Recent studies have shown that adding polymeric additives to hydrocarbon-based fuels can lead to suppression of their splashing behavior, as well as enhance their burning rates. However, there is a lack of objective data on polymeric additives settling times in these fuels. Choosing Dodecane as a representative of diesel-based fuels, present research experimentally investigates the settling behavior of polymeric additives (graphene) when mixed in with Dodecane, and the effects of various surfactants on such behavior. Methodology for experimental setup, data collection and data analysis is presented. Various concentrations of additives and surfactants are analyzed, and trends for settling times are shown.

Journal bearings of high torque diesel engines are used to cater for high combustion loads which are applied intermittently. A lubrication layer is provided between journal (crankshaft) and bearing to avoid contact between them. The relative velocity between crankshaft and journal bearing results in viscous shear heating among the different layers of lubricating oil. The shear heating reduces the viscosity of the lubricant that ultimately reduces the load carrying ability of the journal bearing. It offers a physical contact and reduces the designed life of crankshaft. In this study the 2-D transient numerical lubrication model is developed by employing the Reynolds equation to calculate the pressure and film thickness profiles as a function of crankshaft speed. The shear heating effects are determined by coupling the energy equation with lubrication model. The finite difference method is used and an appropriate numerical scheme is employed to simulate the conduction and convection based thermal energy transfer in transient and steady state journal bearing lubrication model. The lateral displacement of crankshaft is incorporated in the thermal model to analyze the effect of secondary dynamics of crankshaft. The viscosity and temperature relationship are used to ascertain its variation with temperature. The characteristic of three different viscosity-grade lubricates are incorporated separately in the model to carry out the comprehensive comparative analysis. The results are simulated for particular application where low operating speed and length to width ratio of journal bearing is fixed and analyzed the results for complete 720 degrees of crankshaft in its two revolutions. The results show that the oil with high viscosity produces high hydrodynamic pressures as compared to the oil that have low viscosity. The viscous shearing temperature reduces the hydrodynamic pressures but still the high viscosity lubricating oil have enough pressures to uplift the shaft after incorporating the shear heating effects. This study determines the hydrodynamic pressure, and variation of density, viscosity and thermal-conductivity with temperature for three different lubricating oils. These analyses will facilities towards the selection of appropriate lubricant for high torque low speed diesel engine in order to enhance the life of crankshaft.

Simulation of turbulent boundary layers for flows characterized by unsteady driving conditions is important for solving complicated engineering problems such as combustion, blood flow in stenosed arteries, and flow over immersed structures. These flows are often dominated by complex vortical structures, regions of varying turbulence intensities, and fluctuating pressure fields. Pulsating channel flow is one such case that presents a unique set of challenges for newly developed and existing turbulence models used in computational fluid dynamics (CFD) solvers. In the present study, performance of the dynamic hybrid RANS-LES model (DHRL) with exponential time averaging (ETA) is evaluated against Monotonically Integrated Large Eddy Simulation (MILES) and a previously documented LES study for a fully developed channel flow with a time-periodic driving pressure gradient. Results indicate that MILES over predicts mean streamwise velocity for all forcing frequencies while the DHRL model with ETA provides a method for improved results, especially for the lower frequencies. It is concluded that a hybrid RANS-LES model with ETA is a useful alternative to simulate unsteady non-stationary flows but further work is needed to determine the appropriate filter width for ETA to significantly improve the predictive capabilities of the DHRL model.

Dispersion of nanoparticles in pure fuels alters their key fuel physical properties, which could affect their atomization process, and in turn, their combustion and emission characteristics in a combustion chamber. Therefore, it is essential to have a thorough knowledge of the atomization characteristics of nanofuels (nanoparticles dispersed in pure fuels) to better understand their latter processes. This serves as the motivation for the present work, which attempts to gain a good understanding of the atomization process of the alternative, gas-to-liquid (GTL), jet fuel based nanofuels. The macroscopic spray characteristics such as spray cone angle, liquid sheet breakup, and liquid sheet velocity are determined by employing shadowgraph imaging technique. The effect of nanoparticles weight concentration and ambient pressures on the spray characteristics are investigated in a high pressure-high temperature constant volume spray rig. To this end, a pressure swirl nozzle with an exit diameter of 0.8 mm is used to atomize the fuels. The macroscopic spray results demonstrate that the nanoparticles dispersion at low concentrations affect the near nozzle region. The spray liquid sheet breakup distance is reduced by the presence of nanoparticle due to the early onset of disruption in the liquid sheet. Consequently, the liquid sheet velocity in that spray region is higher for nanofuels when compared to that of pure fuels. Also, the ambient pressure has a significant effect on the spray features as reported in the literature.

