High Hydrocarbon Emissions Research Articles

Investigation of gas exchange parameters of small two stroke engine correlated with hydrogen fuel supplement

Due to the lack of complete dedicated suction and exhaust strokes and obviate the need of valvetrain assembly in two stroke engines, the bottom surface of the piston and the crankcase is used as a scavenging pump leads to that about one fifth of the fresh charge is short-circuited to the exhaust results in very high hydrocarbon emissions and poor fuel consumption. It is suggested that a combination of gasoline and hydrogen could be a superior solution combining the advantages of both engine itself and hydrogen doping. An accurate amount of hydrogen that has high flame propagation speed blended with gasoline could provide faster combustion of fuel mixture over the few crank angle degrees in the short gas exchange process reducing short-circuited charge with little modifications to the engine system. In this paper hydrogen-gasoline blend as an alternative fuel in a 63.3 cc, air cooled single cylinder, crankcase scavenged two stroke engine is tested. The unseen decommissioning of small two stroke engine in near future, the attractiveness of studying alternative fuel specially hydrogen and absence of investigation of the effect of hydrogen fuel supplement on gas exchange parameters molded this paper.

Evaluating potential of increasing flow intensity and reducing crevice volume to improve thermal efficiency and hydrocarbon emission in spark-ignition natural gas engines

Low thermal efficiency and high hydrocarbon emissions caused by slow combustion rates and high methane emissions hinder the development of natural gas (NG) engines. Engine structure modifications have always been an important means of improving the combustion effects of engines. This study investigates the effects of combustion chamber improvements on the thermal efficiency and hydrocarbon emissions of stoichiometric spark-ignition NG engines through numerical simulations. The improvements aimed to enhance squish flow, organize high tumble flow, and reduce crevice volume. The results indicate that strengthening the squish intensity by increasing the squish area of the piston can accelerate flame propagation and reduce exhaust loss. However, this improvement is hindered by a significant rise in heat transfer loss, which limits further gains in thermal efficiency. Compared to the traditional high swirl combustion chamber, a high tumble combustion chamber (dual straight intake port combined with a hemispherical piston) can promote flame propagation in the early stages of combustion and increase thermal efficiency by 1.43%. However, the accelerated flame propagation rate resulting from increased flow intensity has little potential to reduce hydrocarbon emissions due to the small contribution of flame quenching to unburned hydrocarbon production. The primary source of hydrocarbon emissions from NG engines is unburned methane in the piston crevice. Therefore, when addressing hydrocarbon emissions from NG engines, the first consideration should be to minimize the volume of the piston crevice, which will significantly reduce methane emissions and incomplete combustion loss.

Impact of engine control variables on low load combustion efficiency and exhaust emissions of a methane-diesel dual fuel engine

A conventional diesel engine when operated in the reactivity-controlled compression ignition (RCCI) combustion strategy faces challenges of high total hydrocarbon (THC) and carbon monoxide (CO) emissions leading to poor combustion efficiency at low engine loads. The oxides of nitrogen (NOx) versus smoke trade-off, encountered in conventional diesel combustion, is replaced by the NOx-THC trade-off in the RCCI operation. This work focuses on addressing the NOx-THC trade-off issue by systematically investigating the effects of engine control variables, such as, fuel injection timing, exhaust gas recirculation (EGR) and intake throttling, on a light duty compression ignition engine running in a methane-diesel dual fuel mode. The engine is operated at a load of 3 bar gross indicated mean effective pressure and at a speed of 1500 rev/min. Based on relationships identified between engine control variables, combustion parameters, emissions and engine performance, a bottom-up approach is used to combine the control variables synergistically to improve the NOx-THC trade-off. A combination of advanced start of injection timing of diesel (−35 degree crank angle (°CA) after top dead centre), 50% premix ratio and 55% EGR levels along with the end of port fuel injection of methane in the middle of the intake stroke (−270°CA), has resulted in a ∼34 percentage points (from 56% to 90%) improvement in combustion efficiency and a ∼9.5 percentage points improvement in thermal efficiency compared to the baseline low load dual fuel operation while maintaining good combustion stability. THC emission is reduced from 105 to ∼25 g/kWh whilst maintaining low levels of NOx (<0.3 g/kWh).

