Electric Propulsion Applications Research Articles

Portable Thomson scattering system for temporally resolved plasma measurements under low density conditions.

We present the development of a portable Thomson scattering diagnostic system allowing simultaneous spatially and temporally resolved plasma property measurements for low density plasmas. The setup uses a compact pulsed Nd:YAG laser (532nm) as the light source with suppression by two volume Bragg grating notch filters and dispersion with a single-stage spectrometer before measurement with an intensified camera. A key issue is the detailed light collection and how it impacts the sensitivity and elastic light suppression, for which we have investigated two optical configurations, one based on a 7 × 1 linear fiber bundle and the other based on a slit spatial-filter. We find that the configuration with the slit spatial-filter provides a higher sensitivity by a factor of ∼2 along with more uniform spatial response. We have developed a custom pulsed-plasma setup with a modulation at 20kHz, representative of the Hall thruster breathing mode oscillation, to show the possibility of temporally resolved measurements for electric propulsion applications. We have successfully recorded the variations in electron number density and temperature with sub-mm spatial resolution and capturing ten temporal points over the 50 µs modulation period. The detection limit of electron density (with the spatial-filter configuration) is ∼1.6 × 1017m-3, which is ∼1/10 of the plasma density in the acceleration channel of Hall thrusters.

Laser-induced fluorescence detection of nitroxyl (HNO) formed from the thermal decomposition of hydroxylammonium nitrate vapor

The decomposition of the ionic liquid hydroxylammonium nitrate (HAN) produces gas phase products which have utility in spacecraft propulsion systems. Among the various gas phase species generated from HAN decomposition is the nitroxyl (HNO) radical, a highly reactive molecule with implications in both chemical and electric propulsion applications. The work described here used a laser-induced fluorescence platform to directly detect the relative density of the HNO radical formed by passing HAN vapor through heated porous disks of varying composition. The use of heated porous 316-stainless steel and aluminum disks showed significant HNO density production and is attributed to a surface hydrogen abstraction mechanism. There was also evidence of surface modification to the metal disks which resulted in a shift in the HNO density temperature profiles. The results reported demonstrate that use of a heated porous material can easily generate a molecular vapor at moderate temperatures for combustion and electric propulsion applications.

Time-resolved ion energy measurements using a retarding potential analyzer for electric propulsion applications.

To completely characterize the evolving state of a plasma, diagnostic tools that enable measurements of the time-resolved behavior are required. In this study, a gridded ion source with superimposed oscillations was utilized to verify the functionality of a high-speed retarding potential analyzer (HSRPA), at frequencies equivalent to the low frequency oscillations occurring in Hall effect thrusters (HETs). The verification of this device provides an effective alternative to existing diagnostics for measuring time-resolved ion energies. Retarding potential analyzers (RPAs) have established themselves as a fundamental diagnostic in the field of electric propulsion (EP), enabling the measurement of ion energy distributions within the plumes of EP thrusters. The work presented here has demonstrated the capability of a standard RPA in conjunction with high-speed circuitry and data fusion techniques to produce time-resolved ion energy distribution functions (IEDFs) at higher frequencies and beam potentials than have previously been investigated. Tested frequencies ranged between 20 and 80kHz with 10V peak-to peak oscillations at a mean beam potential of 570V. In addition, measurements were conducted with several waveforms, functioning as the superimposed oscillation, including a sine wave, triangle wave, and noisy sine wave. Data from the HSRPA were successfully reconstructed into time series utilizing two data fusion techniques: the empirical transfer function method and shadow manifold interpolation. Time-resolved IEDFs were produced at all frequency set points and waveforms. This investigation has demonstrated the HSRPA effectiveness at producing time-resolved measurements under conditions similar to those occurring in HETs.

