Improving Engine Performance and Efficiency by Minimisation of Knock Probability Project nº ENK6-CT Edgar C. Fernandes Ilídio Guerreiro Nuno Rolo Laboratory of Thermofluids, Combustion and Environmental Systems Instituto Superior Técnico -Technical University of Lisbon, Portugal M in K nock WP2 : Advanced experimental analysis of auto ignition Task 2.1 Fundamental Experiments Stuttgart, 2 nd of December of 2005

Main Objective Experimental Setup Combustion chamber Techniques Working conditions Output Results Software development (Matlab-interactive soft) Deliverables, Reports Academic formation -MSc -Final year project-Graduation Two planned papers Presentation Outline

Flow topology wall Flame boundary n U W Sd burned unburned ? Flow topology characterization

Experimental Setup

Techniques Kodak CCD High speed camera-512 x 512 Spectra Physics Ar-Ion Laser-5W Typical data: 1000fps ; 1/2000-1/5000s Spatial resolution for flame front displacement: 0.5mm Spatial resolution for velocity vectors: 21vectors/45mm=1vector/2mm

Lean & Rich flames Premixed propane-air  =0.7 ; 1.3 Symmetric flame Non-Symmetric flame Plane wallInclined wall Forced/Natural disturbances Cases Studied

Mixture preparation        t [s] Clockwise vortex Counter-Clockwise vortex V  U  0.05 m/s “Low turbulence” field V  U   m/s 30

Data post-processing (PIV) 1 m/s 1mm

Software – Main Selection of images Framerate Scale factor Selection of region Determination of flamefront and displacement velocities Determination of flow velocities Crossing results Plotting Export and close Save continue to another

Software - MatPIV Selection of images (predefined in main) Filtering procedures Masking Determination of scale factor (perdefined in main) PIV conditions

Software – flamefront calculation Images / preview of determined flamefrons Filtering procedures Reflex reduction

h/D r/D Wall h/D r/D Wall h/D Wall h/D r/D Wall 0.6 Plane-wall / Symmetric Flame “undisturbed flame” Wall f = 0,7

Plane-wall / Symmetric Flame A typical result for a disturbed rich A typical result for a disturbed rich flame Wall 0.6 Wall r/D h/D r/D

Plane-wall / Symmetric Flame Unburned gas velocity, PIV 14 ms

Plane-wall / Symmetric Flame K, K c, K s and S d along a flame front

Plane-wall / Symmetric Flame K, K c, K s and S d along a flame front

Plane-wall / Non-Symmetric Flame A typical result for a lean flame with a “non-symmetric” perturbation r/D h/D r/D Wall h/D r/D Wall

Plane-wall / Non-Symmetric Flame  Unburned gas velocity, PIV

Plane-wall / Non-Symmetric Flame

K, K c, K s and S d along a K, K c, K s and S d along a flame front

Plane-wall / Non-Symmetric Flame S d along a flame front

Flow topology-Plane wall Stagnation points wall flame U wall -modulus of k and Sd decreases as the flame approaches the wall - Kc >> Ks -Flame survives after passing the critical “quenching” distance of about 1mm -The propagation of a symmetric flame generates lower U velocity, close to the wall, when compared with asymmetric flame propagation This SP moves upwards toward the wall, during flame propagation wall

Inclined-wall / Non-Symmetric Flame A typical result for a lean flame with a “non-symmetric” perturbation

Inclined-wall / Non-Symmetric Flame Flame front detection and flame front displacement velocity (W)  Wall

Inclined-wall / Non-Symmetric Flame

K, K c, K s and S d along a flame front

S d v.s. K n U W Sd

S d v.s. K Lean (0.7) Rich (1.4)

Data presentation

Flame speed variation Lean (0.7) Rich (1.4)

Stretch Distribution Lean Rich

Flamefront orientation Lean Rich wall n wall n flame  d

Resume wall flame U wall This SP moves upwards toward the wall, during flame propagation wall KsKs KcKc