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Technical Paper

Comparison of long-chain alcohol blends, HVO and Diesel on spray characteristics, ignition and soot formation

2019-01-15
2019-01-0018
Spray characteristics of fossil Diesel fuel, hydrotreated vegetable oil (HVO) and two oxygenated fuel blends were studied to elucidate the combustion process. The fuels were studied in an optically accessible high-pressure/high-temperature chamber under non-combusting (623 K, 46.9 bar) and combusting (823 K, 60.4 bar) conditions. The fuel blends contained the long-chain alcohol 2- ethylhexanol (EH), HVO and either 20 vol.% Diesel or 7 vol.% rapeseed methyl ester (RME) and were designed to have a Diesel-like cetane number (CN). Injection pressures were set to 1200 bar and 1800 bar and the gas density was held constant at 26 kg/m3. Under non-combusting conditions, shadow imaging revealed the penetration length of the liquid and vapor phase of the spray. Under combusting conditions, the lift-off length and soot volume fraction were measured by simultaneously recording time-resolved two-dimensional laser extinction, flame luminosity and OH* chemiluminescence images.
Technical Paper

Estimation of the Fuel Efficiency Potential of Six Gasoline Blendstocks Identified by the U.S. Department of Energy's Co-Optimization of Fuels and Engines Program

2019-01-15
2019-01-0017
Six blendstocks identified by the Co-Optimization of Fuels & Engines Program were used to prepare fuel blends using a fixed blendstock for oxygenate blending and a target RON of 97. The blendstocks included ethanol, n-propanol, isopropanol, isobutanol, diisobutylene, and a bioreformate surrogate. The blends were analyzed and used to establish interaction factors for a non-linear molar blending model that was used to predict RON and MON of volumetric blends of the blendstocks up to 35 vol%. Projections of efficiency increase, volumetric fuel economy increase, and tailpipe CO2 emissions decrease were produces using two different estimation techniques to evaluate the potential benefits of the blendstocks. Ethanol was projected to provide the greatest benefits in efficiency and tailpipe CO2 emissions, but at intermediate levels of volumetric fuel economy increase over a small range of blends than other blendstocks.
Technical Paper

Investigation of an Advanced Combustion System for Stoichiometric Diesel to Reduce Soot Emissions

2019-01-15
2019-01-0023
Diesel engines are losing market-share in the light-duty and small non-road segments, primarily due to the high relative cost of emissions control systems for lean-burn diesel engines. Advancements in gasoline engine technology have decreased the operating cost advantage of diesels to the extent that the high relative initial-cost disadvantage is now too large to sustain a strong business position. SwRI has focused several years of research efforts toward enabling diesel engine combustion systems to operate at stoichiometric conditions. This would allow the application of a low-cost three-way catalyst emission control system which has been well developed for gasoline spark-ignited engines. One of the main barriers of this combustion concept is the result of high smoke emissions from poor fuel/air mixing.
Technical Paper

Kinetics Modeling of Ammonia-SCR and Experimental Studies over Monolith Cu-ZSM-5 Catalyst

2019-01-15
2019-01-0024
Ammonia-selective catalytic reduction (SCR) systems have been introduced commercially in diesel vehicles, however catalyst systems with higher conversion efficiency and better control characteristics are required to know actual driving emissions and emissions in random test cycles. Computational fluid dynamics (CFD) is effective when applied to SCR catalyst development, and many models have been proposed, but these models need experimental verification and are limited in the situations they apply to. Further, there are a few models taking account of the copper redox cycle, and this causes a low validity of SCR reaction calculations in the transient conditions of engine operation. Model development considering the redox reactions in a zeolite catalyst, Cu-ZSM-5, is an object of the research here, and the effects of exhaust gas composition on the SCR reaction and ammonia oxidation at high temperatures are investigated.
Technical Paper

Optical Investigation on the Combustion Process Differences between Double-Pilot and Closely-Coupled Triple-Pilot Injection Strategies in a LD Diesel Engine

