Search Results

This paper presents the major results of an International Consortium study carried out by IFP and focused on the evaluation of fuel impacts on Controlled Auto Ignition (CAI) combustion. The formulation and tests of two adapted fuel matrix have allowed identifying and evaluating the main fuel properties that can improve CAI combustion for a maximum enlargement of the CAI operating range. CAI combustion mode appears as one promising solution for the development of low CO2 gasoline engines. Fuel properties can then be key parameters to improve the performances of CAI engines. During a first step of the study, steady state tests have been performed on a single cylinder Port Fuel Injection Spark Ignition (PFI SI) engine, with real fuels.

In former high compression ratio Diesel engines a single injection was used to introduce the fuel into the combustion chamber. With actual direct injection engines which exhibit a compression ratio between 17:1 and 18:1 single or multiple early injections called “pilot injections” are also added in order to reduce the combustion noise. For after-treatment reasons a late injection during the expansion stroke named “post injection” may also be used in some operating conditions. Investigations have been conducted on lower compression ratio Diesel engine and in high EGR rate operating conditions to evaluate the benefits of multiple injection strategies to improve the trade off between engine emissions, noise and fuel economy.

In nowadays diesel engine, the turbocharger system plays a very important role in the engine functioning and any loss of the turbine efficiency can lead to driveability problems and the increment of emissions. In this paper, a VGT turbocharger fault detection system is proposed. The method is based on a physical model of the turbocharger and includes an estimation of the turbine efficiency by a nonlinear adaptive observer. A sensitivity analysis is provided in order to evaluate the impact of different sensors fault, (drift and bias), used to feed the observer, on the estimation of turbine efficiency error. By the means of this analysis a robust variable threshold is provided in order to reduce false detection alarm. Simulation results, based on co-simulation professional platform (AMEsim© and Simulink©), are provided to validate the strategy.

Tracer laser induced fluorescence (LIF) imaging of piston-top fuel films has been performed within the combustion chamber of an optically-accessible, single cylinder Diesel engine. The first objective of the study was to adapt the tracer LIF technique so as to perform in-cylinder imaging of the fuel films under reacting (i.e. combustion) conditions. The results obtained in a wall-guided, combustion chamber operating under highly dilute, Diesel low temperature combustion (LTC) conditions reveal the significant presence of late-cycle piston-top fuel films. Furthermore, it is believed that these fuel films contribute to engine-out hydrocarbon (HC) emissions via a mechanism of flash boiling. An attempt was also made to evaluate the role of fuel volatility on fuel film lifetimes. This was achieved by using a 50/50 fuel mixture of two single component fuels whose boiling points correspond to moderately high and low volatility components of standard Diesel fuel.

In order to address the CO₂ emissions issue and to diversify the energy for transportation, CNG (Compressed Natural Gas) is considered as one of the most promising alternative fuels given its high octane number. However, gaseous injection decreases volumetric efficiency, impacting directly the maximal torque through a reduction of the cylinder fill-up. To overcome this drawback, both independent natural gas and gasoline indirect injection systems with dedicated engine control were fitted on a RENAULT 2.0L turbocharged SI (Spark Ignition) engine and were adapted for simultaneous operation. The main objective of this innovative combination of gas and liquid fuel injections is to increase the volumetric efficiency without losing the high knocking resistance of methane.

The reduction of NOx emissions required by the future Euro 6 standards leads engine manufacturers to develop Diesel Homogeneous Charge Compression Ignition (HCCI) combustion processes. Because this concept allows reducing both NOx and particulates simultaneously, it appears as a promising way to meet the next environmental challenges. Unfortunately, HCCI combustion often increases CO and HC emissions. Conventional oxidation catalyst technologies, currently used for Euro 4 vehicles, may not be able to convert these emissions because of the saturation of active catalytic sites. As a result, such increased CO and HC emissions have to be reduced under standard levels using innovative catalysts or emergent technologies. The work reported in this paper has been conducted within the framework of the PAGODE project (PSA, IFP, Chalmers University, APTL, CRF, Johnson Matthey and Supelec) and financed by the European Commission.

