Modelling and Simulation of a Rotary Range Extender

Modelling and Simulation of a Rotary Range Extender Engine Andrew Pennycott, Giovanni Vorraro, Matt Turner, Jamie Turner University of Bath AVL Simulation Conference 2019

Presentation Overview 2 • ADAPT Project Introduction • Vehicle Application: Pod-On-Demand Vehicles • Methods: Modelling and Validation of Range Extender Engine • Simulation and Testing Results • Conclusions and Future Work 07/02/2019

ADAPT Project 3 • Development of hybrid powertrain with rotary engine • Test technology application for autonomous pods • Funded by Innovate UK • Project managed by Advanced Propulsion Centre (APC) 07/02/2019

Pod-on-Demand (POD) Vehicles • Applied in “last mile” transportation • Alternative to feeder buses • Examples in the United Kingdom: o Heathrow POD – 6 minute journey o Greenwich Intercontinental Hotel to Greenwich Peninsula 4 07/02/2019

Pod-on-Demand (POD) Advantages 5 • Low carbon emissions: typically electric or hybrid powertrain • Low waiting times • Reduction in congestion • Potential for safety and vehicle connectivity advantages 07/02/2019

ADAPT Goal: Range Extender for POD Vehicle 6 • Limited range of pure battery solution • Mitigation using small internal combustion engine (ICE) • Desirable characteristics: o Lightweight and compact o Favourable noise, vibration and harshness (NVH) characteristics o Efficiency is not primary concern 07/02/2019

Hybrid Powertrain Architecture 7 • Single electric motor drives front-wheel drive differential • Range extender drives generator to recharge battery 07/02/2019

Overview of the Wankel Engine 8 • First patented in 1929 • Runs on Otto cycle • Three-pointed rotor within a fixed housing • Lightweight and compact • Favourable NVH characteristics 07/02/2019

Rotary Engine: Operation Shaft eccentricity allows different phases: 1. Intake 2. Compression 3. Ignition 4. Exhaust Shaft turns three times for each rotor rotation J Spreitzer et al, Implementation of a Rotary Engine (Wankel Engine) in a CFD Simulation Tool with Special Emphasis on Combustion and Flow Phenomena, SAE Technical Paper 2015 -01 -0382, 2015 9 07/02/2019

225 CS – 40 BHP Engine 10 Characteristic Value Power Output 30 k. W Torque 37 Nm @ 8000 rpm Displacement 225 cc Compression ratio 9. 6: 1 Mass 10 kg 07/02/2019

Why Model the Powertrain? • Useful tool for design and optimisation • Rotary engines sensitive to length, shape of intake and exhaust piping o Effects on work output, fuel consumption and volumetric efficiency 11 • Investigate influence of different factors on performance / emissions • Experimental investigation of all scenarios expensive 07/02/2019

One-Dimensional Modelling • Based on the unsteady Navier-Stokes equations • 1 D equations derived using control volumes • Conservation of mass, momentum and energy • 12 Fluid motion, pressure waves, heat transfer, etc. 07/02/2019

One-Dimensional Solution 13 • Flow path discretized into small control volumes • Components connected by boundary conditions • Every engine cycle is divided into small time steps 07/02/2019

Zero-Dimensional Engine Modelling 14 07/02/2019

Rotary Engine: Basic Geometry 15 07/02/2019

AVL Boost Model • AVL Boost software package used to simulate engine • Built-in rotary engine component: o Chamber volume and surface area modelled o Difficult to model using equivalent reciprocating engine model* • Used to simulate engine performance characteristics *M Peden et al, Comparison of 1 -D Modelling Approaches for Wankel Engine Performance Simulation and Initial Study of the Direct Injection Limitations, SAE Technical Paper 2018 -01 -1452, 2018 16 07/02/2019

AVL Boost Model: Overview Basic model components: 17 • Pipes • Throttle • Three injectors • Rotary engine • Silencer (plenums) 07/02/2019

AVL Boost Component Parameters 18 Component Parameters Pipe Length, diameter, bending radius Throttle Diameter, flow coefficient table Rotary Engine Geometry, combustion and heat transfer models Plenum Volume, orientation, flow coefficient 07/02/2019

AVL Boost Model: Inputs and Parameters 19 • Heat release and friction mean effective pressure: experimental data • Injection and spark timing: taken from ECU maps • Piping dimensions: CAD drawings • Model assumes stoichiometric air-fuel ratio 07/02/2019

AVL Boost Model: Outputs 20 • Air and fuel mass flow rates • Combustion behaviour – in-cylinder pressure • Engine outputs – torque and power • Exhaust temperature 07/02/2019

Engine Testing 21 • Different conditions tested on engine dynamometer • Rubber coupling used in dynamometer connection • Tests conducted at wide open throttle from 3000– 6500 rpm • Data allow validation and tuning of AVL Boost model 07/02/2019

Model Validation Results: Air and Fuel Flowrates 22 07/02/2019

Model Validation Results: Combustion Pressure 23 07/02/2019

Model Validation Results: Torque and Exhaust Temperature 24 07/02/2019

Future Work 25 • Incorporation of expander unit • CFD modelling of combustion • Injector & spark control via MATLAB API • Design and fabrication of hybrid vehicle prototype 07/02/2019

Conclusions 26 • Modelling basis for range extender engine developed in AVL Boost • Initial validation with engine dynamometer testing data • Modelling tool can be used to design and optimise hybrid POD vehicle • Future work will focus on emissions and vehicle development 07/02/2019

With thanks to our funders 27 07/02/2019