Technologies for Clean Engines Future Power Train 2019 February 2019 Professor Robert Morgan Joint Secretary of UnICEG Deputy Head of the AEC
Scope of presentation 2 What I won t do - make a case for the future need for engines. Please see the Nick Owen, Dolphin N2 presentation in session 7 tomorrow. What I will do - show how an internal combustion engine can achieve ultra low emissions and high thermal efficiency.
Chemical reactions do not have to be fast or hot 3 A fast oxidation reaction high temperature A slow oxidation reaction low temperature
How to get low emissions out of a conventional engine 4 Fuel and air naturally burns at lambda 1 - This produces lots of NOx! Why not operate here? Ngwaka et al 2016 Dilution of the mixture, such as with exhaust gases can cool the reaction to avoid NOx production HCCI combustion can force the engine to operate lean and cool, but in a narrow window between misfire and knock
Low emissions combustion can be achieved, but with compromises to other attributes 5 Late Injection Low Temperature Combustion Low emissions, easy to control but at a 6-11% fuel consumption penalty Morgan 2016 Reactivity Controlled Compression Ignition Low emissions, no fuel consumption penalty but difficult to control and load limited Benjes 2016
Conventional engine cycles compromise low emissions combustion 6 Early Phasing Early LTC HCCI RCCI Late Phasing Late LTC Fuel burns in a contracting volume making control challenging Fuel burns in an expanding volume reducing the rate of temperature and pressure rise
A new combustion led approach to engine design is proposed STEP 1: Definition of the ideal thermodynamic conditions for low emissions and high efficiency using 0D modelling of a constant volume reactor STEP 2: Translate the learning from 0D to 3D analysis of a variable volume reactor STEP 3: Identify a practical engine architecture that achieves the required thermodynamic conditions
The Recuperated Split Cycle Engine a new low emission engine architecture Precise control of the temperature at the start of combustion is achieved through separating the compression and expansion processes and air pre-heating High efficiency is achieved through reducing compression work with isothermal compression and intra cycle waste heat recovery Efficiency is decoupled from compression ratio, and therefore the temperature at the start of combustion T-s Diagram Optimal combustion phasing for high efficiency is retarded after top dead centre
Combustion retarded after top dead centre, in an expanding volume 9 Air injection into the combustion chamber Pressure waves Ignition retarded (13 ATDC in this case) Up Stroke
>55% break efficiency predicted <106ppm engine out NOx at motorway cruise <5ppm tailpipe NOx with SCR (SULEV) 10 Typical Euro VI truck engine out Air low NOx plateau N2 low NOx plateau + SCR
Conclusions 1. Very low emissions can be achieved by reacting the fuel in a dilute mixture at low temperatures 2. These conditions can be achieved in conventional engine architectures, but with compromises to efficiency, control and operating range 3. Changing the fundamental thermodynamic cycle can remove these constraints and deliver high efficiency and very low emissions
Next Steps 1. The technology will be commercialised by a new tech start up, Dolphin N2 2. Funding has been secured through Innovate UK to build a multi cylinder prototype 3. Develop a full CFD model of the spray air interaction to explore the mixing processes 4. Keep gathering data this is a completely new combustion system and does not follow the normal rules!