The purpose of the ELEVATE (European Low Emission V4 Automotive Two-stroke Engine) industrial research project is to develop a small, compact, light weight, high torque and highly efficient clean gasoline 2-stroke engine of 120 kW which could industrially replace the relatively big existing automotive spark ignition or diesel 4-stroke engine used in the top of the mid size or in the large size vehicles, including the minivan vehicles used for multi people and family transportation. This new gasoline direct injection engine concept is based on the combined implementation on a 4-stroke bottom end of several 2-stroke engine innovative technologies such as the IAPAC compressed air assisted direct fuel injection, the CAI (Controlled Auto-Ignition) combustion process, the D2SC (Dual Delivery Screw SuperCharger) for both low pressure engine scavenging and higher pressure IAPAC air assisted DI and the ETV (Exhaust charge Trapping Valve).

Low temperature combustion concept as HCCI is one of the most promising research ways to comply future emission regulations of Diesel passenger vehicles. IFP promoted this concept with NADI™ (Narrow Angle Direct Injection) combustion design whose original approach lies on a fuel spray guided by the bowl central tip to the re-entrant. For full load operating range, one of the key issue for success is to use as much as possible available air in the combustion chamber in order to reach low value of air fuel ratio, and therefore high value of specific power and specific torque. In this study, engine tests on a single cylinder engine with NADI™ concept are performed at full load; 3-D calculations as well as air/fuel mixing process visualizations in a constant volume vessel with optical access allowed to establish criteria for helping future combustion system design for full load operation.

The mixing and combustion processes of short double Diesel injections are investigated by optical diagnostics. A single hole Common Rail Diesel injector allowing high injection pressure up to 120MPa is used. The spray is observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. Three configurations are studied: a single short injection serving as a reference case and two double short injections with short and long dwell time (time between the injections). Several optical diagnostics were performed successively. The mixing process is studied by normalized Laser Induced Exciplex Fluorescence giving access to the vapor fuel concentration fields. In addition, the flow fields both inside and outside the jets are characterized by Particle Imaging Velocimetry.

A tracer laser-induced fluorescence (LIF) technique for the visualisation of fuel distribution in the presence of oxygen was developed and then used sequentially with high speed chemiluminescence imaging to study the correlation between the mixing and auto-ignition processes of high pressure Diesel jets. A single hole common rail Diesel injector allowing high injection pressures up to 150MPa was used. The reacting fuel spray was observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. Both free jet and flat wall impinging jet configurations were studied. Several tracers were first considered with the objective of developing a tracer-LIF technique in the presence of oxygen. 5-nonanone was selected for its higher fluorescence efficiency.

The air entrainment of multi-hole diesel injection is investigated by high speed Particle Image Velocimetry (PIV) using a multi-hole common rail injector with an injection pressure of 100 MPa. The sprays are observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a diesel engine during injection. Typical ambient temperature of 800K and ambient density of 25 kg/m3 are chosen. The air entrainment is studied with the PIV technique, giving access to the velocity fields in the surrounding air and/or in the interior of two neighboring jets. High acquisition rate of 5000 Hz, corresponding to 200 μs between two consecutive image pairs is obtained by a high-speed camera coupled with a high-speed Nd:YLF laser. The effect of neighboring jets interaction is studied by comparing four injectors with different numbers of holes (4, 6, 8 and 12) with similar static mass flow rate per hole.

The reduction of particulate emissions from Diesel engines is a key issue to meet future emission standards. Particulate traps represent an attractive solution to the problem of this source of pollution. However, they have the disadvantage of requiring periodic and safe regeneration to release exhaust back pressure and to recover filtration efficiency. Natural regeneration of the particulate filter may occur. Nevertheless, with light-duty vehicles and their low level of exhaust gas temperature, it may be necessary to facilitate or force the regeneration. The objective of this work is to give an overview of the possibilities offered by the engine management system to increase significantly exhaust gas temperatures. Thus, different engine tunes, through injection timing, boost pressure or EGR rate, may be sufficient to ensure safe regeneration of the trap.

In the context of modern engine control, one important variable is the individual Air Fuel Ratio (AFR) which is a good representation of the produced torque. It results from various inputs such as injected quantities, boost pressure, and the exhaust gas recirculation (EGR) rate. Further, for forthcoming HCCI engines and regeneration filters (Particulate filters, DeNOx), even slight AFR unbalance between the cylinders can have dramatic consequences and induce important noise, possible stall and higher emissions. Classically, in Spark Ignition engine, overall AFR is directly controlled with the injection system. In this approach, all cylinders share the same closed-loop input signal based on the single λ-sensor (normalized Fuel-Air Ratio measurement, it can be rewritten with AFR as they have the same injection set-point.

