Search Results

A three-way automotive catalyst's ability to store oxygen is still a crucial performance metric for modern day catalyst applications. With more stringent emissions legalisation, the oxygen storage capacity (OSC) within a catalyst can assist with converting different harmful exhaust gases such as CO, THC and NOx under transient operating conditions. Additionally, OSC is currently the only onboard catalyst performance metric recorded during a vehicle's useful life. Catalyst performance is correlated to this OSC measurement. OSC in three-way automotive catalysts can be split into two main OSC types. "Latent" OSC deep within the washcoat and "dynamic" OSC on the surface of the catalyst washcoat. Dynamic OSC is more commonly applied in the evaluation of useful OSC of the catalyst during practical operation.

A Three-way automotive catalyst's ability to store oxygen is still a crucial performance metric for modern day catalyst applications. With more stringent emissions legalisation, the oxygen storage capacity (OSC) within the catalyst can assist with converting different exhaust gases such as CO, THC and NOx under transient operating conditions. OSC is currently the only onboard catalyst performance metric recorded during a vehicle's useful life. Catalyst performance is correlated to this OSC measurement. Rhodium is a precious metal used in automotive catalysts to help with the conversion of NOx. The price of rhodium is increasing drastically, requiring original equipment manufacturers (OEMs) to look at cost-effective alternatives to maintain NOx conversion within the exhaust stream. OSC in the catalyst is possible due to ceria in the washcoat. Stored oxygen can help promote other reactions in the catalyst bed to help with the conversion of NOx.

The results of this paper will show the reader how to quantify a minimum light-off temperature to meet the required emissions standards with the use of a 3-way catalytic converter. The method can be applied to both motorcycle and larger automotive catalysts to help meet their respective emissions standards (Euro 5/Euro 7). The ability to predict a light-off temperature for any catalyst at the beginning of the project saves both time and resource. With an emphasis on how the shape of the light-off curve affects the cumulative tailpipe emissions and how shape of the light-off curves change with the ageing process. Changes in the light-off curves will be reviewed to understand how the chemical reactions and pore diffusion mechanisms within the catalyst deplete to negatively affect performance over its life time.

This paper outlines a novel method employed to accurately age catalysts to the required OBD limit for European motorcycles legalisation Euro 5 using a combination of modelling and testing. The method applies several strategies, including thermal ageing and catalyst poisoning, to reduce catalyst activity in order to mirror real-world catalyst ageing. Predictions were made using a combined global and micro kinetic model to specify catalyst activity to a matching light-off condition. The model simulated a motorcycle operating on a WMTC (World Motorcycle Test Cycle) and adjusted catalyst activity (Precious metal and Oxygen Storage Capacity) until tailpipe emissions matched the limits for Euro 5 OBD II. The same model ran a simulated light-off test to predict the light-off point for the catalyst. The catalyst was then aged to match this light-off performance using a RAT ageing cycle with additional poisoning to reach the target deactivation.

This paper describes the development and on-vehicle validation testing of next generation parallel hybrid electric powertrain technology for use in urban buses. A forward-facing MATLAB/Simulink powertrain model was used to develop a rule-based deterministic control system for a post-transmission parallel hybrid urban bus. The control strategy targeted areas where conventional powertrains are typically less efficient, focused on improving fuel economy and emissions without boosting vehicle performance. Stored electrical energy is deployed to assist the IC engine system leading to an overall reduction in fuel consumption while maintaining vehicle performance at a level comparable with baseline conventional IC engine operation.

With a transition towards electric vehicles for the transport sector, there will be greater reliance put upon battery packs; therefore, battery pack modelling becomes crucial during the design of the vehicle. Accurate battery pack modelling allows for: the simulation of the pack and vehicle, more informed decisions made during the design process, reduced testing costs, and implementation of superior control systems. To create the battery cell model using MATLAB/Simulink, an electrical equivalent circuit model was selected due to its balance between accuracy and complexity. The model can predict the state of charge and terminal voltage from a current input. A battery string model was then developed that considered the cell-to-cell variability due to manufacturing defects. Finally, a full battery pack model was created, capable of modelling the different currents that each string experiences due to the varied internal resistance.

