Light-duty Engine Research Articles

Numerical Investigations on Reducing Unburned Hydrocarbon and Carbon Monoxide Emissions in Reactivity-Controlled Compression Ignition Using Partial Reactivity Stratification with Alternative Fuels and Additive

<div>A numerical investigation has been performed in the current work on reactivity-controlled compression ignition (RCCI), a low-temperature combustion (LTC) strategy that is beneficial for achieving lower oxides of nitrogen (NO<sub>x</sub>) and soot emission. A light-duty diesel engine was modified to run in RCCI mode. Experimental data were acquired using diesel as HRF (high-reactivity fuel) and gasoline as LRF (low reactivity fuel) to check the accuracy and fidelity of predicted results. Blends of ethanol and gasoline with DTBP (di-tert-butyl peroxide) addition in a small fraction on an energy basis were used in numerical simulations to promote ignitability and reactivity enhancement of PFI charge. Achieving stable, smooth, and gradual combustion in RCCI is challenging at low loads, especially in light-duty engines, due to misfiring and poor combustion stability. DTBP is known for enhancing cetane number and accelerating combustion, and it is mixed in a PFI blend to avoid combustion deterioration. The factors governing reactivity stratification to achieve optimal combustion phasing were investigated in the present study. DTBP decomposition and its low-temperature oxidation chemistry were found to be responsible for affecting combustion phasing, heat release patterns, and emission trends. DTBP additive and different in-cylinder strategies were applied and studied to reduce unburned emissions. Adopting a multiple injection approach utilizing dual-pulse assisted in reducing HC and CO levels. It enhances combustion quality by providing adequate control over combustion phasing. Altering operating parameters like intake temperatures reduced HC, CO, and soot emissions by 97.6%, 57.6%, and 52.8%, respectively, compared to baseline gasoline/diesel RCCI data. Optimizing the injection timings of the first and second pulse helps achieve optimal combustion phasing and a 72.95% reduction in NO<sub>x</sub> emissions. The higher injection pressure of DI helped lower the CO and soot emissions by 53.33% and 51.84%, respectively.</div>

Investigation on combustion and emission characteristics of diesel polyoxymethylene dimethyl ethers blend fuels with exhaust gas recirculation and double injection strategy

As a kind of renewable and high oxygen content fuel, polyoxymethylene dimethyl ether (PODE) can be added in diesel to realize energy saving and emissions reduction. To evaluate the combustion and emission characteristics of a diesel engine fueled with diesel and diesel/PODE mixtures, exhaust gas recirculation (EGR) and main-pilot injection strategies with various injection timings were applied. PODE was blended with diesel by volume to form mixtures which were marked as D100 (pure diesel), D90P10 (90% diesel + 10% PODE), and D80P20 (80% diesel + 20% PODE). The results showed that the ignition delay (ID) and combustion duration (CD) of D80P20 were the shortest because of the highest cetane number (CN) and high oxygen content of PODE, indicating more concentrated heat release. At low and medium loads, D80P20 achieved the highest peak heat release ratio (PHRR) and peak combustion temperature (PCT) among the three fuels, and it was 14.3% and 3.6% higher than those of D100. PODE blending with diesel can significantly reduce particulate matter (PM) and D80P20 has the lowest PM emissions at all loads. Compared with D100, both PM and nitrogen oxide (NOx) emissions of PODE blends decreased simultaneously with 20% EGR at all loads. With the increase of pilot-main interval, the ID and CD of all test fuels increased, while the NOx and PM emissions decreased. The conclusions of the present research provide a state of the application in light-duty engines fueled with diesel/PODE blends in future work.

