Design and development of a particulate emission monitor

In the last two decades, numerous studies have revealed that atmospheric particulates and especially those emitted by diesel engined vehicles pose a serious health and environmental hazard. This thesis describes the design and development of a co-axial capacitance transducer as well as the ancillary solids dispersion production unit for the on-line measurement of particulates concentration in air in real time basis. The primary application of the device is as a particulate monitor for diesel engine exhausts although the reported experimental results also evaluate and establish its feasibility for monitoring solids/gas dispersions during their pneumatic conveying. Briefly, the transducer comprises two different diameter metallic cylindrical electrodes placed co-axially within one another so that an annulus is formed. The latter constitutes the sensing volume of the capacitance transducer following the application of a voltage between the two electrodes. The principle of the operation of the device relies on the fact that the effective dielectric constant of a solids-gas dispersion driven between the electrodes is proportional to the concentration of the entrained solids. In practice therefore, the concentration of a test powder is determined by measuring capacitance and referring to a previously prepared calibration chart. The feasibility and reliability of the transducer have been verified by conducting a series of experiments investigating its performance characteristics in response to changes in a number of design and operating parameters in conjunction with different powders of various size, density, and electrical properties. The design parameters investigated include variations in electrode diameters, length and separation distance. The various operating parameters on the other hand deal with changes in air relative humidity (8 - 78 %), temperature (20 °C - 100 °C), flow velocity (6.5 - 15 ms-1), solids flow pattern (e.g. from homogeneous to slug flow) as well as variations in the frequency of the applied voltage (1-100 kHz). The results indicate that the transducer's sensitivity increases with a decrease in the separation distance between the two cylindrical electrodes, whereas the electrodes' length has no profound effect on it. On the other hand, the effective dielectric constant, ϵeff of all solids-gas dispersions tested was found to be directly proportional to the solids concentration and unaffected by variations in air humidity, air velocity, electric field frequency, and solids flow regime. However, ϵeff for dispersions of insulating powders, in contrast to that of conducting powders, was found to be dependent on the respective dielectric constant of the solid particles as well as their size. Furthermore, in the case of mixtures of two insulating powders simultaneously dispersed in air, ϵeff was found to be dependent not only to the total solids concentration but also on the volumetric ratio of the two powders in the mixture. The transducer's baseline capacitance (zero solids concentration) varied linearly with the average surface temperature of the cylindrical electrodes. Finally, a 'temperature capacitor coefficient' was calculated in order to account for the effect of temperature on capacitance. This was found to be in close agreement with the coefficient of thermal expansion of the electrodes' material of construction (c.f. 0.0001/°C with 0.00012/°C)

Characterisation of flow structures inside an engine cylinder under steady state condition

