Refine Your Search



Search Results

Technical Paper

Water Injection to Improve Direct Injection Spark Ignition Engine Efficiency

The increasing use of downsized turbocharged gasoline engines for passengers cars and the new European homologation cycles (WLTC and RDE) both impose an optimization of the whole engine map. More weight is given to mid and high loads, thus enhancing knock and overfueling limitations. At low and moderate engine speeds, knock mitigation is one of the main issues, generally addressed by retarding spark advance thereby penalizing the combustion efficiency. At high engine speeds, knock still occurs but is less problematic. However, in order to comply with thermo-mechanical properties of the turbine, excess fuel is injected to limit the exhaust gas temperature while maximizing engine power, even with cooled exhaust manifolds. This also implies a decrease of the combustion efficiency and an increase in pollutant emissions. Water injection is one way to overcome both limitations.
Journal Article

Using Ethanol’s Double Octane Boosting Effect with Low RON Naphtha-Based Fuel for an Octane on Demand SI Engine

The efficiency of spark ignition (SI) engines is usually limited by the occurrence of knock, which is linked to fuel octane number. If running the engine at its optimal efficiency requires a high octane number at high load, a lower octane number can be used at low load. Saudi Aramco, along with its long-term partner IFP Energies nouvelles, has been developing a synergistic fuel engine system where the engine is fed by fuel with an octane number adjusted in real time, on an as needed basis, while running at its optimal efficiency. Two major steps are identified to develop this “Octane on Demand” (OOD) concept: First, characterize the octane requirement needed to run the engine at its optimal efficiency over the entire map. Then, select the best dual fuel combination, including a base fuel and an octane booster to fit this concept.
Technical Paper

The Impact of Intake Valve Dynamics on Knock Propensity in a Dual-Fuel SI Engine

In this study, the impact of the intake valve timing on knock propensity is investigated on a dual-fuel engine which leverages a low octane fuel and a high octane fuel to adjust the fuel mixture’s research octane rating (RON) based on operating point. Variations in the intake valve timing have a direct impact on residual gas concentrations due to valve overlap, and also affect the compression pressure and temperature by altering the effective compression ratio (eCR). In this study, it is shown that the fuel RON requirement for a non-knocking condition at a fixed operating point can vary significantly solely due to variations of the intake valve timing. At 2000 rpm and 6 bar IMEP, the fuel RON requirement ranges from 80 to 90 as a function of the intake valve timing, and the valve timing can change the RON requirement from 98 to 104 at 2000 rpm and 14 bar IMEP.
Technical Paper

System Optimization for a 2-Stroke Diesel Engine with a Turbo Super Configuration Supporting Fuel Economy Improvement of Next Generation Engines

The objective of this paper is to present the results of the GT Power calibration with engine test results of the air loop system technology down selection described in the SAE Paper No. 2012-01-0831. Two specific boosting systems were identified as the preferred path forward: (1) Super-turbo with two speed Roots type supercharger, (2) Super-turbo with centrifugal mechanical compressor and CVT transmission both downstream a Fixed Geometry Turbine. The initial performance validation of the boosting hardware in the gas stand and the calibration of the GT Power model developed is described. The calibration leverages data coming from the tests on a 2 cylinder 2-stroke 0.73L diesel engine. The initial flow bench results suggested the need for a revision of the turbo matching due to the big gap in performance between predicted maps and real data. This activity was performed using Honeywell turbocharger solutions spacing from fixed geometry waste gate to variable nozzle turbo (VNT).
Journal Article

Stabilization of Highly Diluted Gasoline Direct Injection Engine using Innovative Ignition Systems

Dilution is a promising way to improve fuel economy of Spark-Ignited (SI) gasoline engines. In this context, influence of innovative ignition systems on the dilution acceptance of a 400cc optical GDI engine has been studied. Several systems were tested and compared to a conventional coil: a dual-coil system and two nanosecond scaled plasma generators. Two operating points were studied: 2.8bar IMEP (net) at 2000rpm and 9bar IMEP (net) at 1200rpm. Two diluents were evaluated: real EGR and air (lean combustion). High-speed imaging at frequency up to 10kHz was performed to visualize both spark and combustion initiation and propagation. Voltage and current were measured to infer the energy deposited in the spark plug gap. The dual-coil DCO™ system and the nanosecond multi-pulse plasma generator at their maximum power showed an ability to extend the dilution range of the engine.
Journal Article

