1994-09-01

Further Exhaust Emission Control for Two-Stroke Engines 941686

Two-stroke engines are being utilized in large numbers as small utility, lawn and garden equipment engines. The following two subjects were examined with regards to exhaust emission control.
The first subject was to compare the theoretical values of a combustion model simulation with the experimentally measured values of the base line emission of two-stroke volume as follows in detail.
  • Considering high short-circuiting and residual gas characteristics peculiar to two-stroke engines, comparison analysis between measured exhaust emissions and calculated values by a thermodynamic combustion model simulation.
  • Comparison analysis of the trapping efficiency-corrected HC, NOx, CO mass emission rates by the fuel flow and the fuel and air flow method.
  • Analysis of influence to engine power and mass emission rates by the cylinder thermal load change with varing air-fuel ratio of the charge mixture.
Thus, in small utility two-stroke engines, it was considered that, using the correction by the trapping efficiency ηtr, the evaluations for the theoretically estimated and experimentally measured values of exhaust emissions could be done sufficiently accurately.
The second subject was to examine the emission conformability to the 1995 and 1999 California Air Resources Board(CARB) exhaust emission regulations (California Regulations for 1995 and Later Utility and Lawn and Garden Equipment Engine, adopted at March 20, 1992, amended, at November 3, 1993 [1]*, was used in our paper abridging as “the 1995 and/or 1999 US-CARB exhaust emission regulations.”) in two-stroke engines with various combinations between various fuels, fuel supply systems and scavenging systems.
For this subject it was determined that the emission control systems based on the lean combustion can be used to meet the 1995 CARB exhaust emission regulations. However, it was also concluded that to meet the 1999 CARB exhaust emission regulations, various emission control systems with various combinations regarding such parameters as fuels, scavenging systems and exhaust systems must be used.

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