What the Engines Are and What They Are Powered By

Nowadays, the reciprocating or piston engine with spark-plug ignition has received the maximum distribution and is currently installed on a significant part of passenger cars.

It is light, cheap, quiet, maintainable, and studied longitudinally and transversely. However, humanity is constantly trying to come up with an alternative to this engine, both in terms of the device and the use of another working body — fuel. Sometimes, engineers invent very interesting examples.

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Compressed air

In 2013, PSA introduced the Hybrid Air system, which operates on compressed air. The French were not the first. Two years before, Toyota tested the Ku Rin prototype, which was able to drive on a single ‘charge’ of compressed air for more than 3 km — a record at that time. A year later, Tata Motors’ engineers presented the preproduction Tata Airpod — a three-seat and three-wheeled car for the poorest segments of the population, also running on compressed air.

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Unlike its predecessors, PSA’s development was more elegant and simpler. Two compressed air cylinders, a compressor that pumps air, and a hydraulic motor that transmits compressed air energy to the gearbox. The system itself replenished air supplies, which was qualitatively different from the same Indian miracle (the Tata Airpod needed to be «pumped» every 200 km). Naturally, the classic 3-cylinder ICE that played the role of a pump and auxiliary motor was supposed to be installed in addition to the ‘air installation’ of the Hybrid Air.

The company promised that if the speed did not exceed 70 km/h, the energy from compressed air would be used for 60-80% of the time. Fuel efficiency, which varied from zero consumption and emissions, valued to 2.9 liters per 100 km and 69 g/km when using an ICE, respectively. In 2016, PSA planned to start equipping the current models with the Hybrid Air, but it did not work out.

Hydrogen fuel cell

There are three types of hydrogen engines: the first works as a conventional ICE, the second – as a gas-turbine engine, and the third uses the chemical reaction of hydrogen. The first ICE powered by hydrogen appeared in 1806. The hydrogen in it burned like ordinary gasoline. Today, the number of such original engines tends to zero — it is very expensive to use them. In gas-turbine units, the gas is compressed and heated, and then the energy released is converted into mechanical energy. Almost any fuel that can be dispersed can be used as a fuel: from gases themselves (including hydrogen) to solid bodies.

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But the most interesting of the hydrogen powertrains is the chemical ones. In March 2020, BMW and Toyota introduced the i Hydrogen NEXT SUV based on the current X5. Its powertrain consists of an electric motor, a lithium-ion battery, fuel cell stacks, a converter and a pair of 700 bar tanks with 6 kg of hydrogen. The fuel cell stack converts hydrogen fuel into electricity stored in the battery, which in turn feeds the electric motor. The electrochemical generator produces 125 kW, and the total output of the installation is 275 kW. The only conversion product is water vapor. BMW says it plans to release the first batch of hydrogen fuel cell vehicles by 2022.

Diesel engine

More than a hundred years ago, on February 23, 1892, Rudolf Diesel patented his miracle engine. The main feature of his unit was that the fuel in it was heated by rapid compression not by spark as in the piston engine. But the funny thing is that the first diesel engines did not run on diesel but on vegetable oils. Moreover, the inventor originally proposed coal dust as the ideal fuel, since there were no oil reserves in Germany.

Diesel engine Diesel engine

The range of fuels for diesel engines is generally very wide. This includes all fractions of oil refining from kerosene to residual oil and a number of products of natural origin: rapeseed oil, frying fat, palm oil, and many others. The diesel engine can run with some success even on crude oil.

Rotary engine

The oldest of all heat engines is the rotary one, whose progenitor appeared as early as the 1st century AD. In the 19th century, manufactures actively used rotary steam engines. These units were as efficient as the modern ones.

Rotary engine Rotary engine

In 1957, Felix Wankel and Walter Freude showed the public a fully functional Wankel engine. Just some 7 years of development, and this engine was already on the NSU Spider, which became the first production car with a Wankel engine. This unit is devoid of a large number of moving parts. The special design of the engine allows carrying out any 4-stroke cycle of Diesel, Stirling or Otto without using a special gas distribution mechanism. However, due to the design features, the rotary engine has an extremely low resource, high oil and fuel consumption, although a decent power output.

Due to these ‘features’, Mazda, apart from NSU Motorenwerke, was the only company that mass-produced cars with a Wankel engine. The legendary Mazda RX-8 was more of an image model than a commercial one. As a result, even the stubborn Japanese company gave up working with Wankel engines in the early 2000s.

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