Engine-out Nitrogen Oxides Emissions Research Articles

Study on Control Strategies on NOX Emissions to Meet Real Driving Emissions.

The aim of this study was to fulfill the NOx emissions standards for a light-duty diesel vehicle under real driving emissions (RDE) testing conditions by implementing various control strategies. In this study, RDE tests were performed by adjusting the air mass quantity and postinjection quantity in order to analyze engine-out and tail-pipe nitrogen oxides (NOx) emissions for different phases of RDE. The results showed that reducing in air mass quantity enabled the engine to operate in higher exhaust gas recirculation (EGR) rate regions, resulting in a 32.5% reduction in engine-out NOx emissions and an 80.4% decrease in tail-pipe NOx emissions. Increasing the postinjection quantity primarily enhanced the NOx conversion efficiency for the urban phase by 7.5%, leading to a 22.6% reduction in tail-pipe NOx emissions. By employing both strategies, vehicles can comfortably meet the CN6b emission regulations by a substantial margin.

Emission Reduction from a Light-Duty Diesel Vehicle over Two Driving Cycles through Dynamic Correction Calibration.

The potential of a method of transient control of model-based engine charge control (MCCT) is investigated to minimize nitrogen oxide (NOx) emissions of a light-duty diesel vehicle over two driving cycles, the worldwide harmonized light-duty test cycle (WLTC) and real driving emission (RDE) cycle. The MCCT function was switched on by calibrating factor maps corrected for several parameters. In addition, the relationship between electronic control unit signals and nitrogen oxide (NOx) emissions was analyzed under the WLTC and RDE. The engine-out and tail-pipe NOx emissions in the WLTC and RDE could achieve varying degrees of reduction with MCCT.

Understanding elevated real-world NOx emissions: Heavy-duty diesel engine certification testing versus in-use vehicle testing

For the first time, nitrogen oxide (NOx) emissions were systematically investigated during different operating conditions from a single test article on a chassis dynamometer, under real-world (on-road) conditions, on an engine dynamometer after the engine was pulled out of the vehicle, and again on a chassis dynamometer when the engine was installed back in the vehicle. The main goal of this study was to understand the discrepancies between certification and in-use NOx emission rates from a heavy-duty diesel vehicle (HDDV) with an engine with diesel particulate filter (DPF) and selective catalytic reduction (SCR) aftertreatment. The results showed that in-use NOx emissions over urban driving cycles were above the 0.2 g/bhp-hr NOx standard for most test conditions, ranging from 0.16 to 0.7 g/bhp-hr, with the highest NOx emissions for the chassis dynamometer testing. For the freeway/steady-state testing, the results were generally lower compared with the results of urban driving cycles, with values of 0.3 g/bhp-hr or less. For the Urban Dynamometer Driving Schedule (UDDS) cycle, NOx emissions were lowest for the engine dynamometer testing, followed by the on-road testing, and the chassis dynamometer testing. The differences between the tailpipe NOx emissions for the different types of tests could be attributed to differences in SCR inlet temperatures and engine-out NOx emissions.

Energy management strategies comparison for a parallel full hybrid electric vehicle using Reactivity Controlled Compression Ignition combustion

Reactivity Controlled Compression Ignition combustion technology potentials are well known for the capability to drastically reduce the engine-out nitrogen oxides and soot emissions simultaneously. Its implementation in mid-term low-duty diesel engines can be beneficial to meet the upcoming regulations. To explore the potential of this solution, experimental data are used from a compression ignition 1.9 L engine, which is operated under two combustion-modes: Reactivity Controlled Compression Ignition and conventional diesel combustion. Meanwhile, also the carbon dioxide emissions limitations must be fulfilled. To achieve this goal, the benefits associated to powertrain electrification in terms of fuel economy, can be joined with the benefits of RCCI combustion. To do so, two different supervisory control strategies are compared: Adaptive Equivalent Minimization Control Strategy and Rule-Based Control strategy, while dynamic programming is used to size the electric grid of the powertrain to provide the best optimal solution in terms of fuel economy and emissions abatement. The analysis of the designed hybrid powertrain is carried out numerically with GT-Suite and Matlab-Simulink software. The results show a great potential of the parallel full-hybrid electric vehicle powertrain equipped with the dual-mode engine to reduce the engine-out emissions, also to increase fuel economy with respect to the homologation fuel consumption of the baseline vehicle. The optimal supervisory control strategy was found to be the emissions-oriented Adaptive Equivalent Minimization Control Strategy, which scores a simultaneous reduction of 12% in fuel consumption, 75% in engine-out nitrogen oxides emissions and 82% in engine-out soot, with respect to the baseline conventional diesel combustion engine vehicle.

