Engine efficiency improvement is very critical for medium to heavy-duty vehicles to reduce Diesel fuel consumption and enhance U.S. energy security. The tradeoff between engine efficiency and NO x emissions is an intrinsic property that prevents modern Diesel engines, which are generally equipped with exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT), from achieving the optimal engine efficiency while meeting the stringent NO x emission standards. The addition of urea-based selective catalytic reduction (SCR) systems to modern Diesel engine aftertreatment systems alleviate the burden of NO x emission control on Diesel engines, which in return creates extra freedom for optimizing Diesel engine efficiency. This paper proposes two model-based approaches to locate the optimal operating point of EGR and VGT in the air-path loop to maximize the indicated efficiency of turbocharged diesel engine. Simulation results demonstrated that the engine brake specific fuel consumption (BSFC) can be reduced by up to 1.6% through optimization of EGR and VGT, compared to a baseline EGR-VGT control which considers both NO x emissions and engine efficiency on engine side. The overall equivalent BSFCs are 1.8% higher with optimized EGR and VGT control than with the baseline control. In addition, the influence of reducing EGR valve opening on the non-minimum phase behavior of the air path loop is also analyzed. Simulation results showed slightly stronger non-minimum phase behaviors when EGR is fully closed.

The purpose of this study is evaluate emission characteristics, such as nitrogen oxides (NO x ), hydrocarbon, carbon monoxide, and particulate matter (PM), of excavator with Tier-4f level diesel engine in the real work conditions. The test excavator has an engine power of 124 kW at an engine speed of 1800rpm, and it has various after-treatment devices, such as exhaust gas recirculation (EGR), selective catalytic reduction (SCR), and diesel oxidation catalyst (DOC), to reduce the engine-out emissions. The emissions including carbon monoxide (CO), carbon dioxides (CO 2 ), and NO x , were measured by portable emission measurement system (PEMS). The PEMS device conducted a correlation analysis with the emission bench on the engine dynamometer before being used to measure the real-work to confirm the reliability of the equipment. The tests were carried out in four categories: idling, driving, excavations and flattening. It revealed that the average power output for each operation mode was higher in the order of flattening, excavation, and drive. On average, those are higher than that for the non-road transient cycle (NRTC) certification mode as 1.5 to 1.9 times. It may be determined that the power output is higher in conditions where there are more boom and bucket movements than the movement of the vehicle itself. In emission analysis, NOx and HC emission in driving mode are higher than other two modes: excavation and flattening. The real time NO x have been low in most test conditions, but large quantities of NO x have been released due to the deactivation of the SCR catalyst during cold start period or immediately after the non-working.

Tightening global emissions regulations are motivating interest in the development and implementation of Selective Catalytic Reduction + Filtration (SCRF) systems, which are designed to reduce the concentration of tailpipe particulate matter (PM) and NOx emissions. These systems allow designers to combine the NOx reduction capability of an SCR with the filtration capability of a particulate filter on a single unit. Practical implementation of these systems requires reliable measurement and diagnosis of their state — both with respect to trapped particulate matter as well as adsorbed ammonia. Currently, these systems rely on a variety of gas sensors, mounted upstream or downstream of the system, that only provide an indirect inference of the operation state. In this study, a single radio frequency (RF) sensor was used to perform simultaneous measurements of soot loading and ammonia inventory on an SCRF. Several SCRF core samples were tested at varying soot and ash loads in a catalyst reactor bench. Soot levels were measured by monitoring changes in the bulk dielectric properties within the catalyst using the sensor, while ammonia levels were determined by feeding selected regions of the RF spectrum into a pretrained generalized regression neural network model. Results show the RF sensor is able to directly measure the instantaneous ammonia inventory, while simultaneously providing soot loading measurements within 0.5 g/L. These results confirm that simultaneous measurements of both the PM and ammonia loading state of an SCRF are possible using a single RF sensor via analysis of specific features in the full RF spectrum. The results indicate significant potential to remove the control barriers typically associated with the implementation of advanced SCRF systems.

