Rotary engine concept passes with flying colours

Dean Palmer reports on a revolutionary new ultra-compact design of rotary engine that offers much improved efficiencies and reduced emissions

UK start-up company Lontra and its revolutionary 'Lindsey' rotary engine, which Eureka has been keeping a watchful eye on over the last 12 months, has recently passed phase two of its development with flying colours, outperforming current competing engine types in recent tests. Steve Lindsey, technical director at the company told Eureka: "In June, the detailed proof of concept phase including the engine, compressor and expander technologies was completed on time and slightly under budget, with broadly positive results." Unfortunately at this stage of the development, Lindsey does not wish the details of the design to be made public, but take it from Eureka, the design of the engine is truly revolutionary. Cosworth Technology (now Mahle Powertrain) thinks so too. Along with a seals and bearings specialist and a mathematical simulation company, it has been investigating the feasibility of the Lindsey engine design for some time. Simon Hombersley, business development director at Lontra said that the results from this work "broadly support earlier theoretical investigations into the benefits of optimising combustion and compression". Lindsey said that Cosworth's work also identified further potential benefits of the engine's design, from the benefit of the compressor in its own right; the value of variable demand matching whilst maintaining efficiency; levels of emissions (specifically answering the Carbon Trust questions regarding Euro IV and V compliance); and the potential of the design with other fuels, in particular hydrogen. Cosworth concluded that the advantages of the design include: optimising compressor and expander for improved heat management; the engine's ability to run differing compression and expansion ratios enabling greater work to be extracted; variable inlet and exhaust ports will significantly reduce pumping losses; rotational motion is good for high speeds and low NVH; clever, compact and adjustable compressor design; high power density and small size; and low theoretical emissions. According to the Cosworth report, the one potential disadvantage is a low peak cylinder pressure. Uncertainties remain with turbulence and combustion, sealing and friction. But Lindsey told Eureka that these were "not problems per se, but areas where further clarification was required". In tests, the most exciting result was that the Lindsey engine demonstrated an increase in part load efficiency of 37% over a traditional engine, making it ideal for use as a generator, for combined heat and power (CHP), or for automotive applications. The design of the engine allows for optimization of each element of the cycle with few compromises. This makes it far easier to develop the engine for different fuels. Advantages identified by Cosworth included the use of hydrogen, including the capacity to manage the gas' tendency to auto-ignite and to knock (through the reduced peak cylinder pressure). Hydrogen has a fast burn rate and so the design allows for optimisation of turbulence, potentially variable, to maximise efficiency. Analysis of emissions tests showed that the increased fuel efficiency would reduce carbon emissions. Also, the engine has no need for exhaust tuning, meaning that a catalyst can be positioned close to the back of the exhaust valves. The catalytic converter would light off very quickly, becoming usefully hot and reducing emissions. With variable demand matching for CHP applications, Lindsey told Eureka that his engine produced a heat to power ratio of better than 2:1, significantly better than the 8:1 ratio provided by most Stirling engine-based micro CHP systems.