Propulsion Technology Research Articles

Conceptual design and integration of a propulsion system for a supersonic transport aircraft

Despite 50 years of technological advancement since the inception of Concorde, research on supersonic passenger aircraft has only recently resulted in design and flight test of several small 12 to 55-passenger business jets with supersonic cruises between Mach 1.2 and 2.2. Analytical research designs of larger 300-passenger aircraft have been conducted only to speeds of Mach 2.0 and 2.2, mainly avoiding moving beyond turbojet propulsion. This research extends on an earlier multifactor regression sizing study to determine in greater design detail whether the configuration of a 200-passenger Mach 3.0 aircraft is feasible using extant technology. This research article is the second part of two and covers a suitable and cost-effective propulsion system for the executive supersonic passenger aircraft. Through this high-speed design, the research examines modern propulsion technology and the performance advancements it affords through higher efficiencies, higher metallurgical thermal limits, variable cycle engines and variable stator technology. The analysis was conducted on several potential propulsion systems using GasTurb software to obtain engine performance data. The performance results led to a combined cycle turbofan–ramjet engine as being the engine that could yield the most extensive range for the aircraft. Further investigation is needed on aircraft noise, engine emissions, the accuracy of the thrust-critical lift-to-drag ratios and the aeroelastic effects that can be closely coupled to noise and performance.

Flow Structure within an Aggressive S-Shaped Intermediate Compressor Duct

As part of Clean Sky 2 (Engines ITD), a working group, formed by the DLR Institute of Propulsion Technology, MTU Aero Engines and GKN Aerospace, is setting up a complete compression system module (LPC/ICD/HPC). The aim of the project is to shorten the intermediate compressor duct (ICD), which connects the low pressure compressor (LPC) and high pressure compressor (HPC). This leads to a reduction of the axial length and weight of the overall engine and thus a reduction of the specific fuel consumption. In order to identify measurement-technologies and mitigate risks for this experimental set-up, a non-rotating testrig was set up in advance to investigate two different test vehicles. In a first step an ICD demonstrator was set up, which had a reduced axial length of 25%, compared to currently operating designs. This design predicted no separation or performance losses inside of the aggressive s-shaped contour. In a second step another demonstrator was installed with an even shorter axial length of 50% axial length reduction, compared to todays state of the art configurations. In this demonstrator the design was chosen to exceed the functional limit according to today’s CFD prediction and thus explore the potential for further length reduction in the future and to create a data base for numerical tool validation. The two configurations were tested at DLR Cologne. The test channel offers the possibility to use a variety of different measurement techniques to determine the flow behavior inside the ICD. This paper presents the oil streak pattern taken on the hub area between the struts and the ones taken on the pressure and suction side of the outlet guide vanes (OGV- LPC) for both demonstrators.

Tehnologije propulzije broda s pomoću vjetra – mogu li one pomoći u smanjenju emisija?

According to International Maritime Organization, emissions coming from global shipping are expected to increase 50% to 250% by the year 2050. This concern led to the introduction of various regulations that aims to encourage ship owners and builders to explore innovative renewable technologies. The main focus of this article is on wind-assisted ship propulsion technologies, as a complement to ship propulsion, such as rigid sail, soft sail, wing sail, kite, and Flettner rotor. These technologies are not widely accepted because ship owners have doubts due to the lack of real-life results and their implementation and efficiency greatly depends on ship design and purpose. This article shows the progress in the field of wind-assisted ship propulsion in the last 15 years which proved the concept as they have the potential to reduce fuel consumption, thus emissions, by double digits. The conclusion is drawn, from fuel savings percentages, that rotor and soft sails technologies have great potential in the future of the shipping industry.

Toward More Sustainable River Transportation in Remote Regions of the Amazon, Brazil

This paper explores means of achieving more efficient and sustainable river transport in remote regions by making relatively simple, practical modifications to boats or implementing new technologies for propulsion and energy generation. The research focuses on the case of the simple boats used to transport children to school in riverine communities of the Brazilian Amazon. A range of options to improve the efficiency of existing boats is described. Under normal operational conditions, small improvements to these boats may have long-term environmental and socioeconomic benefits. Implementing changes such as those suggested, it may also be possible to boost sources of employment in these regions and elsewhere, where industrial and technological limitations are significant.

Harnessing wind energy on merchant ships: case study Flettner rotors onboard bulk carriers.

