Two simultaneous strategies were used to reduce diesel engine emissions. Optimized manifold designs were used with 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°), but 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 number of turns. The same combination also reduced the pressure raise 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 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 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.
Smoke emissions and particulate matter (PM) size distributions were investigated on a direct-injection (DI) single-cylinder diesel engine running on both gas-to-liquid (GTL) and diesel fuels utilizing a novel spiral-helical intake manifold design. Smoke opacity was measured at a wide range of engine loads and speeds with both fuels to examine the effect of using the new manifold on smoke emissions. In addition, total PM numbers of fine particles (PM diameter ≤ 1.0 μm) and coarse particles (˃1.0 μm) were quantified with both fuels. Moreover, high-resolution transmission electron microscopy (HRTEM) images were taken with different resolutions to observe the PM sizes produced from each fuel when using the new and normal manifolds. The results showed that using the novel manifold reduced smoke emissions for both GTL and diesel fuels with about 36% at low loads and 7% at high loads. However, using the new manifold with GTL fuel showed superior performance to reduce smoke with about 60% at low loads and 10% at high loads. For the PM size distribution, the new manifold reduced total PM emissions in general. However, significant reductions were obtained with fine PM sizes (0.3–1.0 μm) when GTL fuel was used with about 30% for constant load tests, and about 40% for constant speed tests. On the other hand, the new manifold tended to increase slightly the coarse PM sizes. The HRTEM images of the PM structure for both manifolds and fuels have confirmed the above results.
The main purpose of this work was to investigate the performance of heated shock tube (ST) with different pressure ratios and diaphragm positions numerically and experimentally. The numerical model was developed to simulate the fluid flow inside a shock tube test facility located at Qatar University. The shock tube was a cast‐iron hollow tube with 6 m length, 50 mm internal diameter and 10 mm thickness. ST driver and driven sections were filled with helium–argon mixture and air. The driven section was heated up to 150°C using coils. At the middle of the ST, the diaphragm was made of aluminium sheet (0.5 mm) layers. Five different pressure ratios were implemented during the experiment, and performance evaluation depended on the strength of the incident shock Mach number. The inviscid numerical model solver used transient two‐dimensional time‐accurate Navier–Stokes CFD. The model introduced a parametric study regarding three different diaphragm positions (1m, 2m and 3m) and five pressure ratios (6–10) for each position. In addition to yielding the incident and reflected wave Mach number, reflected wave temperature was also considered a shock tube performance indicator. The incident Mach numbers for the diaphragm middle position from the experiment were compared against those conducted from the model, and good matching was observed. The parametric study results showed that at high‐pressure ratios, diaphragm Positions 1 and 3 could generate a 7.4% increase in shock wave Mach number compared with the diaphragm position‐2 model. Moreover, the diaphragm position‐3 model tends to have a 2% increase in the temperature behind the reflected shock wave compared with the other two positions.
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