scholarly journals Emission Modes in Electrospray Thrusters Operating with High Conductivity Ionic Liquids

Aerospace ◽  
2020 ◽  
Vol 7 (10) ◽  
pp. 141
Author(s):  
Nolan M. Uchizono ◽  
Adam L. Collins ◽  
Anirudh Thuppul ◽  
Peter L. Wright ◽  
Daniel Q. Eckhardt ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Steady State ◽  
High Speed ◽  
Liquid Propellant ◽  
Long Distance ◽  
Flow Rates ◽  
Extraction Voltage ◽  
Wide Range ◽  
Emission Behavior ◽  
Definition Of

Electrospray thruster life and mission performance are strongly influenced by grid impingement, the extent of which can be correlated with emission modes that occur at steady-state extraction voltages, and thruster command transients. Most notably, we experimentally observed skewed cone-jet emission during steady-state electrospray thruster operation, which leads to the definition of an additional grid impingement mechanism that we termed “tilted emission”. Long distance microscopy was used in conjunction with high speed videography to observe the emission site of an electrospray thruster operating with an ionic liquid propellant (EMI-Im). During steady-state thruster operation, no unsteady electrohydrodynamic emission modes were observed, though the conical meniscus exhibited steady off-axis tilt of up to 15°. Cone tilt angle was independent over a wide range of flow rates but proved strongly dependent on extraction voltage. For the geometry and propellant used, the optimal extraction voltage was near 1.6 kV. A second experiment characterized transient emission behavior by observing startup and shutdown of the thruster via flow or voltage. Three of the four possible startup and shutdown procedures transition to quiescence within ∼475 μs, with no observed unsteady modes. However, during voltage-induced thruster startup, unsteady electrohydrodynamic modes were observed.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Experimental Investigation Of Detailed Structure Of Gas-Liquid Flow In Rectangular Microchannel

2016 ◽  
Vol 11 (1) ◽  
pp. 73-79
Author(s):  
German Bartkus ◽  
German Bartkus ◽  
Vladimir Kuznetsov ◽  
Vladimir Kuznetsov
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Detailed Structure ◽  
Rectangular Microchannel ◽  
Flow Rates ◽  
Wide Range ◽  
Gas Liquid Flow ◽  
Vertical Microchannel

The detailed structure of upward gas-liquid flow of water and nitrogen in a vertical microchannel with a rectangular cross-section 420 × 280 µm was experimentally investigated. The experiments were conducted using the methods of high-speed video and laser-induced fluorescence. In a wide range of flow rates the characteristic regimes of the gas-liquid flow were defined, velocity of elongated bubbles and the local thickness of the liquid film were measured. The dependence of the local film thickness on the capillary number was determined and it was found that the Taylor Law for rectangular channel is not fully implemented due to the deformation of the interface and the contraction of the liquid into the corners of the channel by capillary force.

scholarly journals Improved evaluation of granular media flows using an X-ray scanning compatible cone-plate setup

2021 ◽  
Vol 249 ◽  
pp. 03020
Author(s):  
Zohreh Farmani ◽  
Jing Wang ◽  
Ralf Stannarius ◽  
Martina Bieberle ◽  
Frank Barthel ◽  
...  
Keyword(s):  
Granular Materials ◽  
High Speed ◽  
Granular Media ◽  
Flow Behavior ◽  
Three Dimensional ◽  
High Speed Imaging ◽  
Flow Measurements ◽  
Flow Rates ◽  
X Ray ◽  
Wide Range

To understand the typically heterogeneous flowing behavior of granular materials, it is important to combine flow tests with three-dimensional imaging. To probe the flow behavior of granular materials over a wide range of flow rates, it is imperative to be able to impose such flow rates in a well controlled manner while performing imaging tests that are compatible with all imposed flow rates. Achieving both flow control and bulk imaging capacity is challenging for a number of reasons. Here, we describe the design of a setup in which we are able to do imaging while imposing a constant overall shear rate on a granular material. We characterize the setup in which flow tests will be performed, which consists of a bottom-driven cone-plate or double-cone design. We show that the setup can be integrated in x-ray microtomography devices to aid particle tracking based flow measurements. The design is also compatible with typical rheometer setups. We also perform high speed imaging of a granular flow in an ultra-fast x-ray scanner, for which we provide proof-of-principle data in a simplified shear setup. The designed flow geometry is also compatible with said high speed imaging facility, where particle image velocimetry can be employed to extract quantitative flow field data.

