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The main problem related to thermal energy is that the thermal energy must be used directly and immediately as generated. For example, the thermal energy of solid waste combustion can be directly utilized for power generation. However, studied of thermal energy storage technology is still placed on the second opinion on waste to heat energy. The heat can be stored using a simple or mobilized system which can store thermal energy and can be brought to somewhere it is needed, for example on domestic heating or drying usage. This article studied and evaluated a micro thermal energy storage system from household waste combustion into a warm water that is great for washing clothes, dishes, shower, and other purposes of household needs. System considered was a simple manner and water is used as the heat energy storage medium. In this study, the equations for initial parameter calculation were presented theoretically based on thermodynamic principle. This paper is hopefully beneficial to the researchers and engineers for preliminary design and development of a heat storage systems technology.

In this study, we characterized a variety of light-absorbing carbonaceous aerosols generated from a controlled combustion system using two different photoacoustic measurement techniques: the RGB-DP...

It is shown that the modernization of boilers for a low-temperature vortex (LTV) technology of coal combustion can provide a comprehensive increase in their energetic and environmental performance characteristics and the efficiency of ash collectors. Specific emissions of heavy metals with ash particles carried into the atmosphere per unit of generated energy in a boiler unit with a low-temperature vortex technology are much lower than those in a boiler with a traditional combustion system.

Using Modelica language, a mathematical model combining static and dynamic contributions of the dense phase region of a 130 t/h biomass circulating fluidized bed boiler combustion system was established on MWorks simulation platform. The mathematical model adopted modular packaging to increase the universality of the model, and it used an implicit, high-order, and multi-step Dassl integration algorithm to conduct the simulation. Under the design condition parameters, the relative error between the bed temperature of the dense phase region obtained by the simulation model and the actual temperature was less than 3.8%, which indicated that the static characteristics of the established simulation model were accurate. The effects of biomass feed and primary air volume step changes on the bed temperature, oxygen content in the flue gas, height of the dense phase region, and the bed pressure difference in the dense phase region were investigated. Both the biomass feeding and the primary wind step of 10% reduced the temperature, and it was obvious that the primary wind had a greater impact on the bed temperature. Meanwhile, the primary wind had a greater impact on the bed pressure difference than the biomass feeding.

This paper studies the effect of internozzle spacing on the lean blow-off of a linear combustor array. The combustor’s lean operability limit did not have a monotonic relationship with internozzle ...

A novel combustion system, consisting of moving fuel-lean nozzles from the arches to the front/rear walls, rearranging staged air, and introducing separated over-fire air (SOFA), has been proposed and successfully applied in a 600 MWe Foster Wheeler down-fired boilers to reduce high NOx emissions while limiting the carbon content in the fly ash. This study comprehensively evaluates the effect of SOFA angles on flow, combustion characteristics and NOx emissions for the novel combustion system by numerical simulation and in-situ experiment. The numerical simulation shows in acceptable consistence with the in-situ experiment. The simulated results show that significant NOx reduction is obtained for all five SOFA angles compared to the original combustion system. O2 and CO concentrations at the furnace outlet, as well as the carbon content in the fly ash decrease significantly with increasing SOFA angle from 0° to 40°. NOx emissions increase slightly and the average temperature at the re-heater entrance changes slightly with the increase of SOFA angle from 0° to 30°. However, with further increasing SOFA angle from 30° to 40°, NOx emissions increase substantially due to the smaller reducing region below the SOFA and the average temperature at the re-heater entrance falls significantly. Taking combustion, NOx and steam parameters into account, a SOFA angle of 30° is advisable. The actual industrial measurements also show that the steam can achieve the designed values when the SOFA angle is set at 30° instead of 40°. Significant NOx reduction (over 50 %) and good performance are attained after adopting the novel combustion technology of 30 °SOFA angle.

We present the current performance of the in situ radiocarbon (14C) extraction line at the University of Bern with an improved extraction and combustion system. After three major steps of improvement, the extraction of sample CO2gas now takes place inside a platinum crucible, supported by an outer quartz-glass crucible. This setup allows us to operate the line as a closed system for several samples without breaking the vacuum. Measurements of procedural blanks and samples from our reference strewn field, Jiddat al Harasis 073, performed in our system all show a good reproducibility and, for the strewn field samples, consistency with published data. We describe each improvement step in detail, discussing the advantages and disadvantages of all tested setups. By sharing our knowledge, we aim to inform and prevent others from making the same or similar detours in establishing14C extraction systems for extraterrestrial samples.