With emission legislations becoming ever more stringent, there is an increased pressure on after-treatment systems and more specifically three-way catalysts. With recent developments in emission legislations, there is a requirement for more complex after-treatment systems and understanding of the aging process. Whilst the body of understanding on catalyst deactivation and, in particular, catalyst aging is growing, there are still significant gaps in understanding, particularly how real world variations in temperature, flow rate and gas concentrations affect catalyst behavior. Under normal driving conditions, the catalyst can experience varying oxygen concentrations, such as under heavy acceleration or cruising down a hill will show a variation in oxygen from the engine emissions. The effect that varying oxygen concentrations has on the rate of aging is not fully understood and hence the total deactivation and conversion efficiencies are not known throughout the catalyst lifetime.

With emission legislations becoming ever more stringent there is an increased pressure on the after-treatment systems, and more specifically the three-way catalysts. With recent developments in emission legislations, there is requirement for more complex after-treatment systems and understanding of the aging process. With future legislation introducing independent inspection of emissions at any time under real world driving conditions throughout a vehicle life cycle this is going to increase the focus on understanding catalyst behavior during any likely conditions throughout its lifetime and not just at the beginning and end. In recent years it has become a popular approach to use accelerated aging of the automotive catalysts for the development of new catalytic formulations and for homologation of new vehicle emissions.

In this paper a dynamic, modular, 1-D vehicle model architecture is presented which seeks to enhance modelling flexibility and can be rapidly adapted to new vehicle concepts, including hybrid configurations. Interdependencies between model sub-systems are minimized. Each subsystem of the vehicle model follows a standardized signal architecture allowing subsystems to be developed, tested and validated separately from the main model and easily reintegrated. Standard dynamic equations are used to calculate the rotational speed of the desired driveline component within each subsystem i.e. dynamic calculations are carried out with respect to the component of interest. Sample simulations are presented for isolated and integrated components to demonstrate flexibility. Two vehicle test cases are presented.

Accelerated aging of automotive catalysts has become a routine process for the development of new catalytic formulations and for homologation of vehicle emissions. In the standard approach, catalyst samples are subjected to temperatures in excess of 800°C on a predefined test cycle and aged for precise timescales representative of certain vehicle mileage. The high temperature feed gas is traditionally provided by a large gasoline engine but, increasingly, alternative bench-aging techniques are being applied as these offer more precise control and considerable cost savings, as well as offering more development possibilities. In the past few years, emissions control of light duty vehicles has become increasingly prominent as more stringent emissions legislations require more complex after-treatment systems. Aging of the catalysts are not fully understood as they are subjected to many varying environments, including temperature and gas concentrations.

Catalyst aging is presently one of the most important aspects in aftertreatment development, with legislation stating that these systems must be able to meet the relevant emissions legislation up to a specified mileage on the vehicle, typically 150,000 miles. The current industry approach for controlling aging cycles is based solely on the detailed specification of lambda (air-fuel mixture concentration ratio), flow rate and temperature without any limitations on gas mixture. This is purely based upon the experience of engine-based aging and does not take into account any variation due to different engine operation. Although accurate for comparative testing on the same engine/engine type, inconsistencies can be observed across different aging methods, engine types and engine operators largely driven by the capability of the technology used.

The internal combustion (IC) engines exploits only about 30% of the chemical energy ejected through combustion, whereas the remaining part is rejected by means of cooling system and exhausted gas. Nowadays, a major global concern is finding sustainable solutions for better fuel economy which in turn results in a decrease of carbon dioxide (CO2) emissions. The Waste Heat Recovery (WHR) is one of the most promising techniques to increase the overall efficiency of a vehicle system, allowing the recovery of the heat rejected by the exhaust and cooling systems. In this context, Organic Rankine Cycles (ORCs) are widely recognized as a potential technology to exploit the heat rejected by engines to produce electricity. The aim of the present paper is to investigate a WHR system, designed to collect both coolant and exhausted gas heats, coupled with an ORC cycle for vehicle applications.

This study describes an innovative monolith structure designed for applications in automotive catalysis using an advanced manufacturing approach developed at Imperial College London. The production process combines extrusion with phase inversion of a ceramic-polymer-solvent mixture in order to design highly ordered substrate micro-structures that offer improvements in performance, including reduced PGM loading, reduced catalyst ageing and reduced backpressure. This study compares the performance of the novel substrate for CO oxidation against commercially available 400 cpsi and 900 cpsi catalysts using gas concentrations and a flow rate equivalent to those experienced by a full catalyst brick when attached to a vehicle. Due to the novel micro-structure, no washcoat was required for the initial testing and 13 g/ft3 of Pd was deposited directly throughout the substrate structure in the absence of a washcoat.

