Diesel Engine Exhaust Gas Research Articles

Performance evaluation of neural networks in modeling exhaust gas aftertreatment reactors

A comprehensive evaluation of neural network (NN) methods to model exhaust gas aftertreatment reactors is presented in this study. A combination of non-linear autoregressive model with exogenous inputs (NARX) network and static NN is utilized to capture the dynamic behavior of the state and outlet variables, such as coverage fractions, temperatures, and conversions, of monolith reactors used in the abatement of automobile emissions. The efficacy of this methodology is illustrated by modeling the diesel oxidation catalyst (DOC) and selective catalytic reduction (SCR) reactors of a diesel engine exhaust gas aftertreatment system. The final NN topology is designed by carefully comparing the model performances in the training and testing datasets. Model parsimony quantified by Akaike’s Information Criterion is employed for choosing the number of input and feedback delays in the NARX network. The novelty of this work lies in generating quality training and validation data using a physics-based system level model comprising of the engine and aftertreatment reactor components. The accuracy and generalizability of the NN models are demonstrated by comparing the model predictions with physical model simulation results in five disparate test datasets used in vehicle certification protocols. Overall, the NN models are found to reproduce all the qualitative trends in the various state and output variables while needing minimum computing resources resulting in better than real-time performance. Therefore, with appropriate training, these models can be embedded in the electronic control unit (ECU) and utilized for model-based predictive control systems.

ОЦЕНКА ВОЗДЕЙСТВИЯ ДИЗЕЛЕЙ ЖЕЛЕЗНОДОРОЖНОГО ПОДВИЖНОГО СОСТАВА НА ПАРНИКОВЫЙ ЭФФЕКТ

The paper analyses influence that greenhouse gases emissions contained in exhaust gases of diesel engines render on formation of the greenhouse effect. The author shows that except СО2 in the total balance of greenhouse gases emissions it is necessary to consider also nitrogen oxides emissions that more aggressively than the carbon dioxide affect the air environment.

Advanced Exergy Scrutiny of a Dual-loop Organic Rankine Cycle for Waste Heat Recovery of a Heavy-duty Stationary Diesel Engine

In this paper, the normal exergy scrutiny (NES) and advanced exergy scrutiny (AES) of a waste heat recovery (WHR) system was performed. The proposed system contains a dual-loop organic Rankine cycle (DORC) which recovers the available waste heat of the intake air, exhaust gas, and coolant streams of a 12-cylinder heavy-duty stationary diesel engine. A well-known method of the AES called the thermodynamic cycle approach is utilized to determine each component exergy destruction parts namely exogenous/endogenous, unavoidable/avoidable, etc. Results showed that 59.04 kW from the 258.69 kW total exergy destruction rate of the system could be eliminated (22.82% of the total exergy destruction rate). The total avoidable exergy destruction part of the low-temperature loop accounts for 46.62 kW, which indicates that it requires more attention than that of the high-temperature loop by 12.42 kW. Furthermore, it is revealed that to enhance the overall productivity of the system, there is a relatively significant difference in priority order regarding the improvement of system components. The AES has proposed this ranking for improvement priority of components: condenser, expander 2, expander 1, respectively. While the NES has specified the priority as the evaporator 1, condenser, expander 2, respectively.

Comparison of Heat Transfer rates for Water and Ethylene Glycol mixtures for Diesel engine exhaust gas heat recovery using Shell and Tube Heat Exchanger.

