Search Results

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.

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.

As the late combustion phase in SI engines is of high importance for a further reduction of fuel consumption and especially emissions, the impacts of unburnt mass, located in a small volume with a relatively large surface near the wall and in the top land volume, is of high relevance throughout the range of operation. To investigate and quantify the respective interactions, a state of the art Mercedes-Benz single cylinder research SI-engine was equipped with extensive measurement technology. To detect the axial and radial temperature distribution, several surface thermocouples were applied in two layers around the top land volume. As an additional reference, multiple surface thermocouples in the cylinder head complement the highly dynamic temperature measurements in the boundary zones of the combustion chamber.

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.

State-of-the-art powertrain concepts with automatic transmission must comply with increasingly stringent legislation on emissions and fuel consumption while fulfilling or surpassing customers' expectations as to driveability. In this respect, automated manual transmissions (AMT) and automated shift transmissions (AST) must compete with conventional automatic transmissions (AT) and continuously variable transmissions (CVT). In order to exploit the theoretical advantages of ASTs and put them into practice, complex ECU functions are needed to coordinate engine and transmission. Adaptive control, sophisticated clutch management and an intelligent shifting strategy allow shifting quality and shifting points to be simultaneously optimized to the effect that performance and comfort are increased while fuel consumption is reduced.

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).

The reduction of particulate emissions is one of the most important challenges facing the development of future gasoline engines. Several studies have demonstrated the impact of fuel chemical composition on the emissions of particulate matter, more particularly, the detrimental effect of high boiling point components such as heavy aromatics. Fuel contamination is likely to become a critical issue as new regulations such as Real Driving Emissions RDE involves the use of market fuel. The objective of this study is to investigate several experimental approaches to detect the presence of Diesel contamination in Gasoline which is likely to alter pollutant emissions. To achieve this, a fuel matrix composed of 12 fuels was built presenting diesel fuel in varying concentrations from 0.1 to 2% v/v. The fuel matrix was characterized using several original techniques developed in this study.

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.

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.

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…).

Accurately predicting the future behavior of the surrounding traffic, especially the velocity of the lead vehicle is important for optimizing the energy consumption and improve the safety of Connected and Automated Vehicles (CAVs). Several studies report methods to predict short-to-mid-length lead vehicle velocity using stochastic models or other data-driven techniques, which require availability of extensive data and/or Vehicle-to-Vehicle (V2V) communication. In the absence of connectivity, or in data-restricted cases, the prediction must rely only on the measured position and relative velocity of the lead vehicle at the current time. This paper proposes two velocity predictors to predict short-to-mid-length lead vehicle velocity. The first predictor is based on a Constant Acceleration (CA) with an augmented stop mode. The second one is based on a modified Enhanced Driver Model (EDM-LOS) with line-of-sight feature.

Under the persistent pressure to further reduce fuel consumption worldwide, it is necessary to advance the processes that influence the efficiency of gasoline engines. In doing so, harnessing the entire potential of fully variable mechanical valve trains will involve targeting efforts on optimizing all design parameters. A new type of valve timing system is used to portray thermodynamic and mechanical as well as electronic aspects of developing fully variable mechanical valve timing and lift systems

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.

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.

Global warming is a climate phenomenon with world-wide ecological, economic and social impact which calls for strong measures in reducing automotive fuel consumption and thus CO2 emissions. In this regard, turbocharging and the associated designing of the air path of the engine are key technologies in elaborating more efficient and downsized engines. Engine performance simulation or development, parameterization and testing of model-based air path control strategies require adequate performance maps characterizing the working behavior of turbochargers. The working behavior is typically identified on test rig which is expensive in terms of costs and time required. Hence, the objective of the research project “virtual Exhaust Gas Turbocharger” (vEGTC) is an alternative approach which considers a physical modeled vEGTC to allow a founded prediction of efficiency, pressure rise as well as pressure losses of an arbitrary turbocharger with known geometry.

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.

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.

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.

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.

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.