The catalytic generation of ammonia from a liquid urea solution is a critical process determining the performance of SCR (Selective Catalytic Reduction) systems. Solid deposits on the catalyst surface from the decomposition of urea have to be avoided, as this leads to reduced system performance or even failure. At present, reactor design is often empirical, which poses a risk for costly iterations due to insufficient system performance. The presented research project proposed a performance prediction and modelling approach for SCR hydrolysis reactors generating ammonia from urea. Different configurations of hydrolysis reactors were investigated experimentally. Ammonia concentration measurements provided information about parameters influencing the decomposition of urea and the system performance. The evaporation of urea between injection and interaction with the catalyst was identified as the critical process driving the susceptibility to deposit formation. The spray of urea solution was characterised in terms of velocity distribution by means of particle-image velocimetry. Results were compared with theoretical predictions and calculation options for processes in the reactor were determined. Numerical simulation was used as an additional design and optimisation tool of the proposed model. The modelling approach is presented by a step-by-step method which takes into account design constraints and operating conditions for hydrolysis reactors.

Motivated by increasingly strict NO x limits, engine manufactures have adopted selective catalytic reduction (SCR) technology to reduce engine-out NO x below mandated levels. In the SCR process, nitrogen oxides (NO x ) react with ammonia (NH 3 ) to form nitrogen and water vapor. The reaction is influenced by several variables, including stored ammonia on the catalyst, exhaust gas composition, and catalyst temperature. Currently, measurements from NO x and/or NH 3 sensors upstream and downstream of the SCR are used with predictive models to estimate ammonia storage levels on the catalyst and control urea dosing. This study investigated a radio frequency (RF) -based method to directly monitor the ammonia storage state of the SCR catalyst. This approach utilizes the SCR catalyst as a cavity resonator, in which an RF antenna excites electromagnetic waves within the cavity to monitor changes in the catalyst state. A mmonia storage causes changes in the dielectric properties of the catalyst, which directly impacts the RF signal. Changes in the RF signal relative to stored a mmonia (NH 3 ) were evaluated over a wide frequency range as well as temperature and exhaust conditions. The RF response to NH 3 storage, desorption, and oxidation on the SCR was observed to be well-correlated with changes in the catalyst state. Calibrated RF measurements demonstrate the ability to monitor the adsorption state of the SCR to within 10 % of the sensor full scale. The results indicate direct measurement of SCR ammonia storage levels, and resulting catalyst feedback control, via RF sensing to have significant potential for optimizing the SCR system to improve NO x conversion and decrease urea consumption.

Environmental regulations have put stringent requirements on NOx emissions in the transportation industry, essentially requiring the use of exhaust after-treatment on diesel fueled light and heavy-duty vehicles. Urea-Water-Solution (UWS) based Selective Catalytic Reduction (SCR) for NOx is one the most widely adopted methods for achieving these NOx emissions requirements. Improved understanding and optimization of SCR after-treatment systems is therefore vital, and numerical investigations can be employed to facilitate this process. For this purpose, detailed and numerically accurate models are desired for in-cylinder combustion and exhaust after-treatment. The present paper reports on 3-D numerical modeling of the Urea-Water-Solution SCR system using Computational Fluid Dynamics (CFD). The entire process of Urea injection, evaporation, NH3 formation and NOx reduction is numerically investigated. The simulation makes use of a detailed kinetic surface chemistry mechanism to describe the catalytic reactions. A multi-component spray model is applied to account for the urea evaporation and decomposition process. The CFD approach also employs an automatic meshing technique using Adaptive Mesh Refinement (AMR) to refine the mesh in regions of high gradients. The detailed surface chemistry NOx reduction mechanism validated by Olsson et al. (2008) is applied in the SCR region. The simulations are run using both transient and steady-state CFD solvers. While transient simulations are necessary to reveal sufficient details to simulate catalytic oxidation during transient engine processes or under cyclic variations, the steady-state solver offers fast and accurate emission solutions. The simulation results are compared to available experimental data, and good agreement between experimental data and model results is observed.

