Xavier Tauzia

Performance Simulation of Sequentially Turbocharged Marine Diesel Engines With Applications to Compressor Surge

This paper presents the SELENDIA code designed for the simulation of marine diesel engines. Various measured and simulated results are compared for the performance of a sequentially turbocharged marine diesel engine during a switch from one to two turbochargers. The results show a good agreement between measured and simulated data. Surge loops that are experimentally observed in case of an anomaly are analyzed using simulated results, Finally, the predictive capabilities of the simulation code are utilized to investigate the influence of the inlet manifold volume on the engine and air charging system performance with a special focus on compressor surge.

Measurement and Simulation of Instantaneous Emissions of a Heavy Truck Diesel Engine During Transients

During the last decades, pollutant emissions from internal combustion engines used for transportation have become a major concern. Today, not only steady state emissions but also emissions during transients are regulated and have to be studied in order to be reduced. In this paper, we describe a new methodology developed to measure the instantaneous level of gaseous emissions from a internal combustion engine during transients, using an analyzer initially designed for steady state operation. Moreover, a new phenomenological thermodynamical combustion model is proposed in order to compute emissions during transients. The results of these two methods are compared on various transients. The measurement method seems to give good results (except for hydrocarbon (HC) measurements), as long as the speed and load variations are not too fast. Otherwise, the frequency of the analyzer which was used becomes the limiting factor. The new combustion heat release developed to simulate transients, coupled with an existing two-zone model for emission calculations, leads to satisfactory results for CO 2 and O 2 concentrations and NO x emissions. The agreement with measurements is good for smooth transients and seems promising for faster dynamics. The initial goal was reached, although some improvements are still necessary concerning HC measurements and the fastest transients. These results could be helpful when trying to reduce the amount of pollutant emissions at the exhaust during transients, directly or with after treatment devices.

Inflow boundary condition for one-dimensional gas dynamics simulation code of internal combustion engine manifolds

Abstract The modelling of pressure wave propagation into internal combustion engine manifolds implies the knowledge of multi-dimensional phenomena. However, computational times can be very important and this complex system requires reducing the order of the models. In the current paper, a new one-dimensional modelling of the inflow boundary conditions for a plain open end is proposed. This is obtained with the use of a computational fluid dynamics code and an experimental test bench under unsteady state conditions. Numerical and experimental analyses show that the pressure losses can be modelled with a coefficient that depends on the Mach number as well as geometrical parameters. Finally, numerical results are compared with experimental data in a shock tube application with an intake manifold of internal combustion engine. The code enhancements significantly improve flow calculations.

Some Basic Elements to Achieve a Future 1D Simulation of Wave Propagation in I.C.E. Pipes

The assumption of one-dimensional unsteady flows in the inlet and exhaust systems of turbocharged diesel engines is widely used although multi-dimensional simulations using fluid dynamics are also possible. However, difficulties persist concerning the boundary conditions, particularly at the pipe ends (inflow or outflow) and at the intra-pipe boundary conditions (sudden or gradual area changes, bends, junctions, etc.). This paper focuses on the two first steps leading to a 1D flow simulation code: the selection of a numerical scheme and the study of an open end boundary condition. The first section compares several numerical algorithms, including Lax-Wendoff, Flux-Corrected-Transport methods (FCT), and Harten-Lax-Leer (Riemann solver), extended to the second order. The selection criterion is the best compromise between numerical instabilities and computational time. A numerical study using the Fluent CFD code is then presented on a constant area duct in order to determine some characteristics at the pipe end, specifically the dead zone length and the throat area. Finally, a model parameterized by the pressure ratio between inlet and outlet is proposed.Copyright

Influence des circuits de liaison moteur/compresseur sur le fonctionnement des moteurs Diesel à suralimentation bi-étagée

In pulsed flow, the surge line of a centrifugal compressor is highly dependent on the upstream and downstream piping systems. In this study, the shift of this surge line in the case of two two-stage turbocharged marine Diesel engines is calculated using a numerical simulation of the compressor/pipe work assembly for each engine. The linkage of two programs using the ACSL language (in a global solution procedure) allows the understanding and quantification of the connection circuits influence on the operating limits. The tendencies observed on the test bed are reproduced by the simulation, confirming the chosen methodology. This procedure also permits an analysis and understanding of the observed phenomena, especially the identification of the compressor which initiated the surge effects and the explanation of irregularities in the operating limit.

