Using engine cycle simulation in truck engine development - design tools

Diesel Progress North American Edition, August, 2003 by Joachim Weiss

Fuel consumption results are seen in Fig. 6. Variant A turns out to be an acceptable alternative for a lower rated engine, because its cycle fuel consumption is not extraordinarily high. With two-stage turbocharging, the lowest fuel consumptions can be obtained with variants B1, B2 and D Charge-air intercooling seems to be necessary in terms of efficiency (variant B1 compared with B3), but it might be less important by use of a twin entry turbine (B2 compared with B1). The result of B4 indicates that internal EGR is not efficient under the boundary conditions considered here. Also EGR cooling does not appear essential in every case, as seen from comparison of variants C1 and C2. Based on the BSFC results, engine tests with both high and medium-pressure EGR loop (variants B1, B2, D) are recommended.

[FIGURE 6 OMITTED]

It has been shown that GT-POWER cycle simulation is able to yield reliable results concerning the engine behavior. With the jet model, fairly safe predictions on N[O.sub.x] can be obtained, even at varying injection timing and EGR rate. As a result, truck engine development has at its disposal a tool for the preselection of different solutions to meet the Euro 4 emission limits. This will be achievable by optimizing the engine to low emissions and additional use of the so-called PM-Kat aftertreatment system. For obtaining EGR rates higher than 20 percent at acceptable air-fuel ratios, two-stage turbochanging will be essential for high rated engines. In the majority of cases, variants with an EGR cooler and intercooler are advantageous. Further tests, in which the transient behavior too will be investigated, will subject this result to closer scrutiny.

Fig. 6. Calculated brake specific fuel consumption results within the
ESC.

          Fuel Consumption
VARIANT       (g/kW-h)

A              214.2
B1             207.6
B2             207.3
B3             212.1
B4             216.0
C1             210.6
C2             209.5
D              206.6

Note: Table made from bar graph.

Dr. Joachim Weiss is a senior engineer responsible for engine thermodynamics at MAN Nutzfahrzeuge, Nuernberg, Germany.