Showing papers on "Propulsion published in 2019"

Fuel-Optimal Rocket Landing with Aerodynamic Controls

Abstract: Aerodynamic forces are not negligible for a reusable rocket returning back to Earth. How the aerodynamic controls and propulsion should be coordinated to realize fuel-optimal precise landing is add...

Preliminary Sizing Method for Hybrid-Electric Distributed-Propulsion Aircraft

Abstract: The use of hybrid-electric propulsion (HEP) entails several potential benefits such as the distribution of power along the airframe, which enables synergistic configurations with improved aerodynamic and propulsive efficiency. This paper presents a comprehensive preliminary sizing method suitable for the conceptual design process of hybridelectric aircraft, taking into account the powertrain architecture and associated propulsion–airframe integration effects. To this end, the flight-performance equations are modified to account for aeropropulsive interaction. A series of component-oriented constraint diagrams are used to provide a visual representation of the design space. A HEPcompatible mission analysis and weight estimation are then carried out to compute the wing area, powerplant size, and takeoff weight. The resulting method is applicable to a wide range of electric and hybrid-electric aircraft configurations and can be used to estimate the optimal power-control profiles. For demonstration purposes, the method is applied to a regional HEP aircraft featuring leading-edge distributed propulsion (DP). Three powertrain architectures are compared, showing how the aeropropulsive effects are included in the model. Results indicate that DP significantly increases wing loading and improves the cruise lift-to-drag ratio by 6%, although the growth in aircraft weight leads to an energy consumption increase of 3% for the considered mission.

A Hybrid Electric Vehicle Motor Cooling System—Design, Model, and Control

Abstract: Hybrid electric vehicle motors offer propulsion while accelerating and charge the battery pack when braking or decelerating. Though electric motors have high operating efficiency, considerable heat is generated based on required operating torque and speed. Thus, an efficient motor cooling system is needed to maintain the temperature within a prescribed range. The traditional motor liquid cooling system is effective but consumes energy to run the coolant pump and radiator fan. This paper examines the performance of a hybrid cooling system, combining heat pipes with conventional liquid cooling in a compact thermal cradle. This innovative design allows heat removal via an integrated thermal pathway by regulating various actuators (e.g., centrifugal fans, radiator pump, and fan) to minimize energy consumption. A reduced order thermal model predicts the motor's internal temperatures. Cooling performance is evaluated based on the Urban Assault driving cycle for different conditions. Numerical results show that the electric motor temperature is maintained at approximately the target value of 70 °C. Additionally, up to approximately 370 kJ of energy is saved as compared to a conventional liquid cooling system for a specific 85 kW e-motor within 1500 s run time.

Modeling and Analysis of Electric Motors: State-of-the-Art Review

Abstract: This paper presents a comprehensive state-of-the-art review of the modeling and analysis methods for the multidisciplinary design of electric motors for various applications including vehicular power and propulsion systems and electrified powertrains. It covers the important aspects of different engineering domains, such as dynamic modeling, loss calculations, demagnetization analysis, thermal modeling, acoustic noise and vibration analysis, and mechanical stress modeling. This paper intends to guide the electric motor designers through examples and results on how to apply different analysis techniques on electric motors.

Coupled aeropropulsive design optimisation of a boundary-layer ingestion propulsor

Abstract: Airframe–propulsion integration concepts that use boundary-layer ingestion (BLI) have the potential to reduce aircraft fuel burn. One concept that has been recently explored is NASA’s STARC-ABL aircraft configuration, which offers the potential for fuel burn reduction by using a turboelectric propulsion system with an aft-mounted electrically driven BLI propulsor. So far, attempts to quantify this potential fuel burn reduction have not considered the full coupling between the aerodynamic and propulsive performance. To address the need for a more careful quantification of the aeropropulsive benefit of the STARC-ABL concept, we run a series of design optimisations based on a fully coupled aeropropulsive model. A 1D thermodynamic cycle analysis is coupled to a Reynolds-averaged Navier–Stokes simulation to model the aft propulsor at a cruise condition and the effects variation in propulsor design on overall performance. A series of design optimisation studies are performed to minimise the required cruise power, assuming different relative sizes of the BLI propulsor. The design variables consist of the fan pressure ratio, static pressure at the fan face, and 311 variables that control the shape of both the nacelle and the fuselage. The power required by the BLI propulsor is compared with a podded configuration. The results show that the BLI configuration offers 6–9% reduction in required power at cruise, depending on assumptions made about the efficiency of power transmission system between the under-wing engines and the aft propulsor. Additionally, the results indicate that the power transmission efficiency directly affects the relative size of the under-wing engines and the aft propulsor. This design optimisation, based on computational fluid dynamics, is shown to be essential to evaluate current BLI concepts and provides a powerful tool for the design of future concepts.