Development and Analysis of Dual Three-Phase PMSM with Phase-Shifted Hybrid Winding for Aircraft Electric Propulsion Application

Development and Analysis of Dual Three-Phase PMSM with Phase-Shifted Hybrid Winding for Aircraft Electric Propulsion Application

System design study of a VLEO satellite platform using the IRS RF helicon-based plasma thruster

To achieve a feasible lifetime of several years, most satellites are deployed in orbits higher than 400 km. Drag of residual atmosphere causes a slow orbit decay, resulting in the deorbit of the spacecraft. However, e.g. optical instruments or communication devices would significantly benefit from lower altitudes in the range of 150–250 km. A solution to achieve this could be the application of atmosphere-breathing electric propulsion (ABEP), where the residual atmosphere is used to generate continuous thrust that compensates the drag.Within the EU-funded DISCOVERER project, the Institute of Space Systems (IRS) developed an electrode-less RF Helicon-based Plasma Thruster (IPT) suitable for such applications. Ignition and preliminary discharge characterizations of the IPT have been carried out at IRS facilities, using argon, nitrogen and oxygen. To further characterize the plasma plume, a torsional pendulum has been designed to determine the (local) momentum flux in the plasma jet, as well as a three-axis magnetic B-dot probe to carry out time-varying magnetic field measurements. Various intake designs were investigated, opening the possibility to conduct studies on potential satellite platforms within the frame of the ESA-funded project RAM-CLEP.A design study for an Earth Observation and Telecommunication satellite operating at 150–250 km with an extended mission lifetime is currently being carried out. The first system assessment focused on the comparison of different spacecraft configurations (“slender body” and “flat body”) and intake designs (specular or diffuse) with regard to overall drag and ABEP performance requirements.In this contribution, the design approaches for the current thruster and the diagnostic methods are depicted. Moreover, the current status of the system assessment is presented. Upcoming experimental studies of the ABEP system e.g. within the ESA-project RAM-CLEP and additional activities planned on system assessment are outlined.

Assessment of Electric Propulsion Application in Light Rail Transit (LRT)

In this paper, one of the most important parts of self-propelled vehicles is presented, namely the Light Rail Transit (LRT), especially the propulsion system. LRT is already operating in several major cities in the world, but in Indonesia its construction has just been completed and is currently operating in Palembang, South Sumatra, and Greater Jakarta area (Jakarta-Bogor-Depok-Bekasi). The methodology used to describe and analyse the LRT propulsion system begins by first reviewing the literature on the development of LRT-type mass transportation in developed countries, then a study of technological developments is carried out on each component of the propulsion system, especially for the propulsion of rail facilities. One of the main components of the LRT-type rail propulsion system that will be used and developed in Indonesia is the VVVF inverter, which functions to regulate the speed of the traction motor which is designed to work in a certain frequency range, for example between 0 Hz to 70 Hz. The VVVF inverter output is controlled by a very popular principle used in railways, namely the constant V/f setting technique. The initial start of the LRT requires high torque to overcome train resistance and to accelerate in a few minutes. To meet these needs while still paying attention to energy savings, the traction power (traction effort) is adjusted, which is the power needed to move the train from a speed of 0 km/hour to 30 km/hour. Traction power is adjusted by varying the frequency to control the speed, the terminal voltage is also varied so that the ratio of the constant V/f constant is maintained at 15.7 V/Hz. The maximum torque of the motor becomes constant at every speed change.

A framework for Li-ion battery prognosis based on hybrid Bayesian physics-informed neural networks

Li-ion batteries are the main power source used in electric propulsion applications (e.g., electric cars, unmanned aerial vehicles, and advanced air mobility aircraft). Analytics-based monitoring and forecasting for metrics such as state of charge and state of health based on battery-specific usage data are critical to ensure high reliability levels. However, the complex electrochemistry that governs battery operation leads to computationally expensive physics-based models; which become unsuitable for prognosis and health management applications. We propose a hybrid physics-informed machine learning approach that simulates dynamical responses by directly implementing numerical integration of principle-based governing equations through recurrent neural networks. While reduced-order models describe part of the voltage discharge under constant or variable loading conditions, model-form uncertainty is captured through multi-layer perceptrons and battery-to-battery aleatory uncertainty is modeled through variational multi-layer perceptrons. In addition, we use a Bayesian approach to merge fleet-wide data in the form of priors with battery-specific discharge cycles, where the battery capacity is fully available or only partially available. We illustrate the effectiveness of our proposed framework using the NASA Prognostics Data Repository Battery dataset, which contains experimental discharge data on Li-ion batteries obtained in a controlled environment.