Low temperature and dilute Homogenous Charge Compression Ignition (HCCI) and Spark Assisted Compression Ignition (SACI) can improve fuel economy and reduce engine-out NO x emissions to very low values, often less than 30 ppm. However, these combustion modes are unable to achieve stringent future regulations such as SULEV 30 without the use of lean aftertreatment. Though active selective catalytic reduction (SCR) with urea injection and lean NO x traps (LNT) have been investigated as options for lean gasoline engines, a passive TWC-SCR system is investigated in this work because it avoids the urea storage and dosing hardware of a urea SCR system, and the high precious metal cost of an LNT. The TWC-SCR concept uses periodic rich operation to produce NH 3 over a TWC to be stored on an SCR catalyst for subsequent NO x conversion during lean operation. In this work a laboratory study was performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation, or between lean and rich SI (spark ignited) combustion, to evaluate NO x conversion and reduced fuel consumption. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system simulations are also presented that compare system performance for different levels of stored NH 3 . With the configuration used in this study, lean/rich HCCI/SACI operation showed a maximum NO x conversion efficiency of 10%, while lean/rich SI operation showed a maximum NO x conversion efficiency of 60%. However, if the low conversion efficiency of lean/rich HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, simulation results indicate TWC-SCR aftertreatment has the potential to provide near-zero SCR-out NO x concentration and increased system fuel efficiency. In these simulations, fuel efficiency improvement relative to stoichiometric SI were 7 to15% for lean/rich HCCI/SACI with zero tailpipe NO x and −1 to 5% for lean/rich SI with zero tailpipe NO x emissions. Although previous work indicated increased time for NH 3 to start forming over the TWC during rich operation, less NH 3 production over the TWC per fuel amount, and increased NH 3 slip over the SCR catalyst for advanced combustion systems, if NO x conversion efficiency could be enhanced, improvements in fuel economy and low engine-out NO x from advanced combustion modes would more than make up for these disadvantages.

Lean NOx Traps (LNTs) are often used to reduce NOx on smaller diesel passenger cars where urea-based Selective Catalytic Reduction (SCR) systems may be difficult to package. However, the performance of LNTs at temperatures above 400°C needs to be improved. The use of Rapidly Pulsed Reductants (RPR) is a process in which hydrocarbons are injected in rapid pulses ahead of the LNT in order to improve its performance at higher temperatures and space velocities. This approach was developed by Toyota and was originally called Di-Air (Diesel NOx aftertreatment by Adsorbed Intermediate Reductants) [1]. There is a vast parameter space that needs to be explored in order to maximize the NOx conversion at high temperatures and flow rates while minimizing the fuel penalty associated with the hydrocarbon injections. Four parameters were identified as important for RPR operation: (1) the flow field and reductant mixing uniformity; (2) the pulsing parameters including the pulse frequency, duty cycle, and rich magnitude; (3) the reductant type; and (4) the catalyst composition, including the type and loading of precious metal, the type and loading of NOx storage material, and the amount of oxygen storage capacity (OSC). In this study, RPR performance was assessed between 150°C and 650°C with several reductants including dodecane, propane, ethylene, propylene, H 2 , and CO. A novel injection and mixer system was designed that allowed for the investigation of previously unexplored areas of high frequency injections up to f = 100Hz. Under RPR conditions, H 2 , CO, dodecane, and C 2 H 4 provided approximately 80% NOx conversion at 500°C, but at 600°C the conversions were significantly lower, ranging from 40 to 55%. The NO x conversion with C 3 H 8 was low across the entire temperature range, with a maximum conversion of 25% near 300°C and essentially no conversion at 600°C. In contrast, C 3 H 6 provided greater than 90% NOx conversion over a broad range of temperature between 280°C and 630°C. Among the hydrocarbons, this suggested that the high temperature NO x conversion with RPR improves as the reactivity of the hydrocarbon increases.

This paper reports on the experimental results of the combustion and emission characteristics of a conventional diesel engine mixed ammonia (NH 3 ) gas into the intake air, and discusses its usability. In the experiments, NH 3 gas was injected into the intake pipe of the diesel engine by a gas injector. The diesel engine has a natural aspiration single cylinder with 7.7 kW rated power at 1500 rpm and a diesel injection system to inject diesel fuel into the cylinder. As experimental results on the combustion characteristics, it was confirmed that the compression and maximum pressures in the cylinder decreased and the ignition timing delayed with increasing the NH 3 gas injection quantity. On the emission characteristics in the exhaust gas, NH 3 , water (H 2 O) and nitrous oxide (N 2 O) increased and carbon dioxide (CO 2 ) decreased proportionally to the NH 3 gas injection quantity. In contract, the nitrogen oxide (NO) was nearly the same. Moreover, it was confirmed that NH 3 can be reduced by reacting with NO in a selective catalytic reduction (SCR) system.

