Lower Exhaust Gas Temperature Research Articles

Influence of transition metal based SCR catalyst on the NOx emissions of diesel engine at low exhaust gas temperatures

In this experimental study, silver nitrate (AgNO3) – tetraamin palladium (II) nitrate solution (Pd(NO3)2·4NH3) – titanium dioxide (TiO2) based catalyst was synthesized with the impregnation method for hydrocarbon-selective catalytic reduction (HC-SCR) system. In this system, 2-propanol and different mixtures of 2-propanol and adBlue were used as reducing agents and the effect of the synthesized catalyst on NOx conversion efficiency was investigated. The structural and chemical properties of the catalysts were performed by Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD) and Brunauer-Emmett-Teller (BET) instruments. Experiments were conducted using the prepared catalyst in a temperature ranging from 170 °C to 300 °C at intervals of 10 °C, and 1 space velocity (SV) of 30000 h−1 at the SCR exhaust test performance system. The tests were also performed using 2 cylinders, V-type diesel engine with constant speed of 3000 rpm and at four different engine loads (1, 2, 3 and 4 kW). In conclusion, the highest NOx conversion rate recorded in the tests was 68.1% at 4 kW engine load, 100% 2-propanol spraying condition. In addition to this, it was demonstrated that 2-propanol has positive effect on NOx conversion rate in comparison with abBlue reductant.

Properties of ethyl alcohol-water mixtures as a reductant in a SCR system at low exhaust gas temperatures

ABSTRACT In this experimental study, effects of ethyl alcohol-water mixtures as reducing agents in the presence of Ag/Cu-based catalyst on NOx conversion efficiency were investigated. The Ag/Cu-based catalyst was synthesized with the impregnation method. In this method, cordierite structure was immersed into the solution including nanoparticle materials and then the solvent was evaporated. The analysis done by SEM and XRD revealed the structural and chemical properties of the catalyst. In order to obtain information on how the addition of water affects the activity of the NOx conversion in the SCR exhaust test performance system, tests were carried out depending on a temperature window of 170-260°C, two different space velocities (20000 h−1, and 40000 h−1), and three different reductants (100% Ethyl alcohol (E), 4% water + 96% Ethyl alcohol (E4 W), and 8% water + 92% Ethyl alcohol (E8 W)). The increase in the engine load showed a little increase in the NOx conversion rates. Taking into account the space velocity, the NOx conversion rates were higher at 20000 h−1 in comparison at 40000 h−1. The highest NOx conversion rate recorded in the tests was 68% at 4 kw engine load, 100% ethyl alcohol spraying, and 20000 h−1. However, the results of the tests showed that when the water content of the reductants increased from 4% to 8%, the NOx conversion rates decreased at both 20000 h−1 and 40000 h−1 SV. The highest NOx conversion rates of the tests conducted with E4 W and E8 W reductants were 62.75% and 61.78%, respectively, at 4 kw engine load and 20000 h−1. Also, the highest NOx conversion rates of the same reductants were 55.8% and 55.01%, respectively, at 4 kw engine load and 40000 h−1. It was concluded that the water added to ethyl alcohol has a negative effect on NOx reduction.

Fuel Injection Strategy for Utilization of Mineral Diesel-Methanol Blend in a Common Rail Direct Injection Engine

AbstractMethanol fueled internal combustion (IC) engines have attracted significant attention due to their contributions in reducing environmental pollution and fossil fuel consumption. In this study, a single-cylinder research engine was operated on MD10 (10% (v/v) methanol blended with mineral diesel) and baseline mineral diesel to explore an optimized fuel injection strategy for efficient combustion and reduced emissions. The experiments were conducted at constant engine speed (1500 rpm) and load (3 kW) using two different fuel injection strategies, namely, single pilot injection (SPI) and double pilot injection (DPI) strategy. For each pilot fuel injection strategy, the start of main injection (SoMI) timing was varied from −3 to 6° crank angle (CA) before top dead center (bTDC). To examine the effect of fuel injection pressure (FIP), experiments were performed at three different FIPs (500, 750, and 1000 bars). Results showed that the MD10 fueled engine resulted in superior combustion compared with baseline mineral diesel, which was further improved by DPI at higher FIPs. The use of DPI strategy was found to be more effective at higher FIPs, resulting in higher brake thermal efficiency (BTE), lower exhaust gas temperature (EGT), and reduced oxides of nitrogen (NOx) emissions compared with SPI strategy. Detailed investigations showed that the addition of methanol in mineral diesel reduced particulates, especially the accumulation mode particles (AMP). Different statistical analysis and qualitative correlations between fuel injection parameters showed that higher FIP and advanced SoMI timings were suitable for particulate reduction from the MD10 fueled engine.

