scholarly journals A model of gas flow with friction in a slotted seal

2016 ◽  
Vol 37 (3) ◽  
pp. 95-108 ◽  
Author(s):  
Damian Joachimiak ◽  
Piotr Krzyślak
Keyword(s):  
Friction Coefficient ◽  
Mass Flow ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Accurate Determination ◽  
Gas Temperature ◽  
Total Enthalpy ◽  
Proposed Model ◽  
Adiabatic Transformation

AbstractThe paper discusses thermodynamic phenomena accompanying the flow of gas in a slotted seal. The analysis of the gas flow has been described based on an irreversible adiabatic transformation. A model based on the equation of total enthalpy balance has been proposed. The iterative process of the model aims at obtaining such a gas temperature distribution that will fulfill the continuity equation. The model allows for dissipation of the kinetic energy into friction heat by making use of the Blasius equation to determine the friction coefficient. Within the works, experimental research has been performed of the gas flow in a slotted seal of slot height 2 mm. Based on the experimental data, the equation of local friction coefficient was modified with a correction parameter. This parameter was described with the function of pressure ratio to obtain a mass flow of the value from the experiment. The reason for taking up of this problem is the absence of high accuracy models for calculating the gas flow in slotted seals. The proposed model allows an accurate determination of the mass flow in a slotted seal based on the geometry and gas initial and final parameters.

scholarly journals New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 611
Author(s):  
Yeon-Woong Choe ◽  
Sang-Bo Sim ◽  
Yeon-Moon Choo
Keyword(s):  
Friction Coefficient ◽  
Accurate Determination ◽  
Mean Velocity ◽  
Friction Coefficients ◽  
Flow Discharge ◽  
Comparison Results ◽  
Flow Loss ◽  
Key Variables ◽  
New Equation

In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse’s experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.

An analytical and experimental investigation of the velocities of particles entrained by the gas flow in nozzles

1968 ◽  
Vol 33 (1) ◽  
pp. 131-149 ◽  
Author(s):  
John H. Neilson ◽  
Alastair Gilchrist
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Particle Velocity ◽  
Flow Rate ◽  
Relative Velocity ◽  
Gas Flow ◽  
Wall Surface ◽  
Erosion Damage ◽  
Limiting Value

Among the parameters which determine the erosion damage sustained by the walls of a nozzle, in which a mixture of gas and particles is flowing is the speed attained by the particle before collision with the wall surface. This work is concerned with the determination of the particle velocity, and a number of relationships are given from which the variation in particle velocity can be obtained for a variety of gas conditions. The changes of state and velocity of the gas, occasioned by the interchange of heat and work between the gas and the particles are dependent on the ratio of the mass flow rate of particles to the mass flow rate of gas. It is shown that if this ratio is small the particle velocity may be obtained without serious error by assuming that the gas conditions are not affected by the presence of particles. Figures for the limiting value of this ratio for certain flows are given. The effects of particle size, density and initial relative velocity are investigated analytically and experimentally.

scholarly journals Roll Attitude Determination of Spin Projectile Based on GPS and Magnetoresistive Sensor

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Dandan Yuan ◽  
Wenjun Yi ◽  
Jun Guan
Keyword(s):  
Mathematical Model ◽  
Attitude Determination ◽  
Accurate Determination ◽  
Blind Spot ◽  
Gps Measurements ◽  
Guidance And Control ◽  
Magnetoresistive Sensor ◽  
Proposed Model ◽  
And Control

Improvement in attack accuracy of the spin projectiles is a very significant objective, which increases the overall combat efficiency of projectiles. The accurate determination of the projectile roll attitude is the recent objective of the efficient guidance and control. The roll measurement system for the spin projectile is commonly based on the magnetoresistive sensor. It is well known that the magnetoresistive sensor produces a sinusoidally oscillating signal whose frequency slowly decays with time, besides the possibility of blind spot. On the other hand, absolute sensors such as GPS have fixed errors even though the update rates are generally low. To earn the benefit while eliminating weaknesses from both types of sensors, a mathematical model using filtering technique can be designed to integrate the magnetoresistive sensor and GPS measurements. In this paper, a mathematical model is developed to integrate the magnetoresistive sensor and GPS measurements in order to get an accurate prediction of projectile roll attitude in a real flight time. The proposed model is verified using numerical simulations, which illustrated that the accuracy of the roll attitude measurement is improved.

scholarly journals Spectrum of the Anomalous Microwave Emission in the North Celestial Pole withWMAP7-Year Data

