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Internal Combustion Engines

The Effect of Intake Valve Deactivation on Lean Stratified Charge Combustion at an Idling Condition of a Spark Ignition Direct Injection Engine

[+] Author and Article Information
Ronald O. Grover, Edward R. Masters, Paul M. Najt

 General Motors R&D, Warren, MI 48090

Junseok Chang1

 General Motors R&D, Warren, MI 48090

Aditya Singh2

 General Motors Technical Center India, Bangalore 560066, India

1

Currently affiliated with Saudi Aramco R&D.

2

Currently affiliated with Shell India.

J. Eng. Gas Turbines Power 134(9), 092804 (Jul 23, 2012) (11 pages) doi:10.1115/1.4006711 History: Received November 20, 2011; Revised February 28, 2012; Published July 23, 2012; Online July 23, 2012

A combined experimental and analytical study was carried out to understand the improvement in combustion performance of a four-valve spark ignition direct injection (SIDI) wall-guided engine operating at lean, stratified idle with enhanced in-cylinder charge motion by deactivating one of the two intake valves. A fully warmed-up engine was operated at low speed, light load by injecting the fuel from a pressure-swirl injector during the compression stroke to produce a stratified fuel cloud surrounding the spark plug at the time of ignition. Steady state flow-bench measurements and computational fluid dynamics (CFD) calculations showed that valve deactivation primarily increased the in-cylinder swirl intensity as compared with opening both intake valves. Engine dynamometer measurements showed an increase in charge motion led to improved combustion stability, increased combustion efficiency, lower fuel consumption, and higher dilution tolerance. A CFD study was conducted using in-house models of spray and combustion to simulate the engine operating with and without valve deactivation. The computations demonstrated that the improved combustion was primarily driven by higher laminar flame speeds through enhanced mixing of internal residual gases, better containment of the fuel cloud within the piston bowl, and higher postflame diffusion burn rates during the initial, main, and late stages of the combustion process, respectively.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the (a) piston and (b) targeting of swirl injector relative to the combustion system

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Figure 2

Steady state flow rig measurement of swirl and tumble index with and without valve deactivation

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Figure 3

Emissions index of (a) unburned hydrocarbons (EIHC) and (b) carbon monoxide (EICO) as a function of air fuel ratio with and without intake valve deactivation

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Figure 4

Fuel consumption reduction contour of lean stratified idle with respect to COV of IMEP and EINOx design constraint for (a) both intake valves open and (b) one intake valve deactivated

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Figure 5

Hexahedral computational meshes for the (a) gas exchange and (b) injection and combustion processes

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Figure 6

Valve profile for CFD calculations (solid lines) relative to the parked position (dotted lines) where the exhaust valve opens at 126 CA deg and closes at 420 CA deg and the intake valve opens at 315 CA deg and closes at 610 CA deg

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Figure 7

Comparison of in-cylinder flow structures comparing the effect of valve deactivation on the mean velocity field

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Figure 8

Distribution of residual gases as predicted by the CFD gas exchange calculation

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Figure 9

Comparison of computed spray parcels and experimental Mie images taken in a static vessel for the 70 deg swirl injector

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Figure 10

Comparison of in-cylinder spray shapes from (a) endoscope measurements and (b) CFD predictions for a deactivated valve case (image comparison is not the same scale)

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Figure 11

Equivalence ratio contours at 20 deg BTDC firing with the ignition model turned off

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Figure 12

Equivalence ratio of a 5 mm diameter sphere surrounding the spark gap

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Figure 13

Top view comparison of fuel isosurfaces showing the interaction of the fuel cloud with the in-cylinder charge motion: orange—equiv. ratio = 0.5, green—equiv. ratio = 1.0, blue—equiv. ratio = 1.5; ignition is not turned on

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Figure 14

Quantification of fuel containment between the activated and deactivated cases in terms of (a) bowl air-fuel ratio and (b) fuel outside the bowl region having equivalence ratio less than 0.5 to track the lean fringe of the mixture cloud

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Figure 15

Distribution of burned gas for the both valves activated and one valve deactivated case during the compression stroke

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Figure 16

Laminar flame speed comparison at the spark gap with the ignition model turned off

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Figure 17

Experimental measurements and heat release calculations for the activated case compared to CFD results of (a) in-cylinder pressure trace and (b) mass fraction burned history as percent of total fuel injected

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Figure 18

Propagation of flame in the cylinder from a top view perspective where the flame is colored by burned gas fraction

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Figure 19

Temporal flame equivalence ratio for the (a) both valves activated and (b) one valve deactivated cases

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Figure 20

Comparison of (a) postfuel rich intermediates of combustion formed behind the flame during combustion and (b) the rate of diffusion burn of the postfuel gases

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