HYDRAULIC HYBRID SYSTEM

 

Introduction To Hydraulic Hybrid Vehicles:

Hybrid vehicles use two sources of power to drive the wheels. In a hydraulic hybrid vehicle (HHV) a regular internal combustion engine and a hydraulic motor are used to power the wheels.

Hydraulic hybrid systems consist of two key components:

• High pressure hydraulic fluid vessels called accumulators, and
• Hydraulic drive pump/motors.

Working of Hydraulic Hybrid Systems:

The accumulators are used to store pressurized fluid. Acting as a motor, the hydraulic drive uses the pressurized fluid (Above 3000 psi) to rotate the wheels. Acting as a pump, the hydraulic drive is used to re-pressurize hydraulic fluid by using the vehicle’s momentum, thereby converting kinetic energy into potential energy. This process of converting kinetic energy from momentum and storing it is called regenerative braking.

The hydraulic system offers great advantages for vehicles operating in stop and go conditions because the system can capture large amounts of energy when the brakes are applied.

The hydraulic components work in conjunction with the primary. Making up the main hydraulic components are two hydraulic accumulator vessels which store hydraulic fluid compressing inert nitrogen gas and one or more hydraulic pump/motor units.

The hydraulic hybrid system is made up of four components.

• The working fluid
• The reservoir
• The pump or motor
• The accumulator

The pump or motor installed in the system extracts kinetic energy during braking. This in turn pumps the working fluid from the reservoir to the accumulator, which eventually gets pressurized. The pressurized working fluid then provides energy to the pump or motor to power the vehicle when it accelerates. There are two types of hydraulic hybrid systems – the parallel hydraulic hybrid system and the series hydraulic hybrid system. In the parallel hydraulic hybrid, the pump is connected to the drive-shafts through a transmission box, while in series hydraulic hybrid, the pump is directly connected to the drive-shaft.

There are two types of HHVs:

• Parallel and
• Series.

Parallel Hydraulic Hybrid Vehicles:

In parallel HHVs both the engine and the hydraulic drive system are mechanically coupled to the wheels. The hydraulic pump-motor is then integrated into the driveshaft or differential.

Series Hydraulic Hybrid vehicles:

Series HHVs rely entirely on hydraulic pressure to drive the wheels, which means the engine does not directly provide mechanical power to the wheels. In a series HHV configuration, an engine is attached to a hydraulic engine pump to provide additional fluid pressure to the drive pump/motor when needed.

Advantages:

• Higher fuel efficiency.  (25-45 percent improvement in fuel economy)
• Lower emissions.  (20 to 30 percent)
• Reduced operating costs.
• Better acceleration performance.

SKYACTIV TECHNOLOGY

Highlights of the SKYACTIV technologies:

• SKYACTIV-G: a next-generation highly-efficient direct-injection gasoline engine with the world’s highest compression ratio of 14.0:1
• SKYACTIV-D: a next-generation clean diesel engine with the world’s lowest compression ratio of 14.0:1
• SKYACTIV-Drive: a next-generation highly-efficient automatic transmission
• A next-generation manual transmission with a light shift feel, compact size and significantly reduced weight
• A next-generation lightweight, highly-rigid body with outstanding crash safety performance
• A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride

– First product to be equipped with SKYACTIV technology will be a Mazda Demio featuring an improved, fuel-efficient, next-generation direct-injection engine that achieves fuel economy of 30 km/L.

Overview of the SKYACTIV technologies

1. SKYACTIV-G

A next-generation highly-efficient direct-injection gasoline engine that achieves the world’s highest gasoline engine compression ratio of 14.0:1 with no abnormal combustion (knocking)

• The world’s first gasoline engine for mass production vehicles to achieve a high compression ratio of 14.0:1
• Significantly improved engine efficiency thanks to the high compression combustion, resulting in 15 percent increases in fuel efficiency and torque
• Improved everyday driving thanks to increased torque at low- to mid-engine speeds
• A 4-2-1 exhaust system, cavity pistons, multi hole injectors and other innovations enable the high compression ratio

2. SKYACTIV-D

A next-generation clean diesel engine that will meet global emissions regulations without expensive NOx after treatments — urea selective catalytic reduction (SCR) or a Lean NOx Trap (LNT) — thanks to the world’s lowest diesel engine compression ratio of 14.0:1

• 20 percent better fuel efficiency thanks to the low compression ratio of 14.0:1
• A new two-stage turbocharger realizes smooth and linear response from low to high engine speeds, and greatly increases low- and high-end torque (up to the 5,200 rpm rev limit)
• Complies with global emissions regulations (Euro6 in Europe, Tier2Bin5 in North America, and the Post New Long-Term Regulations in Japan), without expensive NOx after treatment