Implementation and Assessment of a Model-Based Controller of Torque and Nitrogen Oxide Emissions in an 11 L Heavy-Duty Diesel Engine

A previously developed model-based controller of torque and nitrogen oxides emissions has been implemented and assessed on a heavy-duty 11 L FPT prototype Cursor 11 diesel engine. The implementation has been realized by means of a rapid prototyping device, which has allowed the standard functions of the engine control unit to be by-passed. The activity was carried out within the IMPERIUM H2020 EU Project, which is aimed at reducing the consumption of fuel and urea in heavy-duty trucks up to 20%, while maintaining the compliance with the legal emission limits. In particular, the developed controller is able to achieve desired targets of brake mean effective pressure (BMEP) (or brake torque) and engine-out nitrogen oxides emissions. To this aim, the controller adjusts the fuel quantity and the start of injection of the main pulse in real-time. The controller is based on a previously developed low-throughput combustion model, which estimates the heat release rate, the in-cylinder pressure, the BMEP (or torque) and the engine-out nitrogen oxide emissions. The controller has been assessed at both steady-state and transient operations, through rapid prototyping tests at the engine test bench and on the road.

A New Control-Oriented Semi-Empirical Approach to Predict Engine-Out NOx Emissions in a Euro VI 3.0 L Diesel Engine

The present study is focused on the development of a new control-oriented semi-empirical model to predict nitrogen oxide (NOx) emissions in a light-duty diesel engine under both steady-state and transient conditions. The model is based on the estimation of the deviations of NOx emissions, with respect to the nominal engine-calibration map values, as a function of the deviations of the intake oxygen concentration and of the combustion phasing. The model also takes into account the effects of engine speed, total injected quantity, and ambient temperature and humidity. The approach has been developed and assessed on an Fiat Powertrain Technologies (FPT) Euro VI 3.0 L diesel engine for light-duty applications, in the frame of a research project in collaboration with FPT Industrial. The model has also been tested on a rapid prototyping device, and it was shown that it requires a very short computational time, thus being suitable for implementation on the Engine Control Unit (ECU) for real-time NOx control tasks.

Exploitation of injection fusion strategies in diesel engines equipped with solenoid injectors

Pilot–main injection strategies are investigated in the short dwell-time range at medium load and speed conditions for a low-temperature combustion diesel engine endowed with indirect-acting solenoid injectors. Dwell-time sweeps have been carried out for pilot injections with different energizing times under steady-state working conditions and constant combustion phasing. The experimental results on the engine are combined with in-cylinder analyses of pressure, heat release rate, temperature and emission time histories. As the electric dwell time is reduced toward zero, combustion noise reaches a minimum at a dwell time of 120–140 µs, and a reduction of 1–4.5 dB is possible compared to levels at dwell time = 500 µs. This decrease in combustion noise is obtained in conjunction with a local reduction in engine-out nitrogen oxide emissions, but penalties occur for engine-out soot emissions and brake-specific fuel consumption. The pilot and main injection shots feature fusion phenomena at the shortest dwell-time values, thus giving rise to rate-shaped single injections, which resemble the boot-shaped profiles in direct-acting piezoelectric injectors. The increase in the velocity of the needle, which occurs during the nozzle opening phase pertaining to the main injection for closely coupled injections as dwell time is reduced, is shown to be not the primary cause responsible for the observed trends in combustion noise and soot emissions as dwell-time changes. The combination of simulation and experimental data supports the theory that the main injection interacts with the pilot mixture field: the relative phasing between pilot and main combustion and the in-cylinder equivalent ratio distribution are the dominant aspects in the definition of the engine performance in the short dwell-time range.