The in-cylinder flow of internal combustion (IC) engines, formed during the intake stroke, is one of the most important factors that affect the quality of air-fuel mixture and combustion. The inducted airflow through the inlet valve is primarily influenced by the intake port design, intake valve design, valve lift and valve timing. Such parameters have a significant influence on the generation and development of in-cylinder flow motion. In most combustion systems the swirl and tumble motions are used to aid the air-fuel mixing with the subsequent decay of these bulk flow motions generating increased turbulence levels which then enhance the combustion processes in terms of rate of chemical reactions and combustion stability. Air motion formed inside the engine cylinder is three-dimensional, transient, highly turbulent and includes a wide spectrum of length and time scales. The significance of in-cylinder flow structures is mainly reflected in large eddy formation and its subsequent break down into turbulence kinetic energy. Analysis of the large scale and flow motions within an internal combustion engine are of significance for the improvement of engine performance. A first approximation of these flow structures can be obtained by steady state analysis of the in-cylinder flow with fixed valve lifts and pressure drops. Substantial advances in both experimental methods and numerical simulations provide useful research tools for better understanding of the effects of rotational air motion on engine performance. This study presents results from experimental and numerical simulations of in-cylinder flow structures under steady state conditions. Although steady state flow problem still includes complex three-dimensional geometries with high turbulence intensities and rotation separation, it is significantly less complex than the transient problem. Therefore, preliminary verifications are usually performed on steady state flow rig. For example, numerical investigation under steady state condition can be considered as a precondition for the feasibility of calculations of real engine cylinder flow. Particle Image Velocimetry (PIV) technique is used in the experimental investigations of the in-cylinder flow structures. The experiments have been conducted on an engine head of a pent-roof type (Lotus) for a number of fixed valve lifts and different inlet valve configurations at two pressure drops, 250mm and 635mm of H2O that correlate with engine speeds of 2500 and 4000 RPM respectively. From the 2-D in-cylinder flow measurements, a tumbling vortex analysis is carried out for six planes parallel to the cylinder axis. In addition, a swirl flow analysis is carried out for one horizontal plane perpendicular to the cylinder axis at half bore downstream from the cylinder head (44mm). Numerically, modelling of the in-cylinder flow is proving to be a key part of successful combustion simulation. The numerical simulations require an accurate representation of turbulence and initial conditions. This Thesis deals with numerical investigation of the in-cylinder flow structures under steady state conditions utilizing the finite-volume CFD package, STAR CCM+. Two turbulence models were examined to simulate the turbulent flow structure namely, Realizable k-ε and Reynolds Stress Turbulence Model, RSM. Three densities of generated mesh, which is polyhedral type, are examined. The three-dimensional numerical investigation has been conducted on the same engine head of a pent-roof type (Lotus) for a number of fixed valve lifts and both valves are opened configuration at two pressure drops 250mm and 635mm of H2O that is equivalent to engine speeds of 2500 and 4000 RPM respectively. The nature and modelling of the flow structure together with discussions on the influence of the pressure drop and valve lift parameters on the flow structures are presented and discussed. The experimental results show the advantage of using the planar technique (PIV) for investigating the complete flow structures developed inside the cylinder. It also highlighted areas where improvements need to be made to enhance the quality of the collected data in the vertical plane measurements. Based on the comparison between the two turbulence models, the RSM model results show larger velocity values of about 15% to 47% than those of the Realizable k-ε model for the whole regions. The computational results were validated through qualitative and quantitative comparisons with the PIV data obtained from the current investigation and published LDA data on both horizontal and vertical cross sections. The calculated correlation coefficient, which is above 0.6, indicated that a reasonable prediction accuracy for the RSM model. This verifies that the numerical simulation with the RSM model is a useful tool to analyse turbulent flows in complex engine geometries where anisotropic turbulence is created

Technological approaches to improve the engine efficiency and to reduce pollutant emissions of automotive diesel engines.

The research work was mainly focused on the technological approach to improve engine efficiency and reduce pollutant emissions applicable to diesel engines which are very often incompatible were assessed through a set of full- scale tests on a real diesel engine in order to satisfy the new emissions limits. (1) The first strategy evaluated in this work to improve the engine efficiency was the reduction of the mechanical losses: through the incorporation of nanomaterials in the lubricant formulation. The effect of the lubricant oil additivated with MoS2 nanopowders was assessed through a set of full - scale tests on a real diesel engine – several engine points and cooling water temperatures were investigated for both a reference oil and a MoS2-additivated one. (2) Other strategy to reduce pollutant emissions included in this PhD thesis was the effects of using a 30% by volume blend of a renewable fuel, called Farnesane, and fossil diesel in a small Euro 5 displacement passenger car diesel engine. (3) And finally, the CeO2/BaO/Pt system was selected in order to perform an NO2-assisted soot oxidation, as a aftertreatment strategy to reduce pollutant emissions. The aim of such catalytic system is to couple the catalytic functionality for soot abatement during DPF regeneration, namely CeO2, and an embedded lean NOx trap (LNT) functionality given by BaO, for NOx storage, whose oxidation over Pt to form adsorbed nitrates is facilitated by the presence of CeO2 itself

Colloidal Organic Pollutants in Road Runoff: Sources, Emissions and Effective Treatment Technologies

