Experimental and Theoretical Studies of a Novel Venturi Lean Premixed Prevaporized (LPP) Combustor

2000 ◽  
Vol 123 (3) ◽  
pp. 567-573 ◽  
Author(s):  
N. A. Ro̸kke ◽  
A. J. W. Wilson
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Liquid Fuel ◽  
Flame Stabilization ◽  
Gas Generator ◽  
Throat Region ◽  
Low Emission ◽  
Lean Premixed ◽  
Fuel Staging ◽  
Performance And Emissions

A new gas turbine engine using a unique layout patented in Norway has a low-emission combustion system under development. The gas generator uses entirely radial rotating components and employs a dual entry LP radial compressor, a radial HP compressor, and a radial HP turbine. The power turbine is of a two-stage axial design, coupled to an epicyclical gear embedded in the exhaust duct. Several combustor concepts have been tested and evaluated during the development of the engine. The engine is targeted for marine, power generation, and train propulsion. For the marine and train application liquid fuel operation is needed, thus the primary focus in the development has been for a lean premixed prevapourised system. An interesting concept utilizing two venturi premixers has been studied intensively. By utilizing venturi premixers the following advantages can be achieved: (1) low overall pressure drop but high injector pressure drop and velocities in the mixing region (throat region), (2) high shear forces and drag imposed on the droplets enhancing droplet shedding and evaporation, and (3) excellent emission behavior at designated load conditions. Although these advantages can benefit gas turbine low-emission combustion, the challenges in using venturi premixers are: (1) venturis are susceptible to separation and thus flame stabilization within the venturi which is detrimental and (2) inlet flow disturbances enhance the tendency for separation in the venturis and must be minimized. Studies were launched to investigate a proposed combustor configuration. These studies included analytical studies, computational fluid dynamics (CFD) calculations of isothermal and combusting flow inside the combustor together with rig tests at atmospheric, medium, and full pressure. Finally, engine tests within the full operating range were conducted with very favorable emission figures for lean premixed prevaporized (LPP) operation. The system was capable of running at below 20 ppm NOx and CO, at elevated power for liquid fuel. Control of part load performance and emissions is by variable fuel staging of the two venturi stages. The paper highlights the features of the venturi combustor development and discusses the characteristics in terms of flow conditions and droplet motion, heat transfer, ignition delay time, and emissions.

Experimental and Theoretical Studies of a Novel Venturi LPP Combustor

2000 ◽  
Author(s):  
Nils A. Røkke ◽  
Andrew J. W. Wilson
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Liquid Fuel ◽  
Gas Generator ◽  
Turbine Engine ◽  
Throat Region ◽  
Low Emission ◽  
Lean Premixed ◽  
Fuel Staging ◽  
Performance And Emissions

A new gas turbine engine using a unique layout patented in Norway has a low emission combustion system under development. The gas generator uses entirely radial rotating components and employs a dual entry LP radial compressor, a radial HP compressor and a radial HP turbine. The power turbine is of a two stage axial design, coupled to an epicyclical gear embedded in the exhaust duct. Several combustor concepts have been tested and evaluated during the development of the engine. The engine is targeted for marine, power generation and train propulsion. For the marine and train application liquid fuel operation is needed, thus the primary focus in the development has been for a lean premixed prevapourised system. An interesting concept utilising two venturi premixers has been studied intensively. By utilising venturi premixers the following advantages can be achieved: • Low overall pressure drop but high injector pressure drop and velocities in the mixing region (throat region) • High shear forces and drag imposed on the droplets enhancing droplet shedding and evaporation • Excellent emission behaviour at designated load conditions Although these advantages can benefit gas turbine low emission combustion the challenges in using venturi premixers are: • Venturis are susceptible to separation and thus flame stabilisation within the venturi which is detrimental • Inlet flow disturbances enhance the tendency for separation in the venturis and must be minimised Studies were launched to investigate a proposed combustor configuration. These studies included analytical studies, Computational Fluid Dynamics (CFD) calculations of isothermal and combusting flow inside the combustor together with rig tests at atmospheric, medium and full pressure. Finally engine tests within the full operating range were conducted with very favourable emission figures for Lean Premixed Prevapourised (LPP) operation. The system was capable of running at below 20 ppm Nox and CO, at elevated power for liquid fuel. Control of part load performance and emissions is by variable fuel staging of the two venturi stages. The paper highlights the features of the venturi combustor development and discusses the characteristics in terms of flow conditions and droplet motion, heat transfer, ignition delay time and emissions.

