Adaptive Closed-Loop Control on an Atmospheric Gaseous Lean-Premixed Combustor

2003 ◽  
Author(s):  
A. J. Riley ◽  
S. Park ◽  
A. P. Dowling ◽  
S. Evesque ◽  
A. M. Annaswamy
Keyword(s):  
Time Delay ◽  
Flow Rate ◽  
Atmospheric Conditions ◽  
Loop Control ◽  
Fuel Flow ◽  
Lean Premixed ◽  
Self Tuning ◽  
Industrial Gas Turbine ◽  
Measured Pressure ◽  
Primary Instability

Active control of pressure oscillations has been successfully applied to a lean premixed prevapourised (LPP) combustion rig operating at atmospheric conditions. The design of the rig is based on the primary stage of the Rolls-Royce RB211-DLE industrial gas turbine. Control was achieved by modulating the fuel flow rate in response to a measured pressure signal. The feedback control is an adaptive, model-based self-tuning regulator (STR), which only requires the total time delay between actuation and response to achieve control. The STR algorithm achieves a reduction of up to 30 dB on the primary instability frequency. This performance was an improvement of 5–15 dB over an empirical control strategy (simple time-delay controller) specifically tuned to the same operating point. Initial robustness studies have shown that the STR retains control for a 20% change in frequency and a 23% change in air mass flow rate.

Advanced Closed-Loop Control on an Atmospheric Gaseous Lean-Premixed Combustor

2004 ◽  
Vol 126 (4) ◽  
pp. 708-716 ◽  
Author(s):  
A. J. Riley ◽  
S. Park ◽  
A. P. Dowling ◽  
S. Evesque ◽  
A. M. Annaswamy
Keyword(s):  
Time Delay ◽  
Flow Rate ◽  
Atmospheric Conditions ◽  
Loop Control ◽  
Fuel Flow ◽  
Lean Premixed ◽  
Self Tuning ◽  
Industrial Gas Turbine ◽  
Measured Pressure ◽  
Primary Instability

Active control of pressure oscillations has been successfully applied to a lean premixed prevaporized (LPP) combustion rig operating at atmospheric conditions. The design of the rig is based on the primary stage of the Rolls-Royce RB211-DLE industrial gas turbine. Control was achieved by modulating the fuel flow rate in response to a measured pressure signal. The feedback control is an adaptive, model-based self-tuning regulator (STR), which only requires the total time delay between actuation and response to achieve control. The STR algorithm achieves a reduction of up to 30 dB on the primary instability frequency. This performance was an improvement of 5–15 dB over an empirical control strategy (simple time-delay controller) specifically tuned to the same operating point. Initial robustness studies have shown that the STR retains control for a 20% change in frequency and a 23% change in air mass flow rate.

scholarly journals Experimental Investigation of the Liquid Fuel Evaporation in a Premix Duct for Lean Premixed and Prevaporized Combustion

1996 ◽  
Author(s):  
Michael Brandt ◽  
Kay O. Gugel ◽  
Christoph Hassa
Keyword(s):  
Experimental Investigation ◽  
Air Temperature ◽  
Flow Rate ◽  
Liquid Fuel ◽  
Operating Conditions ◽  
Dispersion Characteristics ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Lean Premixed ◽  
Fuel Evaporation

Liquid fuel evaporation was investigated in a premix duct, operating at conditions expected for lean premixed and prevaporized combustion. Results from a flat prefilming airblast atomizer are presented. Kerosine Jet A was used in all experiments. Air pressure, air temperature and liquid fuel flow rate were varied separately, their relative influences on atomization, evaporation and fuel dispersion are discussed. The results show, that at pressures up to 15 bars and temperatures up to 850 K, nearly complete evaporation of the fuel was achieved, without autoignition of the fuel. For the configuration tested, the fuel distributions of the liquid and evaporated fuel sbow very little differences in their dispersion characteristics and were not much affected by a variation of the operating conditions.

