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WJ5 Turboprop engine

MAI decided in September 1965 that ZEF would develop the WJ5 engines. Its take-off equivalent power was 1,874 kW (2,550 hp) and it would be used in Y-7 transport aeroplanes. This factory had a very good foundation in technology and management, and the staff members and workers had high initiatives. Therefore, they soon finished the detail drawings; completed the design and manufacture of several thousands of toolings and equipments; solved about 50 technical difficulties such as the broach of turbine disc grooves and the welding of the annular combustion chambers; and produced and assembled the complete engines. By the end of 1966, the WJ5 prototype engine went through the 100 hours test. In 1968, because of the shifting of tasks, the WJ5 engine was transferred to HEF for continuous development. HEF made 13 times endurance tests using 8 prototype engines from the latter part of 1968 to 1976. The accumulat test time was 5,678 hours. They also did flight tests and actual operation and solved various technical problems. The design was certified by the State in January 1977.

WJ5A Engine

In 1969, in order to raise the take-off power and satisfy the need of a water-based aircraft the development of the WJ5A started. The main points for design modifications were: t increase the take-off equivalent power from 1,874 kW to 2,315 kW (3,150 hp); to raise the power-weight ratio from the original 4.25 to 5.25; to increase the ambient temperature limit keeping the take-off power from 25C to 30C to improve the take-off performance in hot area. For this the engine needed further 147 kW (200 hp) reserved power. Thus, at 30C temperature, the modification design had to increase the equivalent power by 588 kW (800 hp).

Soon after the task was defined, HEF formed a modification design team, and gained support from SARI and Harbin Military Engineering Institute. Through the evaluation of the proposals, it was decided to use hollow air-cooled turbine blades, for it could increase TET by 150 C , and hence there was an increase of 441 kW (600 hp) in power. When the aircraft took-off at high ambient temperature conditions, by increasing 500 r.p.m. of the engine for a short while, another 147 kW could be gained to meet the requirement.

During the modification design, attention was paid to the combination of inheritance and creation, they bravely adopted new techniques, new processes and new materials to make the critical parts related to the performance increase. For instance, in newly designed turbine parts, the blades and vanes were high temperature alloy castings which had good plastic property; the turbine casing. had integral stainless steel double layer construction and the NGV was in segments as opposed to a welded single layer construction which could not sustain the high temperature. The turbine blade was designed short in airfoil, with 7 straight cooling holes, shrouds, deep root, less separations, and narrow chord, and was assembled in pairs. The adoption of the advanced technology ensured the improvement of the turbine efficiency, reduced the size, improved the heat resistance and stress conditions, maintained the long life structure and reduced the total weight by 14 kg. There were also some other technical improvements, but original parts were used to their maximum extent. Therefore, there were only 126 newly designed parts and components, which was 8% of the total number of the engine parts. The modification design of the WJ5A was to the full extent a combination of practicality, inheritance and advancement.

In April 1970, all modification design drawings were released and the first prototype was made in less than half a year and followed by the ground test. There were then difficulties in running tests and also a lot of troubleshootings. By the end of 1970, when the engine ran to 28 hours, an incident occurred in which the turbine blades were broken to pieces and the engine was on fire, Sha Lingpu, Director of HEF's Design Institute, and other engineers carried out in-depth investigations, inspected hundreds of flakes, analysed the trace of the trouble, and found that the failure was caused by improper thermal centralization of the LP turbine outer shroud. During the operation the shroud shrank in bore diameter and hit the highly rotated turbine blades. They sought advice from domestic and foreign sources and used thermal centralization of free expansion of each stage's outer shroud, thus solving the problem. They finally completed the modification design, and in January 1980, the WJ5A engine was certified and released for small batch production.

The successful development of the WJ5A engine was a contribution to the SH-5 water bomber which would serve China's Navy air force. It also pushed forward the R& D of turboprop engines. In the meantime, it created conditions for the Y-7 aeroplane to serve the airline.

WJ5A I Engine

The Y-7 aeroplane with the original WJ5 engines could not take-off with full load in the hot season and on plateau, due to insufficient power, thus greatly limiting the use of the aeroplane. In 1979, MAI decided that HEF would try to modify the WJ5A and to install it in the Y-7 aeroplane. During the re-engine process, a readjustment of the power distribution proportion between the turbine stages of the WJ5A engine was carried out to limit the take-off equivalent power to 2,132 kW (2,900 hp), and the ambient temperature limit was re-set to 38 C . This modified version was designated as the WJ5A I engine.

The first batch of the modified engines passed the endurance test and then the performance matching flight test was completed. The result showed: the engine had high take-off power and good temperature characteristics and hence the aircraft had a greater climb rate and a faster cruise speed. The second batch of modified engines were stressed on the improving of the structure and the material, aiming at extending the engine operation life. The Y-7 aeroplane with WJ5A I engines experienced flight tests in the hot season and on plateau. It took-off with full load of 21 tons smoothly from Wuhan airport when it was 38.5 t , and from Zhongchuan airport where it was 1,948 m above sea level and Keermu airport where it was 2,840 m above sea level. The modification of the WJ5A I engine took 3 years. The engine was certified for series production in 1982.

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