What is a screw compressor and how does it work? 

A screw compressor is a positive displacement machine that uses a pair of intermeshing rotors to produce compression. The rotors comprise of helical lobes affixed to a front and rear shaft. One rotor is called the male rotor and it will typically have three bulbous lobes. The other rotor is the female rotor and this has valleys machined into it that match the curvature of the male lobes. Typically the female rotor will have five valleys. The rotors never touch, but are timed by a pair of gears operating in a lubricated chamber, which is separated from the rotor chamber.  With the 3-5 rotor combination, the male rotor turns 1.66 times to every one time of the female rotor. 

The number of lobes on the male and female rotor will vary from one compressor manufacturer to another. However, the female rotor will always have numerically more valleys that the male rotor has lobes. Because of the number of male lobes, there are three compression cycles per revolution, which means that the resulting compressed air has small pulsations compared to a reciprocating compressor. By the time that the compressed air leaves the package, it is to all intents and purposes pulsation free. 

Where did the screw compressor come from?  

Heinrich Krigar in Germany on March 24th, 1878, patent #4121, first patented the principle of the screw compressor. He modified and improved his designs later that year and lodged a second patent (number 7116) on August 16^th, 1878. Both of these patents are amongst the earliest on record, as the German Patent Office had only been formed just one year earlier. 

Heinrich Krigar resided in Hannover and his illustrations clearly show a two-lobe rotor assembly, each rotor having the same profile as each other. In fact the rotor configuration resembles the Roots design, exhibited in Europe during 1867, with the exception that the rotors in the Krigar screw compressor twist through an angle of 180 deg along their length. 

At that time it was not possible to develop the idea any further because of the lack of manufacturing technology. 

Half a century later, a Swedish steam turbine manufacturer called Ljungstroms Angturbin AB appointed a new Chief Engineer, his name was Alf Lysholm and he was to be the pivotal in the development of the modern screw compressor. At that time, Lysholm was looking into lightweight compressors for gas and steam turbine use.  

By this time the original patent rights had expired. Lysholm developed the profile of the screw compressor and tested various configurations and rotor lobe combinations. Not only was the shape of the rotors important, he solved the problem and patented the method for accurately machining the rotors. The 1935 patent clearly shows his asymmetric 5 female - 4 male lobe rotor design, although the shapes have been 'fine tuned' over the years, the screw compressor had at last been born. 

Ljungstroms Angturbin AB changed its name to Svenska Rotor Maskiner AB in 1951. This company is well known throughout the world as SRM, and has issued manufacturing licensees to almost every screw compressor manufacturer that exists today. 

When did the screw compressor reach the automotive market? 

Sprintex (1980)

In the early 80’s, Sprintex used some out of patent Lysholm rotor designs to create one of the first twin-screw superchargers. The results were very promising, both parasitic losses and discharge temperatures were far superior to other positive displacement superchargers. Some of its first units were produced in the early 1980’s but manufacturing was still very expensive which hampered its marketability.  

In 1988, Art Whipple of Whipple Superchargers felt the little known “screw-type” supercharger had superior efficiency and was certainly the supercharger for the future. Whipple became the first North American Company to utilize the screw compressor for a production supercharger kit, but again, manufacturing cost hampered its true marketability. Whipple also found that compressor size was a problem. The original units were designed for smaller engines of Europe, the US market needed larger compressors with more airflow capacity. 

Opcon Autorotor (1990)

In 1990, SRM formed a sister company named Opcon Autorotor. This company was formed specifically to develop twin-screw compressors for use on internal combustion engine applications. With the vast knowledge and history of SRM, Autorotor used a later generation D-profile rotor design.  By 1991, Autorotor signed an exclusive agreement with Art Whipple of Whipple Industries, which had already been producing supercharger systems using the Sprintex supercharger. This relationship was a tremendous success and quickly helped put the screw compressor in the automotive market. By 1992, the Autorotor compressor had adopted the name “Whipple Charger” which is still used today.  

In the early 90’s Whipple Superchargers was over-burdened with building “systems” that they decided to only concentrate on General Motor vehicles. Whipple then agreed to supply Kenne Bell the “Whipple Charger” compressors for use on Ford applications. In 1995, Opcon Autorotor went through some difficult times and split from SRM. 

Lysholm Technologies (1995)

When Autorotor decided to part ways from SRM, the general partners of SRM formed a new supercharger company named Lysholm Technologies after the original chief engineer of SRM, Mr. Alf Lysholm. This company was formed to create a true OEM quality twin-screw compressor for internal combustion engines. In 1999, Lysholm Technologies formed a partnership with Eaton Corporation for the OEM rights. This allowed Lysholm Technologies to adapt some of the same mechanical principles that was so successful and proven with the Eaton roots-type superchargers.   

At this time, the screw compressor was being prepared for mass production for future OEM quantity levels. This joint venture increased the reliability and durability as well as validating the screw compressor technology but took years for it to reach the OEM level. It wasn’t until 2004 that Lysholm begin delivering their first true OEM application via Eaton Corporation for the famed Ford GT super car.   

Opcon Group (2004)

In 2004, Lysholm Technologies and the Opcon Group merged, in hope of combining forces and taking the screw compressor to the next level of high volume production.  Although this seemed good on paper, this created issues with delivery to the aftermarket distributors.  The last quarter of 2004 and first two quarters of 2005 showed very little production of twin-screw compressors through Lysholm Technologies.  This put a tremendous strain on the world’s largest aftermarket twin-screw compressor distributor, Whipple Industries. 

Whipple Superchargers (2005 and up)

Due to the lack of delivery and sever back order level, Whipple Superchargers began development of their own line of superchargers.  With their extensive knowledge and years of experience, Whipple developed an entirely new supercharger lineup that featured all of the latest technology in rotor profile, housing, rotor coating and bearing design. The results were astounding, not only did production begin in the USA, Whipple also increased compressor efficiency, lowered overall noise level, increased reliability, engineered the ability to update and repair (some are non-repairable) and increased it’s durability for a wider variety of applications.