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Technical Paper

Failure of Aircraft Structural Joints Under Impulse Loading

1996-10-01
965584
Numerical simulations indicate that blast loading on aircraft structural joints can impart loading rates in excess of 10 Mlb/sec (ten million pounds per second, Reference 1). Experimental evidence, on the other hand, suggests that mechanical joint failure loads are highly loading rate dependent; for example, the failure load for a dynamically loaded tension joint can double from its static value. This paper discusses the progress and to-date findings of research on the assessment of strength failure of aircraft structural joints subjected to loading rates expected from an internal explosive detonation, and several associated experimental procedures to generate such dynamic loading. This work is conducted at MDC and at the University of Dayton Research Institute (UDRI) in support of the FAA Aircraft Hardening Program.
Technical Paper

AGILITY AND HIGH ANGLE OF ATTACK: AN AIR FORCE RESEARCH PERSPECTIVE

1991-09-01
912145
Current efforts to extend controlled flight into the post-stall regime will bring about major changes in aircraft dynamic capability. These changes will have far-reaching implications in terms of the specification, design, evaluation, and operational use of future fighter aircraft. Significant research continues to be accomplished in developing the technologies required to design and build supermaneuverable fighters. This paper discusses some of the background to current agility research and addresses the research which must be accomplished in order for the Air Force to specify requirements for and evaluate these aircraft.
Technical Paper

Petroleum-Based and Bio-Derived Jet Fuel Efficiency Optimization Using Fuel Injection in a 34cc 4- Stroke Spark-Ignition Engine

2011-11-08
2011-32-0601
Many of the engines used in Remotely Piloted Aircraft (RPA), come directly from the remote-control (R/C) aircraft market, which turn a propeller but are not necessarily built for the greatest efficiency or reduced fuel consumption. The DoD “single fuel concept” is pushing these platforms to be able to operate with JP-8 using an Otto Cycle engine. Additionally, with increased environmental concern with fossil fuels, possible future DoD requirements could require the use of bio-derived liquid fuels. The research presented in this paper takes steps to satisfying both the efficiency and single fuel requirements. The Fuji BF-34EI engine was successfully shown to operate effectively with JP-8, Diesel, Algae-based Diesel and Camelina based Hydroprocessed Renewable Jet fuel. When generally compared over the entire engine operating map, between AVGAS and JP-8, the latter is shown to present a 10-20% lower brake specific fuel consumption (BSFC).
Technical Paper

An Integrated Chemical Reactor-heat Exchanger based on Ammonium Carbamate

2012-10-22
2012-01-2190
In this work we present our recent effort in developing a novel heat exchanger based on endothermic chemical reaction (HEX reactor). The proposed HEX reactor is designed to provide additional heat sink capability for aircraft thermal management systems. Ammonium carbamate (AC) which has a decomposition enthalpy of 1.8 MJ/kg is suspended in propylene glycol and used as the heat exchanger working fluid. The decomposition temperature of AC is pressure dependent (60°C at 1 atmosphere; lower temperatures at lower pressures) and as the heat load on the HEX increases and the glycol temperature reaches AC decomposition temperature, AC decomposes and isothermally absorbs energy from the glycol. The reaction, and therefore the heat transfer rate, is controlled by regulating the pressure within the reactor side of the heat exchanger. The experiment is designed to demonstrate continuous replenishment of AC.
Technical Paper

Energy Analysis of Electromechanical Actuator under Simulated Aircraft Primary Flight Control Surface Load

2014-09-16
2014-01-2182
The purpose of this study is to set up a laboratory test apparatus to analyze aircraft flight control EMAS' electrical and thermal energy flow under transient and dynamic flight profiles. A hydraulic load frame was used to exert load to the EMA. The actuator was placed within an environmental chamber which simulates ambient temperature as function of altitude. The simulated movement or stroke was carried out by the EMA. The under test EMA's dynamic load, stroke, and ambient temperature were synchronized through a real time Labview DAQ system. Motor drive voltage, current, regenerative current, and motor drive and motor winding temperature were recorded for energy analysis. The EMA under test was subjected to both transient and holding load laid out in a test matrix.
Technical Paper

Characterization of Small-Scale Turbochargers for Unmanned Aerial Systems

2016-11-08
2016-32-0078
Aircraft engine power is degraded with increasing altitude according to the resultant reduction in air pressure, temperature, and density. One way to mitigate this problem is through turbo-normalization of the air being supplied to the engine. Supercharger and turbocharger components suffer from a well-recognized loss in efficiency as they are scaled down in order to match the reduced mass flow demands of small-scale Internal Combustion Engines. This is due in large part to problems related to machining tolerance limitations, such as the increase in relative operating clearances, and increased blade thickness relative to the flow area. As Internal Combustion Engines decrease in size, they also suffer from efficiency losses owing primarily to thermal loss. This amplifies the importance of maximizing the efficiency of all sub-systems in order to minimize specific fuel consumption and enhance overall aircraft performance.
Journal Article

Measurement of Loss Pathways in Small, Two-Stroke Internal-Combustion Engines

2017-03-14
2017-01-9276
The rapid expansion of the market for remotely piloted aircraft (RPA) includes a particular interest in 10-25 kg vehicles for monitoring, surveillance, and reconnaissance. Power-plant options for these aircraft are often 10-100 cm3 internal combustion engines. Both power and fuel conversion efficiency decrease with increasing rapidity in the aforementioned size range. Fuel conversion efficiency decreases from ∼30% for conventional-scale engines (>100 cm3 displacement) to <5% for micro glow-fuel engines (<10 cm3 displacement), while brake mean effective pressure decreases from >10 bar (>100 cm3) to <4 bar (<10 cm3). Based on research documented in the literature, the losses responsible for the increase in the rate of decreasing performance cannot be clearly defined. Energy balances consisting of five pathways were experimentally determined on two engines that are representative of Group-2 RPA propulsion systems and compared to those in the literature for larger and smaller engines.
Journal Article

Analysis and Control of Energy Storage in Aircraft Power Systems with Pulsed Power Loads

2016-09-20
2016-01-1981
One of the main challenges in the power systems of future aircraft is the capability to support pulsed power loads. The high rise and fall times of these loads along with their high power and negative impedance effects will have an undesirable impact on the stability and dc bus voltage quality of the power system. For this reason, studying ways to mitigate these adverse effects are needed for the possible adoption of these type of loads. One of the technologies which can provide benefits to the stability and bus power quality is Energy Storage (ES). This ES is designed with the capability to supply high power at a fast rate. In this paper, the management of the ES to mitigate the effects of pulsed power loads in an aircraft power system is presented. First, the detailed nonlinear model of the power network with pulsed power loads is derived. Due to the large size of this model, a model order reduction is performed using a balanced truncation and a second order approximation.
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