Most of the researchers have claimed that high compression engines (diesel engines) are performing slightly above of 1/3rd of their potential and remaining heat energy is wasted in the form of exhaust gas. Efforts are going on to improve the design of these engines and investigations are being carried out to recover this waste energy from exhaust gases and utilize for different applications.In the present work, initially water is used as a heat exchange medium for three different loads on diesel engine viz., 50%, 60% and 70%, which extracts heat energy to evaluate the exhaust heat attainable from exhaust gases of the engine. The exhaust gas is passed through the tube side of the heat exchanger which is obtained from an exhaust manifold of a four stroke single cylinder diesel engine. Water is passed through the shell side of the shell and tube heat exchanger. Later this work is repeated for two different cooling medium i.e. water-ethylene glycol mixtures with 25% and 50%. The results are compared for 60% engine load conditions. The counter flow type heat exchanger arrangement is considered for the analysis. The temperatures were recorded for hot gases and cold medium at inlet and outlet points of the shell side and tube side flow. Heat calculations are carried out for each combination and detailed in the result–discussion and conclusion chapter. The objective of this work is to assess the exhaust gas heat recovery capacity using the ethylene glycol-water mixture and come out with a mixture for higher heat recovery capacity. This work is undertaken with segmental baffle heat exchanger of zero degree inclination. Also the work is repeated for inclined baffle heat exchangers of 10-degree and 20-degree baffle inclination to assess the effectiveness of liquid in recovering the heat from exhaust gases. It is observed that the water and Ethylene glycol mixtures have performed satisfactorily in all three baffle setups showing only 1.5% - 2.0% less heat recovery when compared with only water.

Влияние регулируемых параметров рабочего процесса на образование оксидов азота в водородном дизеле

The article considers formation of nitrogen oxides in a hydrogen diesel engine with direct injection of gaseous hydrogen depending on the adjustable parameters of the working process: excess air ratio, cyclic hydrogen supply, advance angle and duration of hydrogen injection. It was found that in a number of cases the effect of these parameters on the working process and the emission of nitrogen oxides leads to results that differ significantly from those in traditional diesel engines running on hydrocarbon fuel. It is shown that by varying the specified controlled parameters, it is possible to minimize the concentration of nitrogen oxides in the exhaust gases of a hydrogen diesel engine.

A 1D–3D Approach for Fast Numerical Analysis of the Flow Characteristics of a Diesel Engine Exhaust Gas

It is necessary to analyze the intake/exhaust gas flow of a diesel engine when turbocharger matching and when installing emission control devices such as exhaust gas recirculation (EGR), selective catalytic reduction (SCR), and scrubbers. Analyzing the intake/exhaust gas flow using a 3D approach can use various analytical models, but it requires a significant amount of time to perform the computation. An approach that combines 1D and 3D is a fast numerical analysis method that can utilize the analysis models of the 3D approach and obtain accurate calculation results. In this study, the flow characteristics of the exhaust gas were analyzed using a 1D–3D coupling algorithm to analyze the unsteady gas flow of a diesel engine, and whether the 1D–3D approach was suitable for analyzing exhaust systems was evaluated. The accuracy of the numerical analysis results was verified by comparison with the experimental results, and the flow characteristics of various shapes of the exhaust system of a diesel engine could be analyzed. Numerical analysis using the 1D–3D approach was able to be computed about 300 times faster than the 3D approach, and it was a method that could be used for research focused on the exhaust system. In addition, since it could quickly and accurately calculate intake/exhaust gas flow, it was expected to be used as a numerical analysis method suitable for analyzing the interaction of diesel engines with emission control devices and turbochargers.

Effects of Diesel-Biodiesel-Ethanol Fuel Blend on a Passive Mode of Selective Catalytic Reduction to Reduce NO x Emission from Real Diesel Engine Exhaust Gas.

