Lower Exhaust Gas Temperature Research Articles

An Efficient Method for Heat Recovery Process and燭emperature燨ptimization

Flue gas heat loss accounts for a significant component of the overall heat loss for coal-fired boilers in power plants. The flue gas absorbs more heat as the exhaust gas temperature rises, which reduces boiler efficiency and raises coal consumption. Additionally, if the exhaust gas temperature is too high, a lot of water must be used to cool the flue gas for the wet flue gas desulfurization system to function well, which has an impact on the power plant’s ability to operate profitably. It is consequently vital to take steps to lower exhaust gas temperatures in order to increase boiler efficiency and decrease the amount of coal and water used. Desulfurization performance may be enhanced and water use can be decreased by reasonable flue gas characteristics at the entry. This study analyzed the unit’s energy consumption, investment, and coal savings while proposing four coupling strategies for regulating flue gas temperature and waste heat recovery. A graded flue gas conditioning and waste heat recovery plan was presented under the condition of ensuring high desulfurization efficiency, along with the notion of minimizing energy loss owing to energy inflow temperature difference. Numerical results show that the proposed methods improved the system performance and reduced the water consumption and regulated the boiler temperature.

Promotion of the NO-to-NO2 Conversion of a Biofueled Diesel Engine with Nonthermal Plasma-Assisted Low-Temperature Soot Incineration of a Diesel Particulate Filter

High-concentration biodiesel-diesel fuel blends are an alternative fuel widely used for compression ignition engines. However, commercial diesel engines are not designed and set up for high-concentration biodiesel-diesel fuel blends. Hence, the aim of this research was to investigate the nonthermal plasma (NTP) activities during an NOx reduction and the soot characteristics on an unmodified diesel engine (Euro V) that is fueled with various biodiesel blends with diesel under a low exhaust gas temperature (<250 °C). The experiment found that the soot composition of biodiesel fuel produces lower levels of soot when compared with diesel, in terms of both number and mass. In addition, the activation energies (Ea) of carbon oxidation under an oxygen atmosphere were found to be approximately 154.57–173.64 kJ/mol.

Effect of a Plasma Burner on NOx Reduction and Catalyst Regeneration in a Marine SCR System

The problem of environmental pollution by the combustion of fossil fuels in diesel engines, to which NOx emission is a dominant culprit, has accelerated global environmental pollution and global and local health problems such as lung disease, cancer, and acid rain. Among various De-NOx technologies, SCR (Selective Catalytic Reduction) systems are known to be the most effective technology for actively responding to environmental regulations set by the IMO (International Maritime Organization) in marine diesel applications. The ammonia mixes with the exhaust gas and reacts with the NOx molecules on the catalyst surface to form harmless N2 and H2O. However, since the denitrification efficiency of NOx can be rapidly changed depending on the operating temperature from 250 °C to 350 °C at 0.1% sur contents of the catalyst used in the SCR, a device capable of controlling the exhaust gas temperature is essential for the normal operation of the catalyst. In addition, when the catalyst is exposed to SOx in a low exhaust gas temperature environment, the catalyst is unable to reduce the oxidation reaction of the catalyst, thereby remarkably lowering the De-NOx efficiency. However, if the exhaust gas temperature is set to a high temperature of 360–410 °C, the poisoned catalyst can be regenerated through a reduction process, so that a burner capable of producing a high temperature condition is essential. In this study, a plasma burner system was applied to control the exhaust gas temperature, improving the De-NOx efficiency from the engine and regenerating catalysts from PM (Particulate Matter), SOOT and ABS (ammonia bisulfate), i.e., catalyst poisoning. Through the burner system, the optimum De-NOx performance was experimentally investigated by controlling the temperature to the operating region of the catalyst, and it was shown that the regeneration efficiency in each high temperature (360/410 °C) environment was about 95% or more as compared with the initial performance. From the results of this study, it can be concluded that this technology can positively contribute to the enhancement of catalyst durability and De-NOx performance.

Experimental investigation on sucrose/alumina catalyst coated converter in gasoline engine exhaust gas.

