Diesel emissions technology is a bridge for sustainable industrial development and environment protection. PS Suri shares more on the emerging trends in diesel emissions technology in India.
It has been said that whatever harm does man have carried out on Mother Earth is nothing as compared to the harm that can be caused to man in turn; ecological imbalances and natural catastrophes thereof is a reminder that it is in man’s own interest that we preserve nature as much as we can.
Simultaneously, industrial development including urbanisation is a reality and hence sustained industrial development along with a responsible preservation of our environment is in everyone’s interest.
The diesel engine has been at the heart of industrial development and this article tries to summarise diesel engine emission technologies contribution to clean air. In order to be specific in nature, this discussion is limited to on and off-road diesel engines used in India’s truck and construction equipment.
Diesel engines emit carbon dioxide, carbon monoxide, sulphur dioxide, sulphur monoxide, nitric oxide, nitrous oxide, black carbon, unburned diesel among some more pollutants. These effect human health directly and indirectly, so while India records about 6 lakh premature deaths every year due to air pollution, what is interesting is that the diesel engine is a relatively low polluter; electronic engine management systems controlling fuel injection and air intake and exhaust after treatment devices have upgraded diesel engines to such an extent that it pollutes less than a petrol engine of the same power consuming less fuel.
Much has changed in diesel engine design; today’s engines weigh half as much, produce nine times the power and 28 times the fuel injection pressure as they did in 1930; primary pollutants still are oxides of nitrogen (NOx), particulate matter (PM), hydrocarbon (HC) and carbon monoxide (CO); the latter two are very less in diesel engines and hence our discussion is focused on NOx and PM only.
Specific to non-road equipment (including mining, generators, construction, ports and so on) for the United States (US) and the European Union (EU) alone, this segment has contributed to 20-45 per cent of total PM and 15-20 per cent of total NOx in that geography. The US and EU have put in place several compliance measures the last few years with Asia to follow suit very closely.
Evolution of off-road emission specifications from on-road
Worldwide, the on-road specifications and emissions reduction technology has led the engine industry with off-road adopting these with a lag of few years. Figure 1 shows on-road norms for heavy-duty trucks for NOx and PM and is measurement of transient emissions, not steady state; values for PM are multiplied by 10 in this chart for reading purpose; the data very clearly communicates the stage-wise reduction of these two emissions. For off-road emissions, the limits of NOx and PM are decided based on power bands and hence the Figure 1 details is an overall indication of the emissions reduction.
By April 1, 2017, all new LCV, MCV and HCV on-road vehicles in India will conform to BS IV (equivalent to Euro IV); Off-road wheel mounted equipment like backhoes continue to conform to BS III (Euro III) and crawler-mounted equipment like excavators do not have a specification of conformance presently. The construction equipment industry has a tentative road map to adopt BS IV in 2020 for wheel-mounted equipment.
Emission reduction strategies adopted by on-road OEMs will be generally what construction equipment OEMs will adopt; for example, Ashok Leyland has evolved cooled Exhaust Gas Recirculation (EGR) technology to be their main model to achieve Euro IV NOx compliance and so also does JCB India for backhoes; it is interesting to note that similar to the US and Europe there is initially a diversity in respective OEMs strategies but by Euro V and Euro VI, there will be high convergence.
Tata Motors uses Cummins engines exclusively for trucks of 16-45 MT payload and hence has approached NOx reduction through the Selective Catalytic Reducer (SCR) route which Ashok Leyland too will adopt for Euro V compliance. Cummins Emissions Technologies has evolved its business model to develop and market SCRs, DPFs and other catalysts to support Cummins and non-Cummins engines and it will be known very soon whether or not Ashok Leyland use Cummins catalysts or another design.
As mentioned above, as the construction industry prepares itself for 2020 BS IV emission standards, high percentage EGR and SCR will both become prevalent based on individual OEM experience in the US and Europe.
For tighter norms in line with BS VI, one more after-treatment strategy, viz Diesel Particulate Filter (DPF) will be employed in order to balance combustion optimisation, fuel economy and emission targets. So clean air is a very serious and investment hungry business; transportation and engine industry is mature to have adopted all these in order to ensure sustained development; costs and investment is part of any business and any industry segment as part of being in harmony with one’s environment and health.