The effects of ethanol on combustion and emission were investigated on a single-cylinder unmodified diesel engine. The ethanol content of 10–50 vol % was chosen to blend with diesel and biodiesel fuels. Selective catalytic reduction (SCR) of nitrogen oxides (NOx) in the passive mode was also studied under real engine conditions. Silver/alumina (Ag/Al2O3) was selected as the active catalyst, and H2 (3000–10000 ppm) was added to assist the ethanol-SCR. The low cetane number of ethanol resulted in longer ignition delay. The diesel–biodiesel–ethanol fuel blends caused an increase in fuel consumption due to their low calorific value. The brake thermal efficiency of the engine fuelled with relatively low ethanol fraction blends was higher than that of diesel fuel. Unburned hydrocarbons (HC) and carbon monoxide (CO) increased, while NOx decreased with ethanol quantity. The higher ethanol quantity led to increases in the HC/NOx ratio which directly affected the performance of NOx-SCR. Addition of H2 considerably improved the activity of Ag/Al2O3 for NOx reduction. The proper amount of H2 added to promote the ethanol-SCR depended strongly on the temperature of the exhaust where a high fraction of H2 was required at a low exhaust temperature. The maximum NOx conversion of 74% was obtained at a low engine load (25% of maximum load), an ethanol content of 50 vol %, and H2 addition of 10000 ppm.

Safety analysis of routing and planning of the transportation of dangerous goods by water transport

The transportation of dangerous goods makes up a substantial proportion of the world cargo turnover. The role of water transport in the transportation of such goods as the cheapest form of transport in international trade is also growing. Hazardous substances can be extremely harmful to both the environment and human health. Their leakage can lead to global catastrophes and damage caused by them can amount to millions of dollars. Nowadays one of the main problems of emergencies in water transport is a violation of the existing transportation rules, including the transportation of dangerous goods. In this paper their characteristics and classification are given on the basis of the considered existing normative documents (conventions and agreements) and the analysis of the existing system for the transportation of dangerous goods by water transport. The concept of “dangerous goods” is defined. The issues related to accidents, labeling of dangerous goods, training of service staff are considered. The issue of limits on sulfur oxides (SOx) in the exhaust gases of marine diesel engines is considered after the initial review of the current regulations for the carriage of dangerous goods by water. Possible risks arising in connection with the transportation of dangerous goods are presented.

Study on removing NO from simulated marine diesel engine exhaust gas using the novel composite system of Ozone-Na2SO3/(NH2)2CO

The pollutants from the marine exhaust gas seriously threaten air quality and human health. Wet absorption is one of the most efficient NOx control pathways. The strict emission control regulations require the wet NOx control technology to have high NOx removal efficiency and the nitrate concentration of the absorption solution to be below 60 mg/L. The novel system of ozone-Na2SO3/(NH2)2CO could not only make the NOx absorption efficiency and the amount of nitrate residue fully meet the regulations but also effectively reduce the (NH2)2CO consumption and the nitrite concentration. The final product of NO was mainly N2 instead of nitrate. The effects of O3 concentration, Na2SO3 concentration, (NH2)2CO concentration, O2 concentration, SO2 concentration, initial pH value, and temperature were thoroughly investigated. The experimental results showed that the NOx removal efficiency was mostly influenced by the O3 concentration, Na2SO3 concentration, and the initial pH value. Moreover, the nitrate concentration was mainly controlled by Na2SO3 concentration and initial pH value. While the nitrite concentration was governed by the (NH2)2CO concentration and initial pH value. The increase of O3 concentration and Na2SO3 concentration promote NOx absorption. Although the decrease of initial pH value resulted in a slight increase of nitrate, it greatly reduced the content of nitrite. Furthermore, the increase of Na2SO3 concentration helped to improve the NOx removal efficiency and inhibited the generation of nitrate. Initial pH value was the critical parameter for the NO absorption process. Ozone-Na2SO3/(NH2)2CO composite system showed great application potential in the field of marine wet NOx control technology.

REDUCTION OF TOXICITY OF BURNT DIESEL GASES WITH THE ADDITIONAL FEEDING SYSTEM

As a result of the introduction of new environmental emission standards, manufacturers of motor vehicles and fuels have to use a variety of technologies, systems and units to reduce harmful substances in the exhaust gases of diesel engines. Modern development of automobile internal combustion engines takes place in the following directions: increase of fuel economy and ecological purity; subincrease of unit power and weight reduction; creation of hybrid power plants with an internal combustion engine (ICE); dieselization of transport; increasing reliability of work and resources; use of alternative fuels (gas, hydrogen); control of internal combustion engines with the help of microprocessor technology. One of the ways to solve the problem is to develop technologies related to the installation of additional equipment on an existing engine in order to reduce harmful emissions into the environment.

