Numerical Investigations of High Frequency Pulsed Fuel Injection into Supersonic Crossflows

2016 ◽  
Author(s):  
Nehemiah J. Williams ◽  
Trevor M. Moeller
Keyword(s):  
High Frequency ◽  
Fuel Injection ◽  
Numerical Investigations

Combustion Instability and Emission Control by Pulsating Fuel Injection

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Ephraim Gutmark
Keyword(s):  
High Frequency ◽  
Fuel Injection ◽  
Low Frequency ◽  
Nox Emissions ◽  
Modulation Amplitude ◽  
Pulsation Frequency ◽  
Symmetric Mode ◽  
Instability Mode ◽  
Secondary Fuel ◽  
Symmetric Instability

Open-loop control methodologies were used to suppress symmetric and helical thermoacoustic instabilities in an experimental low-emission swirl-stabilized gas-turbine combustor. The controllers were based on fuel (or equivalence ratio) modulations in the main premixed combustion (premixed fuel injection (PMI)) or, alternatively, in the secondary pilot fuel. PMI included symmetric and asymmetric fuel injection. The symmetric instability mode responded to symmetric excitation only when the two frequencies matched. The helical fuel injection affected the symmetric mode only at frequencies that were much higher than that of the instability mode. The asymmetric excitation required more power to obtain the same amount of reduction as that required by symmetric excitation. Unlike the symmetric excitation, which destabilized the combustion when the modulation amplitude was excessive, the asymmetric excitation yielded additional suppression as the modulation level increased. The NOx emissions were reduced to a greater extent by the asymmetric modulation. The second part of the investigation dealt with the control of low frequency symmetric instability and high frequency helical instability by the secondary fuel injection in a pilot flame. Adding a continuous flow of fuel into the pilot flame controlled both instabilities. However, modulating the fuel injection significantly decreased the amount of necessary fuel. The reduced secondary fuel resulted in a reduced heat generation by the pilot diffusion flame and therefore yielded lower NOx emissions. The secondary fuel pulsation frequency was chosen to match the time scales typical to the central flow recirculation zone, which stabilizes the flame in the burner. Suppression of the symmetric mode pressure oscillations by up to 20dB was recorded. High frequency instabilities were suppressed by 38dB, and CO emissions reduced by using low frequency modulations with 10% duty cycle.

A STUDY ON FRACTURE CHARACTERISTICS OF THE SM53C USED IN THE CAM SHAFT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1846-1852 ◽  
Author(s):  
HYUN-BAE JEON ◽  
TAE-HOON SONG ◽  
SUNG-HO PARK ◽  
SUN-CHUL HUH ◽  
WON-JO PARK
Keyword(s):  
High Frequency ◽  
Fuel Injection ◽  
High Hardness ◽  
Induction Hardening ◽  
Injection Timing ◽  
Surface Strength ◽  
Fracture Characteristics ◽  
Fuel Injection Timing ◽  
Hardening Heat Treatment ◽  
High Frequency Induction

This experimental study investigates the fracture characteristics of the camshaft made with newly developed SM53C material. As part of the countermeasure, use the surface hardening heat treatment. Cam shaft which is a part of automobile engine is very essential when traveling and significant to fuel injection timing. Stiffness and efficiency are important for automobile sash which have a durability of the engine. High hardness and durability are necessary, because engine output is affected by cam shaft directly. So, high-frequency induction hardening is very important because of increasing the surface strength. The shape of hardening depth, hardened structure, hardness, and fracture characteristics of SM53C composed by carbon steel are also investigated.

Dynamics of a Rocking Horizontal Pendulum Under High Frequency Excitation

2012 ◽  
Author(s):  
Si Mohamed Sah ◽  
Clark McGehee ◽  
Brian P. Mann
Keyword(s):  
Dynamic Equation ◽  
High Frequency ◽  
Slow Dynamic ◽  
Numerical Investigations ◽  
Stable Equilibria ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Parameter Values ◽  
Horizontal Pendulum ◽  
Good Agreement

In this work, we investigate the effect of high frequency excitation on a pendulum positioned at a given distance from a tilted platform. The tilted platform is subjected to high frequency excitation. The method of direct partition of motion is applied to the governing equation to obtain the slow dynamic equation. It is shown that two stable equilibria may coexist for certain parameter values. The analytical results are in a good agreement with the numerical investigations.

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