Transient Simulations of a T100 micro Gas Turbine Converted into a micro Humid Air Turbine

Micro Gas Turbines (mGTs) have arisen as a promising
technology for Combined Heat and Power (CHP) thanks to their
overall energy efficiencies of 80% (30% electrical + 50% thermal)
and the advantages they offer with respect to internal combustion
engines. The main limitation of mGTs lies in their rather
low electrical efficiency: whenever there is no heat demand, the
exhaust gases are directly blown off and the efficiency of the unit
is reduced to 30%. Operation in such conditions is generally not
economical and can eventually lead to shutdown of the machine.
To address this issue, the mGT cycle can be modified so that in
moments of low heat demand the heat in the exhaust gases is used
to warm up water which is then re-injected in the cycle, thereby
increasing the electrical efficiency. The introduction of a saturation
tower allows for water injection in mGTs: the resulting
cycle is known as a micro Humid Air Turbine (mHAT).
The static performance of the mGT Turbec T100 working
as an mHAT has been characterised through previous numerical
and experimental work at Vrije Universiteit Brussel (VUB).
However, the dynamic behaviour of such a complex system is key
to protect the components during transient operation. Thus, we
have modelled the Turbec T100 mHAT with the TRANSEO tool in order to simulate how the cycle performs when the demanded
power output fluctuates. Steady-state results showed that when
operating with water injection, the electrical efficiency of the
unit is incremented by 3:4% absolute. The transient analysis revealed
that power increase ramps higher than 4:2 kW/s or power
decrease ramps lower than 3:5 kW/s (absolute value) lead to oscillations
which enter the unstable operation region of the compressor.
Since power ramps in the controller of the Turbec T100
mGT are limited to 2 kW/s, it should be safe to vary the power
output of the T100 mHAT when operating with water injection.

Jaar van publicatie:2015