Thermoacoustic Oscillations in Multipath Heated Fuel Circuits

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Steven Hunt ◽  
Stephen Heister
Keyword(s):  
Characteristic Length ◽  
Pressure Oscillation ◽  
Acoustic Mode ◽  
Large Temperature ◽  
Phase Lag ◽  
Flow Conditions ◽  
Fuel Flow ◽  
Lower Frequency Mode ◽  
Thermoacoustic Oscillations ◽  
Fuel Tube

Pressure oscillations in supercritical jet-A fuel flowing through four parallel heated tubes connected to common manifolds have been observed in this study. Tests were performed with fuel inlet temperatures ranging from 70 °F to 700 °F, and fuel pressures ranging from 360 to 700 psi. Total fuel flow rate ranged from 5 to 55 lb/h. Tubes were heated by blowing 800–950 °F nitrogen over them. Acoustic-mode oscillations, typically ranging from 100 to 500 Hz, occurred only when a large temperature gradient was created inside the heated fuel tubes. Pressure oscillation amplitudes ranged from 0.1 to 1.0 psi. Oscillations at the inlet and outlet manifolds that were caused by a mode with the characteristic length of a single fuel tube were separated by a phase lag that was a function of the manifold cross-passage diameter. A lower frequency mode was also observed, which had a characteristic length based on the summed lengths of a single fuel tube and a single manifold passage. An acoustic simulation using the comsol acoustics module was performed to predict frequencies based on geometry and flow conditions of the experiment.

Thermoacoustic Oscillations of Jet-A Fuel in Parallel Heated Flowpaths

2015 ◽  
Author(s):  
Steven A. Hunt
Keyword(s):  
Time Pressure ◽  
Pressure Oscillation ◽  
Acoustic Mode ◽  
Phase Lag ◽  
Fuel Flow Rate ◽  
Pressure Oscillations ◽  
Single Tube ◽  
Outlet Pressure ◽  
Fuel Flow ◽  
Thermoacoustic Oscillations

Pressure oscillations in supercritical Jet-A fuel flowing through four parallel, heated tubes connected to common manifolds have been observed in this study. Tests were performed with fuel inlet temperatures ranging from 200°F to 700°F, and fuel pressures ranging from 360–700 psi. Total fuel flow rate ranged from 7–37 lb/hr. Tubes were heated by blowing 850–870°F nitrogen over them. Acoustic-mode oscillations, typically ranging from 300–350 Hz, occurred only when a single tube was heated at a time. Pressure oscillation amplitudes ranged from 0.1–1.0 psi. Tube inlet and outlet pressure waveforms were separated by a phase lag that was a function of the manifold cross-passage diameter.

Spray Formation and Fuel Flow Rate at the Multi-Stage Injections Injected From the Swirl Nozzle

2003 ◽  
Author(s):  
Kokichi Sawada ◽  
Shinji Nakao ◽  
Tsuneaki Ishima ◽  
Tomio Obokata ◽  
Katsuyoshi Kawachi ◽  
...  
Keyword(s):  
Flow Rate ◽  
Gasoline Engine ◽  
Fuel Injection ◽  
Pressure Oscillation ◽  
Injection Rate ◽  
Fuel Flow Rate ◽  
Two Stage ◽  
Fuel Flow ◽  
Piv Measurement ◽  
Valve Opening

The structure, droplet characteristics and instantaneous fuel injection rate of two stage injection spray designed for direct injection gasoline engine were analyzed experimentally. A particle image velocimetry (PIV) to evaluate the instantaneous two-dimensional velocity field, a phase Doppler anemometer (PDA) and an instantaneous fuel flow rate meter based on a laser Doppler anemometer (LDA flow rate meter) were applied for the measurements. A swirl nozzle injector was used and injection conditions were 25 Hz of spray frequency, 2 ms and 1ms of the first and the second injection durations and 2.4, 3.3 and 9.1 ms of valve opening intervals. The initial jet of the second stage injection can overtook the main spray body of the first stage injection under the valve opening interval of 2.4 and 3.3 ms. The LDA flow rate meter made the injection rate measurement with sufficient accuracy in the two stage injection and showed the unstable second injection due to remaining pressure oscillation in the injection pipe. Both time averaged and time resolved PDA results were compared in the intermittent spray. The interaction between the first and the second sprays was also demonstrated in vector map obtained by the PIV measurement.