Increasingly stringent emissions standards have accounted for continuing increases in the end-user cost of a modern diesel engine, most of which due to complex and expensive emissions after treatment devices such as selective catalytic reduction (SCR), which relies on urea to be injected into a catalyst bed to remove nitrogen oxide emissions from the engine exhaust. Prior to the current emissions standards the diesel industry had been able to meet NOx levels by reducing the combustion temperature in the engine via charge gas dilution, through cooled EGR. Although successful in reducing emissions, large levels of EGR have undesirable effects on oil quality, engine longevity, overall efficiency and warranty returns. There is also a limit to the efficacy of EGR in lowering NOx emissions such that at the current EPA mandated 0.2g/kWh, it is no longer sufficient. Another well-known NOx mitigating solution has been the introduction of water into the diesel engine combustion chamber. This has been known to decrease peak combustion temperatures and decrease NOx emissions but usage so far has been limited to stationary and marine applications due to the requirement of a separate water tank and thereby a two-tank system. Combustion of hydrocarbon fuels produces between 1.35 and 2.55 times their mass in water. As an enabler to water injection, this paper will also demonstrate a technique where the exhaust is first cooled via a heat exchanger, and then passed through a cyclonic separator to separate heavier liquid particles from the exhaust gas flow. Through vortex separation over 100% of the burned fuel mass can be recovered as liquid water from the exhaust. A prototype system was developed and installed on a VW TDI diesel engine. Tests were conducted with and without after-treatment and results have been discussed in subsequent sections. The water was then utilized in conjunction with EGR to control NOx emissions, allowing a reduction of over 97%, thus achieving the 0.2g/kWh standard with no after treatment.

There are many NO x removal technologies: exhaust gas recirculation (EGR), selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), miller cycle, emulsion technology and engine performance optimization. In this work, a numerical simulation investigation was conducted to explore the possibility of an alternative approach: direct aqueous urea solution injection on the reduction of NO x emissions of a biodiesel fueled diesel engine. Simulation was performed using the 3D CFD simulation software KIVA4 coupled with CHEMKIN II code for pure biodiesel combustion under realistic engine operating conditions of 2400 rpm and 100% load. To improve the overall prediction accuracy, the Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) spray break up model was implemented in the KIVA code to replace the original Taylor Analogy Breakup (TAB) model for the primary and secondary fuel breakup processes modeling. The KIVA4 code was further modified to accommodate multiple injections, different fuel types and different injection orientations. A skeletal reaction mechanism for biodiesel + urea was developed which consists of 95 species and 498 elementary reactions. The chemical behaviors of the NO x formation and Urea/NO x interaction processes were modeled by a modified extended Zeldovich mechanism and Urea/NO x interaction sub-mechanism. Developed mechanism was first validated against the experimental results conducted on a light duty 2KD FTV Toyota car engine fueled by pure biodiesel in terms of in-cylinder pressure, heat release rate. To ensure an efficient NO x reduction process, various aqueous urea injection strategies in terms of post injection timing and injection rate were carefully examined. The simulation results revealed that among all the four post injection timings (10 °ATDC, 15 °ATDC, 20 °ATDC and 25 °ATDC) that were evaluated, 15 °ATDC post injection timing consistently demonstrated a lower NO emission level. In addition, both the urea/water ratio and aqueous urea injection rate demonstrated important roles which affected the thermal decomposition of urea into ammonia and the subsequent NO x removal process, and it was suggested that 50% urea mass fraction and 40% injection rate presented the lowest NO x emission levels.

With the introduction of the EPA Tier 4 NOx emission limits for rail diesel engines this year, engine developers are forced to implement more advanced emission control technologies such as selective catalytic reduction (SCR) or cooled external exhaust gas recirculation (EGR). The integration and control of these systems for ensuring optimum performance throughout the operating range brings about new challenges on top of the well-known requirement for unconstrained operability in a very wide range of conditions. As a consequence, engines and their subsystems have to be designed for maximum flexibility. The turbocharging system in particular needs to be capable of dealing with extreme ambient conditions associated with high altitudes, hot summers, severe winters, tunnel operation, etc. This flexibility must be achieved without compromising reliability and while ensuring continuous in-use compliance with the emissions standards throughout the life of the installation. At the same time, engine performance should be maintained at the highest level possible. This study demonstrates that all of these targets can be met by combining two-stage turbocharging and EGR with suitable control elements. Two-stage turbocharging, which has become increasingly popular in other industry sectors due to its potential for improving the bsfc / NOx emissions trade-off when used in combination with correspondingly optimized valve actuation (Miller timing), is starting to be adopted also for rail applications. A variety of EGR concepts was proposed or put into practice over the past few years, and the most important or promising of these have been taken into consideration for this study. Extensive simulations of the resulting engine and turbocharging systems have been performed using ABB’s in-house simulation platform, based on a generic engine model that can be considered representative of the rail sector. It is shown that integration of EGR, two-stage turbocharging and appropriate control elements is highly attractive as it offers outstanding operational flexibility and very high fuel efficiency without any compromise in terms of reliability. The selection and specification of control elements and turbocharging system components depends on the EGR concept applied. As is shown below, this can be tailored to the application to ensure optimum performance and flexibility. In view of these obvious benefits, we are very confident that such integrated EGR / two-stage turbocharging systems will be adopted more widely on railway engines.

