Fluid and Machinery Dynamics

The Institute's fluid and machinery dynamics program encompasses machinery and piping technology, structural dynamics, acoustics, multiphase/multicomponent flow, microgravity fluid dynamics, fluid/thermal systems diagnostics, and computational fluid dynamics. Investigations cover a wide spectrum, including such diverse activities as the development of space fluid systems, research with gas industry consortia on advanced technology, and solving noise and vibration problems for automotive manufacturers and other industries.

The Gas Research Institute's (GRI) Metering Research Facility (MRF) is located at the Institute and operated by Institute engineers, scientists, and technicians. This year, activities have focused on developing data aimed at revising gas industry standards for orifice flow meters and gas pipeline sampling methods as well as developing a new industry standard for ultrasonic flow meters. Research at the facility is being funded primarily by the GRI, with additional funding provided by the American Petroleum Institute, the U.S. Department of Energy, and individual gas companies. The MRF also provides services for prototype testing and flow meter calibration for meter manufacturers and end users. The Institute is also active in multiphase flow metering technology development and evaluation. Current work involves wet gas metering research for a major oil company and manufacturing and technology support for a multiphase, oil/gas/water meter manufacturer. In addition, SwRI provides technical training to gas industry personnel involved in flow measurement and offers field service support for diagnosis and analysis of flow-related problems at pipeline meter stations.

Accurate metering of natural gas remains an industry-wide concern. To better understand the problems associated with liquid entrained in natural gas pipelines, SwRI engineers determined the flow meter measurement accuracy for different amounts of liquid in the pipeline. A clear model of an orifice meter was fabricated so that liquid flow to the meter could be observed.

The Institute first developed piping acoustic simulation techniques for the Pipeline and Compressor Research Council (PCRC) in 1952. Since that time, SwRI has designed more than 6,000 compressor, pump, and piping systems in the PCRC Design Facility. Recently, the Institute added digital control and data acquisition to the Design Facility's compressor and piping design model. Whereas previous technology used single-screen photographs from oscilloscopes, digital files now can be viewed in various formats to allow for better analysis by the piping designer, providing quick and consistent model calibration and rapid data acquisition and storage.

Compressor operation represents the largest single cost item for the natural gas transmission industry - more than $1.5 billion annually - and is a promising target for cost control using advanced technology. With funding from PRC International and the GRI, Institute engineers are studying operations, maintenance, and fuel use by the industry as well as the cost and quality impacts of decisions related to equipment operations and purchases.

SwRI is pioneering efforts to apply sophisticated, risk-based maintenance decision analysis to address problems encountered by the natural gas industry. The first application of this methodology assists pipeline engineers in deciding whether specific reciprocating compressor foundations should undergo rebuilding or repair. The methodology uses available measurement and nondestructive evaluation (NDE) techniques to gather information about compressor foundation block condition. Statistical techniques yield reasonable estimates of damage that cannot be seen or easily detected. Probability of failure projections then are used to drive an economic model to calculate the optimum timing for repairs based on maximum net present value to the company. The methodology provides a rigorous decision analysis framework for maintenance decisions that previously have relied on individual experience.

WEBMAP^TM for Windows^TM, a new software program developed for the PCRC, assists in the analysis and interpretation of compressor crankshaft alignments. The software analyzes web deflections and crankshaft geometry to determine bearing misalignment and the resulting deformed crankshaft shape. The results are presented in tabular and graphical formats including a special three-dimensional image that permits the deformed crankshaft to be magnified and rotated for viewing from any angle. Users of the software can determine when, and to what extent, compressor realignment is needed. Analysis provided by the program is proving invaluable for sustaining compressor reliability.

The ongoing restructuring of the natural gas pipeline industry has increased the demand for specialized engineering and field services to the industry. Institute engineers are solving difficult problems in gas flow measurement, machinery vibration and alignment, structural assessment, machine and process performance measurement, piping system acoustic excitation, and turbo-machinery installation and operation. Using a multidisciplinary approach that emphasizes total problem solution, the Institute is satisfying this need by developing new field data acquisition systems, analytical tools, and battery-powered, field-portable instrumentation. This hardware and software can be transported easily and operated reliably worldwide, with the capability to monitor data on-site or remotely.

