scholarly journals Modelling of nozzle start-up for underexpanded jet generation

2021 ◽  
pp. 1-30
Author(s):  
Maria Alexandrovna Kiryushina ◽  
Tatiana Gennadyevna Elizarova
Keyword(s):  
Low Temperatures ◽  
Complex Geometry ◽  
Main Element ◽  
Pressure Gradients ◽  
Dynamic Algorithm ◽  
Underexpanded Jet ◽  
Open Platform ◽  
High Speeds ◽  
Start Up ◽  
Flow Pressure

A numerical simulation of hydrogen jet in the micronozzle is carried out, which is used as the main element in the experimental installation to study the properties of rarefied gases at high speeds and low temperatures. The features of the transient jet flow - pressure gradients, velocities and the complex geometry of the problem are uniformly described within the framework of the quasi-gas dynamic algorithm included in the open platform OpenFOAM.

The Role of High Performance Foil Bearings in Advanced, Oil-Free, High-Speed Motor Driven Compressors

2003 ◽  
Author(s):  
James F. Walton ◽  
Michael J. Tomaszewski ◽  
H. Heshmat
Keyword(s):  
High Speed ◽  
High Performance ◽  
Development Program ◽  
Foil Bearings ◽  
High Speeds ◽  
Start Up ◽  
Rolling Element ◽  
Temperature Capability ◽  
Full Speed ◽  
Bearing System

The demand for high power density, reliable, low maintenance, oil-free turbomachinery imposes significant demands on the bearing system. The full benefits of high speed, motor driven machines, for example are realized at speeds exceeding the capabilities of rolling element bearings. The high speeds, and requirement for oil-free operation in fuel cell applications also make conventional liquid lubricated bearings an undesirable alternative. The modern, oil-free foil bearing provides an excellent alternative, with its low power loss, damping for smooth high-speed operation and shock tolerance, elevated temperature capability and long maintenance free life. In this paper, the application of modern foil bearings to two different high-speed, oil-free compressors is discussed. In each application, foil bearings support a multi-component rotor operating at speeds above 70,000 RPM. Stable and reliable operation over the full speed range is demonstrated in each case. These applications also required low bearing start-up torque for compatibility with the torque characteristics of the integral motor. This work discusses the rotor bearing system design, the development program approach, and the results of testing to date.

COMPARISON OF CHARACTERISTICS OF SEARCHING SYSTEMS OF MOBILE MEANS OF RAILS OF RAIL DEFECTOSCOPY

2020 ◽  
pp. 40-48
Author(s):  
V. F. Tarabrin
Keyword(s):  
Low Temperatures ◽  
High Reliability ◽  
Type System ◽  
Propagation Time ◽  
Search System ◽  
Rail Head ◽  
High Speeds ◽  
Working Face ◽  
Rolling Surface ◽  
Complex Design

The characteristics of wheel-type search systems and sliding systems used for ultrasonic rail monitoring are considered, and their comparison is performed. It is shown that the use of a wheel-type system, the acoustic path of which contains a liquid medium with an increased propagation time of ultrasonic vibrations, limits the control speed to 60 km/h. It is noted that when passing a wheel-type search system of curved sections of track and rails with lateral wear, a change in the direction of propagation of the ultrasonic beam is observed due to a change in the tilt of the wheel relative to the rolling surface of the rail head, which reduces the reliability of detection of rail defects. The disadvantages of the wheel system also include a complex design, low maintainability, poor protection when operating at low temperatures and mechanical stresses, limitations on the ability to operate at high speeds, complicated alignment and, in general, the complexity of maintenance. The characteristics of the retrieval sliding system developed by the specialists of JSC Firma TVEMA are given that provide detection of rail defects with high reliability, operate at low temperatures, and realize a control speed of up to 140 km/h, including in curved sections of the track. The advantages of the proposed non-contact magnetic centering system of the search system, excluding mechanical contact with the rail and the dependence of the centering accuracy on the state of the working face of the rail head, providing unhindered passage of turnouts, including without reducing the speed of control, are presented.

