Decrease In Soot Emissions Research Articles

Hardware-in-the-loop validation of a power management strategy for hybrid powertrains

Previously, a hybrid powertrain management strategy was developed that controls the power sources based on frequency content, mitigating aggressive engine transients. This article presents a hardware-in-the-loop validation of this strategy, with a real engine and battery integrated into a diesel hybrid electric vehicle simulation, thereby allowing for a realistic evaluation of fuel economy, soot emissions, and battery life. Considering an aggressive drive cycle and a state-of-charge regulation strategy as a benchmark, the frequency-based strategy yields 5.9% increase in fuel economy, 62.7% decrease in soot emissions, and 23% reduction in effective Amp-hours processed, which should yield an increase in battery life.

Development of a Emission Compliant, High Efficiency, Two-valve DI Diesel Engine for Off-road Application

Nowadays, environmental concerns are posing a great challenge to DI Diesel engines. Increasingly tightening emission limits require a higher attention on combustion efficiency. A high efficiency Diesel engine can be developed only mastering all the parameters that can affect the combustion and, therefore, NOx and soot emissions. In this scenario, computational fluid-dynamics can prove its power guaranteeing a deeper understanding of mixture formation process and combustion.In this work, the development of an engine in order to fulfill Tier 4i emission standard will be presented, the Tier 4i compliance must be reached without an excessive increase of the final cost of the engine. Originally, the engine was a two-valve engine supplied with a DPF, since no SCR aftertreatment is supplied, NOx emission target are achieved through external exhaust gas recirculation and retarding the start of injection.Through combustion process simulations, performed with the CFD code KIVA3D, varying different geometric parameters and the intensity of the swirl ratio, the interaction between the swirl flow field, generated by the intake duct, the reverse squish motion, and motions aerodynamically generated by spray has been investigated leading to a better interaction between the flow field, the fuel spray and the piston bowl geometry and to the definition of a new engine lay-out. The study shows how, given the need of retarded injection for limiting NOx emission, the decrease of swirl ratio, when combined with a proper piston bowl design, allows a significant decrease of soot emissions and the achievement of Tier 4i emission standard.The study has been validated comparing the intake phase simulations, performed with the CFD code Fire v2009 v3, followed by the combustion process performed with the KIVA3D code, with the experimental result obtained from the engine assembled following the developed design.

Laser-induced fluorescence measurements in venturi cascaded propane gas jet flames

<title/>A propane jet diffusion flame at a burner exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi cascading technique resulted in a decrease of 33% in NO emission index along with a 24% decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). The temperature measurements showed that, in the near-burner region, the venturi cascaded flame has an average temperature lower by 5% than the baseline flame. However, in the mid-flame and far-burner regions, it has a temperature 13 and 12% higher, respectively. The NO composition measurements revealed that in the near-burner, mid-flame and far-burner regions, the venturi cascaded flame has lower NO concentrations by 16, 5 and 3%, in average values respectively, compared to the baseline case. In order to understand the above results and observations, Laser induced fluorescence (LIF) spectroscopy was employed to detect the minor species (OH, CH and CN) in the baseline and venturi cascaded flames. The LIF measurements, in the near-burner region of the venturi cascaded flame, indicated an average decrease of 18, 24 and 12% in OH, CH and CN radical species respectively, from their baseline values. However, in the mid-flame region, a 40% average increase in OH, from its baseline value, was observed. In this particular region, the CH or CN radicals were not detected. The LIF results were used to understand the thermochemical processes involved including soot and NO formation. It showed that OH radical, in the downstream locations, was mostly affected by soot rather than by temperature. In addition, prompt NO mechanism appeared to play a significant role besides the conventional thermal NO mechanism.

Mechanism of Oxygen Concentration Effects on Combustion Process and Emissions of Diesel Engine

The mechanism of oxygen concentration effects on the combustion process of diesel combustion and the effects of injection pressure and intake pressure on low-temperature combustion are investigated by CFD simulation. The oxygen concentration is modulated by CO2. The results indicate: with the decrease of oxygen concentration, the peak of the average in-cylinder pressure decreases and the ignition delay becomes long. Decreasing oxygen concentration is the most effective method to control NOx emissions. With the decrease of oxygen concentration, soot emissions increase first and then decrease. It is the essential reason of low soot emissions at low oxygen concentrations that the low in-cylinder combustion temperature leads to the inhibition of soot formation. With the increase of injection pressure, the flow velocity and turbulent kinetic energy in the cylinder increase, which are beneficial to improving the mixing of fuel and air; soot emissions decrease; and NOx emissions increase. The enhancement of intake pressure improves the condition of oxygen lack at lower oxygen concentration. With the increase of intake pressure, ignition delay becomes long. Soot and NOx emissions decrease.