In this study, a modified catalytic converter was employed to treat the harmful exhaust gas pollutants of a twin-cylinder, four-stroke spark-ignition engine. This research mainly focuses on the emission reduction of unburnt hydrocarbons, carbon monoxide, and nitrogen oxides at low light-off temperatures. A sucrolite catalyst (sucrolite) was coated over the metallic substrate present inside the catalytic converter, and exhaust gas was allowed to pass through it. A scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy were used to investigate the changes in morphology, chemical compounds, and functional group elements caused by the reactions. Catalytic reactions were studied by varying the engine loads and bed temperatures, and the results were compared with those of the commercial catalytic converter. The results show that sucrose present in the catalyst was suitable at low temperatures while alumina was suitable for a wide range of temperatures. In the case of the modified catalytic converter, the maximum catalytic conversion efficiencies achieved for oxidizing CO and HC were 70.73% and 85.14%, respectively, and for reduction reaction at NOx was 60.22% which is around 42% higher than in commercial catalytic converter. As a result, this study claims that sucrolite catalyst is effective for low-temperature exhaust gas.

Optimization of flame stabilization methods in the premixed microcombustion of hydrogen–air mixture

AbstractThe premixed combustion of a lean hydrogen–air mixture is analyzed in this study to examine various properties and flame stabilization. A two‐dimensional (2D) analysis of a microscale combustor is performed with various shapes of bluff bodies (e.g., circular and triangular). Nine bluff bodies are placed at the entrance of the microscale combustor and solved with 2D governing equations. The analysis is performed with the three velocities of 10, 20, and 30 m/s, but the equivalence ratio is fixed in all cases. The various characteristics of the microscale combustor are studied such as the temperature of the wall, difference in peak temperature, the mean velocity at the outlet, and temperature of the exhaust gases. Flame stabilization depends on various factors such as bluff body shape and size, and the velocity of the fuel–air mixture at the inlet and recirculation zone. In comparison to all bluff body cases, we observe that the wall blade bluff body is the most efficient (low exhaust gas temperature, large recirculation zone, low mean velocity at the outlet of the microcombustor, and high wall temperature) compared with all eight other bluff body cases. Combustion efficiency is directly proportional to the wall temperature, meaning that the microcombustor with wall blade bluff bodies is more efficient with a stabilized flame. The simulation results are compared with published data on an L/D ratio of 15.

RETRACTED: Effects of advanced injection timing and inducted gaseous fuel on performance, combustion and emission characteristics of a diesel engine operated in dual-fuel mode

The current study aims to investigate the effects of advanced injection timing combined with dual-fuel mode on the diesel engine's overall performance, emission, and combustion characteristics under various loading conditions. In this study, blends of waste oil methyl ester (WOME) at 10%, 20%, and 30% v/v concentration and diesel fuel were used as injected fuel, while biogas was the inducted gaseous fuel through the inlet manifold with a flow rate of 0.8 kg/h. Experimentations were carried out on a 4-stroke single-cylinder water-cooled diesel engine, in which engine speed, injection pressure, and compression ratio were fixed at 1500 rpm, 220 bar, and 17.5:1, respectively. Based on experimental data, dual-fuel mode of WOME20-biogas combined with advanced injection timing to 24°bTDC depicted the most positive results. Indeed, the higher brake thermal efficiency (2.40%), lower exhaust gas temperature (15.77%), but increased brake-specific fuel consumption (3.12%) and brake-specific energy consumption (1.85%) compared to diesel fuel were found at the highest load. Furthermore, increasing trends of in-cylinder pressure (7.48%) and heat release rate (4.71%), but diminished ignition delay (6.96%) as opposed to diesel fuel at higher loads were also reported. For emission analysis, a significant reduction of unburnt hydrocarbon (44.5%), carbon monoxide (61.72%), oxide of nitrogen (64.13%), and smoke intensity (47.42%) was obtained in comparison to conventional diesel fuel. Generally, the test diesel engine working on dual-fuel mode of WOME20-biogas combined with advanced injection timing of 24°bTDC would be helpful to enhance the overall efficiency and emission characteristics.

