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At the limit

11/30/2012 | Words: Lucie Maluck | Pictures: Dennis Gering, Robert Hack

Extreme Bedingungen

Jogging at a temperature of minus 10°C is not pleasant – but it is possible. At minus 15°C, just the breathing is painful. At minus 20°C the body is no longer capable of warming up the cold air before it hits the lungs – jogging then becomes a health risk. Physical exertion at temperatures over 60°C is not advisable either. And most joggers avoid steep uphill gradients as well. MTU engines, on the other hand, have to run in all conditions – whether it is at temperatures of minus 60°C in Russia’s so-called refrigeration zone or on the high seas, battling giant waves which cause other vessels to founder. They must never fail, not even in an earthquake.

It is a bizarre sight. As if out of nothing, ice crystals start to form on the engine on MTU Test Stand No. 132. Just a few to begin with; then more and more. As in the fairy tale, the ice envelops the engine like a second skin. Within a few hours, the silver engine has been transformed into a crystalline, white work of art. Then the engine starts up, and inside a few minutes the ice melts away.

Winter on MTU Test Bench No. 132: developers cool the engine to minus 25°C to test out and improve its starting characteristics at such temperatures. The water that condenses on the surface of the engine freezes in just a few minutes to form a sort of icy armor-plating. Then once the engine starts, the sparkling white coat melts away again.?
Winter on MTU Test Bench No. 132: developers cool the engine to minus 25°C to test out and improve its starting characteristics at such temperatures. The water that condenses on the surface of the engine freezes in just a few minutes to form a sort of icy armor-plating. Then once the engine starts, the sparkling white coat melts away again.

The engine in winter

On Test Stand 132 the starting capabilities of MTU engines are tested at extremely low temperatures. Air conditioning compressors are used to lower the engine’s cooling system temperature to as cold as minus 25°C. That allows the developers to test how easily the engine starts at different temperatures. To improve starting characteristics, MTU developers optimize fuel injection pressure, volume and timing. The data are then stored in the engine management system and are adapted for engine start-up on the basis of outside temperature and coolant temperature. This comes into play on the haul trucks that are in constant use in the Aikhal diamond mine in Siberia, for example. This spot in the Republic of Yakutia is known as Russia’s refrigerator with good reason. According to an ancient myth, when God created the Earth he sent an angel with a sack full of riches to Siberia. When the angel flew over Yakutia, his fingers froze with cold and he dropped the sack. All of the riches – gold, silver and platinum – were scattered all over the ground. Out of anger at the loss, God punished the area with frozen winters.

In the Aikhal diamond mine in Siberia haul trucks have to carry on working reliably at temperatures as low as minus 60°C.?
In the Aikhal diamond mine in Siberia haul trucks have to carry on working reliably
at temperatures as low as minus 60°C.

Engines adapted to the cold

If you work in Aikhal, you are allowed to retire earlier. You are also paid an extra allowance and sent on a rest and recuperation holiday on the Black Sea every two years. That is unless you are a haul truck. They have to carry on working reliably at temperatures as low as minus 60°C – when people find it difficult just to breathe. “In the beginning I was skeptical as to whether MTU’s high-performance engines could really cope, but they work perfectly,” recounted Vladimir Koyhevnikov, chief engineer for the mine operator Alrosa. They only have to be serviced every 30,000 hours. That is no more frequently than engines in any other mines. And it is down to the fact that they have been specially prepared for the arctic Siberian conditions. Because the polar diesel used in the region has a kerosene content of 60%, and is therefore substantially less viscous than normal winter diesel, MTU modified the fuel injectors so that the very thin fuel does not destroy them. Louvers in front of the radiator prevent the engine being overcooled. They are closed whenever the temperature is too cold. Consequently the engine can still be reliably started even at extremely low outside temperatures. The engine controller automatically adjusts fuel volume and injection timing to the air temperature. Also, depending on the ambient temperature, pilot injection is activated in addition to main injection during start-up.

High-altitude kit for deployment in Chile

So that vehicles – be they tanks or haul trucks – function reliably even in the thin air at altitudes above 4,000m, they are equipped with a special high-altitude kit.?
So that vehicles – be they tanks or haul trucks – function
reliably even in the thin air at altitudes above 4,000m,
they are equipped with a special high-altitude kit.

