A Study of Heat Driven Pressure Oscillations in a Gas

1970 ◽  
Vol 92 (3) ◽  
pp. 536-540 ◽  
Author(s):  
K. T. Feldman ◽  
R. L. Carter
Keyword(s):  
Mechanical Energy ◽  
Heat Engine ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Energy Output ◽  
Driving Mechanism ◽  
Physical Explanation ◽  
Pressure Oscillations ◽  
Regenerative Heat ◽  
Steady Heat

Large amplitude acoustical pressure oscillations can be generated in a gas by a steady heat addition. The thermoacoustical oscillation known as the Sondhauss oscillation occurs in a pipe having only one closed end. Experiments were performed to determine thermoacoustic oscillator characteristics for different system geometries and for different operating conditions. Based on these experimental studies, a physical explanation of the mechanism causing Sondhauss thermoacoustical oscillations is presented. The driving mechanism consists of two separate components, that of driving by simple thermal expansion, and that of expansion by the mixing of hot and cold gas in the pipe. The initiation of the oscillations is discussed. Thermoacoustic oscillation phenomena are shown to be analogous to the interaction occurring in a regenerative heat engine, where a steady heat input causes an oscillating mechanical energy output. A comparison of experiment and generalized theory is presented.

scholarly journals Design Optimization of Flexure Springs for Free-Piston Stirling Engines and Experimental Evaluations with Fatigue Testing

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5156
Author(s):  
Chang-Whan Lee ◽  
Dong-Jun Kim ◽  
Sung-Kwon Kim ◽  
Kyuho Sim
Keyword(s):  
Fatigue Testing ◽  
Design Method ◽  
Heat Engine ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Geometric Constraints ◽  
Outer Diameter ◽  
Optimized Design ◽  
Free Piston ◽  
Regenerative Heat

The free-piston Stirling engine is a closed-cycle regenerative heat engine that converts heat energy into mechanical work, and requires a spring element for vibratory operations of the displacer and power pistons. In this study, the geometry of the flexural spring design was optimized through structural finite element analyses and fatigue test evaluations. First, we constructed a target design space considering the required natural frequency of the displacer spring assembly under the geometric constraints of total mass and module height. The design of experiments was employed to construct simulation cases for design factors such as the outer diameter, thickness, and number of spirals in the spring sheet. As a result, the optimized design values were obtained to satisfy the design requirements. We also fabricated a test spring specimen and conducted fatigue tests using a linear actuator system developed to have the same motion as the engine. The test results indicated that the optimized spiral spring had no fracture under operating conditions with the design piston amplitude, revealing the effectiveness of the design method.

scholarly journals Ethanol/Gasoline Blends as Alternative Fuel in Last Generation Spark-Ignition Engines: A Review on CO and HC Engine Out Emissions

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4034
Author(s):  
Paolo Iodice ◽  
Massimo Cardone
Keyword(s):  
Physicochemical Properties ◽  
Alternative Fuels ◽  
Experimental Studies ◽  
Alternative Fuel ◽  
Exhaust Emissions ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Spark Ignition Engines ◽  
The Impact

Among the alternative fuels existing for spark-ignition engines, ethanol is considered worldwide as an important renewable fuel when mixed with pure gasoline because of its favorable physicochemical properties. An in-depth and updated investigation on the issue of CO and HC engine out emissions related to use of ethanol/gasoline fuels in spark-ignition engines is therefore necessary. Starting from our experimental studies on engine out emissions of a last generation spark-ignition engine fueled with ethanol/gasoline fuels, the aim of this new investigation is to offer a complete literature review on the present state of ethanol combustion in last generation spark-ignition engines under real working conditions to clarify the possible change in CO and HC emissions. In the first section of this paper, a comparison between physicochemical properties of ethanol and gasoline is examined to assess the practicability of using ethanol as an alternative fuel for spark-ignition engines and to investigate the effect on engine out emissions and combustion efficiency. In the next section, this article focuses on the impact of ethanol/gasoline fuels on CO and HC formation. Many studies related to combustion characteristics and exhaust emissions in spark-ignition engines fueled with ethanol/gasoline fuels are thus discussed in detail. Most of these experimental investigations conclude that the addition of ethanol with gasoline fuel mixtures can really decrease the CO and HC exhaust emissions of last generation spark-ignition engines in several operating conditions.

