Propulsion Technology Research Articles

Medium-Range Aircraft Conceptual Design from a Local Air Quality and Climate Change Viewpoint

This paper presents an overall performance assessment of hybrid-electric medium-range transport aircraft, with the aim to evaluate the potential of such a propulsion technology towards the reduction in the environmental impact of aviation transport, in terms of both local air quality degradation in airport areas and climate change. The proposed approach presents distinct analyses of the environmental impact of transport aircraft, distinguishing climate-changing effects from local pollution effects so that the integration of hybrid-electric propulsion is carried out to face the two issues specifically. The proposed analysis, although of conceptual nature, presents a clear scenario in which, given the technological limitations of batteries, the use of hybrid-electric propulsion on medium-haul aircraft can only be useful to reduce local pollution. In contrast, other solutions are needed to mitigate the climate-changing impact.

Effects of hydrogen addition on laminar dilute n-dodecane spray flames

With the increasing demand for carbon–neutral propulsion technology, hydrogen addition appears to be a viable short-to-medium-term solution. This study investigates the dynamics of overall lean, laminar dilute n-dodecane spray flames in premixed hydrogen/air mixture by simulating one-dimensional dilute spray flames over a wide range of hydrogen addition and n-dodecane droplet diameter. The characteristic residence time and evaporation time are analyzed to reveal the pre-evaporation mode, and examine the distinct evaporation characteristics throughout the flames. The flame structure and flame propagation speed are then examined, with the impact of subtle fuel chemistry coupling at low-temperature-chemistry regime being revealed. At atmospheric pressure conditions, the flame speed monotonically increases with hydrogen addition due to the enhanced reactivity. However, it has a nonmonotonic trend with initial droplet diameter due to the subtle coupling of evaporation and chemical kinetics. More interestingly, at engine-relevant conditions, the flame propagation speeds firstly decrease and then increase with hydrogen addition, this is because small hydrogen addition inhibits the low-temperature reaction pathway that could offset the effects of enhanced high-temperature reactivity on flame propagation. In addition, the flame propagation speeds are less sensitive to the droplet diameter unless the droplets are sufficiently large and the long evaporation process reduces the effective local equivalence ratio of the overall fuel-lean mixtures.

An articulating wingsail design for Wind Assisted Ship Propulsion (WASP) applications

A novel articulating wingsail design for WASP is developed and an 8.25 m2 prototype has been constructed. This wingsail has potential as a supplementary source of propulsion for cargo shipping. By using wind power, the greenhouse gas emissions from shipping can be significantly reduced. To further develop this wingsail concept, detailed 2D Computational Flow Dynamics simulations have been performed. These suggest that the articulating wing has the potential to provide up to 30% more lift than a fixed aerofoil of the same cross section. These results further suggest that the articulating wingsail concept has potential as a Wind Assisted Ship Propulsion technology.

Exploring the Feasibility of a Power-Generating Pulsed Nuclear Magnetic Nozzle

Crewed missions to Mars and robotic missions to the gas giant planets are challenging because of the current lengthy trip times (2 years to Mars, ~20+ years to the gas giants) with current propulsion technology. These trips endanger astronauts due to the harmful effects of radiation and microgravity and represent a significant fraction of a PI’s (Principal Investigator's) lifespan for uncrewed gas giant missions. To make these trips safer and more reliable, trip times need to be reduced dramatically. Pulsed nuclear fusion propulsion systems promise to reduce these trip times down to 1-3 months for the Mars mission and 1-4 years for gas giant missions. However, widespread use of these systems is hampered by many technical factors, including efficient conversion of directed jet power for thrust and generation of input power for fusion reactor operation. To address both challenges, the present authors propose using the novel power-generating magnetic nozzle; this nozzle uses high-strength magnetic fields for thrust generation and low-strength fields for power generation. Most approaches in the literature consider the effect of either the high-strength fields or the low-strength fields but, for this work, the authors would like to show their combined effect. To address this, we use two computational tools in tandem from prior work: the Smoothed Particle Fluid with Maxwell equation solver (SPFMax) and a plasma flux compression generator code. The former will determine the effect of the high-strength fields and the latter will determine the effect of the low-strength fields. Combined, they show the effect on thrust, efficiency, and power generation. The present authors find that the inclusion of a power-generation system reduces nozzle efficiency by 7% and thrust by the same amount, however, this is a relatively small reduction. The authors also confirm prior work regarding non-dimensional scaling parameters of the power generation system. These results reduce the technical risk associated with these nozzles, hopefully allowing for their application in current concepts/programs, make interplanetary trips safer and more reliable, and allowing humanity to venture out and explore the solar system. Keywords: Mars, Plasma, Magnet, Nuclear, Power