The Environment Protection Agency (EPA) Tier 4 emission standard requires locomotive engines to meet emission compliance at any ambient humidity for an ambient temperature of 60 to 105 F and an altitude level of up to 7000 ft. The engine tests were run at a range of intake air humidity and temperature to determine oxides of Nitrogen (NOx) emissions sensitivity to humidity, intake air temp for large bore diesel engines and compared with humidity correction factor recommended by EPA. Further, the change in NOx concentration altered conversion efficiency of the Selective Catalytic Reduction (SCR) catalyst. Hence, the change in Ammonia to NOx ratio and amount of DEF fluid required to achieve target NOx emissions reduction were studied. Considering this effect, the doser and DEF tank sizing strategy was defined based on in-use ambient humidity, temperature and altitude test conditions in order to mitigate risk of running out of DEF fluid during in-use operation of locomotives.

The combustion system of a large bore four stroke diesel engine was developed using the Analysis Led Design (ALD) process. A combustion strategy of particulate matter (PM) control in-cylinder and oxides of nitrogen (NO x ) controlled through urea based selective catalytic reduction (SCR) of the engine exhaust, was adopted. Combustion analysis tools and single cylinder engine (SCE) tests were used to determine key combustion parameters like in-cylinder swirl, fuel injector configuration and, combustion chamber design to meet the EPA Tier4 final emission regulations at the different notch settings of the locomotive test cycle. Experimental validation of the ALD recommended hardware was accomplished on the SCE and the best combination was selected. Engine out PM and NO x target compliance was demonstrated on the multi cylinder diesel engine (MCE) over the composite locomotive notch cycle. Selective fuel Injector strategy was applied to control excessive unburned hydrocarbons (UHC) at low load engine operating conditions within the locomotive notch cycle.

Over the past few decades there has been considerable progress made in understanding the processes leading to formation and evolution of particulate matter (PM) emissions from heavy duty diesel engines (HDDE). This progress has been primarily made under controlled laboratory conditions with the use of constant volume sampling (CVS) systems and to a limited extend through on-road chase studies. West Virginia University (WVU) is attempting to close the present knowledge gap by conducting detailed experiments in a custom designed and constructed environmental wind tunnel. The understanding and knowledge has recently been further extended to new emission reduction technologies, such as the diesel particulate filter (DPF) which has dramatically changed the size distribution and chemical composition of PM. Additionally, the selective catalytic reduction (SCR) technology has shown to further enhance the formation of nucleation mode particles as well as alter their morphology. Even with advances in technology there remains a considerable gap in the current level of understanding of PM formation and evolution, since the combustion generated PM from diesel engines is not discernible from the atmospheric background PM measured beyond 300m from highways. After being emitted from the vehicle exhaust system, the process of dilution in the atmosphere leads to a multitude of PM transformation phenomena, such as volatilization, coagulation, and condensation. The work presented herein has been divided into two parts which are published separately from each another. The first part describes the design and commissioning process of the wind tunnel focusing on both, aerodynamic and structural constraints, which ultimately led to the definition of the main characteristics of the facility. The resulting design is a subsonic, non-recirculating, suction type tunnel, with a 16ft high and 16ft wide test section capable of housing a full-size heavy-duty tractor cab. A 2,200hp suction fan is employed to provide up to 80 mph wind speeds. The 115ft test cell length guarantees for a 2 second residence time for the exhaust plume evolution (at 35 mph) and complies with turbulence intensity (less than 1%) and quality flow requirement as identified for this type of application. In addition, the West Virginia University (WVU) wind tunnel has been equipped with a custom made sampling system able to move in all three dimensions in order to measure spatially resolved plume characteristics. The second part will describe the actual test procedures and the experimental results and will be published in a separate paper.

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.

