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Technical Paper

Assessing the Effect of Compression Ratio on the Performance, Combustion and Emission Characteristics of a Spark-Ignition Engine, and Optimum Spark Advance at Different Operating Conditions

2018-09-10
2018-01-1668
Nowadays, emission regulations and the requirement to reduce greenhouse gas emissions have escalated engine development efforts. In the present work, the effect of compression ratio on the performance, combustion and emission characteristics of a spark-ignition engine is evaluated at different operating conditions. A single-cylinder, water-cooled, spark-ignition engine (modified from a compression-ignition version) was used, with combustion chamber geometry consisted of flat cylinder head and a hemispherical bowl in the piston. Results showed that the brake thermal efficiency was increased from 9.8% to 12.9% when compression ratio was increased from 6.7:1 to 9.4:1 at low operating load of 5 N-m. Carbon monoxide emission was decreased when compression ratio was increased at all operating loads. However, as expected, nitric oxide emission was increased with the increase in compression ratio, with lower difference at low loads compared to medium and high loads.
Technical Paper

A Computational Study of Lean Limit Extension of Alcohol HCCI Engines

2018-09-10
2018-01-1679
The purpose of present numerical study was to extend the operating range of alcohol (methanol and ethanol) fueled Homogeneous Charge Compression Ignition (HCCI) engine under low load conditions. Ignition of pure methanol and ethanol under HCCI mode of operation requires high intake temperatures and misfires at low loads are common in HCCI engines. Three methods have been adapted to optimize the use of methanol and ethanol for HCCI operation without increasing the intake temperature. First, blending methanol and ethanol with ignition improver, namely di-methyl ether (DME) and di-ethyl ether (DEE), was used to increase the cetane number and ignitability of premixed charge. Second, based on the blended fuels, the spark assistance was used to reduce required intake temperature for auto-ignition. Third, DME and DEE were directly injected to methanol and ethanol operated HCCI engine, in the form of RCCI combustion.
Technical Paper

POMDME as an Alternative Pilot-Fuel for Dual-Fuel Engines: Optical Study in a RCEM and Application in Automotive Size Dual-Fuel Diesel Engine

2018-09-10
2018-01-1734
Dual-fuel natural gas engines are seen as an attractive solution for simultaneous reduction of pollutant and CO2 emissions while maintaining high engine thermal efficiency. However, engines of this type exhibit a tradeoff between misfire as well as large UHC emissions for small pilot injection amounts and higher emissions of soot and NOX for operation strategies with higher pilot fuel proportion. The aim of this study was to investigate POMDME as an alternative pilot fuel having the potential to mitigate the emissions tradeoff, enabling smokeless combustion due to high degree of oxygenation, and being less prone to misfire due to its higher cetane number. Furthermore, POMDME can be synthetized carbon neutrally. First, characteristics of POMDME ignition in methane/air mixture and the transition into premixed flame propagation were investigated optically in a rapid compression-expansion machine (RCEM) by employing Schlieren and OH* chemiluminescence imaging.
Technical Paper

Polycyclic Aromatic Hydrocarbons in Diesel Engine Exhaust Both With and Without Aftertreatment

2018-09-10
2018-01-1812
Since the conception of the internal combustion engine, smoky and ill-smelling exhaust was prevalent. Over the last century, significant improvements have been made in improving combustion and in treating the exhaust to reduce these effects. One group of compounds, polycyclic aromatic hydrocarbons (PAH), usually occur at very low concentrations in diesel engine exhaust. Some of these compounds are considered carcinogenic, and most are considered hazardous air pollutants (HAP). Many methods have been developed for sampling, handling, and analyzing PAH, but an improved method for dilute exhaust sampling was used for sampling the PAH in diesel engine exhaust. This sampling method was performed during transient engine operation both with and without aftertreatment to show the effect of aftertreatment.
Technical Paper

Severe Soot Oxidations in Gasoline Particulate Filter Applications

2018-09-10
2018-01-1699
With the start of EU6 in 2017 gasoline particulate filters (GPF) have been introduced to production vehicles. It is expected that by 2019 all gasoline direct injection engines sold in Europe will be equipped with a GPF. A similar trend is observed in China with a slight delay compared to Europe, but covering all gasoline engines including those with port fuel injection technology. With the introduction of GPFs, new requirements are introduced to the management of gasoline engines and their aftertreatment. One requirement is to protect the aftertreatment components from excessive temperatures and damage as result of uncontrolled soot oxidations. While the general fundamentals are similar to those in diesel applications, significant differences exist in the relevant details.
Technical Paper

