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Natural gas is a potential alternative to conventional liquid fuels for use in automotive internal combustion engines. The primary goal of this study is to understand how gas composition changes might impact the performance or emissions of a natural gas vehicle or engine. For this study, a waste hauler truck equipped with a 2001 Cummins 8.3L C Gas Plus lean burn spark-ignited engine and an oxidation catalyst was operated on the William H. Martin Refuse Truck Cycle (RTC). This cycle was developed to simulate waste hauler operation and consists of a transport segment, a curbside pickup segment, and a compaction segment.

We assessed gaseous and particulate matter (PM) emissions from a current technology stoichiometric natural gas waste hauler equipped with a 2011 model year 8.9L Cummins Westport ISL-G engine with cooled exhaust gas recirculation (EGR) and three-way catalyst (TWC). Testing was performed on five fuels with varying Wobbe and methane numbers over the William H. Martin Refuse Truck Cycle. The results showed lower nitrogen oxide (NOx) emissions for the low methane fuels (i.e., natural gas fuels with a relatively low methane content) for the transport and curbside cycles. Total hydrocarbon (THC) and methane (CH4) emissions did not show any consistent fuel trends. Non-methane hydrocarbon (NMHC) emissions showed a trend of higher emissions for the fuels containing higher levels of NMHCs. Carbon monoxide (CO) emissions showed a trend of higher emissions for the low methane fuels.

EmiSense Technologies, LLC (www.emisense.com) is commercializing its electronic particulate matter (PM) sensor that is based on technology developed at the University of Texas at Austin (UT). To demonstrate the capability of this sensor for real-time PM measurements and on board diagnostics (OBD) for failure detection of diesel particle filters (DPF), independent measurements were performed to characterize the engine PM emissions and to compare with the PM sensor response. Computational fluid dynamics (CFD) modeling was performed to characterize the hydrodynamics of the sensor's housing and to develop an improved PM sensor housing with reproducible hydrodynamics and an internal baffle to minimize orientation effects. PM sensors with the improved housing were evaluated in the truck exhaust of a heavy duty (HD) diesel engine tested on-road and on a chassis dynamometer at the University of California, Riverside (UCR) using their Mobile Emissions Laboratory (MEL).

The primary purpose of this study was to obtain gas-phase and particular matter (PM) emissions from newer Tier 4 final off-road construction equipment using a Portable Emissions Measurement System (PEMS). This information can be used to provide accurate estimates of emissions from off-road construction equipment under real-world scenarios. Emission measurements were made for 10 pieces of Tier 4 final construction equipment including 3 excavators, 3 wheel loaders, 2 crawler tractors and 2 backhoe/loaders. The duty cycles included a pre-defined combined sequence of a cold-start phase, trenching, backfilling, travelling, and idling. For all types of equipment, the highest emissions were seen for the cold start phase, which showed NOx emissions levels ranging from 3.4 to 6.3 g/bhp-hr, from 15.8 to 26.1 g/kg-fuel and from 107 to 249 g/hour, with an average exhaust temperature around 100°C.The next highest emissions were found for the travel mode.

Goods movement and port related activities are a significant source of emissions in many large urban areas. Electrification of diesel cargo handling equipment is one method of reducing community exposure to these emissions, that also provides the potential for reducing greenhouse gas emissions. This study evaluated the performance of several pieces of zero emission cargo transfer equipment for a demonstration conducted at two terminal locations at the Port of Long Beach (POLB). This included the data logging of three battery-electric top handlers and one battery-electric yard tractor, as well as two baseline diesel top handlers and one diesel yard tractor. The battery-electric equipment typically operated about 5 hours per day, while using between 34 to 50% of the battery pack state of charge (SOC). In general, the battery-electric equipment was able to provide comparable hours of operation to the diesel equipment over a typical 8-hour shift.

The emissions of two ultralow NOx heavy-duty (HD) vehicles equipped with 0.02 g/bhp-hr low NOx natural gas (NG) engines were evaluated on a chassis dynamometer. This included a waste hauler and a city transit bus, each with a 0.02 g/bhp-hr NOx L9N near zero (NZ) natural gas engine. The vehicles were tested over a variety of different cycles, including the Urban Dynamometer Driving Schedule (UDDS), port drayage cycles, transit bus cycles, and a refuse truck cycle. For both vehicles, the NOx emissions results were below the 0.02 g/bhp-hr level for most cycles, with the exception of some cold start tests. For the waste hauler, NOx emissions averaged between 0.014 and 0.002 g/bhp-hr for the hot start tests, and from 0.043 to 0.014 g/bhp-hr for the cold start tests. This represented NOx emissions reductions from 97%-100% of compared with previous ISL G 8.9 engines.

Emissions, fuel economy, and performance are determined over a light and a heavy driving cycle designed to represent the vehicles in-use driving patterns. The vehicles are 2010 class 8 Freightliner tractor trucks equipped with Cummins engines with Selective Catalytic Reduction and Diesel Particulate Filter emission control systems. The hybrid has lower carbon dioxide emissions, better fuel economy, and nitrogen oxide emissions statistically the same as the conventional. The CO emissions are well below the standards for both vehicles, but they are higher from the hybrid. The higher CO emissions for the hybrid are primarily related to the cooling of the Diesel Oxidation Catalyst (DOC) during the standard 20 minute key-off soak between repeats of the driving cycles. With a 1 minute key-off soak the CO emissions from the hybrid are negative.