Engine NOx Emissions Research Articles

Numerical Investigation on NOx Emission of a Hydrogen-Fuelled Dual-Cylinder Free-Piston Engine

The free-piston engine is a type of none-crank engine that could be operated under variable compression ratio, and this provides it flexible fuel applicability and low engine emission potential. In this work, several 1-D engine models, including conventional gasoline engines, free-piston gasoline engines and free-piston hydrogen engines, have been established. Both engine performance and emission performance under engine speeds between 5–11 Hz and with different equivalent ratios have been simulated and compared. Results indicated that the free-piston engine has remarkable potential for NOx reduction, and the largest reduction is 57.37% at 6 Hz compared with a conventional gasoline engine. However, the figure of NOx from the hydrogen free-piston engine is slightly higher than that of the gasoline free-piston engine, and the difference increases with the increase of engine speed. In addition, several factors and their relationships related to hydrogen combustion in the free-piston engine have been investigated, and results show that the equivalent ratio φ=0.88 is a vital point that affects NOx production, and the ignition advance timing could also affect combustion duration, the highest in-cylinder temperature and NOx production to a large extent.

Study on Combustion and Emission Performance of Dual Injection Strategy for Ammonia/Hydrogen Dual-Fuel Engine

To realize zero carbon emission in internal combustion engines and boost the growth of ammonia fuel, we mixed a few hydrogens into ammonia fuel to boost the atomization and combustion performance in the combustion chamber. We study hydrogen and ammonia mixed and injected directly through two injectors, the intake temperature is 551k, to find the best injection advance angle combination to ensure the overall working performance of the ammonia Dual fuel engine. The investigation shows that when the main/auxiliary fuel injection timing is 704°CA, the knock value is less than 2, the combustion in the cylinder is gentle, and the negative work phenomenon of knock combustion is avoided. The engine power is the highest and the best economy. The emissions of soot, CO, HC, and CH2O are at a very low level, the CO2 content before and after combustion increases to zero, and the NOx emission is slightly higher than the original engine. We will improve engine NOx emission through SCR Technology in the future. The investigation results will boost the development of an ammonia and hydrogen compression ignition engine and boost the internal combustion engine to zero carbon combustion mode.

Influence of Driving Cycles on Emission Parameters of Vehicles

The vehicle emissions tests, which are performed using the Portable Emissions Measurement Systems (PEMS), indicate that the diesel cars produce several times more NOx emissions on the road than during certification realised according to the methodology New European Driving Cycle (NEDC). This fact initiated the infamous "dieselgate" affair. It is a well-known reality that the current emission limits are very strict and therefore a serious problem arises for the motor car producers to meet the demanding emission requirements. The main task of the presented research work was testing of 10 passenger cars with regard to true values of their exhaust gas emissions. These cars were equipped with the diesel engines and gasoline engines that officially meet the Euro 4-6 standards. Based on the measured results it was found that the real NOx emissions of the diesel engines significantly exceed the values measured by NEDC. The results obtained using the NEDC cycle also contradict the findings from two alternative driving cycles: CADC (Common Artemis Driving Cycle; Artemis - Assessment and Reliability of Transport Emission Models and Inventory Systems) and WLTC (Worldwide harmonized Light vehicles Test Cycle).

Comparative Study of Spark-Ignited and Pre-Chamber Hydrogen-Fueled Engine: A Computational Approach

