NOx Emissions Of Diesel Engine Research Articles

Air-fraction modeling for simultaneous Diesel engine NOx and PM emissions control during active DPF regenerations

This study develops a control-oriented air-fraction model which can accurately predict the air-fraction dynamics for a Diesel engine and the coupled aftertreatment system (mainly Diesel oxidation catalyst (DOC)) during active DPF regenerations. NOx and particulate matter (PM) emissions are the two main concerns for modern Diesel engine development. Diesel particulate filters (DPFs) have become a standard device for reducing the PM emissions from Diesel engine powertrains. To maintain high filtration efficiencies and avoid high back pressures, active DPF regenerations have to be implemented periodically by significantly elevating the exhaust gas temperatures. However, during active DPF regenerations, the selective catalytic reduction (SCR) deNOx performance may be significantly decreased, while the high temperature durability and total hydrocarbon (THC) poisoning of SCRs may be potential issues. To simultaneously meet the NOx emission standard, high-pressure loop EGR needs to be applied. Since in-cylinder NOx reduction relies heavily on the in-cylinder oxygen content, an accurate air-fraction model is necessary, and the effects of recycled THC and CO emissions should be considered. The developed air-fraction model has been experimentally validated to show its capability of capturing the actual air fraction dynamics accurately. Such a model can be instrumental in simultaneous NOx and PM emission control during active DPF regenerations and in advanced combustion mode control.

Research on SSCR Technology to Reduce NOx Emissions for Diesel Engines

Mainly due to the current reduction of NOx that is SCR technology which has some problems, it is difficult to meet the increasingly stringent emission regulations.Then people study the SSCR system that uses solid reducing agent, the solid reducing agent has large ammonia density.SSCR system injects NH3 directly into the tail in the airway through the injection system ,which is directly mixing with the exhaust. Comparing with SCR system,the decomposition temperature is low,the mixing time is shorter,that also reduces the negative impact caused by injection.

Development of a control-oriented model to optimise fuel consumption and NOX emissions in a DI Diesel engine

This paper describes a predictive NOX and consumption model, which is oriented to control and optimisation of DI Diesel engines. The model applies the Response Surface Methodology following a two-step process: firstly, the relationship between engine inputs (intake charge conditions and injection settings) and some combustion parameters (peak pressure, indicated mean effective pressure and burn angles) is determined; secondly, engine outputs (NOX and consumption) are predicted from the combustion parameters using NOX and mechanical losses models. Splitting the model into two parts allows using either experimental or modelled combustion parameters, thus enhancing the model flexibility. If experimental in-cylinder pressure is used to obtain combustion parameters, the mean error of predicted NOX and consumption are 2% and 6% respectively, with a calculation time of 5.5ms. Using modelled parameters reduces the calculation time to 1.5ms, with a penalty in the accuracy. The model performs well in a multi-objective optimisation, reducing NOX and consumption in different amounts depending on the objective of the optimisation.

Study on NOx and Soot Emissions in Diesel Engines with Multi-Stage Injection Based on a Stochastic Combustion Model

Study on NOx and Soot Emissions in Diesel Engines with Multi-Stage Injection Based on a Stochastic Combustion Model

Impact of nozzle holes configuration on fuel spray, wall impingement and NOx emission of a diesel engine for biodiesel–diesel blend (B20)

A diesel engine fueled with biodiesel-diesel blend (B20) decreases CO, HC and smoke emissions drastically. However, NOx emission and chance of wall impingement increased significantly leading to the problems of the diesel engine for use of the biodiesel-diesel blend. Hence, the study is aimed at reduction in NOx emission of the engine at source level and chance of wall impingement using the modified nozzle configuration (5 (base) and 6 (modified) holes). NOx emission of the engine for B20 fuel decreased from 7.4 g/kW-hr with the base nozzle configuration to 6.6 g/kW-hr with modified nozzle configuration due to reduction in in-cylinder temperature, retarding in dynamic injection timing, reduction in spray penetration distance. The spray penetration distance for B20 with the modified nozzle configuration is lesser resulting in less chance of wall impingement resulting in solution to the main durable issues of diesel engines for B20. The spray characteristics including sauter mean diameter, penetration distance and air entrainment are analyzed for B20 fuel in detail. The NOx emission is well correlated with spray penetration distance. The modification of nozzle configuration (number of holes) is a solution to reduce NOx emission of biodiesel fueled diesel engine at source level and also the chance of wall impingement with tangible benefits of HC, CO, smoke and BSEC reduction.

