-1- ANALYSIS OF POTENTIAL INCREASES IN ENERGY EFFICIENCY FOR PISTON COMBUSTION MACHINES WITH UNCONVENTIONAL GEOMETRY ICSAT conference Dr.-Ing. Andreas Gotter, gofficient, Kaarst Dr. Boris Schapiro, RKM, Berlin

-2- The RKM engine principle RKM (Rollkolbenmotor) engine has different geometry than other IC engines Principle: Rolling piston instead of oscillating piston Different variants possible: Inner piston Outer piston For more details, have a look at the geometry presentations of RKM engines

-3- Objective Target: Analysis of the potential of the RKM engine How can that be estimated ? a) Simulation of a final designed RKM engine and compare to start of the art IC engine - not possible due to to many uncleared parameters yet - would achieve only weak answer for potential (more for the individual design) b) Identification of boundaries of conventional IC engines, which can be shifted and simulation of benefit of shifting that boundaries - simulation can be done independent from individual design parameters - gives an good overview of thermodynamic potential Method of choice

-4- Thermodynamics Short excurse to basic thermodynamics of Combustion engines Overall process efficiency is limited to basic thermodynamic lawa and depends mainly on - Compression ratio - Isentropic coefficient of process medium Limitations Compression ratio is limited by knock behaviour, if gasoline engine is used Isentropic coefficient depends on exhaust gas and drops with raising temperature Limiting effects in real engine - Non-ideal combustion - Wall heat losses - Friction - Backpressure by exhaust components not perfect valve timing - etc

-5- Boundary conditions Which boundary conditions a) Limit current IC engine efficiency b) Could be moved by other engine concepts such as RKM ? These parameters were identified: ParameterCurrent limitation Investigation of up to… Maximum peak pressure ~120 bar (Otto) 400 bar ~200 bar (Diesel) Compression ratio ~20 (Diesel) 50 Break mean effective pressure~25 bar 100 bar (a.m.a.p) Friction mean effective pressure~0.5 bar 0.1 bar

-6- Simulation software SimEngine The used simulation software is SimEngine - A product of gofficient - Has capability of complex thermodynamic simulation of all kinds of - internal combustion engines - water/steam processes - Is the unique simulation software for integrated simulation of different processes Features - Simulates real gas behaviour and has database for many fluids and gases - Stationary and transient calculation of fluid dynamics - Great component library for internal combustion engines - Lots of special analysis functions - Integration of calibration and control database (currently in development)

-7- Some screenshots of SimEngine Component library drawing area data input Analysis windows Simulation software SimEngine

-8- Results Variation of Injection timing Test : Movement of WOT injection timing to earlier comustion angles Effects : Rising max. pressure, small efficiency improvement with optimum ~6°CA earlier

-9- Results Variation of Compression ratio Test : Raising compression ratio to extreme values Effects : Strong rising max. pressure, efficiency improvement of ~2%-points raising friction optimum (eta e) ~ 28, optimum (eta i) ~ 32

-10- Results Variation of A/F ratio Test : Variation of A/F ratio at WOT conditions at const imep (variaton of charge air pressure for compensation) Effects : slowly rising max. pressure with lean mixture efficiency improvement of > 2%-points

-11- Results Charge Air pressure Test : Raising charge air pressure ratio to extreme values at constant compression ration of 19.5 Effects : Strong rising max. pressure & imep efficiency improvement of up to 2%-points

-12- Results Charge Air pressure Test : Raising charge air pressure ratio to extreme values at constant compression ration of 26 Effects : Strong rising max. pressure & imep efficiency improvement of up to 2%-points

-13- Results Charge Air pressure Test : Raising charge air pressure ratio to extreme values at constant compression ration of 26 and lean A/F ratio of 1.6 Effects : Strong rising max. pressure, further efficiency improvement, but also raising friction pmax: 47.1% indicated and 45.3% effective

-14- Conclusion Friction The assumption for friction have been calculated with similarity to conventional engines If fmep could be reduced, the indicated efficiency is the upper efficiency limit Conclusion -By exceeding the current boundaries of mechanical engines, there could an efficiency increasement potential of 7% (=3%-points) be achieved (if other paramters would stay constant) -Imep and bmep can be increased to values of ~50bar, while engine speed will probably be lower

-15- Outlook Alternative engine designs such as RKM engines may be an alternative for special applications with highest demands Due to high possible pressure ratio and various speed, RKM engines can also be used as compressors or expanders, e.g. for steam processes Simulation is an important tool to discover potentials and application

-16- Thank you for the attention