What is a lambda controller in auxiliary diesel engines

In auxiliary diesel engines, a lambda controller, also known as an air-fuel ratio controller or oxygen sensor controller, is a device used to monitor and control the air-fuel ratio during combustion. The lambda controller ensures that the engine operates at the optimal air-fuel ratio for efficient and clean combustion.
Here's how a lambda controller works in an auxiliary diesel engine:
Oxygen sensor: The lambda controller is typically connected to an oxygen sensor installed in the exhaust system of the engine. The oxygen sensor measures the amount of oxygen present in the exhaust gases, which provides an indication of the combustion efficiency.
Air-fuel ratio control: The lambda controller continuously receives feedback from the oxygen sensor regarding the oxygen content in the exhaust gases. Based on this feedback, the controller adjusts the fuel supply to maintain the desired air-fuel ratio.
Lambda value: The air-fuel ratio is often expressed in terms of the lambda (λ) value, which is the ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio for complete combustion. A lambda value of 1 indicates a stoichiometric air-fuel ratio, where all the fuel is completely burned with no excess oxygen or unburned fuel.
Closed-loop control: The lambda controller operates in a closed-loop control system. It compares the measured lambda value from the oxygen sensor with the desired lambda value, which is typically set by the engine manufacturer or based on emission regulations. If the measured lambda value deviates from the desired value, the controller adjusts the fuel supply accordingly to bring it back to the target range.
Fuel adjustment: The lambda controller adjusts the fuel supply by modulating the fuel flow rate or controlling fuel injectors, depending on the engine design. It can increase or decrease the fuel supply to achieve the optimal air-fuel ratio.
Emission control: By maintaining the correct air-fuel ratio, the lambda controller helps optimize combustion efficiency and minimize emissions of pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC). This is particularly important for compliance with emission regulations in marine and stationary applications.
The lambda controller in an auxiliary diesel engine plays a crucial role in achieving efficient combustion and reducing emissions. It continuously monitors the air-fuel ratio through feedback from an oxygen sensor and adjusts the fuel supply to maintain the desired ratio. This helps improve engine performance, fuel efficiency, and environmental sustainability.