Effect of Producer Gas from Redgram Stalk and Combustion Chamber Types on the Emission and Performance Characteristics of Diesel Engine

The engine performance has been improved by modifying the combustion chamber shape of the diesel engine for dual-fuel operation with liquid fuel and producer gas (PG). The combined effect of gaseous fuel from redgram stalk and combustion chamber type on the emission and performance of blended-fuel of diesel and HOME biodiesel–PG has been investigated. In this experimental study, four varieties of combustion chambers hemispherical (HCC), low swirl (LSCC), dual swirl (DSCC), and toroidal re-entrant (TRCC) were analyzed comprehensively. The results presented that the TRCC configuration with a given nozzle geometry has 9% improved brake thermal efficiency (BTE) and 10.4% lower exhaust gas temperature (EGT). The smoke, unburnt hydrocarbon (UBHC), and carbon monoxide (CO) decreased by 10–40%, but a 9% increase in nitrogen oxides (NOX) emission levels was observed with TRCC. The delay period and combustion period were decreased by 5% and 7%. The fuel replacement of about 71% for the diesel–PG combination with HCC and 68% for the HOME–PG combination with TRCC was achieved.

Synergies in renewable fuels and exhaust heat thermochemical recovery in low carbon vehicles

The impact of renewable fuels on exhaust energy recovery using catalytic thermochemical process in modern gasoline direct injection is studied with main aim of reducing vehicle carbon footprints. It is proven that supplying the engine with increased calorific value reformate would be beneficial in terms of CO2 reduction and fuel economy. In this research, the influence of butanol and ethanol on heat recovery, H2 production, and reforming efficiency are analytically and experimentally studied under various key parameters, including steam to carbon molar ratio and reactor inlet temperature under lean engine operating condition. Gibbs free energy and chemical equilibrium analyses are implemented to identify the key reaction pathways in reforming of the fuels. At lower exhaust gas temperatures where the reactions are thermodynamically limited the conversion rate is mainly controlled by the steam to carbon molar ratio and reducing fuel flow rate leads to a significant increase in fuel conversion levels. Maximum calorific value was achieved by ethanol reforming at 600 °C. However, at higher temperatures and steam to carbon molar ratios, butanol generally indicates better performance in terms of engine fuel economy, energy replacement by reformate, and CO2 reduction. These advantages are attributed to higher calorific value and higher reforming process efficiency of butanol compared to ethanol. In contrast, at lower temperatures, ethanol reforming generates more H2 as a result of highly endothermic nature of butanol steam and dry reforming reactions compared to ethanol with weaker molecular bonds and higher molecular diffusivity rate which leads to efficient use of the catalyst.

Experimental evaluation of diesel engine operating with A TERNARY BLEND (BIODIESEL-DIESEL-ETHANOL)

The present investigation aims to study the future potential fuel of a non-edible tamanu oil (calophyllum inophyllum). The raw oil of tamanu oil was converted into biodiesel in two-step esterification process and different test fuel blends with biodiesel were prepared with conventional diesel and ethanol as an additive to evaluate its effect on engine characteristics such as BP, BTE, and BSFC, EGT and smoke density on a 4.4 kW rated power, single-cylinder four-stroke of constant rpm C.I. engineat different loads (25%, 50%, 75%, and 100% of rated power). The fuel blends were prepared with biodiesel in the ratio of 40%,100% coded as B40 and B100 respectively along with diesel fuel and ethanol as an additive in the fixed ratio of 10%, 15%, and 20%. It was found that B40E20D40 showed a reduction in smoke density and BSFC of 14.28% and 5.9% respectively, 18.3% increase in BTE and 3.73% reduction in exhaust gas temperature at full load whereas B100 showed a maximum reduction in smoke density of 15.97% with 4.53% increase in BSFC and a marginal increase in EGT of 0.53%. B40E20D40 gave a better performance in a diesel engine from the perspective of minimum BSFC, lower exhaust gas temperature and higher BTE among all other blends.

An Assessment of the Economic Viability of Engine Wash Procedures on the Lifecycle Costs of an Aircraft Fleet.

