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Technical Paper

Probabilistic Approach to Predict Abnormal Combustion in Spark Ignition Engines

2018-09-10
2018-01-1722
This study is performed to predict the outcome of combustion process based on a given RANS solution by performing statistical analysis of Sa number and refined ignition theory proposed by Im et.al [1]. A criterion to predict strong auto-ignition/detonation a priori is used in this study, which is based on Sankaran-Zeldovich criterion. The Sankaran number, Sa, is normalized by sound speed and is calculated for the bulk mixture with temperature and equivalence ratio stratifications. The initial conditions from previous pre-ignition simulations were used to calculate the Sankaran number, probability density function of Sa, and the detonation probability, PD. Sankaran number decreased and detonation probability increased significantly with increase of temperature. The mean Sankaran number calculated for the entire computational domain and the predicted Sankaran number were found to be nearly identical.
Technical Paper

Comparing large Eddy Simulation of a Reacting Fuel Spray with Measured Quantitative Flame Parameters

2018-09-10
2018-01-1720
In order to reduce engine out CO2 emissions, it is a main subject to find new alternative fuels from renewable sources. For identifying the specification of an optimized fuel for engine combustion, it is essential to understand the details of combustion and pollutant formation. For getting a better understanding of the flame behavior, dynamic structure large eddy simulations are a method of choice. In the investigation presented in this paper, an n-heptane spray flame is simulated under engine relevant conditions starting at a pressure of 50 bar and a temperature of 800 K. Measurements are conducted at a high-pressure vessel with the same conditions. Liquid penetration length is measured with Mie-Scatterlight, gaseous penetration length with shadowgraphy and lift-off length as well as ignition delay with OH*-Radiation. In addition to these global high-speed measurement techniques, detailed spectroscopic laser measurements are conducted at the n-heptane flame.
Technical Paper

Deterioration Characteristic of Catalyzed DPF Applied on Diesel City Bus Durable Ageing

2018-09-10
2018-01-1701
Catalyzed DPF (Diesel Particle Filter), CDPF, can significantly reduce primary and secondary particulates from the diesel vehicles, which has promising and extensive application market. However, the problem that CDPF often face with catalytic activity deterioration due to chemical poisoning and thermal ageing is lack of fundamental data of deterioration characteristic of CDPF applied on diesel vehicle durable ageing. In this paper, based on various characterization techniques (XRD, XPS, etc.), it was researched on deterioration characteristic of full-scale CDPFs (CDPF-1, -2, -3) coated with three various concentration of precious metal (15, 25 and 35 g/ft3), which had been carried out 60 000 thousand kilometer durable ageing on diesel city buses. Moreover, the deterioration characteristics of the inlet, middle and outlet layers of the aged CDPF were studied.
Technical Paper

Effects of Injection Rate Profiles on Auto-ignition in Ignition Quality Tester

2018-09-10
2018-01-1695
Ignition quality tester (IQT) is a standard experimental device to determine ignition delay time of liquid fuels in a controlled environment in the absence of gas exchange. The process involves fuel injection, spray breakup, evaporation and mixing, which is followed by auto-ignition. In this study, three-dimensional computational fluid dynamics (CFD) is used for prediction of auto-ignition characteristics of diethyl ether (DEE) and ethanol. In particular, the sensitivity of the ignition behavior to different injection rate profiles is investigated. Fluctuant rate profile derived from needle lift data from experiments performs better than square rate profile in ignition delay predictions. DEE, when used with fluctuant injection rate profile resulted in faster ignition, while for ethanol the situation was reversed. The contrasting results are attributed to the difference in local mixing.
Technical Paper

Outwardly Opening Hollow-Cone Diesel Spray Characterization Under Different Ambient Conditions

2018-09-10
2018-01-1694
The combustion quality in modern diesel engines depends strictly on the quality of the air-fuel mixing and, in turn, from the quality of spray atomization process. So air-fuel mixing is strongly influenced by the injection pressure, geometry of the nozzle duct and the hydraulic characteristics of the injector. In this context, spray concepts alternative to the conventional multi-hole nozzles could be considered as solutions to the extremely high injection pressure increase to assure a higher and faster fuel-air mixing in the piston bowl, with the final target of increasing the fuel efficiency and reducing the engine emissions. The study concerns an experimental depiction of a spray generated through a prototype high-pressure hollow-cone nozzle, under evaporative and non-evaporative conditions, injecting the fuel in a constant-volume combustion vessel controlled in pressure and temperature up to engine-like gas densities in order to measure the spatial and temporal fuel patterns.
Technical Paper