Comparative study on combustion and emission characteristics of gas-to-liquid with diesel on a burner and a naturally aspirated compression ignition engine

ABSTRACT Due to the consumption of fossil fuels and the generation of harmful emissions by diesel engines, researchers are seeking alternative fuels for diesel, for example, gas-to-liquid (GTL). However, most studies on combustion and emission of GTL focused on the fuel burned on turbocharged heavy-duty diesel engines. The purpose of this study is to reveal the combustion, fuel economy, and emission characteristics of GTL by a burner and a naturally aspirated (NA), fuel direct injection compression ignition light-duty engine. Comparative experiments of the GTL to fossil diesel were carried out, respectively. The burner has good consistency with the diesel engine in revealing emission trends. The results of the burner test showed that GTL produced less flame smoke and its flame height was 5.3% lower than diesel. The results of the engine bench test revealed that the combustion and emissions of the GTL with diesel were significantly different. Compared to diesel, the ignition of GTL began earlier from 1.5°CA to2.5°CA though the combustion was slower in contrast to diesel. The diffusion combustion maximum pressure was considerably 4.8% higher and occurred earlier with 2.2°CA-3°CA, and the premixed combustion peak pressure of GTL was slightly beyond the diesel. The peak of premixed combustion heat release rate (HRR) for GTL was less than that of diesel by 18.9%. While the peak HRR of diffusion combustion was greater by 38.4%. The maximum PRR value of GTL was lower than that of diesel leading to soft combustion. In all test conditions, the brake specific fuel consumption of GTL averagely reduced by 4.7% against diesel, and the brake thermal efficiency was on average 4.3% higher. GTL engine can reduce regular emissions of carbon monoxide, hydrocarbons, nitrogen oxide (NOx), smoke, and particle number (PN) simultaneously. It is worth noting that GTL improved the trade-off issue of NOx and smoke, simultaneously reducing 18.8% NOx and 24.1% smoke on average. The experimental results reveal the GTL is an appropriate alternative fuel for light-duty diesel engine without modification of mechanical fuel system.

Simulation of a rapid compression machine for evaluation of ignition chemistry and soot formation using gasoline/ethanol blends

Due to the projected decline of demand for gasoline in light duty engines and the advent of ethanol as a green fuel, the use of gasoline/ethanol blend fuels in heavy duty applications are being investigated as they are projected to have lower cost and lower lifecycle green house gas (GHG) emissions. In heavy duty engines, the primary mode of combustion is mixing controlled combustion where wide range of mixture conditions (equivalence ratio) exist. Soot emissions of these fuels in richer conditions are not well understood. The goal of this research is to evaluate some commercially available soot modeling codes for the particulate matter emissions from gasoline/ethanol fuel blends, especially at fuel rich conditions. A Rapid Compression Machine (RCM) is modeled in a three-dimensional numerical simulation using CONVERGE computational software using a reduced chemical kinetic mechanism with SAGE chemistry solver and a RANS k-ϵ turbulence model with a sector model including the creviced piston. The creviced piston is used in the experimental setup to reduce boundary layer effects and to maintain a homogeneous core in the reaction cylinder. Computational fluid dynamics simulations are conducted for different gasoline-ethanol fuel blends from E10 (10% ethanol v/v) to E100. The fuel blend is modeled as a surrogate mixture of toluene, iso-octane, n-heptane for gasoline content, and ethanol. The computational results were validated against experimental results using pressure measurements and laser extinction diagnostics. Different soot models are investigated to evaluate their capability of predicting the sooting tendencies of fuel blends, especially in richer conditions experienced during mixing-controlled combustion. The experimental combustion characteristics such as the ignition delay of different blends of fuel are reasonably well predicted. The Particulate Size Mimic (PSM) model accurately predicts the soot generation characteristics of the different fuels, but the Hiroyasu-NSC model falls short in this regard. For accurate prediction of soot with the PSM model, the thermodynamic conditions during combustion must be accurately modeled. While the current computational modeling tools can produce accurate results for the prediction of particulate matter emissions, there is much work to be done in improving our understanding of the underlying fundamental processes.

Hydrocarbon and particulate matter evolution in the exhaust manifold of a spark-ignited engine under cold-start operation