Effect of Control Parameters on Hybrid Electric Propulsion UAV Performance for Various Flight Conditions: Parametric Study

Nowadays, great efforts of ongoing research are devoted to hybrid-electric propulsion technology that offers various benefits, such as reduced noise and pollution emissions and enhanced aircraft performance and fuel efficiency. The ability to estimate the performance of an aircraft in any flight situation in which it may operate is essential for aircraft development. In the current study, a simulation model was developed that allows estimating the flight performance and analyzing the mission of a fixed-wing multi-rotor Unmanned Aerial Vehicle (UAV) with a hybrid electric propulsion system (HEPS), with both conventional and Vertical Takeoff and Landing (VTOL) capabilities. The control is based on the continuous specification of pitch angle, propulsion thrust, and lift thrust to achieve the required conditions of a given flight segment. Six different missions were considered to analyze the effect of control parameters exhibiting the most influence on the UAV mission performance. An appropriate set of control parameters was selected through a multidimensional parametric study. The results show that the control parameters, if not well tuned, affect the mission performance: for example, in the deceleration transition, a longer time to reduce the cruise speed to stand still may be the result because the controller struggles to adjust the pitch angle. In addition, the implemented methodology captures the effects of transient maneuvers, unlike typical quasi-static analysis without the complexity of full simulation models.

Exploiting Active Subspaces for Geometric Optimization of Cavity-Stabilized Supersonic Flames

With the increased demand for hydrogen for carbon-neutral propulsion technologies, understanding the coupling effect of the fuel injection and cavity on flow characteristics is essential and an open issue for cavity-based hydrogen supersonic flame stabilization and optimizations. In this paper, the active subspace (AS) method is exploited to quantitatively reveal the intrinsic connections between the flow and flame stabilization with various fuel injection and cavity geometric parameters. A flame stabilization metric connecting the flame stabilization mode with nonreacting flows is proposed for the AS analysis and multiobjective optimizations. The results show that there exist one-dimensional active subspaces for key performance metrics, for example, the total pressure loss , residence time , and . The fuel injection pressure, cavity length-to-depth ratio, and cavity depth are three leading factors that govern the total pressure loss while the cavity residence time is dominated by the cavity depth. The proposed reasonably maps the flame stabilization mode with nonreacting flows. Using the response lines obtained by the AS, the tradeoff between and is quantitatively formulated with a clear visualization of candidate sets in the input space, demonstrating the advantages of the AS method for the combustor designs involving multiple objectives.

Modeling of Iodine Feeding System to Achieve Flow Control under the Coupling of Multiple Conditions

The design of an iodine working medium storage and supply system is one of the key technologies for the electrical propulsion of iodine working medium. Solid iodine sublimates into a gaseous state in the storage tank, and is transported to the thruster through flow control through components such as a proportional valve or throttle tube. However, iodine working medium has corrosive properties and poor thermal conductivity, which can easily cause condensation in the throttle tube and throttle valve, affecting the accuracy of experimental results or blocking the pipeline, leading to the suspension of the experiment. Based on the system level modeling of the iodine working medium electric propulsion storage and supply system, and taking into account the impact of the coupling effects of various conditions such as the physical parameters of iodine vapor, storage tanks, pipelines, outlet conditions, and proportional valves on the outlet mass flow rate of the iodine storage and supply system, the control of the outlet mass flow rate is achieved by adjusting the valve opening of a comparative example, providing a reference for the selection of the size of the throttle tube in future ground experiments or the control of the proportional valve opening.

Seakeeping analysis of a tanker with hard sail-based wind propulsion system in various seaways

A hard sail is a type of wind-assisted ship propulsion (WASP) technology that incorporates wind energy to propel the ship with the help of sails and can significantly reduce the ship's energy consumption. This study focuses on the seakeeping analysis of a hard sail-assisted KVLCC2 ship in different wave conditions. A numerical simulation of the aerodynamic performance of a sail system consisting of two sails was done on ANSYS Fluent and compared with corresponding experimental data. The motion response and added resistance of a KVLCC2 hull in regular waves were numerically predicted in STAR CCM + software and compared with corresponding seakeeping experimental test data. The numerical results obtained for the tanker in regular waves show reasonable accuracy in predicting the hydrodynamic responses of the ship as compared to experimental data. A static analysis was conducted in MAXSURF software to verify the stability of the full-scale ship after the installation of the hard sails. Finally, computational analysis was carried out for the sail-installed KVLCC2 hull to evaluate its hydrodynamic performance for different wave conditions like the regular and irregular head sea as well as beam sea conditions along with expected operational and severe wind speeds corresponding to the model scale hull. The results show that the added resistance and motion amplitudes for the sail-assisted KVLCC2 ship do not change significantly in both operational and severe head sea conditions. However, in the case of a beam sea, there is a significant increase in both added resistance and motion amplitudes.

