Pravesh Chandra Shukla

Assessment of toxic potential of primary and secondary particulates/aerosols from biodiesel vis-à-vis mineral diesel fuelled engine

Abstract Toxicity of engine out emissions from primary and secondary aerosols has been a major cause of concern for human health and environmental impact. This study aims to evaluate comparative toxicity of nanoparticles emitted from a modern common rail direct injection engine (CRDI) fuelled with biodiesel blend (B20) vis-à-vis mineral diesel. The toxicity and potential health hazards of exhaust particles were assessed using various parameters such as nanoparticle size and number distribution, surface area distribution, elemental and organic carbon content and polycyclic aromatic hydrocarbons adsorbed onto the particle surfaces, followed by toxic equivalent factor assessment. It was found that biodiesel particulate toxicity was considerably lower in comparison to mineral diesel.

Development of low cost mixed metal oxide based diesel oxidation catalysts and their comparative performance evaluation

A four cylinder transportation diesel engine was used to evaluate the performance of two non-noble metal based diesel oxidation catalysts (DOC) with respect to various emission parameters such as particulate mass, elemental/organic carbon (EC/OC) content, and trace-metal content in particulates. Two new non-noble metal based DOCs were prepared and evaluated using mixed oxide (Co3O4–CeO2) and perovskite catalysts with ceria support. Emissions were evaluated before and after the use of a commercial DOC for comparison. Experimental results showed that newly prepared DOCs were effective in reducing the organic carbon content of particulates. The effectiveness of these DOCs increased with higher engine loads. Performance of these two prepared DOCs was comparable to the commercial DOC. Trace metal concentration in particulates increased for most metals detected, primarily due to reduced organic carbon content of particulates emitted from the DOC. Prepared DOCs showed significant reduction in organic carbon at 50% and higher engine loads. Significant organic carbon reduction was found to be responsible for particulate reduction.

Effectiveness of non-noble metal based diesel oxidation catalysts on particle number emissions from diesel and biodiesel exhaust.

Two new formulations of non-noble metal based diesel oxidation catalysts based on CoCe based mixed oxide (DOC2) and perovskite catalysts (DOC3) were prepared and retrofitted in a 4-cylinder diesel engine fueled by diesel and Karanja biodiesel blend (KB20). In this study, their effectiveness in reducing raw exhaust particulate emissions vis-à-vis a commercial diesel oxidation catalyst (DOC1) was evaluated. Emission characteristics such as particle number-size distribution, mass-size distribution, and surface area-size distribution, total particle number concentration and count mean diameter as a function of engine load at constant engine speed were evaluated. Variations in total particle number concentration as a function of engine speed were also determined. The prepared DOCs and the commercial DOC showed varying degrees of performance as a function of engine operating conditions. Overall, effectiveness of the prepared DOCs appeared to be more fuel specific. For diesel exhaust, overall performance of DOC1 was more effective compared to both prepared DOCs, with DOC2 being superior to DOC3. In case of KB20 exhaust, the overall performance of DOC2 was either more effective or nearly comparable to DOC1, while DOC3 being not so effective. This showed that the DOCs based on CoCe based mixed oxide catalysts have potential to replace commercial noble metal based DOCs, especially in engines fueled by biodiesel.

Macroscopic Spray Parameters of Karanja Oil and Blends: A Comparative Study

Diesel engines are very efficient prime movers in their power range. Fuel is directly injected into the combustion chamber. Performance and emission characteristics of diesel engines are highly influenced by the fuel spray parameters and atomization of the injected fuel. As the emission regulations become stringent, it is very important to optimize the combustion in internal combustion engines for different fuels including alternative fuels. Spray visualization using optical techniques play a very important role to analyze macroscopic spray parameters and fuel atomization behavior. In the present experimental study, an important alternative CI engine fuel, Karanja oil and its blends with diesel have been investigated for their spray parameters and fuel atomization relative to mineral diesel. These parameters are different for the two fuels because of difference in the viscosity and density of the fuels. Combustion chamber pressure is a dominant factor, which strongly influences the spray characteristics. This research is a comparative study of the effect of ambient pressure on macroscopic spray parameters such as spray tip penetration, spray cone angle and spray area, of mineral diesel, Karanja oil (K100) and blends (K5, K20). Experiments were carried out in a constant volume spray visualization chamber under different chamber filling pressure (1, 4, 7 and 9 bars) at a fuel injection pressure of 200 bars. The light intensity on the illuminated spray was analyzed to find the atomization level of different fuels. Spray parameter like spray tip penetration, cone angle and the spray area were found to be higher for Karanja oil (K100) as compared to blends (K20 and K5) and mineral diesel. It was observed that as the concentration of Karanja oil in the blend decreases, atomization actually improves. It was also found that with increasing chamber pressure, atomization of fuel becomes relatively superior.

Performance evaluation of a biodiesel fuelled transportation engine retrofitted with a non-noble metal catalysed diesel oxidation catalyst for controlling unregulated emissions

In present study, engine exhaust was sampled for measurement and analysis of unregulated emissions from a four cylinder transportation diesel engine using a state-of-the-art FTIR (Fourier transform infrared spectroscopy) emission analyzer. Test fuels used were Karanja biodiesel blend (B20) and baseline mineral diesel. Real-time emission measurements were performed for raw exhaust as well as exhaust sampled downstream of the two in-house prepared non-noble metal based diesel oxidation catalysts (DOCs) and a baseline commercial DOC based on noble metals. Two prepared non-noble metal based DOCs were based on Co-Ce mixed oxide and Lanthanum based perovskite catalysts. Perovskite based DOC performed superior compared to Co-Ce mixed oxide catalyst based DOC. Commercial noble metal based DOC was found to be the most effective in reducing unregulated hydrocarbon emissions in the engine exhaust, followed by the two in-house prepared non-noble metal based DOCs.