scholarly journals LQR state feedback controller with precompensator for magnetic levitation system

2021 ◽  
Vol 2111 (1) ◽  
pp. 012004
Author(s):  
A Winursito ◽  
G N P Pratama
Keyword(s):  
Steady State ◽  
High Speed ◽  
State Feedback ◽  
Magnetic Levitation ◽  
Feedback Controller ◽  
Steel Ball ◽  
State Feedback Controller ◽  
Wide Range ◽  
Levitation System ◽  
Magnetic Levitation System

Abstract Magnetic levitation system (MLS) is a nonlinear system that attracts the attention of many researchers, especially control engineers. It has wide range of application such as robotics, high-speed transportation, and many more. Unfortunately, it is not a simple task to control it. Here, we utilize state feedback controller with Linear-Quadratic Regulator (LQR) to regulate the position of a steel-ball in MLS. In addition, we also introduce the precompensator to nullify the steady-state errors. The linearized model, controller, and precompensator are simulated using Matlab. The results and simulation verify that the state feedback controller and precompensator succeed to stabilize the position of steel-ball at the equilibrium for 0.1766 seconds and no steady-state errors.

Initial tool wear behavior in high-speed turning of Inconel 718

2020 ◽  
Vol 44 (3) ◽  
pp. 395-404
Author(s):  
Morvarid Memarianpour ◽  
Seyed Ali Niknam ◽  
Sylvain Turenne ◽  
Marek Balazinski
Keyword(s):  
Steady State ◽  
Tool Wear ◽  
Inconel 718 ◽  
High Speed ◽  
Wear Behavior ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Industrial Applications ◽  
Wide Range ◽  
Tool Wear Mechanism

Three distinctive regions of tool wear, known as initial wear, steady-state wear, and accelerated wear, are well understood. However, the effects of cutting parameters on the initial tool wear mechanism, morphology, and size have received less attention as compared to the other two regions. Knowing that adequate control of initial tool wear may lead to extended tool life, in particular in hard-to-cut metals such as superalloys, this topic has become a source of attention. Amongst superalloys, Inconel 718 is considered as one of the most difficult to cut materials, which has a wide range of industrial applications. This study intends to evaluate the effects of cutting parameters on initial tool wear, as well as tool wear progression, when turning Inconel 718. Therefore, microstructural evaluation of the initial tool wear mode under various cutting conditions, as well as tool wear measurements, were conducted. It was observed that certain elements of the workpieces were migrated to the insert flank face. This is evidence of adhesion at the initial moments of the cutting process. In contrast to many other easy-to-cut materials, the steady-state wear period when turning Inconel 718 is significantly short under a higher level of cutting speed and feed rate.

scholarly journals Comparative Study of High-Speed Passenger Rail Deployment in Megaregion Corridors: Current Experiences and Future Opportunities

2011 ◽  
Author(s):  
Sevara Melibaeva ◽  
Joseph Sussman ◽  
Travis P. Dunn
Keyword(s):  
High Speed ◽  
Long Distance ◽  
High Speed Rail ◽  
Passenger Rail ◽  
International Experiences ◽  
Wide Range ◽  
The Us ◽  
The World ◽  
The Impact ◽  
Rail Service

Deployment of high-speed passenger rail services has occurred around the world in densely-populated corridors, often with the effect of either creating or enhancing a unified economic “megaregion” agglomeration. This paper will review the technical characteristics of a variety of megaregion corridors, including Japan (Tokyo-Osaka), France (Paris-Lyon), and Germany (Frankfurt-Cologne), and their economic impacts. There are many lessons to be drawn from the deployment and ongoing operation of high-speed passenger rail service in these corridors for other countries now considering similar projects, such as the US and parts of the European Union. First, we will review three international cases, describing the physical development of each corridor as well as its measured impacts on economic development. In each case, the travel time reductions of the high-speed service transformed the economic boundaries of the urban agglomerations, integrating labor and consumer markets, while often simultaneously raising concerns about the balance of growth within the region. Moreover, high-speed travel within the regions has had important implications for the modes and patterns of travel beyond the region, particularly with respect to long-distance air travel. An example is the code-shared rail-air service between DeutscheBahn and Lufthansa in the Frankfurt-Cologne corridor. Next, we will examine the implications of these international experiences for high-speed rail deployment elsewhere in the world, particularly the US and Portugal, one of the EU countries investing in high-speed rail. Issues considered include the suitability of high-speed passenger rail service in existing megaregions as well as the potential for formation of megaregions in other corridors. By understanding the impact of high-speed passenger service on economic growth, labor markets, urban form, and the regional distribution of economic activity, planners can better anticipate and prepare countermeasures for any negative effects of high-speed rail. Examples of countermeasures include complementary investments in urban and regional transit connections and cooperation with airlines and other transportation service operators. High-speed passenger rail represents a substantial investment whose implementation and ultimate success depends on a wide range of factors. Among them is the ability of planners and decision-makers to make a strong case for the sharing of benefits across a broad geography, both within and beyond the megaregion (and potential megaregion) corridors where service is most likely to be provided. This paper provides some useful lessons based on international experiences.