Cold-start, as defined by the time between first engine crank and three-way catalyst light-off, is responsible for a large percentage of NOx, unburned hydrocarbon, and particulate matter (PM) emissions in light-duty engines. Minimizing emissions during cold-start is a trade-off between achieving faster three-way catalyst light-off, and engine out emissions during that period. In this study, various exhaust gas and PM species were measured at three locations in the exhaust manifold using advanced hydrocarbon and PM speciation methods in addition to standard exhaust-gas-analyzers to characterize how or if these species evolve downstream of the exhaust port during cold-start operation. A gasoline direct injected spark ignited (DISI) single cylinder engine was run at 2-bar net indicated mean effective pressure (NIMEP) at spark timings ranging from normal-SI operation relevant early spark timing of -10 degrees after top dead center firing (dATDCf) to more cold-start-relevant retarded spark timing of 25dATDCf. At the retarded spark timings, the exhaust manifold gas temperature increased downstream of the exhaust port indicating the presence of oxidation reactions that counteract heat transfer losses; a trend also supported by oxidation of total hydrocarbons (THC), CO, and H2 observed downstream of the exhaust port. Additionally, increase in NOx emissions downstream of the exhaust port indicated presence of high temperature required to drive NOx chemistry. Aromatics were the largest exhaust hydrocarbon species group detected at all spark timings, while the paraffins were under-represented from their fuel composition fraction. Organic carbon accounted for more than 95% of the PM mass at exhaust port for all spark timings. At retarded spark timings, the PM mass reduced downstream of the exhaust port primarily driven by organic carbon oxidation. Particle number and size measurements at retarded spark timings indicated a reduction in particle count downstream of the exhaust port with an accompanying increase in particle size possibly due to agglomeration.

Supercritical water injection in a single cylinder research engine: a PIV study

This work presents the experimental results of a fluid dynamic investigation to characterize the injection of supercritical water in the combustion chamber of an internal combustion engine. Particle Image Velocimetry (PIV) analysis is carried out in an optically accessible 2-stroke Diesel engine. A prechamber, equipped with two optical accesses is connected to the main cylinder through a tangential duct so that the piston stroke induces a swirled motion field with angular velocities typical of light duty engines for automotive application. The engine is equipped with an injection system for the production and injection of supercritical water, with the possibility to independently regulate the injection pressure, temperature, duration, and timing. Tests have then been carried out under different operating conditions to evaluate the impact of the fluid dynamics in the combustion chamber on the water spray. First, the airflow velocity field has been characterized at different engine crank train angles. The water spray has been macroscopically characterized for an injection temperature of 300°C and pressure of 30Mpa. Then, the supercritical water/air interaction has been explored, at different injection pressure, temperature, and Start of Injection (SOI) to provide global information in terms of spray morphology, tip penetration, and velocity vector distribution of the water droplets within the combustion chamber for different injection strategies.

Numerical investigation on selecting appropriate piston bowl geometry and compression ratio for gasoline-fuelled homogeneous charge compression ignited light-duty diesel engine

The gasoline-fuelled homogeneous charge compression ignition (HCCI) combustion is a promising approach to mitigate the significant limitations of the traditional compression-ignition combustion for light-duty engine applications. In the present work, the required autoignition quality of gasoline was achieved by blending 2-ethylhexyl nitrate (EHN) with gasoline to ensure combustion stability at the achieved engine loads. A reduced chemical reaction mechanism consisting of 185 species and 219 reactions was developed in the present study for EHN-gasoline-fuelled-HCCI combustion. The mechanism was validated by conducting multi-dimensional computational fluid dynamics (CFD) simulations of HCCI combustion in a modified light-duty diesel engine. A detailed numerical study was done using the validated CFD model to select the suitable piston bowl geometry and geometric compression ratio for better engine performance and lower regulated emissions. Eleven different piston bowl geometries were explored, which also included piston bowl designs popular in traditional compression-ignition (toroid) and spark-ignition (flat) engines. The results indicated that the flat-shaped piston bowl exhibited a 17% improvement in the gross indicated thermal efficiency and a 16% and 40% reduction in UHC and CO emissions while maintaining very low NOx and smoke levels compared to the baseline hemisphere-shaped piston bowl. The engine performance remained the same for the flat-shaped piston bowl geometry even for a 17% increased compression ratio with the added benefit that the reduced EHN concentration (by 48 vol.%) was needed to achieve the same combustion phasing. Thus, the present numerical work proposes a promising approach to improve the overall performance of gasoline-fuelled HCCI combustion by piston bowl design and compression ratio optimization.

