What Is Hydrogen Combustion Engine – Pros & Cons

We are back with yet another theme that is very relevant in our times. With stricter becoming emission regulations day by day, carmakers are looking at various alternative methods to keep a check on the pollution levels. This includes electrification, hybrid powertrains, modern combustion techniques and alternate fuels among other things. Today, we shall discuss what is hydrogen combustion engine, which is nothing but an alternate combustion technique with Hydrogen as the fuel. What are the features of this technique and will it be able to replace the internal combustion engine with petrol and diesel as fuels, let us try to understand in detail.

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Hydrogen Combustion Engine

What is Hydrogen Combustion Engine

Toyota has been one such automobile company that always looks for new techniques to improve the efficiency of internal combustion engines or reduce emissions. This time around, it has been testing a hydrogen-powered combustion engine to analyze the results. Essentially, the combustion engine remains more or less the same, but there are various new mechanical components that are needed to be added to the car in order for this technology to work. As we will discuss later, Hydrogen has various unique properties and it is not easy to handle or manufacture Hydrogen compared to petrol and diesel. Hence, hydrogen-powered vehicles come with their own set of challenges and peculiarities.

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Construction

Using Hydrogen as the fuel to power an automobile results in adding some new components to the car. This includes a massive storage tank for Hydrogen because the energy density of Hydrogen is substantially low compared to petrol or diesel fuels. Hence, to achieve a meaningful performance, large amounts of Hydrogen must be used. Additionally, because high amounts of it are required to be stored, the storage pressure is in the range of 700 bar. Such high pressures in the storage tanks can pose a bit of a health and safety hazard and hence, a lot of care has to be taken while handling the hydrogen as a fuel in a vehicle.

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Working Principle

The overall combustion process remains the same as in regular petrol or diesel-powered engine with normal 4-strokes: Intake, Compression, Power and Exhaust. However, the injection system requires direct fuel injection technology and high-pressure injectors. This is because, in the case of port injection, Hydrogen has the tendency to catch fire even through small cracks and crevices. So, if the intake valve remains open for even a slight duration during the combustion, there is a danger of the fire spreading through the intake manifold which could damage various components. During combustion, the cylinder temperatures are high, as a result of which the NOx emissions are produced from the combustion. These are harmful emissions and needed to be kept in check to ensure that the latest emissions standards are met. With this, we believe, you can now better understand what is hydrogen combustion engine all about.

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Challenges for Hydrogen Combustion Engine

The Hydrogen powered internal combustion engines are not in production yet due to various challenges that they pose. We shall try to look at these problems in detail and also look at the possible solutions for them.

  • Due to added components, the overall weight of the vehicle is increased substantially. Also, the packaging of the large storage tanks for Hydrogen is a nightmare in this day and age where the weight and space utilization of the carmakers tends to be very compact and practical.
  • Having extremely less energy density means that the power and torque output will be much less than the petrol or diesel-powered counterparts even if the hydrogen is huge.
  • Cold start conditions require compression ratios as high as 40:1 which is not easy to achieve. (Typical petrol engine has a compression ratio of 8:1 to 10:1).
  • Knock and Pre-Ignition are huge problems because the Hydrogen fuel burns relatively easily and with high temperatures inside the combustion cylinder, auto-ignition can cause knocking which, over time, could severely damage the engine and components.
  • Also, backfiring is a problem with Hydrogen if the port injection is used which could be dangerous for not only the engine but also for the occupants.
  • Production of hydrogen is not easy and it might actually leave a larger carbon footprint than petrol or diesel, which defeats the entire purpose of using Hydrogen as a fuel in the first place.
  • Higher production costs combined with less energy density and large storage space requirements cause some serious challenges for the mass adoption or even consideration of hydrogen as a fuel.

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Advantages of Hydrogen Combustion Engine

  • With Hydrogen as a fuel, the exhaust gases include just water which is the main motivation behind trying this sort of technique to begin with. Occasionally, there might be some Carbon Dioxide in the exhaust from the engine oil that might somehow end up in the combustion cylinder.
  • The thermal efficiency of such an engine would be around 45% which is substantially higher than that of petrol engines (around 25-30%) and also higher than diesel engines (30-38%).
  • The NOx emissions are almost negligible which is essential to deal with the strict emission norms that will definitely come into place every now and again.
  • Hydrogen Fuel Cell is a better alternative than Hydrogen as a gas due to various factors and could be potentially developed further to offer to the masses at affordable prices.

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These are the features, challenges and benefits of a Hydrogen combustion engine and it is a decent avenue to explore further when such technologies are the only way forward to tackle the growing pollution due to vehicles globally. While these techniques are relatively modern and not been polished enough, these could be used in combination with petrol and diesel fuels to mark the beginning of the change which is inevitable. It is the same thing that we see with hybrid powertrains until the full-electric powertrains become the norm. .

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