Hydrogen is a promising future fuel to enable the transition of transportation sector toward carbon neutrality. The direct utilization of H2 in internal combustion engines (ICEs) faces three major challenges: high NOx emissions, severe pressure rise rates, and pre-ignition at mid to high loads. In this study, the potential of H2 combustion in a truck-size engine operated in spark ignition (SI) and pre-chamber (PC) mode was investigated. To mitigate the high pressure rise rate with the SI configuration, the effects of three primary parameters on the engine combustion performance and NOx emissions were evaluated, including the compression ratio (CR), the air–fuel ratio, and the spark timing. In the simulations, the severity of the pressure rise was evaluated based on the maximum pressure rise rate (MPRR). Lower compression ratios were assessed as a means to mitigate the auto-ignition while enabling a wider range of engine operation. The study showed that by lowering CR from 16.5:1 to 12.5:1, an indicated thermal efficiency of 47.5% can be achieved at 9.4 bar indicated mean effective pressure (IMEP) conditions. Aiming to restrain the auto-ignition while maintaining good efficiency, growth in λ was examined under different CRs. The simulated data suggested that higher CRs require a higher λ, and due to practical limitations of the boosting system, λ at 4.0 was set as the limit. At a fixed spark timing, using a CR of 13.5 combined with λ at 3.33 resulted in an indicated thermal efficiency of 48.6%. It was found that under such lean conditions, the exhaust losses were high. Thus, advancing the spark time was assessed as a possible solution. The results demonstrated the advantages of advancing the spark time where an indicated thermal efficiency exceeding 50% was achieved while maintaining a very low NOx level. Finally, the optimized case in the SI mode was used to investigate the effect of using the PC. For the current design of the PC, the results indicated that even though the mixture is lean, the flame speed of H2 is sufficiently high to burn the lean charge without using a PC. In addition, the PC design used in the current work induced a high MPRR inside the PC and MC, leading to an increased tendency to engine knock. The operation with PC also increased the heat transfer losses in the MC, leading to lower thermal efficiency compared to the SI mode. Consequently, the PC combustion mode needs further optimizations to be employed in hydrogen engine applications.

Study on injection strategy of ammonia/hydrogen dual fuel engine under different compression ratios

In order to achieve zero carbon emissions in the field of internal combustion engines, ammonia/hydrogen hybrid fuel engines are one of the best solutions. However, due to the poor ignition and combustion performance of ammonia fuel, the ammonia/hydrogen mixed fuel engine has the problems of high NOx emissions and long ignition delay, poor power performance. Therefore, this paper will study the injection strategy of ammonia/hydrogen dual fuel engine under different compression ratio to optimize the engine performance, and find the best combination of compression ratio and ammonia/hydrogen mixed fuel injection timing. In the simulation study, there are four groups of compression ratios from 13.5 to 16.5, and each group of compression ratios corresponds to eight groups of injection timing from 12°CA BTDC to 24°CA BTDC. The results show that after delaying the injection timing of ammonia/hydrogen mixture fuel, the power performance and economy of the engine are reduced, the ignition delay period is shortened, HC, CH2O, CO and soot emissions are gradually increased but at a very low level, and NOx emissions are significantly improved; After the compression ratio is increased, the engine's power performance and economy are greatly improved, HC, CH2O, CO and soot emissions are slightly higher, and NOx and N2O emissions are gradually increased. Under any combination of compression ratio coupling injection timing, the engine NOx emission can meet the Tier II emission standard. When the injection timing of ammonia/hydrogen mixed fuel is 12°CA BTDC and the compression ratio is 13.5, the NOx emission of this operation combination of ammonia hydrogen dual fuel engine can meet the Tier III emission standard. The research results of this paper can promote the engine field to zero carbon emissions and meet the Tier III emission standards, while ensuring that the engine has sufficient power.

The effects of diesel-OME1 blended fuel on combustion characteristics of a heavy-duty compression ignition engine by a numerical study

Diesel engines are playing an important role in the transportation system and regardless to their acceptable efficiency (near 40 %), the main problems are the amounts of CO2 and soot production of these engines. In this research, Oxymethylene ether is used as a blend with diesel by a numerical study, and engine performance, fuel economy, and emission analyses have been investigated. The OM355 engine with Euro II emission standard is selected as the base engine and the percentages of Soot, NOx, CO2, flame speed, flame surface density, brake specific fuel consumption, specific power, and specific torque has been studied from 0 to 60% of diesel-OME1 compounds. Overall results of this numerical investigation indicate that OME1 can be a suitable component due to positive effects on the exhaust emissions. Initial estimates show that engine soot and NOx emissions can be reduced more than 80% and CO2 also near to 66% reduced compared to pure paraffinic diesel. In fact, due to a lower combustion temperature of OME1, soot and NOx emissions would barely produce due to their formation limit temperature, hence the engine operates much cleaner. The main disadvantage of this synthetic fuel is the low amount of heating value and lower cetane number in comparison to diesel, which in turn leads to a performance loss and a higher amount of fuel consumption for producing a specific amount of power and torque output.