Anyone who has traveled through high mountains knows the feeling: the air gets thinner, breathing becomes difficult. The oxygen content of the air decreases with every meter of ascent. Anyone used to hiking at altitude would not notice too much difference at 3,000 meters or so. However, those of us used to lowland areas may well experience breathing difficulties at 1500 meters. And the situation is the same for the Leopard 2 tanks which have formed the backbone of the Chilean army for the last three years and which have to deliver top performance at altitudes up to 4,300 meters. This presents a particular challenge for the vehicles’ turbochargers which increase their speed but still feed less combustion air into the engine. As a result, exhaust temperature rises and the service life of many components decreases. To stop this happening, a new compressor wheel in the turbocharger acts together with the sensors in the exhaust temperature monitoring system to ensure that the engine does not overheat and engine output is throttled back almost unnoticeably. In this way, the engine is able to deliver the high levels of performance demanded of it, even high up in the mountains.

Crashing waves, biting spray and freezing temperatures. Lifeboats are usually called out when the wind is at its strongest, the waves at their highest and other vessels cannot cope with the conditions. So that the lifeboats do not become rescue cases themselves, they are self-righting in case they capsize. “We design our engines specifically to cope with such extreme conditions and to make sure that there is always enough oil available to coat the moving parts with a lubricating film, we also test them on a special tilting test stand,” explained Dr Carsten Baumgarten, Test Team Leader for Series 2000 engines. The engines are tilted over at angles up to 45° on the special test stand and subjected to all load and speed combinations. The tests enable the developers to answer questions such as what the oil pressure is, how much air there is in the oil or how much oil there is in the engine’s blow-by, which is fed back into the intake air via the crankcase venting system. Engines that are used in haul trucks or excavators have to be able to operate at inclinations up to 15° in any direction. For marine engines, that figure is significantly larger in some cases. In armored vehicles, some MTU engines are required to operate at inclinations as extreme as 45°. To do so, they are equipped with a special type of drysump lubrication system. The oil is pumped continuously from the sump into a smaller reservoir from which it is delivered to the engine. This ensures that sufficient oil always reaches the engine lubrication points.

MTU developers can tilt engines over to an angle of 45° on a test stand. In that way they can simulate the conditions on steep ascents or descents or in heavy seas.?
MTU developers can tilt engines over to an angle of 45° on a test stand. In that way they can simulate the conditions on steep ascents or descents or in heavy seas.

The engines in the lifeboats of the British Royal National Lifeboat Institution, for instance, have things even harder. They have to be able to roll over around their own longitudinal axis and still keep running. No easy undertaking, because overturning could potentially cause the engine oil to run out through the crankcase venting system and so find its way into the cylinders, where it would burn uncontrollably. MTU designers have therefore designed the crankcase venting system and the engine oil cavities so that the oil cannot run into the intake system if the engine completes a 360° rotation.

Emergency power in an earthquake

And what if there is an earthquake? Emergency generator sets – regardless of whether they provide the backup supply for nuclear power plants, data centers or hospitals – must not fail even in such conditions. In California the earth moves 10,000 times a year; and quakes are far from a rarity in the rest of the world, so they are something that MTU Onsite Energy gensets have to be able to contend with. The developers at MTU Onsite Energy in Mankato, USA, therefore recently simulated an earthquake on a special test stand at UC Berkeley PEER Labs in northern California. A 3,250kW MTU Series 4000 genset was placed on a special platform and then subjected to the violent effects of an earthquake. Prior to and directly following subjecting this unit to the considerable stresses it will encounter during an earthquake, the unit was tested under load and performed its intended function of supplying power to critical loads. This qualified the genset to adhere to compliance with the International Building Code (IBC). IBC is increasingly referenced as the standard for seismic qualification in specifications in the US when a unit must perform after a seismic event.

IFrame

Up to the limit

MTU developers recently carried out the ultimate extreme endurance test on a Series 890 engine. They simulated a descent down a mountain road and increased engine speed up to failure point. “At 5,555rpm we had to abort the test due to a mechanical fault,” said Frank Skrzypinski, MTU team leader for Engine Trials. And was it still approved? “Yes,” answered Skrzypinski with confidence. “Because that is 800rpm above the maximum speed of 4,700rpm that the engine was designed for.”

The content of the stories reflects the status as of the respective date of publication. They are not updated. Further developments are therefore not taken into account.

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