Once again referring to Figure 1, the cost of components and R&D is the highest while moving from BS III to BS IV and again when moving from BS V to BS VI as in the first case there is a steep drop in PM and in the second case there is a steep drop in NOx.
Since India has legislated for BS VI ( Euro VI) in 2020, there is a lot of activity on the exhaust after-treatment industry these days, but before having a look at how to effectively treat exhaust to meet compliance, it is logical to peer into what exactly happens during combustion and how OEMs have had significant success by reducing emissions ‘in-cylinder’.
SEE-SAW management of NOx & PM
When we successfully reduce one, the other increases dramatically! NOx production which affects lungs is directly proportional to peak combustion temperature. This peak combustion temperature has been increasing with increased fuel injection pressure (1,400 Bar typical) for combustion optimisation. So engineers achieved lower NOx in the Euro II era by fuel injection retardation (combustion de-optimisation) and further extended the concept by introducing cooled EGR into the intake manifold successfully achieving NOx compliance; in the process however, and quite logically, PM starts increasing. This PM increase is countered by superior air intake management – piston swirl and turbocharging assisted by precise fuel injection through CRDi development. Step up in oil detergent dispersancy by way of API CH-4, API CI-4 specifications ensured that this high pressure engine’s components were well maintained facilitating design durability.
Conversely, was to maximise combustion optimisation by increasing peak pressures and temperatures with improved fuel economy and low PM. But high NOx which is treated suitably in an SCR device in the exhaust stream before tail pipe, the NOx is reduced to harmless nitrogen and water in the presence of a urea dozed into the catalyst.
ULTRA Group is a supplier of this automotive urea which is stored on board vehicle and has an approximate consumption of about 5 per cent of diesel consumed. The SCR strategy has the advantage of superior inherent fuel economy as the negative effects of EGR are absent. It however has a demerit that there is a cost of on-board urea and the catalyst cost itself is a factor.
As with regard to homologating engine oil specifications and safe change period, it is not expected to have any deviation from the present Indian market products of API CI-4 SAE 15W-40 for both the above Euro IV compliant methods as OEMs validate it prior to market introduction.
Re-engineering combustion on its own is futile without the assistance of right fuel quality, specifically the level of sulphur. From 1990 till 2010, automotive industry has been leading the fuel industry in India in terms of environment-friendly technology. Now the opposite seems to be the case where Indian diesel sulphur has been progressively reducing from 500 ppm in year 2000 to 350 ppm in 2005 down to 50 ppm in 2017 keeping time with India’s emission regulation time lines of BS II, BS III, BS IV, and finally achieving 10 ppm in 2020 for BS VI (1 per cent is equal to 10,000 ppm).
Diesel sulphur not only directly correlates to PM formation, but also sulphur reduction is an important contribution to overall combustion efficiency. Indian refineries have significantly upgraded diesel quality; but there is one area still to be addressed which is socio-economic related, ie, abuse of our Public Distribution System (PDS) of blue kerosene used as an adulterant to clean diesel. ULTRA Lab has been assisting mining machine OEMs to audit diesel supply by detecting chlorine which is a by-product of the bleaching of blue kerosene; piston ring, liner, head, FIP devastation due to chlorine present even in small quantities now will extend from in-cylinder to the SCR catalyst too. ULTRA Lab detects chlorine at very low levels of even 10 ppm assisting customers and operators to modify diesel purchase sources when in doubt.
So even as electrification
and hybridisation are making significant achievements in transportation, the diesel engine shows no signs of becoming extinct in the near to medium term. Globalisation of all relevant industries has facilitated quick adaptation of the latest knowledge world over. Industrialisation will continue to be a need, fortunately it need not come at an environmental cost.
Indian refineries have significantly upgraded diesel quality; but there is one area still to be addressed which is socio-economic related, ie, abuse of our Public Distribution System (PDS) of blue kerosene used as an adulterant to
The author is Vice President, Ultra Plus Lubes, a consultancy organisation for lubricating oil industry and a value-added service provider for manufacturing of lube oil and speciality products.