Numerical Modeling and Experimental Studies of the Operational Parameters of the Earth-To-Air Heat Exchanger of the Geothermal Ventilation System

2021 ◽  
Vol 23 ◽  
pp. 42-64
Author(s):  
Boris Basok ◽  
Ihor Bozhko ◽  
Maryna Novitska ◽  
Aleksandr Nedbailo ◽  
Myroslav Tkachenko
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Ventilation System ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Operational Parameters ◽  
Cross Sectional ◽  
Distinctive Features ◽  
Sectional Shape ◽  
Experimental Bench

This article is devoted to the analysis of the heat engineering characteristics of the operation of an Earth-to-Air Heat Exchanger, EAHE, with a circular cross-sectional shape, which is a component of the geothermal ventilation system. The authors analyzed literature sources devoted to the research of heat exchangers of the soil-air type of various designs and for working conditions in various soils. Much attention is paid to the issues of modeling the operation of such heat exchangers and the distinctive features of each of these models. Also important are the results of experimental studies carried out on our own experimental bench and with the help of which the numerical model was validated. The results of these studies are the basis for the development of a method for determining the optimal diameter of an EAHE under operating conditions for soil in Kyiv, Ukraine.

ADVANCED TYPES OF CHECKERWORK OF REGENERATIVE HEAT EXCHANGERS FOR GLASS FURNACES

2021 ◽  
pp. 3-10
Author(s):  
O. Koshelnik ◽  
S. Hoisan
Keyword(s):  
Phase Transition ◽  
Heat Exchangers ◽  
Heat Storage ◽  
Point Of View ◽  
Operating Conditions ◽  
Flue Gases ◽  
Regenerative Heat ◽  
Exchange Processes ◽  
Glass Furnaces ◽  
Refractory Bricks

One of the ways to increase glass furnaces energy efficiency is to apply heat exchangers for flue gases thermal potential utilization. Flue gases losses is up to 25-40 % of the total amount of heat supplied in the furnace. These losses are influences by such factors as fuel type, furnace and burners design and manufactured product type. Regenerative heat exchangers with various types of heat storage packing is more efficient for high-power furnaces. Such types of regenerator checkerwork as Cowper checkerwork, two types of Siemens checkerwork, Lichte checkerwork and combined checkerwork have already been sufficiently researched, successfully applied and widely used for glass furnaces of various designs. All of its are made of standard refractory bricks. Basket checkerwork and cruciform checkerwork that are made of fused-cast molded refractory materials have been widely used recently as well. Further improvement of regenerative heat exchangers thermal efficiency only by replacing the checkerwork does not seem possible unless their size being increased. But this enlarging is not always realizable during the modernization of existing furnaces. From this point of view heat storage elements with a phase transition, where metal salts and their mixtures are used as a fusible agent look promising for glass furnaces. These elements can accumulate additional amount of heat due to phase transition, which allows to increase significantly heat exchanger thermal rating without its size and operating conditions changing. However, it is necessary to carry out additional studies of this type of checkerwork dealing with analysis of complex unsteady heat exchange processes in regenerators and selection of appropriate materials that satisfy the operating conditions of regenerative heat exchangers so that the checkerwork can be widely used for glass furnaces.

scholarly journals Measurement of Air-Fuel Ratio Fluctuations Caused by Combustor Driven Oscillations

1998 ◽  
Author(s):  
Rajiv Mongia ◽  
Robert Dibble ◽  
Jeff Lovett
Keyword(s):  
Power Spectrum ◽  
Mole Fraction ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Lean Premixed Combustion ◽  
Lean Premixed

Lean premixed combustion has emerged as a method of achieving low pollutant emissions from gas turbines. A common problem of lean premixed combustion is combustion instability. As conditions inside lean premixed combustors approach the lean flammability limit, large pressure variations are encountered. As a consequence, certain desirable gas turbine operating regimes are not approachable. In minimizing these regimes, combustor designers must rely upon trial and error because combustion instabilities are not well understood (and thus difficult to model). When they occur, pressure oscillations in the combustor can induce fluctuations in fuel mole fraction that can augment the pressure oscillations (undesirable) or dampen the pressure oscillations (desirable). In this paper, we demonstrate a method for measuring the fuel mole fraction oscillations which occur in the premixing section during combustion instabilities produced in the combustor that is downstream of the premixer. The fuel mole fraction in the premixer is measured with kHz resolution by the absorption of light from a 3.39 μm He-Ne laser. A sudden expansion combustor is constructed to demonstrate this fuel mole fraction measurement technique. Under several operating conditions, we measure significant fuel mole fraction fluctuations that are caused by pressure oscillations in the combustion chamber. Since the fuel mole fraction is sampled continuously, a power spectrum is easily generated. The fuel mole fraction power spectrum clearly indicates fuel mole fraction fluctuation frequencies are the same as the pressure fluctuation frequencies under some operating conditions.

scholarly journals IMPROVING DYNAMIC REGIME OF ROLLING FOR INCREASING DURABILITY OF BALL-ROLLING MILL ROLLS

2019 ◽  
Vol 61 (12) ◽  
pp. 927-932 ◽  
Author(s):  
V. Yu. Rubtsov ◽  
O. I. Shevchenko ◽  
M. V. Mironova
Keyword(s):  
Contact Pressure ◽  
Rotational Speed ◽  
Rolling Mill ◽  
Experimental Studies ◽  
Rolling Process ◽  
Operating Conditions ◽  
Frequency Method ◽  
Rolling Mills ◽  
Ball Rolling ◽  
Progressive Technology

