Since the 1990s, when the US, Japan and the European Union passed legislation regulating the exhaust emissions from off-road vehicles, a revolution has been underway in engine technology, yielding a range of exciting new engine designs and innovations. The laws have come into effect over the years in ever more stringent phases, called ‘tiers’ in the US and ‘stages’ in Europe. In 2014, the legislation will enter its latest, most rigorous phase: from January 1, all off-road engines with output over 75 kW (in the US) and 130 kW (in the EU) will have to meet Tier 4 Final/Stage IV requirements, which reduce NOx and PM emissions by 99% over pre-legislation levels.
But not all Tier 4f engines are created equal. While there are several ways an engine can be configured to meet Tier 4f emissions levels, leading engine manufacturer Volvo Penta has put customer needs at the heart of its design process, creating a new line of powerful low-maintenance, low-emissions engines that’s set to hit the market in 2014.
Why lower emissions?
The legislation regulates several kinds of harmful exhaust emissions, including nitrous oxides (NOx) and particulate matter (PM). The importance of lowering NOx and PM levels cannot be understated. Particulate matter presents itself as black soot and smoke; besides creating an unpleasant odor, it can cause lung irritation and, in some cases, cancer and heart disease. Nitrous oxide, on the other hand, is responsible for creating acid rain, as well as producing ground-level ozone and smog.
The emissions paradox
But in the process of eliminating these two harmful substances, there’s an unfortunate tradeoff: whenever NOx is decreased, PM will increase, while if PM levels are lowered, NOx levels will rise.
To meet each phase of the legislation, Volvo Penta has configured its base engines to emit very low levels of PM. However, due to a high combustion temperature, these engines produce NOx if they’re not further altered in some way. And NOx emissions are in sharp focus in the Tier 4 Final phase: while Tier 4 Interim had drastically reduced both NOx and PM from Tier 3 levels, Tier 4f required NOx levels to drop even further, from 2.0 g/kWh to 0.4 g/kWh — a massive 80% reduction.
The solution was to improve the selective catalytic reduction (SCR) technology that Volvo Penta had already implemented in its Tier 4i engine generation. With SCR technology, AdBlue™ is injected into the exhaust line and reacts with NOx in the catalytic converter to turn the harmful compound into nitrogen and water. Another crucial part of Volvo Penta’s Tier 4f solution is light exhaust gas recirculation (light EGR). Because NOx is created at very high temperatures, the EGR further contributes to reducing NOx by lowering the peak combustion temperature.
How it’s different
Many of Volvo Penta’s competitors have attacked the problem from another angle, configuring their base engines’ combustion rate to produce low levels of NOx but emit high levels of PM. Their solution is to add a diesel particulate filter (DPF), which captures the soot and periodically incinerates it down to harmless ash in a process called regeneration. Though effective, this approach has its own drawbacks, including higher fuel consumption. Furthermore, a DPF requires costly maintenance and must be replaced regularly. Overall, a DPF system requires many extra parts — from air pumps and compressors to ignition coils — all of which can fail or need replacing.
While most engine manufacturers installed a DPF to meet Tier 4i and SCR to meet Tier 4f regulations, Volvo Penta uses just SCR in its Tier 4F engines — a simpler, more straightforward solution for customers, with fewer parts and less maintenance than a DPF.
“Because we believed that reducing NOx and PM emissions to Tier 4f levels could be achieved with just SCR, we put all our effort into improving that technology — and making sure we didn’t need to use a DPF, which can end up being more hassle for customers,” says David Hanngren, manager of industrial product planning at Volvo Penta. “It would have been far easier for us to use a DPF, which was already an existing technology. And ultimately our competitors’ engines with DPFs emit the same low levels of PM and NOx as ours do. But because they’re configured to perform at optimum levels, burn less fuel and produce very little smoke, our Tier 4f engines have ended up being a much better solution.”
Though Tier 4 Final is major step forward, the process of lowering emissions in off-road engines isn’t over yet — there are more stringent regulations in the pipeline for years to come. Volvo Penta is already working with innovative technologies to meet future regulations — while continuing to keep customer needs at the forefront of every new advancement it makes in emissions reduction.
Volvo Penta Tier 4 Final engines
Volvo Penta’s range of five new Tier 4f engine platforms will be available for delivery in 2014. The engines share a common design concept, making installation easy and intuitive for OEMs that use multiple engine sizes in their products.
Five liters: The TAD570/71/72VE, a 4-cylinder, 105-160 kW engine with a max torque of 900 Nm.
Eight liters: The TAD870/71/72/73VE, a 6-cylinder, 160-235 kW engine with a max torque of 1300 Nm.
Eleven liters: The TAD1170/71//72VE, a 6-cylinder, 235-285 kW engine with a max torque of 1950 Nm.
Thirteen liters: The TAD1371/72/73/74/75VE, a 6-cylinder, 285-405 kW engine with a max torque of 2650 Nm.
Sixteen liters: The TAD1670/71/72VE, a 6-cylinder, 405-515 kW engine with a max torque of 3200 Nm.
Volvo Penta will also introduce a bi-fuel engine for power generation, powered by natural gas and diesel fuel and tailored to applications in the oil and gas exploration markets.
Sixteen liters: The TWG1663GE, a 6-cylinder, 60 Hz/1800 rpm (with fan) engine. Prime power: 595 kWm/559 kWe/699 kVa. Standby: 654 kWm/615 kWe/768 kVa. Generator efficiency: 94%.