Holistic development of future low NOx emission concepts for heavy-duty applications

2018-09-10
2018-01-1700
Further tightening of NOx emission standards as well as CO2 emission limits for commercial vehicles are currently under discussion. In the on-road market, lowering NOx emissions up to 90%, down to 0.02 g/bhp-hr, has been proposed by CARB and is being evaluated by US EPA. Testing for in-service conformity using PEMS is currently under review in the US. In Europe, CO2 emission limits are anticipated and, at the moment, a CO2 monitoring program is ongoing. PEMS legislation has been recently tightened, and further restrictions can be expected. Tier V legislation has been introduced in Europe, and it is foreseeable that further tightening of off-road machinery will take place in the future. This study deals with virtual development and evaluation of future engine and exhaust aftertreatment (EAT) technology solutions to fulfill the diverse future emission requirements, with emphasis on off-road applications.
Technical Paper

Real-Time Heavy-Duty Vehicle NOX and CO2 Emission Monitoring using a Remote Wireless On-Board Diagnostic (OBD) Approach

2018-09-10
2018-01-1817
Recently, much attention has been paid to real-time vehicle emissions in real-world conditions by researchers and makers. In this study, we collected the remote OBD datasets of three heavy-duty diesel trucks, three diesel buses and three HEV bused from the ‘China condition program’ in China. A total of 2160 h of second-by-second data on their instantaneous NOX and CO2 and emissions and driving conditions were analyzed. We evaluated the real-time NOX and CO2 emissions of the buses based on the remote OBD data and explored the relationship between operating conditions and emissions. This paper aims to construct a method for the remote OBD-based monitoring, research the difference between the emission characteristics of different vehicles and can inform policy makers how to take advantage of these features in monitoring in-use vehicles.
Technical Paper

Optimization of the lubrication distribution in multi plate wet-clutches for HVT transmissions: an experimental – numerical approach

2018-09-10
2018-01-1822
The paper investigates the lubrication flow within multi plate wet-clutches for hydro-mechanical variable transmissions in order to optimize the oil distribution and to reduce the thermo-mechanical stresses on the plates. Since experimental measurements are very difficult to carry out on a real system, CFD numerical tools are used for predicting the flow distribution in a real geometry under actual operating conditions. A modular approach is adopted for the domain subdivision in order to represent accurately the three dimensional geometrical features, while the volume of fluid approach is used to model the multi-phase flow that characterizes the component. Poor lubrication is predicted where high thermal stresses were observed during tests. Furthermore, the numerical modeling is validated against measurements carried out on an ad-hoc designed test rig, which adopts transparent PMMA and 3D-printed inserts for the flow investigation.
Technical Paper

An alternative Method to evaluate the Compression Ratio in IC Engines with Thermal Barrier Coatings

2018-09-10
2018-01-1778
Objectives The objective of this study is to verify and further develop a method to assess the geometrical compression ratio without the need for modeling or estimating heat losses. The method is to be used in experiments involving the evaluation of insulating materials. As the compression ratio is an important parameter used in heat release calculations, a good estimate of the actual geometrical compression ratio is of high importance. In a thesis work [1] an alternative method for compression ratio estimation was evaluated using cylinder pressure data under motoring conditions and evaluating the energy balance close to top dead center. Current methods to find the compression ratio from motored operation are based on fitting engine models to the experimental data. These models use heat loss correlations from uncoated engines and those do not apply when working with insulation.
Technical Paper

Investigation of Late Stage Conventional Diesel Combustion - Effect of Additives

2018-09-10
2018-01-1787
The accepted model of conventional diesel combustion [ Dec SAE 970873] assumes a rich premixed flame slightly downstream of the maximum liquid penetration. The soot generated by this rich premixed flame is burnt out by a subsequent diffusion flame at the head of the jet. Even in situations in which with centre of combustion (CA50) is phased optimally to maximise efficiency, slow late stage combustion can still have a significant detrimental impact on combustion efficiency. Data is presented on a Euro VI compliant HD engine at a range of speed and load points. The operating conditions (e.g. injection timings, EGR levels) were based on a EURO VI calibration which targeted 3 g/kWh of engine-out NOx. Rates of heats release were determined from the pressure sensor data. To investigate late stage combustion, particular focus was made on the position in the cycle at which 90% of the fuel had combusted (CA90). An EN590 compliant fuel was tested.
Technical Paper

