Salah's Model for Diesel Engine Intake Airflow
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Salah's model[1] is an analytical framework developed by Salah Elmoselhy[2] that provides a physically motivated, closed-form solution for estimating the intake air mass flow into diesel engine cylinders, accounting explicitly for the effects of a flexible crankshaft. The model addresses a key shortcoming in existing simulation frameworks like GT-Power and CMEM, which generally assume rigid crankshafts.[3]
Background
Crankshaft flexibility, although often ignored in traditional engine models, introduces notable inertial and pressure variations that can affect intake dynamics, especially at high rotational speeds. Salah Elmoselhy proposed a refined intake airflow model that integrates these dynamic effects through first-principle derivations.
Salah’s Analytical Model
The model, also referred to as Salah’s model, is derived from Newtonian mechanics and thermodynamic considerations of the intake process. The in-cylinder pressure during the intake phase is computed as a sum of:
- Manifold pressure,
- Vacuum effect due to piston acceleration,
- Flow-induced losses,
- Inertial effects from crankshaft rotation.
This results in a compact expression for the overall cylinder pressure, and subsequently for the total intake air mass flow.
Validation
Salah’s model has been validated using real-world drive cycles and has demonstrated improved accuracy over GT-Power and CMEM. It achieved mean prediction errors of:
- ~7.5% for the ORNL standard freeway cycle,
- ~11% for the EPA freeway cycle.
Impact
Salah’s model enables accurate, fast, and transparent airflow predictions for diesel engines operating under flexible mechanical conditions. It opens up new avenues for emission reduction strategies and control-oriented modeling.
See also
Bibliography
- ^ Elmoselhy, Salah A. M.; Faris, Waleed F.; Rakha, Hesham A. (2022-08-22). "Validated Analytical Modeling of Eccentricity and Dynamic Displacement in Diesel Engines with Flexible Crankshaft". Energies. 15 (16): 6083. doi:10.3390/en15166083. ISSN 1996-1073.
- ^ "Center for Physics of the University of Coimbra". cfisuc.fis.uc.pt. Retrieved 2025-07-12.
- ^ "How the crankshaft works - All the details". How a Car Works. Retrieved 2025-07-12.