Effects of hydrogen-rich products from methanol steam reforming on the performance enhancement of a medium-speed marine engine

In order to improve the heat utilization of exhaust gas from the small and medium-sized ships without exhaust boilers, a methanol steam reforming (MSR) is proposed in the study. The combustion model of marine engine blended hydrogen-rich reforming gas was developed, and verified in terms of cylinder pressure, BSFC, and NO emissions. The compositions of reforming gas were obtained by the MSR model and employed to investigate the effect of reforming gas at different blending ratios on the combustion and emission characteristics of the marine diesel engine in the AVL-Fire environment. The results obtained show that the performance, emission, and economic characteristics are improved due to the existence of reforming gas. Specifically, the indicated power is decreased by 0.5%–4.26% and the NO mass fraction is reduced by 2.95%–18.25% at different loads, but the CO mass fractions increased by 20.21%–54.73%. Similarly, the NOx weighted emission is reduced by 34.10%, which is close to the NOx emission limit of Tier II, but the CO weighted emission is increased by 30.89%. In addition, the equivalent fuel consumption rate is reduced by 0.45%–3.59% at the maximum blending ratio, and the converted fuel cost is reduced by 6%–10% at medium and high loads. Finally, based on the comprehensive performance analysis, the optimized blending ratio at each load is obtained as follows: Rg7.5 or Rg12.5 for 100% load, Rg10 for 75% load, Rg7.5 for 50% load, and Rg2.5 for 25% load. Thus, the MSR reaction is feasible to improve the energy efficiency and reduce NOx emission of the marine engine.

Effect of assisted hydrogen on combustion and emission characteristics of a diesel engine fueled with biodiesel

In this paper, the effects of hydrogen assisted biodiesel with different fatty acid methyl esters (FAMEs) proportion on cylinder pressure, cylinder temperature, indicated thermal efficiency (ITE), NOx emission, HC emission and CO emission of a marine medium speed diesel engine are studied. The corresponding CFD model is executed by CONVERGE coupled to CHEMKIN, and a chemical kinetic mechanism with 314 reactions and 98 species is developed to accurately simulate the fuel injection and combustion processes. The results show that cylinder pressure, cylinder temperature and ITE increased with increasing HEF. Compared with rapeseed methyl ester (RME) and cottonseed methyl ester (CSME), the cylinder pressures are increased by 16.39% and 16.30% for CSME-6%H2 and RME-6%H2 at 100% load, respectively. The cylinder temperatures are increased by 7.42% and 7.14%, and ITE increased by 3.73% and 3.9%, respectively. In addition, the HC and CO emissions decreased significantly with the increase in HEF, while NOx emission increased. Compared with pure CSME and RME, HC emissions are reduced by 70.97% and 72.22% for CSME-6%H2 and RME-6% H2, and CO emissions are reduced by 41.89% and 38.12% for CSME-6%H2 and RME-6% H2 at 100% load, respectively. Overall, the strategy of using CSME-6% H2 mixed fuel for engine is not only economical and practical, but also can prevent performance loss and reduce emissions.

Application and Development of Selective Catalytic Reduction Technology for Marine Low-Speed Diesel Engine: Trade-Off among High Sulfur Fuel, High Thermal Efficiency, and Low Pollution Emission

