CO2 Mass Fraction Research Articles

Effects of hydrogen-rich products from methanol steam reforming on the performance enhancement of a medium-speed marine engine

In order to improve the heat utilization of exhaust gas from the small and medium-sized ships without exhaust boilers, a methanol steam reforming (MSR) is proposed in the study. The combustion model of marine engine blended hydrogen-rich reforming gas was developed, and verified in terms of cylinder pressure, BSFC, and NO emissions. The compositions of reforming gas were obtained by the MSR model and employed to investigate the effect of reforming gas at different blending ratios on the combustion and emission characteristics of the marine diesel engine in the AVL-Fire environment. The results obtained show that the performance, emission, and economic characteristics are improved due to the existence of reforming gas. Specifically, the indicated power is decreased by 0.5%–4.26% and the NO mass fraction is reduced by 2.95%–18.25% at different loads, but the CO mass fractions increased by 20.21%–54.73%. Similarly, the NOx weighted emission is reduced by 34.10%, which is close to the NOx emission limit of Tier II, but the CO weighted emission is increased by 30.89%. In addition, the equivalent fuel consumption rate is reduced by 0.45%–3.59% at the maximum blending ratio, and the converted fuel cost is reduced by 6%–10% at medium and high loads. Finally, based on the comprehensive performance analysis, the optimized blending ratio at each load is obtained as follows: Rg7.5 or Rg12.5 for 100% load, Rg10 for 75% load, Rg7.5 for 50% load, and Rg2.5 for 25% load. Thus, the MSR reaction is feasible to improve the energy efficiency and reduce NOx emission of the marine engine.

Measurements and correlation of hydraulic resistance for H2O/CO2 mixtures at supercritical pressure

Hydraulic resistance of H2O/CO2 mixtures for supercritical conditions, typical for a promising power generation system, has been a knowledge gap. In this work, it was experimentally investigated in a high-temperature, high-pressure, and multi-function apparatus and was further correlated. For the experimental conditions, the CO2 mass fractions were 10, 15, and 18.5%, the pressure was 24 MPa, the temperatures were 300–430℃, and the mass fluxes were 900–1500 kg m−2s−1. Results show that the friction factor curve for supercritical H2O/CO2 mixtures features a pit near the pseudo-critical point, which is more significant and wider compared to supercritical pure water. This is caused by crossing two-phase region and distinct thermophysical property variation with the temperature. Based on these understandings, a new friction factor correlation with a root mean square error as low as 7.9% was developed for supercritical H2O/CO2 mixtures. The friction factor of the supercritical pure water was used as the basis and two correction factors were used to interpret the two-phase effect and the thermophysical property variations.

Investigation of piston bowl geometry, injection timing, and EGR mass fraction to improve the performance of ISM 370 diesel engine

In addition to the high price of clean fuels such as hydrogen and bio-propane, redesigning a diesel engine for clean fuels can be a costly task. It seems an affordable option is to improve the baseline engine specifications by slight changes in the injection strategy or piston bowl shape. In this paper, the emission and combustion characteristics of the ISM 370 heavy-duty diesel engine were numerically investigated by evaluating three distinct piston bowls (P1, P2, and P3), different injection timings, and an exhaust gas recirculation (EGR) system. After that, the outcomes were compared with previous works related to the use of clean fuels in the ISM 370 engine. The simulation was performed at 1200 rpm engine speed and full load state. The rate of heat released and the mean in-cylinder pressure results were compared with experimental data and an appropriate accord was obtained. The results showed that the best injection timing considering a balanced state between the emission and combustion characteristics was determined 2 deg before the top dead center (BTDC). The same carbon dioxide (CO2) mass fraction was predicted for all considered piston bowls at almost the exhaust valve opened. P2 had better thermal efficiency and internal power by around 12% and the same nitrogen monoxide (NO) emissions as well as lesser soot emission by 10.5% compared to P1. A more complete combustion reaction was detected for the engine equipped with P2 led to reducing the CO mass fraction by 20% compared to P1. In addition, a 10% EGR mass fraction reduced the NO by 37% and increased the CO2 by 6.4%. It was found that the use of P2 had better peak pressure compared to the use of methanol fuel by 20.9% and was competitive with dimethyl ether fuel at almost equal peak pressure and 30% lesser soot emission.