Pilot-Scale Aftertreatment Using Nonthermal Plasma Reduction of Adsorbed NOx in Marine Diesel-Engine Exhaust Gas

Regulations governing marine diesel engine NOx emissions have recently become more stringent. As it is difficult to fulfill these requirements by combustion improvements alone, effective aftertreatment technologies are needed to achieve efficient NOx reductions. In this study, we develop an effective NOx-reduction aftertreatment system for a marine diesel engine that employs combined nonthermal plasma (NTP) and adsorption. Compared with selective catalytic reduction, the proposed technology offers the advantages of not requiring a urea solution or harmful heavy-metal catalysts and low operating temperatures of less than 150 °C. The NOx reduction comprises repeated adsorption and desorption flow processes using NTP combined with NOx adsorbents made of MnOx–CuO. High concentrations of NOx are treated by NTP after NOx adsorption and desorption, and this aftertreatment system demonstrates excellent energy efficiencies of 161 g(NO2)/kWh, which fulfills the most recent International Maritime Organization emission NOx standards in the Tier II–III regulations for 2016 and requires only 4.3 % of the engine output power.

Diesel engine NOx emissions control: An advanced method for the O2 evaluation in the intake flow

In recent decades, the increasingly tight emissions regulations, along with the ever-increasing price of fuels and the request for more power from the engines, has pushed the world car industry to improve the performances of the applications of electronics, designed to control the internal combustion engines (ICE) and the pollutant emissions systems. At present, one of the main problems, in the development of diesel engines is represented by the achievement of an increasingly strict control on the systems used for the pollutant emission reduction. In particular, as far as NOx gas is concerned, EGR systems are mature and widely used, but increased efficiency in terms of emissions abatement, is necessary in order to determine as best possible the actual oxygen content in the charge at the engine intake manifold. The present work compares the ability of the ANN and Neuro-Fuzzy approach (ANFIS) to predict the volumetric oxygen concentration at the intake, using experimental data acquired on a compression ignition engine in transient operational conditions. In an off-line evaluation of results, both models show good predicting abilities; in particular the ANFIS model presents an absolute error value for the training and test phases respectively equal to 0.7 and 0.9 (as a percentage of 3.5% and 4.5%), while, the same evaluation obtained using the ANN-BP model provides 0.92 and 0.9 (as a percentage of 4.6% and 4.5%). The comparison shows that the ANFIS model produces more accurate solutions in less time, using linear rules that bind the input variables with the output. The linearity of the rules is a key feature to decrease the convergence time especially when the model is used for the on-board periodic training activity due to the aging of the engine.

Investigation of the effects of steam injection on performance and emissions of a diesel engine fuelled with tobacco seed oil methyl ester

Although biodiesel is renewable, nontoxic, biodegradable and has low emission profiles, the main drawback of using biodiesel in diesel engines is higher NOx. In this study, steam injection has been used as a method to reduce NOx emissions of a direct injection diesel engine fuelled with tobacco seed oil methyl ester (TSOME). The effects of 10% (S10) and 20% (S20) steam ratio have been investigated in terms of performance and emissions of a diesel engine fuelled with 20% (B20) TSOME. Steam is injected into the inlet manifold during inlet period. It is shown that steam injection into the engine fuelled with B20 fuel improved torque, effective power, effective efficiency and specific fuel consumption (SFC) decreased. Whilst S10 has been found optimum at the low engine speeds, S20 is optimum at the high speeds for the performance. However, S10 has been found as optimum for the exhaust emissions. At this injection ratio, both NOx and smoke emissions decrease. As a result, steam injection is a found powerful tool for reducing NOx emissions of the diesel engines running with biodiesel blend.