Simulation and Optical Diagnostics to Characterize Low Octane Number Dual Fuel Strategies: a Step Towards the Octane on Demand Engine

Reduction of CO2 emissions is becoming one of the great challenges for future gasoline engines. Downsizing is one of the most promising strategies to achieve this reduction, though it facilitates occurrence of knocking. Therefore, downsizing has to be associated with knock limiting technologies. The aim of the current research program is to adapt the fuel Research-Octane-Number (RON) injected in the combustion chamber to prevent knock occurrence and keep combustion phasing at optimum. This is achieved by a dual fuel injection strategy, involving a low-RON naphtha-based fuel (Naphtha, RON 71) and a high-RON octane booster (Ethanol, RON107). The ratio of fuel quantity on each injector is adapted to fit the RON requirement as a function of engine operating conditions. Hence, it becomes crucial to understand and predict the mixture preparation, to quantify its spatial and cycle-to-cycle variations and to apprehend the consequences on combustion behavior - knock especially.
Technical Paper

Selection of the Most Promising Alternative Fuels for Aircraft Development: ALFA-BIRD Proposal

Air traffic has been steadily increasing for the last years. Moreover, fuel availability at a reasonable cost seems more and more uncertain. Climate change implies that greenhouse gases emissions should be reduced. In this context, the search for new alternative fuels for aircraft seems to be a promising solution. Nevertheless, aeronautic represents a very specific transportation mode, due to its usage (short range, middle range, long range with the same fuel, worldwide distribution of the fuel…) and its compulsory security constraints. In the first part of the European project ALFA-BIRD (Alternative Fuels and Biofuels for Aircraft development - FP7), a selection of the best candidates to become the fuels for the future of aircraft has been done. The selection process was very complex, due to multiple criteria (physical properties, economical issued, environmental issues…).
Technical Paper

Potential of Naphtha-like Fuel on an Existing Modern Compression Ignition Engine

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOX and particulates emissions when used in diesel engines. Indeed, fuels highly resistant to auto-ignition provide more time for fuel and air mixing prior to the combustion and therefore a more homogeneous combustion. Nevertheless, major issues still need to be addressed, particularly regarding UHC and CO emissions at low load and particulate/noise combustion trade-off at high load. The purpose of this study is to investigate how an existing modern diesel engine could be operated with low-cetane fuels and define the most appropriate Cetane Number (CN) to reduce engine-out emissions. With this regard, a selection of naphtha and gasoline blends, ranging from CN30/RON 57 to CN35/RON 41 was investigated on a Euro 5, 1.6L four-cylinder engine. Results were compared to the conventional diesel running mode using a minimum NOX level oriented calibration, both in steady state and transient conditions.
Technical Paper

Potential of CN25 Naphtha-Based Fuel to Power Compression Ignition Engines

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOx and particulate emissions when used in Diesel engines. In this context, straight-run naphtha, a refinery stream directly derived from the atmospheric crude oil distillation process, has been identified as a highly valuable fuel. The current study is one step further toward naphtha-based fuel to power compression ignition engines. The potential of a cetane number 25 fuel (CN25), resulting from a blend of hydro-treated straight-run naphtha CN35 with unleaded non-oxygenated gasoline RON91 was assessed. For this purpose, investigations were conducted on multiple fronts, including experimental activities on an injection test bed, in an optically accessible vessel and in a single cylinder engine. CFD simulations were also developed to provide relevant explanations.
Technical Paper

Oxidation Stability of Diesel/Biodiesel Blends: Impact of Fuels Physical-Chemical Properties over Ageing During Storage and Accelerated Oxidation

Current and future engine technologies and fuels are mutually dependent. The increased use of alternative fuels has been linked to deterioration in performance of injectors, fuel filters and engines as a result of insoluble deposit formation. The present work aimed to study the impact of Diesel/biodiesel blends formulation (biodiesel feedstock and content) and temperature on the oxidation stability based on total acid number (TAN). The biofuels used in the fuel matrix were: rapeseed, soy and palm methyl esters (RME, SME and PME respectively). The Diesel/biodiesel blends were made with 0%v/v, 5%v/v, 10% v/v and 20%v/v of biodiesel blended with additive-free new Diesel. The oxidation stability of Diesel/biodiesel blends was to evaluate during 6 months fuels storage, under 20°C and 40°C, and fuels severe oxidation into a reactor vessel to better understand the parameters leading to fuel oxidation on-board.
Technical Paper

