Emissions regulation leads to efficiency gains

Innovative technology is use is providing efficient, clean burning engines - Mike Woof reports

The development of new diesel engine technology has, for the off-highway equipment sector, been the single most expensive research field for the industry since these machines first started being manufactured. Aimed at reducing the emissions of nitrous oxide as well as particulate matter, in a phased series of stages the engine emission improvements will make major changes to the construction sector. In real world terms, the total quantities of exhaust emissions from construction machines are miniscule when compared with those from the transport sector. Yet legislating bodies have opted to introduce the requirements for North America, the EC and Japan, so engine suppliers and equipment manufacturers have had to comply.

This research and development has come at a major financial cost for the engine firms and, combined with the additional cost of the emissions control equipment needed, results in customers having to pay more for the new diesels. Fuel quality is another important issue as the low emission engines can only run on high quality diesel with very low sulphur content. High sulphur fuels used in some countries would cause rapid wear and failure. This in itself has created another issue, as machines in developed countries have traditionally been sold off secondhand to developing countries. Questions remain as to how this will affect secondhand machine sales and resale values, whether engines can have emissions equipment removed, or whether those developing countries will soon have cleaner fuels available.

But there have been benefits for customers. The development of these new generation engines has resulted in diesels that are not only cleaner and quieter in operation, but also deliver better economy with fuel savings ranging generally from 5-10%, and provide overall performance increases. To meet the new emissions regulations many firms have been concentrating on smaller, more compact engines that deliver greater power outputs. This has allowed equipment firms to select diesels with smaller blocks and retain low profile machine designs for operator visibility for instance.
One of the key technologies has been the development of new generation, high pressure fuel systems. Different firms have varying technologies for fuel delivery but these include multiple fuel bursts, combined with optimised inlet and head design to ensure that more efficient combustion occurs. Variable geometry turbochargers have been another development, with several different technologies now in use.

The rival firms have chosen from an array of technologies, using a range of similar concepts but varying the detailed design, system integration and implementation. At the same time, manufacturers have opted for varying solutions in even their own large and small engine ranges. These many different emissions control technologies have spawned an array of acronyms and notably, DOC, DPF, EGR and SCR.

Diesel oxidation catalysts (DOC) have been available for some time and are being employed by a number of engine firms as part of the emissions package. The diesel particulate filter (DPF) is being widely used by engine firms and helps reduce particulate emissions. The DPF units do require regenerating at periodic intervals, using fuel to burn out accumulated particulates as the machine operates, while also needing replacement at set intervals. With exhaust gas recirculation, a portion of the exhaust gas is flowed back into the inlet, which lowers combustion temperature, reducing emissions of nitrogen dioxide. Meanwhile selective catalytic reduction (SCR) is used to convert nitrogen oxides into nitrogen and water, with the aid of a catalyst.

For 178 Caterpillar’s six cylinder 7.1litre C7.1 engine, an SCR catalyst and diesel exhaust fluid dosing system are used as part of the exhaust after-treatment process for Stage IV emissions compliance. Meanwhile the 13litre C13 features an SCR and diesel exhaust fluid after-treatment system, but retains the active regeneration process to meet the Stage IV emissions requirements. In these forms the C7.1 offers power ratings from 116-225kW while the larger C13 has ratings from 287-387kW. Caterpillar also says that both engines are around 5% more economical on fuel (as well as diesel exhaust fluid) than the Stage IIIB variants.

At the smaller end of the market, the QSF2.8 from 196 Cummins is the most compact diesel from the firm so far to be equipped with the full-authority electronic controls required for high-pressure common rail injection. This four cylinder engine is offered in both naturally aspirated and turbocharged variants, offering 37kW and 55kW respectively, and shows how engine firms have been able to tailor even compact diesels to meet emissions requirements using new technology. Weight has been reduced to 230kg (wet) due to the use of a sculpted cylinder block along with composite materials for the oil pan, oil filter and valve cover.

