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The commercial turbofan trend of increasing bypass ratio and decreasing fan pressure ratio has seen its latest market entry in Pratt & Whitney's PurePower™ product line, which will power regional aircraft for the Bombardier and Mitsubishi corporations, starting in 2013. The high-bypass-ratio, low-fan-pressure-ratio trend, which is aimed at diminishing noise while increasing propulsive efficiency, combines with contemporary business factors including the escalating cost of testing and limited availability of simulated altitude test sites to pose formidable challenges for engine certification and performance validation. Most fundamentally, high bypass ratio and low fan pressure ratio drive increased gross-to-net thrust ratio and decreased fan temperature rise, magnifying by a factor of two or more the sensitivity of in-flight thrust and low spool efficiency to errors of measurement and assumption, i.e., physical modeling.

Due to a rapid development of air transportation there is a need for the assessment of real environmental risk related to the aircraft operation. The emission of carbon monoxide and particulate matter is still a serious threat~constituting an obstacle in the development of combustion engines. The applicable regulations related to the influence of the air transportation on the environment introduced by EPA (Environmental Protection Agency), ICAO (International Civil Aviation Organization) contained in JAR 34 (JAA, Joint Aviation Requirements, JAR 34, Aircraft Engine Emissions), FAR 34 (FAA, Federal Aviation Regulations, Part 34, Fuel Venting and Exhaust Emission Requirements for Turbine Engine Powered Airplanes), mostly pertain to the emission of noise and exhaust gas compounds, NOx in particular. They refer to jet engines and have stationary test procedures depending on the engine operating conditions.

As aircraft programs currently ramp up, productivity of assembly processes needs to be improved while keeping quality, reliability and manufacturing cost requirements. Efficiency of the drilling process still remains an issue particularly in the case of CFRP/metal stacks: hot and long metallic chips are difficult to remove and often damage the surface of CFRP holes. Low frequency axial vibration drilling has been proposed to solve this issue. This innovative drilling process allows breaking up the metallic chips in such a way that jamming is avoided. This paper presents a case of CFRP/Ti6Al4V drilling on a CNC machine where productivity must be increased. A comparison is made between the current regular process and the MITIS drilling process. First the analysis and comparison method is presented. The current process is analyzed and its limits are highlighted. Then the vibration process is implemented and its performances are studied.

This paper presents a set of numerical computations with different turbulence model on an air jet flowing tangentially over the curved surface. It has been realized that jet deflection angle and the corresponding thrust are important parameter to determine with great care. Through the grid independence analysis, it has been found that without resolution of the viscous sub-layer, it is not possible to determine the computationally independent angle of jet deflection and boundary layer thickness. The boundary layer analysis has been performed at different radius of curvature and at jet Reynolds number ranging from approximately about 2400-10,000. The boundary layer thickness has been determined at the verge of separation and found a relation with the radius of curvature and jet Reynolds number. The skin-friction coefficient has been also studied at the verge of separation in relation to the surface radius and jet Reynolds number.

Particles are one of the pollutants that affect air quality. The assessment of air pollution degree is conducted, among others, on the basis of parameters regarding the mass concentration of particles (PM2.5 and PM10). The growing awareness of the processes accompanying particles emissions is causing a growing interest in their other parameters such as number and diameter. Particles dimensions are important in determining their impact on human health. The most dangerous are particles of the smallest size; characteristic for internal combustion engines, mainly jet engines. The assessment of individual means of transport from the point of view of their ecological aspects is carried out in relation to fuel consumption, while in the case of particles; the analysis must be extended by their individual parameters. The article presents a comprehensive analysis of particles emissions from a jet engine during stationary tests.

The National Aeronautics and Space Administration (NASA) conducted a full scale ice crystal icing turbofan engine test using an obsolete Allied Signal ALF502-R5 engine in the Propulsion Systems Laboratory (PSL) at NASA Glenn Research Center. The test article used was the exact engine that experienced a loss of power event after the ingestion of ice crystals while operating at high altitude during a 1997 Honeywell flight test campaign investigating the turbofan engine ice crystal icing phenomena. The test plan included test points conducted at the known flight test campaign field event pressure altitude and at various pressure altitudes ranging from low to high throughout the engine operating envelope. The test article experienced a loss of power event at each of the altitudes tested.