Aircraft operators find themselves in a highly complex and competitive environment in which the economic pressure on companies is constantly increasing. In addition, annual air traffic is expected to increase by 4-5% (despite the Covid-19 pandemic), which requires significant improvements of aircraft efficiency. To address this on European and global scale, long-term economic and ecologic goals have been defined in the "Flightpath 2050" by the European Commission. One way to reduce both operating costs and environmental impact is to reduce aircraft fuel consumption. Regularly performed engine washes can reduce the accumulation of dirt and debris in the engine and partially restore the performance degradation as well as lower the wear and tear of the engine. This results in lower exhaust gas temperature and a slower aging engine with longer intervals between required maintenance events. 
 Most engine wash studies have drawn their system boundary around the engine and consider only the one-time improvements that result from a wash. Long term effects that build on these improvements, such as changes in maintenance and replacement cycles, are usually not considered. Few studies are available that extend their system boundary and consider changes in maintenance costs. Yet the value of engine wash processes is often quantified on an insufficient setting, especially when environmental conditions and fleet effects are neglected. To estimate the overall benefit and assess the impact on lifecycle costs, a full evaluation of engine wash within an entire fleet is required and fleet effects such as the possibility of downrating the engine for a smaller aircraft should be considered. 
 The aim of this work is to quantify the true value of engine wash procedures considering both physical constraints as well as operational fleet wide considerations. Using discrete event simulations at fleet level, a detailed investigation of the primary and secondary effects and a quantification of lifecycle costs will be performed. Particular attention will be paid to the influence on maintenance costs as well as the economic effect of increased time on wing. With the help of an improved environmental modeling and with the consideration of fleet effects, a holistic statement is possible.
 To investigate this problem, a lifecycle costing method, named LYFE, developed by DLR will be used. LYFE uses discrete event simulation to model the product lifecycle from order to operation until disposal of an aircraft fleet. For this analysis the tool will be extended to separate the lifecycles of the engines and those of the aircraft, so the engines can change the aircraft and the downrating of the engine for a smaller aircraft can be modeled. In order to represent the contamination and the performance degradation of the engines as realistically as possible, data on the outside air temperature, dust, pollution and other particles in certain regions at the various airports are also included in the tool. Furthermore, the option of derating the engine’s thrust is considered. The lifecycle of two different fleets will be simulated and studied. The difference between the two fleets is that the baseline fleet does not perform any engine washes, while the study fleet performs engine washes. Both fleets consist of different types of aircraft, so that downrating of the engines is possible and the entire lifecycles of the aircraft can be mapped. The evaluation follows two approaches: firstly, the engine wash is carried out and examined regularly; secondly, the intervals at which the engine wash is carried out are optimized in such a way that the lifecycle costs of the fleet are as low as possible. In both cases the number of engines necessary to operate the fleet will be the basis for an overall statement.
 With this holistic view of how engine washes within a fleet affect its lifecycle costs, a much more realistic statement about this on-wing maintenance action is possible.

Effects of porous media on partially premixed combustion and heat transfer in meso-scale burners fuelled with ethanol

Porous media (PM) have the potential to enhance the flame stability and improve thermal performance in a micro/meso-scale burner. In this work, zirconia foam and high-porosity nickel foam are used in the meso-scale burners and partially premixed submerged combustion of liquid ethanol is achieved. An experimental investigation of the effects of foamed PM on flame structure, detailed temperature distributions, emissions, and thermal performance is undertaken. A blue flame can be observed in the nickel foam and the transient features of flame front is obtained. The flame front propagates intermittently when the combustion zone moves upstream. The maximum instantaneous flame speed in the PM is 6.519 mm/s and the average flame speed is 0.225 mm/s. The foamed PM in the meso-scale burners are shown to significantly improve the heat transfer efficiency. The burner in submerged combustion has a lower reaction zone temperature (806 °C vs. 1721 °C), lower exhaust gas temperature (419 °C vs. 1227 °C) and higher wall temperature than that with free flame. The heat transfer efficiency of the submerged flame is about twice that of the free flame.

Energy and Exergy Analysis of an Organic Rankine Cycle used for Ylang-Ylang Essential Oil Distillery Waste Heat Recovery for Power Production in Anjouan Island

In the ylang-ylang essential oil distillers in Anjouan Island, the used energy is 100% firewood biomass. A large amount of this energy is dissipated in the environment just in the combustion chamber itself. As it turns out, the flue gases in this process take away the most part of it. Thus, in a process of energy efficiency of stills, the present work aims at assessing the possibility to convert the residual heat from the process into electricity. For that purpose, energy and exergy modeling of an organic Rankine cycle was implemented. It was found that a large amount of exergy is destroyed in the evaporator. Similarly, it emerges that the exergy efficiency of the cycle depends on the inlet temperatures of the exhaust gases in the evaporator and on the inlet pressure of the working fluid in the turbine, and that it is much better for low exhaust gas temperatures. At these low values of gas temperatures, it appears that the improvement in exergy efficiency and energy efficiency are linked to the increase in the inlet pressure of the working fluid in the turbine. It follows from the obtained results that the discharged hot water and the residual heat of gases having temperatures ranging from 180°C to 300 °C, could be used for power production which can reach electrical powers between 1.4kW and 4.5kW