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier III emission regulations, an after-treatment device must be installed in the exhaust system of the ship power plant to reduce the ship NOx emissions. At present, selective catalytic reduction technology (SCR) is one of the main technical routes to resolve excess NOx emissions of marine diesel engines, and is the only NOx emission reduction technology recognized by the IMO that can be used for various ship engines. Compared with the conventional low-pressure SCR system, the high-pressure SCR system can be applied to low-speed marine diesel engines that burn inferior fuels, but its working conditions are relatively harsh, and it can be susceptible to operational problems such as sulfuric acid corrosion, salt blockage, and switching delay during the actual ship tests and ship applications. Therefore, it is necessary to improve the design method and matching strategy of the high-pressure SCR system to achieve a more efficient and reliable operation. This article summarizes the technical characteristics and application problems of marine diesel engine SCR systems in detail, tracks the development trend of the catalytic reaction mechanism, engine tuning, and control strategy under high sulfur exhaust gas conditions. Results showed that low temperature is an important reason for the formation of ammonium nitrate, ammonium sulfate, and other deposits. Additionally, the formed deposits will directly affect the working performance of the SCR systems. The development of SCR technology for marine low-speed engines should be the compromise solution under the requirements of high sulfur fuel, high thermal efficiency, and low pollution emissions. Under the dual restrictions of high sulfur fuel and low exhaust temperature, the low-speed diesel engine SCR systems will inevitably sacrifice part of the engine economy to obtain higher denitrification efficiency and operational reliability.

Optimization Analysis of Locomotive Diesel Engine Intake System Based on Matlab-Simulink and GT-Power

In this paper, based on the coupling calculation of Simulink software and GT-Power software, an Optimizer model method was proposed for a 16V265H diesel engine to study the effects of different ratios of biodiesel (B0, B10, and B20) on the performance of a 16V265H diesel engine at 1000 rpm and 75% load. Firstly, the four parameters of diesel engine power, BSFC, soot emission, and NOx emission were taken as the result variables of the optimization model. Taking the intake and exhaust timing of the diesel engine as the independent variable of the optimization model, the maximum power, minimum BSFC, and minimum diesel engine emission were studied and analyzed. Finally, the performance parameters were comprehensively analyzed to determine the best intake and exhaust valve timing. Moreover, based on the model optimization, the diesel engine’s BSFC and power performance were compared, and the optimal intake timing scheme for the diesel engine with different biodiesel ratios at 75% operating conditions was obtained. The results showed that the maximum power, optimum BSFC, and minimum emissions of the 16V265H diesel engine with different ratios of biodiesel and different intake valve timing angles were also different. Under 75% load conditions, the BSFC reduction rate was up to 6.32%, and the power increase rate was up to 5.87%. In addition, by optimizing the model with B10 biodiesel and the intake valve timing close to 202°CA and the exhaust valve timing close to 98°CA, the diesel engine had the lowest NOx emission; with B10 biodiesel and the intake timing at 180°CA, the diesel engine had the lowest BSFC; and with B10 biodiesel and the intake valve timing close to 179.5°CA, the diesel engine had the maximum power. In conclusion, the diesel engine is best with B10 biodiesel. This research method can provide a reference for implementing variable intake system technology for the 16V265H diesel engine.

Chemical Kinetic Investigation on Nox Emission of Si Engine Fueled with Gasoline-Ethanol Fuel Blends

Chemical Kinetic Investigation on Nox Emission of Si Engine Fueled with Gasoline-Ethanol Fuel Blends

Feasibility study on mornitoring NOx emissions of China-VI natural gas engines with the NOx sensor

Based on a heavy-duty stoichiometric natural gas engine which can meet the requirement of China-VI regulations, steady-state and transient cycles were carried out to measure the exhaust NOx concentration out of TWC by a NOx sensor and a gaseous emission analyzer simultaneously. The results show that the measurement results of NOx sensor are relatively higher when the NOx emission concentrations are lower than 50 ppm, and the accuracy is not high enough. Due to the obviously smaller proportion of lower NOx concentrations, especially for the concentrations below 10ppm, the average concentration measured by the NOx sensor was 24.3% higher than the average concentration measured by the emission analyzer during the whole testing process. When the NOx concentrations are higher than 50ppm, the frequency distributions of NOx concentration measured by NOx sensor and emission analyzer are almost the same, and the deviations of average NOx concentrations between these two measurement methods can be within ±4.5%, which represent a significantly high reliability of NOx sensor.

