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

The Interactions of In-Cylinder Flow and Fuel Spray in a Gasoline Direct Injection Engine With Variable Tumble

[+] Author and Article Information
Xianhui Zhang

State Key Laboratory of Engines,
Tianjin University,
Weijin Road 92,
Tianjin City 300072, China
e-mail: zhangxianh@tju.edu.cn

Tianyou Wang

State Key Laboratory of Engines,
Tianjin University,
Weijin Road 92,
Tianjin City 300072, China
e-mail: wangtianyou@tju.edu.cn

Ming Jia

School of Energy and Power Engineering,
Dalian University of Technology,
Dalian City 116024, China
e-mail: jm2020jm@gmail.com

Wei Li

State Key Laboratory of Engines,
Tianjin University,
Weijin Road 92,
Tianjin City 300072, China
e-mail: Liwei1@tju.edu.cn

Lei Cui

State Key Laboratory of Engines,
Tianjin University,
Weijin Road 92,
Tianjin City 300072, China
e-mail: cuilei@tju.edu.cn

Xigang Zhang

State Key Laboratory of Engines,
Tianjin University,
Weijin Road 92,
Tianjin City 300072, China
e-mail: xigang@tju.edu.cn

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 November 1, 2014; final manuscript received November 10, 2014; published online January 7, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(7), 071507 (Jul 01, 2015) (11 pages) Paper No: GTP-14-1603; doi: 10.1115/1.4029208 History: Received November 01, 2014; Revised November 10, 2014; Online January 07, 2015

Particle image velocimetry (PIV) system was used to measure the tumble structure of the in-cylinder airflow in a four-valve optical gasoline direct injection (GDI) engine. The tumble ratio was controlled by a flap in the manifold and a baffle in the intake port. With proper orthogonal decomposition (POD) method, the velocity field was decomposed into four parts, i.e., the mean, coherent, transitional, and turbulent. The effect of tumble motion on the cycle-to-cycle variation (CCV) of airflow and spray was investigated by calculating the shear strain vorticity. The results indicate that the flow structure can be effectively changed through the combination of flap and baffle by forming a single large-scale tumble flow with the tumble ratio three times higher than the original one. According to POD analysis, it is revealed that the large-scale strong tumble motion leads to the energy occupation ratio of the mean part greatly increase by up to 30%, while the energy transferred to the coherent part is reduced. The above process also decreases the CCV of the coherent part by 50%; thus, the CCV of the whole airflow in the cylinder can be suppressed. A single large-scale tumble increases the maximum shear strain rate up to 2400 s−1. Meanwhile, the maximum vorticity increases to about 6000 s−1 by rolling up of the airflow. The contact area between spray droplets and air becomes larger, and the momentum exchanges between them contribute to wider sprays cone angle and shorter penetration distance when the flap is closed. The statistics of the measurements illustrate that a single large-scale tumble can promote the formation of homogeneous mixture and reduce the fluctuation between multicycles.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Schematic of the optical engine setup and the PIV system for tumble measurements

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Fig. 2

Schematic of the positions of intake and exhaust valves, the visual window range, and the measured middle plane

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Fig. 3

Configurations of the variable tumble system

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Fig. 4

The cutoff mode determination of the mean subfield in the central plane P1 for case P1. (a) Standard deviation of the first three modes. (b) Correlation of fields with adjacent mode numbers over all cycles.

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Fig. 5

Correlation between the reconstruction fields with adjacent modes numbers in central plane for case P1 (a) coherent flow field and (b) turbulent flow field.

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Fig. 6

Tumble intensities as the valve lift under steady flow condition

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Fig. 7

The averaged velocity distributions of 100 cycles on the vertical symmetric plane

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Fig. 8

Evolution of the energy distributions of the four subfields

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Fig. 9

Standard deviations of the temporal coefficients of the four part flow fields

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Fig. 10

Tumble ratio as a function of crank angle at different engine speeds

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Fig. 11

The shear strain rate distributions of sprays

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Fig. 12

The averaged velocity distributions of 60 cycles at 91.5 °CA ATDC without spray (1.6 ms ASOI, 1200 rev/min)

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Fig. 13

The vorticity distributions of sprays

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Fig. 14

The maximum velocity relative to injection duration

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Fig. 15

The spray distribution at intake stroke (a) 1.0msASOI and (b) 1.6msASOI

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Fig. 16

The statistic of entropy in accordance with the crank degrees

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Fig. 17

The averaged velocity distributions on the vertical symmetric plane without spray (at 180 °CA ATDC,1200 rev/min)

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