2019-01-15
2019-01-0022
The combustion processes of three injection strategies in a light-duty (LD) diesel engine at a medium load point are captured with a high speed video camera. A double-pilot/main/single-post injection strategy representative of a LD Euro 6 calibration is considered as the reference. There is a modest temporal spacing (dwell) after the first pilot (P1) and second pilot (P2). A second strategy, “A,” adds a third pilot (P3). The dwell after both P2 and P3 are several times shorter than in the reference strategy. A third strategy, “B,” further reduces all dwells. In all three cases, the fuel from P1 combusts via sequential autoignition. For the reference and A strategies, the ignition of P2 occurs at its interface with the existing combustion regions. This fuel burns as a propagating premixed flame. For B, the start of injection of P2 occurs before the autoignition of P1 becomes fully developed.
Technical Paper

Piston detergency and anti-wear performance of non-phosphorus and non-ash engine oil

2019-01-15
2019-01-0021
It has been recently reported that sulfated ash derived from engine oil deteriorates DPF performance due to accumulation on the filter surface. In addition, it has been commonly understood that phosphorus from engine oil adsorbs onto catalytic metal surface and degrades the performance. From this background, sulfated ash and phosphorus in engine oil have been reduced. From this point of view, the authors have developed the novel engine oil (NPNA) which includes no phosphorus and no sulfated ash from metal detergent and ZnDTP and also introduced its competent performance by several engine tests for piston detergency and anti-wear performance. However, piston detergency performance of NPNA needs to be enhanced for engines which are operated under more severe conditions. Therefore, we have examined several additives which do not contain any metal elements and evaluated the performance of piston detergency using some laboratory test methods such as a hot tube tester.
Technical Paper

Theoretical and Experimental Investigation on Power Loss of Vehicle Transmission Synchronizers with Spray Lubrication

2019-01-15
2019-01-0028
Besides optimal engine systems, high-efficiency vehicle transmissions are generally also required to improve fuel economy in automotive applications. For the energy loss analysis in transmissions, most researches focused on the major mechanical components, such as gears, bearings and seals, while the other mechanical losses, like synchronizer losses, were usually not considered. With increasing number of synchronizers in modern transmissions, a recent study of transmission power losses indicates that the power loss analysis of synchronizers should also be developed and appended for a more accurate investigation on overall power losses in transmissions. The synchronizer is an essential component of vehicle transmissions for equalizing the different rotational speeds of shafts and gear wheels by frictional torques, for which the synchronizers must be cooled and lubricated in order to enhance their service life.
Technical Paper

A Statistical Approach to Improve the Accuracy of the DPF Simulation Model under Transient Conditions

2019-01-15
2019-01-0027
For reduction of Particulate Matter (PM) emitted from a diesel engine, a Diesel Particulate Filter (DPF) is mounted on a diesel car in general. Since a high pressure drop through the DPF causes low engine performance, it is important to predict the pressure drop with high accuracy. The purpose of this study is to improve the accuracy of the DPF simulation model under transient condition by means of an improved parameter optimization. The DPF model had been created that consisted of an inlet channel, a cake layer, wall layers and an outlet channel. The pressure drop is influenced by the soot deposition place, mass and density.
Technical Paper

Integrated AHP and WED Based Approach to Select Optimal Combination of Operating Parameters on Spark Ignition Engine

2019-01-15
2019-01-0025
The influence of operating parameters on the performance of spark ignition engine has attracted the interest of engine manufacturers and researchers. In this instance, selection of optimal combination of operating parameters based on experimental results is expressed as a multi criteria decision making (MCDM) problem. In this study a mathematical model which is an integration of Analytic hierarchy process (AHP) and Weighted Euclidean distance based approach (WED) is proposed to select optimal combination of operating parameters. The parameters chosen are compression ratio (6,7,8,9), fuel blends (E10, E20, E30, E40) and load (25%, 50%, 75%, 100%). Consistency check of weights of attributes was carried out by AHP and the weighted distance of attributes from the most and least favorable situations was evaluated using WED. Operating parameters with the combination of compression ratio of 8, fuel blend of E20 at load of 100% was found to be optimum.
Technical Paper

Variation in Squish Length and Swirl to reach higher levels of EGR in a CNG engine

