Low Engine Load Research Articles

Evaluation of energy-exergy performance and sustainability index of a DI engine integrated with designed electromechanical EGR cooling system

Exhaust Gas Recirculation (EGR) system is a commonly used pretreatment technique to improve pollutant emissions from modern diesel engines. Recently, the EGR cooling strategy focuses on improving combustion stability, NOx emission and fuel consumption values by controlling oxygen dilution, in-cylinder and exhaust gas temperatures. However, there are not enough studies focusing on energy and exergy analysis to improve the deterioration caused by hot EGR gas in engine performance and energy distributions. Therefore, in this study, classical and electronically controlled external EGR cooling systems are designed. The present study investigates the effect of the various EGR rates and EGRout gas temperatures on classical/electromechanics EGR cooling systems in a DI diesel engine and reveals the effects of energy-exergy distributions on each other and the sustainability index (SI) perspective. The tests are performed with various EGR rates (5%, 10%, 15%) and EGRout gas temperatures (75 °C, 90 °C, 110 °C) at 1700 and 2000 rpm. At 1700 rpm test conditions, the highest thermal-exergetic efficiencies for low and high load are recorded at 15% EGR rate-75 °C EGRout gas temperature and 5% EGR rate-75 °C EGRout gas temperature, respectively. At 2000 rpm test conditions, the highest thermal-exergetic efficiencies for low and high load are achieved at 15% EGR rate-110 °C EGRout gas temperature and 5% EGR rate-90 °C EGRout gas temperature, respectively. The main findings show that the EGR rate rather than the EGRout gas temperature has a more dominant effect on the in-cylinder combustion performance and thermal-exergetic efficiency. While the increase in the EGR rate from 5% to 15% contributes positively to the thermal-exergetic efficiency and SI performance at low engine load, the opposite is observed at high load. The study recommends that the EGR rate and EGRout gas temperature should be chosen at the optimum level for the engine performance and energy efficiency.

An investigation into the ICCI mode to low engine load extension and its achievable operational range at different intake pressure

In this paper, the effect of biodiesel and butanol direct injection strategies, intake conditions were modulated to extend the ultra-low engine load and optimize the engine performance at different intake pressure in a brand-new dual-fuel combustion mode called intelligent charge compression ignition (ICCI). A four-cylinder, direct injection, turbocharger diesel engine was modified into the ICCI mode on the fourth cylinder to take this experiment. The results indicated that increased butanol energy ratio and retarded biodiesel direct injection timing allowed the engine to achieve high efficiency and stable combustion under the indicated mean effective pressure (IMEP) of 1 bar and 2 bar. The maximum indicated thermal efficiency was above 43% and 44% at the IMEP of 1 bar and 2 bar, respectively. A higher butanol energy ratio and more retarded biodiesel injection timing increased the ignition duration, and shortened the combustion duration, leading to the higher nitrogen oxide (NOx) emissions and lower hydrocarbon and carbon monoxide emissions. The applicable intake pressure for ICCI steady operation could ease the combustion efficiency and adjust combustion phasing, optimizing heat release profiles. The intake pressure shown insignificant effect on the indicated thermal efficiency and pollutant emissions when the engine load increased to the IMEP of 8 bar to 12 bar. However, the NOx emissions were ultra-low when the IMEP was 4 bar to 10 bar for all intake pressure conditions, in which the NOx emissions were less then 40 ppm. The unregulated emissions were further reduced at higher intake pressure, but with an increase of particle matter emissions.

Numerical study on the load-range extension of gasoline-fueled homogeneous charge compression ignition combustion in a light-duty diesel engine