Air-fuel ratio is an important parameter in high-temperature and high-speed heat-airflow test system. If air-fuel ratio of the system is too low, the fuel cannot be fully burned, which will not only reduce the control performance of the gas temperature, but also increase the pollutant emissions of the combustor. In order to solve this problem, it is necessary to identify the air-fuel ratio of the system, get the prediction model of the air-fuel ratio, and adjust the fuel input according to the prediction value of the air-fuel ratio. In order to realize the accurate identification of the air-fuel ratio of the system, this paper briefly analyses the mathematical model of the air-fuel ratio in high-temperature and high-speed heat-airflow test system, and proposes an identification method of the air-fuel ratio based on support vector machine. On the basis of the experimental data, the air-fuel ratio of the system is identified by using different kernels, i.e. firstly, the experimental scheme is designed, and the fuel mass flow rate, air mass flow rate, gas temperature and actual air-fuel ratio of the system are collected under different experimental conditions; then, the collected data are divided into training datasets and test datasets, and the training datasets are trained by support vector machine to obtain identification model of the air-fuel ratio; finally, the identification model is validated with test datasets under different conditions, and the accuracy of the model is obtained. The identification results show that the support vector machine has good identification performance and can accurately approximate the actual dynamic process of the air-fuel ratio. The average absolute error of the identification model is less than 0.05, and the average relative error is less than 0.5% when the test datasets are smaller than the training datasets.

CCS (Carbon Dioxide Capture and Storage) is one of the technologies able to adequately displace CO2 from fossil fuel fired power plants and the only technology capable of reducing large-scale emissions. In particular, coal emits a lot of CO2, although it is an important energy resource in terms of energy security. To address this situation, IHI had developed oxyfuel combustion technology to capture CO2 from coal-fired power plants, and the demonstration using a 30MWe unit in Australia was successfully carried out. In order to commercialize the technology widely, how to configure the primary gas system is one of the important examination items. When adding oxygen into the primary gas system, depending on the type of mill, pulverized coal deposited in the mill may ignite spontaneously. To investigate the spontaneous combustion characteristics of the deposited pulverized coal under oxyfuel conditions, therefore, laboratory-scale experiments were carried out. The pulverized coal was deposited in a 100mm square mesh box, and it was installed in a thermostatic chamber. Then the mixed gas of N2/O2 or CO2/O2 was introduced into the chamber, and the temperature in the coal sample was measured. From the results, there was little temperature difference at which spontaneous combustion occurred between N2/O2 and CO2/O2 atmosphere, while there was a tendency that it might be relatively hard to occur under CO2/O2 atmosphere. The results also showed a tendency that the influence of temperature was stronger than the oxygen concentration.

This work was predicated on the design and costing of a packed column absorber required to remove SO2 from an air/SO2 mixture. The absorber is intended to be developed into an already existing combustion system as a retrofit. The gas flow rate basis of the computation was 40,000Kg/h. The Onda Method was used to estimate the column height as 9m and the column diameter as 2.5m while the column wall thickness as well as the domed head thickness was found to be 9mm using the BS 5500 Standard Method. In order to limit expenses, H2O was utilized as the absorber solvent and a flow rate of 29.5Kg/s to limit solvent usage. A pressure drop of 20mmH2O/m was assumed in the design with metal pall rings of diameter 51mm and surface area of 102m2/m3 chosen as the packing material. The study estimated a profound $306,559.87 as the cost of the absorber required to remove 95% SO2 content from the combustion waste stream.

This study had developed a combustion experiment system for a cool flame research in microgravity environment. For the development of the system, various combustion experiment devices used on the ISS were reviewed, and the shape, size, thickness, and material of the combustion chamber were designed by the standard requirements based on the Korea Standard (KS) and Japan Industrial Standard (JIS). The system was loaded on a reduced-gravity aircraft (so-called, parabolic flight campaign) at Zero-G Corporation in the United States for the cool flame experiment. For the experiment in the aircraft which simulated microgravity environment, structural analysis of a combustion chamber under the condition of pressurized and depressurized cases using a finite elements method was carried out. Furthermore, the factor of safety for the combustion system in the aircraft where hyper-gravity (9G) occurred was calculated. It was confirmed that the system was structurally safe for parabolic flight experiment under microgravity.