Modeling of exhaust gas cleaning by acid pollutant conversion to aerosol particles

Sulfur and nitrogen oxides (SOx and NOx) are harmful pollutants emitted into the atmosphere by industry and transport sectors. In addition to being hazardous gases, SOx and NOx form sulfuric and nitric acids which contribute to the formation of airborne particulate matter through nucleation and condensation, hence magnifying the environmental impact of these species. In this work, we build a modeling framework for utilizing this phenomenon for low-temperature exhaust gas cleaning. It has been reported that ammonia gas can be used to facilitate particle formation from the aforementioned acids, and thus remove these gaseous pollutants by converting them into ammonium sulfate and nitrate particles. Here we provide comprehensive modeling tools for applying this idea to exhaust gas cleaning by combining detailed models for nucleation, gas–particle mass exchange and particle population dynamics. We demonstrate how these models can be used to find advantageous operating conditions for a cleaning unit. In particular, the full model is computationally cheap and enables optimization of the particle formation efficiency and particle growth, hence ensuring sufficient conversion of gaseous pollutants into collectable particulate matter. This constitutes a ground for future engineering tools for designing next-generation sustainable exhaust gas cleaners.

Influence of calophyllum inophyllum and Jojoba oil methyl ester blended with n-pentanol additive upon overall performance, combustion and emission characteristics of a TDI engine operated in natural aspirated mode

The present manuscript briefly elaborates the performance, combustion and emission behaviour of a turbocharged direct injection diesel engine operated in dual mode where calophyllum inophyllum and Jojoba oil methyl ester are the injected fuel while in second case the above said test fuel blends were mixed homogeneously with n-pentanol that acts as an additive during the experimentation. The main objective of using n-pentanol is its five straight chain carbon atoms that has better possibility of homogeneous blending with biodiesel blends due to its high cetane number, stability and density in contrast to other alcohol based additives helping in improving engine performance and diminished exhaust emissions. During the experimentation, engine parameters like compression ratio (17.5:1), injection timing (21°bTDC), injector opening pressure (220 bar), speed (1500 rpm) were kept constant. Results concluded CIME20–P20 blend to be reliable and potential alternative fuel to partially replace conventional diesel fuel. Considering performance and emission characteristics calophyllum inophyllum oil methyl ester and pentanol blend (CIME20–P20) depicts a higher brake specific fuel consumption of 3.41% while lower exhaust gas temperature and brake thermal efficiency of 13.46% and 1.18% in contrast to diesel fuel. Moving on to emission analysis, carbon dioxide, hydrocarbon, oxides of nitrogen and smoke opacity for CIME20–P20 were 57.02%, 59.37%, 17.39% and 41.53% lower than conventional diesel fuel. Hence, coming to the overall summary, CIME20–P20 depicts better performance and diminished exhaust emission thereby making it more potential to substitute the conventional fuel without any engine alteration for better environmental sustainability and energy security.

Deposit Formation in SCR-Systems - Optical Investigations

<div class="section abstract"><div class="htmlview paragraph">The permanently tightening emission regulations for nitrogen oxides (NOx) pollutants force further development of mobile exhaust aftertreatment systems with selective catalytic reduction (SCR). Of particular interest is the long-term reliability of SCR-systems with regard to unfavorable operating conditions, such as high injection rates of urea water solution (UWS) or low exhaust gas temperatures. Both may lead to the formation of solid deposits which decrease system efficiency by increasing backpressure and impairing ammonia formation.</div><div class="htmlview paragraph">In order to study the most relevant processes of deposit formation, an optical box with heat resistant glass was designed. Three UWS injectors with different spray characteristics were used to study their influence on the deposit formation under a wide range of stationary and transient operating conditions. Infrared thermography was applied to observe spray-induced wall cooling, both below and above the Leidenfrost point. The formation of a liquid fluid film on a hot surface as well as deposit growth and decomposition were monitored by video recording. A chemical analysis of obtained solid deposits complemented the experimental investigations.</div><div class="htmlview paragraph">This paper describes influences on deposit formation and decomposition. A strong impact of spray properties, such as droplet Weber number and spray area load, on the critical wall temperature for film formation was found. Different types of liquid film propagation were observed for different surface temperatures. The impact of operating conditions, such as exhaust gas temperature and gas flow rate, on the amount and the chemical composition of the deposits was determined. The experimental observations revealed different impact factors on the persistence of solid deposits.</div><div class="htmlview paragraph">The obtained experimental results show the complexity of physical and chemical processes leading to formation of solid deposits in SCR systems. Based on that, the requirements of CFD models for modeling of deposit formation and decomposition were defined in terms of physical and chemical properties as well as the necessary simulated time scales.</div></div>

