I found a use for Dynamic Compression Ratio other than to determine temperature and pressure.
DCR is directly related to Thermal Efficiency.
DCR......Thermal Efficiency
7..........54.32%
8..........56.50
9..........58.47
10.........60.26
11.........61.71
As long as compression temperature stays under control, shoot for a higher DCR.
Static Compression VS Dynamic compression
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Re: Static Compression VS Dynamic compression
David, do those numbers take into account the Miller Cycle effect of a shorter effective compression stroke with an unchanging power stroke?
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Re: Static Compression VS Dynamic compression
Bill,
I kept the engine parameters unchanged and only changed the chamber volumes. I could have changed IVC as well.
The change in SCR did not matter since it is not used in the calcs.
Re: Static Compression VS Dynamic compression
Between that and more cylinder pressure wouldn't that give a more complete burn of the fuel. The correct fuel of coarse.David Redszus wrote: ↑Thu Jun 27, 2019 4:25 pm I found a use for Dynamic Compression Ratio other than to determine temperature and pressure.
DCR is directly related to Thermal Efficiency.
DCR......Thermal Efficiency
7..........54.32%
8..........56.50
9..........58.47
10.........60.26
11.........61.71
As long as compression temperature stays under control, shoot for a higher DCR.
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
Re: Static Compression VS Dynamic compression
Wouldn't changing the chamber volume change the SC?David Redszus wrote: ↑Thu Jun 27, 2019 6:02 pmBill,
I kept the engine parameters unchanged and only changed the chamber volumes. I could have changed IVC as well.
The change in SCR did not matter since it is not used in the calcs.
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
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- Guru
- Posts: 9633
- Joined: Tue Nov 27, 2007 9:27 am
- Location: Chicago
- Contact:
Re: Static Compression VS Dynamic compression
Gary, the higher DCR values would produce higher temperatures and pressures, which should cause a faster burn rate, raising combustion peak pressure and advancing the burn angle. Yes, that should result in a more complete fuel burn which is important since we can only actually burn a quantity of fuel predicted by air mass and stoich value. We can't burn more but we certainly can burn less.GARY C wrote: ↑Thu Jun 27, 2019 6:38 pmBetween that and more cylinder pressure wouldn't that give a more complete burn of the fuel. The correct fuel of coarse.David Redszus wrote: ↑Thu Jun 27, 2019 4:25 pm I found a use for Dynamic Compression Ratio other than to determine temperature and pressure.
DCR is directly related to Thermal Efficiency.
DCR......Thermal Efficiency
7..........54.32%
8..........56.50
9..........58.47
10.........60.26
11.........61.71
As long as compression temperature stays under control, shoot for a higher DCR.
Re: Static Compression VS Dynamic compression
Thanks, that kind of explains why cylinder pressure and DCR are looked at in reference to a pump gas engine that would be operating primarily at low rpm, high heat and on substandard fuel.David Redszus wrote: ↑Thu Jun 27, 2019 7:29 pmGary, the higher DCR values would produce higher temperatures and pressures, which should cause a faster burn rate, raising combustion peak pressure and advancing the burn angle. Yes, that should result in a more complete fuel burn which is important since we can only actually burn a quantity of fuel predicted by air mass and stoich value. We can't burn more but we certainly can burn less.GARY C wrote: ↑Thu Jun 27, 2019 6:38 pmBetween that and more cylinder pressure wouldn't that give a more complete burn of the fuel. The correct fuel of coarse.David Redszus wrote: ↑Thu Jun 27, 2019 4:25 pm I found a use for Dynamic Compression Ratio other than to determine temperature and pressure.
DCR is directly related to Thermal Efficiency.
DCR......Thermal Efficiency
7..........54.32%
8..........56.50
9..........58.47
10.........60.26
11.........61.71
As long as compression temperature stays under control, shoot for a higher DCR.
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!