CFD analysis of combustion and emission characteristics of biodiesel under conventional and late-injection based premixed combustion conditions

The simultaneous reduction in NOx and smoke emissions can be achieved with biodiesel under a late-injection based low temperature combustion (LTC) strategy. However, this occurs at the expense of a substantial increase in unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. It is worthwhile to understand the reasons behind the formation of these emissions, emphasizing comparison with conventional combustion, which is known to result in significantly low HC and CO emission levels, particularly with oxygenated biodiesel fuel. The present investigation attempts to examine the same with 3D CFD simulation. Experimental data were obtained from a light-duty diesel engine using biodiesel from non-edible Karanja oil. The unmodified engine with OEM low-pressure mechanical fuel injection system was utilized for conventional combustion operation. It is replaced with a modified common rail injection system for a late-injection-based LTC mode of operation. By combining retarded high-pressure injection with EGR, sufficient premixing was sustained to enable late injection-based premixed combustion (LI LTC). The combustion simulation was performed using CONVERGE CFD tool, utilizing a two-component surrogate of methyl butanoate (MB) and n-dodecane to represent biodiesel. A reduced chemical kinetic mechanism, developed and validated in an earlier investigation on biodiesel combustion, was utilized in the current study. The mechanism was solved using the SAGE Detailed CHEMKIN solver in CONVERGE. Validation was conducted at two engine operating conditions defining low and high loads for both combustion modes. The cylinder pressure and heat release rates were predicted with a maximum error of 1.5 and 13%, respectively. The validated CFD tool was employed to compare and analyze the equivalence ratio, in-cylinder gas temperatures, and HC and CO contours between conventional and LI LTC modes. Under LTC mode, the cylinder pressure and heat release rates were predicted with a maximum error of 10 and 15%, respectively. The comparison revealed fuel-rich regions concentrated near the bowl in conventional combustion, while the fuel was spread throughout the combustion chamber in LI LTC mode with over-rich and over-lean regions near the cylinder wall. The cylinder temperature is significantly higher for conventional combustion than LI LTC mode. The O and OH radical concentrations are higher for conventional combustion, corroborating with lower CO emissions, as they aid in CO oxidation. Fuel-rich regions contribute to increased CO emissions, whereas over-lean regions at a low-temperature result in high HC emissions, exhibited by the emission contours. Possible countermeasures to reduce high HC and CO emissions in LI LTC mode include maintaining higher coolant temperatures to enable HC and CO oxidation in the near-wall regions and fuel injection system modification to alter the air–fuel mixing.

Effects of split diesel injection strategies on combustion, knocking, cyclic variations and emissions of a natural gas-diesel dual fuel medium speed engine

Accelerated by the harms and depletion risk of fossil fuels, transition to low-carbon or renewable fuels have become an urgent need for combustion engines to decarbonize transport sectors. Natural gas-diesel dual-fuel combustion is a promising method to achieve these goals by allowing the usage of natural gas in diesel engines. However, this concept has drawbacks of low combustion efficiency, high unburned hydrocarbon (HC) emissions and high cyclic variations at low engine loads. These drawbacks hinder the benefits of dual-fuel such as low NOx and soot emissions. To find solutions to these drawbacks, split diesel injections with variable injection timings and mass split ratios (ratio of first injection diesel mass to total diesel mass) were investigated experimentally and numerically on a medium speed marine engine at low load using constant natural gas and diesel amounts.Experimental results of the split injection were compared to single injection dual-fuel and conventional diesel operation. Single injection case resulted in slightly lower HC emissions and cyclic variations and higher NOx emissions than split cases in a narrow injection timing interval. Apart from that, split injections increased combustion efficiency and decreased cyclic variations in a broader timing interval. For split cases, early first injection timing prevented high premixed heat release peak, suppressed NOx emissions and knocking. Especially, using 70% split ratio with retarded second injections increased combustion efficiency, decreased knocking level and provided simultaneous reduction of HC and NOx emissions compared to lower split ratio cases. In short, despite not giving the minimum values at all conditions, split injection showed potential to find a remedy to high HC emissions and cyclic variations issues by keeping robust operation in a wider injection timing interval.The numerical results support the experiments in which better combustion and decreased HC emissions are attained using sufficiently early diesel injections. Simulations show that, compared to late single injection, early single injection dual-fuel case enables more homogeneous temperature distribution and better oxidization of methane near the cylinder wall and central region above the piston crown. Besides, split injection shows improved methane oxidation near the cylinder wall and inside top-land crevice volume.

