Rotary Engine May Make Comeback as Range Extender for Electric Vehicles, Hybrids

Wankel Rotary Engine architecture (left)
compared to LiquidPiston Rotary "X" Engine.

Remember the Wankel Rotary Engine that powered the Mazda RX-7?

Today, the original Mazda RX-7 power plant continues to have a devoted cult following of enthusiasts, even though it never achieved wide commercial success. That said, Mazda did continue producing rotary engine cars until 2012, the last one being the RX-8, and plans to release its next rotary engine next year, according to Fox News.

Meanwhile, LiquidPiston Inc., an  advanced internal combustion engine technology company based in Bloomfield, CT, has other plans for a new engineering approach to the rotary engine. The company envisions its Rotary "X" engine as a better alternative for range extension in electric vehicles and hybrids.

To make their case, LiquidPiston exhibited and presented two peer-reviewed technical papers at SAE International’s WCX World Congress Experience in Detroit, April 10-12: one paper titled “Performance of a Low-Blowby Sealing System for a High Efficiency Rotary Engine,” and another titled “Preliminary Development of a 30 kW Heavy Fueled Compression Ignition Rotary ‘X’ Engine with Target 45% Brake Thermal Efficiency.” Both papers were officially published by SAE International ahead of the show.

The rotary ‘X’ engine developed by LiquidPiston offers an efficient, compact, lightweight, quiet, and vibration-free power solution. The ‘X’ engine, essentially the “inverse” of a Wankel type rotary engine, operates on a higher efficiency thermodynamic cycle, fundamentally improving engine efficiency. The R&D efforts presented at WCX illustrate the engine’s unique low-blowby sealing approach, addressing the challenges of prior generation Wankel rotary engines. The second paper presents a development update toward a high efficiency 30kW engine operating with Compression Ignition on Diesel fuel, in a platform that fits in a 10” box, and targets 45% brake thermal efficiency.

“As autonomous vehicles become a reality and demand grows for alternative engine technology to power hybrids and EV’s, we’re witnessing a resurgence of the rotary engine,” said Dr. Alexander Shkolnik, co-founder and CEO of LiquidPiston. “The efficiency and the power-to-weight ratio of next-generation rotary X engines make them the ideal solution to extend the range of EV’s, allowing vehicle manufacturers to use smaller, lighter, cheaper batteries, and allowing drivers the ability to rapidly refuel their vehicle with existing infrastructure.”