For the Tier 4 Interim/Stage IIIB emissions requirements, 695 Doosan is using exhaust gas recirculation in its latest DL06K engine. Weighing 900kg this 5.9litre, six cylinder diesel delivers up to 91kW. Common rail, direct injection is also used and the firm is using an air to air intercooler for the turbo charging system in some installations such as excavators.
201 Deutz AG says that its Deutz Variable Emission Reduction Technology (D-Vert) system uses combustion chamber management along with an array of tools to meet Stage IV/Tier 4 regulations. For the 3.6litre TCD3.6L for example the emissions package includes a DOC and SCR package, while the larger engines from 4.1-16 litre (the TCD4.1L to TCD16L models) use diesel particulate filters as well as SCR after-treatment. Combined with sophisticated fuel systems, Deutz claims its new engines will offer fuel savings of up to 5%. Because the D-Vert system is modular, Deutz says that it is possible to remove components if required and this would allow exports of secondhand machines to markets that are unregulated with regard to emissions. But the firm has not revealed how much work is required to remove the components or how long this process takes.

John Deere has said that it will now use SCR technology in its engines to meet Stage IV/Tier 4 Final compliance. The company originally said it was keen to employ other technologies to achieve the necessary performance but after extensive research, decided SCR was its best option for minimising NOx and particulate emissions. The company will use an SCR catalyst and diesel exhaust fluid dosing unit on diesels in its line-up with power ratings from 56-560kW. The SCR exhaust catalyst and exhaust fluid dosing technology will be integrated with the firm’s existing EGR, DOC and DPF systems used on the Tier 4 Interim/Stage IIIB compliant engines. This new package is called the Integrated Emissions Control system and has been specifically developed for use in rugged off-highway applications. 257 John Deere says that new engines equipped with this integrated emissions technology will offer reduced fuel consumption in the 1-3% range but retain engine performance. Meanwhile the 8,000hour life of the DPF before it requires cleaning helps keep running costs low. According to the firm, its Integrated Emissions Control system will also reduce the consumption of diesel exhaust fluid compared to rival technologies. Because the system uses less diesel exhaust fluid, this will reduce the size of the fluid tank required and help minimise the space required for then engine package. In addition the engines can also run on B5-B20 blends of biofuels, as long as these meet the necessary low sulphur requirements. The introduction of the engines will be phased, depending on territory and power rating with diesels rated at 130kW or more becoming available in 2014.

This will then be followed by engines having lower power outputs, and with the entire Stage 4 Final/Tier IV range being available to markets where compliance is required by 2016.

2300 Komatsu is offering an array of technologies across its engine range, some of which have been developed through its long running partnership with Cummins. Heavy-duty EGR technology is used to lower combustion temperatures and cut NOx while variable geometry turbocharging allows variable control of air flow for example. Diesel particulate filters are used and the firm is offering a novel exchange programme to reduce costs for clients. Other key technologies include a new combustion system, sophisticated electronic controls and heavy duty, high-pressure common rail fuel injection.
2277 Lombardini is offering two new emission compliant KDI engines, with a third coming soon. The three cylinder 1.9litre and four cylinder 2.5litre engines will share technical features with the four cylinder 3.4litre unit due shortly and all three will be able to meet the emissions regulations without requiring a DPF, extending maintenance intervals. These diesels feature common rail injection pressures up to 2,000bar, EGR, electronic engine management and turbocharging.

The 2.5litre and 3.4litre engines also offer greater capacity than the firm’s previous diesels, with the previous range having been topped by a 2.2litre unit. High power densities are claimed for the new engines, the 3.4litre diesel is rated at up to 100kW, allowing machine manufacturers to use a diesel with a smaller block than was possible in the past. Meanwhile fuel consumption has been reduced by some 15%, although the new emissions technology means that the diesels will be up to 20% more costly than previous engines from the firm.

For 299 Perkins a twin turbocharger forms part of the emissions solution, along with SCR, DOC and DPF technologies. The firm’s six cylinder, 7litre 1206F-E70TTA diesel will offer up to 225kW and meet the Tier 4 Final/Stage IV requirements. The SCR technology is new for this engine and comes in addition to the DOC and DPF equipment Perkins used before. However, the new diesel is no larger than the previous engine from the company in this class.