Effect of Water Injection and Spatial Distribution on Combustion, Emission and Performance of GDI Engine – A CFD Analysis

2018-09-10
2018-01-1725
Water injection in diesel engines is a successful way to reduce NOx emissions and enhance brake power output. The advantages of water injection are because of its high enthalpy of vaporization and high specific heat capacity by which it absorbs heat from the in-cylinder mixture. The benefits of water injection depend on the rate of water vaporization and its spatial distribution in the combustion chamber. However, detailed effects of these parameters are very rarely studied in the past. Therefore, in the present study, an attempt has been made to assess the effect of water injector configuration on performance of a GDI engine by CFD analysis. Here, the analysis is done mainly to study and enhance the evaporation and spatial distribution characteristics of the water injection inside the combustion chamber. Water is directly injected into the cylinder of a naturally aspirated, four-stroke GDI engine.
Technical Paper

POD-based Analysis of In-cylinder Flow Data from Molecular Tagging Velocimetry in a Spark-Ignition Engine

2018-09-10
2018-01-1770
The fluid motion inside the engine cylinder is transient, three-dimensional and highly turbulent. It is also well known that cycle-to-cycle flow variations have a considerable influence on cycle-to-cycle combustion variations. Laser-based diagnostic techniques, for example, particle image velocimetry (PIV) or molecular tagging velocimetry, can be used to measure two or three components of the velocity field simultaneously at multiple locations over a plane. The use of proper orthogonal decomposition (POD) allows quantification of cycle-to-cycle flow variations, as demonstrated using PIV data [1]. In the present work, POD is used to explore the cycle-to-cycle flow variations utilizing molecular tagging velocimetry data. The instantaneous velocity fields were obtained over a swirl measurement plane when engine was operated at 1500 rpm and 2500 rpm.
Technical Paper

Impacts of demanding low temperature urban operation on the real driving emissions performance of three European diesel passenger cars

2018-09-10
2018-01-1819
In Europe, the development and implementation of new regulatory test procedures including the chassis dynamometer (CD) based World Harmonised Light Duty Test Procedure (WLTP) and the Real Driving Emissions (RDE) procedure, has been driven by the close scrutiny that real driving emissions and fuel consumption from passenger cars have come under in recent times. This is due to a perceived divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx emissions from diesel cars. The RDE test is certainly more versatile and relevant than CD test cycles, but certification RDE cycles will rarely include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx aftertreatment systems.
Technical Paper

Effect of single and double-deck pre-chamber designs to the combustion characteristics of premixed CH4/air

2018-09-10
2018-01-1688
An experiment was carried out to investigate the effect of the single and double-deck pre-chamber spark plug on the combustion characteristics of premixed CH4/air in a constant volume vessel using schlieren method. A special design was proposed for the visualization of the pre-chamber. Combustion with different initial temperatures (300K, 400K, 500K) were observed at lean to stoichiometric air fuel ratios. The combustion characteristics of premixed CH4/air was characterized by considering both the 0-10% and the 10-90% burn durations of the pressure rise because of combustion. Results revealed that both of pre-chamber designs have the shorter 10-90% burn duration when the initial temperature is 300K, while the 0-10% burn duration is longer. The double-deck pre-chamber exhibited the longer 10-90% burn duration comparing with the single-deck pre-chamber, and the gap is larger as the mixed gas is more lean.
Technical Paper

Waste Frying Oil Conversion to Biodiesel in Presence of advanced Alumina Heterogeneous Catalyst

2018-09-10
2018-01-1750
This paper reports experimental conversion of spent vegetable oil with bio-ethanol to long chain biodiesel fuel in presence of a new developed solid K3PO4 heterogeneous catalyst. Examined catalyst was synthesized following dipping impregnation of γ-Al2O3 solid support in an aqueous solution of potassium phosphate tri-basic K3PO4. K3PO4/γ-Al2O3 catalyst samples were distinguished based on their percentage loadings of K3PO4 〖(C〗_(K_3 PO_4 )) and averaged particle size (d_p ). Produced catalyst samples were characterized in terms of their textural and surface properties using nitrogen adsorption-desorption isotherms and carbon dioxide & ammonia temperature programmed desorption techniques respectively. While the liquid phase of the product was analyzed using a GC-Mass spectroscopy technique. Ethanolysis runs were carried out following surface response methodology, central composite design (CCD).
Technical Paper

