Active Blade Vibration Control Being Developed and Tested

Gas turbine engines are currently being designed to have increased performance, lower weight and manufacturing costs, and higher reliability. Consequently, turbomachinery components, such as turbine and compressor blades, have designs that are susceptible to new vibration problems and eventual in-service failure due to high-cycle fatigue. To address this problem, researchers at the NASA Glenn Research Center are developing and testing innovative active blade vibration control concepts. Preliminary results of using an active blade vibration control system, involving a rotor supported by an active magnetic bearing in Glenn's Dynamic Spin Rig, indicate promising results (see the photograph). Active blade vibration control was achieved using feedback of blade strain gauge signals within the magnetic bearing control loop. The vibration amplitude was reduced substantially (see the graphs). Also, vibration amplitude amplification was demonstrated; this could be used to enhance structural mode identification, if desired. These results were for a nonrotating two-bladed disk. Tests for rotating blades are planned. Current and future active blade vibration control research is planned to use a fully magnetically suspended rotor and smart materials. For the fully magnetically suspended rotor work, three magnetic bearings (two radial and one axial) will be used as actuators instead of one magnetic bearing. This will allow additional degrees of freedom to be used for control. For the smart materials work, control effectors located on and off the blade will be considered. Piezoelectric materials will be considered for on-the-blade actuation, and actuator placement on a stator vane, or other nearby structure, will be investigated for off-the-blade actuation. Initial work will focus on determining the feasibility of these methods by performing basic analysis and simple experiments involving feedback control

Plastic Curtain Wall Use for Barn Venting

Barn ventilation systems using gravity (natural) airflow that enters through wall openings and goes out top ridge vents have been used a long time in swine, dairy, beef, and poultry barns (Figure 1). A comparatively new development is to use a plastic curtain, adjustable up and down, for the full height and length of each wall, particularly in dairy barns. This ventilation system is being adapted in northern states after many years use in poultry barns in the southeastern United States

Power Requirements Determined for High-Power-Density Electric Motors for Electric Aircraft Propulsion

Future advanced aircraft fueled by hydrogen are being developed to use electric drive systems instead of gas turbine engines for propulsion. Current conventional electric motor power densities cannot match those of today s gas turbine aircraft engines. However, if significant technological advances could be made in high-power-density motor development, the benefits of an electric propulsion system, such as the reduction of harmful emissions, could be realized

Magnetic Suspension for Dynamic Spin Rig

NASA Lewis Research Center's Dynamic Spin Rig, located in Building 5, Test Cell CW-18, is used to test turbomachinery blades and components by rotating them in a vacuum chamber. A team from Lewis' Machine Dynamics Branch successfully integrated a magnetic bearing and control system into the Dynamic Spin Rig. The magnetic bearing worked very well both to support and shake the shaft. It was demonstrated that the magnetic bearing can transmit more vibrational energy into the shaft and excite some blade modes to larger amplitudes than the existing electromagnetic shakers can

A Magnetic Suspension and Excitation System for Spin Vibration Testing of Turbomachinery Blades

The Dynamic Spin Rig (DSR) is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. A heteropolar radial active magnetic bearing was integrated into the DSR to provide non-contact magnetic suspension and mechanical excitation of the rotor to induce turbomachinery blade vibrations. The magnetic bearing replaces one of the two existing conventional radial ball bearings. Prior operation of the DSR used two voice-coil type linear electromagnetic shakers which provided axial excitation of the rotor. The new magnetic suspension and excitation system has provided enhanced testing capabilities. Tests were performed at high rotational speeds for longer duration and higher vibration amplitudes. Some characteristics of the system include magnetic bearing stiffness values up to 60,000 lb./in., closed loop control bandwidth around 500 Hz, and multi-directional radial excitation of the rotor. This paper reports on the implementation and operation of this system and presents some test results using this system