Experimental validation and numerical assessment of a temperature-controlled thermoelectric generator concept aimed at maximizing performance under highly variable thermal load driving cycles

Although the internal combustion engine (ICE) dominance in mobility is being challenged, ICE R&D enables a non-disruptive transition towards sustainable transportation through hybridization and carbon neutral fuels. The efficiency improvement of ICE-based mobility through Waste Heat Recovery (WHR) is thus a priority, especially in the area of hybrid, plugin hybrid and long-haul transportation, where the recovery potential is high, and ICEs will still be used for a long time. Thermoelectric (TE) Generators (TEGs) have been assessed as a possible low maintenance WHR solution for long. However, viable market solutions are still not a reality. While material costs are steadily being overcome with novel affordable TE materials, there is still the issue of low average conversion efficiency under realistic driving conditions. This is caused by the fact that the efficiency of TEGs is further deprecated by the big challenge of thermally optimizing the TEGs under highly variable conditions of exhaust flow rate and exhaust temperature during real-world driving. This thermal optimization mainly means that the hot side temperature should be as close as possible to the maximum allowable temperature of the modules, but not higher.The authors have been exploring exhaust heat exchanger (HX) concepts that allow achieving this thermal optimization under highly variable thermal loads by using phase change. The strategy used incorporates the spreading of excess heat along the HX by variable conductance heat pipes (VCHPs) embedded in it, thus enabling to maximize the energy conversion without thermal dilution under low thermal loads or overheating risk under high thermal loads. This was done by pre-regulating the pressure of the non-condensable gas (NCG) present inside the VCHPs so that these devices would start performing the spreading of excess heat from over-heated to under-heated regions of the HX at a precise phase change temperature, optimized to the optimal thermal level of the thermoelectric generators.The merit of the aforementioned strategy was confirmed through modelling and illustrated in previous work. The scientific novelty of present study relatively to previous work by the authors or other researchers is that it finally provides a full experimental validation of this concept with two different prototypes attached to a light duty engine. The experimental proof-of-concept results were successfully compared against predictions. Finally, theoretical performance analysis of the impact of the application on a light duty vehicle in terms of fuel economy and GHG emissions during the WLTC class 3 b was assessed with the help of driving cycle and engine simulations performed with AVL Suite software.The unique heat spreading and temperature control features of the concept were confirmed experimentally. In addition, predictions made by the model were far beyond the current state of the art for light duty automotive TEG generators. Namely, maximum output powers exceeding 2 kW and 1.2 kW were predicted during the WLTC cycle when using commercial bismuth telluride and the silicide-Tetrahedrite modules explored by the authors, respectively. Average fuel/CO2 savings of 4% were predicted for the WLTC cycle, with these savings raising to 12% during the highway portion of the cycle. This unparalleled performance is explained by the possibility of achieving both an optimized hot face temperature and a high heat exchanger effectiveness even under highly variable thermal loads.

Experimental study on combustion and emission characteristics of fatty acid methyl esters and hydrogenated catalytic biodiesel/diesel blends under world harmonized steady state cycle

Clean and renewable biodiesel demonstrates excellent potential for replacing fossil-based fuels and reducing CO2 emissions. However, comparative studies on the applicability of fatty acid methyl ester and hydrogenated catalytic biodiesel still need to be included in practical application conditions of light-duty engines. Therefore, a comparative study on the combustion and emission performance of fatty acid methyl ester/diesel and hydrogenated catalytic biodiesel/diesel blends was conducted based on the World Harmonized Steady State Cycle in this research. The results show that except for the idling condition Region E, compared with D100, D80H20 has lower CA50 and ignition delay period, higher maximum cylinder pressure; while D80B20 has lower CA10, lower maximum cylinder pressure. The brake specific fuel consumption of all fuels is the lowest in mode 10, and the brake specific fuel consumption of D80B20 is 1.49% higher than that of D100. While D80H20 is 0.86% lower than that of D100. In Mode 8, NOx and CO2 emissions were the lowest for all fuels, and compared to D100, NOx and CO2 emissions were 4.7%, 3.8%, 4.83%, and 2.81% lower for D80H20 and D80B20, respectively. The brake specific fuel consumption, NOx, and THC emissions of D80H20 were reduced by 4.15%, 5.42%, and 6.52%, respectively, compared to D100 in all models, while the NOx, THC and CO2 emissions of D80B20 were reduced by 6.9%, 23.1%, and 4.9%, respectively. Relative to D80B20, D80H20 has a better economy, but the emission problem cannot be ignored. Model 11 performs best from a combined economy and emission characteristics perspective.

