Caterpillar industrial engines for Stage V emission levels

1. CURRENT EMISSION STANDARDS

On 14 September 2016, the European Parliament issued Regulation 2016/1628, regulating requirements for gaseous and particulate emissions limits and type approval for internal combustion engines intended for non-road mobile machinery. The regulation replaced Directive 97/68/EC, which had previously been in use.

To avoid unnecessary misunderstandings at the outset, it is worth making it clear that Regulation 2016/1628 DOES apply to:

• Drives of road vehicles (cars, motorcycles, etc.)
• Drives of agricultural and forestry tractors
• Maritime vessels requiring a valid maritime navigation certificate
• Drives of inland waterway vessels with a net power of less than 19 kW

The exact list of engines excluded from the application of Regulation 2016/1628 is specified in Article 2(2) of the Regulation.

IMPORTANT

For this article, we will deal only with internal combustion engines applicable to industrial machinery. Regulation 2016/1628 also specifies emission standards for railroad engines, but these will not be described in this study. These will be described in a separate text for railroad engines.

In addition, Regulation 2016/1628 defines exactly what a “non-road mobile machine” is. According to Article 3 of the Regulation, it is any mobile machine, transportable equipment or vehicle with or without bodywork or wheels, not intended for the transport of passengers or goods on roads, and includes machinery installed on the chassis of vehicles intended for the transport of passengers or goods on roads.

It follows that the regulation also covers non-self-propelled machinery, such as motor pumps, compressors or power generators that are not stationary. According to the regulation “stationary machinery” is a machinery that is to be permanently installed in one location of its first use, not intended to be moved by road or otherwise, except during shipment from the place of manufacture to the place of first installation.  Such stationary machines are not covered by Regulation 2016/1628.

Before we take a closer look at the detailed emission limits of Regulation 2016/1628, I would like to go back to the previous Directive 97/68/EC. The following tables show the harmful emissions limits for stages III and IV established by the directive. Stade III was divided into two sub-stages: Stage IIIA and Stage IIIB.

 

Regulation 2016/1628 introduces Stage V, which has even stricter limits for PM (particulate matter), CO (carbon oxides), HC (hydrocarbons) and NOx (nitro oxides) in the exhaust gas. According to the table below, the greater the power of the engine, the less harmful substances may be present in the exhaust gas it generates. It is also important to note the appearance of a new PN parameter that was not present in the previous directive. PM stands for the maximum permissible mass of particulate matter in the exhaust gas, which is given in g/kWh. PN stands for the maximum permissible number of particulate matter contained in the exhaust gas per kWh of engine operation. The new regulation thus limits the non-maximum content of CO, HC and NOx in the exhaust gas given in mass units, or g/kWh.

2. WHAT DOES THIS MEAN FOR MACHINERY MANUFACTURERS?

 Introduced emission levels affect manufacturers of machinery with diesel engines. Here are three key dates relevant to machinery manufacturing. These dates apply to those manufacturers that produce more than 100 machines per year.

• 1 JANUARY 2019: the end of production and sales of diesel engines meeting European Stage IV emission levels intended for operation on non-stationary machinery not moving on public roads.
• 1 JUNE 2020: end of production of non-road mobile machines equipped with diesel engines meeting European Stage IV emission levels.
• 1 JANUARY 2021: non-stationary non-road machines equipped with diesel engines that meet European Stage IV emission levels cannot be put on the market any more*

* The above timeframes do not apply to engines with power ranges from 56 to 130 kW. Such units have an additional 12 months (marked in green in Table 3).

 

Machinery manufacturers, producing limited numbers of machines per year, may have serious difficulties redesigning their fleets within the standard transition period. These manufacturers tend to be small and medium-sized enterprises (“SMEs”) that have limited engineering capacity and often receive information about future Stage engines later than other original equipment manufacturers. This is particularly the case for agricultural machinery manufacturers producing limited numbers of units per year, who would face a significant structural challenge in moving to Stage V emission limits.

For NRE engines, member states allow the extension of the transition period and the 18 months mentioned above for an additional 12 months for original equipment manufacturers whose total annual production is less than 100 units of non-road mobile machinery equipped with internal combustion engines. To calculate this total annual production, all original equipment manufacturers under the control of the same natural or legal person are considered one original equipment manufacturer.

  

3. CATERPILLAR OFFER

The first EU regulations on exhaust emissions for mobile non-road machines were announced on 16 December 1997. This legislation came into effect in two stages: Stage I introduced in 1999 and Stage II introduced between 2001 and 2004, depending on engine power. In subsequent years, more stages were introduced: Stage IIIA (2006), Stage IIIB (2012), Stage IV (2014) and Stage V (2019). Each stage increasingly lowered the limits of pollutants in the exhaust gases. The charts below show how much PM and NOx emissions have been reduced over the years for two sample engine power levels: 100 kW and 300 kW.

 

In the 1990s, Caterpillar began developing several potential technology pathways to meet the requirements of the announced emission regulations. Meeting the requirements of Stages I and II could be achieved by tuning the fuel and air delivery systems in the engine’s electronic control units. Stage III, however, required much more complex engineering solutions. While some engine manufacturers have complied with regulations by redesigning individual components in their engines, Caterpillar invested in a long-range plan. As part of this plan, entire engines and their support systems were redesigned. This ultimately resulted in a new line of engines based on ACERT technology that was able to meet the requirements of Stage III and beyond.

