Diesel carburettor backfires?

[Sybarite]

A diesel engine has a very much higher compression ratio than a petrol engine typically something like 20:1. This increased pressure causes a correspondingly higher temperature on compression which is significative enough to ignite the diesel fuel without the need for a sparking plug. Because of the enhanced pressure the engine has to be built in a more robust manner which explains why diesel engines are heavier than petrol ones.

 

[macd]

A diesel engine has a very much higher compression ratio than a petrol engine typically something like 20:1.

To be more accurate, that's only true if you define a diesel engine as a compression-ignition engine running on diesel oil (which isn't unreasonable, although "CI" and "diesel" are commonly used interchangeably, and the "diesel" comes from a bloke, not the oil*). The exceptions mentioned above rely on the fact that other fuels for compression-ignition engines are available, which self-ignite at much lower pressures. In the case of the Honda I mentioned, that other fuel is pump petrol.

* Although, post-Brexit, you'll probably be calling them all Boyle engines. Two-stroke diesels will become Boyle-Clerk engines, unless any Scottish referendum votes to split.

 

[Grumpybear]

To be more accurate, that's only true if you define a diesel engine as a compression-ignition engine running on diesel oil (which isn't unreasonable, although "CI" and "diesel" are commonly used interchangeably, and the "diesel" comes from a bloke, not the oil*). The exceptions mentioned above rely on the fact that other fuels for compression-ignition engines are available, which self-ignite at much lower pressures. In the case of the Honda I mentioned, that other fuel is pump petrol.

* Although, post-Brexit, you'll probably be calling them all Boyle engines. Two-stroke diesels will become Boyle-Clerk engines, unless any Scottish referendum votes to split.

To misquote Sellars and Yeatman, these engines are much easier to start than steam engines because:

"Watts's pots never Boyle".......

 

[JumbleDuck]

To be more accurate, that's only true if you define a diesel engine as a compression-ignition engine running on diesel oil (which isn't unreasonable, although "CI" and "diesel" are commonly used interchangeably, and the "diesel" comes from a bloke, not the oil*).

Technically a Diesel cycle engine is one in which the heat input (ie combustion) happens at constant pressure rather than at constant volume as in the Otto cycle. The way to get combustion at constant pressure is to squirt fuel in progressively as the piston moves down a bit, and since a sparking plug depends on fuel being there and ready to light, the progressive combustion is most easily done with compression ignition.

* Although, post-Brexit, you'll probably be calling them all Boyle engines. Two-stroke diesels will become Boyle-Clerk engines, unless any Scottish referendum votes to split.

Boyle was Irish!

 

[macd]

...rather than at constant volume as in the Otto cycle...
Boyle was Irish!

Shouldn't that be something like "approximates to a constant volume"?

True. But he didn't think much of the place. His law was developed at Oxford (and quite likely wasn't his, anyway). Come to think of it, "Power engines" would have a certain ring to it.