false alarm rate and missed alarm rate, a fault diagnosis algorithm for position sensors is formed as a whole. Finally, an algorithm validation was conducted for the 2∶2 singular fault mode of the position sensor. The results showed that the fault diagnosis algorithm based on the Hall sensor model can effectively solve the problems caused by 2∶2 singular faults, greatly improve the availability of sensor signals, and ensure the control accuracy and fault tolerance of the servo closed-loop.

Fabrication and Test of a 400 kW-Class Fully Superconducting Synchronous Motor Using REBCO Tape for an Electric Propulsion System

Fabrication and Test of a 400 kW-Class Fully Superconducting Synchronous Motor Using REBCO Tape for an Electric Propulsion System

Comparative study of electric power structure of hydrogen fuel cell electric propulsion ship system

Abstract Aiming at the problem of the applicability of active and semi-active structures of hybrid energy storage units to the complex working conditions of ships in the hydrogen fuel cell electric propulsion system of ships, a comparative study of such structures is carried out in terms of the control strategy, capacity design and optimization effect, respectively. The hybrid energy storage unit in the active structure, supercapacitor and battery, are both connected to the DC bus through the converter. In the hybrid energy storage unit in the semi-active structure, the battery is connected to the low-voltage DC bus through the converter flow in parallel with the supercapacitor, and then connected to the DC bus through the converter. Two kinds of hydrogen fuel cell electric propulsion ship system topology simulation models were established by MATLAB/Simulink respectively, and simulation verification was carried out. The simulation results show that the hybrid energy storage unit with an active structure has stronger adaptability in complex working conditions during ship operation.

Research and analysis on the rotation of high-voltage electric propulsion harnesses under low temperatures and complex trajectories

Research and analysis on the rotation of high-voltage electric propulsion harnesses under low temperatures and complex trajectories

Pressure scaling laws for partial discharges in wedge-shaped, dielectric-bounded gas gaps

A pressure scaling law for the partial discharge inception voltage (PDIV) of wedge-shaped, dielectric-bounded gas gaps is derived and experimentally validated. The investigated prototypical electrode geometry is of relevance in a number of practical applications, such as contacting enameled wires in electric motors or transformers. The derived pressure scaling law is of particular interest for electric propulsion in aviation systems. The results show that the PDIV can be accurately parametrized from first principles as a function of the scaling parameter p⋅s/εr , where p is the gas pressure, s is the thickness of the insulating coating and ɛ r its relative dielectric permittivity. Previously published empirical relationships between the PDIV and pressure are shown to be local approximations of the presented general scaling law. In particular, the often assumed linear relation of PDIV with pressure is shown to not be generally valid.

Design of Radial Flux PM Synchronous Motor for EV Applications

Abstract: High-performance electric propulsion systems are becoming increasingly important as the automotive industry rapidly shifts to electric cars (EVs). The electric motor is an essential part of these systems as it determines the power, efficiency, and overall performance of the vehicle.This project uses Altair Flux, a full-featured finite element analysis (FEA) software suite, to build and optimize a radial flux motor (RFM) with permanent magnet synchronous motor (pmsm) . The main goal is to increase the power density and efficiency of the electric propulsion system for electric cars by utilizing Altair Flux's simulation and analytical capabilities.

The Effect of Carbon Nanotubes and Carbon Microfibers on the Piezoresistive and Mechanical Properties of Mortar

Sustainability, safety and service life expansion in the construction sector have gained a lot of scientific and technological interest during the last few decades. In this direction, the synthesis and characterization of smart cementitious composites with tailored properties combining mechanical integrity and self-sensing capabilities have been in the spotlight for quite some time now. The key property for the determination of self-sensing behavior is the electrical resistivity and, more specifically, the determination of reversible changes in the electrical resistivity with applied stress, which is known as piezoresistivity. In this study, the mechanical and piezoresistive properties of mortars reinforced with carbon nanotubes (CNTs) and carbon micro-fibers (CMFs) are determined. Silica fume and a polymer with polyalkylene glycol graft chains were used as dispersant agents for the incorporation of the CNTs and CMFs into the cement paste. The mechanical properties of the mortar composites were investigated with respect to their flexural and compressive strength. A four-probe method was used for the estimation of their piezoresistive response. The test outcomes revealed that the combination of the dispersant agents along with a low content of CNTs and CMFs by weight of cement (bwoc) results in the production of a stronger mortar with enhanced mechanical performance and durability. More specifically, there was an increase in flexural and compressive strength of up to 38% and 88%, respectively. Moreover, mortar composites loaded with 0.4% CMF bwoc and 0.05% CNTs bwoc revealed a smooth and reversible change in electrical resistivity vs. compression loading—with unloading comprising a strong indication of self-sensing behavior. This work aims to accelerate progress in the field of material development with structural sensing and electrical actuation via providing a deeper insight into the correlation among cementitious composite preparation, admixture dispersion quality, cementitious composite microstructure and mechanical and self-sensing properties.

