Search Results

A non-destructive neutron radiography technique was used to measure the thickness of diesel soot deposited in the tubes of exhaust gas recirculation (EGR) cooling devices. Measurements were performed to characterize the fouling in single-tube and three-tube devices for laminar and turbulent flows. Measurements were also performed to characterize the effect that the design of the inlet header had on the deposition characteristics in the device. The analysis of the neutron images showed that the soot deposition in the single-tube device occurred at a faster rate for a turbulent flow than for a laminar flow. The deposition thickness decreased along the tubes for both flow regimes. More soot deposited in the center tube of the three-tube bundle for the expansion angle 45° inlet header suggesting there was an uneven distribution of the exhaust gas flow in the tube bundle.

An investigation was performed to characterize the effect of the short twisted-tape inserts on the performance of EGR cooling devices for diesel engine applications. The results showed that the addition of the twisted-tape insert reduced the soot deposition and the blockage of the entrance region observed in the cooling devices tested without inserts. The addition of the inserts improved the thermal performance of the cooling devices for lower mass flow rates per tube with a relatively intermediate penalty of the long-time pressure drop build-up. At high flow rates, there was only smaller improvement of the heat transfer and a larger pressure drop penalty was observed. The results suggested that the addition of short twisted-tape inserts could be used to improve some current under performing designs of cooling devices. Optimization in terms of the tape-to-tube length ratio, tube diameter, and number of tubes is required in future studies for higher potential EGR rates.