Search Results

Exhaust Gas Recirculation (EGR) coolers are commonly used in on-road and off-road diesel engines to reduce the recirculated gas temperature in order to reduce NOx emissions. One of the common performance behaviors for EGR coolers in use on diesel engines is a reduction of the heat exchanger effectiveness, mainly due to particulate matter (PM) deposition and condensation of hydrocarbons (HC) from the diesel exhaust on the inside walls of the EGR cooler. According to previous studies, typically, the effectiveness decreases rapidly initially, then asymptotically stabilizes over time. Prior work has postulated a deposit removal mechanism to explain this stabilization phenomenon. In the present study, five field aged EGR cooler samples that were used on construction machines for over 10,000 hours were analyzed in order to understand the deposit structure as well as the deposit composition after long duration use.

Full-load HCCI operation with extremely low emissions was demonstrated. Experiments were performed on a 1.8L single cylinder heavy-duty diesel engine equipped with variable valve actuation system. Extensive study was made for the effects of EGR ratio, intake manifold temperature, air-fuel ratio and intake valve close timing on HCCI operation. With appropriate selection of the above variables, operation range was extended up to 2.0MPa of IMEP with diesel fuel. NOx emission was extremely low (0.01g/kWh) with retaining low smoke level (0.1BSU).

This paper proposes a new flexible system concept applicable to diesel engines which will achieve the compatibility of high BMEP (Break Mean Effective Pressure) and low fuel consumption. The high BMEP means constant power from low speed to high speed (the power density will be 60ps/liter for truck applications, 87ps/liter for marine applications and 109ps/liter for racing boats). BMEP will be over 32kg/cm2. The low fuel consumption means a wide range of speed and torque having a good match to the best turbocharger efficiency. Before feasibility testing of an engine a basic simulation has been done and is introduced in this paper.

1 Iridium (Ir) HC deNOx catalyst system for industrial heavy-duty diesel engine was investigated. The emission performance of the engine used for this examination satisfied EPA Tier 1 regulation. Though it was confirmed that applying the HC deNOx catalyst to Tier 1 level engine made it meet Tier 3 environmental regulation, the resulting in penalty of fuel consumption was seen as a big problem. To overcome this problem, the combined system comprising of hot EGR and Ir HC deNOx catalyst was examined. As the result of this study, the following points became clear: First, when there is high NOx concentration in front of catalyst, NOx conversion increases with the amount of HC. However, it saturates at a certain level, and after that, it gets worse. Second, when the NOx concentration at the inlet of deNOx catalyst is decreased with addition of the EGR system to base engine, the ability of NOx conversion gets worse with the decrease of NOx concentration at catalyst inlet.

A lot of small fans with three-dimensional, wide chord length, forward swept figure, and/or shroud ring have been developed and manufactured by injection molding. When we see large size fans, they are still two-dimensional old-fashioned steel fans. Therefore, a new series of hybrid fans (plastic blades + steel hub) was developed to meet the requirement of low noise and high efficiency. Key technologies of high performance hybrid fans are blade contours that generate gradual load change and the best compromise among noise, efficiency and strength. Using CFD and FEM, several blade contours are investigated varying curvature distribution and blade turning angles. Further, the total cooling system was re-examined to increase the effect of new fans. One candidate is the attachment of noise-absorbing material around the fan and the other is selecting most appropriate shroud contour.

THIS paper reports the latest investigation of the relative merits of loop scavenging versus through scavenging. The authors hope that the conditions of the work permitted an objective evaluation of the two types of engines. The results of the study may be summarized as follows: 1. With symmetrical timing, neither cylinder shows significant advantage in trapping efficiency. 2. With symmetrical timing, the best ratio of exhaust-port to inlet-port effective area seems to be about 0.6. 3. Unsymmetrical timing is an effective method of improving trapping efficiency. 4. The value of net indicated fuel economy shows no significant difference between the two cylinders. The authors point out that because the areas were equal it is unlikely that the optimum port design of each type was used in comparing the cylinders. If optimum porting had been used, the two types might have shown more difference.

The conventional concept of soot and ash wall deposits (i.e. cake-layers) gradually building up along the channels of a ceramic honeycomb and then periodically or continuously being swept downstream toward the end-plugs of the channels may not always occur in practice. When deposits irregularly form on or detach from the walls, causing premature clogging usually around the mid-sections of the channels (also known as Mid-Channel Collapse), and the particulate filter is prone to experiencing significantly elevated back pressure, resulting in the need for earlier repair or replacement than desired. Here we describe related experiments that were performed, accompanied by analysis and simulation, in order to investigate the factors that contribute to the patterns of wall deposits that form-particularly of ash-and the effects of these irregular patterns.