A Systematic Experimental and Computational Investigation of a Class of Contoured Wall Fuel Injectors

The performance of a particular class of fuel injectors for scramjet engine applications is addressed. The contoured wall injectors were aimed at augmenting mixing through axial vorticity production arising from interaction of the fueVair interface with an oblique shock. Helium was used to simulate hydrogen fuel and was injected at Mach 1.7 into a Mach 6 airstream. The effects of incoming boundary layer height. injector spacing, and injectant to freestream pressure and velocity ratios were investigated. Results from threedimensional flow field surveys and Navier-Stokes simulations are presented. Performance was judged in terms of mixing, loss generation and jet penetration. Injector performance was strongly dependent on the displacement effect of the hypersonic boundary layer which acted to modify the effective wall geometry. The impact of the boundary layer varied with injector array spacing. Widely-spaced arrays were more resilient to the detrimental effects of large boundary layers. Strong dependence on injectant to free stream pressure ratio was also displayed. Pressure ratios near unity were most conducive to losseffective mixing and strong jet penetration. Effects due to variation in mean shear associated with non-unity velocity ratios were found to be secondary within the small range of values tested

Design and Characterization of a Liquid-Fueled Microcombustor

As part of an effort to develop a microscale gas turbine engine, this paper presents the design and experimental characterization of a microcombustor that catalytically burns JP8 fuel. Due to the high energy densities of hydrocarbon fuels, microscale heat engines based on them may enable compact power sources with specific energies higher than those of current battery systems. In addition, utilizing a commonly available logistics fuel would provide advantages for military applications. Thus, a microscale engine burning JP8 fuel is attractive as a portable power source. A liquid-fueled microcombustor with a combustion chamber volume of 1.4 cm 3 and an overall die size of 36.4×36.4×6.5 mm 3 was designed, microfabricated, and experimentally characterized. Two configurations were tested and compared, one with the combustion chamber entirely filled with a catalyst and the other with the combustion chamber partially filled with a catalyst. In the configuration filled with a catalyst, JP8 combustion was sustained at mass flow rates up to 0.1 g/s and an exit gas temperature of 780 K; an overall combustor efficiency of 19% and a power density of 43 MW/ m 3 were achieved. The primary limitation on increasing the mass flow rates and temperature further was the structural failure of the device due to thermal stresses. With the partially filled configuration, a mass flow rate of 0.2 g/s and a corresponding power density of 54 MW/ m 3 were obtained. The exit gas temperature for the partially filled configuration was as high as 720 K, and the maximum overall efficiency was over 22%. Although the reduced amount of catalyst led to incomplete combustion, smaller thermal losses resulted in an increase in the overall combustor efficiency and power density. A nondimensional operating map was constructed based on the experiment, and it suggests that improving the thermal efficiency would be necessary to achieve higher efficiencies in the device.United States. Defense Advanced Research Projects Agency (Contract DAAD19-01-2-0010)United States. Army Research Office (Contract DAAD19-01-2-0010

Shock enhancement and control of hypersonic mixing and combustion

The possibility that shock enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air has been studied in experimental and computational investigations. Early numerical computations indicated that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be well approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. An experimental investigation of the latter process has been carned out in the Caltech 17 Inch Shock Tube in experiments in which the laser induced fluorescence of byacetyl dye is used as a tracer for the motion of the helium gas after shock waves have passed across the helium cylinder. The flow field has also been studied using an Euler code computation of the flow field. Both investigations show that the shock impinging process causes the light gas cylinder to split into two parts. One of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly; about 60% of the light gas mixes rapidly with the ambient fluid. The geometry of the flow field and the mixing process and scaling parameters are discussed here. The success of this program encouraged the exploration of a low drag injection system in which the basic concept of shock generated streamwise vorticity could be incorporated in an injector for a Scramjet combustor at Mach numbers between 5 and 8. The results of a substantial computational program and a description of the wind tunnel model and preliminary experimental results obtained in the High Reynolds Number Mach 6 Tunnel at NASA Langley Research Center are given here

Planar Rayleigh scattering results in helium-air mixing experiments in a Mach-6 wind tunnel

Planar Rayleigh scattering measurements with an argon—fluoride excimer laser are performed to investigate helium mixing into air at supersonic speeds. The capability of the Rayleigh scattering technique for flow visualization of a turbulent environment is demonstrated in a large-scale, Mach-6 facility. The detection limit obtained with the present setup indicates that planar, quantitative measurements of density can be made over a large cross-sectional area (5 cm × 10 cm) of the flow field in the absence of clusters

Estimation of the global impacts of aviation-related noise using an income-based approach

