So, I've been playing around with the numbers.
The Golf Diesel get 30/45 mpg. Unabated NOx allowance 0.07 grams/mile. Most of my industry looks at PPM level for exhaust.
I found one reference for Air to Fuel Ratio
Quote:
When we dyno vehicles to fault find, we also check boost pressure and air fuel ratio with a wide band lamba senor at the exhaust pipe.
The ideal ratio is 18:1 for good power and very minimal smoke emmisions.
This has also been proven after we reconditioned the pump and injectors for this vehicle. Too low a/f and they get smokey, too high they can lack power. At a cruise situation they can go as high as 40:1.
You can go lower with a/f but the exhaust temps start to rise pretty quickly on a turbo application.
Hope this helps.
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Diesel fuel/air ratio - Engine & fuel engineering - Eng-Tips
So, I figure that the allowable limit of 0.07g/mile at the 18:1 and the 40:1 ratios.
45 mpg
3220.63 grams per gallon
71.57 grams per mile
AFR 40 to 1 - Under cruise
2934.37 grams per mile
23.9 ppm
AFR 18 to 1
1359.83 grams per mile
51.5 ppm
While these number seem high school to me, they are supposed to be without SCR or water injection, on a compression ignition engine, vs. continuous flow gas turbines. I know unabated numbers on the GTs with diesel would be well over 600 ppm with the old standard combustors.
The latest requirements are 3 ppm, but this is natural gas which is "easier" keep in the low NOx ppm regions. No one is making Gas Turbines without water injection for diesel fuel under 42 ppm. And even then, you make LOTS of CO, which is now a no-no.