High Compression Ratio Engine Operation on Biomass Producer Gas 2011-01-2000
Experimental investigations have been conducted with two
identical small scale SI gas engines gen-sets operating on biomass
producer gas from thermal gasification of wood. The engines where
operated with two different compression ratios, one with the
original compression ratio for natural gas operation 9.5:1, and the
second with a compression ratio of 18.5:1. It was shown that high
compression ratio SI engine operation was possible when operating
on biomass producer gas from a TwoStage gasifier. The results
showed an increase in the electrical efficiency from 31% to 35%
when the compression ratio was increased.
The influence of ignition timing on emissions was investigated
during high compression ratio operation. It was shown that for
λ=1.4 the NOx emission decreases by almost a factor 3,
when the timing is retarded from 13° to 7° before top dead center.
In order to further investigate the combustion properties of the
biomass producer gas, the laminar flames speed has been determined
from experiments and a thermodynamic model. The experiments have
been done in a constant volume combustion bomb, and measurements
with Danish natural gas have been conducted for comparison. The
natural gas with a methane content of 90% had a flame speed of
0.32-0.33 m/s at λ=1.22, while, the laminar flame speed for the
biomass producer gas was determined to 0.45 m/s at λ=1.05 and 0.35
m/s at λ=1.44.