Estimating Maintenance Costs for Mixed Higher Speed Passenger and Freight Rail Corridors

2010 ◽  
Author(s):  
Allan M. Zarembski ◽  
Pradeep Patel
Keyword(s):  
Steady State ◽  
High Speed ◽  
Maintenance Costs ◽  
Track Maintenance ◽  
Passenger Traffic ◽  
Passenger Rail ◽  
Mixed Use ◽  
Wide Range ◽  
Infrastructure Maintenance ◽  
The Cost

In order to reduce the cost of new intercity passenger rail corridors, the operation of higher speed passenger networks on existing freight corridors is being examined and considered. The issues to be addressed in such operations include the one-time upgrade of the track to allow for this higher speed passenger traffic and the ongoing maintenance costs necessary to maintain this track for the mixed higher speed passenger and freight operations. This latter issue is usually addressed in the access agreements for the corridor, and must include how these costs are to be shared. A recent US Federal Railroad Administration study specifically addressed the issue of “steady state” maintenance costs for mixed use corridors consisting on this class of higher speed passenger operations and concurrent freight operations, to include heavy axle load freight operations. The result of that study was a “planner’s handbook” for estimating these track maintenance costs, as part of the overall analysis of the feasibility and cost of operating higher speed passenger traffic on existing freight corridors. This paper presents the methodology used in the development of the methodology for estimating maintenance costs for mixed higher speed passenger and freight rail corridors (Classes 4, 5 and 6). Specifically, it addresses the estimation of these “steady state” infrastructure maintenance costs for a range of operating scenarios with different combination of passenger and freight traffic densities and operating speeds. These infrastructure costs include track, bridge and building (B&B), and communications and signal (C&S) costs. The resulting costs are presented as a set of cost matrices both in terms of a total cost per track mile and in terms of cost per passenger train mile. The cost matrices cover a range of combinations of traffic and track configuration, with minimum and maximum costs developed for each cell in the cost matrices. The minimum costs are based on maintenance standards geared to typical Class I freight railroad practice, such as where passenger trains currently operate on a freight railroad right of way, while the maximum costs reflect maintenance practices on existing high speed railroad track. This paper provides a description of the analytic models used to generate the costs, and the process by which those models were calibrated to actual cost data to develop costs for a wide range of traffic and track combinations. Sample application of the methodology to include several proposed mixed use corridors is also presented.

Numerical and Experimental Analysis of Flow Phenomena in a Centrifugal Pump Operating Under Low Flow Rates

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Yanxia Fu ◽  
Jianping Yuan ◽  
Shouqi Yuan ◽  
Giovanni Pace ◽  
Luca d'Agostino ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Internal Flow ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Low Flow ◽  
Flow Rates ◽  
Wide Range

The characteristics of flow instabilities as well as the cavitation phenomenon in a centrifugal pump operating at low flow rates were studied by experimental and numerical means, respectively. Specially, a three-dimensional (3D) numerical model of cavitation was applied to simulate the internal flow through the pump and suitably long portions of the inlet and outlet ducts. As expected, cavitation proved to occur over a wide range of low flow rates, producing a characteristic creeping shape of the head-drop curve and developing in the form of nonaxisymmetric cavities. As expected, the occurrence of these cavities, attached to the blade suction sides, was found to depend on the pump's flow coefficient and cavitation number. The experiments focused on the flow visualization of the internal flow patterns by means of high-speed digital movies and in the analysis of the inlet pressure pulsations near the impeller eye by means of fast response pressure transducers. The experimental results showed that the unsteady behavior of the internal flow in the centrifugal pump operating at low flow rates has the characteristics of a peculiar low-frequency oscillation. Meanwhile, under certain conditions, the low-frequency pressure fluctuations were closely correlated to the flow instabilities induced by the occurrence of cavitation phenomena at low flow rates. Finally, the hydraulic performances of the centrifugal pump predicted by numerical simulations were in good agreement with the corresponding experimental data.

scholarly journals Athlete Monitoring in Rugby Union: Is Heterogeneity in Data Capture Holding Us Back?