Partially premixed combustion of diesel-di-ethyl ether blends in light-duty commercial engine

Diethyl ether (DEE) has evolved as a potential alternative for partial diesel replacement in compression ignition (CI) engines. In this study, a light-duty commercial diesel engine was operated in partially premixed combustion (PPC) mode. This work investigated the engine characteristics with lower and higher DEE-diesel blends in PPC mode. The split ratio and the start of the main injection (SoMI) timings were maintained at 70:30 (Main: Pilot) and 9° bTDC, respectively, while the start of the pilot injection (SoPI) timing was varied from 25 to 40° bTDC. The performance, combustion, and regulated emission characteristics of the PPC engine were compared with the conventional diesel combustion (CDC) mode as a baseline. The PPC mode exhibited higher/ comparable brake thermal efficiency (BTE) than the baseline CDC mode. The DEE-diesel blends exhibited higher BTE than the diesel in PPC mode generally. The DEE40 showed greater improvement in BTE than DEE20 at lower brake mean effective pressure (BMEP). PPC mode fuelled with diesel and diesel-DEE blends showed lower brake specific fuel consumption (BSFC) than baseline CDC mode at lower BMEP, but it was comparable at higher BMEP. PPC mode showed higher carbon monoxide (CO) emissions than baseline CDC mode. CO emissions increased with advancing SoPI timing for all BMEPs, except 5.6 bar. Although, the PPC mode exhibited higher hydrocarbon (HC) emissions than the CDC mode. Diesel-DEE blends showed slightly higher HC emissions than diesel in PPC mode at lower engine BMEPs. NOx emissions in the PPC mode were 1.5 to 2 times the baseline CDC mode. This indicated that the PPC mode engine performance requires further optimization similar to CDC mode, which had optimized exhaust gas recirculation (EGR), and significantly reduced the nitrogen oxide (NOx) emissions.

Experimental study on the effect of piston bowl geometry on the combustion performance and pollutant emissions of methane-diesel common rail dual-fuel engine

In dual-fuel operations, high methane substitution negatively affects combustion performance and creates high hydrocarbon (HC) and carbon monoxide (CO) pollutant emissions. Piston bowl geometry is proven an effective method for improving combustion performance and emissions. In the available study, combustion chamber geometry is experimentally indicated to succeed in dramatically reducing HC and CO pollutant emissions uncompromising nitrogen monoxide (NO) and smoke pollutant emissions.In this study, the effect of piston bowl geometry on the combustion performance and pollutant emissions of a single-cylinder methane-diesel common rail dual-fuel engine was studied experimentally. High-performance piston bowl geometries (Toroidal and Toroidal re-entrant) of conventional diesel operations were used versus original combustion chamber (OCC) geometry in diesel and dual fuel operation for enhancing combustion performance and reducing pollutant emissions. The experiments were conducted at constant 1850 r/min and five different engine loads. The methane energy fraction was set to 50% of the total energy fraction in dual fuel operations. Experimental results showed that the Toroidal re-entrant combustion chamber (TRCC) geometry reduced the long ignition delay period that was due to the methane addition and ensured more stable combustion at all torque conditions. In dual fuel operation, the TRCC geometry improved smoke, HC, and CO pollutant emissions by an average of 18%, 10%, and 3% for all loads, respectively, compared to the OCC geometry. However, NO pollutant emissions were an average of 2.5% higher than OCC geometry for the TRCC geometry. In sum, use of the TRCC geometry is an effective way for providing more complete combustion and reducing emissions under dual fuel operations at all torque conditions between 3 and 9 Nm.