Emission Reduction Strategies for Small Single Cylinder Diesel Engine Using Valve Timing and Swirl Ratio

Small diesel engines are widely used for commercial vehicle and passenger car applications due to their higher torque requirements, fuel economy, and better thermal efficiency. These engines are exposed to different operating and environmental conditions and hence emissions from these engines are erratic. Strategies are required to enhance performance and reduce engine-out emissions considering environmental pollution and regulations. The main objective of this experimental study is to develop strategies for performance improvement and emission reduction for naturally aspirated engines, which can further be used for emission reduction of the multicylinder engine. Experimental work has been carried out on a single-cylinder naturally aspirated diesel engine to study the impact of engine operating parameters like valve timing, swirl ratio, and injection pressure on engine performance and emissions. Parameters considered for the study are: three intake valve opening timings, two fuel injection pump pressures, two-cylinder head swirls, and three start of injection timings. Results showed improvement in performance, lower exhaust gas temperature, and reduction of engine-out emission. Exhaust gas temperature was reduced by 5-18% with advanced valve opening and lower cylinder head swirl option. NOx emission was reduced by 5-50% at advanced intake valve opening (IVO) options with retarded start of injection (SOI) and lower swirl cylinder head. This has a penalty on CO and HC emissions since the availability of fresh air is less due to higher internal exhaust gas recirculation (EGR). Higher pressure fuel injection pump helps in improving engine torque with an adverse effect on engine-out NOx emission. As these engines are of low power capacity segment and are used in few countries, research on these engines is limited. All research work has been carried out in the field of intake valve closing timings, swirl ratio and injection timings; however, very limited research is available for the effect of intake valve opening timings due to practical limitations of the lower valve to piston clearance in diesel engines.

Porous TiO2 aerogel-modified SiC ceramic membrane supported MnOx catalyst for simultaneous removal of NO and dust

As the main atmospheric pollutants, the nitrogen oxides (NOx) and dust from industrial exhaust have caused a series of environmental problems. Catalytic membrane is one of the most important technologies for integrated denitration and dust removal, which can achieve the efficient treatment of multiple pollutants. In order to achieve the simultaneous removal of NO and dust in low-temperature exhaust, a novel MnOx/TiO2/SiC catalytic membrane was developed. The using of TiO2 aerogel as the transition layer could increase the loading capacity of MnOx by more than twice, but has little effect on gas permeance of SiC ceramic membrane. The MnOx/TiO2/SiC catalytic membrane also exhibit excellent filtration performance with dust rejection rate exceeding 99.97% and thus preventing adverse effects of dust on the catalyst. In the NO and dust coexistence system, the obtained catalytic membrane exhibits good catalytic activity owing to its high loading capacity and outstanding filtration performance, which lead to the high NO conversion rate above 80% with the temperature range of 120–180 °C. Meanwhile, the catalytic membrane exhibits remarkable stability in simulation environment, and the NO conversion rate could maintain at 90% within 65 h. The novel MnOx/TiO2/SiC catalytic membrane showed great promise for low-temperature exhaust gas purification.

