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
What is the primary purpose of EPA's locomotive emissions smoke opacity testing?
Answer: To visually verify that particulate emissions remain within regulatory limits
Smoke opacity testing uses a Ringelmann scale or opacity meter to verify that visible particulate emissions from locomotive exhaust do not exceed EPA limits.
Which fuel property most directly affects the formation of sulfur dioxide (SO₂) emissions from diesel locomotives?
Answer: Fuel sulfur content
SO₂ emissions are directly proportional to the sulfur content in diesel fuel; lower-sulfur ultra-low sulfur diesel (ULSD) significantly reduces SO₂ output.
A locomotive equipped with a Tier 4 engine must use which grade of diesel fuel to protect after-treatment components?
Answer: Ultra-low sulfur diesel (15 ppm max)
Tier 4 after-treatment systems (DPF, SCR, DOC) require ultra-low sulfur diesel (≤15 ppm sulfur) to prevent catalyst poisoning and premature failure.
What happens to a locomotive's power output if the after-treatment system becomes severely clogged and triggers a derate mode?
Answer: Power is reduced by the engine control module to protect the system
Engine control modules activate derate mode, limiting power output to protect the engine and after-treatment system when critical faults are detected.
In the context of locomotive emissions, what does PM2.5 refer to?
Answer: Particulate matter with aerodynamic diameter of 2.5 microns or less
PM2.5 refers to fine particulate matter with an aerodynamic diameter of 2.5 micrometers or less, which is regulated due to its deep lung penetration health risks.
Which operational practice can reduce NOx emissions from a diesel locomotive without modifying hardware?
Answer: Using lower throttle notches and smoother acceleration
Lower throttle notches reduce peak combustion temperatures and pressures, which directly lowers NOx formation during locomotive operation.
What is the function of the NOx sensor located downstream of the SCR catalyst?
Answer: It monitors SCR conversion efficiency and detects catalyst degradation
A downstream NOx sensor measures residual NOx after the SCR catalyst, allowing the engine control unit to calculate conversion efficiency and detect catalyst failure.