scholarly journals Numerical Comparison of Transpiration Cooling Designs Using Real Gas Effects and Approximate Gas Model

2021 ◽  
Vol 2097 (1) ◽  
pp. 012021
Author(s):  
Meng Wang ◽  
Jianhua Wang ◽  
Fei He ◽  
Kang Qian ◽  
Yadong Wu ◽  
...  
Keyword(s):  
Thermal Protection ◽  
Vibrational Excitation ◽  
Leading Edge ◽  
Aerodynamic Heating ◽  
Transpiration Cooling ◽  
Numerical Comparison ◽  
Number Range ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effects

Abstract In the severe high-temperature environment caused by aerodynamic heating, the vibrational excitation, dissociation and ionization of gas may successively occur, which are known as real gas effects. Under the real gas effects, the thermodynamic properties of gas vary drastically and significantly influence the performances of the active thermal protection system of hypersonic vehicles, especially in the case with coolant outflow, for example transpiration cooling. This paper numerically investigates the transpiration cooling performance with the consideration of the interaction between coolant outflow and hypersonic flow under the real gas effects. The mathematical models and coupled numerical strategy are firstly validated by experimental data, then the influences of real gas effects on the transpiration cooling of a wedged leading edge (WLE) are studied under a flight Mach number range from 8 to 12 and a flight height of 40 km. The analysis and discussions of the numerical results reveal some important phenomena and demonstrate the need to consider real gas effects.

A Study of the Three-Dimensional Unsteady Real-Gas Flows Within a Transonic ORC Turbine

2014 ◽  
Author(s):  
Andrew P. S. Wheeler ◽  
Jonathan Ong
Keyword(s):  
Three Dimensional ◽  
Organic Rankine Cycle ◽  
Leading Edge ◽  
Rankine Cycle ◽  
Gas Flows ◽  
Cfd Simulations ◽  
Significant Drop ◽  
Real Gas ◽  
Turbine Efficiency ◽  
Real Gas Effects

In this paper we investigate the three-dimensional unsteady real-gas flows which occur within Organic Rankine Cycle (ORC) turbines. A radial-inflow turbine stage operating with supersonic vane exit flows (M ≈ 1.4) is simulated using a RANS solver which includes real-gas effects. Steady CFD simulations show that small changes in the inducer shape can have a significant effect on turbine efficiency due to the development of supersonic flows in the rotor. Unsteady predictions show the same trends as the steady CFD, however a strong interaction between the vane trailing-edge shocks and rotor leading-edge leads to a significant drop in efficiency.

An Experimental Investigation on Transpiration Cooling for Supersonic Vehicle Nose Cone Using Porous Material

2014 ◽  
Vol 541-542 ◽  
pp. 690-694 ◽  
Author(s):  
Lian Jin Zhao ◽  
Jia Lin ◽  
Jian Hua Wang ◽  
Jin Long Peng ◽  
De Jun Qu ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Porous Material ◽  
Supersonic Jet ◽  
Leading Edge ◽  
Injection System ◽  
Aerodynamic Heating ◽  
Hypersonic Vehicles ◽  
Transpiration Cooling ◽  
Cone Model ◽  
Nose Cone

During hypersonic flight or cruise in the near space, the aerodynamic heating causes a very high temperature on the leading edge of hypersonic vehicles. Transpiration cooling has been recognized the most effective cooling technology. This paper presents an experimental investigation on transpiration cooling using liquid water as coolant for a nose cone model of hypersonic vehicles. The nose cone model consists of sintered porous material. The experiments were carried out in the Supersonic Jet Arc-heated Facility (SJAF) of China Academy of Aerospace Aerodynamics (CAAA) in Beijing. The cooling effect in the different regions of the model was analyzed, and the shock wave was exhibited. The pressure variations of the coolant injection system were continuously recorded. The aim of this work is to provide a relatively useful reference for the designers of coolant driving system in practical hypersonic vehicles.

scholarly journals Direct Numerical Simulation of Real-gas Effects within Turbulent Boundary Layers for Fully-developed Channel Flows

2021 ◽  
Vol 5 ◽  
pp. 216-232
Author(s):  
Tao Chen ◽  
Bijie Yang ◽  
Miles Robertson ◽  
Ricardo Martinez-Botas
Keyword(s):  
Outer Layer ◽  
Gas Flow ◽  
Reynolds Shear Stress ◽  
Turbulent Viscosity ◽  
Spanwise Direction ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effect ◽  
Real Gas Effects ◽  
Gas Effect

