G3500H Generator Set Engine Air/Fuel Ratio Control - NO<SUB>X</SUB> Feedback Caterpillar


Air/Fuel Ratio Control - NOX Feedback
`
G3500H Generator Set Engine [M0078629]
FUEL SYSTEM
CONTROL GP-FUEL RATIO
G3500H Generator Set Engine Air/Fuel Ratio Control - NO<SUB>X</SUB> Feedback
1.1. Required Inputs from the Customer
2.2. Fuel Quality
3.2. Engine Load
4.1. Mode of Operation
5.1. Open Loop Mode
6.1. NOx Feedback

The Electronic Control Module (ECM) provides control of the air/fuel mixture for maximum performance and for efficiency at low emission levels. The system includes several factors: maps in the ECM, output drivers in the ECM, sensors, and customers input via the AVSpare Electronic Technician (ET).

Refer to Illustration 1 for a diagram of the main components and inputs for the system.



Illustration 1g06146860
Diagram of the air/fuel ratio control

Required Inputs from the Customer

to control the air/fuel ratio, the control system depends on these inputs from the customer:

  • Fuel Quality

  • Engine Load

Fuel Quality

Before the initial start-up, a current gas analysis is required. Data from the gas analysis must be entered into AVSpare Software, LERW4485, "Gas Engine Rating Pro (GERP)". The results are programmed into the ECM.

Note: Is important to use the AVSpare Software, LERW4485, "Gas Engine Rating Pro (GERP)". Use of only the data from the gas analysis can result in incorrect settings.

The ECM must have values for the following parameters. The values are entered via the "Configuration" screen of Cat ET:

  • "Fuel Quality Input Type Configuration"

  • "Fuel Quality"

  • "Fuel Quality Sensor LHV Lower Setpoint"

  • "Fuel Quality Sensor LHV Upper Setpoint"

  • "Gas Specific Gravity"

  • "Fuel Specific Heat Ratio"

The "Fuel Quality Input Type Configuration" parameter setting will be determined by the consistency of the fuel supply.

Select "Configured Value" for engines that run on a consistent fuel supply.

Select "4-20 mA" for engines that utilize a 4-20 mA signal from a fuel quality sensor due to an inconsistent fuel supply.

The following parameter is used only when the "Fuel Quality Input Type Configuration" is set to "Configured Value":

  • Fuel Quality

A fixed LHV will be entered in the "Fuel Quality" parameter for engines that run on a consistent fuel supply.

The ECM uses the LHV to help determine the fuel command to the fuel metering valve.

The fuel command is sent to the fuel metering valve via the CAN data link.

The following parameters are used only when the "Fuel Quality Input Type Configuration" is set to "4-20 mA":

  • Fuel Quality Sensor LHV Lower Setpoint

  • Fuel Quality Sensor LHV Upper Setpoint

The ECM provides the following information to the fuel metering valve via the CAN data link:

  • "Fuel Specific Heat Ratio"

  • "Gas Specific Gravity"

Note: For more details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".

Engine Load

The ECM must have values for the following parameters. The values are entered via the "Configuration" screen of Cat ET:

  • "Engine Load Input Configuration"

  • "Engine Output Power"

  • "Engine Driven Accessory Load Configuration"

  • "Generator Output Power Input Type Configuration" and data range

  • "Generator Efficiency"

Note: For more details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".

Mode of Operation

The air/fuel ratio control has two basic modes of operation:

  • Open loop

  • NOX feedback

The mode of operation is determined by the "Emissions Feedback Mode Configuration" parameter. Cat ET is used to change the mode of operation.

Select "Feedback Disable" to activate the open loop mode.

Select "NOx Feedback" to activate the feedback mode.

Open Loop Mode

The open loop mode of operation uses no feedback.

During operation in this mode, the ECM controls the air/fuel ratio with maps and with calculations for the desired air/fuel ratio.

The air/fuel ratio is controlled in the open loop mode from start-up until the engine load becomes greater than 40 percent. Above 40 percent the engine operates in feedback mode. When, operating in feedback mode the engine load must be dropped below 25 percent for the control system to switch to open loop mode.

The ECM uses a Fuel Correction Factor (FCF) to help determine the fuel command to the fuel metering valve. During operation in the open loop mode, the FCF is always 100 percent.

The ECM uses the LHV to help determine the fuel command to the fuel metering valve.

The LHV can be varied in the customer programmable "Fuel Quality" parameter to affect the air/fuel ratio.

Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust" .

NOx Feedback

During operation in the feedback mode, the ECM continues to calculate the desired air/fuel ratio. The result is still used to calculate the fuel command.

The ECM uses the following to calculate the desired NOX factor.

  • "Desired Engine Exhaust NOx Level Setting"

  • Engine load

  • Engine speed

  • The measured NOX level in the exhaust.

Exhaust NOX concentration is communicated to the ECM from the NOX sensor via the CAN data link.

The customer programmable "Desired Engine Exhaust NOx Level Setting" can be varied to affect the air/fuel ratio.

The calculation for the desired NOX level is used to adjust the FCF.

Because some of the factors for calculating the desired NOX level will vary during operation, the FCF will also vary during operation.

The reaction of the FCF can be adjusted further with the following configuration parameters:

  • Desired Engine Exhaust NOx Level Setting

  • Air/Fuel Proportional Gain

The ECM determines the fuel command to the fuel metering valve. The command is sent to the fuel metering valve via the CAN data link.

Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust" .

Information System:

12M Series 3, 140M Series 3, 160M Series 3, 140, 150 and and 160 Motor Graders Blade Cushion - If Equipped
2013/11/13 New Exhaust Temperature Sensor Groups Are Used on Certain 3500, 3600, C175, and C280 Marine and Petroleum Off-Shore Applications {1408, 1900, 1906, 1919, 1921, 1922, 1928, 1929, 7498}
C15 and C18 On-Highway Engines Engine Oil Cooler - Remove and Install - C15
C15 and C18 On-Highway Engines Engine Oil Cooler - Remove and Install - C18
C280-08 Marine Engine After Stopping Engine
Installation Procedure For The New Throttle Body Cooling Lines On Certain G3500 Engines{1380}
C280-12 Marine Engine Engine Power Ratings
CX31-P600 Petroleum Transmission Transmission Planetary
CX31-P600 Petroleum Transmission General Information
C15 and C18 On-Highway Engines Air Inlet Elbow - Remove and Install
C9 Petroleum Engine Product Description
C280-08 Marine Engine Engine Power Ratings
C15 and C18 On-Highway Engines Engine Oil Filter Base - Remove and Install - C18
G3500H Generator Set Engine Lubrication System
C15 and C18 On-Highway Engines Engine Oil Filter Base - Remove and Install - C15
G3500H Generator Set Engine Cooling System
Reuse and Salvage for Engine Dampers {1202, 1205}
C15 and C18 On-Highway Engines Engine Oil Pump - Remove and Install
2014/02/20 New Anti Drift Valves are Now Used on Certain 345D and 349D Excavators {5059}
CX31-P600 Petroleum Transmission Visual Inspection
CX31-P600 Petroleum Transmission Torque Converter Troubleshooting
C15 and C18 On-Highway Engines Water Temperature Regulator Housing - Remove and Install
CX31-P600 Petroleum Transmission Transmission Planetary Troubleshooting
C15 and C18 On-Highway Engines Flywheel - Remove and Install