Does the igniting temperature of biodiesel in the cylinder vary from that of fossil diesel.

I ask that because, back in the old days (40 years plus) when black diesel was used in plant machinery operates say that they had more hours (or kms) from the same tank size. That meant more bang for your buck.

Would the burning temperature of the fuel in the cylinder be the feature I am looking for?

There are a number of temperatures to be considered.

Bang for your buck involves the heat value of the fuel, nothing to do with burning temperature.
Igniting temperature is the flashpoint and as long as that temp is exceeded in the combustion chamber the fuel will ignite on injection. The flashpoint of bio is higher than mineral diesel but still plenty low enough for good ignition.

The burning temp (peak combustion temp) is probably very slightly higher for bio as I have heard that if produces more NOx.

I think I have seen, elsewhere on this forum, a comparison of heat values but for bio it will depend on what it is made from. I understand animal fat gives more 'bang for your buck' than vegetable oil.

Most info is here somewhere if you know what you are looking for.

98,
a minor correction, animal fat and palm oil have similar specific energy (possibly because they are shorter molecules) but have a higher specific energy than the liquid oils.

From my research, oils and fats are basically the same apart from their melting point. Fats = solid at room temp, oils = liquid at room temp.
The presence of high proportions of Lauric, Myristic,Palmitic and/or Stearic acids in the oils, indicate that the oils will be solid at room temp.

I sill start a thread with a listing of the MP, IV and composition of the various fatty acide which comprise our oils. It also has the MP od methyl esters and ethyl esters fo these fatty acids.

Regards,
Tony

This is not completely correct.
Flashpoint is not what you have to exceed to establish combustion in the cylinder.
The definition of 'FLASHPOINT' is
The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapor may cease to burn when the source of ignition is removed. A slightly higher temperature, the fire point, is defined as the temperature at which the vapor continues to burn after being ignited. Neither of these parameters are related to the temperatures of the ignition source or of the burning liquid, which are much higher. The flash point is often used as one descriptive characteristic of liquid fuel, but it is also used to describe liquids that are not used intentionally as fuels.

What you are thinking of is the 'AUTOIGNITION TEMP'
The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

So what we really have happening is spontaneous combustion on each and every injection. Or should that be we hope we do.

Thanks for your replies. I am loving this learning. Keep the information flowing as I try to take it all in.

How does the old "black" diesel fit into this comparison?

By "Black Diesel" do you mean diesel with sump oil added?
I have not heard that term used for any other fuel.

Tony

No, no sump oil had been added. I have been working with some cane farmers here in north Queensland and they say that years ago (about 40 years plus) they could buy "black" diesel to run their plant - D4 tractors, harvesters etc. They claim that they could get more operating hours from a tank full of that diesel than the diesel they buy now.
That talk generated the thread I posted. Thanks for your question Tony.

possibly just a very high sulfur diesel fuel??

i found this on wiki but its for greece apparently. Maybe we had it then.?

Marine dieselany black dye

__________________
Cheers
Nick.

Roidio 2001 Holden Rodeo 4x4 2.8L TD. 2.5" Straight through exhaust sytem, heat exchanger shower system. 2" Body Lift,
And lots of fruit, B100 for 25,000 no problems.

Elsa 1983 Mercedes-Benz W123 300D. The Fastest Merc in Oz, Loving B100 Burgers

Being as it was in a farming/agricultural area, and a long time ago, they may have been referring to "black market" diesel which they could get on the cheap.

I can't see how they would be able to prove they could get more operating hours than the current diesel fuel because they don't have the same vehicles as they did then so they can't compare. It is amazing how memory makes things from the distant past seem better than their equivalents now.

>"I can't see how they would be able to prove they could get more operating hours than the current diesel fuel because they don't have the same vehicles as they did then so they can't compare. It is amazing how memory makes things from the distant past seem better than their equivalents now. "<

I appreciate your words rherber1. The farmer I am talking about has his two sons operating the farm now. He owns a lot of machinery in harvesters, dozens, graders, tractors and trucks. I am visiting them this weekend and will gain more knowledge on this "black diesel".

I like this forum as I read some interesting points of view on different topics.