Simulation of the Effect of Intake Pressure and Split Injection on Lean Combustion Characteristics of a Poppet-Valve Two-Stroke Direct Injection Gasoline Engine at High Loads

2018-09-10
2018-01-1723
Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur in the cylinder at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 30% at a given amount of fuel in a cycle.
Technical Paper

Line Voltage Control of Induction Motor for Increase its Efficiency in Stable Area Operation

2018-09-10
2018-01-1830
. Regular induction motors operate at a constant value of line voltage. They operate from zero external load to rated value. At low loads motors works with reserve of power. At low loads, motor can work with lower voltage, with lower current and lower power losses. In the paper, we consider speed controller by changing value of linear voltage of control. In this controller, value of linear voltage determined by the external load. In the controller, should be limits on maximum and minimum values of voltages. This controller have additional function (controller) for limiting starting current by decreasing linear voltage during motor start. First, we consider theoretical basics design of speed controller for induction motor in stable area of operation. With this speed controller, mechanical characteristic of motor, in the stable area, is almost vertical. Voltage controller includes controlled (thiristor) rectifier or pulse width modulated converter of linear voltage.
Technical Paper

Blending octane number of 1-butanol and Iso-octane with low octane fuels in HCCI combustion mode

2018-09-10
2018-01-1681
Higher efficiency is a key factor in determining the future of internal combustion engines and is limited by antiknock quality of present fuels and energy economics in octane enhancement. Alcohol based fuels have been recognized as a replacement to fossil fuels with high octane number. The author has recently published work where ethanol, methanol and toluene were used as high octane fuels. For this work, 1-Butanol with a RON 96 was selected as the high octane fuel and three low octane fuels were used as base fuel. These were FACE (Fuels for Advanced Combustion Engines) gasolines, more specifically FACE I, J and also primary reference fuels (iso-octane/n-heptane) were used. In addition, iso-octane with octane number 100 was also selected as high octane fuel and was added to the base fuels. A Cooperative Fuel Research (CFR) engine was used to conduct the experiments. The engine was also operated in HCCI mode to get the auto ignition properties at lean conditions.
Technical Paper

The use of ozone in low temperature methane control for natural gas applications

2018-09-10
2018-01-1702
Lean operating natural gas heavy duty applications have advantages in terms of lower CO2 and PM compared to Diesel applications. This makes operating heavy duty applications on natural gas attractive and currently, they do not have to implement an exhaust particulate filter. However, the challenge is controlling methane emissions over a range of vehicle operating conditions. Methane is extremely stable and light off occurs at temperatures above 400oC and requires high precious metal catalysts in the range of 150 – 200 g/ft3. Under stoichiometric conditions, 400oC can be met in many engine operating points however, for lean operating applications, the exhaust temperature can be significantly lower than 400oC posing a significant challenge for exhaust catalytic CH4 control. This paper will discuss synthetic gas reactor study results using ozone in the feed gas to perform low temperature methane control.
Technical Paper

Design Features of optically accessible engines for flow and combustion studies – A Review

2018-09-10
2018-01-1775
For long time, the measurement of spatially and temporally varying quantities like in-cylinder flow, mixing, and burning in an internal combustion engine remained impossible due to the lack of access to the engine cylinder. Hence, for quite some time, in-cylinder pressure remained the only quantity that could be temporally measured during an engine cycle, and the variations of quantities like temperature, heat release deduced from it. However, to guide modern engine developments for improved fuel economy and reduced emissions, understanding the intricacies of in-cylinder processes are essential. The advent of optical engine in conjunction with laser-based diagnostic techniques enabled measurement of various in-cylinder processes and study their influences on the combustion process. This paper highlights some key design features of optically accessible engines for flow and combustion studies.
Technical Paper

Investigation of the hybrid operating modes regarding efficiency, emissions and comfort for the parallel-series hybrid powertrain concept DE-REX

