Poomin Park

Active power management system for an unmanned aerial vehicle powered by solar cells, a fuel cell, and batteries

200W class, low-speed, long-endurance unmanned aerial vehicle (UAV) that employs solar cells, a fuel cell, and a battery pack as its power sources is considered. This study applies an active power management method that directs each individual source to generate the appropriate power, depending on the power supply and demand, instead of the passive method in which the power sources irresponsibly generate power, depending on their characteristics. The power management system (PMS) under active management determines the power output from each source. The flight test of the UAV with a PMS onboard is conducted for 3.8 h. The active PMS verifies its own feasibility as it successfully keeps the power sources within their proper operational bounds and maintains a target state-of-charge of 45%, while responding to the various conditions associated with the power required. In addition, through a comparison of flight test results with a power simulation of the passive method, the usefulness, advantages, and disadvantages of an active power management method over a passive method are investigated.

Power Characteristic Variation Simulation of Hybrid Electric Propulsion System for Small UAV

It is conducted that power characteristic variation simulation of electric propulsion system that uses fuel cells, solar cells and a battery as power sources. Combining each power source, 400W electric propulsion system have been modeled and verified. In result, without active control logic, it is confirmed that battery`s power response is faster than other power sources at starting and transient condition, fuel cell and solar cell are a major electrical power during cruise condition. After completing flight, SOC is 24.2% at the winter solstice and is 93% at the summer solstice, It is revealed that active power control for sustaining proper SOC is necessary as a securing the system safety and effective power distribution.

Effects of CO2 dilution on combustion instabilities in dual premixed flames

There has been a rapid increase in the demand for biogas applications in recent years, and dry low NOx and dry low emission gas turbine combustors are promising platforms for such applications. Combustion instability is the most important drawback in dry low NOx gas turbine combustors and has, therefore, attracted considerable research interest lately. As a fundamental study towards the use of biogas in dry low NOx and dry low emission gas turbine combustors, this article investigates the influence of CO2 in surrogate biogas on combustion instability. Tests were conducted using a dry low NOx type, a dual lean premixed gas turbine combustor. For a dual flame with dual swirl, the pilot fuel mass fraction affects the flame structure, and the flame structure, in turn, determines the temperature distribution in the combustion chamber and the combustion instability. The effects of the pilot fuel mass fraction, which is an important parameter of the combustor, and the CO2 dilution rate, which is a major contributor of biogas combustion, on the combustion characteristics and instability are investigated through dynamic pressure signal and phase-resolved OH* images. Combustion instability decreases for higher CO2 dilution rates, whose effects depend on the pilot fuel mass fraction. The instability reaches its maximum at a pilot fuel mass fraction of 0.3. Tests confirm that combustion instability diminishes with CO2 dilution, as it reduces the perturbation in the heat emission, and the flame speed decreases resulting in a greater flame surface or volume. Further, investigation of the Rayleigh Index, which represents the coupling strength of the heat release fluctuation and the natural frequency, shows that CO2 dilution weakens the coupling strength, resulting in less combustion instability.

Flight Test of Hybrid Propulsion System for Electrically Powered UAV

This paper deals with the flight test of propulsion system of middle size electrically powered UAV (EAV2, Electric Aerial Vehicle 2) which is under development in KARI. EAV2 is low speed endurance type UAV whose wing span is 6.9 m, and weight is 18 kg. The UAV has flown for 22 hours in June of 2012. The flight test result showed that the propulsion system worked well suppling power for any circumstances during the test flight. Each power source worked according to the design purpose.

A Study on Optimum Takeoff Time of the Hybrid Electric Powered Systems for a Middle Size UAV

The target system is a middle size UAV, which is a low-speed long-endurance UAV with a weight of 18 kg and wingspan of 6.4 m. Three electric power sources, i.e. solar cells, a fuel cell, and a battery, are considered. The optimal takeoff time is determined to maximize the endurance because the generated solar cell`s energy is heavily dependent on it. Each power source is modeled in Matlab/Simulink, and the component models are verified with the component test data. The component models are integrated into a power system which is used for power simulations. When takeoff time is at 6 pm and 2 am, it can supply the power during 37.5 hrs and 27.6 hrs, respectively. In addition, the thermostat control simulation for fuel cell demonstrates that it yields more power supply and efficient power distribution.

Performance Tests for Development of a Dry Low NOx Combustor

A 5MW-gas turbine engine (DGT-5) for power generation is currently under development by Doosan Heavy Industries, funded under a national RD NOx emissions<20ppm; PF<7.6%; Pressure pulsation amplitude <2kPa at low pressure (3bar, a), 100% load and FR 0.2 conditions.Copyright

Start-up Combustor Development for GT/FC Hybrid Power Generation System

Currently, 60kW class gas turbine fuel cell hybrid power generation system is being developed by Korea Aerospace Research Institute. In this system, gas turbine combustor acts as a component which supplies hot gas to the highly efficient power generating fuel cell as well. Because of connection problems between gas turbine and fuel cell, the combustor is necessarily to have flame stability and wide flamability range at the starting stages. Furthermore, in order to enhance the efficiency of the whole system, high combustion efficiency and low pressure loss are required. It also should satisfy the temperature limitations of turbine blade by supplying sufficiently low and uniform thermal energy. In the present study, for the optimization of the combustor, its stability characteristics are tested with change of various operating conditions such as injector shape, swirler air mass flow rate etc. For the basic performance factor survey, effects of combustor exit temperature, pressure loss, combustion efficiency and exhaust gas compositions are also investigated.