Shifting of the flame front in a small-scale commercial downdraft gasifier by water injection and exhaust gas recirculation

Steady-state experiments were conducted on a 12.4L, six-cylinder heavy-duty engine to investigate the influence of port-injected water and dilution via exhaust gas recirculation (EGR) on combustion and emissions for diesel and gasoline operation. Adding a diluent to the combustion process reduces peak combustion temperatures and can reduce the reactivity of the charge, thereby increasing the ignition-delay and, allowing for more time to premix air and fuel. Experiments spanned water/fuel mass ratios up to 140mass% and exhaust gas recirculation ratios up to 20vol% for gasoline and diesel operation with different injection strategies. Diluting the combustion process with either water or EGR resulted in a significant reduction in nitrogen oxide emissions along with a reduction in brake thermal efficiency. The sensitivity of brake thermal efficiency to water and EGR varied among the fuels and injection strategies investigated. An efficiency breakdown revealed that water injection considerably reduced the wall heat transfer; however, a substantial increase in exhaust enthalpy offset the reduction in wall heat transfer and led to a reduction in brake thermal efficiency. Regular diesel operation with main and post injection exhibited a brake thermal efficiency of 45.8% and a 0.3% reduction at a water/fuel ratio of 120%. The engine operation with gasoline, early pilot, and main injection strategy showed a brake thermal efficiency of 45.0% at 0% water/fuel ratio, and a 1.2% decrease in brake thermal efficiency for a water/fuel ratio of 140%. Using EGR as a diluent reduced the brake thermal efficiency by 0.3% for diesel operation, comparing ratios of 0% and 20% EGR. However, a higher impact on brake thermal efficiency was seen for gasoline operation with early pilot and main injection strategy, with a reduction of about 0.8% comparing 0% and 20% EGR. Dilution by means of EGR exhibited a reduction in nitrogen oxide emissions up to 15 g/kWh; water injection showed only up to 10 g/kWh reduction for the EGR rates and water/fuel ratio investigated.

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Experimental Investigation for NOx Emission Reduction in Hydrogen Fueled Spark Ignition Engine Using Spark Timing Retardation, Exhaust Gas Recirculation and Water Injection Techniques

Journal of Thermal Science ◽

10.1007/s11630-019-1099-3 ◽

2019 ◽

Vol 28 (4) ◽

pp. 789-800 ◽

Cited By ~ 2

Author(s):

Ramesh Jeeragal ◽

K. A. Subramanian

Keyword(s):

Experimental Investigation ◽

Emission Reduction ◽

Water Injection ◽

Exhaust Gas Recirculation ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Exhaust Gas ◽

Spark Timing ◽

Injection Techniques ◽

Gas Recirculation

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Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

International Journal of Engine Research ◽

10.1177/1468087420933124 ◽

2020 ◽

Vol 21 (10) ◽

pp. 1857-1877 ◽

Cited By ~ 2

Author(s):

Tim Franken ◽

Fabian Mauss ◽

Lars Seidel ◽

Maike Sophie Gern ◽

Malte Kauf ◽

...

Keyword(s):

Carbon Monoxide ◽

Nitrogen Oxide ◽

Water Injection ◽

Exhaust Gas Recirculation ◽

Low Pressure ◽

Exhaust Gas ◽

Nitrogen Oxide Emissions ◽

Direct Water Injection ◽

Tabulated Chemistry ◽

Gas Recirculation

This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at λ = 1 at full load using water–fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air–fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air–fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions.

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