Lambda Control with NOx Sensor for Gasoline Engine Emissions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lambda control systems for gasoline engines struggle to maintain optimal emissions conversion due to shifts in sensor characteristic curves and catalytic converter aging, leading to increased emissions that go unnoticed.
Innovation Solution
The introduction of an NOx sensor allows for direct measurement of emissions, enabling the detection of shifts in sensor characteristic curves and catalytic converter aging. This information is used to adjust the lambda control through a cascade control system involving multiple controllers, ensuring the engine operates within the optimal lambda window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a binary lambda sensor is used for trim control, then the lambda window can be controlled, but the control becomes unreliable when the characteristic curve shifts due to cross-sensitivities or sensor temperature
Solution Approach 1:
An NOx sensor is introduced as an intermediary measurement device to detect whether the catalytic converter is operating within the lambda window. This additional sensor provides direct feedback on conversion effectiveness, allowing the control system to verify and correct lambda control accuracy when binary lambda sensor characteristics drift.
Solution Approach 2:
The system implements feedback control by continuously monitoring NOx emissions and using this information to adjust the lambda setpoint. When the NOx sensor detects elevated emissions indicating the lambda window has been lost, the control system responds by adjusting fuel injection or ignition timing to restore optimal lambda conditions.
2Device complexity
If trim control is performed using only lambda sensors, then the system remains simple, but emissions can increase unnoticed due to undetected shifts in sensor characteristics or catalytic converter aging
Solution Approach 1:
The NOx sensor acts as an intermediary that directly measures harmful emissions, providing objective feedback on catalytic converter performance. This allows the system to detect when emissions are increasing due to sensor drift or converter aging, enabling corrective action before environmental damage occurs.
Solution Approach 2:
The system replaces reliance on indirect lambda sensor measurements with direct chemical analysis of exhaust gases via the NOx sensor. This substitution provides more accurate and reliable detection of emission levels and lambda window status, enabling better control despite the added complexity.
3Measurement precision
If the lambda sensor cannot measure emissions directly, then the sensor system remains simple, but the optimum conversion remains undetected and the catalytic converter is no longer operated in the lambda window
Solution Approach 1:
The NOx sensor serves as an intermediary measurement device that directly quantifies emission levels and provides objective evidence of catalytic converter performance. This enables the control system to detect when optimum conversion is no longer achieved, even though the lambda sensors themselves cannot directly measure emissions.
Data Source
AI summary
A device for lambda control of a gasoline engine includes a first three-way catalytic converter, a second three-way catalytic converter, a linear lambda sensor, a binary lambda sensor and an NOx sensor. The first three-way catalytic converter is arranged upstream of the second three-way catalytic converter. The linear lambda sensor is arranged upstream of the first three-way catalytic converter. The binary lambda sensor is arranged downstream of the first three-way catalytic converter or the binary lambda sensor is arranged in the first three-way catalytic converter or in the second three-way catalytic converter and is arranged upstream of the second three-way catalytic converter. The NOx sensor is arranged downstream of the second three-way catalytic converter, and the linear lambda sensor, the binary lambda sensor and the NOx sensor are connected to a control device for lambda control.