Hemanth Kappanna

Characterization of Particulate Matter Emissions from a Current Technology Natural Gas Engine

Experiments were conducted to characterize the particulate matter (PM)-size distribution, number concentration, and chemical composition emitted from transit buses powered by a USEPA 2010 compliant, stoichiometric heavy-duty natural gas engine equipped with a three-way catalyst (TWC). Results of the particle-size distribution showed a predominant nucleation mode centered close to 10 nm. PM mass in the size range of 6.04 to 25.5 nm correlated strongly with mass of lubrication-oil-derived elemental species detected in the gravimetric PM sample. Results from oil analysis indicated an elemental composition that was similar to that detected in the PM samples. The source of elemental species in the oil sample can be attributed to additives and engine wear. Chemical speciation of particulate matter (PM) showed that lubrication-oil-based additives and wear metals were a major fraction of the PM mass emitted from the buses. The results of the study indicate the possible existence of nanoparticles below 25 nm formed as a result of lubrication oil passage through the combustion chamber. Furthermore, the results of oxidative stress (OS) analysis on the PM samples indicated strong correlations with both the PM mass calculated in the nanoparticle-size bin and the mass of elemental species that can be linked to lubrication oil as the source.

Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles

Chassis dynamometer emissions testing of 11 heavy-duty goods movement vehicles, including diesel, natural gas, and dual-fuel technology, compliant with US-EPA 2010 emissions standard were conducted. Results of the study show that three-way catalyst (TWC) equipped stoichiometric natural gas vehicles emit 96% lower NOx emissions as compared to selective catalytic reduction (SCR) equipped diesel vehicles. Characteristics of drayage truck vocation, represented by the near-dock and local drayage driving cycles, were linked to high NOx emissions from diesel vehicles equipped with a SCR. Exhaust gas temperatures below 250 °C, for more than 95% duration of the local and near-dock driving cycles, resulted in minimal SCR activity. The low percentage of activity SCR over the local and near-dock cycles contributed to a brake-specific NOx emissions that were 5-7 times higher than in-use certification limit. The study also illustrated the differences between emissions rate measured from chassis dynamometer testing and prediction from the EMFAC model. The results of the study emphasize the need for model inputs relative to SCR performance as a function of driving cycle and engine operation characteristics.

Waste Heat Recovery in Heavy-Duty Diesel Engines: A Thermodynamic Analysis of Waste Heat Availability for Implementation of Energy Recovery Systems Based Upon the Organic Rankine Cycle

In the past decade automotive industries have focused on the development of new technologies to improve the overall engine efficiency and lower emissions in order to satisfy the always more stringent emission standards introduced all around the world. Technical progress has primarily focused on two aspects; the optimization of the air-fuel mixture in the combustion chamber as well as the combustion process itself, leading to simultaneous improvements in both, efficiency (lowering fuel consumption for same power output) and emissions levels which ultimately result from the optimized combustion process. Although engine technology has made significant progress, even modern Diesel combustion engines do not exceed a maximum efficiency of approximately 40%. Hence, around 60% of the available energy carried by the fuel and entering the combustion chamber is dissipated as heat to the environment. The next steps in engine optimization will see the integration of waste heat recovery systems (WHRS) to increase the overall energy efficiency of the propulsion system by means of recovering parts of the waste heat generated during normal engine operation. The presented was aimed at analyzing the availability as well as the quality of heat to be used in WHRS for the case of heavy-duty Diesel (HDD) engines employed in Class-8 tractors, which are suitable candidates for optimization via WHRS implementation as their engines spend most of their time operating at quasi steady state conditions, such as highway cruise. Three different primary energy sources have been considered: exhaust gas recirculation (EGR) cooling system, engine cooling system and exhaust gas stream. Experimental data has been gathered at West Virginia University’s Engine and Emissions Research Laboratory (EERL) facility in order to quantify individual heat flows in a model year (MY) 2004 Mack® MP7-355E HDD engine operated over the 13 modes of the European Stationary Cycle (ESC). Analysis based on second law efficiency underlined that not the whole amount of waste heat can be successfully used for recovery purposes and that heat sources which offer a large amount of waste energy reveal to be inappropriate for recovery purposes in case of low operating temperature. Time integral analysis revealed that engine modes which appear to offer high recovery potential in terms of waste power may not be suitable engine operating conditions when the analysis is performed in terms of waste energy, depending on the particular engine cycle. Finally a simple thermodynamic model of a micro power unit running on an Organic Rankine Cycle (ORC) has been used to assess the theoretical improvement in engine efficiency during steady state operations based on a second law efficiency analysis approach.Copyright

