Ricardo WAVE Research Articles

Down-speeding diesel engines with two-stage turbochargers: Analysis and control considerations

Diesel engines continue to be used in truck applications, so reducing fuel use and hence CO2emissions, is a priority. Single-stage turbocharged diesel engines are known to be fuel efficient under steady load at low speeds. However, the engine’s ability to track load transients becomes limited by emission constraints due to the rate of production values for smoke and the resulting higher nitrogen oxides (NOx). Modern air-path solutions including a variable geometry turbine (VGT) and high pressure exhaust gas recirculation (EGR) can be used to improve dynamic response without increasing NOxemissions, but lead to complex interactions that can be difficult to control. This paper develops a two-stage, in-series, air-path configuration, which improves the typical part-load performance at low engine-speeds through adjustments to the turbine expansion ratios. Better EGR rates (for NOxreduction) at low engine speeds can be achieved whilst the engine transient response is maintained. The air-path system is simulated using Ricardo Wave software and analysed for steady-state and transient behaviour in order to identify the relationships, constraints and performance measures for different operating regions that specify the controller requirements.

Preliminary Investigation of the Performance of an Engine Equipped with an Advanced Axial Turbocharger Turbine

Stringent emission regulations and increased demand for improved fuel economy have called for advanced turbo technologies in automotive engines. The use of turbochargers on smaller engines is one such concept, but they are limited by a time delay in reaching the required boost during transient operation. The amount of turbocharger lag plays a key role in the driver’s perceived quality of a passenger vehicle’s engine response. This paper investigates an alternative method to the conventional design of a turbocharger turbine to improve the transient response of a passenger vehicle. The investigation utilises the Ford Eco-Boost 1.6 L petrol engine, an established production engine, equipped with a turbocharger of similar performance to the GT1548 produced by Honeywell. The commercially available Ricardo WAVE was used to model the engine. Comparing the steady-state performance showed that the axial turbine provides higher efficiencies at all operating conditions of an engine. The transient case demonstrated an improved transient response at all operating conditions of the engine. The study concluded that, by designing a similar sized axial turbine, the mass moment of inertia can be reduced by 12.64% and transient response can be improved on average by 11.76%, with a maximum of 21.05% improvement. This study provides encouragement for the wider application of this turbine type to vehicles operating on dynamic driving cycles such as passenger vehicles, light commercial vehicles, and certain off-road applications.

Application of dual-stage exhaust system using an expansion chamber and resonator for formula SAE

Typical vehicle mufflers utilize a series of expansion chambers and resonators to reduce engine noise. Both components behave like acoustic filters by changing the impedance of the exhaust system. Expansion chambers act as low-pass filters, which mitigate noise above a cut-off frequency determined by the geometry of the chamber. Meanwhile, resonators target specific frequencies to attenuate like a notch-filter. The present work explored tuning a muffler system containing an expansion chamber and a resonator to reduce engine noise of a Formula SAE racecar. The exhaust system design was completed using custom MATLAB scripts, Ricardo WAVE, and iterative prototyping. After determining the frequencies where the engine produced maximum sound output, the components were fabricated to damp the amplitude of the offending frequencies. The transmission loss of the prototype exhaust system was tested in an anechoic chamber by measuring the frequency responses of each separate component and the entire system. Based on this experimentation, the exhaust system had an expected overall transmission loss of 45 dB. Installed on the vehicle, the operational transmission loss was 18 dB. This discrepancy is likely due to operational conditions that could not be replicated in the laboratory experiment, such as increased temperature and gas flow.

Data Driven In-Cylinder Pressure Diagram Based Optimization Procedure

An engine optimization model is developed to fit the calculated in-cylinder pressure diagram to the experimental data by finding the optimal values of the start angle of injection and the amount of injected fuel for different engine loads. Firstly, the engine model is built in Ricardo Wave software and some parts are calibrated using data collected from the manufacturer. Then, an optimization process is performed based on the fitness function that includes the objective of the study and the penalty functions to express constraints. This optimization environment simulates the performance of a marine generator system for three different loads by minimizing the mean absolute percentage error (MAPE) between the in-cylinder pressure simulated data and the measured data along 40 degrees of the combustion process and by verifying the firing pressure and the engine brake power. The percentage of error between the calculated and the real thermodynamic data does not exceed 3.4% and the MAPE between the calculated and the real in-cylinder pressure diagram along the combustion process does not exceed 5.7% for the different loads. The proposed method can be further used to find the optimal value of different input parameters during the calibration process of different engine numerical models.

