Showing papers on "Propulsion published in 2013"

Bio-inspired magnetic swimming microrobots for biomedical applications.

Abstract: Microrobots have been proposed for future biomedical applications in which they are able to navigate in viscous fluidic environments. Nature has inspired numerous microrobotic locomotion designs, which are suitable for propulsion generation at low Reynolds numbers. This article reviews the various swimming methods with particular focus on helical propulsion inspired by E. coli bacteria. There are various magnetic actuation methods for biomimetic and non-biomimetic microrobots, such as rotating fields, oscillating fields, or field gradients. They can be categorized into force-driven or torque-driven actuation methods. Both approaches are reviewed and a previous publication has shown that torque-driven actuation scales better to the micro- and nano-scale than force-driven actuation. Finally, the implementation of swarm or multi-agent control is discussed. The use of multiple microrobots may be beneficial for in vivo as well as in vitro applications. Thus, the frequency-dependent behavior of helical microrobots is discussed and preliminary experimental results are presented showing the decoupling of an individual agent within a group of three microrobots.

Present Status and Future Trends in Electric Vehicle Propulsion Technologies

Abstract: In this paper, the current status and the requirements of primary electric propulsion components-the battery, the electric motors, and the power electronics system-are reviewed. The future trends in the electric propulsion systems, battery charging, and the types of power trains are presented. Possible future electric vehicle powertrain systems based on lithium air battery and plug-in fuel cell vehicles are also discussed.

Scaling laws for the thrust production of flexible pitching panels

Abstract: We present experimental results on the role of flexibility and aspect ratio in bio-inspired aquatic propulsion. Direct thrust and power measurements are used to determine the propulsive efficiency of flexible panels undergoing a leading-edge pitching motion. We find that flexible panels can give a significant amplification of thrust production of and propulsive efficiency of when compared to rigid panels. The data highlight that the global maximum in propulsive efficiency across a range of panel flexibilities is achieved when two conditions are simultaneously satisfied: (i) the oscillation of the panel yields a Strouhal number in the optimal range ( ) predicted by Triantafyllou, Triantafyllou & Grosenbaugh (J. Fluid Struct., vol. 7, 1993, pp. 205–224); and (ii) this frequency of motion is tuned to the structural resonant frequency of the panel. In addition, new scaling laws for the thrust production and power input to the fluid are derived for the rigid and flexible panels. It is found that the dominant forces are the characteristic elastic force and the characteristic fluid force. In the flexible regime the data scale using the characteristic elastic force and in the rigid limit the data scale using the characteristic fluid force.

Gas Turbine Engine Health Management: Past, Present and Future Trends

Abstract: Engine diagnostic practices are as old as the gas turbine itself. Monitoring and analysis methods have progressed in sophistication over the past 6 decades as the gas turbine evolved in form and complexity. While much of what will be presented here may equally apply to both stationary power plants and aero-engines, the emphasis will be on aero propulsion.Beginning with primarily empirical methods centering around monitoring the mechanical integrity of the machine, the evolution of engine diagnostics has benefited from advances in sensing, electronic monitoring devices, increased fidelity in engine modeling and analytical methods. The primary motivation in this development is, not surprisingly, cost. The ever increasing cost of fuel, engine prices, spare parts, maintenance and overhaul, all contribute to the cost of an engine over its entire life cycle. Diagnostics can be viewed as a means to mitigate risk in decisions that impact operational integrity. This can have a profound impact on safety, such as In-Flight Shut Downs (IFSD) for aero applications, (outages for land based applications) and economic impact caused by Unscheduled Engine Removals (UERs), part life, maintenance and overhaul and the overall logistics of maintaining an aircraft fleet or power generation plants.This paper will review some of the methods used in the preceding decades to address these issues, their evolution to current practices and some future trends. While several different monitoring and diagnostic systems will be addressed, the emphasis in this paper will be centered on those dealing with the aero-thermodynamic performance of the engine.© 2013 ASME

The Science, Technology, and Implementation of TiAl Alloys in Commercial Aircraft Engines

Abstract: The present article will describe the science and technology of titanium aluminide (TiAl) alloys and the engineering development of TiAl for commercial aircraft engine applications. The GEnxTM engine is the first commercial aircraft engine that is flying titanium aluminide (alloy 4822) blades and it represents a major advance in propulsion efficiency, realizing a 20% reduction in fuel consumption, a 50% reduction in noise, and an 80% reduction in NOx emissions compared with prior engines in its class. The GEnxTM uses the latest materials and design processes to reduce weight, improve performance, and reduce maintenance costs. GE’s TiAl low-pressure turbine blade production status will be discussed along with the history of implementation. In 2006, GE began to explore near net shape casting as an alternative to the initial overstock conventional gravity casting plus machining approach. To date, more than 40,000 TiAl low-pressure turbine blades have been manufactured for the GEnxTM 1B (Boeing 787) and the GEnxTM 2B (Boeing 747-8) applications. The implementation of TiAl in other GE and non-GE engines will also be discussed.