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Anna Bonaldi ◽  
Sara Ricciardi
Keyword(s):  
Accurate Determination ◽  
Peak Frequency ◽  
Microwave Emission ◽  
Neutral Medium ◽  
Gas Temperature ◽  
The North ◽  
Celestial Pole ◽  
Hydrogen Ionization ◽  
Component Separation Method

We estimate the frequency spectrum of the diffuse anomalous microwave emission (AME) on the North Celestial Pole (NCP) region of the sky with the Correlated Component Analysis (CCA) component separation method applied toWMAP7-yr data. The NCP is a suitable region for this analysis because the AME is weakly contaminated by synchrotron and free-free emission. By modeling the AME component as a peaked spectrum we estimate the peak frequency to be21.7±0.8 GHz, in agreement with previous analyses which favoredνp< 23 GHz. The ability of our method to correctly recover the position of the peak is verified through simulations. We compare the estimated AME spectrum with theoretical spinning dust models to constrain the hydrogen densitynH. The best results are obtained with densities around 0.2–0.3 cm−3, typical of warm ionised medium (WIM) to warm neutral medium (WNM) conditions. The degeneracy with the gas temperature prevents an accurate determination ofnH, especially for low hydrogen ionization fractions, where densities of a few cm−3are also allowed.

Volumetric Gas Flow Standard With Uncertainty of 0.02% to 0.05%

2003 ◽  
Vol 125 (6) ◽  
pp. 1058-1066 ◽  
Author(s):  
John D. Wright ◽  
Michael R. Moldover ◽  
Aaron N. Johnson ◽  
Akisato Mizuno
Keyword(s):  
Gas Flow ◽  
Time Interval ◽  
Equilibration Time ◽  
The Novel ◽  
Gas Temperature ◽  
Expanded Uncertainty ◽  
Collection System ◽  
Measured Time ◽  
High Flows

A new pressure, volume, temperature, and time (PVTt) primary gas flow standard for calibrating flowmeters has an expanded uncertainty k=2 of between 0.02% and 0.05%. The standard diverts a steady flow into a collection tank of known volume during a measured time interval. The standard spans the flow range of 1 slm1 to 2000 slm using two collection tanks (34 L and 677 L) and two flow diversion systems. We describe the novel features of the standard and analyze its uncertainty. The thermostatted collection tank allows determination of the average gas temperature to 7 mK (0.0023%) within an equilibration time of 20 min. We developed a mass cancellation procedure that reduced the uncertainty contributions from the inventory volume to 0.017% at the highest flow rate. Flows were independently measured throughout the overlapping flow range of the two systems and they agreed within 0.015 %. The larger collection system was evaluated at high flows by comparing single and double diversions; the maximum difference was 0.0075%.

Connection of Thermal and Emissions- Performance of GT-Plants

2006 ◽  
Author(s):  
Axel W. von Rappard ◽  
Helmer Andersen
Keyword(s):  
Mass Flow ◽  
Thermal Performance ◽  
Gas Flow ◽  
Performance Test ◽  
Heat Rate ◽  
Emission Measurement ◽  
Exhaust Gas ◽  
Emission Data ◽  
Fuel Flow

The new issue of the PTC22 performance test code explains the evaluation of power and heat rate, as well the determination of the exhaust gas mass flow and its composition. The verification of emission requirements is normally tested independently from the thermal performance test and the actual EPA methods refer normally to an extensive determination of the exhaust gas flow, by measuring the velocity profile in the stack or the exhaust gas system of the gas turbine. This paper explains an easier way of determining the exhaust gas volume- or mass flow that is used as reference for all emission data. Additionally it shows that the emission measurement can easily be used as a verification of the exhaust gas mass flow determined in the thermal performance test. The basis for both tests is, however, an accurate fuel flow measurement. Since this measurement is also used for the heat rate or thermal efficiency determination it can certainly be used for the verification of the emissions performance. An uncertainty analysis has been added as well. The authors try to explain the procedure in a way the performance engineers on site can understand.

