Lambda Control for Gaseous Engines Using Inner Pressure Loop

Solution Overview

Problem

Existing gaseous fueled internal combustion engines face performance issues due to the large volume between the fuel control valve and the exhaust gas oxygen sensor, leading to inadequate closed loop lambda control and poor responsiveness to speed/load transients.

Innovation Solution

The introduction of an inner control loop based on the pressure of gaseous fuel downstream of the fuel control valve and upstream of the carburetor, combined with operating point based dynamic parameter scheduling in the lambda feedback control loop, utilizing a fuel delta pressure sensor and dynamic parameter adjustments to optimize lambda control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fuel control valve is introduced downstream of the pressure regulator and upstream of the carburetor to enable closed loop lambda control, then lambda control capability is improved, but the large volume between the valve and sensor introduces significant dynamics that worsen engine responsiveness

Engineering Contradiction:

Improvelambda control capabilityVSAvoidengine responsiveness

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The control system is segmented into two independent control loops: an inner loop that controls fuel pressure using a pressure sensor located close to the carburetor, and an outer loop that controls lambda using the EGO sensor. This segmentation allows the inner loop to respond quickly to fuel delivery changes without being constrained by the slow dynamics of the exhaust gas sensor, thereby resolving the contradiction between lambda control capability and engine responsiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Fuel pressure is introduced as an intermediary controlled variable between the fuel control valve and the lambda control objective. By controlling fuel pressure directly through the inner loop, the system achieves faster response to fuel delivery changes compared to directly controlling lambda based on exhaust gas oxygen feedback, thus improving engine responsiveness while maintaining lambda control capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the fuel control valve position is adjusted quickly to improve responsiveness, then engine responsiveness is improved, but lambda control stability deteriorates due to the large volume dynamics

Engineering Contradiction:

Improvefuel control valve response speedVSAvoidlambda control stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The control system is segmented into two independent control loops: an inner loop that controls fuel pressure using a pressure sensor located close to the carburetor, and an outer loop that controls lambda using the EGO sensor. This segmentation allows the inner loop to respond quickly to fuel delivery changes without being constrained by the slow dynamics of the exhaust gas sensor, thereby resolving the contradiction between lambda control capability and engine responsiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inner fuel pressure control loop performs preliminary action by adjusting fuel pressure in advance to compensate for load changes and transient conditions. This preliminary adjustment of fuel delivery prevents large lambda excursions, allowing the outer lambda control loop to operate more stably even when the fuel control valve responds quickly.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If aggressive tuning is applied to improve lambda control performance, then lambda control precision is improved, but the system becomes unstable due to the large volume dynamics between valve and sensor

Engineering Contradiction:

Improvelambda control precisionVSAvoidcontrol loop stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The control system is segmented into two independent control loops: an inner loop that controls fuel pressure using a pressure sensor located close to the carburetor, and an outer loop that controls lambda using the EGO sensor. This segmentation allows the inner loop to respond quickly to fuel delivery changes without being constrained by the slow dynamics of the exhaust gas sensor, thereby resolving the contradiction between lambda control capability and engine responsiveness.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inner fuel pressure control loop performs preliminary action by adjusting fuel pressure in advance to compensate for load changes and transient conditions. This preliminary adjustment of fuel delivery prevents large lambda excursions, allowing the outer lambda control loop to operate more stably even when the fuel control valve responds quickly.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7958866B2Method and system for closed loop lambda control of a gaseous fueled internal combustion engine

Publication Date: 2011.06.14 CUMMINS INTELLECTUAL PROPERTY INC

AI summary

A method and system in accordance with the present invention provides for improved lambda control utility that includes the following: the introduction of an inner control loop to the lambda control based on the pressure of the gaseous fuel downstream of the fuel control valve and upstream of the carburetor relative to the pressure of the air at the inlet of the carburetor, and the introduction of operating point based dynamic parameter scheduling in the lambda feedback control loop. The combination of these enhancements, working together, will allow an engine system to consistently meet the mandated performance requirements via tighter lambda control in the presence of set point changes and load disturbances.