Effect of pilot injection strategy on the methanol-mineral diesel fueled reactivity controlled compression ignition combustion engine

Amongst all low-temperature combustion (LTC) strategies, reactivity-controlled compression ignition (RCCI) combustion garners more debate from researchers because of its excellent combustion and performance characteristics and lower emissions over a wide operating range. In this experimental investigation, the consequences of the start of diesel injection (SoIdiesel) timing using different pilot injection techniques, such as single and double pilot injection (SPI and DPI, respectively), have been investigated. Tests were performed at a fixed engine speed and load (1500 rpm and 3 bar BMEP, respectively) using different premixed ratios (rp: 0, 0.25, 0.50, and 0.75) of methanol on an energy basis. Experimental results indicated that the start of combustion (SoC) and combustion phasing (CP) advanced with advancing SoIdiesel. However, too advanced and retarded SoIdiesel timings resulted in combustion noise and misfire. The use of pilot injection was found suitable for the RCCI mode, especially at lower rp. However, SPI and DPI strategies didn’t show significant variations in the combustion characteristics. Exhaust gas temperature (EGT) showed a random trend with SoIdiesel timing, and it decreased with the increasing number of pilot injections. RCCI mode produced higher hydrocarbon (HC) and carbon monoxide (CO) and lower oxides of nitrogen (NOx) emissions. All these gaseous emissions decreased with advancing the SoIdiesel. Particulate matter (PM) analysis showed that the RCCI mode emitted relatively lower PM than the baseline CI mode, further reducing with increased methanol fuelling. PM emissions also decreased by retarding SoIdiesel, in which reduction in smaller particles was dominant. The analysis of critical parameters such as brake thermal efficiency (BTE), HC, NOx, and PM emissions suggested that the optimum rp of methanol and suitable injection strategy can significantly improve the combustion, performance, and emissions characteristics of the RCCI mode.

Effects of Changing Drive Control Method of Idling Wood Size Reduction Machines on Fuel Consumption and Exhaust Emissions

Operating conditions often fluctuate during processing of branches and sawmill offcuts using low-power wood size reduction machines (WSRMs), mainly due to changes in wood supply frequency. This results in relatively high proportions of idling time. Fuel consumption and associated exhaust emissions of WSRMs with combustion engines can be reduced by using innovative drive unit control systems during idling. The objective of the research was to determine the effects of two speed control systems on the fuel consumption and exhaust emissions of a WSRM with a two-cylinder cutting mechanisms driven by a small 9.5 kW spark ignition engine. Speed control system A (commercially available) had a substantially higher rotational speed than system B (an innovative, adaptive solution subject to patent application No. P433586). Pine (Pinus sylvestris L.) wood sawmill offcuts (average cross-sectional area, length and water content: 25×40 mm, 3000 mm and ca. 12, respectively) were used in system tests at a feed rate of ca. 5 pieces min-1. Material of this size is typically processed by such machines. Operating conditions were monitored by recording the rotational speed and torque. Emissions of harmful exhaust compounds–carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), and nitrogen oxides (NOx) – were recorded using a portable emission measurement system. Fuel consumption values were also calculated from the data. The following effects were observed: application of innovative system B resulted in 33% lower fuel consumption, as well as 30%, 37% and 33% lower CO, CO2 and NOx emissions, respectively, than system A, but at the same time 290% higher HC emissions were registered. In operating conditions with higher proportions of idling time, solution B provides even higher reductions in fuel consumption and exhaust emissions.

Novel strategies to extend the operating load range of a premixed charge compression ignited light-duty diesel engine