우레아염 퇴적 방지를 위한 믹서 위치 및 하우징 형상에 따른 벽면 유동특성에 관한 연구

Abstract: The Urea-SCR system commercialized shows a remarkable performance to reduce NOx emission in heavy duty diesel engines. However, Urea-water solution injected upstream a mixer, which is set up inside a exhaust pipe to promote exhaust gas-atomized droplet mixing, bumps up against the wall of a exhaust pipe as the droplets flow downstream through the exhaust gas. The urea deposited on the wall of the exhaust pipe is changed into the Urea-salt, resulting in the decreased life-time of the SCR catalysts. Therefore, the develop-ment of the urea deposition avoidance technologies is being treated as an important issue of the Urea-SCR systems. An experimental study was carried out to investigate the effects of the wall flow characteristics around the mixer-housing assembly with the variation of the mixer housing surrounding and supporting the mixer, which is designed to increase the wall flow and then to reduce droplet deposition. The flow character-istics was investigated by using a hot-wire anemometry for 2-D simplified duct model, and the housing tilt angles and the position of the mixer were changed : angle of 0°, 1°, 2°, 3°, and mixer positions of 0L, 0.5L, 1L. The results showed that the wall flow onto the exhaust pipe was improved with changing the tilt angle of the mixer housing, and the wall flow improved more when the position of the mixer was on 1L.

Combustion mode switching control in a HCCI diesel engine

HCCI (Homogeneous Charge Compression Ignition) combustion has the potential to significantly reduce NOx and PM emission of diesel engines due to its nature of even mixture and low temperature combustion. This combustion mode is only applicable in part load and low speed area so far. This range limitation results in frequently combustion mode switching from HCCI to CI and vice versa in real applications. HCCI realized by late injection with heavy EGR rate is investigated, which is also named PCCI (Premixed Charged Compression Ignition) sometimes. By changing control parameters (including injection timing, injection pressure and EGR rate) individually, the influences of these parameters on HCCI combustion and emissions are identified. Based on the evaluation of the influences, one pre-defined step-by-step air–fuel coordination strategy is presented. Additionally one hysteresis combustion mode determination method is proposed to avoid target mode fluctuation due to variation of engine speed or engine load in a small range. Torque deficiency occurs in acceleration transients as a result of fuel limitation to reduce soot emission, especially during HCCI to CI transitions. One ISG (Integrated Starter Generator) motor is applied to perform dynamic torque compensations in transient operations. Engine friction torque is estimated by means of cylinder pressure information from in-cylinder pressure sensors. On the basis of torque estimation, the difference between desired engine brake torque and actual engine brake torque is obtained. The torque output of ISG motor accounts for this torque gap and the torque pre distributed to ISG motor. The strategy is verified by engine tests. Experimental results indicate that, with the finely defined air–fuel coordination, less unstable combustion occurs and the target modes are established more quickly during transitions both in steady states and in transients. The torque deficiency during acceleration operations could be well compensated by the ISG motor.

Experimental investigation to reduce emissions of CI (compression ignition) engine fuelled with methyl ester of cottonseed oil using antioxidant

Biodiesel offers cleaner combustion over conventional diesel fuel, including reduced particulate matter, carbon monoxide and unburned hydrocarbon (HC) emissions. However, several studies point to increase in NOx emissions (about 13%) for biodiesel fuel compared with conventional diesel fuel. In this paper, the experimental investigation on the effect of antioxidant additive (l-ascorbic acid) on NOx emissions in a methyl ester of cottonseed oil- (MECSO) fuelled direct injection diesel engine has been reported. The antioxidant additive is mixed in various proportions (100–400 mg) with MECSO and was tested in computerised four-stroke water-cooled single-cylinder diesel engine of 3.5 kW rated power. Results show that the antioxidant additive is effective in controlling the NOx and HC emissions of MECSO-fuelled diesel engines.

Design and Experimental Study on the Urea-SCR Converter Exhaust System of the Marine Diesel Engine

Urea-SCR catalytic converter can effectively reduce the NOx emission of diesel engines, but meanwhile catalytic converter will cause some pressure loss in the exhaust system, which has negative influences on the engine performances. In this paper, the method of theoretical analysis calculated the pressure loss of the SCR catalytic converter, and designing a new type of exhaust gas pipe. Through the test to meet the design requirements,the results can provide a reference for optimum design of SCR catalytic converters and assembling.

