Coal slurry fuel technology

Volatile oil markets experienced in the seventies have promoted renewed interest in coal-based fuel technologies. Coal-slurry fuels have emerged as viable technical alternatives for oil and gas in utility and industrial boilers. Despite current low prices and the abundance of oil, concerns over its long-term availability and price, as well as strategic considerations, make coal-slurry technology attractive. Initially, coal-slurry fuels were based on coal-oil mixtures, now the emphasis is largely on coal-water fuels. This review assesses the status of the relevant technology. It covers the preparation of coal-slurry fuels, slurry properties, combustion characteristics, emissions, current applications and concludes with their future outlook.     

Specific features of combustion in gasoline-driven internal combustion engines

Physical and chemical processes of gasoline combustion in internal combustion engines are considered. A model of combustion evolution in gasoline-driven engines, which explains some specific features of the processes in internal combustion engines, is proposed.     

Theoretical limits of scaling-down internal combustion engines

Small-scale energy conversion devices are being developed for a variety of applications; these include propulsion units for micro aerial vehicles (MAV). The high specific energy of hydrocarbon and hydrogen fuels, as compared to other energy storing means, like batteries, elastic elements, flywheels and pneumatics, appears to be an important advantage, and favors the ICE as a candidate. In addition, the specific power (power per mass of unit) of the ICE seems to be much higher than that of other candidates.However, micro ICE engines are not simply smaller versions of full-size engines. Physical processes such as combustion and gas exchange, are performed in regimes different from those that occur in full-size engines. Consequently, engine design principles are different at a fundamental level and have to be re-considered before they are applied to micro-engines. When a spark-ignition (SI) cycle is considered, part of the energy that is released during combustion is used to heat up the mixture in the quenching volume, and therefore the flame-zone temperature is lower and in some cases can theoretically fall below the self-sustained combustion temperature. Flame quenching thus seems to limit the minimum dimensions of a SI engine. This limit becomes irrelevant when a homogeneous-charge compression-ignition (HCCI) cycle is considered. In this case friction losses and charge leakage through the cylinder-piston gap become dominant, constrain the engine size and impose minimum engine speed limits.In the present work a phenomenological model has been developed to consider the relevant processes inside the cylinder of a homogeneous-charge compression-ignition (HCCI) engine. An approximated analytical solution is proposed to yield the lower possible limits of scaling-down HCCI cycle engines. We present a simple algebraic equation that shows the inter-relationships between the pertinent parameters and constitutes the lower possible miniaturization limits of IC engines.     

Modeling the self-ignition of methane—Air mixtures in internal combustion engines

An approximate method for modeling the self-ignition delay for internal combustion engines is proposed. The method allows the calculation of the time of chemical reaction for self-ignition at a constant volume (or constant pressure), which is equivalent to the real time of engine operation with a moving piston. The self-ignition delay calculated using a detailed kinetic mechanism is compared with corresponding experimental data.Institute of Physical Chemistry, Russian Academy of Sciences, 117334 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 7–14, March–April, 1994.     

精细水煤浆在小型高速内燃机上的燃烧理论分析

根据在内燃机气缸内燃烧水煤浆的试验,计算了精细水煤浆的热值;通过对汽缸内热力分析,得出精细水煤浆燃烧可以完全满足汽缸内的工况要求,同时分析了精细水煤浆在气缸内的燃烧过程。     

Performance characteristics of air intake pleated panel filters for internal combustion engines in a two-stage configuration

Previous numerical studies that have used computational fluid dynamics (CFD) and experimental software to address the effects of the geometric parameters of pleats on the pressure drop and air flow rate through a fibrous filter are analyzed. The analysis establishes that using a test dust with gradually smaller particle sizes (10, 5, and 1?μm) results in a more intense increase in the filter pressure drop, thus decreasing the service life of the filter. The benefits of using a multicyclone as the first stage of air filtration are discussed. Selecting the air filter by determining the active surface of the filter medium A_c based on the allowable filtration rate is not sufficient; to select the filter medium of a motor vehicle air filter, the dust mass retained per unit of filtration area (mass loading of dust k_m) must be known for a specific allowable pressure drop Δp_fdop. New methods and conditions for determining the mass loading of dust k_m for filter paper and non-woven fabric in single-stage and two-stage filtration systems are presented. The characteristics of the separation efficiency and filtration performance as well as the pressure drop of a filter set comprising a single cyclone and a filter element with a specific filter medium surface are determined. The effects of the particle size distribution of the dust in the air downstream of the cyclone on the mass loading of dust k_m of the filter paper and non-woven fabric in a two-stage filtration system are presented. The mileage of a truck fitted with a single-stage or two-stage filtration system in a “multicyclone–panel filter” configuration is estimated based on the calculated mass loading of dust k_m of the filter paper and non-woven fabric.