Exhaust waste heat recovery from a heavy-duty truck engine: Experiments and simulations

Waste heat recovery using an (organic) Rankine cycle is an important and promising technology for improving engine efficiency and thereby reducing the CO2 emissions due to heavy-duty transport. Experiments were performed using a Rankine cycle with water for waste heat recovery from the exhaust gases of a heavy-duty Diesel engine. The experimental results were used to calibrate and validate steady-state models of the main components in the cycle: the pump, pump bypass valve, evaporator, expander, and condenser. Simulations were performed to evaluate the cycle performance over a wide range of engine operating conditions using three working fluids: water, cyclopentane, and ethanol. Additionally, cycle simulations were performed for these working fluids over a typical long haul truck driving cycle. The predicted net power output with water as the working fluid varied between 0.5 and 5.7 kW, where the optimal expander speed was dependent on the engine operating point. The net power output for simulations with cyclopentane was between 1.8 and 9.6 kW and that for ethanol was between 1.0 and 7.8 kW. Over the driving cycle, the total recovered energy was 11.2, 8.2, and 5.2 MJ for cyclopentane, ethanol, and water, respectively. These values correspond to energy recoveries of 3.4, 2.5, and 1.6%, respectively, relative to the total energy requirement of the engine. The main contribution of this paper is the presentation of experimental data on a complete Rankine cycle-based WHR system coupled to a heavy-duty engine. These results were used to validate component models for simulations, allowing for a realistic estimation of the steady-state performance under a wide range of operating conditions for this type of system.

Impact of High-Voltage Discharge After-Treatment Technology on Diesel Engine Particulate Matter Composition and Gaseous Emissions.

Diesel particulate matter (DPM) and oxides of nitrogen (NOx) are the emissions from diesel engines (compression ignition engines) of the most concern and are currently strictly regulated. In this work, we present an alternative diesel emission control technique to assist in further emission reduction. An experiment-oriented study on diesel engine emission abatement using low-power, low-frequency, high-voltage discharge (HVD) treatment was carried out in a laboratory-scale reactor with whole diesel engine exhaust gas. A dielectric barrier discharge (DBD) reactor was used in direct contact with diesel exhaust gas at atmospheric temperature with an input energy density between 200 and 400 J/L. An investigation of the direct effect of the high-voltage discharge reactor on the diesel exhaust gas treatment was carried out to characterize both diesel particle and gaseous emissions. The proposed HVD system demonstrated up to 95% particulate matter reduction by mass or 64% reduction by number, and 63% reduction of the diesel soot particle geometrical mean diameter by HVD-generated O3 oxidation. Thermogravimetric analysis revealed the significant change in the diesel soot compositions and oxidation characteristics. HVD-treated particulate matter demonstrated a lower reactivity in comparison to untreated soot. Gas composition analysis indicated the generation of free radicals (e, O, OH, O3, and N) by the HVD system, as mainly indicated by the increase of the NO2/NO ratio and concentration of CO and O2. The pattern of CO2 reduction while CO and O2 increased indicated the dissociation of CO2 by HVD. Free radicals generated by HVD directly affected DeNO, DeNOx, NO2/NO ratio, and CO and CO2 selectivities.

