Low calorific value (LCV) gaseous fuels are generated as by-products in many commercial sectors. Their efficient exploitation can be a considerable source of primary energy. Typically, product gases from biomass are characterized by low lower heating values (LHV) due to their high concentration of inert gases and steam. At the same time, their composition varies strongly based on the initial feedstock and may contain unwanted components in the form of tars and ammonia. These properties make the design of appropriate combustion systems very challenging and issues such as ignition, flame stability, emission control, and combustion efficiency must be accounted for. By employing a proprietary gas turbine burner at the TU Berlin, the combustion of an artificial LCV gas mixture at stoichiometric conditions has been successfully demonstrated for a broad range of steam content in the fuel. The current work presents the stability maps and emissions measured with the swirl-stabilized burner at premixed conditions. It was shown that the flame location and shape primarily depend on the steam content of the LCV gas. The steam content in the fuel was increased until flame blow-out occurred at LHVs well below the target condition of 2.87MJ/kg (2.7MJ/Nm3). The exhaust gas is analyzed in terms of the pollutants NOx and CO for different fuel compositions, moisture contents, and thermal powers. Finally, OH* measurements have been carried out in the flame. A simple reactor network simulation was used to confirm the feasibility of the experimental results.

A numerical investigation of pollutant emissions of a novel dry low-emissions burner for heavy-duty gas turbine applications is presented. The objective of this work is to develop and assess a robust and cost-efficient numerical setup for the prediction of NO x and CO emissions in industrial gas turbines and to investigate the pollutant formation mechanisms, thus supporting the design process of a novel low-emission burner. To this end, a comparison against experimental data, from a recent experimental campaign performed by BHGE in cooperation with University of Florence, has been exploited. In the first part of this work, a Reynolds-averaged Navier–Stokes (RANS) approach on both a simplified geometry and the complete domain is adopted to characterize the global flame behavior and validate the numerical setup. Then, unsteady simulations exploiting the scale adaptive simulation (SAS) approach have been performed to assess the prediction improvements that can be obtained with the unsteady modeling of the flame. For all simulations, the flamelet generated manifold (FGM) model has been used, allowing the reliable and cost-efficient application of detailed chemistry mechanisms in computational fluid dynamics (CFD) simulation. However, FGM typically faces issues predicting flame emissions, such as NO x and CO, due to the wide range of time scales involved, from turbulent mixing to pollutant species oxidation. Specific models are typically used to predict NO x emissions, starting from the converged flow-field and introducing additional transport equations. Also CO prediction, especially at part-load operating conditions could be an issue for flamelet-based model: in fact, as the load decreases and the extinction limit approaches, a superequilibrium CO concentration, which cannot be accurately predicted by FGM, appears in the exhaust gases. To overcome this issue, a specific CO-burn-out model, following the original idea proposed by Klarmann, has been implemented in ANSYS fluent . The model allows to decouple the effective CO oxidation term from the one computed by FGM, defining a postflame zone where the source term of CO is treated following the Arrhenius formulation. In order to support the design process, an indepth CFD investigation has been carried out, evaluating the impact of an alternative burner geometrical configuration on stability and emissions and providing detailed information about the main regions and mechanisms of pollutants production. The outcomes support the analysis of experimental results, allowing an indepth investigation of the complex flow-field and the flame-related quantities, which have not been measured during the tests.

The combustion of conventional fuels (diesel and Jet A-1) with 10–20% vol oxygenated biofuels (ethanol, 1-butanol, methyl octanoate, rapeseed oil methyl ester (RME), diethyl carbonate, tri(propylene glycol)methyl ether, i.e., CH 3 (OC 3 H 6 ) 3 OH, and 2,5-dimethylfuran (2,5-DMF)) and a synthetic paraffinic kerosene (SPK) was studied. The experiments were performed using an atmospheric pressure laboratory premixed flame and a four-cylinder four-stroke diesel engine operating at 1500 rpm. Soot samples from kerosene blends were collected above a premixed flame for analysis. Polyaromatic hydrocarbons (PAHs) were extracted from the soot samples. After fractioning, they were analyzed by high-pressure liquid chromatography (HPLC) with UV and fluorescence detectors. C 1 to C 8 carbonyl compounds (CBCs) were collected at the diesel engine exhaust on 2,4-dinitrophenylhydrazine coated cartridges (DNPH) and analyzed by HPLC with UV detection. The data indicated that blending conventional fuels with biofuels has a significant impact on the emission of both CBCs and PAHs adsorbed on soot. The global concentration of 18 PAHs (1-methyl-naphthalene, 2-methyl-naphthalene, and the 16 U.S. priority EPA PAHs) on soot was considerably lowered using oxygenated fuels, except 2,5-DMF. Conversely, the total carbonyl emission increased by oxygenated biofuels blending. Among them, ethanol and 1-butanol were found to increase considerably the emissions of CBCs.