A novel piezoelectric inertial rotary motor for actuating micro underwater vehicles

Abstract: With developments of micro-machining and advanced functional materials, smart actuators have been developed and applied in various micro underwater vehicles (MUVs) or micro underwater robots. Since there is a tradeoff between the miniature size and output performance for MUVs driven by traditional electromagnetic motors, piezoelectric motors with features of compact structure, large force or torque at small size and no electromagnetic interference provide another promising alternative for actuating MUVs. However, there is a few research to explore the possibility of utilizing piezoelectric motors to realize underwater actuations. In this paper, a novel piezoelectric inertial rotary motor is designed to power the underwater vehicle, which is capable of forward swimming, rotating, rising and diving. This motor consists of two rotors and one disk type stator. One piece of piezoelectric wafer adhered to the bottom face of the stator’s metal disk is used to excite the radial in-plane vibration mode of stator’s outer ring, which is converted into the revolved motion of the inner tube through the connection beams. To utilize the inertial driving mechanism, the motor works at a “slip-slip” mode by the saw-tooth type driving signal. One prototype motor with the appearance size of Φ 20 mm × 20 mm and weight of 3.6 g is designed, fabricated and characterized. Experimental results show that the prototype motor could rotate at a steady speed of 2200 r/min with 150 Vp-p driving voltage. In addition, the motor also performs well with a slightly decrease of operating speed in underwater environments when the silver electrode is coated by waterproof material. Consequently, sealing ring is not necessary for the proposed motor as immersed in water, which is different with conventional electromagnetic motors and enables the actuation unit to be smaller. And then, the prototype motor is coupled with a propeller to build a thruster, which could output the steady speed and maximum propulsion force of 1200 r/min and 4.6 mN, respectively. Finally, the thruster is installed in a spherical swimming robot, and the velocity of the robot could reach 80 mm/s. With merits of simple structure, compact size and great waterproof feasibility, the proposed piezoelectric inertial motor opens a new avenue for developing advanced and flexible MUVs.

Lightweight Design of Fully Superconducting Motors for Electrical Aircraft Propulsion Systems

Abstract: This paper describes and discusses fully superconducting motors (FSCMs) for electrical aircraft propulsion systems. The FSCM structures have a potential to reach over 20 kW/kg, thanks to air cored structure and higher current density coils while permanent magnet synchronous motors reached 5 kW/kg. We designed 3 and 5 MW FSCMs with YBCO field coils and MgB 2 armature windings. The FSCM output density is aiming to achieve over 20 kW/kg. To satisfy the output density, we considered back iron thickness and magnetic flux leakage with FEM. The design results show that an output density of the 3 and 5 MW motors reached 19.4 and 25.2 kW/kg, respectively. Also, magnetic flux leakage at a distance of almost 100 mm from the motors was on the order of tens of mT.

An Analytical Design-Optimization Method for Electric Propulsion Systems of Multicopter UAVs With Desired Hovering Endurance

Abstract: Multicopters are becoming increasingly important both in civil and military fields. Currently, most multicopter propulsion systems are designed by experience and trial-and-error experiments, which are costly and ineffective. This paper proposes a simple and practical method to help designers find the optimal propulsion system according to the given design requirements. First, the modeling methods for four basic components of the propulsion system including propellers, motors, electric speed controls, and batteries are studied, respectively. Second, the whole optimization design problem is simplified and decoupled into several subproblems. By solving these subproblems, the optimal parameters of each component can be obtained, respectively. Finally, based on the obtained optimal component parameters, the optimal product of each component can be quickly located and determined from the corresponding database. Experiments and statistical analyses demonstrate the effectiveness of the proposed method. The proposed method is so fast and practical that it has been successfully applied to a web server to provide online optimization design service for users.

Consecutive aquatic jump-gliding with water-reactive fuel

Abstract: Robotic vehicles that are capable of autonomously transitioning between various terrains and fluids have received notable attention in the past decade due to their potential to navigate previously unexplored and/or unpredictable environments. Specifically, aerial-aquatic mobility will enable robots to operate in cluttered aquatic environments and carry out a variety of sensing tasks. One of the principal challenges in the development of such vehicles is that the transition from water to flight is a power-intensive process. At a small scale, this is made more difficult by the limitations of electromechanical actuation and the unfavorable scaling of the physics involved. This paper investigates the use of solid reactants as a combustion gas source for consecutive aquatic jump-gliding sequences. We present an untethered robot that is capable of multiple launches from the water surface and of transitioning from jetting to a glide. The power required for aquatic jump-gliding is obtained by reacting calcium carbide powder with the available environmental water to produce combustible acetylene gas, allowing the robot to rapidly reach flight speed from water. The 160-gram robot could achieve a flight distance of 26 meters using 0.2 gram of calcium carbide. Here, the combustion process, jetting phase, and glide were modeled numerically and compared with experimental results. Combustion pressure and inertial measurements were collected on board during flight, and the vehicle trajectory and speed were analyzed using external tracking data. The proposed propulsion approach offers a promising solution for future high-power density aerial-aquatic propulsion in robotics.

