Showing papers on "Propulsion published in 2018"

Supersonic Combustion in Air-Breathing Propulsion Systems for Hypersonic Flight

Abstract: Great efforts have been dedicated during the last decades to the research and development of hypersonic aircrafts that can fly at several times the speed of sound. These aerospace vehicles have revolutionary applications in national security as advanced hypersonic weapons, in space exploration as reusable stages for access to low Earth orbit, and in commercial aviation as fast long-range methods for air transportation of passengers around the globe. This review addresses the topic of supersonic combustion, which represents the central physical process that enables scramjet hypersonic propulsion systems to accelerate aircrafts to ultra-high speeds. The description focuses on recent experimental flights and ground-based research programs and highlights associated fundamental flow physics, subgrid-scale model development, and full-system numerical simulations.

Harnessing bistability for directional propulsion of soft, untethered robots.

Abstract: In most macroscale robotic systems, propulsion and controls are enabled through a physical tether or complex onboard electronics and batteries. A tether simplifies the design process but limits the range of motion of the robot, while onboard controls and power supplies are heavy and complicate the design process. Here, we present a simple design principle for an untethered, soft swimming robot with preprogrammed, directional propulsion without a battery or onboard electronics. Locomotion is achieved by using actuators that harness the large displacements of bistable elements triggered by surrounding temperature changes. Powered by shape memory polymer (SMP) muscles, the bistable elements in turn actuate the robot’s fins. Our robots are fabricated using a commercially available 3D printer in a single print. As a proof of concept, we show the ability to program a vessel, which can autonomously deliver a cargo and navigate back to the deployment point.

A Review of Distributed Electric Propulsion Concepts for Air Vehicle Technology

Abstract: The emergence of distributed electric propulsion (DEP) concepts for aircraft systems has enabled new capabilities in the overall efficiency, capabilities, and robustness of future air vehicles Distributed electric propulsion systems feature the novel approach of utilizing electrically-driven propulsors which are only connected electrically to energy sources or power-generating devices As a result, propulsors can be placed, sized, and operated with greater flexibility to leverage the synergistic benefits of aero-propulsive coupling and provide improved performance over more traditional designs A number of conventional aircraft concepts that utilize distributed electric propulsion have been developed, along with various short and vertical takeoff and landing platforms Careful integration of electrically-driven propulsors for boundary-layer ingestion can allow for improved propulsive efficiency and wake-filling benefits The placement and configuration of propulsors can also be used to mitigate the trailing vortex system of a lifting surface or leverage increases in dynamic pressure across blown surfaces for increased lift performance Additionally, the thrust stream of distributed electric propulsors can be utilized to enable new capabilities in vehicle control, including reducing requirements for traditional control surfaces and increasing tolerance of the vehicle control system to engine-out or propulsor-out scenarios If one or more turboelectric generators and multiple electric fans are used, the increased effective bypass ratio of the whole propulsion system can also enable lower community noise during takeoff and landing segments of flight and higher propulsive efficiency at all conditions Furthermore, the small propulsors of a DEP system can be installed to leverage an acoustic shielding effect by the airframe, which can further reduce noise signatures The rapid growth in flight-weight electrical systems and power architectures has provided new enabling technologies for future DEP concepts, which provide flexible operational capabilities far beyond those of current systems While a number of integration challenges exist, DEP is a disruptive concept that can lead to unprecedented improvements in future aircraft designs

Modern Electric, Hybrid Electric, and Fuel Cell Vehicles, Third Edition [Book News]

Abstract: This book explains the dynamic modeling, simulation, and optimization needed for hybrid electric vehicles. It presents a comprehensive overview of technologies and how they are designed, integrated, and controlled. The book begins with environmental issues and transportation history, before continuing to fundamentals of vehicle propulsion and braking, theoretical bases of internal combustion engines, and explanations about vehicle transmission. Next, the authors explain in a wellstructured, clear, and concise manner, information about electric vehicles (EVs), hybrid EVs (HEVs), fuel cell vehicles (FCVs), and propulsion electric motors together with their controllers. The authors analyze design principles of series, parallel, series–parallel, and soft hybrid electric drive trains, and they explain design and control principles for plug-in hybrid electric vehicles, with examples showing simulation results using the overall drive train system, not just the individual components. A good grasp of such principles is essential for understanding the modeling before conducting research on advanced control methods for switching power converters. Storage (batteries, supercapacitors, fuel cells) and regenerative braking, together with off-road vehicles and their requirements, are expansively analyzed and discussed in this third edition. The book’s concluding chapters cover optimization of full-size engine HEVs and power-trains and include a guide for a multiobjective optimization toolbox. The authors are known around the world as specialists in power electronics; motor drives; hybrid vehicles and their control systems; architecture, modeling, and design of electric and hybrid electric drive trains; energy management and power-train control; mechatronic systems; and sustainable energy engineering.

