Ricardo,
thanks for the chart but you'd better disregard what I said in my reply email.
I have now engaged brain and given it some more thought.
I suggested that for engines this should not normally be a problem as they measure the viscosity online and do not usually calculate the injection temperature.
However, it may not be this simple and you may need to ask the engine manufacturer some pertinent questions.
Fuel oil heater control is normally done using a viscometer in the high pressure circuit to the engine. This has been the standard for over 40 years.
What has changed recently has been, for some engines, the pressure in the high pressure circuit. I suggested that if the pressure increased and caused an increase in the viscosity that it wouldn't matter since the viscometer would report the higher viscosity and hence the heating would increase to maintain the optimum viscosity.
Idiot. The comment in the article was that injector pressures have been increasing which is not the same thing.
The problem is a real one if the pressure at the injectors has increased and is significantly higher than in the high pressure fuel circuit to the engine where the viscometer is installed.
This means that if the injection pressure has increased significantly then if the original set point for heater control was 14cst then this viscosity would increase at the injectors to some value above 14cst e.g.20cst. However, if the injector pressure has increased such that this viscosity is now 30cst say, then the viscosity set point in the high pressure circuit should be reduced to reduce the injection pressure viscosity back to 20cst.
Thus the viscometer set point would also be reduced, but to what value if the pressure in the high pressure circuit is also significant and has also increased?
Here is where the chart is a bit simplistic. The temperature viscosity data presented is at atmospheric pressure. This is fine, if as shown, one computes the injection temperature based on the injection pressure and the optimum viscosity at the injectors.
However, if a viscometer is used to control heating it is necessary to know the pressure in the high pressure circuit also as it will record a higher viscosity than derived from the atmospheric temperature viscosity data i.e. it will be measuring a viscosity somewhere on the line between B and C.
The conventional place for the viscometer is in the high pressure circuit where pressures have been increased for some engines. The questions for the engine manufacturer are:
[ul]
[li]What is the pressure in the high pressure circuit?[/li]
[li]What is the injector pressure?[/li]
[li]Is the optimum viscosity reported as the optimum viscosity at the injectors or the optimum viscosity as measured by the viscometer?[/li]
[li]If injector pressures and or pressure in the high pressure circuit have changed, does the optimum viscosity reflect this? e.g. as the measured viscosity by a viscometer in the high pressure circuit.[/li][/ul]
In other words, if the manufacturer recomends 14cst as the optimum viscosity, are they refering to the injector viscosity? or are they refering to the viscosity measured in the high pressure circuit?
The problem posed is that both pressures could have changed and hence the questions to the engine manufacturers.
Incidentaly, I am supposing that for burner operations the problem is irrelevant since the pressures are much lower and it doesn't matter whether they use temperature as a set-point or viscosity, where they use viscometers for heater control... which isn't many since historically viscometers have not worked so well with burners as with engines. But I am ready to be corrected on this as well.
JMW