A Solid-State Circuit Breaker Without Current Limiting Inductor

This paper presents a high-density, high-efficiency megawatt (MW) medium-voltage (MV) solid-state circuit breaker (SSCB) for aviation hybrid electric propulsion applications. The proposed SSCB is based on the mature silicon (Si) insulated gate bipolar transistor (IGBT) devices. With reduced IGBT gate voltage, the proposed SSCB can limit the peak fault current without the fault current limiting inductor. Thus, the specific power density of the SSCB is substantially improved compared with the traditional design. This method has negligible impact on SSCB efficiency, reliability and energy absorbed by the metal-oxide varistor (MOV), while providing additional mechanical layout freedom for power density and insulation enhancement. The potential design challenges due to the extremely high ramp rate of the system fault current and the corresponding solutions are also discussed. The performance of the proposed SSCB is validated with experimental results.

Second Life Management From Battery Storage System of Electric Waterborne Transport Applications: Perspectives and Solutions

In electric naval applications, battery storage management plays a key role. The second-life battery use is a fundamental part of the sustainable development of these waterborne transport systems. The article deals with the perspective and solutions of the second-life storage battery systems from the electric ship traction area. This paper presents an overview of the topic of second-life use, application, and future direction with a special focus on battery systems from electric propulsion ships. In particular, a modular converter-battery approach in the storage system structure arrangement is considered. The modular battery storage approach in electric naval propulsion applications is the target of SEABAT project. This proposed solution allows both controls of the electrical quantities of the storage output and monitoring of the battery’s electrical parameters to always have its health status available. The advantages of the modular multilevel battery-converter structure developed within the SEABAT project towards second-life use are presented and evaluated, leading to an estimated cost saving of 35% during the whole life time of the batteries. Besides, the integration of multiple battery technology with different degradation state is enabled. Moreover, the power converter features for second-life applications are explored and discussed. Furthermore, the manufacturing and disassembly processes aspects of the SEABAT converter-battery system (CBS) are also investigated to validate the effectiveness of the proposed modular storage solution. The SEABAT project targets a 246 kWh demonstrator with a 1000 V output.

Vacuum Arc Plasma Coating for Polymer Surface Protection— A Plasma Enhanced In-Orbit Additive Manufacturing Concept

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently under exploration. Still, a solution for protection of the UV and IR radiation sensitive polymers is needed in order to prevent their early mechanical failure under space conditions. Vacuum arc plasma based process is widely applied on earth for thin protective coating deposition. Its major advantage is its scalability—from tiny size used in electric propulsion to large scale coating devices. The usability of the vacuum arc process in space conditions was shown in electric propulsion applications in nano-satellites. In this work we discuss and demonstrate the integration of vacuum arc process as a post processing step after Fused Filament Fabrication (FFF) for additive manufacturing and functionalization of long polymer structures. Here we address the concept for technical realization, which integrates the vacuum arc into additive manufacturing process chain. More over we present a laboratory prototype, which implements this concept together with a use case, where a previously printed PEEK structure is coated with aluminum based coating suitable for UV radiation protection.

