Potential and Challenges of MILD Combustion Control for Gas Turbine Applications

2015 ◽  
pp. 181-195 ◽  
Author(s):  
Thivaharan Albin ◽  
Aline Aguiar da Franca ◽  
Emilien Varea ◽  
Stephan Kruse ◽  
Heinz Pitsch ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Combustion Control ◽  
Mild Combustion

The Role of the Recirculating Gases at the Mild Combustion Regime Formation

2007 ◽  
Author(s):  
Y. Levy ◽  
V. Sherbaum ◽  
V. Erenburg
Keyword(s):  
Gas Turbine ◽  
Ignition Delay ◽  
Ignition Delay Time ◽  
Combustion Process ◽  
Combustion Regime ◽  
Reaction Products ◽  
Gas Turbine Combustor ◽  
Mild Combustion ◽  
Recirculation Rate ◽  
Co Emission

The present work is concerned with the thermodynamic and chemical kinetics of gas turbine combustor operating in the Moderate or Intense Low-oxygen Dilution (MILD) combustion regime. The objective of the present study is to evaluate analytically the effect of the recirculation rate of combustion products within the FLOXCOM gas turbine combustor on a number of combustion parameters, mainly on the ignition delay time, NOx and CO emission, minimum ignition temperature, rate of pollutant formation and the dilution rate. The study also refers to the mechanism of influence of the recirculation rate on these values. Combustion pressure and inlet air temperature are used as parameters. The gas turbine is fueled with methane. The analysis is mainly based on CHEMKIN simulations where the calculation scheme of the combustion process in the combustor is modeled by a combination of plug reactors and mixers. Due to the unique characteristics of gas turbines, inlet air temperature is directly linked to combustion pressure while assuming conventional adiabatic compression efficiencies. It is shown that free radicals, which are part of the reaction products and exists for only a short period of time within the recirculated gases, decrease ignition delay time. The importance of shortening the ignition delay is further highlighted because of the adverse effect oxygen dilution has on this parameter (dilution of the reactants by the reaction products). It was found that there is an optimal recirculation rate, which corresponds to maximum heat density. In addition, results indicate that CO emission values rise with the recirculation rate, however the NOX values are more complicated. NOX depends on recirculation rate when flame temperatures are kept held constant. The NOX emission increases and the CO emission decreases with compressor pressure ratio. The CO concentration that is evaluated in the combustion process is further reduced during last dilution stage. Finally, basic rules for design optimization of the combustor are drafted. These are based on conventional one-dimensional fluid and thermodynamic relations and on the CHEMKIN simulations.

Actuation Studies for Active Control of Mild Combustion for Gas Turbine Application

2014 ◽  
Author(s):  
Emilien Varea ◽  
Stephan Kruse ◽  
Heinz Pitsch ◽  
Thivaharan Albin ◽  
Dirk Abel
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Active Control ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Air Flow ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Low Oxygen ◽  
Mild Combustion

MILD combustion (Moderate or Intense Low Oxygen Dilution) is a well known technique that can substantially reduce high temperature regions in burners and thereby reduce thermal NOx emissions. This technology has been successfully applied to conventional furnace systems and seems to be an auspicious concept for reducing NOx and CO emissions in stationary gas turbines. To achieve a flameless combustion regime, fast mixing of recirculated burnt gases with fresh air and fuel in the combustion chamber is needed. In the present study, the combustor concept is based on the reverse flow configuration with two concentrically arranged nozzles for fuel and air injections. The present work deals with the active control of MILD combustion for gas turbine applications. For this purpose, a new concept of air flow rate pulsation is introduced. The pulsating unit offers the possibility to vary the inlet pressure conditions with a high degree of freedom: amplitude, frequency and waveform. The influence of air flow pulsation on MILD combustion is analyzed in terms of NOx and CO emissions. Results under atmospheric pressure show a drastic decrease of NOx emissions, up to 55%, when the pulsating unit is active. CO emissions are maintained at a very low level so that flame extinction is not observed. To get more insights into the effects of pulsation on combustion characteristics, velocity fields in cold flow conditions are investigated. Results show a large radial transfer of flow when pulsation is activated, hence enhancing the mixing process. The flame behavior is analyzed by using OH* chemiluminescence. Images show a larger distributed reaction region over the combustion chamber for pulsation conditions, confirming the hypothesis of a better mixing between fresh and burnt gases.