Analysis of Exhaust Gas Emissions on Dual Fuel Diesel Engine Single Cylinder Four-stroke with LPG-Diesel Oil

Diesel engine is one of type of internal combustion engine that is applied in industry, including the maritime industry. The increasing use of diesel engines, has a effect on increasing emissions. Diesel engines emissions consist of SOx, NOx, HC, and others. To reduce the emissions, there are many method, one of them is using dual-fuel system. The alternative fuel can be used is Gas, which is easily available, namely LPG or liquefied petroleum gas. To supply LPG to combustion chamber, a converter-kit are needed to be install on diesel engine. There are several previous research that prove that LPG can be used as an alternative in a dual-fuel system and can reduce the emissions. One of them by Ma’amuri (2016) who designed a mechanical LPG-diesel oil as dual-fuel, using a membrane converter. Result of this research provide that good diesel engine performance. In this research, LPG-diesel oil as dual-fuel using converter kit based on ECU or electronic control unit, and then, analyze the diesel engine emissions with experimental method. The purpose of this research is to determine the emissions produced by LPG-diesel oil as dual-fuel with converter kit based ECU. After taking and analytical data, known that the NOx emission from dual fuel diesel engine using ECU-based converter kit is lower than NOx emission from conventional diesel engine with B30 diesel fuel with percentage is 25,61 % for 3ms opening duration of gas injector, 39,99 % for 4 ms opening duration of gas injector and 26,5 % for 5 ms opening duration of gas injector. The NOx emission of conventional diesel engine is 2,46 g/kWh.

Energy and exergy analyses of hydrogen addition in a diesel engine

In the study, the effect of hydrogen addition with air taken from the intake manifold at different rates on performance and emissions in a single-cylinder, four-stroke diesel engine has been numerically investigated. The first and second law analyses of thermodynamics are performed for each hydrogen addition condition. Numerical analysis has been performed with ANSYS-Forte, energy and exergy calculations have been carried out according to the analysis results. The results of the analysis show that with the addition of hydrogen, CO emissions decrease while the engine performance and NOx emissions increase.

Influence of post-injection strategies and CeO2 nanoparticles additives in the C30D blends and diesel on engine performance, NOX emissions, and PM characteristics in diesel engine

This study investigates the influences of post-injection (PI) strategy and adding two concentrations (50 and 100 mg/l) of Cerium oxide (CeO2) nanoparticles to the diesel-castor oil (C30D) and diesel on engine performance, NOX emissions, and characteristics of PM. The adding CeO2 nanoparticles to the C30D and diesel were tested under with PI and W/O PI strategy. The results indicated that the BTE increased by 9.42% from the blends of C30D + CeO2 compared with diesel + CeO2 under with and without PI strategy. Furthermore, the BSFC decreased by 16.46% from C30D + CeO2 nanoparticles compared with diesel + CeO2 nanoparticles. The cylinder pressure and ROHR increased with addition of CeO2 nanoparticles to the C30D compared to the C30D, diesel, and diesel + CeO2 under different PI strategy. For the same CeO2 concentration, the results showed that the NOX emissions decreased by 10.64% when adding 100 mg/L of CeO2 to the C30D compared with diesel + CeO2 nanoparticles by 8.73%. The adding 50 and 100 mg/L of CeO2 to the C30D reduced the concentration of PM by 28.62 and 42.72%, respectively, compared C30D without additives. Besides, the adding both concentrations of CeO2 to the diesel decreased the concentration of PM by 16.74 and 24.83%, respectively, compared without additives into the diesel fuel. It is found that the size of primary particles (dpo ) slightly increased with addition of CeO2 nanoparticles to the C30D and diesel under with and W/O PI strategy. The data of this experiment revealed that introduce the PI strategy and 100 mg/L of CeO2 nanoparticles gives positive effect on engine performance, NOX emissions, and total concentration of PM. Highlights The cylinder pressure and rate of heat release increased with addition of CeO2 nanoparticles to the C30D. Adding nanoparticles to C30D decreased the BSFC and increased BTE compared with those of the C30D and diesel without additives. The blends of C30D + CeO2 decreased the concentration of PM. Adding different concentration of CeO2 nanoparticles increased the average particle diameter. The NOX emissions decreased with addition CeO2 nanoparticles to the C30D and diesel.

