Feature Extraction of Oscillating Flow with Vapor Condensation of Moist Air in a Sonic Nozzle

The sonic nozzle is commonly used in flow measurement. However, the non-equilibrium condensation phenomenon of moist air in the nozzle has a negative effect on the measuring accuracy. To investigate this complex phenomenon, the experiments on the oscillating condensation flow of moist air were conducted by an adjustable humidification apparatus with different relative humidity (0-100%), temperature (30-50° C) and carrier gas pressure (1-6 bar), where the micro size pressure measuring system was designed by Bergh-Tijdeman (B-T) Model. The accurate mathematical model of nonequilibrium condensation was also built and validated by the experimental data of time-averaged pressure distribution. Then, the frequency and intensity of pressure fluctuation of oscillating flow at a wide range of operation condition were obtained combining experimental data and physical simulation model. Importantly, a new semi-empirical relation of dimensionless frequency deduced from dimensionless analysis was identified accurately by experimental data. Finally, the signal nonstationarity was also observed by using the continuous wavelet transform (CWT). The instantaneous frequency saltation and the energy attenuation of pressure signals were observed in the condensation flow

Prediction of dehydration performance of supersonic separator based on a multi-fluid model with heterogeneous condensation

Supersonic separation is a novel technology. A multi-fluid slip model for swirling flow with homogenous/heterogenous condensation and evaporation processes in the supersonic separator was built to estimate the separation efficiency. This model solves the governing equations of compressible turbulent gas phase and dispersed homogenous/heterogenous liquid phase considering droplet coalescence and interphase force. Its prediction accuracy for condensation and swirling flows was validated. Then, the flow field, slip velocity and droplet trajectory inside the separators with different swirl strengths were investigated. The maximum values of radial slip velocity are 29.2 and 8.26 m/s for inlet foreign droplet radius of 1.0 and 0.4 micron. It means the larger foreign droplet has a better condensation rate. However, the residence time of larger foreign droplet in core flow is shorten. Thus, the inlet radius of foreign droplet has to be moderate for best separation efficiency. Finally, the dehydration performances of separator were evaluated. The optimal radius of inlet foreign droplet to maximize the dehumidification and efficiency was found. For the separator with swirl strength of 22%, the optimal radius is 0.85 micron at inlet pressure of 250 kPa, where the maximum dew point depression is 42.41 °C and the water removal rate is 87.82%

Investigation of ramp injectors for supersonic mixing enhancement

A comparative study of wall mounted swept ramp injectors fitted with injector nozzles of different shape has been conducted in a constant area duct to explore mixing enhancement techniques for scramjet combustors. Six different injector nozzle inserts, all having equal exit and throat areas, were tested to explore the interaction between the preconditioned fuel jet and the vortical flowfield produced by the ramp: circular nozzle (baseline), nozzle with three downstream facing steps, nozzle with four vortex generators, elliptical nozzle, tapered-slot nozzle, and trapezoidal nozzle. The main flow was air at Mach 2, and the fuel was simulated by air injected at Mach 1.63 or by helium injected at Mach 1.7. Pressure and temperature surveys, combined with Mie and Rayleigh scattering visualization, were used to investigate the flow field. The experiments were compared with three dimensional Navier-Stokes computations. The results indicate that the mixing process is dominated by the streamwise vorticity generated by the ramp, the injectors' inner geometry having a minor effect. It was also found that the injectant/air mixing in the far-field is nearly independent of the injector geometry, molecular weight of the injectant, and the initial convective Mach number

Bibliography of Lewis Research Center technical publications announced in 1989

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1989. All the publications were announced in the 1989 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Bibliography of Lewis Research Center Technical Publications announced in 1991

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific engineering work performed and managed by the Lewis Research Center in 1991. All the publications were announced in the 1991 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Aeronautical engineering: A continuing bibliography with indexes (supplement 323)

This bibliography lists 518 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Thermofluid optimisation of turboexpanders for mobile organic Rankine cycle systems

The Organic Rankine Cycle (ORC) is a closed-loop thermodynamic cycle used for low-temperature heat recovery, from sources as diverse as solar, geothermal and industrial processes. Within the ORC, power is produced with the use of a dense-gas vapour expansion in a suitable device and the efficiency of this process is a key influence on cycle efficiency. This thesis therefore investigates the design, optimisation and validation of nozzled radial-inflow turboexpanders, applied to the recovery of vehicle exhaust waste heat. A 1-dimensional meanline performance prediction methodology is developed, capable of modelling the real-gas effects prevalent in dense, organic working fluids. In addition, choking effects within flow passages are explicitly accounted for in both nozzle and rotor, allowing accurate prediction at the high Pressure Ratios typically observed in ORC expanders. A validation case is subsequently presented, tuning loss correlation coefficients to match 6 high Pressure Ratio experimental test cases, reducing average mass flow rate and efficiency errors to 1.33% and 2.04%, respectively. This 1D model is used to create a methodology in which expander optimisation is performed across an entire vehicle duty cycle. A discretised heat exchanger model is developed, capable of modelling multiple fluid phases and real gas effects. A number of simplifications including surrogate models generated by neural network fits, lead to an O(10^3) reduction in computing effort. A case study is performed to quantify benefits to a 11.7 L diesel engine running a 1200-point Non-Road Transient Cycle, resulting in a 21.9% improvement in total cycle energy recovery against a single-point baseline case. The methodologies contained within this thesis are used to design a turboexpander for an industrial research project, focusing on a 15 L diesel Tier 4 engine. Across two generations of design, a combination of computational and experimental methods are applied to produce an expander containing non-radial rotor inlet blading, producing a simulated power output of 12.4 kW at the design point. Finally, in order to facilitate validation of real-gas Computational Fluid Dynamics (CFD) simulations and better understand the underlying flow physics, a blowdown facility is constructed for working fluid r1233zd(E), centred around a converging-diverging test section producing a Mach 2 expansion at the exit plane. Comparison of CFD and centreline pressure measurements for both nitrogen and refrigerant produced maximum errors in Pressure Ratio of 5.7% and 12.1% respectively, suggesting an overestimation by computational methods in predicting expander output power. The methodologies, designs and experimental results contained within this thesis provide improvements to the modelling, optimisation and validation of dense-gas turboexpanders, with the aim of improving design processes and aiding the implementation of ORC for vehicle waste heat recovery.Open Acces

Research and technology

The NASA Lewis Research Center's research and technology accomplishments for fiscal year 1987 are summarized. It comprises approximately 100 short articles submitted by staff members of the technical directorates and is organized into four sections: aeronautics, aerospace technology (which includes space communications), space station systems, and computational support. A table of contents by subject was developed to assist the reader in finding articles of special interest