Development Of Combustion System Research Articles

Lateral Swirl Combustion System Development of Dual Fuel Diesel Engine Piston to Improve Efficiency and Reduce NOx Emission: a Brief Review

Lateral Swirl Combustion System Development of Dual Fuel Diesel Engine Piston to Improve Efficiency and Reduce NOx Emission: a Brief Review

Thermodynamic and exergy assessment of a biomass oxy-fuel combustion with supercritical carbon dioxide cycle under various recycle flue gas conditions

The ongoing development of second-generation oxy-fuel combustion system with higher oxygen concentration have presented a potential pathway for efficient biomass utilization. It also signified the meticulous role of recycled flue gas in altering the combustion behaviour in the combustor. Accordingly, investigation into different recirculation modes focusing on recycle ratio, wet/dry conditions, and excess oxygen ratio are conducted with an indirect supercritical power cycle integrated biomass oxy-fuel combustion system. Energy and exergy analyses, as well as composition of flue gas produced are presented. Energy and exergy efficiencies increased with reducing recycle ratio, with respective highest efficiency of 31.33% and 44.37% obtained at excess oxygen ratio of 1.01 and recycle ratio of 0.5 under wet condition. Investigation of CO2 and H2O concentration in produced flue gas depicted a separated stage profile under dry recycle condition, different from the slight diverging profile observed under wet condition when the recycle ratio varied. Concentration of NOx and SOx increased with decreasing recycle ratio and are generally higher under dry condition. Selective exergy analyses of the proposed power cycle presented highest exergy loss in the combustor, followed by the air separation unit, heat exchanger, CO2 compression and purification unit, and turbine generator. Based on the obtained result, wet recycle flue gas enhanced the combustion performance in the combustor but slightly impaired the convective heat transfer in the heat exchanger. The performance of proposed biomass power cycle is optimized at low recycle ratio of 0.5 under wet recycle condition.

Modeling Ammonia-Hydrogen-Air Combustion and Emission Characteristics of a Generic Swirl Burner

Abstract The combustion process of both pure NH3 and a NH3/H2 fuel blends is here analyzed using two kinetics processors, i.e., Chemkin-Pro-and CANTERA: detailed kinetic mechanisms have been tested and compared in terms of laminar flame speed and ignition delay time (IDT) with the aim to identifying the most suitable ones for the evaluation of NOx emissions. The generic swirl burner being used in Cardiff University's Gas Turbine Research Center has been considered as validation test case. In addition, this paper presents an experimental campaign followed by a computational fluid dynamics (CFD) approach for the assessment of NOx emission using axisymmetric Reynolds-Averaged Navier–Stokes (RANS) simulations, leading to a significant reduction of the computational time. Different pressures and mass flow rates are evaluated to understand correlations of NOx formation for pollutants reduction purpose. A direct comparison between experimental and numerical results is carried out in terms of flow field, flame shape, and NOx emissions. Results show that the increase in pressure from 1.1 bar to 2 bar results in reduction of NOx emissions from 2515 ppmv to 885 ppmv, also indicating guidelines for using a simplified RANS analysis, which leads to improved computational efficiency, allowing wide sensitivity and optimization analysis to support the design development of an industrial combustion system.

The Research and Development of a Jet Disturbance Combustion System for Heavy-Duty Diesel Engines

Herein, a diesel engine jet disturbance combustion system was proposed to achieve efficient and clean combustion under heavy load conditions in heavy-duty diesel engines. The key components of the combustion system were designed, and a research platform was constructed. Focusing on the internal combustion conditions of the disturbance chamber and the developmental path of high-speed jets, the design and comprehensive optimization of the jet disturbance combustion system were carried out. Following optimization, the peak internal heat release rate increased from 86 J/deg to 269 J/deg, and the cumulative heat release increased by 112 J, significantly enhancing the energy of the disturbance chamber jet. Then, considering combustion optimization and the heat transfer loss from the piston, it was determined that the optimal configuration for the disturbance chamber jet channel angles was 60 deg inter-channel angle and 10 deg channel incidence angle. This configuration allowed the disturbance chamber jet to precisely disturb the concentrated mixture area in the middle and late stages of combustion. The intervention of the disturbance chamber jet provided sufficient energy for the fuel–air mixing process and complicated the gas flow state in the main combustion chamber. Despite its low-momentum density, the residual mixture in the cylinder maintained a high mixing rate after the end of the fuel injection process. Single-cylinder engine test results showed that a diesel engine using this jet disturbance system and a 180 MPa common rail pressure fuel system achieved 52.12% thermal efficiency.