Current practices for assessing the monetary impacts of aviation noise typically use hedonic pricing methods that estimate noise-induced property value depreciation. However, this approach requires detailed knowledge of local housing markets, which is not readily available at a fine resolution for most airport regions around the world. This paper proposes a new noise monetization method based on city-level personal income, which is often more widely available. Underlying the approach is a meta-analysis of 63 hedonic pricing studies from eight countries, conducted between 1970 and 2010, which is used to derive a general relationship between average city-level personal income and the Willingness to Pay for noise abatement. Applying the new model to income, noise, and population data for 181 airports worldwide, the global capitalized monetary impacts of commercial aviation noise in 2005 are estimated to be $23.8 billion, with a Net Present Value of$36.5 billion between 2005 and 2035 when a 3.5% discount rate is applied. Comparison with previous results based on real estate data yields a difference of −34.2% worldwide and −9.8% for the 95 US airports in the analysis. The main advantages of the income-based model are fewer data limitations and the relative ease of implementation compared to the hedonic pricing methods, making it suitable for assessing the monetary impacts of aviation noise reduction policies on a global scale.National Science Foundation (U.S.). Graduate Research FellowshipUnited States. Federal Aviation Administration. Office of Environment and Energy (FAA Award DTFAWA-05-D-00012, Task Orders 0002, 0008, and 0009

Economic and emissions impacts of renewable fuel goals for aviation in the US

The US Federal Aviation Administration (FAA) has a goal that one billion gallons of renewable jet fuel is consumed by the US aviation industry each year from 2018. We examine the economic and emissions impacts of this goal using renewable fuel produced from a Hydroprocessed Esters and Fatty Acids (HEFA) process from renewable oils. Our approach employs an economy-wide model of economic activity and energy systems and a detailed partial equilibrium model of the aviation industry. If soybean oil is used as a feedstock, we find that meeting the aviation biofuel goal in 2020 will require an implicit subsidy from airlines to biofuel producers of $2.69 per gallon of renewable jet fuel. If the aviation goal can be met by fuel from oilseed rotation crops grown on otherwise fallow land, the implicit subsidy is$0.35 per gallon of renewable jet fuel. As commercial aviation biofuel consumption represents less than 2% of total fuel used by this industry, the goal has a small impact on the average price of jet fuel and carbon dioxide emissions. We also find that, under the pathways we examine, the cost per tonne of CO[subscript 2] abated due to aviation biofuels is between $50 and$400.United States. Federal Aviation Administration. Office of Environment and Energy (FAA Award 06-C-NE-MIT, Amendments 018 and 028)United States. Federal Aviation Administration. Office of Environment and Energy (FAA Award 09-C-NE-MIT, Amendments 007, 020, and 025)United States. Federal Aviation Administration. Office of Environment and Energy (FAA Award DTFAWA-05-D-00012, Task Order 0009

Uptake Coefficients of Some Volatile Organic Compounds by Soot and Their Application in Understanding Particulate Matter Evolution in Aircraft Engine Exhaust Plumes

To assist microphysical modeling on particulate matter (PM) evolution emitted from aircraft engines, uptake coefficients of some volatile organic compounds on soot were experimentally determined in this study. The determined values vary from (1.0±0.1)×10⁻⁶ for water-miscible propylene glycol to (2.5±0.1)×10⁻⁵ for 2,6-dimethylnaphthalene, a polycyclic aromatic hydrocarbon. An inverse power-law correlation between uptake coefficient on soot and solubility in water was observed. Using the correlation, microphysical simulations were performed for the exhaust plume evolution from an idling aircraft, and we found that the model-predicted volatile PM composition on soot is comparable with those results from past field measurements.United States. Department of Defense (Contract W912HQ-08-C-0052

Reduction of turbomachinery noise

In the invention, propagating broad band and tonal acoustic components of noise characteristic of interaction of a turbomachine blade wake, produced by a turbomachine blade as the blade rotates, with a turbomachine component downstream of the rotating blade, are reduced. This is accomplished by injection of fluid into the blade wake through a port in the rotor blade. The mass flow rate of the fluid injected into the blade wake is selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake. With this fluid injection, reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved. In a further noise reduction technique, boundary layer fluid is suctioned into the turbomachine blade through a suction port on the side of the blade that is characterized as the relatively low-pressure blade side. As with the fluid injection technique, the mass flow rate of the fluid suctioned into the blade is here selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake; reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved with this suction technique. Blowing and suction techniques are also provided in the invention for reducing noise associated with the wake produced by fluid flow around a stationary blade upstream of a rotating turbomachine

Ion impact induced Interatomic Coulombic Decay in neon and argon dimers

We investigate the contribution of Interatomic Coulombic Decay induced by ion impact in neon and argon dimers (Ne$_2$ and Ar$_2$) to the production of low energy electrons. Our experiments cover a broad range of perturbation strengths and reaction channels. We use 11.37 MeV/u S$^{14+}$, 0.125 MeV/u He$^{1+}$, 0.1625 MeV/u He$^{1+}$ and 0.150 MeV/u He$^{2+}$ as projectiles and study ionization, single and double electron transfer to the projectile as well as projectile electron loss processes. The application of a COLTRIMS reaction microscope enables us to retrieve the three-dimensional momentum vectors of the ion pairs of the fragmenting dimer into Ne$^{q+}$/Ne$^{1+}$ and Ar$^{q+}$/Ar$^{1+}$ (q = 1, 2, 3) in coincidence with at least one emitted electron