Search Results (3)

Improving the performance of internal combustion engines (ICE), together with lowering emissions, are the main targets for specialists in the automotive field. One option for increasing engine efficiency is creating a considerable amount of boost for the inlet combustion air by means of supercharging. In addition to common turbochargers, an alternative solution that has interested researchers for almost a century is the pressure wave supercharger (PWS). This paper is, at first, a complimentary tribute to most of the researchers that studied, experimented with and improved PW supercharging technology from the 50′s to the present. Second, this review emphasizes the performance achieved by ICEs when using PW supercharging, highlighting the limits of these main parameters in different operating conditions, based on the main reported results in the literature. It also provides an overview of PW supercharging technology, with its main advantages and disadvantages and suggests some technical solutions or geometric adjustments to improve its operation. Even though in recent years this technology has registered a decrease of interest, there are still preoccupations, especially in the aeronautical industry, justified by the profitability and simplicity of PW devices. The results of this theoretical work can be exploited practically in PWS design and applications. Full article

To increase the efficiency of a natural gas engine, the use of a Miller camshaft was analysed. To avoid a decline in the low-end torque and also in the transient response, a pressure wave supercharger (Comprex™) was compared to the conventional single-stage turbocharger. The analyses for this conceptual comparison were performed experimentally, and the data were then used to run simulations of driving cycles for light commercial vehicles. A torque increase of 49% resulted at 1250 rpm when the Comprex™ was used in combination with a Miller camshaft. Despite the Miller camshaft, the Comprex™ transient response was still faster than the turbocharged engine. Using the same camshaft, the turbocharged engine took 2.5-times as long to reach the same torque. Water injection was used to increase the peak power output while respecting the temperature limitations. As the Comprex™ enables engine braking by design, we show that the use of friction brakes was reduced by two-thirds. Finally, a six-times faster catalyst warmup and an up to 90 ${}^{°}$C higher exhaust gas temperature at the three-way catalytic converter added to the benefits of using the Comprex™ supercharger. The known drawbacks of the Comprex™ superchargers were solved due to a complete redesign of the machine, which is described in detail. Full article

Water pipe sediment removal should be implemented as an integral part of water mains maintenance in order to steadily supply consumers with drinking water of high quality. Considering the number of different water pipe sediment removal methods, the article aims to evaluate the currently used methods to remove water pipe sediment from the pipes of the drinking water distribution system. The evaluation compares the implementation requirements of each method as well as the quality and the quantity of the removed products. The tested methods were unidirectional flushing, Comprex^®, and Ice Pigging^®. The results of the comparison are expressed in terms of total suspended solids (TSS) recovery, metals mass concentration and water consumption. Since contamination can settle along the entire surface of the pipeline, it is most appropriate to recalculate the results per unit area of the pipeline. The results point at the following efficiency the Comprex^® method was the most efficient in removing TSS, Ice Pigging^® was the next and unidirectional flushing removed a negligible amount of TSS compared to the other two methods. The absolute recovery of TSS was 0.12–3.01 g·m⁻² in unidirectional flushing of plastic pipes, 1.58–8.54 g·m⁻² in unidirectional flushing of metal pipes, 4.36–47.53 g·m⁻² in Ice Pigging^®, and 5.19–69.23 g·m⁻² in Comprex^®. The composition of the sediment was strongly influenced by particle origin: Pipe material affected the crystalline phase of the sediment and the water source and the age of the pipe affected the amorphous phase of the sediment. Therefore, it was found that evaluation of efficiency based on the amount of TSS removed is only suitable for sites that meet the same conditions as pipe material, water source and ideally the pipe age. It has further been found that the Comprex^® method can be advantageously used in real conditions to clean pipes with insufficient hydraulic conditions (such as with a high level of incrustation), as the cleaning has low water flow velocity requirements. Full article