Low-temperature combustion (LTC) is an alternative combustion mode to conventional diesel combustion (CDC) that offers a simultaneous reduction in oxides of nitrogen (NOx) and particulate matter (PM) emissions while retaining higher thermal efficiency. Premixed charge compression ignition (PCCI) is a promising LTC strategy that utilizes the early direct injection of diesel and exhaust gas recirculation (EGR) to reduce NOx and PM emissions simultaneously. A limited operating load range and high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are the significant shortcomings to be addressed to realize PCCI as a commercially viable option. The present work aims to address these limitations based on experimental investigations carried out in a production light-duty diesel engine. An existing mechanical fuel injection system is replaced with a flexible common rail direct injection (CRDI) system to implement PCCI in the test engine. Based on initial parametric investigations, it was found that a combination of early direct injection, lower injection pressures, and EGR was deemed necessary to achieve PCCI mode in the test engine. However, the achievable load range was limited to 40% of the rated load, along with high HC and CO emissions. Novel approaches are attempted to address these limitations, including replacing diesel with diesel-gasoline blends with 30% gasoline by volume and utilizing a dual charge dilution strategy with water vapour induction and EGR. The start of fuel injection (SOI) sweeps from 30 to 70 deg. CA bTDC were performed to find optimal timing at each load condition to maximize the thermal efficiency within a stable combustion regime between a misfire and knocking. For loads above 40%, EGR in the range of 14% to 26.5% was used to bring the combustion within knock limits. By combining the proposed novel strategies, the engine operating load range could be extended from 40% to 80% of the rated load in PCCI. The NOx and soot emissions were significantly reduced up to 98.5% and 99.1%, respectively, compared to CDC. The engine brake thermal efficiency is increased by up to 1.6%. However, there was a significant penalty regarding HC and CO emissions.

Computational study of diesel injection strategies for methane-diesel dual fuel engine

Methane-diesel dual fuel engine is an effective solution for partial replacement of conventional diesel fuel and pollutant reduction in compression ignition engine. However, it has several challenges from the large scale market acceptability perspective such as low combustion and thermal efficiency and high hydrocarbon (HC) and carbon monoxide (CO) emission. These problems can be addressed with the optimization of injection strategies of diesel fuel. The present work explores the effect of diesel injection strategies on combustion, performance and emission characteristics of methane-diesel dual fuel engine. Firstly, injection timing of diesel fuel is varied for single injection case. After that split injection strategy is explored with varying pilot mass amount (15%, 30% and 45%) and varying pilot injection timing (12°bTDC to 30°bTDC) at fixed main fuel injection timing (8°bTDC). The results revealed that 8°bTDC injection timing is obtained as optimum injection timing for single injection case for methane-diesel dual fuel engine from enhanced performance, combustion and reduced emissions point of view. In case of split injection, advancement of pilot injection (SOI1) timing till 24°bTDC decreased the methane slip, HC and CO emissions. SOI1 timing earlier to 24°bTDC increased the methane slip, HC and CO emissions for all pilot mass injections (15, 30 and 45%). Higher pilot mass injection resulted in higher methane slip, HC and CO emission in SOI1 range of 24–30°bTDC. SOI1 timing exhibited different trends of soot and NO x emission with different pilot mass injection. GTE reduced with advanced SOI1 injection timing. Overall, with split injection technique, 24°bTDC is optimum pilot injection (SOI1) timing, and 15% pilot mass amount is optimum amount and 8°bTDC is optimum main injection (SOI) timing for methane-diesel dual fuel engine. • Effect of diesel injection strategies on characteristics of methane-diesel dual fuel engine. • Single injection as well as split injection have been investigated. • For single injection case 8°bTDC is found as optimum timing. • In split injection, injection timing were varied from 12°bTDC to 30°bTDC. • Pilot injection amount (15%, 30% and 45%) were also varied.

CFD-guided optimization of the injector and injection parameters for light-duty GCI engine

In this study, computational fluid dynamics (CFD) and machine learning (ML) were used to investigate the effects of and optimize the injector design parameters for light-duty gasoline compression ignition (GCI) engine. This study was performed at part- (6 bar) and high-load (22 bar) indicated mean effective pressure (IMEP) conditions. The effects of number of nozzles (nNoz), spray angle (SA) and plume angle (PA) while maintaining total nozzle area (TNA) and start of injection (SOI) were first investigated. The increased nNoz and PA enhanced fuel/air mixing, especially in the bowl region, by even spray distribution at part-load condition, but the effects are negligible at high-load mixing-driven combustion due to high in-cylinder temperature and pressure at the time of main injection. On the other hand, SA had significant effect on the air utilization and hence engine performance and emissions at both part- and high-load conditions. The best design from this manual parametric study produced a balanced air utilization between piston bowl and squish region resulting from the fuel spray targeting the upper lip of the bowl. The second phase of this study focused on the optimization of the injector and injection parameters including nNoz, SA, nozzle hole diameters (dNoz) and SOI using design of experiment (DoE) approach. 32 DoE cases were generated and best design was selected at each load point. It was found that the SA and SOI are the most influential injection parameters. Specifically, two optimum SOI regimes at part-load conditions have been identified. These are a) early injection resulting in retarded combustion and low pressure rise rate and b) late injection yielding high combustion efficiency and low hydrocarbon emission. At high-load condition, SOI right before top dead center (TDC) is most preferable and early injection should be avoided to minimize pressure rise rate. The narrow SA (90 degrees (deg) in this study) as well as wide SA were found to produce optimum performance. Subsequently, ML algorithm was used to further optimize the injector and injection parameters. As a result of this optimization study, 10.7% reduction of fuel consumption at part-load and 7.5% reduction at high-load were achieved.

