Mohammed T. Gergawy

Bio: Mohammed T. Gergawy is an academic researcher from Qatar University. The author has contributed to research in topics: Combustion & Diesel engine. The author has an hindex of 1, co-authored 1 publications receiving 7 citations.

Investigating the Effect of Utilizing New Induction Manifold Designs on the Combustion Characteristics and Emissions of a Direct Injection Diesel Engine

Abstract: New induction manifold designs have been developed in this work to enhance the turbulence intensity and improve the mixing quality inside diesel engine cylinders. These new designs employ a spiral-helical shape with three different helical diameters (1D, 2D, 3D; where D is the inner diameter of the manifold) and three port outlet angles: 0 deg, 30 deg, and 60 deg. The new manifolds have been manufactured using three-dimensional printing technique. Computational fluid dynamics simulations have been conducted to estimate the turbulent kinetic energy (TKE) and the induction swirl generated by these new designs. The combustion characteristics that include the maximum pressure raise rate (dP/dθ) and the peak pressure inside the cylinder have been measured for a direct injection (DI) diesel engine utilizing these new manifold designs. In addition, engine performance and emissions have also been evaluated and compared with those of the normal manifold of the engine. It was found that the new manifolds with 1D helical diameter produce a high TKE and a reasonably strong induction swirl, while the ones with 2D and 3D generate lower TKEs and higher induction swirls than those of 1D. Therefore, dP/dθ and peak pressure were the highest with manifolds 1D, in particular manifold m (D, 30). Moreover, this manifold has provided the lowest fuel consumption with the engine load by about 28% reduction in comparison with the normal manifold. For engine emissions, m (D, 30) manifold has generated the lowest CO, SO2, and smoke emissions compared with the normal and other new manifolds as well, while the NO emission was the highest with this manifold.

Experimental and Numerical Study on the Formation Mechanism of Flow Field in a Side-Ported Rotary Engine Considering Apex Seal Leakage

Abstract: The aim of this research is to investigate the influences of apex seal leakage on the formation mechanism of flow field in a side-ported rotary engine by particle image velocimetry (PIV) and computational fluid dynamics (CFD). In this study, a PIV was used to acquire the two-dimensional (2D) flow field on the rotor housing central plane at an engine speed of 700 rpm. A three-dimensional (3D) dynamic simulation model considering leakage through apex seals was established and verified by the 2D-PIV experiment results. Thereafter, CFD analysis was used to further understand the 3D flow field in combustion chamber under the action of apex seal leakage. The simulation results showed that for the three engine speeds (2000, 3500, and 5000 rpm), in the intake stroke, the vortex generated in the front end of combustion chamber under the condition with no leakage, was strengthened and destroyed by the effects of the small (0.02 mm) and the large (0.08 mm) apex seal leakage gaps, respectively. As the apex seal leakage gap increased, the volume efficiency and the peak pressure decreased continuously. The volume efficiency and the peak pressure caused by any fixed apex seal leakage gap decreased with the increase of the engine speed. Compared with the volumetric efficiency of the condition with no leakage at 2000 and 5000 rpm, the volumetric efficiency of apex seal leakage gap of 0.08 mm decreased only by 24.6% at 5000 rpm, but by 41.2% at 2000 rpm.

Prediction of Ultra-Lean Spark Ignition Engine Performances by Quasi-Dimensional Combustion Model with a Refined Laminar Flame Speed Correlation

Abstract: The turbulent combustion in gasoline engines is highly dependent on laminar flame speed SL. A major issue of the quasi-dimensional (QD) combustion model is an accurate prediction of the SL, which is unstable under low engine speeds and ultra-lean mixture. This work investigates the applicability of the combustion model with a refined SL correlation for evaluating the combustion characteristics of a high-tumble port gasoline engine operated under ultra-lean mixtures. The SL correlation is modified and validated for a five-component gasoline surrogate. Predicted SL values from the conventional and refined functions are compared with measurements taken from a constant-volume chamber under micro-gravity conditions. The SL data are measured at reference and elevated conditions. The results show that the conventional SL overpredicts the flame speeds under all conditions. Moreover, the conventional model predicts negative SL at equivalence ratio ϕ ≤ 0.3 and ϕ ≥ 1.9, while the revised SL is well validated against the measurements. The improved SL correlation is incorporated into the QD combustion model by a user-defined function. The engine data are measured at 1000–2000 rpm under engine load net indicated mean effective pressure (IMEPn) = 0.4–0.8 MPa and ϕ = 0.5. The predicted engine performances and combustions are well validated with the measured data, and the model sensitivity analysis also shows a good agreement with the engine experiments under cycle-by-cycle variations.

Impact of secondary fuel injector in various distance on direct injection diesel engine using acetylene-bio diesel in reactivity controlled compression ignition mode

Abstract: Many researchers utilized acetylene fuel in conventional diesel engine in dual fuel mode. Dual fuel Reactivity Controlled Compression Ignition (RCCI) engine is established by modifying the Conventi...

Combustion and Emissions of a Gas-to-Liquid Diesel Engine Utilizing Optimized Spiral-Helical Intake Manifold Designs

Abstract: Two simultaneous strategies were used to reduce diesel engine emissions. Optimized manifold designs were used with gas-to-liquid (GTL) fuel and its blend with diesel fuel. Six new spiral-helical manifolds were tested, which could be divided into two groups. The first group is with the same inner diameter (2.6 cm) and outlet angle (30 deg), but the different number of spiral turns (1t, 2t, etc.). The second group is with different inner diameters. The results showed that the highest pressure and heat release were achieved by m(2.6,30,1t) with the diesel–GTL blend. In addition, the heat release rate decreases with the increase in the number of turns. The same combination also reduced the pressure rise rate (dP/dθ) by about 24% compared to the normal manifold. For the emissions, the maximum reduction in CO emissions was achieved by using m(2.6,30,3t) and GTL with about 34%. In addition, the maximum hydrocarbon (HC) reduction was achieved by m(2.1,30,3t) and GTL, which is about 99% lower than that of the normal manifold. NO emissions were reduced by about 25% when m(2.6,30,4t) and GTL are used. The total particulate matters (PM) were the lowest for m(2.6,30,1t) and normal manifold in the case of diesel. Generally, it was found that the combination of m(2.6,30,1t) with GTL and its blend gave the optimum performance and low emissions among all manifolds.