Effect of Drag-Reducing Agents in Multiphase Flow Pipelines

1998 ◽  
Vol 120 (1) ◽  
pp. 15-19 ◽  
Author(s):  
C. Kang ◽  
R. M. Vancko ◽  
A. S. Green ◽  
H. Kerr ◽  
W. P. Jepson
Keyword(s):  
Multiphase Flow ◽  
Pressure Gradient ◽  
Slug Flow ◽  
Annular Flow ◽  
Flow Regimes ◽  
Reducing Agents ◽  
Pressure Gradients ◽  
Horizontal Pipes ◽  
Flow Pressure ◽  
Inclined Pipes

The effect of drag-reducing agents (DRA) on pressure gradient and flow regime has been studied in horizontal and 2-deg upward inclined pipes. Experiments were conducted for different flow regimes in a 10-cm i.d., 18-m long plexiglass system. The effectiveness of DRA was examined for concentrations ranging from 0 to 75 ppm. Studies were done for superficial liquid velocities between 0.03 and 1.5 m/s and superficial gas velocities between 1 and 14 m/s. The results indicate that DRA was effective in reducing the pressure gradients in single and multiphase flow. The DRA was more effective for lower superficial liquid and gas velocities for both single and multiphase flow. Pressure gradient reductions of up to 42 percent for full pipe flow, 81 percent for stratified flow, and 35 percent for annular flow were achieved in horizontal pipes. In 2 deg upward inclination, the pressure gradient reduction for slug flow, with a concentration of 50 ppm DRA, was found to be 28 and 38 percent at superficial gas velocities of 2 and 6 m/s, respectively. Flow regimes maps with DRA were constructed in horizontal pipes. Transition to slug flow with addition of DRA was observed to occur at higher superficial liquid velocities.

scholarly journals Supercapacitors and starting modes of a hybrid car engine

2021 ◽  
Author(s):  
V.S. Antipenko ◽  
S.V. Antipenko ◽  
S.A. Lebedev
Keyword(s):  
Quality Of Life ◽  
Low Temperatures ◽  
Internal Combustion Engines ◽  
Metropolitan Areas ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Hybrid Car ◽  
Start Up

Reducing the start-up time of internal combustion engines, especially at low temperatures and when the batteries are discharged, the use of supercapacitors leads to a reduction in emissions into the atmosphere, improving the quality of life in large metropolitan areas.

Rapid start-up of nitrifying MBBRs at low temperatures: nitrification, biofilm response and microbiome analysis

2017 ◽  
Vol 40 (5) ◽  
pp. 731-739 ◽  
Author(s):  
Bradley Young ◽  
Robert Delatolla ◽  
Turki Abujamel ◽  
Kevin Kennedy ◽  
Edith Laflamme ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Microbiome Analysis ◽  
Start Up

scholarly journals EFFECT OF AIR HEATING AT THE INTAKE ON THE ENERGY AND ENVIRONMENTAL PERFORMANCE OF A TRANSPORT ENGINE WHEN RUNNING ON ALCOHOL-CONTAINING GASOLINE AT LOW TEMPERATURES

2021 ◽  
Vol 1 (50) ◽  
pp. 46-56
Author(s):  
Gutarevych Y ◽  
◽  
Shuba Y ◽  
Syrota A ◽  
Trifonov D ◽  
...  
Keyword(s):  
Power System ◽  
Environmental Performance ◽  
Low Temperatures ◽  
Gasoline Engine ◽  
Fuel Efficiency ◽  
Road Transport ◽  
Supply System ◽  
Warm Up ◽  
Air Heating ◽  
Start Up

The article discusses the issue associated with the influence of air heating at the intake on the fuel efficiency and environmental performance of an engine with a carburetor power system when using alcohol-containing gasoline with a bioethanol content of about 36%, in the cold start, warm-up and idle modes. The use of inlet air heating is one of the promising areas for the implementation of energy-efficient technologies in road transport. The object of experimental research is a ZAZ-1102 car with a MeMZ-245 gasoline engine with a carburetor power system. The purpose of the work is to determine the effect of air heating at the intake on the energy and environmental performance of a transport engine when operating on alcohol-containing gasoline at low temperatures. The research method is experimental. As a result of the research, it was found that the use of air preheating at the intake with TAPP when using alcohol-containing gasoline with a bioethanol content of about 36% allows for reliable start-up while reducing the engine start-up time; reduce engine warm-up time by 15.8%, total fuel consumption by 34.6%; CO concentration at the beginning of heating decreases by 30.8%, CmHn concentration decreases 4.8 times. 120 seconds after warming up, the CmHn concentration when the engine is running without heating is 730 ppm, and with heating it is 370 ppm. CO concentrations are reduced from 0.37% to 0.25%. To ensure the adaptation of existing engines with a carburetor fuel supply system to the use of alcohol-containing gasolines with a bioethanol content of more than 20%, it is recommended at low temperatures to ensure an intake air temperature within 40 ... 50 ° C, which generally leads to an increase in fuel efficiency. KEY WORDS: ENGINE WITH CARBURETTOR POWER SUPPLY SYSTEM, ALCOHOL-CONTAINING GASOLINE, HEATED AIR AT THE INLET, LOW OPERATING TEMPERATURE, INCREASING ENGINE ENERGY EFFICIENCY.

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