Condenser Design for On-Board ORC Recovery System

In this study, an ORC plant is considered that recovers the heat source from 1800 cc Diesel Engine exhaust gases. The power recovered by the ORC system could be used, as an auxiliary system, to provide energy to the electronic parts of the car. The purpose of this study is to investigate the possibility of allocating this ORC plant into a vehicle and in the design of the condenser, with the purpose of reaching the best configurations that lead to low-pressure drop and compact dimensions. The Organic Rankine Cycle converts thermal energy from low-grade heat sources into electricity. The thermodynamic cycles to produce 5 kW were simulated using a custom software application. The basic cycle was chosen to guarantee the most compact configurations. The selected thermodynamic parameters are based on the need to cope with atmospheric conditions. The working fluid chosen is R245fa, due to its thermodynamic characteristics. Since the electrical part would be partially satisfied by this system, the entire power of the thermal engine would be dedicated to mechanical use. It could also be assumed that, as a consequence of the settings of this plant, a reduction in fuel consumption could be expected, which, although at a percentage that cannot be theoretically evaluated at the moment, is nevertheless predictable. In this first stage of the evaluation, the condenser design is presented and analyzed.

Advanced waste heat recovery system based on organic rankine cycle

In this research, Organic Rankine Cycle (ORC) is used to recover heat from exhaust gas of a four-stroke diesel engine. After retrofitting ORC to the engine, Brake power increased from 10473.91 kW to combined – cycle Brake power of 10736.00kW, thermal efficiency increased from 36.01% to combined – cycle thermal efficiency of 51.32% and Exhaust gas temperature decrease from 358oC to 120oC at the exit of the turbocharger. ORC with R12, R22, R134a and R290 as working fluids at saturation and superheated temperatures, pressures and condenser pressures at different ranges were used to compare refrigerants performance in converting low grade exhaust gas waste heat into useful work. This research presents theoretical analysis on four different refrigerants. Applying the above-mentioned refrigerants as working fluid superheated vapour temperature for R12 is 131.72oC, R134a is 129.37oC, R22 is 113.40oC and R290 is 116.95oC. ORC Power generated by turbine gives 94.98kW, 95.56kW. 130.32kW. 262.64kW respectively, ORC Thermal efficiency gives 36%, 29%, 37% and 38% for R12, R22, R134a, and R290 respectively. Combined – cycle power for each of the refrigerant gives 10568.89kW, 10604.23kW, 10569.47kW and 10736.00kW respectively, combined – cycle thermal efficiency for each refrigerant gives 51.14%, 51.18%, 51.14% and 51.32% for R12, R134a, R22 and R290 respectively. R290 offers optimal performance compared to other refrigerants used in this research. The retrofitting of the ORC has saved some supposedly waste exhaust heat energy and has increased both combined cycle power output and thermal efficiency of the engine cycle.

Effects of thermal treatments on characteristics and morphological variations in the deposits of urea-SCR systems

Selective catalytic reduction (SCR) systems are employed by automobile manufacturers for the abatement of environmental pollutants like oxides of nitrogen (NOx) emitted from exhaust gases of diesel engines. In SCR, the urea-water solution (UWS) is injected to exhaust gases in the form of a spray to generate the reducing agent NH3. Deposit formation at lower temperatures is a major concern with this technology. The deposits not only create backpressure but also leak NH3 to the environment as they deplete. It is very important to know the depletion characteristics of deposits formed at lower temperatures in order to assess the NH3 leakage to the environment when the engine exhaust gases attain higher temperatures. In the present work, deposits formed at a low-temperature range of 150–200°C for continuous run along with UWS injection were investigated. Additionally, they were aged at 300°C in the absence of UWS to check the variation in characteristics with the rise of temperature. By gravimetric analysis, it is inferred that the deposits formed at higher pre-age temperatures are less prone to depletion as the temperature increases. The elemental analysis using energy-dispersive X-ray spectroscopy (EDX) indicates slight variation in carbon, nitrogen and oxygen compositions for all the pre-age conditions. As an extended study, the byproducts at pre-age and post-age conditions were investigated through X-ray diffraction (XRD). The compounds like cyanuric acid (CYA) and biuret were not observed when pre-age samples were aged at 300°C. Instead, the compounds like ammelide, ammeline, triuret and melamine were observed. Scanning electron microscope (SEM) study revealed morphological changes in both pre-age and post-age samples. Further, the crystallinity variations were also observed for the changes in the heating cycles during deposit formation. The gravimetric analysis of deposits in pre-age and post-age conditions helps in predicting the amount of deposits for transient load cycles.