Optimal Online Energy Management for Diesel HEV: Robustness to Real Driving Conditions

This paper addresses the robustness of an optimal online energy management for diesel hybrid electric vehicle (HEV). Optimal strategy is based on the Equivalent Consumption Minimization Strategy (ECMS). Optimal torque split between engine and electric motor is found by minimizing fuel consumption and Nitrogen Oxides (NOx) emissions. Online adaptation is made in order to ensure battery charge sustainability and good driveability when driving conditions are unknown. The strategy is tested in simulation over one hundred driving cycles representative of real-world conditions. Results obtained with the online strategy are compared with those of an offline optimal strategy (knowing the driving cycle a priori). Even if a slight degradation is noticed in comparison to optimal case, fuel economy and NOx reduction - provided by hybridization - are conserved with the online strategy.
Journal Article

Optical Investigation of Dual-fuel CNG/Diesel Combustion Strategies to Reduce CO2 Emissions

Dual-fuel combustion strategies combining a premixed charge of natural gas and a pilot injection of diesel fuel offer the potential to reduce CO2 emissions as a result of the high Hydrogen/Carbon (H/C) ratio of methane gas. Moreover, the high octane number of methane means that dual-fuel combustion strategies can be employed on compression ignition engines without the need to vary the engine compression ratio, thereby significantly reducing the cost of engine hardware modifications. The aim of this investigation is to explore the fundamental combustion phenomena occurring when methane is ignited with a pilot injection of diesel fuel. Experiments were performed on a single-cylinder optical research engine which is typical of modern, light-duty diesel engines. A high-speed digital camera recorded time-resolved combustion luminosity and an intensified CCD camera was used for single-cycle OH*chemiluminescence imaging.
Journal Article

On the Effects of EGR on Spark-Ignited Gasoline Combustion at High Load

EGR dilution is a promising way to improve fuel economy of Spark-Ignited (SI) gasoline engines. In particular, at high load, it is very efficient in mitigating knock at low speed and to decrease exhaust temperature at high speed so that fuel enrichment can be avoided. The objective of this paper is to better understand the governing mechanisms implied in EGR-diluted SI combustion at high load. For this purpose, measurements were performed on a modern, single-cylinder GDI engine (high tumble value, multi-hole injector, central position). In addition 0-D and 1-D Chemkin simulations (reactors and flames) were used to complete the engine tests so as to gain a better understanding of the physical mechanisms. EGR benefits were confirmed and characterized at 19 bar IMEP: net ISFC could be reduced by 17% at 1200rpm and by 6% at 5000rpm. At low speed, knock mitigation was the main effect, improving the cycle efficiency by a better combustion phasing.
Technical Paper

Modeling of a Thermal Management Platform of an Automotive D.I Diesel Engine to Predict the Impact of Downsizing and Hybridization during a Cold Start

Thermal management is a key issue to minimize fuel consumption while dealing with pollutant emissions. It paves the way for developing new methods and tools in order to assess the effects of warm up phase with different drivetrains architectures and to define the most suitable solution to manage oil and coolant temperatures. DEVICE (Downsized hybrid Diesel Engine for Very low fuel ConsumptIon and CO2 Emissions) project consists in designing hybrid powertrain to cut off significantly CO2 emissions. It combines a 2-cylinder engine with an electric motor and a 7-gear dual clutch transmission. Hybridization and downsizing offer a great improvement of fuel economy and it is valuable to study their effects on thermal management. Hence, a dedicated AMESim platform is developed to model the fluids temperatures as well as the energy balance changes due to the powertrain architecture.
Technical Paper

Low RON Gasoline Calibration on a Multi-Cylinder Compression Ignition Engine to Fulfill the Euro 6d Regulation

Reducing the CO2 footprint, limiting the pollutant emissions and rebalancing the ongoing shift demand toward middle-distillate fuels are major concerns for vehicle manufacturers and oil refiners. In this context, gasoline-like fuels have been recently identified as good candidates. Straight run naphtha, a refinery stream derived from the atmospheric crude oil distillation process, allows for a reduction of both NOx and particulate emissions when used in compression-ignition engines. CO2 benefits are also expected thanks to naphtha’s higher H/C ratio and energy content compared to diesel. In previous studies, wide ranges of Cetane Number (CN) naphtha fuels have been evaluated and CN 35 naphtha fuel has been selected. The assessment and the choice of the required engine hardware adapted to this fuel, such as the compression ratio, bowl pattern, nozzle design and air-path technology, have been performed on a light-duty single cylinder compression-ignition engine.
Technical Paper