Thousands of organic substances circulate in our society and are diffusely emitted through traffic, combustion and leaching from constructions and building materials into the urban environment. The research in this PhD thesis focuses on road runoff as the highest concentrations of pollutants are frequently found in runoff from areas with high traffic intensity. Many organic pollutants (OPs) emitted from vehicles and traffic-related activities exhibit environmental persistence and a tendency to bioaccumulate and may have detrimental long-term effects on aquatic life. Road runoff contains a cocktail of both particulate and non-particulate OPs. Hydrophobic OPs such as higher petroleum hydrocarbons, phthalates, and polycyclic organic hydrocarbons (PAHs) are not exclusively bound to particles, but also present in runoff in colloidal and truly dissolved forms. These hydrophobic compounds can also form nano- and microsized emulsions that may carry pollutants in stormwater. Hence, it is of great importance to develop treatment technologies that can remove non-particulate OPs from contaminated stormwater. The overall aim of this PhD research was to evaluate the best options to manage the colloidal fraction of OPs in road runoff, including road dust, water and sediments. The research also included to study the sources, emissions and the transport processes of OPs in road runoff. In Paper I approximately 1100 compounds were chosen for further studies after comprehensive screening and assessment. The results of the developed iterative selection process used for identifying and selecting priority pollutants in urban road environments showed the following priority order: PAHs > aliphates C20–C40 > alkylphenols > phthalates > aldehydes > phenolic antioxidants > bisphenol A > oxygenated-PAHs > naphtha C5–C12 > amides > amines. Among these, PAH-16 were chosen for a substance flow analysis (SFA), which was performed for a highway case study area. The SFA showed that the main sources of PAHs emitted in the area were vehicle exhaust gases, followed by tyre wear, motor lubricant oils, road surface wear, and brake linings. Only 2–6% of the total 5.8–29 kg/ha annually emitted PAHs end up in the stormwater sewer system.Particle size distribution and zeta potential measurements was performed on simulated road runoff, using laboratory prepared mixtures of ultrapure water and specific OPs with and without addition of humic acid and iron colloids (Paper II). The aim was to provide an understanding of the transport routes of OPs in the environment, and to determine whether OPs are transported with nano- and microparticles in the form of emulsions The following simulation mixtures were identified as potential emulsions: diesel (aliphates); alkylphenols (APs) and their ethoxylates (APEOs); diesel with APs and APEOs; phthalates, and a mixture of all OPs (including PAH-16) with and without colloids. Most of the particles in the samples were found in the nano-range of 30–660 nm, and a smaller portion of particles < 28% were found to be micro-sized.In Paper III the potential of street sweeping to reduce the amounts of OPs and nano/microparticles reaching stormwater was investigated in a case study that included sampling road dust and washwater from a street sweeping machine, road dust before and after sweeping, and stormwater. The compound groups generally found in the highest concentrations in all matrices were aliphates C5–C35 > phthalates > aromates C8–C35 > PAH-16. The concentrations of aliphates C16–C35 and PAHs in washwater were extremely high at ≤ 53,000 \ub5g/L and ≤ 120 \ub5g/L, respectively, and the highest concentrations were found after a 3-month winter break in sweeping. The washwater contains a wide range of small particles, including nanoparticles in sizes from just below 1 nm up to 300 nm, with nanoparticles in the size range 25–300 nm present in the highest concentrations.The design of an experimental car wash and subsequent laboratory analysis with a focus on OPs and particle size distributions was performed in Paper IV. The car wash experiment simulated high and a low intensity rain and carwash using conventional and eco-friendly detergents. Per driven km phthatales were emitted by 0.10\uad–0.40 \ub5g, aliphates by 0.020–0.60 \ub5g and PAH-16 by 2.5 710-4–2.5 710-3 \ub5g, and were the OPs emitted in largest amounts from all cars. . The dominant phthalate was the high molecular weight di-iso-nonylphthalate (DINP) quantified up to 640 \ub5g/L. \ua0Nanoparticles in the size range 10–450 nm were also released in large amounts from the cars and the waters contained up to 3.3 7106 of particles per liter.In Paper V a pilot plant using column bed-filters of sand as a pre-filter, in combination with sorption filters of granulated activated carbon, Sphagnum peat or Pinus sylvestris bark, was used to investigate the removal of non-particulate OPs from urban stormwater. Samples from the filter effluents were collected weekly; during or after rain events; and during stress tests when incoming water was spiked with contaminated sediment and petrol or diesel. All sorption filters showed efficient reduction of aliphatic diesel hydrocarbons C16–C35, benzene, and the PAHs phenanthrene, fluoranthene, and pyrene during most of the operation time, which was 18 months. During the stress test events, all sorption filters showed 100% reduction of PAH-16, petrol and diesel aliphates C5–C35.The following recommendations are suggested to prevent further spread of OPs and nanoparticles to the urban environment: (1) Frequent street sweeping of the most polluted streets in urban areas should be introduced as soon as possible; (2) Frequent washing of vehicles in urban areas should be mandatory, especially during winter when emissions of exhaust gases and vehicle wear are greatest; (3) The final step for treating highly polluted stormwater must contain sorption filters to effectively remove OPs and especially OPs in colloidal forms. Future research should perform multi-criteria decision analyses to compare the treatment options studied in this research with other options to find the most sustainable solutions to remove OPs and nanoparticles from stormwater