Flight of an aeroplane with solid-state propulsion

Abstract: Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forces accelerate ions in a fluid1,2, has been proposed as an alternative method of propelling aeroplanes—without moving parts, nearly silently and without combustion emissions3–6. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelled heavier-than-air aeroplane. We flew a fixed-wing aeroplane with a five-metre wingspan ten times and showed that it achieved steady-level flight. All batteries and power systems, including a specifically developed ultralight high-voltage (40-kilovolt) power converter, were carried on-board. We show that conventionally accepted limitations in thrust-to-power ratio and thrust density4,6,7, which were previously thought to make electroaerodynamics unfeasible as a method of aeroplane propulsion, are surmountable. We provide a proof of concept for electroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions. A solid-state propulsion system can sustain powered flight, as demonstrated by an electroaerodynamically propelled heavier-than-air aeroplane.

Large electric machines for aircraft electric propulsion

Abstract: To achieve benefits similar to those seen in hybrid-/all-electric ground-based and marine vehicles, electric propulsion has been proposed for large commercial aircraft. Among the main drivers of this are improved fuel economy, reduced harmful emissions, and lower audible noise. In converting to electric propulsion, the added electrical components' masses must be minimised so that the benefits that the components enable - improved turbine efficiency, distributed propulsion and propulsion-airframe integration - are not cancelled out by their weight penalty. This puts stringent requirements on the large electric machines used in the system, both those that generate electric power from the turbine shaft and those that drive propellers or ducted fans, because they are among the heaviest of the added electric components. A key machine design metric in this application is the specific power (SP), or the power-to-mass ratio. This study gives a comprehensive overview of large electric machines for aircraft electric propulsion applications, with a focus on methods for mass reduction and SP improvement.

Conceptual Design of Operation Strategies for Hybrid Electric Aircraft

Abstract: Ambitious targets to reduce emissions caused by aviation in the light of an expected ongoing rise of the air transport demand in the future drive the research of propulsion systems with lower CO2 emissions. Regional hybrid electric aircraft (HEA) powered by conventional gas turbines and battery powered electric motors are investigated to test hybrid propulsion operation strategies. Especially the role of the battery within environmentally friendly concepts with significantly reduced carbon footprint is analyzed. Thus, a new simulation approach for HEA is introduced. The main findings underline the importance of choosing the right power-to-energy-ratio of a battery according to the flight mission. The gravimetric energy and power density of the electric storages determine the technologically feasibility of hybrid concepts. Cost competitive HEA configurations are found, but do not promise the targeted CO2 emission savings, when the well-to-wheel system is regarded with its actual costs. Sensitivity studies are used to determine external levers that favor the profitability of HEA.

Concept Vehicles for VTOL Air Taxi Operations

Abstract: Concept vehicles are presented for air taxi operations, also known as urban air mobility or on-demand mobility applications. Considering the design-space dimensions of payload (passengers and pilot), range, aircraft type, and propulsion system, three aircraft are designed: a single passenger (250-lb payload), 50-nm range quadrotor with electric propulsion; a six-passenger (1200-lb payload), 4x50 = 200-nm range side-by-side helicopter with hybrid propulsion; and a fifteen-passenger (3000-lb payload), 8x50 = 400-nm range tiltwing with turbo-electric propulsion. These concept vehicles are intended to focus and guide NASA research activities in support of aircraft development for emerging aviation markets, in particular VTOL air taxi operations. Research areas are discussed, illustrated by results from the design of the concept vehicles.

A Three-Phase Integrated Onboard Charger for Plug-In Electric Vehicles

Abstract: A three-phase onboard charger, integrated with the propulsion system of a plug-in electric vehicle, is presented. It is constructed by connecting an add-on three-phase power electronics interface to the propulsion system. The propulsion motor is utilized as a coupled DC inductor for the charger. The charging power level of the proposed charger could be as high as that of the propulsion system. The charger topology is capable of three-phase power factor (PF) correction and battery voltage/current regulation. Detailed analyses of the circuit operation and modeling of the circuit are presented. Experimental results of a 3.3-kW three-phase integrated charger, using a permanent magnet synchronous machine (PMSM), are provided. A nearly unity PF and 4.77% total harmonic distortion are obtained with a maximum efficiency of 92.6%.