One  of  the  important  reasons  for  the  downtime  of  ball  rolling  mills  is  replacement  of  rolls  due  to  their  wear  and  tear.  The  degree  and  zones  of  critical  wear  of  ball  rolling  rolls  are  investigated  in  the  article, where the greatest wear is observed over the flanges in zone of billet  capture.  Conditions  necessary  to  capture  the  blank  and  to  perform  rolling  process  are  analytically  determined.  Variable  frequency  method  of  roll  rotations  is  proposed  as  a  progressive  technology  for  blank supply. The results of tests for its variations in accordance with  linear  and  quadratic  law  are  presented.  Known  formulas  determining  average  strain  rate  at  rolls  rotational  speed  change  are  converted  for  linear and quadratic dependences. Experimental studies have been carried  out  in  conditions  of  EVRAZ  Nizhnetagilsky  Metallurgical  Plant  ball rolling mills during rolling of 60mm ball made of Sh-3G steel. Experiments  were  performed  for  given  parameters  of  manual  change  in  rolls rotation speed at blank capture by rollers. The results have shown  a  significant  effect  of  change  in  rotational  speed  on  average  specific  pressure during blank capture. Evaluation of torque-time and average  contact  pressure  for  calculated  and  experimental  data  are  presented.  Empirical characteristics are also described at variable rotational speed  of rolls according to linear and quadratic law. Acceptable convergence  of results of calculated and empirical characteristics is determined. Engineering solution has been proposed for that task. It consists in installation of a thyristor converter. This solution allows reduction of rolls  speed before blank capture. Also, this solution will increase frequency  to  the  nominal  value  according  to  the  given  law  after  blank  capture.  As an obtained result, there is uniform distribution of average contact  pressure over the entire length of the roll under different operating conditions  of  mill  in  automatic  mode. Application  of  this  technique  will  reduce wear degree of the rolling tool. At the same time, productivity  of ball rolling mill will be maintained. Rolls consumption and number  of rolls change will decrease due to rolls wear.

scholarly journals ДОСЛІДЖЕННЯ ГІГІЄНІЧНИХ ВЛАСТИВОСТЕЙ МАТЕРІАЛІВ НАТІЛЬНОЇ ЛІКАРНЯНОЇ БІЛИЗНИ

2020 ◽  
Vol 140 (6) ◽  
pp. 38-47
Author(s):  
І. О. Іванов ◽  
Н. П. Супрун ◽  
Ю. О. Ващенко
Keyword(s):  
Comparative Analysis ◽  
Materials Science ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Raw Material ◽  
Experimental Investigations ◽  
Textile Materials ◽  
Composition And Structure ◽  
Innovative Materials ◽  
Basic Functions

Investigation of the influence of the peculiarities of raw material composition and structure of traditional and innovative linen textile materials on their hygienic properties. Theoretical and experimental investigations are based on the main positions of textile materials science. In experimental studies, modern standardized methods for determining the hygienic properties of textile materials were used, as well as techniques specially developed taking into account the peculiarities of the operating conditions of underwear. The peculiarities of the operating conditions and the basic functions of hospital underwear were determined. The comparative analysis of hygienic properties of traditional and modern fabrics for underwear was carried out. Using the standardized and the developed methods, adapted to the peculiarities of the conditions of use of the products, the indicators characterizing the processes of water absorption of the materials were experimentally determined. On the basis of the obtained values of quality indicators, a comprehensive assessment of the ability of materials to transfer moisture and air, with the calculation of the arithmetic complex quality index was done. This allowed to determine the material that is optimal in properties, which provides thermophysiological comfort when operating hospital underwear. Using the developed methods, which take into account the specifics of the operating conditions, a comparative analysis of the hygienic properties of traditional and innovative materials for underwear was carried out. A new range of textile materials for underwear has been proposed, taking into account the peculiarities of the operational situation of consumption.

scholarly journals Simulation Study of the Process of Friction in the Working Elements of a Car Braking System at Different Degrees of Wear

2018 ◽  
Vol 12 (3) ◽  
pp. 221-226 ◽  
Author(s):  
Andrzej Borawski
Keyword(s):  
Simulation Study ◽  
Friction Pair ◽  
Experimental Studies ◽  
Real Life ◽  
Operating Conditions ◽  
Heating Process ◽  
Passenger Cars ◽  
The Road ◽  
Emergency Braking ◽  
Braking System

