The water droplet erosion (WDE) on high-speed rotating wheels appears in several
engineering fields such as wind turbines, stationary steam turbines, fuel cell
turbines, and turbochargers. The main reasons for this phenomenon are the high
relative velocity difference between the colliding particles and the rotor, as
well as the presence of inadequate material structure and surface parameters.
One of the latest challenges in this area is the compressor wheels used in
turbochargers, which has a speed up to 300,000 rpm and have typically been made
of aluminum alloy for decades, to achieve the lowest possible rotor inertia.
However, while in the past this component was only encountered with filtered
air, nowadays, due to developments in compliance with tightening emission
standards, various fluids also collide with the spinning blades, which can cause
mechanical damage. One such fluid is the condensed water in the low-pressure
exhaust gas recirculation channel (LP-EGR) formulated at cold starts and
low-speed high load conditions. This kind of design has been developed to reduce
nitrogen oxide emissions and is used in both gasoline and diesel engines. This
article presents a state-of-the-art review of this WDE process, focusing on the
formation of the condensed water before the compressor wheel, summarizing the
influencing factors of WDE and the effects of the damage including using
component testbench experiences and simulation methodologies. Inspection
possibilities such as high-speed camera measurement and vibration analysis are
also an important part of the document.
