Variable Valve Actuation: Design and Performance Impact on Advanced Powertrains

Engine valvetrain systems have become more capable and increasingly more compact in the quest to improve efficiency. The developments parallel the advancements in other key engine components such as fuel injection or spark systems, turbocharging, aftertreatment, base engine and controls. While the gasoline sector has seen a steady rise in the adoption of Variable Valve Actuation (VVA), Diesel systems have lagged behind and only a few systems have seen production. The level of VVA activity however in the Diesel sector is beginning to increase as tighter regulations of CO2 emissions approach. Valve control plays a strong role in a number of key areas: turbocharger systems, allowing for better optimization matching across wide engine operating flows; enabling advanced combustion strategies where control over the charge mass and temperature are important; and cold start, where valve timing can be extremely effective for engine warm up compared with other strategies that rely on additional fueling.

This seminar will cover the range of Variable Valve Actuation technologies present in the market, their operation principles, and their effect on engine performance. Both gasoline and Diesel applications will be covered including how they impact the in-cylinder combustion as well as the aftertreatment. Participants will have the opportunity to perform hands-on exercises to examine the effects of the engine valve profiles on performance and are asked to bring a laptop computer, with Excel, to the seminar for class exercises.

What Will You Learn

By attending this seminar, you will be able to:
  • Describe and differentiate the variable valve actuation technologies present in the automotive industry
  • Describe the defining features of each of these technologies, their requirements for engine design layouts, required actuators, lube oil, and need for control and ECU interface
  • Apply basic tools to gage the thermodynamic impact effected by varying the valve profiles: impact on pumping efficiency, resulting charge mass trapped in cylinder, estimated bulk and adiabatic flame temperatures
  • Articulate the contribution of valve timing and control over the engine performance and aftertreatment in modern engines in the context of today's emissions standards
  • Describe the limitations of current technologies towards more efficient and cleaner engines and the future role of valve actuation and its integration aspects with other advanced powertrain components

Is This Course For You

This seminar is designed for engineers, managers, and other technical personnel from OEMs and support industries concerned with the design and development of optimized diesel and spark ignition engine systems, including calibration, performance, fuel economy and emissions for passenger car, light truck and heavy duty engines. It will be particularly interesting to Diesel engineers who will likely adopt some of the technologies developed in the gasoline sector for further improvements in emissions control and gains in fuel economy. It will be also of interest to combustion researchers as VVA will play a strong enabling role to exploring advanced combustion strategies.

Materials Provided

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Course Requirements

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  • Motivation and Objectives
    • Near and long term landscape
    • Fuel Economy, performance and emission standards
    • Key engine technologies
    • Overview of VVA landscape
  • VVA Timeline
    • Efficiency improvements and synergies with other technologies
    • Industry trends and benchmarking
  • Basic Engine Definitions
    • Work, fuel consumption, efficiency, exhaust gas recirculation (EGR)
    • Class exercise: engine performance calculator sheet
    • Thermodynamics and chemistry
    • Class exercise: EGR and valve timing effects on combustion
  • Variable Valve Actuation Designs
    • Valvetrain overview: lift, timing, valve overlap
    • Cam phasing, cam switching, continuous variable lift
    • Lost motion systems including cylinder cut-off
    • Camless systems, electro-hydraulic, fully electro-magnetic
    • Case study: continuously variable valve system design
  • VVA Case Studies and Impact on Gasoline Engine Performance
    • Continuously variable valve system on gasoline engine
    • Atkinson cycle with a hybrid plugin powertrain
    • Miller Cycle
  • VVA Case Studies and Impact on Diesel Engine Performance
    • Loss motion system to enable LTC on a MD Diesel engine
    • Electro-hydraulic system on HD Diesel engine
  • Engine Brake Systems
    • System description and competitive advantages
    • Class exercise: hydraulic layout of brake system
  • Transient Performance
    • Response
    • Engine warm-up strategies
    • Gas exchange interactions (turbochargers)
  • Modeling and Controls
    • Physical modeling of air system
    • Integration of multiple actuator systems
    • Enhancing combustion stability
  • Future Trends
    • Enabling roles of VVA in advanced combustion engines
    • Stretched efficiency concepts