Combined Effects of a Biobutanol/Ethanol-Gasoline (E10) Blend and Exhaust Gas Recirculation on Performance and Pollutant Emissions.

Butanol is attracting more attention as an alternative fuel. The performance and emissions of butanol/ethanol–gasoline (E10) was investigated in a spark ignition engine. Exhaust gas recirculation (EGR) was employed to improve the engine performance and emissions in this reported test. The experimental results showed that high brake thermal efficiency (BTE) was observed with a high proportion of blended fuels in comparison to E10. During EGR operation, the introduction of butanol changed the combustion behavior, including prolonged ignition delay, shortened rapid burning duration, a reduced knock number, and knock intensity. The brake-specific fuel consumption (BSFC) increased with butanol addition, and when EGR was introduced, it decreased similarly to E10. The butanol–E10 blends exhibited lower exhaust gas temperature in comparison to E10 at various EGR rates. Hydrocarbon emissions from the blends increased slightly with the increased EGR rate, whereas CO emissions decreased. EGR exhibited high inhibition of NOx emissions for both blended fuels and E10, which were reduced by more than 80%. The NOx emissions from the blended fuels were 20–30% less than that of E10 with or without EGR conditions. Finally, EGR contributed to a reduction in BSFC and improvement in BTE for the butanol–E10 engine. The butanol–E10 blends exhibited a similar power performance, slightly reduced combustion stability, and acceptable emissions with respect to the baseline conditions.

Study on the thermal decomposition rate of ammonium carbamate for a diesel NOx reducing agent-generating system

Ammonium carbamate (AC) is a substance that exists in solid state at room temperature and decomposes into ammonia and carbon dioxide upon heating. In this study, AC was thermally decomposed to produce ammonia gas, which is used as a reducing agent for reduction of NOx emitted from a diesel engine. Currently, most diesel engines utilize a UWS (urea-water solution) as a reducing agent. However, the need for significant heat energy for evaporation and thermal decomposition is one of the reasons driving low NOx reduction efficiency at low exhaust gas temperature conditions. On the other hand, the alternative method of supplying gaseous ammonia by thermal decomposition of solid AC has an advantage of relatively high NOx reduction efficiency at low exhaust gas temperature conditions. Recently, there have been studies on material properties of AC and system feasibility in order to use the AC as a diesel NOx reducing agent. In this study, a simple system for generating diesel NOx reducing agent upon thermal decomposition of AC was mathematically modeled. In addition, the thermal decomposition rate of the AC was expressed via an Arrhenius equation through TGA (thermo-gravimetric analysis) experiments, and the activation energy and pre-exponential factor of the Arrhenius equation were determined. Using the mathematical model and the Arrhenius equation of the thermal decomposition of AC, the effect of various parameters required for designing a reactor and system operation were investigated for a heavy-duty diesel engine with a displacement of 3.9L.

Potentials of EGR and lean mixture for improving fuel consumption and reducing the emissions of high-proportion butanol-gasoline engines at light load

Biobutanol is a promising alternative fuel, but it is accompanied by a fuel consumption penalty. To mitigate the fuel penalty, air dilution was investigated in a turbocharged gasoline direct injection engine fueled with isobutanol-gasoline (B73). To overcome issues of NOx emissions during air dilution operation, exhaust gas recirculation (EGR) and the combination of EGR and air dilution (EGR-Air) were investigated to reduce NOx emissions and enhance engine performance. The effects of these applications on particulate emissions (PM) were also assessed. Compared to EGR, there was more pronounced improvement in brake thermal efficiency (BTE) for butanol-gasoline engine under EGR-Air. The combustion stability under EGR-Air was acceptable but slightly decreased relative to that under EGR. Lower exhaust gas temperature was observed under EGR-Air with respective to EGR. EGR-Air exhibited similar effective inhibition of NOx emissions, as with EGR, which was more pronounced in reducing NOx emissions at high EGR rate, while EGR-Air reduced NOx by up to 90%. CO emissions were clearly reduced under EGR-Air conditions, which realized a better balance between BTE and NOx emissions with very low NOx concentrations. For a butanol-gasoline engine, the PM emissions under EGR-Air were further lowered compared to EGR, which showed a bimodal size distribution, and the particle sizes corresponding to the particle number peak was in the range of 10–30 nm. The observed particle diameters under EGR-Air were smaller than that with and without EGR.

