Flow Sensor Patent Awarded to NETL Researchers

	This is a prototype bidirectional flow sensor in proof-of-concept testing.

NETL researchers have invented an ionization based multi-directional flow sensor for monitoring flow speed and direction in advanced power systems.

Researchers Ben Chorpening and Kent Casleton have been awarded a patent for the method, system, and apparatus for real-time monitoring of flow speed and direction with fast response and minimal pressure drop.

The sensor has potential applications in advanced power systems including hybrid fuel cell/turbine systems.

The patented method uses ion transport in flames to sense changes in flow.

The concept originated from NETL research and development work on flame ionization sensing, which is the underlying technology behind NETL’s patented Combustion Control and Diagnostics Sensor (CCADS).

The new flow sensing technology has application for monitoring air flows at critical locations in low pressure drop flow systems especially in systems where flow reversal can be detrimental to performance.

Additional development of the sensor technology is needed to enhance prospects for commercial deployment.

NETL Studies Low Emission Hydrogen Flames

	Nate Weiland observes an experiment in NETL’s Fundamental Combustion Laboratory. This lab provides important data that relates to the use of hydrogen as a fuel.

Researchers at NETL are developing new combustion technologies to enable efficient, clean utilization of biomass and coal fuels for power generation.

Describing their research in NETL’s Fundamental Combustion Lab that investigates flame stability issues which limit the operational performance of high-hydrogen gas turbine combustors, the researchers have published an article Combustion Science and Technology.

Carbon management strategies being considered involve carbon removal from the fuel, using gasification of biomass and coal fuels.  The resulting fuel gas is typically high in hydrogen which presents several challenges for combustion systems.

The NETL research uses an approach called dilute diffusion flame combustion to avoid flashback and auto-ignition issues associated with the use of premixed hydrogen flames.

Reduction in NOx emissions from this type of burner is partially accomplished by diluting the hydrogen fuel with nitrogen (a byproduct from the gasifier’s air separation unit in an IGCC plant) to reduce peak flame temperatures. The remaining NOx reductions are attained by reducing the fuel jet’s exit diameter and increasing its velocity to reduce the flame residence time.

For operation at high velocities, the static stability of these hydrogen/nitrogen diffusion flames becomes a limiting factor, and little existing data is available to help predict the stability limits of these flames.

The journal article focuses on two flame types encountered in the course of NETL’s study and suggests probable stability mechanisms that allow these flames to stabilize in their observed locations. In addition, the article identifies criteria that can be used to determine the allowable stability regimes of a particular combustor geometry as a function of combustor flow conditions.

The NETL research has practical application for equipment manufacturers who are developing high-hydrogen gas turbine combustors. The research is also of interest to the scientific combustion community, as some of the lifted flame types and stability limits examined have not been studied previously.

NETL’s Active Combustion Throttle Enters Prototype Testing Phase

	Dr. Jeff Vipperman, right, and Ph.D. student Pat Schimoler test the actuator function of the Active Combustion Throttle. The project is entering the prototype testing phase.

A team of engineers from NETL and the University of Pittsburgh has produced and begun testing the first fully integrated valve body and flow control actuator.

The active combustion throttle (ACT) concept uses a fast acting control valve to modulate fuel flow in a combustor to control emissions and improve combustion stability. The ACT concept was conceived by NETL and the design was developed working with the University of Pittsburgh as part of NETL’s University Research Initiative.

The valve design includes a unique approach to valve actuation which should enable high speed operation up to 1000 Hz. A joint patent application by NETL and the University of Pittsburgh has been filed.

Originally intended for trimming fuel flows for gas turbines for control of combustion dynamics and NOx emissions, the valve is being developed for use in any gas-burning system. In particular, the valve could have utility for enabling fuel flexible combustion systems capable of operation with a range of gaseous fuels such as natural gas, liquified natural gas, coal syn-gas or biomass generated fuels.