scholarly journals Investigation on Acoustic Properties of Thruster Chamber with Coaxial Injectors and Plenum Chamber

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Dekun Gao ◽  
Jianxiu Qin ◽  
Huiqiang Zhang
Keyword(s):  
Acoustic Pressure ◽  
Rocket Engine ◽  
Pressure Oscillation ◽  
Acoustic Mode ◽  
Acoustic Properties ◽  
Pressure Oscillations ◽  
Plenum Chamber ◽  
Model Chamber ◽  
Pressure Peak ◽  
Tuning Frequency

Based on the URANS equation, a numerical simulation is carried out for acoustic properties of the thruster chamber with coaxial injectors and plenum chamber in a liquid rocket engine. Pressure oscillations with multiacoustic modes are successfully excited in the chamber by using the constant volume bomb method. FFT analysis is applied to obtain the acoustic properties of eigenfrequencies, power amplitudes, and damping rates for each excited acoustic mode. Compared with the acoustic properties in the model chamber with and without an injector as well as with and without the plenum chamber, it can be found that the injector with one open end and one half-open end still can work as a quarter-wave resonator. The power amplitudes of the acoustic mode can be suppressed significantly when its eigenfrequency is close to the tuning frequency of the injector, which is achieved by Cutting down the pressure Peak and Raising up the pressure Trough (CPRT). Compared with the acoustic properties in the model chamber with and without the plenum chamber, it can be found that 1L acoustic pressure oscillation is inhibited completely by the plenum chamber and other acoustic pressure oscillations are also suppressed in a different extent. The injector and plenum chamber have a little effect on the eigenfrequencies and damping rate of each acoustic mode. For multimode pressure oscillation, it is better for tuning frequency of the injector closing to the lower eigenfrequency acoustic mode, which will be effective for suppression of these multiacoustic modes simultaneously.

Potential-flow instability theory and alluvial stream bed forms

2000 ◽  
Vol 418 ◽  
pp. 101-117 ◽  
Author(s):  
S. E. COLEMAN ◽  
J. D. FENTON
Keyword(s):  
Sediment Transport ◽  
Potential Flow ◽  
Flow Model ◽  
Flow Instability ◽  
Phase Lag ◽  
Flow Conditions ◽  
Local Flow ◽  
Flow Models ◽  
Flow Systems ◽  
Bed Waves

The present work constitutes a reassessment of the role of potential-flow analyses in describing alluvial-bed instability. To facilitate the analyses, a new potential-flow description of unsteady alluvial flow is presented, with arbitrary phase lags between local flow conditions and sediment transport permitted implicitly in the flow model. Based on the present model, the explicit phase lag between local sediment transport rate and local flow conditions adopted for previous potential-flow models is shown to be an artificial measure that results in model predictions that are not consistent with observed flow system behaviour. Previous potential-flow models thus do not provide correct descriptions of alluvial flows, and the understanding of bed-wave mechanics inferred based upon these models needs to be reassessed. In contrast to previous potential-flow models, the present one, without the use of an explicit phase lag, predicts instability of flow systems of rippled or dune-covered equilibrium beds. Instability is shown to occur at finite growth rates for a range of wavelengths via a resonance mechanism occurring for surface waves and bed waves travelling at the same celerity. In addition, bed-wave speeds are predicted to decrease with increasing wavelength, and bed waves are predicted to grow and move at faster rates for flows of larger Froude numbers. All predictions of the present potential-flow model are consistent with observations of physical flow systems. Based on the predicted unstable wavelengths for a given alluvial flow, it is concluded that bed waves are not generated from plane bed conditions by any potential-flow instability mechanism. The predictions of instability are nevertheless consistent with instances of accelerated wave growth occurring for flow systems of larger finite developing waves. Potential-flow description of alluvial flows should, however, no longer form the basis of instability analyses describing bed-form (sand-wavelet) generation from flat bed conditions.