scholarly journals Evaporation Characteristics of Spray in a Lean Premixed-Prevaporization Combustor for a 100 KW Automotive Ceramic Gas Turbine

1994 ◽  
Author(s):  
Youichlrou Ohkubo ◽  
Yoshinorl Idota ◽  
Yoshihiro Nomura
Keyword(s):  
Gas Turbine ◽  
Mass Fraction ◽  
Liquid Fuel ◽  
Three Dimensional ◽  
Flame Stabilization ◽  
Fuel Spray ◽  
Inlet Temperature ◽  
Lean Combustion ◽  
Swirl Chamber ◽  
Lean Premixed

Spray characteristics of liquid fuel air-assisted atomizers developed for a lean premixed-prevaporization combustor were evaluated under two kinds of conditions: in still air under non-evaporation conditions at atmospheric pressure and in a prevaporization-premixing tube under evaporation conditions with a running gas turbine. The non-evaporated mass fraction of fuel spray was measured using a phase Doppler particle analyzer in the prevaporization-premixing tube, in which the inlet temperature ranged from 873K to 1173K. The evaporation of the fuel spray in the tube is mainly controlled by its atomization and distribution. The NOx emission characteristics measured with a combustor test rig were evaluated with three-dimensional numerical simulations. A low non-evaporated mass fraction of less than 10% was effective in reducing the exhausted NOx from lean premixed-prevaporization combustion to about 1/6 times smaller than that from lean diffusion (spray) combustion. The flow patterns in the combustor are established by a swirl chamber in fuel-air preparation tube, and affect the flame stabilization of lean combustion.

Development of a Lean-Premixed Two-Stage Annular Combustor for Gas Turbine Engines

1994 ◽  
Author(s):  
Fred C. Bahlmann ◽  
B. Martien Visser
Keyword(s):  
Gas Turbine ◽  
Turbine Engines ◽  
Emission Characteristics ◽  
Gas Turbine Engines ◽  
Two Stage ◽  
Low Emission ◽  
Lean Premixed ◽  
Annular Combustor

The development, from concept to hardware of a lean-premixed two-stage combustor for small gas turbine engines is presented. This Annular Low Emission Combustor (ALEC) is based on a patent of R.J. Mowill. Emission characteristics of several prototypes of this combustor under a variety of conditions are presented. It is shown that ultra-low NOx levels (< 10 ppm) can be reached with satisfactory CO levels (< 50 ppm).

The Reheat Concept: The Proven Pathway to Ultra-Low Emissions and High Efficiency and Flexibility

2007 ◽  
Author(s):  
Felix Gu¨the ◽  
Jaan Hellat ◽  
Peter Flohr
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Flame Propagation ◽  
High Efficiency ◽  
Flame Stabilization ◽  
Auto Ignition ◽  
Fuel Flexibility ◽  
Stage Combustion ◽  
Low Emission ◽  
Key Topics

Reheat combustion has proven now in over 80 units to be a robust, and highly flexible gas turbine concept for power generation. This paper covers three key topics to explain the intrinsic advantage of reheat combustion to achieve ultra-low emission levels. First, the fundamental kinetic and thermodynamic emission advantage of reheat combustion is discussed analyzing in detail the emission levels of the first and second combustor stages, optimal firing temperatures for minimal emission levels, as well as benchmarking against single-stage combustion concepts. Secondly, the generic operational and fuel flexibility of the reheat system is emphasized, which is based on the presence of two fundamentally different flame stabilization mechanisms, namely flame propagation in the first combustor stage and auto-ignition in the second combustor stage. Finally, the present fleet status is reported by highlighting the latest combustor hardware upgrade and its emission performance.

scholarly journals Investigations of the Working Process in a Dual-Fuel Low-Emission Combustion Chamber for an FPSO Gas Turbine Engine

2020 ◽  
Vol 27 (3) ◽  
pp. 89-99
Author(s):  
Serhiy Serbin ◽  
Badri Diasamidze ◽  
Marek Dzida
Keyword(s):  
Nitrogen Oxides ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Liquid Fuel ◽  
Turbulent Flame ◽  
Dual Fuel ◽  
Working Process ◽  
Fuel Supply ◽  
Low Emission ◽  
Gas Turbine Combustion