Boiler systems have many factors that affect the efficiency of the air conditioning process. A traditional control system is complicated and requires physical hardware and software programming. The modern operator console is more compact and works better. Regardless of the boiler system, the operator can run it automatically, allowing changes in many variables such as fuel input, air combustion, water feed flow, steam temperature, etc. In fact, it is impossible to control all of these variables simultaneously in the manual mode. Modern systems have been developed to a high degree of precision that can provide excellent results in maintaining high levels of efficiency, reliability, and safety. The Programmable Logic Controller (PLC) was developed in 1968, and since then it has improved rapidly and applied to many manufacturing industries. Besides the Allen Bradley PLC, other modules were developed such as Human Machine Interface (HMI), Variable Frequency Drives (VFDs), and safety components. In this paper, the Allen Bradley PLC ControlLogix family 1756 model is used to control the boiler system. In addition, this work focuses on improving the boiler efficiency by comparing between the manual and automatic control the fuel-air ratio.

The twentieth century has seen a rapid twenty-fold increase in the use of fossil fuels. Personal and commercial transportation consumes 2% of the total world energy. The main products of combustion of fossil fuel are carbon mono oxide (CO), unburned hydrocarbons (HC), Carbon dioxide (CO 2 ), oxides of sulfur (SO x ), oxides of nitrogen (NO x ) and particulate matter. Oxides of nitrogen (NO x ) are the major diesel engine pollutants and referred to as mixtures of nitric oxide (NO) and nitrogen dioxide (NO 2 ). NO x emissions are required to be controlled because NO and NO 2 contribute to the formation of smog, an environmental and human health hazard. NO 2 is also directly of concern as a human lung aggravation. To reduce NO x emissions from a diesel engine, the introduction of water in the combustion chamber of a diesel engine is a promising option as vaporization of water reduces adiabatic flame temperature and micro-explosion phenomena lead to improved mixing. In the present study, stable D/W emulsion, with varying water content, up to 3% were prepared using span 80 as a surfactant. The results indicated a reduction in NO x and smoke with increasing water volume fraction in the emulsion compared to diesel baseline. However, beyond 2% water content led to increased ignition delay and higher diffusion phase heat release resulting in noisy engine operation. Therefore, it can be concluded that diesel-water emulsion with 2% water could be used for significant reduction of NO x emissions from diesel and biodiesel operation of a CI Engine.

Climate change is a serious threat to sustainability. Anthropogenic climate change is due to the accumulation of greenhouse gases (GHG) in the atmosphere beyond natural levels. Anthropogenic GHG emissions are mostly associated with carbon-dioxide (CO 2 ) originated in the combustion of fossil fuels used for heat, power, and transportation. Globally, transportation contributes to 14% of the global GHG emissions. The transport sector is one of the main contributors to the greenhouse gas emissions of Ecuador. In Guayaquil, the road mass transportation system comprises regular buses and the bus rapid transit (BRT) system. Electricity in Ecuador is mostly derived from hydropower, hence incurs relatively low GHG emissions along its life cycle. Therefore, electrification of transport has been seen as an opportunity for mitigation of GHG emissions. In this study, the effect of partial replacement of the bus rapid system fleet is investigated. Feeders have been chosen as the replacement target in five different scenarios. GHG emissions from diesel-based feeders have been calculated using the GREET Fleet Footprint Calculator tool. The GHG emissions associated with the electricity used for transportation is calculated using the life cycle inventory of the electricity generation system of Ecuador. Three energy mix scenarios are used for this purpose. The 2012 mix which had 61% hydropower; the mix of 85% hydropower and the marginal electricity scenario, which supposed the extreme case when the new demand for electricity occurs during peak demand periods. Results indicate that mitigation of GHG emissions is possible for almost all scenarios of percentage fleet replacement and all mix scenarios. Electric buses efficiency and the carbon intensity of the electricity mix are critical for GHG mitigation.

