Modelling a novel orbital IC engine to aid further design.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
This project was aimed at developing an orbital internal combustion engine (ICE) technology that is able to combust a wide range of fuels that can be converted into useable energy that currently are not being utilized. The key difference that sets this engine apart from all other internal combustion engine’s is that the combustion chambers themselves rotate with the output shaft around a fixed cam. Similar orbital engine’s were used earlier in the 20th century predominantly in aircrafts. These engine’s faded out of production in the 1950’s due to high maintenance demands due to worn cams and lubrication issues. With the today’s technologic improvements, the shortfalls of the engine can now be mitigated with advances in material science lubricants and manufacturing. These engine’s offer comparatively high outputs and never before have they been modeled to explore their true potential. The concept engine being investigated operates at a very slow speed and has the advantage of being able to alter the piston trajectory by altering the cam geometry. This level of customization is impossible in traditional crank slider configurations. The slower rpm allows the combustion of very low grade fuels that are currently not being utilized commercially as an energy source while producing good output when compared to current internal combustion technologies. Conventional engine simulation software was used to explore the performance potential for this engine configuration. An initial simulation model was verified against an existing prototype and a second model was created to aid in a second generation engine that is currently being developed. These models were used to explore the engine’s capability and optimal configuration. The results of a multitude of simulations were used to create a calculator for industry that uses Microsoft excel to access and interpolate from the data to predict performance for possible variants and to aid in future prototype designs without the need for the software package. The primary focus of the research was to investigate how engine performance was affected by manipulating the piston trajectory, velocity and dwell time near TDC and BDC by adjusting the cam profile. This has proven to have very large implications concerning the engine’s output. It was discovered that by prolonging the time the piston spent at the extremities of its stroke (relative to crank rotation, or in this case, engine rotation) greatly improved combustion and engine performance. Prolonging the time the piston spends near bottom dead centre (BDC) allowed more time for air and fuel to enter the combustion chamber. With the addition of a highly pressurized crankcase, this proved to highly successful in improving performance at higher RPM. Prolonging the time the piston spends near top dead centre (TDC) after ignition lead too much higher pressure being developed during the power stroke, which is advantageous for volumetric efficiency and combusting slower burning fuels. Increasing the dwell time at TDC had the most benefit to performance predominantly at lower RPM. These tuning capabilities make the engine very versatile and highly desirable. The results of tuning the piston trajectories using Ricardo Wave software has lead to a potential 60% increase in peak torque on the engine as well as raising the torque delivery over the entire RPM spectrum. This analysis also provided critical information to aid in the development of the 2nd generation engine in respect to breathing and the forces acting on each of the engine components. This research into the influence of dwell and how it can be manipulated to improve the efficiency of combustion is likely to have influences in other ICE applications and development and help push the envelope for better efficiencies and the use of alternative fuels.