AbstractThis investigation is devoted to an analysis of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. The low-emission gas turbine combustion chamber with partial pre-mixing of fuel and air inside the outer and inner radial-axial swirlers was chosen as the object of research. When modelling processes in a dual-flow low-emission gas turbine combustion chamber, a generalized method is used, based on the numerical solution of the system of conservation and transport equations for a multi-component chemically reactive turbulent system, taking into consideration nitrogen oxides formation. The Eddy-Dissipation-Concept model, which incorporates Arrhenius chemical kinetics in a turbulent flame, and the Discrete Phase Model describing the interfacial interaction are used in the investigation. The obtained results confirmed the possibility of organizing efficient combustion of distillate liquid fuel in a low-emission gas turbine combustion chamber operating on the principle of partial preliminary formation of a fuel-air mixture. Comparison of four methods of liquid fuel supply to the channels of radial-axial swirlers (centrifugal, axial, combined, and radial) revealed the advantages of the radial supply method, which are manifested in a decrease in the overall temperature field non-uniformity at the outlet and a decrease in nitrogen oxides emissions. The calculated concentrations of nitrogen oxides and carbon monoxide at the flame tube outlet for the radial method of fuel supply are 32 and 9.1 ppm, respectively. The results can be useful for further modification and improvement of the characteristics of dual-fuel gas turbine combustion chambers operating with both gaseous and liquid fuels.

Performance and Emission Analysis of a Variable Load Operated Gas Turbine

2000 ◽  
Author(s):  
Fabio Bozza ◽  
Maria Cristina Cameretti ◽  
Antonio Marro ◽  
Raffaele Tuccillo
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Pollutant Emission ◽  
Formation Mechanisms ◽  
Variable Load ◽  
Gas Generator ◽  
Emission Analysis ◽  
Performance And Emission ◽  
Wide Range ◽  
Performance And Emissions

Abstract The authors present a methodology for the prediction of performance and emissions of a gas turbine under a wide range of load conditions. The engine, of the aero-derivative type, is employed in a natural gas recompression plant. The paper deals, in its first part, with the reconstruction of the whole operating region of both the gas generator set and the power turbine including its matching with the centrifugal compressor for natural gas delivery in the pipeline. This phase also leads to an effective prediction of pollutant emission, with a chemical kinetics based sub-model. Next, a refined CFD based simulation analyzes a number of operating cases, so providing a detailed insight of the actual phenomena which control the combustion chamber temperature distribution and the activation of the pollutant formation mechanisms.

Off-Design Performance Investigation of a Low Calorific Gas Fired Two-Shaft Gas Turbine

2009 ◽  
Author(s):  
Pontus Eriksson ◽  
Magnus Genrup ◽  
Klas Jonshagen ◽  
Jens Klingmann
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Gas Generator ◽  
Dimensional Parameter ◽  
Gaseous Fuels ◽  
Surge Margin ◽  
Power Turbine ◽  
Lean Premixed ◽  
Wobbe Index ◽  
Compressor Map

Gas turbine systems are predominantly designed to be fuelled with gaseous fuels within a limited Wobbe index range (typically HHV = 45–55 MJ/Nm3 or 1200–1480 Btu/scf). When low calorific fuel gases are fired, the engine will be forced to operate outside its design envelope. The added mass flow will typically raise the cycle pressure ratio and in two-shaft designs also raise the gas generator shaft speed. Typical constraints to be considered due to the altered fuel composition are pressure loads, shaft torques, shaft overspeeds, centrifugal overloading of disks and blades, combustor flameout, surge and flutter limits for the turbomachinery. This poses limitations to usable fuel choices. In this study, the response of a natural gas fired simple cycle two-shaft gas turbine is investigated. A lean premixed combustor is also included in the model. Emphasis has been put on predicting the turbomachinery and combustor behavior as different amounts of N2 or CO2 are added to the fuel path. These two inerts are typically found in large quantities in medium and low calorific fuels. The fuels lower heating value is thus gradually changed from 50 MJ/kg (21.5 kBtu/lb) to 5MJ/kg (2.15 kBtu/lb). A model, based on the Volvo Aero Corp. VT4400 gas turbine (originally Dresser Rand DR990) characterized by one compressor and two expander maps is considered. The free turbine is operated at fixed physical speed. The operating point is plotted in the compressor map and the turbine maps at three distinct firing temperatures representing turndown from full load to bleed opening point. Gas generator speed and shaft power are shown. Surge margin and power turbine power is plotted. Overall efficiency is computed. The behavior of the Volvo lean premixed combustor is also discussed. Air split, primary zone equivalence ratio and temperature is plotted. Combustor loading, combustion intensity and pressure drop is graphed. Results are, as far as possible, given as non-dimensional parameter groups for easy comparison with other machines.

