| Abstract |
A high temperature downholemotor has been developed in a project sponsored by NEDO (New Energy and Industrial Technology Development Organization in Japan). We studied about three technical matters to achieve this development, and carried out the performance test with a scaled model of the downholemotor. Under high temperature conditions, many kinds of elastomers were tested, in order to find out a suitable one for the stator. Compression tests for elastic recovery, abrasion tests between the rotor and the stator, and measurement of thermal expansion were carried out for each elastomer. The most suitable materials for the stator have been found now. The downholemotor is a helicoidal type. In their cross sections, the rotor and the stator are designed with trochoidal curves, on which they gear into each other. These trochoidal curves, which are created as the off-set of the cycloid curve, improve endurance performance and provide a sealing function between a rotor and a stator even in a high temperature environment. Both the rotor and the stator, designed with these curves, are manufactured by a numerical controlled machining center, whose positional accuracy is within 0.05 millimeters. So they fit into each other smoothly and so high endurance performances are realized. The scaled models of this high temperature downholemotor were fabricated for the performance test. Its outer diameter is 190.00 millimeters(almost 6-3/4 in) and its length is about 600 millimeters(1.95 ft) down to the full-scaled downholemotor, which is 171.5 millimeters (6-3/4 in) in its outer diameter and 6,000 to 8,000 millimeters (20 to 26.5 ft) in length. This performance test shows that its rotation is from 0 to 60 rpm and its torque is about 250 N-m (185 ft-lbf) maximum under 200 degree Celsius. We confirmed that the downholemotor can operate continuously over 30 hours under any temperature condition. These performances are nearly the same as those of downholemotors on the market restricted to normal temperature use. |