1. Unlike reciprocating engines, where one piston addresses only one cycle, the rotor in a Wankel engine has three zones operating at different temperatures, resulting in uneven expansion and consequently, poor energy isolation.
2. The combustion chamber does not have a uniform cross-section, but is instead spread out between two surfaces. This results in a slow and incomplete process that increases inefficiencies due to the unburnt charge being expelled from the system.
3. Unlike reciprocating engines, which are sealed by means of circular piston rings, it is difficult to seal rotors, as sealing elements on the vertices are unable to withstand tremendous pressure for extended periods of time.
Applications of a Wankel Engine
1. Motorsports – Multi-rotor Wankel engines have been used in automotive and motorcycle racing with great success in the past. They have been prominently used by manufacturers such as Mazda, Citroen, Rolls Royce, Norton and MZ.
2. Aviation – Due to their high RPM operating capacities and compactness, they are suitable for light aircraft. Wankel engines do not need much time to idle and warm up, so they can consequently reduce waiting times for aircraft during their pre-flight inspection tests.
What the future holds for Wankel engines
While Wankel engines have some inherent benefits over reciprocating engines, its combustion-related inefficiencies make it unfavorable for automotive applications. However, their compact nature makes them conducive for auxiliary power support in electric vehicles, should they run out of charge midway. Apart from combustion-related applications, Wankel engines are also being explored for use in compressors and pumps where sealing-related losses don’t really affect the performance of the devices.