Shipping faces challenges of reducing the dependence on fossil fuels to align with the international regulations of ship emissions reduction. The maritime industry is in urgent need of searching about alternative energy sources for ships. This paper highlights the applicability of harnessing wind power for ships. Flettner rotors as a clean propulsion technology for commercial ships are introduced. As a case study, one of the bulk carrier ships operating between Damietta port in Egypt and Dunkirk port in France has been investigated. The results showed the high influence of the interaction between ship course and wind speed and direction on the net output power of Flettner rotors. The average net output power for each rotor will be 384 kW/h. Economically, the results reveal that the use of Flettner rotors will contribute to considerable savings, up to 22.28% of the annual ship’s fuel consumption. The pay-back period of the proposed concept will be 6 years with a considerable value of levelized cost of energy. Environmentally, NOx and CO2 emissions will be reduced by 270.4 and 9272 ton/year with cost-effectiveness of $1912 and $55.8/ton, respectively, at annual interest rate of 10%.

The Study of the Single Event Effect in AlGaN/GaN HEMT Based on a Cascode Structure

An attractive candidate for space and aeronautic applications is the high-power and miniaturizing electric propulsion technology device, the gallium nitride high electron mobility transistor (GaN HEMT), which is representative of wide bandgap power electronic devices. The cascode AlGaN/GaN HEMT is a common structure typically composed of a high-voltage depletion-mode AlGaN/GaN HEMT and low-voltage enhancement-mode silicon (Si) MOSFET connected by a cascode structure to realize its enhancement mode. It is well known that low-voltage Si MOSFET is insensitive to single event burnout (SEB). Therefore, this paper mainly focuses on the single event effects of the cascode AlGaN/GaN HEMT using technical computer-aided design (TCAD) simulation and heavy-ion experiments. The influences of heavy-ion energy, track length, and track position on the single event effects for the depletion-mode AlGaN/GaN HEMT were studied using TCAD simulation. The results showed that a leakage channel between the gate electrode and drain electrode in depletion-mode AlGaN/GaN HEMT was formed after heavy-ion striking. The enhancement of the ionization mechanism at the edge of the gate might be an important factor for the leakage channel. To further study the SEB effect in AlGaN/GaN HEMT, the heavy-ion test of a cascode AlGaN/GaN HEMT was carried out. SEB was observed in the heavy-ion irradiation experiment and the leakage channel was found between the gate and drain region in the depletion-mode AlGaN/GaN HEMT. The heavy-ion irradiation experimental results proved reasonable for the SEB simulation for AlGaN/GaN HEMT with a cascode structure.

Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods

Pump-jet propulsion, a new propulsion technology, is primarily designed for underwater vehicles. Because of its concealment and excellent performance, it has been widely used, but due to its confidentiality and complexity, few studies have been published. To explore the relevant design theory of pump-jet propulsion with the aim of increasing its performance, in this study, we applied the direct and inverse design methods to construct a three-dimensional pump-jet model. The direct design method was carried out by comparing the lifting and lifting-line design methods, followed by further geometric optimization of the better model. In a numerical study using computational fluid dynamics (CFD) simulations, the Reynolds Averaged Naviere-Stokes (RANS) equations with SST k-ω turbulence model were solved in a cylindrical computational domain around the pump-jet propulsion device. A numerical investigation of the E779A propeller was carried out beforehand, using different advance ratios, in order to validate the accuracy of the numerical simulation method. The results show that for the direct method, although the model designed using the lifting-line method produced a greater thrust and the pump-jet designed using the lifting method was more efficient and stable, which is more suitable for small and medium underwater vehicles. When considering the inverse design method, the pump-jet propeller obviously accelerated the fluid, and the speed was obviously greater than that designed using the direct design method, while the turbulent kinetic energy in the flow field was higher, as well as the energy loss. Therefore, for small- and medium-sized underwater vehicles, if the priorities are high thrust and high efficiency, the inverse design method is the best option, whereas if stability and lower energy loss are preferred, the direct design method should be adopted.

A Comeback of Wind Power in Shipping: An Economic and Operational Review on the Wind-Assisted Ship Propulsion Technology

Wind-assisted ship propulsion (WASP) technology seems to be a promising solution toward accelerating the shipping industry’s decarbonization efforts as it uses wind to replace part of the propulsive power generated from fossil fuels. This article discusses the status quo of the WASP technological growth within the maritime transport sector by means of a secondary data review analysis, presents the potential fuel-saving implications, and identifies key factors that shape the operational efficiency of the technology. The analysis reveals three key considerations. Firstly, despite the existing limited number of WASP installations, there is a promising trend of diffusion of the technology within the industry. Secondly, companies can achieve fuel savings, which vary depending on the technology installed. Thirdly, these bunker savings are influenced by environmental, on-board, and commercial factors, which presents both opportunities and challenges to decision makers.

