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Ahh - but that is the point. If you look at the scientific literature (most of it from engine manufacturers) - there are lots of papers on C/LNG/diesel engines (running 80-100% C/LNG), however I can't find a single paper on LPG/diesel systems.Quote:
Originally Posted by DeeJay
I never missed your point.Quote:
Originally Posted by DeeJay
The dual fuel systems that you are referring to are a completely different kettle of fish. They are nothing like the diesel fumigation systems that are being added on to vehicles, like this thread was about.
The dual fuel systems have been researched and used for many, many years, for some years they have used LPG, propane, natural gas, etc. as fuel.
Natural gas has characteristics and cost advantages that have made it prominent with dual fuel engines. I recall hearing that the buses where I am were to use it.
Natural gas is mostly (~90%) methane (CH4). Methane has good anti-detonation properties, unlike long chain hydrocarbons like propane or LPG. Natural gas is abundant and relatively cheap compared to diesel
The common types of combustion systems used in dual fuel engines are:
- Conventional dual fuel.
- Low NOx (also called lean burn).
- Gas injection direct into the combustion chamber (similar to how diesel is injected). The best know user of this system is Wartsila Diesel of Finland (ship engines, etc.), also MAN (joint development with Mitsui).
- General Electric 'H-process' - a hybrid of 1 and 3, widely used in locomotives in North America
None of these can be compared with diesel fumigation.
Dual fuel systems use only a small quantity of diesel for ignition - typically 5 to 8% of what would be used if running full load on diesel alone.
Diesel fumigation systems use only a small quantity of propane/LPG.
Edit:
A diesel engine requires extensive modification to use any the dual fuel systems.
Only the direct gas injection systems offer similar power to diesel - all others produce considerably less. On the positive side they emit much less NOx compared to diesel.
In the case of the Wartsila and MAN gas injection engine they were made to take advantage of gas produced at the oil well (where the engines are located) or given off the crude oil in the tankers transporting the crude from oil well to shore. Essentially using what would otherwise be wasted.
I was talking $$$ & you guys are talking techo stuff.:confused:
first 300 klm, 19ltrs LPG and 18 ltrs diesel
no melted pistons.
oh it was in the hills as well
will have some more numbers when i top off the tanks again
:D:D cant argue with that aye :D:D:DQuote:
Originally Posted by bee utey
Please tell me you're running an egt gauge.
As Dougal said and Gerry reiterated, please fit an EGT asap. DaveS and I almost killed an NA 4BD1 with retarded ignition. An EGT would have helped a great deal.Quote:
Originally Posted by clean32
Why? As i posted before. EGT although a measure of gas temperature it is also an indicator of pressure pre turbo. Or in other words back pressures created buy the turbo. i don’t have a turbo as well as the fact the exorst gas temperatures would be of little value or really no value. I am interested in CC and head temps. all which are well with in spec so far.Quote:
Originally Posted by isuzurover
Oh and my pistons haven’t melted either.
Actually that’s not correct. Energy being extracted is a very misleading way of trying to explain it just as saying a turbo uses waste energy,Quote:
Originally Posted by Dougal
The turbo uses the pressure differential between pre turbine and post turbine. this pressure differential ( you read 2.5 times inlet pressure for a turbo to work is a measure of the differential and not a measure against ambient) is generated buy the induced back pressure of the turbo its self. in inlet tract of the turbo being shaped like a nozzle to increase the gas velocity as it flows from the high pressure side to the low pressure side.
the difference in temperature is a simple calculation of the same amount of energy ( heat in this case) occupying a smaller volume ( pre turbo) and a larger volume ( post turbo), admittedly there is some energy in the form of head being extracted by soak though the casting of the turbo its self but this is neglable in the over all scheme of things.
If you doubled the volume from preturbo temp of 750 deg you would get about 500deg
I suggest some reading on the Brayton cycle to learn how gas turbines work and how to predict the temperatures and pressures required by one to run.Quote:
Originally Posted by clean32
I run with boost and backpressure gauges when making any turbo changes, they clearly show that as turbine inlet temps rise, the backpressure required by the turbo drops. Demonstrating quite clearly that turbos do feed on waste heat.
At cruiser with EGT's of 430C it takes 12-13psi backpressure to deliver 9psi boost.
Under heavy load with EGT's at 600C it requires 20psi backpressure to deliver 20psi boost.
Above 600C my current turbo delivers more boost than it requires in backpressure.
Your explanation of simple volume increase for turbo temperature drop does not fit with observed results or the theory.
2.5 times inlet pressure for drive pressure is unheard of. You would need an extremely inefficient turbo with was operating outside it's map.
Indeed if a turbo did not feed on heat, then there would be no boost increase when the fuel was increased at steady rpm. For example cruise at 100km/h and then plant your foot. The only thing you have changed in the first instant is the turbo inlet temperature, the immediate result is the turbo works harder and produces more boost.
Running at 15psi with a boost/backpressure ratio of 1.5 you run 730C into the turbine and you get 530C out according to well established thermodynamics (Brayton Cycle, 65% efficent turbine).
Trying to apply adiabatic expansion across the turbine (treating it like a nozzle) would result in a 304C drop to 426C. Which we could get if we had a 100% efficient turbine. Sadly we don't have 100% efficient turbines.