Impact of Multi-Component Surrogates on the Performances, Pollutants, and Exergy of IC Engines.

Even though there is a pressing interest in clean energy sources, compression ignition (CI) engines, also called diesel engines, will remain of great importance for transportation sectors as well as for power generation in stationary applications in the foreseeable future. In order to promote applications dealing with complex diesel alternative fuels by facilitating their integration in numerical simulation, this paper targets three objectives. First, generate novel diesel fuel surrogates with more than one component. Here, five surrogates are generated using an advanced chemistry solver and are compared against three mechanisms from the literature. Second, validate the suggested reaction mechanisms (RMs) with experimental data. For this purpose, an engine configuration, which features a reacting spray flow evolving in a direct-injection (DI), single-cylinder, and four-stroke motor, is used. The RNG k-Epsilon coupled to power-law combustion models is applied to describe the complex in-cylinder turbulent reacting flow, while the hybrid Eulerian-Lagrangian Kelvin Helmholtz-Rayleigh Taylor (KH-RT) spray model is employed to capture the spray breakup. Third, highlight the impact of these surrogate fuels on the combustion properties along with the exergy of the engine. The results include distribution of temperature, pressure, heat release rate (HRR), vapor penetration length, and exergy efficiency. The effect of the surrogates on pollutant formation (, , ) is also highlighted. The fifth surrogate showed 47% exergy efficiency. The fourth surrogate agreed well with the maximum experimental pressure, which equaled 85 Mpa. The first, second, and third surrogates registered 400, 316, and 276 g/kg fuel, respectively, of the total CO mass fraction at the outlet. These quantities were relatively higher compared to the fourth and fifth RMs.

Numerical investigation of the hydrogen swirl combustion flow in a micro gas turbine burner

The influence of swirl angle and hydrogen mixing ratio on the performance of micro gas turbine combustor is discussed by numerical simulation based on computational fluid dynamics (CFD) method, the parameters such as combustion characteristics and pollutant emissions are analyzed. The realizable k-epsilon model is adopted for turbulence simulation, the combustion model is general finite rate model. The results indicated that increasing swirl number reduces the temperature and NO emission. As hydrogen content in the fuel increases, flame length is slightly shortened, temperature in the combustion chamber rises, and temperature distribution becomes more uniform, NO emission at central axis becomes highly, while CO2 and CO emissions decrease. When hydrogen mixing ratio is 50%, the maximum NO emission is about 3 times that of pure methane combustion, and CO2 mass fraction is reduced by 43.9%, moreover, outlet CO emission is reduced by nearly 70%. The hydrogen mixing ratio has a greater impact on pollutant emissions, the sensitivity level of NO and CO emissions to hydrogen mixing ratio reaches 0.25 and 0.39 respectively. As hydrogen mixing ratio and swirl number increases, pressure loss grows, and average turbulent kinetic energy on central plane gradually rises, mainly in outlet region and recirculation zone. Increasing swirl number makes the synergy better, but hydrogen mixing has little effect on the synergy distribution.

Study of increasing thermodynamic efficiency and hydrogen amount in the process of solid fuels and biomass gasification

