Test your diesel emission systems knowledge

Many of today’s Perkins diesel engines are very different from previous generations largely due to the systems included to meet EU Stage V and U.S. EPA Tier 4 Final emission standards. We have created a short True or False quiz designed to help people who depend on those engines understand the changes and the technologies behind them.

Have fun, and see how many answers you already know.

True or False: Eliminating black smoke is the major focus of emission standards.

False. The unburned carbon particles, or Particulate Matter (PM), that cause black smoke are only one of the regulated emissions, and over the last 25 years they have reduced by up to 27 times. Equally important, however, are reductions in hydrocarbons, carbon monoxide (CO) and nitrogen oxides (NOx).

Hydrocarbons, carbon monoxide and particulate matter are all products of incomplete combustion which is addressed with technologies including common rail fuel systems and multiple valves per cylinder as well as Diesel Particulate Filter (DPF) aftertreatment.

True or False: Perkins technology makes Diesel Particulate Filter (DPF) regeneration completely transparent to the operator.

True. Particulate matter is mainly carbon particles from unburned diesel fuel and lubrication oil. The DPF traps these particles to remove them from the exhaust stream. The emission control system periodically generates high temperatures in the DPF to completely oxidise the trapped particles and ‘regenerate’ the filter. Perkins technology makes this process transparent to the operator.

True or False: Higher combustion temperatures produce less nitrogen oxides (NOx) in the exhaust gas.

False. NOx is produced by the reaction of nitrogen and oxygen contained in the combustion air. More NOx is produced at the higher temperatures produced by today’s more efficient combustion processes.

Perkins emission control technologies, including Exhaust Gas Recirculation (EGR) and Selective Catalytic Reduction (SCR), are used to reduce the NOx produced in today’s more efficient engines.

True or False: Exhaust Gas Recirculation (EGR) alone is enough to control NOx emissions.

False: EGR was one of the earliest technologies used for NOx reduction and it still has an important role. But today it works with Selective Catalytic Reduction (SCR) using Diesel Exhaust Fluid (DEF) as an integrated system to control NOx emissions.

EGR works by capturing and cooling a small amount of exhaust gas and then recirculating it back into the combustion chamber to dilute the oxygen level and lower combustion temperatures. Lower combustion temperatures increase hydrocarbons, carbon monoxide and particulate matter so the EGR system has to be carefully balanced with the other emissions control technologies in use. Adding SCR to reduce NOx outside the combustion chamber allows more efficient use of EGR within the combustion chamber.

DEF is used to generate ammonia within the SCR which catalyses a chemical process that reduced NOx to nitrogen and water. The entire system—EGR, SCR and DEF—is regulated and balanced by the engine’s emission control software and requires no operator attention beyond adding DEF periodically.

True or False: There is more than one type of crankcase ventilation system used to control crankcase emissions.

True. Actually, Perkins uses three different crankcase ventilation systems; open circuit, filtered open circuit and closed circuit. All remove gases that leak past the piston and build up in the crank case. They need to be removed to avoid pressure build up that could eventually escape past oil seals and gaskets. They are, however, considered to be emissions so crankcase ventilation systems have to be designed and serviced to meet standards.

Open circuit systems are simply vented to the atmosphere through a gauze filter in the valve cover and a hose running down the side of the engine.

Filtered open circuit systems add a filter/separator that route fluids back into the engine and allows gases to be vented to the atmosphere.

Closed circuit systems vent the gases directly into the air intake, so they are recirculated through the combustion system.

All three systems use a filter which needs to be maintained at regular intervals as recommended in the engine’s service manual.

Creating diesel engines that meet Stage V and Tier 4 Final emission standards has required profound changes. Everything from the materials used; to the way fuel is delivered, regulated and burned; the technologies used to treat exhaust gases; and even the manufacturing processes used to build them has been impacted. While the engineering behind those changes was driven largely by the need to meet emission standards, the end result is a more efficient, power-dense and responsive engine that delivers solid value for the Original Equipment Manufacturers (OEMs) and end users who depend on them.

We hope you enjoyed this. Watch for another Diesel Knowledge Quiz in the Quarter 4 edition of Powernews.