Effects of fuel oxygenation and ducted fuel injection on the performance of a mixing-controlled compression-ignition optical engine with a two-orifice fuel injector
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33 ADVANCED PROPULSION SYSTEMS↗
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Liquid hydrogen turbopump rapid start program
Effort was directed toward the completion of the coated feed system testing and data analysis of both the uncoated and coated system tests. A total of 11 tests were conducted with the coated feed system during three days of testing. Chill data was acquired for thermal conditioning of the system from ambient initial conditions, using a duct inlet propellent pressure of 72 psig. After three tests to determine steady state pump performance and nominal start transient operation, three coated system turbopump starts were attempted with various degrees of prechill.
Wong, G. S.↗
A unique method to study acoustic transmission through ducts using signal synthesis and averaging of acoustic pulses
An acoustic impulse technique using a loudspeaker driver is developed to measure the acoustic properties of a duct/nozzle system. A signal synthesis method is used to generate a desired single pulse with a flat spectrum. The convolution of the desired signal and the inverse Fourier transform of the reciprocal of the driver's response are then fed to the driver. A signal averaging process eliminates the jet mixing noise from the mixture of jet noise and the internal noise, thereby allowing very low intensity signals to be measured accurately, even for high velocity jets. A theoretical analysis is carried out to predict the incident sound field; this is used to help determine the number and locations of the induct measurement points to account for the contributions due to higher order modes present in the incident tube method. The impulse technique is validated by comparing experimentally determined acoustic characteristics of a duct-nozzle system with similar results obtained by the impedance tube method. Absolute agreement in the comparisons was poor, but the overall shapes of the time histories and spectral distributions were much alike.
Salikuddin, M.↗
Phase 2 program on ground test of refanned JT8D turbofan engines and nacelles for the 727 airplane. Volume 3: Ground tests
The NASA Refan Program included full-scale performance and noise ground tests of both a current production (JT8D-15) and a refanned (JT8D-115) engine. A description of the two ground tests including detailed propulsion, noise, and structural test results is presented. The primary objectives of the total test program were comparison of JT8D-15 and JT8D-115 overall propulsion system performance and noise characteristics and determination of incremental component noise levels. Other objectives of the test program included: (1) determination of acoustic treatment effectiveness; (2) measurement of internal sound pressure levels; (3) measurement of inlet and exhaust hardware performance; (4) determination of center-engine surge margin; and (5) evaluation of certain structural characteristics associated with the 727 refan center-engine inlet duct and JT8D refan engine exhaust system. The JT8D-15 and -115 tests were conducted during September 1974 and January to March 1975, respectively. Analyses of the test data indicated that the JT8D-115, as compared to the JT8D-15, demonstrates a 12.5 percent to 13.2 percent reduction in static specific fuel consumption, and a reduction of 6 to 7 PNdB in a weighted average value of static tone corrected perceived noise level. Separated into noise components, a significant reduction was shown for the inlet fan, aft fan, exhaust duct flow, turbine, and jet noises. However, core noise was increased. Photographs of test stands and test equipment are shown.
Source record↗
Room Return Path Sensitivity
Standard practice for HVAC return design has evolved from running a dedicated return to each room with a supply, to systems with returns in more centrally located areas of the home with jump ducts, transfer grilles, or simply door undercuts used as return air pathways from isolated rooms. In these latter systems, hallways and stairwells act as large open ducts for conveying air back to a single (or sometimes multiple) central return. When partition doors to an isolated room are closed, the return airflow resistance goes up, significantly impacting airflow balance if an adequate relief pathway is not installed. Airflow imbalances can lead to comfort and building durability issues and increased envelope leakage. To combat this, some jurisdictions have requirements for return air pathways. The supply system topology–or layout–impacts the airflow balance stability in response to adjustments of return pathway resistances. Branching supply topologies typically have reduced static pressure after each split. The static pressure at the final split will be lower than the primary supply plenum. Because of this, if