Adaptive Variable Bias Magnetic Bearing Control

Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. With the existence of the bias current, even in no load conditions, there is always some power consumption. In aerospace applications, power consumption becomes an important concern. In response to this concern, an alternative magnetic bearing control method, called Adaptive Variable Bias Control (AVBC), has been developed and its performance examined. The AVBC operates primarily as a proportional-derivative controller with a relatively slow, bias current dependent, time-varying gain. The AVBC is shown to reduce electrical power loss, be nominally stable, and provide control performance similar to conventional bias control. Analytical, computer simulation, and experimental results are presented in this paper

TRANSFORMING THE BUILT ENVIRONMENT IN CUMBERLAND COUNTY, NORTH CAROLINA: THE CREATION OF AN ACCOUNTABLE CARE COMMUNITY TO REDUCE ASTHMA-RELATED EMERGENCY DEPARTMENT USE AND HOSPITALIZATIONS IN BLACK CHILDREN AGE BIRTH TO FIVE YEARS

Social determinants of health are the conditions where people are born, live, work, worship and play that affects their overall health and wellbeing. The built environment is a social determinant that includes housing, transportation, safety, greenspace, pollutants, and overall geographical environment. In Cumberland County, NC, the built environment within the county, specifically poor-quality housing, disproportionately impacts the rate of asthma-related emergency department (ED) visits and hospitalizations, disproportionately affecting Black children from birth to five. To address this inequity, we proposed the formation of an Accountable Care Community (ACC). The goal of the ACC is to provide funding for the implementation of the Community Asthma Initiative program and passing a mandatory annual building inspection policy. Both interventions will identify and remove asthma triggers to improve the county’s built environment and reduce asthma-related ED visits and hospitalizations for children from birth to five by 40% over a five-year period.Master of Public Healt

Locating the intense interstellar scattering towards the inner Galaxy

We use VLBA+VLA observations to measure the sizes of the scatter-broadened images of 6 of the most heavily scattered known pulsars: 3 within the Galactic Centre (GC) and 3 elsewhere in the inner Galactic plane. By combining the measured sizes with temporal pulse broadening data from the literature and using the thin-screen approximation, we locate the scattering medium along the line of sight to these 6 pulsars. At least two scattering screens are needed to explain the observations of the GC sample. We show that the screen inferred by previous observations of SGR J1745-2900 and Sgr A*, which must be located far from the GC, falls off in strength on scales < 0.2 degree. A second scattering component closer to (< 2 kpc) or even (tentatively) within (< 700 pc) the GC produces most or all of the temporal broadening observed in the other GC pulsars. Outside the GC, the scattering locations for all three pulsars are ~2 kpc from Earth, consistent with the distance of the Carina-Sagittarius or Scutum spiral arm. For each object the 3D scattering origin coincides with a known HII region (and in one case also a supernova remnant), suggesting that such objects preferentially cause the intense interstellar scattering seen towards the Galactic plane. We show that the HII regions should contribute > 25% of the total dispersion measure (DM) towards these pulsars, and calculate reduced DM distances. Those distances for other pulsars lying behind HII regions may be similarly overestimated.Comment: 16 pages, 10 figures, MNRAS, in pres

Context matters: influence of organizational, environmental, and social factors on civic environmental stewardship group intensity

Civic environmental stewardship groups actively take care of their local environment and are known to work in urban contexts. Research on the geographies of this urban environmental stewardship is young. Understanding where stewardship groups work and the associated organizational and neighborhood contexts advances the understanding of the environmental outcomes of stewardship efforts. We examine the organizational, socioeconomic, and environmental contexts associated with the number of stewardship groups at the Census block group and neighborhood scales for four diverse U.S. cities (Baltimore, MD; Chicago, IL; New York, NY; and Seattle, WA). We found relatively consistent and strong relationships with both average professionalization (staff and budget index) and diversity of groups’ focus and the number of groups’ activity areas in a block group or neighborhood, suggesting a potential density dependence effect. Overall, the number of stewardship groups correlates with social and environmental aspects at both scales across all cities, but variation across cities for specific variables indicates the need for further analyses to unpack why we observe these different patterns across cities. Strong relationships with organizational factors suggest future directions for stewardship research and that the organizational landscape may affect how many groups work in a place more than socioeconomic or environmental conditions