Magnetic nozzle radiofrequency plasma thruster approaching twenty percent thruster efficiency

Development of a magnetic nozzle radiofrequency (rf) plasma thruster has been one of challenging topics in space electric propulsion technologies. The thruster typically consists of an rf plasma source and a magnetic nozzle, where the plasma produced inside the source is transported along the magnetic field and expands in the magnetic nozzle. An imparted thrust is significantly affected by the rf power coupling for the plasma production, the plasma transport, the plasma loss to the wall, and the plasma acceleration process in the magnetic nozzle. The rf power transfer efficiency and the imparted thrust are assessed for two types of rf antennas exciting azimuthal mode number of m=+1 and m=0, where propellant argon gas is introduced from the upstream of the thruster source tube. The rf power transfer efficiency and the density measured at the radial center for the m=+1 mode antenna are higher than those for the m=0 mode antenna, while a larger thrust is obtained for the m=0 mode antenna. Two-dimensional plume characterization suggests that the lowered performance for the m=+1 mode case is due to the plasma production at the radial center, where contribution on a thrust exerted to the magnetic nozzle is weak due to the absence of the radial magnetic field. Subsequently, the configuration is modified so as to introduce the propellant gas near the thruster exit for the m=0 mode configuration and the thruster efficiency approaching twenty percent is successfully obtained, being highest to date in the kW-class magnetic nozzle rf plasma thrusters.

Primary parameters design method for distributed electric propulsion unmanned aerial vehicle

Distributed electric propulsion technology brings new ideas to the design of unmanned aerial vehicle(UAV), such as improving aerodynamic efficiency and propulsive efficiency, and new concept of vertical/short takeoff and landing configurations. However, compared with conventional UAV, the propulsion system of distributed electric propulsion UAV is more complex, which brings difficulties and challenges to the design of distributed electric propulsion UAV. Based on its special aerodynamic/propulsive coupling characteristics, this paper studies the design method and process of primary parameters of distributed electric propulsion UAV. A short takeoff and landing UAV with distributed electric propulsion system is taken as an example for the conceptual design and primary parameter design, and the influence of design parameters on the takeoff mass and endurance is analyzed. Finally, the validity of the established design method is verified by the flight test of the prototype. Results indicate that the distributed electric propulsion system accounts for more than 20% of the takeoff mass; the electric ducted fan efficiency, mass specific power of the motor, mass specific power of the electronic speed controller and the resistivity of power wires are the most significant design parameters that affect the performance of the UAV; with the improvement of technologies, the takeoff mass is expected to be reduced by more than 20%, and the endurance is expected to be increased by more than three times.

Linear transfer guidance based on Lyapunov method

Low-thrust propulsion technology is widely used in space missions. However, traditional methods are not appropriate for the general case. In this study, a linearization Lyapunov method for constant thrust control is proposed. Based on relative orbit elements (ROEs), analytical constant-thrust linear equations are introduced. Moreover, via Lyapunov method, the linear constant-thrust control strategy is obtained. Numerical simulations are conducted to demonstrate the validation of the proposed method. Given different thrust magnitudes, the accuracy meets the requirement in these cases. Thus, it proves to be a practical choice for engineering applications.

Investigation on Key Parameters of NI HTS Field Coils for High Power Density Synchronous Motors

As global environment regulations are gradually strengthened, active research has been conducted on electric propulsion applications. High power density is one of the major research interests, as well as a machine's efficiency for a high-performance propulsion system. Among various electric propulsion technologies under development, a motor incorporating the no-insulation (NI) high-temperature superconducting (HTS) winding has the advantages of high current density and robustness to external disturbances, which are suitable for high specific power. However, still, there is little research on the motor with NI HTS coil. Therefore, as basic research, we investigated the potential application of the NI HTS motor, then derived required machine parameters and NI HTS coil designs in this paper. For that, first, basic parameters of the existing propulsion motors were investigated, then the target application and performance of the NI HTS motor were determined. Based on the target performance, conceptual designs of a motor with NI HTS coil were obtained by changing key design parameters including rated power, main dimensions, operating temperature, and width of air-gap. Calculated parameters were numerically compared, and expected design requirements and challenges were suggested.

