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Technical Paper

Design Parameters for Small Engines Based on Market Research

2018-09-10
2018-01-1717
Small internal combustion engines outperform batteries and fuel cells in regards to weight for a range of applications, including consumer products, marine vehicles, small manned ground vehicles, unmanned vehicles, and generators. The power ranges for these applications are typically between 1 kW and 10 kW. There are numerous technical challenges associated with engines producing power in this range resulting in low power density and high specific fuel consumption. As such, there is a large range of engine design solutions that are commercially available in this power range to overcome these technical challenges. A market survey was conducted of commercially available engines with power outputs less than 10 kW. The subsequent analysis highlights the trade-offs between power output, engine weight, and specific fuel consumption.
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 obtaining 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

Detonation Peninsula for TRF-Air Mixtures: Assessment for the Analysis of Auto-Ignition Events in Spark-Ignition Engines

2018-09-10
2018-01-1721
Controlling abnormal auto-ignition processes in spark-ignition engines requires understanding how auto-ignition is triggered and how it propagates inside the combustion chamber. The original Zeldovich theory regarding auto-ignition propagation was further developed by Bradley and coworkers, who highlighted different modes by considering various hot spot characteristics and thermodynamic conditions around them. Dimensionless parameters (ε, ξ) were then proposed to classify these modes and to define a detonation peninsula for H2-CO-air mixtures. This article deals with numerical simulations undertaken to check the relevancy of this original detonation peninsula when considering realistic gasoline fuels. 1D calculations of auto-ignition propagation are performed using the Tabulated Kinetics for Ignition model.
Technical Paper

Probabilistic Approach to Predict Abnormal Combustion in Spark Ignition Engines

2018-09-10
2018-01-1722
This study presents a computational framework to predict the outcome of combustion process based on a given RANS initial condition by performing statistical analysis of Sankaran number, Sa, and ignition regime 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. In the context of detonation, Sa is normalized by a sound speed, and is spatially calculated for the bulk mixture with temperature and equivalence ratio stratifications. The initial conditions from previous pre-ignition simulations were used to compute the spatial Sa distribution followed by the statistics of Sa including the mean Sa, the probability density function (PDF) of Sa, and the detonation probability, PD. Sa is found to be decreased and detonation probability increased significantly with increase of temperature.
Technical Paper

Investigation of a Cylinder Activation Concept for a Turbocharged Direct-Injection Gasoline Engine

2018-09-10
2018-01-1713
Today, downsizing through active displacement control is in series production using cylinder deactivation (CDA) concepts. However, current systems deactivating two cylinders of a four-cylinder engine are limited regarding the effective CO2 saving potential due to the confined usable operating range of the two-cylinder mode. Therefore, the objective of the current investigation is a three-cylinder engine with the possibility to activate an additional (fourth) cylinder. For this purpose, a four-cylinder series engine was modified to the firing order of a three-cylinder engine for the first three cylinders. The exterior cylinders 1 and 4 are operated in parallel, with the fourth cylinder deactivated in efficiency mode. Launching and idle mode are also operated with three active cylinders. Additional modifications to the valve train were carried out in order to further exploit the increased residual gas tolerance due to the load point shift.
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

Effective Suppression of Surge Instabilities in Turbocharger Compression Systems through a Close-Coupled Compressor Inlet Restriction

2018-09-10
2018-01-1714
The current work demonstrates effective suppression of compression system surge instabilities by installing a variable cross-sectional flow area restriction within the inlet duct of a turbocharger centrifugal compressor operating on a bench-top facility. This restriction couples with the compressor, similar to stages in a multi-stage turbomachine, where the effective pressure ratio is the product of those for the restriction and compressor. During experiments at constant compressor rotational speed, the compressor is stable over the negatively sloped portion of the pressure ratio vs. flow rate characteristics, so the restriction is eliminated within this operating region to preserve compressor performance. At low flow rates, the slope of the compressor alone characteristics reaches a positive value, and the unrestricted compression system enters mild surge. Further reduction of flow rate with the unrestricted compressor inlet results in a sudden transition to deep surge instabilities.
Technical Paper

Novel Rankine Cycle for Hybrid Vehicles

2018-09-10
2018-01-1711
The European Union (EU) has defined legally-binding targets for the fleet of new cars allowing 95 grams CO2 per kilometer in 2021. It is already under discussion to reduce average emissions of the EU car fleet by further 15% in 2025 and again by 30% in 2030 compared to 2021 goal. Therefore, improvement of fuel economy is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future fuel economy targets without further development of additional measures. This paper presents the analysis of a Rankine cycle unit applied to improve the overall efficiency of a hybrid electric vehicle (HEV). The authors propose a new concept for recovering a considerable part of exhaust waste heat from an HEV with spark ignition internal combustion engine (ICE) by applying a bottoming Rankine cycle with a Ruths storage tank.
Technical Paper