Mems-Based Satellite Micropropulsion Via Catalyzed Hydrogen Peroxide Decomposition

Abstract: Micro-electromechanical systems (MEMS) techniques offer great potential in satisfying the mission requirements for the next generation of "micro-scale" satellites being designed by NASA and Department of Defense agencies. More commonly referred to as "nanosats", these miniature satellites feature masses in the range of 10-100 kg and therefore have unique propulsion requirements. The propulsion systems must be capable of providing extremely low levels of thrust and impulse while also satisfying stringent demands on size, mass, power consumption and cost. We begin with an overview of micropropulsion requirements and some current MEMS-based strategies being developed to meet these needs. The remainder of the article focuses the progress being made at NASA Goddard Space Flight Center towards the development of a prototype monopropellant MEMS thruster which uses the catalyzed chemical decomposition of high concentration hydrogen peroxide as a propulsion mechanism. The products of decomposition are delivered to a micro-scale converging/diverging supersonic nozzle which produces the thrust vector; the targeted thrust level approximately 500 N with a specific impulse of 140-180 seconds. Macro-scale hydrogen peroxide thrusters have been used for satellite propulsion for decades; however, the implementation of traditional thruster designs on a MEMS scale has uncovered new challenges in fabrication, materials compatibility, and combustion and hydrodynamic modeling. A summary of the achievements of the project to date is given, as is a discussion of remaining challenges and future prospects.

Motors/generators for traction/propulsion applications: A review

Abstract: The growing interest in electrification has led to a growing interest in hybrid/electrical traction applications. Many hybrid/electrical vehicles have been commercially introduced. Various technologies for the traction motors/generators have been developed. The requirements for motors/generators for hybrid/electrical traction applications are very demanding in terms of power density, efficiency, and cost. This article will provide a comprehensive review of the state of the art highlighting the key global trends and tradeoff of various technologies. The article will also discuss future trends and potential areas of research. The article will cover light-duty vehicles (with more focus), medium- and heavy-duty vehicles, off-highway vehicles (OHVs), locomotives, and ship propulsion. The goal of the article is to serve as a comprehensive reference for engineers working in the traction/propulsion area.

A Survey of Intelligent Control and Health Management Technologies for Aircraft Propulsion Systems

Abstract: Intelligent Control and Health Management technology for aircraft propulsion systems is much more developed in the laboratory than in practice. With a renewed emphasis on reducing engine life cycle costs, improving fuel efficiency, increasing durability and life, etc., driven by various government programs, there is a strong push to move these technologies out of the laboratory and onto the engine. This paper describes the existing state of engine control and on-board health management, and surveys some specific technologies under development that will enable an aircraft propulsion system to operate in an intelligent way--defined as self-diagnostic, self-prognostic, self-optimizing, and mission adaptable. These technologies offer the potential for creating extremely safe, highly reliable systems. The technologies will help to enable a level of performance that far exceeds that of today s propulsion systems in terms of reduction of harmful emissions, maximization of fuel efficiency, and minimization of noise, while improving system affordability and safety. Technologies that are discussed include various aspects of propulsion control, diagnostics, prognostics, and their integration. The paper focuses on the improvements that can be achieved through innovative software and algorithms. It concentrates on those areas that do not require significant advances in sensors and actuators to make them achievable, while acknowledging the additional benefit that can be realized when those technologies become available. The paper also discusses issues associated with the introduction of some of the technologies.

Initial Feasibility Assessment of a High Altitude Long Endurance Airship

Abstract: A high altitude solar powered airship provides the ability to carry large payloads to high altitudes and remain on station for extended periods of time. This study examines the feasibility of this concept. Factors such as time of year, latitude, wind speeds and payload are considered in establishing the capabilities of a given size airship. East and West coast operation were evaluated. The key aspect to success of this type of airship is the design and operation of the propulsion and power system. A preliminary propulsion/power system design was produced based on a regenerative fuel cell energy storage system and solar photovoltaic array for energy production. A modular system design was chosen with four independent power/propulsion units utilized by the airship. Results on payload capacity and flight envelope (latitude and time of year) were produced for a range of airship sizes.

