Investigating the mechanical erosion of the solid rocket motor C-D nozzle is essential to overcome its development barriers. Consequently, the break-up mechanism of the aluminum oxide agglomerates was studied to determine the influence of the exhaust gas flow acceleration during the flight. Water and air flows were used as a substitute for aluminum oxide and exhaust gases. Experiments were conducted at different water flow rates and constant air velocity, where the results were used to validate a numerical model. The results revealed an excellent acceptance between the numerical, the experimental data (6-19%), and the effect of increasing the water flow rate on the break-up mechanism. The validated numerical model was further used to study the airflow acceleration impact on the break-up process. It was found that applying acceleration to the airflow subjects the water surface to rapid and sudden changes in the relative velocity between the gas and liquid, thus separating more water fragments from the primary liquid. In other words, it enhances the break-up process by reducing the average diameter with a range from 6.5% to 9% compared to the no-acceleration case and increasing the average droplets' number [8.5-17%].

Flare gas is considered a global environmental concern. Flaring contributes to wasting limited material and energy resources, economic loss, and greenhouse gas emissions. Utilizing flared gas as a fuel feed to industrial cracking furnaces grants advantages in terms of fuel economy and emissions reduction. This work presents the results obtained by ansys fluent simulation of a flare hydrocarbon gas utilized in a steam-cracking furnace of ethylene process when combusting hydrocarbons flare gas in a low-NOx burner. In addition, the study determined the suitability of different hydrocarbon fuel mixtures in satisfying the required adiabatic flame temperature. The flared stream is assumed to be inlet from both primary and secondary staged fuel burners. The simulation results illustrated the detailed temperature profiles along the furnace flue gas side. They also presented the influence of flare stream compositions and Wobbe Index (WI) on the temperature profile. It was found that having an alternative fuel with a heating value or WI similar to that of methane would not result in the same temperature profile of methane, as the current fuel source. In addition, using different excess air percentages has no linear effect on the burner’s temperature profile. However, the results showed that the best replacement of methane, as the main fuel source, is a flare mixture with the same WI of methane as well as a certain H2 content needs to be added to every flare mixture composition to reach the same temperature profile of methane.

A natural gas-fueled homogeneous charge compression ignition (HCCI) engine is coupled to an exhaust gas operated turbine driven two-phase ejector cycle to generate power and cooling energy, simultaneously. By establishing a thermodynamic model, the simulation of the proposed system and its parametric analyses are conducted. Energetic and exergetic investigations are carried out to study the role of equivalence ratio, engine speed, condenser temperature, refrigeration evaporator temperature, air-conditioning evaporator temperature, and ejector nozzle efficiency on the thermodynamic performance parameters of the combined cycle. The analysis of two-phase ejector cooling cycle using three working fluids including R717, R290, and R600a is conducted. Results reveal that the thermal efficiency of HCCI engine is increased from 47.44% to 49.94%, and for the R600a operated combined cycle it is increased from 60.05% to 63.26% when the equivalence ratio is promoted from 0.3 to 0.6. Distribution of fuel exergy results show that out of 100% exergy input, in case of R717 operated combined cycle, 139.79 kW (38.72%) is the total exergy output, and 164.21 kW (45.49%) and 57 kW (15.79%) are the values for exergy destruction and exergy losses. It is further shown that change in refrigerant minorly influence the percentages of exergy distribution.