Application of Dielectric Barrier Discharge to Improve the Flashback Limit of a Lean Premixed Dump Combustor

2011 ◽  
Author(s):  
Philippe Versailles ◽  
Wajid Ali Chishty ◽  
Huu Duc Vo
Keyword(s):  
Natural Gas ◽  
Dielectric Barrier Discharge ◽  
Flow Rate ◽  
Gas Turbines ◽  
Barrier Discharge ◽  
Operating Conditions ◽  
Diffusion Type ◽  
Dielectric Barrier ◽  
Fuel Flow ◽  
Lean Premixed

In recent years, lean-premixed (LP) combustors have been widely studied due to their potential to reduce NOx emissions in comparison to diffusion type combustors. However, the fact that the fuels and oxidizers are mixed upstream of the combustion zone makes LP type of combustors a candidate for upstream flame propagation (i.e., flashback) in the premixer that is typically not designed to sustain high temperatures. Moreover, there has been a recent demand for fuel-flexible gas turbines that can operate on hydrogen-enriched fuels like Syngas. Combustors originally designed for slower kinetics fuels like natural gas can potentially encounter flashback if operated with faster burning fuels like those containing hydrogen as a constituent. There exists a clear need in fuel-flexible lean-premixed combustors to control flashback that will not only prevent costly component damage but will also enhance the operability margin of engines. A successful attempt has been made to control flashback in an atmospheric LP combustor, burning natural gas-air mixtures, via the application of Dielectric Barrier Discharge (DBD). A low-power DBD actuator was designed, fabricated and integrated into a premixer made out of quartz. The actuator was tuned to produce a low magnitude ionic wind with an intention to modify the velocity profile in the premixer. Flashback conditions were created by decreasing the air flow rate while keeping the fuel flow rate constant. Within this experimental setup, flashback happened in the core flow along the axis of the cylindrical premixer. Results show that the utilization of the DBD delays the occurrence of flashback to higher equivalence ratios. Improvements as high as about 5% of the flashback limit have been obtained without compromising the blowout limit. It is anticipated that this novel application of DBD will lead to future demonstrations of the concept under realistic gas turbine operating conditions.

Characterizing the Mechanism of Lean Blowout for a Recirculation-Stabilized Premixed Hydrogen Flame

2012 ◽  
Author(s):  
Megan F. Karalus ◽  
K. Boyd Fackler ◽  
Igor V. Novosselov ◽  
John C. Kramlich ◽  
Philip C. Malte
Keyword(s):  
Induction Period ◽  
Flow Rate ◽  
Flow Reactor ◽  
Chemical Mechanism ◽  
Single Element ◽  
Flame Extinction ◽  
Cfd Simulations ◽  
Lean Blowout ◽  
Fuel Flow ◽  
Lean Premixed

The stability of hydrogen combustion under lean premixed conditions in a back-mixed jet-stirred reactor (JSR), is experimentally and numerically investigated. The goal is to understand the mechanism of flame extinction in this recirculation-stabilized flame environment. Extinction is achieved by holding the air flow rate constant and gradually decreasing the flow rate of the hydrogen fuel until a blowout event occurs. In order to gain insight on the mechanism controlling blowout, two dimensional computational fluid dynamic (CFD) simulations are carried out for the lean premixed combustion (LPM) of hydrogen as the fuel flow rate is reduced. The CFD model illustrates the evolution of the flow-field, temperature profiles, and flame structure within the JSR as blowout is approached. A single element chemical reactor network (CRN) consisting of a plug flow reactor (PFR) with recirculation is constructed based on the results of the CFD simulations, and its prediction of blowout is in good agreement with the experimental results. The chemical mechanism of Li et al. is used in both the CFD and CRN models, and GRI is used in the CRN for comparison. The modeling suggests that lean blowout does not occur with the flame in a spatially homogeneous condition, but rather under a zonal structure. Specifically, the flame is stabilized by the entrainment of combustion products from the re-circulation zone into the base of the reactant jet. The mixture of hot products and incoming premixed reactants proceeds through an ignition induction period followed by an ignition event. As the fuel flow decreases, the induction period increases and the ignition event is pushed further around the recirculation zone. Eventually, the induction period becomes so long that the ignition is incomplete at the point where the recirculating gas is entrained into the jet. This threshold leads to overall flame extinction.

scholarly journals Gas Turbine Tubular Combustor Main Injector Optimization for Low Emission Combustion

