High-performance turbomolecular pump with titanium alloy rotor blade

A turbomolecular pump (TMP) with both a higher pumping speed and compression ratio has been developed by increasing the rotational speed of the rotor blade using a higher specific strength material than the conventional aluminum alloy. Titanium alloy, Ti–6Al–4V, was selected as the high-specific-strength material for the rotor blade. Finite element analysis showed that the rotor blade of Ti–6Al–4V can be safely operated at 1.23 times the normal rotational speed of the existing TMP of the same configuration, without excessive stress or over-deformation. A prototype TMP with Ti–6Al–4V rotor blades was successfully manufactured, and the pumping speed and compression ratio were systematically measured at rotational speeds ranging from 680 rps (conventional) to 835 rps (1.23 times higher). The measurement results showed that the pumping speed for nitrogen and hydrogen increased by 21% and 42%, respectively, compared to the normal rotational speed through increasing the rotational speed. The measured pumping speed for hydrogen agreed with the result of the direct simulation Monte Carlo method within about 10%. The compression ratio for nitrogen and hydrogen also increased 9.3 times and 6.3 times, respectively. Since TMP is one of the most widely used vacuum pumps in high-vacuum or ultrahigh-vacuum regions, those improvements in TMP performance will contribute to many vacuum applications.