Development of a Common Waste Combustion System for Generating Electricity at Remote Area

Malaysia’s daily amount of municipal solid waste (MSW) has rapidly increased. This causes the landfills number to increase due to inadequate waste management systems. Apart from that, Malaysia depends on non-renewable resources for electricity generation which could have a significant effect on the environment. Therefore, this study proposed to reduce landfills in Malaysia in a proper way and supply electricity using municipal solid waste as a renewable resource. In this study, the combustion of municipal solid waste (MSW) produces steam, which will rotate a turbine that is connected to a dynamo. Then, the energized dynamo will supply electricity to appliances including a direct current motor. The motor shaft then rotates the dynamo shaft in the pulley system which causes the electricity to flow in a closed loop. In this system, a pressurized container is crucial to produce sufficient steam. Based on the experimental setup, it was observed that continuous electricity was successfully achieved by looping the system using a pulley on the dynamo and motor.

Future HD Diesel and Hydrogen-Fueled Concepts: Emissions Challenges and System Solutions

<div class="section abstract"><div class="htmlview paragraph">Future heavy-duty (HD) concepts should fulfill very tight tail-pipe NO<sub>x</sub> emissions and simultaneously fulfill the fuel efficiency targets. In current HD Euro VII discussions, real working cycles become key to ensure emission conformity. For instance, cold start and cold ambient conditions during testing with low load profiles starting from 0% payload, require external heating measures. Knowing the trade-off between fuel consumption and tail-pipe NO<sub>x</sub> emissions a holistic engine and EAT system optimization with innovative thermal management is required.</div><div class="htmlview paragraph">Towards a carbon neutral mobility, Hydrogen combustion engines are one of the key solutions. Advanced combustion system development enables maximal usage of lean burning as the major advantage of the Hydrogen fuel for efficiency improvement and NO<sub>x</sub> reduction. Considering future NO<sub>x</sub> regulations in real-world working cycles, an efficient exhaust after-treatment (EAT) system which is well optimized to the air-path and the Hydrogen combustion characteristics is required.</div><div class="htmlview paragraph">In this paper, a systematic investigation is carried out by means of the model-based holistic approach. The target is an optimization of both engine and EAT layout, including advanced thermal management for future HD concepts. Both Diesel and Hydrogen HD concepts are investigated.</div><div class="htmlview paragraph">The model-based emission conception is based on both the conventional WHTC cycle as well as on selected real field cycles. Close-coupled dual-stage SCR with twin dosing is considered with multiple system layouts in order to minimize the Diesel engine fuel penalty during the heat up phases. A comparison between the emission behavior and after-treatment systems of Diesel and Hydrogen engines is performed.</div><div class="htmlview paragraph">In addition, external EAT heating such as electric heated catalyst is investigated for Diesel applications and the potentials regarding CO<sub>2</sub> emissions compared to conventional engine-based thermal management measures are shown.</div><div class="htmlview paragraph">The optimized system layout for both Diesel and Hydrogen HD concepts are compared, especially for the EAT technology and layout. As outlook, future potentials and optimization possibilities for combustion systems and future emission reduction technologies are described.</div></div>

Development of an Oxy-Fuel Combustion System in a Compression-Ignition Engine for Ultra-Low Emissions Powerplants Using CFD and Evolutionary Algorithms

