Lean burn natural gas engines as a possible power unit in urban fleets of heavy duty vehicles with low environmental impact

Increasingly restrictive limits on NOx levels are driving the change from lean-burn to stoichiometric combustion strategies on heavy-duty on-highway natural gas engines in order to take advantage of inexpensive and effective three-way catalyst technology. The change to stoichiometric combustion has led to increased tendency for engine knock due to higher in-cylinder temperatures. Exhaust Gas Recirculation (EGR) has been proposed as a method to suppress knock via charge dilution while maintaining a stoichiometric air-fuel ratio. Two of the more common EGR driving architectures and the challenges associated with each architecture are described. A series of engine tests were devised and performed on a 7-liter heavy-duty natural gas engine to explore the relationships between EGR knock suppression and engine backpressure. A unique concept for an external EGR pumping cart which allowed for the exploration of higher EGR rates independent of backpressure is also described. Results showed that for the conditions tested, increasing EGR rates beyond a certain point did not result in decreased knock tendency. 1D Simulation showed that the effectiveness of the EGR is limited by trapped hot residual gasses which resulted in higher in-cylinder temperatures and nullified the cooling effects of the EGR. These results suggest that attention must be paid to reducing backpressure via efficient EGR system architecture design in order to achieve the highest possible efficiency.

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Effect of water vapor on the activity and stability of Pd/SZ and Co/ZrO2 in dual-catalyst treatment of simulated exhaust from lean-burn natural gas engines

Applied Catalysis B Environmental ◽

10.1016/j.apcatb.2010.02.040 ◽

2010 ◽

Vol 96 (3-4) ◽

pp. 421-433 ◽

Cited By ~ 15

Author(s):

Burcu Mirkelamoglu ◽

Umit S. Ozkan

Keyword(s):

Water Vapor ◽

Natural Gas ◽

Lean Burn ◽

Natural Gas Engines ◽

Effect Of Water

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Numerical Simulations of Mixture Formation in Combustion Chambers of Lean-Burn Natural Gas Engines Incorporating a Sub-Chamber

10.4271/2017-01-2280 ◽

2017 ◽

Author(s):

Yuzuru Nada ◽

So Morimoto ◽

Yoshiyuki Kidoguchi ◽

Ryu Kaya ◽

Hideaki Nakano ◽

...

Keyword(s):

Natural Gas ◽

Numerical Simulations ◽

Combustion Chambers ◽

Mixture Formation ◽

Lean Burn ◽

Natural Gas Engines

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3 kW Thermoelectric Generator for Natural Gas-Powered Heavy-Duty Vehicles—Holistic Development, Optimization and Validation

Energies ◽

10.3390/en15010015 ◽

2021 ◽

Vol 15 (1) ◽

pp. 15

Author(s):

Lars Heber ◽

Julian Schwab ◽

Timo Knobelspies

Keyword(s):

Natural Gas ◽

Thermoelectric Generator ◽

Functional Model ◽

Simultaneous Optimization ◽

Heavy Duty ◽

Holistic Model ◽

Average Deviation ◽

Vehicle Class ◽

Thermoelectric Modules ◽

Heavy Duty Vehicles

Emissions from heavy-duty vehicles need to be reduced to decrease their impact on the climate and to meet future regulatory requirements. The use of a cost-optimized thermoelectric generator based on total cost of ownership is proposed for this vehicle class with natural gas engines. A holistic model environment is presented that includes all vehicle interactions. Simultaneous optimization of the heat exchanger and thermoelectric modules is required to enable high system efficiency. A generator design combining high electrical power (peak power of about 3000 W) with low negative effects was selected as a result. Numerical CFD and segmented high-temperature thermoelectric modules are used. For the first time, the possibility of an economical use of the system in the amortization period of significantly less than 2 years is available, with a fuel reduction in a conventional vehicle topology of already up to 2.8%. A significant improvement in technology maturity was achieved, and the power density of the system was significantly improved to 298 W/kg and 568 W/dm3 compared to the state of the art. A functional model successfully validated the simulation results with an average deviation of less than 6%. An electrical output power of up to 2700 W was measured.

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