Recent research on homogeneous charge compression ignition (HCCI) engines has demonstrated that these engines can complement traditional compression-ignition engines. The higher octane number and vapor pressure make gasoline-like fuels more suitable for port fuel-injected HCCI engines. Doping gasoline with ignition promoters eliminates intake charge preheating or turbocharging requirements and reduces cyclic variations in combustion, especially at lower engine loads. Seeding the intake charge with suitable diluents enables higher load extension of doped gasoline-fueled HCCI engines by preventing knocking. In the present study, HCCI experiments in a 0.662-litre, light-duty diesel engine using 2-Ethylhexyl nitrate (EHN)/gasoline blends formed a database for validating computational fluid dynamic (CFD) simulations. The CFD tool could capture the qualitative trends of HCCI combustion, performance, and emission parameters. The validated CFD tool was then used to investigate a suitable ignition promoter other than EHN to blend with gasoline such that a constant combustion phasing was achieved. Di-tert butyl peroxide (DTBP), hydrogen peroxide, nitric oxide, nitrogen dioxide (NO2), and ozone were the investigated ignition promoters. Further, the effects of adding diluents, including exhaust gas recirculation, nitrogen, carbon dioxide (CO2), and water vapor (H2O) on EHN-gasoline HCCI combustion, were studied for a constant combustion phasing retardation of 5 °CA towards aTDC. The primary objective of the present study was to select the most suitable ignition promoter and diluent for gasoline-fueled HCCI combustion. The results show that the least quantity of EHN and CO2 was required to control HCCI combustion phasing among the tested ignition promoters and diluents. Using NO2 as an ignition promoter and H2O vapor as a diluent improved the gross indicated thermal efficiency by 24% and 17%, respectively, compared to DTBP and EGR, which produced the lowest gross indicated thermal efficiency.

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.

Optimization study on the production of argemone mexicana biodiesel and its impact on diesel engine combustion stability: Taguchi model and wavelet analysis

A research study is being conducted to investigate the potential use of Argemone mexicana oil (adulterated with mustard oil and non-edible) as a biodiesel source in a compression ignition (CI) engine to replace the maximum amount of fossil fuel in the engine. This research aims to optimize transesterification reaction parameters to achieve high yields of Argemone mexicana biodiesel (AGB). The study employed the Taguchi method to optimize the appropriate combination of transesterification reaction parameters. A transesterification reaction at 60 °C, 90 min, with a molar ratio of 6:1, produced a maximum yield of 95%. Additionally, the present study explores the combustion stability of a 4-cylinder turbocharged CRDI engine using AGB/diesel blended fuels. The wavelet transform (WT) analysis has also been used to observe temporal and spectral variations in the combustion parameters of various AGB/diesel blends. The global wavelet spectrum (GWS) and wavelet power spectrum (WPS) analyses showed that the AB10 blend exhibited the lowest cyclic fluctuations in indicated mean effective pressure (IMEP) combustion parameter at a low engine load. The study of the spectral variations of the IMEP combustion parameter based on the in-cylinder pressure feedback can be used to develop better fuel injection control strategies.

Experimental investigation into the effects of Argemone biodiesel/diesel blends on cyclic variations in a multi-cylinder CRDI engine

Abstract Internal combustion engines suffer from high cyclic variations that result in higher emissions, lower efficiency, higher fuel consumption and poor drivability. The purpose of this study is to investigate how Argemone mexicana biodiesel (AGB)/diesel blended fuels affect the cyclic variability of combustion parameters such as maximum cylinder pressure (Pmax) and indicated mean effective pressure (IMEP) in a four-cylinder turbocharged intercooled common-rail direct injection engine under various engine loading conditions. The chemical and physical properties of AGB produced from A. mexicana oil were measured and compared according to the ASTM D6751 standards. In various volumetric ratios, AGB and diesel fuel were blended as D100, AB10 (10% AGB + 90% D100), AB20 (20% AGB + 80% D100) and AB30 (30% AGB + 70% D100). The IMEP and Pmax time-series data were collected over 200 consecutive cycles at low, partial and high engine loads at a constant engine speed of 2000 rpm. The coefficients of variation (COV) of combustion parameters (Pmax and IMEP) were measured for different AGB/diesel blends and found to be within acceptable limits. The results show that COVPmax and COVIMEP decrease as the engine load increases. It was observed that at low load, AB10 has the lowest COV (Pmax, IMEP), and at partial and high load, AB20 has the lowest COV (Pmax, IMEP) among all the blends.