Software Reliability Growth Modeling: Comparison Between Non-Linear- Regression Estimation and Maximum-Likelihood-Estimator Procedures

2018-09-10
2018-01-1772
Automotive software complexity has been growing rapidly with time. The demand for automation in automotive segment including autonomous automobiles and software based products has caught the attention of researchers. Hence, it is necessary to check the complexity of automotive software and their reliability growth. Testing in the field of software artefact is resource intensive exercise. If project managers are able to put forward testing activities well then the testing resource consumptions may be much more resource/cost efficient. Reliability is checked under the software testing phase of software engineering using CASRE. Software reliability growth models(SRGMs) are used to determine the reliability change. Reliability is analysed using different models which may be based on Non-Homogeneous Poisson Process (NHPP), Markov process or Bayesian models.
Technical Paper

A Comparative Study on Knock Occurrence for Different Fuel Octane Number

2018-09-10
2018-01-1674
Combustion with knock is an abnormal phenomenon which constrains the engine performance, thermal efficiency and longevity. The advance timing of the ignition system requires it to be updated with respect to fuel octane number variation. The production series engines are calibrated by the manufacturer to run with a special fuel octane number. In this research, the update value for ignition timing generated as a knock envelope using experimental data and engine simulation software. In the experiment, the engine was operated at different speeds, load, spark advance and consumed commercial gasoline with research octane numbers (RON) 95, 97 and 100. A 1-dimensional validated engine combustion model was run in the GT-Power software to simulate the engine conditions required to define the knock envelope at the same engine operation conditions as experiment.
Technical Paper

Super Low Viscosity ATF; AW-2

2018-09-10
2018-01-1756
Torque loss reduction at automatic transmissions is highly demanded for further improvement of fuel economy. One promised way is to decrease the viscosity of Automatic Transmission Fluids (ATFs) for minimizing the churning loss. Aisin AW and JXTG Nippon Oil & Energy Corporation have successfully developed a super low viscosity ATF named AW-2, which has approximately 60% lower kinematic viscosity at 40 degree C compared to DEXRON-VI ATF or MERCON-LV ATF. It is generally known that too much low viscosity may have a negative impact on the fatigue life at the components such as gears or bearings, and possibly cause wear or seizure. AW-2 was designed to overcome these problems by applying two key technologies. First one is a high performance base oil with low traction coefficient, which means low viscosity under a high pressure condition.
Technical Paper

Loss analysis of a direct-injection hydrogen combustion engine

2018-09-10
2018-01-1686
Title: Loss analysis of a direct-injection hydrogen combustion engine In the discussion on the avoidance of CO2 emissions and other pollutants in the transport sector, hydrogen, as a carbon-free fuel, is a useful alternative to conventional fuels. The use of hydrogen in modern internal combustion engines provides a quick and cost-effective way of sustainable decarbonisation of the transport sector. In comparison with conventional fuels, the efficiency of the internal combustion engine can increase by the use of hydrogen. The Chair of Energy Conversion Systems for Mobile Applications works in cooperation with some industrial partners on the use of hydrogen in internal combustion engines. To exploit the entire efficiency potential of a hydrogen internal combustion engine, it is expedient that the injection takes place directly into the combustion chamber of the engine.
Technical Paper

Numerical Analysis on the Potential of Reducing DPF Size Using Low Ash Lubricant Oil

2018-09-10
2018-01-1760
Diesel particulate filter (DPF) is necessary for diesel engines to meet the increasingly stringent emission regulations. Many studies have demonstrated that the lubricant derived ash has a significant effect on DPF pressure drop and engine efficiency, and this effect becomes more and more severe with the increasing of operating hours of the DPF because the ash accumulated in the DPF cannot be removed by regeneration. It is reported that most of the DPFs operated with more ash than soot in the filter for more than three quarters of the time in its lifetime. In order to mitigate this problem, the original equipment manufacturers (OEMs) tend to use a large size DPF. However, it will increase the costs of the DPF. With the development of the lubricant additives technology, some OEMs and lubricant oil manufacturers are concerning that if there is any possibility of reducing DPF size using low ash lubricant oil.
Technical Paper

