Simulation of automobile diesel engine under transient operating conditions

A phenomenological multizone combustion model is developed for use in the transient condition analysis of a turbocharged direct injection (DI) diesel engine. The main processes in the cylinder, such as spray penetration, droplet evaporation, air-fuel mixing, spray wall interaction, ignition and fuel combustion, are taken into consideration. In order to predict cylinder pressure and NOx emissions in a wide range of engine speeds, loads and air-fuel ratios under transient conditions, the model has been improved in many respects, especially in the velocity distribution of fuel spray, zonal entrainment and the calculation of gas properties and chemical equilibrium compositions of combustion products including solid carbon. With respect to the turbocharged engine with a high pressure in the cylinder, the compression factor is added to the ideal gas equation of state in order to simulate cylinder pressure accurately. Cylinder pressure, heat release and NOx emission histories for different operating conditions are calculated for two types of engines. The agreement between calculated and measured results is good for a wide range of operating conditions. This indicates that the model has the ability to predict cylinder pressures and NOx emissions in both steady state and transient operating conditions.

Diesel engines are widely used in many application domains. The recent drive to reduce emissions, improve efficiency and implement on board diagnostic tools has resulted in a real need for improved models for the simulation of Diesel engines. This paper evaluates three different Diesel engine dynamic models of varying levels of complexity. The assumptions for the models and the equations are presented. The equations are implemented in a computer simulation environment. The models describe the dynamic relationship between indicated pressure and engine speed. The first model is a detailed analytical non-linear dynamic model, including dynamometer dynamics, instantaneous friction components, viscosity variations with temperature and inertia variations with piston pin offset. In-cycle calculations are performed at each crank-angle. The second model is a nonlinear dynamic model which includes a mean friction model for the engine components and dynamometer dynamics, but does not include the piston pin offset as well as the inertia variations. The third model is obtained by an identification procedure to find a low-order linear transfer function between the engine input and output. The three models are used to predict the behaviour of a Diesel engine. The models are compared using experimentally measured engine speeds, under steady state and transient operating conditions. The paper discusses the suitability of the models for various control applications such as engine simulation, fuelling control system design and fault diagnostics.

A study of soot measurement deviation using a diffusion charger sensor with three dilution ratios was conducted in order to obtain an optimum setting that can be used to obtain accurate measurements in terms of soot mass emitted by a light-duty diesel engine under transient operating conditions. The paper includes three experimental phases: an experimental validation of the measurement settings in steady-state operating conditions; evaluation of the proposed setting under the New European Driving Cycle; and a study of correlations for different measurement techniques. These correlations provide a reliable tool for estimating soot emission from light extinction measurement or from accumulation particle mode concentration. There are several methods and correlations to estimate soot concentration in the literature but most of them were assessed for steady-state operating points. In this case, the correlations are obtained by more than 4000 points measured in transient conditions. The results of the new two correlations, with less than 4% deviation from the reference measurement, are presented in this paper.

Applications of computational fluid dynamic (CFD) techniques to hydropower have increased rapidly in the last three decades. The majority of the experimental investigations of hydraulic turbines were supported by numerical studies and this has become a standard practice. In the paper, applied numerical techniques and flow modeling approaches to simulate the hydraulic turbines are discussed. Both steady-state and transient operating conditions of the turbines are considered for the review. The steady-state conditions include the best efficiency point (BEP), high load (HL), and part load (PL). The transient conditions include load variation, startup, shutdown, and total load rejection. The performance of the applied numerical models and turbulence modeling with respect to the operating conditions are discussed. The recently developed numerical technique (transient blade row modeling) using the Fourier transformation (FT) method is discussed. This technique allows guide vane and blade passages to be modeled with the pitch ratio other than unity. Numerical modeling and simulation of hydraulic turbines during the transient operating conditions is one of the most challenging tasks because guide vanes' angular movement is time-dependent and mesh should be dynamic/moving. Different approaches applied to simulate the transient conditions and their limitations are discussed. Overall, this review summarizes the role of numerical techniques, advantages, limitations, and upcoming challenges within hydropower.

A time-series turbofan engine successive fault diagnosis under both steady-state and dynamic conditions