The effect of fuel composition such as hard coal and biomass in fluidized bed on the thermodynamic efficiency of three gasifier types, low heating value (LHV) and syngas composition was studied by simulation in CFD program. The paper presents various small gasification systems with fluidized bed of water-coal mixture and water-biomass mixture both with oxygen (air) and without oxygen. The work presents the extended mathematical model of gasification process taking into account also 13 kinetic chemical reactions enabled to apply them in CFD program. The chemical model is based on surface reactions given in the model of Equivalent Reactor Network (ERN) in Ansys Energetico. Simulation of gasification of different reactor designs enabled to obtain the mass concentration of chemical compounds in the syngas which influenced on thermodynamic efficiency and LHV. Additionally, heating of the gasifier walls by electrical system without air gives higher mass ratio of hydrogen (15%) and carbon monoxide (75%) in the syngas than in the oxidized gasification system. The simulation tests showed high thermodynamic efficiency, taking into account the exergy above 80%, both for the oxygen gasification of hard coal-slurry and biomass as well as for the externally heated gasifier without the supply of oxygen. The highest thermodynamic efficiency 90.5% was obtained during gasification of energy willow in the oxidation reactor due to the large difference in LHV of syngas and fuel. Obtaining the maximum possible mass ratio of H2 in syngas and a high thermal efficiency for the OXGR system from the gasification of subbituminous coal dust occurs at a ratio C/O2 = 0.314 and at almost stoichiometric ratio of C/H2O = 0.63. In the case of gasification of biomass in the form of finely ground energy willow in the OXGR system, these ratios were respectively: O2/C = 1.82 and C/H2O = 0.47. While maintaining the almost stoichiometric ratio C/H2O = 0.75, resulting from the water-gas shift reaction, low heating value of the syngas for the analysed gasification systems was over 25 MJ/kg. The paper shows comparison of mass fractions of CO, H2, H2O, H2S, CO2, O2, CH4, tar and other chemical compounds in the syngas. Application of the gasification reactor with external heated walls and without oxygen inflow produces the syngas without tar and volatile species in comparison to the systems with additional oxygen supply. In oxidized reactors the syngas contains a large amount of CO2 about 25–30% of total mass.

Study on the Flame Acceleration and Transition from Deflagration to Detonation of N2O/C2H4/CO2

AbstractThe application of nitrous oxide (N2O) as a candidate oxidant provides new opportunities for green propellants and propulsion systems. In this study, flame propagation, acceleration, and transition to detonation characteristics of stoichiometric N2O/C2H4 diluted with CO2 were investigated in 2 m cylindrical channels at 1 atm and 293 K. The flame propagation and acceleration were monitored by a high‐speed video. Pressure transducers were located at different positions along the channel to collect data concerning DDT and detonation development. The influence rules of various mass fractions of CO2 on the above performance were evaluated. The results indicated that the process of flame propagation for N2O/C2H4 was divided into three stages, ignition stage, DDT and detonation stage. Both the process of flame acceleration (FA) and peak overpressure for all the test mixtures decreased with an increase of CO2 concentration in the initial stage, and detonation wave propagation was stabilized with the increase of CO2, then the corresponding propagation velocity was close to the C−J velocity.

Fundamental Study of CH4-Air Combustion Under an Axisymmetric Small-scale Rectangular Combustor Using Computational Modeling

The optimization of the design and operating conditions of industrial combustors depends on the fundamental study of combustion dynamics and flow behaviors. Complete combustion increases the thermal efficiency as well as reduces the emission significantly. A study of this kind also allows exploring alternative fuels that would increase the combustion efficiency thus the life cycle of the systems. To develop a highly-performed combustion system for rocket engines or power plants, fundamental research under an axisymmetric small-scale combustor is considered in this study. The k-Ɛ (2 Eqn.) and species transport model (STM) are used to study the flow turbulence and combustion behavior, respectively. A Parallel flow injection configuration of fuel and air is considered. In this study, combustion behavior is investigated at a wide range of fuel and air flowrate conditions while keeping the air slot dimension (240 mm) and fuel injection slot diameter (10 mm) constant. The fuel velocity (FV) and air velocity (AV) are changed from 2 m/s to 30 m/s so that a better test matrix could be proposed. At each run, turbulence, the flame temperature, reaction heat release rate, mass fraction of CO2, etc are studied. It is seen that the combustion temperature increases with the increase in fuel injection velocity. The static flame temperature reaches its maximum (2177 K-2287 K) and falls within the standard limits of CH4-Air combustion. The mass fraction of CO2 is found to be within the acceptable limit (0.121-0.153). The heat of the reaction is found to be high at variable Reair and ReCH4 conditions. It is observed that the computational models used in this study are capable of predicting the flow and combustion behaviors accurately.

