One-Dimensional Simulations of Jet Fuel Thermal-Oxidative Degradation and Deposit Formation Within Cylindrical Passages

2000 ◽  
Vol 122 (4) ◽  
pp. 229-238 ◽  
Author(s):  
J. S. Ervin ◽  
S. Zabarnick ◽  
T. F. Williams
Keyword(s):  
Fluid Dynamics ◽  
Jet Fuel ◽  
Thermal Oxidative Degradation ◽  
Fuel System ◽  
Flow Conditions ◽  
Surface Deposition ◽  
Deposition Rates ◽  
Fuel Oxidation ◽  
One Dimensional ◽  
Dissolved O2

Flowing aviation fuel is used as a coolant in military aircraft. Dissolved O2 reacts with the heated fuel to form undesirable surface deposits which disrupt the normal flow. For purposes of aircraft design, it is important to understand and predict jet fuel oxidation and the resulting surface deposition. Detailed multi-dimensional numerical simulations are useful in understanding interactions between the fluid dynamics and fuel chemistry. Unfortunately, the detailed simulation of an entire fuel system is impractical. One-dimensional and lumped parameter models of fluid dynamics and chemistry can provide the simultaneous simulation of all components which comprise a complex fuel system. In this work, a simplified one-dimensional model of jet fuel oxidation and surface deposition within cylindrical passages is developed. Both global and pseudo-detailed chemical kinetic mechanisms are used to model fuel oxidation, while a global chemistry model alone is used to model surface deposition. Dissolved O2 concentration profiles and surface deposition rates are calculated for nearly isothermal and nonisothermal flow conditions. Flowing experiments are performed using straight-run jet fuels, and the predicted dissolved O2 concentrations and surface deposition rates agree reasonably well with measurements over a wide range of temperature and flow conditions. The new model is computationally inexpensive and represents a practical alternative to detailed multi-dimensional calculations of the flow in cylindrical passages. [S0195-0738(00)01204-8]

scholarly journals Aspects of Jet Fuel Oxidation

1997 ◽  
Author(s):  
Steven Zabarnick ◽  
Shawn D. Whitacre
Keyword(s):  
Oxidation Rate ◽  
Oxygen Sensor ◽  
Jet Fuel ◽  
Jet Fuels ◽  
Surface Deposition ◽  
Fuel Oxidation ◽  
Headspace Oxygen ◽  
Sensor Technique ◽  
Metal Deactivator ◽  
Alkylperoxy Radicals

A quartz crystal microbalance (QCM)/Parr bomb system with a headspace oxygen sensor is used to measure oxidation and deposition during thermal oxidative stressing of jet fuel. The advantages of the oxygen sensor technique in monitoring fuel oxidation is demonstrated. Simultaneous measurement of deposition using the QCM shows a strong correlation between oxidation and deposition in jet fuels. Studies performed over the temperature range 140 to 180°C show that surface deposition peaks at an intermediate temperature, while bulk deposition increases with temperature, in studies of jet fuel antioxidants, we find that rapid increases in oxidation rate occur upon consumption of the antioxidant. The antioxidant appears to be consumed by reaction with alkylperoxy radicals. In studies of metal deactivator (MDA) additives, we find that MDA is consumed during thermal stressing, and this consumption results in large increases in the oxidation rate of metal containing fuels. Mechanisms of MDA consumption are hypothesized.

Aspects of Jet Fuel Oxidation

1998 ◽  
Vol 120 (3) ◽  
pp. 519-525 ◽  
Author(s):  
S. Zabarnick ◽  
S. D. Whitacre
Keyword(s):  
Oxidation Rate ◽  
Oxygen Sensor ◽  
Jet Fuel ◽  
Jet Fuels ◽  
Surface Deposition ◽  
Fuel Oxidation ◽  
Headspace Oxygen ◽  
Sensor Technique ◽  
Metal Deactivator ◽  
Alkylperoxy Radicals

A quartz crystal microbalance (QCM)/Parr bomb system with a headspace oxygen sensor is used to measure oxidation and deposition during thermal oxidative stressing of jet fuel. The advantages of the oxygen sensor technique in monitoring fuel oxidation is demonstrated. Simultaneous measurement of deposition using the QCM shows a strong correlation between oxidation and deposition in jet fuels. Studies performed over the temperature range 140 to 180°C show that surface deposition peaks at an intermediate temperature, while bulk deposition increases with temperature. In studies of jet fuel antioxidants, we find that rapid increases in oxidation rate occur upon consumption of the antioxidant. The antioxidant appears to be consumed by reaction with alkylperoxy radicals. In studies of metal deactivator (MDA) additives, we find that MDA is consumed during thermal stressing, and this consumption results in large increases in the oxidation rate of metal containing fuels. Mechanisms of MDA consumption are hypothesized.

