: Department of Engineering and Applied Sciences - New Building Laboratories - Dalmine (BG)
The Group of Energy Systems and Turbomachinery is involved in research activities covering the whole spectrum of conventional and advanced technologies to generate electrical and thermal energy, ranging from small scale applications to large power stations. EST Group has matured over the years specific expertise in modeling procedure and measurements techniques for evaluating performance of complex energy systems for power generation, with the aim of improving the energy efficiency.
Staff: 2 full professors, 2 associate professors, 2 technicians and a variable number of temporary research fellows and PhD candidates.Tenured staff
The research activities span over the following topics:
1. Conventional and Advanced Power Plants and Energy Efficiency in Industry
Modeling procedures of conventional and advanced / renewable energy systems are carried out to evaluate performance of different plant configurations. The models are able to accurately predict the power plant behavior both for design and off-design conditions, as well as the behavior of single components (boilers, heat exchangers, pumps and turbines, condenser?).
Simulation procedures have been developed combining in-house-made programs (Matlab®, Fortran®, VBA) with commercial codes (Thermoflex®, TRNSYS®). This allows covering a wide range of energy systems based on: gas turbines (GT), steam turbines, cold thermal storages for GT inlet air cooling, wet, dry or even wet and dry condenser, compression or absorption chillers, solar cooling systems, low temperature desalination systems and Concentrated Solar Power (CSP) plants.
Power augmentation systems in a Combined Cycle by means of inlet air cooling and cold water storage (see figures below) have been investigated and optimized by using the above mentioned simulation methodology.
Combined cycle with air cooling system
Air cooling effects on gas turbine inlet temperature and power output
2. Concentrated Solar Power Plants
CSP research activity consists in developing accurate performance prediction tools able to simulate the real behavior of different CSP plant layouts over an entire year, taking into account site weather conditions (irradiation, temperature, humidity). All the possible layout solutions by varying power block (i.e. Steam Rankine Cycle or Integrated Solar Combine Cycle), solar field (Parabolic Troughs or Solar Tower), heat transfer fluid and storage can be simulated. The modeling is based on the interaction between Thermoflex code, for the power block, and TRNSYS code for the solar field, receiver and storage. All the main design options can be taken into account:Power block Technologies
: Steam Turbine, Integrated Solar Combined Cycle, Solar Organic Rankine CycleSolar Field and Receiver
: Parabolic Troughs, Fresnel, Heliostats, Solar TowerHeat transfer fluid
: Thermal Oil, Molten Salt, Direct SteamStorage
CSP plant model (TRNSYS® and ThermoFlex®)
3. Turbomachinery - Gas Turbine Aerodynamic and Thermal Investigations
Activities in the turbomachinery field focus on thermo-fluid dynamic aspects of stator and rotor turbine cascades in gas turbine engines. The group has strong expertise in wind tunnel testing of high and low pressure turbine vanes and blades in linear cascades, both in solid and cooled configurations. Detailed surveys of aerodynamic and thermal measurements are collected thorough experimental campaigns, aiming at evaluating different design solutions and improving cascade performance. For these purposes advanced measuring techniques are applied to investigate highly complex three-dimensional, steady / unsteady, subsonic / transonic flows. At the EST laboratory
three wind tunnels fully equipped with advanced instrumentation are available for vane and blade cascade aerodynamic and thermal investigations.
3.1. Aerodynamic performance of turbine vanes and blades
Secondary flows in vanes and blade cascades are investigated for different operating conditions, such as incidence angle, Mach number and vane/blade profile. The influence of endwall contouring on secondary flow development is assessed, with or without fillet. The flowfield downstream of the airfoil is measured by miniaturized 5 hole probes to quantify profile and secondary losses, as well as vorticity and flow deviation (overturning and underturning). Additional aerodynamic measurements include vane loading and boundary layer profiles. Furthermore, oil and dye visualizations are used to qualitatively detect flow structures.
Secondary flows downstream a blade cascade
Oil flow visualizations in a vane cascade
3.2. Thermal performance of film cooled stator / rotor cascades
Measurements techniques such as Thermocromic Liquid Cristal and Pressure Sensitive Paint are used to get surface distributions of adiabatic film cooling effectiveness for cooled airfoils and endwalls. Cooling schemes include trailing edge cutback film cooling, leading edge film cooling through showerhead holes, array of film cooling holes along the endwall and the airfoil pressure/suction side.
Adiabatic effectiveness distribution on a vane endwall
3.3. Flat plate film cooling
The flat plate model in the low speed wind tunnel allows for a complete characterization of the aero-thermal features of different cooling hole shapes (cylindrical, conical, fan-shaped holes). The experimental data include mean and turbulent flow measurements, flow visualizations, film cooling effectiveness distributions and "off the wall" profiles of temperature and velocity, by varying the coolant flow rate. The basic goal is to study the coolant interaction with the mainstream, at increasing coolant flow rate.
Flat plane film cooling: flow velocity distributions
4. Building energy efficiency
Building envelope and related energy systems are modelled in detail, in order to carry out accurate simulations predicting both thermal load and transient behavior of the energy plant throughout an entire year of operation. Simulations allow assessing the energy use of a building with the aim of quantifying the savings attributable to different design solutions. Effects of site location, building massing and orientation as well as internal gains depending on scheduling of lighting, equipment, and occupants can be included as inputs to properly size heating, cooling, and ventilation systems. The software environment is TRNSYS, mostly used for dynamic building simulation, integrated with Google Sketch-Up.
TRNSYS deck and thermal load results
5. Automotive component tests
Experimental investigations both on aerodynamic and thermal characteristics are carried out in the EST laboratory
aiming to improve the performance in heat dissipation of automotive components. Dedicated facilities are available for testing ventilated brake discs, fans and radiators.
Velocity and temperature distributions in a ventilated brake disk