Chinese Engine Development

gelgoog said:

A bit. To be honest hearing about thrust-to-weight ratio in a turbofan of 1:20 seems kind of mythical or nonsensical. Kinda like Intel's roadmap to having 10 GHz processors by 2010. Some kind of pie in the sky goal. That would likely require using denser fuel and an alternate engine cycle. I doubt you can achieve it with a regular turbofan. Maybe something like the SABRE engine would work. You use some sort of cryogenic fuel like liquid methane to chill incoming air to liquefy it and then you burn that. Outside of rocket engines thrust-to-weight ratios like that are unheard of.

I doubt you can get to a thrust-to-weight ratio of 20 with a turbofan. Simply too many parts. I sincerely even doubt something like that is all that useful either. Human pilots would hit G limits if the acceleration was too high.

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Since the first aircraft gas turbines were built in the late 1940s, overall efficiency—fuel flow to propulsive power—has improved from about 10 percent to its current value, approaching 40 percent (see

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). It is likely that the rate of improvement of these engines can continue at about 7 percent per decade for the next several decades given sufficient investment in technology. The potential for overall improvement is best considered in terms of the constituent efficiencies: thermodynamic efficiency of the motor and propulsive efficiency of the propulsor.
As noted above, it is not clear how close to the theoretical limits it may be possible to come with a gas turbine for commercial aircraft given aviation’s important constraints of safety, weight, reliability, and cost. Several authors have considered the question of the practical limits for simple cycle gas turbines given the potential for new materials, engine architectures, and component technologies. Their estimates of the individual limits of thermodynamic and propulsive efficiency differ somewhat (and may divide losses differently between thermodynamic and propulsive efficiency), but they agree that an improvement of 30-35 percent in overall efficiency compared with the best engines today may be achievable. As shown in

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, motor thermodynamic efficiencies of 65-70 percent and propulsive efficiencies of 90-95 percent may be possible.
Gas turbine engines have considerable room for improvement, with overall efficiencies improving by 30 percent or more compared to the best engines in service today. Improvements will come from many relatively small increments rather than a single breakthrough technology.
Some studies suggest that improvements in turbomachinery performance and reduction in cooling losses could improve thermodynamic efficiency by 19 percent and 6 percent, respectively.

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This magnitude of gain is not achieved by simply inserting new technology in existing engines. Rather it requires optimization of the cycle given specific levels of component performance characteristics, temperature capability, and cooling. Practical intercooled or recuperated cycles could increase efficiency by another 4.

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Improved fans and propellers could also increase propulsive efficiency by 10 percent.

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Of course, the practical limits to propulsive efficiency cannot be addressed at the engine level alone without reference to airplane configuration and propulsion integration, as discussed in

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.
To summarize, aircraft gas turbine engines have considerable room for improvement, with a potential to improve overall efficiencies by 30 percent or more over the best engines in service today, with the potential for improvement of propulsive efficiency being about twice that of thermodynamic efficiency. This level of performance will require many technology improvements and come in the form of a number of relatively small increments, a few percent or less, rather than through a single breakthrough technology. The following section discusses many of these technologies.

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latenlazy said:

Maybe the way they do it is by reducing the mass of the parts...

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silentlurker said:

What's a possible material that could do this? 50% less weight would require a revolutionary leap in materials science, which seems unlikely given the maturity of the field

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by78 said:

The ZF850 turbojet from Jiangxi Zhongfa Tianxin Engine Technology Ltd. It will soon be used on the Cloud Shadow UCAV. Two pre-production samples have already been delivered, with four more to be delivered by year end 2020. Serial production will commence in 2021. The company is currently exhibiting the engine at the ongoing Nanchang Aviation Conference/Show.

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Temstar said:

This could be WS-20

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Tirdent said:

Seems plausible - the blades clearly do not take advantage of 3D aerodynamic design to the extent that the CJ-1000A does, which is expected. Similar to the V2500 or CFM56-7B, which is again credible.

As for engine TWR, a great deal can be achieved by simplifying the architecture, that is to say reducing stage count. Compressor and turbine disks are pretty much the heaviest parts, so that helps a lot. A turbofan (as opposed to turbojet) cycle works against this by increasing complexity, generally most features that improve fuel consumption and durability come at a weight penalty.

Once exception is possibly turbine inlet temperature as that requires improved cooling or more exotic materials but also improves specific thrust (thrust per mass flow). Since mass flow relates to area, you get more net thrust without increasing the size of the engine and with clever engineering you might be able to make this benefit outpace the weight gain from better cooling.

20:1 for a turbofan that is supposed to last a few thousand hours is clearly an ambitious goal, but not totally unrealistic. Almost 60 years ago, short-life turbojets intended as lift engines for VTOL aircraft (where minimizing dead weight in cruise was paramount) were practically there already:

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With the immense progress in materials and design since then I would not dismiss the possibility out of hand.

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by78 said:

The ZF850 turbojet from Jiangxi Zhongfa Tianxin Engine Technology Ltd. It will soon be used on the Cloud Shadow UCAV. Two pre-production samples have already been delivered, with four more to be delivered by year end 2020. Serial production will commence in 2021. The company is currently exhibiting the engine at the ongoing Nanchang Aviation Conference/Show.

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