Torrefaction is a thermal pretreatment process which usually takes place at temperatures between 200–300°C. Torrefied biomass has been proven in numerous studies to have superior combustion properties compared to raw biomass. The objective of this study is to develop a model to estimate solid energy yield, elemental compositions and enthalpy of solid and volatile yield. Formation enthalpy of raw and torrefied biomass is calculated using the correlations developed for elemental compositions and HHV of torrefied biomass. Solid yield is determined by anhydrous weight loss model for torrefied wood. Specific heat correlations for raw biomass and char are used to calculate the sensible heat required for torrefaction process. Sensible heat and formation enthalpy give the total enthalpy for raw and torrefied biomass. During torrefaction, a mixture of volatile compositions is released. Experimental mass fractions of the volatiles components are taken from published literature, which allowed us to determine the enthalpy of formation and specific heat of the volatiles. Finally, the model results associated with the torrefaction process are compared with experimental data.

Biomass gasification is the devolatilization and incomplete combustion of biomass resulting in the production of a combustible gas mixture including carbon monoxide (CO), hydrogen (H 2 ) methane (CH 4 ), and traces of other hydrocarbons (C n H m ), and referred to as producer gas. Producer gas can be cleaned and then used in various engines or can be converted to various biofuels. This paper presents an experimental and simulation-based evaluation of producer gas quality resulting from corn kernel gasification in a two-stage downdraft gasifier. Test conditions were selected, based on the results of previous studies, to yield high conversion efficiency and low tar production. Experimental tests were performed with an air flow of 25 Nm 3 /h and with 80% of the air supplied to the first gasification stage. Simulations based on a chemical and thermal equilibrium model were carried out to examine the effect of equivalence ratio (ER) changes. Both the experimental and modelling results show that using a two-stage air supply leads to a significant reduction in the tar content of the producer gas, while maintaining a high gasification efficiency.

Marine current energy is a clean energy source and is a solution to the problems faced by burning fossil fuels such as global warming and climate change. Once tapped, the useful shaft power can be converted into electrical energy. To make this practical, the designed energy converter should be capable of operating at low marine current velocities, it should be suitable for installation at locations that have low water depths and should have lower manufacturing, installation and maintenance costs. A ducted cross-flow turbine has all the above features and it will be suitable for Pacific Island countries (PICs) for extracting marine current energy. The ducted cross-flow turbine was designed, modelled and analyzed in commercial Computational Fluid dynamic (CFD) code ANSYS-CFX. The inlet and outlet duct sizes were optimized for maximum output. Before the analysis of full model, the CFD results were validated with experimental results. Simulations for the 1:10 ducted cross-flow turbine (having a diameter of 150 mm) were performed with 400,000 nodes, as increase in the grid size did not make much difference other than increasing the simulation time significantly. The maximum difference in the power coefficient between CFD and experimental results was 6%. Simulations were then performed for the full-scale prototype, which has a duct (nozzle) inlet of 3.5 m × 3.5 m and a turbine diameter of 1.5 m, at three freestream velocities of 0.65 m/s, 1.95 m/s and 3.25 m/s. Analysis of the prototype performance showed that the ducted cross-flow turbine can reach a maximum efficiency of 56% and can produce 21.5 kW of power at a current speed of 1.95 m/s and 103.6 kW at 3.25 m/s. The designed cut-off speed was 4 m/s.

The change in laminar burning speed and ignition delay time of iso-octane with the addition of oxygenated fuels are investigated. As oxygenated fuels, ethanol and 2,5 dimethyle furan (DMF) are used. To confirm the process and mechanism a detailed validation is done on laminar burning speed and ignition delay time. Further, three different blending ratios of 5%, 25% and 50% for both ethanol/iso-octane and DMF/iso-octane are investigated separately. Wide range of equivalence ratio from 0.6–1.4 is considered in calculating laminar burning speed. Ignition delay time is measured under various temperatures from 650 K to 1100 K. Results of each blending are compared with the pure fuels. A comparison is also done between the effects of these two oxygenates. It has found that for each blending case presence of DMF brings larger change in the behavior of iso-octane than ethanol. This observation refers to further study on comparison of these two oxygenates.

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NO x , CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COV IMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

3D CFD IC engine simulations that use a simplified combustion model based on the flamelets concept can provide acceptable results with minimum computational costs and reasonable running times. More, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct-injection CI engine, which was converted to port-fuel injection SI operation. 3D IC engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the simulation results agreed well with the experimental pressure trace. The results show that including the crevice volume affected the mass of unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.