2019-01-15
2019-01-0081
Gaseous methane fuel for internal combustion engines has proven to be a competitive source of propulsion energy for heavy duty truck engines. Using biogas can even reduce the carbon footprint of the truck to near zero-levels, creating a fully environmental friendly transport. Gas engines have already been on the market and proved to be a popular alternative for buses and waste transport. However, for long haulage these engines have not been on par with the equivalent diesel engines. In order to improve the power and efficiency of the EURO VI gas engines running stoichiometric the direct way forward is adding more boost and spark advance in combination with more EGR to mitigate knock. By achieving a higher mixing rate through increased in-cylinder turbulence, the fuel can still be combusted efficiently even though the fraction of inert gases increased.
Technical Paper

A Study on the Combustion Characteristics of a methane jet flame in a Pressurized Hot Vitiated Co-flow

2019-01-15
2019-01-0082
This work presents the study of the methane jet flame in a pressurized vitiated co-flow burner (PVCB) ,which can provide a controllable high pressurized temperature zone and oxygen atmosphere and simulate the temperature of the first stage low temperature exothermic combustion of the homogeneous charge compression ignition (HCCI) engine. The lift-off length and the stabilization of the methane jet flame under different environment pressures, co-flow temperatures, co-flow rates and jet velocities have been studied, and a Chemkin numerical simulations with Gri-mech 3.0 were analyzed as well. The results could provide theoretical supports for the research of the natural gas engine combustion stabilization control to increase the indicated thermal efficiency of internal combustion engine.
Technical Paper

Methane Direct Injection in an Optical SI Engine – Comparison between Different Combustion Modes

2019-01-15
2019-01-0083
Natural gas, biogas, and biomethane are attractive fuels for compressed natural gas (CNG) engines because of their beneficial physical and chemical characteristics. This paper examines three combustion modes – homogeneous stoichiometric, homogeneous lean burn, and stratified combustion – in an optical single cylinder engine with a gas direct injection system operating with an injection pressure of 18 bar. The combustion process in each mode was characterized by indicated parameters, recording combustion images, and analysing combustion chemiluminescence emission spectra. Pure methane, which is the main component of CNG (up to 98%) or biomethane (> 98 %), was used as the fuel. Chemiluminescence emission spectrum analysis showed that OH* and CN* peaks appeared at their characteristic wavelengths in all three combustion modes. The peak of OH* and broadband CO2* intensities were strongly dependent on the air/fuel ratio conditions in the cylinder.
Technical Paper

The Rotating Liner Engine (RLE) preliminary testing.

2019-01-15
2019-01-0084
The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2-4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential of eliminating the metal-to-metal contact / boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high. In 2005, our team published results of the friction testing of our first rotating liner test rig as compared to a baseline. This test rig was a single cylinder engine conversion of a light duty engine, but was tested only under motoring conditions. With warm coolant and oil, we proved a substantial friction reduction at low engine speeds which exceeded 40 kPa of FMEP.
Technical Paper

Isobaric Combustion: A Potential Path to High Efficiency, in Combination with the Double Compression Expansion Engine (DCEE) Concept

2019-01-15
2019-01-0085
The internal combustion engine efficiency is highly dependent on the peak pressure the engine operates at. The new compound engine concept, the Double Compression Expansion Engine (DCEE), utilizes a two-stage compression and expansion cycle to reach ultra-high efficiencies. This engine is expected to take advantage of its high-integrity structure adapted to high pressures, reaching 300 bar peak motored pressure. However, this will make conventional combustion cycles, such as the Seiliger-Sabathe (mixed) or Otto (isochoric) cycles, not feasible as they involve a further pressure rise due to combustion. This paper investigates the concept of isobaric combustion at relatively high peak-motored pressures and compares this concept with more traditional combustion modes in terms of efficiency and emissions.
Technical Paper

Dynamic Exhaust Valve Flow 1-D Modelling during Blowdown Conditions

2019-01-15
2019-01-0058
To conduct system level studies on internal combustion engines reduced order models are required in order to keep the computational load under reasonable limits. By its nature a reduced order model is a simplification of reality and may introduce modeling errors. However what is of interest is the size of the error and if it is possible to reduce the error by some method. A popular system level study is gas exchange and in this paper the focus is on the exhaust valve. Generally the valve is modeled as an ideal nozzle where the flow losses are captured by reducing the flow area. As the valve moves slowly compared to the flow the process is assumed to be quasi-steady, i.e. interpolation between steady-flow measurements can be used to describe the dynamic process during valve opening. These measurements are generally done at low pressure drops, as the influence of pressure ratio is assumed to negligible.
Technical Paper