This paper presents an experimental study carried out in an industrial furnace for frits production using different configurations of burners based on different combustion techniques such as enriched air combustion, flat-flame oxy-combustion and preheater air combustion. The residence time of combustion gases inside the furnace also was modified. Several combustion configurations were tested and its effects on productivity and thermal energy specific consumption and efficiency were determined. The results show that higher residence time of the combustion gases can decrease significantly the specific consumption of fuel, while the change of the burners and combustion techniques did not show significant effects on decreasing the energy consumption. However, it is highlighted that the oxy-combustion flat-flame burners produced the lowest specific consumption of fuel. Even though the experiments were conducted in a furnace for frit production, the corresponding results can also be applied to guide or improve other industrial high temperature processes. Resumen En este trabajo se presenta un estudio experimental realizado en un horno industrial para la producción de fritas utilizando diferentes configuraciones de quemadores con diferentes técnicas de combustión, con aire enriquecido, oxicombustión de llama plana y aire precalentado. También se modificó el tiempo de permanencia de los gases de combustión en el horno. Se determinó el efecto en la productividad, el consumo específico y la eficiencia utilizando las diferentes configuraciones y técnicas de combustión. Los resultados muestran que un mayor tiempo de residencia de los gases de combustión disminuye el consumo específico de combustible, mientras que el cambio de quemadores y técnicas de combustión no mostró efectos significativos en el consumo de energía. Sin embargo, los quemadores de llama plana de oxi-combustión produjeron el menor consumo específico de combustible. Los resultados obtenidos también se pueden aplicar para guiar o mejorar otros procesos industriales de alta temperatura.

This paper presents a new computational fluid dynamics (CFD) approach for the assessment of NOx emission. The methodology is validated against the experimental data of a heavy-duty gas turbine annular combustor. Since the NOx formation involves time scales that are different from the fuel oxidation time, this work defines the transport equation source terms for NOx basis on a dedicated NOx-Damköhler number. The latter parameter allows to properly distinguish the “in-flame” contribution from the “postflame” one. While the former is a mix of several mechanisms (prompt, N2O-pathway, thermal), the latter is dominated by the thermal contribution. The validation phase is developed in a large-eddy simulation (LES) framework where the extended turbulent flame speed model is implemented to consider the influence of both heat loss and strain rate on the progress variable source term. The accuracy of the model against the most important operability parameters of the combustor is verified. A strong focus on the fuel composition effect onto NOx is presented as well. For any simulated operating condition, the present methodology is able to provide a limited percentage error if compared with the data, considering also different combustion regimes. Leveraging this alignment, the last portion of the paper is dedicated to detailed postprocessing highlighting the role of some key factors on NOx formation. In particular, the focus will be dedicated to the impact of the fuel gas composition and the pilot split.

In systems that involve super-critical liquid fuel combustion, the temperature of the propellants is in the sub-critical state when they are injected into the combustion chamber. However, during the process of combustion, the system experiences a shift in its state of thermodynamics from subcritical to supercritical. The present study predicts the ignition behavior for super-critical liquid fuel combustion through the techniques of computational fluid dynamics (CFD). Simulations are carried out for a single shear coaxial injector’s test case of the combustion chamber. For super-critical combustion, the present research uses kerosene as a fuel and gaseous oxygen as the oxidizer. Simulations are carried out at a steady state for various values of rich flammability limit (RFL). The real gas model, Soave-Redlich-Kwong (SRK) is used for performing simulations in the present study. On the other hand, for the various values of rich flammability limit (RFL), transient simulations are carried out for ideal gas. It has been observed that the simulations performed for steady-state closely approximate the experimental data in comparison to transient simulations. It is also observed that the inherent stability issues involved in transient simulations emphasize the use of an ideal gas model for its computation.

Industrial gas turbines serve in a variety of markets involving wide ranging duty cycles, fuel types and quality and emission requirements. For the Oil & Gas markets, applications range from mechanical drive, compressor sets and electrical generation that may be located in developed, remote or off-shore areas requiring a backup fuel (usually a liquid fuel). Upstream applications often require the gas turbine to burn a wide Wobbe range of fuels with varying gas compositions. For Power Generation applications, flexibility in operating range and low emissions are usually required. This paper describes Solar’s latest SoLoNOx™ (DLE) combustion system developments for the Titan 250 for both gaseous and liquid fuels with a focus on fuel type and quality, operability and emissions from both rig and engine tests. Several combustion systems will be discussed including gas only, dual fuel and a dual fuel Lean Direct Injection (LDI) system for burning lower quality liquid fuels. Engine tests were performed with blends of reactive gases (propane and butane), inert gas (carbon dioxide) and natural gas covering a wide Wobbe range from 30 to 60 WI (MJ/Nm3). Full engine qualification testing was performed which included operability, emissions and combustion stability for both the gas only and LDI combustion systems. The LDI system is based on the dry low emissions combustion system used for gas operation and thus offers low NOx emissions on gaseous fuels with the ability to burn lower quality liquid fuels for backup operation. A dual fuel lean premixed combustion system was also fully engine qualified for natural gas and liquid fuel. High pressure single injector rig tests using hydrogen blends with pipeline quality natural gas were also performed to qualify these fuels for engine operation in the dry low emission combustion systems with up to 30% hydrogen. The primary focus of testing was to determine overall operability, turndown, flashback risk and emissions.