Aero-propulsion coupling effects and installation characteristics of a distributed propulsion system

The ducted fan, as a quintessential propulsion device utilized in Distributed Electric Propulsion (DEP) aircrafts, exhibits a significant influence on the aero-propulsion coupling effects due to its installation characteristics on the wing. In this paper, we employed steady-state numerical analysis techniques in conjunction with actuator disk models and overset mesh to investigate aero-propulsion coupling effects and installation characteristics of a DEP configuration with 5 ducted fans distributed along the wing's trailing edge. We compared various conditions to the wing baseline airfoil under hover condition and cruise condition of the fan tip speed ratio λ from 1.44 to 4.32 and fan installation angle δT from 0 to 90°. The results indicate that DEP system affects the flow over the wing downstream of the maximum thickness point of the baseline airfoil profile at an installation angle of 0. A higher tip speed ratio the flow is accelerated in the upper surface region near the wing's trailing edge, whereas the low energy fluid fails to be accelerated at lower λ, instead forming a local flow blocking. With the increase of the fan installation angle, the overall system lift increases, but the thrust decreases, and both trends increase with the increase of the tip speed ratio. Specifically, the thrust provided by the distributed fans is reduced, and the inlet becomes one of the drag sources when the installation angle is high.

A Novel Design of a Torsional Shape Memory Alloy Actuator for Active Rudder.

SMA actuators are a group of lightweight actuators that offer advantages over conventional technology and allow for simple and compact solutions to the increasing demand for electrical actuation. In particular, an increasing number of SMA torsional actuator applications have been published recently due to their ability to supply rotational motion under load, resulting in advantages such as module simplification and the reduction of overall product weight. This paper presents the conceptual design, operating principle, experimental characterization and working performance of torsional actuators applicable in active rudder in aeronautics. The proposed application comprises a pair of SMA torsion springs, which bi-directionally actuate the actuator by Joule heating and natural cooling. The experimental results confirm the functionality of the torsion springs actuated device and show the rotation angle of the developed active rudder was about 30° at a heating current of 5 A. After the design and experiment, one of their chief drawbacks is their relatively slow operating speed in rudder positioning, but this can be improved by control strategy and small modifications to the actuator mechanism described in this work.

Issues of ensuring the resistance of high-voltage solar arrays of spacecraft to the effects of secondary arc discharges

We have considered the issues of ensuring the resistance of high-voltage solar battery (SB) of spacecraft to the effects of secondary arc discharges. Research in this area has been going on for more than 50 years, but the answer to all the questions has not yet been found. First of all, this is due to the complexity of the electrophysical processes occurring on the surface of the spacecraft in space and in laboratory conditions. The second reason is the random nature of secondary vacuum arc discharges, which requires the use of special test methods to confirm the effectiveness and reliability of selected design and technological solutions. Tests in conditions close to full-scale conditions do not allow us to solve this problem. We have given a retrospective review of publications on the physical features of secondary arcs arising on SB of spacecraft, the mechanisms of their initiation, experimental research and testing methods. We paid considerable attention to the issues of the occurrence of secondary arc discharges SB of the spacecraft in the conditions of ionospheric plasma and plasma generated by electric propulsion thrusters. We have shown that despite the large amount of accumulated data and knowledge, the transition from low-voltage SB to high-voltage SB remains a difficult scientific and technical problem, which requires additional research to solve. In addition, it is already necessary to start training personnel who possess a wide range of knowledge and are able to work on this topic. To do this, it seems advisable to organize sectoral research, as well as the allocation of targeted funds for the training of highly qualified specialists and their independent research. This approach will make it possible to solve the problem of creating high-voltage SB in the shortest possible time and prepare personnel for the development of this technology.