Dresser‑Rand®

Enginuity® RELi E³
Air-Fuel Ratio Controller

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Introduction
The Dresser‑Rand Reliable, Intelligent, Enginuity®, Engine and Emissions (RELi E3)
air-fuel ratio control (AFRC) is one of the most innovative and comprehensive AFRC
systems available for carbureted, four stroke, natural gas reciprocating engines. The
RELi E³ control applies a holistic systems approach to keep your engine’s emissions
precisely controlled. Closed-loop air-fuel ratio control is dictated by the post-catalyst
oxygen (O²) sensor, providing dependable regulation of engine emissions. System
controls based on pre-catalyst O² sensors alone do not provide a true indication
of emissions, which is why the automotive industry abandoned pre-catalyst control
years ago. The RELi E³ systems also use speed inputs, manifold air temperatures
and manifold air pressures to provide a surrogate load calculation, which is fed
back into the system algorithms for ensured AFR control at all process conditions.
Furthermore, the system monitors catalyst conditions and detects misfires to protect
your catalyst from premature damage. Lastly, the RELi E³ AFRC employs new
sensor technologies and control algorithms to help ensure that your engine remains
in control in all operating scenarios.

Advanced Sensor Technology
Advanced Features
•t Sensor technology
•t Fuel control algorithm
•t Catalyst protection
•t Monitoring of critical
engine parameters

Dresser‑Rand uses the StableSense™ Heated Exhaust Gas Oxygen Sensors
(HEGO) that are manufactured specifically for industrial natural gas applications.
These HEGOs differ from the automotive sensors used with other air-fuel ratio
controllers, because they have been specially developed to detect oxygen in
natural gas exhaust and are far less sensitive to the methane (CH4) and hydrogen
(H²) found in this environment. The StableSense sensors do not experience drift
or interference from these natural gas combustion products, unlike the gasoline
O² sensors used by the automotive industry. The sensitivity and accuracy of these
newly-developed sensors let them respond quickly to changes in the O² levels in the
exhaust stream, allowing tighter control of the engine’s air-fuel ratio, and therefore
emissions. The StableSense O² sensors are more rugged than automotive sensors
and are designed for a nominal 2,000 hour operating life.

Dithering Algorithm
The dithering, or switching, of an air-fuel ratio from slightly rich to a slightly lean
mix of the air-fuel ratio set point produces better pollutant removal efficiencies in
the catalyst. Dithering technology has proven to work with three-way catalysts