Herbert Kopecek

Experimental Study on Laser-Induced Ignition of Swirl-Stabilized Kerosene Flames

Conventional ignition systems of aeroengines are an integral part of the combustion chambers structure. Due -to this hardware-related constraint, the ignition spark has to be generated in the quench zone of the combustion chamber, which is far from the optimum regarding thermo- and aerodynamics. An improved ignitability of the fuel-air mixture can be found in the central zone of the combustor, where higher local equivalence ratios prevail and where mixing is favorable for a smooth ignition. It would be a major advancement in aeroengine design to position the ignition kernel in these zones. A laser system is able to ignite the fuel-air mixture at almost any location inside of the combustion chamber. Commercial laser systems are under development, which can replace conventional spark plugs in internal combustion engines and gas turbines. This study was conducted to evaluate the applicability of laser ignition in liquid-fueled aeroengines. Ignition tests were performed with premixed natural gas and kerosene to evaluate the different approaches of laser and spark plug ignition. The experiments were carried out on a generic test rig with a well-investigated swirler, allowing sufficient operational flexibility for parametric testing. The possibility of the free choice of the lasers focal point is the main advantage of laser-induced ignition. Placing the ignition kernel at the spray cones shear layer or at favorable locations in the recirculation zone could significantly increase the ignitability of the system. Consequently, the laser ignition of atomized kerosene was successfully tested down to a global equivalence ratio of 0.23. Furthermore, the laser outperformed the spark plug at ignition locations below axial distances of 50 mm from the spray nozzle.

Experimental Investigation of an Organic Rankine Cycle Prototype Plant Being Developed to Boost the Electric Output of Gas Engine Power Stations

With nowadays rising fuel prices and increasing regulations on CO2 emissions [1, 2] Organic Rankine Cycle (ORC) plants are potential candidates to utilize the waste heat of large stationary combustion engines and convert it into additional electricity, hence boosting the net electric output power and increase the efficiency of the overall power plant. ORCs have the potential to increase the engine net power output by up to 10% without additional fuel consumption. Here our group presents the experimental results of an ORC prototype plant [3]. The facility was designed to take about 250 kW of heat at about 100°C as an input and turn it into electric power of several kilowatts. A water boiler was used as heat source to simulate the hot engine coolant of a gas engine. Both, steady state system response and plant behavior at the complete operating envelope of cycle pump and turbine have been analyzed. The system response data shows linear behavior around the operating point for the most system outputs. Only pressure ratio over the expander and net electric efficiency demonstrate a nonlinear behavior. The plant operation maps reveal that respecting the typical boundary conditions still at least one degree of freedom is not constrained and can be used for operating conditions optimization.Copyright