Comparing CFD with Combustion Capabilities NOx and CO2 Production to Physical Results in a Swirled-Air,
Liquid-Fuel Combustion Chamber
With a grant from NASA administered through Dryden Flight Research Center (DFRC),
the Multidisciplinary Flight Dynamics and Control Laboratory (MFDCLab) at California State University,
Los Angeles has conducted research, both physical and virtual in the reduction of NOx and CO2 in the
processes that occur in a simulated jet engine combustion chamber. A 2.7 ft long, swirled-air, liquid
fuel combustion chamber was designed, constructed, and assembled. Kerosene, sprayed at 0.75 gallons
per hour in the shape of a solid cone, at an angle of 30 degrees was used as the fuel and ambient
air as the oxidizer. There are three air inlets: axial, tangential, and a secondary or dilution zone;
all three combined produce airflow of 16.99 cubic feet per minute (cfm) maintaining a stoichiometric
fuel to air ratio of 1. A stronger swirl, more tangential than axial air, and therefore a higher swirl
number, has yielded a decrease in the production of NOx and CO2 (carbon dioxide) as well as physical
solid particulate formation. Maintaining a constant fuel to air ratio is critical to obtaining results
that do not depend on the addition of air but on a changing proportion of air from both the axial and
tangential air ports. With a constant secondary air flow, manipulating both the tangential and axial flow
rate varies the swirl number. A stronger swirl produces what is know as a flow reversal zone just after
the fuel spray/diffuser inlet and aids in the mixture of the fuel and air. Also, a strong flame holding
region is produced in and around this flow reversal area. This experiment will compare combustion products
of NOx and CO2 from a physical model to those produced by the virtual model, in the context of simulating
a jet engine combustion chamber and validating the software. The comparison between physical and CO2
emissions from the CFD is presented in the figure as well as swirl effect on flame.
Dynamic Response of a Proton Exchange Membrane Fuel Cell in an Uninhabited Air Vehicle
The use of PEM fuel cells to power uninhabited air vehicles is a relatively new application of fuel cell
technology presenting several challenges with respect to fuel cell efficiency. When flight conditions warrant
rapid increases in throttle settings, additional current is drawn from the fuel cell stack causing a voltage drop.
The addition of a secondary power source such as a battery or capacitor can supplement the required power but must
be configured and sized in a manner that justifies the additional weight and circuit components needed for their
integration. A balance between maximizing power and electrical efficiency while minimizing weight and electrical
losses requires careful analysis of a dynamic system. Considerations from the disciplines of thermodynamics,
mechanical and electrical engineering design, chemistry and aerodynamics present an exciting challenge in development
of fuel cell powered UAVÂs.
Sang Bum Choi
Development of Fuel Cell Powered UAV for Long Endurance
In conjunction with Oklahoma State University, a long endurance Unmanned Aerial Vehicle (UAV) is being developed
to break the world endurance record of 15 hours and 37 minutes. The electric motor and propeller propulsion system will
be powered by a proton exchange membrane hydrogen fuel cell with assistance from lithium polymer batteries for extra power.
The hydrogen will be stored in a high pressure tank. The main advantages of using fuel cells are its excellent power to
weight ratio, efficiency, environmentally friendly, and as a replacement to internal combustion engines. The project will
prove the advantages of using new alternative energy technology.
Unmanned Aerial Vehicle Platform - Autopilot Integration
The term Unmanned Aerial Vehicle (UAV) is given to any aircraft that is capable of flying without a pilot onboard.
Typically these vehicles are controlled via numerous ways ranging from a pilot in a ground-station, through
pre-programmed flight plans, or with complex dynamic control systems. The applications of UAVs are wide and varied
from target and decoy for military training, to reconnaissance missions in hostile situations, to civil missions such
as search and rescue, firefighting and police operation.
A need arises for the Multidisciplinary Flight Dynamics and Control Laboratory (MFDCLab) to become actively involved
with UAV technology. The primary goal of the project is to create an UAV Platform that can be used as a learning tool
for future MFDCLab members. The UAV platform is being developed in a three-phase process. The first phase includes the
selection and built of an almost ready to fly (ARF) aircraft. The aircraft chosen was Tower Trainer 60 shown in
Figure 1. The first phase also includes, the aerodynamic analysis of
the aircraft, using hand calculations and computational fluid dynamic (CFD) code FLUENT and the first remotely piloted
(RC) flight test. Figure 2 shows the mesh used for the CFD analysis.
The second phase of the project involves hardware in the loop set up, development of our aircraftÂs simulator,
hardware in the loop simulations and a modified RC flight. Hardware in the loop (HIL) is needed to detect errors in the
systems prior to flight and to program the autopilot. The autopilot being used for this project is Cloud Cap TechnologyÂs
Piccolo Plus, as shown in Figure 3. The complete HIL set up can be seen
in Figure 4. The third and final phase will be adjustments of autopilot
gains and ultimately autonomous flight.