Carbon dioxide emissions reduction in the atmosphere is the major driver of technological innovations, in particular in energy and industrial sectors. Those sectors are dominated by the use of fossil fuels whose main concern on the combustion gases is the presence of CO 2 . Their emission in atmosphere accumulates Carbon, the main cause of global warming. The only way to continue to make reference to fossil fuel in the medium-long term and to avoid the carbon accumulation in the atmosphere is to use technologies capable to capture and sequester the carbon in the flue gases (CCS). In the sector of electricity production, several technologies have been proposed for the capture CO 2 , including absorption, adsorption, cryogenic distillation or membrane separation. All of them offer flexibility and easiness of application, but they need external energy to operate. On the other hand, particular interest is reversed to those technological options that are able to remove CO 2 without energy consumption; even more attention is reserved to those technologies which, suitably integrated with other conversion systems, can produce electrical energy at the same time, so increasing the electricity production with respect to the original plant. They are defined active systems and one of these is represented by Molten Carbonate Fuel Cells (MCFCs). In fact, MCFCs are fuel cell capable to concentrate CO 2 at anode exhaust, making easier its capture, separation and storage and in parallel to contribute to the electricity production. In this paper, a comprehensive model of the MCFC is used to assess the opportunity related to its use as a CO 2 remover from a flue gas as a CCS active device, without energy penalties related to traditional carbon capture methods (MEA, pre and post-combustion, oxy-combustion, etc.). Hence, it has been integrated in a wider system with auxiliary components: compressors to overcome pressure drops, steam generator (also using heat recovered from MCFC exhausts) for fuel dilution, fresh air integration in cathode inlet section, heat exchangers for thermal management and recovery. A CO 2 compression and drying section has been considered and represented as a multi-step intercooled compression. The so-defined system can be used as a plug-in device able to be coupled to flue gases with different compositions and thermodynamic operating parameters (temperature, pressure, flow rates). Finally, it has been applied to a case study (a Natural Gas Combined Cycle power plant - NGCC) and the performance of the MCFC in terms of CO 2 removal capacity, electrical power generation and size have been evaluated as well the energetic and environmental impact on the reference NGCC power plant.

This paper investigates the combustion performance of a commercial cooktop burner operating on natural gas and renewable biogas. Various blends of carbon dioxide and methane are used to simulate biogas and fed as fuel to the cooktop burners. Combustion operation on standard pipeline natural gas is taken as a reference for comparison with other fuel classes. In this study, different configurations of cooktop burners available in the market were investigated to establish similarities and differences. Based on the current regulations and testing standards, a protocol for testing and evaluating the cooktop burner combustion performance was generated and adopted in this research. Experimental investigation of the flame characteristics, ignition properties, cooking efficiency, and emissions (CO, NO x , UHC) were studied as a function of gas composition. The results indicate that, based on the overall performance of the cooktop burners, up to 5% CO 2 can be added to pipeline natural gas without impacting operation. Different methodologies of analyzing emissions were compared with each other, which can provide insight into future emission regulations on open-air residential or light industrial burners.

In order to investigate the performance and emissions behavior of a high compression ratio Compression Ignition (CI) engine operating in Partially Premixed Charge Compression Ignition (PPCI) mode, a series of experiments were conducted using a single cylinder naturally aspirated engine with a high-pressure rail fuel injection system. This included a moderately advanced direct injection strategy to attempt PPCI combustion under low load conditions by varying the injection timing between 25° and 35° Before Top Dead Center (BTDC) in steps of 2.5°. Furthermore, during experimentation the fuel injection pressure, engine speed, and engine torque (through variance of the fuel injection quantity) were kept constant. In-cylinder pressure, emissions, and performance parameters were measured and analyzed using a zero-dimensional heat release model. Compared to the baseline conventional 12.5° BTDC injection, in-cylinder pressure and temperature was higher at advanced timings for all load conditions considered. Additionally, NO x , PM, CO, and THC were higher than conventional results at the 0.5 N-m load condition. While PM emissions were lower, and CO and THC emissions were comparable to conventional injection results at the 1.5 N-m load condition between 25° and 30° BTDC, NO x emissions were relatively high. Hence, there was limited success in beating the NO x -PM tradeoff. In addition, since Start of Combustion (SOC) occurred BTDC, the resulting higher peak combustion pressures restricted the operating condition to lower loads to ensure engine safety. As a result, further investigation including Exhaust Gas Recirculation (EGR) and/or variance in fuel Cetane Number (CN) is required to achieve PPCI in a high compression ratio CI engine.