there is a restriction in a room’s return path, supply airflow will tend to redistribute to adjacent ducts at the end of the branch. A properly designed trunk and branch supply system can effectively equalize static pressure by reducing the cross sectional area after each takeoff . Maintaining static pressure within the trunk will reduce the system’s sensitivity to changes in return paths. However, in practice, it is difficult to design and time consuming to install a complex supply plenum. Velocity effects and poor takeoff placement also impact airflow balance. This report considers return systems in three main categories: distributed, with a return duct to each room; multiple central, with one return grille on each floor of a home; and single central, with a single return grille located near the air handling unit. Three supply categories are also considered: radial splitter box, trunk and branch, and home-run with all ducts connecting directly to a central manifold.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Designing for Supply and Return Air System Interaction in Residential Buildings
Standard practice for HVAC return design has evolved from running a dedicated return to each room with a supply, to systems with returns in more centrally located areas of the home with jump ducts, transfer grilles, or simply door undercuts used as return air pathways from isolated rooms . In these latter systems, hallways and stairwells act as large open ducts for conveying air back to a single (or sometimes multiple) central return. When partition doors to an isolated room are closed, the return airflow resistance goes up, significantly impacting airflow balance if an adequate relief pathway is not installed. Airflow imbalances can lead to comfort and building durability issues and increased envelope leakage. To combat this, some jurisdictions have requirements for return air pathways. The supply system topology – or layout - impacts the airflow balance stability in response to adjustments of return pathway resistances. Branching supply topologies typically have reduced static pressure after each split. The static pressure at the final split will be lower than the primary supply plenum. Because of this, if there is a restriction in a room’s return path, supply airflow will tend to redistribute to adjacent ducts at the end of the branch. A properly designed trunk and branch supply system can effectively equalize static pressure by reducing the cross sectional area after each takeoff . Maintaining static pressure within the trunk will reduce the system’s sensitivity to changes in return paths. However, in practice, it is difficult to design and time consuming to install a complex supply plenum. Velocity effects and poor takeoff placement also impact airflow balance. This fact sheet considers return systems in three main categories: distributed, with a return duct to each room; multiple central, with one return grille on each floor of a home; and single central, with a single return grille located near the air handling unit. Three supply categories are also considered: radial splitter box, trunk and branch, and home-run with all ducts connecting directly to a central manifold. A complete description of the modeling work and results can be found in the companion technical report.
buildings↗
Experimental evaluation of a pilot multinozzle-duct apparatus
A pilot multinozzle and duct were tested at ambient enthalpy to evaluate the suitability of such apparatus for testing thermal protection system panels mounted in the sidewalls of the duct downstream of the nozzle array. The flow field in the duct was complex: effects of wakes and shock waves from the nozzle dominated the flow field; the wakes continually mixed with the surrounding fluid; the boundary layer on the sidewalls of the duct was nonuniform; and near the exit of the duct the sidewall pressure variation was as much as 8.5 percent about the mean wall pressure. Starting loads on the duct walls were higher than those of a similar conventional nozzle and duct. It was concluded that the multinozzle-duct apparatus was not suitable for testing TPS panels, although the design and flow-field information should be of interest to designers of high-energy gasdynamic lasers.
Puster, R. L.↗
Condensate Recycling in Closed Plant Growth Chambers
Water used in the the Controlled Ecological Life Support System (CELSS) Breadboard Project at the Kennedy Space Center is being recycled. Condensation is collected in the air ducts, filtered and deionized, and resupplied to the system for nutrient solutions, supplemental humidification, solvents and diluents. While the system functions well from a process control standpoint, precise and accurate tracking of water movement through the system to answer plant physiological questions is not consistent. Possible causes include hardware errors, undetected vapor loss from chamber leakage, and unmeasured changes in water volume in the plant growth trays.
