bei Google ScholarTitelangaben
Diwisch, Pascal ; Dinkel, Christian ; Rieg, Frank ; Hackenschmidt, Reinhard:
Development and implementation of an innovative gas engine applicable to cogeneration plants.
2016
Veranstaltung: iSEneC Integration of Sustainable Energy Conference 2016
, 11.-12.Juli 2016
, Nürnberg.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Vortrag
)
Abstract
Generating electrical energy usually causes a large amount of thermal energy. Combined heat and power (CHP) enables the application of both forms of energy, which leads to a considerable increase in utilization ratio of the primary energy. Not only fuel cells, gas turbines and Stirling engines but also conventional Otto and Diesel engines can serve as heat engines [1]. Here, the mechanical energy generated by a combustion engine is converted to electrical energy in an generator. Furthermore, the remaining thermal energy can be used for both heating purposes and hot water supply through integrated heat exchangers.
Currently, only those engines are applied that operate according to the four-stroke principle [1]. Two-stroke engines, however, are avoided in combined heat and power stations due to higher exhaust emissions. Still, two-stroke engines have considerable advantages. These particularly include a substantially simpler design, which leads to both savings in construction as well as production and a significantly decreased maintenance expenditures. Since the piston controls the charge exchange, two-stroke engines do not need valves, a camshaft and a camshaft drive. As a result, the rotating masses are significantly smaller than those of four-stroke engines. Moreover, the friction of the crank drive is reduced considerably due to the application of rolling bearings [2]. Owing to these advantages and their compact design, a possible application of two-stroke engines is the usage in cogeneration plants.
Conventional two-stroke engines apply loop scavenging, which leads to an increased proportion of hydrocarbon in the exhaust gas. However, a significant decrease of this amount can be achieved by a split-single two-stroke engine based on a racing engine of DKW developed in the 1930s [3]. This concept served as a basis for the development of a split-single two stroke engine by the Chair for Engineering Design and CAD (Figure 1). According to this design, two pistons share one combustion chamber. Since specific design features enable the closure of the outlet ports before the intake ports, the outlet ports open first during the power circle. This leads to the escape of exhaust gases due to small combustion pressure. Afterwards the intake ports are opened by the inlet piston. While both intake and outlet ports are opened the uniflow scavenging process takes place. By closing the outlet ports before the inlet ports an additional supercharging can be achieved. This simple and solid design further enables the development of a bivalent fuel-driven engine operated by bioethanol or biogas.
Besides its compact design, this concept can be characterized by a high power density, a more even torque curve, an economical production and decreased attrition. In order to obtain an optimized split-single two-stroke engine for combined heat and power stations, extensive theoretical considerations, numerical simulations and an engine test stand are essential. Therefore, experiments on an engine test stand using a prototype of the split-single engine are performed in a first step to validate numerical simulations. These tests provide information about thermal properties as well as exhaust emissions and measure realistic boundary conditions. Eventually, in a second step, both the gas exchange and the power density are optimized through numerical simulations.
[1] Schmitz, K.W., Schaumann, G.: Kraft-Wärme-Kopplung. 3.Auflage, Berlin Heidelberg: Springer Verlag, 2005
[2] Merker, G.P., Teichmann, R.: Grundlagen Verbrennungsmotoren–Funktionsweise, Simulation, Messtechnik. 7.Auflage, Wiesbaden: Springer-Verlag, 2014
[3] Laimböck, F., "Die Ladungswechselgeometrie von Zweirad-Zweitaktmotoren", TU-Graz Institut für Verbrennungskraftmaschinen und Thermodynamik, 1985.