Diesel engine manufacturer boosts ability to meet emissions regulations with Simcenter Amesim

Altering engine design

Diesel engine emissions have been regulated for almost four decades, and the standards are about to get even more daunting. The Environmental Protection Agency (EPA) Tier 4 emissions and European Union (EU) Stage IV regulations call for a 90 percent reduction in particulate matter (PM) along with a 50 percent drop in nitrogen oxides (NOx). Final Tier 4/Stage IV emissions regulations, which will be fully implemented by 2015, will take PM and NOx emissions to nearzero levels for engines above 56 kilowatts (kW). This will have a significant effect on the engine architecture.

Although emission limits have become one of the most important innovation drivers for diesel engine manufacturers, they have to take many other important aspects into account, including performance, fuel efficiency, noise and vibration, engine weight and cost of ownership.

Grasping the issues

Hatz Diesel (Hatz), a leading German diesel engine manufacturer that has about a 1,000 employees, including more than five percent in research and development (R&D), faced these market changes, which raised a lot of engineering questions, most prominently: what could they do to develop powerful engines while satisfying low NOx emissions?

In addition, when choosing an engine, customers take into account issues such as the maximum power needed to satisfy the application, weight and fuel consumption, so Hatz engineers needed to understand how customers use their machinery. They asked questions such as: how high is the average utilization of engines in applications? How much time is spent on full load operation? How long is the duration of full load events?

Hatz realized that peak power consumption as well as the duration of the application was the vital criteria for choosing an engine. For instance, the time shares of full load operation are rather small for some applications, such as wheel loaders, while shredders have considerably higher time shares for heavy duty operation, but the duration of a single event is rather short. As a consequence, for a number of applications, it would be possible to replace a larger, higher-rated power engine with a smaller system that could provide an over boost for a limited period of time; in other words, complementing a downsizing strategy with a boosting technology.

As a result, Hatz decided to design a new engine family, the 4H50, in order to expand its engine lineup. Based on extensive research, Hatz chose to use Simcenter Amesim™ software from Siemens Digital Industries Software in the concept phase of the hydraulic power boost system.

Enhancing customer value

“We’re now able to compare different architectures within five minutes whereas it takes days for the test department to set up and run several sessions,” says Tobias Winter, manager of the simulation department at Hatz. “Simcenter Amesim enables us to design more robust products, eliminate guesswork and respect timeto-market. We’re confident that our new engine will be a success, bringing high value to our customers. Simcenter Amesim will be one of the reasons for that success. “We’ve been using Simcenter Amesim for four years and started with fuel injection systems design in which Simcenter Amesim was the reference. But we understand that the power of Simcenter Amesim goes beyond the pure hydraulics: its unrivaled multi-domain approach enables you to build one complete engine with one model, taking into account all parameters of the physics.”

The Hatz 2-liter diesel engine, intended to support the 4L43 series, brings a number of technical advancements with it as it is the most compact engine in its class, and has the best power density compared to its competitors. With 1951 cubic centimeters (CC), the engine has a maximum power of 56 kW and a maximum torque of 240 Newton meter (Nm), which is already available from as low as 1,600 revolutions per minute (RPM).

Besides a main power takeoff, an auxiliary power takeoff will be provided with a hydraulic power boost system that can be permanently loaded with up to 130 Nm. Efforts have also been made on combustion chamber geometry as well as one common rail system, enabling considerable reduction of the particulate emissions. The 4H50 was the first engine at Hatz to be designed under the extensive use of simulation techniques. Starting from structural to reduce friction, reaching to cooling system design (Simcenter Amesim) and CFD optimization of the water jackets, EGR system and so on. As a result, Hatz was able to achieve the exhaust emissions standards EU stage IV and EPA Tier 4 Final without the use of a diesel particulate filter. This new line of engine also has the advantage of low cost of ownership since it consumes only 210 grams of fuel per kilowatt hour and because of a service interval of 500 hours.

Reducing complexity

In the first step of the simulation project, a model was built using Simcenter Amesim, enabling the accumulator and pump sizing to define boost times and torques. But the main objective is to install smart, controlled systems that would know when to boost and how to recharge the system. As a consequence, Simcenter Amesim will be used to support the design of governance and intelligence thanks to model-in-the-loop (MIL) on the engine test bench.

The next step is to install the complete hardware on the engine. This will enable Hatz to validate the hydraulic control unit (HCU) by simulating the presence of the control unit on the test bench.

Without the simulation provided by Simcenter Amesim, this step would be quite complex as two governances are working against each other: the engine ECU is trying to keep engine RPM constant, and when the loads demand is higher than the engine power output, the RPM starts to decrease, making the HCU start to fire the hydraulic motor and support the engine.

“With the help of Simcenter Amesim, we’re able to evaluate different possible architectures and come up with a new system using engine oil that is usable for a wide scope of applications,” says Winter. “We’re very confident in the fact that Simcenter Amesim will help us to design a system that exceeds what is expected as far as NOx regulations and power demands.”

Speeding product development

Simcenter Amesim has been the mechatronic system simulation platform of choice for the new engine design project. The unique and user-friendly modeling environment, application-oriented validated libraries of components (mechanical, thermal, and thermalhydraulics) as well as powerful analysis tools and real-time capabilities have helped Hatz develop the engine in an expedited timeframe. Hatz also appreciates the excellent support provided by Siemens Digital Industries Software.

In addition, the 3D animation tool is a very useful tool that can be widely used during management validation meetings as it enables Hatz to highlight the main results and empowers engineers to make smarter architecture decisions. Even if the engine prototype testing has not been completely removed, system simulation has enabled them to dramatically reduce the effort required for testing, especially testing different topologies of systems required by a variety of customer configurations.