Details:

Creators:
Barrows, Timothy M.
Corporate Creators:
John A. Volpe National Transportation Systems Center (U.S.)
Corporate Contributors:
United States. Urban Mass Transportation Administration
Subject/TRT Terms:
[+]
Buses Continuously Variable Transmissions Energy Storage Systems Flywheels Regenerative Braking Simulation Transmissions Vehicle Design
Publication/ Report Number:
DOT-TSC-UMTA-81-54;UMTA-MA-06-0119-81-4
DOI:
https://doi.org/10.21949/1526823
Resource Type:
Tech Report
Geographical Coverage:
United States
Corporate Publisher:
United States. Urban Mass Transportation Administration
Abstract:
Numerous studies have been conducted on the concept of flywheel energy storage for buses. Flywheel systems require a continuously variable transmission (CVT) of some type to transmit power between the flywheel and the drive wheels. However, a CVT can provide some fuel economy benefit with or without an energy-storing flywheel, which is the focus of this report. This computer study and literature review is intended to provide insight into the potential applicability of CVTs to buses. It has been suggested that such transmissions may be of interest for two reasons: (1) simple substitution of a CVT in the place of a conventional transmission may offer fuel savings by allowing the engine to operate at its most efficient speed, and (2) the combination of a CVT and a flywheel allows regenerative braking, in which the vehicle kinetic energy during deceleration is captured for later re-use. This computer study and literature survey considers several examples of CVTs in buses, both with and without flywheel energy storage, and finds a predicted energy savings of 10 to 32 percent. The analysis focuses on the use of a CVT alone, without regenerative braking. Computer simulations are made to compute the fuel use of a bus with two different CVTs--one with a ratio range of 6, and the other of an infinite ratio range. For the former, assuming an efficiency of 85 percent, a fuel savings of 12 to 22 percent is predicted, depending upon the driving cycle. It is shown that a substantial part of this saving arises from the simple fact that the accessories operate at a lower speed. For this reason, a separate study of accessory speed control has been conducted, yielding a predicted fuel saving of as high as 17 percent. The report concludes that such accessory speed control may represent an attractive way to reduce fuel consumption. In comparison with the CVT, the concept is more compatible with present bus technology.
Format:
PDF
Collection(s):
Volpe
Main Document Checksum:
[+]
urn:sha256:60cad4cdb6bebcebb5da8524306a2f1f38c0facb93a01bca2cc5977cc80e8083
Download URL:
https://rosap.ntl.bts.gov/view/dot/10671/dot_10671_DS1.pdf
File Type:

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