This study uses an optimization approach for developing a combustion system in a compression–ignition engine that is able to operate under oxy-fuel conditions, and produces mainly CO2 and H2O as exhaust gases. This is achieved because the combustion concept uses pure oxygen as an oxidizer, instead of air, avoiding the presence of nitrogen. The O2 for the combustion system can be obtained by using a mixed ionic–electronic conducting membrane (MIEC), which separates the oxygen from the air onboard. The optimization method employed maximizes the energy conversion of the system, reducing pollutant emissions (CxHy, particulate matter, and carbon monoxides) to levels near zero. The methodology follows a novel approach that couples computational fluid dynamics (CFD) and particle swarm optimization (PSO) algorithms to optimize the complete combustion system in terms of engine performance and pollutant generation. The study involves the evaluation of several inputs that govern the combustion system design in order to fulfill the thermo-mechanical constraints. The parameters analyzed are the piston bowl geometry, fuel injector characteristics, air motion, and engine settings variables. Results evince the relevance of the optimization procedure, achieving very low levels of gaseous pollutants (CxHy and CO) in the optimum configuration. The emissions of CO were reduced by more than 10% while maintaining the maximum in-cylinder pressure within the limit imposed for the engine. However, indicated efficiency levels are compromised if they are compared with an equivalent condition operating under conventional diesel combustion.

Development and Integration of the Dual Fuel Combustion System for the MGT Gas Turbine Family

Abstract Industrial gas turbines like the MGT6000 are often operated as power supply or as mechanical drives. In these applications, liquid fuels like “diesel fuel no. 2” can be used either as main fuel or as backup fuel if natural gas is not reliably available. The MAN gas turbines (MGT) operate with the advanced can combustion (ACC) system, which is capable of ultralow NOx emissions for gaseous fuels. This system has been further developed to provide dry dual fuel capability. In this paper, we describe the design and detailed experimental validation process of the liquid fuel injection, and its integration into the gas turbine package. A central lance with an integrated two-stage nozzle is employed as a liquid pilot stage, enabling ignition and startup of the engine on liquid fuel only. The pilot stage is continuously operated, whereas the bulk of the liquid fuel is injected through the premixed combustor stage. The premixed stage comprises a set of four decentralized nozzles based on fluidic oscillator atomizers, wherein atomization of the liquid fuel is achieved through self-induced oscillations. We present results illustrating the spray, hydrodynamic, and emission performance of the injectors. Extensive testing of the burner at atmospheric and full load high-pressure conditions has been performed, before verification within full engine tests. We show the design of the fuel supply and distribution system. Finally, we discuss the integration of the dual fuel system into the standard gas turbine package of the MGT6000.

Quantitative 1-D LIBS measurements of fuel concentration in natural gas jets at high ambient pressure

Fuel concentration information is critical to the development of high-efficiency combustion system of direct-injection natural gas engines. In this study, a one-dimensional (1-D) measurement approach based on laser induced breakdown spectroscopy (LIBS) is developed to quantitatively measure 1-D fuel concentration distributions in gas jets at high ambient pressures. Except for the spectral dimension, another dimension of the intensified charge coupled device (ICCD) is employed for the spatial resolution of measurements. The effects of laser energy and ambient pressure on plasma dynamics are investigated to explore the feasibility of 1-D LIBS in concentration measurements at high ambient pressure. Since the peak intensity ratio (PIR) of H656/N746 shows significant spatial variations in the plasma volume, a 1-D calibration strategy is developed by establishing respective calibration curves at different spatial positions to quantify the fuel concentration distributions. The measurement uncertainties are evaluated, including both the systematic and random errors. The temporal variations of the 1-D fuel concentration distributions in methane jets are presented, and the shot-to-shot fluctuations are analyzed in detail. The results show that the coefficient of variation of equivalence ratio is lowest at the end of injection (EOI), suggesting that ignition at the EOI could enable a relatively stable flame kernel formation. Along the radial direction of the jet, a high ignitable mixture percentage appears at approximately 3.0 mm from the jet axis at the EOI, suggesting an optimal ignition position. The results reveal that the 1-D LIBS could be a powerful tool for calibration of numerical models and optimal designs of combustion engines taking advantage of high-pressure gas jets.

Technology of low-emission fuel combustion and conceptual structure of the combustion chamber of a gas-turbine power plant

Currently, the priority for improvement of the combustion chambers of aircraft gas turbine engines and ground-based gas turbine plants is associated with a decrease in the concentration of harmful substances in the exhaust gases while ensuring fuel economy and operational efficiency. Pride of place in the design of a gas turbine power plant goes to solving the problem of organizing the combustion process, i.e. the development of a low-emission combustion system that provides high efficiency and environmental safety. Thus, ecology today determines not only the appearance of a combustion chamber, but also that of a gas turbine power plant as a whole. Below, an attempt is made to summarize the results of developing a low-emission combustion system for various types of combustion chambers of convertible gas turbine power plants and to present a unified approach to the problem of designing a conceptual structure of a low-emission combustion chamber.

