Combustion in Spark Ignition Engines


Laser beams entering the combustion chamber through a quartz windowA single cylinder engine with extensive optical access is being used with a wide range of laser diagnostic techniques, some of which have been developed by Prof Paul Ewart in the Clarendon Lab. Prof. Ewart has developed a number of laser diagnostic techniques for combustion (such as broadband Degenerate Four Wave Mixing) that can be used for identifying temperatures and concentrations of species such as the hydroxyl radical (OH) and nitric oxide (NO).

This model is able to predict temperature and NO and OH concentrations, but previously there had been no direct validation. Also being studied are cycle-by-cycle variations in combustion, and the differences between cycle-by-cycle modelling and mean cycle modelling. Mean cycle modelling is invariably used, despite the substantial cycle-by-cycle variations that can occur in spark ignition engines, most notably with highly diluted combustion. Techniques have been developed for the cycle-by-cycle estimation of the completeness of combustion and the temperatures of the burnt and unburnt gases. This has led to a significant refinement to the classic Rassweiler and Withrow burn rate analysis method.

Predictions of Gas Engine Performance:

Predictions of Gas Engine Performance (a)Predictions of Gas Engine Performance (b)Predictions of Gas Engine Performance (c)Predictions of Gas Engine Performance (d)

Involved Parties

Group : R. Stone, J. Ball, R. Williams; G Lloyd, P Ewart (Clarendon Lab)
Project Support : EPSRC, British Gas, Rover.