A start-up called LiquidPiston has a new take on the rotary engine that shows a lot of promise. LiquidPiston has created a rotary engine that delivers roughly five times the power-by-weight of a normal motor at almost double the fuel efficiency.
LiquidPiston drastically improves on rotary engine
Some might wonder why rotary engines haven’t caught on, since rotary engines deliver comparable power as a traditional engine twice its size and with only one cylinder. Mostly, it’s because they produce more emissions, burn oil like crazy and get worse fuel economy, which is why Mazda discontinued its last rotary-powered model, the RX-8 and you can’t get one at any Houston, Boise, or Valpariso Mazda dealership.
A startup called LiquidPiston, according to AutoGuide, might have cracked the puzzle as to how to clean up emissions and get better fuel economy out of a rotary, though. The company has come up with a prototype which they claim can achieve 50 percent mechanical efficiency, compared to around 30 percent for most motors.
The design is such that an 80-pound LiquidPiston engine makes 40 horsepower. A comparable diesel engine tips the scales 400 pounds.
How the darn thing works
LiquidPiston asserts the production version of the prototype, called the X1, according to Popular Mechanics, will weigh 50 pounds. When it actually gets to market remains to be seen, but field testing is said to begin next year.
The company radically altered the design of the rotary engine. The geometry of the engine chamber was one of the largest alterations, especially the piston seal. In a rotary engine, the piston is a round-ish triangle, with all three points forming a seal in the chamber, called an “apex seal.” The seal creates “pockets,” which draw in air and fuel, compresses, ignites and ejects it through the exhaust, almost like a paddle-wheel. The seals in the X-1 are formed by the crankcase itself.
The engine has an 18:1 air-to-fuel mix, a very high compression. Combined with the piston chamber’s design that keeps a constant volume of air and fuel, it causes the fuel to ignite by itself, not unlike a diesel engine. Auto-ignition leads to more fuel and air being burned, which means more of the power is harnessed and drastically less exhaust, and thus emissions, is produced.
Barely needs cooling
A traditional gas engine regularly churns out high volumes of exhaust air and particles and wastes up to 80 percent of the fuel’s energy potential. The LiquidPiston X1 is capable, in theory, of 75 percent thermal efficiency, or in other words using 75 percent of the energy created by combustion. The company is aiming to get 57 percent thermal efficiency in practice. The typical engine has a thermal efficiency of 20 percent.
It also doesn’t need much cooling; the X1 doesn’t even have a water pump. It can skip an ignition cycle to take in air. So far, according to GigaOm, the company intends on using diesel as the main fuel, since it uses a similar ignition process, but it can accept multiple fuels. Given drastically less exhaust, it runs much quieter as well.
The goal is to use it in applications such as for long-haul trucks, military vehicles, boats and possibly range-extended hybrid vehicles before sticking one in a car.