A Comparative Study of Fuzzy SMC with Adaptive Fuzzy PID for Sensorless Speed Control of Six-Phase Induction Motor

Multi-phase motors have recently replaced three-phase induction motors in a variety of applications due to the numerous benefits they provide, and the absence of speed sensors promotes induction motors with variable speed drives. Sensorless speed control minimizes unnecessary speed encoder cost, reduces maintenance, and improves the motor drive’s reliability. The performance comparison of the fuzzy sliding mode controller (FSMC) with adaptive fuzzy proportional integral derivative (AFPID) control methods for sensorless speed control of six-phase induction motors was analyzed in this study, and the proposed control system has an advantage for multiphase machines, specifically six-phase induction motors (IMs) in this study, as they are the current active research area for electric vehicles, hybrid electric vehicles, aerospace, ship propulsion, and high-power applications. The speed control of a six-phase induction motor was performed by using an AFPID controller and FSMC. The comparative performance analysis was based on sensorless speed control of the six-phase induction motor. A proportional integral derivative (PID) controller is commonly employed as it is used to eliminate oscillations, but it has several drawbacks, such as taking a long time to decrease the error and stabilize the system at constant speed. The fuzzy type-2 and PID controllers were hybridized so as to obtain the advantages of both to enhance the system performance. Finally, the comparison result revealed that the FSMC preforms significantly better by achieving good tracking performance. The control technique maintains the sliding mode approach’s robustness while providing reduced overshoots with a smooth control action, and the FSMC revealed good dynamic response under load variations when compared to the AFPID controller.

A 1-MHz GaN-Based $LCLC$ Resonant Step-Up Converter With Air-Core Transformer for Satellite Electric Propulsion Application

A gallium nitride (GaN)-based resonant step-up converter is proposed for the application in the satellite electric propulsion (EP) system. This converter consists of a full-bridge inverter, a resonant tank, and a multistage Cockcroft–Walton voltage multiplier to provide a high voltage gain. Additionally, the air-core transformer is introduced due to the megahertz switching frequency allowed by the GaN device. Thus, the limited magnetizing inductance of transformer and the remarkable junction capacitance of diode have to be carefully considered in the resonant tank design, especially after considering that this converter normally operates at the light load in the EP system. In this work, the fourth-order <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ LCLC$</tex-math></inline-formula> resonant converter is investigated. The recommended parameter selection for the fourth-order resonant tank is also provided. A 1.2-MHz, 23-V/2.5-kV, and 6-W prototype is demonstrated. It achieves a low harmonics distortion and a low power loss with the zero voltage switching.

The Control of PMSM Motor to Drive Propeller in Ship Propulsion System

Electric propulsion has advantages such as high maneuverability, good safety and reliability, being able to operate optimally with a control system. It is a future green technology which is environmentally friendly. The application of electric propulsion for ship is that the propeller is driven by using electric motor by regulating speed and/or torque. in this research, an permanent magnet synchronous motor (PMSM) is used to drive propeller of ship propulsion. The controller of proportional integral (PI) scheme is proposed to drive electric motor. The method of Ziegler Nichols stability margin tuning rule algorithm is performed to search the controller parameters. The optimal working point of propeller is determined by the cross intersection between the propeller loading curve to the coefficient of thrust curve of open water test propeller. The speed from the result of propeller working point analysis is set as control input reference. Based on the results of simulation, the proposed control of electric propulsion using PMSM motor is able to achieve the reference of speed.

Electromagnetic characteristic analysis of a REBCO magnet with a current bypass/distribution winding technique under an asynchronous rotating magnetic field