The current research assessed the evolution of gases from pyrolysis of biomass and from the subsequent combustion of bio-chars. Raw and torrefied biomass was pyrolyzed in nitrogen or carbon dioxide under high heating rates (10 4 K/s) and high temperatures (1450 K). Pyrolyzates gases were monitored for carbon, nitrogen, and sulfur oxides. Subsequently, generated bio-chars were burned in both conventional (air) and simulated oxy-combustion (O 2 /CO 2 ) gases. In principle, the oxy-combustion of renewable biomass coupled with carbon capture and utilization/sequestration can help remove atmospheric CO 2 . Pyrolysis of biomass in CO 2 generated lower char yields, lower SO 2 and NO, and higher CO 2 , CO, and HCN mole fractions, compared with pyrolysis in N 2 . HCN was the most prominent among all measured nitrogen-bearing gases (HCN, NH 3 , and NO) from biomass pyrolysis. Compared with their combustion in air, bio-chars burned more effectively in 30%O 2 /79%CO 2 and less effectively in 21%O 2 /79%CO 2 . Emissions of CO were the lowest in 21%O 2 /79%CO 2 . Emissions of HCN were the highest in air combustion and decreased with increasing O 2 mole fraction in oxy-combustion; emissions of NO were highest in 30%O 2 /79%CO 2 , and emissions of NO were dominant during bio-char oxy-combustion compared with other N-compounds. In oxy-combustion, bio-chars released the lowest emissions of SO 2 . Finally, the emissions of CO, NO, HCN, and SO 2 from the combustion of distiller’s dried grains with solubles bio-chars were higher than those from rice husk bio-chars because of different physicochemical properties.

In this study, an experimental investigation was presented on the oxidation behaviors of bituminous coal for different inert gases (N 2 and CO 2 ) at different concentrations (oxygen concentration indexes 21%, 18.4%, 15.8%, and 13.1%) using a temperature-programmed experimental device. The purpose of this research was to examine the oxidation patterns of bituminous coal under different inert conditions. The results showed that: (1) the oxidative heating of the coal underwent two stages: an initial slow heating stage and a fast heating stage. The injection of both inert gases would result in a delay in the crossing point temperature (CPT) of the coal, but the injection of N 2 resulted in greater delays in the CPT of the coal; (2) the injection of both N 2 and CO 2 inhibited the concentrations of CO and alkane/olefin gases produced from the oxidative heating of the coal, with CO 2 displaying higher inhibition efficiencies than that of N 2 ; (3) Under a non-inerting environment, the C 2 H 4 and C 2 H 6 generation temperatures were 110 °C and 100 °C. Under an inerting environment, when N 2 was injected, the higher the N 2 concentration, the higher the initial C 2 H 4 and C 2 H 6 generation temperatures; when CO 2 was injected, the higher the CO 2 concentration, the lower the initial C 2 H 4 and C 2 H 6 generation temperatures; and (4) under a non-inerting environment, the C 3 H 8 generation temperature was 90 °C; and when an inert gas was injected, there was a hysteresis in the C 3 H 8 generation temperature for all concentrations. The above research results can be used to predict the spontaneous combustion of residual coal in an inert environment and prevent fires.

Biomass torrefaction is a mild pyrolysis thermal treatment process carried out at temperatures between 200 and 300 °C under inert conditions to improve fuel properties of parent biomass. Torrefaction yields a higher energy per unit mass product but releases noncondensable and condensable gases, signifying energy and mass losses. The condensable gases (volatiles) can result in tar formation on condensing, hence, system blockage. Fortunately, the hydrocarbon composition of volatiles represents a possible auxiliary energy source for feedstock drying and/or torrefaction process. The present study designed a low-pressure volatile burner for torrefaction of pine wood chips and investigated energy recovery from volatiles through clean co-combustion with natural gas (NG). The research studied the effects of torrefaction pretreatment temperatures on the amount of energy recovered for various combustion air flow rates. For all test conditions, blue flames and low emissions at the combustor exit consistently signified clean and complete premixed combustion. Torrefaction temperature at 283–292 °C had relatively low volatile energy recovery, mainly attributed to higher moisture content evolution and low molecular weight of volatiles evolved. At the lowest torrefaction pretreatment temperature, small amount of volatiles was generated with more energy recovered. Energy conservation evaluation on the torrefaction reactor indicated that about 27% of total energy carried by the exiting volatiles and gases has been recovered by the co-fire of NG and volatiles at the lowest temperature, while around 19% of the total energy was recovered at the intermediate and highest torrefaction temperatures, respectively. The energy recovered represents about 23–45% of the energy associated with NG combustion in the internal burner of the torrefaction reactor, signifying that the volatiles energy can supplement significant amount of the energy required for torrefaction.