Exhaust gas ammonia measurements with NH3 sensor

2018-09-10
2018-01-1814
Measuring ammonia (NH3) from the exhaust gas is mandatory for heavy-duty engine certification in Europe and recommended in U.S. UN-ECE Regulation 49 (Regulation for heavy-duty engine measurements) lists two allowed measurement methods of NH3measurements; Laser Diode Spectrometer (LDS) and Fourier Transform Infrared (FTIR) analyser. Both methods are meant for laboratory use and are rather expensive. For on-road measurements, R&D and monitoring purposes (e.g. OBD systems) NH3 sensor could be a useful tool. In this research project NH3 sensor was used for measuring ammonia from different exhaust sources. The sensor is designed for diesel vehicle applications using selective catalytic reduction (SCR) system and in most cases diesel particulate filter is also a part of the exhaust gas aftertreatment system. In this project the performance of the sensor was measured not only with vehicle applications but also with marine engines.
Technical Paper

Combined CFD – PIV methodology for the characterization of Air Flow in a Diesel Engine

2018-09-10
2018-01-1769
It is known that in-cylinder airflow structures during intake and compression strokes deeply affects the combustion process in Compression Ignition (CI) engines. This work presents a methodology for the analysis of the swirling structures by means of the CFD proprietary code Converge 2.3. The methodology is based on the CFD modelling and the comparison of results with in-cylinder velocity fields measured by Particle Image Velocimetry (PIV). Furthermore, the analysis is extended to the accuracy evaluation of other methods available to define the flow in the cylinder of internal combustion engines, such as experiments in steady flow rigs. These methods, in junction with simple phenomenological models, have been traditionally used to determine some of the fundamental variables that define the in-cylinder flow in ICE engines. The CFD analysis is focused in the flow structures around Top Dead Centre (TDC) at the end of the compression stroke.
Technical Paper

A review of the requirements for injection systems and the effects of fuel quality on particulate emissions from GDI engines

2018-09-10
2018-01-1710
Particulate emissions from Gasoline Direct Injection (GDI) engines have been an important topic of recent research interest due to their known environmental effects. This review paper will characterise the influence of different gasoline direct injection fuel systems on particle number (PN) emissions. The findings will be reviewed for engine and vehicle measurements with appropriate driving cycles (especially real driving cycles) to evaluate effects of the fuel injection systems on PN emissions. Recent technological developments alongside the trends of the influence of system pressure and nozzle design on injector tip wetting and deposits will be considered. Besides the engine and fuel system it is known that fuel composition will have an important effect on GDI engine PN emissions. The evaporation qualities of fuels have a substantial influence on mixture preparation, as does the composition of the fuel itself.
Technical Paper

Effects of clamping force on the operating behavior of PEM fuel cell

2018-09-10
2018-01-1718
Proton exchange membrane (PEM) fuel cell is widely recognized as an outstanding portable power plant and expected to be possibly commercialization in the near future. As is well known, mechanical stresses implemented on the bipolar plates during the assembly procedure should have prominent influences on mass and heat transfer behavior inside the cell, as well as the resultant performance. In this study, an analytical model is proposed to comprehensively investigate the influence of clamping force on the mass transport, electrochemical properties and overall cell output capability of a PEM fuel cell. The results indicate that proper clamping force not only benefits the gas leakage prevention but also increases the contact area between the neighboring components to decrease the contact ohmic resistance.
Technical Paper

Characterizing spray propagation of GDI injectors under crossflow conditions

2018-09-10
2018-01-1696
In DISI engines spray distribution and atomization directly influence mixture formation, the quality of combustion and the resulting emissions. Constant volume chambers (CVC) are commonly used to characterize sprays of gaso-line injectors. The CVCs provide good optical access but the flow condition of the engine cannot be reproduced. Optical accessible engines in contrast deliver realistic flow conditions but have restricted optical access. In former investigations we compared the spray propagation of different injectors in constant volume chambers and in optical accessible engines. These results showed a clear difference of the spray propagation in the CVC and the engine, especially at high charge motion conditions in the engine. To find an appropriate way for investigating the impact of different charge motion a flow channel was built with adjustable crossflow velocities from 5- 50 m/s. The flow channel has a transparent rectangular shape.
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