Generally, high-temperature superconducting rotating machines (HTSRMs) are considered synchronous machines. If the output of the HTSRM fluctuates based on frequent changes in the electrical or mechanical loads, there is the concern that an asynchronous rotating magnetic field (RMF) is applied from the stationary copper armature winding to the high-temperature superconducting (HTS) field winding in the rotary. This may act as a magnetic disturbance to the HTS field magnet, resulting in permanent damage. To enhance the reliability of HTS magnets in wind power and electric propulsion applications, winding methods with current bypass/distribution characteristics, such as no-insulation (NI) and metal-insulation (MI), have attracted scholarly attention because of their high thermal and electrical stabilities, resulting in their self-stabilizing and protective performances. To verify the feasibility of the NI and MI winding techniques for wind power generators, the basic characteristics under a time-varying magnetic field must be studied, contrary to HTS magnet applications under a time-static magnetic field. Therefore, the electromagnetic characteristics of rare-earth barium copper oxide (REBCO) magnets applied with NI and MI winding technologies were compared and analyzed in this study, considering the magnetically transient situations in which an asynchronous RMF is applied to REBCO magnets. In addition, we developed a characteristic evaluation device similar to a synchronous rotating machine to generate the unsynchronized RMF. Moreover, various basic tests were performed to target the small racetrack-type field windings. The critical current, n-value, terminal voltage, and center magnetic field are investigated under various values of the frequency and current amplitude of the three-phase armature winding, and their behaviors are discussed in detail based on the characteristic resistances of the two test magnets.

Modeling of Supercritical CO2 Shell-and-Tube Heat Exchangers Under Extreme Conditions. Part I: Correlation Development

Abstract High-temperature supercritical CO2 Brayton cycles are promising possibilities for future stationary power generation and hybrid electric propulsion applications. Heat exchangers are critical components in supercritical CO2 thermal cycles and require accurate correlations and comprehensive performance modeling under extreme temperatures and pressures. In this paper (Part I), new Colburn and friction factor correlations are developed to quantify shell-side heat transfer and friction characteristics of flow within heat exchangers in the shell-and-tube configuration. Using experimental and computational fluid dynamics (CFD) data sets from existing literature, multivariate regression analysis is conducted to achieve correlations that capture the effect of multiple critical geometric parameters. These correlations offer superior accuracy and versatility as compared to previous studies and predict the thermohydraulic performance of about 90% of the existing experimental and CFD data within ±15%. Supplementary thermohydraulic performance data are acquired from CFD simulations with supercritical CO2 as working fluid to validate the developed correlations and demonstrate its capability to be applied to supercrtical CO2 heat exchangers.

Effects of Total Pressure Distribution on Performance of Small-Size Counter-Rotating Axial-Flow Fan Stage for Electrical Propulsion

Abstract Counter-rotating fan provides significant benefits over the conventional fan in terms of overall performance and size. For electric propulsion application, a counter-rotating fan provides compactness and reduction in weight to achieve higher pressure rise with less power consumption as compared to the unducted propeller. Past literature suggests counter-rotating fans, designed with higher loading in the front rotor, have a flat performance map and a wider range of stable operation. The recommendation of higher aerodynamic loading is not clear what needs to be the aerodynamic load split amongst the rotors. This, in particular, benefits the electrical vehicle to have higher maneuver capability during operation. The paper discusses the design methodology of counter-rotating fans for application in roadable electric aircraft and the effect of different aerodynamic load distributions for both rotors on its overall performance. Fans are designed for different total-pressure rise and loading distributions as (1) 50–50%, (2) 55–45%, (3) 60–40%, and (4) 65–35% in front and rear rotor. It is observed that, as the loading increases for the front rotor, blade camber increases and hence to more prone toward flow separation near the trailing edge under an adverse pressure gradient. Wake coming from the front rotor grows thicker with higher loading, leading to flow acceleration (thus total-pressure loss) in the axial gap between these rotors. As a consequence, flow incidents on the rear rotor other than the design incidence, and thus the rear rotor operates under off-design. With 55–45% loading, both the rotors achieve desired total-pressure rise and stable operating range. The detailed flow field study is discussed to bring important outcomes for achieving the desired performance.