3. SKYACTIV-Drive

A next-generation highly efficient automatic transmission that achieves excellent torque transfer efficiency through a wider lock-up range and features the best attributes of all transmission types

• Combines all the advantages of conventional automatic transmissions, continuously variable transmissions, and dual clutch transmissions
• A dramatically widened lock-up range improves torque transfer efficiency and realizes a direct driving feel that is equivalent to a manual transmission
• A 4-to-7 percent improvement in fuel economy compared to the current transmission

4. SKYACTIV-MT

A light and compact next-generation manual transmission with crisp and light shift feel like that of a sports car, optimized for a front-engine front-wheel-drive layout

• Short stroke and light shift feel
• Significantly reduced size and weight due to a revised structure
• More efficient vehicle packaging thanks to its compact size
• Improved fuel economy due to reduced internal friction

5. SKYACTIV-Body

A next-generation lightweight, highly-rigid body with outstanding crash safety performance and high rigidity for greater driving pleasure

• High rigidity and lightness (8 percent lighter, 30 percent more rigid)
• Outstanding crash safety performance and lightness
• A “straight structure” in which each part of the frame is configured to be as straight as possible. Additionally, a “continuous framework” approach was adopted in which each section functions in a coordinated manner with the other connecting sections
• Reduced weight through optimized bonding methods and expanded use of high-tensile steel

6. SKYACTIV-Chassis

A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride feel to realize driving pleasure

• Newly developed front strut and rear multilink suspension ensures high rigidity and lightness (The entire chassis is 14 percent lighter than the previous version.)
• Mid-speed agility and high-speed stability — enhanced ride quality at all speeds achieved through a revision of the functional allocation of all the suspension and steering components

Artificial photosynthesis

Artificial photosynthesis is one of the newer ways researchers are exploring to capture the energy of sunlight reaching earth.

Photosynthesis:

Photosynthesis is the conversion of sunlight, carbon dioxide, and water into usable fuel and it is typically discussed in relation to plants where the fuel is carbohydrates, proteins, and fats. Using only 3 percent of the sunlight that reaches the planet, plants collectively perform massive energy conversions, converting just over 1,100 billion tons of CO2 into food sources for animals every year.

Photovoltaic Technology:

This harnessing of the sun represents a virtually untapped potential for generating energy for human use at a time when efforts to commercialize photovoltaic–cell technology are underway. Using a semiconductor–based system, photovoltaic technology converts sunlight to electricity, but in an expensive and somewhat inefficient manner with notable shortcomings related to energy storage and the dynamics of weather and available sunlight.

Artificial Photosynthesis:

Two things occur as plants convert sunlight into energy:

• Sunlight is harvested using chlorophyll and a collection of proteins and enzymes, and
• Water molecules are split into hydrogen, electrons, and oxygen.

These electrons and oxygen then turn the CO2 into carbohydrates, after which oxygen is expelled.

Rather than release only oxygen at the end of this reaction, an artificial process designed to produce energy for human use will need to release liquid hydrogen or methanol, which will in turn be used as liquid fuel or channeled into a fuel cell. The processes of producing hydrogen and capturing sunlight are not a problem. The challenge lies in developing a catalyst to split the water molecules and get the electrons that start the chemical process  to produce the hydrogen.

There are a number of promising catalysts available, that, once perfected, could have a profound impact on how we address the energy supply challenge:

• Manganese directly mimics the biology found in plants.
• Titanium Dioxide is used in dye-sensitized cell.
• Cobalt Oxide is very abundant, stable and efficient as a catalyst

Artificial Photosynthesis Operation:

Under the fuel through artificial photosynthesis scenario, nano tubes embedded within a membrane would act like green leaves, using incident solar radiation (H³) to split water molecules (H2O), freeing up electrons and oxygen (O2) that then react with carbon dioxide (CO2) to produce a fuel, shown here as methanol (CH3OH). The result is a renewable green energy source that also helps scrub the atmosphere of excessive carbon dioxide from the burning of fossil fuels.

History:

Plants use organic compounds that need to be continuously renewed. Researchers are looking for inorganic compounds that catalyze the needed reactions and are both efficient and widely available.

The research has been significantly boosted by the application of nano technology. It’s a good example of the step wise progress in the scientific world.

Studies earlier in the decade showed that crystals iridium efficiently drove the reduction of CO2, but iridium is extremely rare so technology that required its use would be expensive and could never be used on a large scale.

Cobalt crystals were tried. They worked, and cobalt is widely available, but the original formulations weren’t at all efficient.

Things changed with the introduction of nano technology.

The main point is that this unique approach increasing appears to be feasible. It has the advantage of harnessing solar energy in a form that can be stored and used with greater efficiency than batteries and it is at least carbon neutral.