Impacts of gasoline fuel components on GDI engine performances: Part 1, influence on gaseous toxic pollutants

In this paper, effects of different components in gasoline fuel on GDI engine emission characteristics were investigated. To simplify this investigation, model fuel CDTRF (composed of n-heptane, iso-pentane, diisobutylene, cyclohexane and toluene) instead of real gasoline fuel were used. To see how components of gasoline fuel affect engine performances, iso-pentane, diisobutylene, cyclohexane or toluene in CDTRF was substituted by other iso-alkanes, olefins, naphthenes and aromatics for comparative researches. N-heptane fraction is varied to balance fuel octane number. It is found that variation of fuel components obviously affect engine regulated and unregulated emissions. While, such effects vary when engine operation condition varies and are more distinct under lower engine speed or load conditions. Fuel components affect engine emission not just simply via chemical manner, but also through accompanying thermal-power process (cylinder pressure and temperature history). Thus variation of fuel components remarkably affects engine NOx emission. Alkanes, olefins and alkynes, aromatics contribute most to VOC emission followed by aldehydes. While, proportion of alcohols in VOC is negligible. However, variation of fuel components does not remarkably affect the proportion of alkanes, olefins and alkynes, aromatics as well as aldehydes in VOC although it affects total VOC emission obviously. Olefins and alkynes contribute most to OFP followed by aromatics and aldehydes. The contribution of alkanes is relatively low although it takes significant proportion in VOC. While, variation of fuel components remarkably affects total OFP of VOC though it does not obviously affect OFP composition. According to the results, it is hinted that more short chain i-paraffins and less branch chained cyclohexane in gasoline fuel would potentially help to reduce OFP of VOC.

Effect of jet momentum flux and heat density on NOx emission in a flameless gas turbine combustor

Experimental testing and validated CFD models have been used to evaluate the performance of the FC4GT flameless gas turbine (GT) combustor operating at a global equivalence ratio of 0.44. The methane-fuelled combustor was tested at atmospheric pressure, modelled at elevated pressures up to 25 bar, and optimised for a combustor pressure of 15 bar. The combustor was analysed for firing rates between 15 kW and 16 MW, which correspond to heat density range between 0.15 MW/m3.bar and 150 MW/m3.bar, respectively. The performance of the combustor was also evaluated with pure hydrogen. Overall, the flow fields while using both fuels, are found to be similar; exhibiting highly uniform spatial (temperature and oxygen) distributions, and low exhaust NOx emissions. Volumetric histograms of temperature and oxygen in the combustor are identified as a powerful analysis tool for quantifying the level of uniformity of the scalar mixing and combustion field, NOx emission, and for determining the combustion regime.The momentum flux of the primary air jet has been identified as a key parameter in controlling NOx emission. Across the power generation mode for GT operation with a heat density of 5–150 MW/m3.bar, the predicted NOx emission (15% O2 dry) for methane was 34–6 ppmv, respectively, and for hydrogen 353–33 ppmv, respectively. At 50 MW/m3.bar, the predicted NOx emission for methane was 17 ppmv, and 146 ppmv for pure hydrogen. This is a significant outcome for a non-premixed combustor considering that the NOx emission of the GE6FA GT engine using partially premixed combustion at 50 MW/m3.bar, is 15 ppmv for methane, and 200 ppmv for 85% hydrogen. Overall, the low NOx emission, for methane and hydrogen, combined with the highly uniform spatial temperature and oxygen distributions, and supported by experimental visualisation provide irrefutable proof that a flameless combustion regime has been achieved. It also demonstrates the plausibility of a non-premixed flameless combustor achieving comparable NOx emission to premixed flames.