Biobutanol is an attractive, economical, and sustainable alternative fuel to petroleum oil which are depleting in sources due to the diminishing oil reserves and creating an increase in the concentrations of greenhouse gases in the atmosphere. Alternative routes to sustainable bacterial fermentation for the production of biobutanol are being sought and prepared for commercialization. The challenges for implementing an economically competitive fermentation process for biobutanol production include the availability of cheaper feedstock by improvement toward large-scaled production, improvement of fermentation efficiency, and better strategies for solvent recovery. The development of biobutanol production was analyzed and various methods to increase the fermentative butanol production were discussed in detail. It was found that the implementations of metabolic engineering of the Clostridia sp., advanced fermentation techniques, and utilization of renewed substrates are among the potential and economically viable technology in the production butanol production. Besides, this review outlines several challenges and potential future work for the advancement of fermentative butanol production.

Carbon nanotubes (CNTs) have high surface areas and excellent mechanical, electrical, and chemical properties, thus they can be useful in applications related to extraction and conversion of energy. They can be readily produced from hydrocarbon feedstocks. In this work, ethylene, the most voluminously produced hydrocarbon, was used as a CNT feedstock. It was pyrolytically decomposed at elevated temperatures (984–1130 K) to generate CNTs, by catalytic chemical vapor deposition (CVD) on stainless steel substrates. To explore possible utilization of carbon dioxide, a typical combustion byproduct, the ethylene gas was introduced to a preheated CVD reactor at the presence of various amounts of CO 2 , in a balance of inert nitrogen gas. The ethylene pyrolyzates were assessed at the presence/absence of catalysts and CO 2 to identify the gaseous carbon growth agents. Experimental findings were also contrasted to predictions of a detailed chemical kinetic model. It was found that whereas decomposition of ethylene was somewhat inhibited by CO 2 at the presence of the catalyst support, its conversion to CNTs was promoted. CNTs consistently formed at 5% CO 2 . Maximum yields of CNTs occurred at 1130 K, whereas highest CNT quality was achieved at 1080 K. Hydrogen and 1,3-butadiene (C 4 H 6 ) were experimentally found to be the most abundant species of ethylene thermal decomposition. This was in agreement with the model, which also highlighted the importance of unimolecular hydrogen elimination.

A power-law mixing rule has been developed to determine apparent diffusion coefficient of a binary gas mixture on the basis of molecular diffusion coefficients for pure gases in heavy oil. Diffusion coefficient of a pure gas under different pressures and different temperatures is predicted on the basis of the Hayduk and Cheng's equation incorporating the principle of corresponding states for one-dimensional gas diffusion in heavy oil such as the diffusion in a pressure–volume–temperature (PVT) cell. Meanwhile, a specific surface area term is added to the generated equation for three-dimensional gas diffusion in heavy oil such as the diffusion in a pendant drop. In this study, the newly developed correlations are used to reproduce the measured diffusion coefficients for pure gases diffusing in three different heavy oils, i.e., two Lloydminster heavy oils and a Cactus Lake heavy oil. Then, such predicted pure gas diffusion coefficients are adjusted based on reduced pressure, reduced temperature, and equilibrium ratio to determine apparent diffusion coefficient for a gas mixture in heavy oil, where the equilibrium ratios for hydrocarbon gases and CO 2 are determined by using the equilibrium ratio charts and Standing's equations, respectively. It has been found for various gas mixtures in two different Lloydminster heavy oils that the newly developed empirical mixing rule is able to reproduce the apparent diffusion coefficient for binary gas mixtures in heavy oil with a good accuracy. For the pure gas diffusion in heavy oil, the absolute average relative deviations (AARDs) for diffusion systems with two different Lloydminster heavy oils and a Cactus Lake heavy oil are calculated to be 2.54%, 14.79%, and 6.36%, respectively. Meanwhile, for the binary gas mixture diffusion in heavy oil, the AARDs for diffusion systems with two different Lloydminster heavy oils are found to be 3.56% and 6.86%, respectively.

