|The BladeBoost demonstrator was the third iteration of the compressor for a vehicle application. Click to enlarge.|
UK-based clean technology developer Lontra has released performance results of the BladeBoost supercharger demonstrator—an efficient, variable mass flow, positive displacement supercharger for heavily downsized engines—following the conclusion of a development project supported by the UK’s Technology Strategy Board, in partnership with Ford Motor Company and Ricardo. (Earlier post.)
The BladeBoost uses the core design of the Blade Compressor, optimized for engine package and performance requirements. A key feature of the compressor is its ability to use a simple variable inlet port that allows dynamic control of mass flow rate and internal compression ratio without changing rotational speed. This enables the boost of downsized engines to be completely controlled at any point on the operating cycle, including part-load.
The compressor is designed for high volumetric and thermal efficiency, and the geometry of the compressor allows high efficiency heat recovery. It is oil free, and other features include small size, low vibration and quiet operation. The compressor is a rotary device with a wrapped toroidal chamber. Key features include are a rotating blade, which passes through a slot in a rotating disc once per cycle. The unit is therefore a compact, double-acting rotary compressor.
The BladeBoost vehicle demonstrator developed as part of the project with Ford and Ricardo represents the third iteration of the compressor for a vehicle application.
|Development stages of the BladeBoost vehicle demonstrator|
|Volume (L)||Displacement (cc)||Speed (max rpm)||Flowrate (max @ 100% vol. eff., L/s)||Pressure ratio||Diameter (max, mm)||Length (mm)|
|Prototype 1, concept demonstrator||1.0||875||6000||87.5||2||331||300|
|Prototype 2, dev model||1.08||978||9000||146.7||3||324||373|
The graphs below show the measured shaft power from Lontra’s test stand, with the BladeBoost variable inlet port set at its maximum and minimum opening:
|Measured shaft power. Click to enlarge.|
|Performance on engine. Click to enlarge.|
The chart to the right plots the measured performance of the BladeBoost against the latest Eaton R900 TVS supercharger, using the published map of thermal efficiency. At a drive ratio of 3:1 the R900 theoretically delivers similar flow rate to BladeBoost. Assumptions were that the engine mass flow rate is proportional to absolute manifold pressure; when throttled, Eaton supercharger efficiency is same as un-throttled (despite higher PR); theoretical power is calculated from PR and mass flow rate, without friction; and inlet air was assumed at a constant 20 °C.
The detailed data set shows how the Blade Supercharger is able uniquely to deliver the pressure and flow required for downsized engines, Lontra says.
In parallel to the physical hardware development, Lontra has been developing a detailed mathematical model of the compressor over the past four years. This is now a powerful tool that allows the company to test modifications to existing devices, or new devices for customers, before committing to costly hardware.
During the build of BladeBoost, the team identified four key, simple areas for improvement:
- The chamber bleed hole was in the wrong position and so should be moved to the correct position.
- The abradeable coating could be run-in more effectively in one key area (outer rotor).
- The remaining clearances could be reduced to the design specification (some components were machined outside of specification).
- The outlet port could be optimized.
The analysis model allows the developers to see what the effect of these improvements will be.
The next generation of Blade Supercharger (beyond BladeBoost) is under development. The new system will be smaller and more tightly packaged with a number of improvements including the capability to accept boosted inlet air for a post turbo-charger installation. This design of this device is complete including manufacturing drawings with some parts already manufactured, the company said.