Development of a New 1.8L Down-Speeding Turbocharged Gasoline Engine with Miller Cycle

2018-09-10
2018-01-1712
Upcoming China 4th stage of fuel consumption regulation and China 6a emission legislation require improvement of many existing engines. This paper summarizes an upgrade of combustion system and mechanical layout for a four-cylinder engine family. Based on an existing production process for a naturally aspirated 2.0-liter gasoline engine, a 1.8-liter down-speeded and turbocharged gasoline engine is derived. Starting development by analysis of engine base geometry, a layout for a Miller-Cycle gas exchange with early closing of intake valves is chosen. Requirements on turbocharger configuration are investigated with one-dimensional gas exchange simulation and combustion process will be analyzed by means of 3D-CFD simulation. Challenging boundary conditions of a very moderate long-stroke layout with a stroke/bore-ratio of only 1.037 in combination with a cost efficient port fuel injection system and fixed valve lift profiles are considered.
Technical Paper

A Physical-Based Approach for Modeling the Influence of Different Operating Parameters on the Dependency of External EGR Rate and Indicated Efficiency

2018-09-10
2018-01-1736
External Exhaust Gas Recirculation (EGR) provides an opportunity to increase the efficiency of turbocharged spark-ignition engines. Of the competing technologies and configurations, Low-Pressure EGR (LP-EGR) is the most challenging in terms of its dynamic behavior. Only some of the stationary feasible potential can be used during dynamic engine operation. To guarantee fuel consumption-optimized engine operation with no instabilities, a load point-dependent limitation of the EGR rate or alternatively an adaptation of the operating point to the actual EGR rate is crucial. For this purpose, a precise knowledge of efficiency and combustion variance is necessary. Since the operating state includes the actual EGR rate, it has an additional dimension, which usually results in an immense measuring effort.
Technical Paper

Cylinder Selective Combustion, the New Diesel Dual Fuel Combustion Control Concept for Low Load Operating Condition

2018-09-10
2018-01-1733
Diesel dual fuel (DDF) operated under moderate load condition emits a lot of CH4 and CO. Even these emissions have been improved significantly by Dual Fuel Premixed Charge Compression Ignition: DF-PCCI [3] combustion control technique which was proposed by the authors. However, the emission was still high as compared to diesel emissions. To overcome this problem, the new combustion control concept so called Cylinder Selective Combustion (CSC) has been proposed. From the fact that at low load condition, diesel combustion has lower CH4 and CO emissions than DDF combustion and DDF emissions can be improved significantly by DF-PCCI concept at higher load. So, in the new concept, some cylinder was selected to run with very low IMEP diesel combustion and some cylinder was selected to run with higher IMEP DF-PCCI combustion. The IMEP ratios between DF-PCCI and diesel have been optimized for each engine speed and engine load.
Technical Paper

Dual Fuel Injection (DI + PFI) for Knock and EGR Dilution Limit Extension in a Boosted SI Engine

2018-09-10
2018-01-1735
Combined direct and port fuel injection (i.e., dual injection) in spark ignition engines is of increasing interest due to the advantages for fuel flexibility and the individual merits of each system for improving engine performance and reducing engine-out emissions. Greater understanding of the impact of dual injection will enable deriving the maximum benefit from the two injection systems. This study investigates the effects of dual injection on combustion, especially knock propensity and tolerance to exhaust gas recirculation (EGR) dilution at different levels of EGR. A baseline for comparison with dual injection results was made using direct injection fueling only. A splash blended E20 fuel was used for the direct injection only tests. For the dual injection tests, gasoline, representing 80% by volume of the total fuel, was injected using the direct injector, and ethanol, representing 20% by volume of the total fuel, was injected using the port fuel injector.
Technical Paper

Application of Models of Short Circuits and Blow-Outs of Spark Channels under High-Velocity Flow Conditions to Spark Ignition Simulation

2018-09-10
2018-01-1727
This report describes the implementation of the spark channel short circuit and blow-out submodels, which were described in the previous report, into a spark ignition model. The spark channel which is modeled by a particle series is elongated by moving individual spark particles along local gas flows. The equation of the spark channel resistance developed by Kim et al. is modified in order to describe the behavior of the current and the voltage in high flow velocity conditions and implemented into the electrical circuit model of the electrical inductive system of the spark plug. Input parameters of the circuit model are the following: initial discharge energy, inductance, internal resistance and capacitance of the spark plug, and the spark channel length obtained by the spark channel model. The instantaneous discharge current and the voltage are obtained as outputs of the circuit model.
Technical Paper