2018 ◽  
Vol 26 (10) ◽  
pp. 1-12
Author(s):  
Arkan Khikhal Husain ◽  
Mahmood Attallah Mashkoor ◽  
Fuad Abdul Ameer Khalaf
Keyword(s):  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
High Performance ◽  
Atmospheric Conditions ◽  
Air Mass ◽  
Fuel Flow ◽  
Low Emission ◽  
Gas Fuel

This work presents the experimental investigation results of high performance and low emission colorless combustion in a gas turbine tubular combustor at atmospheric conditions. Low emission and colorless oxidation reaction is characterized by dispersed flame and temperature under the conditions of preheated air. System performance, emissions of CO and UHC are recorded up to achieve low emission colorless combustion, the flame capturing, Measurements of temperature, inlet air mass flow rate and gas fuel LPG flow rate for variable of fuel main injector holes diameter. concluded that maximal air mass flow rate, with choked fuel flow in the main injector for each cases promotes the formation of colorless pal blue flame combustion, for 3.2 g/s of fuel flow rate with 6 holes and 1mm main injector holes diameter and lower CO emissions and decreasing in UHC emissions (70 → 10) ppmv with increasing in power generation (0.5 → 3.42) kW and decreasing in S.F.C. (21.5 → 3.49) kg/kwh.

Application of Dielectric Barrier Discharge to Improve the Flashback Limit of a Lean Premixed Dump Combustor

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Philippe Versailles ◽  
Wajid Ali Chishty ◽  
Huu Duc Vo
Keyword(s):  
Natural Gas ◽  
Dielectric Barrier Discharge ◽  
Flow Rate ◽  
Gas Turbines ◽  
Barrier Discharge ◽  
Operating Conditions ◽  
Diffusion Type ◽  
Dielectric Barrier ◽  
Fuel Flow ◽  
Lean Premixed

In recent years, lean-premixed (LP) combustors have been widely studied due to their potential to reduce NOx emissions in comparison to diffusion type combustors. However, the fact that the fuels and oxidizers are mixed upstream of the combustion zone makes LP type of combustors a candidate for upstream flame propagation (i.e., flashback) in the premixer that is typically not designed to sustain high temperatures. Moreover, there has been a recent demand for fuel-flexible gas turbines that can operate on hydrogen-enriched fuels like Syngas. Combustors originally designed for slower kinetics fuels like natural gas can potentially encounter flashback if operated with faster burning fuels like those containing hydrogen as a constituent. There exists a clear need in fuel-flexible lean-premixed combustors to control flashback that will not only prevent costly component damage but will also enhance the operability margin of engines. A successful attempt has been made to control flashback in an atmospheric LP combustor, burning natural gas-air mixtures, via the application of dielectric barrier discharge (DBD). A low-power DBD actuator was designed, fabricated and integrated into a premixer made out of quartz. The actuator was tuned to produce a low magnitude ionic wind with an intention to modify the velocity profile in the premixer. Flashback conditions were created by decreasing the air flow rate while keeping the fuel flow rate constant. Within this experimental setup, flashback happened in the core flow along the axis of the cylindrical premixer. Results show that the utilization of the DBD delays the occurrence of flashback to higher equivalence ratios. Improvements as high as about 5% of the flashback limit have been obtained without compromising the blowout limit. It is anticipated that this novel application of DBD will lead to future demonstrations of the concept under realistic gas turbine operating conditions.

Experimental Investigation of the Liquid Fuel Evaporation in a Premix Duct for Lean Premixed and Prevaporized Combustion

1997 ◽  
Vol 119 (4) ◽  
pp. 815-821 ◽  
Author(s):  
M. Brandt ◽  
K. O. Gugel ◽  
C. Hassa
Keyword(s):  
Experimental Investigation ◽  
Air Temperature ◽  
Flow Rate ◽  
Liquid Fuel ◽  
Operating Conditions ◽  
Dispersion Characteristics ◽  
Fuel Flow Rate ◽  
Fuel Flow ◽  
Lean Premixed ◽  
Fuel Evaporation

Liquid fuel evaporation was investigated in a premix duct, operating at conditions expected for lean premixed and prevaporized combustion. Results from a flat prefilming airblast atomizer are presented. Kerosine Jet A was used in all experiments. Air pressure, air temperature, and liquid fuel flow rate were varied separately; their relative influences on atomization, evaporation, and fuel dispersion are discussed. The results show that at pressures up to 15 bars and temperatures up to 850 K, nearly complete evaporation of the fuel was achieved, without autoignition of the fuel. For the configuration tested, the fuel distributions of the liquid and evaporated fuel show very little difference in their dispersion characteristics and were not much affected by a variation of the operating conditions.

