Investigation of Cyclic Variation of IMEP Under Lean Burn Operation in Spark-Ignition Engine

This paper deals with Numerical Study of 4-stoke, Single cylinder, Spark Ignition, Extended Expansion Lean Burn Engine. Engine processes are simulated using thermodynamic and global modeling techniques. In the simulation study following process are considered compression, combustion, and expansion. Sub-models are used to include effect due to gas exchange process, heat transfer and friction. Wiebe heat release formula was used to predict the cylinder pressure, which was used to find out the indicated work done. The heat transfer from the cylinder, friction and pumping losses also were taken into account to predict the brake mean effective pressure, brake thermal efficiency and brake specific fuel consumption. Extended Expansion Engine operates on Otto-Atkinson cycle. Late Intake Valve Closure (LIVC) technique is used to control the load. The Atkinson cycle has lager expansion ratio than compression ratio. This is achieved by increasing the geometric compression ratio and employing LIVC. Simulation result shows that there is an increase in thermal efficiency up to a certain limit of intake valve closure timing. Optimum performance is attained at 90 deg intake valve closure (IVC) timing further delaying the intake valve closure reduces the engine performance.

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Tumbling flow analysis in a four-valve spark ignition engine using particle image velocimetry

International Journal of Engine Research ◽

10.1243/14680870260189262 ◽

2002 ◽

Vol 3 (3) ◽

pp. 139-155 ◽

Cited By ~ 11

Author(s):

Y Li ◽

H Zhao ◽

Z Peng ◽

N Ladommatos

Keyword(s):

Particle Image Velocimetry ◽

Velocity Fluctuation ◽

Cylinder Head ◽

Particle Image ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Cyclic Variation ◽

Compression Stroke ◽

Image Velocimetry ◽

Exhaust Valves

Tumble motion in the cylinder of a four-valve spark ignition (SI) engine with a production-type cylinder head was studied using cross-correlation digital particle image velocimetry (PIV). The in-cylinder flow field was measured on three planes: the vertical symmetric plane of the combustion chamber, the vertical plane through centres of the intake and exhaust valves, and a horizontal plane 12 mm below the cylinder head. Ensemble-averaged mean velocity, velocity fluctuation distribution and cyclic variation of the instantaneous velocity field were analysed. Analysis results show that the tumble vortex is formed in the early stage of the compression stroke and distorted in the late stage of the compression stroke. The tumble centre is nearly in the centre of the cylinder when the tumble forms. Then it moves gradually to the underneath of the exhaust valves as the piston moves up. It is found that the cyclic variation of the tumble motion at a tumble ratio of 0.9 is so great that the ensemble-averaged flow characteristics hardly represent any individual cycle flow behaviours. Distribution of the velocity fluctuation field is inhomogeneous during the whole compression process. As the engine speed changes the large-scale flow structure seems to remain unaffected.

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