Search Results

The present work introduces an extended particulate filter model focusing on capabilities to cover catalytic and surface storage reactions and to serve as a virtual multi-functional reactor/separator. The model can be classified as a transient, non-isothermal 1D+1D two-channel model. The applied modeling framework offers the required modeling depth to investigate arbitrary catalytic reaction schemes and it follows the computational requirement of running in real-time. The trade-off between model complexity and computational speed is scalable. The model is validated with the help of an analytically solved reference and the model parametrization is demonstrated by simulating experimentally given temperatures of a heat-up measurement. The detailed 1D+1D model is demonstrated in a concept study comparing the impact of different spatial washcoat distributions.

The present work describes an existing transient, non-isothermal 1D+1D particulate filter model to capture the impact of different types of particulate matter (PM) on filtration and regeneration. PM classes of arbitrary characteristics (size, composition etc.) are transported and filtered following standard mechanisms. PM deposit populations of arbitrary composition and contact states are used to describe regeneration on a micro-kinetical level. The transport class and deposit population are linked by introducing a splitting deposit matrix. Filtration and regeneration modes are compared to experimental data from literature and a brief numerical assessment on the filtration model is performed. The filter model as part of an exhaust line is used in a concept study on different coating variants. The same exhaust line model is connected to an engine thermodynamic and vehicle model. This system model is run through a random drive cycle in office simulation.

Spark Ignited (SI) combustions engines in combination with different degrees of hybridization are expected to play a major role in future vehicle propulsion. Due to the combustion principle and the related thermodynamic efficiency, it is especially challenging to meet future CO2 targets. The layout and optimization of the overall system requires novel methods in the development process which feature a seamless transition between real and virtual prototypes. Herein, engine models need to predict the entire engine operating range in steady-state and transient conditions and must respond to all relevant control inputs. In addition, the model must feature true real-time capability. This work presents a holistic and modular modeling framework, which considers all relevant processes in the complex chain of physical effects in SI combustion.

The physical 1-D model of a radial turbine consists of a set of gas ducts featuring total pressure and/or temperature changes and losses. Therefore, the wave propagation and filling/emptying plays a significant role if a turbine is subjected to unsteady gas flow. The results of unsteady turbine simulation using the basic modules of generalized 1-D manifold solver in GT Power are demonstrated. The turbine model calibration parameters can be identified by means of 1-D steady model used in optimization code loop. The examples of model results are compared to steady flow map predictions of turbine efficiency and engine pumping loop work. The model may be used for prediction of turbine data in out-of-design points as presented in the paper. The other important role of a model, however, is an accurate evaluation of turbine parameters from pressure and speed measurements at an engine in operation.

The objective of this paper is to complete a thorough investigation of the pressure wave supercharger (PWS) to explore the potential of this technology in engine applications. The PWS is a non-steady flow device that uses shock waves to pressurize fluids by transferring energy from a high-pressure flow to a low-pressure flow without separation by physical walls. The paper introduces a 1-D model of PWS in GT-SUITE calibrated by experiments on steady flow test rig. The 1-D model respects both exhaust and fresh air in each of the cells, friction and heat transfer in the cells as well as the continual opening and closing of the cells. Moreover, the cell wall temperature is computed and the leakage flow between the cells and housings modeled. The limits of PWS operation regarding pressures, temperatures and mass flows are first mapped on the virtual test rig utilizing the calibrated 1-D code based on the Mazda Comprex device.

The presented paper deals with a methodology to model cycle-to-cycle variations (CCV) in 0-D/1-D simulation tools. This is achieved by introducing perturbations of combustion model parameters. To enable that, crank angle resolved data of individual cycles (pressure traces) have to be available for a reasonable number of engine cycles. Either experimental data or 3-D CFD results can be applied. In the presented work, experimental data of a single-cylinder research engine were considered while predicted LES 3-D CFD results will be tested in the future. Different engine operating points were selected - both stable ones (low CCV) and unstable ones (high CCV). The proposed methodology consists of two major steps. First, individual cycle data have to be matched with the 0-D/1-D model, i.e., combustion model parameters are varied to achieve the best possible match of pressure traces - an automated optimization approach is applied to achieve that.

The paper describes a zero-dimensional crank angle resolved combustion model which was developed for the analysis and prediction of combustion in compression ignition (CI) engines. The model relies on the multi zone combustion model (MZCM) approach of Hiroyasu. The main sub-models were taken from literature and extended with additional features described in this paper. A special procedure described in a previous paper is used to identify the mechanisms of the combustion process on the basis of the measured cylinder pressure trace. Based on the identified mechanisms the present work concentrates on the analysis of the causal effects that predominantly control the combustion process and the formation of NOx and Soot. The focus lies on the changes of the thermodynamic states and the composition of the reaction zones caused by different emission control strategies.

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 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.

The new simulation tool consists of an iterative loop of a 3-D code in parallel to a 1-D code that is employed to simulate transient engine cycles. The 1-D code yields the basic pattern of initial and boundary conditions and the 3-D simulations at several typical engine operating points are used to crosscheck the performance as well as aid in the model calibration. A flexible regression model of the fuel burn rate and the associated ROHR has been developed in conjunction with the 3-D simulations using a combination of three added Vibe functions. The emissions at the end of the expansion stroke are also predicted. The parameters of the Vibe functions and emissions are found via nonlinear regression based on state parameters such as engine speed, relative A/F ratio, EGR/rest gas contents, injection timings, etc. Additional 3-D simulations that are made at specific engine operating points complement this compact burn rate parameter library.

The paper deals with investigation of flow characteristics of turbocharger turbine under real operating conditions on engine by means of combination of experimental data and advanced 1-D code for combustion engine simulation. Coupling simulations tools with the results of measurements provides the engineers with data which are difficult or impossible to measure. For instance by means of a three pressure analysis (TPA) applicable on engine cylinder the engineers can obtain burn rate, valve flow and residual gas compound from measured pressure traces in cylinder and at inlet and outlet ports. A method for turbocharger turbine on engine identification similar in principle to the three pressure analysis has been applied on radial turbine with variable geometry. A new computational module has been developed to allow identification of instantaneous flow and efficiency characteristics of the turbine.

One-dimensional simulation methods for unsteady (transient) engine operations have been developed and published in previous studies. These 1-D methods utilize heat release and emissions results obtained from 3-D CFD simulations which are stored in a data library. The goal of this study is to improve the 1-D methodology by optimizing the control strategies. Also, additional independent parameters are introduced to extend the 3-D data library, while, as in the previous studies, the number of interpolation points for each parameter remains small. The data points for the 3-D simulations are selected in the vicinity of the expected trajectories obtained from the independent parameter changes, as predicted by the transient 1-D simulations. By this approach, the number of time-consuming 3-D simulations is limited to a reasonable amount.

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.

Flow control by fluidic devices - without moving parts - offers advantages of reliability and low cost. As an example of their automobile application based on authors'' long-time experience the paper describes a fluidic valve for switching exhaust gas flow in a NOx absorber into a by-pass during regeneration phase. The unique feature here is the fluidic valve being of monostable and of axisymmetric design, integrated into the absorber body. After development in aerodynamic laboratory, the final design was tested on engine test stand and finally in a car. This proved that the performance under high temperature and pulsation existing in exhaust systems is reliable and promising. Fluidic valves require, however, close matching with aerodynamic load. To optimize the exhaust system layout for the whole load-speed range and reaching minimum counter- pressure, both the components of exhaust system and control strategy have to be properly adopted.

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.