Development of an Optimized Rotary Screw Air Compressor for the Electrical Vehicle Air Brake Systems/Suspension Systems on Trucks and Buses
Abstract:
Air brake systems and their reciprocating air compressors are incumbent, legislated, and mature technologies integral to commercial trucks and especially the Class 8 Diesel Semi-Truck industry. The introduction of the Class 8 Electric-Semi Truck (electric-semi) will displace diesel driven trucks over time. The air brake systems and the requirement for an air compressor will not be displaced for the foreseeable future and the requirements will be inherited by the new electric-semi industry. The industry shall have to work hard to optimize the air compressor for this new electric platform that demands high energy density, high efficiency, low mass, excellent NVH management, small space claim, high levels of durability and reliability, low and easy maintenance over a life of 20 years. As with all systems on an electric-semi truck the benefits must be delivered with the best-in-class total cost of ownership to ensure fleet customers’ switching costs are low and their investment has a rapid payback.
Reciprocating compressors traditionally used in this market are not optimized for these new requirements. Alternative compressor technologies will be adopted, such as rotary screw, scroll, rotary vane, or possibly other technologies may replace piston compressor technology completely as part of the electrification of semi-trucks. Successful compressors in the electric-semi market can be expected to deliver solutions to the electric bus markets too if they have the capability of being highly reliable at very high duty cycles.
Each of the compressor technologies weak points must be addressed to the extent possible and must be designed specifically for the application by the technology specialists in order to compete in this market.
“The Company” has 35 years’ experience developing, manufacturing, and supporting their rotary screw technology on mobile platforms globally. “The Company” has taken on the challenge of developing an EV screw compressor solution for the electric-semi and bus application.
Based upon potential commercial electric-semi manufacturer demands the author analyzes the inherent advantages and disadvantages of different compressor technologies, their working boundary conditions and creates the basic technology specifications to meet the air deliver rate and discharge pressure requirements. Screw compressor technology has a reputation of high reliability, high energy efficiency and it is suited for extreme climatic conditions. It will be one potential candidate for electric-semi air brake systems. The primary design output requirements are considered to be 354 LPM (liter per minutes) or 12.5 CFM (cube feet per minutes) with discharge pressure range 1.02~1.36 MPa or 150~200 PSI. This broad air and pressure range is possible due to the characteristic of the screw compressor air deliver/RPM curve being flat.
This paper describes the unique approach “THE COMPANY” has taken to optimize rotary screw compressor technology to deliver the performance required by electric-semi’s and electric buses. This development introduces a single stage rotary screw technology into the mini-compressor world for a high air pressure application. The product is currently being prepared for low - medium volume production with high volume production potential in 2022. The performance and unique technology features as they pertain to the electric-semi market are described in this paper. “THE COMPANY” has verified that dramatically decreasing the size of the rotary screw technology addresses the high efficiency, size, mass, space claim, and reliability for this new application.
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