The general PI controller employed in FPLG is illustrated in Figure 10.
In this article, a compression ratio tracking controller of FPLG is designed by using in-cylinder pressure feedforward control.
Finally, the efficiency of FPLG is going to be the next research emphasis.
TABLE 1 Main parameters of FPLG. Cross sectional area of piston 0.002 [m.sup.2] Clearance volume 5708.79 [mm.sup.3] Positon of exhaust port 22.8 mm Specific heat ratio 1.3 Scavenging chamber pressure 1.52 x [10.sup.5] Pa Effective stroke of piston 54.8 mm Mass of piston 3.75 kg Low calorific value of fuel 44000 J/g
For the FPLG the strategy including an internal exhaust gas recirculation (EGR) was chosen.
In general there are two different types of piston motion for the control of the FPLG. In the first mode the piston motion is fixed and can be defined for example by a lookup table.
By influencing [F.sub.mag] the controller of the FPLG ensures that the system runs stable and hits the desired dead centers but the motion equation (1) is still fulfilled.
Since the piston motion of the FPLG can vary from cycle to cycle the calculation of several parameters is different compared to conventional crank train engines.
According to strategy 1 the SI operating point which is based on the previous simulation results is adjusted for the freely oscillating FPLG system.
In summary, this process can be described as a self-regulating effect of the HCCI auto ignition in the FPLG. The initially missing start of the heat release decelerates the piston motion.
Consequently, IMEP limits for HCCI operation in conventional engines do not necessarily apply to the FPLG. Here it is to investigate new load limits particularly for free-piston engines.
For a better comparability with conventional engines the value is converted into bar per crank angle degree (CAD) since the FPLG has no crank train.