Experimental investigations of mineral diesel/methanol-fueled reactivity controlled compression ignition engine operated at variable engine loads and premixed ratios

Global warming and stringent emission norms have become the major concerns for the road transport sector globally, which has motivated researchers to explore advanced combustion technologies. Reactivity controlled compression ignition combustion technology has shown great potential to resolve these issues and deliver high brake thermal efficiency and emit ultra-low emissions of oxides of nitrogen and particulate simultaneously. In this experimental study, baseline compression ignition combustion mode and reactivity controlled compression ignition combustion mode experiments were performed in a single-cylinder research engine using mineral diesel as high-reactivity fuel and methanol as low-reactivity fuel. All experiments were carried out at constant engine speed at four engine loads (brake mean effective pressure: 1–4 bar). For efficient combustion and lower emissions, four premixed ratios ( rp = 0, 0.25, 0.50, and 0.75) were tested to assess optimized premixed ratio at different engine loads. In these experiments, primary and secondary fuel injection parameters were maintained identical. Combustion results showed that reactivity controlled compression ignition combustion was more stable compared to compression ignition combustion and resulted in lesser knocking. Reactivity controlled compression ignition combustion delivered higher brake thermal efficiency and lower exhaust gas temperature and oxides of nitrogen emissions, especially at maximum engine loads. Addition of methanol as secondary fuel reduced particulate emissions. Particulate analyses depicted that reactivity controlled compression ignition combustion mode emitted significantly lower accumulation mode particles; however, emission of nucleation mode particles was slightly higher. A significant reduction in particulate mass emitted from reactivity controlled compression ignition combustion was another important finding of this study. Particulate number–mass distributions showed that increasing the premixed ratio of methanol led to a dominant reduction in particulate number concentration compared to particulate mass. Analysis for critical performance and emission characteristics suggested that optimization of the premixed ratio of methanol at each engine load should be done in order to achieve the best results in reactivity controlled compression ignition combustion mode.

Emission Characteristics of Methyl Ester of Rice Bran Oil Blends with Ethanol in CI Engine

Increasing demand and rapid depletion of fossil fuels have together prompted the researchers of many countries to look for alternate renewable fuels. This study is an attempt to test the feasibility of rice bran oil as fuel in C. I. engine in its original and in its refined form. It is generally produced from rice bran which is a by-product produced during paddy processing. Its viscosity though relatively higher than diesel can be reduced by natural sedimentation process. In this attempt, the performance and emission characteristics of rice bran oil and its refined form were studied and compared with diesel by employing them as a fuel in a single cylinder, direct injection, 4.4 KW, air cooled diesel engine. The performance characteristics revealed that the brake thermal efficiency of the rice bran oil was higher than its refined form and were marginally lower than that of diesel. Emission measurements were carried out using MRU Delta 1600L gas analyzer and the soot concentration was measured with AVL smoke meter. It was found that though blends of rice bran oil with ethanolexhibited greater soot concentration characteristics than rice bran oil and diesel at all loads, it exhibited desirable characteristics for other emissions such as lower CO, HC, NOx emissions and lower exhaust gas temperatures with increasing load.

A Fast Modeling Approach for the Numerical Prediction of Urea Deposit Formation

<div class="section abstract"><div class="htmlview paragraph">The permanently tightening emission regulations for NOx pollutants force further development of automotive exhaust aftertreatment systems with selective catalytic reduction (SCR). Of particular interest is the long-term reliability of SCR systems with regard to unfavorable operating conditions, such as high injection rates of urea water solution (UWS) or a low exhaust gas temperature. Both of them may lead to formation of solid deposits which increase backpressure and impair ammonia uniformity.</div><div class="htmlview paragraph">A fast modeling approach for numerical prediction of deposit formation in urea SCR systems is desired for optimization of system design. This paper presents a modified methodology for the modeling of deposit formation risk. A new determination of the initial footprint of the spray, where the deposit formation is inhibited, is proposed. The threshold values for the evaluation of the film transport were validated based on experimental results. To achieve a more realistic simulation in terms of wall wetting and cooling, the impingement heat transfer as well as the impingement model were modified based on optical investigations.</div><div class="htmlview paragraph">In order to accomplish the modeling of deposit formation with typical time ranges of several minutes, a recently developed injection source approach was applied. The substitution of the Lagrange-particles with source terms of mass, momentum and energy allowed to reduce simulation time by a factor of 30. The presented modeling approach was validated against both, the experimental data from an optical box and an exhaust aftertreatment system. The comparison of measured and simulated results shows the capability of the presented modeling approach to predict the position and the severity of solid deposits.</div></div>