scholarly journals In situ measurement and closed-loop control for powder supply processes

2021 ◽  
Author(s):  
Philipp Peter Breese ◽  
Tobias Hauser ◽  
Daniel Regulin ◽  
Stefan Seebauer ◽  
Christian Rupprecht
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Closed Loop ◽  
In Situ Measurement ◽  
Closed Loop Control ◽  
Loop Control ◽  
Powder Feeder ◽  
Powder Mass

AbstractThe powder mass flow rate is one of the main parameters regarding the geometrical precision of built components in the additive manufacturing process of laser metal deposition. However, its accuracy, constancy, and repeatability over the course of the running process is not given. Reasons among others are the performance of the powder conveyors, the complex nature of the powder behavior, and the resulting issues with existing closed-loop control approaches. Additionally, a direct in situ measurement of the powder mass flow rate is only possible with intrusive methods. This publication introduces a novel approach to measure the current powder mass flow rate at a frequency of 125 Hz. The volumetric powder flow evaluation given by a simple optical sensor concept was transferred to a mass flow rate through mathematical dependencies. They were found experimentally for a nickel-based powder (Inconel 625) and are valid for a wide range of mass flow rates. With this, the dynamic behavior of a vibration powder feeder was investigated and a memory effect dependent on previous powder feeder speeds was discovered. Next, a closed-loop control with the received sensor signal was implemented. The concept as a whole gives a repeatable and accurate powder mass flow rate while being universally retrofittable and applicable. In a final step, the improved dynamic and steady performance of the powder mass flow rate with closed-loop control was validated. It showed a reduction of mean relative errors for step responses of up to 81% compared to the uncontrolled cases.

scholarly journals Influence of Time Delay on Controlling the Non-Linear Oscillations of a Rotating Blade

Symmetry ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 85
Author(s):  
Yasser Salah Hamed ◽  
Ali Kandil
Keyword(s):  
Time Delay ◽  
Natural Frequency ◽  
Multiple Scales ◽  
Control Process ◽  
Control Force ◽  
Specific Level ◽  
Loop Control ◽  
Positive Displacement ◽  
Non Linear ◽  
Linear Vibrations

Time delay is an obstacle in the way of actively controlling non-linear vibrations. In this paper, a rotating blade’s non-linear oscillations are reduced via a time-delayed non-linear saturation controller (NSC). This controller is excited by a positive displacement signal measured from the sensors on the blade, and its output is the suitable control force applied onto the actuators on the blade driving it to the desired minimum vibratory level. Based on the saturation phenomenon, the blade vibrations can be saturated at a specific level while the rest of the energy is transferred to the controller. This can be done by adjusting the controller natural frequency to be one half of the blade natural frequency. The whole behavior is governed by a system of first-order differential equations gained by the method of multiple scales. Different responses are included to show the influences of time delay on the closed-loop control process. Also, a good agreement can be noticed between the analytical curves and the numerically simulated ones.

scholarly journals Robust Stabilization of Interval Plants with Uncertain Time-Delay Using the Value Set Concept

Mathematics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 429
Author(s):  
Pedro Zamora ◽  
Alejandro Arceo ◽  
Noé Martínez ◽  
Gerardo Romero ◽  
Luis E. Garza
Keyword(s):  
Time Delay ◽  
Robust Stabilization ◽  
Parametric Uncertainty ◽  
Exclusion Principle ◽  
Control Synthesis ◽  
Classical Orthogonal Polynomials ◽  
Loop Control ◽  
Value Set ◽  
Interval Plants ◽  
Uncertain Time

This paper considers the robust stabilization problem for interval plants with parametric uncertainty and uncertain time-delay based on the value set characterization of closed-loop control systems and the zero exclusion principle. Using Kharitonov’s polynomials, it is possible to establish a sufficient condition to guarantee the robust stability property. This condition allows us to solve the control synthesis problem using conditions similar to those established in the loopshaping technique and to parameterize the controllers using stable polynomials constructed from classical orthogonal polynomials.

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