Ranking of four dual loop EGR modes

Modern Diesel engines contain sophisticated control systems to keep their environmental impact low for sustainable road transport. One of these systems is the dual loop exhaust gas recirculation, which can change combustion properties in several ways. This article presents an engine dyno measurement based on analyzing the duel loop EGR with a medium-duty Diesel engine. Intake throttles and exhaust brakes for the highest freedom in the air-fuel ratio setting support the EGR systems. The EGR modes are compared from fuel consumption, NOx emission, and exhaust gas opacity in steady and transient operations. There are expected results, for instance, in the HP EGR’s faster reaction time or the LP EGR’s boost pressure holding property. Unexpected results are also presented. Contrary to theory, LP EGR generally provides a fuel consumption advantage in many operation points due to its higher boost pressure. Typically, HP EGR can provide lower fuel consumption at higher engine power. In the emission results, LP EGR is favourable both in NOx emission and exhaust gas opacity, whereas the intake throttle-supported HP EGR usually shows the highest emission. Besides, with high EGR rates at lower engine loads, LP EGR can realize low-temperature combustion, where both emissions decrease. No difference can be detected between the LP EGR’s support valves’ results. HP EGR was faster in the transient operation, with about half the reaction time. The results can be utilized for dual-loop EGR layout and control design.

Analysis of Performance of Passive Pre-Chamber on a Lean-Burn Natural Gas Engine under Low Load

Stable ultra-lean combustion is an effective way for natural gas engines to reduce NOx emissions, but it also has higher requirements for ignition stability. The passive pre-chamber can effectively increase the ignition energy and extend the lean-burn limit of natural gas engines. However, the scavenging capacity of the pre-chamber limits its performance under low engine load. In this paper, several passive pre-chambers are designed, and the CFD simulation is carried out to investigate the influence of direction, number and diameter of the nozzle on the scavenging process. The discharge of residual gas in the pre-chamber is mainly affected by the nozzle diameter, which varies from 5.9% to 1% when the nozzle diameter increases from 0.8 mm to 1.6 mm. At the same time, claw-shaped electrodes are applied in the pre-chamber to increase the combustion rate, which is validated in a cylinder combustion simulation. Finally, the passive pre-chamber is tested on a 6-cylinder natural gas engine under 25% load. The results show that, under the proper ignition timing, the excess air ratio (λ) can reach 1.9 under 25% load of propulsion characteristic with a low level of cyclic variation. At this time, the NOx emission can be as low as 0.34 g/kWh without aftertreatment equipment.

Experimental Evaluation of Pilot and Main Injection Strategies on Gasoline Compression Ignition Engine—Part 2: Performance and Emissions Characteristics

<div>Internal combustion (IC) engines play an important role in the global economy by powering various transport applications. However, it is a leading cause of urban air pollution; therefore, new combustion strategies are being developed to control emissions. One promising advanced low-temperature combustion (LTC) technology is gasoline compression ignition (GCI). This experimental study assesses the performance of a two-cylinder engine, emissions, and exhaust particulate characteristics using G80 (80% v/v gasoline and 20% v/v diesel) blend operating in GCI mode vis-à-vis baseline conventional diesel combustion (CDC) mode using diesel. The effects of double pilot injection, Pilot-1 proportion (10–30%), and main injection timing were investigated on the GCI combustion. Experiments were performed at different engine loads (3, 4, and 5 bar brake mean effective pressure [BMEP]) at a constant engine speed (2000 rpm). GCI combustion showed higher brake thermal efficiency (BTE) than CDC mode at medium loads. Hydrocarbon (HC) and carbon monoxide (CO) emissions increased in GCI mode, but oxides of nitrogen (NOx) were reduced than the baseline CDC mode. High pilot ratio and late main injection timing tests showed higher HC and CO emissions in the GCI mode at low engine loads. The GCI mode engine emitted higher nucleation mode particles and nanoparticles than baseline CDC mode at high engine loads. Using a triple injection strategy, GCI engines simultaneously reduced NOx and particulate matter (PM) emissions, especially at high loads. Controlling these emissions in baseline CDC mode engines is otherwise quite challenging.</div>

Numerical study on the combustion and emission characteristics of a direct injection natural gas engine ignited by diesel/n-butanol blends