IN TEA PICKING MACHINES, THE PROSPECT OF USING A NEW CUTTING MACHINE

Tea represents the economy's main field in agriculture and plays a crucial role in growing and cultivation, proper performance and operation of machine technologies. In the areas where small peasant farms and cooperatives have been formed, and operation of heavy-duty machines is inappropriate, the labor costs should be decreased. Therefore, analysis of machines, which allow high tea leaf plucking quality without destroying the inefficient and unnecessary shoots should be refined and become technically perfect. In this scientific research presents interaction of bearing-less cutting machines with a rubber finger with the stem as a working cutting device, this gives opportunities of a lossless and high tea leaf harvesting quality in the small contoured sloped areas by using machines, based on light-duty engines

Gasoline compression ignition (GCI) combustion in a light-duty engine using double injection strategy

Controlling the oxides of nitrogen (NOx) and particulate matter (PM) emissions is one of the vital goals of compression ignition (CI) engines. Implementing stringent emissions regulations has motivated researchers to adopt various strategies for controlling emissions. Gasoline compression ignition (GCI) has emerged as a prime technology to control emissions and increase engine efficiency, while using low-octane gasoline as fuel in CI engines. Preheated air, hot exhaust gas recirculation (EGR), and negative valve overlap, are required to manage the combustion instabilities in the GCI engines. However these techniques have not been used in this study in order to reduce system complexity. Low octane test fuel was prepared (G80) by blending 80 % v/v gasoline and 20 % v/v diesel. This study involved experiments to evaluate the effects of main injection timing, split injection quantities (10–30 %), and engine load (brake mean effective pressure (BMEP): 3–5 bar) on a two-cylinder GCI engine’s performance, combustion, cyclic variability, emissions, and particulates. Conventional diesel combustion (CDC) mode experiments were performed using diesel. The results indicated a 5 % higher brake thermal efficiency (BTE) and comparable exhaust gas temperature (EGT) for the GCI mode compared to the baseline CDC mode. GCI combustion with low split ratio showed higher in-cylinder pressure than CDC mode. Baseline CDC mode showed < 3 % coefficient of variation of indicated mean effective pressure and peak pressure, whereas these parameters varied from 1 % to 9 % in the GCI mode. GCI mode engine exhibited ∼ 60 and 50 % lower NOx and PM emissions than baseline diesel mode engine. The double injection strategy improved GCI engine's performance and emission characteristics.

Alternative fuel production from waste plastics and their usability in light duty diesel engine: Combustion, energy, and environmental analysis

Green biofuels have long been touted as a potential solution to society's reliance on fossil fuels and pollution emission problems. Commercially available renewable fuels like waste plastics oil alternative (P) made from waste plastic oil could take the place of fossil fuels, especially in diesel engines. Binary alternatives and diesel blends that partially replace diesel can be used in diesel engines without requiring major modifications. A four-stroke diesel engine used in the experiment was fed waste plastics oil alternative (up to 40% volumetric content), and diesel (D) mixes. Each binary blend is stabilised by a volumetric concentration and is composed of varying oil proportions. The investigations, therefore, relate partial diesel replacements to assessments of engine performance and mix combustion under various load conditions (25–100%), speeds (1200–1800 rpm), and compression ratios (15–19). Results showed that alternative-diesel mixtures up to 40% can still operate reliably. Thermal efficiency was somewhat lower than for diesel which was 100%. The experiment revealed higher fuel use, smoke, and NO emissions. The conclusion of the present research states that waste product oils can compete with fossil fuels in terms of engine performance, combustion, and emission characteristics when utilized in light-duty engines.

