[Stoves] PM emissions from engines

[Andrew Heggie]

On 6 June 2017 at 20:59, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:
>>>Huh? "The article is misleading in that very few spark ignition engines are
> direct injection?"
>
>>When did you last have to tune a carburettor?

Last week on a motorbike
>
> Most are indirect injection. I don't see that it can make much difference, but the article claims it does. Indirect injection is into the intake port just before the intake valve instead of into the combustion chamber at high pressure. ‎

The difference is that with the multipoint injection into the inlet
ports the petrol has all the intake stroke and compression stroke to
mix and volatilise, so it is a premixed burn. With direct injection
the petrol is injected toward the top of the compression stroke just
before the spark, this allows for the air at the bottom of the
cylinder to remain stratified and not supply oxygen to the fuel. So
there is less pre mixing plus the burn overall is much leaner. This
means the engine can be run at a higher volumetric efficiency, which
is similar to a diesel, but the burn is also cooler as it has to heat
the whole mass of air.

Even with carburettors  similar stratification is already done with
chainsaw engines but this is more to do with cutting the carry over of
fresh fuel into the exhaust port

Andrew