Study for the Gas Flow Through a Critical Nozzle

2003 ◽  
Author(s):  
Heuy Dong Kim ◽  
Jae Hyung Kim ◽  
Kyung Am Park
Keyword(s):  
Reynolds Number ◽  
Mass Flow ◽  
Gas Flow ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Pressure Ratio ◽  
Nozzle Throat ◽  
Critical Nozzle ◽  
Flow Through ◽  
Diffuser Angle

The critical nozzle is defined as a device to measure the mass flow with only the nozzle supply conditions, making use of flow choking phenomenon at the nozzle throat. The discharge coefficient and critical pressure ratio of the gas flow through the critical nozzle are strongly dependent on Reynolds number, based on the diameter of nozzle throat and nozzle supply conditions. Recently a critical nozzle with small diameter is being extensively used to measure mass flow in a variety of industrial fields. For low Reynolds numbers, prediction of the discharge coefficient and critical pressure is very important since the viscous effects near walls significantly affect the mass flow through critical nozzle, which is associated with working gas consumption and operation conditions of the critical nozzle. In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through critical nozzle. In order to investigate the effect of the working gas and turbulence model on the discharge coefficient, several kinds of gases and several turbulence models are employed. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the standard k-ε turbulence model with the standard wall function gives a best prediction of the discharge coefficient. The discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.

scholarly journals Experimental determination of compressor map of the DGEN 380 engine compressor using the WESTT CS/BV turbine engine simulator

2021 ◽  
Author(s):  
Marek Orkisz ◽  
Karolina Pazura
Keyword(s):  
Experimental Determination ◽  
Mass Flow ◽  
Experimental Work ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Turbine Engine ◽  
Engine Compressor ◽  
Compressor Map ◽  
To Receive

Currently aviation focuses mainlly on increasing the economy and ecology of engines. Production of NOx, CO2 and SO adversaly impacts the environment. Parallel goal to minimize SFC to achieve both lower: emission and mission costs. The optimization of components is thus very important. One of the ways of optimizing cycle is doing that based on compressor maps. However it is very expensive to plot one since experimental work needs to be done. The aim of this article is to present a methodology of creating compressor map based on ENGINE ANALOGY. There was used the virtual bench WESTT CS/BV for tests to receive pressure ratio and mass flow of DGEN 380 for three different values of flight speed and altitude, while the rotational speed was changed. The construction similarity of CFM 56-5B and APS 3200 gives the opportunity to plotted compressor maps using the engine analogy without the need for an experiment or using the virtual bench.

scholarly journals THE MODIFIED MODEL OF DIFFUSION FLOW OF MULTICOMPONENT COMBUSTIBLE GAS

2015 ◽  
pp. 93-97
Author(s):  
R. A. Shtykov
Keyword(s):  
Gas Diffusion ◽  
Diffusion Combustion ◽  
Gas Temperature ◽  
Active Components ◽  
Simple Modification ◽  
Modified Model ◽  
Total Enthalpy ◽  
Combustible Gas ◽  
Excess Concentration

The model of gas diffusion combustion developed by Zeldovich Ya.B., despite of the fairly satisfactory agree-ment of the obtained data with the experiment shows a non-universality and a large volume of the algorithm for de-termining the concentrations of the components when a number of active components and their composition change. In this regard, it became necessary to develop a different, simple modification of Zeldovich’s model, which would lead to the least number of operations for determination of the gas temperature and density at known values of rela-tively excess concentration and total enthalpy.

Study of Gas Flow Through a Stirling Engine Regenerator

2017 ◽  
Author(s):  
E. Rogdakis ◽  
P. Bitsikas ◽  
G. Dogkas
Keyword(s):  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Small Deviation ◽  
Three Dimensional ◽  
Stirling Engine ◽  
Gas Temperature

In the present work, a three dimensional (3D) Computational Fluid Dynamics (CFD) analysis is applied to a designed small compact regenerator with specific porosity and wire diameter. The regenerator was studied as a part of a Stirling Engine designed in a simple way. The gas temperature along the regenerator followed an approximately linear profile, while the metal temperature showed a small deviation during the engine cycle. The heat transfer coefficient between the gas and the matrix of the regenerator, along with the associate heat transferred were also derived. The heat exchanged in the regenerator is significantly higher to the respective heat in the engine’s heater and cooler. Additionally, the pressure drop and the related energy dissipation are studied. Their variation is largely dependent on both mass flow-rate and working gas velocity. The friction factor coefficient for the designed regenerator is correlated with Reynolds number and an equation of two variables is derived. Finally, the results of the CFD simulation are compared to those produced by a one-dimensional numerical model. These results include gas mass, mass flow-rate and Reynolds number, as well as the heat transferred between the gas and the regenerator matrix. Except for the case of the exchanged heat, the deviation between the two approaches is very small.

Sign in / Sign up

Export Citation Format

Share Document