Multiple-objective optimization of Jet Controlled Compression Ignition (JCCI) mode with dual-direct injection in a high-speed light-duty engine

Jet Controlled Compression Ignition (JCCI) mode with dual-direct injection of diesel and gasoline has been demonstrated by the engine experiments to provide an effective control on the combustion process without sacrificing the advantages on efficiency and emissions performance. The multiple-objective optimization of JCCI mode based on the 186FA engine at 75 % engine load with an engine speed of 3000 r/min was carried out in this research by the combination of Three-Dimensional (3D) Computational Fluid Dynamics (CFD) and Genetic Algorithm (GA). The simulation results indicate that the ignition timing and the combustion phasing can be effectively controlled by the jet-injection diesel, and the pre-injection gasoline mainly affects the combustion stage from CA50 to CA90. With the increase of the pre-injection energy ratio, higher initial in-cylinder temperature is required to ensure the engine performance. The optimal results present that JCCI mode can achieve high efficiency and low emissions simultaneously when the combustion phasing is at 5 ∼ 9 °CA ATDC. The low EISFC, NOx and soot emissions can be realized when SOIpre and SOIjet are retarded to −63 and −28 °CA ATDC, respectively, which prepares the appropriate premixed charge considering the equivalence ratio and reactivity. The comparisons of the typical cases reveal that the high-temperature combustion process gradually translates to the two-stage characteristics when the SOIjet retards from −27.77 to −18.88 °CA ATDC, the combustion duration is prolonged slightly and the in-cylinder temperature is decreased, resulting in the reduction of pmax by 0.42 MPa, NOx emissions by 0.07 g/kWh, associating with the lower heat transfer loss and exhaust loss. In addition, the NOx emissions in JCCI mode are mainly generated within the high-temperature combustion region of the jet-injection diesel spray target location.

Optical diagnostics of methanol active-thermal atmosphere combustion in compression ignition engine

Methanol has become one of the research hotspots of internal combustion engine in recent years. One method of methanol compression ignition is that create in-cylinder active-thermal atmosphere to ignite direct injection (DI) of methanol. However, the combustion essences and related mechanisms in methanol active-thermal atmosphere combustion (ATAC) have not been comprehended. In current study, the characteristics of methanol ATAC were investigated on a light-duty engine using different optical diagnostics. Polyoxymethylene dimethyl ethers (PODE2) and n-heptane were chosen as port injection (PI) fuel respectively, and methanol was used as DI fuel. The experiment results indicate that methanol ATAC with PI of PODE2 is divided into two combustion processes. One process is the premixed combustion of PODE2 and the partially premixed combustion (PPC) of methanol, which appears that the premixed blue flames of PODE2 and the partially premixed yellow flames of methanol. The other is PODE2 premixed combustion and methanol diffusion combustion, which presents that the premixed blue flames of PODE2 and the yellow spray diffusion flames of methanol. Both the heat release rate and the flame structure of methanol ATAC can be adjusted by changing DI timing. The increase of PI energy proportion advances the timing of premixed blue flames of PODE2. The DI of methanol is driven by spray diffusion flames unless the methanol injection timing is earlier than high temperature heat release of PODE2. The capability of PODE2 to make methanol auto-ignited is higher than that of n-heptane. The methanol energy proportion can achieve 70% in PODE2 case, while achieve merely 30% in n-heptane case. Kinetic analysis reveals that the ignition delay times of PODE2 are lower than that of n-heptane even at lower equivalence ratio. The KL factor of methanol diffusion flame ranges from 0.02 to 0.04, which is remarkable lower than diesel spray flames. The methanol ATAC achieves higher substitution rate of methanol and the flexible combustion process can be obtained using PODE2 as PI fuel.

Development and Application of an Engine Test Method to Rate the Internal Injector Deposit Formation of Diesel Fuels and Additives

