Research Papers

Humidity Effects on Experimental Compressor Performance—Corrected Conditions for Real Gases

[+] Author and Article Information
Reid A. Berdanier

Purdue University,
500 Allison Road,
West Lafayette, IN 47907
e-mail: rberdani@purdue.edu

Natalie R. Smith

Purdue University,
500 Allison Road,
West Lafayette, IN 47907
e-mail: smith773@purdue.edu

John C. Fabian

Purdue University,
500 Allison Road,
West Lafayette, IN 47907
e-mail: fabian@purdue.edu

Nicole L. Key

Associate Professor
Purdue University,
500 Allison Road,
West Lafayette, IN 47907
e-mail: nkey@purdue.edu

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 28, 2014; final manuscript received August 13, 2014; published online October 7, 2014. Editor: Ronald Bunker.

J. Turbomach 137(3), 031011 (Oct 07, 2014) (10 pages) Paper No: TURBO-14-1185; doi: 10.1115/1.4028356 History: Received July 28, 2014; Revised August 13, 2014

The effects of humid air on the performance of a multistage research compressor and new methods of humidity accounting to ensure appropriate representation of performance parameters are investigated in this paper. Turbomachinery textbooks present methods of correcting speed and mass flow rate using perfect gas assumptions, but these methods can reduce the ability to achieve repeatable compressor performance when using unconditioned air in a climate where absolute humidity may vary. Instead, a new method is introduced, which models humid air as a real gas and circumvents the need for assumptions in the correction process. In the area of compressor research, the ability to measure small changes in performance parameters and ensure repeatable results is essential. Errors of more than 0.5% can result from using perfect gas assumptions to calculate corrected speed, which can lead to misrepresented performance parameters beyond the uncertainty of the measurements. Multiplicative correction factors based on analytical data are also introduced as an alternate method of applying the new real-gas method, and these correction factors are compared to those derived by previous authors applying ideal gas methods for humidity accounting. This is the first time in open literature that experimental results for a component of a gas turbine engine are presented comparing a humid air correction method with traditional correction methods.

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Fig. 1

Effect of humidity on corrected conditions as a function of inlet weather conditions. (a) Effect on calculated mechanical speed as lines of constant percent difference given by Eq. (12). (b) Effect on actual mass flow rate as lines of constant percent difference given by Eq. (13).

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Fig. 2

Correction factors to incorporate humidity effects with corrected conditions. (a) Mechanical speed. (b) Mass flow rate.

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Fig. 3

Purdue three-stage axial compressor research facility

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Fig. 4

Locations of measurement planes

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Fig. 5

Compressor speedlines using different correction methods

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Fig. 7

Corrected mass flow rate error for dry air as a perfect gas with and without the application of a correction factor, CFm·

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Fig. 8

Speedline featuring fan law scaling procedure

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Fig. 9

Effects of major research areas on compressor performance compared to humidity effects [29-33]

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Fig. 6

Isentropic efficiency calculated using humid air and dry air methods



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