Computational Model of Rotary Engine Thermodynamic Cycle

During the engine prototype design period the performance predictions are the key subject of the development. For the piston reciprocating engines a wide spectrum of the analytical approaches was developed as well as the numerical software (GT-Suite, Ricardo Wave etc.) is being used often. The increasing demand for the high-power output engines with a low displacement and weight for the UAV and marine applications, makes Wankel rotary engine a sensible option. The commercially available software for the performance prediction does not include required algorithms for the rotary engine calculation. This paper provides an approach to be used in the simulation model setup as well as the comparison of the simulation outcome with the measured data.

Thermodynamic analysis of waste heat recovery using Organic Rankine Cycle (ORC) for a two-stroke low speed marine Diesel engine in IMO Tier II and Tier III operation

In the present study, a complete thermodynamic model of a two-stroke, low speed, 13.6 MW marine Diesel engine of Winterthur Gas & Diesel has been developed using the engine simulation software Ricardo WAVE. The model has been first validated against experimental data. A Low Pressure (LP) EGR architecture has then been implemented in order to assess the engine performance in the frame of the IMO Tier III regulations. The computational results have been used as inputs to a thermodynamic process simulation model, developed in Engineering Equation Solver, able to quantify the performance of different Organic Rankine Cycle (ORC) architectures and working fluids, with the scope of obtaining the maximum net power output for all engine operating points considered. The outcome of the present study is that, through the combined use of innovative emission reduction strategies, such as LP EGR, and waste heat recovery systems, such as ORC, it is possible to develop marine Diesel engines which exhibit fuel consumption levels comparable to those of Tier II operation, at substantially reduced levels of pollutant emissions. A preliminary economic analysis has yielded annual financial savings in fuel cost of the order of 5% for operation with ORC, as compared to operation without ORC.

A High-Efficiency Two-Stroke Engine Concept: The Boosted Uniflow Scavenged Direct-Injection Gasoline (BUSDIG) Engine with Air Hybrid Operation

Abstract A novel two-stroke boosted uniflow scavenged direct-injection gasoline (BUSDIG) engine has been proposed and designed in order to achieve aggressive engine downsizing and down-speeding for higher engine performance and efficiency. In this paper, the design and development of the BUSDIG engine are outlined discussed and the key findings are summarized to highlight the progress of the development of the proposed two-stroke BUSDIG engine. In order to maximize the scavenging performance and produce sufficient in-cylinder flow motions for the fuel/air mixing process in the two-stroke BUSDIG engine, the engine bore/stroke ratio, intake scavenge port angles, and intake plenum design were optimized by three-dimensional (3D) computational fluid dynamics (CFD) simulations. The effects of the opening profiles of the scavenge ports and exhaust valves on controlling the scavenging process were also investigated. In order to achieve optimal in-cylinder fuel stratification, the mixture-formation processes by different injection strategies were studied by using CFD simulations with a calibrated Reitz–Diwakar breakup model. Based on the optimal design of the BUSDIG engine, one-dimensional (1D) engine simulations were performed in Ricardo WAVE. The results showed that a maximum brake thermal efficiency of 47.2% can be achieved for the two-stroke BUSDIG engine with lean combustion and water injection. A peak brake toque of 379 N·m and a peak brake power density of 112 kW·L−1 were achieved at 1600 and 4000 r·min−1, respectively, in the BUSDIG engine with the stoichiometric condition.

Performance of a Heavy-Duty Turbocharged Diesel Engine Under the Effect of Air Injection at Intake Manifold During Transient Operations

The effectiveness of an air injection technique for the improvement in transient response of heavy-duty turbocharged diesel engines has been investigated but only to a limited extent. In the present work, the investigations are performed to improve the response characteristic of a heavy-duty turbocharged diesel engine under the transient event of rapid acceleration at low engine speeds. The engine model is developed using Ricardo wave software; and after the validation with the data obtained from the real engine, wave model is used to investigate the effectiveness of an air injection system for the improvement in performance of turbocharged diesel engine. The effect of air injection is observed by varying the air injection pressure and the time of acceleration. The turbocharger’s response parameters such as the compressor exit pressure, turbine inlet temperature and turbine inlet pressure have been monitored to quantify the turbocharger lag. A pressure value of 1 bar is found to be the optimum injection pressure value that significantly reduces the turbocharger lag corresponding to all the selected parameters. Furthermore, faster recovery time is observed for the tests with 1 s duration of acceleration than that with 2 s duration of acceleration. Turbo lag reduction in percentage per unit energy is found to be 29.0%, 39.2% and 55.5% per Joule based on compressor exit pressure, turbine inlet pressure and turbine inlet temperature, respectively, at 1 bar of air injection pressure.