Correction to Characterization of Particulate Matter Emissions from a Current Technology Natural Gas Engine

the figure showed a high mass fraction of lubrication oil derived elements and metals. Figure 4 of this erratum shows the corrected mass fraction of PM after the calculation error was addressed. The corrections of the error results in the conclusion that the mass fraction of lubrication oil derived elements and metals are less than 10% of total mass of PM. The comparison of distance-specific emissions of lubricationoil-derived elements from this study with previous SCRequipped diesel work presented by Hu et al. is discussed in Line 2, second column of page 8239 of the original manuscript. The original manuscript suggested that the distance-specific emissions of lubrication-oil-derived elements are an order of magnitude higher from TWC-equipped natural gas vehicles compared to DPF-SCR-equipped diesel over the UDDS driving cycle. As a result of the correction to the calculation, the results now conclude that the distance-specific emissions of lubrication-oil-derived elements from TWC-equipped natural gas engines are up to 2 times higher than the retrofit DPF-SCR equipped diesel engines. The overall conclusions of the study remain unchanged after the correction of the error. The original manuscript suggests the possibility of lubrication oil-derived elements from TWCequipped natural gas engines to contribute more toward particle number count in the 10 nm size range. The manuscript also suggests that renucleation of inorganic lubrication oil additives, passing through the combustion chamber of the engine to be the primary contributor to particle number count in this size range.

Evaluation of Drayage Truck Chassis Dynamometer Test Cycles and Emissions Measurement

In 2006, the ports of Long Beach and Los Angeles adopted the final San Pedro Bay Ports Clean Air Action Plan (CAAP), initiating a broad range of programs intended to improve the air quality of the port and rail yard communities in the South Coast Air Basin. As a result, the Technology Advancement Program (TAP) was formed to identify, evaluate, verify and accelerate the commercial availability of new emissions reduction technologies for emissions sources associated with port operations, [1]. Container drayage truck fleets, an essential part of the port operations, were identified as the second largest source of NOx and the fourth largest source of diesel PM emissions in the ports’ respective 2010 emissions inventories [2, 3]. In response, TAP began to characterize drayage truck operations in order to provide drayage truck equipment manufacturers with a more complete understanding of typical drayage duty cycles, which is necessary to develop emissions reduction technologies targeted at the drayage market.As part of the broader TAP program, the Ports jointly commissioned TIAX LLC to develop a series of drayage truck chassis dynamometer test-cycles. These cycles were based on the cargo transport distance, using vehicle operational data collected on a second-by-second basis from numerous Class 8 truck trips over a period of two weeks, while performing various modes of typical drayage-related activities. Distinct modes of operation were identified; these modes include creep, low-speed transient, high-speed transient and high-speed cruise. After the modes were identified, they were assembled in order to represent typical drayage operation, namely, near-dock operation, local operation and regional operation, based on cargo transport distances [4].The drayage duty-cycles, thus developed, were evaluated on a chassis dynamometer at West Virginia University (WVU) using a class 8 tractor powered by a Mack MP8-445C, 13 liter 445 hp, and Model Year (MY) 2011 engine. The test vehicle is equipped with a state-of-the-art emissions control system meeting 2010 emissions regulations for on-road applications. Although drayage trucks in the San Pedro Bay Ports do not have to comply with the 2010 heavy-duty emissions standards until 2023, more than 1,000 trucks already meet that standard and are equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) technology as used in the test vehicle. An overview of the cycle evaluation work, along with comparative results of emissions between integrated drayage operations, wherein drayage cycles are run as a series of shorter tests called drayage activities, and single continuous drayage operation cycles will be presented herein. Results show that emissions from integrated drayage operations are significantly higher than those measured over single continuous drayage operation, approximately 14% to 28% for distance-specific NOx emissions. Furthermore, a similar trend was also observed in PM emissions, but was difficult to draw a definite conclusion since PM emissions were highly variable and near detection limits in the presence of DPF. Therefore, unrepresentative grouping of cycle activity could lead to over-estimation of emissions inventory for a fleet of drayage vehicles powered by 2010 compliant on-road engines.Copyright