УДОСКОНАЛЕННЯ КОНСТРУКЦІЇ ГЛУШНИКІВ ДЛЯ ЗМЕНШЕННЯ РІВНЯ ЗВУКОВОГО ТИСКУ НА ОПЕРАТОРІВ МАЛОГАБАРИТНИХ ТРАКТОРІВ

Noise background, as an important factor in the working conditions of agricultural operators, has a direct impact on human health and productivity. This topic is especially relevant for small tractors, which in most cases are not equipped with cabs. One of the main means of reducing the sound pressure on the operator are the mufflers of exhaust gases, which mainly have a labyrinth-absorbing type of action. The paper proposes a fundamental approach to the design of the muffler by the criterion of reflection and scattering of sound waves with the verification of efficiency by computer simulation. The purpose of research: - to improve the working conditions of operators of small tractors that are not equipped with cabs, by reducing the sound pressure level from internal combustion engines; - to improve the noise-absorbing properties of mufflers of exhaust gases of engines with observance of requirements to manufacturability of process of their manufacturing; - to develop a structural scheme of the exhaust gases muffler based on the results of preliminary modeling and analysis of the trajectory of the gas flow in the cavity of its working part. Methods. Determination of the sound pressure level of the engine of a small tractor by mathematical (computer) modeling of the behavior of the exhaust gas flow in the muffler cavity in different frequency ranges. Results. The article analyzes the main sources of noise during the operation of agricultural machinery with internal combustion engines (ICE). On the basis of literature sources and methods, their separate degree of influence on the complex picture of noise pollution of the working space of the operator of a small tractor is established. A comparative analysis of the efficiency of mufflers, created on the generally accepted principles and approaches to the design of such devices. According to the results of previous tests, shortcomings and limitations in the application of design concepts were identified, an additional analysis of external causes and factors was made, and adjustments were made to the method of creating muffler designs. An alternative design approach to the creation of internal combustion engine mufflers of small tractors is proposed and computer modeling of the processes of sound pressure distribution and sound waves in their cavity is performed. Conclusions. 1. A layout diagram of the design of the exhaust muffler, containing a resonator chamber and a shell module, which is made in the form of a three-stage ribbed diffuser of oscillations of the exhaust flow pulses with an additional surface layer of the vibration absorber. The parameters of the exhaust flow of exhaust gases of a typical diesel engine of a small tractor with a capacity of 24 hp are calculated. (pressure - 11652 Pa, acceleration – 90-105 m / s2, frequency - 1950-3300 Hz), which performed computer simulations of the process of gas movement in the muffler cavity of the proposed layout. Optimal design parameters were selected to ensure the maximum possible noise absorption with a body diameter of 150 mm and a length of 600 mm. The calculated sound pressure when working at the crankshaft speed (1700-2000) rpm does not exceed 72 dB. At the same time, the design of the muffler is made in compliance with the requirements for economic feasibility, manufacturability and in accordance with the capabilities of industrial production. A further direction of research is the manufacture of an experimental sample of the muffler and testing for the efficiency of its noise absorption in the conditions of operation of small tractors.

Physical, data-driven and hybrid approaches to model engine exhaust gas temperatures in operational conditions

ABSTRACT Fast diesel engine models for real-time prediction in dynamic conditions are required to predict engine performance parameters, to identify emerging failures early on and to establish trends in performance reduction. In order to address these issues, two main alternatives exist: one is to exploit the physical knowledge of the problem, the other one is to exploit the historical data produced by the modern automation system. Unfortunately, the first approach often results in hard-to-tune and very computationally demanding models that are not suited for real-time prediction, while the second approach is often not trusted because of its questionable physical grounds. In this paper, the authors propose a novel hybrid model, which combines physical and data-driven models, to model diesel engine exhaust gas temperatures in operational conditions. Thanks to the combination of these two techniques, the authors were able to build a fast, accurate and physically grounded model that bridges the gap between the physical and data driven approaches. In order to support the proposal, the authors will show the performance of the different methods on real-world data collected from the Holland Class Oceangoing Patrol Vessel.