Effects of Plateau Environment on Combustion and Emission Characteristics of a Plateau High-Pressure Common-Rail Diesel Engine with Different Blending Ratios of Biodiesel

Taking a plateau high-pressure common-rail diesel engine as the research model, a model was established and simulated by AVL FIRE according to the structural parameters of a diesel engine. The combustion and emission characteristics of D, B20, and B50 diesel engines were simulated in the plateau atmospheric environment at 0 m, 1000 m, and 2000 m. The calculation results show that as the altitude increased, the peak in-cylinder pressure and the cumulative heat release of diesel decreased with different blending ratios. When the altitude increased by 1000 m, the cumulative heat release was reduced by about 5%. Furthermore, the emission trend of NO, soot, and CO was to first increase and then decrease. As the altitude increased, the mass fraction of NO emission decreased. As the altitude increased, the mass fractions of soot and CO increased. Additionally, when the altitude was 0 m and 1000 m, the maximum temperature, the mass fraction of OH, and the fuel–air ratio of B20 were higher and more uniform. When the altitude was 2000 m, the maximum temperature, the mass fraction of OH, and the fuel–air ratio of B50 were higher and more uniform. Lastly, as the altitude increased, the maximum combustion temperature of D and B20 decreased, and combustion became more uneven. As the altitude increased, the maximum combustion temperature of B50 increased, and the combustion became more uniform. As the altitude increased, the fuel–air ratio and the mass fractions of OH and NO decreased. When the altitude increased, the soot concentration increased, and the distribution area was larger.

Contents of Nineteen Chemical Elements in Thyroid Benign Nodules and Tissue adjacent to Nodules investigated using X-Ray Fluorescence and Neutron Activation Analysis

Thyroid benign nodules (TBNs) are the most common diseases of this endocrine gland and are common worldwide. The etiology and pathogenesis of TBNs must be considered as multifactorial. The present study was performed to clarify the role of some chemical elements (ChEs) in the etiology of these thyroid disorders. Thyroid tissue levels of Ag, Ca, Cl, Co, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Na, Rb, Sb, Sc, Se, Sr, and Zn were prospectively evaluated in nodular tissue and tissue adjacent to nodules of 79 patients with TBNs. Measurements were performed using X-ray fluorescence and instrumental neutron activation analysis. Results of the study were additionally compared with previously obtained data for the same ChEs in “normal” thyroid tissue. It was observed that mass fractions of Ag, Cl, Co, Cr, Cu, Fe, Hg, Mn, Na, and Sc contents in “nodular” tissue were higher, while Ca and I content was lower in comparison with contents of these ChEs in normal gland. Mass fractions of Ag, Cl, Hg, Na, and Rb in “adjacent” group of samples were approximately 31, 2.7, 32, 1.6, and 1.3 times higher, respectively, than in “normal” thyroid. Contents of Cr, Fe, Sc, and Se were lower, while mass fraction of Hg and I higher in “adjacent” group of samples in comparison with nodular tissue. At that, level of I in “adjacent” group of samples was over 2 times higher than in nodular tissue and almost equals the normal value. This study provides evidence on many ChEs level alteration in nodular and adjacent to nodule tissue and shows the necessity to continue ChEs research of TBNs. The little reduced level of I content in nodular tissue could possibly be explored for differential diagnosis of TBNs and thyroid cancer.

Turbulence Enhancement and Mixing Analysis for Multi-Inlet Vortex Photoreactor for CO2 Reduction

In this article, we describe a prototype photoreactor of which the geometrical configuration was obtained by Genetic Algorithms to maximize the residence time of the reactant gases. A gas reaction mixture of CO2:H2O (1:2 molar ratio) was studied from the fluid dynamic point of view. The two main features of this prototype reactor are the conical shape, which enhances the residence time as compared to a cylindrical shape reference reactor, and the inlet heights and position around the main chamber that enables turbulence and mass transfer control. Turbulence intensity, mixing capability, and residence time attributes for the optimized prototype reactor were calculated with Computational Fluid Dynamics (CFD) software and compared with those from a reference reactor. Turbulence intensity near the envisioned catalytic bed was one percentage point higher in the reference than in the optimized prototype reactor. Finally, the homogeneity of the mixture was guaranteed since both types of reactors had a turbulent regime, but for the prototype the CO2 mass fraction was found to be better distributed.