This study investigates the self-adjusted cutting parameter technique to improve the drilling of multi-stacked material. The technique consists in changing the cutting strategy automatically, according to the material being machined. The success of this technique relies on an accurate signal analysis, whatever the process setting. Motor current or thrust force are mostly used as incoming signals. Today, analyses are based on the thresholding method. This consists in assigning lower and upper limits for each type of material. The material is then identified when the signal level is stabilized in between one of the thresholds. Good results are observed as long as signal steps are significantly distinct. This is the case when drilling TA6V-CFRP stacks. However, thrust force level remains roughly unchanged for AA7175-CFRP stacks, leading to overlapping thresholds. These boundary limits may also change with tool geometry, wear condition, cutting parameters, etc.

Radical new electrically propelled aircraft are being considered to meet strict future performance goals. One concept design proposed is a Turboelectric Distributed Propulsion (TeDP) aircraft that utilises a number of electrically driven propulsors. Such concepts place a new and significant reliance on an aircraft's electrical system for safe and efficient flight. Accordingly, in addition to providing certainty that supply reliability targets are being met, a contingency analysis, evaluating the probability of component failure within the electrical network and the impact of that failure upon the available thrust must also be undertaken for architecture designs. Solutions that meet specified thrust requirements at a minimum associated weight are desired as these will likely achieve the greatest performance against the proposed emissions targets.

Honeywell has developed a unique turbofan engine for application to the super mid-size business aviation market, the HTF7000. This paper will describe the design of this engine including aeromechanical design of its components. The unique design features of this engine will be described along with the technology growth path to keep the engine current. This paper will also describe several features which have been developed for this engine in response to new regulatory requirements. Some aspects of the engine to aircraft integration will also be described.

The current pressure for fuel burn savings and increasing performance in the commercial aerospace market demands highly complex engine control systems to optimize fuel consumption throughout the engine operating envelope, as well as meet the regulatory requirements in terms of safety and performance. These conflicting objectives normally lead to trade-off solutions that are difficult to precisely estimate. Therefore some decisions to characterize the engine controller still reside on experience from previous designs and, as a result, add subjectivity and increase the potential for wrong parameter selection. This paper proposes an algorithmic approach to design a turbojet engine controller in a multivariable, two-degree-of-freedom configuration, obtaining H-infinity robust stabilization.

A review of the research accomplished in 2009 in the System-Level Design, Analysis and Simulation Tools (SLDAST) of the NASA's Airspace Systems Program is presented. This research thrust focuses on the integrated system-level assessment of component level innovations, concepts and technologies of the Next Generation Air Traffic System (NextGen) under research in the ASP program to enable the development of revolutionary improvements and modernization of the National Airspace System. The review includes the accomplishments on baseline research and the advancements on design studies and system-level assessment, including the cluster analysis as an annualization standard of the air traffic in the U.S. National Airspace, and the ACES-Air MIDAS integration for human-in-the-loop analyzes within the NAS air traffic simulation.

This paper outlines power system architecture trades performed on the N3-X hybrid wing body aircraft concept under NASA's Research and Technology for Aerospace Propulsion (RTAPS) study effort. The purpose of the study to enumerate, characterize, and evaluate the critical dynamic and safety issues for the propulsion electric grid of a superconducting Turboelectric Distributed Propulsion (TeDP) system pursuant to NASA N+3 Goals (TRL 4-6: 2025, EIS: 2030-2035). Architecture recommendations focus on solutions which promote electrical stability, electric grid safety, and aircraft safety. Candidate architectures were developed and sized by balancing redundancy and interconnectivity to provide fail safe and reliable, flight critical thrust capability. This paper outlines a process for formal contingency analysis used to identify these off-nominal requirements. Advantageous architecture configurations enabled a reduction in the NASA's assumed sizing requirements for the propulsors.

In the 1980's, USBI introduced automated waterjet coatings removal into NASA's Space Shuttle program by activating robot cells to remove thermal protection coatings from solid rocket booster components. In the 1990's, USBI has applied this technology to coatings removal from jet engine components. Using this environmentally compatible, pollution prevention technology USBI has demonstrated the removal of ceramic coatings from vanes; magnesium zirconate coatings from combustion chambers and burner cans; plasma coatings from stator rings, knife edge seals, and Up segments; plasma and rubber coatings from high pressure compressor cases; hardface coatings from inner vane supports; tin bismuth shuttles removed from blades; boron nitrite coatings from forged disks; and aluminum oxide coatings from blades.

