Model Based Control of Emissions and Pulsations in a Premixed Combustor Using Fuel Staging

2009 ◽  
Author(s):  
Arnaud Lacarelle ◽  
Jonas P. Moeck ◽  
Christian O. Paschereit ◽  
Gregor Gelbert ◽  
Rudibert King
Keyword(s):  
Time Delays ◽  
Mixing Model ◽  
Extremum Seeking ◽  
Step Response ◽  
Nox Emissions ◽  
Pressure Pulsations ◽  
Model Based Control ◽  
One Dimensional ◽  
Mixing Quality ◽  
Fuel Staging

A mixing model of a swirl inducing premixed burner is derived from non-reacting investigation and used to control the fuel staging of the burner to ensure stability and low NOx emissions. The convective time delays, critical for the combustor stability, are obtained after identification of a step response of the outlet concentration with a one dimensional mixing model. The steady mixing is used to evaluate quantitatively the mixing quality which correlates with NOx emissions. Time delays as well as scalar unmixedness criteria derived from those measurements are used to predict the combustor stability and NOx emissions maps for different injection configurations at one operating point. The resulting model is used to extend an Extremum Seeking Controller, which adjusts the fuel repartition to reduce the pressure pulsations and NOx emissions.

Assessment of a Gas Turbine NOx Reduction Potential Based on a Spatiotemporal Unmixedness Parameter

2013 ◽  
Author(s):  
Stefan Dederichs ◽  
Peter Habisreuther ◽  
Nikolaos Zarzalis ◽  
Christian Beck ◽  
Werner Krebs ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Flame Front ◽  
Gas Turbine ◽  
Equivalence Ratio ◽  
Reduction Potential ◽  
Nox Emissions ◽  
Reaction Progress ◽  
One Dimensional ◽  
Mixing Quality

The paper presents a one-dimensional approach to assess the reduction potential of NOx emissions for lean premixed gas turbine combustion systems. NOx emissions from these systems are known to be mainly caused by high temperatures; not only from an averaged perspective but especially related to poor mixing quality of fuel and air. The method separates the NOx chemistry in the flame front zone and the post flame zone (slow reaction). A one-dimensional treatment enables the use of detailed chemistry. A look up table parameterized by reaction progress and equivalence ratio is used to improve the computational efficiency. The influence of mixing quality is taken into account by a probability density function of the fuel element based equivalence ratio, which itself translates into a temperature distribution. Hence, the NOx source terms are a function of reaction progress and equivalence ratio. The reaction progress is considered by means of the two-zone approach. Based on unsteady CFD data, the evolution of the probability density function with residence time has been analyzed. Two types of definitions of an unmixedness quantity are considered. One definition accounts for spatial as well as temporal fluctuations and the other is based on the mean spatial distribution. They are determined at the location of the flame front. The paper presents a comparison of the modeled results with experimental data. A validation and application have shown very good quantitative and qualitative agreement with the measurements. The comparison of the unmixedness definitions has proven the necessity of unsteady simulations. A general emissions - unmixedness correlation can be derived for a given combustion system.

Assessment of a Gas Turbine NOx Reduction Potential Based on a Spatiotemporal Unmixedness Parameter

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Stefan Dederichs ◽  
Nikolaos Zarzalis ◽  
Peter Habisreuther ◽  
Christian Beck ◽  
Bernd Prade ◽  
...  
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Flame Front ◽  
Gas Turbine ◽  
Equivalence Ratio ◽  
Reduction Potential ◽  
Nox Emissions ◽  
Reaction Progress ◽  
One Dimensional ◽  
Mixing Quality

