The WP13 was the powerplant of J-7III and J-8II fighters. It was a twin spool turbojet engine developed on the basis of many years achievements in modification of the WP7 engines. Compared with the WP7, it had a better structure integrity; there was a major improvement on the compressor, which doubled the surge margin; an intermediate bearing was added to LP rotor to reduce the vibration; and titanium alloy was used on the compressor disks and blades, which reduced the engine weight. A metal chip detector was added to the oil system for condition monitoring. An apparent improvement was made in the engine operation stability and reliability. The TBO increased and the maximum dry thrust and reheat thrust were 5.1% and 14.9% more than those of the original WP7 engine respectively.
At this time a major reform occurred in that Guizhou Engine Factory (GEF) and the Chengdu Engine Factory (CEF) formed a joint organization to coordinate the design, production and development of WP13 engines. The leaders of the two factories, Wang Xinmin and Wang Yunhan, were assigned as the Director and Deputy Director, and also Chief and Vice-Chief Engineer respectively. Yao Kepei was appointed Chief Engineer, and Wen Junfeng and Qiu Zizhen were appointed Chief Engineer and Deputy Chief Designer respectively. GEF was given responsibility for compressor casing, combustion and afterburner, and CEF was given responsibility for compressors, turbine rotors and turbine casings. The work-split between the two factories was roughly 50-50, and they exchanged parts and components and carried out final assembly, test and delivery separately. Following this, Vice Minister of MAI, Jiang Xiesheng, pushed forward the joint organization idea. The practice proved that this mode of operating, with two factories sharing the work, promoted cooperation and shortened development lead time. This was the first successful attempt at new management in engine development.
The development of the WP13 started in 1978. By the end of 1980, the first 3 engines were assembled separately in Guizhou and Chengdu and tested, and by 1984, simulated reliability tests, simulated altitude tests, open test bed calibration tests and pre-certification endurance tests had been completed with 10 engine prototypes. During this period, a total of 16 part and component tests, including the HP and LP compressor performance rig tests, thermal-shock tests on turbine blades, and overspeed test for turbine disc were carried out successfully. In 1985, the engine passed the State ground appraisal test and it was turned into the State flight appraisal test.
Based on the successful development of the WP13 engine, GEF and CEF both made further improvements to the engine. The major modifications to the WP13AII were: changing the 2nd to 7th compressor steel cases to titanium casting cases to reduce the weight; using hollow air-cooled blades for the first stage turbine blade to increase the thrust; and certain modifications on combustor and afterburner. After various tests by GEF, the WP13AII proved to be a reliable engine with good compatibility, a high residual thrust margin and stable operation.
Using the castings and forgings of creep resistant titanium alloy for the compressor disc and casing was a main feature of the WP13 engine. At the beginning of 1980, Cao Chunxiao and Gu Mingxin of BAMI and the Guizhou Aero-Forging Factory in cooperation with persons from Shanghai No.5 Steel works and CEF, developed the TC11 creep resistant titanium alloy for the die-forged part of the WP13 compressor disc, which could work for a long time at 500 t . They succeeded in 1982, and created the precedent for aeroengines to adopt the titanium die forged part. It was greatly beneficial-both in economy and in technique. In 1983, it won the first class award of MAI science and technical achievements.
In the meantime, Zhang Tixin and his colleagues of BAMI, supported by GEF, worked for 4 years and successfully applied the ZT3 creep resistant casting titanium alloy containing rare earth metals to the 4th to 7th HP compressor casings of the WP13 engine, which was first invented by Zhou Yanbang of BAMI. This reduced the engine weight by 12.6 kg. Xue Zhiyang and others successfully applied the ZT4 casting titanium alloy to the 2nd and 3rd compressor casings, Which reduced the engine weight by 6.9 kg. The two modifications in turn reduced the weight of J-7 III and J-8 II. It was the first time casting titanium casing instead of casting steel casing had been used in China. A considerable breakthrough in design and manufacture. The ZT3 and ZT4 casting titanium alloy and its WP13 compressor casing gained the MAI first and 2nd award for science and technology achievements respectively in 1984.
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