Extension of Crocco's Theorems to Flows Having Non-Uniform Stagnation Enthalpy

1948 ◽  
Vol 73 (2) ◽  
pp. 186-186 ◽  
Author(s):  
R. C. Prim
Keyword(s):  
Stagnation Enthalpy

scholarly journals A Physical Interpretation of Stagnation Pressure and Enthalpy Changes in Unsteady Flow

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
H. P. Hodson ◽  
T. P. Hynes ◽  
E. M. Greitzer ◽  
C. S. Tan
Keyword(s):  
Unsteady Flow ◽  
Physical Interpretation ◽  
Body Force ◽  
Static Pressure ◽  
Stagnation Pressure ◽  
Fluid Particle ◽  
Stagnation Temperature ◽  
Tip Leakage Flow ◽  
Enthalpy Changes ◽  
Stagnation Enthalpy

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.

A Physical Interpretation of Stagnation Pressure and Enthalpy Changes in Unsteady Flow

2009 ◽  
Author(s):  
H. P. Hodson ◽  
T. P. Hynes ◽  
E. M. Greitzer ◽  
C. S. Tan
Keyword(s):  
Unsteady Flow ◽  
Physical Interpretation ◽  
Body Force ◽  
Static Pressure ◽  
Stagnation Pressure ◽  
Fluid Particle ◽  
Stagnation Temperature ◽  
Tip Leakage Flow ◽  
Enthalpy Changes ◽  
Stagnation Enthalpy

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, the influence on mixing losses of turbine wake behavior in 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 at that point.

Test Time in a 1.5-Inch-Diameter High-Stagnation-Enthalpy Shock Tube

AIAA Journal ◽  
1963 ◽  
Vol 1 (5) ◽  
pp. 1236-1237
Author(s):  
V. A. SANDBORN ◽  
H. WEISBLATT ◽  
R. F. FLAGG
Keyword(s):  
Shock Tube ◽  
Test Time ◽  
Stagnation Enthalpy

scholarly journals Analysis of Fan Stage Conceptual Design Attributes for Boundary Layer Ingestion

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
D. K. Hall ◽  
E. M. Greitzer ◽  
C. S. Tan
Keyword(s):  
Boundary Layer ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Design Flow ◽  
Surface Geometry ◽  
Local Flow ◽  
Performance Loss ◽  
Inlet Distortion ◽  
Design Attributes ◽  
Stagnation Enthalpy

This paper describes a new conceptual framework for three-dimensional turbomachinery flow analysis and its use to assess fan stage attributes for mitigating adverse effects of inlet distortion due to boundary layer ingestion (BLI). A nonaxisymmetric throughflow analysis has been developed to define fan flow with inlet distortion. The turbomachinery is modeled using momentum and energy source distributions that are determined as a function of local flow conditions and specified blade camber surface geometry. Comparison with higher-fidelity computational and experimental results shows the analysis captures the principal flow redistribution and distortion transfer effects associated with BLI. Distortion response is assessed for a range of (i) design flow and stagnation enthalpy rise coefficients, (ii) rotor spanwise work profiles, (iii) rotor–stator spacings, and (iv) nonaxisymmetric stator geometries. Of the approaches examined, nonaxisymmetric stator geometry and increased stage flow and stagnation enthalpy rise coefficients provide the greatest reductions in rotor flow nonuniformity, and may offer the most potential for mitigating performance loss due to BLI inlet distortion.

Paper 26: The Concurrent Measurement of Momentum and Stagnation Enthalpy in a High-Quality Wet Steam Flow

1967 ◽  
Vol 182 (8) ◽  
pp. 250-257 ◽  
Author(s):  
D. J. Ryley ◽  
G. A. Kirkman
Keyword(s):  
Capillary Tube ◽  
Total Momentum ◽  
Momentum Balance ◽  
Maximum Diameter ◽  
Wet Steam ◽  
High Quality ◽  
Sampling Probe ◽  
In Series ◽  
Wet Steam Flow ◽  
Stagnation Enthalpy

This paper describes the problems encountered in the design, operation, and calibration of a small momentum balance fitted within an isokinetic sampling probe located in the test section of a wet steam ‘wind’ tunnel. The probe is suitable for use in air, dry steam, or wet steam. It has an opening of ½ in diameter, a maximum diameter of 1¼ in, and a length of 4½ in, and will detect momentum forces greater than 0·001 lbf. The signal is transmitted by causing the impulse cage to compress a bellows. Turpentine enclosed therein raises the level of its meniscus in a capillary tube and the change in level is observed with a micrometer microscope. An electrical superheating calorimeter is employed in series with the impulse-measuring probe to determine the stagnation enthalpy of the sample. Results are reported for air and steam. For steam the ranges of the respective variables are: pressure, 20–25 inHg vacuum; velocity, 200–500 ft/s; and wetness, 0–10 per cent by weight. Owing to the small size of the momentum cage it was not possible to isolate the contribution to the total momentum made by the entrained liquid.

Metering of Steam-Water Two-Phase Flow by Sharp-Edged Orifices

1965 ◽  
Vol 180 (1) ◽  
pp. 549-572 ◽  
Author(s):  
Russell James
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Critical Flow ◽  
Water Mixture ◽  
Two Phase ◽  
In Series ◽  
Trial And Error Method ◽  
Error Method ◽  
Stagnation Enthalpy

This paper describes work conducted on the passage of steam-water mixtures through standard sharp-edged orifices for the prediction of flow conditions. When the stagnation enthalpy or alternatively the dryness fraction at the orifice is known, it is shown that the mass flow rate can be approximately determined. For the case where a steam-water mixture passes through a pipeline to the atmosphere or to a low-pressure receiver so that critical flow occurs at the outlet, both the mass flow rate and the stagnation enthalpy may be approximately evaluated using an orifice meter in series with a pressure tapping located at the point of critical flow. In this case, a trial-and-error method is necessary. The experimental results were within a range of dryness fractions from 1 per cent to 56 per cent, orifice pressures from 75 to 275 lb/in2 abs., differentials from 15 to 780 mmHg under water and flow rates from 54 700 to 508 000 lb/h. Orifices of 5.591 and 6.615 in diameter were installed in 7.9-in diameter pipes which were equipped with radius ( D and D/2) taps. The method employs a correlation between the homogeneous dryness fraction x, and a corrected dryness fraction x m necessary for evaluating the two-phase density used in the conventional single-phase meter equation.

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