Research Projects

Project at a Glance

Project Status: complete

Title: Adaptive low emission microturbine for renewable fuels

Principal Investigator / Author(s): Werts, Hack, McDonell

Contractor: UC Irvine

Contract Number: icat 6-12


Research Program Area: Emissions Monitoring & Control

Topic Areas: ICAT Grants / Technology, Mobile Sources & Fuels


Abstract:

The objective of this Innovative Clean Air Technology research project was to reduce and maintain low emissions and improve the efficiency and reliability of a microturbine generator (MTG) system designed to burn renewable fuels. Some renewable fuels, such as methane emissions from landfills, vary in composition and are, as a result, challenging to burn efficiently and cleanly. To accomplish this, an Active Combustion Control System (ACCS) with a novel feedback sensor was implemented on an MTG. The ACCS uses a sensor, control logic, and variable geometry injectors to provide control of combustor fuel/air ratio independent of generator load. Active control provides a method to achieve low emissions while compensating for variation in fuel composition in both new and retrofit installations by allowing the system to monitor the combustion process and adapt to systematic and environmental changes. Information about the state of the combustion is obtained via various sensors incorporated into the injector. Woodward Incorporated worked with UC Irvine on the design of the injectors, including the actuation, control, and sensor integration and also provided key sensor and data recording equipment for the project. Using this equipment and the “smart injectors”, data from the reaction were obtained in the form of both light emission and electrical current. These data were analyzed and correlations with CO and NOx emissions levels were developed. Woodward provided key support relative to interpretation and analysis of the signals obtained. A transfer function between emissions, fuel valve position, and the sensor outputs was developed using systematically controlled fuel compositions as provided by the gas blending facility at UC Irvine. Relations between NOx emissions and ion mean signals were demonstrated which were insensitive to CO2 concentrations. In addition, analyses of the dynamic aspect of the signal were related to CO concentration. Ultimately, however, the transfer functions proved overly sensitive to ion-probe position to be robustly integrated into a full closed loop system. This was noted through repetition of the tests with different ion-probe build ups. As a result, while a control system was conceptually developed around the ion signal and the actuated injectors, it could not be fully implemented on the engine due to this transfer function variability. Despite this, the engine was deployed with the variable geometry injectors developed for the project at a waste water treatment facility to evaluate the integrity of the variable geometry injectors and actuators. This > 3700 hour trial demonstrated the integrity of the injectors and actuators which is a significant accomplishment. Further, the impact of the injector geometry on pollutant emissions was demonstrated, indicating that the variable geometry injectors were successful in reducing emissions. As a result, once a suitable robust sensing strategy is identified (e.g., pressure transducers or optical methods) the control system can likely be implemented successfully for closed loop operation to minimize emissions in light of variation in ambient conditions, engine wear, and fuel composition.


 

For questions regarding research reports, contact: Heather Choi at (916) 322-3893

Stay involved, sign up with ARB's Research Email Listserver

preload