Fuel Effects on Regulated and Unregulated Emissions from Two Commercial Euro V and Euro VI Road Transport Vehicles

Substantial advances in European road vehicle emissions have been achieved over the past three decades driven by strengthening revisions in emissions legislation and enabled by advances in fuel, vehicle engine and emissions control technologies. As both vehicle technology and emissions legislation in Europe continue to evolve, Concawe has conducted a study to examine the effects that fuels can have on emissions, in this case from commercial road vehicles. A bus certified to Euro VI emissions level and a delivery truck certified to Euro V emissions level have been tested on a chassis-dyno over the World Harmonized Vehicle Cycle (WHVC) and Transport for London Urban Inter-Peak (TfL UIP) test cycles with six fuels: an EN590-compliant B5 (petroleum diesel containing 5% biodiesel by volume), a bioderived paraffinic diesel, a 50:50 blend of the aforementioned fuels, a low-density petroleum-derived B5, a B30 and the same B30 additized with a high dose of cetane number improver (CNI). Results show reduced NOx reductant (AdBlue) consumption with paraffinic diesel in the Euro VI bus due to lower engine-out NOx emissions. More surprisingly, higher hydrocarbon emissions were observed with some low-density hydrocarbon fuels in the Euro V truck. Compared to B5, B30 with and without CNI did not affect tank-to-wheel (TTW) CO2, volumetric fuel consumption or NOx by statistically significant margins. When considered with the findings of a complementary light-duty study, it is apparent that low-density diesel fuels could offer overall benefits to both emissions affecting local air quality and to greenhouse gas emissions on a TTW basis. The addition of higher fatty acid methyl ester (FAME) levels to fuels can be used to increase renewable fuel contribution resulting in no penalty in NOx emissions from modern technology vehicles. Compatibility of these fuels with the existing vehicle fleet would require further specific consideration. Outside of fuel properties considerations, Euro VI aftertreatment systems can increase N2O emissions at the tailpipe through chemical reactions in the catalyst. This can translate into about 10% contribution of N2O emissions to the overall GHG emissions of the vehicle.

Environment‐friendly fuel Cymbopogon flexuosus: Analysis of fuel properties, performance, and emission parameters of a Direct Injection Compression Ignition research engine

AbstractThe novelty of this study discusses on the influence of neat lemongrass oil (LGO) on fuel analysis, performance and emission analysis, naturally aspirated diesel engine. The critical parameters include iodine value, flash point, kinematic viscosity, saponification and cetane numbers, calorific value, Fourier transform infrared spectroscopy (FT‐IR), and gas chromatography–mass spectroscopy (GC‐MS) studies were investigated. The oxygenated elements, such as naphthalene, caryophyllene, pentadecanoic acid, dihydropyridine, d‐limonene are observed using GC‐MS analysis. The higher hydrocarbon (HC) chain length indicates a rise in energy density and boiling point with a reduction of volatility. Using FT‐IR analysis, C–H stretching vibrations are found at a frequency of 1672 cm−1. The C≐C stretching vibrations at 1740 cm−1 reveals the availability of the alkenes/fingerprint phase. Experiments were conducted at four different volumetric blend ratios of LGO‐diesel blends at typical injection parameters under different loading conditions. Brake thermal efficiency (BTE) decreased for all the test combinations of LGO than diesel. BTE is observed as 30.79% at diesel, 30.06% at LGO25, 28.71% at LGO50, 27.77% at LGO75%, and 27.23% at LGO100. The cylinder pressure and heat release rate increased proportionately with the LGO fuel mixture. Carbon monoxide, HC, and smoke emissions are reduced by LGO mixtures than diesel at the full load of the engine. It was noted that greater blends of LGO and diesel resulted in increased nitrogen oxide (NOx) emissions and engine tribological characteristics. The NOx is increased by 21.2% at LGO25, 24.3% at LGO50, 26.5% at LGO75 and 30.8% at LGO100 when compared with diesel. Without any chemical processing, Cymbopogon flexuosus oil can be blended directly with diesel fuel.

