Clearstone Engineering
April 19, 2012
Executive Summary
Clearstone Engineering Ltd. conducted a study of natural gas fuelled internal combustion engines to better understand the relationship between NOx and GHG emissions and fuel consumption. The study included a literature review and field studies of Waukesha VHP GSI engines operating in the upstream oil and gas industry.
Five Waukesha L7042GSI engines modified with the installation of REMVue air to fuel ratio control systems were tested to characterize fuel consumption and emissions during a series of tests at different Lambda values. Overall load values tested ranged from 750 bhp to 1366 bhp. The nominal rated power output of current L7042GSI engines is 1480 bhp at 1200 rpm. However, previous versions were rated at levels of 1100 bhp at 1000 rpm. The engines tested included those rated at both 1100 and 1400 bhp. All engines were tested at condition that attempted to achieve NOx emission levels of 2.0 g/bhp-h (2.7 g/kWh) and all were tested in the lean burn region of operation compatible with the application of REMVue AFR control technology. Lambda values were in the range of 1.22 to 1.59. One engine appeared to be turbo limited and could not achieve NOx levels lower than about 4.0 g/bhp-h (5.4 g/kWh).