Improvement of performance by 2-Step variations of intake runner length and intake valve timing in the induction system of a SI engine

In this research, intake runner length, and valve timing are varied individually and simultaneously over a range of values to capitalize the induction pressure waves to boost volumetric efficiency. 1-D model of the stock engine built in Ricardo Wave software is validated with 90% accuracy against experimental test results. The volumetric efficiency of the engine is boosted by an average of 3.2% over the speed range of the engine when infinitely variable runner lengths are used. When only two variations in runner length are used, the volumetric efficiency has boosted by around 1.4% on average. On the other hand, when infinitely variable valve timings along with two variations in runner lengths are used, the volumetric efficiency has boosted by an average of 7.78 %. Due to the existence of two different runner lengths, the span of variations required in valve timing is reduced further optimizing the volumetric efficiency. However, to ensure feasibility of the design, manufacturing, assembly and operation, it is better to use only two valve timings. The co-presence of only two different runner lengths and two different valve-opening timings, the average boost of 5.40 % in volumetric efficiency throughout the operating speed range of the engine is encountered.

Design and Development of Inertia Dynamometer for FSAE Application

This paper discusses the development process of a reliable and cost-effective inertia dynamometer for FSAE application.The testing procedure is to accelerate an inertial mass (flywheel) from rest to its maximum speedand calculate the engine power versus speed using the inertia of the flywheel and its rate of change of angular speed. The dimensions of the inertial load, bearings, shaft and foundation have been selected based on theoretical calculations and structural analysis. A Hall- effect sensor has been used to measure instantaneous speed during test. This data is logged through Arduino-Uno and processed using MATLAB and Ms-Excel. The results were satisfactorily similar to that from the power curve supplied by the OEM and engine model developed on Ricardo WAVE software hence proving the accuracy of the dynamometer.

Investigating the effect of increasing specific heat and the influence of charge cooling of water injection in a TGDI engine

Adding water to the intake air of gasoline engines efficiently improves operations and is highly influential to knock occurrence and NOx emissions. These factors largely benefit from the high latent heat of vaporization as well as the high specific heat of water. In this paper, based on a 1.5 L turbocharged gasoline direct injection engine, those impacts were deeply studied by separating the effect of charge cooling from the influence of increasing specific heat. An experimental test was undertaken to validate the effect of water introduction on the basic engine as well as to confirm boundary conditions and basic parameters for numerical analysis which was based on Ricardo WAVE code. Results indicate that the water introduction technique did improve engine output and thermal efficiency. Engine operations however, were primarily influenced by the impact of increasing specific heat. The charge cooling effect merely reduced the intake air temperature and had a minor impact on in-cylinder thermodynamics. Findings show the impact of water introduction on knock occurrence, engine output, thermal efficiency, and reduction in NOx emissions were mainly boosted by enhancing the specific heat of the operating medium and the effect of charge cooling was found to be insignificant.

Exhaust Tuning of an Internal Combustion Engine by the Combined Effects of Variable Exhaust Pipe Diameter and an Exhaust Valve Timing System

Changes to engine geometry and specifications can produce better torque, power, volumetric efficiency and more. The technique known as wave tuning can lead to better engine torque and power. This paper focuses on increasing the engine torque by improving the exhaust fluid flow through the exhaust manifold. Phasing and intensity of the pressure waves in the exhaust manifold have significant effects on scavenging, valve overlapping and pumping losses. In this research, individual and combined effects of variable exhaust runner diameter and exhaust valve timing on the fluid flow from exhaust of the engine are studied using computer simulation. An engine simulation software, Ricardo Wave, is utilized in this research. The analysis is conducted on a 1-D model of a KTM 510 cc single cylinder, four-stroke Sl engine. The data gathered shows that varying only the exhaust pipe diameter continuously with speed yields an average of 4.23% improvement in torque from the original engine model. However, due to practical constraints, the diameter is limited to vary in three steps (36 mm, 45 mm and 60 mm). This has reduced the average improvement of torque to 3.78%. Varying the valve timing alone gains an average of 1.94% improvement in torque. Varying both the exhaust pipe diameter in three steps and the exhaust valve timing yields an average of 4.69% improvement in torque. This average is conducted over the engine speed ranges from 2000 to 11,000 rpm.