Statistical and analytical investigation of methanol applications, production technologies, value-chain and economy with a special focus on renewable methanol

Methanol could be considered one of four important basic chemicals, and is produced at the rate of more than 98 million tons yearly. About 30% of methanol is utilized in fuel applications for industrial boilers, transportation sector, and cooking. Approximately two-thirds of the produced methanol is utilized to make other chemicals. The consumption and production of methanol result in 10% of total chemical sector. The annual production of renewable methanol is limited to less than 0.2 million tons. It is estimated that by 2050, the cost of making renewable methanol will reduce between USD 250 to USD 630 per metric ton due to price reductions in renewable energy. With the aim of promoting renewable methanol production, the present contribution provide a statistical and analytical overview of the worldwide methanol value chain in terms of the demand and production of methanol, the most recent updates of production methods from different feedstocks, and the downstream applications of substances in. The benefits and drawbacks of using methanol as a clean fuel and energy source for transportation are evaluated. The capabilities of renewable methanol to power future propulsion technologies are examined and the commercial potentials of the two principal forms of renewable methanol, bio-methanol and e-methanol were investigated. The review concludes by identifying the key challenges and opportunities for the development of a sustainable value chain for methanol.

Adopting different wind-assisted ship propulsion technologies as fleet retrofit: An agent-based modeling approach

The maritime shipping industry will increasingly switch to low carbon fuels and adopt energy saving technologies (ESTs) to achieve the industry target of decarbonization. Among ESTs, deck equipment, including those based on wind propulsion technologies (WPTs), represents the largest potential fuel savings and a source of increasing innovation initiatives by industry actors. Previous contributions to WPT innovation have addressed barriers and drivers for increased adoption in the industry but failed to consider the specific aspects of the fleet retrofitting market. Through an agent-based simulation model, this work studies the effects of different policy and market scenarios (subsidies, fuel prices, and networking) on the adoption of WPT retrofitting solutions. The proposed model incorporates two decision steps for each vessel to adopt the technology (acquiring awareness of the technology, and a utility decision process to determine the WPT option). The study also expands on previous knowledge by modeling three WPT options and by integrating real world data of technology costs and their fuel savings as well as vessel features. Insights from simulations allow to identify the most convenient policies as well as the potential of alternative models to reduce introduction barriers (e.g., product-service business models).

Decarbonization potential of future sustainable propulsion—A review of road transportation

AbstractModern automotive propulsion technologies must achieve the highest CO2 reduction potential quickly to abide by the requirements of the Paris Climate Agreement. A collective utilization of renewable fuels, e‐fuels, hydrogen, and electrical energy will be able to meet different mobility and transport requirements in an optimal and CO2‐neutral approach. The well‐to‐wheel greenhouse gas emissions of a propulsion system are determined by two factors, that is, the energy efficiency of the system and the carbon intensity of the energy source. Regardless of the CO2 emission generated during the battery manufacturing and recycling process, the carbon intensity of the battery electric vehicles during operation is mainly decided by the carbon intensity of the electricity being consumed. The relatively low fleet ratios of battery electric and hydrogen‐powered vehicles and the massive remaining useful life of current internal combustion engine vehicle stock limit their impact on decarbonization in the near term. The expansion of charging infrastructure requires significant acceleration for the success of large‐scale and rapid electric vehicle adoption. For internal combustion engines, the focus is to further improve energy efficiency and the adoption of low‐to‐zero carbon renewable fuels. Hybrid and plug‐in hybrid vehicles are demonstrating the advantages of combining state‐of‐the‐art technologies to reduce both energy consumption and carbon emissions. In this review, the present status of propulsion systems is reviewed in detail, considering both the market penetration and well‐to‐wheel carbon emissions. The decarbonization potentials of various propulsion systems are then discussed.