This paper presents a new CFD approach for the assessment of the NOx emission. The methodology is validated against the experimental data of a heavy-duty gas turbine annular combustor. Since the NOx formation involves time scales that are different from the fuel oxidation time, the present work defines the transport equation source terms for NOx on the basis of a dedicate NOx-Damköhler number. The latter parameter allows to properly distinguish the “in-flame” contribution from the “post-flame” one. While the former is a mix of several mechanisms (prompt, N2O-pathway thermal), the latter is dominated by the thermal contribution. The validation phase is developed in a Large-Eddy Simulation (LES) framework where the Extended Turbulent Flame Speed model is implemented to consider the influence of both heat loss and strain rate on the progress variable source term. The accuracy of the model against the most important operability parameters of the combustor is verified. A strong focus on the fuel composition effect onto NOx is presented as well. For any simulated operating condition, the present methodology is able to provide a limited percentage error if compared with the data, considering also different combustion regimes. Leveraging this alignment, the last portion of the paper is dedicated to a detailed post processing highlighting the role of some key factors on to NOx formation. In particular, the focus will be dedicated to the impact of the fuel gas composition and the pilot split.

Enabled by national commercialization of massive shale resources, Gas Turbines continue to be the backbone of power generation in the US. With the ever-increasing demand on efficiency, GT combustion sections have evolved to include shorter combustion lengths and multiple axial staging of the fuel, while at the same time operating at ever increasing temperatures. This paper presents the results of very detailed Large Eddy Simulations of one (or two) combustor can(s) for a 7HA GE Gas Turbine Engine over a range of operating parameters. The model of the simulated combustor can(s) includes (include) all the details of the combustor from compressor diffuser to the end of the stationary part of the first stage of the turbine. It includes the geometries of multiple pre-mixers within the combustion can(s) and the complete design features for axial fuel staging. All simulations in this work are performed using the CharLES flow solver developed by Cascade Technologies. CharLES is a suite of massively parallel CFD tools designed specifically for multiphysics LES in high-fidelity engineering applications. Thermo acoustic results from LES were validated first in the physical GE lab and then in full-engine testing. Both the trend as well as the predicted amplitudes for the excited axial dominant combustion mode matched the data produced in the lab and in the engine. The simulations also revealed insight into the ingestion of hot gases by different hardware pieces that may occur when machine operates under medium to high combustion dynamics amplitudes. This insight then informed the subsequent design changes which were made to the existing hardware to mitigate the problems encountered.

This work highlighted the prediction of the emission rates of the products of combustion using a fuel oil of specific gravity of 0.9. The two reaction pathways of complete combustion and incomplete combustion were used differently to ascertain the emission rates. Ultimate analysis were conducted on the fuel oil to show the percentage composition of elements using ASTM 3178 method for carbon and hydrogen, Kjedahl method for nitrogen, ASTM D1552 for sulphur and the differences used to compute that of oxygen. The estimated percentages of the various elements were the stoichiometrically used to compute the emissions rates at standard conditions. The basis of the computation was a fuel oil flow rate of 10Tonnes/h and the following emission rates were predicted for the complete combustion reaction pathway: 31,246Kg/h for CO2, 65Kg/h for H2O, 158Kg/h for NO2 and 20Kg/h for SO2 while 9,940Kg/h for CO2, 15,623Kg/h for CO, 11,700Kg/h for H2O, 11Kg/h for H2S and 158Kg/h for NO2 were predicted for the incomplete combustion pathway. The study noted that this predictive path should be taken where effective devices or logistics are not in place to measure emissions from combustion systems.

