UHF Turbine Wheel
Next-Generation Turbine Aero
Xona Rotor’s second-generation turbine wheel has arrived. Known as UHF (Ultra High Flow), its mission was to maximize flow capacity and raise efficiency.
UHF is Xona Rotor’s most advanced wheel yet. Among other details, UHF’s patent pending splitter-blade design allowed the blade loading to be fine-tuned in order to achieve its performance objectives.
Turbine design is a multi-variable juggling act. One feature that heavily influences a turbine’s mass flow “swallowing capacity” is the throat region located near the exit of the wheel. An effective method to increase the throat area is to decrease the number of blades. While reducing blade count tends to increase the turbine’s flow capacity, efficiency typically suffers.
Introducing splitter blades provides an elegant solution to the trade-off between flow and efficiency. The splitter blades alleviate the blockage in the throat area while preserving the fluid momentum at the wheel inlet.
The result is that UHF has the swallowing capacity of a low blade-count turbine with the efficiency of a high blade-count configuration. Its improvements were observed analytically, validated experimentally on a gas stand and then confirmed in on-vehicle testing.
Why Flow Capacity Matters
So why all this effort to maximize the turbine’s flow capacity? For a given engine operating point – say, full boost near redline – a higher-flowing turbine operates at reduced expansion ratio than a lower-flowing turbine. The lower expansion ratio translates directly to reduced exhaust manifold pressure (“EMAP”).
Lower EMAP means more engine power – the engine’s pumping work is reduced and volumetric efficiency improves. If the engine’s valve events (i.e., overlap) and ignition timing are modified to take advantage of the reduction in EMAP, further gains can be reaped. In the bargain, with reduced EMAP, the engine becomes less knock-sensitive and less prone to overheating.