Sand and other formation solids can cause serious fouling or erosion in downhole and surface oil and gas production equipment. Sand control screens commonly are placed at the bottom of oil and gas wells to remove sand from the production fluids. To be effective, the screens must be resistant to plugging and erosion. A multi-client project has been initiated at SwRI to investigate mechanisms that cause screen erosion. The program will ascertain the downhole conditions that cause erosion and compare the erosion resistance of several different sand screen designs. Laboratory tests are being conducted on sample and full-size screens to determine the parameters that control erosion rates. Results will provide industry with data necessary for proper design of reliable sand screens.

The Liquid Motion Experiment (LME), a spaceflight experiment under development at the Institute for many years, was flown aboard the space shuttle Atlantis during its May 1997 flight. Atlantis astronauts conducted a variety of tests using the LME, with the help of ground personnel from the Institute and NASA's Lewis Research Center. Ten hours of test data were acquired in the weightless environment of space. Tests were designed to investigate the characteristics of liquid motions in the propellant tanks of spinning, nutating spacecraft. These liquid motions, which can cause the spinning spacecraft to become unstable, have been an unresolved problem since the first communication satellites were launched in the early 1970s. Experimental results will provide information and analytical models that will allow corrective actions to be taken by manufacturers in the design phase of a spacecraft to prevent liquid motion problems in flight, increasing the orbital lifetime of spacecraft and preventing instabilities.

An innovative compression mass gauge, built to determine the volume of cryogenic liquids remaining in spacecraft tanks during conditions of weightlessness, was designed jointly by NASA and SwRI, and a laboratory-scale model was constructed for and evaluated by NASA. As a result of these evaluations and further developments by the Institute, the gauge has been tentatively selected for use in NASA's upgrade of the space shuttle orbital maneuvering system (OMS). Additionally, SwRI is currently engaged in several projects for NASA to develop a prototype flight demonstration gauge for testing as part of NASA's Cryogenic Liquid Acquisition, Storage, and Supply experiment (CLASS). The CLASS flight experiment is a joint project between NASA's Johnson Space Center, Lewis Research Center, and Marshall Space Flight Center, the Institute, and several aerospace prime contractors. CLASS will demonstrate and validate the advanced technologies needed for the OMS upgrade.

A NASA mission specialist operates SwRI's Liquid Motion Experiment onboard the May 1997 flight of the space shuttle Atlantis. Results from the experiment will help designers better understand how liquid propellants behave in spinning satellites and improve the performance, reliability, and lifetime of such spacecraft.

The Institute is actively supporting NASA's initiative to decrease the cost of launching spacecraft. For the X-33 launch vehicle, a single-stage-to-orbit reusable rocket being developed by a consortium led by Lockheed Martin, SwRI is designing flexible baffles and other tank internals to control the slosh dynamics of the liquid oxygen and liquid hydrogen propellants in the X-33's unique double-lobe, teardrop-shaped tanks. The Institute is also assisting in design verification. For the X-34 vehicle, a smaller rocket that is launched from a large airplane, SwRI is assisting the prime contractor, Orbital Sciences, Inc., to develop a variety of flow control valves to ensure the correct flow of propellants through tank compartments during thrusting and to prevent back-flow if the rocket engines are shut down prematurely. In addition, the Institute is a member of several prime contractor teams developing a series of very low-cost, lightweight launch vehicles and boosters collectively known as the NASA Bantam System Technology.

SwRI is assisting the U.S. Air Force in solving bearing reliability problems. Failure of flight-critical bearings in aircraft accessory devices can result in the loss of electrical and hydraulic power in an aircraft, with subsequent catastrophic consequences. Manufacturing and lubricant quality are essential to adequate bearing service life. An SwRI design team has helped redesign and modernize a bearing testing device that applies realistic torque, thermal, electrical, and hydraulic loads simulating actual in-flight conditions for the bearings as mounted in their accessory drive. Groups of new and used bearings that are part of the T-38 aircraft airframe-mounted accessory drive have been analyzed and tested to determine failure modes as a function of manufacturing and lubricant quality.

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