The contribution of CNG powered vehicles in the transition to zero emission mobility - example of the light commercial vehicles fleet

The aim of paper was to discuss contribution of bi-fuel CNG powered light commercial vehicles to the Well-To-Wheel CO2 equivalent emissions, both today and in the coming decades in which the development of new fuels and new vehicles is expected. Field research was done in Belgrade, during one year, using Euro 5 diesel/LPG/CNG light commercial vehicles driving under low vehicle speed, low engine load, low exhaust gas temperature and high number of stops. WTW as neutral methodology was applied for understanding of each fuel pathway in terms of reducing greenhouse gas emissions and increasing energy efficiency. Calculation showed that total energy consumption per km is the lowest for diesel vehicles since petrol/LPG and petrol/CNG vehicles use 21% and 7 % more energy. Tank-To-Wheel emission of CO2e is most favorable for petrol/CNG with 28.8 % and 6.7 % less CO2e with petrol/LPG and diesel vehicles. The same conclusion brings Well-To-Wheel analysis showing that diesel/CNG CO2e emission is 13.5 % less than petrol/LPG, apropos 1.5 % less than diesel operated vehicles considered within this field research. Figures are not as high as previous, due to the results of Well-To-Tank emission, that were most favorable for petrol/LPG powered vehicles, with almost 51% and 32% better results regarding to petrol/CNG and diesel, respectively. Within same time, lowest fuel cost per km was achieved by petrol/CNG vehicles, with 32% and 35% less cost than petrol/LPG and diesel vehicles. The available CNG technology should not be neglected, waiting for new solutions to be proven.

Feasibility study on a vehicular thermoelectric generator coupled to an exhaust gas heater to improve aftertreatment’s efficiency in cold-starts

Low exhaust gas temperatures of internal combustion engines, resulting from cold-starts, low loads or low temperature ambient conditions, can compromise the performance of the automotive aftertreatment system. In this situation, the engine is running far from its design point, with a very low performance of the catalytic converter since it has not reached its optimal temperature. This effect can result in more than 20% of the total emissions for nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) during a driving cycle.This study presents a new approach for vehicular thermoelectric generators to reduce NOx, HC and CO emissions and solve the cold-start issue. Authors propose the use of a thermoelectric generator coupled to an exhaust gas heater. This system, that operates autonomously, is designed to transform the waste heat into electric heat that can quickly raise the exhaust gas temperature to the optimal level.Results show that an improvement up to 94% of the mean catalyst’s efficiency can be achieved. In addition, the system could reduce up to 94%, 91%, and 97% the pollutant emissions of NOx, HC and CO, respectively, in a WLTC driving cycle with a threshold exhaust gas temperature of 350 °C.

Effect of n-butanol/diesel blends on performance, emission, noise and vibration characteristics of a diesel engine generator

Simple diesel engine generators in general are noisy and pollute air. It is urgently needed to find alternative fuels applicable for new as well as old engines without structural modifications and along with keeping the environment clean. Diesel-alcohol blends could be such alternatives fuels. For that purpose, in this study tests were carried out using diesel fuel first then, were carried out using three of n-butanol/diesel blends on volume bases with n-butanol concentrations of 5, 10 and 15%, identified as nBu5, nBu10 and nBu15. The engine under study is a single cylinder, four stroke, air cooled diesel engine generator and the tests have been carried out at a fixed 3000 rpm and five different load conditions without any hardware modifications. Total noise, engine block vibration, NOx, HC, CO, BSFC, BTE and EGT have been observed of diesel and n-butanol/diesel blends. The following conclusions can be drawn with nbutanol/ diesel fuel blends against diesel fuel; (i) According to engine performance test results; a little higher specific fuel consumption was observed with corresponding slight increase of brake thermal efficiency and little lower exhaust gas temperatures. (ii) According to engine emission test results; the NOx was slightly reduced, this reduction being higher the higher the percentage of butanol in the blend. The CO emissions were reduced, on the contrary, HC emissions were increased, this increase being higher the higher the percentage of butanol in the blend. According to engine vibration and noise test results; Noise and vibration characteristics are somewhat better especially at lesser loads.

