Development of Fluid-Curtain Sealing Technology to Improve the Efficiency and Operational Flexibility of Large Power Generation Turbines

Fluidic curtain sealing has recently been shown to offer significantly reduced leakage in rotating turbomachinery seals. The seal type uses an additional flow injected into the leakage path to reduce some existing leakage flow. Shrouded steam turbine tip seals were the focus of research in this thesis, but the seal has potential applications in blade tip seals, stator root seals, shaft seals, and end gland seals in steam turbines as well as in gas turbines. The implementation of such a seal may be simplified in the case of gas turbines since secondary flows of air are already built into the machine to provide cooling flows to high temperature components. The fluidic curtain seal is especially effective when a combination of fluidic curtain and a conventional labyrinth seal is used, and the research presented will generally feature a fluidic curtain placed upstream of a labyrinth fin type restriction. The new addition to knowledge on fluidic curtain sealing described in this work is in characterising seal performance in terms of its design parameters. Better characterisation of the seal allows the development of a set of realistic design rules to specify how fluidic curtains may be applied to the design of new, high performance turbomachinery seals. Two main advances in characterising fluidic curtain seals resulted from the research. The first advance was to numerically and experimentally test basic geometric parameters and their influence on performance to identify design rules which maximize the performance gain of incorporating a fluidic curtain. A series of fundamental dimensionless geometric ratios were proposed and the design space created by these parameters was explored and validated experimentally using a simple annular test rig. CFD was then used to demonstrate that it is possible to incorporate a high performance design into a labyrinth seal independent of the existing labyrinth seal geometry. The second advance is to explore the effect of swirl velocity at the leakage channel inlet on overall seal performance. This was first achieved using CFD to model the selected realistic tip seal design with different levels of inlet swirl. This CFD study was then validated by building the design in a rotating annular test rig where the inlet swirl velocity was controlled. The research findings resulted in a proposed design process for new fluidic curtain seals (Section 8.2) which considers; the geometry of an existing seal, fluid conditions in the leakage path and elsewhere in the turbine stage, rotational speed, and minimum allowable physical clearances

A cumulative index to Aeronautical Engineering: A special bibliography, January 1976

This publication is a cumulative index to the abstracts contained in NASA SP-7037 (54) through NASA SP-7037 (65) of Aeronautical Engineering: A Special Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, contract, and report number indexes

Aeronautical engineering: A continuing bibliography with indexes (supplement 257)

This bibliography lists 560 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Space programs summary no. 37-45, volume IV FOR the period April 1, 1967 to May 31, 1967. Supporting research and advanced development

Space exploration projects on systems, guidance and control, environmental simulation, space sciences, propulsion, telecommunications, and engineering mechanic

Mixture preparation of gaseous fuels for internal combustion engines using optical diagnostics

The flow and mixing behaviour of high pressure directly injected fuel is important in the study of spark-ignition engines owing to its strong influence on the combustion process. This in turn governs emissions and power generation, which are important considerations in contemporary vehicle design. Whilst liquid fuel delivery has and continues to be a topic of detailed research, there is a deficit in the understanding of gaseous fuel delivery. Three topics remain largely neglected for high pressure CNG fuel injection in spark-ignition engines: i. the targeting and dispersion behaviour of the gaseous fuel jet, ii. the transient jet behaviour near the nozzle exit region (“nearfield”) and iii. the effects of the jets on the in-cylinder flow and turbulence. Using optical diagnostics that include schlieren high-speed imaging and particle image velocimetry (PIV), this work addresses the knowledge deficit. The investigation primarily covers jets issued from a direct injector for gaseous fuels that was constructed in-house. A constant volume chamber was employed to replicate engine-like conditions quiescently, allowing isolation of the injection delivery phenomena. For topic i, jet targeting behaviour was characterised by axial and radial penetration, spread angle and projected area. The targeting profile of a freestream jet is in good agreement with previously established density normalised incompressible jet relationhips. Additionally, empirical correlation is provided between the jet dispersion and pressure ratio (8.3 < PR < 400) for conditions when the jet impinges on the cylinder boundaries. For topic ii, the injector needle lift profile was found to be a dominant factor in controlling nearfield compressible and incompressible flow structures. The presence of the needle was shown to reduce the Mach disc location downstream of the nozzle by ~45%, at steady-state conditions. Moreover, in transient conditions the Mach disc location and diameter are shown to correlate strongly with the needle lift profile. The high-resolution characterisation of the compressible is important for stratified engine operation where a slightly mistimed jet may result in misfire due to the large velocities across the spark-plug electrode In relation to topic iii, PIV was used to capture the flow velocity in two key regions: the air in the nearfield and the ignition zone where a spark plug would be conventionally placed. The rate of air entrainment into the jet is shown to be proportional to the fuel delivery rate and to steadily increase with increasing delivery time aSOI. Spatially, the nearfield entrainment coefficient, K’2, is shown to remain constant at a mean value of K’2 = 0.123. Moreover, the displacement of air caused from the impinging induced jet vortices is shown to feed air into the nearfield entrainment region. Consequently, for the highest PR experiments (PR320 and 400) the nearfield entrainment coefficient, K’2, is shown to increase ~65%, relative to the lower PR experiments. Ignition region turbulent kinetic energy levels induced by the impinging jet are conducive to good flame propagation where mean values (0.5-19 m2/s2) are similar to those created by typical air induction bulk-flow. Mean flow velocities are also within an acceptable spark plug ignition range (1.8-21.0 m/s). Both flow properties are shown to be heavily influenced by the proximity of the jet boundary. As a result of the ignition and nearfield region measurements, a clear understanding of the transient nearfield processes has been developed to help one design appropriate fuel delivery and combustion strategies

The Fifth Annual Thermal and Fluids Analysis Workshop

The Fifth Annual Thermal and Fluids Analysis Workshop was held at the Ohio Aerospace Institute, Brook Park, Ohio, cosponsored by NASA Lewis Research Center and the Ohio Aerospace Institute, 16-20 Aug. 1993. The workshop consisted of classes, vendor demonstrations, and paper sessions. The classes and vendor demonstrations provided participants with the information on widely used tools for thermal and fluid analysis. The paper sessions provided a forum for the exchange of information and ideas among thermal and fluids analysts. Paper topics included advances and uses of established thermal and fluids computer codes (such as SINDA and TRASYS) as well as unique modeling techniques and applications

Aeronautical engineering: A continuing bibliography with indexes (supplement 284)

This bibliography lists 974 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1992. The coverage includes documents on design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems. It also includes research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles

Aeronautical engineering: A special bibliography with indexes, supplement 34

This special bibliography lists 462 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1973