Adjusting the composition of pilot fuel has been regarded as an effective method for the improvement of performance and emissions of pilot ignited direct injection natural gas engines. In this paper, the effects of employing diesel/n-butanol blends as the pilot fuel in a direct injection natural gas engine were assessed by numerical simulations. The results indicated that adding n-butanol into the pilot fuel will result in notable extensions in ignition delay and obvious reductions in combustion duration at low and medium engine loads; at high engine loads, the effects of n-butanol blending on combustion parameters are relatively small. In terms of engine performance, thermal efficiency could be improved by up to 2.3% and 6.5% by adding n-butanol into the pilot fuel at low and medium engine loads, whereas lower than 2% reduction in thermal efficiency would be induced by n-butanol addition at high engine load. With regard to emissions, more than 30% reductions in CO and soot emissions could be achieved by adjusting n-butanol blending ratio at low and medium engine loads; at low and high engine loads, blending n-butanol into the pilot fuel is favorable for the control of NOx emissions while at medium engine load, n-butanol blending could result in up to 34.7% increases in NOx emissions.

Comparative Assessment of Supervisory Control Algorithms for a Plug-In Hybrid Electric Vehicle

The study examines alternative on-board energy management system (EMS) supervisory control algorithms for plug-in hybrid electric vehicles. The optimum fuel consumption was sought between an equivalent consumption minimization strategy (ECMS) algorithm and a back-engineered commercial rule-based (RB) one, under different operating conditions. The RB algorithm was first validated with experimental data. A method to assess different algorithms under identical states of charge variations, vehicle distance travelled, and wheel power demand criteria is first demonstrated. Implementing this method to evaluate the two algorithms leads to fuel consumption corrections of up to 8%, compared to applying no correction. We argue that such a correction should always be used in relevant studies. Overall, results show that the ECMS algorithm leads to lower fuel consumption than the RB one in most driving conditions. The difference maximizes at low average speeds (<40 km/h), where the RB leads to more frequent low load engine operation. The two algorithms lead to fuel consumption differences of 3.4% over the WLTC, while the maximum difference of 24.2% was observed for a driving cycle with low average speed (18.4 km/h). Further to fuel consumption performance optimization, the ECMS algorithm also appears superior in terms of adaptability to different driving cycles.

Aeromechanical Optimization of Scalloping in Mixed Flow Turbines

Abstract Scalloping of radial and mixed-flow turbocharger turbine rotors has been commonplace for many years as a means of inertia reduction and stress relief. The interest in turbine rotor inertia reduction is driven by transient loading requirements of turbocharged internal combustion engines, as this is a key factor in the time taken to meet transient engine torque requirements. Due to the high-density materials used in turbine rotors, any material removal from the turbine wheel has a significant impact on turbocharger inertia, and thus the transient response of the engine. It is well known that scalloping reduces not only inertia, but also efficiency. This study aimed to identify if it was possible to produce a new scallop design which reduced the scalloping efficiency penalty without increasing inertia or compromising mechanical constraints. This was carried out with the aim of developing design recommendations for scalloping where a complete minimization of inertia is not the design goal. A multipoint, multi-physics numerical optimization, with constraints on inertia and back disc stress, was carried out to determine what efficiency benefit could be realized by aerodynamically designing mixed-flow turbine scalloping. An efficiency benefit was identified across the entire turbocharger operating line, with increased benefit at low engine load, whilst not exceeding the design constraints. Scalloping losses for the baseline design were found to be greatest at low engine load, where the turbine experienced a low expansion ratio, mass flow, and speed. This explains why an aerodynamic redesign yields the greatest benefit under those operating conditions. These performance predictions were experimentally validated on the cold flow test rig at Queen's University Belfast, with good agreement between simulated and measured data. To conclude the study, a detailed loss audit was carried out to identify key loss generating flow structures and to understand how changes in geometry affected the formation and development of these flow structures throughout the passage. A large vortex which entered the passage from the scalloped region and interacted with the tip leakage vortex along the suction surface of the blade was identified as the main source of loss due to scalloping. The optimized design was found to better control the location of entry of this vortex into the blade passage, thus reducing the associated loss and facilitating a performance improvement. Geometric design guidelines were then proposed based on these findings.