A fast and accurate physics-based model for the NOx emissions of Diesel engines

To date, models for the nitrogen-oxide emissions of Diesel engines are either of empirical or phenomenological nature. The former are fast and quantitatively accurate in the identified region, but lack the generality and extrapolation capability of the latter. The model presented in this work combines the advantages of both model types and thus complies with typical requirements of computationally intensive fields such as dynamic optimisation and model-based control. This unique aggregation of features is achieved by extracting the most relevant physical phenomena and extending them by physically motivated empirical elements. Exploiting the assumptions made and using a setpoint-relative formulation leads to a simple model structure, comprising one map and 10 scalar parameters only. Execution speed is roughly 500 times faster than real-time and throughout the entire engine operating-range, also during transient operation, relative errors are below 10% even for the largest allowable, simultaneous variation of all inputs. Apart from engine speed and injected fuel-mass, the model requires the cylinder-charge, its composition, and the start of combustion with the corresponding pressure and temperature as inputs. The latter can either be obtained from measured in-cylinder pressure signals, or may be calculated from quantities provided by a model for the air path of the engine.

Measurement and prediction of the speed of sound of biodiesel fuels

Speed of sound is an important fuel thermophysical property that directly characterizes the fuel injection and the NOx emissions in diesel engines especially for injectors activated with pressure. Nevertheless, the experimental data of speed of sound for biodiesel fuels are very scarce in the literature. Thereby, this work aims at measuring the speed of sound for biodiesels fuels and evaluating some predictive models to estimate the speed of sound from the composition of fatty acid methyl esters in the biodiesel.For that purpose the measurement of speeds of sound for three fatty acid methyl esters and ten biodiesel fuels at atmospheric pressure and temperatures from 288.15 to 343.15K was done. The ability of two versions of Auerbach’s relation, and the ideal mixture mixing rule to describe the speed of sound of biodiesels was evaluated. The results evinced that, with the exception to the original version of Auerbach’s relation, the other models studied provide a good estimate of the experimental data. The modified Auerbach’s relation displays an overall average relative deviation of 1.64%, and the ideal mixture mixing rules predict the biodiesel speed of sound with only 0.37% of overall deviation. Moreover, the dependency of speed of sound on pressure was also correlated with a linear equation, presenting only an overall deviation of 0.56%. These models can thus be a good tool to estimate the speeds of sound using only information about the biodiesel composition.

Impact of Intake CO2 Addition and Exhaust Gas Recirculation on NOx Emissions and Soot Reactivity in a Common Rail Diesel Engine

The impact of intake CO2 addition and exhaust gas recirculation (EGR) on engine combustion characteristics, NOx emissions, and soot oxidative reactivity was studied in a common rail diesel engine equipped with a cooled EGR system. The engine test results and the heat release analysis show that the reduced flame temperature, induced by the reduction of the oxygen concentration (dilution effect) is the dominant mechanism via which CO2 and EGR lower NOx emissions in diesel engines. On the other hand, the collected soot from the engine tests was examined for its oxidative reactivity using a thermogravimetric analyzer (TGA). Results show that EGR has a significant effect on soot reactivity and results in higher initial active sites compared to the CO2 case. We conclude that the reduced flame temperature (thermal effect) which is a consequence of the dilution effect is responsible for the observed increase in soot reactivity. These results confirm observations from our past work on flame soot, which showed that the peak adiabatic flame temperature is the governing factor affecting soot reactivity. These findings imply that driving the combustion concepts toward low temperature is favorable to effectively control engine pollutants, including soot reactivity.

Research on a diesel HCCI engine assisted by an ISG motor

HCCI combustion can substantially reduce NOx and soot emissions of diesel engines. However it is hard for diesel HCCI to obtain the same level of fuel economy as traditional diesel engines. This paper presents a way to improve the fuel economy of diesel HCCI by adopting Integrated Starter Generator (ISG). A set of diesel parallel hybrid power system (in this article, we name it “hybrid engine”) is constructed by installing an ISG motor on a diesel engine, which applies HCCI–CI combined combustion. Based on a lot of investigation on diesel HCCI, this paper is focus on improving HCCI engine performance, especially the fuel economy, by adopting ISG motor assist control. The coordination control strategies of engine and ISG motor in HCCI transient states, HCCI–CI transition, engine quick start and braking energy regeneration are developed. The results of equivalent New European Driving Cycle (NEDC) tests show that, by using ISG assistance, the fuel consumption of the diesel HCCI engine is greatly reduced. Meanwhile the NOx and soot emission are also improved.