Bledsoe, J. O.↗
Plants Clean Air and Water for Indoor Environments
Wolverton Environmental Services Inc., founded by longtime government environmental scientist B.C. "Bill" Wolverton, is an environmental consulting firm that gives customers access to the results of his decades of cutting-edge bioremediation research. Findings about how to use plants to improve indoor air quality have been published in dozens of NASA technical papers and in the book, "How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office." The book has now been translated into 12 languages and has been on the shelves of bookstores for nearly 10 years. A companion book, "Growing Clean Water: Nature's Solution to Water Pollution," explains how plants can clean waste water. Other discoveries include that the more air that is allowed to circulate through the roots of the plants, the more effective they are at cleaning polluted air; and that plants play a psychological role in welfare in that people recover from illness faster in the presence of plants. Wolverton Environmental is also working in partnership with Syracuse University, to engineer systems consisting of modular wicking filters tied into duct work and water supplies, essentially tying plant-based filters into heating, ventilation, and air conditioning (HVAC) systems. Also, the company has recently begun to assess the ability of the EcoPlanter to remove formaldehyde from interior environments. Wolverton Environmental is also in talks with designers of the new Stennis Visitor's Center, who are interested in using its designs for indoor air-quality filters
Source record↗
Hydrogen Storage for Load-Following and Clean Power: Duct-firing of Hydrogen to Improve the Capacity Factor of NGCC Plants (Final Report, Phase I Conceptual Study)
The 12-month Feasibility study in Phase I study was completed and confirmed the system is feasible and the proposed system is an improvement over alternate low carbon dispatchable power options. Our demonstration will include 54 MWh of hydrogen storage. CO 2 capture inherent to the CHG process can capture 90% of the CO 2 (with upgrades to >98%) in a commercial system (~300 MWth) for sequestration or other uses. The hydrogen will be utilized in a duct burner in a Heat Recovery Steam Generator (HRSG) integrated with the existing Southern Company fossil asset. Here, the firing rate of the duct burner is varied to let the plant respond to fluctuations of electrical load. However, H 2 production is relatively constant by storing H 2 , and revenues are improved by arbitrage between use of low-cost off-peak variable electricity generation or use of stored H 2 under peak demand. The study enabled the fidelity of the concept to be improved and allowed identification of the requirements for the system. Defining the individual system and component requirements was performed via system requirements review with the whole team. These requirements were then incorporated into/iterated with our Heat & Mass Balance models and process flow diagrams were generated to reflect the overall system. This information was then used to complete the TEA and show economic feasibility. Our system generates power at 17.4% lower cost than other low carbon approaches for the H 2 generation, H 2 compression and storage, carbon sequestration, and HRSG added electricity production for a large-scale duct-fired system. Our team recommends completing the Phase II Pre-FEED study for the proposed system as the next step for the project and its tasks will achieve the overall objective and be ready to launch the FEED. The Pre-FEED tasks include updating the requirements, Concept of Operations, plant scope/process description, component modeling, system modeling, performance estimates, emission estimates, block flow diagrams, fluid/process conditions (PFD), utility usage, and facility sizing/definition. The approach will be to complete these updates in a greater level of detail for the selected site. The approach for developing the EIV is to use the updated results, including model outputs, for carbon dioxide and waste streams.
03 NATURAL GAS↗
A Hardened CARS System Utilized for Temperature Measurements in a Supersonic Combustor
A coherent anti-Stokes Raman scattering (CARS) system has been hardened for use in a NASA Langley supersonic combustion test cell. The system can obtain temperature cross sections of the flow at three locations. The system is environmentally protected and remotely operated. Measurements were made in a scram-jet combustor model consisting of a rear- ward-facing step, followed by an expansion duct. The duct is nominally 4 feet in length. The free stream conditions were Mach 2, with static pressure which ranged from 0.8 to 1.9 atm, and a static temperature of approximately 800K. Three vertical slots were machined into each side of the duct to allow optical access. The CARS system utilized a planar BOXCARS beam arrangement. This arrangement allowed the laser beams to pass through the vertical slots in the tunnel. Translation stages were utilized to move the focussing volume within the tunnel. These stages allowed complete cross sections to be obtained at each slot location. A fiber optic carried the signal to a remotely located monochrometer and reticon detector.Data for two different flow conditions were taken at each of the three slot locations. These two conditions provided a comparison between reacting and non-reacting mixing of injected hydrogen fuel with the combustion heated supersonic stream.
Antcliff, Richard R.↗
Displaying Data From Duct/Fluid Calculations
DUCT6D is FORTRAN program for enhancing postprocessing of data computed by programs based on line-element mathematical models, especially dynamical models of ducts and fluids contained in them. Based partly on assumption that coupled duct/fluid-dynamic system analyzed by use of line elements representing beam properties of duct and one-dimensional acoustical properties of fluid. Inputs include geometric data from model and static, modal, or transient-displacement data from solution. Output represents geometry of coupled duct/fluid system and results of analysis by use of three-dimensional shell elements. Written in FORTRAN.
Saxon, Joe B.↗
Research study on multi-KW-DC distribution system
A detailed definition of the HVDC test facility and the equipment required to implement the test program are provided. The basic elements of the test facility are illustrated, and consist of: the power source, conventional and digital supervision and control equipment, power distribution harness and simulated loads. The regulated dc power supplies provide steady-state power up to 36 KW at 120 VDC. Power for simulated line faults will be obtained from two banks of 90 ampere-hour lead-acid batteries. The relative merits of conventional and multiplexed power control will be demonstrated by the Supervision and Monitor Unit (SMU) and the Automatically Controlled Electrical Systems (ACES) hardware. The distribution harness is supported by a metal duct which is bonded to all component structures and functions as the system ground plane. The load banks contain passive resistance and reactance loads, solid state power controllers and active pulse width modulated loads. The HVDC test facility is designed to simulate a power distribution system for large aerospace vehicles.