Thermodynamic and numerical analysis of intake air humidification of a turbocharged GDI engine

Reducing the temperature and increasing the specific heat capacity of working medium of gasoline engines are the most efficient methods of mitigating knock tendency. The charge cooling effect of intake air humidification is helpful for decreasing the initial temperature of intake air, and the increase of the specific heat capacity of working medium can reduce the temperature rise in the in-cylinder process. This study established a mathematical model of intake air humidification of gasoline engines, and analyzed the effects of the technique on the thermodynamic process of a turbocharged gasoline engine with Ricardo WAVE Code. The results indicated that the intake air humidification is an isenthalpic process; the vapor influences the working process of the engine by altering the thermodynamic parameters of the working medium. A decrease in the initial temperature and adiabatic index and an increase in the specific heat capacity of working medium lowered the in-cylinder temperature and pressure, hence suppressing the knock occurrence. After the humidification of intake air, the engine performance slightly increased, and the thermal efficiency showed different levels of improvements at all the working conditions.

Analysis of the Scavenging Process of a Two-Stroke Free-Piston Engine Based on the Selection of Scavenging Ports or Valves

The free-piston engine generator (FPEG) is a linear energy conversion device with the objective of utilisation within a hybrid-electric automotive vehicle power system. In this research, the piston dynamic characteristics of an FPEG is compared with that of a conventional engine (CE) of the same size, and the difference in the valve timing is compared for both port scavenging type and valve scavenging type, with the exhaust valve closing timing is selected as the parameter. A zero-dimensional simulation model is developed in Ricardo WAVE software (2016.1), with the piston dynamics obtained from the simulation model in Matlab/SIMULINK (R2017a). For the CE and FEPG using scavenging ports, in order to improve its power output to the same level as that of a CE, the inlet gas pressure is suggested to be improved to above 1.2 bar, approximately 0.2 bar higher than that used for a CE. If a CE cylinder with exhaust valves is adopted or referred to during the development of an FPEG prototype, the exhaust valve is suggested to be closed earlier to improve its power output, and a higher intake pressure is also suggested if its output power is expected to be the same or higher than that of a CE.

ORC units driven by engine waste heat – a simulation study

ORC (organic Rankine cycle) technology is promising in industry for utilizing low-grade heat to generate electricity. It is acknowledged that in an internal combustion engine, only a small amount of primary fuel energy can be effectively used for the power generation, and the other part of the energy lost through exhaust gas, cooling of elements and overcoming friction. The heat in exhaust gas and cooling system (jacket water) can be used as a heat source to drive ORC units for power generation. In this way, the energy lost can be recovered to generate extra power. In this study, Ricardo Wave software was used to investigate the amount of waste heat available from a 1-cylinder diesel engine and THERMOLIB toolbox in SIMULINK was used to simulate and evaluate the performance of a small ORC unit designed for the application. The simulation results from the engine and ORC models were validated against experimental data from other researchers. Two different heating methods to the ORC were used: a) directly driven by the exhaust gas and jacket water (EG-JW); b) thermal oil (TO) was used to collect the waste heat from the engine exhaust gas; the heated thermal oil together with jacket water were then used to drive the ORC. It was found that the performance of the ORC was improved and it was more stable when using TO under different engine running conditions than that directly driven by EG-JW.

Organic Rankine cycle – review and research directions in engine applications

Waste heat to power conversion using Organic Rankine Cycles (ORC) is expected to play an important role in CO 2 reductions from diesel engines. Firstly, a review of automotive ORCs is presented focusing on the pure working fluids, thermal architectures and expanders. The discussion includes, but is not limited to: R245fa, ethanol and water as fluids; series, parallel and cascade as architectures; dry saturated, superheated and supercritical as expansion conditions; and scroll, radial turbine and piston as expansion machines. Secondly, research direction in versatile expander and holistic architecture (NO x + CO 2 ) are proposed. Benefits of using the proposed unconventional approaches are quantified using Ricardo Wave and Aspen HYSYS for diesel engine and ORC modelling. Results indicate that, the implementation of versatile piston expander tolerant to two-phase and using cyclopentane can potentially increase the highway drive cycle power by 8%. Furthermore, holistic architecture offering complete utilisation of charge air and exhaust recirculation heat increased the performance noticeably to 5% of engine power at the design point condition.