Unsteady Fluid/Solid Numerical Simulations to Evaluate Thermal Solicitations in PWR Nuclear Plant Mixing Zones

2005 ◽  
Author(s):  
Thomas Pasutto ◽  
Christophe Pe´niguel ◽  
Marc Sakiz ◽  
Jean-Michel Ste´phan
Keyword(s):  
Fluid Flow ◽  
Temperature Fluctuations ◽  
Large Temperature ◽  
Phase Lag ◽  
Joint Paper ◽  
Nuclear Plants ◽  
3D Effects ◽  
Instantaneous Temperature ◽  
Unsteady Fluid ◽  
Thermal Striping

Thermal fatigue of the coolant circuits of PWR plants is a major issue for nuclear safety. The problem is especially accute in mixing zones, like T-junctions, where large differences in water temperature between the two inlets and high levels of turbulence can lead to large temperature fluctuations at the wall. Until recently, studies on the matter had been tackled at EDF using steady methods: the fluid flow was solved with a CFD code using an averaged turbulence model, which led to the knowledge of the mean temperature and temperature variance at each point of the wall. But, being based on averaged quantities, this method could not reproduce the unsteady and 3D effects of the problem, like phase lag in temperature oscillations between two points, which can generate important stresses. Benefiting from advances in computer power and turbulence modelling, a new methodology is now applied, that allows to take these effects into account. The CFD tool Code_Saturne, developped at EDF, is used to solve the fluid flow using an unsteady L.E.S. approach. It is coupled with the thermal code Syrthes, which propagates the temperature fluctuations into the wall thickness. The instantaneous temperature field inside the wall can then be extracted and used for structure mechanics computations (mainly with EDF thermomechanics tool Code_Aster, see joint paper [1]). The purpose of this paper is to present the application of this methodology to the simulation of a straight T-junction mockup, similar to the Residual Heat Remover (RHR) junction found in N4 type PWR nuclear plants, and designed to study thermal striping and cracks propagation. The results are generally in good agreement with the measurements; yet, in certain areas of the flow, progress is still needed in L.E.S. modelling and in the treatment of instantaneous heat transfer at the wall.

Development of Fuel Control System for More Electric Engine

2015 ◽  
Author(s):  
Naoki Seki ◽  
Noriko Morioka ◽  
Hitoshi Oyori ◽  
Yasuhiko Yamamoto
Keyword(s):  
Control Method ◽  
Pressure Oscillation ◽  
System Stability ◽  
Gear Pump ◽  
Engine Fuel ◽  
Fuel System ◽  
Loop Control ◽  
Fuel Flow ◽  
Electric Engine ◽  
Experimental Rig

This paper describes the experimental rig test result and an investigation into issues of system stability and pressure oscillation transmission in the MEE (More Electric Engine) fuel system. This system employs an electric motor-driven pump and directly meters the fuel flow based on the motor rotating speed. The MEE is a system architecture concept for the aircraft turbine engine that reduces fuel consumption and environmental load while improving safety, reliability and maintainability. The improvements were demonstrated by conducting a feasibility study of MEE system for small sized turbofan engine [5, 6]. The authors also conducted an experimental rig test showing capabilities in terms of fuel-metering range, accuracy and response [7]. The capability of the feedback loop control under the engine start condition was shown by the result, but meanwhile, pressure oscillation under the higher fuel flow condition was also observed. The authors repeated the rig test to investigate its root cause. This paper describes the study, which investigates the characteristics of the MEE fuel system and seeks stable control methods under conditions of higher pressure fluctuation, higher instrumentation noise or applying worn gear pump. The paper also describes the study of the pressure oscillation transmission from pump to engine combustor, which may damage the engine combustor and structures. As a result of these studies, a novel control method for the MEE fuel system is proposed, with improved oscillation stability.