An Introduction to Thermodynamic Performance Analysis of Aircraft Gas Turbine Engine Cycles Using the Numerical Propulsion System Simulation Code

Abstract: This document is intended as an introduction to the analysis of gas turbine engine cycles using the Numerical Propulsion System Simulation (NPSS) code. It is assumed that the analyst has a firm understanding of fluid flow, gas dynamics, thermodynamics, and turbomachinery theory. The purpose of this paper is to provide for the novice the information necessary to begin cycle analysis using NPSS. This paper and the annotated example serve as a starting point and by no means cover the entire range of information and experience necessary for engine performance simulation. NPSS syntax is presented but for a more detailed explanation of the code the user is referred to the NPSS User Guide and Reference document (ref. 1).

Advanced high power-density interior permanent magnet motor for traction applications

Abstract: Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis and testing of an advanced interior permanent magnet (IPM) machine that was developed to meet the FreedomCar 2020 specifications. The 12 slot/10 pole machine has segmented stator structure equipped with fractional-slot concentrated-windings (FSCW). The rotor has a novel spoke structure. Several prototypes with different thermal management schemes have been built and tested. The paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes.

Small Hot Jet Acoustic Rig Validation

Abstract: The Small Hot Jet Acoustic Rig (SHJAR), located in the Aeroacoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center in Cleveland, Ohio, was commissioned in 2001 to test jet noise reduction concepts at low technology readiness levels (TRL 1-3) and develop advanced measurement techniques. The first series of tests on the SHJAR were designed to prove its capabilities and establish the quality of the jet noise data produced. Towards this goal, a methodology was employed dividing all noise sources into three categories: background noise, jet noise, and rig noise. Background noise was directly measured. Jet noise and rig noise were separated by using the distance and velocity scaling properties of jet noise. Effectively, any noise source that did not follow these rules of jet noise was labeled as rig noise. This method led to the identification of a high frequency noise source related to the Reynolds number. Experiments using boundary layer treatment and hot wire probes documented this noise source and its removal, allowing clean testing of low Reynolds number jets. Other tests performed characterized the amplitude and frequency of the valve noise, confirmed the location of the acoustic far field, and documented the background noise levels under several conditions. Finally, a full set of baseline data was acquired. This paper contains the methodology and test results used to verify the quality of the SHJAR rig.

Biomimetic Vortex Propulsion: Toward the New Paradigm of Soft Unmanned Underwater Vehicles

Abstract: A soft robot is presented which replicates the ability of cephalopods to travel in the aquatic environment by means of pulsed jet propulsion In this mode of propulsion, a discontinuous stream of fluid is ejected through a nozzle and rolls into a vortex ring The occurrence of the vortex ring at the nozzle-exit plane has been proven to provide an additional thrust to the one generated by a continuous jet A number of authors have experimented with vortex thrusting devices in the form of piston-cylinder chambers and oscillating diaphragms Here, the focus is placed on designing a faithful biomimesis of the structural and functional characteristics of the Octopus vulgaris To do so, the overall shape of this swimming robot is achieved by moulding a silicone cast of an actual octopus, hence offering a credible replica of both the exterior and interior of an octopus mantle chamber The activation cycle relies on the cable-driven contraction/release of the elastic chamber, which drives the fluid through a siphon-like nozzle and eventually provides the suitable thrust for propelling the robot The prototype presented herein demonstrates the fitness of vortex enhanced propulsion in designing soft unmanned underwater vehicles

Electric solar wind sail mass budget model

Abstract: . The electric solar wind sail (E-sail) is a new type of propellantless propulsion system for Solar System transportation, which uses the natural solar wind to produce spacecraft propulsion. The E-sail consists of thin centrifugally stretched tethers that are kept charged by an onboard electron gun and, as such, experience Coulomb drag through the high-speed solar wind plasma stream. This paper discusses a mass breakdown and a performance model for an E-sail spacecraft that hosts a mission-specific payload of prescribed mass. In particular, the model is able to estimate the total spacecraft mass and its propulsive acceleration as a function of various design parameters such as the number of tethers and their length. A number of subsystem masses are calculated assuming existing or near-term E-sail technology. In light of the obtained performance estimates, an E-sail represents a promising propulsion system for a variety of transportation needs in the Solar System.

New Method for Computing Performance of Choked Reacting Flows and Ram-to-Scram Transition

Abstract: An improved method has been developed to compute the thrust of a dual-mode scramjet, which is an engine with a combustor that operates both subsonically and supersonically This strategy applies to any internal flow that can be modeled one-dimensionally To handle the mathematical singularity at the location of thermal choking, the simple Shapiro method is expanded to create a new method that includes finite-rate chemistry and high-temperature gas properties A forward shooting method is employed to find appropriate initial conditions for integration of the governing equations, which results in a unique transonic (choked) condition capable of reaching a supersonic state at the end of the domain Solutions of the governing equations are computed using the propulsion code MASIV, which has been integrated into a hypersonic vehicle flight dynamics code Computations for both ram-mode and scram-mode operations are compared to experimental results Predictions are made for flight conditions of a hypersonic vehi

Advantages of natural propulsive systems

Abstract: The screw propeller has been the mainstay of marine propulsion, but new developments in biomimetic propulsion can provide advantages in terms of speed, maneuverability, efficiency, and stealth. The diversity of aquatic animals provides designs for drag-based paddling and lift-based oscillatory hydrofoils that can be incorporated into engineered propulsive systems for enhanced performance. While the screw propeller will remain the prominent propulsive device, the choice of alternative biomimetic propulsive systems will be dependent on particular applications, where the specifications dictate improved performance criteria.