Finite-rate chemical effects at gas turbine conditions lead to incomplete combustion and well-known emissions issues. Although a thin flame front is preserved on an average, the instantaneous flame location can vary in thickness and location due to heat losses or imperfect mixing. Postflame phenomena (slow CO oxidation or thermal NO production) can be expected to be significantly influenced by turbulent eddy structures. Since typical gas turbine combustor calculations require insight into flame stabilization as well as pollutant formation, combustion models are required to be sensitive to the instantaneous and local flow conditions. Unfortunately, few models that adequately describe turbulence–chemistry interactions are tractable in the industrial context. A widely used model capable of employing finite-rate chemistry is the eddy dissipation concept (EDC) model of Magnussen. Its application in large eddy simulations (LES) is problematic mainly due to a strong sensitivity to the model constants, which were based on an isotropic cascade analysis in the Reynolds-averaged Navier–Stokes (RANS) context. The objectives of this paper are: (i) to formulate the EDC cascade idea in the context of LES; and (ii) to validate the model using experimental data consisting of velocity (particle image velocimetry (PIV) measurements) and major species (1D Raman measurements), at four axial locations in the near-burner region of a Siemens SGT-100 industrial gas turbine combustor.

Stringent emissions standards for NO x and carbon monoxide (CO) prompt lean combustor development. With this motivation, combustion stability issues emerge since the desired operating point approaches the lean blowout limit. In this paper, an atmospheric, 15 kW lean premixed prevaporizing-type swirl burner, equipped with a plain jet airblast atomizer, was investigated at various atomizing pressures and combustion air flow rates, using quarls from 0 deg to 60 deg in 15 deg steps. Both the 15 deg and the 30 deg quarls provided a 42% higher lean blowout stability on average in terms of mean mixing tube discharge velocity, compared to the baseline burner. However, the superior stability regime was encumbered by a rapidly increasing CO emission. In parallel, the NO x emission vanished due to the more dilution air and incomplete combustion. The 60 deg quarl provided a moderately extended blowout stability limitation, while the NO x emission slightly increased and the CO emission reduced compared to the baseline burner.

The major exhaust gas pollutants from heavy duty gas turbine engines are CO and NO x . The difficulty of predicting the concentration of these combustion products originates from their wide range of chemical time scales. In this paper, a combustion model that includes the prediction of the carbon monoxide and nitric oxide emissions is tested. Large eddy simulations (LES) are performed using a compressible code ( O pen FOAM ). A modified flamelet generated manifolds (FGM) approach is applied with an artificially thickened flame approach (ATF) to resolve the flame on the numerical grid, with a flame sensor to ensure that the flame is only thickened in the flame region. For the prediction of the CO and NO x emissions, pollutant species transport equations and a second, CO based, progress variable are introduced for the flame burnout zone to account for slow chemistry effects. For the validation of the models, the Cambridge burner of Sweeney et al. (2012, “The Structure of Turbulent Stratified and Premixed Methane/Air Flames—I: Non-Swirling Flows,” Combust. Flame, 159 , pp. 2896–2911; 2012, “The Structure of Turbulent Stratified and Premixed Methane/Air Flames—II: Swirling Flows,” Combust. Flame, 159 , pp. 2912–2929.) is employed, as both carbon monoxide and nitric oxide [Apeloig et al. (2016, “PLIF Measurements of Nitric Oxide and Hydroxyl Radicals Distributions in Swirl Stratified Premixed Flames,” 18th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Lisbon, Portugal, July 4–7.)] data are available.

It is anticipated that the contribution of rotorcraft activities to the environmental impact of civil aviation will increase in the future. Due to their versatility and robustness, helicopters are often operated in harsh environments with extreme ambient conditions. These severe conditions not only affect the performance of the engine but also affect the aerodynamics of the rotorcraft. This impact is reflected in the fuel burn and pollutants emitted by the rotorcraft during a mission. The aim of this paper is to introduce an exhaustive methodology to quantify the influence adverse environment conditions have in the mission fuel consumption and the associated emissions of nitrogen oxides (NO x ). An emergency medical service (EMS) and a search and rescue (SAR) mission are used as case studies to simulate the effects of extreme temperatures, high altitude, and compressor degradation on a representative twin-engine medium (TEM) weight helicopter, the Sikorsky UH-60A Black Hawk. A simulation tool for helicopter mission performance analysis developed and validated at Cranfield University was employed. This software comprises different modules that enable the analysis of helicopter flight dynamics, powerplant performance, and exhaust emissions over a user-defined flight path profile. For the validation of the models implemented, extensive comparisons with experimental data are presented throughout for rotorcraft and engine performance as well as NO x emissions. Reductions as high as 12% and 40% in mission fuel and NO x emissions, respectively, were observed for the “high and cold” scenario simulated at the SAR role relative to the same mission trajectory under standard conditions.