Machine Learning Algorithm for the Prediction of Idle Combustion Uniformity

<div class="section abstract"><div class="htmlview paragraph">Combustion stability is a key contributor to engine shake at idle speed and can impact the overall perception of vehicle quality. The sub-firing harmonics of the combustion torque are used as a metric to assess idle shake and are, typically, measured at different levels of engine break mean effective pressure (BMEP). Due to the nature of the combustion phenomena at idle, it is clear that predicting the cycle-to-cycle and cylinder-to-cylinder combustion pressure variations, required to assess the combustion uniformity, cannot be achieved with the state of the art simulation technology.</div><div class="htmlview paragraph">Inspired by the advancement in the field of machine learning and artificial intelligence and by the availability of a large amount of measured combustion test data, this paper explores the performance of various machine learning algorithms in predicting the idle combustion uniformity. The algorithms that are explored include Neural Network (NN), Support Vector Machine (SVM), Ensembles of Trees (EOT) and Gaussian Process (GP). The variables selected as inputs to these algorithms include BMEP, indicated mean effective pressure (IMEP), pumping mean effective pressure (PMEP), spark timing, crank angle at 10% fuel burn (Burn0010), crank angle at 90% fuel burn (Burn1090), and crankshaft timing at 50% fuel burn (CA50). The algorithms output the amplitude of 0.5 order, 1.0 order and the 1.5 order harmonics of the combustion torque.</div><div class="htmlview paragraph">The results presented in this paper show the superiority of the Gaussian Process algorithm in predicting the combustion torque harmonics. Using this algorithm, this paper further investigates the sensitivity of the engine torque harmonics to the parameters, used as inputs to the algorithm, in order to establish potential design guidelines for upfront combustion system development.</div></div>

The wall-flow-guided and interferential interactions of the lateral swirl combustion system for improving the fuel/air mixing and combustion performance in DI diesel engines

The lateral swirl combustion system was designed based on and to improve upon the traditional ω-type combustion system. Previous research has verified the outstanding combustion performance of the lateral swirl combustion system. In this study, to reveal the interaction mechanisms between the lateral swirl combustion chamber and spray jets, experimental and numerical study was conducted at various spray incident angles (φ) where the relations between the combustion chamber and spray jets are different. The spray impinging processes and combustion performance were measured in a single-cylinder diesel engine with an endoscopic system. The distribution of velocity and the equivalence ratio was analyzed through simulation. Then, under the optimal φ, the fuel/air mixing quality and combustion performance was verified in comparison with a double swirl combustion system.The results show that fuel consumption and soot emissions of the lateral swirl combustion system decreased with an increasing spray incident angle. When φ reached its maximum, the combustion system exerted the best combustion performance, because the wall-flow-guided interaction between the chamber and spray jets and the interferential interaction from the neighboring wall jets were optimized. This combined effect promoted in-cylinder fuel/air mixing and combustion. Under this circumstance, the indicated thermal efficiency of the lateral swirl combustion system increased by 3.4–6.8% compared with the double swirl combustion system, and the soot emissions decreased in the ranges of 45–73%. It was concluded that the lateral swirl combustion system with a maximum spray incident angle significantly improves the combustion performance of DI diesel engines due to the wall-flow-guided and interferential interactions between the combustion chamber and spray jets. These findings are key to the design and development of a high-efficiency lateral swirl combustion system for DI diesel engines.

Assessment of primary air on corn straw in a fixed bed combustion using Eulerian-Eulerian approach

In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimensional bench combustion test rig, and the effects of the primary air flow rate are assessed over a wide range. Due to complex solid combustion mechanisms and inadequate knowledge of the process, the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis, although the development of a complete model for this type of combustion system remains a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is displaying the process of initiating the combustion in numerical modelling. This study finds that the volatile release and combustion of char increases, thus increasing the amount of primary air up to a critical point, where the starting time of ignition becomes shorter as the primary air flow rate increases. The peak concentration of NO decreases with the increase of primary air, whereas with the increase in the amount of air, there is a reduction in the release of SO2 as well as a reduction in CO emissions in the bed.