무인기용 터보차저 장착 SI 엔진 시스템 성능해석

A performance analysis of a gasoline engine with a 2-stage turbocharger system for unmanned aerial vehicle(UAV) was conducted. One dimensional system analysis was conducted for the requirements of turbochargers and adequate turbochargers were selected from commercially available models for automobiles. Modeling and simulation were performed by Ricardo WAVE. Gasoline engine modeling was based on a 2.4 L 4-cylinder engine specification. The selected turbochargers and intercoolers were added to the engine model and simulated at 40,000 ft altitude condition. The results of the engine model and 2-stage turbocharger system model simulation showed break power 93 kW which is appropriate power required for the engine operation at the ambient conditions of 40,000 ft altitude.

Analysis of the backpressure effect of an Organic Rankine Cycle (ORC) evaporator on the exhaust line of a turbocharged heavy duty diesel power generator for marine applications

In marine and power generation sectors, waste heat recovery technologies are attracting growing attention in order to increase heavy duty diesel engines efficiency and decrease fuel consumption, with the purpose of respecting stringent emissions legislations.In this work, the backpressure effect of an Organic Rankine Cycle (ORC) evaporator on the exhaust line of a turbocharged, V12 heavy duty diesel engine, for typical marine and power generation applications has been investigated using the commercial software Ricardo WAVE. Three different state-of-the art turbocharging strategies are assessed in order to counterbalance the increased pumping losses of the engine due to the boiler installation: fixed turbine, Waste-Gate (WG) and Variable Geometry Turbine (VGT). At the same time, the steady-state thermodynamic performance of two different ORC configurations, simple tail-pipe evaporator and recuperated simple tail-pipe evaporator layouts, are assessed, with the scope of further increasing the engine power output, recovering unutilized exhaust gas heat. Several different working fluids, suitable for medium-high temperature waste heat recovery, are evaluated and screened, considering, as well, health and safety issues. Thermodynamic cycle parameters such as, for example, evaporation and condensing pressures, working fluid mass flow and cycle temperatures, are optimized in order to obtain the maximum improvement in Brake Specific Fuel Consumption (bsfc).From the engine side point of view, a VGT turbocharger is the most favorable solution to withstand increased backpressure, while, regarding the ORC side, between the considered fluids and layouts, acetone and a recuperated cycle show the most promising performance.

Enhancement on Sound Transmission Loss for Various Positioning of Inlet and Outlet Duct of the Muffler

Muffler acts as noise reduction element on exhaust system. Noise from an automotive application is the major source of noise pollution. Here the transmission loss of central inlet and central outlet muffler of single expansion chamber has been compared and validated in three methods namely transfer matrix method, finite element analysis and an experimental method for this purpose an experimental setup has been built up which is based on two load method. Several researchers have worked in the area of noise attenuation on central inlet by changing the position of outlet as side outlet but no one emphasizes on offset of the central inlet and central outlet position. Thereafter the finite element analysis tool Ricardo wave 1-D and comsol multiphysics is used to evaluate transmission loss for various offset position of inlet and outlet duct of the muffler. The very purpose to improve the acoustic performance of central inlet with offset outlet pipe by measuring transmission loss of offset inlet with offset outlet with various positions by keeping same space. Finite element analysis shows that higher attenuation can be achieved by increasing offset distance of central inlet & outlet outlet towards radial direction of the expansion chamber with the variation of 0.2r, 0.4r and 0.6r. Here ‘r’ is radius of single expansion chamber. The result shows that high transmission loss can be achieved by increasing the offset radial distance of the inlet pipe and outlet pipe. Further higher attenuation can also be achieved in case of fixed the distance of offset inlet and outlet at 0.6r by rotating the offset outlet which is also offseted at 0.6r distance by 0 o

Comparison of Engine Simulation Software for Development of Control System

Most commonly used commercial engine simulation packages generate detailed estimation of the combustion and gas flow parameters. These parameters are required for advanced research on fluid flow and heat transfer and development of geometries of engine components. However, engine control involves different operating parameters. Various sensors are installed into the engine, the combustion performance is recorded, and data is sent to engine control unit (ECU). ECU computes the new set of parameters to make fine adjustments to actuators providing better engine performance. Such techniques include variable valve timing, variable ignition timing, variable air to fuel ratio, and variable compression ratio. In the present study, two of the commercial packages, Ricardo Wave and Lotus Engine Simulation, have been tested on the capabilities for engine control purposes. These packages are compared with an in-house developed package and with reference results available from the literature. Different numerical experiments have been carried out from which it can be concluded that all packages predict similar profiles of pressure and temperature in the engine cylinder. Moreover, those are in reasonable agreement with the reference results while in-house developed package is possible to run simulations with changing speed for engine control purpose.