Search Results

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.

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).

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).

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.

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.

The modeling of thermal phenomena in transient state in a vehicle, typically the studies of heat exchanges in the engine or the heat exchange in the exhaust line leads to the use of nodal methods or lumped parameters in systems approach. This lumped parameters vision has led to important formalization studies these past years leading to two important concepts: the multiport concept of which bond-graphs constitute the theoretical framework, and the polymorphic modeling concept leading to the definition of a minimum of basic elements allowing to build a maximum of situations. This article proposes to demonstrate how these concepts have been used to bring about the development of a library of basic elements. Its application is demonstrated by the modeling of the different modules composing the engine (lubrication, cooling, exhaust and metal masses).

The combination of air charging and downsizing is known to be an efficient solution to reduce CO2 emissions of modern gasoline engines. The decrease of the cubic capacity and the increase of the specific performance help to reduce the fuel consumption by limiting pumping and friction losses and even the losses of energy by heat transfer. Investigations have been conducted on a highly downsized SI engine to confirm if a strong decrease of the displacement (50 %) was still interesting regarding the fuel consumption reduction and if other ways were possible to improve further more its efficiency. The first aim of our work was to identify the optimal design (bore, stroke, displacement, …) that could maximize the consumption reduction potential at part load but also improve the engine's behaviour at very high load (up to 3.0 MPa IMEP from 1000 rpm). In order to do that, four engine configurations with different strokes and bores have been tested and compared.

The authors present the supervisory control of a parallel hybrid powertrain, focusing on several issues related to the real-time implementation of optimal control based techniques, such as the Equivalent Consumption Minimization Strategies (ECMS). Real-time implementation is introduced as an intermediate step of a complete chain of tools aimed at investigating the supervisory control problem. These tools comprise an offline optimizer based on Pontryagin Minimum Principle (PMP), a two-layer real-time control structure, and a modular engine-in-the-loop test bench. Control results are presented for a regulatory drive cycle with the aim of illustrating the benefits of optimal control in terms of fuel economy, the role of the optimization constraints dictated by drivability requirements, and the effectiveness of the feedback rule proposed for the adaptation of the equivalence factor (Lagrange multiplier).

In the whole engine development process, 0D/1D simulation has become a powerful tool, from conception to final calibration. Within the context of control strategy design, a turbocharged spark ignition (SI) engine with variable camshaft timing has been modelled on the AMESim platform. This paper presents the different models and the methodology used to design, calibrate and validate the simulator. The validated engine model is then used for engine control purposes related to downsizing concept. Indeed, the presented control strategy acts on the in-cylinder trapped mass, the in-cylinder burnt gas fraction and the air scavenging from the intake to the exhaust. Consequently, it permits to reduce not only the fuel consumption and pollutant emissions but also to improve the transient response of the turbocharger

While fuel efficiency has to be improved, future Diesel engine emission standards will further restrict vehicle emissions, particularly of nitrogen oxides. Increased in-cylinder filling is recognized as a key factor in addressing this issue, which calls for advanced design of air and exhaust gas recirculation circuits and high cooling capabilities. As one possible solution, this paper presents a 2-stage boosting breathing architecture, specially dedicated to improving the trade-off between emissions and fuel consumption instead of seeking to improve specific power on a large family vehicle equipped with a 1.6-liter Diesel engine. In order to do it, turbocharger matching was specifically optimized to minimize engine-out NOx emissions at part-load and consumption under common driving conditions. Engine speed and load were analyzed on the European driving cycle. The key operating points and associated upper boundary for NOx emission were identified.

The purpose of the 4-SPACE (4-Stroke Powered gasoline Auto-ignition Controlled combustion Engine) industrial research project is to research and develop an innovative controlled auto-ignition combustion process for lean burn automotive gasoline 4-stroke engines application. The engine concepts to be developed could have the potential to replace the existing stoichiometric / 3-way catalyst automotive spark ignition 4-stroke engines by offering the potential to meet the most stringent EURO 4 emissions limits in the year 2005 without requiring DeNOx catalyst technology. A reduction of fuel consumption and therefore of corresponding CO2 emissions of 15 to 20% in average urban conditions of use, is expected for the « 4-SPACE » lean burn 4-stroke engine with additional reduction of CO emissions.

In the context of CO₂ emission regulations and increase of energy prices, the downsizing of engine displacement is a widely discussed solution that allows a reduction of fuel consumption. However, high power density is required in order to maintain the power output and a good driveability. This study demonstrates the potential to strongly increase the specific power of High Speed Diesel Injection (HSDI) diesel engines. It includes the technological requirements to achieve high specific power and the optimal combination of engine settings to maximize specific power. The results are based on experimental work performed with a prototype single-cylinder engine (compression ratio of 14). Tests were conducted at full load, 4000 rpm. Part load requirements are also taken into account in the engine definition to be compatible with the targets of new emission standards.