Numerical investigation of axisymmetric intake flowfield and performance for scramjet-powered ascent flight

Air intakes play a crucial role in the operation of scramjet engines, one of the most promising hypersonic airbreathing propulsion technologies for efficient and flexible space transportation, it is thus essential to accurately understand and predict the flowfields for high-performance intake design, especially in varying operating conditions. Axisymmetric intake flowfields are investigated numerically assuming a typical scramjet operation on a constant dynamic pressure ascent trajectory, aiming to achieve scramjet-powered access-to-space. Physical insight into scramjet flowfields at various flight altitudes and Mach numbers have been gained by means of high-resolution simulation to resolve the viscous flowfields. High levels of adaptive mesh refinement have identified detailed flow phenomena including shock reflection, interactions, and boundary layer as well as their aerodynamic and aerothermal effects on pressure and temperature fields. In particular, Mach reflection characterized by a Mach disk has been found to occur at the centerline, even in the operating conditions where regular reflection would result from computational simulation without mesh adaption. The intake performance has been evaluated with respect to the compression efficiency, drag, and exit temperature. The intake drag has been found to decrease at higher Mach numbers at higher altitudes on a constant dynamic pressure trajectory during acceleration due to reduced pressure drag while viscous drag varies little. Rather little influence of varying wall conditions has been observed on the intake drag between the isothermal and adiabatic wall conditions due to counteracting behavior between viscous and pressure drag components.

Chemorheology and Kinetics of High‐Performance Polyurethane Binders Based on HMDI

AbstractAliphatic diisocyanates, such as 1,6‐hexamethylene diisocyanate (HMDI), are preferred curing agents for the formation of polyurethanes (PUs) in applications where resistance to abrasion or degradation by ultraviolet light takes precedence. Aside from the final properties, the curing agent plays a key role in the bulk manufacturing of such materials, and it mainly affects the polymerization kinetics and their rheology. The copolymerization of HMDI and a metallo‐prepolymer derivative from hydroxyl‐terminated polybutadiene (HTPB) is studied under isothermal conditions (50–80 °C). This study is carried out by means of an indirect method, using both rotational viscometry and dynamic rheometry. At the beginning of the process, the viscosity growth fit well to a first‐order kinetic model. Afterward, the reactive system passes through gelation, from which only rheology is allowed for the investigation of the entire polymerization process. This transition is analyzed in depth together with predictions from percolation theory. The conversion degree is determined from rheological measurements, and then an autocatalytic kinetic model is applied to describe the overall process. Finally, an isoconversional method allows the evolution of activation energy to be studied. This analysis merits attention for the development of high‐performance binders that are of great interest in aerospace propulsion technology.

Повышение удельного импульса ионного двигателя зонной инженерией твердотельного полевого катода

With the rapid development of space technology, the scale of human space exploration is expanding significantly. However, the growing demand for deep space travel cannot be met with conventional chemical engines. Thus, the need for new mechanisms for providing jet thrust, including electric motors, becomes clear. Electric propulsion technology has significant advantages over traditional chemical engines in deep space flight due to its characteristics such as high specific impulse, small size, long service life. A negative feature of electric motors can be called low thrust, however, firstly, in open space this is insignificant and, secondly, the thrust of electric motors can be significantly increased, and for this, there are reserves available at the current level of technology development. Ways to increase the thrust of electric ion thrusters will be detailed and discussed in this work. The increase in the power of ion engines is limited to a large extent by the erosion of the control grids; the ion flow hits the surface of the solid material of the control grid electrode with energetic ions and gradually leads to the failure of this electrode. In this work, the authors will show that the use of field emission as a source of electron beams ionizing the working medium can solve the problem of erosion of control electrodes, due to which it will be possible to significantly increase the strength of the working fields for ion engines, which in turn will increase the specific impulse, efficiency, flow rate and power of the ion engine as a whole.

Electric Propulsion Methods for Small Satellites: A Review

Over 2500 active satellites are in orbit as of October 2020, with an increase of ~1000 smallsats in the past two years. Since 2012, over 1700 smallsats have been launched into orbit. It is projected that by 2025, there will be 1000 smallsats launched per year. Currently, these satellites do not have sufficient delta v capabilities for missions beyond Earth orbit. They are confined to their pre-selected orbit and in most cases, they cannot avoid collisions. Propulsion systems on smallsats provide orbital manoeuvring, station keeping, collision avoidance and safer de-orbit strategies. In return, this enables longer duration, higher functionality missions beyond Earth orbit. This article has reviewed electrostatic, electrothermal and electromagnetic propulsion methods based on state of the art research and the current knowledge base. Performance metrics by which these space propulsion systems can be evaluated are presented. The article outlines some of the existing limitations and shortcomings of current electric propulsion thruster systems and technologies. Moreover, the discussion contributes to the discourse by identifying potential research avenues to improve and advance electric propulsion systems for smallsats. The article has placed emphasis on space propulsion systems that are electric and enable interplanetary missions, while alternative approaches to propulsion have also received attention in the text, including light sails and nuclear electric propulsion amongst others.