Effects of Fuel Ratio on Performance and Emission of Diesel-Compressed Natural Gas (CNG) Dual Fuel Engine


 
 
 Recent research breakthrough reveals that diesel-CNG dual fuel (DDF) combustion can potentially reduce exhaust emission of internal combustion engines. However, problem arises when knock phenomenon occurs producing high carbon monoxide (CO) and hydrocarbon (HC) emission due to uncontrolled blending ratio of diesel-CNG fuel on specific engine load. This study will determine the limit of dual fuel ratio before knock occurrence while analysing performance and exhaust emission of an engine operating with diesel and DDF fuel mode. A 2.5 litre 4-cylinder direct injection common-rail diesel engine was utilised as a test platform. The models tested were 100% Diesel, 90% DDF, 80% DDF and 70% DDF, representing diesel to CNG mass ratio of 100:0, 90:10, 80:20 and 70:30 respectively. It was found that DDF engine performance was lower compared to diesel engine at 1500 rpm engine speed. At higher engine speed, the 70% DDF showed engine performance comparable to diesel engine. However, high HC emission with knock onset and a decrease of Nitrogen Oxide (NOX) emission were recorded. This study suggests the preferred limit of dual fuel ratio should not be lower than 70% DDF which will be able to operate at high engine speed without the occurrence of knock and poor exhaust emission.
 
 

Investigation of partially pre-mixed charge compression ignition engine characteristics implemented with toroidal combustion chamber and exhaust gas recirculation

ABSTRACT Many pre- and post-treatment strategies have been instigated in compression ignition engines to meet the stringent vehicular emissions norms. The partially pre-mixed charged compression ignition (PCCI) combustion technique has shown a significant reduction in emissions without much affecting the efficiency of the conventional diesel engine by emitting low nitrogen oxides and smoke emissions simultaneously. However, the PCCI engine has also shown some limitations by producing higher hydrocarbon (HC) and carbon monoxide (CO) emissions from the engines. The toroidal combustion chamber has proven its potential to reduce the HC and CO emissions from the conventional engine. Therefore, in the current experimental study, PCCI engine characteristics were investigated with toroidal piston geometry and compared with conventional engine characteristics having hemispherical combustion chamber (HCC). The experiments were performed on single-cylinder, four strokes, direct injection, diesel engine modified to operate on PCCI mode. The homogeneous mixture for PCCI combustion was obtained with an external mixture formation technique with a fuel vaporizer (retrofit device). The tests were conducted with 15% and 30% diesel vapor without and with 10% exhaust gas recirculation and then compared with the conventional engine. The investigation results show that better air–fuel mixing results in low engine emissions. NOx emissions were reduced by 29% and 36%, and smoke opacity was decreased by 33% and 38% with 15% and 30% diesel vapor with EGR with a marginal decrement in thermal efficiency compared to conventional engine.

Emission characteristics study of Gasoline-Diesel and Gasoline-Diesel/pentanol blend

Increase in vehicular emission affects the environment due to air pollution. Emission laws are formulated to control vehicular emission and all nations show their intensive interest in alternative fuel for pollution reduction and fuel economy. In the present work, experiment was carried out in a direct diesel inject 4-S engine; for diesel, Gasoline-Diesel and Gasoline-Diesel/pentanol blend (D70/P30). For dual fuel mode, Diesel is supplied from main injection and Gasoline was injected into the port at 5 bar. The result indicates high hydrocarbon emission at no load condition for both Gasoline-Diesel (1200 PPM) and Gasoline-Diesel/Pentanol blend (1170 PPM). Maximum NOx emission was observed for D70-P30 blend. Low CO emission (<2%), CO2 emission (<6%) and smoke emission (<70 PPM) was observed in blended fuel up to 60% load condition.