Resistive MHD modes in hollow cathodes external plasma

A significant number of plasma instabilities occur in the region just outside of hollow cathodes, depending on the injected gas flow, the current level and the application of an external magnetic field. In particular, the presence of an axial magnetic field induces a helical mode, affecting all the plasma parameters and the total current transported by the plasma. To explore the onset and behavior of this helical mode, the fluctuations in the plasma parameters in the current-carrying plume outside of a hollow cathode discharge have been investigated. The hollow cathode was operated at a current of 25 A, and at variable levels of propellant flow rate and applied magnetic fields. Electromagnetic probes were used to measure the electromagnetic fluctuations, and correlation analysis between each of the probe signals provided spatial-temporal characterization of the generated waves. Time-averaged plasma parameters, such as plasma potential and ion energy distribution function, were also collected in the near-cathode plume region by means of scanning emissive probe and retarding potential analyzer. The results show that the helical mode exists in the cathode plume at sufficiently high applied magnetic field, and is characterized by the presence of a finite electromagnetic component in the axial direction, detectable at discharge currents ⩾25 A. A theoretical analysis of this mode reveals that one possible explanation is consistent with the hypotheses of resistive magnetohydrodynamics, which predicts the presence of helical modes in the forms of resistive kink. The analysis has been carried out by linear perturbation of the resistive MHD equations, from which it is possible to obtain the dispersion relation of the mode and find the k–ω unstable branch associated with the instability. These findings provided the basis for more detailed investigation of resistive MHD modes and their effect in the plume of hollow cathodes developed for electric propulsion application.

Impact of stator slot geometry on the windage loss in a high‐speed linear switched reluctance motor

A linear switched reluctance motor (LSRM) is designed for electric propulsion application in a Magnetically Levitated (Maglev) train with the base speed of 7.6 m/s and operating at a maximum of 27.8 m/s. In such high-speed LSRMs, windage loss is one of the key issues of concern. Usually, windage loss accounts for approximately 0.5% below the base speed, 20% above the base speed, and 45% at higher speeds of the total loss of the LSRM. One of the many parameters affecting this windage loss is the stator slot profile. This research work studies about different stator slot structures, thereby aiming to reduce the windage loss through computational fluid dynamics analysis. Furthermore, experimental testing of the LSRM is also done to verify the simulation results.

Global plasma modeling of a magnetized high-frequency plasma source in low-pressure nitrogen and oxygen for air-breathing electric propulsion applications

This work presents a global plasma model of a gridded air-breathing electric propulsion concept based on magnetized high-frequency plasma operating in the pressure range of 10−3 Pa to 1 Pa. We illustrate that the global plasma model reproduces the experimental measurements of the extracted current over two orders of magnitude in pressure. Consequently, we use the model to investigate the theoretical scalability of the plasma source, finding that the plasma source performance scales reasonably well with the average absorbed power per molecule, even though this scaling factor has its limits. The global model presented in this work is a model of a specific laboratory device and, in future, it can be adapted to very low Earth orbit conditions by adjusting the boundary conditions. The model was implemented using PlasmaSolve p3s-globalmodel software and the configuration file containing all the equations is provided to the community as supplementary material.

Fluid modeling of inductively coupled iodine plasma for electric propulsion conditions

Iodine is being studied as an alternative propellant for electric propulsion application as it has numerous advantages over commonly used xenon gas. In spite of numerous experimental studies for the conditions typical for electric propulsion, there are very few computational modeling studies of iodine plasmas: all with reduced geometric representations in zero or one dimension. In the present paper, we use self-consistent two-dimensional fluid model coupled with Maxwell's equations to analyze the inductively coupled plasma generated in low-pressure iodine. We compare the plasma parameters for two values of the background pressure: 1.0 and 2.5 Pa. We find that ∼99% of the molecular iodine is converted into atomic iodine. As a result, plasma consists of electrons, ions I+, and a significant number of negative ions I−. The density of molecular ions I2+ is much smaller than the density of I+. We analyze the transport of these species for two pressures and show that there are different regimes of plasma diffusion realized for the conditions of our studies. We also study how the discharge power influences the plasma parameters such as the electron and ion densities and the electron temperature.