Equally important, ACERT’s technology has not only met emission standards but also provided continued reliability, durability and long service life to our clients’ engines.

The main principle of ACERT technology is relatively simple: if you control the combustion process better, you lower peak combustion temperatures and significantly reduce emissions. Improving the combustion process required ACERT technology to advance in four key engine systems:

• Electronic control
• Airflow optimisation
• Optimisation of the operation of the fuel system, based on direct injection of fuel into the combustion chamber
• Use of an external exhaust after-treatment system only when necessary

Improvements in the fuel mixture combustion process have effectively reduced NOx emissions. To reduce PM, an exhaust after-treatment system was used that consisted of two basic components:

• A diesel oxidation catalyst (DOC) that chemically converts hydrocarbons and carbon monoxide into harmless carbon dioxide and water vapour
• Diesel particulate filter  (DPF) that collects particulate matter. The process is fast, efficient and reliable.

STAGE V

As for previous stages, Caterpillar undertook a major design and engineering effort to bring to market a complete range of Stage V-compliant engines in all power ranges from 10 kW to nearly 1,000 kW. Our engines, despite meeting very demanding emission standards, are characterised by high power and torque parameters, as well as high reliability (backed by excellent service support).

The exhaust after-treatment technologies currently used in our engines are:

• Diesel oxidation catalyst – DOC
• Diesel particulate filter – DPF
• Selective Catalytic Reduction (using urea solution) – SCR

Diesel oxidation catalyst – DOC

A diesel oxidation catalyst (DOC), sometimes referred to as an oxidation reactor, oxidises hydrocarbons (HC) and carbon monoxide (CO) via a chemical reaction occurring as the exhaust gas flows through the catalyst. The DOC reactor also oxidises soluble organic fractions, which are hydrocarbons attached to particulate matter (PM). To some extent, the reactor also reduces the amount of nitrogen oxides (NOx) in the exhaust gas.

 

Diesel particulate filter – DPF

The diesel particulate filter is used to capture soot and ash. Soot consists of carbon particles formed by incomplete combustion of fuel in the cylinder. Ash is the residue left over from unburned engine oil or fuel.

The passive diesel particulate filter has a cellular structure that uses an alternating arrangement of channels, open at one end and closed at the other.

The passive DPF has a “wall” design that allows exhaust gas to flow into the open end of the ducts and blocks it from exiting the other end. This forces the flow of gases through the pores of the chamber walls, which act as filter elements. The filtered exhaust gases leave the adjacent ducts, which are open at the bottom of the stream. Solid particles that are too large to flow through the pores accumulate on the walls of the channel.

Filtr cząstek stałych DPF

Filtr cząstek stałych do silników diesla (DPF) służy do wychwytywania sadzy i popiołu. Sadza składa się z cząstek węgla powstałych w wyniku niepełnego spalania paliwa w cylindrze. Popiół to pozostałość po niespalonym oleju silnikowym lub paliwie.

Pasywny filtr cząstek stałych do silników wysokoprężnych ma strukturę komórkową, w której wykorzystuje się naprzemienny układ kanałów, otwartych na jednym końcu i zamkniętych na drugim.

Pasywny filtr cząstek stałych DPF ma konstrukcję “ścienną”, która umożliwia przepływ spalin do otwartego końca kanałów i blokuje go przed wyjściem z drugiego końca. Wymusza to przepływ gazów przez pory ścianek komory, które działają jak elementy filtrujące. Przefiltrowane spaliny opuszczają sąsiednie kanały, które są otwarte w dolnej części strumienia. Cząsteczki stałe, które są zbyt duże, aby przepływać przez pory, gromadzą się na ściankach kanału.

 

Under most operating conditions, the engine exhaust is hot enough to oxidise the soot through the passive regeneration described above. However, in some cases, a higher temperature is required. For example, Caterpillar’s C9.3 Stage IV engines use a DPF system with active soot-burning called the Cat Regeneration System. This “active” regeneration system uses an external heat source to increase the temperature of the exhaust gas, which promotes oxidation and removes soot from the DPF.

Selective Catalytic Reduction – SCR

The SCR is a system used to convert nitrogen oxide molecules into water and nitrogen (without harmful NOx). Diesel Exhaust Fluid (DEF), i.e. an approx. 32% urea solution (commonly referred to as Ad-Blue), is injected into the SCR, where the reaction takes place converting NOx to H₂O and N₂.

 

 

If you have any questions or concerns, please contact our sales department directly.

Written by: Andrzej Jankowski

Sales Engineer in Industrial Engines Department

Sources:

Regulation (EU) 2016/1628 of the European Parliament and of the Council

(https://eur-lex.europa.eu/legal-content/PL/TXT/PDF/?uri=CELEX:32016R1628&from=PL)

Directive 97/68/EC of the European Parliament and the Council (EU)

(https://eur-lex.europa.eu/legal-content/PL/TXT/PDF/?uri=CELEX:31997L0068&from=PL)

dieselnet.com Online portal

(https://dieselnet.com/standards/eu/nonroad.php)

Caterpillar internal materials