Innovative Approach and Tools to Design Future Two-Wheeler Powertrain

As congestion increases and commute times lengthen with the growing urbanization, many customers will look for effective mobility solutions. Two-wheeler are one of the solutions to deal with these issues, in particular if equipped with electrified powertrains for minimized local noise and air pollutant emissions. Scooters powertrain technology is predominantly based on Spark Ignition Engine (ICE) associated with a Continuously Variable Transmissions (CVT) and a Centrifugal Clutch. Nevertheless, even though CVT gives satisfaction in simplicity, fun to drive, cost effectiveness and vehicle dynamics, its efficiency is an undeniable drawback. Indeed, a conventional CVT is wasting more than 50% of ICE effective power in customer driving conditions. Consequently, those vehicles have high fuel consumption relative to their size, and are equipped with overpowered and heavy internal combustion engines, allowing a large area for further improvements.
Technical Paper

How to Improve Light Duty Diesel Based on Heavy Duty Diesel Thermodynamic Analysis?

The Diesel engine has now become a vital component of the transport sector, in view of its performance in terms of efficiency and therefore CO2 emissions some 25 % less than a traditional gasoline engine, its main competitor. However, the introduction of more and more stringent regulations on engine emissions (NOx, PM) requires complex after-treatment systems and combustion strategies to decrease pollutant emissions (regeneration strategies, injection strategies, …) with some penalty in fuel consumption. It becomes necessary to find new ways to improve the Diesel efficiency in order to maintain its inherent advantage. In the present work, we are looking for strategies and technologies to reduce Diesel engine fuel consumption. Based on the observation that large Diesel engines have a better efficiency than the smaller ones, a detailed thermodynamic combustion analysis of one Heavy Duty (HD) engine and two Passenger car (PC) engines is performed to understand these differences.
Journal Article

HC-SCR on Silver-Based Catalyst: From Synthetic Gas Bench to Real Use

The challenge for decreasing the emissions of compression ignition engines now remains mainly on NOx control. If the Lean NOx Trap (LNT) and Selective Catalytic Reduction by Urea (Urea-SCR) are very efficient, their extra-cost and management are a major issue for the OEMs. In that context, the selective catalytic reduction by hydrocarbons (HC-SCR) appears to be an interesting alternative solution, with a more limited NOx conversion efficiency but an easier packaging (diesel fuel as a reductant) and a limited price (reasonable coating cost / no PGM). In the framework of the RedNOx project, a prototype catalyst made of 2% silver on Alumina coated on cordierite was manufactured and tested on a synthetic gas bench. In parallel, an exhaust implementation study has been led to ensure the most suited conditions for injection. Thanks to SGB and simulation results, adapted engine tests have been designed and performed.
Technical Paper

Exploring and Modeling the Chemical Effect of a Cetane Booster Additive in a Low- Octane Gasoline Fuel

Novel combustion systems such as SACI (Spark Assisted Compression Ignition), GCI (Gasoline compression combustion) or lean combustion concepts are being developed for better performances. These combustion systems share a common objective : control the reactivity in order to have a proper combustion phasing and to lower emissions. Fuel additives have been used for decades to enhance combustion properties. However, their chemical effects is not fully understood especially when considering novel combustion systems. In order to evaluate the additive use approach, this study proposes a 0D simulation regarding the reactivity effect of a widely known diesel additive : 2-ethylhexylnitrate.
Technical Paper

Experimental and Numerical Analysis of Diluted Combustion in a Direct Injection CNG Engine Featuring Post- Euro-VI Fuel Consumption Targets

The present paper is concerned with part of the work performed by Renault, IFPEN and Politecnico di Torino within a research project founded by the European Commission. The project has been focused on the development of a dedicated CNG engine featuring a 25% decrease in fuel consumption with respect to an equivalent Diesel engine with the same performance targets. To that end, different technologies were implemented and optimized in the engine, namely, direct injection, variable valve timing, LP EGR with advanced turbocharging, and diluted combustion. With specific reference to diluted combustion, it is rather well established for gasoline engines whereas it still poses several critical issues for CNG ones, mainly due to the lower exhaust temperatures. Moreover, dilution is accompanied by a decrease in the laminar burning speed of the unburned mixture and this generally leads to a detriment in combustion efficiency and stability.