Latest emissions standards impose very low NOx and particle emissions that have led to new Diesel combustion operating conditions, such as low temperature combustion (LTC). The principle of LTC is based on enhancing air fuel mixing and reducing combustion temperature, reducing raw nitrogen oxides (NOx) and particle emissions. However, new difficulties have arisen. LTC is typically achieved through high dilution rates and low CR, resulting in increased auto-ignition delay that produces significant noise and deteriorates the combustion phasing. At the same time, lower combustion temperature and reduced oxygen concentration increases hydrocarbon (HC) and carbon oxide (CO) emissions, which can be problematic at low load. Therefore, if LTC is a promising solution to meet future emission regulations, it imposes a new emissions, fuel consumption and noise trade-off. For this, the injection strategy is the most direct mean of controlling the heat release profile and fuel air mixture.

Facing the CO2 emission reduction challenge, the combination of downsizing and turbocharging appears as one of the most promising solution for the development of high efficiency gasoline engines. In this context, as knock resistance is a major issue, limiting the performances of turbocharged downsized gasoline engines, fuel properties are more than ever key parameters to achieve high performances and low fuel consumption's levels. This paper presents a combustion study carried out into the GSM consortium of fuel quality effects on the performances of a downsized turbocharged Direct Injection SI engine. The formulation of two adapted fuel matrix has allowed to separate and evaluate the impacts of three major fuel properties: Research Octane Number (RON), Motor Octane Number (MON) and Latent Heat of Vaporization (LHV). Engine tests were performed on a single cylinder engine at steady state operating condition.

Diesel particulate filter (DPF) technology is becoming increasingly established as a practical method for control of particulate emissions from diesel engines. In the year 2000, production vehicles with DPF systems, using metallic fuel additive to assist regeneration, became available in Europe. These early examples of first generation DPF technology are forerunners of more advanced systems likely to be needed by many light-duty vehicles to meet Euro IV emissions legislation scheduled for 2005. Aspects requiring attention in second generation DPF systems are a compromise between regeneration kinetics and ash accumulation. The DPF regeneration event is activated by fuel injection, either late in the combustion cycle (late injection), or after normal combustion (post injection), leading to increased fuel consumption. Therefore for optimum fuel economy, the duration of regeneration and/or the soot ignition temperature must be minimised.

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures, and hence the measurement of the performance maps of both compressor and turbine. Automotive manufacturers use mainly numerical simulations for internal combustion engines simulations, hence the need of an accurate extrapolation model to get a complete turbine performance map. These complete maps are then used for internal combustion engines calibration. Automotive manufacturers use commercial softwares to extrapolate the turbine narrow performance maps, both mass flow characteristics and the efficiency curve.

The energy management of a hybrid vehicle defines the vehicle power flow that minimizes fuel consumption and exhaust emissions. In a combined hybrid the complex architecture requires a multi-input control from the energy management. A classic optimal control obtained with dynamic programming shows that thanks to the high efficiency hybrid electric variable transmission, energy losses come mainly from the internal combustion engine. This paper therefore proposes a sub-optimal control based on the maximization of the engine efficiency that avoids multi-input control. This strategy achieves two aims: enhanced performances in terms of fuel economy and a reduction of computational time.

Due to their high thermal efficiency coupled with low CO2 emissions, Diesel engines are promised to an increasing part of the transport market if their NOx and particulate emissions are reduced. Today, adequate after-treatments, NOx and PM traps are under industrialization with still concerns about fuel economy, robustness, sensitivity to fuel sulfur and cost because of their complex and sophisticated strategy. New combustion process such as Homogeneous Charge Compression Ignition (HCCI) are investigated for their potential to achieve near zero particulate and NOx emissions. Their main drawbacks are too high hydrocarbons (HC) and carbon monoxide (CO) emissions, combustion control at high load and then limited operating range and power output. As an answer for challenges the Diesel engine is facing, IFP has developed a combustion system able to reach near zero particulate and NOx emissions while maintaining performance standards of the D.I Diesel engines.

Recent developments on highly downsized spark ignition engines have been focused on knocking behaviour improvement and the most advanced technologies combination can face up to 2.5 MPa IMEP while maintaining acceptable fuel consumption. Unfortunately, knocking is not the only limit that strongly downsized engines have to confront. The improvement of low-end torque is limited by another abnormal combustion which appears as a random pre-ignition. This violent phenomenon which emits a sharp metallic noise is unacceptable even on modern supercharged gasoline engines because of the great pressure rise that it causes in the cylinder (up to 20 MPa). The phases of this abnormal combustion have been analysed and a global mechanism has been identified consisting of a local ignition before the spark, followed by a propagating phase and ended by a massive auto-ignition. This last step finally causes a steep pressure rise and pressure oscillations.