Experimental analysis of the influence of coolant and oil temperature on combustion and emissions in an automotive diesel engine

Since many trips are of short duration and include a cold start, automotive engines run quite often without having reached their nominal temperature. This is known to have some major drawbacks, such as increased fuel consumption and higher emissions due to lower efficiency of after-treatment devices, but detailed description of these various effects is seldom presented in the literature. In this article, experiments were conducted on an automotive diesel engine by varying independently the coolant and oil temperatures between 30 °C and 90 °C. Three different operating conditions (low, mid and full load) were studied. The experimental set-up is briefly described as well as the uncertainty of the associated measurements and the development of analytic tools. Then, the evolution of volumetric efficiency, energy share, combustion heat release and exhaust emissions (NOx, particulate matter, CO, unburned hydrocarbons) are described in detail and analysed. Several strategies were considered, including some corrections used in the standard engine control unit to compensate for the low coolant temperature. Some effects of the coolant and oil temperature reduction were clear: increase in friction losses, volumetric efficiency and ignition delay and decrease in NOx emissions. On the contrary, the evolution of brake thermal efficiency, particulate matter, CO and unburned hydrocarbon emission depended on the operating point.

An investigation of instability in a domestic gas boiler by simulation

Abstract The experimental investigation of a domestic gas boiler revealed an unstable operation mode under certain circumstances and geometry. This paper presents the development, validation, and analysis of the modelling of a complete sealed gas boiler. The modelling uses a non-dimensional/one-dimensional non-linear solution of the mass, momentum, and energy conservation equations. The sealed vessel is divided into three zones separated by the burner and the heat exchanger. A special focus is placed on the burner which was determined to play a major role in the occurrence of instabilities. The comparison between measured and simulated results shows a good agreement at steady state. The investigation of unstable configurations reveals the ability of the simulation model to locate unstable zones in a qualitative manner and provides the influence of the control parameters over the systems stability. An attempt is made at explaining the differences observed in the quantitative results. Finally, a few potential solutions to prevent or reduce unstable zones are evaluated with the simulation model.

Experimental Method for the Determination of Instantaneous Diesel Engine Pollutant Emissions During Transients

This paper presents a method to estimate instantaneous diesel engine emissions during transients using analytical means usually adopted for steady state investigations. The initial emphasis is on the inability of the conventional analysis systems to directly provide instantaneous levels of gaseous emissions during transients. In the ensuing section, a signal reconstruction technique used to rebuild instantaneous pollutant emissions at the engine exhaust is described. This reconstruction is based on a transfer function, which is the ratio of known measured and applied pollution signals. As a validation of this technique, the inversion of the transfer function is then applied to measurements obtained during basic tests consisting of steps and ramps. Finally, a method for estimating diesel particulates during transients through a correlation established from the measurements of carbon monoxide and smoke opacity is presented.Copyright

MÉRIMÉE: A Simulation Software to Study Diesel Engines Used for Military Propulsion

The design and development of internal combustion engines, and by extension of complete powertrains for ground vehicles, constitute a particularly complex, costly and time consuming task. As a result, numerical simulation is now commonly used by engine manufacturers and vehicle designers in addition to test bench experiments. Engine simulation codes can be divided into three main categories, with very different objectives and levels of complexity: CFD codes, thermodynamic codes and real time codes. This paper presents the MERIMEE simulation code, which belongs to the second category (MERIMEE is the French acronym for Computer Research and Study Model for Engines and their Equipment). Jointly developed by Ecole Centrale de Nantes (for the models) and the CS-SI Company (for the software development) it is used by ETAS (French Army) for the development and study of complete powertrains designed for military ground propulsion. The main models used to simulate the engine behavior are first briefly described. Then, the software architecture, the interface as well as the programming and numerical aspects are described. Finally, some significant results are shown and compared with experimental data. They deal with steady state and transient engine behavior in addition to the evaluation of pollutant emissions.Copyright