Comparative evaluation of biodiesel production and engine characteristics of Jatropha and Argemone Mexicana oils

This paper deals with a performance evaluation of locally made 20L batch type reactor and JP and AM biodiesels produced by using this reactor. The inputs for transesterification process were Jatropha and Argemone Mexicana oils, with an alcohol to oil molar ratio of 6:1, 1% NaOH catalyst, 55 °C reaction temperature, an hour settling time and 600 rpm agitation speed. The conversion ability of the reactor for Jatropha and Argemone Mexicana oil seeds has shown a 94% and 94.5%, respectively. The property of these biodiesels has analyzed and its result was within the limit of ASTM D6751. Performance and emission behavior of different blends of these oils such as B10, B20, B30 and pure diesel were evaluated in a single cylinder, four stroke CI engine with rated speed of 1500 rpm and rated power of 4 kW. The B10 blend has shown closer characteristics in terms of specific fuel consumption, brake thermal efficiency and exhaust gas temperature at different loads to diesel. On the other hand, B10 has resulted with higher CO2 and CO and lower NOx emission potential compared to the two blends. The lower NO2 emission is due to its lowest exhaust gas temperature. The biodiesels finally pass standard tests of EPE by fulfilling the standard parameters that made them competitive and substitute options to diesel fuel.

Performance and emission characteristics of conventional diesel combustion/partially premixed charge compression ignition combustion mode switching of biodiesel-fueled engine

In this experimental study, a production grade engine was modified to operate in two combustion modes, namely conventional diesel combustion (CDC) and premixed charge compression ignition (PCCI) combustion, depending on the engine load. For mode switching, an open electronic control unit was programmed to operate the engine in PCCI combustion mode up to medium engine loads and then automatically switching it to CDC mode at higher engine loads, by varying the fuel injection parameters and the exhaust gas recirculation rate. For performance and emission characterization in the entire load range (idling-to-full load) of the test engine, a test cycle of 300 s was used, which included CDC mode, PCCI combustion mode, and transition between these two modes. Results showed that both mineral diesel and B20 (20% biodiesel blended with mineral diesel, v/v) fueled PCCI combustion resulted in significantly lower NOx and particulate emissions compared to baseline CDC. Relatively lower exhaust gas temperature in PCCI combustion mode led to slightly inferior engine performance and higher concentration of unregulated emission species such as SO2, HCHO, and so on. B20-fueled engine resulted in relatively lower unregulated emission species and particulates compared to the mineral diesel–fueled engine in both the combustion modes. In CDC mode, contributions of accumulation mode particles were significantly higher compared to nucleation mode particles. Relatively lower emission of aromatic compounds in PCCI combustion mode compared to CDC mode was another important finding of this study; however, B20-fueled engines resulted in slightly higher emissions of aromatic compounds.

Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

High nitrogen oxide levels of the conventional diesel engine combustion often requires the introduction of exhaust gas recirculation at high engine loads. This can adversely affect the smoke emissions and fuel conversion efficiency associated with a reduction of the in-cylinder air-fuel ratio (lambda). In addition, low exhaust gas temperatures at low engine loads reduce the effectiveness of aftertreatment systems necessary to meet stringent emissions regulations. These are some of the main issues encountered by current heady-duty diesel engines. In this work, variable valve actuation–based advanced combustion control strategies have been researched as means of improving upon the engine exhaust temperature, emissions, and efficiency. Experimental analysis was carried out on a single-cylinder heady-duty diesel engine equipped with a high-pressure common-rail fuel injection system, a high-pressure loop cooled exhaust gas recirculation, and a variable valve actuation system. The variable valve actuation system enables a late intake valve closing and a second intake valve opening during the exhaust stroke. The results showed that Miller cycle was an effective technology for exhaust temperature management of low engine load operations, increasing the exhaust gas temperature by 40 °C and 75 °C when running engine at 2.2 and 6 bar net indicated mean effective pressure, respectively. However, Miller cycle adversely effected carbon monoxide and unburned hydrocarbon emissions at a light load of 2.2 bar indicated mean effective pressure. This could be overcome when combining Miller cycle with a second intake valve opening strategy due to the formation of a relatively hotter in-cylinder charge induced by the presence of internal exhaust gas recirculation. This strategy also led to a significant reduction in soot emissions by 82% when compared with the baseline engine operation. Alternatively, the use of external exhaust gas recirculation and post injection on a Miller cycle operation decreased high nitrogen oxide emissions by 67% at a part load of 6 bar indicated mean effective pressure. This contributed to a reduction of 2.2% in the total fluid consumption, which takes into account the urea consumption in aftertreatment system. At a high engine load of 17 bar indicated mean effective pressure, a highly boosted Miller cycle strategy with exhaust gas recirculation increased the fuel conversion efficiency by 1.5% while reducing the total fluid consumption by 5.4%. The overall results demonstrated that advanced variable valve actuation–based combustion control strategies can control the exhaust gas temperature and engine-out emissions at low engine loads as well as improve upon the fuel conversion efficiency and total fluid consumption at high engine loads, potentially reducing the engine operational costs.

Selective catalytic reduction of NOx emissions by hydrocarbons over Ag–Pt/Al2O3 catalyst in diesel engine

Selective catalytic reduction is an application used to control NOx pollutants in diesel engines. Aqueous urea solution, commercially called AdBlue and obtained by mixing pure water and NH3, is the most commonly used reductant while the V2O5–WO3/TiO2 structure has a widespread use as catalyst in SCR technology. However, the SCR systems included AdBlue and V2O5–WO3/TiO2 structure have low NOx conversion efficiency at low exhaust gas temperatures. The use of hydrocarbons as reductant and catalysts containing silver improves the conversion efficiency of selective catalytic reduction systems at low exhaust temperatures. In this work, selective catalytic reduction of NOx emissions from diesel engines in the presence of hydrocarbons has been studied. While ethanol and biodiesel mixtures were used as hydrocarbons, the Ag–Pt/Al2O3 structure was preferred as the catalyst. Scanning electron microscope and X-ray fluorescence analyses of the catalyst produced by the impregnation method were carried out. In order to determine the NOx conversion efficiency of ethanol–biodiesel mixtures in the selective catalytic reduction system, tests were carried out at different engine loads and different exhaust gas temperatures under actual operating conditions. As a result of the tests carried out, it was concluded that the reductant, which consists of 15% biodiesel and 85% ethanol, has the highest conversion performance.

Potential of long-chain oxymethylene ether and oxymethylene ether-diesel blends for ultra-low emission engines

Oxymethylene ether (OMEn) has recently drawn high attention due to its high pollutant emission reduction potential and the sustainable synthesis pathways involving carbon capture and renewable hydrogen. In this work, five blends of OMEn in diesel fuel in addition to pure OME3-5 and diesel fuel as reference were investigated in a single cylinder engine. Each OMEn-Diesel blend was prepared with a different chain length, ranging from OME1 to OME5. The blending ratio of OMEn in fossil diesel fuel was set to 35 vol%, corresponding to a ∼23.5% diesel fuel substitution on a heating value basis. We find that OMEn contributes to improved oxidation conditions, resulting in a more complete combustion compared to conventional diesel fuel operation. This is reflected by reduced emissions of unburned hydrocarbons and carbon monoxide (up to 90%), higher burned mass fractions after the main combustion phase, higher indicated efficiencies (up to +3%) and lower exhaust gas temperatures (up to −70 °C). Furthermore, while pure OMEn burns soot-free, a significant soot reduction was measured for the OMEn-Diesel blends.Based on the findings of this work, it is concluded that from a combustion and emission point of view, the OMEn chain length is of minor importance for applications where OMEn is blended with diesel fuel up to a ratio of 35 vol%. Thus, the main considerations for an optimal OMEn chain length range should focus on aspects like fuel properties and OMEn synthesis. In this regard, a simple and efficient synthesis process (e.g. synthesis of OME1) must be weighed up against favorable fuel properties of the synthesis product (e.g. OME3-5). Hence, bearing in mind that OMEn is not a drop-in fuel and will always demand a dedicated engine, the preference of long chain OMEn over OME1 is not straight forward and strongly depends on the application.