Experimental and Numerical Investigations of MILD Combustion in a Model Combustor Applied for Gas Turbine

2018 ◽  
Author(s):  
Huan Zhang ◽  
Zhedian Zhang ◽  
Yan Xiong ◽  
Yan Liu ◽  
Yunhan Xiao
Keyword(s):  
Gas Turbine ◽  
Reaction Zone ◽  
High Speed ◽  
Equivalence Ratio ◽  
Low Noise ◽  
Combustion Characteristics ◽  
Doppler Velocity ◽  
Exhaust Gas ◽  
Mild Combustion ◽  
Jet Velocity

The Moderate or Intense Low-oxygen Dilution (MILD) combustion is characterized by low emission, stable combustion and low noise for various kinds of fuel. MILD combustion is a promising combustion technology for gas turbine. The model combustor composed of an optical quartz combustor liner, four jet nozzles and one pilot nozzle has been designed in this study. The four jet nozzles are equidistantly arranged in the combustor concentric circle and the high-speed jet flows from the nozzles will entrain amount of exhaust gas to make MILD combustion occur. The combustion characteristics of the model combustor under atmosphere pressure have been investigated through experiments and numerical simulations. The influence of equivalence ratio and jet velocity on flow pattern, combustion characteristics and exhaust emissions were investigated in detail, respectively. Laser Doppler velocity (LDV) was utilized to measure the speed of a series of points in the model combustor. The measurement results show that a central recirculation existed in the combustion chamber. As the jet velocity of the nozzles increases, the amount of entrained mass by the jet increases simultaneously, however, the central recirculation zone is similar in shape and size. The recirculation of the model combustor will remain self-similar when the jet velocity varies in the range. The calculation model and method were verified through comparing with experimentally LDV data and be used to optimize the model combustor. Planar laser-induced fluorescence of hydroxyl radical (OH-PLIF) approaches were adopted to investigate the flame structure, the reaction zone and the OH distribution. OH distribution of the paralleled and crossed sections in the model combustor were measured, the whole reaction zone have been analyzed. The results show that the OH distribution was uniform in whole combustor. The exhaust gas composition of the combustor was measured by the “TESTO 350” Exhaust Gas Analyzer. All measurements emission results were corrected to 15% O2 in volume. Experimental results showed that NOx and CO emissions were less than 10 ppm@15%O2 when the equivalence ratio ranges from 0.63 to 0.8.

High Response Valve for Active Combustion Control

2001 ◽  
Author(s):  
Dong N. Wu ◽  
Joseph W. Michalski ◽  
Link C. Jaw ◽  
Kenneth Semega
Keyword(s):  
Gas Turbine ◽  
Piezoelectric Actuator ◽  
High Response ◽  
Turbine Engines ◽  
Bench Test ◽  
Gas Turbine Engines ◽  
Combustion Control ◽  
Flow Rates ◽  
Active Combustion Control ◽  
Modulation Control

This paper describes the development of a prototype high response fuel valve using piezoelectric actuator for fuel modulation control in gas turbine engines. In flow bench test, this prototype valve demonstrated 5∼11% peak-to-peak modulation strength at flow rates up to approximately 1500 pph and frequencies up to 500 Hz.

A novel air injection scheme to achieve MILD combustion in a can-type gas turbine combustor

Energy ◽  
2020 ◽  
Vol 194 ◽  
pp. 116819 ◽  
Author(s):  
Saurabh Sharma ◽  
Arindrajit Chowdhury ◽  
Sudarshan Kumar
Keyword(s):  
Gas Turbine ◽  
Air Injection ◽  
Gas Turbine Combustor ◽  
Mild Combustion ◽  
Injection Scheme

Model Based Active Combustion Control Concept for Reduction of Pulsations and NOx Emissions in Lean Premixed Gas Turbine Combustors

2008 ◽  
Author(s):  
Ernst Schneider ◽  
Stephan Staudacher ◽  
Bruno Schuermans ◽  
Haiwen Ye
Keyword(s):  
Gas Turbine ◽  
Gaussian Processes ◽  
Nox Emissions ◽  
Combustion Control ◽  
Model Based Control ◽  
Thermoacoustic Instabilities ◽  
Gas Turbine Combustors ◽  
Model Based ◽  
Lean Premixed ◽  
Control Concept