Emission Characteristics of a Natural Gas Engine Operating in Lean-Burn and Stoichiometric Modes

AbstractTo comply with the stringent Euro VI emission standards, two techniques have been proposed for natural gas engines, namely, lean-burn combustion with oxidation catalyst (OC) and stoichiometric combustion with three-way catalyst (TWC). In this paper, comparisons are drawn between the two techniques in terms of carbon monoxide (CO), nitrogen oxides (NOx), and methane (CH4) emissions and fuel economy. The results indicated that the postcatalyst CO emissions of lean-burn combustion with OC are lower, whereas the postcatalyst NOx and CH4 emissions are higher than those of stoichiometric combustion with TWC. This can be explained by the combined effects of lower engine-out CO emissions and higher engine-out NOx and CH4 emissions as well as lower overall conversion efficiency for all emissions with the adoption of lean-burn combustion with OC. Thus, it can be concluded that although the fuel economy of stoichiometric combustion with TWC is inferior to lean-burn combustion with OC, it is still considered ...

Disturbance Rejection in Diesel Engines for Low Emissions and High Fuel Efficiency

This brief presents a novel and time-efficient control design for modern heavy-duty diesel engines using a variable geometry turbine and an exhaust gas recirculation valve. The goal is to simultaneously and robustly achieve low fuel consumption and low emissions of nitrogen oxides (NOx) and particulate matter (PM). A new combination of three controlled outputs is used: 1) specific engine-out NOx emissions; 2) air-fuel equivalence ratio; and 3) the pressure difference between intake and exhaust manifold, which reflect NOx and PM emissions and fuel efficiency, respectively. It is shown that this combination allows for effective disturbance rejection and results in a well-conditioned system. An underactuated input-output system is formed, for which a linear feedback controller is designed. In addition to this feedback controller, a feedforward controller is implemented, which improves the torque response and lowers the PM emissions during fast changes in torque demand. The combined control system is suitable for the full range of speed and load variations. This new controller is tested experimentally on a modern heavy-duty engine running a hot world harmonized transient cycle and compared with a baseline controller. The new controller reduces the NOx and PM emissions by 3.9% and 11.7%, respectively, without a fuel penalty.

Diesel pressure departure ratio algorithm for combustion feedback and control

The pursuit for higher efficiency and ultra-low exhaust emissions from diesel engines requires the combustion process to be precisely controlled so as to minimize departures from the intended engine operation. The combustion control system must be able to perform corrective actions on a cycle-by-cycle basis, with a robust feedback on the combustion process. The combustion phasing, commonly represented by the crank angle of 50% heat release and derived from the measured cylinder pressure data, shows a strong correlation to the efficiency and the engine-out nitrogen oxide emissions. To accurately estimate the combustion phasing from the derived heat-release rate, the authors previously introduced and experimentally validated a computationally efficient diesel pressure departure ratio algorithm, against selected cases of boost, engine load and exhaust gas recirculation. In this work, the formulation of the pressure departure ratio algorithm is presented in detail along with its implementation to enable combustion control during both transient and steady-state engine operations. Engine tests demonstrate that the algorithm was effective in stabilizing the combustion process on a cycle-by-cycle basis for a range of engine speeds, load and exhaust gas recirculation, which included conventional and low-temperature diesel combustion modes.

Enhancing the NO 2/NOx ratio in compression ignition engines by hydrogen and reformate combustion, for improved aftertreatment performance

Enhanced NO 2 production (without raising total NOx) in a diesel engine combustion chamber can improve the performance of several catalytic aftertreatment systems. Thus this can facilitate a further reduction in key regulated emissions such as nitrogen oxides (NOx) and particulate matter (PM) emissions. The oxidation of NO to NO 2 is an important intermediate step involved in all current aftertreatment systems that are designed for NOx and PM catalytic removal. The performance of both NOx control systems and catalysed particulate filters depend highly on the NO 2 concentration. In this work we have examined the influence of using hydrogen (H 2) and simulated reformate (H 2, CO and EGR gases) as a supplement to diesel fuel on NO 2 production. In actual engine applications a reformer will be integrated within the engine EGR system. This will not only provide the engine with recirculated exhaust gas (i.e. EGR), but will enrich it with H 2 and CO. The effects of adding H 2 or reformate results in a significant decrease in total engine-out NOx emissions, as well as an increase in both NO 2 concentration and NO 2/NOx ratio. The influence of the simulated reformate combustion on the NO 2 production is dependent on the engine load and in-cylinder conditions. It was observed that both reformate composition and concentration significantly influence the NO 2/NOx ratio of the exhaust gas. Air/fuel ratio, combustion efficiency and in-cylinder temperatures were the most influential parameters in this study. The NO 2 production was dependent on the EGR addition and air/fuel ratio.