© 2018 American Association for Aerosol Research     

Fundamentals‐based low‐dimensional combustion modeling of spark‐ignited internal combustion engines

A four‐mode low‐dimensional model for the in‐cylinder combustion process in an internal combustion engine is developed. The lumped parameter ordinary differential equation model is based on two mixing times that capture the reactant mixing limitations inside the cylinder and mixing limitations caused by the input and exit stream distribution. For a given inlet and operating conditions, the model predicts the exhaust composition of regulated gases (total unburned HCs, CO, and NO_x) as well as the in‐cylinder pressure and temperature. The model is able to capture the qualitative trends observed with change in fuel composition (gasoline and ethanol blending), air/fuel ratio, spark timing, engine load, and speed. The results show good qualitative and fair quantitative agreement with the experimental results published in the literature and demonstrate the possibility of such low‐dimensional model for real‐time control. Improvements and extensions to the model are discussed. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Thermochemical conversion of fuels into hydrogen-containing gas using recuperative heat of internal combustion engines

The problem of the thermochemical recuperation of heat from the exhaust gases of internal combustion engines (ICEs) as a method of increasing of the efficiency of fuels has been considered. The thermodynamic analysis of thermochemical recuperation conditions was performed, and maximum efficiency conditions were determined. Catalysts for the steam conversion of oxygen-containing fuels into syngas were developed, and the Co-Mn/Al₂O₃ catalyst was shown to be the most promising. The model of a thermochemical heat recuperation system was developed and manufactured, and its bench tests in the conversion of alcohols were performed using the simulated exhaust gases from a heating device. Mathematical models for calculating units of the heat recuperation system were developed. A recuperation system was manufactured and tested in the ICE-free and ICE-integrated variants. Based on the test results, the equivalent fuel consumption characteristics of a recuperative ICE was revealed to decrease by 11–22% depending on its load with a decrease in the concentration of hazardous emissions by 8–12 times for CO, 2–3.5 times for CH, and 18–25 times for NO _x .     

Development and evaluation of a catalytic stripper for the measurement of solid ultrafine particle emissions from internal combustion engines

Abstract

Solid particle number vehicle exhaust measurements necessitate an aerosol conditioning system that removes efficiently volatile particles, does not create artifacts, and minimizes solid nucleation particle losses. Here, we present the development and evaluation of a catalytic stripper (CS) based on a unique dual-function monolithic reactor that oxidizes hydrocarbons and stores sulfur material. The CS was tested for its tetracontane particle removal efficiency, sulfur adsorption capacity with sulfur dioxide, and particle penetration with solid CAST-generated particles. The optimal operation conditions were examined including different aerosol flows and configurations, i.e., as a stand-alone device and as part of a volatile removal system with a hot and a cold dilution stage upstream and downstream of the CS, respectively. The CS managed to comply with current legislation requirements for solid particle number measurements down to 23?nm as a stand-alone device and showed great potential as part of a volatile particle removal (VPR) system for measurements at least down to 10?nm. Finally, we compared the performance of two VPR systems that use the developed CS (VPR-CS) and an evaporation tube (VPR-ET), respectively. Our results suggest that the VPR-CS exhibits higher volatile removal efficiency without creating artifacts while the particle losses are lower with the VPR-ET. Nevertheless, when measuring solid nucleation particles generated by a diesel engine with the VPR-CS, the measurement uncertainty was very low due to its high particle penetration fractions.     

The fuel properties of three-phase emulsions as an alternative fuel for diesel engines

Diesel engines are employed as the major propulsion power for in-land and marine transportation vehicles primarily because of their rigid structure, low breakdown rate, high thermal efficiency and high fuel economy. It is expected that diesel engines will be widely used in the foreseeable future. However, the pollutants emitted from diesel engines (in particular nitrogen oxides and particulate matter) are detrimental to the health of living beings and ecological environment have been recognized as the major air pollution source in metropolitan areas and have thus attracted much research interest. Although diesel oil emulsion has been considered as a possible approach to reduce diesel engine pollutants, previous relevant applications were restricted to two-phase emulsions. Three-phase emulsions such as oil-in-water-in-oil briefly denoted as O/W/O emulsions and water-in-oil-in-water, denoted as W/O/W, have not been used as an alternative fuel for any combustion equipment. Studies on the properties of three-phase emulsion as fuel have not been found in the literatures. The emulsification properties of an O/W/O three-phase diesel fuel emulsion were investigated in this experimental study. The results show that the mean drop size of the O/W/O emulsion was reduced significantly with increasing homogenizing machine revolution speed. An increase in inner phase proportion of the O/W/O emulsion resulted in increasing the emulsion viscosity. The viscosity of O/W/O emulsion is greater than that for water-in-oil (denoted briefly as W/O emulsion) for the same water content. More stable emulsion turbidity appeared for three-phase O/W/O diesel emulsions added with emulsifier with HLB values ranging from 6 to 8. In addition, three-phase O/W/O emulsions with greater water content will form a larger number of liquid droplets, leading to a faster formation rate and greater emulsion turbidity at the beginning but a faster descending rate of emulsion turbidity afterwards. The potential for using O/W/O emulsions as an alternative fuel for diesel engines was also evaluated.     