In this paper, we present a modification of the fast phasor extremum-seeking control for the fast optimization of a class of Wiener-Hammerstein nonlinear dynamical systems. The proposed technique provides a significant improvement of the closed-loop system's performance. This study introduces a new adaptive amplitude technique that is used to adaptively adjust the perturbation amplitude to a small predetermined value in a neighbourhood of the system's unknown optimal equilibrium. An analysis of the system demonstrates that semi-global practical stability analysis of the overall system to the unknown optimum is achieved. The effectiveness of the proposed approach is illustrated using numerical examples. The approach is also implemented for the optimal operation of a lean burn combustion system.

This paper focuses on the description, function and working principles of the wet gas scrubber required to control air pollution emissions from a combustion system of a boiler. Important points to note in the selection and operation of the scrubber as well as the different types of scrubbers commonly deployed in the industries to cut down on emissions were addressed. A comprehensive reviews of the removal mechanisms and schemes of the scrubber were reported for various research on the subject. The packed tower scrubber, however, was recommended because of varying advantages and ease of operations.

The average burning velocities S¯b of premixed, spherically expanding iso-octane flames are reported for flame radii from 0.75 to 1.75 cm between 400 and 900 K, near 1 atm. Measurements are perform...

Within the next thirty years the evolutionary approach to aero engine development will struggle to keep abreast with increasingly stringent environmental targets. Therefore radical approaches to aero-engine development in terms of energy savings need to be considered. One particular concept involves the inclusion of a pressure-rise combustion system, within the architecture of an aero-engine, to provide additional shaft power. The nutating disc engine concept is a strong contender due to its power density. The feasibility of the nutating disc engine has been previously investigated for unmanned vehicle applications. However, this paper investigates the performance benefits of incorporating a nutating disc core in a larger geared open rotor engine for a potential entry in to service in 2050. In addition, a methodology is presented to estimate the size and weight of the nutating disc core. This methodology is pivotal in determining the overall performance of the novel aero-engine cycle. The outcome of this study predicts a potential 9.4% fuel burn benefit, over a state of the art geared open rotor in the year 2050. In addition, the sensitivity of the nutating disc design variables highlights the possible fuel burn benefits compared against a comparable year-2000 aircraft mission.

The prediction of thermo-acoustic instabilities is of paramount importance for gas-turbine combustion systems to meet the emission and efficiency targets. To predict the frequencies and amplitudes ...

A new combustion system, which consists of an evaporator and a tubular flame burner with multi-stage inlets, has been developed to meet the growing concerns over the fuel flexibility and flame stab...

The synergistic removal of mercury by injecting activated carbon between the selective catalytic reduction (SCR) and fabric filter (FF) as well as some influencing factors were investigated in a pi...

This paper provides the methodology to achieve pseudo 1-D combustion system of specific polymeric materials without any complex physical effect (e.g., deformation, bubble bursting etc.) by adopting a low pressure technique with a fuel-layered approach. The adopted pressure level in this study is as low as 20 kPa and the size of the specimen is sub-millimeter scale. By utilizing pressure modeling to keep the Grashof number small, the gravity effect is relatively minimized at low pressure to mimic an ideal 1-D combustion process. A molten PMMA layer formed over a ceramic ball (suspended by thin SiC fiber) was used as the burning specimen to fulfil the purpose of this study. Results show that a spherical flame without any apparent bubble bursting is successfully achieved during the entire burning event when the pressure is sufficiently lower (~ 20 kPa) for both 20% and 30% ambient oxygen concentration. A well-known d-square law and pseudo steady burning process is confirmed at the post-ignition stage. Direct comparison of burning rate, K, between what was obtained in this study and that obtained under microgravity ensures that the present methodology is effective to simulate an ideal 1-D combustion system, just like one that can be achieved in microgravity, without the need for microgravity facilities.

The quest to achieve higher muzzle velocity is one of the key goals for researchers in the fields of propulsion and ballistic. Based on the conventional chemical propulsion, the two-stage combustion system as a new launch principle can provide higher muzzle velocity without exceeding the maximum pressure in the chamber. In this paper, the modified two-fluid model with two moving boundaries is proposed to simulate the detailed multi-dimensional flow and energy conversion behaviors of the combustion gas and propellant grains in the two-stage chamber. The dynamic self-adapting mesh update method is developed to expand and merge the computational domain for both projectile and piston motions. The application to a standard virtual gun as a standard benchmark for interior ballistic codes is used to validate the accuracy and reliability. The calculation results are in good agreement with those of codes in different countries. After that, a two-stage chamber system is set up based on the standard virtual gun. The numerical results present deep understanding of the two-phase flow behaviors in the two-stage chamber. Then the effects of design parameters on the performances in the additional chamber are numerically investigated. Finally, a suggested scheme of the additional chamber is proposed. The findings of the study put a further prediction tool for the understanding and design of the two-stage combustion system with moving boundaries.

