By following an unconventional approach, MTT has developed a new and innovative concept for an efficient very small gas turbine engine configuration. This long term development project is based on a rotating combustion chamber combined with an efficient compressor.
Efficiency and losses
Gas turbine thermal efficiency to a large extent depends on losses resulting from flow leakage, thermal losses and friction. These losses become more dominant when down-scaling a gas turbine in size and power, due to blade tip clearance and volume-surface ratio scale effects. Moreover, when decreasing size (lower Reynolds number) viscous friction losses become larger in conventional turbo machinery. As a result, there is a fundamental limitation to efficiency of micro turbines with a conventional configuration.
The rotating combustor concept is not suffering from above-mentioned scale-effects. The key feature is a monolithic rotor, see figure. Basically, the turbine comprises of a single rotor including a centrifugal compressor, a rotating combustion chamber and reaction turbine. With the rotating combustor, the compressor does not have a diffuser and the turbine does not have stator vanes.
Although several challenges have to be resolved before the rotating combustor concept can be commercialized, the technology offers the following advantages:
- Leakage losses are eliminated,
- Friction losses around diffuser and stator vanes are absent,
- The absence of stator vanes located near fast moving rotor
blades reduces noise level,
- Effects of deviating flow-blade angles at off-design conditions
The baseline configuration is focused on a power output of 1 kW with a 30-40 mm diameter rotor, rotating at speeds up to 250,000 rpm. With the absence of a compressor diffuser, the cycle pressure ratio is relatively low. Consequently also thermal efficiency is limited. However, with the very low cost of the turbine, opportunities exist for applications in combined heat & power generation.
The simplicity of the design makes the MTT rotating combustor concept particularly suitable for mass production at a low cost price. This provides an interesting new alternative in a wide variety of small scale power generation applications for the energy and automotive markets. Power output of the MTT rotating combustor concept ranges from 100 W up to 30 kW.
The technology is covered by 4 international patents.