Effects of Combustor Acoustics on Fuel Spray Dynamics

2004 ◽  
Author(s):  
Wajid A. Chishty ◽  
Uri Vandsburger ◽  
William R. Saunders ◽  
William T. Baumann
Keyword(s):  
Control Systems ◽  
Liquid Fuel ◽  
Separated Flow ◽  
Fuel Spray ◽  
Reacting Flow ◽  
Thermoacoustic Instability ◽  
Response Characteristics ◽  
Frequency Response Characteristics ◽  
System Characteristics ◽  
Insight Into

An experimental liquid fuel LDI combustor, developed to study thermoacoustic instability processes and to test active combustion control systems, was found to demonstrate three distinct stability regimes, with system characteristics not reported in earlier literature. These observations led to a series of further investigations, both in reactive and non-reactive conditions, to gain an insight into effects of combustor acoustics on fuel spray dynamics. This paper presents only the non-reacting flow results, from both experimental and modeling investigations. The experimental setup and construction details of an isothermal acoustic rig are presented. Phase-locked PDA measurements of droplet velocities and diameters from a simplex atomizer spray were acquired, with and without combustor swirl co-airflow, under varying acoustic forcing conditions and spray feed pressures. Measurements made at four locations in the spray are related, in the paper, to these variations in mean and unsteady inputs. The dynamic behavior of the spray is then presented in terms of frequency response characteristics related to acoustic fields imposed on the spray. Finally, results from non-reacting spray modeling, predicting droplet trajectories, are reported. The modeling was done using the deterministic separated flow approach. These trajectories are compared to the reported experimental results to support preliminary explanations for the unique experimental observations of the swirl-stabilized kerosene flame in a single can combustor geometry.

Analysis of frequency response characteristics of polymer ultrasonic transducers

1992 ◽  
Vol 25 (3) ◽  
pp. 155
Author(s):  
H. Ohigashi ◽  
T. Itoh ◽  
K. Kimura ◽  
T. Nakanishi ◽  
M. Suzuki
Keyword(s):  
Frequency Response ◽  
Ultrasonic Transducers ◽  
Response Characteristics ◽  
Frequency Response Characteristics

Comparative studies of the set up of two-dimensional pneumatic arm systems by muscle and rotational actuators

2007 ◽  
Vol 221 (5) ◽  
pp. 743-748 ◽  
Author(s):  
Y-T Wang ◽  
R-H Wong ◽  
J-T Lu
Keyword(s):  
Control Systems ◽  
Fuzzy Controller ◽  
Control Algorithms ◽  
Two Dimensional ◽  
Pneumatic Control ◽  
Learning Mechanism ◽  
Set Up ◽  
And Control ◽  
Self Learning ◽  
System Characteristics

As opposed to traditional pneumatic linear actuators, muscle and rotational actuators are newly developed actuators in rotational and specified applications. In the current paper, these actuators are used to set up two-dimensional pneumatic arms, which are used mainly to simulate the excavator's motion. Fuzzy control algorithms are typically applied in pneumatic control systems owing to their non-linearities and ill-defined mathematical model. The self-organizing fuzzy controller, which includes a self-learning mechanism to modify fuzzy rules, is applied in these two-dimensional pneumatic arm control systems. Via a variety of trajectory tracking experiments, the present paper provides comparisons of system characteristics and control performances.

Root-Locus Analysis of Structural Coupling in Control Systems

1959 ◽  
Vol 26 (2) ◽  
pp. 205-209
Author(s):  
R. H. Cannon
Keyword(s):  
Control System ◽  
Control Systems ◽  
Natural Frequency ◽  
Feedback System ◽  
Structural Member ◽  
Root Locus ◽  
Structural Coupling ◽  
Root Locus Analysis ◽  
Platform System ◽  
System Characteristics

Abstract When a feedback system is devised to control a mechanical member that is structurally limber, unstable (“self-excited”) vibrations may be encountered at approximately a natural frequency of the structural member. Cures are generally easy to effect once the phenomena are understood. Two interesting cases are described: ground vibrations of an airplane control system due to a limber fuselage, and vibrations of a stable platform system due to limberness in the platform structure. The investigations are carried out using the root-locus technique, which provides a plot of system characteristics as explicit functions of control strength. In the case of the stable platform, the analysis is found to be more reliable than physical intuition.

Fuel Composition Effects on Forced Ignition of Liquid Fuel Sprays

2018 ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Physical Properties ◽  
Liquid Fuel ◽  
Chemical Properties ◽  
Reaction Rates ◽  
High Energy ◽  
Fuel Spray ◽  
Successful Outcome ◽  
Fuel Composition ◽  
Ignition Probability ◽  
Fuel Sprays

In gas turbine combustors, ignition is achieved by using sparks from igniters to start a flame. The process of sparks interacting with fuel/air mixture and creating self-sustained flames is termed forced ignition. Physical and chemical properties of a liquid fuel can influence forced ignition. The physical effects manifest through processes such as droplet atomization, spray distribution, and vaporization rate. The chemical effects impact reaction rates and heat release. This study focuses on the effect of fuel composition on forced ignition of fuel sprays in a well-controlled flow with a commercial style igniter. A facility previously used to examine prevaporized, premixed liquid fuel-air mixtures is modified and employed to study forced ignition of liquid fuel sprays. In our experiments, a wall-mounted, high energy, recessed cavity discharge igniter operating at 15 Hz with average spark energy of 1.25 J is used to ignite liquid fuel spray produced by a pressure atomizer located in a uniform air coflow. The successful outcome of each ignition events is characterized by the (continued) presence of chemiluminescence 2 ms after spark discharge, as detected by a high-speed camera. The ignition probability is defined as the fraction of successful sparks at a fixed condition, with the number of events evaluated for each fuel typically in the range 600–1200. Ten fuels were tested, including standard distillate jet fuels (e.g., JP-8 and Jet-A), as well as many distillate and alternative fuel blends, technical grade n-dodecane, and surrogates composed of a small number of components. During the experiments, the air temperature is controlled at 27 C and the fuel temperature is controlled at 21 C. Experiments are conducted at a global equivalence ratio of 0.55. Results show that ignition probabilities correlate strongly to liquid fuel viscosity (presumably through droplet atomization) and vapor pressure (or recovery temperature), as smaller droplets of a more volatile fuel would lead to increased vaporization rates. This allows the kernel to transition to a self-sustained flame before entrainment reduces its temperature to a point where chemical rates are too slow. Chemical properties of the fuel showed little influence, except when the fuels had similar physical properties. This result demonstrates that physical properties of liquid fuels have dominating effects on forced ignition of liquid fuel spray in coflow air.

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