The industry has made several attempts to design variable compression engines over time. All these attempts have failed mainly because they were based on modifying conventional piston-rod-camshaft systems, making them too complicated, too heavy, too large, and too expensive.
The proprietary VCR engine utilizes a variable piston rod length system to seamlessly change the compression ratio, thereby creating an engine that can run on a wide variety of fuels. This enables the transition from fossil fuels to any e-fuels for the internal combustion engine.
By replacing the traditional crankshaft with a new architectural design called Linear Rod Technology (LRT), we have made it possible to realize technical principles that up till now has not been viable.
The LRT design is the cornerstone to implement a virtual vibration free mechanical solution to geometrically change the compression ratio during engine operation. A key feature to handle multiple fuels and give the ICE a sustainable future
The idea behind the LRT is to simplify the movements in the crankshaft and create only rotating and linear movements to avoid mass forces that create vibrations.
The LRT architecture consists of a 3 yoke system. Two yokes are connected to the combustion chambers and one yoke (the middle) is connected to the auxiliary cylinders. This middle yoke has the same weight as the two yokes connected to combustion cylinders and creates a perfect counterweight.
Since the system contains only pure reciprocating and rotating parts, all inertial forces are in full balance, resulting in an engine that is virtually vibration free leading to higher efficiency, reduced maintenance issues and lifecycle benefits.
With the VCR engine it is possible to run on gasoline on day 1 and switch seamlessly to green methanol on day 2 without any modifications to the engine. This is a key feature of the VCR flex-fuel engine. Variable compression ratio has for decades been a recognized method of improving the efficiency of engines. It is also the key feature to utilize different fuel properties and be a true flex-fuel engine.
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 ratio is changed, otherwise it will remain passive.
With the ability to adjust the compression ratio according to workload, RPM and fuel properties while the engine is running, it is possible to have an engine with optimized fuel efficiency under different working conditions.
In traditional combustion engines, not all fuel is fully burned in the engine cylinder. In the VCR engine, exhaust gas from the primary cylinders provide the energy source for an auxiliary pair of cylinders for up to a 30 % additional energy gain.
After expansion in the combustion cylinders, the associated discharge valve is opened and the exhaust will be transferred to the two upper and lower expansion cylinders whose pistons are in top position. The residual exhaust pressure then forces the two expansion pistons downwards. As they reach the bottom position, the final exhaust valves open and the exhaust from both auxiliary cylinders as well as from the main cylinders is released during the next 180° rotation of the camshaft.
This design also results in an exhaust that is half the temperature of a conventional internal combustion engine. Additionally, the "back side" auxiliary cylinders also function as a compressor system.
Theoretical studies done by the University in Agder (UiA), indicate an improvement in fuel efficiency of 15 %. This principle works both for spark ignited engines and compression ignited engines.
Existing dual-fuel engines suffer from major increases in carbon monoxide (CO) and hydrocarbon (HC) emissions and loss of fuel efficiency at light loads. This is because they operate unthrottled, so that the air-fuel mixture becomes leaner as the load is reduced. As the mixture becomes leaner, combustion eventually degrades, leaving large amounts of partial reaction products in the exhaust. Cylinder Cut Out and increase of the amount of diesel pilot injection are methods that partially counteract the disadvantage.
CCV is a mechanism that controls the closing time (crank angle) of one of two intake valves and thereby the cylinder charge. This feature signifantly improves effiency at light loads and reduces emmissions.
Our prototype VCR-DCE 4×72 has logged more than 100 operational hours since 2020. The video shows the engine, running at 1100 RPM, with a vineglass placed on the testbed to vizualize the very low vibration from the engine.