Review of Vehicle Engine Efficiency and Emissions

Abstract

<div class="section abstract"><div class="htmlview paragraph">This review covers advances in regulations and technologies in the past year in the field of vehicular emissions. We cover major developments towards reducing criteria pollutants and greenhouse gas emissions from both light- and heavy-duty vehicles and off-road machinery. To suggest that the transportation is transforming rapidly is an understatement, and many changes have happened already since our review last year [<span class="xref">1</span>]. Notably, the US and Europe revised the CO<sub>2</sub> standards for light-duty vehicles and electrification mandates were introduced in various regions of the world. These have accelerated plans to introduce electrified powertrains, which include hybrids and pure electric vehicles. However, a full transformation to electric vehicles and the required grid decarbonization will take time, and policy makers are accordingly also tightening criteria pollutant standards for internal combustion engines. California has published the Advanced Clean Cars II standards and Europe has held various workshops outlining the core elements of future Euro 7 regulations. These will likely be the last major regulations for criteria pollutants, and compliant vehicles will likely be zero-impact emitting, that is with tailpipe emissions at or lower than the ambient concentrations. Meeting these regulations will require adoption of several advanced engine and emission control technologies which we discuss here. Emphasis will be on reducing cold start emissions, likely requiring active thermal management strategies. The challenge will be to lower criteria pollutants while also reducing fuel consumption, and we review some approaches being considered. The story is similar for heavy-duty vehicles, where meeting California’s Low NOx regulations and Euro VII scenarios require significantly improved engine controls and after-treatment systems. New system solutions and hardware additions show a pathway to meeting the regulations, although we caution that much more work is needed ahead to achieve the reductions over extended durability limits and with healthy engineering margins. We also review the impact of alternative fuels on reducing well-to-wheels (WTW) greenhouse gas emissions, along with recommendations to continue improving market fuel quality to reduce negative impact on criteria pollutants. Finally, while this paper does not intend to provide a detailed review of battery electric or fuel cell vehicle technology, we touch upon a few studies which discuss the outlook of powertrain diversification from a total cost of ownership and greenhouse gas reduction perspective.</div></div>

Construction of a Highly Active Rh/CeO₂-ZrO₂-Al₂O₃ Catalyst Based on Rh Micro-Chemical State Regulation and Its Three-Way Catalytic Activity

“…Environmental pollution caused by vehicle exhaust has become one of the primary sources of urban air pollution environment with the increase of vehicle ownership year by year 1 . Three-way catalysts (TWCs), as the most satisfactory and efficient catalytic converter system, have been widely used over the last decades.…”

The Effect of Potassium Inclusion in a Silver Catalyst for N2O-Mediated Oxidation of Soot in Oxidising Exhaust Gases

“…Even so, it will be 2-3 decades before the global transportation fleet is no longer reliant on the internal combustion engine, and perhaps even longer if e-fuels (hydrocarbons manufactured by reaction of waste CO 2 with green hydrogen) are proven to have an advantage over batteries in terms of lifecycle CO 2 emissions [3]. In the meantime, there will still be a need for improved aftertreatment technologies as ever more demanding emissions legislation comes into force, such as the Euro 7 standards [4] which are expected to take effect from 2025.…”

RDE cycle simulation by 0D/1D models to investigate IC engine performance and cylinder-out emissions

“…Nowadays the urgent environmental concern has led to the adoption of stringent policies to reduce the impact of human activity on the overall balance of CO 2 . In the automotive field the main consequence has been the introduction of the recent Euro6D emission regulation, and the upcoming Euro7, which now consider more realistic testing procedures, such as Real Driving Emission (RDE) cycles 1,2 along with a reduction of the emitted pollutants. From a technical point of view, the challenge will be to comply with the emission regulation during real world cycles, where the engine may be turned off most of the time in the case of Plug-in Hybrid Electric Vehicles (PHEV), emphasizing the need of reducing the impact of multiple cold starts.…”