The very same exact feeling from me.
I believe This is FWS-15( or to be precise, the 18 tons thrust of FWS-15), not the alleged FWS-10B.
I agree with you on this account, that the real FWS-15, of 18 tons thrust, with the configurations of 2-5-1-1 is not used to the first batch of J-20. But I don't think we need to wait that long to see it as per your prediction. Next year is the latest is my judgement based on all relevant information made publicly.
Sorry Asok, I have to differ with you on this one.
Based on what i read, I believe initially the J-20 is powered by this so-alleged FWS-10B, of 15.5 tons trust. Some people called it "FWS-15 interim version", some called it "status A". According to those in the know, this FWS-10B is the original design of FWS-15 with 3-6-1-1 configurations to power the J-20 and J-10C. The FWS-15 of 18 tons thrust we know of now is the result of adopting the new breakthrough in "the magnitude blade technology of the aviation engine compressor" -"大小叶片压气机" to the original 3-6-1-1 core design, reducing one stage of low-pressure and one stage of high-pressure compressor to become 2-5-1-1.The 24 tons version people started talking about recently maybe the ultimate goal for FWS-15 when the numbers of LP and HP compressor stages are further reduced, or maybe even reduced to single stage.
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This is the news in 2013 about how this technology was first used on Chinese WZ-6 engine:
陈懋章院士长期从事叶轮机气动力学和粘性流体动力学研究的教学与研究工作,在航空发动机领域卓有建树。在他指导并参加的某型发动机跨音压气机改型设计中,敢于闯入科学研究的“禁区”,提出了一种新型压气机处理机匣,保证了发动机在整个飞行包线内稳定可靠工作,排除了空中熄火故障。它为解决高负荷高通流压气机获得高效率、高喘振裕度的难题,提供了实用而有效的方法,对促进我国发动机设计研制具有重要意义和实用价值。该项研究成果1999年获国家技术发明二等奖。作为项目负责人之一,他主持完成的“低速大尺寸压气机实验装置及转子流场动态测量技术”,是研制航空核心压气机和研究其流场精细结构的重要设备,技术含量很高,对提高我国压气机设计水平有重要作用。该项成果1993年获国家科技进步一等奖。另外,陈懋章院士在叶轮机三维流理论与应用以及粘流理论研究也取得多项成果,特别是在压气机大小叶片先进气动布局、边界层转捩过程中三维不稳定波发展的理论描述和旋转物体的边界层 流动研究等方面处于国内领先水平。2000年获何良何利基金科学与技术进步奖。
直8直升机是我国目前现役最大吨位的国产直升机,在我国陆海空三军和民用领域有着广泛的应用。常州兰翔机械总厂作为直8直升机国产涡轴6发动机的承制单位、国内大功率直升机发动机主要制造企业,在我国航空发动机和直升机产业发展史上占有一席之地。
WZ6增大功率改型,将在大小叶片技术验证机的基础上,全面改进压气机,燃烧室以及涡轮,将WZ6的功率提高到2000马力以上,同时将发动机的首翻期提高到1500小时以上。
Mind you I heard there is also another FWS-15 for J-31.All these engines can be referred as FWS-15, this is so Chinese that only a Chinese can understand why.
One of the reason I can think of is that because the benefit of reduced weight,size and component parts resulting from the reduced stage of compressor can only be maximized by other changes also need to be made on combustion, HP turbine, LP turbine and FADEC, thus very time consuming, therefore J-20 can't wait but use FWS-10B.
Hope i am right and hope it can solve your puzzle.