Mitigating Power Fluctuations in Electric Ship Propulsion With Hybrid Energy Storage System: Design and Analysis

Abstract: Shipboard electric propulsion systems experience large power and torque fluctuations on their drive shaft due to propeller rotational motion and waves. This paper explores new solutions to address these fluctuations by integrating a hybrid energy storage system (HESS) and exploring energy management (EM) strategies. The HESS combines battery packs with ultracapacitor banks. Two strategies for real-time EM of HESS are considered: one splits the power demand such that high- and low-frequency power fluctuations are compensated by ultracapacitors and batteries, respectively; another considers the HESS as a single entity and designs an EM strategy to coordinate the operations of the ultracapacitors and batteries. For both strategies, model predictive control is used to address power tracking and energy saving under various operating constraints. To quantitatively analyze the performance of HESS and its associated controls, a propeller and ship dynamic model, which captures the underlying physical behavior, is established to support the control development and system optimization. Power fluctuation mitigation and HESS loss minimization, the main objectives, are evaluated in different sea conditions. Simulation results show that the coordination within HESS provides substantial benefits in terms of reducing fluctuations and losses.

Hybrid Electric Vehicles: Energy Management Strategies [Bookshelf]

Abstract: Hybrid electric vehicles have a long history, dating as far back as the development of the Lohner-Porsche Mixte in 1899. A hybrid vehicle, by definition, is one with multiple propulsion power sources, one example being the combination of an internal combustion engine plus an electric drive. The tools of dynamic programming and optimal control lend themselves quite elegantly to the hybrid vehicle energy management problem. This has motivated a very substantial body of peer-reviewed conference and journal papers on the application of optimal control theory to hybrid vehicle energy management. This textbook addresses a critical gap in that it introduces students, scholars, and practitioners to the main ideas in the literature and the interconnections between these ideas.

Space Propulsion Technology for Small Spacecraft

Abstract: As small satellites become more popular and capable, strategies to provide in-space propulsion increase in importance. Applications range from orbital changes and maintenance, attitude control and desaturation of reaction wheels to drag compensation and de-orbit at spacecraft end-of-life. Space propulsion can be enabled by chemical or electric means, each having different performance and scalability properties. The purpose of this review is to describe the working principles of space propulsion technologies proposed so far for small spacecraft. Given the size, mass, power, and operational constraints of small satellites, not all types of propulsion can be used and very few have seen actual implementation in space. Emphasis is given in those strategies that have the potential of miniaturization to be used in all classes of vehicles, down to the popular 1-L, 1-kg CubeSats and smaller.

Two Forces Are Better than One: Combining Chemical and Acoustic Propulsion for Enhanced Micromotor Functionality

Abstract: Engines and motors are everywhere in the modern world, but it is a challenge to make them work if they are very small. On the micron length scale, inertial forces are weak and conventional motor designs involving, e.g., pistons, jets, or flywheels cease to function. Biological motors work by a different principle, using catalysis to convert chemical to mechanical energy on the nanometer length scale. To do this, they must apply force continuously against their viscous surroundings, and because of their small size, their movement is "jittery" because of the random shoves and turns they experience from molecules in their surroundings. The first synthetic catalytic motors, discovered about 15 years ago, were bimetallic Pt-Au microrods that swim in fluids through self-electrophoresis, a mechanism that is apparently not used by biological catalytic nanomotors. Despite the difference in propulsion mechanisms, catalytic microswimmers are subject to the same external forces as natural swimmers such as bacteria. Therefore, they follow similar scaling laws, are subject to Brownian forces, and exhibit a rich array of biomimetic emergent behavior (e.g., chemotaxis, rheotaxis, schooling, and predator-prey behavior). It was later discovered, quite by accident, that the same metallic microrods undergo rapid autonomous movement in acoustic fields, converting excitation energy in the frequency (MHz) and power range (up to several W/cm2) that is commonly used for ultrasonic imaging into axial movement. Because the acoustic propulsion mechanism is fuel-free, it can operate in media that have been inaccessible to chemically powered motors, such as the interior of living cells. The power levels used are intermediate between those of ultrasonic diagnostic imaging and therapy, so the translation of basic research on microswimmers into biomedical applications, including in vivo diagnostics and drug delivery, is possible. Acoustic and chemical propulsion are applied independently to microswimmers, so by modulating the acoustic power one can achieve microswimmer functionalities that are not accessible with the individual propulsion mechanisms. These include motion of particles forward and backward with switching between chemical and acoustic propulsion, the assembly/disassembly equilibrium of particle swarms and colloidal molecules, and controllable upstream or downstream propulsion in a flowing fluid. This Account relates our current understanding of the chemical and acoustic propulsion mechanisms, and describes how their combination can be particularly powerful for imparting enhanced functionality to micromotors.

