969 research outputs found
Plasma torch for ignition, flameholding and enhancement of combustion in high speed flows
Preheating of fuel and injection into a plasma torch plume fro adjacent the plasma torch plume provides for only ignition with reduced delay but improved fuel-air mixing and fuel atomization as well as combustion reaction enhancement. Heat exchange also reduced erosion of the anode of the plasma torch. Fuel mixing atomization, fuel mixture distribution enhancement and combustion reaction enhancement are improved by unsteady plasma torch energization, integral formation of the heat exchanger, fuel injection nozzle and plasma torch anode in a more compact, low-profile arrangement which is not intrusive on a highspeed air flow with which the invention is particularly effective and further enhanced by use of nitrogen as a feedstock material and inclusion of high pressure gases in the fuel to cause effervescence during injection
Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter
Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene
Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter
Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene
Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz
Active control of aircraft engine inlet noise using compact sound sources and distributed error sensors
An active noise control system using a compact sound source is effective to reduce aircraft engine duct noise. The fan noise from a turbofan engine is controlled using an adaptive filtered-x LMS algorithm. Single multi channel control systems are used to control the fan blade passage frequency (BPF) tone and the BPF tone and the first harmonic of the BPF tone for a plane wave excitation. A multi channel control system is used to control any spinning mode. The multi channel control system to control both fan tones and a high pressure compressor BPF tone simultaneously. In order to make active control of turbofan inlet noise a viable technology, a compact sound source is employed to generate the control field. This control field sound source consists of an array of identical thin, cylindrically curved panels with an inner radius of curvature corresponding to that of the engine inlet. These panels are flush mounted inside the inlet duct and sealed on all edges to prevent leakage around the panel and to minimize the aerodynamic losses created by the addition of the panels. Each panel is driven by one or more piezoelectric force transducers mounted on the surface of the panel. The response of the panel to excitation is maximized when it is driven at its resonance; therefore, the panel is designed such that its fundamental frequency is near the tone to be canceled, typically 2000-4000 Hz
Experimental Measurement of Transonic Fan Wake Response to Uniform and Simulated Boundary Layer Ingesting Inlet Flows
BWB Aircraft with embedded engines and BLI inlets offer attractive advantages in terms of reduced noise from engines and increased range and fuel economy. The BLI inlet produces inlet distortion patterns that can reduce fan performance and stall margin, and can produce undesirable forced responses. Knowledge of the dynamic response of fan flow when subjected to flow distortions of the type produced by BLI inlets is important for the design of distortion tolerant fans. This project is investigating fan response to flow distortion by measuring the response of the fan of a JT15D engine to a flow pattern following the results of the NASA Inlet A BLI wind tunnel tests
DSM-5 criteria for substance use disorders: recommendations and rationale.
Since DSM-IV was published in 1994, its approach to substance use disorders has come under scrutiny. Strengths were identified (notably, reliability and validity of dependence), but concerns have also arisen. The DSM-5 Substance-Related Disorders Work Group considered these issues and recommended revisions for DSM-5. General concerns included whether to retain the division into two main disorders (dependence and abuse), whether substance use disorder criteria should be added or removed, and whether an appropriate substance use disorder severity indicator could be identified. Specific issues included possible addition of withdrawal syndromes for several substances, alignment of nicotine criteria with those for other substances, addition of biomarkers, and inclusion of nonsubstance, behavioral addictions.This article presents the major issues and evidence considered by the work group, which included literature reviews and extensive new data analyses. The work group recommendations for DSM-5 revisions included combining abuse and dependence criteria into a single substance use disorder based on consistent findings from over 200,000 study participants, dropping legal problems and adding craving as criteria, adding cannabis and caffeine withdrawal syndromes, aligning tobacco use disorder criteria with other substance use disorders, and moving gambling disorders to the chapter formerly reserved for substance-related disorders. The proposed changes overcome many problems, while further studies will be needed to address issues for which less data were available
Is type II diabetes mellitus (NIDDM) a surgical disease?
Since February 1, 1980, 515 morbidly obese patients have undergone
the Greenville gastric bypass (GGB) operation. Of these,
212 (41.2%) were euglycemic, 288 (55.9%) were either diabetic
or had glucose intolerance, and 15 (2.9%) were unable to complete
the evaluation. After the operation, only 30 (5.8%) patients remained
diabetic (and 20 of these improved), 457 (88.7%) became
and have remained euglycemic, and inadequate data prevented
classification of the other 28 (5.4%). The patients who failed to
return to normal glucose values were older and their diabetes
was of longer duration than those who did. The effect of the
GGB was not only limited to the correction of abnormal glucose
levels. The GGB also corrected the abnormal levels of fasting
insulin and glycosylated hemoglobin in a cohort of 52 consecutive
severely obese patients with non-insulin-dependent diabetes. The
GGB effectively controls weight. If morbid obesity is defined as
100 pounds over ideal body weight, 89% of the patients are no
longer "morbidly" obese within 2 years. In most patients, the
control of the weight has been well maintained during the 11
years of follow-up; most of the upward creep in weight of 20.8%
between 24 and 132 months was from the 49 (9.5%) patients
who had staple line breakdowns between the large and small
gastric pouches. Non-insulin-dependent diabetes, previously
considered a chronic unrelenting disease, can be controlled in
the severely obese by the gastric bypass. Whether the correction
of glucose metabolism affects the complications of diabetes is
unknown. Whether the gastric bypass should be considered for
patients with advanced non-insulin-dependent diabetes but who
are not severely obese deserves consideration. The GGB has an
unacceptably high rate of staple line failure. Accordingly, the
authors have recently changed their procedure to one that divides
the stomach rather than partitions it with staples. Originally published Annals of Surgery, Vol. 215, No. 6, June 199
Finite flavour groups of fermions
We present an overview of the theory of finite groups, with regard to their
application as flavour symmetries in particle physics. In a general part, we
discuss useful theorems concerning group structure, conjugacy classes,
representations and character tables. In a specialized part, we attempt to give
a fairly comprehensive review of finite subgroups of SO(3) and SU(3), in which
we apply and illustrate the general theory. Moreover, we also provide a concise
description of the symmetric and alternating groups and comment on the
relationship between finite subgroups of U(3) and finite subgroups of SU(3).
Though in this review we give a detailed description of a wide range of finite
groups, the main focus is on the methods which allow the exploration of their
different aspects.Comment: 89 pages, 6 figures, some references added, rearrangement of part of
the material, section on SU(3) subgroups substantially extended, some minor
revisions. Version for publication in J. Phys. A. Table 12 corrected to match
eq.(256), table 14 and eq.(314) corrected to match the 2-dimensional irreps
defined on p.6
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