This manuscript presents experimental results on the reduction of sulfur oxide emissions from combustion of a high-sulfur content pulverized bituminous coal (Illinois #6 Macoupin) using a dry sorbent injection method. The coal particles were in the size range of 90–125 μ m and were blended with calcium-, sodium-, potassium-, and magnesium-containing powdered sorbents at different proportions. The alkali/sulfur molar ratios were chosen to correspond to stoichiometric proportions (Ca/S = 1, Mg/S = 1, Na 2 /S = 1, and K 2 /S = 1) and the effectiveness of each alkali or alkali earth based sorbent was evaluated separately. Combustion of coal took place in a drop-tube furnace, electrically heated to 1400 K under fuel-lean conditions. The evolution of combustion effluent gases, such as NO x , SO 2 , and CO 2 was monitored and compared among the different sorbent cases. The use of these sorbents helps to resolve the potential of different alkali metals for effective in-furnace sulfur oxide capture and possible NO x reduction. It also assesses the effectiveness of various chemical compounds of the alkalis, such as oxides, carbonates, peroxides, and acetates. Reductions in SO 2 emissions were in the range of 5–72%, with sodium being the most effective metal followed by potassium, calcium, and then magnesium. Acetates were effective as dual SO 2 and NO x reduction agents.

In critical situations such as floods and earthquakes, the relief forces require a refrigeration for pharmaceuticals and vaccines, which could operate without an electrical energy and the alternative energies, such as solar energy, engine exhaust gases heat, and wind energy. In this paper, a refrigeration cycle has been modeled as an adsorption refrigeration cycle with an activated carbon/methanol as adsorbent/adsorbate pair and two sources of energy—solar energy and engine exhaust gases heat. The solar cycle had a collector with area of 1 m 2 and the exhaust gas cycle included a heat exchanger with 100 °C temperature difference between inlet and outlet gases. The temperature profile in adsorbent bed, evaporator, and condenser was obtained from modeling. Moreover, the pressure profile, overall heat transfer coefficient of collector and adsorbent bed, concentration, and the solar radiation were reported. Results represented the coefficient of performance (COP) of 0.55, 0.2, and 0.56 for complete system, solar adsorption refrigeration, and exhaust heat adsorption refrigeration, respectively. In addition, exhaust heat adsorption refrigeration has a value of 2.48 of specific cooling power (SCP). These results bring out a good performance of the proposed model in the climate of Iran.

Chemical-looping combustion (CLC) is an emerging carbon capture technology that is characterized by a low energy penalty, low carbon dioxide capture costs, and low environmental impact. To prevent the contact between fuel and air, an oxygen carrier is used to transport the oxygen needed for fuel conversion. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal, is gasified in the fuel reactor (FR), and the products from gasification are oxidized by the oxygen carrier. There are promising results from the electrically heated 100 kW th unit at Chalmers University of Technology (Sweden) or the 1 MW th pilot at Technische Universität Darmstadt (Germany) with partial chemical-looping conditions. The 1 MW th CLC pilot consists of two interconnected circulating fluidized bed reactors. It is possible to investigate this process without electrically heating due to refractory-lined reactors and coupling elements. This work presents the first results of autothermal operation of a metal oxide CLC unit worldwide using ilmenite as oxygen carrier and coarse hard coal as fuel. The FR was fluidized with steam. The results show that the oxygen demand of the FR required for a complete conversion of unconverted gases was in the range of 25%. At the same time, the carbon dioxide capture efficiency was low in the present configuration of the 1 MW th pilot. This means that unconverted char left the FR and burned in the air reactor (AR). The reason for this is that no carbon stripper unit was used during these investigations. A carbon stripper could significantly enhance the carbon dioxide capture efficiency.

When using fluidized bed in oxyfuel combustion, process parameters must be adjusted to maintain combustion and control air leakage into the system as there are important changes in gases properties, flow, and temperature. In this sense, this work makes a description of the retrofit of air combustion to oxyfuel combustion in a 0.25 MWth bubbling fluidized pilot plant. Process parameters were analyzed and mass and energy balances were developed to compare air and oxyfuel combustion. Air leakage and fluidization showed to be important to control when proceeding transition to oxyfuel combustion and temperature increase was consequence of radiation mechanism changes.