Abstract Among the many elements of a modern vehicle, the braking system is definitely among the most important ones. Health, and, frequently, life, may rest upon the design and reliability of brakes. The most common friction pair used in passenger cars today is a disc which rotates with the road wheel and a cooperating pair of brake pads. The composite material of the pad results in changing tribological properties as the pad wears, which was demonstrated in experimental studies. The change is also facilitated by the harsh operating conditions of brakes (high and rapid temperature changes, water, etc.). This paper looks into how changing tribology reflects on the heating process of disc and pads during braking. And so a simulation study was conducted, as this method makes it possible to measure temperature in any given point and at any time, which is either impossible or extremely difficult in real life conditions. Finite element method analyses were performed for emergency braking events at various initial speeds of the vehicle reflecting the current road speed limits.

scholarly journals Environmental Characteristics of Modern Systems of Domestic Use of Fuel. Part 2. Pollutants Formation by Natural Gas Combustion in Atmospheric Burners: Experimental Studies

2020 ◽  
Vol 63 (5) ◽  
pp. 450-461
Author(s):  
B. S. Soroka ◽  
V. V. Horupa
Keyword(s):  
Thermal Power ◽  
Experimental Studies ◽  
Environmental Indicators ◽  
Gas Pressure ◽  
Operating Conditions ◽  
National Academy Of Sciences ◽  
High Concentration ◽  
Hydrocarbon Gases ◽  
Absolute Level ◽  
Toxic Emissions

The Gas Institute of the National Academy of Sciences of Ukraine performs comprehensive studies of the formation of toxic emissions in the flame of atmospheric burners and beyond the visible burning cones (“rich” primary flame). The experiments are based on the proven significant content of harmful substances in the combustion products of gas fuel in household appliances and on direct contact of consumers with gas emissions during the operation of the stoves. A methodology for the experimental researches of the harmful emissions formation has been proposed while the computerized firing rig serving as the diagnostic facility has been developed for studying the combustion of hydrocarbon gases in the burners of household stoves. Carbon oxides CO and nitrogen oxides NO and NO2 are considered as toxic emissions, while the primary air excess coefficient and the heat load of the burner are considered as variable parameters. Under operating conditions of a gas stove, its variable characteristics are the gas pressure in front of the nozzle of the atmospheric burner and its thermal power. When optimizing the design of burners, the determinant value of the stability of burning, energy and environmental indicators of fuel combustion is the coefficient of excess of primary air λpr at a given gas pressure before the burner. The influence of this coefficient on the formation of CO, NO, NO2 is established, and the possibility of emissions with a high concentration of nitrogen dioxide is proved. Since the concentration of [NO] decreases with an increase in λpr, and the absolute level of [NO2] concentrations is not significantly affected by the value of λpr, it is determined that the proportion of [NO2] concentration in the [NOx] = [NO] + [NO2] compound increases with an increase in the primary air excess coefficient.

scholarly journals Simulation of 2-Way Fluid Structure Interaction in a 3D Model Combustor

2012 ◽  
Author(s):  
Mina Shahi ◽  
Jim B. W. Kok ◽  
P. R. Alemela
Keyword(s):  
Flue Gas ◽  
Fluid Structure Interaction ◽  
Operating Conditions ◽  
Limit Cycle Oscillation ◽  
Structural Domain ◽  
Pressure Oscillations ◽  
Fluid Structure ◽  
Thermoacoustic Instability ◽  
Structure Interaction ◽  
Computational Fluid Dynamics Analysis

The liner of a gas turbine combustor is a very flexible structure that is exposed to the pressure oscillations that occur in the combustor. These pressure oscillations can be of very high amplitude due to thermoacoustic instability, when the fluctuations of the rate of heat release and the acoustic pressure waves amplify each other. The liner structure is a dynamic mechanical system that vibrates at its eigenfrequencies and at the frequencies by which it is forced by the pressure oscillations to which it is exposed. On the other hand the liner vibrations force a displacement of the flue gas near the wall in the combustor. The displacement is very small but this acts like a distributed acoustic source which is proportional to the liner wall acceleration. Hence liner and combustor are a coupled elasto-acoustic system. When this is exposed to a limit cycle oscillation the liner may fail due to fatigue. In this paper the method and the results will be presented of the partitioned simulation of the coupled acousto-elastic system composed of the liner and the flue gas domain in the combustor. The partitioned simulation uses separate solvers for the flow domain and the structural domain, that operate in a coupled way. In this work 2-way fluid structure interaction is studied for the case of a model combustor for the operating conditions 40–60 kW with equivalence ratio of 0.625. This is done in the framework of the LIMOUSINE project. Computational fluid dynamics analysis is performed to obtain the thermal loading of the combustor liner and finite element analysis renders the temperature, stress distribution and deformation in the liner. The software used is ANSYS workbench V13.0 software, in which the information (pressure and displacement) is also exchanged between fluid and structural domain transiently.

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