Lean-burn combustion in SI engines can significantly reduce fuel consumption but NOx reduction becomes challenging because classic three-way catalyst (TWC) is no more efficient. Urea-SCR is then an interesting alternative solution because of its high NOx conversion efficiency without any additional fuel consumption. The coupling between two SI lean-burn engines (stratified and homogeneous combustion) and a urea-SCR catalyst was simulated on the NEDC cycle. Simulation results showed that the SCR efficiency would comply with the limits required by future Euro 5/6 regulations. Associated urea solution consumptions were estimated thanks to a simplified model. Finally, a comparison with a Diesel application was also made. It showed that the required amount of reducing agent remained significantly higher for SI lean-burn engines than for Diesel engine.

Environment protection issues regarding CO2 emissions as well as customers requirements for fun-to-drive and fuel economy explain the strong increase of Diesel engine on European market share in all passenger car segments. To comply future purposes of emission regulations, particularly dramatic decrease in NOx emissions, technology need to keep upgrading; the reduction of the volumetric compression ratio (VCR) is one of the most promising research ways to allow a simultaneous increase in power at full load and NOx / PM trade-off improvement at part load. This study describes the combustion effects of the reduction of compression ratio and quantifies improvements obtained at full load and part load running conditions on a HSDI Common Rail engine out performance (power, fuel consumption, emissions and noise). Potential and limitations of a reduced compression ratio from 18:1 to 14:1 are underlined.

Among the existing concepts that help to improve the efficiency of spark-ignition engines at part load, Controlled Auto-Ignition™ (CAI™) is an effective way to lower both fuel consumption and pollutant emissions. This combustion concept is based on the auto-ignition of an air-fuel-mixture highly diluted with hot burnt gases to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. To minimize the costs of conversion of a standard spark-ignition engine into a CAI engine, the present study is restricted to a Port Fuel Injection engine with a cam-profile switching system and a cam phaser on both intake and exhaust sides. In a 4-stroke engine, a large amount of burnt gases can be trapped in the cylinder via early closure of the exhaust valves. This so-called Negative Valve Overlap (NVO) strategy has a key parameter to control the amount of trapped burnt gases and consequently the combustion: the exhaust valve-lift profile.

The purpose of the European « SPACE LIGHT » (Whole SPACE combustion for LIGHT duty diesel vehicles) 3-year project launched in 2001 is to research and develop an innovative Homogeneous internal mixture Charged Compression Ignition (HCCI) for passenger cars diesel engine where the combustion process can take place simultaneously in the whole SPACE of the combustion chamber while providing almost no NOx and particulates emissions. This paper presents the whole project with the main R&D tasks necessary to comply with the industrial and technical objectives of the project. The research approach adopted is briefly described. It is then followed by a detailed description of the most recent progress achieved during the tasks recently undertaken. The methodology adopted starts from the research study of the in-cylinder combustion specifications necessary to achieve HCCI combustion from experimental single cylinder engines testing in premixed charged conditions.

Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have explored development issues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by the French Ministry of Industry, IFP, PSA-Peugeot-Citroën, Renault and RVI (Renault Véhicules Industriels), has been built to study this point. It is based on a three years program with different steps focused on new engine technologies which will be available in the next 20 years in order to answer to more and more severe pollutant and CO2 emission regulations. This program is divided into three main parts: the first one for Diesel car engines, the second for Diesel truck engines and the third for spark ignition engines.

Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have been exploring development avenues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by FSH (Fonds de Soutien aux Hydrocarbures), IFP, PSA-Peugeot-Citroën, Renault and Renault VI (Véhicules Industriels), has been built to study this point. It is a four years programme with different steps which will focus on new engine technologies: some of them are going to be marketed very soon (gasoline direct injection car engine, and diesel common rail injection car and truck engines) to anticipate the Euro 3 (2000) and the Euro 4 (2005) emissions specifications. The original work reported here is part of this research.

Engine downsizing is one of the most promising engine solutions to improve efficiency, but requires higher specific performance because of a lower engine displacement. The study is based on experimental work performed with an IFP prototype single cylinder engine, representative of passenger car applications. This engine enables very high specific power, with a high level of thermal and mechanical constraints. Tests were carried out on both full load and part load operation with a prototype common rail equipment capable of very high fuel pressure (up to 250 MPa). Results show that increasing fuel flow rate using fuel injection pressure instead of increasing nozzle hole diameter is more advantageous at full load, mainly because a lower nozzle hole diameter improves air entrainment. Benefits observed with increased injection pressure are enhanced when associated with upgraded engine thermo-mechanical limits, and advanced turbo charging system.