A Review of Propulsion, Power, and Control Architectures for Insect-Scale Flapping-Wing Vehicles

Abstract: Flying insects are able to navigate complex and highly dynamic environments, can rapidly change their flight speeds and directions, are robust to environmental disturbances, and are capable of long migratory flights. However, flying robots at similar scales have not yet demonstrated these characteristics autonomously. Recent advances in mesoscale manufacturing, novel actuation, control, and custom integrated circuit (IC) design have enabled the design of insect-scale flapping wing micro air vehicles (MAVs). However, there remain numerous constraints to component technologies—for example, scalable high-energy density power storage—that limit their functionality. This paper highlights the recent developments in the design of small-scale flapping wing MAVs, specifically discussing the various power and actuation technologies selected at various vehicle scales as well as the control architecture and avionics onboard the vehicle. We also outline the challenges associated with creating an integrated insect-scale flapping wing MAV. [DOI: 10.1115/1.4038795]

Prospects and physical mechanisms for photonic space propulsion

Abstract: An abundant source of energy in space, electromagnetic radiation can provide spacecraft with a gentle yet persistent thrust for interplanetary and interstellar missions. Early successes with microlaser and solar propulsion platforms confirm their potential for near-Earth and deep space exploration, although practical realization of reliable photonic devices is not trivial. This Perspective outlines the recent achievements and future outlook in the field of photonic space propulsion. We highlight several light-enabled mechanisms of thrust generation via photon–matter interactions such as photonic pressure and ablation, optical gradient forces, light-induced electron emission and others. Finally, we outline some of the key challenges in the area and possible solutions for practical applications. Recent achievements and future opportunities for light as a propulsion scheme for space vehicles is discussed.

A Study of Non-Symmetric Double-Sided Linear Induction Motor for Hyperloop All-In-One System (Propulsion, Levitation, and Guidance)

Abstract: This paper proposes an all-in-one system for hyperloop that conducts propulsion, levitation, and guidance. Currently demand on high-speed long-distance transportation is increasing, so that hyperloop is getting attention and studied hard globally. Hyperloop is a new innovative transportation in which a levitated subsonic speed train travels through a vacuum cylindrical tube. Hyperloop needs functions of propulsion, levitation, and guidance for its service, and many devices are necessary for those functions. In the tube, a constrained space, many devices make the entire system complicated, and the size of the vehicle and tube are increased. Therefore, the costs of maintenance, manufacture, and construction are increased and control of each device becomes very difficult. But a non-symmetric double-sided linear induction motor (NSDLIM), the subject of this paper, is an all-in-one system that could conduct all functions. In this paper, the concept of NSDLIM was introduced and its possibility was suggested. Requirements of NSDLIM were investigated considering very high acceleration, velocity, and low air pressure. An NSDLIM model was designed and analyzed by using the finite-element method. Then, NSDLIM parameters that affect performance were investigated and adjusted to improve performance. The derived model performance was shown, and its possibility was considered.

Modeling Boundary Layer Ingestion Using a Coupled Aeropropulsive Analysis

Abstract: The single-aisle turboelectric aircraft with an aft boundary layer propulsor aircraft concept is estimated to reduce fuel burn by 12% through a turboelectric propulsion system with an electrically ...

