The initial inflammation can be separated into two phases. During the first phase (ionisation and spark) the stabilisation of the spark may not be disturbed by too high charge flow velocities and Turbulent Kinetic Energy (TKE). Phase two is characterised by the growth of the flame kernel. High levels of TKE in order to brake up the flame for a big flame surface are advantageous and the precondition for a rapid and stable combustion. The flow velocity should be greater than zero but not exceed 10m/s to prevent extinguishing or blowing away of the growing flame kernel. High levels of TKE can whether be generated by squish flow or by dissipation of the charge motion generated by the intake flow.
To ensure a rapid and stable combustion of a lean A/F mixture high levels of TKE are required which are originated by the dissipation (brake-up) of the charge motions flow.
On the other hand too high TKE values at stoichiometric A/F ratio or rich air - fuel mixture and higher load lead to a steep pressure rise and very rapid combustion, hence acoustic and NOx problems might occur. Therefore the special CCBR port design ensures that the correct level of TKE is created at the correct time and place in the combustion chamber.
The carefully tuned carburettor setting of the CCBR engine provides a lean air - fuel mixture at part load for good fuel economy and emissions and a little rich air - fuel mixture at WOT for good performance.
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