Strict environmental regulations demand gas turbine operation at very low equivalence ratios. Premixed gas turbine combustors, operated at very lean conditions, are prone to thermoacoustic instabilities. Thermoacoustic instabilities cause significant performance and reliability problems in gas turbine combustors, so their prevention is a general task. Splitting the fuel mass flow between different burner groups, i.e. using a burner group fuel staging technique, is a possibility to control the thermoacoustic instabilities. The resulting combustion perturbations have also effects on the gas turbine NOx emissions making it necessary to find an optimum balance between pulsations and emissions. This paper presents a model based active combustion control concept for the reduction of pulsations and emissions in lean premixed gas turbine combustors. The model is integrated in an observer structure derived from a Luenberger observer. The control logic is based on a PID algorithm allowing either the direct command of the pulsation level with a continuous monitoring and a potential limit setting of the NOx emission level or vice versa. The gas turbine pulsations and emissions are modelled using Gaussian Processes. - Gaussian Processes are stochastic processes related to Neural Networks that can approximate arbitrary functions. Based on measured gas turbine data they can be implemented in an easy and straightforward manner. The model provides the control system with real time data of the outputs resulting from settings of the staging ratio that is the actuating variable of the system. A model based control concept can significantly alleviate the effects of time delays in the system. The model based control concept allows for fast adaptation of the burner group staging ratio during static and transient operations to achieve an optimum of the pulsation and emission levels. During tests the model based control concept gave good results and proved to be robust even at high disturbance levels.

scholarly journals Analysis of Re Influence on MILD Combustion of Gas Turbine

2013 ◽  
Vol 05 (04) ◽  
pp. 92-96 ◽  
Author(s):  
Lijun Wang ◽  
Dongdong Qi ◽  
Xiaowei Sui ◽  
Xin Xie
Keyword(s):  
Gas Turbine ◽  
Mild Combustion

Mild Combustion in a Novel CCGT Cycle With Partial Flue Gas Recirculation

2003 ◽  
Author(s):  
S. M. Camporeale ◽  
F. Casalini ◽  
A. Saponaro
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Soot Formation ◽  
Combustion Process ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Heavy Fuel Oil ◽  
Mild Combustion ◽  
Turbine Exhaust

A novel Combined Cycle Gas Turbine layout is proposed for using heavy fuel oil in a combustion mode called “Mild Combustion”, characterized by a very low adiabatic flame temperature and flat temperature field in the combustion chamber and low pollutant emissions. “Mild Combustion” is obtained by means of the dilution of reactants with inert gas like combustion product resulting in a very low oxygen concentration of the mixture at the ignition. To stabilize the combustion process in such a condition the reactants temperature has to be raised above the self ignition value. In industrial application this particular preconditioning of the reactants can be reached partially before the combustion chamber and finally in process by means of a performed aerodynamic that further dilute and heat-up the mixture. An experimental analysis of the oil combustion behaviour inside the gas turbine exhaust flow has been arranged at Centro Combustione of Ansaldo Caldaie in Gioia del Colle (Italy). The turbine exhaust gases are simulated by mixing those produced in a gas burner with external air preheated at different temperatures in order to have different final oxygen concentrations and temperature levels. The influence of the main combustion parameters regarding the process feasibility and environmental impact are presented and analysed. Good results in terms of NOx emissions and soot formation have been obtained for heavy oil combustion in a 10% oxygen oxidizer concentration requiring a combustion chamber inlet temperature of about 900K. In order to meet these conditions, a novel CCGT cycle in which about 64% of combustion products are re-circulated before entering the combustion chamber, is proposed. The thermodynamic analysis shows that the efficiency that could be achieved by the proposed cycle is a few percent lower than the efficiency of a combined cycle power plant fuelling natural gas, with the same turbine inlet temperature and similar turbine blade cooling technology.

scholarly journals Active Combustion Control for aircraft gas turbine engines

2000 ◽  
Author(s):  
John DeLaat ◽  
Kevin Breisacher ◽  
Joseph Saus ◽  
Daniel Paxson
Keyword(s):  
Gas Turbine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Combustion Control ◽  
Active Combustion Control
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