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Design efforts to improve the hydraulic efficiency of high-pressure diesel fuel systems and thus further improve overall engine efficiency have resulted in the utilisation of low-spill control valves and reduced injector component clearances to reduce general leakage losses. Overall, these advances have contributed significantly to the high efficiency diesel engines of today. However, the combination of very high fuel pressures, cavitation and low fuel leakage volumes increases the heating of the remaining fuel, increasing temperature and, in turn, the propensity for deposits to form inside the injector. This deposit phenomenon is commonly known as Internal Diesel Injector Deposits (IDID) and can cause rough engine running and failed engine starts requiring injector cleaning or replacement. Methods studying this phenomenon are under development in the industry. Meanwhile this paper describes the development and application of an in-house engine test method to rate the IDID control performance of deposit control additives (DCA). A 2.0L, 4-cylinder light-duty engine is run with a fuel containing a contaminant to provoke the occurrence of deposit formation within a reasonable test duration. In ‘keep clean’ test mode the performance of the DCA is assessed based on its ability to prevent IDID symptoms that routinely manifest in unadditivated test runs, primarily between-cylinder deviation in exhaust port gas temperature as the operation of individual injectors is impaired by deposits. In ‘clean up’ test mode the DCA is assessed on its ability to reverse IDID symptoms that manifested in a preceding unadditivated test run. In initial tests the methodology has proved capable of differentiating between a novel DCA chemistry that exhibits good IDID control behaviour in keep clean and clean up modes and a conventional DCA chemistry that did not. Temperature deviations were reduced applying the novel DCA at premium dose in keep clean mode. In clean up mode, temperature deviations were reduced from the end of dirty up to the end of clean up, with premium plus dose rate of the novel DCA. In both cases the improvements were statistically significant at the 95% confidence level.&lt;/div&gt;&lt;/div&gt;

Thorough evaluation of the available light-duty engine technologies to reduce greenhouse gases emissions in Brazil

Currently, there are serious concerns regards the increase of the Earth's temperature. In addition, studies about global warming have identified many different sources that contribute to the emissions of greenhouse gases in the atmosphere. Previous studies indicate that the transport sector is among the main drivers of global warming. Moreover, the solutions provided so far focus only on the environmental factor in order to reduce emissions. However, this study has the objective to provide a thorough analysis that considers economic, environmental, social, and infrastructure factors. Furthermore, the analysis is focused on the Brazilian scenario, therefore, the factors comprise the unique characteristics of the country. The comparison made includes three engine technologies: electric, flex-fuel, and hybrid. The results show that the flex-fuel engine is the best alternative for a light alternative for light commercial vehicles to reduce greenhouse gas emissions. Moreover, the results indicate that flex-fuel engines have the best economic and environmental performance. Therefore, the government should provide incentives for this engine technology. On the other hand, the results show that electric vehicles are not a suitable solution given the specificities of the country.

Model Based Design, Prototyping and Testing of a Small Size High Speed Electrically Driven Centrifugal Pump

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Within automotive sector, there are several high-performance applications, like, for instance, those referred to racing and motorsport, where cooling needs are usually fulfilled by simple circuits with conventional low-efficiency pumps. The cooling needs in these applications are represented by low flow rates delivered (in the range of 10 - 50 L/min). The operating conditions of these small pumps are usually characterized by very high revolution speeds, which intrinsically cause low efficiency and critical intake phenomena (cavitation) if the design is not specifically optimized to address these concerns.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;Hence, in this paper a small-size pump operating in the racing sector has been designed using a model-based approach, built and tested having reached both high efficiency (aimed to 50%) and absence of intake operational problems (cavitation). Starting from the specific cooling request (design flow rate equal to 14.0 L/min and pressure rise equal to 2.5 bar), the very limited space available on board oriented the design to an operational revolution speed of 12000 RPM. The interest of this study was to introduce a so high revolution speed in more conventional automotive cooling pumps electrically assisted, keeping high efficiency. In fact, the strong reduction of the size of the pump allows an easy and correct positioning on board.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;The model-based design was done by a two-steps procedure. The first made use of a 0D model which, catching main physical phenomena of the flow even in simplified form, leads to an optimum geometrical design for the impeller and the volute. A final refinement has been done with a CFD code predicting the off-design performance and limiting cavitation zones. Cavitation, which is one of the most critical issues of high-speed pumps, was completely investigated through a CFD numerical analysis.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;The pump has been prototyped and tested on a dynamic test bench for pumps, which reproduces homologation cycles and real driving. A good agreement has been reached between theoretical and experimental results, being the mean relative error on pressure rise for all operating point close to 4 %. This model-based procedure opens the way to support the development of electric water pumps for more conventional applications (automotive, light duty engines) in which a redesign will be focused to manage the thermal state of the engine and reduce the energy absorbed during the homologation cycle.&lt;/div&gt;&lt;/div&gt;

A Constant Equivalence Ratio Multi-Zone Approach for a Detailed and Fast Prediction of Performances and Emission in CI Engines