Diabatic Nozzle Flow with Constant Small Stage Efficiency

1960 ◽  
Vol 64 (598) ◽  
pp. 632-635 ◽  
Author(s):  
R. A. A. Bryant
Keyword(s):  
Gas Flow ◽  
Nozzle Flow ◽  
Flow Conditions ◽  
One Dimensional ◽  
Real Flow ◽  
Stage Efficiency ◽  
Frictional Effects

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

Effects of Flow Passage Expansion or Contraction on Jet-Fuel Surface Deposition

2012 ◽  
Vol 28 (4) ◽  
pp. 694-706 ◽  
Author(s):  
Hua Jiang ◽  
Jamie Ervin ◽  
Steven Zabarnick ◽  
Zachary West
Keyword(s):  
Jet Fuel ◽  
Surface Deposition ◽  
Flow Passage ◽  
Fuel Surface

Mathematical Analysis for Off-Design Performance of Cryogenic Turboexpander

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Subrata K. Ghosh ◽  
R. K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Pressure Ratio ◽  
Expansion Ratio ◽  
Flow Conditions ◽  
Flow Properties ◽  
Dimensional Solution ◽  
One Dimensional ◽  
Design Performance ◽  
Fluid Properties ◽  
The Mean ◽  
Inlet Conditions

A study has been conducted to determine the off-design performance of cryogenic turboexpander. A theoretical model to predict the losses in the components of the turboexpander along the fluid flow path has been developed. The model uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. In this analysis, the changes of fluid and flow properties between different components of turboexpander have been considered. Overall, turbine geometry, pressure ratio, and mass flow rate are input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The procedure allows any arbitrary combination of fluid species, inlet conditions, and expansion ratio since the fluid properties are properly taken care of in the relevant equations. The computational process is illustrated with an example.

Effect of temperature and pressure on cavitation characteristics in RP-3 jet fuel

2021 ◽  
pp. 2150375
Author(s):  
Chao Qiu ◽  
Shuxian Chen ◽  
Feng Yan ◽  
Yaoming Fu ◽  
Wuguo Wei
Keyword(s):  
Cavitation Erosion ◽  
Engine Performance ◽  
Jet Fuel ◽  
Effect Of Temperature ◽  
Fuel System ◽  
Fuel Temperature ◽  
Fuel Droplets ◽  
Aircraft Fuel ◽  
Different Temperatures ◽  
Temperature And Pressure

Cavitation usually appears in aircraft fuel system, which is significant for the operation of engine. Uncontrollable cavitation will cause cavitation erosion to the units of fuel system, while the controllable cavitation can enhance the turbulence of fuel and improve the engine performance. This work along with molecular dynamics was used to simulate the cavitation in RP-3 jet fuel with different temperatures and pressures. The influence of fuel temperature and pressure on cavitation characteristics was studied. It is indicated that the higher the temperature is, the more easily the RP-3 jet fuel cavitate. Furthermore, the influence of pressure on cavitation can be divided into two periods. The lower the fuel pressure is, the faster the occurrence and development of cavitation in RP-3 jet fuel. When the temperature and pressure of the RP-3 jet fuel are set at the region between the line [Formula: see text] and [Formula: see text]%, the cavitation erosion can be almost ignored, and the dispersion of fuel droplets is almost the best.

A flow-dependent estimation of constriction size distribution in gap-graded soils: an integrated statistical approach

2022 ◽  
Vol 12 (1) ◽  
pp. 1-25
Author(s):  
S.M. Dassanayake ◽  
A. Mousa
Keyword(s):  
Fluid Dynamics ◽  
Size Distribution ◽  
Statistical Approach ◽  
One Dimensional ◽  
Loading Pattern ◽  
Wide Range ◽  
Hydraulic Gradients ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Estimate Flow

The clogging-unclogging process in gap-graded soils is a result of the migration of seepage-driven fines, which subsequently induces measurable changes in the local hydraulic gradients. This process can be temporally observed in the variations of Darcy's hydraulic conductivity (K). The current study proposes an integrated statistical Monte Carlo approach combining the discrete element method and 2D computational fluid dynamics simulations to estimate the flow-dependent constriction size distribution (CSD) for a gap-graded soil. The computational inferences were supported with experimental results using an internally stable soil, which was subjected to one-dimensional flow stimulating desired hydraulic loadings: a hydraulic gradient lower than the critical gradient applied as a multi-staged loading pattern. The 35th percentile size of the flow-dependent CSD (Dc35) for both internally stable and unstable gap-graded soils becomes approximately equal to Dc35 at steady-state. However, a greater variation of larger constrictions persists for the unstable soils. This pilot study has shown the applicability of the proposed method to estimate flow-dependent CSD for a wide range of experimentally observed K values.

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