This paper provides a physical interpretation of the mechanism of stagnation enthalpy and stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of stagnation enthalpy for that particle. These include absolute stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle instantaneously at that point.

References

References
1.
Kerrebrock
,
J. L.
, 1974, “
Unsteady Flows in Jet Engines,
Project Squid Workshop, United Technologies Research Center
.
2.
Horlock
,
J. H.
, 1966,
Axial Flow Turbines: Fluid Mechanics and Thermodynamics
,
Butterworth and Company, Ltd.
,
London
(reprinted 1973, Robert E. Krieger Publishing Co., New York).
3.
Cumpsty
,
N. A.
, 1989,
Compressor Aerodynamics
,
Longman Group, UK Ltd.
,
London
(reprinted 2004, Robert E. Kreiger Publishing Co., New York).
4.
Kerrebrock
,
J. L.
, 1992,
Aircraft Engines and Gas Turbines
,
MIT Press
,
Cambridge, MA
.
5.
Dean
,
R. C.
, 1959, “
On the Necessity of Unsteady Flow in Fluid Machines
,”
ASME J. Basic Eng.
,
81
, pp.
24
28
.
6.
Preston
,
J. H.
, 1961, “
The Non-Steady Irrotational Flow of an Inviscid, Incompressible Fluid, with Special Reference to Changes in Total Pressure through Flow Machines
”,
Aeronaut. Q.
,
12
, pp.
343
360
.
7.
Horlock
,
J. H.
, and
Daneshyar
,
H.
, 1971, “
Stagnation Pressure Changes in Unsteady Flow
,”
Aeronaut. Q.
,
22
, pp.
207
224
.
8.
Greitzer
,
E. M.
,
Tan
,
C. S.
, and
Graf
,
M. B.
, 2004,
Internal Flow: Concepts and Applications
,
Cambridge University Press
,
Cambridge
.
9.
Smith
,
L. H.
, 1966, “
Wake Dispersion in Turbomachines
,”
ASME J. Basic Eng.
,
88D
, pp.
688
690
.
10.
Thorpe
,
S. J.
,
Miller
,
R. W.
,
Yoshino
,
S.
,
Ainsworth
,
R. W.
, and
Harvery
,
N. W.
, 2005, “
The Effect of Work Processes on the Casing Heat Transfer of a Transonic Turbine
,” ASME Paper No. GT2005-68437.
11.
Hodson
,
H. P.
, and
Dawes
,
W. N.
, 1998, “
On the Interpretation of Measured Profile Losses in Unsteady Wake Turbine Blade Interaction Studies
,”
ASME J. Turbomach.
,
120
, pp.
276
284
.
12.
Meyer
,
R. X.
, 1958, “
The Effect of Wakes on the Transient Pressure and Velocity Distributions in Turbomachines
,”
ASME J. Basic Eng.
,
80
, pp.
1544
1552
.
13.
Smith
,
L. H.
, 1958, “
Recovery Ratio-A Measure of the Loss Recovery Potential of Compressor Stages
,”
ASME Trans.
,
80
, pp.
517
524
.
14.
Smith
,
L. H.
, 1993, “
Wake Ingestion Propulsion Benefit
,”
J. Propul. Power
,
9
, pp.
74
82
.
15.
Valkov
,
T.
, and
Tan
,
C. S.
, 1999, “
Effects of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1 – Framework of Technical Approach and Rotor Wake-Stator Blade Interactions; Part 2 – Rotor Tip Vortex/Streamwise Vortex-Stator Blade Interactions
,”
ASME J. Turbomach.
,
121
(
3
), pp.
377
397
.
16.
Van Zante
,
D. E.
,
Adamczyk
,
J. J.
,
Strazisar
,
A. J.
, and
Okiishi
,
T. H.
, 2002, “
Wake Recovery Performance Benefit in a High-Speed Axial Compressor
,”
ASME J. Turbomach.
,
124
, pp.
275
284
.
17.
Rose
,
M.
,2009, personal communication.
18.
Smith
,
L.H.
, 2009, personal communication.
19.
Kurosaka
,
M.
,
Gertz
,
J. B.
,
Graham
,
J. E.
,
Goodman
,
J. R.
,
Sundaram
,
P.
,
Riner
,
W. C.
,
Kuroda
,
H.
, and
Hankey
,
W. L.
, 1987, “
Energy Separation in a Vortex Street
,”
J. Fluid Mech.
,
178
, pp.
1
29
.
20.
Nolan
,
S. P. R. N.
,
Botros
,
B. B.
,
Tan
,
C. S.
,
Adamczyk
,
J. J.
, and
Gorrell
,
S. E.
, 2008, “
Effects of Upstream Wake Phasing on Transonic Axial Compressor Performance
,” ASME J. Turbomach. 133, 021010 (2011).
21.
Symon
,
K. R.
, 1971,
Mechanics
,
3rd
ed.,
Addison-Wesley Publishers
,
Reading, MA
.
22.
Batchelor
,
G. K.
, 1967,
An Introduction to Fluid Dynamics
,
Cambridge University Press
,
Cambridge
.
23.
Baierlein
,
R.
, 1983,
Newtonian Dynamics
,
McGraw-Hill Book Company
,
NY
.
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