Diesel Particulate Filters (DPFs) are regarded as the most effective technology to reduce particulate matter (PM) emissions from modern diesel engines. PM mass collected inside the filter needs to be periodically oxidized to clean the porous walls in order to avoid excessive backpressure that could negatively affect engine and turbocharger performances leading to higher fuel consumption. Diesel Oxidation Catalysts (DOCs), on the other hand, represent an effective means to reduce hydrocarbon (HC) emissions and set the proper chemical conditions at the inlet of the DPF to enhance soot oxidation during filter regeneration. Due to the impact that these devices have on tailpipe emissions, monitoring functions aimed at assessing the health of these systems need to be implemented in the engine on-board diagnostics (OBD) system. Further, in-depth understanding of filtration and regeneration mechanisms, together with the ability of predicting actual DPF loading conditions, could play a key role in optimizing regeneration strategies adopted to keep the particulate filter within safe operating conditions. Hence, the use of real-time, yet accurate models is of primary importance to face with advanced control challenges, such as the integration of DOCs and DPFs with the engine or other critical aftertreatment components, or to properly develop model-based OBD monitors.;This study aims at addressing the challenges related with real-time modeling of both DOCs and DPFs with special regard to the calibration of key parameters. At first, the development of a 1-D model for the diesel oxidation catalyst is presented;: two different approaches representing two different trade-offs in terms of model complexity/speed are discussed and analyzed. A 1-D model of a DPF is then presented, addressing the coupling of filtration and regeneration over cake, washcoat and wall thicknesses. Moreover, the approach followed to develop the DPF model is innovative as it is directly integrated via analytical functions, thus improving the discretized approach used in similar models. Finally, an innovative model tuning methodology called "Virtual Conditioning" is presented and applied to generate robust model calibrations.;Numerical results are compared with experimental data gathered at West Virginia University's (WVU) Engine and Emissions Research Laboratory (EERL) using a Mack heavy-duty diesel engine coupled to a Johnson Matthey C-CRT aftertreatment system. The study shows that: a) DOC model is capable of predicting outlet emissions concentrations with an accuracy within 15% and minimal computational requirements over both steady-state and transient operating conditions; b) DPF wall and washcoat layer present different regeneration and collection dynamics, whose

<div class="section abstract"><div class="htmlview paragraph">Modern Diesel engines require an integrated development of combustion strategies, air management and exhaust aftertreatment. This study presents a comprehensive simulation approach with the aim to support engine development activities in the virtual environment. A real-time capable engine, vehicle and control model is extended by three key features. First, a pollutant production model is embedded in a two-zone cylinder model. Second, a framework for catalytic pollutant conversion is built focusing on modern diesel exhaust aftertreatment systems. Third, an extended species transport model is introduced considering the transport of pollutants through the air path. The entire plant model is validated on the example of a passenger car Diesel engine. The predicted engine behavior is compared with steady-state measurements. The NO formation model is investigated for a series of steady-state and transient operating conditions. The catalytic conversion performance of a Diesel oxidation catalyst and of a selective catalytic reduction converter is compared to experimental data. The engine, vehicle and control model is used to simulate an NEDC and to investigate the impact of different engine operation strategies on NO emissions at engine and tailpipe outlet.</div></div>

Reactivity Controlled Compression Ignition (RCCI) combustion in a light-duty multi-cylinder engine over transient operating conditions using fast response exhaust UHC1, NO and PM measurement instruments was investigated. RCCI has demonstrated improvements in efficiency along with low NOx and PM emissions by utilizing in-cylinder fuel blending, generally using two fuels with different reactivity in order to optimize stratification. In the present work, a “single-fuel” approach for RCCI combustion using port-injected gasoline and direct-injected gasoline mixed with a small amount of the cetane improver 2-ethylhexyl nitrate (EHN) was studied with custom designed, compression ratio of 13.75:1, pistons under transient conditions. The EHN volume percentage in the mixture for the direct-injected fuel was set at 3%. In an experimental investigation, comparisons were made to transient RCCI combustion operation with gasoline/diesel. The experiments were performed over a step load change from 1 to 4 bar brake mean effective pressure (BMEP) at constant 1,500 rev/min on a General Motors Z19DTH 1.9 liter diesel engine The transients were conducted by changing the accelerator pedal command to provide a desired torque output with a DRIVVEN engine control unit (ECU) that replaced the original Bosch ECU. All relevant engine parameters are adjusted accordingly, based on 2D-tables. Previous to the transient engine operation, 4 steady-state points were used to obtain performance and emission values. Engine calibration at these 4 points, as well as the interpolation of the intermediate points, allowed for smooth operation during the instantaneous step changes. Differences between the steady-state and transient results indicate the complexity of transient operation and show the need for additional controls to minimize undesirable effects. The steady-state points were calibrated by modifying the fuel injection strategy (actual Start of Injection (aSOI) timing, port-fuel injection (PFI) fraction, etc.), EGR and rail pressure in order to obtain predefined values for the crank angle at 50% of total heat release (CA50). Furthermore, emission targets (HC1 < 1500ppmC3, NO < 10ppm, FSN < 0.1 with a maximum pressure rise rate < 10bar/deg) and noise level targets (<95dB) for RCCI combustion were maintained during the calibration and mapping. The tests were performed with a closed-loop (CL) calibration by using a next-cycle (NC) controller to adjust the PFI ratio of each cycle in order to reach the steady-state CA50 values in the table. The results show that single-fuel RCCI operation can be achieved, but requires significant alteration of the operating conditions, and NOx emissions were significantly elevated for gasoline/gasoline-EHN operation. While combustion phasing could not be matched, UHC1 emissions were at a similar level as for gasoline/diesel combustion. It is expected that the implementation of different injection strategies and boosted operation, combined with use of higher compression ratio pistons in order to compensate for the lower reactivity direct injection (DI) fuel, could raise the potential for improved performance.