Internal combustion engine development focuses mainly on two aspects: fuel economy improvement and pollutant emissions reduction. As a consequence, light duty spark ignition (SI) engines have become smaller, supercharged, and equipped with direct injection and advanced valve train control systems. The use of alternative fuels, such as natural gas (NG) and liquefied petroleum gas (LPG), thanks to their lower cost and environmental impact, widely spread in the automotive market, above all in bifuel vehicles, whose spark ignited engines may run either with gasoline or with gaseous fuel. The authors in previous works experimentally tested the strong engine efficiency increment and pollutant emissions reduction attainable by the simultaneous combustion of gasoline and gaseous fuel (NG or LPG). The increased knock resistance, obtained by the addition of gaseous fuel to gasoline, allowed the engine to run with stoichiometric mixture and best spark timing even at full load. In the present work, the authors extended the research by testing the combustion of gasoline–NG mixtures, in different proportions, in supercharged conditions, with several boost pressure levels, in order to evaluate the benefits in terms of engine performance, efficiency, and pollutant emissions with respect to pure gasoline and pure NG operation. The results indicate that a fuel mixture with a NG mass percentage of 40% allows to maximize engine performance by adopting the highest boost pressure (1.6 bar), while the best efficiency would be obtained with moderate boosting (1.2 bar) and NG content between 40% and 60% in mass.

An aircraft mission analysis procedure, accounting for engine aging deterioration and incorporating emission estimation capability, is presented. It consists of three main modules: a flight simulation module, an engine performance simulation module, and an optimizer. A key feature of the approach is the incorporation of engine deterioration modeling. This extends the procedure’s ability to estimate onboard performance of an engine as it ages through time and usage. Additionally, the possibility to investigate environmental impact is offered through pollutant emission semi-empirical correlations, which are coupled to the engine performance calculations. The adaptive character of the models employed allows for accurate performance and emission estimations once an initial set of data is available for the engine. The proposed procedure allows the optimization of a flight scenario for a variety of aircrafts, missions, and engine condition combinations in order to meet predefined criteria. Mission profile characteristics (e.g., cruise, altitude, and speed) providing optimum overall performance in terms of fuel conservation, time related costs, or pollutant production are studied.

During the last decades, pollutant emissions from internal combustion engines used for transportation have become a major concern. Today, not only steady state emissions but also emissions during transients are regulated and have to be studied in order to be reduced. In this paper, we describe a new methodology developed to measure the instantaneous level of gaseous emissions from a internal combustion engine during transients, using an analyzer initially designed for steady state operation. Moreover, a new phenomenological thermodynamical combustion model is proposed in order to compute emissions during transients. The results of these two methods are compared on various transients. The measurement method seems to give good results (except for hydrocarbon (HC) measurements), as long as the speed and load variations are not too fast. Otherwise, the frequency of the analyzer which was used becomes the limiting factor. The new combustion heat release developed to simulate transients, coupled with an existing two-zone model for emission calculations, leads to satisfactory results for C O 2 and O 2 concentrations and N O x emissions. The agreement with measurements is good for smooth transients and seems promising for faster dynamics. The initial goal was reached, although some improvements are still necessary concerning HC measurements and the fastest transients. These results could be helpful when trying to reduce the amount of pollutant emissions at the exhaust during transients, directly or with after treatment devices.