Time-optimal Control Strategies for a Hybrid Electric Race Car

Abstract: Recently, the Formula 1 propulsion system has evolved from being a conventional combustion engine toward a highly integrated hybrid electric powertrain. Since 2014, the vehicles have been equipped with an electric motor for extra boosting and regenerative braking, and an electrified turbocharger to improve the engine’s torque response and to recover waste heat from the exhaust gas. The powertrain is controlled with a dedicated energy management system, which significantly influences the vehicle’s acceleration performance as well as its fuel and electric energy consumption. Therefore, the strategy must be carefully optimized. In this paper, we propose a computationally efficient method to evaluate the theoretic, optimal energy management strategy leading to the best possible lap time. Since the driving path cannot be influenced by the energy management strategy, but is rather determined by the driver’s steering’s input, we separate the optimization of velocity profile and energy management from the problem of finding the optimal driving path. By carefully introducing convex approximations and relaxations, we formulate the problem as a convex optimal control problem that can be solved efficiently using dedicated numerical solvers. The proposed method allows parameter studies to be conducted within a reasonable time frame of a few minutes, while the optimization results serve as a benchmark for any real-time energy management strategy ultimately to be used during a real race.

Chemical/Light-Powered Hybrid Micromotors with "On-the-Fly" Optical Brakes.

Abstract: Hybrid micromotors capable of both chemically powered propulsion and fuel-free light-driven actuation and offering built-in optical brakes for chemical propulsion are described. The new hybrid micromotors are designed by combining photocatalytic TiO2 and catalytic Pt surfaces into a Janus microparticle. The chemical reactions on the different surfaces of the Janus particle hybrid micromotor can be tailored by using chemical or light stimuli that generate counteracting propulsion forces on the catalytic Pt and photocatalytic TiO2 sides. Such modulation of the surface chemistry on a single micromotor leads to switchable propulsion modes and reversal of the direction of motion that reflect the tuning of the local ion concentration and hence the dominant propulsion force. An intermediate Au layer (under the Pt surface) plays an important role in determining the propulsion mechanism and operation of the hybrid motor. The built-in optical braking system allows "on-the-fly" control of the chemical propulsion through a photocatalytic reaction on the TiO2 side to counterbalance the chemical propulsion force generated on the Pt side. The adaptive dual operation of these chemical/light hybrid micromotors, associated with such control of the surface chemistry, holds considerable promise for designing smart nanomachines that autonomously reconfigure their propulsion mode for various on-demand operations.

Determining the Pressure Gain of Pressure Gain Combustion

Abstract: Over the past few decades, there has been significant research into propulsion concepts attempting to employ pressure gain combustion Pressure gain combustion concepts to date have resulted in dynamic, non-uniform gas flows which are difficult to characterize and compare with more conventional forms of propulsion This paper proposes a technique to derive for the pressure gain combustion device an equivalent, steady, uniform gas pressure that is available to do work or provide thrust, thereby providing a direct comparison with conventional propulsive devices

Testing and Characterization of a Fixed Wing Cross-Domain Unmanned Vehicle Operating in Aerial and Underwater Environments

Abstract: This paper presents test results and performance characterization of the first fixed-wing unmanned vehicle capable of full cross-domain operation in both the aerial and underwater environments with repeated transition and low-energy loitering capabilities. This vehicle concept combines the speed and range of an aircraft with the persistence, diving capabilities, and stealth of a submersible. The paper describes the proof-of-concept vehicle including its concept of operations, the approaches employed to achieve the required functions, and the main components and subsystems. Key subsystems include a passively flooding and draining wing, a single motor and propeller combination for propulsion in both domains, and aerodynamic–hydrodynamic control surfaces. Experiments to quantify the vehicle performance, control responses, and energy consumption in underwater, surface, and flight operation are presented and analyzed. Results of several full-cycle tests are presented to characterize and illustrate each stage of operation including surface locomotion, underwater locomotion, water egress, flight, and water ingress. In total, the proof-of-concept vehicle demonstrated 12 full-cycle cross-domain missions including both manually controlled and autonomous operation.

Design, Optimization, and Prototyping of Segmental-Type Linear Switched-Reluctance Motor With a Toroidally Wound Mover for Vertical Propulsion Application

Abstract: Linear switched-reluctance motor (LSRM) is investigated and proved to be an alternative for direct linear driving systems, especially for long-distance transportation applications, such as vertical elevator driving motor. This paper presents the design, sensitivity analysis, and optimization of a toroidally wound mover LSRM with segmental stator. The presented LSRM has much higher copper utilization ratio and flux carrying capability than the conventional LSRM for vertical linear propulsion application. The features of motor performance influenced by various geometrical parameters are described using magnetic circuit and finite element analysis to give the guidelines for selecting the reasonable range of those parameters of this kind of machine. Furthermore, an optimization procedure is performed to obtain the optimal machine dimensions considering active payload ratio and force ripples. Finally, the experimental results from the prototype validate the design procedures and analysis above.