Exergetic Analysis of a Cross-Flow Microchannel Heat Exchanger for Bleed Air Cooling in Aircraft Gas Turbine Engines

2014 ◽  
Author(s):  
Matthew B. Rivera ◽  
Randall D. Manteufel
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Heat Exchanger ◽  
Pressure Ratio ◽  
Cross Flow ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Exergy Destruction ◽  
High Pressure Ratio ◽  
Exergetic Analysis

A current issue with high-pressure-ratio compressors found in aircraft engines is the temperature of the air exiting the compressor. The exiting air is used as coolant for engine components found in later stages of the engine such as first-stage turbine blades, and afterburner walls. A viable option for reducing outlet temperature of high-pressure-ratio compressors is to “bleed-off” a fraction of the air which is cooled in a heat exchanger by rejecting heat into the liquid fuel stream and then use the air for cooling critical components downstream. Bleeding off air from the outlet of the compressor has two benefits: (1) air temperature is reduced, and (2) fuel temperature is elevated. Along with reduced air temperatures, the fuel will ultimately receive the heat lost from the air, making the fuel more ideal for combustion purposes. The higher temperature the fuel is received in the combustion process, the greater the work output will be according to the basics of thermodynamic combustion. The objective of this case study is to optimize the efficiency of the cross-flow micro channel heat exchanger, with respect to (1) volume (1.75–2.75 mm3) and heat transfer, and (2) weight (0.15–.25 N) and heat transfer. The optimization of the heat exchanger will be evaluated within the bounds of the 2nd law of thermodynamics (exergy). The only effective way to measure the 2nd law of thermodynamics is through exergy destruction or its equivalent form: entropy generation as a factor of dead state temperature. With relations and equations obtained to design an optimal heat exchanger, applications to high performance aircraft gas turbine engines is considered through exergy. The importance of developing an exergetic analysis for a thermal system is highly effective for identifying area’s within the system that have the path of highest resistance to work potential through various modes of heat transfer and pressure loss. Thus, optimization to reduce exergy destruction is sought after through this design method alongside verifying other heat exchanger methods through effectiveness.

Design Study of an Advanced Concept Simple Gas Turbine for Possible Use in Low Emission Automobiles

1972 ◽  
Author(s):  
H. C. Eatock ◽  
M. D. Stoten
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Simple Cycle ◽  
Turbine Engines ◽  
Nox Emissions ◽  
Preliminary Design ◽  
Gas Turbine Engines ◽  
High Pressure Ratio

United Aircraft Corporation studied the potential costs of various possible gas turbine engines which might be used to reduce automobile exhaust emissions. As part of that study, United Aircraft of Canada undertook the preliminary design and performance analysis of high-pressure-ratio nonregenerated (simple cycle) gas turbine engines. For the first time, high levels of single-stage component efficiency are available extending from a pressure ratio less than 4 up to 10 or 12 to 1. As a result, the study showed that the simple-cycle engine may provide satisfactory running costs with significantly lower manufacturing costs and NOx emissions than a regenerated engine. In this paper some features of the preliminary design of both single-shaft and a free power turbine version of this engine are examined. The major component technology assumptions, in particular the high pressure ratio centrifugal compressor, employed for performance extrapolation are explained and compared with current technology. The potential low NOx emissions of the simple-cycle gas turbine compared to regenerative or recuperative gas turbines is discussed. Finally, some of the problems which might be encountered in using this totally different power plant for the conventional automobile are identified.

scholarly journals Design Methodology for Splittered Axial Compressor Rotors

1990 ◽  
Author(s):  
K.-L. Tzuoo ◽  
S. S. Hingorani ◽  
A. K. Sehra
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Meridional Flow ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Viscous Effects ◽  
High Pressure Ratio ◽  
Rotor Design ◽  
Work Distribution