Sports ◽  
2019 ◽  
Vol 7 (5) ◽  
pp. 98 ◽  
Author(s):  
Stephen W. West ◽  
Sean Williams ◽  
Simon P. T. Kemp ◽  
Matthew J. Cross ◽  
Keith A. Stokes
Keyword(s):  
High Speed ◽  
Injury Risk ◽  
New Technologies ◽  
Rugby Union ◽  
Central Component ◽  
Significant Heterogeneity ◽  
Athlete Monitoring ◽  
Monitoring Tools ◽  
Wide Range ◽  
Definition Of

In an effort to combat growing demands on players, athlete monitoring has become a central component of professional sport. Despite the introduction of new technologies for athlete monitoring, little is understood about the practices employed in professional rugby clubs. A questionnaire was circulated amongst conditioning staff across the 12 Premiership rugby clubs to capture the methods used, relative importance, perceived effectiveness and barriers to the use of multiple different athlete monitoring measurements. Previous injury, Global Positioning System (GPS) metrics, collision counts and age were deemed the most important risk factors for managing future injury risk. A wide range of GPS metrics are collected across clubs with high-speed running (12/12 clubs), distance in speed zones (12/12 clubs) and total distance (11/12 clubs) the most commonly used. Of the metrics collected, high-speed running was deemed the most important for managing future injury risk (5/12 clubs); however, there was considerable variation between clubs as to the exact definition of high-speed running, with both absolute and relative measures utilised. While the use of such monitoring tools is undertaken to improve athlete welfare by minimising injury risk, this study demonstrates the significant heterogeneity of systems and methods used by clubs for GPS capture. This study therefore questions whether more needs to be done to align practices within the sport to improve athlete welfare.

scholarly journals High Speed Curving Performance of Rail Vehicles

2015 ◽  
Author(s):  
Brian Marquis ◽  
Robert Greif
Keyword(s):  
Steady State ◽  
High Speed ◽  
Field Testing ◽  
Contact Forces ◽  
Track Geometry ◽  
Safety Standards ◽  
Rail Vehicles ◽  
Wide Range ◽  
Final Rule ◽  
Curving Performance

On March 13, 2013, the Federal Railroad Administration (FRA) published a final rule titled “Vehicle/Track Interaction Safety Standards; High-Speed and High Cant Deficiency Operations” which amended the Track Safety Standards (49 CFR Part213) and the Passenger Equipment Safety Standards (49 CFR Part 238) in order to promote VTI safety under a variety of conditions at speeds up to 220 mph [1]. Among its main accomplishments, the final rule facilitates the expansion of higher speed passenger rail by revising the standards governing permissible operating speed in curves, allowing for higher cant deficiencies in all FRA Track Classes. To ensure safety is not diminished, the FRA Track Safety Standards require railroads to maintain their tracks to stricter track geometry standards whenever they operate at these higher curving speeds and cant deficiencies. These revisions were based on studies that examined the dynamic curving performance of various representative rail vehicles. This research investigates the steady-state curving performance of truck designs while traversing curves at various curving speeds and cant deficiencies. During steady-state curve negotiation, the axles of trucks generally offset laterally from the track centerline and develop angles of attack increasing the wheel-rail contact forces. Large lateral forces can develop, particularly in flange contact, resulting in increased wheel and rail wear, track panel shift, and the risk of derailment. Depending on the truck design, such forces become larger at higher cant deficiency. An understanding of the steady-state response of a rail vehicle in a curve is essential as it represents a significant part of the total dynamic response. The curving performance of an idealized rigid truck is analyzed using nonlinear analytical methods for a wide range of operating speeds and unbalance conditions. Emphasis is placed on higher speed curving and the results are used to interpret trends observed during recent field testing with Amtrak’s Acela High-Speed Trainset on the Northeast Corridor.

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