Model based control of the inlet pressure of a sliding vane rotary expander operating in an ORC-based power unit

• Experimental analysis on Sliding Vane Rotary Expander in ORC plant. • Development of a new approach for volumetric losses calculation. • Inlet pressure control strategy based on expander speed variation. • Effectiveness assessment of the proposed control strategy. • Performance optimization through the proposed regulation strategy. Sliding vane rotary expanders (SVREs) are widely used in organic Rankine cycle (ORC)-based power units for low-grade heat recovery because of their capability to deal with severe off-design working conditions. In particular, the speed of SVREs is a very effective operating parameter, together with the speed of the pump, to regulate the recovery unit and to lead the involved components in an acceptable operating behaviour when they are far from the design conditions. In this study, a control strategy based on the variation in revolution speed of a SVRE was developed, where the inlet pressure of the expander is the main controlled property, which must be verified when the flow rate of the working fluid is changed to match the thermal power recovery at the hot source. In fact, pressure level control is a key point of the recovery unit for thermodynamic reasons and for the safety and reliability of the expander and, more generally, of the whole recovery unit. The proposed control strategy is based on an original theoretical procedure that relates the expander speed, inlet pressure, volumetric efficiency, and working fluid mass flow rate in an analytical form. This analytical formulation is widely nonlinear and is simplified for use as a tool for the model-based control of the inlet expander pressure. An experimental activity performed on a SVRE operating in an ORC-based power unit, fed by the exhaust gases of a supercharged diesel engine, was the base of the analytical formulation. This provided the possibility of deriving a simplified model-based control of the expander inlet pressure and assessing its effectiveness and limits during off-design conditions. Higher expander global efficiencies were obtained (up to 45%), allowing a greater mechanical energy recovery (up to 2 kW).

Effects of Temperature and Turbulence on Characteristics and Morphological Variations of Urea Deposits in Urea-SCR Systems. A Study Using SEM and XRD

The Urea-Water Solution (UWS) is sprayed into the diesel engine exhaust gases of automobiles in order to generate reducing agent NH3 in Urea-Selective Catalytic Reduction (SCR) systems adopted to diesel engines of modern automobiles to mitigate oxides of nitrogen (NOx). Although it is a very efficient technique, deposit formation at low temperatures is a major concern. The growth of deposits not only reduces the efficiency of NH3 generation but also generates non-depleting complex compounds. The temperature of exhaust gas and the Reynolds number of the flow have significant effects on this deposit formation. In this study, the compositional variation and the crystallinity of the deposits are investigated using Energy Dispersive X-ray Spectroscopy (EDX) and X-ray diffraction analysis (XRD) with respect to variation in temperature and flow rate at the preliminary stage. The elemental analysis is done for different samples using EDX that indicates urea as a major constituent in most of the deposits for a temperature range of 423-523K for overdosed conditions. The XRD results indicate the evolution of various traces of urea-related compounds at different temperatures and for turbulent flow of Reynolds Number 9000-32000. Using Scanning Electron Microscopy (SEM), the morphological variations of the deposits have been studied for various temperature and flow conditions. The comparative study of the morphology of deposits during the initial stages of deposit formation indicates an extent to which growth can occur and probable areas of deposits for further growth.

High Activity of NH <sub>3</sub>-SCR at High Temperature Over W-Zr / ZSM-5 in the Exhaust Gas of Diesel Engine

High Activity of NH <sub>3</sub>-SCR at High Temperature Over W-Zr / ZSM-5 in the Exhaust Gas of Diesel Engine