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The aim of the current contribution is to develop a tool for the improvement of accuracy of turbocharger turbine simulation during matching of a turbocharger to an engine. The paper demonstrates the possibility of unsteady turbine simulation in pulsating flow caused by an internal combustion engine using the basic modules of generalized 1-D manifold solver with entities (pipes, channels) under centrifugal acceleration in general direction and under non-uniform angular speed, which has not yet been explored. The developed model extrapolates steady operation turbine maps by this way. It uses 1-D model parameters identified from steady flow experiments. Unlike the lumped-parameter standard models of turbocharger turbines, the model takes into account complete 1-D features of a turbine flow path including arbitrary shape of turbine impeller vanes.

The paper deals with model based predictive control of combustion engines. Nonlinear black-box predictive models based on neuro-fuzzy approach are utilized. The structure of the models is optimized within an identification process. The nonlinear models are locally linearized and consequently used for the efficient on-line computation of forthcoming control actions. In desire to respect a fact that the speed of input-output response may vary significantly for different input/output groups, multilevel predictive models are proposed. Predictive control is again applied to approximate the desired behavior of chosen output variables. Potential algebraical constraints between different prediction layers are involved in the control algorithm using quadratic programming. The control scheme is optimized using simplified fast simulation model.

Transient engine operations are modeled and simulated with a 1-D code (GT Power) using heat release and emission data computed by a 3-D CFD code (Kiva3). During each iteration step of a transient engine simulation, the 1-D code utilizes the 3-D data to interpolate the values for heat release and emissions. The 3-D CFD computations were performed for the compression and combustion stroke of strategically chosen engine operating points considering engine speed, torque and excess air. The 3-D inlet conditions were obtained from the 1-D code, which utilized 3-D heat release data from the previous 1-D unsteady computations. In most cases, only two different sets of 3-D input data are needed to interpolate the transient phase between two engine operating points. This keeps the computation time at a reasonable level. The results are demonstrated on the load response of a generator which is driven by a medium-speed diesel engine.

A previously developed CFD-based optimization tool is utilized to find optimal engine operating conditions with respect to fuel consumption and emissions. The optimization algorithm employed is based on the steepest descent method where an adaptive cost function is minimized along each line search using an effective backtracking strategy. The adaptive cost function is based on the penalty method, where the penalty coefficient is increased after every line search. The parameter space is normalized and, thus, the optimization occurs over the unit cube in higher-dimensional space. The application of this optimization tool is demonstrated for the Sulzer S20, a central-injection, non-road DI diesel engine. The optimization parameters are the start of injection of the two pulses of a split injection system, the duration of each pulse, the exhaust gas recirculation rate, the boost pressure and the compression ratio.

The paper deals with the investigation of pressure, flow and temperature sensor performance under unsteady conditions using advanced 1-D codes for simulation of engine operation. Approach of internal combustion engine (ICE) sensor modeling in an engine simulation code is described. Some new external modules have been developed to couple engine-and-pipe model to sensors. Sensor dynamic and engine dynamic effects are separated by combining a sensor model with an engine model. The models were tuned to match real data with the goal of uncovering the transfer function between the measured signal and the actual signal. Procedure for estimation of the in-cylinder pressure pattern from distorted pattern at sensor location using empirical transfer function is presented. The developed model seems to have a wide application, e.g. for investigation of dynamical characteristics of lambda sensors or gas analyzer probes.

The objective of this study is the development of a computationally efficient CFD-based tool for finding optimal engine operating conditions with respect to fuel consumption and emissions. The optimization algorithm employed is based on the steepest descent method where an adaptive cost function is minimized along each line search using an effective backtracking strategy. The adaptive cost function is based on the penalty method, where the penalty coefficient is increased after every line search. The parameter space is normalized and, thus, the optimization occurs over the unit cube in higher-dimensional space. The application of this optimization tool is demonstrated for the Sulzer S20, a central-injection, non-road DI diesel engine. The optimization parameters are the start of injection of the two pulses, the duration of each pulse, the duration of the dwell, the exhaust gas recirculation rate and the boost pressure.

The paper deals with the investigation of turbocharger optimization procedures using amended 1-D simulation tools. The proposed method uses scaled flow rate/effficiency maps for different sizes of a radial turbine together with a fictitious compressor map. The compressor pressure ratio/efficiency map depends on compressor circumference velocity only and predicts the both compressor specific power and achievable efficiency. At the first stage of optimization, it avoids the problems of reaching choking/surge limits. It enables the designer to find a suitable turbine type under realistic unsteady conditions (pressure pulses in exhaust manifold) concerning turbine flow area. Once the optimization of turbine/compressor impeller diameters is finished, the specific compressor map is selected. The proposed method provides the fast way to the best solution even for the case of a VGT turbine. Additional features have been developed for the representation of scaled turbine and compressor maps.

The paper describes the tool of ICE transient response simulation suitable for incorporation into a predictive engine controller. The model is simplified, thus enhancing the simulation speed but keeping its predictive capability at a reasonable level. The main modules of a code suitable for the near-real-time simulation of engine thermodynamics are described in the paper. They include engine cylinder (incl. simplified pressure trace prediction), fuel injection system, main controllers, both inlet and exhaust manifolds, turbocharger and engine dynamics. The laws of conservation are used to describe any of the thermodynamic/hydrodynamic modules of a model. The method of algebraic re-construction of a pressure trace inside a cylinder has been developed and tested for prediction of engine speed variation. The modular structure of a model allows for the implementation of the current operating principles of ICEs.

