A Study on Supercharged HCCI Natural Gas Engines

A chemical kinetically based ignition delay correlation for iso-octane covering a wide range of conditions including the NTC region

“…With many of these alternative schemes combustion chemistry is extremely important. Future designs are expected to employ such novel lean/dilute regimes, sometimes in combination with conventional SI and CI operation, where high boost (inlet pressures up to 5-6 bar) and/or extreme compression ratio (CR to 50:1) could be used to address power density and energy loss issues [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In these engines ignition pressures could reach 100-300 bar, which is substantially higher than in current production engines where 0010 peak pressures are generally limited to ∼200 bar.…”

Natural gas HCCI engines

“…The NOx emission concentration is also extremely low under all conditions. The maximum value of η c improves with decreasing p b , due to the fuel charge reduction 15.29 Effect of boost pressure on engine performance (engine speed 1800 rpm, compression ratio 21, intake air temperature 353K) [6]. required at high boost pressure to limit in-cylinder pressure.…”

“…This is thought to be due to the reduction in cooling loss resulting from the 15.27 Influence of intake air temperature on emission characteristics under supercharging (engine speed 1800 rpm, compression ratio 17, boost pressure 2.5 bar) [6] 15.28 In-cylinder pressure and heat release rate over time (engine speed 1800 rpm, compression ratio 17, boost pressure 2.5 bar). (a) change in p and dq/dθ with intake air temperature, and (b) change in p and dq/dθ for each cylinder at knock limits [6]. lag in heat release starting point, an increase in the fuel charge quantity, and a change in the temperature profile due to the decrease of T in [9].…”

“…The figure also shows that in the range of BMEP from 7.5 bar to 9.0 bar, it is possible to attain a brake thermal efficiency higher than 0.42. 15.31 Brake thermal efficiency and brake mean effective pressure with variation of boost pressure and intake air temperature at a compression ratio of 21 [6]. 15.32 Performance of natural gas supercharged HCCI engine characteristics (engine speed 1800 rpm, assumed turbocharging efficiency 0.64) [6].…”

On the Rate of Heat Release for High-Boost, Low-Temperature Combustion Schemes: Accounting for Compressibility Effects

“…Common themes for these alternatives are reduced combustion temperatures (1600-1800 K peak) and control of local fuel=oxidant=diluent compositions so that NOx and soot production can be simultaneously mitigated. Future engines may employ such low temperature combustion (LTC) schemes where boosted operation (up to 5-6 bar) and=or very high compression ratio (CR $ 50) could be employed to address power density and energy loss issues (e.g., Aoyagi et al, 2006;Buchwald et al, 2006;Cairns & Blaxill, 2005;Chen & Mitsuru, 2003;Edwards et al, 2007;Gharahbaghi et al, 2006;Hyvö nen et al, 2003;Kalghatgi et al, 2006;Kim et al, 2007;Olsson et al, 2004;Sako et al, 2005;Teh & Edwards, 2006;Teh et al, 2008aTeh et al, , 2008b. Under these conditions, ignition pressures could reach 100-300 bar with peak pressures to 500 bar (McIlroy & McRae, 2007); this is substantially higher than for current production engines where maximum pressures are generally limited to 200 bar.…”