High-Speed Lif Imaging for Cycle-Resolved Formaldehyde Visualization in Hcci Combustion

• High-speed laser diagnostics was utilized for single-cycle resolved studies of the formaldehyde distribution in the combustion chamber of an HCCI engine. A multi-YAG laser system consisting of four individual Q-switched, flash lamp-pumped Nd:YAG lasers has previously been developed in order to obtain laser pulses at 355 nm suitable for performing LIF measurements of the formaldehyde molecule. Bursts of up to eight pulses with very short time separation can be produced, allowing capturing of LIF image series with high temporal resolution. The system was used together with a high-speed framing camera employing eight intensified CCD modules, with a frame-rate matching the laser pulse repetition rate. The diagnostic system was used to study the combustion in a truck-size HCCI engine, running at 1200 rpm using n-heptane as fuel. By using laser pulses with time separations as short as 70 μs, cycle-resolved image sequences of the formaldehyde distribution were obtained. Thus, with this technique it is possible to follow the formaldehyde formation and consumption processes within a single cycle. The combustion evolution was studied in terms of the rate and spatial structure of formaldehyde formation and consumption for different engine operating conditions, e.g. different stoichiometries. Also, the impact on the rate of heat-release was investigated.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Annan maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Other Mechanical Engineering (hsv//eng)

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

Nyckelord

Cycle-resolved

Diagnostic systems

Engine operating conditions

Frame-rate

Framing Camera

HCCI combustion

HCCI engine

Heat release

High temporal resolution

High-speed

Image sequence

Image series

Intensified CCD

Laser systems

LIF imaging

n-Heptanes

ND : YAG lasers

Q-switched

Single cycle

Spatial structure

Time separation

HCCI

High-Speed LIF

Formaldehyde

Combustion

Engine

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