nox reduction / fuel consumption
nox reduction / fuel consumption
(OP)
Can anyone advise me of effect on fuel consumption of atempting NOX reduction by adjusting engine timing on 6MW engine running 180cst
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nox reduction / fuel consumption
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nox reduction / fuel consumptionnox reduction / fuel consumption(OP)
Can anyone advise me of effect on fuel consumption of atempting NOX reduction by adjusting engine timing on 6MW engine running 180cst
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RE: nox reduction / fuel consumption
my reaction (as noted in original thread) is that retarding timing to reduce NOx will tend to increase BSFC.
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
Reducing NOx basically requires reducing peak combustion temps. Retarding injection timing from MBT will usually result in lower NOx, but higher HC and SFC.
Charge air cooling and EGR are also effective approaches to reducing NOx.
Hope that helps.
Terry
RE: nox reduction / fuel consumption
PM will also increase with retarded main injection timing (About 20:1 PM:CO2).
Max 4/5 degrees from nominal setting.
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
@ivymike: That's why proper combustion development and any changes to injection strategy should be only one part of a holistic exercise, which may include reshaping of piston bowl geometry. This latter factor in itself also has a huge influence on the aforementioned NOx/PM/NVH/SFC tradeoffs.
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
TDImeister, being already optimised was an assumption, but if we dont assume some constants at least, the OP question is to broad to answer. I only have experience of HSDI engines, from 1000-2500rpm steady state these tradeoff ratios are correct for a good range of engine displacements.
RE: nox reduction / fuel consumption
Don't tell that to the people working on HCCI, PCCI and other forms of LTC.
@70btdc: Granted. A linear proportional assumption is OK when you don't deviate far from the original point.
RE: nox reduction / fuel consumption
Advance doesn't directly cause NOx, temperature causes NOx. The rate of the NOx generating reaction is exponential with temperature (as are many reactions). The peak temperature within the chamber virtually defines the amount of NOx created, because all the lower temperatures in the combustion chamber (in time or geometry) do not contribute very much to the total NOx generation.
RE: nox reduction / fuel consumption
In general timing retard resulted in higher fuel consumption, in the HFO engines actual change was hard to track due to batch to batch fuel variations. Most testing was done with a nominal 4 degree retard. In almost all cases timing was returned to original as NOx reductions were lower than expected and increase in CO, PM, visible smoke and fuel consumption high enough to cause concerns. Exhaust port temps in all cases increased, as did turbo speed. In a few cases we experinced turbo surge.
Are you doing this as a result of regulatory requirements? What are your expected results from the changes you're making?
Mike L.
What are the piston changes? Change to compression ratio? Bowl geometry? Are you changing injection nozzles as well? I'd expect with a piston change that a change in spray angle might be needed to get optimum performance.
RE: nox reduction / fuel consumption
I could understand if the idea was to LOWER coolant temps.
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
Or maybe I just read it wrong...
RE: nox reduction / fuel consumption
What's next to reduce charge air temperature - introduce an air conditioner into the airbox or charge air cooler?
RE: nox reduction / fuel consumption
my thoughts exactly
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
According to GASEQ, at these conditions, the mole fractions of NO and NO2 are 0.00747 and 1.24e-04 moles per mole of air, respectively.
However, that air does not spontaneously combust upon itself and that NOx form only at high temperatures are not in and of themselves factors that make reactions endothermic. Spontaneous oxidation of any oxidizeable material is a function of its autoignition temperature (analog of the energy required to reach and exceed the reaction activation energy). Endothermic reactions can and do also take place at- and below ambient temperatures.
RE: nox reduction / fuel consumption
I would agree with TDIMeister. EGR will reduce NOx without much effect on SFC, until the EGR rate exceeds about 8% to 10%. Exhaust gas is mostly inert (CO2 and nitrogen), and it reduces combustion temps by absorbing heat during combustion while not contributing oxygen to the combustion event.
Intake charge cooling is also effective at reducing NOx without too much of an SFC penalty. Charge cooling reduces NOx by reducing the (T1) temperature at the start of the combustion cycle. The SFC penalty with charge cooling is only due to the heat rejection loss and intake flow losses at the intercooler.
NOx can also be reduced by improving the injection mixing and combustion rate, which would allow a BOI closer to TDC. Higher injection pressures with a greater number of smaller diameter nozzle holes will give a better fuel spray distribution and mixing rate, leading to less ignition delay and more rapid combustion. But such a modification would be expensive.
opsguy says a piston change is planned and this is a land based engine, so I would recommend reducing CR and increasing boost with lots of charge air cooling. This will keep your peak cycle pressures at acceptable levels while decreasing NOx.
Good luck.
Terry
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption
RE: nox reduction / fuel consumption