HIGH INJECTION PRESSURE DME IGNITION AND COMBUSTION PROCESSES: EXPERIMENT AND SIMULATION

With nearly smokeless combustion, Dimethyl Ether (DME) can be pressurized and used as a liquid fuel for compression-ignition (CI) combustion. However, due to its lower heating value and liquid density compared with diesel fuel, DME has a smaller energy content per unit volume. To obtain an equivalent energy content of diesel, approximately 1.86 times more quantity of DME is required. This can be addressed by a larger nozzle size or higher injection pressure. However, the effect of high injection pressure on DME spray combustion characteristics have not yet been well understood. In order to fill this gap, spray and combustion processes of DME were studied extensively via a series of experiments in a constant-volume and optically accessible combustion vessel. In the current study, a hydraulic electric unit injector (HEUI) with a 180 µm single-hole nozzle was driven by an oil-pressurized fuel injection (FI) system to achieve injection pressure of 1500 bar. The liquid and vapor regions of DME jet were visualized using a hybrid Schlieren/Mie scattering at non-reacting conditions. At reacting conditions, high-speed natural flame luminosity of DME combustion was used to capture the flame intensity, and planar laser-induced fluorescence (PLIF) imaging was used to characterize CH2O evolution. Spray and combustion characteristics of DME were compared with diesel in terms of rate of injection (ROI), liquid/vapor penetration and, ignition delay. Flame lift-off length (LOL), flame structure, and formaldehyde (CH2O) formation of DME were also studied through high-speed imaging. The RANS Converge CFD simulation was validated against the experimental and used as a powerful tool to explore the DME spray characteristics under various conditions. Further insights into DME spray and flame structure were obtained through experimentally validated Large Eddy Simulations (LES) simulations

Theoretical and experimental investigation of a CDI injection system operating on neat rapeseed oil - feasibility and operational studies

This thesis presents the work done within the PhD research project focusing on the utilisation of plant oils in Common Rail (CR) diesel engines. The work scope included fundamental experimental studies of rapeseed oil (RSO) in comparison to diesel fuel, the feasibility analysis of diesel substitution with various plant oils, the definition and implementation of modifications of a common rail injection system and future work recommendations of possible changes to the injection system. It was recognised that neat plant oils can be considered as an alternative substitute for diesel fuel offering a natural way to balance the CO2 emissions. However, due to the differences between diesel and plant oils, such as density, viscosity and surface tension, the direct application of plant oils in common rail diesel engines could cause degradation of the injection process and in turn adversely affect the diesel engine’s performance. RSO was chosen to perform the spray characterisation studies at various injection pressures and oil temperatures under conditions similar to the operation of the common rail engine. High speed camera, Phase Doppler Anemometry and Malvern laser techniques were used to study spray penetration length and cone angle of RSO in comparison to diesel. To study the internal flow inside the CR injector the acoustic emission technique was applied. It was found that for oil temperatures below 40°C the RSO viscosity, density and surface tension are higher in comparison to diesel, therefore at injection pressures around 37.50 MPa the RSO spray is not fully developed. The spray penetration and cone angle at these spray conditions exhibit significant spray deterioration. In addition to the lab experiments, KIVA code simulated RSO sprays under CR conditions. The KH-RT and RD breakup models were successfully applied to simulate the non-evaporating sprays corresponding to the experimental spray tests and finally to predict i real in-cylinder injection conditions. Numerical results showed acceptable agreement with the experimental data of RSO penetration. Based on experimental and numerical results it was concluded that elevated temperature and injection pressure could be the efficient measures to overcome operational obstacles when using RSO in the CR diesel engine. A series of modifications of low- and highpressure loops was performed and experimentally assessed throughout the engine tests. The results revealed that the modifications allowed to run the engine at the power and emission outputs very close to diesel operation. However, more fundamental changes were suggested as future work to ensure efficient and trouble-free long-term operation. It is believed that these changed should be applied to meet Euro IV and V requirements

