摘要: |
The objective of this program was to quantify the emissions from heavy-duty vehicles operating on alternative fuels or advanced fuel blends, often with novel engine technology or aftertreatment. In the first year of the program West Virginia University (WVU) researchers determined that a transportable chassis dynamometer emissions measurement approach was required so that fleets of trucks and buses did not need to be ferried across the nation to a fixed facility. A Transportable Heavy-Duty Vehicle Emissions Testing Laboratory (Translab) was designed, constructed and verified. This laboratory consisted of a chassis dynamometer semi-trailer and an analytic trailer housing a full scale exhaust dilution tunnel and sampling system which mimicked closely the system described in the Code of Federal Regulations for engine certification. The Translab was first used to quantify emissions from natural gas and methanol fueled transit buses, and a second Translab unit was constructed to satisfy research demand. Subsequent emissions measurement was performed on trucks and buses using ethanol, Fischer-Tropsch fuel, and biodiesel. A medium-duty chassis dynamometer was also designed and constructed to facilitate research on delivery vehicles in the 10,000 to 20,000lb range. The Translab participated in major programs to evaluate low-sulfur diesel in conjunction with passively regenerating exhaust particulate filtration technology, and substantial reductions in particulate matter were recorded. The researchers also participated in programs to evaluate emissions from advanced natural gas engines with closed loop feedback control. These natural gas engines showed substantially reduced levels of oxides of nitrogen. For all of the trucks and buses characterized, the levels of carbon monoxide, oxides of nitrogen, hydrocarbons, carbon dioxide and particulate matter were quantified, and in many cases non-regulated species such as aldehydes were also sampled. Particle size was also quantified during selected studies. A laboratory was established at WVU to provide for studies which supported and augmented the Translab research, and to provide for development of superior emissions measurement systems. This laboratory research focused on engine control and fuel sulfur issues. In recent years, as engine and aftertreatment technologies advanced, emissions levels were reduced such that they were at or below the Translab detectable limits, and in the same time frame the US Environmental Protection Agency required improved measurement methodologies for engine emissions certification. To remain current and relevant, the researchers designed a new Translab analytic system, housed in a container which can be transported on a semi-trailer. The new system's dilution tunnel flow was designed to use a subsonic venturi with closed loop control of blower speed, and the secondary dilution and particulate matter filter capture were designed to follow new EPA engine certification procedures. A further contribution of the program has been the development of techniques for creating heavy-duty vehicle test schedules, and the creation of schedules to mimic a variety of truck and bus vocations. |