The experimental set up is composed by the evaporation system (EV), the combustion chamber (CC), the compression system (CS) and the gas chromatography (GC).
1. Evaporation System (EV)
In the evaporation system, the liquid and the gas are mixed and evaporate in the evaporator controller at around 180°C. To keep the evaporated fuel in gaseous phase, a heated conduit at 250°C connects the EV and the CC.
2. Combustion Chamber (CC)
The combustion chamber incorporates a movable Spalding-Botha type circular burner with a diameter of 8 cm. A conical quartz nozzle with an angle of 45° is facing the burner surface. A small hole with a diameter of 0.2 mm allows sampling to be performed through the flame.
The CC is connected to a primary vacuum pump that keeps constant the low pressure required by the experiments. Behind the quartz nozzle, a secondary pump is used to further decrease the pressure. The difference of pressure through the nozzle allows a controlled sampling of the gases. The sampled gas is kept at high temperature, using again a heated ribbon at 200°C, mainly to avoid the condensation of the residual fuel.
3. Compression System (CS)
As the experiments are performed at low pressure while the GC is working at atmospheric pressure, a piston compression system is used to increase the pressure of the collected gases before its injection in the gas chromatography.
Due to the limited amount of gas in the cylinder, the process is nearly isothermal with a temperature of 72°C. To avoid condensation from the nozzle to the GC, the piping line is heated at 130°C.
4. Gas Chromatography (GC)
To analyze the different stable chemical compounds of interest from fresh to burned gases, the gas chromatography technique has been used. The GC (TOGA seria) had three columns (a CP SIL CB5 for the hydrocarbon and oxygenated compounds and a Molsieve for the permanent gases in series with a RTX-1 for the analysed gas flow rate restriction before passing though the micro-TCD).
Two detectors have been used, a TCD: thermal conductivity detector and a FID: flame ionization detector. This GC is equipped with a methanizer before the FID, which allowed converting carbon monoxide (CO), carbon dioxide (CO2) and formaldehyde (CH2O) into methane (CH4).
The temperature profiles have been measured using a Pt-30%Rh/Pt-6%Rh thermocouple coated with BeO-7% and Y2O3-93% to avoid catalytic reactions with the platinum. The temperature profiles have been corrected for radiation losses by the electrical compensation method. The experimental standard deviation of the three measured temperature profiles is 2.5% (~50 K).
LTC - Low Temperature Combustion
Low temperature combustion is a technology implemented in advanced piston engines to meet the more and more stringent pollution regulations (Euro 6, 7). A the Thermodynamics and Fluid Mechanics research center we approach this promising technology from both the numerical and the experimental side. New models are being developed to get more insight into the chemical kinetics controlling the LTC mode and a test bench has been created and is completely devoted the the study of LTC in piston engines.
In TFL, 3D CFD models using a detailed description of the flow and of the chemistry inside a RCM are being developed and used. The Rapid Compression Machine (RCM) is an experimental device allowing to study auto-ignition phenomena for engine-relevant conditions in terms of pressure and temperature. The objective is to capture the interactions between the chemical and the physical phenomena arising inside RCMs and to globally achieve a better understanding of the auto-ignition of the fuels themselves.
The LTC test bench can be operated with two different HCCI (Homogeneous-Charge Compression-Ignition) engines. HCCI engines are LTC engines. The first engine is a mono-cylinder engine with which three different compression ratios can be used. It is heavily equipped with sensors to perform fundamental research on various fuels such as hydrogen, methane, biogas/syngas, ammonia, etc. The second engine is a four-cylinder engine with a 18:1 compression ratio. It is turbo-compressed, able to perform EGR and is used to bring the HCCI technology to a more industrial level for stationary applications.