FLOX®, or flameless combustion is characterized by ultralow N O x emissions. Therefore the potential for its implementation in gas turbine combustors is investigated in recent research activities. The major concern of the present paper is the numerical simulation of flow and combustion in a FLOX®-combustor [ Wünning, J. A., and Wünning, J. G., 1997, “Progress in Energy and Combustion Science,” 23, pp. 81–94; Patent EP 0463218 ] at high pressure operating conditions with emphasis on the pollutant formation. FLOX®-combustion is a highly turbulent and high-velocity combustion process, which is strongly dominated by turbulent mixing and chemical nonequilibrium effects. By this means the thermal nitric oxide formation is reduced to a minimum, because even in the nonpremixed case the maximum combustion temperature does not or rather slightly exceeds the adiabatic flame temperature of the global mixture due to almost perfectly mixed reactants prior to combustion. In a turbulent flow, the key aspects of a combustion model are twofold: (i) chemistry and (ii) turbulence/chemistry interaction. In the FLOX®-combustion we find that both physical mechanisms are of equal importance. Throughout our simulations we use the complex finite rate chemistry scheme GRI3.0 for methane and a simple partially stirred reactor (PaSR) model to account for the turbulence effect on the combustion. The computational results agree well with experimental data obtained in DLR test facilities. For a pressure level of 20 bar, a burner load of 417 kW and an air to fuel ratio of λ =2.16 computational results are presented and compared with experimental data.

New computational procedures are proposed for evaluating the exhaust brake specific mass emissions of each pollutant species in internal combustion (IC) engines. The procedures start from the chemical reaction of fuel with combustion air and, based on the measured exhaust raw emissions THC, CH 4 , NO x , CO, O 2 , CO 2 , calculate the volume fractions of the compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The molecular mass of the exhaust gases is then evaluated and the brake specific emissions can be obtained if the exhaust flow rate and the engine power output are measured. The algorithm can also be applied to the evaluation of air-fuel ratio from measured raw volume emissions of IC engines. The new procedures take the effects of various fuel and combustion air compositions into account, with particular reference to different natural gas blends as well as to the presence of water vapor, CO 2 , Ar and He in the combustion air. In the paper, the algorithms are applied to the evaluation of air-fuel ratio and brake specific mass emissions in an automotive bi-fuel Spark Ignition (SI) engine with multipoint sequential port-fuel injection. The experimental tests were carried out in a wide range of steady-state operating conditions under both gasoline and compressed natural gas operations. The specific emissions calculated from the new procedures are compared to those evaluated by applying Society of Automotive Engineers (SAE) and International Standards Organization (ISO) recommended practices and the air-fuel ratio results are compared to those obtained either from directly measured air and fuel mass flow rates or from Universal Exhaust Gas Oxygen (UEGO) sensor data. The sensitivity of the procedure results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NO x formation) and the experimental uncertainties are also determined.

Combustion and pollutant formation in a gas turbine combustion chamber is investigated numerically using the Eulerian particle flamelet model. The code solving the unsteady flamelet equations is coupled to an unstructured computational fluid dynamics (CFD) code providing solutions for the flow and mixture field from which the flamelet parameters can be extracted. Flamelets are initialized in the fuel-rich region close to the fuel injectors of the combustor. They are represented by marker particles that are convected through the flow field. Each flamelet takes a different pathway through the combustor, leading to different histories for the flamelet parameters. Equations for the probability of finding a flamelet at a certain position and time are additionally solved in the CFD code. To model the chemical properties of kerosene, a detailed reaction mechanism for a mixture of n-decane and 1,2,4-trimethylbenzene is used. It includes a detailed NO x submechanism and the buildup of polycyclic aromatic hydrocarbons up to four aromatic rings. The kinetically based soot model describes the formation of soot particles by inception, further growth by coagulation, and condensation as well as surface growth and oxidation. Simulation results are compared to experimental data obtained on a high-pressure rig. The influence of the model on pollutant formation is shown, and the effect of the number of flamelets on the model is investigated.

Close coupling of automotive three-way catalytic converters is becoming a common practice in order to reduce pollutant emissions during cold start. In such applications, the exhaust gas mass flow may fluctuate, as a function of crankshaft angle. A simplified one-dimensional channel model is developed, assuming that pollutant conversion in the catalyst is mass transfer limited. This model is applied to evaluate the effect of pulsations in catalyst performance, and assess the accuracy of the “quasi-steady state” approach usually involved in three-way catalytic converter models, when applied to simulate converters under pulsating flow.

Combined cycle power plants are currently one of the most important options for the construction of new generating capacity as well as for the replacement and repowering of existing units. Due to the complexity and the large number of options and parameters available to such plants, finding optimized solutions for system synthesis, design, and operation is very difficult if not impossible with these traditional methods such as case and parametric tradeoff studies. This is especially true when advanced options as well as thermodynamic, economic, and environmental criteria are considered. A thermoeconomic environomic methodology to deal with these difficulties is presented here. Results for the application of this methodology to a 50 MW cogeneration combined cycle power plant are presented and discussed.