Real-gas effects have a significant impact on compressible turbulent flows of dense gases, especially when flow properties are in proximity of the saturation line and/or the thermodynamic critical point. Understanding of these effects is key for the analysis and improvement of performance for many industrial components, including expanders and heat exchangers in organic Rankine cycle systems. This work analyzes the real-gas effect on the turbulent boundary layer of fully developed channel flow of two organic gases, R1233zd(E) and MDM - two candidate working fluids for ORC systems. Compressible direct numerical simulations (DNS) with real-gas equations of state are used in this research. Three cases are set up for each organic vapour, representing thermodynamic states far from, close to and inside the supercritical region, and these cases refer to weak, normal and strong real-gas effect in each fluid. The results within this work show that the real-gas effect can significantly influence the profile of averaged thermodynamic properties, relative to an air baseline case. This effect has a reverse impact on the distribution of averaged temperature and density. As the real-gas effect gets stronger, the averaged centre-to-wall temperature ratio decreases but the density drop increases. In a strong real-gas effect case, the dynamic viscosity at the channel center point can be lower than at channel wall. This phenomenon can not be found in a perfect gas flow. The real-gas effect increases the normal Reynolds stress in the wall-normal direction by 7–20% and in the spanwise direction by 10–21%, which is caused by its impact on the viscosity profile. It also increases the Reynolds shear stress by 5–8%. The real-gas effect increases the turbulence kinetic energy dissipation in the viscous sublayer and buffer sublayer <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>y</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:mo><</mml:mo><mml:mn>30</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula> but not in the outer layer. The turbulent viscosity hypthesis is checked in these two fluids, and the result shows that the standard two-function RANS model (<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ϵ</mml:mi></mml:math></inline-formula> and <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>k</mml:mi><mml:mo>−</mml:mo><mml:mi>ω</mml:mi></mml:math></inline-formula>) with a constant <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>C</mml:mi><mml:mi>μ</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>0.09</mml:mn></mml:math></inline-formula> is still suitable in the outer layer <inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>y</mml:mi><mml:mo>∗</mml:mo></mml:msup><mml:mo>></mml:mo><mml:mn>70</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math></inline-formula>, with an error in ±10%.

Problems of Hypersonic Aerodynamics— A Survey

1959 ◽  
Vol 63 (585) ◽  
pp. 489-492 ◽  
Author(s):  
R. J. Monaghan
Keyword(s):  
Hypersonic Flow ◽  
Three Dimensional ◽  
Separated Flow ◽  
Low Pressure ◽  
Aerodynamic Heating ◽  
Aerodynamic Efficiency ◽  
Real Gas ◽  
Pressure Drag ◽  
Real Gas Effects ◽  
Hypersonic Aerodynamics

SummaryReal gas effects are among the major complications of hypersonic flow and this is illustrated by examples of the temperatures and pressures attained when a flow is brought to rest. Once dissociation appears, these depend to a marked extent on the type of compression.In designing for the alleviation of aerodynamic heating there are two distinct cases. The first is the uncontrolled re-entry of a freely falling body, for which it is best to have a shape with a high pressure drag. The second is sustained flight, for which a shape with low pressure drag could be better, radiation giving appreciable control of surface temperature.Low pressure drag accords with design for aerodynamic efficiency and there is scope for research on three-dimensional lifting shapes. There is some discussion of this and also of the philosophy of securing maximum amounts of separated flow.Finally, there is continual emphasis on the need for experimental research, since hypersonic flow fields may differ considerably from those that would be expected by extrapolation of conventional supersonic experience.

A computational study of real gas flows through a critical nozzle

2008 ◽  
Vol 223 (3) ◽  
pp. 617-626 ◽  
Author(s):  
J-H Kim ◽  
H-D Kim ◽  
T Setoguchi ◽  
S Matsuo
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Discharge Coefficient ◽  
Stokes Equations ◽  
Hydrogen Gas ◽  
Molecular Volume ◽  
Real Gas ◽  
The Real ◽  
Critical Nozzle ◽  
Real Gas Effects

A critical nozzle is used to measure the mass flowrate of gas. It is well known that the coefficient of discharge of the flow in a critical nozzle is a single function of the Reynolds number, in which the discharge coefficient approaches unity as the Reynolds number increases. However, it has recently been reported that at very high Reynolds numbers, which correspond to high-pressure supply conditions, the discharge coefficient exceeds unity. This impractical value in the discharge coefficient is vaguely inferred to be due to real gas effects. The purpose of the present study is to investigate high-pressure hydrogen gas flow through a critical nozzle. A computational analysis has been carried out to simulate a critical nozzle flow with real gas effects. Redlich—Kwong's equation of state is incorporated into the axisymmetric, compressible Navier—Stokes equations to account for the inter-molecular forces and molecular volume of hydrogen. The computational results show that the critical pressure ratio and the discharge coefficient for ideal gas assumptions are significantly different from those of the real gas, as the Reynolds number exceeds a certain value. It is also known that the real gas effects appear largely in terms of the compressibility factor and the specific heat ratio, and these become more remarkable as the pressure of hydrogen increases.

The Use of Real Gas Properties for Design and Flow Field Simulations of a Small Centripetal Steam Turbine

2009 ◽  
Author(s):  
Jianjun Feng ◽  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Steam Turbine ◽  
Design Procedure ◽  
Flow Fields ◽  
Ideal Gas ◽  
Real Gas ◽  
The Real ◽  
Real Gas Effects ◽  
Applied Design ◽  
Small Capacity ◽  
Gas Properties

In this paper, the applied design procedure for generation of a small-capacity ORC centripetal steam turbine working with the fluid 1, 1, 1, 3, 3-Pentafluoropropane (R245fa) is described with consideration of real gas effects. After specification of the turbine geometry in an iterative process using different commercial design tools which have been enhanced in order to work with real gas conditions, CFD simulations based on the real gas properties of the fluid have been conducted for the originated geometry. The simulations are performed by using the CFD code ANSYS-CFX11 with a pre-prepared real gas property (RGP) table, which comprises the required gas properties at different discrete pressure and temperature values. In addition, the flow fields inside the turbine obtained from the real gas model is compared to those flow fields which are obtained by the ideal gas model and also by the Redlich-Kwong model.

Sign in / Sign up

Export Citation Format

Share Document