In addition, another benefit is that the emissions equipment can be mounted up to 1.8m from the actual engine. Meanwhile, the removal of the previous active regeneration system makes the whole unit some 30kg lighter and the new engine is also said to offer a saving on fuel of up to 8%.

759 Scania says that it can achieve Tier 4 Final/Stage IV emissions compliance without the need for a DPF, due to its use of its novel XPi high pressure common rail injection system and selective catalytic reduction technology.

The new diesels from Scania use a compact DOC that is integrated into the SCR package, reducing space requirements and making the engine package easier to install on machines.

This is an important point as the engines will allow machine manufacturers to retain low profile engine covers that help deliver all-round visibility. The technology has been developed along modular lines to suit use on the five and six cylinder engines, as well as the 16litre V8 in the line-up. The firm is also considering adding an exhaust brake to ensure that the SCR system continues operating effectively when the engine is running in light load conditions.

2394 Volvo Construction Equipment (VCE) was one of the first manufacturers to market Tier 4 Interim/Stage IIIB compliant machines and says that the results pave the way for its Tier 4 Final/Stage IV diesels. Over the last 12 months Volvo machines have clocked over 1.9million accumulated hours using the Tier 4 Interim/Stage IIIB compliant engines in machines including D-Series excavators, F-Series articulated haulers and G-Series wheeled loaders. The company says that these units have proven fuel efficient and productive. The company opted not to use diesel exhaust fluid additive systems as the fluids are not widely available in some of the markets where these low emissions are targeted. Instead, the company relied on the use of a novel variable geometry turbo, as well as an externally-cooled EGR and an independently-fuelled DPF burner. This last is said to allow the filter to be regenerated without affecting engine performance.
For the Tier 4 Final/Stage IV regulations commencing in 2014, Volvo Construction Equipment’s sister firm 783 Volvo Penta has said it will be using the same proven technology as used to meet Tier 4 Interim/Stage IIIB regulations. A development of the SCR catalyst has further reduced NOx levels, while adding an EGR system to its engines delivers additional emissions reduction. Volvo Penta says that the EGR system will also help ensure that the SCR catalyst operates within its optimum temperature range. But the innovative EGR system Volvo Penta is using will either be lightly cooled, or not require any additional cooling at all.

The company says that this will also avoid problems of exhaust gas condensation and any associated corrosion that would require replacement of components. According to Volvo Penta, key benefits include removing the need for DPF regeneration and reducing the need for changes to the engine installation. At the same time, the engines will deliver optimised fuel consumption and low operating costs.

The company intends to offer five basic engines: the 5litre D5; the 8litre D8; the 11litre D11; the 13litre D13; and the 16litre D16. The four larger engines are all six cylinder units, while the all-new D5 is a four cylinder engine offering power outputs from 105-160kW and a maximum torque rating of 900Nm. Like the D5, the D8 is also all-new, with power ratings from 160-235kW and a maximum torque of 1,300Nm. The D11, D13 and D16 have power ratings of 235-285kW, 285-405kW and 405-565kW as well as maximum torque outputs of 1,950Nm, 2,650Nm and 3,200Nm respectively.

Moving back down the engine output scale, 7139 Yanmar is using an ECU-controlled common rail fuel injection system combined with cooled EGR, a new throttle valve and a diesel particulate filter (DPF) for its new diesels with power ratings of 19kW or more.

These diesels meet the Tier 4 Interim/Stage IIIB emissions requirements and are based on the earlier TNV units from the firm. A new diagnostic system called Yanmar SA-D, and the firm’s SA-R remote monitoring system also provide real-time engine status and allow pro-active servicing to be carried out. There are 10 new engines from Yanmar in the line-up, with either direct or indirect fuel injection and power outputs from 10-56kW, while some feature three cylinders and others have four cylinders.