Effects of short chain aromatics in gasoline on GDI engine combustion and emissions

Aromatics are parts of the main components in gasoline which play important roles in affecting engine performances. Short carbon chain aromatics (C8/C8-) takes more part of aromatics in gasoline. In this paper, the effects of toluene, ortho-xylene and ethylbenzene on engine combustion, emission and thermal efficiency are experimentally investigated. Gasoline and three quinary gasoline model fuels containing each of these three aromatics, with diisobutylene, cyclohexane, isooctane, n-heptane being the other four components, are used to support this research. Results show that all the aromatics favor engine combustion and particulate emission while aggravate THC and CO emissions. Toluene, ethylbenzene and ortho-xylene do not obviously affect NOx emission under lower engine speed. However, ethylbenzene and ortho-xylene elevate engine NOx emission much more than toluene does under higher engine speed conditions. Alkenes and alkanes take the vast majority of VOC emission, followed by aromatics and aldehydes. Yet, alkenes take the most responsibility on OFP followed by aldehyde, and then aromatics, alkanes. Ethylene is the major composition of alkenes while formaldehyde contributes the most to aldehydes emission. In compare, toluene would propel alkenes and aldehydes in VOC emissions more than ethylbenzene and ortho-xylene do, however, it greatly alleviates particulate emission. Toluene tends to improve thermal efficiency under low engine speed conditions while ortho-xylene and ethylbenzene improve it under higher engine speed conditions. Results from this paper indicates that short chain aromatics affect engine combustion and emission a lot. So, varying short chain aromatics in gasoline fuel is of great importance in adjusting fuel properties.

Application of response surface methodology for the joint optimization of performance and emission characteristics of a diesel engine

ABSTRACT Multi-injection is an effective strategy to control the NOx emission while maintaining the performance of combustion engines, however, it is difficult to balance emission and performance in practical operations. In this study, the Response Surface Methodology (RSM) was proposed to optimize them simultaneously. The combustion and performance of engine were firstly characterized by varying the multi-injection parameters, including fuel quantity distribution, injection dwell time and injection pressure. Experiments were conducted on a 3.856 L diesel engine, through which the cylinder pressure, torque output, and main emissions were measured, with brake specific fuel consumption (BSFC) and effective thermal efficiency (ηet) being analyzed. The experimental results showed that the fuel injection properties had a significant impact on in-cylinder combustion and emissions. Based on the RSM analysis, the coupling effects between engine performance and NOx emission were then optimized, which were then verified and tested by experimental measurements. The optimal results were obtained when the fuel share ratio, dwell time, and injection pressure were 5, 10.56 °CA and 95 MPa, respectively. Through the verification tests, NOx emission could substantially reduce as much as 31.8% with torque slightly reduced by 3.3%.

Taguchi‐based optimization of design and fuel parameters of partially premixed charge CI engine fuelled with biodiesel and butanol blends

AbstractSimultaneous control of NOx and smoke emission of compression ignition engine was the major challenge for the researchers as their formation mechanisms are inversely proportional to each other. In the present study, combustion process was modified as partially premixed charge combustion (PPCC) which supplies a premixed charge of fuel and air through inlet valve in addition to the fuel injected into the cylinder. This resulted in reduction of combustion temperature with lean air fuel ratio. To investigate the influence of various factors on these emissions, six design factors and two fuel factors of the engine were selected as factors and NOx, smoke, and brake thermal efficiency were selected as responses for the investigation. Experimental test matrix was designed based on Taguchi L18 orthogonal array. Multi response Signal to Noise (MRSN) ratio was calculated for the response variables and the optimum combination level of factors was obtained simultaneously using Taguchi's parametric design and the same was tested experimentally. Influence of each factor and most influencing factor on the chosen objective was determined by analyzing the variance of the MRSN ratio. This investigation reveals that among the factors tested, main injection fuel is the most influencing factor with a maximum percentage contribution of 44.5. It has been observed that normal combustion mode parameters have more influence with a percentage of contribution of 80 when compared with the parameters of PPCC mode. It has also been observed that fuel factors have higher percentage contribution of 53 compared with the design factors contribution of 43.6.