The paper presents a one-dimensional approach to assess the reduction potential of NOx emissions for lean premixed gas turbine combustion systems. NOx emissions from these systems are known to be mainly caused by high temperatures, not only from an averaged perspective but especially related to poor mixing quality of fuel and air. The method separates the NOx chemistry in the flame front zone and the postflame zone (slow reaction). A one-dimensional treatment enables the use of detailed chemistry. A lookup table parameterized by reaction progress and equivalence ratio is used to improve the computational efficiency. The influence of mixing quality is taken into account by a probability density function of the fuel element–based equivalence ratio, which itself translates into a temperature distribution. Hence, the NOx source terms are a function of reaction progress and equivalence ratio. The reaction progress is considered by means of the two-zone approach. Based on unsteady computational fluid dynamics (CFD) data, the evolution of the probability density function with residence time has been analyzed. Two types of definitions of an unmixedness quantity are considered. One definition accounts for spatial as well as temporal fluctuations, and the other is based on the mean spatial distribution. They are determined at the location of the flame front. The paper presents a comparison of the modeled results with experimental data. A validation and application have shown very good quantitative and qualitative agreement with the measurements. The comparison of the unmixedness definitions has proven the necessity of unsteady simulations. A general emissions-unmixedness correlation can be derived for a given combustion system.

CFD Modeling of the Influence of Fuel Staging on the Mixing Quality and Flame Characteristics in a Lean Premixed Combustor

2010 ◽  
Author(s):  
Christina Schro¨dinger ◽  
Michael Oevermann ◽  
Oliver Kru¨ger ◽  
Arnaud Lacarelle ◽  
Christian O. Paschereit
Keyword(s):  
Experimental Data ◽  
Time Delays ◽  
Fuel Injection ◽  
Cfd Modeling ◽  
Reacting Flow ◽  
Fuel Distribution ◽  
Turbulent Schmidt Number ◽  
Mixing Quality ◽  
Fuel Staging ◽  
Flame Shape

In this paper, we investigate the feasibility and limitation of modeling non reacting and reacting flows of a premixed burner with steady RANS. The burner investigated here is a standard industrial swirl-inducing burner equipped with a staging of fuel injection. The simulation results on mixing quality, flame shape and position and convective time delays are compared to measurements which are performed in a water test rig and in a combustion chamber. The RANS simulations can qualitatively capture the trends observed from experimental data. The simulated mixing quality evolves in a similar way as the experimental data when the fuel distribution is changed. Using a turbulent Schmidt number of 0.2, the absolute values are in good agreement with the measured ones. Variations of the fuel injection distribution lead to changes in the flame shape and its stabilization location. The simulated reacting flow optimized with respect to the turbulent Schmidt/Prandtl number (Sct /Prt = 0.55) is able to predict the changes in flame shape and flame position. However, the shifting of the flame is not as distinct as observed in the experiments. This explains that variations in simulated convective time delays are also smaller than in reality. Nevertheless, the qualitative characteristics of the time delays depending on the fuel distribution parameter can be reproduced and absolute values are generally similar to those of the measurements.

Damping of Self-Excited Pressure Pulsations in Petrodiesel Pipeline

2014 ◽  
Vol 630 ◽  
pp. 375-382 ◽  
Author(s):  
Daniel Himr ◽  
Vladimir Haban
Keyword(s):  
Hydraulic System ◽  
Check Valve ◽  
Control Valve ◽  
Sampling Frequency ◽  
Pressure Pulsations ◽  
One Dimensional ◽  
Fuel Storage ◽  
Excited Oscillation ◽  
Subsequent Measurement ◽  
And Control

A pumping station in a fuel storage suffered from pressure pulsations in a petrodiesel pipeline. Check valves protecting the station against back flow made a big noise when disc hit a seat. Due to employees complaints we were asked to solve the problem, which could lead to serious mechanical problems. Pressure measurement in the pipeline showed great pulsations, which were caused by self-excited oscillation of control valves at the downstream end of pipeline. The operating measurement did not catch it because of too low sampling frequency. One dimensional numerical model of the whole hydraulic system was carried out. The model consisted of check valve, pipeline and control valve, which could oscillate, so it was possible to simulate the unsteady flow. When the model was validated, a vessel with nitrogen was added to attenuate pressure pulsations. According to the results of numerical simulation, the vessel was installed on the location. Subsequent measurement proved noticeably lower pulsations and almost no noise.

scholarly journals Droplet Size Effects on NOx Formation in a One-Dimensional Monodisperse Spray Combustion System