Diesel fuel injection process calculations have been performed by means of in-house developed mathematical models. An Eulerian multidimensional code for in-cylinder two-phase flow computations is used in conjunction with a hydrodynamic one-dimensional model of a fuel injection system. The multidimensional model comprehends all basic processes, which play a role in spray formation. The compressible gaseous flow with transport of species is solved together with the flow of dispersed liquid phase using the Eulerian reference frame for both phases. The two-way coupling between the phases in mass, momentum, and energy balances is considered. A detailed description of liquid phase is present, taking into account drop size distribution in terms of the multi-continua approach. The hydrodynamic model capable of simulating common fuel injection systems is used for the rate-of-injection computations to provide realistic boundary conditions to the spray model.

An Eulerian multidimensional model has been developed for computing the behavior of fuel sprays in direct injection internal combustion engines. The model involves a description of all basic processes that take place in two-phase flow with inter-phase exchanges of mass, momentum, and energy. Both the multi-component compressible gas-phase flow as well as the droplet-phase flow equations are solved in Eulerian coordinates. Basic laws of conservation are formulated on finite volumes with arbitrarily movable boundaries to facilitate the modeling of movable boundary problems. The model features a detailed description of droplet-phase accounting for droplet mass change due to evaporation and with possibility of incorporation of potential droplet breakup, collisions, and coalescence. The application chosen to demonstrate the predictive capabilities of the developed model is the injection of hollow-cone spray into high-density air in a cylindrical chamber with moving boundary.

The paper describes experience obtained with a GT-Power code used for a downsized turbocharged gasoline engine modeling. The steady-performance model, calibrated by preliminary experiments, has been modified to the transient response one. Knock limit prediction has been used for compression ratio and boost pressure optimization. New authors′ models have been developed for extrapolation of compressor and turbine maps to cover the field of operation modes during a typical transient response. GT-Power control elements ensured a realistic engine response to accelerator, brake or clutch positions. The Driver element could drive various speed schedules such as maximum acceleration mode, engine braking mode or the European fuel-consumption/emission test.

The paper describes techniques used for optimization of timing, shaping and control of pressure wave exchangers including the prediction of pressure-flow rate characteristics of these devices. BBC Baden and ETH Zürich originally proposed them in 60's using the direct pressure exchange between exhaust gas and fresh air in a narrow channel (the COMPREX® device). A technique allowing COMPREX® pressure exchanger to be simulated in detail in a commercially available 1-D cycle simulation tool has been developed. Before the design of a specific exchanger is started the layout must be carefully optimized concerning distribution gear for both fresh air and exhaust gas. Simulation facilities provided by advanced 1-D codes like GT-Power from Gamma Technologies create a valuable tool to do this task and to find alternative design solutions.

The paper deals with the simulation of properties of IC engine equipped with a chemically inert porous media (PM) to homogenize and stabilize the combustion of CI engines. The purpose of the PM matrix use is to ensure reliable a ignition of lean mixture and to limit maximum in-cylinder temperature during combustion. It is aimed at NO formation reduction. The influence of PM on an engine cycle is examined by means of CFD simulations. Results demonstrating the influence of heat accumulation, heat supply during compression and expansion strokes and self-ignition properties of a fuel on the engine cycle are presented. All simulations involve modeling of NO formation. The homogenization capability and the flame stabilization one of the PM are discussed.

The presented work deals with possibilities of modeling divided combustion chamber using available 1-D/0-D software. It is usable for indirect injection diesel engines, gas SI engines with pre-chambers for very lean mixture ignition, etc. The model solves all layouts where main cylinder is connected to additional volumes. This connection allows for heat and energy transfer between connected parts. The application of standard ROHR functions (Wiebe, etc.) which are normalized to constant fuel mass is limited. A new marker gas concentration algorithm is proposed for the use of empiric ROHR functions. The standard approach (without proposed algorithm) was tested modeling large-bore gas SI engine with pre-chamber where the mixture is ignited and experimental direct injection hydrogen one-cylinder engine with an additional volume between fuel injector and the cylinder itself to protect the injector from very high pressures and temperatures in the cylinder.

The paper deals with an application of advanced simulation methods to modeling of hydrogen fueled engines. Two models have been applied - 0-D algorithm and CFD. The 0-D model has been based on GT-Power code. The CFD model has been based on Advanced Multizone Eulerian Model representing general method of finite volume. The influence of main engine parameters, e.g. air excess, spark timing, compression ratio, on NOx formation and engine efficiency has been investigated. Both models have been calibrated with experimental data. Examples of results and comparison with experiments are shown. The means of reducing NOx formation are discussed.

The 1-D model of a radial centripetal turbine was developed for engine simulation to generalize and extrapolate the results of experiments to high pressure ratio or off-design velocity ratio using calibrated tuning coefficients. The model concerns a compressible dissipative flow in a rotating channel. It considers both bladed or vaneless turbine stators and a twin-entry stator for exhaust pulse manifolds. The experiments were used to find values of all model parameters (outlet flow angles, all loss coefficients including an impeller incidence loss) by an original method using repeated regression analysis. The model is suitable for the prediction of a turbocharger turbine operation and its optimization in 1-D simulation codes.

The paper describes patterns of algorithms for different innovative levels of design at parametric, configuration and conceptual levels. They can be applied to Computer-aided Engine Design (CED). Data structures, process simulation hierarchy, used modules of engine simulation and needs for their further development are described. An example of advanced thermodynamics modeling of combustion engines is included.