C15 and C18 – Clean Emissions Module System Operation


(1) Diesel Oxidation Catalyst (DOC)

(2) Muffler (if equipped)

(3) Diesel Particulate Filter (DPF)

(4) ARD body

(5) Connection for the coolant

(6) ARD head

(7) Pilot fuel line

(8) Main fuel line

(9) Spark plug

(10) Relay for the Heated Nozzle

(11) Line for combustion air

(12) Exhaust from turbocharger

(13) ARD air valve controller

(14) ARD combustion air valve

(15) Compressed air from turbocharger

(16) Ignition coil

(17) ARD fuel manifold

(18) In-line fuel filter

(19) Electric priming pump

(20) Primary fuel filter

(21) Fuel from tank

(22) Electronic Control Module (ECM)

Clean Emissions Module Basics
The clean emissions module contains a number of mechanical and electronic components that aid in reducing the various exhaust emissions emitted from the engine.

The two major functions of the clean emissions module are:

Oxidize Carbon Monoxide and Hydrocarbon emissions through the Diesel Oxidation Catalyst (DOC) and trap particulate matter emissions (soot) in the Diesel Particulate Filter (DPF).
Clean the trapped particulate matter emissions from the DPF using a process called Regeneration.
The Clean Emissions Module (CEM) contains the Aftertreatment Regeneration Device (ARD). The ARD is used to regenerate, or clean, the soot from the DPF. The ARD is made up of a fuel, air, and electrical subsystems. Regeneration is a process which uses diesel fuel and boost air from the turbocharger to create a high temperature flame. The heat from that high temperature flame is introduced to the inlet of the DPF.

In order to regenerate the DPF at the right time, the engine ECM must know how much soot is in the DPF. Measurement of soot is accomplished through the following means:

Delta pressure measurement across the DPF
Calculated model based on developed engine out soot measurements
The information gathered from these three inputs is then converted into a percentage of soot output that is viewable through electronic soot level gauges. These gauges can be found in the various operator displays used with Cat Industrial Engines. The soot level may be displayed as a graphical bar, or as an actual percentage. Soot level can also be viewed through Caterpillar Electronic Technician (ET).

Soot Level Outputs
The soot level percentage that is generated by the engine ECM is used in determining:

When to activate the DPF lamp
When to activate the action lamp (for high soot load events)
When to activate the action alarm (for high soot load events) (if equipped)
When to activate the forced engine low idle strategy
When to activate the forced engine shutdown strategy
Regeneration lockout
When a manual regeneration is allowed
When a low speed regeneration is allowed
When a high speed regeneration is allowed
DPF Lamp – The DPF lamp will be illuminated at an 80 percent soot level.

Action Lamp – The action lamp will be illuminated at a 100 percent soot level. The DPF lamp will remain on with the action lamp.

Action Alarm – The action alarm will be activated at a 116 percent soot level.

Forced low idle strategy – The forced low idle strategy will be activated after the soot level has been at 116 percent for 5 minutes. At this time, the engine will automatically drop to the programmed low idle speed. The only method to unlock the low idle speed is to cycle the key switch or perform a manual regeneration.

Regeneration lockout – All forms of regeneration will be locked out from the operator once the soot level percent has been at 116 percent for 10 minutes. Regeneration can only be performed by using the “Manual DPF Regeneration” service procedure within Cat ET.

Forced engine shutdown strategy – The forced engine shutdown strategy will be activated when the soot level reaches 140 percent soot level. The engine will initially idle for 30 seconds before completely shutting down. The DPF can no longer be regenerated and must be replaced.

Manual Regeneration – Manual regeneration initiated by the force switch is allowed once soot level is greater than 15 percent.

Low Speed Regeneration – Low speed regeneration will be allowed once soot level is greater than 30 percent.

High Speed Regeneration – High speed regeneration will be allowed once soot level is greater than 60 percent.

Note: Other factors are used in determining if regeneration will actually occur. The soot level thresholds simply tell the ECM when the different types of regeneration are allowed. The strategies to determine when regeneration will occur are discussed in the “Regeneration Types and Operating Criteria” section.

Regeneration Basics
Regeneration is accomplished by supplying a regulated supply of diesel fuel and boost air to create a flame that is ignited by a spark. Once the flame is lit, the fuel and air are all that are needed to maintain the flame. The flame detection temperature sensor determines if the flame was successfully lit. Once the flame is lit, the DPF inlet temperature sensor continuously monitors the temperature at the inlet of the DPF. As the temperature changes, the signal from the DPF inlet temperature sensor is sent back to the ECM. The ECM then calculates how much more or less fuel and air are needed to maintain the desired DPF inlet temperature.

Posted in C18

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