New locomotives concept from Bombardier: The clean power of the four engines

Rexroth supplies cooling systems for the new multi-engine locomotives of the Deutsche Bahn.

With the TRAXX P160 DE multi-engine locomotive for freight and passenger transport, which was presented in the middle of 2012 at the Innotrans train fair in Berlin, Bombardier Transportation has implemented a low-emission drive concept. In this diesel electric locomotive, which is based on the successful TRAXX platform, the manufacturer uses four smaller diesel engines instead of one “large” one. Thus, the TRAXX P160 DE ME significantly reduces diesel consumption according to manufacturer specifications and, as the first mainline diesel locomotive in passenger service, conforms to the EU Stage IIIB exhaust emission standards, which have been in force since 2012. Bosch Rexroth has implemented the fan cooler system for the diesel engines, the drive generators and the inverter in close cooperation with Bombardier.

The concept is economically and ecologically fascinating: Until now, large diesel engines have been used in diesel-electric locomotives. In this market, there are only a few suppliers that produce relatively small quantities. As a result of conforming to the EU Stage IIIB exhaust emission standards, the cost of exhaust emissions post-treatment and energy-efficient motor control units are soaring.

Bombardier Transportation has therefore chosen a very different approach: they have replaced the TRAXX P160 DE ME product line (the usual “large” diesel motor for mainline locomotives of this performance class) with four smaller engines from large-scale series production. This reduces the system costs, including exhaust emissions post-treatment. With this innovative concept, the individual diesel engines turn on and off as needed. “This approach reduces both fuel consumption as well as the total lifecycle costs compared to the variants equipped with a large diesel engine by up to 10 percent,” says Juliane Storm-Ohm, Project Manager at Bombardier Transportation GmbH. The testing and certification runs, which have been held since March 2013, confirm the locomotive’s low consumption and emission values simulated at the project start.

On the other hand, this approach places enormous challenges on the cooling system. “With this concept, the available space is even less than usual, but the fan drives still have to provide the cooling capacity as required based on various sensor data,” says Juliane Storm-Ohm, Project Manager at Bombardier Transportation GmbH, outlining the task. In a development partnership with Bombardier, Rexroth, as the engineering service provider, executed the cooling system for the 2,252kW-strong multi-engine locomotive.

Technology-overlapping complete solution

“In the cooling systems for the drive train of the TRAXX DE ME, we combine hydrostatic and electric fan drives with a suitable fan control,” says Gunther Neidlein, Head of Industry Sector Management Transportation Technology at Bosch Rexroth AG, to describe the solution. In addition, for the development of the tailor-made cooling system, the engineers used the Rexroth 4EE system. It exploits the full potential of all drive systems for greater energy efficiency. Already during the design stage, the developers considered the overall system with the Energy System Design. The result: The cooling system for Bombardier consistently focuses on efficiency-optimized components and a needs-based service provision, Energy on Demand.

Smart fan control

For the hydraulic fan drive, the completely redesigned diesel engine cooling system makes use of the benefits of the resolution design of the hydraulic system. Adjustable axial piston pumps generate the output current as required. The extremely compact hydraulic motors drive the fan wheels, whereby the air flow necessary for cooling is generated.

The control unit of the cooling system is based on the BODAS kit for mobile control units by Rexroth. The control units, which are scalable with regard to both hardware and software, have proven themselves in numerous mobile machines, such as excavators, tractors and harvesting vehicles. For the special requirements of railway vehicles, the hardware has been further developed and adapted.
The electronic control unit captures various sensor signals, such as the temperature of the engine cooling water, the air charge, the generator cooling water and the hydraulic oil, and uses these sensor values to calculate the necessary cooling performance. Rexroth has already integrated the relevant algorithms into the software. Based on the cooling requirements, the control unit varies the pressure in the hydraulic circuit and, therefore, the drive torque on the axle of the hydraulic motor.

The efficiency of the fan cooler system is increased due to patented additional functions integrated into the software of the fan control unit. Through these additional functions, the fan speed is readjusted according to demand, taking into account various environmental conditions. “This allows improvements in energy efficiency and the noise emissions of the fan system to be achieved,” says Ralf Kunkel, Project Manager at Bosch Rexroth.

The cooling system for the diesel engines has been supplemented by another system for the cooling of the converter. Electric fan drives are used for this purpose.

Development partnership shortens time to market

In the construction and design of the cooling system, Rexroth worked closely with Bombardier and contributed many years of experience in the development of cooling systems for locomotives. “That reaches from performance calculation and component selection to the software for the control unit and the networking with the entire system,” Gunther Neidlein says, outlining the task: “Overall, for Bombardier, we have coordinated twelve specialty areas at Rexroth and tested the functioning of the entire cooling system in extensive simulations in advance.”

Bombardier has performed extensive flow simulations for air and gas emissions on the moving locomotive so as to determine the best locations for the air intakes for the cooling air supply, in order to provide optimal conditions for the cooling systems. Rexroth was therefore able to help by sharing its expertise, as well as to react flexibly and quickly to the simulation results for the satisfaction of the vehicle manufacturer.

“The special challenge of this project was to implement the innovative multi-motor concept very quickly and on time,” says Juliane Storm-Ohm, Project Manager at Bombardier Transportation GmbH, explaining the specific conditions under which the project was conducted. Obviously, the cooperation with Rexroth has fulfilled expectations, because with the official first presentation at InnoTrans 2012, Bombardier Transportation praised Bosch Rexroth as a special supplier.

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