There is a controversy brewing for about 10 years that hydroelectric power plants are not a clean, renewable source of electricity. The current review indicates that the source of methane is not in the mechanics or mechanical design of the equipment used. The source of the methane is from nature, and man's failure to do the right thing. This methane may be reduced or completely eliminated. If this cannot be accomplished or if it is too expensive to retrofit the hydroelectric plant, then the deep water may be preprocessed (and the methane collected) before being used in the water turbine. Several methods have been introduced and discussed. Details have been omitted so that practicing engineers and other professionals can obtain funds to research and develop or invent the practical solutions suited to conditions local to the problem.

Thermodynamic properties of ionized gases at high temperatures have been calculated by a new model based on local equilibrium conditions. Calculations have been done for nitrogen, oxygen, air, argon, and helium. The temperature range is 300–100,000 K. Thermodynamic properties include specific heat capacity, density, mole fraction of particles, and enthalpy. The model has been developed using statistical thermodynamics methods. Results have been compared with other researchers and the agreement is good.

A simulation model for establishment of performance parameters of a spark ignition engine fueled with landfill gas, methane, and landfill gas-hydrogen mixtures is described. A two zone model was employed to estimate combustion duration, ignition lag, associated mass burning rates, and performance parameters for various operating conditions in an internal combustion engine. The modeling consists of two main modules: (a) a fuel-air and residual gas properties calculation, and (b) equilibrium combustion product properties calculation with 13 species of equilibrium combustion products. The fuel-air and residual gas module calculates gas properties required in compression stroke and the unburned zone of a combustion chamber. The equilibrium combustion products module calculates gas properties for the burned zone during combustion and expansion phases. In addition to engine parameters, combustion duration estimation methods were presented to accommodate the presence of high quantities of diluents such as carbon dioxide and nitrogen in methane to represent landfill gases, generally encountered in practice. Similarly, an effect of the addition of hydrogen in landfill gas on performance of a spark ignition engine was also incorporated in the model. The pressure traces and engine power output parameters were modeled and compared with the experimental observations obtained in a variable compression single cylinder four-stroke spark ignition co-operative fuel research engine for different fuels that include methane, landfill gas, and landfill gas-hydrogen mixtures and found satisfactory agreement. MATLAB was used as the programming software in the model.

Diesel engines are critical in fulfilling transportation and mechanical/electrical power generation needs throughout the world. The engine’s combustion by-products spawn health and environmental concerns, so there is a responsibility to develop emission reduction strategies. However, difficulties arise since the minimization of one pollutant often bears undesirable side effects. Although legislated standards have promoted successful emission reduction strategies for larger engines, developments in smaller displacement engines has not progressed in a similar fashion. In this paper, a reduced-order dynamic model is presented and experimentally validated to demonstrate the use of cooled exhaust gas recirculation (EGR) to alleviate the tradeoff between oxides of nitrogen reduction and performance preservation in a small displacement diesel engine. EGR is an effective method for internal combustion engine oxides of nitrogen ( N O x ) reduction, but its thermal throttling diminishes power efficiency. The capacity to cool exhaust gases prior to merging with intake air may achieve the desired pollutant effect while minimizing engine performance losses. Representative numerical results were validated with experimental data for a variety of speed, load, and EGR testing scenarios using a 0.697 l three-cylinder diesel engine equipped with cooled EGR. Simulation and experimental results showed a 16% drop in N O x emissions using EGR, but experienced a 7% loss in engine torque. However, the use of cooled EGR realized a 23% N O x reduction while maintaining a smaller performance compromise. The concurrence between simulated and experimental trends establishes the simplified model as a predictive tool for diesel engine performance and emission studies. Further, the presented model may be considered in future control algorithms to optimize engine performance and thermal and emission characteristics.

