Refine Your Search

Search Results

Viewing 1 to 5 of 5
Technical Paper

Investigation of Dynamic Roughness Flow Control on NACA 0012 Airfoil at Low Reynolds Number

There is an ever growing need in the aircraft industry to increase the performance of a flight vehicle. To enhance performance of the flight vehicle one active area of research effort has been focused on the control of the boundary layer by both active and passive means. An effective flow control mechanism can improve the performance of a flight vehicle by eliminating boundary layer separation at the leading edge (as long as the energy required to drive the mechanism is not greater than the savings). In this paper the effectiveness of a novel active flow control technique known as dynamic roughness (DR) to eliminate flow separation in a stalled NACA 0012 wing has been explored. As opposed to static roughness, dynamic roughness utilizes small time-dependent deforming elements or humps with amplitudes that are on the order of the local boundary layer height to energize the local boundary layer. DR is primarily characterized by the maximum amplitude and operating frequency.
Technical Paper

Experimental Study of Dielectric Barrier Discharge Driven Duct Flow for Propulsion Applications in Unmanned Aerial Systems

The dielectric barrier discharge (DBD) has been studied significantly in the past two decades for its applications to various aerodynamic problems. The most common aerodynamic applications have been stall/separation control and boundary layer modification. Recently several researchers have proposed utilizing the DBD in various configurations to act as viable propulsion systems for micro and nano aerial vehicles. The DBD produces stable atmospheric-pressure non-thermal plasma in a thin sheet with a preferred direction of flow. The plasma flow, driven by electrohydrodynamic body forces, entrains the quiescent air around it and thus develops into a low speed jet on the order of 10-1 to 101 m/s. Several researchers have utilized DBDs in an annular geometric setup as a propulsion device. Other researchers have used them to alter rectangular duct flows and directional jet devices. This study investigates 2-D duct flows for applications in micro plasma thrusters.
Technical Paper

Laser Spark Plug Development

To meet the ignition system needs of large bore high pressure lean burn natural gas engines a laser diode side pumped passively Q-switched laser igniter was designed and tested. The laser was designed to produce the optical intensities needed to initiate ignition in a lean burn high brake mean effective pressure (BMEP) engine. The experimentation explored a variety of optical and electrical input parameters that when combined produced a robust spark in air. The results show peak power levels exceeding 2 MW and peak focal intensities above 400 GW/cm2. Future research avenues and current progress with the initial prototype are presented and discussed.
Technical Paper

Misfire, Knock and NOx Mapping of a Laser Spark Ignited Single Cylinder Lean Burn Natural Gas Engine

Evermore demanding market and legislative pressures require stationary lean burn natural gas engines to operate at higher efficiencies and reduced levels of emissions. Higher in-cylinder pressures and leaner air/fuel ratios are required in order to meet these demands. The performance and durability of spark plug ignition systems suffer as a result of the increase in spark energy required to maintain suitable engine operation under these conditions. Advancing the state of the art of ignition systems for these engines is critical to meeting increased performance requirements. Laser-spark ignition has shown potential to improve engine performance and ignition system durability to levels required meet or exceed projected requirements. This paper discusses testing which extends previous efforts [1] to include constant fueling knock, misfire, thermal efficiency, and NOx emissions mapping of a single cylinder lean burn natural gas engine.
Technical Paper

CFD Simulation of Metal and Optical Configuration of a Heavy-Duty CI Engine Converted to SI Natural Gas. Part 2: In-Cylinder Flow and Emissions

Internal combustion diesel engines with optical access (a.k.a. optical engines) increase the fundamental understanding of combustion phenomena. However, optical access requirements result in most optical engines having a different in-cylinder geometry compared with the conventional diesel engine, such as a flat bowl-in-piston combustion chamber. This study investigated the effect of the bowl geometry on the flow motion and emissions inside a conventional heavy-duty direct-injection diesel engine that can operate in both metal and optical-access configurations. This engine was converted to natural-gas spark-ignition operation by replacing the fuel injector with a spark plug and adding a low-pressure gas injector in the intake manifold for fuel delivery, then operated at steady-state lean-burn conditions. A 3D CFD model based on the experimental data predicted that the different bowl geometry did not significantly affect in-cylinder emissions distribution.