CIMAC Congress - Schiff & Hafen

Monday, 14 June
Wednesday, 16 June
Thursday, 17 June
Tuesday, 15 June
Stoichiometric operation of natural gas
engines for very low emissions applications
J. Hiltner, M. Flory, Hiltner Combustion Systems,
USA
The utilization of natural gas engines for power generation and
other stationary applications has grown dramatically in the last two
decades, due largely to the favorable emissions characteristics, and
more recently, to the favorable power density and thermal efficiency
of lean burn spark ignited engines relative to their various market
competitors. With minimal required after-treatment and relatively
low-cost controls, open-chamber and pre-chamber lean burn
engines are capable of efficiency and BMEP levels comparable to
similar displacement diesel engines, with an order of magnitude
reduction in NOx and particulate emissions. This rapid development
is now threatened in many markets by proposed emissions
regulations that are below the currently achievable engine out NOx
capabilities of lean burn engines. While SCR aftertreatment offers a
clear technical solution for larger installations where very low NOx
levels are required, these systems represent a significant increase in
system cost and complexity and are not economically feasible for
smaller installations, particularly those operating in remote areas.
This combination of factors is driving many traditional natural gas
engine markets, particularly in North America, away from lean burn
combustion and back to stoichiometric combustion systems where
3-way catalysts can be utilized to reduce overall emissions of NOx,
CO, NMHC and to some extent other trace pollutants. Engines
operating under stoichiometric conditions generally offer lower
performance and suffer from significant durability issues due to
high in-cylinder and exhaust gas temperatures. This paper explores
the roots of the performance penalty paid for a shift to stoichiometric
combustion. Engine test results from a heavy duty natural gas engine
are used to illustrate the impact of heat release rate, charge
thermodynamics, in-cylinder heat transfer, knock limits, engine
breathing and exhaust gas temperature limits on engine performance
under stoichiometric conditions. The individual effects of each of
these parameters is quantified through one-dimensional modeling
of the test engine. The impact of cooled, low pressure EGR is also
discussed in terms of its performance potential relative to
stoichiometric and lean combustion systems. The loss of engine
power density, increase in brake specific engine cost, and the increase
in greenhouse gas emissions of stoichiometric engines are then
quantified relative to their NOx reduction potential with respect to
high performance lean burn engines. This paper seeks to quantify
the performance and market penalties associated with a shift to
stoichiometric engine operation, as well as describing the roots of
these penalties.
15:30 June 15th Room Klokkeklang
(9–4) Turbochargers & Turbomachinery –
Aspects of Turbomachinery
Turbocharger performance stability under
HFO conditions
V. Haueisen, T. Behr, W. Gizzi, ABB Turbo Systems
Ltd., Switzerland
To meet the performance and emission requirements of modern
diesel and gas engines turbochargers must be built using the same
No. 3 | 2010 | Ship & Offshore
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