Toxicity and mutagenicity of exhaust from compressed natural gas: Could this be a clean solution for megacities with mixed-traffic conditions?

Despite intensive research carried out on particulates, correlation between engine-out particulate emissions and adverse health effects is not well understood yet. Particulate emissions hold enormous significance for mega-cities like Delhi that have immense traffic diversity. Entire public transportation system involving taxis, three-wheelers, and buses has been switched from conventional liquid fuels to compressed natural gas (CNG) in the Mega-city of Delhi. In this study, the particulate characterization was carried out on variety of engines including three diesel engines complying with Euro-II, Euro-III and Euro-IV emission norms, one Euro-II gasoline engine and one Euro-IV CNG engine. Physical, chemical and biological characterizations of particulates were performed to assess the particulate toxicity. The mutagenic potential of particulate samples was investigated at different concentrations using two different Salmonella strains, TA98 and TA100 in presence and absence of liver S9 metabolic enzyme fraction. Particulates emitted from diesel and gasoline engines showed higher mutagenicity, while those from CNG engine showed negligible mutagenicity compared to other test fuels and engine configurations. Polycyclic aromatic hydrocarbons (PAHs) adsorbed onto CNG engine particulates were also relatively fewer compared to those from equivalent diesel and gasoline engines. Taken together, our findings indicate that CNG is comparatively safer fuel compared to diesel and gasoline and can offer a cleaner transport energy solution for mega-cities with mixed-traffic conditions, especially in developing countries.

Investigation of Particle Number Emission Characteristics in a Heavy-Duty Compression Ignition Engine Fueled with Hydrotreated Vegetable Oil (HVO)

Diesel engines are one of the most important power generating units these days. Increasing greenhouse gas emissions level and the need for energy security has prompted increasing research into alternative fuels for diesel engines. Biodiesel is the most popular amongst the alternatives for diesel fuel as it is biodegradable, renewable and can be produced domestically from vegetable oils. In recent years, hydro-treated vegetable oil (HVO) has also gained popularity due to some of its advantages over biodiesel such as higher cetane number, lower deposit formation, storage stability etc. HVO is a renewable, paraffinic biobased alternative fuel for diesel engines similar to biodiesel. Unlike biodiesel, the production process for HVO involves hydrogen as catalyst instead of methanol which removes oxygen content from vegetable oil. A modified 6-cylinder heavy-duty diesel engine (modified for operation with single cylinder) was used for studying particle number emission characteristics for HVO fuel. The investigation was performed for varying fuel injection pressure at various engine operating loads (6, 8, 10, 12 and 14 bar IMEP). Five rail pressures were chosen from 800 to 2000 bar at a step of 300 bar. The results show that increase in rail pressure tends to increase nucleation mode particle number concentration (quantify the increase) while increase in engine load results in higher total particle number concentration. No significant differences were observed in soot and oxides of nitrogen (NOx) emission for HVO compared to mineral diesel. The fraction of emitted particles in the nucleation mode was observed to increase with increasing fuel injection pressure. (Less)

Techniques to Control Emissions from a Diesel Engine

Diesel particulate and NO x emission cause several serious health problems; therefore, it is necessary to reduce these emissions from the tailpipe. In the past decades, significant technological advancements have been made in the field of engine emission control. In modern diesel engines, smarter electronic fuel injection strategies are being employed. Control of engine emissions can be put under two baskets: (1) active control techniques, and (2) passive control techniques. Active control techniques are those which restrict the formation of the pollutants in the combustion chamber itself. Passive control techniques refer to after-treatment devices. Active control techniques include advancement in the combustion chamber design, use smarter electronic fuel injection system, exhaust gas recirculation, high-pressure multi-fuel injection with precise injection timing, homogenous charge compression ignition, etc. which if used properly restrict the formation of the pollutants. Some other in-cylinder technologies are also effective in reducing the pollutant emission. Although active control techniques are able to reduce the emission up to some extent, but in order to meet the modern emission regulations, passive techniques are also required in addition to active techniques. Passive control technique involves after-treatment devices like diesel oxidation control, diesel particulate trap, NO x absorber, selective catalytic reduction.

Comparison of Primary and Secondary Emissions from an Internal Combustion Engine

Diesel engines are among the most efficient power sources. Diesel engine emit relatively lower amounts of CO and HC emissions as compared to the gasoline engines but higher amounts of oxides of nitrogen (NO X ) and particulate matter (PM). NO X and PM are both associated with deleterious effects on human health. Polycyclic aromatic hydrocarbons (PAHs) and trace metals are two most toxic and harmful class of chemical species present in the engine exhaust. Diesel emission is composed of a complex mixture of many organic compounds (OC) or soluble organic fraction (SOF), nitrates, sulfate, metals, and irritants (such as acrolein, ammonia, PAHs) which are typically adsorbed over elemental carbon (EC) core.