Hydraulic Launch Assist

Hydraulic Launch Assist ^TM is a trade name for hydraulic hybrid regenerative braking systems introduced by the Eaton Corporation. It also is referred to as the HLA (reg.) system. [Citation
last=Eaton Corporation
title= Hydraulic Launch Assist ^TM (HLA ^TM)
newspaper=Website
date=November 13, 2007
url=http://www.eaton.com/EatonCom/ProductsServices/Hybrid/SystemsOverview/HydraulicHLA/index.htm]

Background

The HLA system recycles energy by converting kinetic energy into potential energy during deceleration via hydraulics, storing the energy at high pressure in a Nitrogen gas filled accumulator. The energy is then returned to the vehicle during subsequent acceleration thereby reducing the amount of work done by the internal combustion engine. This system provides considerable increase in vehicle productivity while reducing fuel consumption in stop-and-go use profiles like refuse vehicles and other heavy duty vehicles. [ Citation
last=Wiebusch
first=
author-link=
title=Hydraulic regenerative braking improves large-truck fuel economy
newspaper=Design News
year=2002
date=June 17, 2002
url=http://www.designnews.com/article/CA220671.html]

Parallel vs. Series Hybrids

The HLA system is a so-called parallel hydraulic hybrid. In parallel systems the original vehicle drive-line remains, allowing the vehicle to operate normally when the HLA system is disengaged. When the HLA is engaged, energy is captured and released during deceleration and acceleration respectively. This is in contrast to so-called series hydraulic hybrid systems which replace the entire mechanical drive-line to provide power transmission in addition to regenerative braking functions.

Hydraulic vs. Electric Hybrids

Hydraulic hybrids are said to be power dense, while electric hybrids are energy dense. This implies that electric hybrids, while able to deliver large amounts of energy over long periods of time are limited by the rate at which the chemical energy in the batteries is converted to mechanical energy and visa-versa. This is largely governed by reaction rates in the battery and amperage ratings of associated components. Hydraulic hybrids on the other hand are capable of transferring energy at a much higher rate, but are then limited by the amount of energy that is stored. For this reason, hydraulic hybrids lend themselves well to stop-and-go applications or applications with high vehicle weights.

Applications

Concept Vehicles

Ford Motor Company included the HLA system in their 2002 F-350 Tonka truck concept vehicle where it was reported to have reduced fuel consumption by 25%-35% in stop-and-go driving. ^[2]

huttle Bus

Eaton, Ford, the US Army, and IMACT Engineering built an E-450 shuttle bus as part of the Army’s HAMMER (Hydraulic Hybrid Advanced Materials Multifuel Engine Research) project. [Citation
last=Siuru
first=
author-link=
title=Off to a quick start: Eaton's Corp.'s Hydraulic launch assist system demonstrated in shuttle bus, delivery van applications
newspaper=Diesel Progress North American Edition
year=2007
date=April 2007
url= http://findarticles.com/p/articles/mi_m0FZX/is_4_73/ai_n19041534]

Refuse

Eaton has been awarded the Texas government’s New Technology Research and Development grant to build 12 refuse vehicles with HLA systems. [Citation
last=Eaton Corporation
title= Eaton’s Greenhouse Gas Emission-Reducing Technologies To Benefit Texas Companies In 2007 Through State Grant For Environmentally Friendly Trucks
newspaper=Press Release
year=2007
date=January 03, 2007
url= http://www.eaton.com/EatonCom/OurCompany/NewsandEvents/NewsList/CT_068498]

Peterbilt Motors has designed a Model 320 chassis that incorporates the HLA system [Citation
last=Peterbilt Motors
title= PETERBILT’S HYBRID STRATEGY UTILIZES ADVANCED TECHNOLOGIES IN DEVELOPING FULL RANGE OF PRODUCT SOLUTIONS
newspaper=Press Release
year=2007
date=March 21, 2007
url= http://www.peterbilt.com/index_new_mor.asp?file=2100] , which was recently featured on the cover of the December 13, 2007 issue of Machine Design. [Citation
last=Bohlman, Davis
title= HYDRAULIC HYBRIDS ARE PICKING UP
newspaper=Machine Design
year=2007
date=December 13, 2007
url= http://machinedesign.texterity.com/machinedesign/20071213/]

References