If you read us regularly, you've probably noticed that I don't think electric cars are a good enough solution for current combustion technology. The industry has been moving in the same direction lately, increasingly betting less on expensive electric cars and moving back towards gasoline engines. In addition, you also know that I'm enthusiastic about them. hydrogen internal combustion engines, and not so much the fuel cell ones.
Well, here I will present you a promising new technology for these hydrogen combustion cars that has not yet been deployed, as is Plasma-assisted hydrogen combustion...
Don't confuse them Hydrogen combustion cars with hydrogen fuel cell cars...
What is plasma-assisted hydrogen combustion?
The fight against climate change requires a significant reduction in greenhouse gas emissions. Traditional combustion processes, especially those that rely on fossil fuels, are a major contributor to this problem, but hydrogen combustion can also generate certain polluting gases, and not just water, because there are more gases in the air than oxygen that will combine with hydrogen, and there may also be other residues from lubricants, etc. In this context, Plasma-assisted hydrogen (H₂) combustion emerges as a promising technology for cleaner and more efficient energy generation.
Plasma, the fourth state of matter, plays a crucial role in enhancing H₂ combustion. Unlike gases, where the particles are relatively independent, in a plasma these particles are ionized, i.e. they have lost or gained electrons, thus acquiring a positive or negative electrical charge. In the case of hydrogen combustion engines, a gas with total ionization is not sought, but rather a gas with a percentage of ionized particles.
The introduction of non-equilibrium plasma, which has a low degree of ionization, into the combustion process offers various advantages:
- thermal enhancement: The plasma rapidly heats the gas by cooling the excited states, accelerating chemical reactions and the oxidation of the fuel, i.e. burning.
- Kinetic improvement: High-energy electrons in the plasma collide with neutral species, creating active radicals such as O, H, and OH. These radicals promote the low temperature fuel oxidation.
- Transportation improvement: Plasma alters the behavior of fuel molecules and influences the combustion process. In addition, ionic wind and acoustic waves from the plasma enhance mixing and turbulence.
El combined effect of these points is a significant improvement in ignition, flame spread and overall combustion efficiency.
However, despite its promise, plasma-assisted H₂ combustion faces some challengesOn the one hand, the generation and control of the plasma, since these methods must be efficient and reliable, and this is a practical problem. On the other hand, there is also the durability and cost of these systems, since they must be sufficiently reliable for vehicles and cheap for mass production at an affordable price. When these can be overcome, this will pave the way for implementing this new technology in future hydrogen internal combustion engines.
And by the way, this technology can be applied not only to hydrogen engines, but also to other types of gas engines, and even to jet engines for aviation, where the efficiency and performance of these engines could be improved with the use of these plasma systems.
Research
Since plasma significantly enhances ignition, researchers are exploring its potential for accelerate the transition of a flame (deflagration) to a high-speed detonation wave in other types of engines. This technology has promising applications in the development of detonation engines and rockets.
For example, some researchers study the effects of nanosecond pulsed discharges in pulsed detonation engines (PDEs). They compared ignition delays and flame core growth using this method versus conventional spark gaps. Their findings showed that nanosecond pulsed gaps significantly reduced ignition delay times in PDEs fueled with various fuels and air-fuel mixtures.
Other researchers studied How nanosecond dielectric barrier discharge (ns-DBD) plasma enhances detonation transition (DDT) in a microchannel at atmospheric pressure. They used a spark discharge to initiate a flame wave, followed by variable pulses of ns-DBD plasma before ignition.
High-speed images revealed a much faster flame front when 15 plasma pre-pulses were used compared to no plasma. This faster propagation is attributed to the generation of active species and radicals, together with the slow and rapid heating of the gas by the plasma.
Interestingly, A further increase in the number of pre-pulses led to a slower DDTThe fuel used (dimethyl ether) has a negative temperature coefficient (NTC), meaning that its burning rate decreases at higher temperatures. This suggests a competition between plasma-enhanced ignition and reduced heat release due to extensive fuel oxidation with too many pre-pulses.
On the other hand, another interesting study focuses on the Experiments using nanosecond pulsed discharges to accelerate turbulent hydrogen-air flames under near ambient conditions. They observed a significant reduction in the distance needed for the flame to transition to detonation. Their setup employed a spark plug to initiate the flame, followed by a plasma discharge generated by multiple electrodes. The flame speed increased dramatically as it passed through the plasma region.
The results identified two possible enhancement mechanisms. In some cases, the interaction of the plasma with a leading shock wave ahead of the main flame accelerated its propagation. In other cases, the plasma discharge acted directly on the flame front, leading to localized acceleration.
These studies demonstrate the potential of plasma to manipulate the transition from deflagration to detonation, paving the way for advances in current engines. I just hope you liked it, and don't hesitate to ask…
Images | canva