Frictional-anisotropy-based systems in biology: structural diversity and numerical model.

Abstract: There is a huge variety in biological surfaces covered with micro- and nanostructures oriented at some angle to the supporting surface. Such structures, for example snake skin, burr-covered plant leaves, cleaning devices and many others cause mechanical anisotropy due to different friction or/and mechanical interlocking during sliding in contact with another surface in different directions. Such surfaces serve propulsion generation on the substrate (or within the substrate) for the purpose of locomotion or for transporting items. We have theoretically studied the dependence of anisotropic friction efficiency in these systems on (1) the slope of the surface structures, (2) rigidity of their joints, and (3) sliding speed. Based on the proposed model, we suggest the generalized optimal set of variables for maximizing functional efficiency of anisotropic systems of this type. Finally, we discuss the optimal set of such parameters from the perspective of biological systems.

Modeling and Experimental Characterization of Propulsion of a Spiral-Type Microrobot for Medical Use in Gastrointestinal Tract

Abstract: In this paper, a spiral-type medical robot based on an endoscopic capsule was propelled in a fluidic and tubular environment using electromagnetic actuation. Both modeling and experimental methods have been employed to characterize the propulsion of the robotic capsule. The experiments were performed not only in a simulated environment (vinyl tube filled with silicone oil) but also in a real small intestine. The effects of the spiral parameters including lead, spiral height, the number of spirals, and cross section of the spirals on the propulsion efficiency of the robot are investigated. Based on the transmission efficiency from rotation to translation as well as the balancing of the microrobot in operation, it is demonstrated that the robot with two spirals could provide the best propulsion performance when its lead is slightly smaller than the perimeter of the capsule. As for the spiral height, it is better to use a larger one as long as the intestine's size allows. Based on the simulation and experimental results presented, this study quantifies the influence of the spiral structure on the capsule's propulsion. It provides a helpful reference for the design and optimization of the traction topology of the microrobot navigating inside the mucus-filled small intestine.

High-Speed Turbofan Noise Reduction Using Foam-Metal Liner Over-the-Rotor

Abstract: A Williams International FJ44-3A turbofan engine was used to demonstrate the high-speed fan noise reduction potential of a foam-metal liner installed in close proximity to the fan rotor. The engine was tested in the NASA Glenn Research Center’s Aeroacoustic Propulsion Laboratory. Two foam-metal liner designs were tested and compared to the hardwall baseline. Traditional single degree-of-freedom liner designs were also evaluated to provide a comparison to the state-of-the art design. This report presents the test setup and documents the test conditions. Far-field acoustic levels and limited engine performance results are also presented. The results show that the foam-metal liner achieved up to 5 dB of attenuation in the forward-quadrant radiated-acoustic power levels, which is equivalent to the traditional single degree-of-freedom liner design. Modest changes in engine performance were noted.

Unmanned aircraft and operation method for the same

Abstract: An unmanned aircraft includes a propulsion system having a diesel or kerosene internal combustion engine and a charger device for engine charging. The propulsion system can be a hybrid propulsion system or a parallel hybrid propulsion system.

Electrically powered aerial vehicles and flight control methods

Abstract: An aerial vehicle includes at least one wing, a plurality of thrust producing elements on the at least one wing, a plurality of electric motors equal to the number of thrust producing elements for individually driving each of the thrust producing elements, at least one battery for providing power to the motors, and a flight control system to control the operation of the vehicle The aerial vehicle may include a fuselage configuration to facilitate takeoffs and landings in horizontal, vertical and transient orientations, redundant control and thrust elements to improve reliability and means of controlling the orientation stability of the vehicle in low power and multiple loss of propulsion system situations Method of flying an aerial vehicle includes the variation of the rotational speed of the thrust producing elements to achieve active vehicle control

System, a method and a computer program product for maneuvering of an air vehicle with tiltable propulsion unit

Abstract: A control system configured to control a deceleration process of an air vehicle which comprises at least one tiltable propulsion unit, each of the at least one tiltable propulsion units is tiltable to provide a thrust whose direction is variable at least between a general vertical thrust vector direction and a general longitudinal thrust vector direction with respect to the air vehicle.