Slide Variable Compression ratio made easy A key feature to Multifuel

Variable compression ratio has for decades been a recognized method of improving the efficiency of engines. It`s also the key feature to utilize different fuel properties and be a true multifuel engine.

VCR, a key feature in a multifuel world

Back in 1920, Sir Henry Ricardo started the first experiments with building a engine where the compression ratio could be changed.  His attempt was motivated of the fact that the quality of fuels where far from consistent, which had the consecuences of pour engine performance.

Todays engines are built on a compromise, or a balance, between performance at full speed and low speed with various loads. The result of this compromise, is that fuel efficiency suffers under normal operational driving conditions, even with the consistent fossile fuel we have today.

When the world is to be transformed into sustainable energy carriers, the engine’s ability to efficiently utilize various fuels will be central. And we are back to  Sir Henry Richardo`s motivation.

Technical headlines

The innovation of LRT has permitted the design of a simple and robust mechanical solution to, geometric,  adjust the compression ratio during operation of the engine. The linear moving piston rods run through coaxial worm gears, which by turning the rods, can elevate the rods up and down on the yoke’s furnished threads, thereby changing the top dead position of the piston.

The compression ratio can be adjusted during operation, depending on the engine’s actual load. Due to the geometric adjustment of the piston, there are few limitations to the upper and lower compressions ratios that are obtainable. The VCR mechanism is moving only when the compression rate is changed, otherwise it will remain passive.

The mechanism that turns the hexagonal piston rod is not a part of the crankshaft movements. It`s fixed in the housing and moves only when the compression ratio is changed. On the first prototype, the compression ratio is adjustable in the interval between 7:1 and 15.4:1, but the engine design is not limited to this range.
On our first prototype, we have manual adjustment of the VCR mechanism just make the construction as simple as possible.

With the ability to adjust the compression ratio according to workload, RPM and fuel properties while the engine is running, it`s possible to have an engine with optimized fuel efficiency under different working conditions. Done in the right way, it`s possible to run on fossil gasoline day 1 and switch to green methanol day 2 without any changes in the configuration. This is the key feature to utilize different fuels and it`s a necessity to be a true multifuel engine