Visual analyses of end of injection liquid structures and the behaviour of nozzle surface-bound fuel in a direct injection diesel engine

2019-01-15
2019-01-0059
Multiple injection strategies are implemented in the majority of modern diesel engines, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potentially contribution to unburnt hydrocarbon emissions. To investigate the underlying processes, high-speed optical measurements at the microscopic scale were performed inside an idling diesel engine. Visualisation of the injector nozzle surface and near nozzle region permitted an in-depth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading.
Technical Paper

The Effects of Injection Strategies on Particulate Emissions from a Dual-Injection Gasoline Engine

2019-01-15
2019-01-0055
European standards have set stringent PN (particle number) regulation (6×1011 #/km) for gasoline direct injection (GDI) engine, posing a great challenge for the particulate emission control of GDI engines. Dual-injection, which combines direct-injection (DI) with port-fuel-injection (PFI), is an effective approach to reduce particle emissions of GDI engine while maintaining good efficiency and power output. In order to investigate the PN emission characteristics under different dual-injection strategies, a DMS500 fast particle spectrometer was employed to characterize the effects of injection strategies on particulates emissions from a dual-injection gasoline engine. In this study, the injection strategies include injection timing, injection ratio and injection pressure of direct-injection.
Technical Paper

Phenomenological Modeling and Experiments to Investigate the Combined Effects of High Pressure and Multiple Injection Strategies with EGR on Combustion and Emission Characteristics of a CRDI Diesel Engine

2019-01-15
2019-01-0056
Nowadays, due to stringent emission regulations, it is imperative to incorporate modeling efforts with experiments. This paper presents the development of a phenomenological model to investigate the effects of various in-cylinder strategies on combustion and emission characteristics of a common-rail direct-injection (CRDI) diesel engine. Experiments were conducted on a single-cylinder, supercharged engine with displacement volume of 0.55 l at different operating conditions with various combinations of injection pressure, number of injections involving single injection and multiple injections with two injection pulses, and EGR. Data obtained from experiments was also used for model validation. The model incorporated detailed phenomenological aspects of spray growth, air entrainment, droplet evaporation, wall impingement, ignition delay, premixed and mixing-controlled combustion rates, and emissions of nitrogen oxides (NOx) and diesel soot.
Technical Paper

Fast NGC: A New On-Line Technique for Fuel Flow Measurement

2019-01-15
2019-01-0062
Knowledge of fuel mass injected in an individual cycle is important for engine performance and modelling. Currently, direct measurements of fuel flow to individual cylinders of an engine are not possible on-engine or in real-time due to a lack of available appropriate measurement techniques. The objective of this work was to undertake real-time Coriolis fuel flow measurement using GDI injectors on a rig observing fuel mass flow rate within individual fuel injections. This has demonstrated the potential of the technology – combining Coriolis Flow Meters (CFMs) with Prism signal processing together known as Fast Next Generation Coriolis (Fast NGC), and serve as a basis for transition to application on an engine. A rig-based feasibility study has been undertaken injecting gasoline through a GDI injector at 150 bar in both single shot mode and at a simulated engine speed of 1788 rpm. The results show that these individual injections events can in principle be measured.
Technical Paper

Large-eddy simulation on the effect of fuel injection pressure on the gasoline spray characteristics

2019-01-15
2019-01-0060
Increasing gasoline injection pressure has a substantial potential to reduce emissions while maintaining the advantage of the high efficiency of spark ignition engine. Present gasoline injectors are operating in the range of 200 to 250 bar, there is an interest in injection pressures of 400 bar, 600 bar and even higher for further emissions reduction and fuel efficiency improvements. A fundamental understanding of gasoline spray characteristics is vital to gain the insight of spray behavior under ultra-high injection pressure. The better understandings also essential to improve model development and facilitate the integration of advanced injection system with elevated injection pressure into future gasoline engines. It is therefore critical to model the high injection pressure gasoline spray using state-of-the-art computational fluid dynamics (CFD) methods with high time and space accuracy.
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