Hydraulic Launch Assist (HLA) is the name of a

hydraulic hybrid Hydraulic hybrid vehicles (HHVs) use a pressurized fluid power source, along with a conventional internal combustion engine (ICE), to achieve better fuel economy in automobiles, fuel economy and reductions in vehicle emissions control, harmful emis ...

regenerative braking Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction mo ...

system for land vehicles produced by the

Eaton Corporation Eaton Corporation plc is an American-Irish multinational power management company with 2021 sales of $19.63 billion, founded in the United States with global headquarters in Dublin, Ireland, and a secondary administrative center in Beachwood, ...

Background

The HLA system recycles energy by converting

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...

into

potential energy In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potentia ...

during deceleration ''via''

hydraulics Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

, storing the energy at high pressure in an accumulator filled with

nitrogen gas Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh ...

. The energy is then returned to the vehicle during subsequent acceleration thereby reducing the amount of work done by the

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...

. This system provides considerable increase in vehicle productivity while reducing

fuel consumption A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

in stop-and-go use profiles like refuse vehicles and other heavy duty vehicles.

Parallel vs. series hybrids

The HLA system is called a 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 during deceleration and released during acceleration, in contrast to series hydraulic hybrid systems which replace the entire traditional drive-line to provide power transmission in addition to regenerative braking.

Hydraulic vs. electric hybrids

Hydraulic hybrids are said to be power dense, while electric hybrids are energy dense. This means 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 Chemical energy is the energy of chemical substances that is released when they undergo a chemical reaction and transform into other substances. Some examples of storage media of chemical energy include batteries, Schmidt-Rohr, K. (2018). "How ...

in the batteries is converted to

mechanical energy In Outline of physical science, physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, t ...

and '. This is largely governed by

reaction rates The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit ...

in the

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

and current ratings of associated components. Hydraulic hybrids on the other hand are capable of transferring energy at a much higher rate, but are limited by the amount of energy that can be stored. For this reason, hydraulic hybrids lend themselves well to stop-and-go applications and heavy vehicles.

Applications

Concept vehicles

Ford Motor Company Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...

included the HLA system in their 2002 F-350

Tonka Tonka is an American producer of toy trucks. The company is known for making steel toy models of construction type trucks and machinery. Maisto International, which makes diecast vehicles, acquired the rights to use the Tonka name in a line of ...

truck

concept vehicle A concept car (also known as a concept vehicle, show vehicle or prototype) is a car made to showcase new styling and/or new technology. They are often exhibited at motor shows to gauge customer reaction to new and radical designs which may or ...

, reported to have lower emissions and better fuel economy than any V-8 diesel truck engine of the time, with HLA designed to eventually improve fuel economy by 25%-35% in heavy truck city driving.

Shuttle bus

Eaton, Ford, the US Army, and IMPACT Engineering, Inc. (of

Kent, Washington Kent is a city in King County, Washington, United States. It is part of the Seattle–Tacoma–Bellevue metropolitan area and had a population of 136,588 as of the 2020 census, making it the fourth-largest municipality in greater Seattle and t ...

), built an E-450

shuttle bus A shuttle bus is a bus that travels a shorter route in comparison to most bus routes. Typically, shuttle buses travel in both directions between two points. Shuttle buses are designed to transport large groups of people who are all travellin ...

as part of the Army's HAMMER (Hydraulic Hybrid Advanced Materials Multifuel Engine Research) project.

Refuse

Eaton has been awarded the Texas government’s New Technology Research and Development grant to build 12 refuse vehicles with HLA systems.

Peterbilt Motors Peterbilt Motors Company is an American truck manufacturer. Established in 1939 from the acquisition of Fageol Truck and Motor Company, Peterbilt specializes in the production of heavy-duty ( Class 8) and medium-duty (Classes 5–7) commercia ...

has designed a Model 320 chassis that incorporates the HLA system, which was featured on the cover of the December 13, 2007, issue of ''

Machine Design ''Machine Design'' () is an American trade magazine and website serving the OEM engineering market. Its print issues reach qualified design engineers and Engineering management, engineering managers twice a month. Key technologies covered include ...

''.

References

{{reflist Green vehicles Hybrid vehicles Hybrid powertrain Hybrid trucks Hydraulics