Berkery, E. A.↗
Propulsion/airframe interference for ducted propfan engines with ground effect
The advanced propfan propulsion systems design of the next-generation subsonic transport aircraft has been of interest to many airline companies in the past several years. This is due to the studies which indicate that an efficient ducted propfan engine technology offers a significant reduction in aircraft fuel consumption. However, because of the geometric complexity of the configuration, one challenge is the integration of the ducted propfan engine with the airframe so that aerodynamic interference effects frequently encountered near the nacelle can be minimized, or perhaps, optimized. To understand this interaction phenomenon better, it is desirable to have a reliable and efficient computational tool that can predict propeller effects on the flowfield around complex configurations.
Arabshahi, Abdollah↗
Analysis of control concepts for gas and shaft-coupled V/STOL aircraft lift fan systems
For lift-fan powered V/STOL aircraft, two unconventional propulsion system types were proposed. The first type uses fans connected by hot gas ducting, and the second type uses fans connected by cross shafting. An analytical study identified the basic steady-state and dynamic characteristics for each type of system. For the gas-coupled system, the control concepts analyzed were variable-area fan turbines and throttling valves in the ducting. For the shaft-coupled system, the control concepts analyzed were variable-pitch fans and variable fan inlet guide vanes. All of these concepts are capable of meeting V/STOL aircraft control moment and transient response requirements when appropriate propulsion controls are used.
Sellers, J. F.↗
Advanced space engine powerhead breadboard assembly system study
The objective of this study was to establish a preliminary design of a Powerhead Breadboard Assembly (PBA) for an 88 964-Newton (20,000-pound) thrust oxygen/hydrogen staged combustion cycle engine for use in orbital transfer vehicle propulsion. Existing turbopump, preburner, and thrust chamber components were integrated with interconnecting ducting, a heat exchanger, and a control system to complete the PBA design. Cycle studies were conducted to define starting transients and steady-state balances for the completed design. Specifications were developed for all valve applications and the conditions required for the control system integration with the facility for system test were defined.
Campbell, R. G.↗
The Prediction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method
A computationally efficient Boundary Integral Equation Method (BIEM) for the prediction of ducted fan engine noise is presented. The key features of the BIEM are its versatility and the ability to compute rapidly any portion of the sound field without the need to compute the entire field. Governing equations for the BIEM are based on the assumptions that all acoustic processes are linear, generate spinning modes, and occur in a uniform flow field. An exterior boundary value problem (BVP) is defined that describes the scattering of incident sound by an engine duct with arbitrary profile. Boundary conditions on the duct walls are derived that allow for passive noise control treatment. The BVP is recast as a system of hypersingular boundary integral equations for the unknown duct surface quantities. BIEM solution methodology is demonstrated for the scattering of incident sound by a thin cylindrical duct with hard walls. Numerical studies are conducted for various engine parameters and continuous portions of the total pressure field are computed. Radiation and duct propagation results obtained are in agreement with the classical results of spinning mode theory for infinite ducts.
Boundary integral equation↗
Progress on Variable Cycle Engines
Progress in the development and future requirements of the Variable Stream Control Engine (VSCE) are presented. The two most critical components of this advanced system for future supersonic transports, the high performance duct burner for thrust augmentation, and the low jet coannular nozzle were studied. Nozzle model tests substantiated the jet noise benefit associated with the unique velocity profile possible with a coannular nozzle system on a VSCE. Additional nozzle model performance tests have established high thrust efficiency levels only at takeoff and supersonic cruise for this nozzle system. An experimental program involving both isolated component and complete engine tests has been conducted for the high performance, low emissions duct burner with good results and large scale testing of these two components is being conducted using a F100 engine as the testbed for simulating the VSCE. Future work includes application of computer programs for supersonic flow fields to coannular nozzle geometries, further experimental testing with the duct burner segment rig, and the use of the Variable Cycle Engine (VCE) Testbed Program for evaluating the VSCE duct burner and coannular nozzle technologies.
Westmoreland, J. S.↗