The great challenges of aero-engine development are not deterring China from trying
China's effort to develop its aviation propulsion industry appears to be increasingly ambitious, with two new engine projects coming to light, including a second high-bypass turbofan of around 30,000-lb. thrust, aimed at military use.
While the push is broad, the prospects for success still look distant. Industry officials emphasize that independent engine development remains extremely challenging for the various subsidiaries of Avic that are involved. “It is not any one aspect of technology,” says one. “For us, it is all hard.”
The China Gas Turbine Establishment, part of Avic Engine, says it is working on two engines for business jets. One, in the 7,000-lb.-thrust class, was revealed in 2008, but the first complete unit has not been built. Parts are being made, officials say, adding that there is no specific entry-into-service date. A key issue involves obtaining Western endorsement of the airworthiness certification, and it appears that cooperation with such agencies as thehas not yet begun. The second business jet engine would generate about 2,200 lb. It is still at the research stage, officials from the establishment told a conference here organized by Oppland.
A much larger engine is under development by Avic's 606 Institute at Shenyang as the powerplant for the 200-metric-ton (440,000-lb.) airlifter whose development was acknowledged in late 2009, says another industry official, who is not affiliated with the Gas Turbine Establishment. It was previously assumed that the airlifter would use Russian engines.
The engine is internally stated to be a high-bypass derivative of the WS-10 Taihang combat-aircraft engine, says the official, who has not seen it. The 606 Institute was involved in development of the Taihang. While the project for a military high-bypass engine has not been officially mentioned, it is apparently not a highly secret one, since the official says there is some peripheral Western involvement with it.
The exact thrust of the Taihang is unknown, but since it powers the single-engine J-10 fighter and two-engine J-11B, a copied Flanker, it should be at least in the region of 30,000 lb. with afterburner. A turbofan version should have a similar output, which would roughly correspond to the needs of the four-engine airlifter.
The Shenyang engine was originally proposed for theairliner, which also needed engines of about 30,000 lb. thrust. Instead, a new subsidiary of Avic called Avic Commercial Aircraft Engines (ACAE) is working on its own CJ1000 Changjiang engine of about the same size. The Chinese industry is keen to stress that military outfits such as the 606 Institute have no connection with ACAE, an avowedly civilian company aiming at the international market. However, engineers from 606 Institute with recent experience developing their high-bypass engine in the 30,000-lb. class are naturally helping ACAE with its effort, says an industry official.
There has long been speculation that the Taihang is based on thecommercial engine's core, which came from the GE F101 engine of the B-1. The F101 was developed into the F110 fighter engine. Another industry official confirms that China was at one point working on a fighter engine based on the CFM56 core; that person does not reveal what results came from the effort, however. If the Taihang is indeed derived from the CFM56, then the core's engineering history has repeatedly oscillated between low- and high-bypass applications. Although high- and low-pressure spools in Western engines are now uncompromisingly designed for their intended application, in the early decades of jets it was common for a design to be heavily modified from a configuration that suited a fighter to one for a transport.
The Gas Turbine Establishment revealed few details of its business jet engines. Neither has a low-pressure compressor behind the fan, and both have single-stage high-pressure turbines. For the smaller of the two, the high-pressure compressor currently has four stages and the low-pressure turbine has one. Given the early stage of development, the configuration could easily change. The designers are aiming for thrust-specific fuel consumption of 0.5 kg per kg-thrust per hr., the operating condition is unstated.
The 7,000-lb. engine has a seven-stage high-pressure compressor, a low-pressure turbine with two or three stages and fuel consumption of 0.42 kg per kg per hr. The project has been explored in one way or another at least since the middle of the last decade, and the configuration has changed in that time, dropping the originally planned low-pressure compressor.
One reason for the interest in business jet engines is that the industry expects Chinese private aviation to grow dramatically over the next decade.
In September a different division of Avic Engine unveiled two turboshaft projects, whileis working with the company on a third.
The biggest publicly acknowledged Chinese engine effort is the Changjiang, a demonstrator of which is tentatively scheduled to run in 2015. ACAE wants to fit the demonstrator as nearly as possible with components that are already proven; the follow-on production version would be more refined.
Comac is predicting 2,300 or 2,400 sales of C919s, say people working on the program. A Western industry executive says ACAE accepts that estimate and is confident it can gain 30% of the market. Foreign suppliers are typically halving ACAE's number as they assess their business cases.
ACAE expects its development budget will mainly come from government handouts, such as research grants, says another person with the program. ACAE is benefiting from a solid understanding among the government's technology development bureaucrats of the challenges that the company is facing. While the upper reaches of the Chinese government, like the general public, probably see ACAE as making just part of an aircraft, which cannot be as hard as making the whole thing, the science and technology officers understand that the aero-engine business is more difficult to penetrate than that of airframes.
So far, ACAE remains small. It had only 15 people when it was established in 2009. That team, expanding gradually, worked out the requirement for the engine and presented it to the engineering team when it arrived in early 2010. The engineers will have a preliminary design ready by the end of the year. A national committee of experts from outside of ACAE will decide whether the engine can proceed in that form. There are now about 100 people in the company.
ACAE has built and displayed a solid titanium fan for the engine as an engineering sample; the final design is expected to be almost the same, but hollow. One highly experienced foreign engine designer commended the configuration of the fan, pointing to its having only 18 blades.
Like some other Avic subsidiaries, ACAE will not be fully, or even mostly, owned by Avic. Chinese cities, including Tianjin and Xi'an, competed to host and invest in the company, seeing it as a potential boost for their economies. Shanghai won. As a result, two municipal corporations, one of them power-generation group Shanghai Electric, have each been allocated 15% of ACAE's equity. Avic has 40% but the remaining 30% is available for another investor. The city's contribution was not just financial; Shanghai Electric has useful technology from its ground-based gas turbine business.