Issue: Feb 2010


TURBINE ENGINES SEEK AUTOMOTIVE USE



by Bob Brooks

Programs to bring the turbine engine into light duty automotive use may at long last have pulled together the ingredients for success. Two firms are in the hunt with advanced hybrid technology which has opened the door with characteristics that turbines can use to advantage..

GM built and demonstrated turbine powered concept cars in the 1950s having first considered the idea in the 1930s but the early turbine concept cars were not competitive in cost and efficiency..

Capstone Turbine Corp, Chatsworth, California (which makes a 30 kW, 41 hp turbine) and a UK team supported by the government backed Technology Strategy Board and a group including Jaguar Land Rover, SR Drives and Bladon Jets are both in the automotive turbine hunt.

Driving the turbine hybrid technology along is a remarkable list of advantages including use of air bearings, no need for lubricating oil or coolant, no need for exhaust emissions control of any kind (verified by the California Air Resources Board), extreme smoothness, very low noise, ability to use virtually any liquid or gaseous fuel, reduced weight by about 100 kg vs conventional engines, very long life (40,000- hr according to Capstone)and ability to run up to 90,000 rpm from cold start in a few seconds.

The Capstone turbine’s poor low speed fuel efficiency is offset by operating as part of a hybrid system mostly at best efficiency high speed. Stored electric power in batteries or capacitors (or both) provide instant electric motor torque for acceleration without lag. Capstone’s recuperated turbine fuel efficiency with a pressure ratio of only 3:1 is not as favorable as one would like yet when applied to city bus use (nearly a hundred have been ordered by New York City for large scale trial), the overall turbine hybrid system in a standard size city bus has demonstrated consumption of only half as much fuel as a conventional diesel powertrain and provides smooth, quiet power says Capstone chief engineer Steve Gilette. He adds that direct coupled SR Drives generator is 97% efficient at 90,000 RPM

While the fuel efficiency advantage may apply to frequent stop/start city bus duty, compared with conventional diesel powertrains, the Capstone turbine’s low pressure ratio likely translates into less favorable fuel efficiency in car highway speed condition at the current stage of development.. .

Capstone powered busses for NYC designated Eco-Saver IV HEV are made by DesignLine International. Gilette, says Capstone has sold 5000 turbine powered generator sets over the past ten years mostly as ultra small stand-by power units and now see an opportunity combined with hybrid technology to move into the automotive arena. .

Another developer of micro turbine based hybrid automotive power systems is the UK team built around the Blandon Jet turbine which the firm’s spokesman, Paul Barrett says has a unique patented axial flow compressor section that achieves excellent fuel efficiency without a recuperater. He declines, however, to give specific fuel efficiency data or the firm’s turbine compressor pressure ratio.

Barrett says the system is well suited for use in larger and high performance passenger vehicles. .. .

Asked about production cost of the Blandon micro turbine, Barrett points out that because it contains only 5% of the parts count vs. reciprocating piston engines, cost is comparable in moderate production quantities.

Considering that the UK micro turbine hybrid system team includes the Jaguar Land Rove group, early automotive adoption may be indicated. While evidently not suited at this stage for popular price high fuel efficiency regular use cars, the long sought wonders of turbine power with no emissions controls or need for lube oil or coolant and with low noise, no vibration and potentially very long life, may be working their way to the automotive starting gate at long last..

Core outstanding questions are the fuel efficiency and cost of advanced small turbine engines with pressure ratios and high temperature power turbine elements suitable for a broad range of automotive uses within regulated fuel efficiency requirements….and whether other firms with turbomachinery expertise will enter the field.

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