Modeling and simulation of a turbulent jet diffusion flame of a biodiesel surrogate composed of MD, n-Hept, MC and EtOH

The more properties of biodiesel one wishes to represent, the more complex the surrogate mixture becomes. Often the aim is to represent the H/C and O/C ratios and molecular weight using a small number of pure components. In this article, a turbulent jet diffusion flame of a biodiesel surrogate, composed of 50% Methyl Decanoate, 40% n-heptane, 9% methyl crotonate and 1% ethanol is modeled and simulated. The strategy used is to apply the Directed Relation Graph technique for a first reduction, and Layerless Neural Network to define the main chain and obtain a skeletal mechanism. The results obtained for temperature and mass fractions of CO2, CO and H2O agree reasonably with literature data for a mechanism of 147 reactions and 45 species. The small number of species facilitates the simulation of the coupling between turbulence and chemical kinetics, a desirable feature of reduced mechanisms.

Performances of Transcritical Power Cycles with CO2-Based Mixtures for the Waste Heat Recovery of ICE.

In the waste heat recovery of the internal combustion engine (ICE), the transcritical CO2 power cycle still faces the high operation pressure and difficulty in condensation. To overcome these challenges, CO2 is mixed with organic fluids to form zeotropic mixtures. Thus, in this work, five organic fluids, namely R290, R600a, R600, R601a, and R601, are mixed with CO2. Mixture performance in the waste heat recovery of ICE is evaluated, based on two transcritical power cycles, namely the recuperative cycle and split cycle. The results show that the split cycle always has better performance than the recuperative cycle. Under design conditions, CO2/R290(0.3/0.7) has the best performance in the split cycle. The corresponding net work and cycle efficiency are respectively 21.05 kW and 20.44%. Furthermore, effects of key parameters such as turbine inlet temperature, turbine inlet pressure, and split ratio on the cycle performance are studied. With the increase of turbine inlet temperature, the net works of the recuperative cycle and split cycle firstly increase and then decrease. There exist peak values of net work in both cycles. Meanwhile, the net work of the split cycle firstly increases and then decreases with the increase of the split ratio. Thereafter, with the target of maximizing net work, these key parameters are optimized at different mass fractions of CO2. The optimization results show that CO2/R600 obtains the highest net work of 27.43 kW at the CO2 mass fraction 0.9 in the split cycle.

A comparative study of flame-wall interaction and flame-cooling air interaction

This paper presents a three-dimensional (3D) direct numerical simulation (DNS) study of flame-wall interaction (FWI) and flame-cooling air interaction (FCAI). A preheated, methane/air mixture enters a channel with constant temperature walls, where the top wall is effusion cooled. An imposed vertical hot sheet near the inlet creates two flame branches interacting with the top and bottom walls. The flame is observed to be leaner in the region where it interacts with the effusion cooling jets. In this region, the flame is longer and features reduced CO mass fraction. The fluctuations in the heat release rate (HRR) and CO mass fraction are also relatively small near the top wall. Near the bottom wall, finger-like flame structures are formed due to the interaction of turbulent vortices with the flame surface. These flame structures initially move away from the wall as they propagate further downstream before eventually collapsing at the wall. This leads to the creation of regions of high wall heat flux and CO. While analysis of the CO thermochemical state shows a complex picture near the bottom wall, two-dimensional (2D) manifolds can be identified near the top wall. Therefore, a framework to estimate CO mass fraction due to FCAI based on 1D freely-propagating flame solutions is proposed showing a good agreement with the DNS results.