Combined cycle performance evaluation of a simple and adapted aeroderivative gas turbines

A combined cycle performance analysis of an aeroderivative gas turbine model in simple, reheat, and recuperation modes respectively is presented. The combined cycle gas turbine (CCGT) was modeled with the CFM 56-5C2 aeroderivative gas turbine version. The investigation considered various heat recovery steam generator (HRSG) efficiencies and steam pressures between 80 to 90 % and 40 to 100 bar respectively in simple, reheat and recuperation gas turbine (GT) modes. Results showed that 58 % overall thermal efficiency (TE) and 26.8 MW power output (PO) were obtained at increasing HRSG efficiency and steam pressures respectively due to low exhaust gas temperature (EGT). Also owing to 1500 K reheating of the aeroderivative gas turbine, the EGT was enhanced by 64% (996.7 K). Overall PO and overall TE of 47.6 MW and 62.3 % respectively were achievable in the CCGT analysis with HRSG efficiency of 90% and increasing steam pressure from 40 to 100 bar. Conversely, a combination of reheat and recuperation had a much higher thermal efficiency of 63.4 % but a little lower exhaust gas temperature of 874.2 K. Therefore, aeroderivatives of the CFM 565-C2 gas turbine is recommended for CCGT applications due to its high thermal efficiency (> 60 %), higher power to weight ratios and high EGTs.Keywords: Combined cycle, performance, aeroderivative, gas turbine, reheat, and recuperation

Performance and Emission Characteristics of a Miller Cycle Engine

In this study, intake and exhaust cams were designed to perform the late intake valve closing (LIVC) Miller cycle operation using spline functions in a single-cylinder, four-stroke, spark-ignition engine. A special camshaft was manufactured and adapted to the engine to adjust valve opening and closing timings. The experiments were conducted at two different LIVC timing and the results were compared with Otto cycle. The tests were conducted at 1700-3200 rpm engine speed range at wide open throttle (WOT). In the experiments, the variation of brake torque, power output, specific fuel consumption (SFC), thermal efficiency, HC, CO, NOx emissions and exhaust gas temperature versus engine speed were investigated. More power output was obtained with Otto cycle than Miller cycles for all engine speeds. Brake torque and engine power decreased by 5.24%, and 1.17% respectively with MA cycle (Miller cycle A) compared to Otto cycle at 2600 rpm engine speed. Thermal efficiency increased by 1.29%, while the SFC decreased 2.08 % with Otto cycle in comparison with MA cycle at maximum brake torque speed. HC and CO increased by 6.48 % and 11.66% respectively with MA cycle compared to Otto cycle at the same operation condition. NOx decreased up to 7.79% with MA cycle compared to Otto cycle due to the lower exhaust gas temperature at maximum brake torque speed of 2600 rpm.

Performance investigation of a freezing system with novel multi-salt sorbent for refrigerated truck

Sorption cooling system for vehicle can reduce the fuel consumption by exhaust heat recovery. Owing to the alleviated hysteresis phenomenon of the multi-salt sorbent, the desorption temperature is decreased and the sorption temperature is increased. A freezing system with multi-salt sorbent of CaCl2/MnCl2 is proposed for the refrigerated truck because of the better adaptability of the multi-salt sorbent under extreme conditions, such as low exhaust gas temperature and high ambient temperature. In the system the modularized sorption bed is designed for the direct heat exchange with the engine exhaust gas and the ambient air intermittently. The characteristics of the freezing system under different working conditions are analyzed. The results show that for the optimum cycle with 65-min the maximum refrigeration capacity is higher than 2.4 kW at the heating temperature of 200 °C and the ambient temperature of about 25 °C. Such a result can meet the demand of the light refrigerated truck. The SCP and COP vary less than 10% when the heating temperature ranges from 200 °C to 250 °C, while both parameters are relatively sensitive to the refrigeration temperature. The average SCP is increased by nearly 100% compared with the existing two-stage sorption freezing system for refrigerated truck.