Paper 13: Liquid Metal Flow in a Complex System of Passages

1967 ◽  
Vol 182 (4) ◽  
pp. 37-46
Author(s):  
D. A. Greene
Keyword(s):  
Complex System ◽  
Heat Transfer ◽  
Liquid Metal ◽  
Metal Flow ◽  
Large Temperature ◽  
Flow Conditions ◽  
Transfer Experiment ◽  
Temperature Changes ◽  
Liquid Metal Flow ◽  
Valve Operation

To achieve the necessary flow conditions in a particular liquid metal heat transfer experiment it has been necessary to design a rather complex pipework system. An analysis of the system has been made, and flow predictions in various parts of the system as functions of valve operation are given. Comparison is made with the experimental results obtained on the rig. The effect of various parameters such as thermal density changes and cavitating flow, caused by large temperature changes and driving pressure heads, is briefly discussed.

scholarly journals Combustion Experiments With a New Burner Air Distribution Concept

1983 ◽  
Author(s):  
Stanley J. Markowski ◽  
Bruce V. Johnson ◽  
Richard L. Marshall
Keyword(s):  
Fuel Injection ◽  
Front Face ◽  
Temperature Pattern ◽  
Flow Conditions ◽  
Pressure Losses ◽  
Air Inlet ◽  
Fuel Flow ◽  
Temperature Distributions ◽  
Total Temperature ◽  
Inlet Conditions

Experiments were conducted with a JT8D-engine sized can combustor which had all the combustion and dilution air entering through the burner front face. The primary and secondary/dilution air inlet geometries the primary fuel injection configuration, the air inlet conditions and the fuel flow rates for the combustor were varied in a series of parametric low power combustion experiments. Measurements included exit plane emissions, total pressure and total temperature distributions and burner liner temperature distributions. Attractive emission levels, temperature pattern factors and wall temperatures were achieved with low burner pressure losses for the good combinations of geometry and flow conditions.

Effects of Equivalence Ratio on the Off-Design Combustion Performance of Adjustable Fuel Feeding Combustor for a Micro-Gas Turbine

2017 ◽  
Author(s):  
Chang Xing ◽  
Penghua Qiu ◽  
Li Liu ◽  
Wenkai Shen ◽  
Yajin Lyu ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Characteristic Number ◽  
Outlet Temperature ◽  
Operation Performance ◽  
Feeding Method ◽  
Micro Gas Turbine ◽  
Combustion Performance ◽  
Fuel Flow ◽  
Combustion Technology ◽  
Fuel Tube

To improve off-design operation performance of micro-gas turbine, we proposed an adjustable fuel feeding combustor (AFFC), and it employed the lean premixed swirling combustion technology and the adjustable fuel feeding method (AFFM). The AFFM was achieved by switching the various working groups of main fuel tube, and represented by its unique characteristic number (U). To verify the availability of adopted models, the AFFC combustion performance was investigated numerically at different equivalence ratios (ϕ) in ANSYS CFX. The results indicate that NO emission has various trends with the rising U under different ϕ due to the coupling influence of fuel flow and jet velocity in each working main fuel tube. Although the AFFM has almost no effect on the distribution of outlet temperature and the length of primary recirculation zone, the maximum and non-uniform coefficient of outlet temperature increase with the rising U.

Avoiding Thermoacoustic Vibration in Burner/Furnace Systems

2002 ◽  
Vol 124 (4) ◽  
pp. 418-424 ◽  
Author(s):  
Frantisek L. Eisinger ◽  
Robert E. Sullivan
Keyword(s):  
Steam Generator ◽  
Mode Shape ◽  
Critical Value ◽  
Acoustic Mode ◽  
Full Scale ◽  
Large Temperature ◽  
Temperature Ratio ◽  
Combined System ◽  
Furnace Gases ◽  
Tube Type

Burner/furnace systems are generally sensitive to thermoacoustic vibration due to the presence of large temperature differentials between the cold burner air and the hot furnace gases. The systems are predicted to vibrate when the temperature ratio between the hot and cold components reaches a critical value and when the acoustic mode shape of the combined system develops into a Rijke or a Sondhauss tube type. Original full-scale large-utility steam generator systems which vibrated in operation and modified systems resisting the vibration are described and explained. Guidelines for designing systems resistant to thermoacoustic vibration are also given to aid the designers.

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