Current research shows that the only hazardous air pollutant of significance emitted from large bore natural gas engines is formaldehyde CH 2 O . A literature review on formaldehyde formation is presented focusing on the interpretation of published test data and its applicability to large bore natural gas engines. The relationship of formaldehyde emissions to that of other pollutants is described. Formaldehyde is seen to have a strong correlation to total hydrocarbon (THC) level in the exhaust. It is observed that the ratio of formaldehyde to THC concentration is roughly 1.0–2.5 percent for a very wide range of large bore engines and operating conditions. The impact of engine operating parameters, load, rpm, spark timing, and equivalence ratio, on formaldehyde emissions is also evaluated. [S0742-4795(00)01004-8]

Methods to analyze, improve, and optimize thermal energy systems have to take into account not only energy (exergy) consumption and economic resources, but also pollution and degradation of the environment. The term “environomics” implies a method that takes thermodynamic, economic, and environmental aspects systematically into consideration for the analysis and optimization of energy systems. For optimization of energy systems, the environmental aspects are quantified and introduced into the objective function. In this particular work, the environomic approach is followed for the analysis and optimal design of a combined-cycle plant. In addition to the basic configuration, two alternatives for NO x abatement are studied: Selective Catalytic Reduction (SCR) and steam injection. The optimization problem is solved for each configuration, and the results are compared with each other. The effect of the unit pollution penalties and of the limits imposed by regulations is studied. Some general conclusions are drawn.

High generating efficiency has compelling economic and environmental benefits for electric power plants. There are particular incentives to develop more efficient and cleaner coal-fired power plants in order to permit use of the world’s most abundant and secure energy source. This paper presents a newly conceived power plant design, the Dual Brayton Cycle Gas Turbine PFBC, that yields 45 percent net generating efficiency and fires on a wide range of fuels with minimum pollution, of which coal is a particularly intriguing target for its first application. The DBC-GT design allows power plants based on the state-of-the-art PFBC technology to achieve substantially higher generating efficiencies, while simultaneously providing modern gas turbine and related heat exchanger technologies access to the large coal power generation market.

Consideration of a hydrogen based economy is attractive because it allows energy to be transported and stored at high densities and then transformed into useful work in pollution-free turbine or fuel cell conversion systems. Through its New Energy and Industrial Technology Development Organization (NEDO) the Japanese government is sponsoring the World Energy Network (WE-NET) Program. The program is a 28-year global effort to define and implement technologies needed for a hydrogen-based energy system. A critical part of this effort is the development of a hydrogen-fueled combustion turbine system to efficiently convert the chemical energy stored in hydrogen to electricity when the hydrogen is combusted with pure oxygen. The full-scale demonstration will be a greenfield power plant located seaside. Hydrogen will be delivered to the site as a cryogenic liquid, and its cryogenic energy will be used to power an air liquefaction unit to produce pure oxygen. To meet the NEDO plant thermal cycle requirement of a minimum of 70.9 percent, low heating value (LHV), a variety of possible cycle configurations and working fluids have been investigated. This paper reports on the selection of the best cycle (a Rankine cycle), and the two levels of technology needed to support a near-term plant and a long-term plant. The combustion of pure hydrogen with pure hydrogen with pure oxygen results only in steam, thereby allowing for a direct-fired Rankine steam cycle. A near-term plant would require only development to support the design of an advanced high pressure steam turbine and an advanced intermediate pressure steam turbine.

The ongoing Japanese Ceramic Gas Turbine (CGT) project, as a part of the New Sunshine Project funded by the Ministry of International Trade and Industry (MITI), aims to achieve higher efficiency, lower pollutant emission, and multifuel capability for small to medium sized gas turbine engines to be used in cogeneration systems. The final target of this project is to achieve a thermal efficiency over 42 percent at a turbine inlet temperature (TIT) of 1350°C. Under this project, Kawasaki Heavy Industries (KHI) is developing the CGT302 (a regenerative twin-spool CGT). The CGT302 has several unique features: simple-shaped ceramic components, KHI’s original binding system for turbine nozzle segments, stress-free structure using ceramic springs and rings, etc. In addition to these features, a high turbine tip speed and a metal plate fin recuperator were adopted. At the end of the fiscal year 1994, an intermediate appraisal was carried out, and the CGT302 was recognized to have successfully achieved its target. The CGT302 endurance test at the intermediate stage required 20 hours’ operation of the basic ceramic engine. The actual testing accomplished 40 hours at over 1200°C TIT, which included 30 hours of operation without disassembling. The target thermal efficiency of 30 percent at 1200°C has almost been reached, 29.2 percent having been achieved. In 1995 the CGT302 successfully recorded 33.1 percent at 1190°C of TIT with no trouble. We will introduce the current status of R&D of the CGT302 and its unique features in this paper.