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Ehresman, C. M.

Publications and source records attributed to Ehresman, C. M..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Two and three-dimensional prediffuser combustor studies with air-water mixture

Two- and three-dimensional gas turbine prediffuser-combustor sectors were experimentally studied under a number of mixture and flow conditions in a tunnel operating with a two-phase, air-liquid film-droplet mixture. It is concluded that water vaporization in the combustor causes changes in both local gas temperature and state of vitiation and reduces reaction rates. Substantial accumulation of water and water vapor takes place in pocket over the combustor volume, even when the air-water mixture is steady in time. The accuracy of determining combustor performance changes increases with a better knowledge of the state of the air-water mixture in the primary zone. To establish flame-out conditions it is considered to be necessary to combine the prediction of detailed flowfield and chemical activity with that of flame stability and motion characteristics.

Laing, Peter↗
NASA NTRS1986

Direct and system effects of water ingestion into jet engine compresors

Water ingestion into aircraft-installed jet engines can arise both during take-off and flight through rain storms, resulting in engine operation with nearly saturated air-water droplet mixture flow. Each of the components of the engine and the system as a whole are affected by water ingestion, aero-thermally and mechanically. The greatest effects arise probably in turbo-machinery. Experimental and model-based results (of relevance to 'immediate' aerothermal changes) in compressors have been obtained to show the effects of film formation on material surfaces, centrifugal redistribution of water droplets, and interphase heat and mass transfer. Changes in the compressor performance affect the operation of the other components including the control and hence the system. The effects on the engine as a whole are obtained through engine simulation with specified water ingestion. The interest is in thrust, specific fuel consumption, surge margin and rotational speeds. Finally two significant aspects of performance changes, scalability and controllability, are discussed in terms of characteristic scales and functional relations.

Murthy, S. N. B.↗
NASA NTRS1985

A stagnation pressure probe for droplet-laden air flow

It is often of interest in a droplet-laden gas flow to obtain the stagnation pressure of both the gas phase and the mixture. A flow-decelerating probe (TPF), with separate, purged ports for the gas phase and the mixture and with a bleed for accumulating liquid at the closed end, has been developed. Measurements obtained utilizing the TPF in a nearly isothermal air-water droplet mixture flow in a smooth circular pipe under various conditions of flow velocity, pressure, liquid concentration and droplet size are presented and compared with data obtained under identical conditions with a conventional, gas phase stagnation pressure probe (CSP). The data obtained with the CSP and TPF probes are analyzed to determine the applicability of the two probes in relation to the multi-phase characteristics of the flow and the geometry of the probe.

Murthy, S. N. B.↗
NASA NTRS1983

Effect of humidity on jet engine axial-flow compressor performance

Two problems related to the ingestion of humid air into jet engine axial compressors have been studied: (1) the changes in the performance of the compressor in the absence of condensation and (2) the changes in the entry conditions to the compressor when condensation occurs. Regarding the first, the extent of changes are predicted and also measured in the case of a six-stage compressor operated with air-methane gas mixture utilizing the similarities in the thermodynamic properties between water vapor and methane. For the condensation process in an inlet, a model is described that takes into account the presence of micro particulates and the flow field changes in the vicinity of the inlet wall. Finally, the effects of humidity on engine performance are discussed in relation to engine trim and control schemes.

Ehresman, C. M.↗