COMPUTATIONAL STUDY ON THE EFFECTS OF NON-PERIODIC FLOW PERTURBATIONS ON THE EMISSIONS OF SOOT AND NOX IN A CONFINED TURBULENT METHANE/AIR DIFFUSION FLAME

A computational investigation on the effects of fuel inlet perturbations in a confined turbulent CH4/air flame has been performed. Non-periodic fluctuations were characterised at the fuel inlet via a pair of sinusoidal harmonics of incommensurate periods with identical amplitude and frequency. Harmonic amplitudes of 2.5%, 7.5%, and 12.5% with respect to the time-averaged fuel inlet velocity have been simulated and their results weighted against the predictions in a steady fuel delivery. The results showed a decrease in soot emissions as the amplitude of the perturbation increased; nonetheless, a logarithmic behaviour was observed, suggesting that soot reduction will stabilise after certain pulse amplitude for a given frequency. The results from the 12.5% incommensurate pulse were also compared with its simple harmonic equivalent. Localized reductions in NO emissions were also observed in the incommensurate flame with respect to the sinusoidal pulse. The case study was based on a 2-dimensional axi-symmetric piloted methane flame with a time-averaged jet Reynolds number of about 7000. Realizable k − ϵ and Eddy Dissipation were employed to solve turbulence transport and chemistry respectively. Magnussen's soot model has been employed to simulate the formation of particulates and the thermal and prompt NOx sources have been considered.

Laser-Induced Fluorescence Measurements in Venturi-Cascaded Propane Gas Jet Flames

Venturi-cascading is a technique to control pollutant emissions from diffusion flames by modifying air infusion and fuel-air mixing rates through changing the flow dynamics in the combustion zone with a set of venturis surrounding the flame. A propane jet diffusion flame at a burner-exit Reynolds number of 5100 was examined with a set of venturis of specific sizes and spacing arrangement. The venturi-cascading technique resulted in a decrease of 33 percent in NO emission index along with a 24-percent decrease in soot emission from the flame, compared to the baseline condition (same flame without venturis). In order to understand the mechanism behind these results, laser-induced fluorescence (LIF) spectroscopy was employed to study the concentration field of the radicals (OH, CH, and CN) in the baseline and venturi-cascaded flames. The LIF measurements, in the near-burner region of the venturi-cascaded flame, indicated an average decrease of 18, 24 and 12 percent in the concentrations of OH, CH, and CN radicals, respectively, from their baseline values. However, in the midflame region, a 40-percent average increase in OH from its baseline value was observed. In this region, CH or CN radicals were not detected. The OH radical concentration in the downstream locations was mostly affected by soot rather than by temperature.

Injection of a H 2O 2/water solution into the combustion chamber of a direct injection diesel engine and its effect on soot removal

Hydrogen peroxide (H2O2) dissolved in water was injected into the combustion chamber of a direct injection (DI) diesel engine at different crank angles. Its effect on the general combustion characteristics was followed by crank angle (CA) resolved pressure and OH radiation measurements inside the combustion chamber. The influence on soot mass in the exhaust gas flow was measured by the Bosch Smoke Number, which is the stadard measurement technique in internal combustion engine research. Additionally, the concentrations of unburned hydrocarbons (HC) and nitric oxides (NOx) were recorded by a gas analyzer. For both, the spray of H2O2/water and pure water, a clear decrease in soot emission was observed for early injection at crank angles −40°<CA<−10o before top dead center (BTDC), which is associated with an increase in the exhaust gas HC concentration. For these conditions, the soot removal is mainly an effect of compressed air coolig, which increases the induction time of the diesel spray, thus resulting in a shift toward more premixed combustion. At injection crank angles CA>+10o, the water and the H2O2/water sprays show an opposite behavior with respect to the exhaust gas soot. The in-cylinder measurements clearly show an increase of OH radiation during cycles with H2O2/water injection compared to the standard engine conditions. The H2O2 decomposition product OH influencs the chemistry of the in-cylinder soot oxidation, which results in a decrease of the soot mass in the engine exhaust gas flow. Concentrations of HC and NOx are not significantly affected. The addition of pure water causes an increase in the exhaust gas soot for spray injection crank angles CA <+10o.

An Experimental Study on Kerosene-Hydrogen Hybrid Combustion in a Gas Turbine Combustor

Kerosene-hybrid combustion was studied in a swirler type combustor. Kerosene was atomized by an air blast atomizer, and geseous hydrogen was supplied to a kerosene spray through an annular slit installed in the atomizer. The following results were obtained. Blow out limit of the flame shifts to the lea side of the air-fuel mixture in the hybrid combustion. Hybrid combustion results in a slight decrease in NOx emission and a remarkable decrease in soot emission. When the hybrid ratio is under 10%, the flame stability is improved by the hybrid combustion. Increasing the hybrid ratio from 10% to 50% produces and increased combustion efficiency and reductions of soot and NOx. While the hybrid ratio is over 50%, the characteristics of the hybrid combustion flame become similar to those of hydrogen gas flame.