Aerosols and Electrical Discharge: 1. Examination of Potential Climate Impact of Mercury Control in Electrostatic Precipitators (ESPs); 2. Instantaneous Bioaerosol Inactivation by Non-Thermal Plasma

One common technology for airstream aerosol (or particulate matter) control is through electrical discharge. Electrical discharge within a neutral gas under atmospheric conditions has two major essential applications related to either its physical or chemical properties. Devices such as electrostatic precipitators (ESPs) are widely applied to reduce stationary PM emission utilizing physical properties of electrical discharge. Separately, the chemical properties of the high voltage discharge can be utilized in several chemical processes, including bioaerosol disinfection. This dissertation had two research focuses related to either the physical or chemical properties of electrical discharge on aerosol control. The first study focus is on potential impact of mercury emission control by powdered activated carbon (PAC) injection to climate change due to low removal efficiency of PAC in ESPs. The injection into the flue gas of PAC is the most mature technology for controlling mercury emissions from coal combustion. However, carbonaceous particles are known to have poor capture in ESPs. Thus, the advent of mercury emissions standards for power plants has the potential for increased emissions of PAC, whose climate change impact is unclear. The study conducted the first comparative measurements of optical scattering and absorption of aerosols comprised of varying mixtures of coal combustion fly ash and PAC. A partially fluidized bed (FB) containing fly ash-PAC admixtures with varying PAC concentrations elutriates aerosol agglomerates. A photo-acoustic extinctiometer (PAX) extractively samples from the FB flow, providing measurements of optical absorption and scattering coefficients of fly ash (FA) alone and FA-PAC admixtures. The results indicate that the increase of carbonaceous particles in the FB emissions can cause a significant linear increase of their mass absorption cross sections. Thus, widespread adoption of activated carbon injection in conjunction with ESPs has the potential to constitute a new source of light absorbing (and climate warming) particle emissions. The second research focus is on packed-bed non-thermal plasma (NTP) discharges and its in-flight inactivation of bacteriophage MS2 and Porcine Reproductive and Respiratory Syndrome virus (PRRSv). To reduce threats of airborne infectious disease outbreaks, there exists a need for control measures that provide effective protection while imposing minimal pressure differential, where NTP can be a solution. In the first part of this study, a low-cost consumer-grade ultrasonic humidifier is proved to consistently suspend dry MS2 aerosols into a constant air flow, and the ultrasonic atomization rate can be monitored in real-time by laser-photodiode light attenuation measurements. In the second part, suspended viral aerosols in a controlled airstream were subjected to NTP exposure within a packed-bed dielectric barrier discharge reactor. Results of plaque assays for MS2 and TCID50 (50% Tissue culture infective dose) for PRRSv showed increasing inactivation of aerosolized viruses (42% to >99%) with increasing applied voltage. No evidence showed that the lipid layer of enveloped PRRSv offered any protection against inactivation, and the virus were inactivated comparably to MS2 by the reactor. Increasing the air flow rate did not significantly impact virus inactivation effectiveness. Activated carbon based ozone filters greatly reduced residual ozone, in some cases down to background levels, while adding less than 20 Pa pressure differential to the 45 Pa differential pressure across the packed bed. The study shows promising results that the prototype packed bed NTP reactor has the potential to reduce airborne infectious disease transmission into indoor environment without significant ozone emission and pressure drop.PHDEnvironmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146103/1/xiatian_1.pd

Characterisation of particulate matter of traffic origin in Singapore

Master'sMASTER OF ENGINEERIN