Design of a 1-Meter Tubular Linear Induction Motor (TLIM) for a Pneumatic Capsule Pipeline (PCP) System

Robert M. O’Connell, University of Missouri-Columbia, U.S.A.

Wisuwat Plodpradista, University of Missouri-Columbia, U.S.A.

Pneumatic capsule pipeline (PCP) systems are being used for freight transportation in selected areas. Smaller PCP systems have found increased use in drive-in banks, hospitals, and airports. Larger systems are used in mining and tunneling operations. However, widespread use of large PCP systems is currently limited because systems in place have prohibitively low throughput rates due to the presence of blowers in the booster stations and the associated time-consuming capsule loading/unloading systems. One solution to this drawback is to replace the blowers with non-intrusive tubular linear induction motors (TLIMs.) The TLIM acting as a pump allows the capsules free passage through the pump, thereby increasing the system throughput rates.

In this paper we describe the design and analysis of a 1-meter diameter, 50-meter long TLIM for a 10-kilometer long section of a PCP with a 20% linefill rate. The TLIM consists of a number of approximately 0.5-meter long, identical three-phase, wye-connected TLIM stator units. The capsules, which comprise the rotor of the TLIM, are assumed to be 4 meters long, to weigh 2,000 kilograms (including loads), and to accelerate to a speed of 15.5 m/s in the TLIM and to run at a steady-state speed of 10 m/s in the pipe. The important air-gap of the TLIM, which is the clearance between the outer wall of the capsule and the inner wall of the pipe, is assumed to be 1 cm.

Given the above-stated assumptions for the PCP system, the appropriate fluid mechanics equations were used to determine the steady-state or rated values of capsule speed inside the TLIM and the associated capsule thrust. These values were then used with the appropriate set of TLIM stator design equations to determine the specific design parameters of four slightly different TLIM stator units. Then, the equivalent circuit model was used to analyze the performance of the designed TLIMs.

The paper will present details on the above-described TLIM design and analysis. The results will show that the designed PCP-TLIM system can efficiently transport freight at competitive throughput rates. Thus, PCP-TLIM systems should make it possible to transport freight at much greater throughput rates than is possible with currently used systems.