The Heat Is On!

In our quest for the most efficient high performance race car ever, it is evident that the conversion of fuel into electric energy should be done as efficient as possible. Getting tremendous amounts of power out of an engine is not that difficult. Doing this efficient is the big challenge. And this challenge is accepted by the InMotion team!

One wants to waste as little energy that is available from the fuel, as possible. When fuel is combusted inside an engine, the chemical energy inside the fuel is converted to thermal energy, in other words, heat. Most 4-stroke engines these days are very good in converting that chemical energy into heat. But then comes the bigger challenge. After heat is produced, the thermal energy has to be converted into mechanical energy. In piston engines this is done by expanding the pressure  due to heating of the gasses inside the engine, by letting the pressure push a piston down. The force on the piston is transferred to the crankshaft, so in the end rotational mechanical energy is produced by the engine which is equal to the Brake Mean Effective Pressure (BMEP). During this process the biggest efficiency-killer of all internal combustion engines shows up: Heat loss. This is shown in the figure on the right.

Heat from the gasses is transferred to the materials of the engine. These materials have a limit in temperature, because they get weaker when getting hot and this could cause engine failure. Therefore the engine needs to be cooled. This cooling takes away the heat from the engine materials and transfers it to the air. This heat is extracted from the gasses and this lowers the pressure inside the engine. Therefore less energy is available to push the piston down. When the piston reaches its lowest position, the exhaust valves open. The temperature of the gasses is still way above the air temperature, so also here heat gets lost when the exhaust gasses are blown out of the engine.

This is all a lot of theoretical bladibla, but in normal internal combustion engines these heat losses come down to over 50% of the energy in the fuel. In other words, the internal combustion engine is better in being a stove than doing what it is designed to do. The aim for the InMotion team is at least to let the engine of the IM01 be better in what it is designed to do then being a stove.

Being able to let the engine run on a constant load facilitates our goal, but does not get us there entirely. Technologies that are currently under development to be able to covert more thermal energy into mechanical energy are Homogeneous Charge Combustion Ignition (HCCI) and Partially Premixed Combustion (PPC). PPC is a promising combustion principle for the IM01 engine with 56% efficiency test results. Major drawback of this principle is the low power-to-weight ratio. This means that for the same amount of output power, the engine weighs more. Off course this is not desirable in a full bred race car which has to be as lightweight as possible. One engine that is capable of covering this drawback is the Wankel engine.

These engines where banned from some race classes because of the major power-to-weight ratio advantage over piston engines. They were simply too fast for the competition. Together with new production techniques and materials InMotion is going to build the best engine that is up and running outside of a conditioned test facility. There are some major hurdles to take, but that is exactly what this team is good at. 

For more information about InMotion's research, visit http://inmotion.tue.nl