Ideal coolant temperature for fuel economy?
Ideal coolant temperature for fuel economy?
(OP)
Any new discoverys on this topic?
Years past adiabatic was the buzz word for diesel economy improvement, what about SI engines?
Also induction temperatures? Ideal for power is cool induction, what about for economy?
Years past adiabatic was the buzz word for diesel economy improvement, what about SI engines?
Also induction temperatures? Ideal for power is cool induction, what about for economy?





RE: Ideal coolant temperature for fuel economy?
For practical, just reverse engineer a state of the art application.
For theoretical, read up on your thermo, choose a heat engine cycle, and do the analysis.
One of the issues encountered with SI engines is that beyond a point, optimization for efficiency reduces power density, due to knock limited BMEP. We're talking about compression ratio and coolant temnperature here. Of course if compression ratio and coolant temperature can be dynamically adjusted with load, then less compromise is necessary.
I'm not as well versed in diesel engines, but I believe one of the limitations encountered with so-called adiabatic engines is the most of the heat not extracted by the absent cooling system is not able to be extracted in the expansion stroke, and instead is lost to the exhaust. The reasons for this I don't recall exactly. I believe it is at least partially due to the need for a rapid process (high power density).
RE: Ideal coolant temperature for fuel economy?
Your question is quite broad.
Most coolant circuit temperatures are established by the coolant properties (ie. boiling point) or by the safe thermal structural limits of the head and block materials. But keeping internal engine surfaces that are exposed to combustion gas at as high a temperature as practical minimizes heat transfer to that surface, which is good for efficiency.
The adiabatic engine sounded great in theory, but in practice it had serious shortcomings. Engine parts like pistons and rings that have sliding contacts need lubrication, and engine lubricants have temperature limits. So the surfaces the lubricant films contact must be kept below a certain temperature, which means they must be actively cooled.
Diesel engines don't have detonation limits, so high intake temperatures aren't a big problem. However, most current turbodiesel engines use lots of charge air cooling to minimize NOx emissions.
Water/glycol is actually a very good coolant, since it is cheap, safe and has good specific heat value. Maybe someone will develop a fluid that is both safe and cheap, but with better specific heat properties than water/glycol.
I'm sure other posters can add much more.
Regards.
Terry
RE: Ideal coolant temperature for fuel economy?
Like everything in engine design, it is about the optimum balance of the various compromises.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
The only reason for real world engines to have a max temp is to keep the material from melting. Theoretical otto/diesel/dual cycles will have higher thermal efficiency with higher compression ratios and tempuratures.
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
Not saying it can be taken out of the realm of theory, just that I could not manage to accomplish it.
Rod
RE: Ideal coolant temperature for fuel economy?
It's fun to dream and call conspiracy between the auto manufacturers and big oil but be serious, you know how to increase a typical engine's power by 43% while also increasing the fuel economy by 25% (numbers are less 5% and not using the higher engine operating temperature) and yet these "secrets" remain untapped even with the millions being spent on engine R&D?
RE: Ideal coolant temperature for fuel economy?
When the first i286 PCs came out in the late 80's, overclockers came up with an ingenious approach to nearly doubling the processing speed on the processors, by upping the supply voltages by 75%. However, they compromised the technology used in the processor, resulting in complete processor failure within 2 months of higher voltage operation.
Likewise, we don't know how much reliability was compromised by changing the operational parameters of an engine. Yes, it might have had better performance and efficiency, but for how long? Higher operating temperatures invariably lead to earlier failures, per Arrhenius relationship.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Chinese prisoner wins Nobel Peace Prize
RE: Ideal coolant temperature for fuel economy?
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Chinese prisoner wins Nobel Peace Prize
RE: Ideal coolant temperature for fuel economy?
Engineering is the art of creating things you need, from things you can get.
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
A simple hot or cold.
RE: Ideal coolant temperature for fuel economy?
Within reasonable limits, hotter charge gives better economy but colder charge gives more power.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
http://www.tourengine.com/technology.html
Perhaps, that answers the question as to how to locally optimize the efficiency of the IC engine
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
Chinese prisoner wins Nobel Peace Prize
RE: Ideal coolant temperature for fuel economy?
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
Engineering is the art of creating things you need, from things you can get.
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
Lower air density means wider throttle for same power. It also means lower power and performance and fuel consumption at WOT.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
Rod
RE: Ideal coolant temperature for fuel economy?
A dirty air filter is still a restriction on the intake side so it creates pumping losses exactly the same as the same restriction generated by a throttle, but yes I see the funny side.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
Lets see, the claim was 30% economy improvement and 48% power improvement. If the engine remained at the same efficiency then a 48% gain in power would require a 48% increase in fuel consumption. Now, there is also a 30% fuel economy improvement, which is implied to be 30% of the origional fuel usage and also implied to occur at the same operating conditions which produce this 48% power increase. So, the motor starts at 100% fuel usage. Add 48% fuel usage for the new power to put the fuel usage to 148%. But, the engine needs to end up at 70% fuel usage, which means cutting the fuel usage by 53%. Are the numbers still believable?
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
You have seriously misinterpreted my posts if you think I support SMOKEY44211s point of view.
I was in fact saying very little of it could be explained and was questioning where the rest came from. 30% power gains from crank counterweight design. Give me a break unless about 2000 grade oil is being used.
Gains by loss of friction should yield the same %age increase to both power and economy I would think.
My comment about smoke and mirrors was both a pun and a cheap shot at Smokey Yunick and his tendency to use bullshit to divert attention from his cheating, just like magicians use smoke and mirrors.
I was trying not to be to confrontational to SMOKEY44211, but I guess that horse has now well and truly bolted.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
RE: Ideal coolant temperature for fuel economy?
Now I see what you are saying and I completely agree.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Ideal coolant temperature for fuel economy?
A simple hot or cold.
dicer,
Once again, that's not a simple question.
In very general terms, combustion cycle efficiency is dependent on pressure ratio and heat release. SI engines are detonation limited, so having a lower T1 allows the use of higher CR's (up to about 14:1), which in turn gives greater cycle efficiency. With GDI, injecting later in the compression phase gives a greater charge temperature reduction due to the fuel latent heat effect, thus reducing the knock tendency.
CI engines are not detonation limited, and a low T1 is not so critical. T1 needs to be high enough such that the T2 is sufficient to ignite the injected fuel, but the lower air density of hot intake air can be compensated for with increased turbocharger work. Indeed, the best efficiency in CI engines is obtained with a CR around 14:1 and very high levels of boost. Current production turbo CI engines all use charge air cooling, but it's for NOx reduction, and the intercooler's flow and thermal losses hurt BSFC.
Finally, there is the extreme example of turbine engines. Turbine engine efficiency is greatly improved with the use of thermal recuperators, which are heat exchangers that transfer heat from the exhaust flow to the compressed intake flow. In this case, it's the hotter the better. To improve thermal efficiency even more, turbine engines also use fuel/oil heat exchangers that cool the engine oil and recover waste heat in the fuel prior to injection into the engine.
RE: Ideal coolant temperature for fuel economy?
Remind me, what is the difference between a regenerator and a recuperator?