Performance of a hydrogen burner to simulate air entering scramjet combustors

Tests were conducted to determine the performance of a hydrogen burner used to produce a test gas that simulates air entering a scramjet combustor at various flight conditions. The test gas simulates air in that it duplicates the total temperature, total pressure, and the volume fraction of oxygen of air at flight conditions. The main objective of the tests was to determine the performance of the burner as a function of the effective exhaust port area. The conclusions were: (1) pressure oscillations of the chugging type were reduced in amplitude to plus or minus 2 percent of the mean pressure level by proper sizing of hydrogen, oxygen, and air injector flow areas; (2) combustion efficiency remained essentially constant as the exhaust port area was increased by a factor of 3.4; (3) the mean total temperature determined from integrating the exit radial gas property profiles was within plus or minus 5 percent of the theoretical bulk total temperature; (4) the measured exit total temperature profile had a local peak temperature more than 30 percent greater than the theoretical bulk total temperature; and (5) measured heat transfer to the burner liner was 75 percent of that predicted by theory based on a flat radial temperature profile

The effect of initial flow nonuniformity on second-stage fuel injection and combustion in a supersonic duct

The effects of flow nonuniformity on second-stage hydrogen fuel injection and combustion in supersonic flow were evaluated. The first case, second-stage fuel injection into a uniform duct flow, produced data indicating that fuel mixing is considerably slower than estimates based on an empirical mixing correlation. The second-case, two-stage fuel injection (or second-stage fuel injection into a nonuniform duct flow), produced a large interaction between stages with extensive flow separation. For this case the measured wall pressure, heat transfer, and amount of reaction at the duct exit were significantly greater than estimates based on the mixing correlation. Substantially more second-stage fuel burned in the second case than in the first case. Overall effects of unmixedness/chemical kinetics were found not to be significant at the exit for stoichiometric fuel injection

Experimental investigation of a swept-strut fuel-injector concept for scramjet application

Results are presented of an experiment to investigate the behavior at Mach 4 flight conditions of the swept-strut fuel-injector concept employed in the Langley integrated modular scramjet engine design. Autoignition of the hydrogen fuel was not achieved at stagnation temperatures corresponding to a flight Mach number of 4; however, once ignition was achieved, stable combustion was maintained. Pressure disturbances upstream of the injector location, which were caused by fuel injection and combustion, were generally not observed; this indicates the absence of serious adverse combustor-inlet interactions. Mixing performance and reaction performance determined from probe surveys and wall pressure data indicate that high combustion efficiency should be obtained with the combustor length provided in the scramjet engine design. No adverse interaction between the perpendicular and parallel fuel-injection modes was observed

Proceedings of the 27th Annual Meeting, Southern Soybean Disease Workers (April 6-8, 2000, Fort Walton Beach Florida)

Contents Southern United States Soybean Disease Loss Estimate for 1999. Compiled by SR Koenning Treasury report. Peggy S King Invited presentation Bean Pod Mottle: A Soybean Disease on the Rise in the New Millennium. SA Ghabrial Contributed papers Response of Selected Mid-South Soybean Varieties to the Reniform Nematode. GW Lawrence, KS McLean, and SM Baird Field Response of Soybean Cultivars to the Reniform Nematode Rotylenchulus reniformis. PS King, DB Weaver, and R Rodriguez-Kabana Approaches to Race Determination in Soybean Cyst Nematode. AJ Palmateer, ME Schmidt, SR Stetina, and JS Russin Nematological Survey of Selected Soybean and Cotton Fields in Alabama. DG Robertson and R Rodriguez-Kabana Soybean Meal-Based Compositions as Organic Amendments for Control of Plant-Parasitic Nematodes. CF Weaver and R Rodriguez-Kabana Cell Selection Approach for Generating Soybean with Resistance to Macrophomina phaseolina. NA Reichert, GL Sciumbato, S-H Lin, L Chen, BL Keeling, and AL Woods Identification of Molecular Markers Linked to a New Gene Conferring Resistance to Frogeye Leaf Spot in \u27Peking\u27 Soybean. W Yang, DB Weaver, J Qiu, and B Nielsen Soil Physical, Chemical, and Biological Properties Associated with Sudden Death Syndrome in Southern Illinois. JP Bond, AJ Hoskins, CM Vick, SK Chong, and JS Russin Response of Soybean Sudden Death Syndrome to Amelioration of the Soil Physical Environment. CM Vick, SK Chong, JP Bond, and JS Russin Differential Enzyme Activity in Two Soybean Cultivars Resistant and Susceptible to Sudden Death Syndrome. SA Bates, DA Lightfoot, O Myers, Y Luo, and JS Russin Evaluation Of Azoxystrobin On Soybean Disease, Yield, and Seed Quality. KS McLean, GW Lawrence, L Carter, and L Campbell Soybean Disease Loss Estimates for the United States from 1996-1998. JA Wrather and WC Stienstra Proceedings of the Southern Soybean Disease Workers are published annually by the Southern Soybean Disease Workers. Text, references, figures, and tables are reproduced as they were submitted by authors. The opinions expressed by the participants at this conference are their own and do not necessarily represent those of the Southern Soybean Disease Workers. Mention of a trademark or proprietary products in this proceedings does not constitute a guarantee, warranty, or endorsement of that product by the Southern Soybean Disease Workers

Passive phloem loading and long-distance transport in a synthetic tree-on-a-chip

Vascular plants rely on differences of osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as M\"unch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power long-distance transport. Whereas most herbaceous plants use active mechanisms to increase phloem concentration above that of the photosynthetic cells, in most tree species, for which transport distances are largest, loading seems to occur via passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the nonlinear dynamics that arise during export and determine the ability of passive loading to drive long-distance transport. We first demonstrate that in our device, phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of M\"unch transport, where phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with the hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive long-distance transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies