Bryan Eisenhower

My work at UTRC:
I worked in the Systems and Controls group which had a diverse focus including reduced order dynamic modeling, numerical simulation, as well as linear and nonlinear analysis of controlled systems.  As UTRC works with all of the business units, I was fortunate to be involved with a diverse set of projects in my tenure their.  These projects are summarized below: 

-Dynamic Modeling of Fuel Cells
My first week at UTRC coincided with a departure of a senior dynamicist at the Fuel Cell business unit.  With him went the knowledge of needed to operate a Fortran code of a fuel cell power plant.  Myself, and a group of a dozen or so engineers with different backgrounds both at the business unit and a UTRC were tasked with developing a new dynamic model of the system, that was 1) quickly adapted to new system designs, and 2) numerically efficient.  We chose Dymola because of its abilities in equation parsing and translation (ie no need for causal modeling), and its DAE solver.  The DAEs in this system arise from the multiple feedback of fluidic loops as well as numerous constraints from interconnection of different dynamic systems (note the DAE solver in Dymola was written by L. Petzold, UCSB).  We were successful in creating a library containing dynamic models of components that make up a fuel cell.  These component could be interconnected using a GUI, translated to create efficient code, and simulated all within a day or so.  This was a huge success and had significant impact on the way on the concept of Fuel Cell design.

 -Transcritical Heat Pump Development:

With a corporate motivation for green products (as well as increasing international pressure through regulation), Carrier was interested in investigating natural refrigerants for their products.  Experts at UTRC performed a technical vs. business case trade study and determined that due to the thermophysical properties of natural refrigerants (CO2 for instance) a hot water heat pump would be the most efficient product for market introduction.  The use of CO2 however created new control challenges due to the transcritical nature of the cycle.  That is, because the cycle traverses the critical point, a new degree of freedom is provided for control.  It was my job to design, implement, and test a controller that capitalizes on this.  This included investigating many adaptive approaches including both LMS and extremum seeking control, as well as nonlinear feedback control to avoid bifurcations in the system.  I was able to work on ~7 patents for this project which was a very useful exercise.

 

-Hardware in the Loop Testing

UTC Power, a new business unit, was formed while I was working at UTRC who’s focus is to offer power related solutions that spanning many domains.  For instance electricity producers from heat (reversed rankine cycle) (product page), or electricity produced from gas (typical microturbine) and cooling and heating produced from the waste heat from these turbines (product page).  Total system efficiencies and emissions are targeted in these ‘total solutions’.  Though the benefits of these integrated solutions are many, they offer technical challenges to the control engineers in charge of integrating them.  The challenges are twofold: 1) integration of systems with controllers crossing different platforms and intellectually protected protocols, and 2) new interactions that arise do to the new coupling interactions between the different dynamical systems.   

To reduce risk when qualifying the functionality of new control algorithms, we used a virtual qualification environment to supplement the experimental testing.  Since the time constants of power/heating/cooling and related equipment are very long, dynamic testing takes quiet some time in order to gather information at many operating situations.  In addition to this, dynamic testing at edges of the operating envelope (ie dangerous areas) is challenging in the laboratory.  A hardware in the loop environment was created to help with these situations.  The technical challenges of this effort was to capture enough physics so that the results of the model simulation was accurate, while still being able to integrate in real time.  We were able to get enough of the physics of the components (including two phase flows) that was sufficient to match control-oriented data while still solvable in an integration step on dSPACE hardware.  These experiments proved to be very helpful as a supplement to the experimental qualification of the new products.

-Augmentor Instabilities

The final year I spent at UTRC, I became involved in studying combustor instabilities again.  Because of the sensitivity and competitiveness in this market, much of what I was doing is not public.  The broad focus was to gain understanding and control of linear and nonlinear oscillations in jet engines.  Fortunately on portion of the work were performing was abstracted to a point that could be communicated to our partners in academia. 

Working with Igor Mezic at UCSB we were able to extract some knowledge of the behavior of DNA chains to help understand the behavior of thermo-acoustic oscillations on an annular domain.  This sparked my interest and has seeded some of my thoughts regarding graduate work at UCSB.