Numerical analysis of NOX formation in CO2 diluted biogas premixed combustion

A further investigation of premixed biogas combustion towards the NOx formation is presented in this study. The purpose of the simulation is to determine the addition of CO2 in biogas fuel to the combustion behavior of premixed biogas on NOx formation, and to determine the occurrence of NOx in the pre-mixed biogas combustion. In this study, the Counterflow Premixed Flame class is used where this class is based on the One Dim class which is the basis for simulations with a 1-dimensional domain. The Counterflow Premixed Flame class uses an axisymmetric stagnation flow domain which has been written based on the equations. Cantera uses Newton's method to solve them. Completion is carried out in two stages. The first stage is to solve the solution using the equilibrium at each z coordinate point that has been determined. Many estimation starting points are determined from the start of the program. The second stage is the recalculation process at each point and then subdivided to get a smoother solution. The premixed excess CO2 biogas fuel and air combustion analyzed using a 1-dimensional numerical study. The diluted CO2 mass fraction ranged between 0–40 %. The CH4/CO2/air volume flow rate was maintained in ±L/min. The analysis implements the 1-D Counter Flow approach. Two counterflow nozzles were 20mm in diameter and the flame stagnation point at 10 mm. The results show that NOx mass fraction formed only on a fuel-lean mixture of CH4/CO2/air and its values decreased along with CO2 added. The addition of CO2 could reduce the NO species mass fraction down to 18 %, and NO2 reduction down to 7 %. This is mainly caused by a decreasing heat release rate of NO+N↔N2+O, N+O2↔NO+O, N+OH↔NO+H, and N+CO2↔NO+CO reactions. The N+CO2↔NO+CO reaction increased as CO2 was added but its values were not as much as the decline of three other reactions

Fluid-CO2 injection impact in a geothermal reservoir: Evaluation with 3-D reactive transport modeling

Geothermal energy is commonly recognized as an environmentally friendly source of energy. However, geothermal fluids have unusually high CO2 content, particularly, in carbonated geothermal reservoirs. An efficient method to mitigate the CO2 emissions of geothermal power plants is to re-inject the captured CO2 with the effluent fluid to mineralize mainly into calcite under reservoir conditions (e.g., reservoir temperatures ranging from 200 to 220 °C). One of the major concerns about the re-injection of the captured CO2 is to predict the geochemical interaction between the injected fluid-CO2 and rock, and the corresponding alterations that occur due to the re-injection in the reservoir parameters. For this study, we have selected one of the largest geothermal fields, which is located in the western part of Turkey. A predictive 3-D reactive transport modeling is carried out using TOUGHREACT v1.2 for potential fluid-CO2 injection into deep metamorphic formation rocks consisting of marble, quartzite, and schist. Each rock type with different mineral constituents is examined in three different scenarios. Moreover, in each scenario, three annual injection rates, 500, 2000, and 4000 tons of CO2 for ten years of continuous injection are tested. The aims of the study are first the evaluation of the dynamic fluid-rock interactions with maximum possible CO2-charged fluid injection and second the identification of the mineralization process. The modeling results indicate that the maximum CO2-charged fluid mixture remains stable as a single-phase in all scenarios. The mineralization process of CO2 in the reservoir is limited due to the different mineral contents of the considered metamorphic rocks and the differences between the CO2 mass fraction of the injected fluid and the reservoir. In addition, the injected fluid temperature, the pH, the convective dispersive fluxes between the wells also affect the chemical process. These results show differences compared to the CarbFix project carried out in basaltic Icelandic geothermal reservoirs where the CO2 mineralization process was successful.

Conditional moment closure method with tabulated chemistry in adiabatic turbulent nonpremixed jet flames

The conditional moment closure (CMC) method with tabulated chemistry is proposed to reduce the computational load for integration of stiff reaction steps in the conventional CMC methods. It is based on the assumption that temperature and all species except CO and CO2 adjust fast enough so that they can be uniquely determined by the single reaction progress variable given as the sum of CO and CO2 mass fractions. The CMC equations are solved for the conditional reaction progress variable, Qpv, whereas the other species mass fractions and the reaction rates including that for Qpv are retrieved from lookup tables. A steady homogeneous form of the conditional variance and covariance equations are solved to construct the second-order closure table to be consistent with Steady Laminar Flamelet Model (SLFM)-based first-order closure. Good agreement is shown between the results by integrated and tabulated chemistry in both the first-order and the second-order CMC for Sandia Flames D, E and F. The overall computational time is reduced to about 0.5% of that by the conventional CMC method involving integration of the detailed reaction mechanism for all species and temperature.