Effects of Hot and Cooled EGR for HC Reduction in a Dual-Fuel Premixed Charge Compression Ignition Engine

2018-09-10
2018-01-1730
Most internal combustion engine makers have adopted after-treatment systems, such as selective catalytic reduction (SCR), diesel particulate filter (DPF), and diesel oxidation catalyst (DOC), to meet emission regulations. However, as the emission regulations become stricter, the size of the after-treatment systems become larger. This aggravates the price competitiveness of engine systems and causes fuel efficiency to deteriorate due to the increased exhaust pressure. Dual-fuel premixed charge compression ignition (DF-PCCI) combustion, which is one of the advanced combustion technologies, makes it possible to reduce nitrogen oxides (NOx) and particulate matter (PM) during the combustion process, while keeping the combustion phase controllability as a conventional diesel combustion (CDC). However, DF-PCCI combustion produces high amounts of hydrocarbon (HC) and carbon monoxide (CO) emissions due to the bulk quenching phenomenon under low load conditions as a huddle of commercialization.
Technical Paper

Evaluating the Efficiency of a Conventional Diesel Oxidation Catalyst for Dual-Fuel RCCI Diesel-Gasoline Combustion

2018-09-10
2018-01-1729
Reactivity controlled compression ignition (RCCI) combustion has demonstrated to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with similar or better thermal efficiency than CDC under a wide variety of engine platforms. However, a major challenge of this concept comes from the high hydrocarbon (HC) and carbon monoxide (CO) emission levels, which are orders of magnitude higher than CDC and similar to those of port fuel injected (PFI) gasoline engines. The higher HC and CO emissions combined with the lower exhaust temperatures during RCCI operation present a challenge for current exhaust aftertreatment technologies. RCCI has been successfully implemented on different compression ignition engine platforms with only minor modifications on the combustion system to include a PFI for feeding the engine with the low reactivity fuel.
Technical Paper

Quantitative Optical Analysis and Modelling of Short Circuits and Blow-Outs of Spark Channels under High-Velocity Flow Conditions

2018-09-10
2018-01-1728
This study models short circuits and blow-outs of spark channels. The short circuit model assumes that a spark channel is short-circuited between two arbitrary locations when the electric potential difference between the two locations exceeds the voltage which enables electrical insulation breakage in-between. The threshold voltage can be raised by increasing the distance between the two locations and decreasing the discharge current. Discharge current, in this model, represents the influence of both the spread and the number of electrically charged particles, i.e., electrons and positive ions, distributed near the two locations. Meanwhile, the blow-out model assumes that a strong flow diffuses electrons and positive ions in the spark channel, and consequently the discharge blows out.
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

Effects of an On-Board Safety Device on the Emissions and Fuel Consumption of a Light Duty Vehicle

2018-09-10
2018-01-1821
Vehicle emissions and fuel consumption are significantly affected by driving behavior. Many studies of eco-driving technology such as eco-driving training, driving simulators and on-board eco-driving devices have reported potential reductions in emissions and fuel consumption. Use of on-board safety devices is mainly for safety, but also affects vehicle emissions and fuel consumption. In this study, an on-board safety device was installed to alert the driver and provide several types of warning to the driver (e.g. headway monitoring warning, lane collision warning, speed limit warning, etc.) to improve driving behavior. A portable emissions measurement system (PEMS) was used to measure vehicle exhaust concentrations, including hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx). The driving parameters including vehicle speed, acceleration and position were also recorded.
Technical Paper

Emission Performance of LPG Vehicles by Remote Sensing Technique in Hong Kong

2018-09-10
2018-01-1820
Since 1st September 2014 the Hong Kong Environmental Protection Department (HKEPD) has been utilising a Dual Remote Sensing technique to monitor the emissions from gasoline and liquified petroleum gas (LPG) vehicles for identifying high emitting vehicles running on road. Remote sensing measures and determines volume ratios of the emission gases of HC, CO and NO against CO2, which are used for determining if a vehicle is a high emitter. Characterisation of each emission gas is shown and its potential to identify a high emitter is established. The data covers a total of about 2,200,000 LPG vehicle emission measurements taken from 14 different remote sensing units. It was collected from 6th January 2012 to 20th April 2017 across a period before and after the launch of the Remote Sensing programme for evaluating the performance of the programme. The results show that the HKEPD Remote Sensing programme is very effective to detect high emitting vehicles and reduce on-road vehicle emissions.
Technical Paper

Impact 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 divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx (oxides of nitrogen) emissions from diesel cars. The RDE test is certainly more relevant than CD test cycles, but currently certification RDE cycles will not necessarily include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx after-treatment systems.
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