2018-09-10
2018-01-1828
The „Two-Drive-Transmission with Range-Extender“ (called DE-REX) is an innovative hybrid powertrain concept using two electric motors and an internal combustion engine. The two electric motors are permanent magnet synchronous motors with a maximum power of 48 kW each. As combustion engine a 3-cylinder, turbocharged engine with a power of 65 kW is used. The aggregates are coupled to a transmission whose layout is characterized by consisting of two parallel 2-speed sub-transmissions. This layout offers a high flexibility and enables both parallel and series hybrid driving. The hybrid control unit (HCU) has to select the optimal driving mode and power distribution between the aggregates in regard to in some extend competing objectives like efficiency, emissions or driving comfort. In particular, the operation of the internal combustion engine with only two gear ratios is challenging.
Technical Paper

The Fuel Economy Improvement through the Knock Margin Expansion in a Turbocharged Gasoline Direct Injection Engine

2018-09-10
2018-01-1671
Knocking combustion confines the downsized gasoline engines’ potential for fuel economy improvement. The high in-cylinder pressure and temperature caused by the adaptation of a turbocharger aggravate the autoignition tendency of endgas. Thus, knocking combustion does not allow further advancing of combustion phase. In this research, the effects of ignition and valve timings on knocking combustion were investigated under steady-state conditions. Moreover, the optimal ignition and valve timings for transient operations were derived with the aim of fuel economy improvement based on the steady-state analysis. A 2.0 Liter turbocharged gasoline direct injection engine with continuously variable valve timing (CVVT) was utilized for this experiment. 2, 10, and 18 bar brake mean effective pressure (BMEP) load conditions were used to represent low, medium, and high load operations, respectively.
Technical Paper

Effects of low temperature reforming (LTR) products of low octane number fuel on HCCI combustion

2018-09-10
2018-01-1682
In order to achieve high-efficiency and clean combustion in HCCI engines, combustion must be controlled reasonably. Species with various reactivity can be produced through low temperature oxidation of fuels, which offers possible solutions for controlling the total fuel reactivity flexibly in engines. In the present work, in-cylinder combustion characteristics with low temperature reforming (LTR) were investigated in an optical engine fueled with low octane number fuel. Single injection strategy with an early injection timing of (-180) ºCA ATDC was utilized to achieve homogenous charge compression ignition (HCCI) combustion. PRF50 was chosen as a feedstock fuel, representative of low-octane gasoline. Before engine tests, reformed products from the established LTR system were quantitatively detected using online gas chromatograph (GC) at different reforming temperature of 423 K and 523 K. High-speed imaging was conducted to illustrate the flame development.
Technical Paper

Holistic Evaluation of CO2 Saving Potentials for new Degrees of Freedom in SI Engine Process Control Based on Physical Simulations

2018-09-10
2018-01-1654
Specific shifting of load-points is an important approach in order to reduce the fuel consumption of gasoline engines. A potential measure is cylinder deactivation, which serves as a study example. Currently CO2 savings of new concepts are assessed through dynamic cycle simulations. Fuel consumption during driving cycles is calculated based on consumption-optimized steady-state engine map. Discrete load point shifts occur as a shift on map. For reasons of comfort, shifts require neutral torque. The work of deactivated cylinders must be compensated by still active cylinders within one working cycle. Due to the greater time constant of the air path, the engine charge must be increased or decreased in order to deactivate or activate cylinders without affecting the torque. Prerequisite is a working-cycle-resolved, continuously variable parameter for process control. Manipulation of ignition timing enables a reduction of efficiency and gained work.
Technical Paper

OH radical and soot concentration structures in diesel sprays under low sooting and non-sooting conditions

2018-09-10
2018-01-1690
In an optically accessible high-pressure / high-temperature (HP/HT) chamber, OH radicals, soot concentration, and OH* chemiluminescence images of reacting diesel sprays were captured simultaneously at a constant ambient temperature of 823 K and a density of 20 kg/m3, with injection pressures of 800-2000 bar using an injector with a nozzle orifice having a diameter of 0.1 mm. Swedish market sold MK1 diesel fuel was used in this study. The optical diagnostic methods used were two-dimensional laser extinction for the soot concentration measurement, planar laser induced fluorescence for the OH radical measurement, OH* chemiluminescence imaging, and natural flame luminosity imaging. The objective of this study is to explore the diesel spray structures under low sooting and non-sooting conditions. In this study, it was found that the OH radical width in the flame’s upstream region increased, and the soot concentration decreased when the fuel injection pressure increased.
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