Increasing the electrical efficiency and thermal management of a photovoltaic module using expanded graphite (EG)/paraffin-beef tallow-coconut oil composite as phase change material

In this study, a new PCM composite of paraffin with beef tallow/coconut oil mixture are used to augment the heat removal from the surface of a PV module. At first, the composite of paraffin-beef tallow/coconut oil (PBTCO) is used as the PCM to thermal regulation of a PV module. The effects of the weight of PCMs (W = 2.1–4.1 kg) on surface temperature and power output of PV module are investigated. In the second step, expanded graphite powders (EG) (X3 = 0.5–10.5 %wt.) are added to PBTCO to augment its thermal conductivity. Response surface methodology is applied to achieve optimal parameters and conditions for the PV/EG-PBTCO system. Measurements show that temperature and output power are as high as 64.02 °C and 4.875 W, respectively, for an uncooled system. The composite of 63.1% paraffin and 36.9% BTCO (mass fraction of BT = 39% and mass fraction of CO = 61%) is the more efficient PCM. In addition, results show that adding EG particles to PBTCO composite has significant added benefits over no using them. The predicted temperature and output power at the optimum point are found to be 32.9 °C and 8.923 W, respectively, at X3 = 9.94 %wt and PCM weight of 3.57 kg.

Simulation of Syngas Addition Effect on Emissions Characteristics, Combustion, and Performance of the Diesel Engine Working under Dual Fuel Mode and Lambda Value of 1.6.

The present work aims to study the combustion characteristics related to syngas-diesel dual-fuel engine operates at lambda value of 1.6 operated by five different replacement ratios (RR) of syngas with diesel, which are (10%, 20%, 30 %, 40 % and 50%). ANSYS Workbench (CFD) was used for simulating the combustion of the syngas-diesel dual-fuel engine. The numerical simulations were carried out on the Ricardo-Hydra diesel engine. The simulation results revealed that the diesel engine’s combustion efficiency was enhanced by increasing the diesel replacement with Syngas fuel. The diesel engine’s combustion efficiency The peak in-cylinder temperature was enhanced from 915.9K to 2790.5K (50% RR). Moreover, the peak pressure was improved from 3659073 Pa to 4525366 pa (23% increase), 4947790 pa (35% increase), 5929709Pa (62% increase) and 6708188 Pa (83%) for diesel fuel mode and dual fuel mode (20%, 30%, 40% and 50%) respectively. Moreover, CO, NO, and CO2 emissions in the engine increased with the increase in syngas’ replacement ratio with diesel. Besides, the emission levels of NO, CO2 and CO from a diesel engine are lower than a dual fuel engine (syngas-diesel). The NO mass fraction values rise from 2.02505E-19 at diesel mode to 0.000834126 (20% RR), 0.004176854 (30% RR), 0.005021933 (40% RR) and 0.007554865 (50% RR). Moreover, the CO2 mass fraction values increase from 5.90944E-07 at diesel mode to 0.033849446 (50% RR).

3D modeling framework and investigation of pollutant formation in a condensing gas boiler

Condensing gas boilers exhibit complex global flow-field patterns, which lead to noteworthy inhomogeneities of the burnt gas temperature distribution and levels of local pollutant formation in the combustion chamber. To enable numerical simulations of realistic heating systems, a modeling framework was developed. Challenges like high computational times and the combined multi-physics aspects that occur in quite complex geometries were addressed. The flamelet progress variable (FPV) model was applied, which tabulates detailed reaction kinetics as a function of progress variable and enthalpy. As the larger timescales of CO and NO formation inhibit a direct lookup of local CO and NO mass fractions from the chemistry table, the so called NOMANI model was utilized for NO and a rescaling model was applied for CO. All models were validated against resolved simulation results and experimental measurements. The multi-hole burner was modeled as a porous medium, because it was computationally unfeasible to resolve each burner hole. While local gas acceleration and preheating was considered, the exact flame structure as well as the recirculation zone behind the flame front could not be represented. To still capture the burnt gas temperature, the missing heat losses from the recirculation zone were modeled and coupled to the conjugate heat transfer (CHT) model. The modeling framework was applied to a commercial condensing gas boiler device at nominal load utilizing a lean methane-air mixture. The simulation shows reasonable agreement with experimentally measured emission levels and critical regions with CO and NOx emissions twice as high as in other regions were identified. Temperature variations of 200 K in the flue gas throughout the combustion chamber and 450 K in the solid region of the multi-hole burner were found. Based on these results, design aspects are correlated to CO and NO formation and suggestions on possible design modifications are discussed to further reduce pollutant emissions of such condensing gas boilers.