A noise and vibration analysis on positive displacement pumps for fluid power application to reduce flow pulsation and cavitation phenomena

The Fluid Power area handles a profound change to achieve the highest efficiency levels requested by the market to compete with other technologies of different fields, like Hybrid-Electric configuration. The noise emission increases its importance in the fluid power field since the other technologies cannot have the same power density, flexibility, and reliability as the Hydraulic. For this reason, hydraulic components, especially positive displacement pumps and motors, are pushing to conform to the dB limits defined by European regulations for working environments (ref. SNSI, Horizon 2020, and Direttiva Macchine 2006/42/CE), both in mobile and indoor applications. The purpose of this research activity is aimed at the optimization of pump geometries using numerical and experimental techniques

Brayton cycle solarized advanced gas turbine

Described is the development of a Brayton Engine/Generator Set for solar thermal to electrical power conversion, authorized under DOE/NASA Contract DEN3-181. The objective was to design, fabricate, assemble, and test a small, hybrid, 20-kW Brayton-engine-powered generator set. The latter, called a power conversion assembly (PCA), is designed to operate with solar energy obtained from a parobolic dish concentrator, 11 meters in diameter, or with fossil energy supplied by burning fuels in a combustor, or by a combination of both (hybrid model). The CPA consists of the Brayton cycle engine, a solar collector, a belt-driven 20-kW generator, and the necessary control systems for automatic operation in solar-only, fuel-only, and hybrid modes to supply electrical power to a utility grid. The original configuration of the generator set used the GTEC Model GTP36-51 gas turbine engine for the PCA prime mover. However, subsequent development of the GTEC Model AGT101 led to its selection as the powersource for the PCA. Performance characteristics of the latter, thermally coupled to a solar collector for operation in the solar mode, are presented. The PCA was successfully demonstrated in the fuel-only mode at the GTEC Phoenix, Arizona, facilities prior to its shipment to Sandia National Laboratory in Albuquerque, New Mexico, for installation and testing on a test bed concentractor (parabolic dish). Considerations relative to Brayton-engine development using the all-ceramic AGT101 when it becomes available, which would satisfy the DOE heat engine efficiency goal of 35 to 41 percent, are also discussed in the report

Optimum design and control of hydraulic systems driven by swash plate pumps using vibration based diagnosis

Swash plate pumps are widely used to drive hydraulic systems, especially because they offer high specific power. In order to improve their performance and make them more reliable, it is necessary to reduce the flow fluctuations, incorporate a control system that is more responsive, and minimize vibration levels. Furthermore, the flow should be controlled according to load requirements and pipe response at the design level. Moreover, there is a need to monitor the health of the system by analysing its vibration signatures. A novel port plate design is used with a pair of deep silencing grooves on the edges of delivery and suction ports, which reduces the flow fluctuations and improves the pump output. In addition to the load information, the pipe dynamics are also used as a control input. Hence, pipe instabilities with different boundary conditions are studied, where simple, accurate and comprehensive expressions to describe the pipe instabilities are produced, solved, and plotted. In swash plate pumps, the control unit changes the pump output according to the load requirements. The current pump design is equipped with a double negative feedback strategy. The inner loop controls the spool position, and the outer loop controls the swash plate angle. Since this design has a high rise time, it was suggested to equip the pump with a single feedback PD controller. Although this reduced the rise time, it introduced high levels of vibration. The present research proposes a new control strategy with a single feedback PID controller that minimizes vibration levels. Results are obtained experimentally. The control strategy is generalized to control the pump flow according to load requirements and pipe vibration levels. A compensation factor is introduced to moderate the negative impact of the pipe vibrations, and to generate a new set value for the inclination angle. For timely detection of faults, the application of wavelet analysis to detect different defects is examined. Some defects are produced, such as pipe flutter, pump dynamic instability, and voltage unbalance in the driving electric motor. Continuous wavelet and discrete wavelet analyses are used to analyze the vibration signature by using Debauches' mother wavelet. The data is collected experimentally. The results show that wavelet analysis is very efficient at identifying defects in the pipe or pump. The results are discussed and appropriate conclusions are drawn based on the present research. Suggestions for future extensions of the research are propose