Development of a catalytic heating system for external combustion engines

A catalytic heater design was proposed for an external combustion engine. This design is based on the partial oxidation or autothermal conversion of hydrocarbon fuel to syngas and its further oxidation with heat generation in a radial catalytic reactor integrated with a tubular heat exchanger. The theoretical analysis of operational regimes for a catalytic heater with a thermal power of 25–50 kW was performed with regard to the distribution of gas and the mathematical modeling of processes in a catalyst bed integrated with a heat exchanger, and some estimates were given for the performance of an external combustion engine. The conditions providing a uniform distribution of gas along the length of a radial reactor with suction of a reaction mixture into the catalyst bed were determined. A design of catalytic heating system elements was developed, and some layout solutions that provide a rational mutual arrangement of system components were created.     

Single droplet combustion of coal-methanol slurry

Coal-methanol slurry (CMS) has attracted special interest as a new coal slurry fuel. In this work, the combustion characteristics of CMS have been investigated experimentally by single droplet combustion with the following results. The scattering of pulverized coal particles was observed during the gas-phase combustion period. The combustion behaviour of CMS was very similar to that of pulverized coal. The overall burning rate coefficient for CMS was apparently increased compared to other coal slurry fuels, using residual heavy fuel oil as the dispersion medium. It was concluded that CMS has excellent properties which can mask the defects of pulverized coal and other coal slurry fuels for combustion, as well as in transportation and handling.     

Nonsteady heterogeneous fuel combustion

A self-similar solution has been constructed for the nonsteady one-dimensional problem of diffusion combustion at the surface of a fuel in purely heterogeneous regime, making it possible to determine the rate of surface burnout, temperature distribution in the gas and fuel, concentration distributions within the gas, and also to study the relationship between the derived characteristics and external determining parameters.Moscow. Translated from Fizika Goreniya i Vzryva, No. 2, pp, 34–40, March–April, 1991.     

水煤浆加压气化工艺技术优化

水煤浆加压气化工艺技术的实施,可生产出合成氨、合成甲醇等工艺所需的氢气和一氧化碳等原料。但是在加压气化的过程中,由于受到原煤质量、气化工艺等因素的影响,水煤浆加压气化的生产效率会受到影响。因而有必要对相关影响因素进行分析研究,然后采取相应的优化措施。主要结合水煤浆加压气化工艺技术的特点,分析影响气化工艺的因素和相关解决措施。     

Development of a microwave-assisted digestion method using ICP-OES to measure metals in gum deposits of internal combustion engines

The heterogeneous nature of gum samples obtained from the deposits of internal combustion engines is the main difficulty in accurate determination of their metal content. A microwave-assisted digestion method was implemented using factorial experimental design. The optimization of this procedure was carried out by first evaluating the effects of variables on the response (i.e., the residual carbon content or RCC). The variables of maximum heating power, heating time and nitric acid volume were studied. The RCC response was measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The time of maximum heating power was essential to obtain a desired RCC. The surface response was constructed with optimal conditions presented at 6 min and heating power of 700 W. Amounts of aluminum (Al), calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) were determined in 26 gum samples by ICP-OES. Ca, Fe, Mg and Zn were found at mg g⁻¹ levels in the samples, while Al, Cu, Mn, Ni and Pb were found at mg kg⁻¹ levels. Principal component analysis (PCA) was used to establish a correlation between the gum samples and the different metal contents. Three distinct groups were separated according to the characteristics of the collected samples.     

The development of a digestion procedure for the determination of metals in gum obtained from deposits in internal combustion engines by ICP-OES

The accurate determination of metals in gum (deposits found in internal combustion engines) is strongly influenced by a selection of the right sample digestion method. The difficult and heterogeneous nature of this kind of sample, and its unpredictable reaction behavior are the major obstacles in getting correct analytical results. The studies were implemented with one sample called “reference sample”. Two digestion procedures were tested in this work. The dry ashing procedure was followed by another dissolution procedure with HF and heating, in order to complete the dissolution of the ash in the samples. The process was performed in 36 h. The second digestion procedure was implemented in closed system (pressurized) with 2 mL of HNO₃ and 2 mL of H₂SO₄. This last one presented a reduction of 80.5% time-consuming in relation to the first one (dry ashing). Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Na, Ni, Pb, Si, and Zn were determined in 14 samples of gum by ICP-OES. The wet closed system digestion procedure showed efficiency in the Cr, Cu, Fe, K, Ni, Pb, Si, and Zn determination. The correlation matrix results contribute to the characterization studies of the gum formation process, as well as the corrosion of the motor parts and fuel quality control.