In any internal combustion engine, the amount of heat rejected from the engine, and associated systems, is a result of the engine inefficiency. Successfully recovering a small proportion of this energy would therefore substantially improve the fuel economy. The Rankine Cycle system has been raising interest for its aptitude to produce systems capable of capturing part of this waste heat and regenerate it as electrical or mechanical power. By integrating these systems into existing hybrid engine environments, it has been proved that Rankine Cycle system, which is more than 150 years old, can play a major role in reducing fuel consumption. The use of such a system for waste heat recovery on a hybrid engine represents a promising compromise in transforming the thermal energy into electricity and feeding this electricity back to the vehicle drivetrain by using the in situ electrical motor system or storing it into batteries.

With emission legislation becoming ever more stringent, automotive companies are forced to invest heavily into solutions to meet the targets set. To date the most effective way of treating emissions is through the use of catalytic converters. Current testing methods of catalytic converters whether being tested on a vehicle or in a lab reactor can be expensive and offer little information about what is occurring within the catalyst. It is for this reason and the increased price of precious metal that kinetic modeling has become a popular alternative to experimental testing. Many kinetic models and kinetic parameters have appeared in literature in recent years, a comparison of these kinetic parameters for the global reaction of CO oxidation is presented.

Computer simulation is now considered to be a crucial stage in the design of automotive catalysts due to the increasing complexity of modern aftertreatment systems. The resulting models almost invariably include surface reaction kinetics that are measured under controlled conditions similar to those found on a vehicle. Repeatability of the measurements used to infer surface reaction rates is fundamental to the accuracy of the resulting catalyst model. To achieve the required level of repeatability, it is necessary to ensure that the catalyst sample in question is stable and that its activity does not change during the test phase. It is therefore essential that the catalyst has been lightly aged, or "de-greened" before testing begins. It is also known that the state of the catalyst's surface prior to testing has an impact on its subsequent light-off performance and that test history can play an important role in catalyst activity.

Understanding the behavior of automotive catalysts formulations under the wide range of conditions characteristic of automotive applications is key to the design of present and future emissions control systems. Platinum-based oxidation catalysts have been in use for some time to treat the exhaust of diesel-powered vehicles and have, as part of an emissions control package, successfully enabled compliance with emissions legislation. However, progressively stringent legislated limits, coupled with the need to reduce vehicle manufacturing costs, is incessantly demanding the development of new and improved catalyst formulations for the removal of pollutants in the diesel exhaust. With the introduction of low sulfur diesel fuel, and the advantageous decline in Palladium prices with respect to Platinum, bimetallic Pt:Pd-based catalysts have found an application in diesel after treatment.

Small off-road engines (SORE) have been recognised as a major source of air pollution. It is estimated that non handheld SORE annually produce over 1 million tonnes of HC+NOx and over 50 million tonnes of CO2. The fuel system design and its operating AFR are of key importance with regard to engine operation and engine out emissions. The conventional low-cost float carburettors used in these engines are relatively ineffective at atomising and preparing the fuel for combustion requiring a rich setting for acceptable functional performance. EPA and CARB have confirmed that Phase 3 limits are achievable for a “durable” engine fitted with a conventional well calibrated and manufactured “stock rich setting” float carburettor together with catalytic oxidation after-treatment and passive secondary air injection.

With annual worldwide production of over 100 million units, small off-road engines (SORE) have been recognised as a major source of air pollution. It is estimated that non handheld SORE products in circulation annually produce over 1 million tonnes of HC+NOx and over 50 million tonnes of CO2. These SORE did not have to meet any emissions control legislation until its introduction in the USA in 1995. Since then the gradual implementation of several stages of increasingly more severe legislation has resulted in a decade of intensive emissions control development for utility engines. New carburetted stratified charge 2-stroke engines and catalytic after-treatment are being developed for the handheld products where weight and multi-orientation operation are key requirements. For the non-handheld 4-stroke dominated market, manufacturers are looking at improved fuel system design, improved engine design and the use of after-treatment to meet current and future legislative requirements.

Since its inception, the internal combustion (IC) engine has undergone continuous improvements with respect to efficiency and performance. Future regulatory and environmental requirements are not only driving still further improvements, but also extending the propulsion system efficiency through hybridization and potentially obsolescing the IC engine with hydrogen fuel cells. This paper describes the potential IC engine improvements to meet tomorrow’s challenges and the associated business and technical challenges in obtaining these challenges. The future propulsion system portfolio mix will encompass gasoline engines, diesel engines, hybrids and fuel cells. The critical role of the IC engine in this portfolio mix is examined.