Integrated Approach for the Assessment of Strategies for the Decarbonization of Urban Traffic

This paper presents a new methodology to derive and analyze strategies for a fully decarbonized urban transport system which combines conceptual vehicle design, a large-scale agent-based transport simulation, operational cost analysis, and life cycle assessment for a complete urban region. The holistic approach evaluates technical feasibility, system cost, energy demand, transportation time, and sustainability-related impacts of various decarbonization strategies. In contrast to previous work, the consequences of a transformation to fully decarbonized transport system scenarios are quantified across all traffic segments, considering procurement, operation, and disposal. The methodology can be applied to arbitrary regions and transport systems. Here, the metropolitan region of Berlin is chosen as a demonstration case. The first results are shown for a complete conversion of all traffic segments from conventional propulsion technology to battery electric vehicles. The transition of private individual traffic is analyzed regarding technical feasibility, energy demand and environmental impact. Commercial goods, municipal traffic and public transport are analyzed with respect to system cost and environmental impacts. We can show a feasible transition path for all cases with substantially lower greenhouse gas emissions. Based on current technologies and today’s cost structures our simulation shows a moderate increase in total systems cost of 13–18%.

Tethered Satellite-Controlled Re-Entry Dynamics From the International Space Station

Payloads left in space at the end of life create debris. A large amount of space debris surrounds our planet and within a few years, experts argue, it will no longer be possible to send payloads safely into space. Our study strives to demonstrate the ability to bring a payload back to Earth without the use of an active propulsion system in close proximity of the International Space Station (ISS). The use of a classical chemical propulsion system near sensitive and inhabited space areas is risky and causes contamination due to the fuel ejection. Consequently, the design of a passive but controlled vehicle, that satisfies safety and free-pollution requirements, needs a new propulsive technology. A possible solution is using a Tether Subsystem, mounted onboard a re-entry capsule, employed to execute the first phase of the release/deployment maneuver. The tether deployment trajectory must be controlled in order to provide a large libration angle of about 40° and a radial velocity near zero at the end of tether deployment. The control algorithm adopted is based on reliable and easy to measure dynamics parameters: the deployed length and length rate are the inputs of the control loop that forces the tethered capsule to follow a predetermine reference trajectory during deployment. Relevant details of the IR sensors (i.e., photocells) that are planned for measuring the input parameters are also presented. The aim of our study is to propose a safe and pollution-free solution for separating small satellites from the ISS, preventing hazards, and minimizing external contamination.

Using Tapered Channels to Improve LAD Performance for Cryogenic Fluids: Suborbital Testing Results

Abstract Improvement of cryogenic fluid storage and transfer technology for in-space propulsion and storage systems is required for long-term space missions. Screened channel liquid acquisition devices (LADs) have long been used with storable propellants to deliver vapor-free liquid during engine restart and liquid transfer processes. The use of LADs with cryogenic fluids is problematic due to low temperatures associated with cryogenic fluids. External heat leaks will cause vapor bubbles to form within the LADs that are difficult to remove in the existing designs. A tapered LAD channel has been proposed to reliably remove vapor bubbles within the device without costly thrusting maneuvers or active separation systems. A model has been developed to predict bubble movement within tapered LAD channels, and subsequent ground testing was completed with a simulant fluid to provide model validation data. Suborbital microgravity testing of tapered LAD technology was recently completed with two different simulant fluids and demonstrated that the concept can passively expel vapor bubbles within the channel. Two additional suborbital flights have been funded to further develop this technology by investigating the performance of larger scale versions of the design.

A review of fuel cell technology for commercial vehicle applications

The demanding energy storage requirements of many commercial vehicle applications are extremely difficult to meet for pure battery electric vehicles (BEVs) due to the limited energy density of batteries. Fuel cells appear to be the only viable propulsion technology that is able to meet commercial vehicle powertrain requirements with zero local greenhouse gas emissions. Since almost all fuel cell vehicles (FCVs) contain a high voltage battery, some additional complexity is introduced since the hybrid energy storage system must be sized and controlled appropriately. An understanding of the strengths and weaknesses of each system is therefore essential in FCV design. The aim of this technology review is to provide an overview of fuel cell technologies in commercial vehicle applications including assessments of alternative powertrain and fuel cell types, advantages and disadvantages of fuel cell and battery systems and the implications of these on the powertrain sizing as well as control considerations of FCVs.