Determination of a suitable set of loss models for centrifugal compressor performance prediction

Performance prediction in preliminary design stages of several turbomachinery components is a critical task in order to bring the design processes of these devices to a successful conclusion.In this paper,a review and analysis of the major loss mechanisms and loss models,used to determine the efficiency of a single stage centrifugal compressor,and a subsequent examination to determine an appropriate loss correlation set for estimating the isentropic efficiency in preliminary design stages of centrifugal compressors,were developed.Several semi-empirical correlations,commonly used to predict the efficiency of centrifugal compressors,were implemented in FORTRAN code and then were compared with experimental results in order to establish a loss correlation set to determine,with good approximation,the isentropic efficiency of single stage compressor.The aim of this study is to provide a suitable loss correlation set for determining the isentropic efficiency of a single stage centrifugal compressor,because,with a large amount of loss mechanisms and correlations available in the literature,it is difficult to ascertain how many and which correlations to employ for the correct prediction of the efficiency in the preliminary stage design of a centrifugal compressor.As a result of this study,a set of correlations composed by nine loss mechanisms for single stage centrifugal compressors,conformed by a rotor and a diffuser,are specified.     

A technique for numerical modeling of liquid film disintegration in the pneumatic injector of aircraft engines

A technique for calculating the two-phase flows in the pneumatic injector of the aircraft engine is developed based on solving the model problem, namely, on verification of the two-phase flow model by means of solving the problem of liquid column disintegration under the effect of an incident airflow. We determine the turbulence models that satisfactorily describe the biphase flow processes.     

Modeling Particle Fluxes and Absorbed Dose for Protection from Cosmic Rays Using the SHIELD Transport Code

Cosmic Research - A special version of the SHIELD transport code has been developed intended for radiation protection purposes in space. The calculation of the fluxes of primary and secondary...     

Satellite Measurements of Plasma Disturbances and Electric Currents Induced in the Midlatitude Ionosphere Modified by High-Power HF Radio Waves

Cosmic Research - We have analyzed the experimental data obtained in 2016–2019 from the measurements of plasma disturbances and electric currents induced at ionospheric altitudes upon the...     

Flight duration,potential and relative efficiency of an electric multicopter

In this paper, it is proposed the flight duration to be assessed by the potential value and the helicopter number. The data on the available power and the relative efficiency for a number of multicopter models are provided.     

Lowering the Systematic Error in Measurements of Local Heat Transfer Coefficient by Electric Heating of a Plane Wall

A technique that allows simultaneous heating of the heat-exchange surface and estimation of its local temperature from the corresponding electrical resistance of the heating element is presented. The systematic error in measurements of the local heat transfer coefficient has been analyzed. A relation that takes possible heat loss into account and minimizes the measurement errors has been obtained.     

On similarity criteria in flight mechanics

With the aim of enhancing the simulation of flow processes and dynamics of aircraft motion, the analysis of the appropriate equations and search for new similarity criteria are carried out. New relations are obtained for the equations of aircraft motion allowing for experiments with overweight models under certain conditions.     

Kelvin–Helmholtz Instability: Lessons Learned and Ways Forward

The Kelvin–Helmholtz instability (KHI) is a ubiquitous phenomenon across the Universe, observed from 500 m deep in the oceans on Earth to the Orion molecular cloud. Over the past two decades, several space missions have enabled a leap forward in our understanding of this phenomenon at the Earth’s magnetopause. Key results obtained by these missions are first presented, with a special emphasis on Cluster and THEMIS. In particular, as an ideal instability, the KHI was not expected to produce mass transport. Simulations, later confirmed by spacecraft observations, indicate that plasma transport in Kelvin–Helmholtz (KH) vortices can arise during non-linear stage of its development via secondary process. In addition to plasma transport, spacecraft observations have revealed that KHI can also lead to significant ion heating due to enhanced ion-scale wave activity driven by the KHI. Finally, we describe what are the upcoming observational opportunities in 2018–2020, thanks to a unique constellation of multi-spacecraft missions including: MMS, Cluster, THEMIS, Van Allen Probes and Swarm.     

OSIRIS-REx Flight Dynamics and Navigation Design

OSIRIS-REx is the first NASA mission to return a sample of an asteroid to Earth. Navigation and flight dynamics for the mission to acquire and return a sample of asteroid 101955 Bennu establish many firsts for space exploration. These include relatively small orbital maneuvers that are precise to ～1 mm/s, close-up operations in a captured orbit about an asteroid that is small in size and mass, and planning and orbit phasing to revisit the same spot on Bennu in similar lighting conditions. After preliminary surveys and close approach flyovers of Bennu, the sample site will be scientifically characterized and selected. A robotic shock-absorbing arm with an attached sample collection head mounted on the main spacecraft bus acquires the sample, requiring navigation to Bennu’s surface. A touch-and-go sample acquisition maneuver will result in the retrieval of at least 60 grams of regolith, and up to several kilograms. The flight activity concludes with a return cruise to Earth and delivery of the sample return capsule (SRC) for landing and sample recovery at the Utah Test and Training Range (UTTR).     

Origin of Molecular Oxygen in Comets: Current Knowledge and Perspectives

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument onboard the Rosetta spacecraft has measured molecular oxygen (O₂) in the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) in surprisingly high abundances. These measurements mark the first unequivocal detection of O₂ in a cometary environment. The large relative abundance of O₂ in 67P/C-G despite its high reactivity and low interstellar abundance poses a puzzle for its origin in comet 67P/C-G, and potentially other comets. Since its detection, there have been a number of hypotheses put forward to explain the production and origin of O₂ in the comet. These hypotheses cover a wide range of possibilities from various in situ production mechanisms to protosolar nebula and primordial origins. Here, we review the O₂ formation mechanisms from the literature, and provide a comprehensive summary of the current state of knowledge of the sources and origin of cometary O₂.