Recent trend toward lightweight, compact compression systems for advanced aircraft gas turbine engines has created a need for very high pressure ratio fan and compressor stages. One way of achieving pressure ratio in excess of 3:1 in an axial blade row is to introduce splitters (partial vanes) between the principal blades, a concept pioneered by Wennerstrom during early 70s for application in a 3:1 pressure ratio single axial stage. This paper presents an advanced methodology for high pressure ratio splittered rotor design. The methodology centers around combining a meridional flow calculation, an arbitrary meanline blade generation procedure, and 3-D inviscid and viscous analyses. Methods for specifying work distribution, solidity, loss, and deviation distributions, as well as the airfoil generation and splitter vane placement are discussed in detail. Importance of 3-D viscous effects along with results from a 3-D viscous calculation for Wennerstrom’s splittered rotor are also presented.

Effect of Specific Heat Ratio, Impeller Tip Running Clearance, and Compressor Insulation on High-Pressure-Ratio Centrifugal Compressor Modeling

1975 ◽  
Vol 97 (2) ◽  
pp. 174-179
Author(s):  
J. A. Block ◽  
P. W. Runstadler
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Specific Heat ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Specific Heat Ratio ◽  
High Pressure Ratio ◽  
Air Inlet ◽  
Stage Efficiency ◽  
Isentropic Efficiency

Results are displayed which show the effect of gas specific heat ratio, impeller tip running clearance, and compressor insulation on modeling of a high-pressure-ratio compressor’s performance. The data were obtained using a low-speed-of-sound gas and a compressor previously tested extensively in air. Duplication of the air inlet specific heat ratio was found to be essential to modeling the air-equivalent flow rate accurately. Stage pressure ratio and stage efficiency were found to be less sensitive to the accurate replication of the air specific heat ratio. For the compressor tested, stage isentropic efficiency increased as impeller-to-shroud tip running clearance was reduced from 15 to 5 percent of the impeller tip axial depth. The measured stage efficiency was found to depend strongly on the heat transfer between the compressor and surroundings.

scholarly journals On the Application of Variable Camber Blading in Axial Flow Fans and Compressors

1996 ◽  
Author(s):  
U. K. Saha ◽  
B. Roy
Keyword(s):  
Performance Studies ◽  
Pressure Ratio ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
High Pressure Ratio ◽  
Coefficient Distribution ◽  
Wide Range ◽  
Design Power

For land and marine based gas turbine engines, heavy duty industrial axial flow fans and compressors, variable camber tandem blading seems to be an attractive proposition in the pursuit of high pressure ratio machines under design and off-design power settings. In the present investigations, experiments have been carried out in a cascade wind tunnel to explore the variable camber capability of a tandem blade at two extreme camber settings. Aerodynamic performance studies have been made qualitatively on the basis of static pressure coefficient distribution, diffusion factor and mass averaged loss coefficient data. Experimental evidences demonstrate the possible operation of variable camber blading within a wide range of 20° camber variation.

Improvements in Part-Load Efficiency by Reducing Pressure Ratio in Regenerative Gas-Turbine Engines

1985 ◽  
Author(s):  
Theodosios P. Korakianitis ◽  
David Gordon Wilson
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Pressure Ratio ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Design Point ◽  
Part Load ◽  
Compressor Pressure Ratio ◽  
Point Pressure

To obtain equal thermal efficiencies in gas-turbine engines, designers have the freedom (if space and mass constraints are not limiting) of exchanging compressor pressure ratio for heat-exchanger effectiveness. Because heat exchangers can have lower losses than compressors, a high-effectiveness heat-exchanger cycle can have a much higher thermal efficiency (theoretically 55–60%) than is possible with unregenerated cycles. What has not been known up to now is the effect of design-point pressure ratio on the part-load efficiency of gas-turbine engines. The work reported here shows that, for similar turbomachinery technology, design-point and part-load efficiencies improve as the design-point pressure ratio decreases and the heat-exchanger thermal ratio increases.

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