Correlations Between Charge Air Cooler (CAC) Distortion Bench Tests and Flexion Fatigue on Test Specimens

摘要

Diesel engine turbochargers are operating and will operate at higher temperatures and pressures due to meeting increasing emissions restriction standards. In order to reduce the emissions, a higher performance is necessary, which is normally obtained at a higher CAC working temperature and pressure. Maximum CAC flow will be reached at 1100 rpm; current Euro 3 test conditions represents 5% of the lifetime of the CAC; Euro 4 test conditions will represent 85% of the lifetime of the truck. However, temperatures of the order of 230 - 260°C, involves the possibility of creep phenomena within some aluminum alloys. For some time, the test temperature has been 205°C; however, new durability tests are requested to be carried out at 230°C. In the last three years, some test data at 230°C has been generated in Valeo. Initial test results are indicating that cycle life is less then the number of cycles than the specification for 205°C. The challenge is to provide a charge air cooler that will survive 500,000 cycles of hot pressure cycle test at 230°C. In this work, strength-enhanced long life alloys have been tested in pure flexion fatigue fully reversed, using specific geometric test specimens. Additionally, bench distortion tests were performed on CAC manufactured with tubes of the same alloys. This way, once that the geometrical and manufacturing parameters are optimized, the time and efforts to make the tests on complete heat exchangers can be simplified and the life of the CAC in this test can be predicted from previous evaluation in pure fatigue test specimens.