Menden, September 2016 – Diesel-powered vehicles are once again the focus of discussions concerning emissions – and some people are even demanding a total ban for diesels. Today already, only vehicles that comply with the emissions stipulations of the low emission zones (LEZs) in force in many European cities and towns are allowed to enter these built-up areas. Moreover, efforts are currently under way to tighten up the restrictions in existing LEZs even further and, in the case of Germany, to introduce and implement a blue sticker to be displayed on vehicles' windscreens.
It is therefore foreseeable that the rules and regulations that apply to commercial vehicles that plough the roads of our towns and cities day in, day out – such as public transport buses – will also be tightened. And although these vehicles have long been kitted out with SCR catalytic converters to reduce their pollutant emissions, a series of challenges still lies ahead. This is because buses that are primarily deployed in inner-city traffic spend a large proportion of their operating time standing at bus stops with their engine running and frequently get caught up in traffic jams. Generally speaking, then, this means that they do not reach the exhaust-gas temperatures required for their SCR catalyst system to function optimally. These "cold phases" clearly limit the effect of the system and its ability to optimally neutralise the toxic nitrogen oxides emitted. The aim must be to take preventive action at an early stage and thereby avoid emissions problems. HJS Emission Technology from Menden/Germany has an answer to this challenge – Thermo Management Technology (TMT), which it will be exhibiting at the 66th IAA Commercial Vehicles in Hanover (Hall 13, Stand B44).
Environmentally friendly vehicles are also of huge importance to city and local authorities. Right now, some 29 German local authorities are the subject of infringement proceedings initiated by the European Union due to the statutory immissions limits being exceeded in their area. As a consequence of these proceedings, we can expect even stricter rules and the tightening-up of low emission zone restrictions. "This will affect fleet operators and public transport companies in particular", says Axel Middendorf, the man in charge of HJS's retrofit business. "One of the contributors to air pollution in our inner cities are public service vehicles, that is, city and regular service buses – and it is absolutely essential that these are able to move freely around cities and conurbations. But in future this will presumably only be possible if their vehicles are kitted out with the very best in emissions reduction technology."
Ever since the launch of the Euro IV standard in October 2005, buses have as a rule been fitted with SCR catalyst systems. However, the problem with this technology is that it only functions optimally as of a certain exhaust-gas temperature.
This is where Thermo Management Technology (TMT) developed by HJS comes in. This innovative system optimises the performance of the SCR system that is installed as standard. By increasing the temperature of the exhausts, the efficiency of the SCR system is improved significantly. The very name of the system indicates the approach followed by HJS during its development. If the low engine load means that the exhaust gases do not reach the temperature levels required, a system needs to be installed that monitors the exhaust temperature and raises it as and when necessary. Two development goals were of particular importance to HJS: the system's design and operating principle needed to be such that costs and therefore the retail price are kept as low as possible and that they also enable the system to be easily installed as a retrofit kit. And HJS succeeded in achieving precisely these two goals with its SCR upgrade – TMT. The system is extremely efficient and inexpensive, and it can also be installed in the vehicle without any complication and any modification to a bus' engine management system. In addition, the impact on fuel consumption has been kept as low as possible. The main components of the upgrade kit are an exhaust flap, a control unit and insulation material for the standard SCR catalyst.
The heart of the TMT system is HJS's ACU control unit, which measures the temperature and pressure of the exhausts upstream and the temperature downstream of the SCR catalyst, as well as other vehicle data. As a rule, the exhaust temperature is measured by means of appropriate sensors; alternatively, the necessary data can also be read out of the engine control unit via the CAN bus. If, on the basis of the measured data, the control unit determines that the exhaust temperature is too low, it actuates an exhaust flap integrated into the TMT system. By changing the position of this flap, the backpressure of the exhausts is increased and this in turn causes the temperature of these gases to increase significantly. This effect is further aided by additional insulation material that is wrapped around the SCR catalyst. Overall, the TMT system is able to increase the exhaust-gas temperature by up to 50°C.
In tests conducted with TMT in real-life inner-city operation, the average temperature of vehicle exhausts was able to be raised from 185°C to over 220°C. This resulted in the share of nitrogen oxides removed from the exhaust gases increasing from 37% to 58% on average.
This makes the system developed and manufactured by HJS a retrofit system that supplements the SCR exhaust treatment systems installed as standard and makes them more efficient. It is available customised to fit specific vehicles. It is an easy-to-install and inexpensive solution for Euro IV, Euro V and EEV buses. The unit is installed downstream of the SCR housing, with the procedure being that simple that any qualified automotive workshop is more than capable of doing the work.
Further information can be found on the HJS stand at the IAA (Hall 13, Stand B44).