Numerical research of the in-cylinder natural gas stratification in a natural gas-diesel dual-fuel marine engine

The urgent need for decarbonization and emission reduction for marine engines is driving the development of alternative low-carbon fuels. One of the best alternative fuels for engines is natural gas, a clean energy source with vast reserves and a low price. However, low-pressure injection dual-fuel engines exhibit poor combustion characteristics at low engine loads, and extinction is likely to occur in the fuel mixture's dilution region. Thus, the Low Pressure Post Injection (LPPI) strategy was proposed in this paper. The major objective of the LPPI mode is to increase monocirculation combustion stability under low to moderate engine loads by achieving a reasonable distribution of NG in the combustion chamber. LPPI was compared with the Low Pressure Injection (LPI) strategy. Results indicate that the LPPI mode could successfully raise the swirl ratio in the cylinder upto 60.7 percent while perfectly avoiding the NG leakage phenomena. Additionally, with the aid of radial-wall distribution of NG and an improved swirl ratio in LPPI mode, the combustion duration is reduced by 33.6 percent, and the lean burn limit of the dual-fuel marine engine can be expanded to 0.30. Although local higher combustion temperature caused an large increase in NOx emission which is more than three times than LPI NOx emission, LPPI mode still meets Tier III NOx emission requirements.

CFD investigation of the radiative heat transfer effects on the adoption of an electrical heated catalyst to increase the abatement efficiency

The thermal transient of the after-treatment system (ATS) during the cold start and the typical urban drive low load engine operations is a crucial point for the conversion efficiency. In this context, the adoption of electrical heating is regarded as an effective solution to promote the catalytic activity and the pollutants abatement. This paper focuses on the evaluation of the radiative heat transfer affecting the operation of an electrical heated catalyst employed to increase the abatement efficiency of a standard catalyst. The modeling methodology relies on a CFD framework based on a Conjugate Heat Transfer (CHT) approach in OpenFOAM, so that a detailed characterization of the thermal transient of the different components of the exhaust line can be achieved. The electrical heating device under investigation is based on a metallic support and it is heated by the Joule effect. The distribution of the heat and its subsequent interaction with the gas flow significantly influence the catalyst operations. In this context, the CFD modeling framework has been further developed so that it is possible to accurately evaluate the radiative heat transfer in correspondence of the porous regions. The description of such features is mandatory for an accurate prediction of the maximum electrical heating device temperatures, resulting in a reliable estimation of the gas flow temperature and its subsequent interaction with the catalyst. The simulation methodology has been applied at first excluding the radiative heat transfer. Then, the developed radiation modeling is applied, so that its influence on the ATS performance can be fully evaluated.

Numerical assessment of fuel physical properties on high-dilution diesel advanced compression ignition combustion

Using traditional lean air-fuel mixture aftertreatment technologies to reduce NOx at low exhaust temperatures is limited below 175°C. Recent low engine load NOx emission regulations encouraged researchers to explore the potential of fuel physical properties to enable low-temperature, low-NOx combustion under challenging conditions in which the selective catalytic reduction device might be unable to treat engine-out NOx. Three diesel range fuels were developed to explore how the distillation profile affects and may enable low-load diesel advanced-compression ignition. The least volatile fuel is a conventional, commercially available diesel #2 fuel with a cetane number of 45.3. The second-most volatile fuel is diesel #1 fuel, which can also be found commercially. The last fuel, which is the most volatile, is a new formulation designed to target a final boiling point approximately 50 K below diesel #1 fuel and was termed diesel #0 fuel. A computational fluid dynamics model was developed and validated against experimental data to investigate the underlying effects of each of the developed fuels in the combustion process. Finally, each fuel physical property (e.g., density, viscosity, etc.) was changed independently to assess its effect under the same operating conditions and identify potential directions for fuel formulation that may enable improved NOx emissions and reduce the reliance on aftertreatment systems for NOx control. The results showed that although changes in the fuel distillation curve and other physical properties affect the air-fuel mixtures substantially, changes were not sufficient to result in a large impact to low-load NOx formation. The maximum predicted NOx reduction was 11% uncorrected by combustion phasing. The results suggest that further research efforts should focus on changing the chemical properties of the fuel, like the cetane number, to allow higher EGR dilution and stable combustion.