Numerical and optical analysis of heterogeneous gas combustion with diesel pilot ignition in a commercial vehicle engine

A new optical measurement technology and a simulation methodology for supporting the combustion system development of a high-pressure gas-diesel combustion system are presented for the first time. With this combustion system, natural gas is directly injected with high pressure into the combustion chamber near top dead center. The simulation methodology is being validated by comparison with a commercial vehicle single-cylinder metal engine and combustion imaging on a commercial vehicle optical engine with full optical access to the combustion chamber through a contoured piston window. For the optical analysis of the gas-diesel combustion system, a measurement setup for the combined two-dimensional imaging of the OH* chemiluminescence and the soot luminescence is being developed. These images allow the ignition characterization and the cyclic stability of combustion to be analyzed. With the support of the simulation methodology, the nozzle-bowl configuration can be designed with regard to optimum mixture formation and low emissions. A thermodynamic validation of the simulation results shows good agreement of the ignition timing and the following combustion phases with heat release rate data obtained from measurements. Furthermore, the end of engine soot concentrations are captured quantitatively well. A local comparison of optical images and simulation data demonstrates that the simulation is able to capture the gas ignition zones well. The combustion intensity and thus the local soot formation are slightly underpredicted in the center of the gas jets. However, the mixture formation and the overall regions of soot formation are in good agreement with the optical images.

Combustion System Development of an Opposed Piston 2-Stroke Diesel Engine

Today, the interest towards 2-stroke, opposed-piston compression-ignition engines is higher than ever, after the announcement of imminent production of a 2.7L 3-cylinder light truck engine by Achates Powers. In comparison to other 2-stroke designs, the advantages in terms of scavenge and thermal efficiency are indisputable: a perfect “uniflow” scavenge mode can be achieved with inexpensive and efficient piston controlled ports, while heat losses are strongly reduced by the relatively small transfer area. Unfortunately, the design of the combustion system is completely different from a 4-stroke DI Diesel engine, since the injectors must be installed on the cylinder liners: however, this challenge can be converted into a further opportunity to improve fuel efficiency, adopting advanced combustion concepts.This paper is based on a previous study, where the main geometric parameters of an opposed piston engine rated at 270 kW (3200 rpm) were defined with the support of CFD 1D-3D simulations. The current work will focus on the influence of an innovative combustion system, developed by the authors by means of further CFD-3D analyses, holding constant the boundary conditions of the scavenging process.The numerical study eventually demonstrates that an optimized 2-S OP Diesel engine can achieve a 10% improvement on brake efficiency at full load, in comparison to an equivalent conventional 4-stroke engine, while reducing in-cylinder peak pressures and turbine inlet temperatures.

Numerical Modelling of Solid Biomass Combustion: Difficulties in Initiating the Fixed Bed Combustion

Abstract Bio mass is a renewable energy which has become an important fuel to produce thermal energy or electricity. It has no adverse effect on environment as it reduces carbon dioxide emissions. Biomass combustion is a difficult phenomenon due to its properties with less carbon, more volatile matters and lower calorific value. Fixed bed combustion is a useful technique for thermal conversion of solid biomass fuels as this can fire up a broad range of fuels with different properties and requires less fuel preparation. But due to complex solid combustion mechanism and inadequate knowledge on process the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis. But developing a complete model for this type of combustion system is a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is initiating the combustion in numerical modelling. The usual way to model biomass combustion is to divide the system in to two phases namely solid phase and gas phase. Modelling the solid phase of this combustion system requires the major effort. In this work, a detailed analysis of difficulties occurred in initiating the biomass combustion has been presented. A complete three-dimensional numerical model is used for transient analysis of fixed bed biomass combustion. The bed is considered as a porous medium and solid phase of the combustion is characterised by using sub models with several variables in a commercial CFD code.