Flickering guiding light from the International Maritime Organisation's policy mix

The maritime shipping sector is one of the hard-to-abate sectors in need of policy guidance for enabling sustainability transitions. Through the lens of policy mix characteristics, specifically consistency and comprehensiveness, we analyse the development of the global policy mix, implemented by the International Maritime Organisation, for reducing ship emissions, and its technology implications regarding ship-owners’ choice of propulsion technology. We elaborate on conceptualisations of policy mix consistency and comprehensiveness, which allow for an improved understanding of the role of policy in transition processes. Our empirical analysis indicates that although the sector has one main regulator, the overall policy mix lacks consistency and comprehensiveness, as the implemented instruments are insufficient to achieve set emission reduction targets. Furthermore, the design of the regulatory framework creates a technological lock-in on fossil fuels and there are insufficient incentives for ship-owners to invest in sustainable technology.

Exploring the Green-Oriented Transition Process of Ship Power Systems: A Patent-Based Overview on Innovation Trends and Patterns

The shipping industry has accelerated the transformation of its carbon emission reduction and decarbonization, and relevant patents are rapidly increasing, but the industry still lacks consensus on the low-carbon development route of ship propulsion technology. We used the Derwent Innovation Index to collect the global patent information on ship power systems between 1965 and 2022 and proposed a new patent information mining framework. It is used for the dynamic tracking and analysis of global technology correlation characteristics, hot technology topics, and competitive situations. The findings indicate that: (1) the innovation of ship power systems is more radical and concentrated in the fuel field represented by LNG technology, whereas technical innovation in the field of pure electric propulsion is more scattered. Small tonnage ships, underwater operations, and recreation technology are among its innovation hotspots. (2) Pure electric propulsion technology is dominated by combined innovation with other propulsion methods (hybrid propulsion technology) and Chinese universities have recently begun to lead this technology. (3) Fuel cells and remote control have become innovation hotspots. Fuel cell technology, which combines electric, fuel, and hybrid power technology, is now on the cutting edge of innovation and has the potential for disruptive innovation.

An atmosphere-breathing propulsion system using inductively coupled plasma source

CubeSats have attracted more research interest recently due to their lower cost and shorter production time. A promising technology for CubeSat application is atmosphere-breathing electric propulsion, which can capture the atmospheric particles as propulsion propellant to maintain long-term mission at very low Earth orbit. This paper designs an atmosphere-breathing electric propulsion system for a 3 U CubeSat, which consists of an intake device and an electric thruster based on the inductively coupled plasma. The capture performance of intake device is optimized considering both particles capture efficiency and compression ratio. The plasma source is also analyzed by experiment and simulation. Then, the thrust performance is also estimated when taking into account the intake performance. The results show that it is feasible to use atmosphere-breathing electric propulsion technology for CubeSats to compensate for aerodynamic drag at lower Earth orbit.

Flying cars economically favor battery electric over fuel cell and internal combustion engine.

Flying cars, essentially vertical takeoff and landing aircraft (VTOL), are an emerging, disruptive technology that is expected to reshape future transportation. VTOLs can be powered by battery electric, fuel cell, or internal combustion engine, which point to entirely different needs for industry expertise, research & development, supply chain, and infrastructure supports. A pre-analysis of the propulsion technology competition is crucial to avoid potential wrong directions of research, investment, and policy making efforts. In this study, we comprehensively examined the cost competitiveness of the three propulsion technologies. Here we show that battery electric has already become the lowest-cost option for below-200-km VTOL applications, covering intra-city and short-range inter-city travels. This cost advantage can be robustly strengthened in the long term under various technology development scenarios. Battery energy density improvement is the key to reducing cost. In particular, a 600 Wh/kg battery energy density provides battery electric with all-range cost advantage, and promises high return in business. Fuel cell and internal combustion engine, under certain technology development scenarios, can obtain cost advantage in long-range applications, but face intense competition from ground transportation such as high-speed rail. The findings suggest a battery-electric-prioritized VTOL development strategy, and the necessity of developing VTOL-customized high-energy-density batteries.

Next Generation Aircraft Propulsion: A Pratt & Whitney Approach

Abstract Aircraft engines that minimize fuel consumption and operate on sustainable aviation fuels are key to meeting the air transportation sector’s commitment to net zero CO2 emissions by 2050. This article reports on work to implement sustainable propulsion technologies, including advanced gas turbine propulsion technologies, engines that are compatible with approved sustainable aviation fuels, hybrid-electric propulsion, and hydrogen propulsion. The article also describes efforts to reduce the environmental footprint related to condensation trails (contrails) from aircraft engine exhaust plumes.

