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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Assessment of Cavitation Models for Flows in Diesel Injectors With Single- and Two-Fluid Approaches

[+] Author and Article Information
Kaushik Saha

Department of Mechanical and
Mechatronics Engineering,
University of Waterloo,
Waterloo, ON N2L 3G1, Canada
e-mail: kaushik.sahaju@gmail.com

Xianguo Li

Department of Mechanical and
Mechatronics Engineering,
University of Waterloo,
Waterloo, ON N2L 3G1, Canada
e-mail: xianguo.li@uwaterloo.ca

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 7, 2015; final manuscript received July 31, 2015; published online August 25, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(1), 011504 (Aug 25, 2015) (11 pages) Paper No: GTP-15-1239; doi: 10.1115/1.4031224 History: Received July 07, 2015; Revised July 31, 2015

Several recent cavitation models for the analysis of two-phase flows in diesel injectors with single- and two-fluid modeling approaches have been evaluated, including the Saha–Abu-Ramandan–Li (SAL), Schnerr–Sauer (SS), and Zwart–Gerber–Belamri (ZGB) models. The SAL model is a single-fluid model, while the other two models have been implemented with both single- and two-fluid approaches. Numerical predictions are compared with experimental results available in literature, qualitatively with experimental images of two-phase flow in an optically accessible nozzle, and quantitatively with measured mass flow rates and velocity profiles. It is found that at low injection pressure differentials there can be considerable discrepancy in the predictions of the vapor distribution from the three models considered. This discrepancy is reduced as the injection pressure differential is increased. Implementation of the SS and ZGB models with single- and two- fluid approaches yields noticeable differences in the results because of the relative velocity between the two phases, with two-fluid approach providing better agreement with experimental results. The performance of the SS and ZGB models implemented with the two-fluid approach is comparable with the SAL single-fluid model, but with significantly more computational time. Overall, the SAL single-fluid model performs comparatively better with respect to the other two models.

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References

Figures

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Fig. 1

Computational domain consisting of a section before the nozzle, the nozzle itself, and a section after the nozzle. For rectangular cross section, d is the width of the nozzle and for circular cross section d is the diameter of the nozzle.

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Fig. 2

Nozzle section of the mesh used in comparison with the experiment [7]

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Fig. 3

Experimental images for three different cases: Pin = 10.0 MPa and Pout = 4.0 MPa, 2.5 MPa and 2.0 MPa [7]

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Fig. 4

Comparison of the vapor volume fraction contours from the three different cavitation models with the single-fluid approach, for three different pressure differentials (ΔP = Pin − Pout): Pin = 10.0 MPa and Pout = 4.0 MPa, 2.5 MPa, and 2.0 MPa at the steady state. (The maximum vapor volume fraction is abbreviated as Max VVF. The same color scheme is used as in the experimental images.)

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Fig. 5

Comparison of the predicted mass flow rates from the three cavitation models using the single- and two-fluid approaches at different pressure differentials (ΔP = Pin − Pout) with the experimental values [7] (the curves for the SS model two-fluid approach and ZGB single-fluid approach overlap in the figure). Comparison of the predicted mass flow rates from the three cavitation models using the single- and two-fluid approaches at different pressure differentials (ΔP = Pin − Pout) with the experimental values [7]. (The curves for the SS model two-fluid approach and the ZGB single-fluid approach overlap in the figure).

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Fig. 6

Comparison of the predicted velocity profiles from the three cavitation models using the single- and two-fluid approaches, at the pressure differential of ΔP ( = Pin − Pout) = 8.5 MPa with the experimental values measured at a location, 53 μm from the nozzle inlet section [7]

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Fig. 7

Comparison of the vapor volume fraction contours using the single- and two-fluid approaches for the ZGB model [20], at the injection pressure differential of 8.0 MPa. (The maximum vapor volume fraction is abbreviated as Max VVF. All the two-fluid results are at 0.5 ms.)

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Fig. 8

Comparison of the residuals for the PC-SIMPLE and multiphase coupled solution methods when used with the two-fluid approach coupled with the ZGB model [20], at the injection pressure differential of 8.0 MPa for Winklhofer nozzle [7]

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Fig. 9

The mesh used for the present cavitation analysis for the axisymmetric nozzle

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Fig. 10

Comparison of the vapor volume fraction contours at the steady state for the axisymmetric nozzle for the three different cavitation models with the single-fluid approach, at the inlet pressures of 15 and 50 MPa and fixed outlet pressure of 5 MPa. (The maximum vapor volume fraction is abbreviated as Max VVF.)

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Fig. 11

Comparison of the vapor volume fraction contours for the axisymmetric nozzle for the ZGB model coupled with the single- and two-fluid approaches at the inlet pressure of 100 MPa and fixed outlet pressure of 5 MPa. (The maximum vapor volume fraction is abbreviated as Max VVF. All the two-fluid results are at 0.5 ms.)

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Fig. 12

Comparison of the liquid volume fraction profiles at the nozzle exit of the axisymmetric nozzle for the three cavitation models coupled with the single-fluid approach at the inlet pressure of 50 MPa and fixed outlet pressure of 5 MPa

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