Directly comparable fuel consumption tests on two locomotives finds GE Class 70 PowerHaul could save 18% of fuel compared with Class 66 in UK fleet
|GE Transportation Class 70 PowerHaul locomotive. Click to enlarge.|
Recent testing commissioned by GE Transportation and overseen by Ricardo found that GE’s Class 70 PowerHaul diesel-electric freight locomotive would save 18% of fuel in comparison with the Class 66 currently representing the majority of the UK’s locomotive fleet. The Class 66 is used for 87% of rail freight movements in the UK.
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.
The Class 70 locomotive is equipped with a V-16, twin-turbo 3,700-GHP engine, an advanced AC traction system and dynamic braking. GE Transportation suggests that the Class 70 can reduce fuel use by up to 9% compared to current operating fleet averages.
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%. 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.
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.
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.
Background. As a part of a study carried out for the UK 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. (Earlier post.)
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.
It is an extremely rare opportunity to be able to carry out directly comparable fuel consumption tests on railway locomotives. 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.—Ricardo head of rail vehicle technology, Jim Buchanan
GB Rail Powertrain Efficiency Improvements (Ricardo report 14 March 2012)