Performance analysis and improvement of a Wankel engine operating at the siutable atmosphere for UAV's applications

Rotary piston engines (Wankel engines), which allow very high power generation from a small engine volume, have many advantages such as low vibration, light weight, compact structure, high power/weight ratio, higher volumetric efficiency and less dependence on knocking. Due to these characteristics, they are preferred in many application areas from the maritime industry to the light aircraft industry. The use of these engines is especially advantageous and common in UAVs where propulsion systems with high power/weight and power/size ratios are inevitable. With the further improvements to be made, the usage advantages can be increased even more. Within the scope of the recent domestic production studies carried out in our country, Wankel engine production is desired due to its power density, especially by the defence industry to be used in UAVs. However, no attempt has been made in this issue yet, since there was no production experiment and knowledge in the past. It was decided to carry out this thesis as a step towards meeting this need. In this context, a computer-aided design (CAD) model of the Wankel engine suitable for the UAVs in the TAF inventory, procured from Vestel Defence Industry (LENTATEK), was created by taking measurements with three-dimensional scanning technology. Then, Wankel engine modeling was carried out as zero-dimensional, 1-dimensional and 3-dimensional, respectively. The goal at this stage is to have information about the performance, combustion characteristics and emissions of the Wankel engine at different altitude conditions as a result of 3D computational fluid dynamics (HAD) simulations. The surface/volume ratio of the Wankel engine is much higher than that of the conventional piston engines. Therefore, it is highly likely that the Wankel engine will have misfire problems with increasing altitude. If the performance and combustion characteristics of the Wankel engine at high altitudes are known, measures can be taken to eliminate the misfire problem. Thanks to the analyses made, it is possible to see such potential problems and take precautions accordingly. In addition, since temperature, pressure and density of the ambient air decreases as the altitude increases, the mixture properties in the combustion chamber also change. For this reason, it is useful to examine the effects of excess air coefficient variations on Wankel engine performance. This is another issue addressed in this study. After determining the effects of altitude increase and air-fuel ratio variations on Wankel engine performance, combustion characteristics and emissions, hydrogen enrichment strategy was applied to the fuel, which is one of the most popular methods to increase Wankel engine performance. The simulation results showed that the hydrogen enrichment approach has a very positive effect on the performance of Wankel engines. When a certain amount of hydrogen was added to the gasoline 4-stroke reference Wankel engine, a significant increase was observed in performance characteristics such as average effective pressure, indicated power, and torque compared to the neat gasoline fuelled Wankel engine, while a decrease in the specific fuel consumption value was observed. In addition, there was a decrease in hydrocarbon (HC) and carbon monoxide (CO) emissions due to the hydrogen enrichment method applied. On the other hand, an increase in Nitrous Oxide (NOx) emissions was observed as warmer operating conditions occur in the reference engine in which the hydrogen enrichment strategy was applied according to the working condition with neat gasoline. It is expected that the simulation findings obtained from this thesis study will contribute to the production studies on the Wankel engine in terms of both geometric and fuel content. In addition to this, negotiations were held with companies on the production of prototypes, especially with the hydrogen contribution of the Wankel engine, and steps were taken in the production of prototypes as a follow-up project after the thesis.