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

Predictions of Flow Separation at the Valve Seat for Steady-State Port-Flow Simulation

[+] Author and Article Information
Tao Fang

Department of Mechanical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15213
e-mail: taof@andrew.cmu.edu

Satbir Singh

Department of Mechanical Engineering,
Carnegie Mellon University,
Pittsburgh, PA 15213
e-mail: satbirs@andrew.cmu.edu

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 22, 2015; final manuscript received April 6, 2015; published online May 27, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(11), 111512 (Nov 01, 2015) (7 pages) Paper No: GTP-15-1104; doi: 10.1115/1.4030501 History: Received March 22, 2015; Revised April 06, 2015; Online May 27, 2015

Steady-state port-flow simulations with static valve lift are often utilized to optimize the performance of intake system of an internal combustion engine. Generally, increase in valve lift results in higher mass flow rate through the valve. But in certain cases, mass flow rate can actually decrease with increased valve lift, caused by separation of turbulent flow at the valve seat. Prediction of this phenomenon using computational fluid dynamics (CFD) models is not trivial. It is found that the computational mesh significantly influences the simulation results. A series of steady-state port-flow simulations are carried out using a commercial CFD code. Several mesh topologies are applied for the simulations. The predicted results are compared with available experimental data from flow bench measurements. It is found that the flow separation and reduction in mass flow rate with increased valve lift can be predicted when high mesh density is used in the proximity of the valve seat and the walls of the intake port. Higher mesh density also gives better predictions of mass flow rate compared to the experiments, but only for high valve lifts. For low valve lifts, the error in predicted flow rate is close to 13%.

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Fig. 1

Flow bench geometry

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Fig. 2

Mesh topology and refinement strategy (using boundary embedding zone A)

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Fig. 3

Mass flow rate versus iteration number

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Fig. 4

Mass flow rate for different valve lifts for the mesh topology shown in Fig. 2

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Fig. 5

Velocity distribution (m/s) at the valve seat and clip position for the mesh topology shown in Fig. 2. (a) Seat cut plane velocity field and (b) seat cut plane position.

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Fig. 6

Velocity distribution at vertical cut plane and the clip position for the mesh topology shown in Fig. 2. (a) Vertical cut plane velocity field and (b) vertical cut plane position.

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Fig. 7

Mesh distribution for valve-aligned mesh

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Fig. 8

Mass flow rate for different valve lifts with nonrotated (Fig. 2) and valve-aligned (Fig. 7) models

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Fig. 9

Mass flow rate when using higher embedding level (level 5) in the port

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Fig. 10

Mesh distribution for longer boundary embedding in the port. (a) Embedding zone B (BE-B) and (b) embedding zone C (BE-C).

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Fig. 11

Mass flow rate when using level 5 embedding for BE-B and BE-C in the port

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Fig. 12

Velocity distribution at valve seat for BE-B (Fig. 10(a)) with embedding level 5

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Fig. 13

Velocity distribution at the wall for valve lift of 17 mm with BE-B (Fig. 10(a)) embedding level 5

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Fig. 14

Velocity distribution at separation zone for BE-A and BE-B using embedding levels 3 and 5




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