Results and Experience From Operation and Testing of ALSTOM’s 30 MW GT10C Gas Turbine

2003 ◽  
Author(s):  
Anders Hellberg ◽  
Georg Norden ◽  
Mats Andersson ◽  
Thomas Widgren ◽  
Christer Hjalmarsson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Liquid Fuel ◽  
Engine Performance ◽  
Liquid Fuels ◽  
Critical Parameters ◽  
Test Rig ◽  
Load Range ◽  
Performance And Emissions ◽  
Inlet Conditions

ALSTOM’s new gas turbine, the GT10C, is a 30 MW industrial gas turbine for mechanical drive and power generation, which has been upgraded from the 25 MW GT10B. The thermal efficiency of the new gas turbine is 37.3% at ISO inlet conditions with no losses. The GT10C features a dual-fuel dry low emission gas turbine, with emissions values of 15 ppm NOx on gaseous fuel and 42 ppm NOX on liquid fuel (also dry). The GT10C was first started and operated on load in November 2001 and the test program is ongoing until the fall of 2002. The program covers a complete package test, including gas turbine, auxiliaries and control system, to ensure package availability. For the tests, a new test rig has been built in Finspong, Sweden, for testing on both natural gas and liquid fuels. The tests have been very successful, achieving the product targets, for example below 15 ppm NOx, without combustor pulsations. This paper discusses operation experience from the test rig, where the engine has been tested on both natural gas and liquid fuel over the whole load range. The engine has been equipped with over 1200 measuring points, covering the complete gas turbine. All critical parameters have been carefully verified in the test, such as turbine blade temperature and stresses, combustor temperatures and dynamics and engine performance. Results from the tests and measurements will be discussed in this paper. Performance and emissions will also be evaluated.

The Effect of Liquid-Fuel Preparation on Gas Turbine Emissions

2006 ◽  
Author(s):  
Sosuke Nakamura ◽  
Vince McDonell ◽  
Scott Samuelsen
Keyword(s):  
Gas Turbine ◽  
Liquid Fuel ◽  
Cylindrical Tube ◽  
Spray Angle ◽  
Preparation Process ◽  
Fuel Injector ◽  
Secondary Importance ◽  
Turbine Engine ◽  
Performance And Emissions ◽  
Air Mixing

The emissions of liquid-fuel fired gas turbine engines are strongly affected by the fuel preparation process that includes atomization, evaporation and mixing. In the present paper, the effects of fuel atomization and evaporation on emissions from an industrial gas turbine engine were investigated. In the engine studied, the fuel injector consists of a co-axial plain jet airblast atomizer and a premixer, which consists of a cylindrical tube with four mixing holes and swirler slits. The goal of this device is to establish a fully vaporized, homogeneous fuel/air mixture for introduction into the combustion chamber and the reaction zone. In the present study, experiments were conducted at atmospheric pressure and room temperature as well as at actual engine conditions (0.34MPa, 740K) both with and without the premixer. Measurements included visualization, droplet size and velocity. By conducting tests with and without the premixing section, the effect of the mixing holes and swirler slit design on atomization and evaporation was isolated. The results were also compared with engine data and the relationship between premixer performance and emissions was evaluated. By comparing the results of tests over a range of pressures, the viability of two scaling methods was evaluated with the conclusion that spray angle correlates with fuel to atomizing air momentum ratio. For the injector studied, however, the conditions resulting in superior atomization and vaporization did not translate into superior emissions performance. This suggests that, while atomization and the evaporation of the fuel are important in the fuel preparation process, they are of secondary importance to the fuel/air mixing prior to, and in the early stages of the reaction, in governing emissions.

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