Assessment of Novel In-Line Particulate Matter Sensor With Respect to OBD and Emissions Control Applications

Upcoming emissions legislations and On-Board-Diagnostics (OBD) system requirements, both in the US and Europe, impose new challenges for particulate matter (PM) control strategies, especially with regard to upcoming EURO-VI regulations that are expected to limit the particulate number (PN) emissions. Indeed, the US-EPA Heavy-Duty-OBD regulations already require monitoring of diesel particulate filters (DPF) in 2010 for at least one engine series, with extension to all engine series by 2013. Due to the current absence of reliable in-line PM sensors to monitor DPF filtration efficiencies, manufacturers adopted alternative methods based on pressure drop measurements and semi-empirical models that require extensive calibration efforts; hence, driving upward the development costs. In order to meet upcoming OBD requirements and reduce unnecessary DPF regeneration frequencies, so as to minimize fuel consumption penalties, reliable sensors need to be integrated into the aftertreatment control environment. These next-generation sensors must be capable of performing actual real-time PM concentration measurements on a continuous basis within the exhaust stream. The primary objective of this study was to assess the capabilities, limitations and sensitivity of a newly developed inline PM sensor, with regard to its future application for OBD monitoring or control strategies of PM filter systems. The operation of the so called Pegasor Particulate Sensor (PPS) [1] is based on the escaping current principle. The instrument is capable of performing continuous PM measurements, directly from the exhaust stack, while providing a real-time signal with a resolution of 100 Hz. The sensor’s output signal can be calibrated to either measure the concentration of mass, surface or number of exhaust particles. Designed as a flow-through device, the PPS has a tungsten corona wire imposing an equal charge on particles that is subsequently measured from the outflowing particles via a built-in electrometer. The system does not involve collection or contact with particles in the exhaust stream, which is especially advantageous for long-term stability and operation without frequent maintenance; hence, best suited for in-use application. A comprehensive test matrix was developed to gain a more pronounced understanding of the sensor’s measurement technology by comparing it to other proven aerosol instruments, namely the Ultrafine Condensation Particle Counter (UCPC), Engine Exhaust Particle Sizer (EEPS™) spectrometer, Tapered Element Oscillating Microbalance (TEOM), and gravimetric PM. Test results demonstrated a stable and repeatable response over consecutive European Transient Cycle (ETC) and Federal Test Procedure (FTP) cycles, as well as over idle and constant load operation with coefficients of variation below 2%, which is a prerequisite for OBD algorithm implementation.Copyright

Development of an Advanced Retrofit Aftertreatment System Targeting Toxic Air Contaminants and Particulate Matter Emissions From HD-CNG Engines

Increasing urban pollution levels have led to the imposition of evermore stringent emissions regulations on heavy-duty engines used in transit buses. This has made compressed natural gas (CNG) a promising fuel for reducing emissions, particularly particulate matter (PM) from heavy-duty transit buses. Indeed, research studies performed at West Virginia University (WVU) and elsewhere have shown that pre-2010 compliant natural gas engines emit an order of magnitude lower PM emissions, on a mass basis, when compared to diesel engines without any exhaust aftertreatment devices. However, on a number basis, particle emissions in the nanoparticulate range were an order of magnitude higher for natural gas fueled buses than their diesel counterparts. There exists a significant number of pre-2007 CNG powered buses in transit agencies in the US and elsewhere in the world. Therefore, an exhaust aftertreatment device was designed and developed by WVU, in association with Lubrizol, to retrofit urban transit buses powered by MY2000 Cummins Westport C8.3G+ heavy-duty CNG engines, and effectively reduce Toxic Air Contaminants (TAC) and PM (mass and number count) exhaust emissions. The speciation results showed that the new exhaust aftertreatment device reduced emissions of metallic elements such as iron, zinc, nonmetallic minerals such as calcium, phosphorus and sulfur derived from lube oil additives to non-detectable levels, which otherwise could contribute to an increase in number count of nanoparticles. The carbonyl compounds were reduced effectively by the oxidation catalyst to levels below what were found in the dilution air. Also, hydrocarbons identified as TAC’s by California Air Resource Board (CARB) [1] were reduced to non-detectable levels. This ultimately reduced the number of nanoparticles to levels equal to that found in the dilution air.Copyright