Low-Temperature H2-deNOx in Diesel Exhaust

For NOx removal from diesel exhaust, the selective catalytic reduction (SCR) is the most common abatement technology. However, low engine load scenarios such as city driving and cold start phases demand efficient NOx reduction clearly below 200 °C, which is difficult to achieve with SCR. Hence, this work investigates the potential of the low-temperature NOx reduction with H2 in diesel exhaust. A monolithic Pt/WOx/ZrO2 catalyst, recently reported as highly active, was evaluated in synthetic and real diesel exhaust. The monolith demonstrated high deNOx activity between 130 and 215 °C in the synthetic exhaust including peak conversion of 90% with N2 selectivity up to 85%. CO/HC components were shown to inhibit the H2-deNOx conversion thus requiring a pre-oxidation catalyst in practice. Furthermore, studies performed in an optical reactor indicated strong heat evolution along the monolith. As a result, the reaction kinetics was accelerated with an enhanced consumption of H2 limiting the H2-deNOx efficiency above 200 °C. Stationary tests in diesel engine exhaust substantiated the low-temperature H2-deNOx performance of the monolith including NOx conversions up to 80% at temperatures as low as 135 °C.

Emissions Characteristics and Engine Performance from the Interaction Effect of EGR and Diesel-Ethanol Blends in Diesel Engine

Recently, most of the researchers focused on provide lower greenhouse gas emissions that emitted from diesel engines by using renewable fuels to be good alternative to the conventional diesel fuel. Ethanol can be derived from renewable sources such as sugar cane, corn, timber and dates. In the current study, the ethanol fuel used in the tests was derived from the dates. The effects of using exhaust gas recirculation (EGR) diesel-ethanol blend (E10) with on engine performance and emissions characteristics have been studied in diesel engine under various engine loads. This study focused the use of oxygen in the bio-ethanol composition to compensate for the decrease occurred by the addition of EGR, which improves the engine performance and reduces its emissions. In this experiment, the ratios of EGR were 10%, 20% and 30% as well as 10% ratio of ethanol was blended into the diesel fuel blend under fixed engine speed. A traditional (without additional systems to reduce emissions) four cylinders direct injection (DI) diesel engine was used for all tests. The brake specific fuel consumption (BSFC) increased with increasing the EGR ratio by 10%, 20% and 30% by 18.7%, 22.4% and 37.4%, respectively. The thermal efficiency decreased under variable conditions of engine load for different ethanol blends. Furthermore, the emissions of NOX decreased when fuelled B10 into the engine in comparison with diesel under low engine load. Significant reduction in the NOx emissions were found when applied EGR in the tests than to the absence EGR for E10 blend and diesel. The NOx reduction rate was 12.3%, 30.6% and 43.4% when EGR rate was 10%, 20% and 30%, respectively. In addition, the concentrations of HC and CO emissions decreased more by 8.23% and 6.4%, respectively, when using E10 in comparison with the diesel for various engine loads. It is indicated that the oxygen reduction by EGR effect was compensated from ethanol blend combustion. The results showed that the combination use of E10 and EGR leads to significant reduction in engine emissions accompanied with partial reduction in the engine performance.

Selective characterization of petroporphyrins in shipping fuels and their corresponding emissions using electron-transfer matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry

In the context of the global transportation of goods, shipping emissions account for a significant proportion of air pollution. Indeed, a focus has been made over recent years on this primary emission source, leading to several regulations with respect to the chemical composition of shipping fuels. However, these regulations mainly concern the fuel sulfur content (FSC) and do not consider other compound classes such as polycyclic aromatic hydrocarbons (PAHs) or metal-containing aromatics, i.e., petroporphyrins, known to be present in bunker fuels. Petroporphyrins are tetrapyrrole-based metal complexes derived from the transformation of chlorophylls through geological time scales. In contrast to PAHs, their fate in the combustion process and effects on environmental health are widely unknown. In this study, we present electron-transfer ionization in matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (ET-MALDI FTICR MS) for the characterization of vanadyl and nickel porphyrins in shipping feed fuels and primary particulate matter emissions. For the first time, these petroporphyrins could successfully be described in the heavy fuel oil (HFO) feeds but also in the particles emitted by the combustion of the respective fuel on a molecular level. Three main alkylated series of porphyrins were observed; these series can be qualified by their double bond equivalent, i.e., 17, 18, and 20, and correspond to various core structures. Our results highlight the molecular fate of the petroporphyrins through combustion and show that a significant amount of petroporphyrins is released unburned or partially dealkylated to the atmosphere. Furthermore, our results suggest that a higher amount of petroporphyrins might be released in harbors than in open sea, due to a less efficient combustion at lower engine load. This last observation motivates a future specific study on porphyrins’ health and environmental effects.

