Extension of the Lean Operating Limit for Natural Gas Fueling of a Spark Ignited Engine Using Hydrogen Blending

Abstract

The performance, emissions and combustion characteristics of lean mixtures of natural gas and hydrogen were studied in a conventional spark ignited engine. Specifically. mixtures of natural gas blended with 5, 10 and 15 percent by volume hydrogen were considered. Engine performance parameters included power (BH P], thermal efficiency (BTE), specific fuel consumption (BSFC), coefficient of variation in mean effective pressure, cumulative energy release schedule, and emissions of CO, NO,r and hydrocarbons. Major conclusions of the work include: (i) at equivalence ratios leaner than 0.80, improvements in BHP, BSFC, and BTE were significant with hydrogen addition; (ii) significant extension of the lean operating limit to lower equivalence ratios was demonstrated with increasing hydrogen concentrations in natural gas; (iii) emissions of CO, NO,r and hydrocarbons decreased as equivalence ratio was reduced until partial burning became predominant; (iv) hydrogen addition appeared to allow stable engine operation with lower pollutant emissions over a relatively broad range oflean equivalence ratios; and (v) the impact of hydrogen blending on performance and emissions was dependent on the volume fraction of hydrogen, although the functional relationship appeared to be non-linear.

An experimental study of premixed laminar methane/oxygen/argon flames doped with hydrogen at low pressure with synchrotron photoionization

“…Engine research showed that adding a small amount of hydrogen into natural gas can improve the combustion characteristics and reduce exhaust emissions [1 6] . Meanwhile, the lean burn limit can be extended by hydrogen addition and lead to further improvement of thermal efficiency and decrease of exhaust emissions [7,8] .…”

Evaluation of NASA Lean Premixed Hydrogen Burner

“…Studies in the literature related to the use of hydrogen as both the primary fuel and a fuel additive have been directed toward the effects of small amounts of hydrogen addition on hydrocarbon flame stability and pollutant formation under fuel-lean conditions. For example, studies in spark ignition engines clearly show the benefits of hydrogen blended with natural gas on exhaust emissions (Larson and Wallace, 1997) and on extending the lean engine operating limits (Meyers and Kubesh, 1997;Bell and Gupta, 1997). Early results in large-scale gas turbine combustors also indicate advantages to hydrogen addition.…”

Effect of ignition timing and hydrogen fraction on combustion and emission characteristics of natural gas direct-injection engine

“…The improvement of engine efficiency and the reduction of emissions could be realized by adding a small amount of hydrogen to natural gas under lean mixture operation [9][10][11]. The lean-burn capability of natural gas could be improved by hydrogen addition leading to further improvement of engine thermal efficiency and reduction in emissions [12,13]. Moreover, hydrogen addition could increase the tolerance of large EGR while maintaining low cycle-by-cycle variations and reducing engine NO x by 80% [14].…”