Ricardo Locomotive Fuel Economy Tests

Published by Gerald Ferreira Date: January 22, 2013
Categories: General News


  • Builds upon recent study for UK Government into potential technology improvements to improve diesel fuel efficiency on the rail network of Great Britain
  • Ricardo contracted by GE to oversee and validate back- to-back locomotive fuel efficiency tests
  • Fuel savings of 18 percent for GE’s state-of-the-art Class 70 locomotive in comparison with the Class 66 currently used for 87 percent of rail freight movements in Great Britain
  • Additional fuel savings would be possible using the Class 70’s Auto Engine Stop/Start (AESS) feature and Auxiliary Power Unit (APU) in duty involving extended stationary periods

Locomotive Fuel Economy

As a part of its study carried out for the Department for Transport in partnership with TRL and reported in March 2012, Ricardo assessed a range of technology packages that could be applied to the Class 66 locomotive which currently represents the backbone of the UK’s rail freight fleet.  At the time of the study the brake specific fuel consumption of the two-stroke engine of the Class 66 was not available, so Ricardo instead produced its own estimates and used these as the basis of comparison of a range of technologies that could be applied to improve the locomotive’s fuel efficiency.

GE Transportation expressed interest in the results of the study because its Class 70 locomotive fitted with its four-stroke PowerHaul® engine not only incorporates many of the features recommended by Ricardo – including the fitment of an APU to facilitate stop-start operation and hence reducing the use of the main engine during frequent stationary periods when it would otherwise be idling – but it also complies with EU Stage IIIa emissions regulations (7.4 g/kW.hr NOx).

To demonstrate the fuel-efficiency credentials of the Class 70 against the Class 66, GE Transportation commissioned back-to-back tests to be carried out in November 2012 at Wabtec Brush Traction’s facility in Loughborough, UK. To ensure that the tests were carried out according to a robust methodology and in an accurate and thoroughly objective manner, GE contracted Ricardo to oversee the work and to validate the test and analysis approach taken as well as the results generated.

“We were very pleased to have been contracted by GE Transportation to oversee these back-to-back locomotive fuel consumption tests,” commented Ricardo head of rail vehicle technology, Jim Buchanan. “This work naturally builds upon the study with the UK Department for Transport that we reported in March 2012, and provides an extremely rare opportunity to evaluate a locomotive typical of the current Great Britain rail freight fleet against a state-of-the-art vehicle comprising many of the technologies that we recommended for consideration in that study.”

Testing Methodology

The Class 70 locomotive tested – which is owned by GE – incorporates common rail fuel injection and Miller timing to achieve compliant emissions while avoiding a natural tendency of increasing fuel consumption to reduce NOx.  In addition to its AESS capability, the APU provides power to auxiliary systems which allows shut down of the main engine and provides power for auxiliary loads.  The locomotive also has the capability to divert power generated during dynamic braking which would otherwise be wasted, to feed the auxiliary loads.

The Class 66 locomotive used for the back-to-back test was loaned by a current UK rail freight operator for this purpose. This locomotive complies with UIC 1 emissions, (up to 12 g/kW.hr of NOx), and is typical of the bulk of the UK’s Class 66 fleet. The locomotive was up to date with its maintenance schedule and the engine had operated for about 14,059 MW.hrs indicating that it was mid-life.

The two locomotives were fed from a fuel tank incorporating a weighing load cell, giving a weight accuracy of about 0.02 percent.  Both locomotives used fuel from the same batch. The main and auxiliary electrical power generated during testing was measured, and in the case of the Class 66, account was taken for the mechanically driven auxiliaries. Shop air was applied to the locomotives to prevent the on-board compressor systems from activating – such activation would have caused a spike of power demand. Each locomotive was run several times in each power notch to ensure operating stability and consistent results in the amount of fuel burn recorded and power generation measured. Corrections were applied for alternator efficiency and fuel energy content, resulting in specific fuel consumption for available traction power at each notch power.

The output from the testing was the net tractive specific fuel consumption in each power notch.  In other words, it was a test of the amount of fuel required to generate each kilowatt of haulage power, along with consumption at idle. Although the tests were undertaken within one week of each other there was a small difference in ambient temperature, and the results were corrected for this. Ricardo has prepared a detailed report for GE Transportation on the testing work, confirming that accurate and fair methods were used to gather and present the results.

Results obtained

Using duty cycle data sourced from UK rail freight operators, based on typical Class 66 locomotives used in normal traffic, it was possible to estimate the time spent in each power notch, including idle. This was broadly similar to the duty cycles adopted in Ricardo’s earlier work for the Department for Transport. By using the power notch net traction specific fuel consumption for each of the locomotives, the fuel consumption over the duty cycle was calculated and compared.

This analysis of the test results showed that the Class 70 PowerHaul® locomotive would save 18 percent of fuel in comparison with the Class 66 currently representing the majority of the UK’s locomotive fleet. In addition, further significant fuel savings could be made by the Class 70 locomotive when closing down the engine during extended idling using the automatic engine stop/start (AESS) system and Auxiliary Power Unit (APU), or by using power from the dynamic brake being used for driving auxiliary loads.

“It is an extremely rare opportunity to be able to carry out directly comparable fuel consumption tests on railway locomotives,” added Buchanan. “I would like to thank GE Transportation for offering this opportunity to Ricardo. The results obtained clearly indicate the significant fuel savings provided by the Class 70 in comparison with the older Class 66 vehicle. This – in addition to the locomotive’s compliance with the latest emissions regulations – will make it an attractive candidate for operators considering new vehicle purchases or lease contracts.  The fact that the measured fuel consumption of the older Class 66 was noticeably higher than the estimates of our report for the Department for Transport makes the case for the retro-fitting of new technology packages in the absence of vehicle replacement all the more compelling.”

“The Class 70 PowerHaul locomotive is one of GE’s most technologically advanced, fuel-efficient and low-emissions diesel-electric freight locomotives to date, providing a clean and efficient solution for rail freight operators,” said Gary Lacy, PowerHaul® Platform Leader of GE Transportation. “By having these back-to-back tests conducted we wanted to demonstrate to our customers and other rail freight stakeholders the true scale of fuel savings that are possible from this product in comparison with the Class 66 vehicle which is still widely used within the UK.  I would like to thank Ricardo for its role in overseeing and validating the testing and analysis methodology. Ricardo’s expertise in powertrain technology, together with its international reputation for unbiased opinion, has been crucial in ensuring the accuracy and objectivity of these locomotive fuel consumption tests.”