Jean-François Hetet

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.

Boundary conditions modelling of one-dimensional gas flows in an internal combustion engine

Abstract The aim of this paper is to improve the boundary conditions modelling for one-dimensional simulation codes. First, a literature survey is made in order to present the main equations and literature models, then a detailed description of the methodology is presented. Cross-sectional area variations and bends are studied using a new methodology. New models are then established that depend on the geometrical configuration and the flow characteristics. Finally, numerical results are compared with experimental results from a shock test bench. The new models are found to give better results for the instantaneous pressure signals and to improve flow calculations significantly.

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

Heat Transfers Characterisations in a Turbocharger: Experiments and Correlations

Unfortunately, the most turbocharger models included in a whole engine simulation rely typically on the direct use of the manufacturers’ maps and on the assumption of adiabaticity of the compressor and the turbine. However, experiments on a turbocharger test bench show that, contrary to general opinions, the heat transfers can influence the turbocharger performances. It seems essential to determine and correlate the different heat transfers occurring in a turbocharger. Furthermore one method is proposed to obtain compressor and turbine isentropic efficiencies, actual mechanical powers and outlet temperatures starting from the manufacturers’ performance maps. This method coupled with the heat transfers correlations obtained experimentally give results in relative good agreement with experimental measures in comparison to their easiness of use.© 2006 ASME

Analysis and Modeling of Plain Open Ends and Bends Inside the Piping Systems of Internal Combustion Engines

Controlling the pressure wave propagation inside the inlet and exhaust systems of internal combustion engines is essential for the optimization of the cylinder filling and emptying as well as the combustion process. In this objective, the authors have been developing a new one-dimensional simulation code for several years. This paper presents an investigation of plain open end boundary conditions and bend elements. First, the pressure waves at the pipe inlet are analyzed with the Fluent CFD code. It appears that the losses can be modeled with the use of a coefficient that depends on the Mach number as well as the ratio between the pipe diameter and thickness. Then, the paper focuses on the modeling of bends. The losses in this type of elements can be modeled by the addition of a friction factor in the gas dynamics equations. This factor depends on the bend angle and the ratio between the tube radius of curvature and diameter. Finally, an experimental study aimed at evaluating the accuracy of the 1D simulation code is presented. The code enhancements significantly improve flow calculations and allow for the optimization of the inlet and exhaust systems of internal combustion engines.Copyright

Dynamic Modeling and Control of an Hybrid Electric Powertrain for Simulation Under Transient Conditions

This article presents a causal, forward looking approach for the hybrid electric vehicle where the typical performance engine map representation has been modified. The need for a more physical model of the power stroke process has been fulfilled with “the filling and emptying” method. The thermodynamic states in the intake and exhaust systems are calculated, while the in-cylinder process is still based on the engine fuel consumption map as a calibrated data. Comparisons with the conventional model are established, most important is the response of the engine torque under the load demand. This notion of an “available” torque is taken into account by the energy management strategy. Changes on the distribution of energy flow in order to meet the required torque at the wheel are observed and influence of this modelisation on the fuel consumption over various driving cycles is evaluated.Copyright

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