Experimental study on the effect of high-pressure and low-pressure exhaust gas recirculation on gasoline engine and turbocharger

The effects of high-pressure and low-pressure exhaust gas recirculation on engine and turbocharger performance were investigated in a turbocharged gasoline direct injection engine. Some performances, such as engine combustion, fuel consumption, intake and exhaust, and turbocharger operating conditions, were compared at wide open throttle and partial load with the high-pressure and low-pressure exhaust gas recirculation systems. The reasons for these changes are analyzed. The results showed EGR system of gasoline engine could optimize the cylinder combustion, reduce pumping mean effective pressure and lower fuel consumption. Low-pressure exhaust gas recirculation system has higher thermal efficiency than high-pressure exhaust gas recirculation, especially on partial load condition. The main reasons are as follows: more exhaust energy is used by the turbocharger with low-pressure exhaust gas recirculation system, and the lower exhaust gas temperature of engine would optimize the combustion in cylinder.

Optimization of performance and operational cost for a dual mode diesel-natural gas RCCI and diesel combustion engine

Diesel-NG fuel blends are increasingly being used in Reactivity Controlled Compression Ignition (RCCI) internal combustion engines due to high Brake Thermal Efficiency (BTE), low NOx and PM emissions. It also has few disadvantages such as high unburned Hydro Carbon (HC) and Carbon Monoxide (CO) emissions and relatively low Exhaust Gas Temperature (EGT). This study determines the optimum combustion mode between RCCI and Conventional Diesel Combustion (CDC) at different loads while meeting the Environmental Protection Agency (EPA) emission regulation. A Cost Function (CF) including Brake Specific Fuel Consumption (BSFC) and Brake Specific Urea Consumption (BSUC) is considered and minimized in this study. The optimization of input variables is done between 3 and 12 bar Indicated Mean Effective Pressure (IMEP) engine load. The study aims to calibrate the dual fuel diesel/NG RCCI engine to meet Tier 3 Bin 20 EPA standard, with or without after-treatment system, while minimizing the cost of operation.New parametric empirical models are developed and validated using experimental data from a light duty 1.9L inline 4 cylinder Compression Ignition (CI) engine as a function of independent input variables. All the experiments were conducted at Advanced Power System (APS) facility at Michigan Technological University. These models predict HC, CO, PM and NOx emissions, EGT and BSFC. These models are then used to predict new operating points to increase the population in the optimization process. The computed EGT is used to estimate the Selective Catalyst Reduction (SCR) and Diesel Oxidation Catalyst (DOC) efficiencies to assess the emission data with different input variables by considering the after-treatment system to see if they meet the tailpipe emission regulation. The optimization results recommend using Diesel/NG RCCI at 7 to 12 bar IMEP operating conditions and use CDC for below 7 bar IMEP operating condition.

Interactions between aftertreatment systems architecture and combustion of oxygenated fuels for improved low temperature catalysts activity

Diesel engine vehicles, despite their good fuel economy and reduced CO2, are receiving significant attention and negative publicity in recent years due to their difficulties in achieving the emissions regulations. This has widely been linked to undesirable environmental impact and health effects.The lower exhaust gas temperatures associated with modern and more efficient hybrid powertrain and diesel engines makes current technology catalytic aftertreatment systems less efficient under range of vehicle operating conditions. This study, demonstrates how changes in the commonly used aftertreatment system architecture and changes in fuel composition in this case through the addition of oxygenated fuels (i.e. butanol) in diesel fuel can provide meaningful low temperature catalyst activity improvements.The catalyst oxidation kinetics of CO and HC species were improved (reduced the light-off temperature by around 20 °C) when a diesel particulate filter (DPF) was placed upstream of the DOC, while the combination of DPF and combustion of oxygenated fuel in diesel led to up to 80 °C improvement in catalyst activity. The prevention of soot reaching the DOC active sites increases the rate of reactions and the species accessibility to the active sites of the catalyst, and thereby the oxidation of emissions (CO, HC, and NO) can occur at lower catalyst temperatures. The combustion of diesel-butanol blend further improved the DOC low temperature activity. The major contributors to the improved catalyst light-off, are the reduced level of soot and hydrocarbon emissions as well as the higher reactivity of the hydrocarbons species emitted under butanol blend combustion.