Aerodynamic Analysis and Design Optimization of a Novel Flapping Wing Micro Air Vehicle in Hovering Flight

Inspired by the challenging and nimble flight dynamics of flying insects and birds, this research investigates bionic propulsion technology to develop an improved flapping wing micro air vehicle (FWMAV) design. Following the bionic formula, a prototype is preliminarily designed to achieve multi-attitude flight. Then, kinematic modeling is employed for further data analysis. A meshless particle hydrodynamics method is adopted to explore an optimized flapping driving mechanism and understand the influence of the flapping frequency, flapping amplitude, and quick-return characteristics of one side of the symmetrical mechanism on aerodynamic performance. Based on the aerodynamic model, force measurement experiments are developed to verify simulation availability and investigate the importance of wing flexibility. The numerical analysis results demonstrate that the average lift is approximately proportional to the flapping frequency, flapping-wing amplitude, and quick-return characteristics. Further optimization is conducted to find the best design parameters setting because of the complicated coupling relationship between the flapping wing amplitude and quick-return characteristics. Moreover, the optimized wing property supports high aerodynamic performance via experimental analysis in hovering flight.

Array of carbon black-based microthrusters for CubeSat applications

Access to space for small private companies requires to improve the ability to bring low-cost satellites into orbit. CubeSats offer a unique opportunity to meet these needs thanks to their reduced production times, the low manufacturing costs and ease of use. In order to be able to communicate with each other, exchange information and interact, it is necessary to place CubeSats in formation: in this context, miniature propulsion technologies, including chemical and electric propulsion, play a critical role in achieving mission requirements and maintaining satellites position. In this article, the feasibility of solid propellant micro rockets, fully integrated in an opposing array of printed thrust chambers is examined: each rocket can be fired together with the others or separately to modulate thrust. Theoretical and experimental results show that the microthruster, made of nylon and carbon fiber, have good mechanical and thermal resistance and simultaneously good performance is achieved. In particular, a microthruster with a diameter of 4 mm and a length of 6 mm, with 55 g of black powder propellant, achieves a thrust of about 3.5 N for about 7 ms.

The Acceleration Phenomenon of Shock Wave Induced by Nanosecond Laser Irradiating Silicon Assisted by Millisecond Laser

The propagating evolution of shock waves induced by a nanosecond pulse laser (ns laser) irradiating silicon assisted by a millisecond pulse laser (ms laser) is investigated experimentally. A numerical model of 2D axisymmetric two-phase flow is established to obtain the spatial distribution of shock wave velocity. Two types of shock wave acceleration phenomenon are found. The mechanism of the shock wave acceleration phenomenon is discussed. The experimental and numerical results show that the initial stage of ms laser-induced plasma can provide the initial ions to increase probability of collision ionization between free electrons and vapor atoms. The velocity of the ns laser-induced shock wave is accelerated. Furthermore, the ms laser-induced plasma as the propagation medium can also accelerate the ns laser-induced shock wave. The shock wave acceleration methods obtained in this paper can promote the development of laser propulsion technology.

Bacterial Virulence and Prevention for Human Spaceflight.

With the advancement in reusable rocket propulsion technology, space tourist trips into outer space are now becoming a possibility at a cost-effective rate. As such, astronauts will face a host of health-related challenges, particularly on long-duration space missions where maintaining a balanced healthy microbiome is going to be vital for human survival in space exploration as well as mission success. The human microbiome involves a whole list of micro-organisms that reside in and on the human host, and plays an integral role in keeping the human host healthy. However, imbalances in the microbiome have been directly linked to many human diseases. Research findings have clearly shown that the outer space environment can directly affect the normal microbiome of astronauts when the astronaut is exposed to the microgravity environment. In this study, we show that the simulation of microgravity on earth can mimic the outer space microgravity environment. Staphylococus aureus (S. aureus) was chosen for this study as it is an opportunistic pathogen, which is part of the normal human skin microflora and the nasal passages. This study's results show that S. aureus proliferation was significantly increased under a microgravity environment compared to Earth's gravity conditions, which complements previous work performed on bacteria in the outer space environment in the International Space Station (ISS). This demonstrates that this technology can be utilised here on Earth to mimic the outer space environment and to study challenging health-related questions. This in return saves us the cost on conducting experiments in the ISS and can help advance knowledge at a faster rate and produce countermeasures to mitigate the negative side effects of the hostile outer space environment on humans.