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The paper illustrates and validates a novel predictive combustion model for the estimation of performances and pollutant production in CI engines. The numerical methodology was developed by the authors for near real-time applications, while aiming at an accurate description of the air mixing process by means of a multi-zone approach of the air-fuel mass. Charge stratification is estimated via a 2D representation of the fuel spray distribution that is numerically derived by an axial one-dimensional control-volume description of the direct injection. The radial coordinate of each control volume is reconstructed a posteriori by means of a local distribution function. Fuel mass clustered in each zone is further split in ‘liquid’, ‘unburnt’ and ‘burnt’ sub-zones, given the local properties of the fuel spray control volumes with respect to space-time location of modelled ignition delay, liquid length, and flame lift-off. Multiple injections are described on the same numerical grid to account for jet-to-jet axial interactions, whose effects reflect on improved ignition characteristics. The multi-zones are open systems which are discretized on the equivalence ratio; mass is allowed to travel from one to another, causing a 2D charge stratification. For each zone, local thermodynamic properties and NOx production are determined to estimate cylinder-average performances and emissions. The apparent heat release rate, in-cylinder pressure, BSFC and NOx emissions are validated against experimental data of full map of a light-duty engine. The computational effort of the model is relatively low, which makes the approach suitable for static optimization, to be used in 1-D simulation codes for transient’s optimization and can be run in parallel with a real time 1-D gas model for the simulation of long driving cycles.&lt;/div&gt;&lt;/div&gt;

Study on the performance of diesel-methanol diffusion combustion with dual-direct injection system on a high-speed light-duty engine

To investigate the high methanol substitution ratio (MSR) combustion performance of diesel-methanol diffusion combustion (DMDC) mode, the engine experiments were conducted based on a high-speed light-duty engine with a dual-direct injection system in this study. Effects of MSR on the combustion, emission and energy distribution characteristics, as well as the difference between the DMDC mode and the conventional diesel combustion (CDC) mode, were investigated in detail under four engine loads at a constant engine speed of 3000 rpm and a similar CA50 of 7.5 °CA ATDC. The experimental results show that the MSR can reach 87% at BMEP = 0.55 MPa. Under all operating conditions, the NOx and soot emissions of the DMDC mode are significantly reduced simultaneously compared to those of the CDC mode, and the reduction is enlarged as both MSR and loads increase. At BMEP = 0.14 MPa, the indicated thermal efficiency (ITE), THC and CO emissions of the DMDC mode are inferior to that of the CDC mode. However, the combustion and emission performances are gradually improved when the BMEP exceeds 0.27 MPa. Especially at BMEP = 0.55 MPa, the THC and CO emissions of the DMDC mode are lower and the ITE increases by 10% compared to the CDC mode, and the ITE is more sensitive to the MSR. According to the energy distribution analysis, it can be found that the heat transfer loss and exhaust loss of the DMDC mode have been dramatically reduced, resulting in the increased ITE compared to the CDC mode.

An experimental study of the effect of condensing water vapour on the cold corrosion wear of marine engine cylinder liners

AbstractThis work presents an experimental study of the cold corrosion wear phenomenon that is experienced on the cylinder liners in large two‐stroke marine diesel engines that burn heavy fuel oil containing sulfur. The wear is caused by condensing sulfuric acid‐ and water vapours (H2SO4 and H2O, respectively) that are formed during combustion. In this work, cold corrosion is studied experimentally with a modified and motored light duty engine that operates at 98 revolutions per minute, in order to match the rotational speed of a large marine engine. The engine works as a tribotester where multiple charge gas compositions with up to 10% H2O and 80 ppm H2SO4 (mole/mole) in dry air are fed to its cylinders to produce realistic marine engine H2O and H2SO4 partial pressures. A lube oil blend that is composed by a conventional two‐stroke marine engine cylinder lube oil and a base oil is used in the experiments. By extracting oil samples from the engine oil swamp during an experiment (that are analysed for iron and sulfur content using an energy dispersive X‐ray fluorescence spectrometer) the cylinder liner wear rate and sulfuric acid condensation rate are determined for the applied charge gas composition and liner surface temperature (primarily 80°C). The method shows that the different charge gas compositions yield distinct liner wear rates and the highest wear rates are experienced at elevated H2O concentrations where the influence of H2SO4 is comparably low.