Direct injection (DI) diesel engines emit a far more disagreeable exhaust odor than gasoline engines, especially at low temperatures and at idling. There is no proper system of odor reduction in these conditions in DI diesel engines. This study investigated a charcoal-adsorption system to reduce exhaust emissions including odor in a DI diesel engine at idling under no load operations, where exhaust temperatures are low. Low temperature exhaust gas is passed through a charcoal adsorber. Charcoal has the property of adsorbing odorous gas components. Here odor is reduced more than 0.5 points, a significant odor reduction depending on the engine and adsorber conditions. Exhaust noise, nitrogen oxides ( N O x ) , and eye irritation are also significantly reduced with the system. This study further investigated water-washing system for odor reduction in DI diesel engines at low exhaust temperature conditions. Exhaust gas is passed through the water in the water tank of the system. Aldehydes, organic acids, and other oxygenated components, which are the main odorous components in exhaust gases, are dissolved in water reducing exhaust odor significantly. Eye irritation of exhaust gases is also significantly reduced. The water-washing system not only reduces the odor and eye irritation but also carbon dioxide ( C O 2 ) , carbon monoxide (CO), N O x , and smoke are reduced more than 20–30%. The sound level of exhaust gases is also reduced 10 – 15 dB with this system. Air dilution is also attempted in this study for odor reduction where a large amount of fresh air is mixed with exhaust gases. Here dilution ratio of 5 is used. Air dilution alone can reduce odor about 0.5 points. However, odor about 1.5–1.6 points (about 60–65%) can be reduced when air dilution is used in combination with charcoal-adsorber and water-washing system, and odor level is lowered below level 2, which is acceptable for all human beings.

An analytical model for the second-law-based thermoeconomic analysis and optimization of a sensible-heat-storage system is derived and discussed, in which the storage element is both heated and cooled by flowing streams of gases. In this analysis, monetary values are attached to the irreversible losses caused by the finite temperature difference heat transfer and pressure drop in the storage system. Important dimensionless parameters are identified and the results are presented in terms of the optimum dimensionless charging time θ S ,opt as a function of a dimensionless temperature difference τ, as well as the optimum number of heat transfer units NTU S ,opt , as a function of the dimensionless unit cost per unit heat conductance γ UA and τ of the storage systems. The systems analyzed are optimized by introducing a new performance criterion described as the cost rate number , Γ*. Several example problems are also presented and the results are compared with that obtained from Krane’s analysis to illustrate the usefulness of the present approach. The influence of important unit cost parameters on NTU S ,opt and θ S ,opt , are also studied in somewhat more detail.

The United States generates the largest amount of solid waste per person in the world. The old practice of direct landfilling and storage is receiving greater public resistance and is attributing to the search for alternative disposal methods. The evergrowing problem of solid wastes requires environmentally benign and good public acceptance for the safe and ultimate disposal of the various kinds of solid wastes. Incineration and various kinds of mass burn-type systems have been used to reduce the volume and mass of the wastes, which can be characterized by their operational temperature. In all types of incineration systems, different kinds of gas clean-up devices are used to meet the local, state, and federal regulations for the gases before being released into the environment. A major concern over these systems have been in the by-products produced from these systems during their normal design and off-design point of operation. Indeed, the by-products generated from some incineration systems, under certain operational conditions, can be a health hazard and the solid residue may be leachable. Recent trends in advanced thermal destruction systems are described which can destroy the solid waste to the molecular level. Advanced systems can be designed to meet almost any emission standards. The use of oxygen-enriched air in place of air for the combustion of gases released from the solid waste reduces the amount of effluent gas, and, hence, the reduced size and cost of the gas clean-up system. The use of an excess enthalpy system offers attractive benefits in which the energy released from the waste is recycled back into the system under controlled conditions with the final desired objectives of reduced emissions, higher efficiency, and lower costs. Thermal destruction of solid wastes using advanced techniques makes good technical, environmental, economical, and human health and safety. The issues concerning recyclability, life cycle integration, and health effects from incineration are only expected to grow in the future.