Selective catalytic reduction (SCR) technology is being
considered as the potential strategy for significant reduction of
NOx emissions from diesel engines. Many challenges exist
in the development of an On-Road SCR retrofit system in terms of
system integration and optimization of control strategy in order to
achieve highest NOx reduction given the diversity of
duty cycles. The main considered challenges are: - The development
of a generic control strategy that would work for a broad range of
engines, - Development of a reliable and durable injection system
that would be able to withstand the harsh environments on a
heavy-duty vehicle, - Packaging of the system to be able to fit on
a number of vehicles with different configurations, - Controlling
ammonia slip and assurance of reducing agent (Urea) availability
and quality.
In this study a prototype SCR system was evaluated over engine
and chassis dynamometer test cycles. Two heavy-duty diesel engines
were used during engine dynamometer evaluations using transient and
steady state test cycles; a 2004 Caterpillar C11 and 2000 Cummins
ISM highway diesel engines. At the completion of the engine test
program, an in-use single-axle heavy-duty truck was obtained with a
similar Caterpillar C11 engine and the same SCR system was
installed for further evaluation during chassis dynamometer tests.
These tests were conducted over transient and constant speed test
cycles at standard and lowered ambient temperature (-15°C). The
engine test results are reported for 4 urea injection calibrations
over transient testing showing 84% NOx reduction with
Calibration-04 at 2 ppm NH₃ slip when run on Caterpillar C11 engine
and urea injection Calibration-04. During the chassis dynamometer
testing with system flashed with Calibration-01, the NOx
emissions were lowered by 50% over the transient cycle and 50, 80,
and 98 percent under steady state tests at 50, 80, and 100
kilometers per hour, respectively.
The goal of this work is to outline the development and
optimization of the control strategy and hardware integration of
the retrofit system; - System development and integration aspects.
- The test results from the calibration of the control strategy
using a Cummins ISM engine over FTP transient cycle. - Test results
of the optimized system that was tested on a Caterpillar C11 engine
over FTP cycle. - A summary of the performance of the field demo
program highlighting component durability.