Cooled EGR 시스템의 EGR률과 연료분사시기가 소형 디젤엔진의 배기 배출물 특성에 미치는 영향에 관한 연구

Cooled EGR system is widely used to reduce NOx emissions in diesel engine. But when EGR rate was increased, combustion stability was worsened and PM level was increased. So determining optimized control point of EGR rate is important. In order to determine this point, it is important to figure out the effect of EGR system on the exhaust emissions. In this research, NOx and PM emissions were analyzed with various coolant temperature supplied to the EGR cooler at several positions such as downstream of turbocharger, upstream and downstream of DPF. Effects of some variables such as EGR rate, hot / cooled EGR and change of injection timing were estimated. And <TEX>$CO_2$</TEX> emissions were measured at exhaust and intake manifold to calculate EGR rate at each engine operating condition. Also combustion analysis was performed in each engine operating conditions. In the result of this study, there was trade-off between NOx emissions and PM emissions. When EGR rate was increased, combustion pressure was decreased and COV of IMEP was increased.

B-splines for Diesel Engine Emission Modeling

The equivalence between linear interpolation and B-spline functions of degree 1 is described. The equivalence is used to express interpolation based diesel engine NOX and soot emission models as B-spline functions, and to apply data fitting methods for B-spline functions to perform calibration of the models. This strategy leads to that the model calibration can be calculated directly by means of analytically solving a minimization problem. The B-spline representation also makes it possible to control the smoothness and extrapolation behavior of the interpolation maps in the models in a controlled manner. The models have been calibrated using measured steady-state data from a 5-cylinder Volvo passenger car diesel engine with a displacement volume of 2.4 liters, equipped with a turbocharger, an exhaust gas recirculation system, and a common rail injection system. The calibrated model for NOX emissions predicts the NOX mass flow with a root mean square error of 1.6 mg/s, and the calibrated model for soot emissions predicts the soot mass flow with a root mean square error of 0.65 mg/s. The described equivalence between linear interpolation and B-spline functions of degree 1 could also be used for calibration of other models of similar structure.

Validation of a zero-dimensional model for prediction of NOx and engine performance for electronically controlled marine two-stroke diesel engines

The aim of this paper is to derive a methodology suitable for energy system analysis for predicting the performance and NOx emissions of marine low speed diesel engines. The paper describes a zero-dimensional model, evaluating the engine performance by means of an energy balance and a two zone combustion model using ideal gas law equations over a complete crank cycle. The combustion process is divided into intervals, and the product composition and flame temperature are calculated in each interval. The NOx emissions are predicted using the extended Zeldovich mechanism. The model is validated using experimental data from two MAN BW one case being data subject to engine parameter changes corresponding to simulating an electronically controlled engine; the second case providing data covering almost all model input and output parameters. The first case of validation suggests that the model can predict specific fuel oil consumption and NOx emissions within the 95% confidence intervals given by the experimental measurements. The second validation confirms the capability of the model to match measured engine output parameters based on measured engine input parameters with a maximum 5% deviation.

Comparison of Filter Smoke Number and Elemental Carbon Mass From Partially Premixed Low Temperature Combustion in a Direct-Injection Diesel Engine

Partially premixed low temperature combustion (LTC) is an established advanced engine strategy that enables the simultaneous reduction of soot and NOx emissions in diesel engines. Measuring extremely low levels of soot emissions achievable with LTC modes using a filter smoke meter requires large sample volumes and repeated measurements to achieve the desired data precision and accuracy. Even taking such measures, doubt exists as to whether filter smoke number (FSN) accurately represents the actual smoke emissions emitted from such low soot conditions. The use of alternative fuels such as biodiesel also compounds efforts to accurately report soot emissions since the reflectivity of high levels of organic matter found on the particulate matter collected may result in erroneous readings from the optical detector. Using FSN, it is desired to report mass emissions of soot using empirical correlations derived for use with petroleum diesel fuels and conventional modes of combustion. The work presented in this paper compares the experimental results of well known formulas for calculating the mass of soot using FSN and the elemental carbon mass using thermal optical analysis (TOA) over a range of operating conditions and fuels from a four-cylinder direct-injection passenger car diesel engine. The data show that the mass of soot emitted by the engine can be accurately predicted with the smoke meter method utilizing a 3000 ml sample volume over a range of FSN from 0.02 to 1.5. Soot mass exhaust concentration calculated from FSN using the best of the literature expressions and that from TOA taken over all conditions correlated linearly with a slope of 0.99 and R2 value of 0.94. A primary implication of the work is that the level of confidence in reporting the soot mass based on FSN for low soot formation regimes such as LTC is improved for both petroleum diesel and biodiesel fuels.