According to the US-based ICCT, transitions to more stringent vehicle emissions standards years would require significant technology changes in the manufacture of new heavy-duty engines.
28 Mar 2016 | 7343 Views | By Shourya Harwani
It is no secret that India is gearing up to leapfrog to BS VI emission norms by 2020 to reduce harmful emissions in line with the emission standards followed by most developed countries in the world. It is also not a secret that this transition will not happen overnight and ...
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It is no secret that India is gearing up to leapfrog to BS VI emission norms by 2020 to reduce harmful emissions in line with the emission standards followed by most developed countries in the world. It is also not a secret that this transition will not happen overnight and there are many challenges ranging from fuel availability to enough time for validation and testing.
While the task at hand is tough and most car manufacturers have already expressed concerns over the deadline, the challenge seems to be even bigger for the heavy commercial vehicle (HCV) industry, given the complete overhaul required to meet the April 2020 deadline.
According to a recently published working paper by the US-based International Council on Clean Transportation (ICCT), transitions to more stringent vehicle emissions standards over the next five years would require significant technology changes in the manufacturing of new heavy-duty engines.
Most heavy duty trucks and buses sold in India are not even compliant with BS IV norms at present, and in 2013-14, only 3 percent of trucks and 27 percent of buses sold in the country met BS IV norms. At present, BS IV norms are applicable in over 60 cities across India, while the rest of the country is still following BS III norms. Since most heavy duty vehicles, especially trucks, are registered in Tier 2 and Tier 3 towns the effective standard for such vehicles is still BS III.
So the shift from the current national standard of BS III to BS VI starting in 2020 is going to require that manufacturers invest in a number of technologies to achieve the target brake-specific levels of NOx and PM (particulate matter) emissions.
These engine technology changes include transitioning from mechanical to electronic controls, improvements in engine combustion and calibration, increased injection and cylinder pressures, refinement in fuel injection systems, and the implementation of NOx and PM after treatment solutions.
The technologies for controlling criteria pollutant emissions often have efficiency impacts. For example, selective catalytic reduction (SCR), which is required to achieve the most stringent NOx levels, allows engines to be tuned for increased fuel efficiency. Moreover, the introduction of electronic controls and more sophisticated fuel injection strategies is a boon to efficiency.
On the other hand, certain emission control strategies such as exhaust gas circulation (EGR) and diesel particulate filters (DPFs) often have negative fuel use ramifications. Engine-specific efficiency standards in the US and Canada have spurred a number of advances, and the technology pathways for the next 10 to 15 years to facilitate these efficiency improvements are reasonably well understood. Moreover, regulatory progress in Japan, China, and the EU are also expected to promote the proliferation of a number of fuel-saving technologies for engines.
The journey from Euro 3 to Euro 6
The research paper highlights the technicalities of the evolution of technology required to upgrade successfully from Euro 3 to Euro 6 norms.
The modernisation in the heavy-duty sector in India requires the continued large scale transition from mechanically to electronically controlled engines and the development of a nationwide urea infrastructure to support vehicles using selective catalytic reduction (SCR) for NOx control. In addition, OBD (on-board diagnostic) systems are required to ensure proper usage of the SCR systems.
Euro 3 and older trucks are typically fitted with direct injection technologies and turbochargers with after-cooling. In-cylinder development for NOx-PM trade-off control includes an increase in valve number (3-4 per cylinder), fuel injection technologies with higher pressures and metering control, and nozzle redesign aimed at improving the fuel spray pattern for better mixing with air and to reduce fuel dribbling at the end of the injection. Further NOX reduction is achieved by using fuel injection timing retardation during some engine conditions (to lower peak combustion temperatures).
The Euro 4 standard requires roughly an 80 percent reduction in PM and 30 percent reduction in NOx, HC, and CO. There are two technical approaches to achieve these levels. First is engine-based PM control and NOX control with after-treatment devices. Second is NOx control through EGR (exhaust gas retreatment and PM control by an after-treatment device. A key benefit of the first approach is that the fuel penalty associated with EGR is avoided and can offset the costs associated with having to supply the vehicle with urea. For both EGR and SCR systems to meet NOx performance expectations across the spectrum of exhaust temperatures, these systems must be designed and tested using test cycles that better encompass the full range of driving conditions— especially low engine loads.
In the move from Euro 4 to Euro 5, only NOx is subject to a more stringent limit, which is approximately 40 percent lower. The fundamental way to keep all regulated pollutants under Euro 5 limits is intensive air–fuel management control involving fuel injection timing, fuel injection pressure, and variable geometry turbochargers.
For the jump from Euro 5 to Euro 6, heavy-duty diesel engines require significant reductions in NOx, PM, and HC emissions—roughly 80 percent, 50 percent, and 70 percent, respectively. The low PM mass value of 0.01 g/kWh and newly instituted particle number limit requires the use of diesel particulate filters.
On-road heavy-duty emission standards are designed to be technology neutral and do not require that specific technologies be used to meet regulatory levels. While manufacturers differ in the specific design parameters of the engine modifications and after treatment they use to meet the standard, in many cases their designs converge toward the most cost-effective option provided by current technology.
These technology advances include improvements to combustion and air handling, reduced friction and parasitic loads, high efficiency after-treatment, and waste heat recovery. Given the large degree of globalisation in the vehicle industry, India can leverage the knowledge and experience from other markets and deploy the technologies that are best suited to local conditions.