Recent studies have shown that addition of nano-sized particles to liquid fuels could significantly enhance major combustion characteristics such as burning rate and ignition delay. Colloidal suspensions are known to have enhanced optical properties and thermal conductivity compared to neat liquids; however, in the case of colloidal fuels, the main mechanism responsible for such enhanced properties is not well understood. To better understand these phenomena, colloidal suspensions of jet fuel and different types of carbon-based nanomaterials (carbon nanoparticles, multi-walled carbon nanotubes, and graphene nanoplatelets) prepared at different particle loadings were experimentally tested for their thermal conductivities. Colloidal suspensions of nanotubes showed higher conductivity compared to that of graphene and nanoparticle. This could justify higher burning rate of these fuels. Furthermore, and to differentiate between the effects of thermal conduction and radiation, droplet evaporations tests were carried out on colloidal suspensions of carbon nanoparticle under forced convection and in the absence of any radiation source. It was found that the presence of nanoparticle in jet fuel initially increases evaporation rate. However, a reduction in evaporation rate was observed at higher concentration as a result of particles agglomeration.

Operational characteristics of an air breathing Rotating Detonation Combustor (RDC) fueled by natural gas-hydrogen blends are discussed in this paper. Experiments were performed on a 152 mm diameter uncooled RDC with a combustor to inlet area ratio of 0.2 at elevated inlet temperature and combustor pressure while varying the fuel split between natural gas and hydrogen over a range of equivalence ratios. Experimental data from short-duration (∼6sec) tests are presented with an emphasis on identifying detonability limits and exploring detonation stability with the addition of natural gas. Although the nominal combustor used in this experiment was not specifically designed for natural gas-air mixtures, significant advances in understanding conditions necessary for sustaining a stable, continuous detonation wave in a natural gas-hydrogen blended fuel were achieved. Data from the experimental study suggests that at elevated combustor pressures (2–3bar), only a small amount of natural gas added to the hydrogen is needed to alter the detonation wave operational mode. Additional observations indicate that an increase in air inlet temperature (up to 204°C) at atmospheric conditions significantly affects RDC performance by increasing deflagration losses through an increase in the number of combustion (detonation/Deflagration) regions present in the combustor. At higher backpressure levels the RDC exhibited the ability to achieve stable detonation with increasing concentrations of natural gas (with natural gas / hydrogen-air blend). However, losses tend to increase at intermediate air preheat levels (∼120°C). It was observed that combustor pressure had a first order influence on RDC stability in the presence of natural gas. Combining the results from this limited experimental study with our theoretical understanding of detonation wave fundamentals provides a pathway for developing an advanced combustor capable of replacing conventional constant pressure combustors typical of most power generation processes with one that produces a pressure gain.

Swiss Roll Combustor of 1 W capacity for micro gas turbine engine is operated with premixed hydrogen air mixture at ultra-lean equivalence ratio. The reaction zone under consideration has volume of 60 mm 3 . The reactant passage and product passage are coiled around the reaction zone facilitating the recovery of heat loss, by preheating the reactants. The reactants are entered through an increasing cross-sectional area passage from 0.6mm × 5mm inlet to 1.5mm × 5mm outlet, thereby reducing the velocity levels in the reactant passage, facilitating stable combustor operation. The combustor performance parameters, temperature levels, pattern factor and emissions are measured is operated at ultra-lean equivalence ratio of 0.12 to lean equivalence ratio of 0.43, for premixed hydrogen air combustion. The results are compared at similar (not same) equivalence ratios for constant area reactant passage. The visual inspection shows stable flame front in the combustion zone for variable area passage and extended flame front in the constant area passage combustor. However, the combustor performance deteriorates drastically above equivalence ratio of 0.43, leading to hot spots generation on walls.

Direct contact condensation occurs when a vapor comes in contact with the liquid of the same fluid and is accompanied by very high heat transfer coefficients compared to the conventional heat exchanging processes. Many researchers have investigated the direct contact condensation of steam jets in a pool of subcooled water. In the last decade, the potential of flowing liquid as an enhanced heat transfer medium in comparison with the stationary pool of liquid was explored by various researchers. Also, in some configurations of staged combustion cycle based rocket engine, the oxygen-rich gas is injected into flowing liquid oxygen to improve the heat transfer characteristics. Hence, there is a need to investigate the direct contact condensation of vapor jets in a cross flow of liquid. A two-fluid particle based multiphase formulation with thermal phase change model has been implemented in the present investigation to capture the direct contact condensation phenomena. The data obtained from numerical simulations are validated with the experimental results of Clerx et al. , [1]. Further, studies on plume shapes, interfacial area and pressure amplitudes are reported.