On-Board Microgrids for the More Electric Aircraft

Abstract: Aircraft transportation holds a tremendous importance in today’s society. Considering the international roadmaps for the intensification of the air travel and the targets concerning the environmental impact, aircraft efficiency has been in the spotlight of scientific research for more than two decades. Electrification of the aircraft subsystems and, in the future, of the propulsion appears to be the way forward to reach these ambitious goals. This Special Section collects contributions related to the more electric aircraft (MEA) technologies, from the power systems to the actuation systems.

Thermal Management of High-Power Density Electric Motors for Electrification of Aviation and Beyond

Abstract: Enhanced cooling, coupled with novel designs and packaging of semiconductors, has revolutionized communications, computing, lighting, and electric power conversion. It is time for a similar revolution that will unleash the potential of electrified propulsion technologies to drive improvements in fuel-to-propulsion efficiency, emission reduction, and increased power and torque densities for aviation and beyond. High efficiency and high specific power (kW/kg) electric motors are a key enabler for future electrification of aviation. To improve cooling of emerging synchronous machines, and to realize performance and cost metrics of next-generation electric motors, electromagnetic and thermomechanical co-design can be enabled by innovative design topologies, materials, and manufacturing techniques. This paper focuses on the most recent progress in thermal management of electric motors with particular focus on electric motors of significance to aviation propulsion.

Modeling and Experimental Testing of an Unmanned Surface Vehicle with Rudderless Double Thrusters.

Abstract: Motion control of unmanned surface vehicles (USVs) is a crucial issue in sailing performance and navigation costs. The actuators of USVs currently available are mostly a combination of thrusters and rudders. The modeling for USVs with rudderless double thrusters is rarely studied. In this paper, the three degrees of freedom (DOFs) dynamic model and propeller thrust model of this kind of USV were derived and combined. The unknown parameters of the propeller thrust model were reduced from six to two. In the three-DOF model, the propulsion of the USV was completely provided by the resultant force generated by double thrusters and the rotational moment was related to the differential thrust. It combined the propeller thrust model to represent the thrust in more detail. We performed a series of tests for a 1.5 m long, 50 kg USV, in order to obtain the model parameters through system identification. Then, the accuracy of the modeling and identification results was verified by experimental testing. Finally, based on the established model and the proportional derivative+line of sight (PD+LOS) control algorithm, the path-following control of the USV was achieved through simulations and experiments. All these demonstrated the validity and practical value of the established model.

Calculation and Optimization of Propulsion Force of a Real-Scale REBCO Magnet for EDS Train

Abstract: Electrodynamic suspension (EDS) train has the unique advantages of excellent levitation and guidance stabilities, large levitation gap, and so on. All of these merits make it a promising candidate for the future ultra-high-speed transportations, in which the high-temperature superconducting (HTS) linearly synchronous driving motor (LSM) plays an important role because of the decrease of energy consumption of HTS magnet. This paper, which serves as a fundamental study on the HTS synchronous driving system of EDS train, is aimed to calculate the propulsion force of LSM and optimize the propulsion fluctuation. First, in order to define the operating current of LSM, the critical current of a real-scale REBCO coil was numerically estimated using the so-called T-A model. Second, based on the Neumann formula and virtual displacement method, an analytic model to estimate the propulsion force of LSM was established and verified by comparing results with a finite-element method (FEM) numerical model. Finally, by resorting to the validated analytic model, the geometric parameters of propulsion coil were optimized, and then using the optimal parameters, the maximum electromagnetic forces of LSM under different operating conditions of EDS train were calculated. It was found that the linearly driving system inherently keeps robust driving stability to the lateral and normal displacements.

Conceptual Assessment of Hybrid Electric Aircraft with Distributed Propulsion and Boosted Turbofans

Abstract: This paper presents the results of a study into the effect of distributed hybrid-electric propulsion on aircraft performance and characteristics. To size these aircraft, a new preliminary sizing method for hybrid-electric aircraft with distributed propulsion, including aero-propulsive interaction, is combined with a modified Class-II weight estimation method where energy consumption is estimated through a mission analysis method. Comparison of the predictions from these new methods to the predictions from a traditional sizing method has shown to be within 5% agreement for a single-aisle aircraft powered by conventional turbofans in terms of wing loading, energy consumption and maximum take-off weight. A boosted turbofan aircraft as well as two aircraft with different distributed, hybrid-electric propulsion systems have been assessed for a 150-pax aircraft designed for a harmonic range of 800nmi. Each of these aircraft designs showed significant increases in propulsion system mass (up to 700%). The distributedpropulsion aircraft showed increases in energy consumption of 34% and 51%, respectively, over the conventional turbofan aircraft. However, the boosted-turbofan aircraft showed a 10% decrease in energy consumption and a 3% reduction in maximum take-off weight. Future studies have to be performed exploring the design space, including all powertrain components, thermal management components, mission parameters and propulsion system layout.