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.
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 aircraft’s 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 Technology’s 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.
Adaptive combustion control to reduce the emissions such as CO2 and NOx
The emissions are going to be reduced using tangential air inlet to make swirling
flame combustion. This method will reduce the emissions and also reduce the flame
temperature as well, which will affect the engine efficiency. It is necessary to find the
optimum swirl number to reduce emissions and raise efficiency in order to design a
controller which will keep the engine combusting at this optimum point.
Also thermoacoustic control will be important to dampen the pressure and temperature
oscillation. CFD analysis will be performed in parallel to predict, compare, and check
combustion. CFD will be especially helpful to find the optimum combustion parameters
to raise the efficiency of the engine while reducing emissions.
Conceptual Design of Solar Powered UAV
A solar powered unmanned aerial vehicle (UAV) is currently being designed in the
Multidisciplinary Flight Dynamics and Control Laboratory (MFDCLab) at California State
University, Los Angeles (CSULA). The aircraft would use high-efficiency flexible
photovoltaic cells or solar cells to power the aircraft. The solar cells integrated
onto the UAV would theoretically provide enough power for the aircraft to fly through
the day and yet still has enough energy to charge a bank of batteries for night flight.
In theory, the cycle should repeat indefinitely, thus making a sustainable flight.
The propulsion system would consist of a high-efficiency electric motor powered by solar
cell/battery hybrid system. The solar UAV may also be able to integrate autopilot system
which has been successfully developed and tested by the MFDCLab. One of the goals is to
utilize clean and renewable energy source from the sun and prove the sustainability and
the feasibility of a multi-day solar powered flight. It would also demonstrate the
advancement of today’s solar cell technology. Moreover, the possible application for
solar powered UAV may include a wide variety of long endurance remote sensing applications.
The development of the solar powered UAV is currently at a conceptual design stage.
Hsueh-Chin Lin (Airs Lin)
Embedded Architecture for Multimedia Data StreamingIn this funding period, we have learned the design constraints of embedded computer systems while meeting the real-time performance requirements of some multimedia data stream applications. We have learned the hardware/software co-design methodology and defined suitable input/output interface for seamless integration of the embedded components. Besides, we focused on the micro kernel based on the Windows CE technology. Windows CE is a variation of Microsoft's Windows operating system for minimalistic computers and embedded systems. It provides us a small footprint, unified kernel, componentized, and 32-bit native hard real-time embedded operating system that runs on multiple processor architectures (ARM, MIPS, SH4, x86). This makes CE the right choice for a variety of smaller footprint devices - ranging from multimedia data streaming, power conscious GPS handhelds to real-time, mission critical industrial controller. In this project, we have studied building a Windows CE kernel for x86 systems and Intel XScale PXA270 (ARM architecture) systems, debugging programs in CE system, the working of real-time in CE system, and the performance of Windows CE. Finally, we developed a multimedia player in Windows CE and investigate the performance of a simplified MPEG decoder on the Windows CE embedded platform.
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 UAV’s.
Development of Data Acquisition System for UAV testbed
Design and test LabVIEW measurement programs and the corresponding electronic circuits
for tests conducted by the UAV team. The goal is to create useful tools that will expedite
the process of designing a UAV. These measurement programs will be accessible to anyone
working in the MFDC lab needing to quickly acquire data for analysis. The programs will
automatically generate MS Office spreadsheet files that will then be able to be analyzed on
any of the labs computers. The current data acquisition program under construction is for
a fuel cell static prop test. The data to be acquired is voltage, current and temperature.