5,500 meters above sea level

At altitude, oxygen is rare

“We already knew our engines are ideal for operation at altitude and we specifically set them up to ensure they deliver 100% power under those conditions. Nevertheless, we were still surprised by just how much better they are than other engines operating in the mine,” reported mtu applications engineer Alexander Richter who conducted commissioning operations in Tibet for haul trucks from both manufacturers. “I had much bigger problems acclimatizing to the environment myself,” he admitted. For one thing, he had to work more slowly. “Right from the start, I had to get used to working at a more measured pace.” The rarefied air is low in oxygen and the human body constantly demands a readily available supply. As a result, people working at altitude have to breathe faster and tend to be constantly out of breath.

Richter and his Asian coworkers used a Landcruiser for their daily commute between the Tibetan regional capital Lhasa and the mine. At first, the 1,700 meter difference in altitude proved a challenge for them all, causing constant headaches. “We found it hard to understand how the Chinese and Tibetan mineworkers were able to work in the thin air at that altitude.” But eventually they got used to the conditions. “After three days, we were acclimatized and working was no longer as difficult,” said Richter.

Fit for operation at altitude thanks to 2-stage turbocharging

Unlike the crew, the mtu engines were on top form from the start – thanks to cutting-edge engine technology. Smart coordination between 2-stage turbocharging, exhaust gas recirculation and high-pressure common rail injection systems meant that the engines met Tier 4 emissions regulations without any need for exhaust gas aftertreatment. “The engines’ 2-stage turbocharging technology is the crucial factor for operation at altitude,” explained Richter. Unlike older units with single-stage turbocharging, the latest engines utilize 2-stage technology to ensure adequate compression and air-feed for combustion. The air first undergoes precompression in a low-pressure turbocharger before it is cooled and then further compressed in a high-pressure turbocharger prior to final cooling. 

As a result, the air is so highly compressed that when it reaches the combustion chamber it again contains all the oxygen the engine needs for combustion. Consequently, no hardware modifications to the engine were needed and mtu engineers simply adjusted the engine control using the ‘virtual engine’ facility. Every mtu engine model has a computerized thermodynamic simulation model validated on the basis of measured data from test stand trials. This enables mtu developers to pre-calculate and program the correct engine control settings for every conceivable set of environmental conditions. These then only need to undergo on-site testing and fine adjustment. 

The engines’ environmental pressure sensors are especially vital for operation at altitude. These measure barometric pressure to allow the engine control system to select exactly the right performance maps that relate to operation at the appropriate altitude. 

No practice-based data available

 “In theory, we knew it would work,” said Richter. Nevertheless, commissioning in Tibet was still a tense process. “Here on site, the engines have to operate at 5,500 meters and we had no relevant practice-based data for that,” he explained. At these altitudes, engines from our competitors have had problems with serious power loss and heavy smoke. Engine damage is frequent. That does not happen with mtu engines.” 

First engines performed well

In their very first tests in Tibet a year ago, mtu engines demonstrated their outstanding altitude-performance capability. Chinese construction machine manufacturer XCMG tested and commissioned a vehicle powered by a 16-cylinder mtu Series 2000 engine. The company has already ordered a further ten engines (due for delivery at the start of 2019) and for the last few months another Chinese construction machinery company NHL has been running altitude trials in Tibet involving two mtu Type 12V 2000 C66 mining engines. “So far, the results have been very impressive,” said Richter. 

Haul trucks from both companies are now in full, regular daily operation carrying 90 and 110 ton loads of copper and spoil at the mine. Their crews may quickly get out of breath in the thin air but their mtu engines definitely do not. Capable of traveling uphill significantly faster than other trucks at the mine, the mtu-powered vehicles deliver greater productivity than other haul trucks at the site.