Full energy recovery from exhaust gases in a turbocharged diesel engine

Energy recovery has become an important solution that drives the transition to more sustainable propulsion, since the amount of thermal energy available from exhaust gases is huge. This energy can be transformed into electrical energy (without significantly affecting the powertrain) and directly used, for instance, in hybrid propulsion or driving auxiliaries.A turbocharged diesel engine equipped with a variable geometry turbine (VGT) was tested to assess the maximum energy recoverable from exhaust gases through two different recovery stages. The first was achieved using the pressure difference between the value at the exhaust valves and the atmospheric datum (turbo-compounding). The second recovery stage was achieved thanks to the temperature of the exhaust gases after the first recovery, and performed using an organic Rankine cycle (ORC)-based power unit.Therefore, these two combined stages of energy recovery were experimentally investigated in the medium–low load region of the ESC-13 homologation test, which is representative for real driving of heavy-duty engines. The first stage was performed on the turbocharging system by recovering the energy lost inside the VGT, through an additional turbine that operates in parallel with the main turbine that drives the compressor. It facilitates the recovery of a mechanical power of up to 3 kW, which was approximately equal to 5 % of the engine brake power at a specific medium–low load. The second stage was performed with an ORC-based unit bottomed to the first recovery section, exploiting the fact that after the first recovery, exhaust gases still have a high temperature, which can be used to feed the additional ORC based recovery unit. This second stage adds up to 3.5 kW of recovered mechanical energy, which represents 5 % of the engine brake power at the same medium–low engine load operating points. Therefore, a total of 10 % of the engine power was recovered in the two stages, which are characterized by proven technologies. Considering the engine working point at maximum power, the value was also higher, the combined recovery achieved a mechanical power of approximately 14 % of the engine brake power.In this study, the detrimental effects related to the engine backpressure produced by the two recovery units and the additional weight of the vehicle were assessed, demonstrating a net overall specific fuel consumption reduction of approximately 5–7% in the medium–low operating region of the engine considered, and higher than 8% at the maximum engine power. The increase in complexity related to the two recovery stages invites to consider this technology for heavy-duty engines for long-hauling vehicles, in which the detrimental effects does not significantly affects fuel consumption.

Investigating cylinder deactivation as a low fuel-penalty thermal management strategy for heavy-duty diesel engines

The upcoming ultra-low-NOx (oxides of nitrogen) emissions standard and in-use NOx emissions requirement requires engine manufacturers to further reduce tailpipe NOx emissions by over 90% from the current United States Environmental Protection Agency 2010 heavy-duty emissions standard. To meet ultra-low NOx standards, significant improvements to the NOx reduction capability of the Selective Catalytic Reduction (SCR) system is required. Low-temperature exhaust conditions and the associated fuel penalty in increasing the exhaust temperatures for improving catalyst activity is an engineering challenge to balance lowering NOx emissions while lowering fuel consumption. Cylinder Deactivation (CDA) in diesel engines has shown the ability to increase exhaust temperatures while maintaining a zero-fuel penalty. This study details the results of the performance of a CDA hardware installed in a modern heavy-duty diesel engine. The study was aimed at developing steady-state engine calibrations to maximize exhaust temperatures while realizing a zero-fuel penalty or improved BTE operation during low-load engine operating conditions for an on-road heavy-duty diesel engine. In addition, the study demonstrated the effect of CDA on lowering aftertreatment cooldown during motoring operation. The results of the study showed close to a 100°C increase in turbine out temperatures (TOT) at idle, 1,000 rpm and 1,200 rpm engine speeds with engine load at 10 and 20% of rated torque. The results also showed that deactivating three of the six cylinders during motoring operation of the low-load cycle delayed after treatment cool down and maintained exhaust temperatures above the SCR activity threshold for a longer duration.