1982 ◽  
Author(s):  
H. Sarv ◽  
A. A. Nizami ◽  
N. P. Cernansky
Keyword(s):  
Physical Properties ◽  
Droplet Size ◽  
Size Effects ◽  
Theoretical Calculations ◽  
Spray Combustion ◽  
Nox Emissions ◽  
Combustion System ◽  
Nox Formation ◽  
One Dimensional ◽  
Aerosol Spray

A one-dimensional monodisperse aerosol spray combustion facility is described and experimental results of post flame NO/NOx emissions are presented. Four different hydrocarbon fuels were studied: isopropanol, methanol, n-heptane, and n-octane. The results indicate an optimum droplet size in the range of 48–58 microns for minimizing NO/NOx production for all of the test fuels. This NOx behavior is associated with droplet interactions and the transition from diffusive type of spray burning to that of a prevaporized and premixed case. Decreasing the droplet size results in a trend of increasing droplet interactions, which suppresses temperatures and reduces NOx. This trend continues until prevaporization effects begin to dominate and the system tends towards the premixed limit. The occurrence of the minimun NOx point at different droplet diameters for the different fuels appears to be governed by the extent of prevaporization of the fuel in the spray, and is consistent with theoretical calculations based on each fuel’s physical properties.

Modelling and performance of a pneumatic brake actuator

2011 ◽  
Vol 226 (8) ◽  
pp. 2077-2092 ◽  
Author(s):  
Jonathan I Miller ◽  
David Cebon
Keyword(s):  
Time Delays ◽  
Function Analysis ◽  
The Novel ◽  
Performance Limits ◽  
Heavy Vehicles ◽  
Describing Function ◽  
One Dimensional ◽  
High Bandwidth ◽  
And Performance ◽  
Actuator Design

Heavy vehicles have sluggish pneumatic brake actuators that limit the control bandwidth of their anti-lock braking systems. In order to implement more effective braking controllers, it is proposed that high-bandwidth, binary-actuated valves are directly placed on the brake chambers. This article details investigations made into modelling and controlling heavy-vehicle pneumatic brake actuators with a view towards implementing the novel brake actuator design. One-dimensional flow theory is combined with simple thermodynamic arguments for polytropic systems to describe the charging and discharging of a brake chamber. Particular attention is paid to the simulation of perceptible vibrations caused by the piston’s motion at relatively low charging pressures, using a hysteresis model. The resulting equations are linearized and used to design a closed-loop pressure controller for the actuator. Finally, the non-linear performance limits of the valves, caused by dead-zones and time delays, are investigated using a describing function analysis.

Jet Shear Layer Size and Number Influences on Grid Plate Direct Fuel Injection Shear Layer Mixing Low NOx Gas Turbine Combustion With Fuel Staging for Power Turn Down

2008 ◽  
Author(s):  
Gordon E. Andrews ◽  
S. A. R. Ahmed
Keyword(s):  
Shear Layer ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Scale Up ◽  
Shear Layers ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Round Jet ◽  
Fuel Staging ◽  
Four Levels

The scale up of jet shear layer low NOx concepts for compact gas turbine applications is considered using natural gas as the fuel with all experiments at one atmosphere pressure and 600K air inlet temperature. A 76mm diameter cylindrical combustor with 4 round jet shear layers was compared with a near double scale combustor with 140mm diameter and 4 round jet shear layers with the same total blockage as for the smaller combustor. This is compared with 16 round jet shear layers of the same diameter as for the smaller combustor. The shear layer air holes were fuelled by eight radial inward fuel injection holes in each shear layer jet. All three designs had acceptable combustion efficiencies, but the NOx emissions were considerably higher for the 4 shear layer design in the larger combustion. When the same shear layer hole size was used and the number increased in the larger combustor the NOx emissions were identical. Changing the shape of the hole from circulat to slot for the same area, considerably reduced the NOx in the four hole 76mm combustor, but had little effect on the 16 hole 140mm combustor. Fuel staging within the array of shear layers was successfully demonstrated for four levels of fuel staging. There was some intermixing of air from the unfuelled jets, but this had only a small effect on the combustion efficiency and flame stability. A practical range of simulated power turndown was demonstrated with little NOx penalty. This was achieved with no wall between the staged shear layer regions and hence leads to very compact combustor designs.

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