Emissions Control Systems Flashcards
7 cards from real LEC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Emissions Control Systems flashcards as text
Which federal regulation establishes the primary emissions standards for in-use locomotive engines in the United States?
Answer: 40 CFR Part 1033
40 CFR Part 1033 contains EPA's emissions standards specifically for locomotives and locomotive engines, covering both new and in-use engines.
What effect does exhaust gas recirculation (EGR) have on combustion temperature?
Answer: It lowers peak combustion temperature to reduce NOx formation
EGR dilutes the intake charge with inert exhaust gases, lowering peak combustion temperatures and thereby reducing NOx formation.
A locomotive engineer observes visible black smoke during a throttle notch increase. Which emissions issue does this most likely indicate?
Answer: Rich fuel mixture causing incomplete combustion
Black smoke indicates incomplete combustion of diesel fuel, often caused by a rich fuel-air mixture, a clogged air filter, or injector problems.
Under EPA regulations, how often must in-use locomotives undergo emissions testing?
Answer: Only at major overhaul
Under 40 CFR Part 1033, locomotives are subject to emissions testing at the time of remanufacture or major overhaul, not at routine annual inspections.
What is the role of an oxidation catalyst in an after-treatment system when the exhaust temperature is below its light-off temperature?
Answer: Its conversion efficiency is significantly reduced
Catalytic converters require minimum light-off temperatures (typically 200–300°C) to activate; below this threshold, conversion efficiency drops sharply.
Which type of emission is primarily responsible for the blue-gray smoke sometimes seen from locomotive exhaust?
Answer: Oil being burned in the combustion chamber
Blue-gray smoke indicates engine oil is entering and burning in the combustion chamber, often due to worn piston rings or valve seals.
When an SCR system detects ammonia slip, what does this mean?
Answer: Excess ammonia is passing through the catalyst unreacted
Ammonia slip occurs when excess urea/ammonia is injected beyond what the catalyst can react with NOx, allowing unreacted ammonia to exit the exhaust.