Three formulations of quasi-two-dimensional flamelet (Q2DF) models are derived from the two-dimensional flamelet formulation on the basis of assumptions regarding the third stream (diluent), and these models are validated by means of a two-dimensional direct numerical simulation (DNS) of a three-feed non-premixed combustion system into which the diluent is injected as the third stream. DNS combined with the Arrhenius formation (ARF) together with a detailed mechanism is also performed as a reference case and compared with the present models. The characteristics of the flamelets in three-feed non-premixed combustion are discussed in detail for ARF in terms of the three mixture fractions, temperature, and major and minor species. Some discrepancies appeared between the ARF and the Q2DF models. The difference in the cross-scalar dissipation rates between Q2DF and the two-dimensional flamelet model is considered the major reason for the deviations. The cross-scalar dissipation rates for the reactor streams an...

Combustion-based micro-power generation is a serious candidate for substitution of traditional batteries. As the volume of combustion system decreases to small-scale combustors, ignition and combustion stability are becoming considerable challenges due to short residence time and large heat loss. To overcome these shortages, several experimental investigations have been implemented to generate micro-power using both moving (micro-turbines) and non-moving (thermophotovoltaic) systems. Although the goal of both systems is to generate micro-power via combustion phenomenon, the approaches to the goal is different. Nevertheless, combustion instability and various shortages in burner and combustor have been noticed by several researchers regardless of the micro-power generation method. In this paper, a review about recent development in application of small-scale combustion in micro-power generation and micro-thruster systems using micro-turbine and thermophotovoltaic systems is presented. The special focus of this paper is on flame regimes, fuel/oxidizer mixing, flame stability conditions, heat recirculation, non-equilibrium transport, flame-wall thermal and kinetic couplings, and improvement of energy conversion efficiency.

In this work, the ignition and combustion characteristics of mixed rice straw and sewage sludge pellets in air atmosphere were investigated using a plasma combustion system. One common pellet shape (solid spherical pellet) and another new shape (hollow spherical) are used in this study. High-speed camera was used to record and observe ignition and combustion process of pellets. In case of hollow pellets, the shape and distribution of flame are found to be better compared to solid pellets. Also, it is clear that the values of volatile combustion times in case of hollow pellets are low compared to solid pellets. The overall heat transfer enhanced in case of hollow pellet due to the large area subjected to hot gases and the high surface to volume ratio. Hollow pellet consumed less time for internal ignition and volatiles char combustion compared to solid pellet. Volatiles and char combustion lasted for 63.05 and 61 s, respectively for hollow pellet while these values were found to be 72.8 and 83 s, respectively for solid pellet.

TMG (TOYOTA Motorsport GmbH) and FEV have jointly conducted a concept study on environmentally friendly engine with indicated thermal efficiency (ɳinet) of 46% and low emissions while fulfilling high-performance criteria i.e. specific power of 103 kW/l and low end torque (LET) of 2.3 MPa BMEP at 2000rpm. An ultra lean-burn combustion concept has been designed by means of 1D and 3D MBD (Model Base Development) methods and subsequently validated experimentally by a single cylinder TC GDI engine as a technology demonstrator in order to fulfill the requirements of both environmental sustainability and fun to drive in passenger cars.

Searching for further reduction of fuel consumption simultaneously with the reduction of toxic compounds emission new systems for lean-mixture combustion for SI engines are being discussed by many manufacturers. Within the European GasOn-Project (Gas Only Internal Combustion Engines) the two-stage combustion and Turbulent Jet Ignition concept for CNG-fuelled high speed engine has been proposed and thoroughly investigated where the reduction of gas consumption and increasing of engine efficiency together with the reduction of emission, especially CO2 was expected. In the investigated cases the lean-burn combustion process was conducted with selection of the most effective pre-combustion chamber. The experimental investigations have been performed on single-cylinder AVL5804 research engine, which has been modified to SI and CNG fuelling. For the analysis of the thermodynamic, operational and emission indexes very advanced equipment has been applied. Based on the measuring results achieved for different pre-chamber config-urations the extended methodology of polioptimization by pre-chamber selection and the shape of main chamber in the piston crown for proposed combustion system has been described and discussed. The results of the three versions of the optimization methods have been comparatively summarized in conclusions.