Development of MGE 1.8T combustion system assisted by numerical simulation

This paper describes the CFD assisted combustion system development for a 1.8 L turbo GDI engine which has been developed by SAIC Motor. The combustion system is a direct injected turbocharged system employing centre-mounted multi-hole injectors. The in-cylinder charge motion, fuel injection, air/fuel mixing and combustion processes in the combustion system were evaluated. Proposed intake port options were numerically investigated and compared. Impingement of fuel droplets on piston crown, and wetting on the walls of combustion chamber and the subsequent impacts on mixture formation and oil dilution were investigated by both CFD tool and engine test approaches. Spray targeting was optimised to minimise oil dilution, and multiple fuel injection strategies were investigated to understand its impact on injection, mixture formation and combustion process. The concentrations of pollutants including CO, NOx, HC and soot were simulated. The present simulation results agree well with the measurement data from engine testing, including cylinder gas pressure.

Development of a syngas-fired catalytic combustion system for hybrid solar-thermal applications

This paper describes the development and operation of a catalytic combustion system for use with syngas as an important component of a hybrid heating source for solar-thermal power generation. The reactor consists of a cylindrical ceramic monolith with porous alumina washcoat in which platinum is distributed as the catalyst. Two fuel-rich equivalence ratios were studied over a range of flow rates. The fuel-rich conditions permit low temperature combustion without the problem of hotspots likely to occur under fuel-lean conditions with hydrogen-containing fuels. Experimental data of temperature and species concentration at the exit of the reactor have been reported for a maximum fuel thermal input of 34kW. The system exhibited quick start-up with a light-off time of around 60s and a steady-state time of around 200s as determined from the transient temperature profiles. The experimental results have also been complemented with detailed two-dimensional numerical simulations for improved understanding of the combustion characteristics in the reactor. The simulations suggest that the combustion system can be operated at a turn-down ratios far in excess of 1.67, which is the maximum value that has been investigated in the present setup. Stable operation, quick startup, and high turn-down ratio are some of the key features that enable the proposed combustion system to accommodate the transients in solar-thermal applications.

G-04 コモンレールとエマルジョン燃料を組み合わせた新しい燃焼システムの開発

G-04 コモンレールとエマルジョン燃料を組み合わせた新しい燃焼システムの開発

Low NOx Lean Premix Reheat Combustion in Alstom GT24 Gas Turbines

Reducing gas turbine emissions and increasing their operational flexibility are key targets in today's gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24 (60 Hz) and GT26 (50 Hz), Alstom has introduced an improved sequential environmental (SEV) burner and fuel lance into its GT24 and GT26 upgrades 2011 sequential reheat combustion system. Sequential combustion is a key differentiator of Alstom GT24/GT26 engines in the F-class gas turbine market. The inlet temperature for the SEV combustor is around 1000 °C and reaction of the fuel/oxidant mixture is initiated through auto-ignition. The recent development of the Alstom sequential combustion system is a perfect example of evolutionary design optimizations and technology transfer between Alstom GT24 and GT26 engines. Better overall performance is achieved through improved SEV burner aerodynamics and fuel injection, while keeping the main features of the sequential burner technology. The improved SEV burner/lance concept has been optimized toward rapid fuel/oxidant mixing for low emissions, improved fuel flexibility with regard to highly reactive fuels (higher C2+ and hydrogen content), and to sustain a wide operation window. The burner front panel features an improved cooling concept based on near-wall cooling as well as integrated acoustics damping devices designed to reduce combustion pulsations, thus extending the SEV combustor's operation window even further. After having been validated extensively in Alstom's high pressure (HP) sector rig test facility, the improved GT24 SEV burner has been retrofitted into a commercial GT24 field engine for full engine validation during long-term operation. This paper presents the obtained HP sector rig and engine validation results for the GT24 (2011) SEV burner/lance hardware with a focus on reduced NOx and CO emissions and improved operational behavior of the SEV combustor. The HP tests demonstrated robust SEV burner/lance operation with up to 50% lower NOx formation and a more than 70 K higher SEV burner inlet temperature compared to the GT24 (2006) hardware. For the GT24 engine with retrofitted upgrade 2011 SEV burner/lance, all validation targets were achieved including an extremely robust operation behavior, up to 40% lower GT NOx emissions, significantly lower CO emissions at partload and baseload, a very broad operation window (up to 100 K width in SEV combustor inlet temperature), and all measured SEV burner/lance temperatures in the expected range. Sector rig and engine validation results have confirmed the expected SEV burner fuel flexibility (up to 18 vol. % C2+ and up to 5 vol. % hydrogen as standard).