Activation of Formation of Hydrocarbon Fluidizites under the Conditions of Shear Geodynamic Regime of the Caspian Region (Russian–Kazakh Sector, Russia)

The paper presents the results of the study of objects spatially related to extremely high hydrocarbon (HC) emissions identified in the North Caspian Sea. The analysis of variable geological–geophysical parameters in these objects showed (i) a high correlation with large destruction zones of the crust, (ii) the occurrence in negative forms of the top of the consolidated crust, (iii) elevated Moho top in areas of their occurrence, and (iv) their coincidence with near-shear depressions in the sedimentary sequence. These objects are revealed on the basis of surface reflection. The study of their spatial location allowed them to be correlated with the main clusters of petroleum formation, which can be identified from geological prospecting data. In the South Caspian Sea, petroleum clusters are studied by both seismic survey and drilling up to 7 km. The results of these comprehensive studies substantiate the conclusion on the formation of excitation sources under certain conditions at a deep horizon of the crust favorable for HC generation. The summarized materials from the North and South Caspian Sea suggest that significant areas of higher HC emissions are caused by large-volume fluidizites that formed in the petroleum clusters. These objects occur in the southern areas of the North Caspian region under dominant shear geodynamic regime. The position of the negative structures of the platform cover near the zones of transregional strike-slip faults causes their near-shear type. The association of HC fluidizites with near-shear depressions is caused by their location in the extension areas of the crust favorable for the formation of pull-apart structures. The correlation of fluidizites with various structural-tectonic and sedimentation factors indicates the key role of the deep geodynamic regime in the formation of similar objects.

1-D mathematical modeling of a diesel oxidation catalyst for transient hot start drive cycle

The need to obey with increasingly stringent emission regulations has amplified the importance of after treatment devices, and therefore, reliable tools need to be developed for the evolution of better aftertreatment devices. Even though the upcoming regulations paved the way for improved combustion engines, their high carbon monoxide and hydrocarbon emissions increased the load on catalytic converters. Numerical modeling is one such tool which is extremely useful in providing the basic information which helps in designing the reactor, understanding its operation, and predicting the performance. In this context, the utmost aim of the numerical modeling is to simulate the driving cycle where inlet conditions to the catalytic converter vary with respect to time. Such a simulation must include the calculations of transient temperature-field of the monolith substrate and converter-out mass emissions. In this paper, a one-dimensional mathematical modeling of an oxidation catalyst has been implemented to simulate a hot start New European Drive Cycle (NEDC). The transient engine data was taken from the literature, and the measured instantaneous traces at the outlet of the catalyst were compared with the model predictions. This model has been developed to investigate the CO conversion performance of the catalyst. The comparison between model predictions and experiments has shown a satisfactory agreement in terms of both substrate temperature and CO emission at the catalyst outlet, confirming the effectiveness of the methodology applied. The reliability of the 1-D model was also proved with the probability density function of the conversion efficiency.

Experimental studies on performance and emission characteristics of reactivity controlled compression ignition (RCCI) engine operated with gasoline and Thevetia Peruviana biodiesel

Abstract Higher fuel economy associated with lower emissions of diesel engines cannot be achieved with conventional low-pressure injection systems. However high-pressure CRDI facilitated diesel engines with electronic control systems can overcome the twin problems of higher emissions of smoke and nitric oxide with acceptable higher brake thermal efficiency as well. Further use of both high-octane fuels like petrol, ethanol as manifold injected fuels along with high pressure CRDI injected high cetane fuels like diesel, biodiesel can successfully overcome the drawbacks of diesel engine emissions. In this direction a newer concept of RCCI operated modified diesel engine was developed in house and was powered with both high octane and high cetane fuels. Comprehensive experiments were conducted on the RCCI engine to obtain its performance, emission characteristics fueled with selected fuel combinations. From the results for B20 and gasoline operation it was concluded that, injection of 10% gasoline drastically reduces the nitric oxide by 6.67% and soot emission by 4.52% compared to diesel mode. However, there was penalty of high hydrocarbon and carbon monoxide emissions by 12.5% and 7.6% respectively.