Automatic and adaptive aircraft engine starting strategy is a complicated subject involving many sets of conflicting requirements both from the standpoint of the engine health situation as well as the engine environmental situation. In previous practice, basically involving the application of hydromechanical control technology, design compromises had to be made which often resulted in a limiting of the ability of the engine to achieve total starting success. This was so because the control had limited ability to allow for variations in engine health and operating conditions. The computing power of digital electronic controls has made possible a major step forward in the ability of the control system to cope with the multiple situations facing the designer of the engine starting system. Many different automatic engine starting strategies could be employed. This paper presents the strategy that has been used in the GE and CFMI family of large, high bypass turbofan engines.

In addition to designing fighter engines for stall-free idle to maximum power operation and stall recoverability, it is important to give proper emphasis to sub-idle operation for successful starting. This permits the pilot to confidently bring the engine on-line following an inadvertent flameout caused by either the airplane departing the flight envelope or by a fuel interrupt due to a malfunction. Thus reliable and fast airstart capability enhances flight safety especially of single engine airplanes. Flight testing, therefore, is substantially devoted to airstart evaluation. The paper first explains the influence of engine design features on airstarting, particularly the advantages of the low bypass ratio cycle F100-PW-229 (PW229) engine, which is an increased thrust derivative (IPE) of the highly successful F100-PW-220 engine. Enhancing airstarting capability of the PW229 using variable geometry features and digital control flexibility is discussed.

The Diagnostics Tested Facility (DTF) at NASA's John C. Stennis Space Center (SSC) in Mississippi was designed to provide a testbed for development of rocket engine exhaust plume diagnostics instrumentation. A 1200-lb thrust liquid oxygen (LOX)/gaseous hydrogen (GH2) thruster is used as the plume source for experimentation and instrument development. Theoretical comparative studies have been performed with aero-thermodynamic codes to ensure that the DTF thruster (DTFT) has been optimized to produce a plume with pressure and temperature conditions as much like the plume of the Space Shuttle Main Engine (SSME) as possible. Operation of the DTFT is controlled by an icon-driven software program using a series of soft switches. Data acquisition is performed using the same software program. A number of plume diagnostics experiments have utilized the unique capabilities of the DTF.

There is a need for a space launch system that can provide ready, reliable, unencumbered access to space. The need exists for a highly reliable launch system that can operate from numerous available sites, that can provide all azimuth launch capability, that is fully reusable, and that can carry significant payloads into low earth orbit. A vehicle concept was developed to demonstrate the ability of near term aeromechanics and propulsion technology to support such a system. The vehicle was composed of two stages. The system takes off horizontally and both stages return to a horizontal landing. Turbojet, ramjet, and rocket propulsion is used. The sensitivity of the system to thrust, drag, weight, and staging Mach number was examined. The two stage system is able to accommodate a range of performance variations yet still retain significant mission potential.

Using LH2 heat sink capacity for air precooling in turbojets allows to increase specific impulse and in many cases to reduce specific mass (mass-to-sea level thrust ratio). A number of precooled turbojet schemes are considered. Classification of turbojet according to the cooled air amount and depth of cooling is proposed. ATR with extended precooling (Tout=100K) is examined in more detail. For propulsion systems including different types of engines, running simultaneously the concept of LH2 heat sink capacity concentration for turbojet air precooling is proposed.

A main objective of the STOL and Maneuver Technology Demonstrator, (S/MTD) Program was to evaluate the operability and performance of its unique engine/nozzle configuration which can deliver thrust in three different modes; conventional, vectored and through variable vanes which give the option of going from forward to reverse thrust. The two-dimensional nozzle and the modified engine were extensively tested during sea level and altitude testing to satisfy all flight clearance requirements. This paper concentrates on the flight test results of the various modes of vectoring and reversing ending with a compilation of the actual usage of the propulsive controls that could be used by designers of similar advanced propulsion systems.

Aerodynamic effects induced from vectoring an exhaust jet are investigated using a well established thin-layer Reynolds averaged Navier-Stokes code. This multiple block code has been modified to allow for the specification of jet properties at a block face. The applicability of the resulting code for thrust vectoring applications is verified by comparing numerically and experimentally determined pressure coefficient distributions for a jet-wing afterbody configuration with a thrust-vectoring 2-D nozzle. Induced effects on the body and nearby wing from thrust vectoring are graphically illustrated.