Figure 6 presents a contour of internal residual as a function of Exhaust Valve Closing (EVC) and Intake Valve Opening
Thermodynamic conditions during the closed cycle (compression, combustion, and expansion) can be directly controlled by adjusting the intake valve opening (IVO) and intake valve closing (IVC) angle, which defines the total intake mass flow rate and the effective compression ratio of the engine .
The RMS error for the predictions is 0.0274 for the intake valve opening, 0.43 for the intake valve closing, 1.82 for the exhaust valve closing, 0.793 for the exhaust valve opening, and 0 for the exhaust valve closing.
The results found that there was more of a uniform air/fuel ratio in the cases of the start of injection at the end of exhaust valve closing and the intake valve opening
at the end of compression .
The peak pressure drop transition is used to determine intake valve opening
This is due to two opposing vortical structures (Figure 10(c)) that form early due to the earlier intake valve opening and the different orientation of the velocity vector, which is a result of the reduced valve lift as stated above.
While the application of Miller cycles can lead to N[O.sub.x] reductions and efficiency improvements [7, 10, 14], intake valve opening timings are very sensitive concerning their influence on the engine flow field.
* Induction of the charge air close to top dead centre, requiring rapid intake valve opening
and closure with a short dwell period of about 30[degrees] crank angle.
In-cylinder injection start is imposed at IVO (Intake Valve Opening
), since it should model port-injected liquid water entering the combustion chamber during the intake stroke.
Test engine specification Exhaust Valve 28 mm Intake Valve Diameter 33.4 mm Diameter Total Engine 1.998 Liters Maximum Exhaust 8.64 mm Displacement Valve Lift Bore 86 mm Maximum Intake Valve 12.5 mm Lift Stoke 86 mm Intake Valve Opening
687 [degrees]CA (1VO) Connecting 144 mm Exhaust Valve Opening 491 [degrees]CA Rod (EVO) Compression 18.2:1 Intake Valve Closing 217 [degrees]CA Ratio (IVC) Valves per 4 Exhaust Valve Closing 10 [degrees]CA Cylinder (EVC) Table 2.
An explanatory model is that the liquid fuel film, which was most likely created during the closed-valve injection and during the event of intake valve opening
, did not evaporate in time.
PFI timing in the experiments are prior to intake valve opening
, and therefore against a closed intake valve.