Evaluation of non-intrusive monitoring for condition based maintenance applications on US Navy propulsion plants

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 107-108).The thesis explores the use of the Non-intrusive Load Monitor (NILM) in Condition Based Maintenance (CBM) applications on US Navy ships as part of the Office of Naval Research Electric Ship Integration (ESI) Initiative. The NILM is a device that measures an electrical component's performance by applying a single voltage and current transducer to a ship's existing power distribution system. The NILM was originally developed to monitor electrical power usage in buildings where it was noticed that it could disaggregate and report the operation of individual loads when many loads were present. The limits of this capability are explored by employing a signal processing script in MATLAB using component data gathered on the USCGC SENECA (WMEC-906). The plausibility of using a few NILMs to provide machinery monitoring information for an entire engineering space, and the resulting opportunity to reduce sensor growth on future Navy ships is explored. Then efforts to monitor naval propulsion plant machinery with the NILM are discussed. Two NILMs were constructed and installed on selected individual components at the Naval Surface Warfare Center Philadelphia DDG-51 Land Based Engineering Site (LBES).(cont.) Monitoring of the Fuel Oil and Low Pressure Air Service Systems was conducted during a week long certification of the pre-commissioning crew of the USS BAINBRIDGE (DDG-96). Data collected was then used to explore the use of the NILM as a diagnostic device for shipboard systems through the evaluation of mechanical transients in the Fuel Oil system and a test leak inserted into the Low Pressure Air System. Additionally, a brief overview of the Multi-function Monitor (MFM), a type of electrical protection equipment installed on many US Navy ships, is provided. The MFM could provide a natural installation point on the ship's power distribution system to monitor a multiple loads. Finally, an evaluation of the NILM as an enabling technology for Navy CBM was conducted. The Integrated Condition Assessment System (ICAS) is the U.S. Navy's "Program of Record" for CBM and is currently installed on over 97 ships fleet wide. NILM data from individual components at the LBES was monitored simultaneously with ICAS and the results are compared.by William C. Greene.S.M

Diesel Engine

Diesel engines, also known as CI engines, possess a wide field of applications as energy converters because of their higher efficiency. However, diesel engines are a major source of NOX and particulate matter (PM) emissions. Because of its importance, five chapters in this book have been devoted to the formulation and control of these pollutants. The world is currently experiencing an oil crisis. Gaseous fuels like natural gas, pure hydrogen gas, biomass-based and coke-based syngas can be considered as alternative fuels for diesel engines. Their combustion and exhaust emissions characteristics are described in this book. Reliable early detection of malfunction and failure of any parts in diesel engines can save the engine from failing completely and save high repair cost. Tools are discussed in this book to detect common failure modes of diesel engine that can detect early signs of failure

Mechanical systems readiness assessment and performance monitoring study

The problem of mechanical devices which lack the real-time readiness assessment and performance monitoring capability required for future space missions is studied. The results of a test program to establish the feasibility of implementing structure borne acoustics, a nondestructive test technique, are described. The program included the monitoring of operational acoustic signatures of five separate mechanical components, each possessing distinct sound characteristics. Acoustic signatures were established for normal operation of each component. Critical failure modes were then inserted into the test components, and faulted acoustic signatures obtained. Predominant features of the sound signature were related back to operational events occurring within the components both for normal and failure mode operations. All of these steps can be automated. The structure borne acoustics technique lends itself to reducing checkout time, simplifying maintenance procedures, and reducing manual involvement in the checkout, operation, maintenance, and fault diagnosis of mechanical systems

NASA Tech Briefs, February 1994

Topics covered include: Test and Measurement; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences; Books and Report

Aeronautical engineering: A continuing bibliography with indexes (supplement 277)

This bibliography lists 467 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1992. Subject coverage includes: the engineering and theoretical aspects of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines); and associated aircraft components, equipment, and systems. It also includes research and development in ground support systems, theoretical and applied aspects of aerodynamics, and general fluid dynamics