This paper details part two of the demonstration of a 2,240 kW (3,005 HP) PR30C-LE locomotive with exhaust aftertreatment containing diesel oxidation catalysts (DOC) and urea-based selective catalytic reduction (SCR). The PR30C-LE is a remanufactured and repowered, six-axle, diesel-electric, line-haul locomotive. Program objectives were to measure emission levels of the locomotive and record locomotive and aftertreatment operations during a 12 month revenue service field trial. Phase 1 of the program involved engine baseline emissions testing as well as emissions testing with the aftertreatment at the beginning of its useful life, or the 0-hour condition. Results from Phase 1 showed engine-out emission levels were within U.S. EPA Locomotive Tier 2 limits. With aftertreatment at beginning of useful life, hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NO x ) were below Tier 4 limits, and particulate matter (PM) was below Tier 3 limits. Phase 2 consisted of a 12 month revenue service field trial and additional emissions testing completed at the midpoint and end of the field trial. On-board GPS data, aftertreatment NO x sensor data, and various locomotive operating parameters were logged continuously during the field trial. The field trial data suggests the impact SCR technology has on locomotive NO x emissions is driven primarily by locomotive utilization and loading factor. Overall the field trial included 3,082 hours of operation and PRLX3004 generated approximately 572 MW-hours of work over the 12 month period. Emission test results at the 1,500-hour and 3,000-hour conditions showed very little change from 0-hour test results. Emission levels remained below Tier 4 limits for HC, CO, and NO x , and below the Tier 3 limit for PM. Phase 2 test results suggest there was no significant degradation in emissions performance during the field trial, and no major issues with the locomotive and aftertreatment were detected. In total there are currently five PR30C-LE locomotives in operation within California and Arizona. Together they have completed a cumulative 30,800 hours of revenue service through June 2012 without report of a major issue.

Two heavy-duty diesel vehicles operating in an underground salt mine were retrofitted with emission control systems based on selective catalytic reduction technology. The vehicles were then released for production in the mine and the emissions were measured periodically over 18 months. The systems were very effective in reducing oxides of nitrogen (NOx) emissions from the diesel vehicle engines. The systems were able to provide NOx reductions of 60% to 65% over typical vehicle duty cycles. This paper will describe the SCR systems, emissions reductions, operability issues and secondary emissions for both vehicles.

For the first time in the locomotive industry, an advanced exhaust aftertreatment system for a locomotive application was successfully demonstrated to reduce nitrogen oxides from 6.46 g/kW·hr to 1.21g/kWhr to meet the needs of local NOx reduction requirements for non-attainment areas. Five 2,240 kW (3,005 horsepower) PR30C line-haul repowered Progress Rail locomotives were equipped with diesel oxidation catalyst and selective catalytic reduction technologies to accumulate more than 27,000 hours in total in revenue service. Full emissions performance including carbon monoxide, hydrocarbons, nitrogen oxides and particulate matter was conducted at Southwest Research Institute on a regular basis to measure the change of emissions performance for two selected locomotives. The emissions performance of the aftertreatment system did not show any degradation during 3,000 hours operation. After 3,000 hours operation, 0.13 g/kW·hr carbon monoxide (89–91% reduction), 0.027 g/ kW·hr hydrocarbons (91% reduction), 1.08–1.21 g/ kW·hr nitrogen oxides (81–83% reduction) and 0.05–0.08 g/ kW·hr particulate matter (38–58% reduction) were measured on the line-haul cycle. The baseline emissions levels of the engine are within Tier 2 EPA locomotive limits. The newly developed close loop control software successfully controlled targeted nitrogen oxides reduction with minimum ammonia slip during the locomotive emission cycle tests.

One approach for nitrogen oxides (NO x ) emission control of medium duty diesel engines is through the use of a combination Lean NO x Trap and Selective Catalytic Reduction (LNT-SCR) catalyst system. In this system, part of the NO x conversion occurs via an NH 3 SCR catalyst that is dependent on the NO 2 to NO x ratio of the feed gas with NO 2 being a more advantageous oxidizer. One benefit of using this system is the conversion of NO to NO 2 over the LNT which increases the NO 2 :NO x ratio of the feed gas to the SCR catalyst. An experimental study has been performed to investigate the NO 2 -NH 3 reaction for an Fe-based zeolite SCR catalyst using a bench top flow reactor. The increase in NO 2 concentration at the inlet of the SCR results in the formation of large quantities of N 2 O from 200°C to 400°C. Further experiments determined that N 2 O and NH 3 react above 350°C. This has led to a hypothesis that one primary SCR reaction (Slow SCR) can be replaced with two reaction steps featuring NH 3 , NO 2 , and N 2 O. As a result, this paper proposes five NO x reduction reactions as part of a global mechanism, which would account for the observed experimental behavior.