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In automotive NVH, the noise generated by a powertrain is still one of the major noise sources especially at low and mid vehicle velocity. For this reason automotive OEMs are continuously focusing on methods to efficiently analyze this noise source. For this purpose, a well-established simulation methodology can provide results thoroughly, within a limited amount of time and with a reduced cost contrary to experiments which are involved in late design phases and are more expensive. This paper aims at presenting an approach to simulate efficiently the acoustic radiation from automotive components. With this aim in mind, the acoustic response of a realistic powertrain unit subjected to working conditions ranging from 1000 RPM to 4500 RPM is studied until 3000 Hz. Several radiating boundary conditions will be assessed in order to detect the most efficient set-up for this kind of problem and to extract the optimized modeling guidelines.

Nowadays, the interior vehicle noise due to the exterior aerodynamic field is an emerging topic in the acoustic design of a car. In particular, the turbulent aerodynamic pressure generated by the air flow encountering the windshield and the side windows represents an important interior noise source. As a consequence PSA Peugeot Citroën is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. In the past, several joint studies have been led by PSA and Free Field Technologies on this topic. In those studies an efficient methodology to predict the noise transmission through the side window has been set up. It relies on a two steps approach: the first step involves the computation of the exterior turbulent field using an unsteady CFD solver (in this case EXA PowerFlow).

Diesel spray experimentation at controlled high-temperature and high-pressure conditions is intended to provide a more fundamental understanding of diesel combustion than can be achieved in engine experiments. This level of understanding is needed to develop the high-fidelity multi-scale CFD models that will be used to optimize future engine designs. Several spray chamber facilities capable of high-temperature, high-pressure conditions typical of engine combustion have been developed, but because of the uniqueness of each facility, there are uncertainties about their operation. For this paper, we describe results from comparative studies using constant-volume vessels at Sandia National Laboratories and IFP.

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.

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.

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 simultaneous reduction of engine-out nitrogen oxide (NOx) and particulate emissions via low-temperature combustion (LTC) strategies for compression-ignition engines is generally achieved via the use of high levels of exhaust gas recirculation (EGR). High EGR rates not only result in a drastic reduction of combustion temperatures to mitigate thermal NOx formation but also increases the level of pre-mixing thereby limiting particulate (soot) formation. However, highly pre-mixed combustion strategies such as LTC are usually limited at higher loads by excessively high heat release rates leading to unacceptable levels of combustion noise and particulate emissions. Further increasing the level of charge dilution (via EGR) can help to reduce combustion noise but maximum EGR rates are ultimately restricted by turbocharger and EGR path technologies.

Single cylinder optical engines are used for internal combustion (IC) engine research as they allow for the application of qualitative and quantitative non-intrusive, diagnostic techniques to study in-cylinder flow, mixing, combustion and emissions phenomena. Such experimental data is not only important for the validation of computational models but can also provide a detailed insight into the physical processes occurring in-cylinder which is useful for the further development of new combustion strategies such as gasoline homogeneous charge compression ignition (HCCI) and Diesel low temperature combustion (LTC). In this context, it is therefore important to ensure that the performance of optical engines is comparable to standard all-metal engines. A comparison of optical and all-metal engine combustion and emissions performance was performed within the present study.

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).

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.

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.

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.

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 paper discusses different alternative choices regarding the simulation and control of combined hybrid vehicles with a simple or compound power split device (PSD). These choices concern the causal representation of PSD both in a vehicle model and in the supervisory controller, the structure of the supervisory controller, and the pathway to generate the setpoints to the component-level controllers. Quasistatic and high-frequency simulations provide the example applications to assess the competing approaches.

A gasoline direct injection engine was operated at elevated EGR levels over a significant portion of the performance map. The engine was modified to use both cooled and un-cooled EGR in high pressure loop and low pressure loop configurations. The addition of EGR at low and part load was shown to decrease NO and CO emissions and to reduce fuel consumption by up to 4%, primarily through the reduction in pumping losses. At high loads, the addition of EGR resulted in higher fuel consumption benefits of 10-20% as well as the expected NO and CO reductions. The fuel economy benefit at high loads resulted from a decrease in knock tendency and a subsequent improvement in combustion phasing as well as reductions in exhaust temperatures that eliminated the requirement for over-fuelling.

The production of vehicles with low noise and vibration level at low costs has been one of the main targets of the automobilist industry. The noise level heard by the passengers inside the vehicle influences directly on the perception they have about the car. On the other hand, low prices are extremely necessary to keep the projects competitive on the sales market. This job analyses the impact caused over the noise heard inside the vehicle when a change was applied on the design of the halfshaft: the substitution of a tubular shaft by a barshaft. The main goal of this design change is the cost reduction.

Facing the stringent constraints on fuel consumption and pollutant emissions, the automotive manufacturers have to produce vehicles with an increasing number of complex systems working together. Numerical simulation for the system design, set-up and control strategies, helps to reduce the development cycle and the global cost. Existing simulation tools usually do not address, with a high level of details, the various physical domains involved in a vehicle powertrain. To overcome this challenge, IFP and IMAGINE, settled a partnership to develop detailed simulation tools dedicated to performance, consumption and emissions for conventional and hybrid vehicles [1]. These tools are integrated in a multi-domain simulation platform (AMESim®) where several levels of detail can be easily reached for each sub-element.

A lumping model has been formulated to calculate the thermodynamic properties required for internal combustion engine multidimensional computations, including saturation pressure, latent heat of vaporization, liquid density, surface tension, viscosity, etc. This model consists firstly in reducing the analytical data to a single (i.e. pure) pseudo-component characterized by its molecular weight, critical pressure and temperature, and acentric factor. For a gasoline fuel, the required analytical data are those provided by gas chromatography. For a Diesel fuel, the required data are a true boiling point (TBP) distillation curve and the fuel density at a single temperature. This model provides a valuable tool for studying the effects of fuel physical properties upon the behavior of a vaporizing spray in a chamber, as well as upon direct injection gasoline and Diesel engines using the multidimensional (3D) KMB code.

Quantitative fuel concentration visualizations are carried out to study the mixing process between fuel and air in Direct Injection (DI) Diesel like conditions, and generate high quality data for the validation of mixing models. In order to avoid the particular complication connected with fuel droplets, a gaseous fuel jet is investigated. Measurements are performed in a high-pressure chamber that can provide conditions similar to those in a diesel engine. A gas injection system able to perform injections in a high-pressure chamber with a good control of the boundary conditions is chosen and characterized. Mass flow rates typical of DI Diesel injection are reproduced. A Laser Induced Fluorescence technique requiring the mixing at high pressure of the fluorescent tracer, biacetyl, with the gaseous fuel, methane, is developed. This experimental technique is able to provide quantitative measurement of fuel concentration in high-pressure jets.

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.