<div class="htmlview paragraph">In order to evaluate the genotoxic potential of DI diesel engine exhaust, Ames tests based on TA98 and TA100 bacteria strains have been conducted. The presence of nitro- and dinitropyrene was proved by comparison of TA98 to TA98NR and TA98 1,8DNP6, respectively. One light and three heavy duty diesel engines, representing past, present and future production, have been tested under steady-state and transient operating conditions.</div> <div class="htmlview paragraph">A correlation between engine load and mutagenic activity has been shown from the particulate extract. Water port injection reveals a dramatic decrease of mutagenicity at high load conditions. In the particulate extract from future very low NOx engines, no nitro- and dinitropyrenes are detected. Engines representing past and present technology however, contain these highly mutagenic compounds.</div> <div class="htmlview paragraph">High quality diesel fuel yields another substantial decrease of mutagenicity.</div> <div class="htmlview paragraph">Tests with human lymphocytes were carried out in order to corroborate bacteria-based findings.</div> <div class="htmlview paragraph">It is clearly shown that the mutagenic activity of diesel exhaust can be influenced either by modifications to the combustion process or by the choice of the proper diesel fuel.</div>

Biological oxidation of hydrogen sulfide under steady and transient state conditions in an immobilized cell biofilter

A physics-based time-varying transport delay oxygen concentration model for dual-loop exhaust gas recirculation (EGR) engine air-paths

This paper describes NOx and COx emissions from the diesel engine on mini-vessel such as 500GT class vessel under transient operating condition and entering and departing conditions, because the reduction of the marine exhaust emissions has been important subject. And the International Maritime Organization (IMO) advances the prevention of air pollution from ships in 1989. The regulated level of NOx emissions will be decided by the Bulk Chemicals (BCH), in recent years. So the emissions of carbon monoxide (CO), carbon dioxide (CO2), total hydrocarbons (THC), sulfur dioxide (SO2), and nitrogen oxide (NOx), occupy an important part. The transient operating conditions have been formed by change of engine speed and PPA whose region are within the range of 500-673rpm, and 11-20deg. NOx concentration in summer voyage changes within the limits of 600- 1000ppm, and CO2concentration changes within the limits of 4-7%.

<div class="section abstract"><div class="htmlview paragraph">Feed-forward low-throughput models have been developed to predict MFB50 and to control SOI in order to achieve a specific MFB50 target for diesel engines. The models have been assessed on a GMPT-E Euro 5 diesel engine, installed at the dynamic test bench at ICEAL-PT (Internal Combustion Engine Advanced Laboratory at the Politecnico di Torino) and applied to both steady state and transient engine operating conditions.</div><div class="htmlview paragraph">MFB50 indicates the crank angle at which 50% of the fuel mass fraction has burned, and is currently used extensively in control algorithms to optimize combustion phasing in diesel engines in real-time. MFB50 is generally used in closed-loop combustion control applications, where it is calculated by the engine control unit, cycle-by-cycle and cylinder by-cylinder, on the basis of the measured in-cylinder pressure trace, and is adjusted in order to reduce the fuel consumption, combustion noise and engine-out emissions.</div><div class="htmlview paragraph">A feed-forward approach has been developed in this paper. This approach is capable of predicting MFB50 on the basis of several parameters, such as, the in-chamber thermodynamic conditions, the injected fuel quantities and timings, the injection pressure, the oxygen concentration and the engine speed and load. The approach has also been inverted in order to predict the start of injection required to achieve a specific MFB50 target in real time. This method can be used in model-based real-time control algorithms to adjust the engine parameters in order to prevent the occurrence of non-optimal combustion cycles.</div></div>

Gas turbine gas path diagnosis under transient operating conditions: A steady state performance model based local optimization approach

<div class="section abstract"><div class="htmlview paragraph">Due to the recent anti-pollution policies, the performance increase in Spark Ignition (SI) engines is currently under the focus of automotive manufacturers. This trend drives control systems designers to investigate accurate solutions and build more sophisticated algorithms to increase the efficiency of this kind of engines.</div><div class="htmlview paragraph">The development of a control strategy is composed of several phases and steps, and the first part of such process is typically spent in defining and investigating the logic of the strategy. During this phase it is often useful to have a light engine simulator, which allows to have robust synthetic combustion data with a low calibration and computational effort.</div><div class="htmlview paragraph">In the first part of this paper, a description of the control-oriented ANalytical Engine SIMulator (ANESIM) is carried out. The latest results about the zero-dimensional knock model presented in a previous paper and some interesting analytical equations which define the main mean-combustion indexes trends (for example maximum in-cylinder pressure, or Pmax, 50 percent fuel mass fraction burned angle, or MFB50, Indicated Mean Effective Pressure, or IMEP) as functions of engine speed and load are analyzed for the entire engine operating range. A detailed sensitivity analysis to the fitting order is presented and the final formulas are showed and used for the calibration.</div><div class="htmlview paragraph">The second part focuses on the model implementation in a Simulink environment and the resulting validation process of the analytic simulator carried out on a Gasoline Direct Injection (GDI) Turbo Charged (TC) engine. ANESIM performance is then tested by comparing the calculated and the experimental data, for both steady state and transient operating conditions.</div></div>