Combining a combustion gas turbine with a heat recovery steam generator and steam turbine results in a combined efficiency greater than either of the two (Brayton cycle/Rankine cycle) by themselves. This is only practical for stationary power plants. You would never want to try anything like this in a car.

Yes, it is indeed possible to combine two different types of engines to create a hybrid engine. In fact, hybrid engines have become increasingly popular in various applications, including automobiles and power generation, as they aim to combine the advantages of different engine technologies while minimizing their disadvantages.

In the context of automobiles, hybrid vehicles typically combine an internal combustion engine (ICE) with an electric motor and a battery. The ICE can be either a gasoline or diesel engine, while the electric motor is powered by a rechargeable battery pack. The hybrid system allows for more efficient fuel consumption, reduced emissions, and improved overall performance compared to conventional vehicles with only an ICE.

The hybrid engine operates by utilizing the strengths of each component. The ICE provides power for high-speed driving and recharges the battery when needed, while the electric motor assists during acceleration, low-speed driving, and regenerative braking, where the energy generated during braking is used to recharge the battery. The combination of both systems allows for optimal efficiency and reduced environmental impact.

Similarly, in power generation, hybrid engines can be created by combining different types of power sources. For example, a hybrid power plant may integrate renewable energy sources such as solar or wind with conventional fossil fuel-based generators. This approach allows for a more stable and reliable power supply, taking advantage of the intermittent nature of renewable energy sources while ensuring continuous power generation.

The hybridization of engines aims to mitigate the limitations and drawbacks of individual engine types. By combining different technologies, it is possible to achieve improved fuel efficiency, reduced emissions, increased power output, enhanced performance, and greater overall energy efficiency.

However, it is important to note that designing and implementing a hybrid engine system can be complex. It requires careful integration of different components, control systems, and energy management strategies to ensure optimal performance and reliability. Additionally, factors such as cost, maintenance, and infrastructure for charging or fueling need to be considered.

Overall, the concept of combining two different types of engines to create a hybrid engine has shown great promise in various applications, offering the potential to reduce the demerits of individual engines and achieve more sustainable and efficient energy solutions.

Kristaq makes a good point. In a hybrid car like a Prius you hope to operate the ICE at its peak efficiency to charge the batteries and utilize that energy through the electric motor, which has a flatter efficiency curve.